Dissertations / Theses on the topic 'Coating durability'

The objectives of this research programme were to examine the influence of manufacturing and processing parameters on the environmental stability of aqueous acrylic based latices and to also extend the programme to an assessment of the behaviour of various stabiliser types suitable to such materials through either end-group modification or direct in-situ addition. During the research programme a number of physical and chemical techniques were assessed to routinely characterise and monitor the photochemical and thermal degradation of acrylic latices. These were based on emulsion polymerised formulations of methyl methacrylate and butyl acrylate. In the first instance, acrylic latices based on different formulations were chosen as homopolymers and copolymers. Here the nature of impurities and oxidation products generated during various stages of their manufacture have to be characterised and inter-related to their influence on subsequent environmental degradation. This involved the use of reflectance FT-IR spectroscopy to show functional group changes together with colourimetric U.V. analysis to determine photochemical generation of hydroperoxides. The early chemical changes and their subsequent influence on the physical and chemical properties of the latices during the later stages of environmental degradation were found to exhibit a close inter-relationship. In this regard the formation and the manufacturing temperatures and periods were crucial. Thermal methods of analysis were also used to characterise differences in the properties of the latices before and during thermal and photochemical oxidation. The nature of the residual persulphate initiator and the compositions of the latices in terms of end group modification were important parameters. De-esterification and hydroperoxide formation were found to be important processes during latex degradation while the use of low levels of co-monomer addition. such as methacrylic acicL to the emulsion reaction gave latices with improved light stability. Subsequent aspects of the research programme involved a detailed investigation into the behaviour and performance of various stabiliser types and formulations. Thus, while coreactive hindered piperidine stabilisers was found to be effective, the incorporation of simple terminal dialkyl acrylamide/methacrylaroide groups were also found to be effective. The efficiency of dialkylamide groups operating through a sacrificial mechanism is discussed. The influence of these processing operations on subsequent stabiliser activity provides valuable information on the mode of action of these stabilisers in such complex media. Further work involved a study into the effect of fluorinated methacrylates used in emulsion polymerised formulations. Here, the presence of residual starting materials in the monomer was found to have a detrimental effect in terms of photostability. Subsequent analysis of acrylic resins, based on solution polymerised formulations of methyl methacrylate and fluorinated methacrylates, was undertaken. The influence of reactive stabiliser types on these resins was important and to improve stabiliser perfonnance, synergistic stabiliser formulations were studied. This project will provide important fundamental information on the behaviour of active chromophores produced during the manufacturing process and hopefully resuh in the development of monitoring methodologies to establish paint quality.

Thesis (Ph. D.)--Ohio State University, 2005.
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Chaque année, environ 500000 personnes en Europe. Dont un cinquième en France, sub issent une opération de pose ou de remplacement de Prothèse Totale de Hanche (PTH). Les prothèses de hanche réalisées jusqu'à présenl ne peuvent pas sClVir plus de 15 années. L'objectif principal de cette étude est donc l'augmentation de la longévité des prothèses (» 15 années) par la minimisation voi r, si possible, l'élimination de la formation de débris sur les surfaces de contact d'articulation. Dans notre cas. Le substrat est une tête sphérique en alliage de titane Ti6AI4 V fro ttant contre une cupule en polyéthylène à po ids moléculaire ultra élevé ( UHMWPE). Or, le titane et ses alliages présentent d'assez médiocres performances caractérisées en frottement. Pour remédier à cet effet. On propose un rcvetemcnt de Ti6Al4V par le diamant s)'mhetique en utilisant une nouvelle technique de dépôt chimique à haute température avec modulation du temps (Time modulated CVO - TMCVD). Cependant. Ce revetemcnt présente quelques difficultés dues à la génération des contraintes résiduelles élevées. La spectroscopie de Raman et la diffraction des rayons X (XRD) onl été utilisées pour mesurer ces contraintes résiduelles. Pour réduire les intensités des contraintes résidue lles ct améliorer J'ad hé sion, nous avons utilisé une couche intennédiai re de DLC (diamond like carbon) entre [e substrat Ti6A I4 V ct le diarnond. En fin, pour évaluer les cOJltraintes rés id uel le d'origine thermique. La méthode des éléments finis a été employée pour simuler le procédé de refroidissement des couches minces de diamant déposées sur ['alliage Ti6AI4 V à des températures s'étendant de 600°C à 900 oc
Orthopaedic implants have improved the quality of life for millions of people over the last quarter of a cenlllly. The chnical objective is 10 rclieve pain and increase case ofmovement in the joint. In this work. We focus on hipjoint replacements. The biomaterial used is Titanium alloys (Ti6AI4 V). Coating Ti6AI4 V with diamond makes it one of the promising strategies 10 improve the alloy wear behavior, The main goal of this study is to obtain such coating with high qualily. Unstressed, conti nuous and well-adhered diamond film on Ti6Al4 V using a new process named time modulated CVD (Tr. . 1CVD). This technique is able to produce ultra-hard, smoolh. And good quality diamond films. Nonetheless, satisfactory adherence of diamond coating tilms to Ti6AI4V will be attainable by the use of an interlayer. In order 10 compensale the large interfacial thermal expansion mismatch between the cOining and substrate material. For thi s, we have used OLC (diamond like carbon) as an inlcrlayer material between diamond coatings and Ti6AI4 V substrate. The residual stresses in the diamond lilm were characterized for the cases with and withou! the OLC intcrlayer using scanning cleClron microscopy (SEM), Raman speclroscopy and X-ray diffraction. Lower values of the rcsidual stresses \Vere obtained for the case \Vith DLC interlayer. Finally, a numcri cal simulation \Vas conduclcd to estimate the thermal residual stresses that dcvelop in the diamond film and in the substratc. Ln this. We simulatcd the cooling process from the deposition temperalurc of diamond (600 10 900 oC) 10 room tcmpcralurc The obtaincd results show that the predicted rcsidunl Stresses are of the sarne order as those measurcd experimcntally

Novel coatings have been designed to solve problems associated with biofouling of marine structures, particularly ship hulls. The best candidates to date are multilayered coatings incorporating silicone rubber technology. These materials are efficient because they exhibit excellent release properties. However, they are very soft and tend to be more susceptible to various forms of mechanical damage. Fundamental analysis of the durability of these coatings has been done using standard laboratory tests. Simulative studies are essential to screen candidates as well as to predict the true life of the systems. The goal of this project was to develop a testing protocol for the evaluation of the durability of elastomeric easy release coatings and to implement it on selected candidate coatings. A brushing apparatus was designed and built to simulate the cleaning processes of ship hulls. Wear was measured with profilometry. The proposed methodology is valuable to study the processes of wear of the coatings, to screen various materials and to identify parameters, either functional or material, which would directly affect their durability. Two groups of candidate coatings were tested: the EXS series and the NRL series. The EXS samples showed better wear resistance than the NRL samples and showed no dependence on the rotational speed of the brushes. The NRL samples showed that increasing the sliding speed resulted in a decrease in wear. An increase in the applied load resulted in increased wear for both sample series. The effect of coating thickness was also investigated and discrimination between the proposed coatings could not be established because the tips of the bristles were sharp and irregular. Scratches matching the path of the brush bristles were observed in the wear scars of both sample types under all load and speed conditions. The NRL samples also exhibited ridges perpendicular to the sliding direction similar to the abrasion pattern.
Ph. D.

The primary cause of corrosion in transportation structures is due to chlorides which are applied to bridge decks as deicing salts. The direct cost of corrosion damage to the countryâ s infrastructure is approximately $8.3 billion per year. One of the most common corrosion abatement methods in the United States is the barrier protection implemented through the application of fusion bonded epoxy coatings. The purpose of this study was to investigate various coating and exposure parameters to determine their effects on the corrosion of reinforcing steel. The parameters investigated were: chloride content at the bar depth, coated bar corroded area, corrosion product color under the coating, epoxy coating adhesion, coating color, coating damage (holidays and holes), coating thickness, TGA, DSC and EDS analysis and SEM coating cracking investigation. This was accomplished by testing new coated bar specimens as well as specimens extracted from 27 bridge decks located in Virginia. This study demonstrated the following: The extracted ECR coating samples presented extensive cracking compared to the new ECR samples in which the coating cracking was limited to only one sample. The DSC results showed that both the extracted samples as well as new samples are not fully cured during the manufacturing process. The coating degree of curing data also showed that the bars are insufficiently and unevenly heated prior to the application of the powder coating. Additionally, the samples investigated presented significant permanent adhesion loss with little or no epoxy coating residue present on the bar surface, while the EDS analysis showed that once adhesion is lost, corrosion will proceed unimpeded under the coating even in the absence of chlorides. The parameters that presented a direct correlation with the observed corrosion activity were the number of holidays and the number of damaged areas per unit length of bar. This indicates that the passivation of the bare steel exposed to the concrete pore solution at the breaches in the epoxy coating is not the same as a bare bar under similar exposure conditions allowing it instead to corrode at lower concrete chloride concentration levels than bare bars. The results also show a distinct loss of quality control in the handling and possibly storage of new coated bars. The new ECR samples had significantly higher damage density than the samples extracted from concrete even though the coating is damaged during the placement of the concrete, while there was no change in the number of holidays and cure condition. Finally, the data presented further evidence that while limited, the non-destructive corrosion assessment methods available for bare steel reinforced structures may also be used on ECR reinforced structures. In particular, the corrosion rate measurements correlated reasonably well with the chloride concentrations at bar level. This indicates that while the chlorides may not influence the corrosion activity under the coating, they do influence the corrosion activity at breaches in the coating.
Ph. D.

Functional coatings produced using scalable and cost-effective processes such as electrodeposition and etching lead to the creation of random roughness at multiple length scales on the surface. The first part of thesis work aims at developing a fundamental mathematical understanding of multiscale coatings by presenting a fractal model to describe wettability on such surfaces. These surfaces are described with a fractal asperity model based on the Weierstrass-Mandelbrot function. Using this description, a model is presented to evaluate the apparent contact angle in different wetting regimes. Experimental validation of the model predictions is presented on various hydrophobic and superhydrophobic surfaces generated on several materials under different processing conditions. Superhydrophobic surfaces have myriad industrial applications, yet their practical utilization has been severely limited by their poor mechanical durability and longevity. Toward addressing this gap, the second and third parts of this thesis work present low cost, facile processes to fabricate superhydrophobic copper and zinc-based coatings via electrodeposition. Additionally, systematic studies are presented on coatings fabricated under different processing conditions to demonstrate excellent durability, mechanical and underwater stability, and corrosion resistance. The presented processes can be scaled to larger, durable coatings with controllable wettability for diverse applications. Apart from their use as superhydrophobic surfaces, the application of multiscale coatings in photo-thermal conversion systems as solar selective coatings is explored in the final part of this thesis. The effects of scale-independent fractal parameters of the coating surfaces and heat treatment are systematically explored with respect to their optical properties of absorptance, emittance, and figure of merit (FOM).
Master of Science

The focus of the project was to alter and optimize the water repellant textile coating formulations to reach enhanced durability. For this purpose, the project was approached with three methods. Firstly, bio-based components were implemented in the mother emulsion to act as surfactant and crosslinking agent and to provide hydrophobic properties. Secondly different binders were added to crosslink and increase the coating resistance towards washes. Lastly additives at nano-scale were added to increase surface roughness in order to obtain higher hydrophobicity and improved of crosslinking capacity due to the presence of more functional groups.  The stability of all emulsions was controlled using different techniques such as optical microscopy to determine particle size, distribution and any observable instability (flocculation etc.), normal aging at room temperature and accelerated aging using higher temperature. All coatings were applied using a laboratory padder on standard PA and PES pieces of textiles and hydrophobic performance was evaluated through ISO 4920 spray test. By standard washing and repeating spray test, durability could be assessed. Further structure and property studies have been run using other tests such as: contact angle measurement, breathability of the coating and SEM observations. Based on the obtained results the incorporation of low HLB, bio-based surfactants in low amount (~0,25%) resulted in an increase in the hydrophobic performance of the tested textiles. However, a decrease in shelf life could be observed with these surfactants at room temperature. Sonication was successfully used to increase both stability and shelf life significantly. Some binders and nanoparticles proved to be successful in increasing the coating quality and thus the durability. Overall many of the developed formulations could enhance performance on PA compared to the already present commercial product. On PES textile, however, the developed strategies yielded hydrophobic effect close to the commercial product.

Aluminized steel pipes are expected to have a long service life, e.g. 75 years. Spiral ribbed aluminized pipes (SRAP) have been widely specified and used by the Florida Department of Transportation (FDOT) for drainage of runoff water. Confidence in the long term durability of SRAP has been challenged by recent unexpected early corrosion failures in various Florida locations. SRAP premature corrosion incidents have occurred in two modalities. Mode A has taken place in near-neutral soil environments and has often been associated with either gross manufacturing defects (i.e. helical cuts) or corrosion concentration at or near the ribs. Mode B took place in pipes in contact with limestone backfill and corrosion damage was in the form of perforations, not preferentially located at the ribs, and not necessarily associated with other deficiencies. These failures motivated this research. The objectives of this work are to establish to what extent the Mode A corrosion incidents can be ascribed to manufacturing defects, that can be rectified by appropriate quality control, as opposed to an intrinsic vulnerability to corrosion of regularly produced SRAP due to ordinary forming strains and to determine the mechanism responsible for Mode B corrosion including the role that limestone backfill played in that deterioration. To achieve those objectives, laboratory experiments were conducted to replicate the conditions for Mode A and Mode B. Overall, the findings of this and previous work suggest that much of the corrosion damage observed in the Mode A incidents were promoted more by manufacturing deficiencies and less by any possible inherent susceptibility of corrosion at the ribs of SRAP that was produced following appropriate quality control. Experiments to explore the causes of Mode B corrosion showed that high pH values, sufficient to cause dissolution of the passive film on aluminum, can develop under exposure of limestone to flowing natural water. The findings substantiate, for the first time, an important vulnerability of aluminized steel in limestone soils and provide an explanation for the rapid onset deterioration observed at the field under Mode B. The findings also provide strong evidence in support of service guidelines to disallow the use of limestone bedding for aluminized steel pipe, including SRAP.

