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Artykuły w czasopismach na temat "Ceramic absorber coating"
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Shen, Yan, Hong Xiang Wang i Yi Peng Pan. "Effect of Current Density on the Microstructure and Corrosion Properties of MAO Coatings on Aluminum Alloy Shock Absorber". Key Engineering Materials 764 (luty 2018): 28–38. http://dx.doi.org/10.4028/www.scientific.net/kem.764.28.
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In order to improve the corrosion resistance of shock absorber for ships, the alumina ceramic coatings are carried out on the surface of aluminum alloy shock absorber by micro arc oxidation (MAO) technology. The microstructure and anti-corrosion performance of the MAO coatings were investigated experimentally. This paper mainly focuses on the experimental work to determine the effect of current density on the structural characteristics and corrosion resistance of MAO coatings. The results show that the current density has a significant influence on the preparation of MAO coating during the process. The surface of the coating becomes more compact and smooth with the cathode voltage of 7 A.dm-2. Furthermore, the anti-corrosion performance of the MAO coatings can effectively be improved at the current density of 7 A.dm-2.
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Killinger, Andreas, Gerd Gantenbein, Stefan Illy, Tobias Ruess, Jörg Weggen i Venancio Martinez-Garcia. "Plasma Spraying of a Microwave Absorber Coating for an RF Dummy Load". Coatings 11, nr 7 (2.07.2021): 801. http://dx.doi.org/10.3390/coatings11070801.
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The European fusion reactor research facility, called International Thermonuclear Experimental Reactor (ITER), is one of the most challenging projects that involves design and testing of hundreds of separately designed reactor elements and peripheric modules. One of the core elements involved in plasma heating are gyrotrons. They are used as a microwave source in electron–cyclotron resonance heating systems (ECRH) for variable injection of RF power into the plasma ring. In this work, the development and application of an alumina-titania 60/40 mixed oxide ceramic absorber coating on a copper cylinder is described. The cylinder is part of a dummy load used in gyrotron testing and its purpose is to absorb microwave radiation generated by gyrotrons during testing phase. The coating is applied by means of atmospheric plasma spraying (APS). The absorber coating is deposited on the inner diameter of a one-meter cylindrical tube. To ensure homogeneous radiation absorption when the incoming microwave beam is repeatedly scattered along the inner tube surface, the coating shows a varying thickness as a function of the tube length. By this it is ensured that the thermal power is distributed homogeneously on the entire inner tube surface. This paper describes a modeling approach of the coating thickness distribution, the manufacturing concept for the internal plasma spray coating and the coating characterization with regard to coating microstructure and microwave absorption characteristics.
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Bensebaa, F., D. Di Domenicantonio, L. Scoles, D. Kingston, P. Mercier i G. Marshall. "Alternative coating technologies for metal–ceramic nanocomposite films: potential application for solar thermal absorber". International Journal of Low-Carbon Technologies 11, nr 3 (26.03.2014): 370–74. http://dx.doi.org/10.1093/ijlct/ctt081.
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Alkan, Gözde, Peter Mechnich i Johannes Pernpeintner. "Improved Performance of Ceramic Solar Absorber Particles Coated with Black Oxide Pigment Deposited by Resonant Acoustic Mixing and Reaction Sintering". Coatings 12, nr 6 (31.05.2022): 757. http://dx.doi.org/10.3390/coatings12060757.
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Spherical particles based on bauxite-type raw materials, commonly referred to as proppants, are state-of-the-art for particle receivers of concentrated solar power plants. Particles are heated in a fluidized reactor by focused sunlight and are transported to a heat-exchanger or a storage tank. Therefore, key properties for absorber particles are high solar absorptance and mechanical endurance. Due to their relatively poor content of color-giving transition-metal cations, bauxite-derived proppants show limited solar absorptance, which is even deteriorating by long-term heat exposure. A deep-black Cu, Mn, Fe- pigment with a spinel structure was employed to coat standard proppants in order to improve solar absorptance. The coating process was performed by high-energy, high-speed mixing of proppants and small quantities of spinel powders in a resonant acoustic mixer. A continuous powder coating is achieved by electrostatic attraction between the proppant surface and the coating particles. Consolidation and strong attachment of the coating is achieved by the subsequent sintering beyond the spinel melting temperature. Chemical reaction and bonding between spinel coating and proppant lead to the incorporation of Al, Mg and Ti into the spinel structure. Coated bauxite proppants exhibit a significantly improved, long-term stable solar absorption accompanied by a promising abrasion resistance. The presented coating methodology is considered to be scalable to industrial production.
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Ding, Ding, Wenjing He i Chunlu Liu. "Mathematical Modeling and Optimization of Vanadium-Titanium Black Ceramic Solar Collectors". Energies 14, nr 3 (26.01.2021): 618. http://dx.doi.org/10.3390/en14030618.
