Дисертації з теми "HEA Coatings"
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1
Aziz, Khan Naveed. "RF Magnetron Sputtered AlCoCrCu0.5FeNi High Entropy Alloy (HEA) and High Entropy Ceramic (HEC) Thin Films." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/24615.
Повний текст джерелаАнотація:
High entropy-based materials in the form of thin films have been of growing interest recently for surface engineering applications due to their exceptional properties including high hardness, superior resistance to oxidation and corrosion, improved thermal stability, and high hydrophobicity. Sputter deposition of thin films comprised of several elements typically requires the use of targets containing multiple elements, making both the chemical composition and microstructure of the resulting films strongly dependent on the process parameters. Therefore, this thesis investigates the growth mechanism, composition variation and key physical properties of AlCoCrCu0.5FeNi high entropy alloy (HEA) and high entropy ceramic (HEC) thin films deposited by radio frequency (RF) magnetron sputtering using advanced characterization methods. The depositions were performed using a single stoichiometric AlCoCrCu0.5FeNi HEA target in non-reactive and reactive modes to explore various high entropy-based materials in the form of metallic HEA and ceramic HEC thin films.
This dissertation explores several key deposition parameters during the thin film growth for the AlCoCrCu0.5FeNi HEA system. The initial studies investigate the deposition of HEA thin films in non-reactive mode using argon only and explored the influence of working pressure and deposition power on the microstructure, composition and physical properties. Subsequent chapters report reactive sputtering deposition with various gas flow fractions (RN) using a combination of argon with nitrogen or argon with oxygen to fabricate ceramic thin films of high entropy nitride (HEN) and high entropy oxide (HEO), respectively. The overall findings elucidate that the modification of deposition conditions could be used to control and tune microstructures and chemical composition which regulate the physical properties of the AlCoCrCu0.5FeNi high entropy-based thin films having important implications for the development of surface protective coatings in the aerospace, energy and nuclear industries.
2
Belous, V. A., S. A. Firstov, V. F. Gorban, A. S. Kuprin, V. D. Ovcharenko, E. N. Reshetnyak, G. N. Tolmachova, and M. G. Kholomeev. "Properties of Coatings Deposited from Filtered Vacuum Arc Plasma with HEA Cathode." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35323.
Повний текст джерелаАнотація:
Ti-V-Zr-Nb-Hf metallic and nitride films were deposited by filtered vacuum arc plasma from a single
equiatomic HEA cathode. The composition, microstructure, mechanical properties, thermal stability and
corrosion properties were investigated.
The deposited metallic film has a two-phase structure with bcc and hcp-lattice. The nitride films were
found to have only an fcc structure. All coatings have nano-grained structures, with grain sizes 5 nm for
metallic and 36 nm for nitride. The nitride coatings have a compressive stress of around – 12,5 GPa, high
hardness ~ 40 GPa and elastic modulus ~ 450 GPa. After annealing in vacuum in range 400-1200 °C, 3 h
for every temperature, hardness decreased to 25 GPa. It was found that both the metallic and nitride coatings
exhibited their best corrosion resistance than steel samples in a 3,5 wt. % NaCl solution. The metallic
coatings showed better corrosion resistance than the nitride coatings.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35323
3
Löbel, Martin, Thomas Lindner, Thomas Mehner, and Thomas Lampke. "Microstructure and Wear Resistance of AlCoCrFeNiTi High-Entropy Alloy Coatings Produced by HVOF." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-230210.
Повний текст джерелаАнотація:
The investigation of high-entropy alloys (HEAs) has revealed many promising properties. HEAs with a high share of Al and Ti are suitable for the formation of lightweight materials. Investigations of the alloy system AlCoCrFeNiTi showed high strength, hardness, ductility, and wear resistance, which makes this special alloy interesting for surface engineering and particularly for thermal spray technology. In this study, the suitability of inert gas-atomised HEA powder for high-velocity-oxygen-fuel (HVOF) thermal spray is investigated. This process allows for high particle velocities and comparatively low process temperatures, resulting in dense coatings with a low oxidation. The microstructure and phase composition of the atomised powder and the HVOF coating were investigated, as well as the wear behaviour under various conditions. A multiphase microstructure was revealed for the powder and coating, whereas a chemically ordered bcc phase occurred as the main phase. The thermal spray process resulted in a slightly changed lattice parameter of the main phase and an additional phase. In comparison with a hard chrome-plated sample, an increase in wear resistance was achieved. Furthermore, no brittle behaviour occurred under abrasive load in the scratch test. The investigation of wear tracks showed only minor cracking and spallation under maximum load.
4
Gupta, Mohit. "Establishment of Relationships between Coating Microstructure and Thermal Conductivity in Thermal Barrier Coatings by Finite Element Modelling." Thesis, Högskolan Väst, Institutionen för ingenjörsvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-3247.
Повний текст джерелаАнотація:
Plasma sprayed Thermal Barrier Coating systems (TBCs) are commonly used for thermal protection of components in modern gas turbine application such as power generation, marine and aero engines. The material that is most commonly used in these applications is Yttria Partially Stabilized Zirconia (YPSZ) because of this ceramic’s favourable properties, such as low thermal conductivity, phase stability to high temperature, and good erosion resistance. The coating microstructures in YPSZ coatings are highly heterogeneous, consisting of defects such as pores and cracks of different sizes which determine the coating’s final thermal and mechanical properties, and the service lives of the coatings. Determination of quantitative microstructure–property correlations is of great interest as experimental procedures are time consuming and expensive. Significant attention has been given to this field, especially in last fifteen years. The usual approach for modelling was to describe various microstructural features in some way, so as to determine their influence on the overall thermal conductivity of the coating. As the analytical models over-simplified the description of the defects, various numerical models were developed which incorporated real microstructure images.This thesis work describes two modelling approaches to further investigate the relationships between microstructure and thermal conductivity of TBCs. The first modelling approach uses a combination of a statistical model and a finite element model which could be used to evaluate and verify the relationship between microstructural defects and thermal conductivity. The second modelling approach uses the same finite element model along with a coating morphology generator, and can be used to design low thermal conductivity TBCs. A tentative verification of both the approaches has been done in this work.
5
Magens, Ole Mathis. "Mitigating fouling of heat exchangers with fluoropolymer coatings." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287467.
Повний текст джерелаАнотація:
Fouling is a chronic problem in many heat transfer systems and results in the need for frequent heat exchanger (HEX) cleaning. In the dairy industry, the associated operating cost and environmental impact are substantial. Antifouling coatings are one mitigation option. In this work, the fouling behaviour of fluoropolymer, polypropylene and stainless steel heat transfer surfaces in processing raw milk and whey protein solution are studied. Methodologies to assess the economics of antifouling coatings are developed and applied. Two experimental apparatuses were designed and constructed to study fouling at surface temperatures around 90 °C. A microfluidic system with a 650 x 2000 µm flow channel enables fouling studies to be carried out by recirculating 2 l of raw milk. The apparatus operates in the laminar flow regime and the capability to probe the local composition of delicate fouling deposit $\textit{in-situ}$ with histological techniques employing confocal laser scanning microscopy. A larger bench-scale apparatus with a 10 x 42 mm flow channel was built to recirculate 17 l of solution in the turbulent flow regime which is more representative of conditions in an industrial plate HEX. Experimental results demonstrate that fluoropolymer coatings can reduce fouling masses from raw milk and whey protein solution by up to 50 %. Surface properties affect the structure and composition of the deposit. At the interface with apolar surfaces raw milk fouling layers are high in protein, whereas a strongly attached mineral-rich layer is present at the interface with steel. Whey protein deposits generated on apolar surfaces are more spongy and have a lower thermal conductivity and/or density than deposits on steel. The attraction of denatured protein towards apolar surfaces and the formation of a calcium phosphate layer on steel at later stages of fouling are explained with arguments based on the interfacial free energy of these materials in water. The financial attractiveness of coatings is considered for HEX subject to linearly and asymptotically increasing fouling resistance and using a spatially resolved fouling model. An explicit solution to the cleaning-scheduling problem is presented for the case of equal heat capacity flow rates in a counter-current HEX. Scenarios where the use of coatings may be attractive or where there is no financial benefit in cleaning a fouled exchanger are identified. Finally, experimental data are used to estimate the economic potential of fluoropolymer coated HEXs in the ultra-high-temperature treatment of milk. In the considered case, the value of a fluoropolymer coating inferred from the reduction in fouling is estimated to be around 2000 US$/m².
6
Ibrahim, Hamdy Ibrahim. "Bioresorbable Magnesium-Based Bone Fixation Hardware: Alloy Design, Post-Fabrication Heat Treatment, Coating, and Modeling." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1503678544356525.