When bonded joints are subjected to harsh environmental conditions, the interphase, the three-dimensional region surrounding the adhesive/substrate interface, becomes critically important. Frequently, failure occurs in this region after adhesively bonded systems are subjected to elevated temperature oxidative aging. In a previous study, this was found to be the case with a polyimide adhesive bonded to chromic acid anodized (CAA) Ti-6Al-4V. The objective of the current research has been twofold: 1) to investigate the effect of thermal aging on the interphase region of polyimide/titanium adhesive joints, and 2) to evaluate the method used in the current study for durability characterization of other adhesive/substrate systems. The method used in this research has been to characterize the effect of elevated temperature aging on the following systems: 1) Notched coating adhesion (NCA) specimens and 2) bulk samples of dispersed substrate particles in an adhesive matrix. The NCA test has the advantages of an accelerated aging geometry and a mode mix that leads to failure through the interphase, the region of interest. The bulk samples have the advantage of an increased interphase volume and allow for the application of bulk analysis techniques to the interphase, a region that is traditionally limited to surface analysis techniques. The adhesive systems studied consisted of one of two polyimide adhesives, LaRC⠢ PETI-5 or Cytec Fiberite⠢ FM-5, bonded to CAA Ti-6Al-4V. The model filled system consisted of a PETI-5 matrix with amorphous titanium dioxide filler. Through the use of the NCA test, it was determined that bonded specimens made with FM-5 lose approximately 50% of their original fracture energy when aged in air at 177°C for 30 days. This aging temperature is well below the glass transition temperature of the adhesive, 250°C. At the same time, the failure location moves from the anodized oxide layer to the adhesive that is directly adjacent to the substrate surface, the interphase region. Through surface analysis of this region, it is determined that the adhesive penetrates the pores of the CAA surface to a depth of 70 to 100 nm, promoting adhesion at the interface. With aging, the adhesive in the interphase region appears to be weakening, although analysis of the bulk adhesive after aging shows little change. This indicates that adhesive degradation is enhanced in the interphase compared to the bulk. Analysis of the model filled system gave similar information. Specimens containing titanium dioxide filler had glass transition temperatures that were approximately 20°C lower than the neat polyimide samples. In addition, the filled samples contained a significant portion of low molecular weight extractable material that was not present in the neat specimens. The tan delta spectra from dynamic mechanical thermal analysis of the filled specimens exhibited a shoulder on the high-temperature side of the glass transition peak. This shoulder is attributed to the glass transition of the interphase, a distinct phase of the polyimide which is constrained by adsorption onto the filler particle surfaces. As a function of aging time at 177° or 204°C, the shoulder decreases substantially in magnitude, which may relate to loss of adhesive strength between the polyimide and the filler particles. From this research, it has been illustrated that information relating to the durability of adhesively bonded systems is gained using an interfacially debonding adhesive test and a model system of substrate particles dispersed in an adhesive matrix
Ph. D.

Diploma work describes speed drill steels and its qualities before and after coating by methods PVD (Physical Vapour Deposition). The theoretic part is concerned with thermic processing of speed drill steels and their qualities with regard to individual alloying elements contained and its mechanical features. Second part of the theoretic part is concerned with particular methods of coating by the help of PVD technologies, kinds of coating with regard to additional elements and their qualities and surface treatments of coated material before and after its coating. The goal of the experimental part was the confrontation of cutting power features of cylindrical four-fluted face mills with straight shank, from speed drill steels non-coated and coated in two basic modes of milling – down-feed method and upfeed method. The results of measurements were interpreted by the help of four basic pictures (source values, power analysis, specific values). The result of all the experiment is that the application of PVD coatings enabled the increasing of cutting speed (with preservation of other cutting requirements) and led to decreasing of cutting force and cutting enforcements and extended durability of cutters.

Fiber reinforced polymer (FRP) composites have become an attractive alternative to conventional methods for external-strengthening of civil infrastructure, particularly as applied to flexural strengthening of reinforced concrete (RC) members. However, durability of the bond between FRP composite and concrete has shown degradation under some aggressive environments. Although numerous studies have been conducted on concrete members strengthened with FRP composites, most of those studies have focused on the degradation of FRP material itself, relatively few on bond behavior under repeated mechanical and environmental loading. This thesis investigates bond durability under accelerated environmental conditioning of two FRP systems commonly employed in civil infrastructure strengthening: epoxy and polyurethane systems. Five environments were considered under three different conditioning durations (3 months, 6 months, and 1 year). For each conditioning environment and duration (including controls), the following were laboratory tested: concrete cylinders, FRP tensile coupons, and FRP-strengthened concrete flexural members. Numerical investigations were performed using MSC MARC finite element software package to support the outcomes of durability experimental tests. Precise numerical studies need an accurate model for the bond between FRP and concrete, a linear brittle model is proposed in this work that is calibrated based on nonlinear regression of existing experimental lap shear data. Results of tensile tests on FRP coupons indicate that both epoxy and polyurethane FRP systems do not degrade significantly under environmental exposure. However, flexural tests on the FRP strengthened concrete beams indicate that bond between FRP and concrete shows significant degradation, especially for aqueous exposure. Moreover, a protective coating suppresses the measured degradation. Also, experimental load-displacement curves for control beams show excellent agreement with numerical load-displacement curves obtained using the proposed bond model. Finally, a bond-slip model is predicted for concrete leachate conditioned beams by matching load-displacement curves for those beams with numerical load-displacement curves.
M.S.
Masters
Civil, Environmental, and Construction Engineering
Engineering and Computer Science
Civil Engineering; Structures and Geotechnical Engineering

Porous zeolite, carbon and aluminophosphate powders have been colloidally assembled and post-processed in the form of monoliths, flexible free standing films and coatings for gas separation and odor removal. Zeolite 13X monoliths with macroporosites up to 50 vol% and a high CO2 uptake were prepared by colloidal processing and sacrificial templating. The durability of silicalite-I supports produced in a binder-free form by pulsed current processing (PCP) were compared with silicalite-I supports produced using clay-binders and conventional thermal treatment. Long-term acid and alkali treatment of the silicalite-I substrates resulted in removal of the clay binder and broadened the size-distribution of the interparticle macropores. Furthermore, strong discs of hydrothermally treated beer waste (HTC-BW) were produced by PCP and the discs were activated by physical activation in CO2 at high temperatures. The activated carbon discs showed high strength up to 7.2 MPa while containing large volume of porosities at all length scales. PCP was further used to structure aluminomphosphate powders (AlPO4-17 and AlPO4-53) into strong functional monoliths. The aluminophosphate monoliths had strengths of 1 MPa, high CO2 uptake and were easy to regenerate. Zeolite Y, silicalite and ZSM5 were selected as potential zeolite adsorbents for removal of sulfur containing compound, e.g. ethyl mercaptan (EM) and propyl mercaptan (PM). A novel processing procedure was used to fabricate free-standing films and coatings of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite; 89 w/w% and 96 w/w%, respectively. Thin flexible free-standing films and coatings of zeolite-CNF on paperboards with thickness around 100 µm and 40 µm, respectively, were produced. Headspace solid phase microextraction (SPME) coupled to gas chromatography- mass spectroscopy (GC/MS) analysis showed that the zeolite-CNF films can efficiently remove considerable amount of odors below concentration levels that can be sensed by the human olfactory system.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.

The thesis deals with the influence of the base material of the coating systems for wood durability when we exposed them to external conditions. The theoretical part is devoted to wood durability and weather resistance with a detailed description of the tests the durability of coating systems. A substantial part of the theory is devoted to description binder component of the coating material. In the practical part was performed the experiment, which examined the influence of the thickness of the coating system, the type of coating material (paint or lasure) as well as the type of binder (water dispersion with an alkyd or acrylic resin, respectively solution coating system with the alkyd resin). All coating systems were exposed to natural and artificial durability tests. The criterions for evaluation were chosen differences of colours.

This diploma thesis deals with HSS cutting taps performance in combination with very hard and tribological PVD coating application and their contribution to increasing of cutting properties. Then is described the mechanisms and forms of cutting tool wear. The goal of the experimental part of the thesis was determine, compare and subsequently evaluate cutting properties of threading tools using taps with different types of PVD coatings. During realization of the experiment, constant cutting conditions have been ensured and the only variable were the different types of coating layers. The result of the experiment was measurement of cutting torques depending on time and rate of wear of cutting tools. Measured value are statistically processed and drawn conclusion.

Water-assisted crack growth at an epoxy/glass interface was measured as a function of applied strain energy release rate, G, and temperature using a wedge test geometry. The specimens consist of two glass plates bonded with a thin layer of proprietary epoxy adhesive. The crack fronts along the epoxy/glass interfaces were measured using an optical stereomicroscope. The relationship between G and the debonding rate, v, can be measured using this method, and the threshold value of strain energy release rate, Gth, can be determined from the measured data. Two types of testing procedures were conducted in this study: ex situ, i.e., pre-conditioned wedge tests and in situ ones, in which wedges were applied before the specimens were submerged into water. A preliminary model was developed based on the thermal activation barrier concept, and allows the prediction of Gth for the temperatures beyond the testing region. Changes in interfacial strain energy release rate caused by thermal residual stresses in a triple-layered specimen were analyzed in Chapter Three. The method is based on linear elastic fracture mechanics and simple beam theory. The curvature of a bimaterial strip was chosen to characterize the residual stress in the specimen, and the strain energy release rate, caused by both tensile and compressive residual stresses in the adhesive, was derived for an asymmetric double cantilever beam (ADCB) geometry. The contribution of the thermal residual and mechanical stress to the global energy release rate was analyzed. The thermally induced energy release rate, GT, is found to be independent of crack length, but is a function of residual stress level and geometric and material parameters of the specimen. The adhesion of films and coatings to rigid substrates is often measured using blister geometries, which are loaded either by an applied pressure or a central shaft. The measurement will be affected if there are residual stresses that make a contribution to the energy release rate. This effect is investigated using analytical solutions based on the principle of virtual displacements. A geometrically nonlinear finite element analysis is conducted for comparison. Furthermore, the relationships among strain energy release rate, load, deflection, and fracture radius are discussed in detail in Chapter Four. Both analytical solutions and numerical results reveal that uniform tensile residual stresses reduce a specimen's deflection if it experiences plate behavior under small loads. However, this effect diminishes when membrane behavior is dominant. The mechanics of a single-lap joint with different boundary conditions subjected to tensile loading are investigated. Closed-form solutions are obtained for a specimen configuration considering different clamping methods. Based on the approach pioneered by Goland and Reissner, the solutions reported in this paper provide a simple but useful way to understand the effects of boundary conditions on this test geometry. The solutions in this study suggest that different grip configurations mainly affect the response of the specimens if the grip position is close to the joint edge or the loads are small. Generally, the influence caused by different gripping methods is only limited to the boundary region, and the behavior of the joint part subjected to tensile loading is almost the same as that for a simply-supported case.
Ph. D.