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The vanadium-titanium black ceramic (VTBC) coating on all-ceramic solar collectors has both high absorptance (0.94) and high emissivity (90%). However, the thermal conductivity of ceramic is very low (1.256 W/mK). To improve the heat collection efficiency of VTBC solar collectors, this paper establishes a mathematical model based on the energy-conservation relationships under steady-state conditions and creates a corresponding computer program. Key parameters for VTBC solar collectors include the heat-removal factor, effective transmittance-absorptance product for the absorber, total heat loss coefficient, etc. Then, via experimental testing, this study proposes a reference model for domestic VTBC solar collectors in a cold location (η = 0.89 − 2.20Tm*). Last, this work analyzes the influences of fin design and transparent cover design on VTBC solar collectors individually, using the created computer program. Results show that the most effective optimization method is to increase the transmittance of the transparent cover. By increasing the transmittance from 0.93 to 0.96, this study creates an optimized VTBC solar collector theoretical model (η = 0.92 − 2.20Tm*).
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Guo, Hui-Xia, Dong-Mei Yu, Cheng-Yu He, Xiao-Li Qiu, Shuai-Sheng Zhao, Gang Liu i Xiang-Hu Gao. "Double-layer solar absorber coating based on high entropy ceramic AlCrMoTaTiN: Structure, optical properties and failure mechanism". Surfaces and Interfaces 24 (czerwiec 2021): 101062. http://dx.doi.org/10.1016/j.surfin.2021.101062.
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Kumar P, Ranjith, Mohammed Adnan Hasan, Arjun Dey i Bikramjit Basu. "Development of ZrB2-Based Single Layer Absorber Coating and Molten Salt Corrosion of Bulk ZrB2–SiC Ceramic for Concentrated Solar Power Application". Journal of Physical Chemistry C 125, nr 24 (15.06.2021): 13581–89. http://dx.doi.org/10.1021/acs.jpcc.1c01984.
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Bekale, Vincent Menvie, Corinne Legros, Gael Sattonnay, Anne Marie Huntz, Bernard Lesage, Christos Argirusis i François Jomard. "Diffusion Study of Cerium and Gadolinium in Single- and Polycrystalline Yttria-Stabilized Zirconia". Defect and Diffusion Forum 258-260 (październik 2006): 46–51. http://dx.doi.org/10.4028/www.scientific.net/ddf.258-260.46.
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Yttria-stabilized zirconia (YSZ) ceramic is considered as an attractive matrix for nuclear applications, such as inert matrix for the destruction of excess plutonium or good host material for nuclear waste storage. Some actinide elements in high-level radioactive wastes can be simulated by cerium as tetravalent actinide, and gadolinium as trivalent actinide or neutron absorber. The present work is focused on the diffusion study of Ce and Gd in YSZ single crystal and high density polycrystals. A thin film of Ce or Gd was deposited either by spin-coating method or by physical vapour deposition on the surface of polished samples. The diffusion experiments were performed from 1173 to 1673 K under air. The Ce or Gd diffusion profiles were determined by secondary ion mass spectrometry. The experiments led to the determination of effective diffusion coefficient, Deff, bulk and grain boundary diffusion coefficients, DB and DGB. The dependence of these diffusion coefficients on temperature is described by means of Arrhenius equations and the diffusivity is compared with literature.
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CHEN, CHUANZHONG, QING DONG i DIANGANG WANG. "MICROSTRUCTURE AND ELEMENT DISTRIBUTIONS OF CERAMIC-LIKE COATINGS ON THE AZ91 ALLOY BY MICRO-ARC OXIDATION". Surface Review and Letters 13, nr 01 (luty 2006): 63–68. http://dx.doi.org/10.1142/s0218625x06007846.
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Ceramic-like coatings were deposited on the substrate of the AZ91 alloy by micro-arc oxidation (MAO). Many methods like X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron diffraction spectroscopy (EDS) were used to analyze the structure and composition of the coating. XRD showed that the MAO coating was mainly composed of MgO . The results of SEM showed that the coating surface possessed a porous microstructure and the pore size was in the range of 1–3 μm. EDS indicated that the coating matrix was relatively dense and had a homogeneous thickness. The element silicon from the applied electrolyte could be absorbed into the coating in the MAO process. The hardness of the MgO coatings could reach 513 HV0.025 that was about four times higher than that of the substrate. It is expected that the coatings have a great potential in the surface protection of magnesium alloys.
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Madruga, Camila Ferreira Leite, Gabriela Freitas Ramos, Alexandre Luiz Souto Borges, Guilherme de Siqueira Ferreira Anzaloni Saavedra, Rodrigo Othávio Souza, Renata Marques de Melo Marinho i Marcela Moreira Penteado. "Stress Distribution in Modified Veneer Crowns: 3D Finite Element Analysis". Oral 1, nr 3 (16.09.2021): 272–80. http://dx.doi.org/10.3390/oral1030026.
