Dissertations / Theses on the topic 'Anti-corrosive'

To enable improvements in the development of anti-corrosive coatings quick methods of evaluation are required and several are available which are both qualitative and quantitative. This investigation reviews both types of method, the first in the form of traditional salt spray exposure and the second in the form of electrochemical techniques. The emphasis in the experimental work reported here is on the Electrochemical Noise Measurement (ENM). ENM has been used to monitor coatings under immersion conditions, the aim being to assist a paint company develop a set of more environmentally friendly coatings. The immersion test has also incorporated a temperature cycle which proved effective at separating ‘good’ coatings within a short timeframe. Results showed good correlation between ENM and salt spray testing. Work is also reported which was done with the aim of making the ENM method more practically useful. The standard configuration (‘Bridge’) requires two separate specimens which is unattractive for site work. The Single Substrate (SS) arrangement was developed to get around this problem but this still requires the metal to be connected to the measuring instrument. This is avoided in the most recent development which needs No Connection to Substrate (NOCS). Results are given for immersed samples monitored using the ENM NOCS arrangement and compared with the standard ‘Bridge’ method and DC resistance. Results are also presented using sets of different electrodes (platinum, calomel and silver/silver chloride). This preliminary work has shown that the NOCS method holds great promise. In the laboratory Electrochemical Impedance Spectroscopy (EIS) is also commonly employed to assess the performance of anti-corrosive coatings. Concluding this work a comparison of the ENM and EIS techniques was undertaken on a set of laboratory samples. Results showed that both methods had the ability to rank the performance of coatings. However ENM’s advantages (as outlined above) were confirmed

Mestrado em Engenharia Química
Este trabalho tem como objetivo aplicar hidróxidos duplos lamelares (LDHs) intercalados com inibidores de corrosão em betão armado por forma a proteger as estruturas de aço da corrosão e aumentar a longevidade do mesmo. Para tal, foram sintetizados LDH-NO3 e LDH-NO2. A partir da suspensão de LDH-NO3, procedeu-se à intercalação com iões citrato e tartarato. Todas as amostras foram caracterizadas utilizando técnicas como espetroscopia de FT-IR, X-RD, potencial zeta, DLS, SEM/TEM e ICP. Realizaram-se estudos de libertação, colocando, em agitação, alíquotas de soluções aquosas de cloreto de sódio (NaCl) às concentrações de 5, 50 e 500 mM com LDH em pó. Recolheram-se alíquotas durante um mês e analisaram-se as amostras por cromatografia líquida (HPLC), para determinar as concentrações dos inibidores em solução ao longo do tempo. Procedeu-se, ainda, a estudos de impedância eletroquímica para avaliação do desempenho dos materiais na prevenção do ataque corrosivo ao aço. Para tal, expôs-se uma placa de aço a suspensões de diferentes concentrações de espécie agressiva (ião cloreto) com LDHs e mediram-se os valores de impedância ao longo do tempo. Com este trabalho conseguiu-se avaliar o desempenho anticorrosivo de diferentes aniões, além dos já conhecidos, e perceber quais trariam vantagens com o seu uso. Observou-se que nas suspensões com maior concentração de espécie agressiva, a libertação de inibidor foi superior. Através dos espetros de FT-IR e imagens de SEM/TEM, depreendeu-se que a encapsulação decorreu com sucesso. Apesar de não se ter tido oportunidade de testar o desempenho dos materiais encapsulados, seria um ponto vantajoso no desenvolvimento do trabalho.
This work consisted in the preparation and characterization of layered double hydroxides (LDHs) intercalated with corrosion inhibitors with the purpose of including them in concrete, to protect steel from corrosion and increase concrete’s longevity. LDH-NO3 and LDH-NO2 were synthesized and, using, LDH-NO3 suspension, intercalation with citrate and tartrate ions was performed. All samples were characterized using FT-IR spectroscopy, X-RD, Zeta potential measurements, DLS, SEM/TEM and ICP. Release studies were performed, mixing NaCl solution at different concentrations (5, 50, 500 mM) with each LDH sample. Several aliquots were collected over a month and analysed by HPLC to determine the concentration of inhibitors released over time. Electrochemical impedance studies were performed to evaluate the performance of LDHs intercalated with inhibitors against steel corrosion. Thus, a carbon steel board was exposed to a suspension with the aggressive specie (chloride ion) at different concentrations and LDHs. Impedance data was collected over time. Therefore, it was possible to analyse the pertinence of the inclusion of the tested materials into concrete’s mixture, when comparing their action against the corrosive process. It was verified that for suspensions with higher concentrations in aggressive specie, the release of the inhibitor was superior. Through FT-IR spectra and SEM/TEM images, it was concluded that the encapsulation occurred successfully. Even though the performance of the functionalized materials was not tested, it would be advantageous for the on-going development of the work.