La durabilité des piles à combustible à membrane échangeuse de protons, jugée à l’heure actuelle insuffisante, est principalement liée à la dégradation des supports de catalyseur cathodiques carbonés. Afin d’augmenter cette durabilité, un fin revêtement de dioxyde d’étain est effectué sur différents types de carbone (nanotubes, noirs et aérogel de carbone). L’objectif est d’obtenir un matériau alliant la morphologie et la conductivité électrique des carbones avec la stabilité thermodynamique du dioxyde d’étain. Plusieurs types de carbone avec des propriétés intrinsèques différentes ont été choisis afin d’avoir un large un panel de textures et de structures. Dans ces travaux de thèse, des études expérimentales ont été effectuées dans le but d’obtenir des revêtements d’oxyde d’étain fins, homogènes et couvrants. Ces études ont mis en l’avant l’influence primordiale de la texture et de la structure du carbone, mais aussi de la valeur du pH du milieu réactionnel sur la qualité et la quantité de revêtement. Il a aussi été montré que les mécanismes de transformation du précurseur en dioxyde d’étain dépendent de la valeur de ce pH. En améliorant les interactions entre la surface des carbones et des espèces réactives, il a été possible dans certains cas de diminuer grandement la quantité de précurseur tout en améliorant la qualité du revêtement. Les dépôts de nanoparticules de platine effectués sur des aérogels de carbone bruts et revêtus ont mis en avant un comportement différent du platine qui a tendance à s’agglomérer lorsqu’il est en contact avec le dioxyde d’étain. Les performances initiales ainsi que la durabilité des électrocatalyseurs en fonction de deux tests de vieillissement accéléré (classique ou démarrage/arrêt) ont ensuite été discutées, mettant en avant des résultats mitigés
The proton exchange membrane fuel cell’s lifespan is insufficient because of the degradation of carbon used as cathodic catalyst supports. In order to reduce this degradation, a thin tin dioxide coating is synthesized on the surface of different carbonaceous materials (nanotubes, carbon blacks and aerogel). The aim is to combine the morphology and the electric conductivity of the carbon with the thermodynamic stability of the tin dioxide. Carbonaceous materials with different intrinsic properties are chosen for this study to test a wide range of textures and structures. Experimental studies were carried out in order to synthesize a thin, homogeneous and covering tin dioxide coating. The major influences of the texture and structure of carbonaceous materials but also the influence of the pH value on the quantity and quality of the coating are highlighted. It turns out that the mechanism of formation of tin dioxide depends on this pH value. Thanks to the improvement of the interactions between the carbon surface and the reactive species, it was possible, in some cases, to reduce drastically the quantity of precursor. Platinum nanoparticles deposition performed on various materials (raw or coated carbon aerogel) highlights a different platinum behavior. In fact, on the tin dioxide surface, nanoparticles tend to agglomerate together instead of making a homogeneous dispersion. Then, the initial performances and the durability of electrocatalysts tested with two accelerated stress tests (load protocol or start/stop protocol) are evaluated, spotlighting mitigate results

La durée de vie en service d’un système barrière thermique (BT) pour aubes de turbines peut être limitée par l’écaillage de la BT sous sollicitation thermomécanique. Afin d’améliorer la durabilité dans ces conditions, la texturation laser à l’interface sous-couche/barrière thermique du système CMSX-4 Plus / SC γ-γ’/ BT EB-PVD a été étudiée.Par l’étude de l’interaction laser-matière, il a été montré que les superalliages monogranulaires à base nickel présentent des comportements similaires face à l’ablation laser et semblent peu endommagés par ce traitement de surface. Néanmoins, la formation de zones de matière fondue au niveau des cavités générées, susceptibles de recristalliser, est récurrente.Diverses morphologies de surface (trous, lignes, quadrillages) ont donc été développées au cours de ce travail dans l’idée de renforcer l’ancrage mécanique sans modifier considérablement la microstructure de la couche céramique. Afin de discriminer les morphologies de surface en évaluant la tenue à l’écaillage des systèmes BT texturés, des essais d’oxydation cyclique à 1150°C ont été effectués. Ensuite, pour valider la pertinence de la solution technologique développée, des essais de fatigue thermomécanique hors phase avec gradient thermique pariétal (TGMF) sur des systèmes texturés ou non, ont été réalisés en environnement brûleur (banc MAATRE). Les résultats témoignent alors que les motifs de texturation ralentissent l’écaillage du système BT, sans être des sites préférentiels d’amorçage de fissures
In service life of Thermal Barrier Coating (TBC) systems for blade applications can be limited by the top-coat (TC) spallation under thermo-mechanical fatigue (TMF) loadings. To improve its TMF life, laser texturing at the bond-coat/top coat interface in the CMSX-4 Plus / γ-γ’ BC/ EB-PVD TC system has been investigated.Thanks to the study of the laser-matter interaction, it seems that the different Ni-based single crystal superalloys have similar laser ablation behaviors and they present almost no sub-surface damage after ablation. Nevertheless, the formation of melted matter near created cavities, possibly recrystallized, is often observed.Different patterns (holes, lines, grids) have been developed at the BC surface, in order to increase the mechanical anchoring without modifying the TC microstructure. To discriminate the surface morphologies by the evaluation of the spallation lifetime of textured TBC systems, 1150°C thermal cycling tests have been carried out. Furthermore, to validate the developed technological solution, thermal gradient mechanical fatigue (TGMF) tests in engine simulated environment have been performed using samples with and without textured surfaces (MAATRE test bench). The results shows that laser textured patterns slow down the spallation of the TC, without promoting crack initiation

Within the theoretical part of the diploma thesis, a list of the main types of accelerated tests designed for the resistance of metal and polymer surface finishes. In the experimental part of diploma thesis, the rate of biological resistance of wood-based board materials is evaluated. Furthermore, the resistance of coating systems is assessed by means of accelerated tests. Resistance of modular building shells is primarily focused on degradation of coatings applied primarily on metal materials and wood materials. The tested coating systems analyze the influence of the materials and chemical base on the final weather resistance.

Магистерская диссертация выполнена на тему: «Исследование износа и стойкости токарных резцов с алмазоподобным покрытием». Расчётно-пояснительная записка содержит 94 листа, 86 рисунков, 6 таблиц, 23 источника, 1 приложение. Объектом исследования данной работы являются токарные резцы с алмазоподобным покрытием. Цель работы – определить наиболее благоприятные условия работы токарных резцов с алмазоподобным покрытием. В результате выполнения работы были проведены исследования износа алмазоподобного покрытия на токарных резцах, построены и проанализированы графики зависимостей этих износов. Проведен анализ полученных результатов и выдвинута гипотеза об еще одной возможной причине разрушения покрытия, в то время как остальные известные причины устранены. Разработаны конструкции токарных резцов и проведено исследование предлагаемой гипотезы. По результатам исследования проведен расчет прочности и подтверждена предлагаемая гипотеза.
The master's dissertation is carried out on the topic: "Investigation of wear and resistance of cutting tools with a diamond-like coating". The settlement and explanatory note contains 94 sheets, 86 figures, 6 tables, 23 sources, 1 attachment. The object of research in this work is diamond-coated lathe tools. The purpose of the work is to determine the most favorable working conditions for lathe tools with a diamond-like coating. In the course of the work, the study of the wear of the diamond-like coating on lathe tools at various cutting modes was carried out, the graphs of the dependences of these wear in time were built and analyzed. The analysis of the results obtained is carried out and a hypothesis is put forward about another possible cause of the destruction of the coating, while the other known causes have been eliminated. To confirm the hypothesis, the designs of lathe tools were developed and a study was carried out. According to the results of the study, the strength calculation was carried out, the proposed hypothesis was confirmed.

Thermal barrier coating (TBC) systems are coating systems containing a metallic bond coat and a ceramic top coat. TBCs are used in gas turbines for thermal insulation and oxidation resistance. Life prediction of TBCs is important as high-temperature exposure degrades the coatings through mechanisms such as thermal fatigue and the formation and growth of thermally grown oxides (TGOs). This thesis presents research on durability assessment and life prediction of air plasma sprayed TBCs. The adhesion of thermal barrier coatings subjected to isothermal oxidation, thermal cycling fatigue and thermal shock was studied. The adhesion strength and fracture characteristics were found to vary with heat treatment type. The influence of interdiffusion between bond coat and substrate was studied on TBCs deposited on two different substrates. The thermal fatigue life was found to differ between the two TBC systems. While fractography and nanoindentation revealed no differences between the TBC systems, the oxidation kinetics was found to differ for non-alumina oxides. The influence of bond coat/top coat interface roughness on the thermal fatigue life was studied; higher interface roughness promoted longer thermal fatigue life. Different interface geometrieswere tried in finite element crack growth simulations, and procedures for creating accurate interface models were suggested. The influence of water vapour and salt deposits on the oxidation/corrosion of a NiCoCrAlY coating and a TBC were studied. Salt deposits gave thicker TGOs and promoted an Y-rich phase. The effect of salt deposits was also evident for TBC coated specimens. A microstructure-based life model was developed using the Thermo-Calc software. The model included coupled oxidation-diffusion, as well as diffusion blocking due to the formation of internal oxides and pores. The model predicted Al-depletion in acceptable agreement with experimental observations.

Объектом исследования данной работы являются концевые фрезы с алмазоподобным покрытием. Цель работы – определить наиболее благоприятные условия работы концевых фрез с алмазоподобным покрытием. В результате выполнения работы были проведены исследования износа алмазоподобного покрытия на концевых фрезах, построены и проанализированы графики зависимостей этих износов. Проведен анализ полученных результатов и выдвинута гипотеза об еще одной возможной причине разрушения покрытия, в то время как остальные известные причины устранены. Проведено исследование предлагаемой гипотезы. По результатам исследования проведен расчет прочности и подтверждена предлагаемая гипотеза.
The object of research in this work is diamond-coated end-milling cutters. The purpose of the work is to determine the most favorable working conditions for end-milling cutters with a diamond-like coating. In the course of the work, the study of the wear of the diamond-like coating on end-milling cutters at various cutting modes was carried out, the graphs of the dependences of these wear in time were built and analyzed. The analysis of the results obtained is carried out and a hypothesis is put forward about another possible cause of the destruction of the coating, while the other known causes have been eliminated. To confirm the hypothesis a study was carried out. According to the results of the study, the strength calculation was carried out, the proposed hypothesis was confirmed.

In paper I the friction between three different superhydrophobic surfaces and water drops were investigated using high‑speed video. The surfaces were two based on a hydrophobic wax and the third was the leaf of a Lotus (Nelumbo Nucifera). The acceleration of water drops was measured as a function of drop size and surface inclination. For small capillary numbers it was shown that the dissipation was dominated by pinning‑depinning transitions along the trailing contact line. A parameter called the superhydrophobic sliding resistance bsh has been introduced. The motion of drops on superhydrophobic surfaces of a general macroscopic topography can be predicted provided that bsh and the drop size are known. This theory also infers the existence of an equilibrium sliding angle, beq, at which the drop acceleration is zero. The effect of line‑shaped defects on the motion of water drops on superhydrophobic surfaces were also investigated using high‑speed video in paper II. It was shown that the motion of the drop in the vicinity of the defect can be approximated by a damped harmonic oscillator. Whether a drop got trapped or not while traversing the defect was determined by the incident speed and the characteristics of the oscillator. In systems with low viscous dissipation it is possible to predict the trapping speed as well as the exit speed using a simple work‑energy consideration. The resistance of wax based superhydrophobic coatings subjected to different types of mechanical damage were investigated in paper III. Scratch tests were performed using atomic force microscopy (AFM) and rubbing with an index finger. Coatings were also subjected to compression with a silicone rubber stamp. The effect of impacting water drops was also investigated. A load of 12 nN was enough to remove the coating from the substrate. The coatings remained superhydrophobic at compression pressures up to 59 kPa but the superhydrophobic properties were lost after only one stroke with a finger. The coatings resisted at least 200 000 impacts of falling water drops without losing their superhydrophobic properties. In paper IV superhydrophobic coatings were fabricated in a semi‑continuous process, where an alkyl ketene dimer (AKD) was dissolved in supercritical carbon dioxide (scCO2) and sprayed onto the substrate. Several different substrates such as: glass, aluminium, paper, poly (ethylene terephthalate) (PET) and poly (tetrafluoroethylene) (PTFE) were successfully coated. The most efficient spray process, considering surface properties and mass of extracted AKD, was obtained at the lowest temperature investigated, 67 °C, and the highest pressure evaluated in this study, 25 MPa. The influence of the pre‑expansion conditions (p, T) on the surface temperature (at a spray distance of 3 cm) was also shown to be negligible.

QC 20141202

Plastics have become a universal material for use in a myriad of commercial and consumer products. One such product, exterior siding, is the focus of this project. Although siding products were originally made from wood, vinyl siding, which offered superior performance, was introduced in the 1950’s. More recently, polypropylene (PP) siding has been introduced; PP provides a stronger product, which allows for deeper patterns and better edge detailing. PP siding, compared to traditional wood siding, doesn’t warp, crack, or degrade as easily with extended exposure to the elements, and is cheaper to maintain. However, even plastic siding must be coated. The requirements of a coating for siding are good adhesion, durability, and a suitable appearance. However, polypropylene, like many plastics, has a low surface energy, making wetting and coating adhesion difficult. One of the many ways to increase the surface energy of polypropylene, thus increasing wettability and adhesion, is plasma treatment. The primary focus of this project was to study how plasma treatment improved adhesion of a water-reducible coating. This coating represented a product used in commercial siding. The surface tension of the panels was increased from ~30 dynes/cm to 60+ dynes/cm with plasma treatment. This increased the adhesion of the coating to the polypropylene panel from virtually no adhesion to almost perfect adhesion. Adhesion was tested according to ASTM D3359, the crosscut adhesion test. Pull-off adhesion testing (ASTM D4541-09) was also conducted, using a Deflesko PosiTest AT-A automatic adhesion tester. The average force needed to remove a dolly from a plasma treated panel was 233 ± 47 psi (1,605 ± 325 kPa), compared to 92 ± 26 psi (634 ± 179 kPa) for non-treated and corona treated panels. The sponsor of the project provided Cal Poly with 16 different compositions of polypropylene containing different amounts of UV stabilizers, adhesion promoters, and lubricants. The effect of substrate composition on coating adhesion and performance was measured. Crosscut adhesion testing results revealed all polypropylene compositions improved from virtually no adhesion to perfect adhesion after plasma treatment. Pull-off adhesion testing revealed the adhesion force of all compositions improved from less than 100 psi to greater than 200 psi. One polypropylene composition, Category 16, resulted in unusually high pull-off forces. This composition was investigated using X-ray Photoelectron Spectroscopy (XPS) and FT-IR spectroscopy. XPS was used to examine the surface composition between non-treated and plasma treated PP panels. It was observed that plasma treatment provides a larger amount of oxygen species and nitrogen when compared to untreated panels. The category 16 panels did not reveal any significant surface differences compared to the category 7 panels (which represented the standard production material). FT-IR spectroscopy of the category 16 panels also showed no unusual characteristics. The secondary focus of this project was to study the durability of coated, plasma treated polypropylene siding. Accelerated weathering testing was conducted on 12 of the 16 different compositions of polypropylene. Changes in gloss and the LAB colorspace of coated, plasma treated polypropylene panels of different compositions, upon exposure to long-term weathering conditions, were monitored via ASTM G53 using a Q-Panel lab product QUV/se weathering tester. After 2400 hours, all PP compositions tested shared negligible changes in color, but the gloss of each category panel showed a steady increase. An approach to improve durability of siding is to apply a clearcoat over already coated PP panels. This approach was tested in a limited manner by adding a clearcoat to coated, plasma treated polypropylene panels. These panels were then exposed to a variety of common, household cleaning agents using a modified double rub test (ASTM D4752 and ASTM D5402). The samples with a clearcoat showed improved cleaning agent resistance compared to samples without the clearcoat.