Повний текст джерела
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Nutter, Brian Vincent. "Thermal Analysis of a Vaporization Source for Inorganic Coatings." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/36319.
Повний текст джерелаАнотація:
A thermal analysis of a conventional vaporization source by finite difference methods, including experimental validation, is presented. Such a system is common to industries whose chief concern is the precipitation of inorganic coatings. Both the physical and the model systems are comprised of a number of layers, or strata, arranged in a rectangular configuration. The model strata represent the component and deposition materials of the physical vaporization source. The symmetry and simplistic geometry of the operational source permit the use of a two-dimensional model, thereby neglecting gradients in the third dimension. The production unit, as well as the numerical model, experience various modes of heat transfer, including radiation, convection, conduction, internal generation, and phase change. Moreover, the system inputs are time-dependent.
The numerical model is subsequently compared to and validated against both simplistic case studies and the physical production system. Data collected from the operational deposition source is examined and analyzed in comparison to corresponding information generated by the numerical model. Sufficient agreement between the data sets encourages the utilization of the numerical model as a practical indicator of the subject system's behavior.
Finally, recommendations for modifications to the physical vaporization source, yielding practical improvements in temperature uniformity, are evaluated based on the predictions of the validated numerical model. The goal is the attainment of an ideally uniform temperature distribution that would correspond to highly desirable performance of the process vaporization system.Master of Science
8
Sethi, Sunny. "Carbon Nanotube Based Functional Superhydrophobic Coatings." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271346171.
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Zhang, Ao. "Diamond coatings as a heat spreader for MRI compatible electrode devices." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1470136547.
Повний текст джерела
10
Yan, Jin. "Aspects of instrumented indentation with applications to thermal barrier coatings." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 177 p, 2007. http://proquest.umi.com/pqdweb?did=1397913961&sid=17&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Повний текст джерела
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Nikhilanandhan, Ganendra S. "Conformal coating of islets of Langerhans in HEMA-MMA." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ45898.pdf.
Повний текст джерела
12
Collins, John Graham. "Production and characterisation of a ceramic insulating coating for a heat resistant alloy." Thesis, University of Sheffield, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363389.
Повний текст джерела
13
Nguyen, Thierry Huu Chi. "CMZP and Mg-doped Al2TiO5 Thin film Coatings for High Temperature Corrosion Protection of Si3N4 Heat Exchangers." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36628.
Повний текст джерелаАнотація:
Silicon nitride (Si3N4) is a potentially good ceramic material for industrial heat exchangers. However, at elevated temperatures and in coal combustion atmospheres its lifetime is severely reduced by oxidation. To increase its corrosion resistance, the formation of a protective oxidation barrier layer was promoted by the deposition of oxide thin films. Homogeneous and crack-free oxide coatings of calcium magnesium zirconium phosphate (CMZP) and magnesium doped aluminum titanate (Mg-doped Al2TiO5) were successfully deposited on Si3N4 using the sol-gel and dip-coating technique. Coated and uncoated samples were then exposed to a sodium containing atmosphere at 1000*C for 360 hours to simulate typical industrial environment conditions. Structural post-exposure analyses based on weight loss measurements and mechanical tests indicated better corrosion resistance and strength retention for CMZP coated Si3N4 compared to as received and Mg-doped Al2TiO5 coated Si3N4. This difference was attributed to the protective nature of the corrosion layer, which in the case of CMZP, significantly impeded the inward diffusion of oxygen to the Si3N4 surface.Master of Science
14
Shepardson, Kevin W. "Diffusion and Phase Change During Heat Treatment of Ni-B Coatings on Steel." Digital WPI, 2008. https://digitalcommons.wpi.edu/etd-theses/416.
Повний текст джерелаАнотація:
Nickel-boron coatings are used to improve friction and wear properties (and, in some cases, corrosion resistance). The nickel-boron coating investigated here is 5-6 wt% boron, and is deposited by electroless plating on a 1018 steel substrate. It is amorphous as-plated, and heat treatment is used to crystallize the coating to improve its hardness. To better understand and predict the effects of heat treatment, samples that had been isothermally annealed at various temperatures from 500ºC to 800ºC for either 2h or 5h were examined by several methods to determine the diffusion effects taking place during annealing. Samples were examined by XRD, both at the coating surface and at multiple depths within the coating. Optical microscopy and SEM were used to view the structure of the coating in cross-section. Cross sections were etched and examined by optical microscopy and SEM, as well as EDS, which was used to develop a Ni-Fe composition profile at the coating-substrate interface. Microhardness measurements were taken and used to develop microhardness profiles. Additional samples were annealed to investigate boron oxidation at the coating surface. Based on the data, there is a reduced amount of Ni3B near the outer surface of the heat-treated coatings, with the thickness of the resultant γ-Ni layer increasing with annealing time and temperature, from 2.4 to just over 13 µm. This low-boron region indicates that boron is diffusing out through the surface of the coating and oxidizing, which the literature indicates should result in the formation of B2O3. Because B2O3 is water-soluble, it is likely that it dissolved during the water quench that concluded most anneals. Diffraction and EDS data also indicate interdiffusion of the nickel in the coating and the iron in the steel substrate. This leads to the formation of a soft interdiffusion layer between the Ni3B coating bulk and steel substrate that appears to be a mix of ferrite and Ni3Fe.
15
Luu, Anton. "Effect of glaze coatings and pressure-heat processing on short-term soft denture liners." [Florida] : State University System of Florida, 1999. http://purl.fcla.edu/fcla/etd/amp7398.
Повний текст джерелаАнотація:
Thesis (M.S.)--University of Florida, 1999.Title from first page of PDF file. Document formatted into pages; contains x, 94 p.; also contains graphics (some colored). Vita. Includes bibliographical references (p. 90-93).
16
Baril-Gosselin, Simon. "Improving Integrally Heated Composite Tooling Through Cold Sprayed Copper Coatings and Heat Transfer Simulations." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24237.
Повний текст джерелаАнотація:
Integrally heated composite tooling (IHCT) is seen as a low cost alternative to autoclave manufacturing of polymer matrix composites (PMCs). IHCTs consist of a composite tool heated by surface heaters; temperature distribution is ensured by a thermally conductive metallic layer. The main original contributions of this thesis was the development of a new method for applying copper coatings onto carbon fibre/epoxy PMCs using pulsed gas dynamic spraying, the production of larger size samples, and the characterisation of the performance of the coatings and laminates obtained. It was shown that this method has potential for producing the thermally conductive layer in an IHCT. Another contribution was the characterisation of parameters affecting temperature distribution across IHCTs through heat transfer simulations, leading to guidelines for IHCT design.
17
PEREIRA, RENATA ARAUJO BARROSO. "EFFECTS OF INTERNAL COATINGS IN TUBES: PARAFFIN DEPOSITION AND HEAD-LOSS IN VISCOPLASTIC FLUIDS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15139@1.
Повний текст джерелаАнотація:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORPETRÓLEO BRASILEIRO S. A.
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Oleos pesados são significativamente importantes no cenário brasileiro e internacional, sendo sua principal característica a alta viscosidade e consequente dificuldade de transporte. Além disso, durante o escoamento destes óleos ocorre a deposição de parafina nas paredes dos oleodutos, particularmente a baixas temperaturas. Esse tipo de petróleo possui características reológicas viscoplásticas, e sob certas condições ainda não muito bem conhecidas, apresentam o fenômeno do deslizamento aparente ao escoar internamente, tendo o potencial de reduzir substancialmente a perda de carga em um escoamento. Neste trabalho foi investigado experimentalmente o deslizamento aparente que ocorre em escoamentos de materiais viscoplásticos bem como foi determinada a tensão cisalhante necessária para descolar uma quantidade de parafina depositada sobre diferentes revestimentos. Devido a uma evidência experimental de que o grau de deslizamento depende de duas propriedades físicas da superfície interna do duto, foram determinadas também a rugosidade e a molhabilidade destas. Foi construída uma planta experimental na qual era possível variar as placas (diferentes revestimentos e rugosidades) que formavam as paredes do canal pelo qual o fluido era forçado a escoar, de forma a se obter a curva vazão x pressão para cada tipo de revestimento. Estes escoamentos foram simulados numericamente supondo ausência de deslizamento. A comparação entre as curvas experimentais e teóricas fornecem uma quantificação do deslizamento ocorrido nos experimentos. Utilizamos um fluido à base de água e um fluido à base de óleo. Foi observado que o deslizamento aparente, existente em escoamentos de materiais viscoplásticos, se manifesta na faixa de baixas tensões adimensionais e que os revestimentos possuem duas funções principais, a da redução da rugosidade e a do aumento da molhabilidade, ambas com o efeito de aumentar o nível de deslizamento e, consequentemente, reduzir a perda de carga, diminuindo os custos operacionais.