Within this work, three physicochemical methods for the hydrophobization of initially hydrophilic solid particles are investigated. The modified particles are then used for the stabilization of oil-in-water (o/w) emulsions. For all introduced methods electrostatic interactions between strongly or weakly charged groups in the system are es-sential. (i) Short chain alkylammonium bromides (C4 – C12) adsorb on oppositely charged solid particles. Macroscopic contact angle measurements of water droplets under air and hexane on flat silica surfaces in dependency of the surface charge density and alkylchain-length allow the calculation of the surface energy and give insights into the emulsification properties of solid particles modified with alkyltrimethylammonium bromides. The measure-ments show an increase of the contact angle with increasing surface charge density, due to the enhanced adsorp-tion of the oppositely charged alkylammonium bromides. Contact angles are higher for longer alkylchain lengths. The surface energy calculations show that in particular the surface-hexane or surface-air interfacial en-ergy is being lowered upon alkylammonium adsorption, while a significant increase of the surface-water interfa-cial energy occurs only at long alkyl chain lengths and high surface charge densities. (ii) The thickness and the charge density of an adsorbed weak polyelectrolyte layer (e.g. PMAA, PAH) influence the wettability of nanoparticles (e.g. alumina, silica, see Scheme 1(b)). Furthermore, the isoelectric point and the pH range of colloidal stability of particle-polyelectrolyte composites depend on the thickness of the weak polye-lectrolyte layer. Silica nanoparticles with adsorbed PAH and alumina nanoparticles with adsorbed PMAA be-come interfacially active and thus able to stabilize o/w emulsions when the degree of dissociation of the polye-lectrolyte layer is below 80 %. The average droplet size after emulsification of dodecane in water depends on the thickness and the degree of dissociation of the adsorbed PE-layer. The visualization of the particle-stabilized o/w emulsions by cryogenic SEM shows that for colloidally stable alumina-PMAA composites the oil-water interface is covered with a closely packed monolayer of particles, while for the colloidally unstable case closely packed aggregated particles deposit on the interface. (iii) By emulsifying a mixture of the corrosion inhibitor 8-hydroxyquinoline (8-HQ) and styrene with silica nanoparticles a highly stable o/w emulsion can be obtained in a narrow pH window. The amphoteric character of 8-HQ enables a pH dependent electrostatic interaction with silica nanoparticles, which can render them interfa-cially active. Depending on the concentration and the degree of dissociation of 8-HQ the adsorption onto silica results from electrostatic or aromatic interactions between 8-HQ and the particle-surface. At intermediate amounts of adsorbed 8-HQ the oil wettability of the particles becomes sufficient for stabilizing o/w emulsions. Cryogenic SEM visualization shows that the particles arrange then in a closely packed shell consisting of partly of aggregated domains on the droplet interface. For further increasing amounts of adsorbed 8-HQ the oil wet-tability is reduced again and the particles ability to stabilize emulsions decreases. By the addition of hexadecane to the oil phase the size of the droplets can be reduced down to 200 nm by in-creasing the silica mass fraction. Subsequent polymerization produces corrosion inhibitor filled (20 wt-%) poly-styrene-silica composite particles. The measurement of the release of 8-hydroxyquinoline shows a rapid increase of 8-hydroxyquinoline in a stirred aqueous solution indicating the release