Les travaux de recherche présentés dans cette thèse portent sur la formulation, caractérisation et modélisation des propriétés physiques et mécaniques des matériaux biosourcés à base de granulats végétaux (paille céréalière) destinés à l’isolation thermique et la réhabilitation énergétique des bâtiments. Les objectifs des travaux de cette thèse, inscrite dans le cadre du projet PEPITE, sont l’optimisation des performances thermiques, mécaniques et hydriques des matériaux biosourcés développés dans le cadre des travaux antérieurs et le développement d’un enduit de protection pour une solution technique de réhabilitation thermique. L’optimisation de la formulation est obtenue en utilisant des adjuvants et d’autres déchets naturels biodégradables et renouvelables, afin de créer une porosité plus importante et de diminuer d’avantage la conductivité thermique des matériaux. En se basant sur les résultats de caractérisation expérimentale, trois formulations ont été retenues. Ces matériaux sont des milieux fortement hétérogènes avec un comportement assez complexe ; dont la compréhension et la prédiction font appel dans le cadre de ce travail aux méthodes d’homogénéisation numérique. L’effet de la microstructure réelle (morphologie, orientation des hétérogénéités) sur les propriétés effectives thermiques et le comportement mécanique non linéaire de ces matériaux a été mis en évidence également dans cette étude. La comparaison des résultats numériques et expérimentaux a confirmé la capacité prédictive et le potentiel de l’approche utilisée pour orienter la formulation des matériaux à partir de critères de performances thermiques. Une caractérisation fine des propriétés hydriques des formulations optimales (perméabilité à la vapeur d’eau, courbes de sorption-désorption, MBV) a été réalisée afin de comprendre la relation entre les propriétés de ces matériaux et la notion du confort hygro-thermique du bâtiment. D'excellentes propriétés hydriques ont été obtenues pour les trois bio-composites étudiés. Pour évaluer leurs performances à long terme, les matériaux ont été exposés à un vieillissement accéléré au laboratoire via des tests d’humidification-séchage et gel-dégel. Cette évaluation environnementale a mis en évidence une réduction significative des propriétés mécaniques après les cycles considérés. Enfin, un enduit de protection des matériaux biosourcés a été développé dans cette étude dans le but de proposer une solution complète de rénovation thermique. L’enduit au comportement optimisé proposé ici en combinant une approche expérimentale et numérique, a fait l’objet d’une caractérisation physique et mécanique afin de mesurer son impact sur les performances des biocomposites. Les caractéristiques, obtenues pour les formulations optimales proposées, répondent parfaitement aux exigences réglementaires relatives aux enduits d'isolation thermique
The research work presented in this thesis focuses on the formulation, characterization and modeling of the physical and mechanical properties of bio-composite materials based on plant aggregates (cereal straw) for thermal insulation and energy rehabilitation of buildings. The objectives of this thesis, part of the PEPITE project, are the optimization of the thermal, mechanical and hydric performances of the bio-based materials developed within the framework of previous work and the development of a protective coating for a technical solution of thermal rehabilitation. The optimization of the formulation is obtained by using additives and other biodegradable and renewable natural waste, in order to create a higher porosity and to further decrease the thermal conductivity of the materials. Based on the results of experimental characterization, three formulations were selected. These materials are highly heterogeneous media with a rather complex behaviour and for which its understanding and prediction call for numerical homogenization methods in the framework of this work. The effect of the real microstructure (morphology, orientation of heterogeneities) on the effective thermal properties and the non-linear mechanical behavior of these materials was also highlighted in this study. The comparison of numerical and experimental results confirmed the predictive capacity and the potential of the approach used to guide the formulation of materials based on thermal performance criteria. A detailed characterization of the hydric properties of the optimal formulations (water vapor permeability, sorption-desorption curves, MBV) was carried out in order to understand the relationship between the properties of these materials and the notion of hygro-thermal comfort of the building. Excellent hydric properties were obtained for the three bio-composites studied. In order to evaluate their long-term performance, the materials were exposed to accelerated ageing in the laboratory through humidification-drying and freeze-thaw tests. This environmental assessment revealed a significant reduction in mechanical properties after the cycles considered. Finally, a protective coating for bio-based materials was developed in this study with the aim of proposing a complete thermal renovation solution. The coating with optimised behaviour proposed here by combining an experimental and numerical approach was the subject of a physical and mechanical characterization in order to measure its impact on the performance of biocomposites. The characteristics obtained for the optimal formulations proposed meet perfectly the regulatory requirements relating for thermal insulation coatings

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CNPQ – Conselho Nacional de Desenvolvimento Científico e Tecnológico
FINEP - Financiadora de Estudos e Projetos
FAPERGS – Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul
A construção civil tem apresentado um grande crescimento nesta última década. Junto à construção, cresce a demanda por matéria prima e há um aumento da geração de resíduos nos canteiros de obras e em indústrias ligadas ao setor. Segundo o Ministério de Minas e Energias (MME) no ano de 2008, a estimativa de produção de areia chegou a 279 milhões de toneladas e estima-se que em 2030 possa chegar a 1,276 bilhões de toneladas. O uso de resíduos de construção e demolição para a produção de argamassas de revestimento pode trazer benefícios econômicos e ambientais, no entanto, sua utilização somente é possível se o revestimento for durável, suportando as ações ambientais. O presente estudo consiste no desenvolvimento, aplicação e comparação entre dois métodos de ensaio de ciclagem térmica. O primeiro se baseia na NBR 15575-4:2013, que estabelece um método para a avaliação da durabilidade de componentes de vedação em edifícios, utilizando caixas térmicas irradiantes, que consiste na exposição unilateral da alvenaria revestida a ciclos de aquecimento e resfriamento simultâneo à molhagem do revestimento. Utilizando-se esse método, também foram submetidos a exposição térmica prismas de cada argamassa, nas dimensões de 40x40x160 mm. No segundo método, o sistema revestido é totalmente exposto a variações de temperaturas, permanecendo em uma câmara climática que executa repetidos ciclos de aquecimento e resfriamento. As argamassas utilizadas foram produzidas no traço 1:1:6 em volume (cimento, cal e areia) utilizando-se cimento CP II F-32, cal CH-I em pasta, areia de rio e fíler produzido a partir de agregado reciclado de concreto (ARC), adicionado nos teores de 2; 4,5; 7 e 9,5% em relação à massa da areia, e aplicadas sobre substrato de cerâmica vermelha. A primeira atividade do programa experimental consistiu no desenvolvimento dos métodos para a realização da ciclagem térmica e em sua avaliação. Posteriormente, foram produzidas as argamassas e revestimentos, e realizadas as ciclagens térmicas. O método que utiliza uma câmara climática para a ciclagem térmica demonstrou menor potencial de degradação das argamassas; o método das caixas térmicas demonstrou maior eficiência no envelhecimento acelerado dos revestimentos e prismas de argamassas. A exposição à ciclagem térmica resultou em expressiva perda das propriedades das argamassas testadas na forma de prisma, em todos os teores de adição de fíler de ARC. A ciclagem dos revestimentos de argamassa aplicados sobre substrato cerâmico apresentou menor degradação que os prismas, sendo que os dois revestimentos com baixo teor de adição (2 e 4,5% de fíler) apresentaram maior degradação nas argamassas e os demais revestimentos (com 7 e 9,5% de fíler) apresentaram as menores resistências de aderência à tração.
Construction industry has shown a significant growth this past decade. With it, grows the demand for raw materials and there is a generation of waste at construction sites and in industries linked to the sector. According to the Ministery of Mines and Energy (MME) in 2008, sand production reached an estimated 279 million tonnes and it is estimated that in 2030 its production can reach 1.276 billion tons. The use of construction and demolition waste for the production of coating mortars can bring economic and environmental benefits, but its use is only possible if the coating is durable, supporting environmental actions. This study is the development, application and comparison between two thermal cycling test methods. The first method is based on the NBR 15575-4:2013 standard, uses radiant boxes and consists in unilateral exposure of masonry coated to simultaneous cycles of heating and cooling under wetting. This method were also underwent to thermal exposure 3 prisms of each mortar, in the dimensions of 40x40x160 mm. In the second method, the coated system is fully exposed to temperature variations and remains in a climatic chamber that performs repeated heating and cooling cycles. The mortars used and applied to ceramic substrates have been produced in a proportion of 1: 1: 6 by volume (cement, lime and sand) using Brazilian cement CP II F-32, CH-I lime putty, river sand and filler produced from recycled concrete aggregate (RCA), in compositions with varying content (2, 4.5; 7 and 9.5%) relative to the mass of sand. The first activity of the experimental program was the development of the methods for performing thermal cycling and in their assessment. Mortars and coatings were produced, and then was performed thermal cycling. The method using a climatic chamber for thermal cycling has showed lower efficiency for the degradation of mortar; the method that uses radiant thermal boxes has demonstrated greater efficiency in the accelerated aging of the coatings. The thermal cycling exposure resulted in a significant loss of properties of the prisms, in all addition levels of ARC’s filler. The thermal cycling in mortar applied on the ceramic substrate showed less degradation than the prisms, and the two coatings with a low content of filler (2% and 4.5%) showed higher degradation in mortars while other coatings (with 7 and 9.5% of filler) had the lowest coating bond strength.

De nombreuses pièces sont sujettes à des sollicitations de frottement à haute température dans le domaine de l’aéronautique. En effet, dans ce domaine, l’augmentation constante des puissances des réacteurs implique une augmentation de la température de fonctionnement des systèmes mécaniques et en particulier des contacts frottants. Cette augmentation de température a pour conséquence la diminution de la durabilité des matériaux lubrifiants solides actuellement utilisés pour ce type de contact. C’est pourquoi il est indispensable de sélectionner de nouveaux revêtements aux propriétés tribologiques à chaud améliorées. Dans cette optique, une thèse ayant pour sujet la durabilité de rotules aéronautiques d’attache mât-moteur de l’A380 soumises à des conditions extrêmes de fonctionnement en termes de température et de conditions glissement, a été effectuée au LTDS. Dans un premier temps, les endommagements de surface (abrasion, adhésion) des pièces réelles ont été analysés, à travers des analyses MEB/EDX du revêtement d’argenture déposé dans le contact entre les bagues intérieure et extérieure de la rotule. Des essais tribologiques en configuration classiquement utilisée, cylindre/plan (sur Cameron-Plint), ont ensuite été réalisés sur le revêtement d’argenture afin de comparer les endommagements observés in situ et sur banc. Dans le but de sélectionner un revêtement ou un couple de revêtements susceptibles de remplacer l’argenture dans le contact étudié, une dizaine de revêtements différents (couches accommodantes et couches dures) ont ensuite été testés individuellement en configuration cylindre/plan dans les mêmes conditions d’essai que dans le cas de l’argenture. Cette campagne d’essai a permis de dégager les plus performants/endurants tribologiquement. Parallèlement, un tribomètre original a été conçu au laboratoire afin de pouvoir simuler au mieux les conditions de contact réelles (sollicitations mécaniques, température de contact…). Ce tribomètre rotatif à haute température (TRHT), utilisable en configuration couronne/plan, permet d’appliquer simultanément au contact une force normale pouvant aller jusqu’à 50 kN, un mouvement rotatif alternatif, et une température de contact pouvant aller jusqu’à 1000°C grâce à un système de chauffage par induction. Les revêtements ayant démontré le meilleur comportement en termes de résistance à l’usure et au frottement au cours des essais en configuration cylindre/plan ont également été testés individuellement sur ce tribomètre en configuration couronne/plan. Les essais finaux ont été réalisés en interface complète, c'est-à-dire avec une couche accommodante déposée sur la pièce représentant la bague intérieure de la rotule, une couche dure déposée sur la pièce représentant la bague extérieure, et une couche à bas frottement (graisse ou vernis). Deux solutions de lubrification de ce type ont été déterminées pour le contact rotulé : une pour les rotules d’attache mât-moteur avant qui fonctionnent jusqu’à 160°C (CuNiIn + vernis Everlub / WC-C) et une pour les rotules d’attache mât-moteur arrière qui fonctionnent jusqu’à 570°C (stellite + vernisEverlub / TiHfCN)
In aeronautics tribology, mechanical parts are required to operate with increasing temperature. The increased functioning temperature of the contacts prone to friction and wear (such as bearings and other structural parts) is a direct consequence of the increasing power of jet engines. In the case of ball bearings, the substrate materials as well as the coating durability are affected by temperature. There is then a pressing need to introduce new coatings demonstrating effective tribological behaviour at high temperature. A PhD research subject was defined in partnership with Airbus Aerospace and SKF Aerospace and conducted at LTDS. The main goal of this research is to study the durability of ball bearings functioning under extreme conditions in terms of temperature and sliding friction. First, SEM/EDX analyses were done on the silver coating deposited in the contact between the ball bearings rings, in order to acknowledge the actual bearings surface damage. Tribological testing of the silver coating was then performed in a standard cylinder-on-flat configuration in order to compare in situ and experimental damages. More than ten different coatings (both soft and hard coatings, with solid lubrication properties and/or wear resistance properties) were then tested in the same configuration and conditions as the silver coating. These tests allowed us to identify the best suitable coatings for the application. An original test rig was also designed in the lab, in order to better simulate the bearings functioning conditions. This tribometer (TRHT) makes it possible to perform tests in ring-on-flat configuration (close contact) and to simultaneously apply a normal force up to 50 kN and a reciprocating rotating motion. Using this tribometer, the final tests were conducted on the best candidates among the different coatings, individually at first to assess their tribological behavior, and then in a configuration as close to reality as possible, with a hard coating covered ring and a soft coating covered flat, the contact between the two being greased or varnished. Finally, several possible solutions were determined, for two different functioning temperatures:160°C (CuNiIn + varnish Everlub / WC-C) and 570°C (stellite + varnish Everlub / TiHfCN)