Heavy oils are significantly important in the Brazilian and international scenario and its particularity is the high viscosity and consequent difficulty of transport. Also, during the flow of these oils occurs the deposition of paraffin on the pipelines walls especially at low temperatures. This type of oil has viscoplastic rheological characteristics, and under certain conditions not yet well understood, exhibits the phenomenon of apparent wall slip during internal flow, with the potential to substantially reduce the head-loss in a flow system. This study investigated experimentally the wall slip that occurs in the flow of viscoplastic liquids. Moreover, it was also determinated, the wall shear stresses necessary to unstick an amount of paraffin deposited on different coatings. Due to an experimental evidence, the amount of wall slip seems to depend on two physical properties of the internal surface of the pipeline, therefore it was determined also the roughness and wettability of these. A test section was designed and built. Plates with different coatings and roughness constitute the parallel channel which the fluid was forced through in order to obtain the curves of dimensionless average velocity versus dimensionless wall shear stress. These flows were also numerically solved referring to the case of no wall slip. Comparisons between the experimental and numerical results could quantify the amount of wall slip that occurs in the experiments. We used an aqueous solution and oil dispersion. It was observed that the wall slip, that occurs during the flow of viscoplastic materials, manifests itself in the range of low dimensionless wall shear stress and that the coatings have two main functions, reduction of the roughness and increase of the wettability, both with the effect of increasing the amount of wall slip and thus reduce the head-loss, diminishing operational costs.
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Barnett, David L. "EVALUATION OF FIRE-FIGHTING HELMET SURFACE TECHNOLOGY FOR HIGH RADIANT HEAT APPLICATIONS." UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_theses/305.
Повний текст джерелаАнотація:
Protective helmets used by fire-fighters must be designed to minimize the amount of heat transferred to the users head while providing durability, comfort, and affordable costs. This thesis highlights the evaluation of new helmet technology specifically tailored to high radiant heat environments to advance the state-of-the-art in head protection for this application. The research focused on the assessment of the outer shells of helmets and the properties of the surfaces. The development included the evaluation of radiation heat transfer, in a laboratory environment, to various helmet shell surface constructions. Industry standards were considered, and critiqued. Experiments were designed to isolate critical design variables for measurement and evaluation. Custom, purpose-built laboratory apparatus for testing helmets were designed, explained and utilized in the testing of specimens. Additionally, market demands for firefighting helmets were explored. Helmet durability was specifically addressed with abrasion criteria established and the reflectivity effects of the abraded surfaces evaluated. Resulting from this study, new surface technologies were identified for possible development in future helmet designs. Various surface materials, finishes, and coatings were compared and contrasted to current industry state-of-the-art equipment. The knowledge discovered further advanced modern head protection science in aim of increased safety and performance of fire-fighting personnel.
19
Sayee, Mohan Kaushik. "Pool Boiling of FC 770 on Graphene Oxide Coatings: A Study of Critical Heat Flux and Boiling Heat Transfer Enhancement Mechanisms." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71873.
Повний текст джерелаАнотація:
This thesis investigates pool boiling heat transfer from bare and graphene-coated NiCr wires in a saturated liquid of FC 770, a fluorocarbon fluid. Of particular interest was the effect of graphene-oxide platelets, dip-coated onto the heater surface, in enhancing the nucleate boiling heat transfer (BHT) rates and the critical heat flux (CHF) value. In the course of the pool boiling experiment, the primary focus was on the reduction mechanism of graphene oxide. The transition from hydrophilic to hydrophobic behavior of the graphene oxide-coated surface was captured, and the attendant effects on surface wettability, porosity and thermal activity were observed. A parametric sensitivity analysis of these surface factors was performed to understand the CHF and BHT enhancement mechanisms.
In the presence of graphene-oxide coating, the data indicated an increase of 50% in CHF. As the experiment continued, a partial reduction of graphene oxide occurred, accompanied by (a) further enhancement in the CHF to 77% larger compared to the bare wire. It was shown that the reduction of graphene oxide progressively altered the porosity and thermal conductivity of the coating layer without changing the wettability of FC 770. Further enhancement in CHF was explained in terms of improved porosity and thermal activity that resulted from the partial reduction of graphene-oxide. An implication of these results is that a graphene-oxide coating is potentially a viable option for thermal management of high-power electronics by immersion cooling technology.Master of Science
20
Schotter, Daniel Keith 1955. "The effects of heat treatment on microindentation hardness, abrasion and corrosion resistance of electroless nickel coatings." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276928.
Повний текст джерелаАнотація:
A study has been carried out to investigate the effects of heat treatment on microindentation hardness, abrasion and corrosion resistance of Electroless Nickel coatings. In particular, a proprietary coating system, NIKLAD 794 has been investigated. Samples of 4130 steel have been plated according to manufacturer's specifications. The plated samples have then been subjected to an array of heat treatment temperatures and times. Post heat treatment tests have been conducted including Taber Abrasion testing, salt fog chamber testing, and Knoop microindentation hardness testing. Results of the individual tests have been compared to determine the effects of heat treatment on, and the interactions between, the parameters examined.
21
Oldani, V. "HYDROPHOBIC COATINGS BASED ON COMMERCIAL PERFLUOROPOLYETHERS FOR FOULING MITIGATION. APPROACH ON A PILOT HEAT EXCHANGER PLANT." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/331713.
Повний текст джерелаАнотація:
This work concerns the mitigation of fouling in heat exchangers, by means of the modification of the interaction between the foulant particles and the solid surfaces involved in the fouling phenomenon. To achieve this goal, hydrophobic coatings containing commercial perfluoropolyethers (PFPE) and metal oxides were prepared. Specifically, three typologies of coatings were prepared for the protection of stainless steel surfaces: commercial α,ω-inorganic substituted PFPE coatings, multilayer coatings containing the commercial PFPE and metal oxides nanopowders, and hybrid coatings containing sol-gel metal oxides networks and the commercial PFPE. All the coatings prepared were fully characterized in order to assess their morphology, composition and thickness. The wettability of the coatings was measured by contact angle (CA) determination, and all the coatings resulted to be hydrophobic, with CA>120°. The chemical and mechanical stability of all the coatings prepared was investigated by means of particular resistance tests, performed in liquid environments. Hybrid coatings appeared as the most resistant coatings against the erosion induced by chemical aggressive liquids, high temperature liquids (343 K), or shear stresses induced by the flowing of water upon the coated surface (0.17 m/s). The experimentation on a heat exchanger pilot plant confirmed the ability of the hydrophobic hybrid coatings to mitigate crystallization fouling on stainless steel heat transfer surfaces. In the condition adopted (transient flow regime and heat exchanging fluids at temperatures of 291-293 K and 318-323 K), the hybrid coating was able to delay the fouling step of about 200 hours and to promote the removal of the fouling deposits progressively formed on the heat transfer surfaces.
22
Shirsekar, Deepali. "Bidirectional Reflectance Measurements of Low-Reflectivity Optical Coating Z302." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/87467.
Повний текст джерелаАнотація:
Black coatings essentially absorb incident light at all wavelengths from all directions. They are used when minimal reflection or maximum absorption is desired and therefore are effective in applications that require control of stray light. Our motivation stems from the use of black coating Lord Aeroglaze® Z302 in aerospace and remote sensing applications and the desire to support the development of bidirectional spectral models that can be used successfully to predict the performance of optical instruments such as telescopes. The bidirectional reflectance distribution function (BRDF) is an indispensable parameter in the optical characterization of such coatings. The current effort involves investigation of the BRDF of the commercial black coating Aeroglaze® Z302. An automated goniometer reflectometer has been designed, fabricated and successfully used for performing the BRDF measurements of Z302 at visible and ultraviolet wavelengths and at both polarizations. The current contribution involves study of Z302 samples prepared at different thicknesses and by different methods, which provides insight about influence of surface roughness on BRDF of Z302.Master of Science
When light falls on different materials it undergoes various phenomenon such as reflection, refraction, absorption and scattering. The amount of each phenomenon varies with the optical nature of a material as well as the wavelength and direction of the light. Therefore, understanding the optical properties of materials at various wavelengths of light is necessary for effectively using those materialsin specific applications which require light to be efficiently reflected or absorbed. This research studies an optical property known as Bidirectional Reflectance Distribution Function (BRDF) of a black coating called Lord Aeroglaze Z302. Black coatings are materials that ideally absorb almost all light that falls on them irrespective of the light’s direction and wavelength. They are used in applications where maximum absorption of light is required. One such application which relates to the motivation for this research is absorbing unwanted light in instruments used in space such as telescopes and radiometers. Z302 is used in the Clouds and the Earth’s Radiant Energy System (CERES) instruments developed by NASA. BRDF is an important parameter which gives information about all other optical properties of a surface and can be used to know optical performance of that surface. The current work describes the experiments and an automated device developed, called reflectometer, to measure the BRDF of Z302 at different angles and wavelengths of light. The results are reported for different thickness samples of Z302 coating, and two different wavelengths of light that belong to the visible and ultraviolet spectrum of light.