of the total content in less than 5 min-utes. The method is extended for the encapsulation of other organic corrosion inhibitors. The silica-polymer-inhibitor composite particles are then dispersed in a water based alkyd emulsion, and the dispersion is used to coat flat aluminium substrates. After drying and cross-linking the polmer-film Confocal Laser Scanning Micros-copy is employed revealing a homogeneous distribution of the particles in the film. Electrochemical Impedance Spectroscopy in aqueous electrolyte solutions shows that films with aggregated particle domains degrade with time and don’t provide long-term corrosion protection of the substrate. However, films with highly dispersed particles have high barrier properties for corrosive species. The comparison of films containing silica-polystyrene composite particles with and without 8-hydroxyquinoline shows higher electrochemical impedances when the inhibitor is present in the film. By applying the Scanning Vibrating Electrode Technique the localized corrosion rate in the fractured area of scratched polymer films containing the silica-polymer-inhibitor composite particles is studied. Electrochemical corrosion cannot be suppressed but the rate is lowered when inhibitor filled composite particles are present in the film. By depositing six polyelectrolyte layers on particle stabilized emulsion droplets their surface morphology changes significantly as shown by SEM visualization. When the oil wettability of the outer polyelectrolyte layer increases, the polyelectrolyte coated droplets can act as emulsion stabilizers themselves by attaching onto bigger oil droplets in a closely packed arrangement. In the presence of 3 mM LaCl3 8-HQ hydrophobized silica particles aggregate strongly on the oil-water inter-face. The application of an ultrasonic field can remove two dimensional shell-compartments from the droplet surface, which are then found in the aqueous bulk phase. Their size ranges up to 1/4th of the spherical particle shell.
Im Rahmen dieser Arbeit wurden drei Oberflächenmodifikationen zur Hydrophobierung von ursprünglich hydrophilen Feststoffpartikeln entwickelt. Die so modifizierten Partikel werden dann zur Stabilisierung von Öl-in-Wasser Emulsionen verwendet. Für sämtliche entwickelte Methoden sind elektrostatische Wechselwirkungen zwischen stark oder schwach dissoziierten chemischen Gruppen essentiell. (i) Kurzkettige Alkyltrimethylammonium Bromide (C4-C12) adsorbieren auf entgegengesetzt geladenen Partikeln. Makroskopische Kontaktwinkelmessungen von Wasser Tropfen in Luft und Hexan auf flachen Siliziumoxid Oberflächen mit variabler Oberflächenladungsdichte und Alkylkettenlänge ermöglichen die Berechnung der Oberflächenenergie und geben Einblicke in die Emulgationseigenschaften von so modifizierten Feststoffpartikeln. Die Messungen zeigen einen Anstieg des Kontakwinkels mit steigender Oberflächenladungsdichte, bedingt durch die verstärkte Adsorption von entgegengesetzt geladenen Alkyltrimethylammonium Bromiden. Die Kontaktwinkel sind zudem größer für längerkettige Alkyltrimethylammonium Bromide. Die Berechnungen der Oberflächenenergie zeigen, dass besonders die Feststoff-Hexan oder Feststoff-Luft Grenzflächenenergie durch die Adsorption verringert wird, wohingegen die Feststoff-Wasser Oberflächenenergie nur bei längeren Alkylkettenlängen und hohen Oberflächenladungsdichten signifikant ansteigt. (ii) Die Schichtdicke und Ladungsdichte von adsorbierten schwachen Polyelektrolyten (z.B. PMAA, PAH) beeinflusst die Benetzbarkeit von Nanopartikeln (z.B. Aluminiumoxid, Siliziumoxid). Der isoelektrische Punkt und der pH Bereich für kolloidale Stabilität solcher Polyelektrolyt modifizierter Partikel hängt von der Dicke der