L'industrie textile s’intéresse depuis longtemps aux propriétés superhydrophobes et auto-nettoyantes. Le dépôt de composés fluorés à longues chaînes carbonées à la surface des textiles est actuellement le moyen le plus efficace d’obtenir de telles propriétés. En raison de leurs effets néfastes sur la santé et l'environnement, ces composés doivent être remplacés conformément à la réglementation REACH. Dans cette thèse, la polymérisation plasma a été choisie pour concevoir des traitements de surface durables, superhydrophobes et respectueux de l'environnement pour textiles. Dans ce contexte, la possibilité de contrôler temporellement et spatialement la cinétique de polymérisation plasma d'un précurseur modèle largement étudié à l'IS2M, à savoir l'anhydride maléique, a été démontrée dans un réacteur original d'un mètre de long. De plus, la possibilité de contrôler les propriétés chimiques et morphologiques des films polymères a été abordée. Suivant une méthodologie expérimentale similaire, le contrôle de la polymérisation plasma d'un précurseur organosiliconé, à savoir l’hexaméthyldisiloxane (HMDSO) a été étudié pour obtenir un revêtement superhydrophobe vert. L'accent a été mis sur la compréhension de la résistance au lavage de ces revêtements en caractérisant la cohésion du revêtement et de son adhérence à la fibre. Enfin, un second précurseur non fluoré a été testé en tant qu’alternative innovante à l’HMDSO. En contrôlant finement les paramètres temporels et spatiaux de la décharge plasma, les performances de superhydrophobie des polymères plasma et leurs durabilités ont pu être modifiées, soulignant l’approche tout à fait pertinente développée dans ce travail de thèse
The textile industry has been interested for long in water-repellency and self-cleaning properties. Deposition of fluorinated compounds with long carbon chains on the surface of textiles is currently the most efficient solution to reach such properties. Because of their harmful effects on health and environment, these chemicals have to be replaced in accordance with REACH specifications. During this PhD work, plasma polymerization process has been chosen as a good candidate to engineer durable, superhydrophobic and eco-friendly surface treatments for textiles. In this context, we successfully demonstrated the possibility to control temporally and spatially plasma polymerization kinetics of a model precursor widely studied at the IS2M, namely maleic anhydride, in an original one-meter long reactor. More than that, the possibility to control the chemical and morphological properties of plasma coatings was particularly addressed. Following a similar experimental methodology, the control of plasma polymerization of an organosilicon precursor, namely hexamethyldisiloxane (HMDSO), was investigated to get eco-friendly superhydrophobic coating. A focus was made on the understanding of thin film resistance to washing by characterizing coating cohesion and adhesion to the textile fiber. Finally, a second fluorine-free precursor was tested as an innovative alternative to HMDSO to engineer eco-friendly superhydrophobic coatings. By a fine tuning of temporal and spatial parameters of the plasma discharge, water-repellency performances of plasma polymer coatings and their durability could be significantly modified, highlighting the interesting approach developed during this PhD work

Le remplacement de monomères d'origine pétrosourcée par des analogues biosourcés améliore la durabilité et diminue la dépendance aux ressources fossiles. De plus, de nouvelles caractéristiques et propriétés sont souvent découvertes. Les polyesters aliphatiques biosourcés ont déjà partiellement remplacé les produits traditionnels. Dans le contexte du projet Sorago, une résine entièrement biosourcée pour les revêtements de prélaquage des produits intérieurs a déjà été introduite sur le marché (Estetic® bio Air, Arcelor Mittal). Pour permettre l'utilisation du produit dans des applications extérieures, sa résistance à la lumière UV et à l'humidité sont à améliorer. Cela pose deux problèmes : Une disponibilité limitée de monomères pouvant introduire de la rigidité dans la résine et la relation entre la structure de la résine et sa dégradation. La vanilline a été choisie comme synthon pour la gamme des monomères rigides et biosourcées. La transformation de sa fonction aldehyde par réaction de Perkin et sa réactivité a été examinée. Dans une série des copolymerisations, l'influence des conditions de réaction sur la composition du produit final a été proposée. Une relation structure-propriétés concernant la température de la transition vitreuse et la viscoélasticité des plusieurs monomères biosourcées a été établie, et comparée avec celle des monomères petrosourcées. Une série des prototypes avec des propriétés très variées a été soumise à un test de vieillissement rapide. Leur dégradation a été suivie sur la base de leur rétention de brillance, par FTIR et par des tests de µ-dureté et d'épaisseur des films. La performance des prototypes biosourcés s'est révélée inférieure à celle d'une résine standard pétrosourcée mais aucune évidence qui suggère que cela est du à la présence des monomères biosourcées n'a été détectée. Cela suggère que la création d'une résine biosourcée et suffisamment durable pour l'extérieur sera possible
Moving away from petroleum and towards biobased materials not only leads to greater sustainability and lower dependence on diminishing fossil resources, but can also catalyse the discovery of new properties. Aliphatic polyesters based on renewable resources have already started to replace traditional products. Within the Sorago project, a fully biobased resin for interior coil coatings has recently been proposed on the market (Estetic® Bio Air, Arcelor Mittal). In order to extend the possible use of the biobased product to exterior applications, an improvement of its resistance to humidity and UV radiation is crucial. This presents two challenges: The limited availability of monomers which provide rigidity in the resin structure and the relationship between the resin composition and its weatherability. Vanillin was chosen as a possible extension to the range of rigid, biobased monomers for polyesterification reactions. The transformation of its aldehyde and its reactivity was studied in terms of catalytic activation and through a series of copolymerisations which revealed the influence of the reaction conditions on the composition of the product. A structure-property relationship concerning the coating glass transition temperature and visco-elastic behaviour of the coating was furthermore established for a series of renewable monomers and contrasted with petroleum based equivalents. Series of prototypes with a wide variety of properties were then subjected to accelerated weathering tests. Their degradation was followed directly by gloss retention and different mechanisms were revealed using FTIR, µ-hardness and film thickness measurements. While the performance of the biobased coating was subpar, no evidence linking its degradation to the presence of renewable monomers was found, suggesting that the creation of a sufficiently durable and renewable exterior coating will be possible

The lap shear strength of chromic acid anodized, primed, Ti-6Al-4V alloy bonded with a high performance FM-5 polyimide adhesive has been investigated as a function of thermal treatment for selected times at various temperatures in air. The research findings indicate that the lap shear strength decreases with the increase in duration of the thermal treatment at constant temperature and with the increase in temperature at constant time. The bond fails increasingly in the oxide coating with increasing treatment temperature and time of treatment. Surface analysis results for debonded specimens suggest that the process leading to failure is the formation of fluorine-containing materials within the oxide, which weakens the adherend-adhesive bond. The formation of the fluorine components is facilitated by treatment at elevated temperatures. This study suggests that the presence of fluoride ions in the anodic oxide coating, prior to bonding, is detrimental to the bond strength of adhesively bonded Ti-alloy when exposed to high temperatures. The wedge test configuration was used to investigate the influence of temperature on the bond durability of adhesively bonded chromic acid anodized Ti-6Al-4V alloy in air. Based on the average crack length vs. exposure time data, the bond durability varied in the order -25°C > 24°C > 177°C. In each case, the bonded joint failed cohesively within the adhesive, irrespective of the temperature of exposure. XPS analysis and scanning electron photomicrographs of failure surfaces revealed that the failure occurred at the scrim cloth/adhesive interface. The influence of thermal treatment history on the bond durability of adhesively bonded chromic acid anodized Ti-6Al-4V alloy immersed in boiling water was also investigated. The average crack length vs. immersion time indicated no significant differences for specimens that were thermally treated and then bonded compared to the non-thermally treated specimens. In addition, the failure mode was cohesive within the adhesive for specimens prepared using various thermal treatment conditions. The crack growths for samples treated for 0.5 hour and 1.0 hour and for non-thermally treated specimens for any given exposure time were equivalent. In addition, cohesive failure (failure within adhesive) was observed for each specimen under each treatment condition. The specimens that were bonded and then thermally treated for 3 hours, failed in the oxide coating immediately upon insertion of the wedge. Surface analysis results for debonded specimens suggest that the process leading to failure is the formation of fluorine-containing materials within the oxide. The measured average activation energy for the formation of aluminum fluoride species is 149 kJ/mol. The high activation energy suggests that the rate of aluminum fluoride formation is substantial only at high temperatures. In summary, the presence of fluorides in the anodic oxide coatings prior to bonding is detrimental to the overall strength and durability of adhesively bonded chromic acid anodized Ti-6Al-4V joints which have been exposed to high temperatures (350°C-399°C).
Ph. D.

Increasing demand for improved fuel economy 'and environmental protection has meant that there has been increased focus on the implementation of non-ferrous materials and coatings which have excellent tribological properties for automotive applications. Since all . . commercially. available lubricants are typically optimised for ferrous materials, it is therefore expected that lubricants will not perform in an optimised way on alternative surfaces: It is therefore crucial to understand how the existing lubricants interact with non- . . ferrous coatings to be able to sensibly approach the design of new additives for non-ferrous surfaces. In this study, CrN and DLC coatings which have excellent generic tribological properties, chosen for a full evaluation of their tribochemistry using both model and fully formulated oils. Tribological tests were performed using three test rigs, namely pin-on-plate, min~ traction machine (MTM) and cam/follower rig. The pin-on-plate tests were performed to evaluate friction, wear and fturability of CrN and DLC coatings under boundary lubrication .. conditions. Based on the results obtained from pin-on-plate tests, a' few coatings were chosen for cam/follower tests. In addition, MTM tests were performed to investigate the effect of slidelroll ratio and lubrication regime on the tribologicalltribochemical performance of a particular DLC coating. Based on the MTM results, the link between the results obtained from pin-on-plate and cam/follower rigs were assessed. Using the state-of-the-art surface analysis techniques such as atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS), both physical and chemical characterisation of tribofilms formed by lubricant additives on CrN and DLC coatings have been characterised. Finally, they are correlated with the tribological results and also compared with those observed in conventional ferrous systems. This study has shown that the tribological performance of CrN and DLC coatings are oil dependent. The physical and chemical analyses of tribofilms suggest that the CrN coating responds in a similar manner to steel surfaces to the conventional additives. Optimisation 'of lubricant additives has been found to be immensely important, especially for the effective lubrication of110n/low-hydrogenated DLC coatings.

This dissertation is focus on the study of solid-electrolyte interphases (SEIs) on advanced lithium ion battery (LIB) anodes. The purposes of this dissertation are to a) develop a methodology to study the properties of SEIs; and b) provide guidelines for designing engineered SEIs. The general knowledge gained through this research will be beneficial for the entire battery research community.

Ce travail est consacré à l'étude du comportement photochimique d'un encapsulant multifonctionnel de cellules photovoltaïques organiques (CPO) dont la finalité est d'augmenter à la fois la durée de vie et le rendement de conversion des cellules. L'étude rapportée dans ce manuscrit porte sur le développement d'un revêtement permettant la conversion lumineuse du rayonnement UV solaire, ce dernier étant un facteur important de dégradation des CPO à base de P3HT et ne contribuant que faiblement à la conversion photovoltaïque. Dans un premier temps cette étude a porté sur l'élaboration d'une couche de conversion à partir d'une matrice polymère en EVA et d'une charge luminescente inorganique (SrAl2O4 : Eu2+, Dy3+). Dans un second temps, l'évolution des propriétés physiques et chimiques de cette couche de conversion sous irradiation à des longueurs d'onde supérieures à 300 nm a été étudiée. La présence des charges s'est révélée être un facteur pro-dégradant des films composites, sans pour autant que le mécanisme de dégradation du polymère ne soit affecté. L'étude des conditions de propagation de la lumière dans les films diffusants par l'application de la théorie de Mie a mis en évidence une possible augmentation du trajet optique des photons dans certains films composites. Ce phénomène pourrait contribuer à expliquer l'origine du comportement photochimique particulier des films étudiés. C'est finalement une preuve de concept qui a été recherchée pour l'utilisation d'un revêtement multifonctionnel pour l'amélioration et la conservation des propriétés de conversion d'une CPO à base de P3HT.