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Edwards, Bronwyn K. "Effect of combined nanoparticle and polymeric dispersions on critical heat flux, nucleate boiling heat transfer coefficient, and coating adhesion." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53288.
Повний текст джерелаАнотація:
Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 123-126).
An experimental study was performed to determine thermal performance and adhesion effects of a combined nanoparticle and polymeric dispersion coating. The critical heat flux (CHF) values and nucleate boiling heat transfer coefficients (HTC) of nickel wires pre-coated using 1.0% alumina, 0.1% alumina, 500ppm polyallylamine hydrochloride (PAH), and 0.1% alumina combined with 500ppm PAH dispersions were determined using the pool-boiling method. The adhesion of 0.1% alumina and combined 0.1% alumina and 500ppm PAH coatings was evaluated using the tape and modified bend test methods. Results of the pool boiling experiments showed that the wire heaters pre-coated with combined 0.1% alumina and 500ppm PAH dispersion increase the CHF in water by -40% compared to bare wire heaters, compared to an enhancement of -37% with a 0.1% alumina coating. The combined 0.1% alumina and 500ppm PAH dispersion degrades the wire HTC by less than 1%, compared to a degradation of over 26% with a 0.1% alumina coating. Results from the tape test indicate qualitatively that the combined 0.1% alumina and 500ppm PAH dispersion coating adheres better than the 0.1% alumina nanoparticle coating. Results from the modified bend test showed that the combined 0.1% alumina and 500ppm PAH dispersion coating did not fail at the failure strain of the 0.1% alumina nanoparticle coating (8.108x 10-4). The addition of PAH to alumina nanofluid for creating a nanoparticle coating through boiling deposition was found to improve both coating thermal performance and adhesion over the pure alumina nanofluid.
by Bronwyn K. Edwards.
S.M.and S.B.
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SIQUEIRA, GONÇALO. "Caracterização microestrutural, mecânica e tratamento térmico da liga AA-6082 obtida pelo processo de conformação por spray." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10151.
Повний текст джерелаАнотація:
Made available in DSpace on 2014-10-09T12:35:20Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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SARANG, SANJAY S. "METHACRYLATE AND Ca-ALGINATE POLYMERS AS BARRIER COATINGS FOR PROTECTION AND CONTROLLED RELEASE OF VITAMIN C." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1078246935.
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Priest, Matthew. "Synthesis of reactive element-modified aluminide coatings on single-crystal Ni-based superalloys by a pack cementation process a thesis presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=26&did=1760523421&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1254926883&clientId=28564.
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Корнієнко, Анатолій Олександрович. "Формування триботехнічних властивостей композиційних електролітичних покриттів на основі нікелю створенням градієнтних структур. Автореферат дисертації на здобуття наукового ступеня кандидата технічних наук". Thesis, Національний авіаційний університет, 2007. http://er.nau.edu.ua/handle/NAU/35678.
Повний текст джерелаАнотація:
Дисертацію присвячено розробленню градієнтних композиційних електролітичних покриттів зміцнених макро- та наночастинками з керованими триботехнічними властивостями. Проведено аналітичні дослідження напружено-деформованого стану одно- та багатошарових градієнтних КЕП, навантажених силами тертя. Експериментально встановлено оптимальні щодо зносостійкості будову та режими нанесення КЕП Ni-SiC. Визначено вплив кількості та розміру частинок наповнювача на триботехнічні властивості покриттів. Проведенням експериментальних досліджень впливу градієнта будови КЕП на триботехнічні властивості встановлено, що більш високою зносостійкістю характеризуються градієнтні КЕП з “прямим” градієнтом будови, що узгоджується з теоретичними розрахунками напружено-деформованого стану. Дослідженнями встановлено, що із введенням одночасно макро- та наночастинок в КЕП значно підвищується зносостійкість таких покриттів. Показано, що оплавленням покриттів Ni-SiC, які містять додатково бор, можна значно підвищити їх фізико-механічні властивості та зносостійкість. При цьому для оплавлення більш ефективним є застосування лазера, а створення дискретно-оплавлених покриттів дозволяє отримати значно вищі триботехнічні властивості порівняно з повністю оплавленими покриттями.Thesis is aim at development of gradient composition electrolytic coatings hardened by macro- and nanoparticles with the guided tribotechnical properties. Analytical researches of the tensely deformed state of single- and multi-layered gradient CEC loaded with forces of friction are conducted. The opti-mum structure and parameters process of CEC Ni-SiC are experimentally established in relation to wear-proofness. Influencing of amount and size of particles of stuff on tribotechnical property of coatings is determined. Experimental researches of influencing of gradient of structure of CEC are conducted on tri-botechnical property. It is established that the higher wearproofness is characterize gradient CEC with the “direct” gradient of structure, that conforms to the theoretical calculations of the tensely deformed state. Researches is established, introduction simultaneously of macro- and nanoparticles into CEC raise wear-proof of such coatings. It is established, meltback of coatings Ni-SiC, which contain the boron additional-ly, it is possible considerably to raise their physical-mechanical properties and wearproofness. Thus for meltback more effective is application of laser, and the creation of discretely meltback coatings allows to get considerably higher tribotechnical properties comparatively with fully meltback coatings
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Wang, Xu. "The influence of process parameters and heat treatment on the microstructure and properties of electrodeposited chromium nickel iron coatings." Thesis, Glasgow Caledonian University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309387.
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Gardon, Ramos Marc. "Titanium Dioxide coatings obtained by Thermal Spray technlologies and their functional application." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/128199.
Повний текст джерелаАнотація:
The main subject of this thesis is the fabrication of functional titanium dioxide coatings by means of Atmospheric Plasma Spray (APS) and Cold Gas Spray (CGS). Functional role may be understood as the capacity of TiO2 surfaces to respond in a determined way under certain conditions.
Firstly, conventional coating processes, sensing mechanisms and overall efficiencies were deeply studied. As regards to experimental results, it was observed that H2 contained in the plasma mixture could reduce TiO2 towards non stoichiometric or stoichiometric compounds such as titanium sub-oxides (TiO2-x) or Magnéli Phases (TinO2n-1) respectively during the in-flight of the particles. Large accumulation of oxygen vacancies in the crystal lattice of rutile led to a donor level to the conduction band. Therefore, a corrosion-resistant ceramic material with a low electrical resistivity was obtained on ceramic tiles. This unexpected procedure led to deposit APS TiO2-x / TinO2n-1 coatings on stainless steel and apply them in electrochemical bi-polar batteries. Then, from the created feedback thin stainless steel and aluminium films, carbon-polymer composites or nickel foams as common standard electrode materials were selected and coated.
Produce the active layer of a metal oxide gas sensor using APS fed by TiO2 was still a target to be accomplished. With the aim of offering more innovation to conventional metal oxide sensors, it was determined to build-up the sensing layer on a thin polymeric flexible substrate. It was possible to reach certain spraying conditions that avoided thermal degradation of the polymer. Furthermore, heterogeneous disposition of the coating, where some areas were coated and certain spots uncoated provided electric contact between the electrodes and structure that eased elastic deformation of the film. Satisfactory performances were obtained testing the response of the device in front of a target gas and radiation.
Thenceforth, transition to thermally less-aggressive technologies was carried out. It was decided to focus the efforts on CGS, which does not require melting the material for being deposited. Subsequently, nanostructured anatase was used as feedstock in order to achieve photocatalytic layers with large specific surfaces for applying them in the degradation of different contaminants. It was used a powder able to create chemical bonds with the substrate and among the particles at the impact. Unfortunately, feeding system was repeatedly clogged because of the high agglomerating capacity of the powder. Blends were prepared with copper and microstructured TiO2 that flowed appropriately so as to avoid the obstruction of the pipelines. First, Cu/nano-TiO2 coatings were deposited using spraying conditions that favoured the deposition of nanostructured anatase at the top surface, which assured the development of the photocatalytic process. Samples successfully degraded toluene in gaseous phase. On the other hand, micro-TiO2/nano-TiO2 blend was not suitably deposited onto steel. Ceramic particles may not deform plastically. Thus, chemical bonds with the substrate and among particles had to be boosted for building-up the coatings. Substrate surface based on APS TiO2-x with controlled roughness provided composition, hardness and required geometry for adhering nano-TiO2 particles. In this way, CGS nano-TiO2 coatings were tested for degrading phenol and formic acid in liquid phase. The obtained results equalized or even improved the performance of sol-gel coatings.