Polyelektrolytschicht ab. Siliziumoxid und Aluminiumoxid Nanopartikel mit adsorbierten PAH bzw. PMAA werden Grenzflächenaktiv und dadurch befähigt Öl-in-Wasser Emulsionen zu stabilisieren, wenn der Dissoziationsgrad der Polyelektrolytschicht geringer als 80 % ist. Die durchschnittliche Tropfengröße von Dodecan-in-Wasser Emulsionen ist abhängig von der Polyelektrolytschichtdicke und dem Dissoziationsgrad. Die Visualisierung von Partikel stabilisierten Öl-in-Wasser Emulsionen durch kryogene REM zeigt, dass im Falle von kolloidal stabilen Aluminiumoxid-PMAA Partikeln die Öl-Tröpfchen mit einer dichtgepackten Partikelhülle belegt sind, während für kolloidal destabilisierte Partikel eine Hülle aus aggregierten Partikeln gefunden wird. (iii) Durch das Emulgieren einer Lösung des Korrosionsinhibitors 8-Hydroxychinolins (8HQ) in Styrol mit Siliziumoxid Nanopartikeln können stabile Öl-in-Wasser Emulsionen in einem pH Fenster von 4 - 6 hergestellt werden. Der amphoterische Charakter von 8HQ ermöglicht eine pH abhängige elektrostatische Wechselwirkung mit den Siliziumdioxid Nanopartikeln, welche diese Grenzflächenaktiv werden lässt. In Abhängigkeit der Konzentration und des Dissoziationsgrads von 8HQ folgt die Adsorption auf Siliziumdioxid aus elektrostatischen oder aromatischen Wechselwirkungen zwischen 8HQ und der Partikeloberfläche. Bei mittleren adsorbierten Mengen wird die Öl Benetzbarkeit der Partikel ausreichend erhöht um Öl-in-Wasser Emulsionen zu stabilisieren. Kryogene REM zeigt, dass die Partikel dann in dicht gepackte Hüllen, mit teilweise aggregierten Domänen auf der Öltröpfchenoberfläche vorliegen. Durch weiter ansteigende adsorbierte 8HQ Mengen wird die Öl-Benetzbarkeit wieder zurückgesetzt und die Emulgationsfähigkeit der Partikel aufgehoben. Durch die Zugabe von Hexadecan zur Öl Phase kann die Tropfengröße durch Erhöhung des Siliziumdioxid Anteils auf 200 nm herabgesetzt werden. Anschließende Polymerisation des Styrols generiert Korrosionsinhibitor gefüllte (20 Gew-%) Polystyrol-Silizumoxid Komposite. Die Messung der Freisetzungsrate von 8HQ zeigt einen schnellen Anstieg der 8HQ Konzentration in einer gerührten wässrigen Lösung innerhalb von 5 Minuten. Die Verkapselungsmethode wird auch für andere organische Korrosionsinhibitoren erweitert. Die Komposite werden dann in einer wasserbasierten Alkydpräpolymeremulsion dispergiert und diese Mischung wird zur Beschichtung von flachen Aluminiumplatten genutzt. Nach Trocknung und Quervernetzung des Films wird Konfokale Laser Mikroskopie dazu verwendet um die räumliche Verteilung der Composite im Film zu visualisieren. Elektrochemische Impedanzspektroskopie zeigt, dass die Barriereeigenschaften des Films durch die Anwesenheit der Komposite verbessert sind. Raster Vibrationselektroden Messungen zeigen, dass die Korrosionsrate in einem Kratzer des Films durch die Anwesenheit der Inhibitor efüllten Komposite reduziert ist. Durch die Ablagerung von 6 Polyelektroytschichten auf Feststoffstabilisierten Emulsionströpfchen verändert sich deren Oberflächenmorphologie deutlich (gezeigt durch REM). Wenn die Ölbenetzbarkeit der äußeren Polyelektrolytschicht ansteigt, dann können solche Polyelektolytbeschichteten Feststoffstabilisierte Emulsionströpfchen selber als Emulsionsstabilisatoren verwendet werden. Diese lagern sich dann in einer dicht gepackten Schicht auf der Oberfläche von größeren Emulsionstropfen ab. In der Gegenwart von 3 mM LaCl3 aggregieren 8HQ modifizierte Siliziumoxid Partikel stark auf der Öl-Wasser Grenzfläche. Der Einsatz von Ultraschall kann aggregierte Schalenbestandteile von der Tropfenoberfläche wegreißen. Diese Wracks können bis zu einem Viertel der Kugelhülle ausmachen und liegen dann als kolloidale Schalen im Wasser vor.