Dans le secteur aéronautique en pleine expansion, les préoccupations environnementales prennent une place de plus en plus importante. Les motoristes recherchent des solutions innovantes pour augmenter les rendements tout en diminuant les coûts. Dans cette perspective, de nouveaux systèmes de barrières thermiques synthétisés par la voie sol-gel à partir de poudres commerciales, de céramiques avec différents facteurs de forme et d'agents porogènes ont été mis en œuvre et évalués. Certains systèmes présentent une durée de vie de plus de 1000 cycles en oxydation cyclique. Malgré tout, cet accroissement des températures de fonctionnement des moteurs, induit une élévation des températures de surfaces des barrières thermiques et peut générer de nouvelles dégradations du système complet : la corrosion à hautes températures par les CMAS. Pour pallier ces inconvénients, il est possible de développer des revêtements anti-CMAS, susceptibles de réagir avec les composés CMAS avant qu'ils n'aient un effet néfaste sur l'intégrité de la barrière thermique. Dans cette étude, nous nous sommes intéressés particulièrement aux revêtements sacrificiels anti-CMAS à base d'yttrine et de systèmes pyrochlore, qui ont été testés sur des barrières thermiques industrielles de type EBPVD. Par ailleurs, les procédés que nous avons développés, basés sur la voie sol-gel, nous permettent, de par leur facilité de mise en œuvre, d'envisager des perspectives prometteuses en termes de réparabilité des barrières thermiques endommagées. En effet, compte tenu du coût élevé de fabrication des pièces, les aubes devraient être réparées plusieurs fois avant d'être mises au rebut. Dans ce travail, un procédé de mise en forme a été évalué dans ce sens. Il s'agit de l'électrophorèse qui est une technique bien adaptée au dépôt sur pièces complexes. L'objectif de ces investigations a donc été double : tout d'abord créer de nouveaux systèmes de barrières thermiques avec des propriétés anti-CMAS par électrophorèse puis réparer les barrières thermiques EBPVD endommagées et leur déposer une couche protectrice anti-CMAS par ce même procédé. Cet aspect " procédé " sera abordé en dernière partie de ces travaux
In the aeronautics sector, environmental concerns are becoming increasingly important. Engine manufacturers are looking for innovative solutions to increase efficiency while lowering costs. The objective is to optimize thermal conductivity and durability with the cyclic oxidation resistance. In this perspective, new thermal barrier systems synthesized by the sol-gel route from commercial powders, ceramics with various form factors and pore-forming agents have been implemented and evaluated. Some systems are a lifetime higher than 1000 cycles in cyclic oxidation. However, this increase in the operating temperatures of the engines induces an increase in the temperature of the surfaces of the thermal barriers and can generate further degradations of the complete system: the corrosion by CMAS. To overcome these disadvantages, it is possible to develop anti-CMAS coatings capable of reacting with CMAS compounds before they have a detrimental effect on the integrity of the thermal barrier. In this study, we were particularly interested in anti-CMAS protective coatings based on yttria and pyrochlore systems, which were tested on industrial thermal barriers realized by EBPVD. Moreover, the processes we have developed, based on the sol-gel path, allow us, because of their ease of implementation, to envisage promising prospects in terms of repair of damaged thermal barriers. Indeed, given the high cost of manufacturing parts, the blades should be repaired several times before being discarded. In this work, a shaping process has been evaluated in this direction. This is electrophoretic deposition which is a technique allowing to deposit on complex parts. The objective of these investigations was therefore twofold: firstly to create new thermal barrier systems with anti-CMAS properties by electrophoretic deposition and then to repair the damaged EBPVD thermal barriers and to deposit an anti-CMAS protective layer by this same process. This "process" aspect will be discussed at the end of this work

This thesis deals with the analysis of properties of hard coatings and wear resistance PVD coated technology. It focuses on the preparation, execution and evaluation of test coatings on the front ball milling cutter.

Cette thèse porte sur la fonctionnalisation de fils en acier inoxydable via des revêtements colorés base titane, élaborés par pulvérisation cathodique avec un magnétron cylindrique. Ce travail s’intéresse à la caractérisation chimique, morpho-structurale et à l’évaluation de la durabilité mécano-chimique des fils revêtus.Premièrement, la vitesse de dépôt et la composition chimique des films sont déterminées dans des conditions statiques. Les hétérogénéités du plasma dans la cathode sont démontrées et reliées aux paramètres tels que la puissance, la pression et la polarisation d’anodes auxiliaires.Les dépôts monocouches de Ti, TiN et TiOx sont ensuite élaborés en continu. La relation entre la couleur du TiN et sa composition chimique est établie. La couleur dorée est obtenue pour des films stœchiométriques contenant peu d’oxygène (< 5 %at.). Les microstructures sont caractérisées par MET-ASTAR et des cartographies d’orientation sont dressées à l’échelle nanométrique. Tandis que les dépôts de TiN sont colonnaires avec une texturation selon <111>, les grains des films de Ti sont plutôt équiaxes et orientés selon <0001>. Pour une température d’élaboration de 650 °C, les éléments du substrat diffusent dans les films et mènent à la formation de phases de Laves. Les dépôts de TiOx, élaborés en mode métallique, présentent des couleurs d’interférence et une composition proche du monoxyde. Les surfaces revêtues de TiN ont une résistance à la corrosion élevée semblable à l’acier inoxydable 316L, contrairement aux fils revêtus de Ti et TiOx. La ténacité et l’énergie d’adhérence des revêtements sont déterminées par traction in-situ sous MEB : Ti et TiN sont particulièrement adhérents au substrat contrairement à TiOx.Enfin, les dépôts sont architecturés avec l’ajout d’un dépôt de titane entre le substrat et le revêtement céramique. Ainsi, l’adhérence du film Ti-TiOx est largement augmentée par rapport au monocouche TiOx (5 à 200 J/m2). Enfin, les études microstructurales et électrochimiques montrent qu’un paramètre clef de la résistance à la corrosion est la présence de porosité ouverte dans les revêtements
This thesis treats of the functionalization of stainless steel wires with colored Ti-based coatings, grown by PVD with a cylindrical magnetron, their chemical and morpho-structural characterization, and the evaluation of the chemico-mechanical durability of the coated wires.First, the deposition rate and the chemical composition of the films are determined under static conditions. Cathode plasma heterogeneities are demonstrated and related to parameters such as power, pressure and polarization of auxiliary anodes.Then, Ti, TiN and TiOx monolayer coatings are grown continuously. The relationship between the color of TiN and its chemical composition is established and golden color is obtained for stoichiometric films with low oxygen content (<5% at.). Microstructures are studied with TEM-ASTAR and orientation maps are obtained with a nanometric resolution. While TiN coatings are columnar with <111> texture, Ti grains are rather equiaxed and <0001> oriented. With a 650 ° C substrate temperature, substrate elements diffuse into the films which results in Laves phase formation. TiOx is grown in metallic mode, presents interference colors and a composition close to monoxide. TiN coated surfaces display high corrosion resistance similar to 316L stainless steel, unlike Ti and TiOx coated wires. The toughness and the adhesion energy of the coatings are determined by SEM in-situ tensile tests: Ti and TiN are particularly adherent to the substrate in contrast to TiOx.Finally, coatings are architectured with the addition of a titanium interlayer between the substrate and the ceramic coating. Thus, Ti-TiOx film adhesion is greatly superior compared to the TiOx monolayer (5 to 200 J/m2). Finally, microstructural and electrochemical studies show that a key parameter of corrosion resistance is the presence of open porosity in the coatings