Metallic Ti coatings were previously deposited onto the polymer by CGS for afterwards spraying nano-TiO2, following the know-how gained in CGS nano-TiO2 photocatalysts. Again, lower layer acted as a bond coat between the original substrate and nanostructured anatase. Osteblast cultures were tested on PEEK, CGS Ti on PEEK and CGS nano-TiO2 deposited on CGS Ti layer. Higher cell adhesion, proliferation and differentiation were obtained as long as CGS coatings were applied, which leads to an improved bioactivity of polymeric implants.El principal objetivo de esta tesis es la fabricación de recubrimientos funcionales de óxido de titanio obtenidos por Atmospheric Plasma Spray (APS) y Cold Gas Spray (CGS). El rol funcional debe ser entendido cómo la capacidad de las superfícies de TiO2 de responder de una manera determinada ante ciertas condiciones. El H2 contenido en el plasma podía reducir el TiO2 hacia compuestos no estequiométricos o estequiométricos como los sub-óxidos de titanio (TiO2-x) o las fases de Magnéli (TinO2n-1). Una gran acumulación de vacantes de oxígeno en la estructura cristalina del rutilo llevó a la formación de un nivel dador hacia la banda de conducción. Este inesperado procedimiento llevó a producir recubrimientos APS TiO2-x / TinO2n-1 sobre acero inoxidable y aplicarlos como electrodos en baterías bi-polares. Posteriormente, se decidió recubrir con este material electrodos típicamente utilizados como láminas finas de acero inoxidable y aluminio, compuestos de carbono-polímero y espumas de níquel. Con la intención de ofrecer más innovación a los sensores convencionales de óxido metálico, se decidió fabricar la capa activa sobre un sustrato polimérico flexible. Fue posible alcanzar ciertas condiciones experimentales que evitaron la degradación térmica del polímero. Se centraron esfuerzos en CGS, que no necesita fundir el material para producir el recubrimiento. De esta forma, anatasa nanoestructurada se utilizó como materia prima con el objetivo de lograr capas fotocatalíticas con gran superfície específica, capaces de degradar diferentes contaminantes. Se utilizó un polvo capaz de crear enlaces químicos con el sustrato. Se prepararon mezclas con otros polvos con el objetivo de mejorar su fluidez y evitar la obstrucción de las tuberías. Primero, recubrimientos Cu/nano-TiO2 fueron depositados utilizando condiciones que favorecieron el anclaje de las partículas de anatasa en la superfície del recubrimiento. Las muestras degradaron tolueno en fase gaseosa con éxito. Por otro lado, la mezcla micro-TiO2/nano-TiO2 no se depositó sobre acero. Se utilizó un sustrato préviamente recubierto con APS TiO2-x. Estos recubrimientos degradaron con éxito fenol y ácido fórmico en fase líquida. Se decidió incrementar la bioactividad del PEEK (polyetheretherketone). Sin embargo, fue posible anclar partículas de TiO2 sobre el polímero previamente recubierto por Ti mediante CGS, obteniendo recubrimientos gruesos con una buena adherencia. Cultivos de osteoblastos fueron analizados sobre PEEK, Ti en PEEK y nano-TiO2 en PEEK. Se obtuvo una mayor adhesión, proliferación y diferenciación celular a medida que los recubrimientos CGS fueron aplicados.
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Elwin, Gareth Steven. "Atmospheric pressure chemical vapour deposition of the nitrides and oxynitrides of vanadium, titanium and chromium." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322369.
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Kang, Jiyuan. "MORPHOLOGY AND PERFORMANCE CHARACTERIZATION OF INTUMESCENT COATINGS FOR FIRE PROTECTION OF STRUCTURAL STEEL." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1544112058459729.
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Hanief, Nasheeta. "Investigating the heat treatment effects on phase transformations and coating morphology in the Cr-Pt coated system." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13196.
Повний текст джерелаАнотація:
Includes bibliographical references.The Cr-Pt system has been extensively studied in recent decades with the aim of providing a reliable thermodynamic description of the phases shown in the equilibrium phase diagram. The Cr-Pt coated system where Pt layers were deposited onto Cr substrates is investigated in this study with particular interest in the formation of Cr-Pt phases and coating morphology as a function of coating thickness and heat treatment parameters (temperature and time). The main aim of this research was to produce the coated system with properties which can be tailored according to the conditions required by their particular application. The system was investigated using several complementary techniques.
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Alam, Tanvir E. "Experimental Investigation of Encapsulated Phase Change Materials for Thermal Energy Storage." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5632.
Повний текст джерелаАнотація:
Thermal energy storage (TES) is one of the most attractive and cost effective solutions to the intermittent generation systems like solar, wind and other renewable sources, compared to alternatives. It creates a bridge between the power supply and demand during peak hours or at times of emergency to ensure the continuous supply of energy. Among all the TES systems, latent heat thermal energy storage (LHTES) draws lots of interests as it has high energy density and can store or retrieve energy isothermally. Two major technical challenges associated with the LHTES are low thermal conductivity of the phase change materials (PCMs), and corrosion tendency of the containment vessel with the PCMs. Macro-encapsulation of the PCM is one of the techniques to encounter the low thermal conductivity issue as it will maximize the heat transfer area for the given volume of the PCM and restrict the PCMs to get in contact with the containment vessel. However, finding a suitable encapsulation technique that can address the volumetric expansion problem and compatible shell material are significant barriers of this approach.
In the present work, an innovative technique to encapsulate PCMs that melt in the 100-350 oC temperature range was developed for industrial and private applications. This technique did not require a sacrificial layer to accommodate the volumetric expansion of the PCMs on melting. The encapsulation consisted of coating a non-reactive polymer over the PCM pellet followed by deposition of a metal layer by a novel non-vacuum metal deposition technique. The fabricated spherical capsules were tested in different heat transfer fluid (HTF) environments like air, oil and molten salt (solar salt). Thermophysical properties of the PCMs were investigated by DSC/TGA, IR and weight change analysis before and after the thermal cycling. Also, the constrained melting and solidification of sodium nitrate PCM inside the spherical capsules of different sizes were compared to explore the charging and discharging time. To accomplish this, three thermocouples were installed vertically inside the capsule at three equidistant positions. Low-density graphene was dispersed in the PCM to increase its conductivity and compared with pure PCM capsules.
A laboratory scale packed-bed LHTES system was designed and built to investigate the performance of the capsules. Sodium nitrate (m.p. 306oC) was used as the PCM and air was used as the heat transfer fluid (HTF). The storage system was operated between 286oC and 326oC and the volumetric flow rate of the HTF was varied from 110 m3/h to 151 m3/h. The temperature distribution along the bed (radially and axially) and inside the capsules was monitored continuously during charging and discharging of the system. The effect of the HTF mass flow rate on the charging and discharging time and on the pressure drop across the bed was evaluated. Also, the energy and exergy efficiencies were calculated for three different flow rates.
Finally, a step-by-step trial manufacturing process was proposed to produce large number of spherical capsules.
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Schmiesing, Nickolas Charles. "Characterizing the Condensation Heat Transfer Performance of Uniform and Patterned Silica Nanospring-Coated Tubes." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1557767797969861.
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Ahmadi, Moghadam Parham. "Steel Sheet Applications and Integrated Heat Management." Thesis, Högskolan Dalarna, Energiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:du-21446.