Des revêtements multicouche anticorrosion, ou peintures anticorrosion, sont utilisés dans de nombreuses applications industrielles telles que la protection d’emballages métalliques utilisés pour le transport ou l’entreposage de matériaux radioactifs. En conditions d’usage, les propriétés fonctionnelles de ces peintures peuvent être dégradées sous l’effet de la température et des conditions environnementales (lumière, dioxygène, humidité, …). Ces évolutions ont été attribuées au vieillissement des différentes couches de peinture constituant le revêtement anticorrosion (vernis de structure acrylique-siloxane, sous couches de type résine époxydique à durcisseur amine). Afin de mener à bien cette étude, une approche dite « multi-échelle ascendante » a été développée. Cette méthodologie, initialement focalisée sur la modification des propriétés physico-chimiques des polymères vierges constituant chaque couche du revêtement (depuis l’évolution de la structure chimique et de l’architecture macromoléculaire, vers les propriétés fonctionnelles), est ensuite progressivement complexifiée par l’ajout d’additifs à la formulation des peintures (pigments, particules barrières à l’oxydation ou anticorrosion, …) avant que le revêtement multicouche complet ne soit analysé dans son ensemble. Ce travail de thèse vise à identifier et à corréler les modifications de la structure chimique et de l’architecture macromoléculaire des différentes couches de peinture responsables de la modification des propriétés fonctionnelles du revêtement anticorrosion
Anti-corrosive multilayer coatings, or anti-corrosive paints, are used in several industrial applications such as metallic package protection used for transportation or storage of radioactive materials. In working conditions, functional properties of these paints could be degraded under the influence heat or environmental conditions (light, oxygen, moisture …). Such evolutions had been attributed to the aging of the different paint layers that constituted the anticorrosive coating (acrylic-siloxane topcoat, epoxy resin with amine hardener undercoats). In order to properly carry out this study, a « bottom-up multiscale approach » has been developed. This methodology, initially focused on the physico-chemical modifications of neat polymers that constituted each layer of the coating (from chemical structure and macromolecular architecture evolutions to functional properties), is then complexified by adding filers to the paint formulations (pigments, barrier or anti-corrosive particles …). The complete multilayer coating analyses are the last steps of that methodology. The aim of this thesis is to identify and correlate the evolution of anti-corrosive multilayer coating functional properties to the chemical and architectural modifications in each different layer

碩士
國立成功大學
化學工程學系碩博士班
95
Electroless Ni-Fe-P alloys have been deposited from a basic plating bath having sodium citrate as a complexing agent. Effects of added reducing agents (sodium hypophosphite and hydrazine hydrate) and pH values of plating bath were studied. The surface morphology and microstructures were examined under a scanning electron microscope equipped with an energy dispersive spectrometer (EDS). The electroless plating using hydrazine hydrate as reductants was found with many crackings on it from SEM photos. The electroless alloys using sodium hypophosphite as reductants and ammonium sulfate as a buffer agent does not contain any crackings. The deposition rate is approximately 10-14 μm/hr. In addition, the percentage of iron and phosphorus in deposits are respectively approximately 2-6 wt.% and 8-10 wt.%. Moreover, composition and the deposition rate of the electroless Ni-Fe-P alloys depend on pH in the bath. The structure of as-plated alloys at all conditions is mainly amorphous. The crystallization behavior of Ni-P-Fe alloys with heat treatment were studied by using X-ray diffractometry. Moreover, the anti-corrosive properties of Ni-Fe-P alloys were measured with a potentiostat.

碩士
國防大學中正理工學院
應用化學研究所
95
In order to protect the environment, a water-borne inorganic Zinc-rich silicate paint is developed in this study. Nano-sized zinc dust (ca. 35 nm) is used in this recipe instead of and mix of micro-sized zinc particle (ca. 7.5 μm). The film formations are accomplished by either coating or spray painting. The influence of Zinc particle sizes (nano or micro scale) on anticorrosion performance and film morphology are compared and the process parameters are thus obtained. Our results show that the effect of H14N on the dispersion degree can be effective. After exposure time of 690 hr, the presence of local rusts areas for all of the samples with or without H14N anionic dispersant are over 30%. It is obvious that the effect of H14N on the anticorrosion is negligible. The nano-sized Zinc particles and water-bone inorganic silicate paint were mixed with a wet grinding machine, and than were sprayed painting coated samples. Our SEM results show that the nano-sized Zinc particles of all samples disperse very well. It is also found that the dispersion degree can be effectively verified by wet grinding and spraying machines and dispersion analyzer. The EIS data show that the anticorrosion mechanisms are different between paints with nano-sized Zinc and those with micro-sized Zinc. Nano-sized Zinc paint protects the metallic surface by acting as a physical barrier, the appearance of sample does not change, the rust only presents on the carved part. Micro-sized Zinc paint protects the metallic substrate by sacrificial cathode protection mechanism. The adhesion between paint and substrate for nano-sized Zinc paint is superior to micro-sized Zinc paint. The adhesion datum determined according to the ASTM 3359 Standard for nano-sized Zinc paint is 5B.