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.02.08 – технологія машинобудування. Об’єкт дослідження – технологічний процес формування функціональних покриттів на поверхні елементів торцевих імпульсних ущільнень турбомашин. Предмет дослідження – закономірності технологічного процесу формоутворення поверхні із заданими експлуатаційними властивостями, що забезпечують необхідну якість (довговічність, зносостійкість, працездатність) торцевих імпульсних ущільнень турбомашин. Метою дослідження є забезпечення працездатності торцевих імпульсних ущільнень (ТІУ) турбомашин шляхом виготовлення кілець із композиційних матеріалів, що поєднують у собі механічну міцність основи й захисні властивості покриттів, підвищують зносостійкість торцевих поверхонь кілець, герметичність і захист елементів вторинного ущільнення від фретинг-корозії. Для досягнення поставленої мети були сформульовані наступні задачі: − Провести аналіз технології виготовлення й особливостей експлуатації ТІУ. − Розробити методику спрямованого вибору технології забезпечення необхідної якості робочих поверхонь кілець ТІУ залежно від умов роботи ущільнення й властивостей навколишнього середовища. − Удосконалити метод електроерозійного легування (ЕЕЛ) для здійснення процесів сульфідування й сульфоцементації енергоефективними й екологічно чистими методами, альтернативними хіміко-термічній обробці. − Розробити новий метод збільшення товщини шару підвищеної твердості шляхом формування на попередньо зміцнених цементацією методом ЕЕЛ торцевих поверхнях кілець ТІУ комбінованих електроерозійних покриттів; − Провести дослідження якісних параметрів поверхневих шарів, сформованих методом іонного азотування, конденсованого іонного бомбардування та карбонітрацією. − Розробити метод зниження фретинг-процесу для контактуючих поверхонь ущільнювальних елементів ТІУ. − Розробити технологічні рекомендації виготовлення ТІУ залежно від умов роботи та перекачуваного середовища. − Упровадити результати досліджень у практику виготовлення ТІУ турбомашин. У вступі обґрунтований вибір теми дисертації та наукових завдань, сформульовані мета й завдання дослідження, визначені наукова новизна й практичне значення одержаних результатів, а також наведена інформація про апробацію, структуру та обсяг роботи. У першому розділі виконано аналіз проблем підвищення якості елементів ТІУ. Наведено загальні відомості про торцеві ущільнення, розглянуті їх конструктивні особливості, галузі застосування, матеріали і види руйнувань. Досліджено технологічні методи підвищення якості робочих поверхонь ТІУ. Все це дозволило сформулювати мету й завдання дисертації. У другому розділі на основі теоретичного розгляду вимог до якості функціональних покриттів робочих поверхонь деталей роторних машин були розроблені система й критерії спрямованого вибору технології забезпечення необхідної якості робочих поверхонь кілець ТІУ шляхом аналізу і синтезу існуючих аналогів, досвіду промисловості та рекомендацій у вітчизняній і зарубіжній літературі. Система спрямованого вибору технології забезпечення необхідної якості робочих поверхонь кілець ТІУ охоплює весь їх життєвий цикл, що включає матеріал кілець та їх елементів, технологію їх виготовлення, технологію ремонту та ін. Всі вони розглядаються через спеціальні методи спрямованого вибору. До того ж враховується вплив обраних методів один на одного, який у кінцевому підсумку буде позначатися на якості виробу. Варіанти реалізації технологій, що задовольняють рішення були подані орієнтованим графом, вузлами якого є етапи розв’язання задачі, а ребрами – трудомісткість їх розв’язання (технологічна собівартість). Результат пошуку зводиться до розв’язання задачі цілочислового програмування комбінаторного виду, в якій розв’язок шукають на кінцевій множині можливих значень змінних. Як метод оптимізації використовували комбінаторний метод «гілок і меж». Результатом спрямованого вибору технології, що забезпечує необхідні експлуатаційні властивості робочих поверхонь торцевих імпульсних ущільнень, обирався мінімізований за критерієм собівартості технологічний процес формування функціональних покриттів. Третій розділ присвячений методиці експериментальних досліджень впливу різних технологій на якість поверхонь елементів ТІУ. Були розглянуті особливості технології електроерозійного легування (ЕЕЛ) при обробці поверхонь елементів ТІУ. Подано результати досліджень процесу обробки торцевих поверхонь ТІУ іонним азотуванням, конденсованим іонним бомбардуванням, карбонітрацією. Наведена методика досліджень трибологічних властивостей елементів ТІУ, виготовлених різними способами. Подано методику дослідження впливу способів виготовлення кілець ТІУ на механічні властивості. Наведені стендові випробування газового торцевого імпульсного ущільнення. У четвертому розділі наведені результати експериментальних досліджень підвищення якості робочих поверхонь елементів ТІУ сформованих різними методами. Розглянуті питання підвищення якості поверхні кілець ТІУ методом ЕЕЛ, іонного азотування, конденсованого іонного бомбардування, карбонітрації. Підвищення зносостійкості робочих поверхонь вуса та втулки. Подані результати досліджень нових технологій сульфідування та сульфоцементаціі реалізованих на базі методу ЕЕЛ. Наведений аналіз особливостей методів, що застосовуються для підвищення якості елементів ТІУ. У п’ятому розділі наведені результати дослідження впливу способів підвищення якості елементів ТІУ на механічні властивості. Подано результати порівняльних трибологічних випробувань поверхонь ковзання ТІУ, сформованих різними методами. Наведені результати впливу припрацювальних покриттів на трибологічні властивості поверхонь ковзання ТІУ, результати досліджень зносостійкості контактуючих поверхонь деталей пар тертя ТІУ. Розроблені технологічні рекомендації спрямованого вибору найкращого матеріалу кілець ТІУ і технологій підвищення їх якості. Згідно з розробленою методикою спрямованого вибору, виходячи з експлуатаційних властивостей функціональних покриттів і показників якості поверхні, таких як: шорсткість, мікротвердість, зносостійкість, мікроструктура поверхневого шару, які необхідно забезпечити, відбувається спрямований вибір технологічних методів, якими можна вирішити поставлену задачу. До того ж критерієм вибору є мінімальна технологічна собівартість реалізації інтегрованої технології в умовах конкретного підприємства. Практична корисність розробленої методики представлена технологічними рекомендаціями, наведеними у зведеній таблиці. Ця таблиця містить механічні й триботехнічні властивості функціонального покриття, а також інформацію про інтегровану технологію, що дозволяє забезпечити ці властивості. Здійснені натурні випробування імпульсного газового торцевого ущільнення для компресора вуглекислого газу. Відповідно до поставленої мети та задач у роботі отримані наступні результати: 1. Аналіз технології виготовлення й експлуатації ТІУ засвідчив, що резервом зниження собівартості й підвищення якості ТІУ можуть бути технологічні методи ЕЕЛ, ЦЕЕЛ, ІА, КІБ, КН та ін., що дозволяють створювати на підкладках зі сталей і сплавів композиційні матеріали, що поєднують захисні властивості покриттів із механічною міцністю основи. 2. На підставі теоретичних досліджень розроблена формалізована методика визначення раціонального варіанта технології виготовлення елементів ТІУ, яка відрізняється тим, що кожному варіанту відповідає план реалізації можливих комбінацій рішень, мінімізований за трудомісткістю виконання. Розроблено модель синтезу інтегрованої технології, що враховує умови експлуатації ТІУ, фізичні принципи роботи устаткування та дозволяє відповідно до технологічних обмежень формувати функціональні покриття на робочих поверхнях елементів ТІУ. Проведені дослідження були передумовами для створення системи спрямованого вибору технології виготовлення ТІУ турбомашин, що дозволяє формувати робочі поверхні кілець ТІУ, а також контактуючої поверхні вторинного ущільнення й захисної втулки із заданими експлуатаційними властивостями. 3. Набув подальшого розвитку метод ЕЕЛ для здійснення процесів сульфідування й сульфоцементації, застосовуваних для запобігання схоплюванню й зміцненню контактуючих поверхонь ТІУ. 4. Визначено, що для зміцнення сталевих кілець ТІУ методом ЕЕЛ найкращим є КЕП складу ВК8 + Cu + ВК8, нікелевих сплавів – ВК8 + ВК8 + Cu і ВК8 + ВК8 + Ni, а для берилієвої бронзи – хром. Водночас товщину зони підвищеної твердості можна збільшити за рахунок попередньої ЦЕЕЛ. 5. Установлено, що при зміцненні методом ІА, сталі 40Х і 38Х2МЮА товщина зміцненого шару досягає 250 і 500 мкм, а мікротвердість – 8 820 і 9 950 МПа відповідно. Найбільша товщина 250 мкм і мікротвердість зміцненого шару 11 190 МПа, при ІА сталі 40Х належать комбінованому способу зміцнення ІА + ЦЕЕЛ. При зміцненні зразків зі сталі 12Х18Н10Т і Р6М5 методом КІБ товщина покриттів становить ~ 2–3 мкм, мікротвердість основи відповідно для сталі Р6М5 і 12Х18Н10Т становить ~ 6,8 і ~ 2,5 ГПа, а покриття – ~ 18 і 14,5 ГПа. При зміцненні зразків зі сталі 38Х2МЮА методом КН формуються поверхневі шари товщиною до 0,5 мм і мікротвердістю ≥ 10 000 МПа. 6. Запропоновано новий спосіб зниження фретинг-корозії контактуючих поверхонь вторинного ущільнення, виготовлених зі сплаву ХН58МБЮД або БрБ2, за якого перед ЦЕЕЛ на одну поверхню сплаву ХН58МБЮД методом ЕЕЛ наносять покриття з міді або нікелю, а на іншу – з міді. Відповідно до іншого способу перед ЦЕЕЛ на одну з контактуючих поверхонь із бронзи БрБ2 наносять покриття з міді. 7. Розроблено технологічні рекомендації виготовлення ТІУ, адаптовані до умов їх роботи. Аналіз поданих даних дозволяє в першому наближенні вибрати найбільш кращий матеріал для їх виготовлення, а також метод підвищення якості їх елементів. Використання в парах тертя припрацьовувальних КЕП сприяє зниженню сили й коефіцієнта тертя. Дослідження показало, що кільця із застосованих матеріалів мають низький, середній і високий параметри PV і їх можна застосовувати в I, II і III категоріях ущільнень. 8. Результати дисертаційної роботи впроваджені на двох підприємствах та в навчальному процесі Наукова новизна одержаних результатів: 1. Вперше розроблена система спрямованого вибору технології виготовлення ТІУ турбомашин, що дозволяє формувати робочі поверхні кілець, а також контактуючі поверхні вторинного ущільнення та захисної втулки із заданими експлуатаційними властивостями. 2. Набула подальшого розвитку технологія ЕЕЛ елементів ТІУ, які працюють в агресивних середовищах і виготовляються зі сталевих, нікелевих та бронзових сплавів, що дозволило формувати торцеві поверхні кілець і контактуючі поверхні вторинного ущільнення з необхідними експлуатаційними характеристиками. 3. Доведена доцільність нанесення на робочі поверхні сталевих кілець і кілець із нікелевих сплавів ТІУ багатошарових комбінованих електроерозійних покриттів, сформованих відповідно послідовностями ВК8 + Сu + ВК8 і ВК8 + ВК8 + Сu та цементації методом ЕЕЛ, що збільшує товщину шару підвищеної твердості. 4. Обґрунтована доцільність застосування технології сульфідування та сульфоцементації, здійснюваних у практиці зміцнення сталевих поверхонь хіміко-термічнною обробкою, альтернативними, екологічно чистими та більш енергоефективними методами ЕЕЛ. 5. Дістав подальшого розвитку взаємозв’язок між технологічними методами формування покриттів, що забезпечують підвищення зносостійкості торцевих поверхонь кілець, та експлуатаційними характеристиками ТІУ. Практичне значення одержаних результатів полягає в розробці технологічних рекомендацій по виготовленню елементів ТІУ, адаптованих до умов роботи насосних та турбокомпресорних агрегатів та перекачуваного середовища. Аналіз поданих даних дозволяє в першому наближенні вибрати найбільш кращий матеріал для їх виготовлення, а також метод підвищення якості їх елементів.
Thesis for granting the Degree of Candidate of Technical sciences in specialty 05.02.08 - Manufacturing Engineering. The object of research is the technological process of forming functional coatings on the surface of the elements of end impulse seals of turbomachines. The subject of the research is the regularities of the technological process of surface formation with the specified operational properties that provide the required quality (durability, durability, efficiency) of end impulse seals of turbomachines. The aim of the research is to ensure the efficiency of the face impulse seals (FIS) of turbomachines by making rings of composite materials that combine the mechanical strength of the substrate and the protective properties of coatings, increase the wear resistance of the end surfaces of the rings, tightness and protection of corrosion elements. To achieve this aim, the following tasks were formulated: - To carry out the analysis of manufacturing technology and features of operation of FIS. - To develop a method of directional selection of technology to ensure the required quality of the working surfaces of the FIS rings, depending on the working conditions of the seal and the properties of the environment. - Improve the method of electro-erosion alloying (EEA) for the implementation of the processes of sulfidation and sulfocarbonization by energy-efficient and environmentally friendly methods alternative to chemical-thermal treatment. - Develop a new method of increasing the thickness of the layer of high hardness by forming on the carbonized by EEA method the end surfaces of the rings of FIS combined electro-erosion coatings; - To study the qualitative parameters of surface layers formed by the method of ion nitriding, condensed ion bombardment and carbonitration. - Develop a method of reducing fretting process for the contact surfaces of the sealing elements of the FIS. - Develop technological guidelines for the production of FIS depending on the operating conditions and the pumped medium. - Introduce research results into the practice of manufacturing FIS for turbomachines. The introduction substantiates the choice of the topic of the dissertation and scientific tasks, formulates the aim and tasks of the research, defines the scientific novelty and practical significance of the obtained results, as well as provides information on the approbation, structure and scope of work. The first chapter analyzes the problems of improving the quality of FIS elements. General information on face seals, their design features, applications, materials and types of fractures are presented. Technological methods of improving the quality of work surfaces of FIS are investigated. All this allowed us to formulate the purpose and tasks of the dissertation. In the second chapter, on the basis of theoretical consideration of the requirements for the quality of functional coatings of the working surfaces of parts of rotary machines, a system and criteria for the directional choice of technology to ensure the required quality of the working surfaces of the FIS rings by analyzing and synthesizing existing analogues, industry experience and recommendations in domestic and foreign. The system of directional choice of technology to ensure the required quality of the working surfaces of the FIS rings covers their entire life cycle, including the material of the rings and their elements, the technology of their manufacture, technology of repair, etc. They are all considered through special directional choice methods. In addition, the impact of the choice methods on each other, which will ultimately affect the quality of the product. Options for implementing the technologies that satisfy the solution were presented by an oriented graph, whose nodes are the steps of solving the problem, and the edges represent the complexity of solving them (technological cost). The result of the search is to solve the integer programming problem of combinatorial form, in which the solution is searched for a finite set of possible values of variables. The combinatorial branch and boundary method was used as the optimization method. As a result of the directional choice of technology that provides the required operational properties of the working surfaces of the FIS, the process of forming functional coatings minimized by the cost criterion was selected. The third chapter is devoted to the method of experimental research of the influence of different technologies on the quality of the surfaces of the FIS elements. The features of electro-erosion alloying technology in the treatment of the surfaces of the FIS elements were considered. The results of studies of the process of treatment of end surfaces of FIS with ionic nitriding, condensed ion bombardment, carbonitration are presented. The technique of investigations of tribological properties of FIS elements made in different ways is presented. The technique of studying the influence of the methods of manufacturing the FIS rings on the mechanical properties is presented. Bench tests of gas face impulse seal are given. The fourth chapter presents the results of experimental research of improving the quality of the working surfaces of the elements of the FIS formed by different methods. The questions of improvement of surface quality of FIS rings by EEA method, ion nitriding, condensed ion bombardment, carbonitration are considered. Increasing the wear resistance of the working surfaces of the mustache and sleeve. The results of researches of new technologies of sulfidation and sulfocarbonization implemented on the basis of EEA method are presented. The analysis of the peculiarities of the methods used to improve the quality of FIS elements is given. The fifth chapter presents the results of a study of the effect of enhancing the quality of FIS elements on mechanical properties. The results of comparative tribological tests of the sliding surfaces of the FIS formed by different methods are presented. The results of the influence of the working coatings on the tribological properties of the sliding surfaces of the FIS, the results of studies of the wear resistance of the contacting surfaces of the parts of the friction pairs of the FIS are presented. Technological recommendations for direct selection of the best material of the FIS rings and technologies for improving their quality have been developed. According to the developed method of directional selection, based on the operational properties of functional coatings and surface quality indicators, such as roughness, microhardness, wear resistance, microstructure of the surface layer to be provided, there is a directional choice of technological methods that can be solved the problem. In addition, the criterion for selection is the minimum technological cost of implementing integrated technology in a particular enterprise. The practical utility of the developed methodology is represented by the technological recommendations given in the summary table. This table contains the mechanical and tribotechnical properties of the functional coating, as well as information about the integrated technology that enables these properties to be ensured. Field tests of pulsed gas end seals for carbon dioxide compressor have been carried out. In accordance with the set aim and tasks in the work the following results were obtained: 1. Analysis of the technology of production and operation of FIS showed that the reserve of reducing the cost and improving the quality of FIS may be technological methods EEA, carbonized by EEA, ion nitriding, condensed ion bombardment, carbonitration, etc., which allow to create composite materials on the substrates of steels and alloys that combine protective properties of coatings with mechanical strength of the substrate. 2. On the basis of theoretical research, a formalized methodology for determining a rational variant of the technology of fabrication of elements of FIS is developed, characterized in that each variant corresponds to the plan of realization of possible combinations of solutions, minimized by the complexity of execution. A model of synthesis of integrated technology was developed, which takes into account the conditions of operation of the FIS, the physical principles of operation of the equipment and allows, in accordance with technological limitations, to form functional coatings on the working surfaces of the FIS elements. The conducted researches were prerequisites for creation of the system of directed choice of technology of production of FIS of turbomachines, which allows to form working surfaces of FIS rings, as well as the contacting surface of the secondary seal and the protective sleeve with the specified operational properties. 3. The EEA method for the implementation of the sulfidation and sulfocementation processes used to prevent the adhesion and strengthening of the contacting surfaces of the FIS has been further developed. 4. It is determined that to strengthen the FIS steel rings of BK8 + Cu + BK8, nickel alloys - BK8 + BK8 + Cu and BK8 + BK8 + Ni, and chromium for beryllium bronze, is best for the reinforcement of FIS steel rings by the EEA method. At the same time, the thickness of the high hardness zone can be increased at the expense of the previous carbonized by EEA. 5. It is found that, when strengthened by the ion nitriding method, 40X and 38X2MЮA steels, the thickness of the hardened layer reaches 250 and 500 μm, and the microhardness is 8 820 and 9 950 MPa, respectively. The maximum thickness of 250 μm and the microhardness of the hardened layer is 11 190 MPa, for ion nitriding steel 40X belong to the combined method of strengthening ion nitriding + carbonized by EEA. When hardening specimens of 12X18H10T and P6M5 steel by condensed ion bombardment method, the coating thickness is ~ 2–3 μm, the microhardness of the substrate, respectively, for the P6M5 and 12X18H10T steel is ~ 6.8 and ~ 2.5 GPa, and the coating is ~ 18 and 14.5 GPa. When hardening the 38X2MЮA steel samples, surface layers of up to 0.5 mm thickness and microhardness ≥ 10,000 MPa are formed by the carbonitration method. 6. A new method of reducing the fretting corrosion of the contact surfaces of the secondary seal made of ХН58МБЮД or БрБ2 alloy is proposed. In this case, copper or nickel coatings are applied to the EEA method on one surface of the ХН58МБЮД alloy by the EEA method, and the other surface is made of copper. According to another method, a copper coating is applied to the carbonized by EEA on one of the БрБ2 bronze contacting surfaces. 7. Technological recommendations for the production of FIS have been developed, adapted to their working conditions. The analysis of the submitted data allows in the first approximation to choose the best material for their production, as well as a method of improving the quality of their elements. The use in the friction pairs of the combined electroerosion coatings contributes to the reduction of the friction force and coefficient. The study showed that the rings of the materials used have low, medium and high PV parameters and can be used in I, II and III seals. 8. The results of the dissertation are implemented at two enterprises and in the educational process. Scientific novelty of the obtained results: 1. For the first time, a system of directional selection of the technology of manufacturing FIS of turbomachines is developed, which allows forming the working surfaces of the rings, as well as the contacting surfaces of the secondary seal and the protective sleeve with the specified operational properties. 2. The EEA technology of FIS elements, which work in corrosive environments and made of steel, nickel and bronze alloys, has been further developed, which allowed to form the end surfaces of the rings and the contact surfaces of the secondary seal with the required performance characteristics. 3. The expediency was proved of coating on the working surfaces of steel nickel alloys FIS rings of multilayer combined electro-erosion coatings formed respectively by the sequences BK8 + Cu + BK8 and BK8 + BK8 + Cu and carbonized by EEA is increases the thickness of the layer of increased hardness. 4. The feasibility of applying the technology of sulfidation and sulfo-cementation carried out in the practice of hardening steel surfaces by chemical-thermal treatment, alternative, environmentally friendly and more energy-efficient EEA methods is substantiated. 5. The further development of the relationship between the technological methods of forming coatings to improve the wear resistance of the face surfaces of the rings, and the performance characteristics of FIS. The practical significance of the obtained results lies in the development of technological recommendations for the production of FIS elements, adapted to the operating conditions of the pump and turbocharger units and the pumped medium. The analysis of the submitted data allows in the first approximation to choose the best material for their production, as well as a method of improving the quality of their elements.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.02.08 – технологія машинобудування. – Національний технічний університет «Харківський політехнічний інститут», Харків, 2019. Дисертація присвячена вирішенню науково-технічної задачі забезпечення працездатності торцевих імпульсних ущільнень (ТІУ) турбомашин шляхом удосконалення технології виготовлення кілець із композиційних матеріалів, що поєднують у собі механічну міцність основи та захисні властивості покриттів. Проведено аналіз технології виготовлення й особливостей експлуатації ТІУ, з метою пошуку технологічних методів, які дозволяють створювати на підкладках зі сталей і сплавів функціональні покриття із заданими експлуатаційними властивостями. Розроблено методику спрямованого вибору технології забезпечення необхідної якості робочих поверхонь кілець ТІУ залежно від умов роботи ущільнення й властивостей навколишнього середовища. Удосконалено технологію виготовлення елементів ТІУ, які працюють в агресивних середовищах і виготовляються зі сталевих, нікелевих та бронзових сплавів, за рахунок застосування енергоефективних та екологічно чистих методів, альтернативних хіміко-термічній обробці. Розроблено новий метод збільшення товщини шару підвищеної твердості шляхом формування на попередньо зміцнених методом цементації електроерозійним легуванням торцевих поверхнях кілець ТІУ комбінованих електроерозійних покриттів. Проведено трибологічні дослідження та дослідження параметрів якості поверхневих шарів, сформованих методом іонного азотування, конденсованого іонного бомбардування та карбонітрацією. Розроблено метод зниження фретинг-корозії для контактуючих поверхонь ущільнювальних елементів ТІУ. Розроблено технологічні рекомендації виготовлення ТІУ залежно від умов роботи та перекачуваного середовища. Економічний ефект від впровадження основних положень роботи у виробництво становить 450 тис. грн.
Thesis for granting the Degree of Candidate of Technical sciences in specialty 05.02.08 - Manufacturing Engineering. - National Technical University "Kharkiv Polytechnic Institute", 2019. The dissertation is devoted to the solution of the scientific and technical problem of ensuring the efficiency of face impulse seals (FIS) of turbomachines by improving the technology of manufacturing rings made of composite materials, which combine the mechanical strength of the substrate and the protective properties of coatings. An analysis of manufacturing technology and features of FIS operation was conducted in order to search for technological methods that allow to create functional coatings with specified operational properties on substrates of steels and alloys. The technique of directional choice of technology for ensuring the required quality of the working surfaces of the FIS rings, depending on the working conditions of the seal and the environmental properties, is developed. The technology of manufacturing FIS elements that work in corrosive environments and made of steel, nickel and bronze alloys has been improved due to the use of energy-efficient and environmentally friendly methods, alternative to chemical-thermal treatment. A new method of increasing the thickness of the layer of increased hardness by forming on the pre-strengthened cementing method by electro-erosion doping of the end surfaces of the FIS rings of the combined electro-erosion coatings is developed. Tribological researches and investigations of quality parameters of surface layers formed by the method of ion nitriding, condensed ion bombardment and carbonitration were carried out. The method of reducing the fretting corrosion for the contact surfaces of the sealing elements of the FIS has been developed. Technological recommendations for the production of FIS depending on the operating conditions and the pumped medium are developed. The economic effect of the introduction of the main provisions of work in production is 450 000 UAH.