Повний текст джерелаАнотація:
Increasing energy use has caused many environmental problems including global warming. Energy use is growing rapidly in developing countries and surprisingly a remarkable portion of it is associated with consumed energy to keep the temperature comfortable inside the buildings. Therefore, identifying renewable technologies for cooling and heating is essential. This study introduced applications of steel sheets integrated into the buildings to save energy based on existing technologies. In addition, the proposed application was found to have a considerable chance of market success. Also, satisfying energy needs for space heating and cooling in a single room by using one of the selected applications in different Köppen climate classes was investigated to estimate which climates have a proper potential for benefiting from the application. This study included three independent parts and the results related to each part have been used in the next part. The first part recognizes six different technologies through literature review including Cool Roof, Solar Chimney, Steel Cladding of Building, Night Radiative Cooling, Elastomer Metal Absorber, and Solar Distillation. The second part evaluated the application of different technologies by gathering the experts’ ideas via performing a Delphi method. The results showed that the Solar Chimney has a proper chance for the market. The third part simulated both a solar chimney and a solar chimney with evaporation which were connected to a single well insulated room with a considerable thermal mass. The combination was simulated as a system to estimate the possibility of satisfying cooling needs and heating needs in different climate classes. A Trombe-wall was selected as a sample design for the Solar Chimney and was simulated in different climates. The results implied that the solar chimney had the capability of reducing the cooling needs more than 25% in all of the studied locations and 100% in some locations with dry or temperate climate such as Mashhad, Madrid, and Istanbul. It was also observed that the heating needs were satisfied more than 50% in all of the studied locations, even for the continental climate such as Stockholm and 100% in most locations with a dry climate. Therefore, the Solar Chimney reduces energy use, saves environment resources, and it is a cost effective application. Furthermore, it saves the equipment costs in many locations. All the results mentioned above make the solar chimney a very practical and attractive tool for a wide range of climates.
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weathers, jeffrey wayne. "COMBINING THE MATRIX TRANSFORM METHOD WITH THREE-DIMENSIONAL FINITE ELEMENT MODELING TO ESTIMATE THE INTERFACIAL HEAT TRANSFER COEFFICIENT CORRESPONDING TO VARIOUS MOLD COATINGS." MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04072005-143359/.
Повний текст джерелаАнотація:
The interfacial heat transfer coefficient is an important variable regarding the subject of metal castings. The error associated with the experimental temperature data must be dealt with appropriately so that they do not significantly affect the resulting interfacial heat transfer coefficient. The systematic and random errors are addressed using a combination of three-dimensional finite element modeling and the matrix transform method, respectively. Experimentally obtained A356 permanent mold casting data was used to estimate the interfacial heat transfer coefficient corresponding to common industrial mold coatings.
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Mahmoudi, Behzad. "Investigation the Effect of Tribological Coatings: WC/a-C:H and Black Oxide on Micropitting Behavior of SAE52100 Bearing Steel." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1444838738.
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Salvatore, Pisasale. "Heat flux measurement device : Designing an experimental system for determining the effectiveness of thermal barrier coating inside a combustion chamber." Thesis, KTH, Maskinkonstruktion (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183999.
Повний текст джерелаАнотація:
This Masters Thesis has been carried out in collaboration with SCANIA CV AB and it concerns the development of an experimental measurement set up to analyze the heat losses in a Diesel engine. This measurement equipment will be used to test a type of coating, called TBC (Thermal Barrier Coating). Scania has been studying this kind of coating for some years and it has been noticed as a way to improve the efficiency of the engine. It is then important for the company to understand the behavior of this coating considering all the combustion’s features of an internal combustion engine. The target of the project has been the replacement of one of the valves of a Diesel engine with a stationary sample holder equipped with a measurement set up in order to measure the heat losses from the combustion chamber. The design has been dimensioned considering the size and the working conditions of a single cylinder test engine at Scania. The concept of the project is the placement of some thermocouples in the holder so that a difference of temperature can be detected and the relative heat flux can be computed. The TBC will be attached to one of the surfaces of the holder in order to test a decrease in the heat loss through the holder itself. The conclusion of the project shows the good operation of the design and a substancial decrease in the heat loss when using the TBC. Scania should continue investigating the behavior of TBC with the use of the same design or a different one which fits different operating conditions of the engine.Detta examensarbete, som har utförts i samarbete med Scania CV AB, handlar om att utveckla en provmetod för att analysera värmeförluster i en dieselmotor. Provmetoden kommer att användas för att undersöka effekten av termiska barriärskikt – TBC (Thermal Barrier Coatings). Scania har under en tid studerat dessa beläggningar, då de har identifierats som ett möjligt sätt att öka motorns verkningsgrad. Det är då viktigt för företaget att förstå hur dessa beläggningar beter sig under de förhållanden som råder i en förbränningsmotor. Målet med detta projekt har varit att ersätta en av ventilerna i en dieselmotor med en stationär provhållare med mätutrustning för att kunna mäta värmeförluster från förbränningsrummet. Provhållaren och omgivande komponenter har dimensionerats utifrån mått och driftpunkter för en encylindermotor på Scania. Termoelement placeras i provhållaren så att temperaturskillnader kan detekteras och värmeflöden beräknas. En av provhållarens ytor kan beläggas med TBC för att kunna mäta förändringen i värmeflöde genom själva provhållaren. Slutsatserna i detta examensarbete är att provhållarens konstruktion fungerar bra i motorn och att det är en väsentlig minskning av värmeflödet genom provhållaren då TBC används. Scania bör fortsätta undersöka TBC med denna konstruktion, eller med en modifierad variant som passar olika driftpunkter.
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Aliyu, Ahmed. "Microstructure and Electrochemical Properties of Electrodeposited High Entropy Alloys Coatings." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5540.
Повний текст джерелаАнотація:
High entropy alloys (HEA) are composed of five or more alloying elements in a nearly equi-atomic ratio. HEAs exhibit high oxidation and corrosion resistance behaviour. In this work, HEA coatings were electrodeposited over mild steel substrate from an aqueous electrolyte bath. Microstructure-corrosion property correlation for as-deposited pristine HEA and HEA-graphene oxide (GO) composite coatings was examined. Four different HEA coating systems were investigated: CrNiCoFeCu, CrNiCoFeMn, AlNiCoFeCu, and AlCrNiCoFeCu HEA coatings. Corrosion behaviour and passive film constitution of CrNiCoFeCu and CrNiCoFeMn coatings were compared, and it was observed that the formation of relatively stable protective Cr, Co, and Mn oxide corrosion products on the surface of the CrNiCoFeMn coating enhanced the corrosion resistance of this coating. In contrast, the formation of Fe, Cr, and Cu oxide corrosion products on the surface of CrNiCoFeCu coating were de-stabilized by the inter-dendritic segregation of the Cu-rich phase leading to the lower corrosion resistance of the CrNiCoFeCu coating. In the case of AlNiCoFeCu and AlCrNiCoFeCu coating, the effect of Cr on the evolution of oxide phase in Al-containing HEA coatings was compared. The formation of a denser and more stable protective oxide layer on the surface of AlCrNiCoFeCu HEA coating resulted in better corrosion resistance performance compared to the AlNiCoFeCu HEA coating, which had a lesser stable and defective protective oxide layer. It was observed that Cr facilitates the formation of other metallic oxides in the passive film, which enhanced its ability to reduce ionic diffusion and improve the corrosion resistance of the Cr containing AlCrNiCoFeCu HEA coating. In the case of CrNiCoFeCu HEA-GO composite coatings, with GO addition, the corrosion current density and corrosion rate reduced. while, the polarization resistance increased, indicating an enhancement in the corrosion resistance property of the CrNiCoFeCu HEA-GO coatings with increase in the GO content. The microstructural characterization of the coatings showed that GO addition into the CrNiCoFeCu matrix resulted in two distinct microstructural changes; one was increase in the Cr-rich phase, and the other was the formation of Cu-rich and Cr-rich layer over the coating surface which can facilitate the formation of the protective oxide film that can hinder the penetration of the electroactive media. These factors, along with the impermeability imparted by GO resulted in enhancement in the corrosion resistance of the CrNiCoFeCu HEA-GO coatings. In the case of CrNiCoFeMn HEA-GO composite coating, morphology of the coating showed that the relative smoothness and compactness of the coatings increased with GO additions. A significant improvement in the corrosion resistance in terms of reduction in the corrosion current density and corrosion rate and increased corrosion potential and polarization resistance was recorded for the GO containing CrNiCoFeMn HEA coatings, which implied enhancement in the corrosion resistance performance of the coatings. Microstructural characterization of CrNiCoFeMn HEA coatings revealed that the GO addition resulted in distinct microstructural changes; with GO addition, the microstructure transformed from a nearly homogenous microstructure to a microstructure containing FeCoNi rich regions embedded in an Mn-Cr rich matrix. The formation of a strongly oxidizing matrix capable of forming relatively stable protective oxide layers and impermeability imparted by the GO were accounted for the observed enhancement in the corrosion resistance of the CrNiCoFeMn HEA-GO composite coatings as compared to the pristine CrNiCoFeMn HEA coating. In the case of AlNiCoFeCu HEA-GO composite coatings, the as-deposited AlNiCoFeCu HEA coating exhibited a granular morphology, which became finer and relatively more compact with increasing in the GO amount. Structural characterization revealed a mixture of BCC and FCC phases, with a fraction of the FCC phase increasing with GO. The coatings' electrochemical properties showed that AlNiCoFeCu HEA-GO composite coatings' corrosion rate progressively decreased with increase in the GO content. Microstructural characterization revealed a highly Al-rich matrix phase and Co, Ni, Cu, and Fe containing dendritic phase in the coating microstructure for the pristine coating. With the addition of GO, the coating microstructure progressively became more compositionally homogeneous. Al distribution between the matrix and dendritic phases became more uniform. Microstructural homogenization reduced the extent of galvanic coupling between phases and uniform distribution of Al, which can form stable and protective alumina phase along with the impermeability properties of GO enhanced the corrosion resistance performance of the AlNiCoFeCu HEA-GO composite coatings when compared to pristine AlNiCoFeCu HEA coating. In the case of AlCrNiCoFeCu HEA-GO composite coatings, the corrosion resistance of the AlCrNiCoFeCu HEA-GO composite coatings was higher than the AlCrNiCoFeCu HEA coating without GO. Corrosion resistance gradually increased with increase in the GO content in the coating. Detailed microstructural characterization revealed that GO addition facilitated microstructural and compositional homogeneity, eliminating localized corrosive attack due to elemental segregation induced galvanic coupling, thereby increasing the corrosion resistance for the AlCrNiCoFeCu HEA-GO composite coatings.