碩士
國立臺灣師範大學
高階經理人企業管理碩士在職專班(EMBA)
105
Sewage system is an essential element of a modernized public infrastructure, it is also an index of civility and quality of life in the municipality. Recently, in order to properly process sewage, Taiwan’s government separated rainwater pipelines from sewage pipelines to divert drainage flow into its respective processing plants. As a result, the sewage is no longer subject to dilution by the rainwater and the concentration of chemicals has vastly increased in the sewage pipes. The material constructs the sewage pipes and processing plants is mainly cement concrete. It is very vulnerable to erosion which shortens its life expectancy. Both household and industrial sewage tend release hydrogen sulfide, which then oxidizes to sulfuric acid that causes erosion of cement sewage pipes. The cement pipes will expand, crack and eventually collapse. During the early stage designing the sewage pipelines, the anti-corrosive materials should be considered for the protection of the concrete surface from sewage. In this project we look into different anti-corrosive materials such as Polyvinyl Chloride (PVC) and High Density Polyethylene (HDPE) anti-corrosive lining, which are used to prolong the lifetime of cement sewage pipeline. If these protective measures are effective in prolonging the lifespan of sewage pipes up to twice as long, it can save up to trillions of dollars in expenditure on reconstruction for our generations to come. This report aims to put forth guidelines and reference for pipeline construction by analyzing the causes of pipe corrosion and comparing the quality and lifespan of domestic and foreign anti-corrosive materials and their respective costs.

博士
國立交通大學
材料科學與工程學系所
103
Generally, polymers are light-weight, flexible, low-cost and easy for process. However, polymers exhibit weak mechanical strength, low thermal and electronic conductivity and poor barrier properties. Fabricating composite materials is an economic way to promote the above shortcomings of polymers. In this thesis, we imports inorganic materials (carbon nanotube and boron nitride) into polymer matrix as fillers. The researches have been reported as three parts: In the first part of this thesis, we present a valuable in situ fabrication process for synthesizing high electrical conductive polyimide/multiwalled carbon nanotube (PI/MWCNT) composite films. The success of this process was achievedthe addition of 2,6-diaminoanthraquinone (DAAQ). The DAAQ is not only an excellent dispersion agent to stably disperse pristine MWCNTs in solvent but also a monomer to directly synthesize PI. The strong interaction between DAAQ with MWCNT was verified by FTIR, UV–Vis, Raman, and fluorescence spectra. The highest value of electrical conductivity of 55.6 S/cm are achieved by the PI composite containing 40 wt.% of MWCNT. Moreover, the electrical conductivity of this film further enhanced to 106 S/cm after the thermal compression process. The MWCNT content at the percolation threshold of conductivity is 0.50 wt.% (or 0.32 vol.%) and the critical exponent is equal to 2.52. The developed in situ fabrication process through DAAQ-derived molecules can also be applied to synthesize other polymers requiring diamine structure. In the second part of this thesis, anti-corrosive polyimide/hexagonal boron nitride (PI/h-BN) compositefilms were prepared with different monomers to offer different polymer backbone rigidity: rigid and soft. In PI/h-BN composite films, different configurations of polymers show different crystallinity trends of the polymer matrix. In our study, the degree of crystallinity in rigid polymer decreases with increasing of the BN content; in flexible polymers it is independent of the BN content. It is worth noting that BN in different PI matrices can effectively enhance the protection of steel from corrosion. With a flexible PI matrix, the PI/h-BN coating exhibited better resistance to water vapor and better anti-corrosion. Only 5 wt.% of h-BN in the composite is enough to offer high anti-corrosion, a positive corrosion voltage In the third part of this thesis, we fabricated polyurethane/boron nitride (PU/BN) composites films via chemical reacting with OH group of hydrolyzed boron nitride (BN) and methylene diphenyl diisocyanate (MDI) as monomer of PU. The covalent bonding of PU and BN enhances the mechanical properties and thermal conductivities. Moreover, because of the excellent compatibility of PU and BN, the degree of phase separation (DPS) is decreasing with adding hydrolyzed BN into PU matrix. The thermal conductivity of PU/BN composite films up to 2.93 w/Km with 50 wt.% hydrolyzed BN.