碩士
國立臺灣科技大學
營建工程系
95
In this research, nano photocatalyst were used on the surface of brick tiles which forms a thin membrane. Furthermore, the brick tiles were placed vertically on the top of the building to test the durability under the influence of the natural factors. The experiment was proceeded in two different settings---indoor and outdoor. In indoor settings, basic properties of initial photocatalyst membrance were explored to differentiate the pollutant ability of decomposition between different products(by using methylene blue to simulate organic pollution), the difference under the change of contacting angle of the water droplet as well. Moreover, UV testing machine was used to imitate the outdoor setting. By doing pollution testing and spraying the methylene blue repeatedly, the decomposed ability of the photocatalyst was under investigation. The result shows that the brick tiles with 15% photocatalyst on the surface are better than the others in durability. Generally, acid resistance of each product is not good in the tests like H2SO4, Na2CO3, and NaCl. In outdoor setting, the relationship between the color difference and the change of contacting angle is not closely related. Some samples even present lower contacting angle before being lightened. In other words, photocatlyst doesn’t definitely lead to the change of contacing angle. Furthermore, the function of decomposition and contacting angle would be discussed separately.

碩士
大葉大學
環境工程學系碩士班
97
Thermal paper has wide range of applications, such as facsimile paper, labels for food retailing and other industries, bus fares, airplane tickets, and other ticket items. The global demands are increasing. Yet thermal paper is a kind of heat-reversible recording paper, its images are liable to fade due to light, temperature, and humidity factors. Thus, how to preserve the thermal-induced images is becoming a critical quality demand. This study was carried out in 3 stages, in the first stage, 7 commercial thermal papers were collected and their surface, optical, and durability characteristics were evaluated to serve as criteria for the subsequent preparations. In the second stage, hollow-core plastic pigment, calcined clay, and a mixture of the 2 were applied as ingredients in the precoating formulation to evaluate their influences on the durability of the thermal paper. In the third stage, different thermal-sensitive particle size ranges of 1.5~1.0, 1.0~0.5 and > 0,5 μm were tested for the ensuing thermal paper durability and application to find out the optimal particle size range. The results indicated that when the commercial thermal papers were tested for light-fastness at a UV wavelength of 351 nm and 60℃, the best performing image intensity retention was 21.7%, and the fading rate was 47.1%; at the dry-heating test condition of 60, the best image intensity retention was 43.0%, and the fading rate was 41.8%; and at the constant temperature and humidity conditions of 40℃ and 90% RH, the best image intention retention was 94.2%, and the fading rate was 5.6%. These were established as criteria for comparisons with the self-prepared samples. The precoating experiments indicated that at a UV wavelength of 351 nm and 60℃condition entailed an optimal image intensity retention of of 59,1% and a fading rate of 21.9%; at the constant temperature and humidity conditions of 40℃ and 90% RH, the best image intensity retention rate was 96.3%, and the fading rate was 1.8%; and at the 60℃ dry heat test condition, the best image intensity retention rate was 95.4% and the fading rate was 0.9%. Adding hollow-core plastic pigment exerted notable enhancements to the resulting thermal paper durability in image intensity, light fastness, temperature and humidity as compared to those precoated with calcined clay and a mixture of calcined clay and hollow-core plastic pigment. In the heat-sensing layer particle size experiments, light fastness tests at 351 nm wavelength and 60℃ resulted in the best image intensity retention of 59.1%, and the fading rate of 21.6%; at a constant temperature and humidity condition of 40℃ and 90% RH, the best image intensity retention was 96.3% and the fading rate was 1.8%; and at the 60℃ dry heating test, the best image intensity retention was 95.4% and the fading rate was 0.9%. The color former particle size 1.5~1.0 μm, color developer particle size 1.0~0.5 μm, and sensitizer particle size 1.5~1.0 μm entailed the best performances. In the study, our self-prepared thermal paper formulation resulted in significant improvements of product durability. Regardless of the environmental conditions applied using light, temperature and humidity, the image intensity retention of the self-prepared thermal paper was superior to the commercial products.

Polymer coated sheet metal components find diverse applications in many industries. The manufacturing of the components generally involves forming of sheet metal into the desired shape and coating of the formed part with organic coating. An alternative manufacturing route is to coat the sheet metal first before forming. The change in the manufacturing sequence can potentially improve cost and reduce environmental impact. This approach, however, requires the coating to survive the deformation process. Thus, the effect of plastic deformation on coating adhesion is of primary interest to many engineers and researchers. This research aims at developing a methodology to predict the adhesion of coating after metal forming processes. A pull-off apparatus that measures the coating pull-off stress was used to indicate the coating adhesion strength. Several types of specimen were designed to obtain uniaxial tension, biaxial tension, and tension-compression deformation modes on pre-coated sheet by using a uniaxial tensile tester. Experimental results from two selected polymer coated sheet metals show that coating adhesion was affected by plastic deformation. An analytical model based on a virtual interface crack concept was developed to indicate the adhesion potential of the coating-substrate interface. From interfacial fracture mechanics, the initial adhesion potential is defined as the energy release rate characterized by the virtual interface crack and the initial pull-off stress. The analytical model was used to predict coating adhesion loss after deformation in uniaxial tension mode. The analytical model predictions agreed well with experimental results. Finite element analysis tool was applied to simulate more complex deformation modes in stamping of coated sheet meals. The stress field near the interface crack tip was used to calculate the energy release rate and predict the adhesion loss under different deformation modes. The predictions obtained from numerical method are also in good agreements with the experimental results in biaxial tension and tension-compression modes. The research has led to a better understanding of the effects of plastic deformation on coating adhesion. The developed adhesion test methods can be used to generate useful information on coating durability for diverse practical use. It is also expected that the results of the research will facilitate the development of better polymer coated sheet metal to be used in sheet metal forming processes.

碩士
國立臺灣海洋大學
材料工程研究所
99
The study focuses on the testing of the external wall coating materials of buildings in the deterioration of the environment of weathering performance. Through the experimental results of the mechanical tests, analysis of chromatic aberration, measurement of pore structure, and assessments of chloride ion intrusion, we understand the changing caused by different temperatures on the properties of cementitious coating materials, and accelerated deterioration of coating materials on the surface color performance conditions. From the research, we found that there is no significant impact for the specimens with or without coating materials for the compressive and tensile strength. Specimens without coating under accelerated deterioration in the oven at 50 and 75 degree C, the tensile strength is significantly impacted, and the compressive strength is less significantly impacted. On Xenon light deterioration, you can find that the chromatic aberration in the deterioration process. But the total chromatic aberration changes slower after 200 hours which is still significant based on the classification in the color range of the United States National Bureau of Standards, and the total chromatic aberration of the acrylic emulsion paints change the most. Acrylic emulsion paints changes the most on the accelerated deterioration of mist testing, but the total chromatic aberration is only according to the classification between minor and major. Although the accelerated deterioration in the oven at 50 and 75 degree C has little effect on the mechanical properties, but the steady-state migration coefficient of chloride does have a greater change. It should be the reaction to raise the temperature in the form of growing micro-crack in the specimens, as verified by the porosity measured by the MIP. Although no degradation in the coating to protect cementitious substrates is detected before deterioration, the nature of the weathering and durability are still negatively impacted by the effect of temperature.