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Min-ChenLo and 羅敏甄. "Evaluation of Heat-Reflection Coatings Applied to Asphalt Pavements." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/8kc66y.
Повний текст джерелаАнотація:
碩士國立成功大學
土木工程學系
102
SUMMARY This study manages to decrease the heat stored in pavements with the materials reflecting radiation wavelengths. Material including TiO2 and ZrO2 are added into adhesives as heat-reflection coatings, which then painted on the surface of asphalt pavements. In order to realize the relationship between reflective materials and radiation wavelengths, reflectivity tests are performed . In addition, it is laboratory lamp test which can probe into more resistant against rutting that we take the advantage of to evaluate cooling effects of asphalt pavements. The experiment indicates that among the reflective material, TiO2 is better than ZrO2. Adding over 10% TiO2 and the coating thickness over 0.6mm could help achieve 80% reflectivity. With regard to the temperature, laboratory lamp test shows that the pavement temperature can be lowered by 12.6°C when the coating thickness is reached to 0.9mm. Due to the reducing temperature of asphalt pavement with coating heat-reflection, it can both reduce the rutting depth by traffic loading and enhance the performance and life of pavements. Key words: heat–reflection, TiO2, reflectivity, laboratory lamp test INTRODUCTION In recent summers, the surface of asphalt pavements may exceed 60°C in Taiwan after a period of exposure to the burning sunlight. This phenomenon not merely affects the thermal comfort of pedestrians significantly but also influences the performance of pavement surfaces. The growing temperature of asphalt pavements may influence strength of pavement, cause permanent rut deformation and hence deteriorate the service quality of the whole pavements. Bearing in mind these problems, it’s imperative to improve the asphalt pavements to defend the high temperature and to lower the blemish of city livings causing from growing temperature. This study will use the heat-reflection coatings applied to dense-grade asphalt pavement to evaluate its effect on pavement and cooling effect for environment. The research organization in Japan has set about the study of the cooling effect of pavement with the basic concepts are coating the heat-reflection on asphalt pavements to reflect some heat radiated from the sun, adding water-retaining material on the pavement surfaces to reduce the heat when the water evaporates, improving pavements to keep away from rutting, and consequently supply pedestrians a more comfortable pathway. From the laboratory lamp test, the pavement temperature is reduced by approximately 13°C with regard to the performance of pavements with heat-reflection coatings, and we can effectively reduce rutting, as the rut depth is approximately half of the conventional dense-graded asphalt pavements. MATERIALS AND METHODS This study measures the reflectivity of coating materials with the UV/VIS/NIR spectrophotometer, under the conditions of first, 5%, 10% and 25% mixed ratio between reflection materials and adhesives and second, 0.6mm, 0.8mm, 0.9mm, and 1mm coating thickness , to find out the proper parameters among them. Then, the study analyses the cooling effect of pavement with coating heat-reflection materials by observing the difference of the depth 2.5cm and 5cm to measure the relativity between depth and its capacity to heat ;and finally evaluate the performance of pavement by rutting test at 60°C, 55°C and 50°C testing temperature. RESULTS AND DISCUSSION The results of reflection test under the conditions that coating thickness between 0.6 and 1mm have showed that the reflectivity of ZrO2 coatings will be rising in sync when the coating thickness enhances, but the reflectivity of TiO2 coatings remains on about 90% no matter how its thickness changes. In addition, if TiO2 added to the adhesives spills over 10 weight percentages, the reflectivity of TiO2 doesn’t show conspicuous variations, nearly reach to a constant value. From the laboratory lamp test, when the coating thickness reaches over 0.7mm, pavements with heat-reflection coatings will achieve the maximum of cooling effect. Furthermore, compared with variations on resistance against rutting, we can find pavements with heat-reflection coatings are much better than conventional pavements, and could improve dynamic stability of pavement for 1.1~1.2 times. CONCLUSION This study presents the performance of heat-reflection coatings on dense-graded pavement. Based on the results of reflectivity test, laboratory lamp test and rutting test, the following conclusions can be described: (1)Under the same percentage of 25 of weight and wavelength 1100nm, the reflectivity of TiO2 and ZrO2 are 90% ＆ 70% showing a better reflective effect compared to the original 4~5% conventional asphalt pavement. In addition, TiO2 surpasses ZrO2 on the effect of reflectivity. (2)When coating thickness reaches above 0.9mm, the reflectivity will achieve its maximum no matter TiO2 or ZrO2, and would not change in sync with its thickness. (3)The coating thickness has remarkable effect on lower the temperature, and will achieve a stable value above 0.7mm. It is 12.6°C lower compared to dense-graded asphalt pavements at the depth of 2.5cm of asphalt pavement. And owing to the effect to reduce the temperature, it could improve dynamic stability of pavement for 1.1~1.2 times than the conventional, significantly enhancing the life of pavement.
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Chiu, Tz-Cheng. "Buckling of graded coatings-A continuum model /." Diss., 1999. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9955144.
Повний текст джерела
42
Hsu, Chin-Chi, and 許進吉. "Surface wettability effects on critical heat flux of boiling heat transfer using nanoparticle coatings." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/52720694857988320636.
Повний текст джерелаАнотація:
博士國立臺灣大學
機械工程學研究所
100
This thesis investigates the effects of various isotropic and interlaced wettability of surface on pool boiling heat transfer. Nano-silica particle coatings were used to vary the wettability of the copper surface from superhydrophilic to superhydrophobic by modifying surface topography and chemistry. Experimental results show that critical heat flux values are higher in the hydrophilic region. Conversely, critical heat flux values are lower in the hydrophobic region. The experimental critical heat flux data of the modified surface do not fit the classical models. Therefore, this study proposes a simple model to build the nexus between the surface wettability and the growth of bubbles on the heating surface. The experimental results revealed that, when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettability of a surface is modified interlacedly, regardless of whether the modified region becomes more hydrophilic or hydrophobic, the critical heat flux is consistently higher than that of the isotropic wettability surface. In addition, this study also observed that CHF was higher when the contact angle difference between the plain surface and the modified region was smaller.
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Ramaswamy, Parvati. "Studies On Thermal Barrier Coatings And Their Potential For Application In Diesel Engines." Thesis, 1999. https://etd.iisc.ac.in/handle/2005/1670.
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Ramaswamy, Parvati. "Studies On Thermal Barrier Coatings And Their Potential For Application In Diesel Engines." Thesis, 1999. http://etd.iisc.ernet.in/handle/2005/1670.
Повний текст джерела
45
Liao, Jun-Yi, and 廖峻毅. "Study of MMA preparation heat / UV dual curing surface hardening coatings." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/06803699947479448273.
Повний текст джерелаАнотація:
碩士國立勤益科技大學
化工與材料工程系
100
In this study, divided into two parts, the first UV-curable acrylic resin were Preparation by using polyurethane acrylate (PUA) and monomer, coating on the PET substrate, and by changing the photoinitiated and monomer content investigate the change in the nature. The second part is by adding methyl methacrylate (MMA) preparation heat / UV dual curing surface hardening coatings, use FTIR spectrometer, Haze meter, Pencil hardness, Cross-cut adhesion analysis of coating properties. The results show photoinitiated 6 % can be used less content to achieve the desired effect, that the pencil hardness is maintained at between 2H ~ 4H, adhesion between the coating and the substrate to reach 5B. Observed in the visible wavelength of 550 nm, all-optical transmittance is maintained at 90.69 ± 1, the haze value is slightly downward trend. By chemical resistance test, the coating chemical resistance are excellent.