碩士
國立臺灣海洋大學
機械與機電工程學系
104
Recently, Ti6Al4V alloy is one of the most popular human body’s implant material in the bio-medical application. In order to decrease the most caused by the blood on physiological fluid contact of Ti6Al4V alloy in the human body, a diamond-like carbon film is coated on the Ti6Al4V alloy to enhance wear resistance and anti-corrosion capability. Due to the low adhesion between diamond-like carbon film and Ti6Al4V alloy, an interlayer of amorphous silicon which can increase the adhesion between them is necessary. However, when the film is used in the human body, the interlayer will occur crevice corrosion and delamination. In this study, titania-silica hybrid composite films were built on Ti6Al4V alloy by sol-gel dip coating technique. Titanium element was originated from TBOT and Silicon element, from TEOS and MTES. The compositions of the composite films were changed by adjusting the Ti/Si ratios of the precursor solutions, and then, sintered at 650 oC under an argon atmosphere. An a-Si coated sample was also prepared as a benchmark. The surface and mechanical properties of titania-silica hybrid composite films were evaluated by using scanning electron microscopy (SEM), atomic force microscopy (AFM), scratch test, and nano-indentation. The composition and structure of titania-silica hybrid composite films were investigated by using thermogravimetric analyzer (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectrometer (XPS). The results showed that an appropriate Ti/Si ratio of the titania-silica hybrid composite films can increase the hardness, in the mean time, significantly promote the adhesion and anti-corrosion capability of the coated-Ti medical alloy compared with the traditional a-Si coated-one.

博士
國立臺灣科技大學
應用科技研究所
106
As part of tremendous efforts towards exploring stable alternatives for replacing the carbonaceous materials, engineering of both the catalysts and their supports towards more resilient platinum catalysts can potentially improve the activity and durability of the electrocatalysts for fuel cell catalysis and significant cost savings. This dissertation is mainly concerned with design, synthesis and characterization of oxide supported platinum catalyst. This is of great importance for both lengthening the operation life and at the same time ensuring the reliability, as well as reducing the cost in the life cycle of PEMFC. Well regulated Magnéli phase oxide support, provides various advantages in terms of conductivity and surface area. The later in particular opens the avenue for highly dispersed and well-anchored Pt catalyst particles over their respective support. The first part of this work emphasized on “High surface area Ti4O7 support material for oxygen reduction reaction. PEG-400 and glucose respectively were used as reducing agents for precursors, namely, Ti (IV) ethoxide and titanium oxide (anatase). The results revealed that pure Ti4O7 phase was successfully fabricated in the former (PEG as reductant) while the later (glucose as reductant) still contains rutile as a dominant phase. High specific surface area was achieved ranging from 135 and 160 m2/g using PEG and Glucose as reductant respectively. Moreover, different ways of removing amorphous carbon residue (6-8 wt. %) in the attained Ti4O7 were also tested using various acid and base treatments. However, carbon residue still cannot be completely removed. Concurrently, sovlothermally prepared anatase precursor was also treated with NaCl before being subjected to freeze drying technology followed by hydrogen reduction at high temperature calcination. However, the acquired Ti4O7 is of limited surface area (2 m2g -1), which also deters its application towards ORR in fuel cell application. The second part of this work is the immediate extension of the first but with a different approach for improvement.” It mainly focuses on the synthesis and characterization of structurally ordered intermetallic Pt3Ti, supported on oxygen deficient titanium oxide, which evolved in situ during the high temperature treatment. A simple strategy was developed to deposit Pt on TiO2 uniformly with polyaniline via a simple modified oxidative polymerization technique followed by high temperature calcination before oxide supported ordered intermetallic Pt3Ti was successfully fabricated. The electrochemical measurement results indicated that the resulting electrocatalyst displayed highly enhanced specific activity (41.6 µA cm-2) as compared to Pt/C (JM 20) with value of 15.7 µA cm-2. The increase in electrocatalytic activity is ascribable to a change by geometric effects, which resulted from smaller lattice constant and shorter neighboring Pt-Pt bond length as compared to its fcc counterpart (as synthesized and Pt/C). The stability test also revealed that the optimal catalyst has shown a gain of 16 % in terms of ECSA; while the commercial based catalyst lost 65 % of its original value, after 2000 potential cycles. This extraordinarily large stability in harsh acidic environment originates from remarkable thermodynamic stability of Pt3Ti due to its high heat of formation. Furthermore, since oxidation is the major deactivation mechanism during long-term operation, inclusion of titanium in the pt lattice raises the oxidation potential for platinum. The third part is concerned with Sodium Chloride mediated transformation of titania towards Magnéli phase supported ordered intermetallic Pt3Ti. This section partly makes use of the fact that an increase of the number of surface atoms relative to the bulk would be achieved by minimizing the size of the particles down to the nanoscale. The strategy not only increasse the surface energy but also reduce the phase-transition temperatures and brings about stabilization of high-temperature phases at relatively lower temperatures. The structural analysis results disclosed that apart from ordered intermetallic Pt3Ti phase, the required Magneli phase oxides, such as Ti3O5, were also evolved at a shorter reaction time in the presence of NaCl. However, this costs rapid increase in Pt crystallite size (about 30 nm) even at lower temperature, (750 °C). Hence, an interplay between the merit (faster phase transformation) and demerit (rapid particle growth) have been sought by controlling the heating stage during the course of calcination. By employing two heating stages, the required oxide supported ordered intermetallic alloys, with smaller Pt crystallite size (about 12-18 nm) have been successfully synthesized when annealed at even higher temperature, 850-950 °C. Optimizations of temperature were carried out in the entire works. Characterizations of the formation of Magneli phase oxides concurrently with these alloys, was investigated. The electrochemical measurement results demonstrate that the optimal catalyst has shown a specific activity of 38.6 µA cm-2, over twice that of commercial based catalyst. The optimal catalyst also demonstrated remarkable resistance against corrosion with only 5 % loss in terms of ECSA. The current work provides feasible approach that can be extended to other technological applications by alloying precious metals with less precious ones to prepare more ordered and corrosion-resistant materials. Keywords: ORR, SMSI, d-band vacancies, intermetallic compound, Ti4O7, PEMFCs

碩士
國立臺灣海洋大學
機械與機電工程學系
102
Amorphous titanium oxycarbide (a-TiCxOy) interlayers were deposited between the fluorinated diamond-like carbon (F-DLC) films and Ti6Al4V substrates by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) technique. The objective is to improve the corrosive drawback of the silicon interlayer and adhesion between F-DLC films and Ti6Al4V substrates. Firstly, the a-TiCxOy films were obtained by using a mixture precursors of titanium tetrachloride (TiCl4) and methane (CH4) gases. Secondly, the DLC film was then deposited on a-TiCxOy films in CH4 gas by the RF-PECVD system. Finally, the F-DLC film was coated on the DLC film by the same CVD system from the precursors of tetrafluoromethane (CF4) and CH4. The structure and surface properties of a-TiCx interlayers were investigated by using X-ray diffraction spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, optical microscope, and scanning electron microscopy. The mechanical properties were evaluated by nano-indentation and the adhesion, by micro-scratch. The corrosion behavior was studied by cyclic voltammetry (CV) in a 0.9 wt.% NaCl physiological solution. An F-DLC coating with a 135 nm a-Si interlayer prepared by physical vapor deposition process was also implemented as a benchmark. The results showed that the anticorrosion capability and the adhesive strength of the F-DLC coatings with an a-TiCxOy interlayer are much better than that with an a-Si one. However, their hardness are lower than that with an a-Si one. The a-TiCxOy interlayer’s thickness increased with increasing flow of CH4. On the contrary, the whole coating’s anticorrosion capability and adhesive strength increased with decreasing CH4 content. The a-TiCxOy interlayers are verified to be beneficial to improve the life of the F-DLC coated Ti6Al4V in physiological conditions.