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Wu, Wen-Chieh, and 巫文傑. "Studies on Heat Insulation Performance of Construction Coatings Using Porous Media." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/4yjzm8.
Повний текст джерелаАнотація:
碩士元智大學
化學工程與材料科學學系
106
This study is divided into three main parts. The first part provides the research background and objectives. The second part introduces the methodology, experimental design, and comparative analysis of experimental data and market research data. The third part summarizes the main results, answers the research questions, and then discusses and concludes them. In the first part of this study, it took the Energy Dispersive Spectroscopy (EDS) analysis results of the commercial insulation coatings to find out the ratio of calcium carbonate mixture, and use its asserted performance data to set this experiment goal. The second part of this study, it describes about the main experiment - Recipe modification of the new improved insulation coatings, and its Insulation capacity, Weatherability test and the cost analysis. Firstly, this study made use of the method of adding porous materials - Vermiculite to the material formula of the commercial insulation coatings to produce this improved insulation coatings with new formula. The experiment explores the change of the formula ratio of the insulation coatings which is adding Vermiculites, and it can easily adjust the apparent density of the insulation coatings. The decreased apparent density results in an increase of the porosity of the insulation coatings, and facilitates the insulation coatings to improve the heat insulating effect. The insulation effect of this improved insulation coatings with adding 1 wt% vermiculite has been approaching the commercial insulation coatings. And this improved insulation coatings can block the heat source 4 ℃ while it is under the constant temperature 42.5 ℃ heating plate. Secondly, it took the Weatherability test to study how the stability of both the commercial insulation coatings and this improved insulation coatings staying in Taiwan which is the high humidity and high sun exposure environment. The observation of the record in the appearance of size changes shows that this improved insulation coatings can welly adhere on two different outdoor building surface materials. Thirdly, it discusses the cost analysis. After market research it found that the cost of this improved insulation coatings is only 8% of the price of the commercial insulation coatings. The third part summarizes the main results, and to know that this improved insulation coatings is competitive in the market.
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Thibblin, Anders. "Thermal Barrier Coatings for Diesel Engines." Licentiate thesis, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-212298.
Повний текст джерелаАнотація:
Reducing the heat losses in heavy-duty diesel engines is of importance for improving engine efficiency and reducing CO2 emissions. Depositing thermal barrier coatings (TBCs) onto engine components has been demonstrated to have great potential to reduce heat loss from the combustion chamber as well as from exhaust components. The overall aim of this thesis is to evaluate the thermal cycling lifetime and thermal insulation properties of TBCs for the purpose of reducing heat losses and thermal fatigue in heavy-duty diesel engines. In the thermal cycling test inside exhaust manifolds, nanostructured yttria-stabilized zirconia (YSZ) performed best, followed by YSZ with conventional microstructure and then La2Zr2O7. Forsterite and mullite could not withstand the thermal cycling conditions and displayed large cracks or spallation. Two sol-gel composite coatings displayed promising thermal cycling performance results in a furnace test under similar conditions. Thermal cycling testing of YSZ coatings having different types of microstructure, in a furnace at temperatures up to 800°C, indicated that the type of microstructure exerted a great influence. For the atmospheric plasma sprayed coatings, a segmented microstructure resulted in the longest thermal cycling lifetime. An even longer lifetime was seen for a plasma spray–physical vapour deposition (PS-PVD) coating. In situ heat flux measurements inside the combustion chamber indicated that plasma-sprayed Gd2Zr2O7 was the TBC material providing the largest heat flux reduction. This is explained by a combination of low thermal conductivity and high reflectance. The plasma-sprayed YSZ and La2Zr2O7 coatings provided very small heat flux reductions. Long-term testing indicated a running-in behaviour of YSZ and Gd2Zr2O7, with a reduction in heat flux due to the growth of microcracks in YSZ and the growth of macrocracks in Gd2Zr2O7.QC 20170821
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Chen, Chih-Wei, and 陳志瑋. "Mechanical properties of the CrAlSiN and coatings by post-deposition Heat Treatments." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/z34p8x.
Повний текст джерелаАнотація:
碩士明道大學
材料科學與工程學系碩士班
97
In this study, CrAlSiN coatings were synthesized by cathodic arc deposition with Ti and Al88Si12 dual cathodes. The as-deposited coatings were following with post-deposition heat treatment in air and nitrogen atmosphere at the temperature of 400oC for 1 hour. And heat treatment air and nitrogen atmosphere at the temperature of 400oC、600oC、800oC for 1 hour. The annealing treatment has an expected effect on the wear resistance and cutting performance. The CrAlSiN coating subjected to heat treatment in nitrogen atmosphere presented the best wear resistance among the tested coatings. The friction coefficient of the CrAlSiN coatings subjected at 400oC in nitrogen atmosphere was decreased due to the effect of the structure modification. Using thermogravimetric analyzer (TGA), the result turned out the better thermal stability of CrAlSiN coating after annealing treatment in nitrogen if compared to that of all the coatings. Cutting test on the hardened steel without lubricants provides the result of better machining performance of the CrAlSiN coating with annealing treatment in nitrogen. Annealing in N2 gas plays a protective role to modify the structure of the CrAlSiN coating during the heating process.
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Ben, Mahmud T., Tahir I. Khan, and M. A. Farrokhzad. "Heat treatment effect on wear behaviour of HVOF-sprayed near-nanostructured coatings." 2016. http://hdl.handle.net/10454/17079.
Повний текст джерелаАнотація:
NoThis study investigates the effect of heat treatment on changes in microstructure and wear behaviour of WC-NiCr coatings. Two feedstock powders with a similar chemical composition and different particle sizes (near nano-structured WC-17NiCr and microstructured WC-15NiCr) were used. High-velocity oxyfuel spraying technique was used to deposit coatings on to a mild steel substrate using identical spraying parameters. Coated samples were then heat treated in a nitrogen atmosphere at 500 and 700°C. The effect of heat treatment on changes in hardness and wear performance of the coatings was studied using microstructural analysis, micro-hardness indentation and abrasive wear tests. The results showed that the heat treatment increased the hardness of both coatings and a corresponding increase in wear resistance was recorded. The formation of a brittle CrWO4 phase in the microstructured coating resulted in brittle fracture of the coating and this gave lower wear resistance compared to the nanostructured coatings.
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Huang, Chun-Hsien, and 黃俊賢. "Experimental Investigations of Boiling Heat Transfer in an Evaporator Using Silica Nanoparticle Coatings." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/72288303003438244606.
Повний текст джерелаАнотація:
博士淡江大學
機械與機電工程學系博士班
102
This study investigated the effects of silica nanoparticle structures on boiling heat transfer at evaporator. The experiment reveals the effect of thermal performance and bubble growth by nanoparticle structures. The nanoparticle coated structures were used in heating surface of evaporator, and the particles are mesoporous silica nanoparticle (MSM-41), silica nanoparticle (SiO2-S) and silica mircoparticle (SiO2-L), respectively. Comparison of TEOS sol and plat structures are thermal performance with silica particles. The MCM-41 and SiO2-S coated structures contact angle were less than 10 and droplets expanding very fast. The experimental method of using level adjustable thermosyphon (LAT) and two phase loop thermosyphon (TPLT) are researched of boiling heat transfer in atmospheric pressure and sub-atmospheric pressure, respectively. The working fluid is DI water. During a cycle of experiment, the primary heat transfer mechanisms of LAT is sequentially from natural convection, nucleate boiling, thin-film evaporation and dryout in atmospheric pressure, as LAT and TPLT were experimental investigated in pool boiling. The experimental results show that silica nanoparticle structures have a higher heat flux, because they have better surface wettability of hydrophilic. In the atmospheric pressure and surface superheat is 20 oC, the SiO2-S structure heat flux is 677 kW/cm2. SiO2-S structure heat flux is 2.4 times of plat structure. In the sub-atmospheric pressure and surface superheat is 30oC, the SiO2-S structure heat flux is 2391 kW/cm2. SiO2-S structure heat flux is four times of plat structure. The maximum heat flux and minimum thermal resistance in turn were SiO2-S, SiO2-L, MCM-41, TEOS and plat structures. Therefore, nanoparticles coated structures has better thermal performance. The thermal performance of MCM-41 is poor than SiO2-S and SiO2-L, because it is difficult to coated on the heating surface.