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(1) Background: to propose a new approach for crown veneers, with the use of an aesthetic porcelain coating, only in part of the zirconia infrastructure, and to analyze its biomechanical behavior to minimize chipping failures. (2) Methods: a maxillary molar was modeled using CAD software, preparing for traditional crowns and veneer crowns with various lengths. Five groups were formed: M—control group (monolithic crown of ultra-translucent zirconia); B—conventional (bilayer crown of ultra-translucent zirconia and ceramic covering); V—veneer (ultra-translucent zirconia crown with reduction only in the buccal and application of covering ceramics); V1—ultra-translucent zirconia crown with buccal reduction and 1 mm occlusal extension for covering ceramic application); V1.5—ultra-translucent zirconia crown with buccal reduction and 1.5 mm occlusal extension for application of covering ceramics. A load of 600 N was performed axially to a fossa bottom to simulate parafunction, and 300 N to the cusp tip to obtain the maximum principal stress results. (3) Results: group B showed a higher stress concentration in the occlusal region of the restorations, while the other groups absorbed the stress and dissipated it throughout the crown, presenting a higher stress concentration in the interface region with the tooth. (4) Conclusion: the highly translucent zirconia ceramic only associated with buccal covering ceramic could add aesthetic gain and rigidity to the system and could be a good option to restore maxillary molars in patients who do not have parafunction.
Rozprawy doktorskie na temat "Ceramic absorber coating"
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Asok, Deepu. "Study of Si(Al)CN functionalized carbon nanotube composite as a high temperature thermal absorber coating material". Kansas State University, 2013. http://hdl.handle.net/2097/16876.
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Master of ScienceDepartment of Mechanical & Nuclear Engineering
Gurpreet Singh
Carbon nanotubes (CNT) and polymer-derived ceramics (PDC) have gained considerable research attention due to their unique structure and physical properties. Carbon nanotubes are known for their exceptional mechanical (Young’s modulus= 1 TPa) and thermal properties (thermal conductivity = 4000 W/m.K). However, CNTs tend to lose their unique -sp2 carbon structure and cylindrical geometry at temperatures close 400°C in air. PDC, which are obtained by the controlled degradation of certain organosilicon polymers however exhibit high temperature stability (upto approx. 1400 °C). To this end, a hybrid composite material consisting of PDC functionalized CNT is of interest as it can combine the unique physical properties of the two materials for applications requiring operation under harsh conditions. Here, we report synthesis and chemical characterization of an Al-modified polysilazane polymer, which was later utilized to functionalize the outer surfaces of four commercially available CNTs. This polymer-CNT composite upon heating in nitrogen environment resulted in Si(Al)CN-CNT ceramic composite. The composite was characterized using a variety of spectroscopic methods such Raman, FTIR and electron microscopy. The thermal stability of the ceramic composite was studied by use of Thermogravimetric analysis (TGA) that showed an improvement in the thermal stability compared to bare nanotubes. Further, we also demonstrate that a stable dispersion of the composite in organic solvents such as toluene can be spray coated on a variety of substrates such as copper disks and foils. Such coatings have application in high energy laser power meters. This research opens new avenues for future applications of this novel material as coatings on surfaces that require both good thermal properties and protection against degradation in high temperature environments. We also suggest the future use of this material as an electrode material in high electrochemical capacity rechargeable batteries.
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Dan, Atasi. "Spectrally selective tandem absorbers for photothermal conversion in high temperature solar thermal systems". Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4952.
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Solar energy is the inexhaustible and abundant energy resources on the earth which can be a best substitute for the fossil fuels. Over the past couple of decades, all the solar technologies are rising very steadily in two main branches including photovoltaics and solar thermal. One of the major components of solar thermal system is receiver, which plays an important role to enhance the photo-thermal efficiency by absorbing maximum amount of solar radiation with a minimum heat loss. In this regard, our objective was to fabricate a spectrally selective absorber coating for receiver which should have a high absorptance of ≥ 0.95 in the solar spectrum (0.25-2.5 μm) and a low thermal emittance of ≤ 0.05 in the infrared region (2.5-25 μm). In addition, while considering the real field applications, these coatings should exhibit exceptional thermal (> 450 °C) and environmental stability in different operational conditions.
In spite of the outstanding thermo-chemical and thermo-physical stability of the ultra-high temperature ceramics (UHTCs), there are only a few reports on the spectral selectivity of these materials. Therefore, in the first part, we have utilized DC and RF magnetron sputtering system to prepare TiB2/TiB(N)/Si3N4 -based multilayer absorber coating. A systematic investigation was carried out to understand the influence of various deposition parameters including target power, deposition time and reactive gas flow on the spectral selectivity of the coating. The optimal process parameters lead to a high absorptance of 0.964 and an emittance of 0.18. However, the film is inadequate in terms of environmental stability.
We have subsequently developed W/WAlN/WAlON/Al2O3 -based multifunctional novel coating using magnetron sputtering. The rationale behind this specific coating design was based on good optical properties and high diffusion block ability of transition metal -based oxides and oxynitrides. The optimally fabricated coating has a superior spectral selectivity with a maximum absorptance of 0.958 and a low emittance of 0.08. Based on the extensive analysis using the transmission electron microscopy (TEM), phase modulated spectroscopic ellipsometry along with computational analysis, we have manifested that the optical constants of each layer decrease from substrate to surface of coating, leading to enhance the photo-thermal efficiency.
A prolonged thermal annealing established that the spectral properties of the coating could be retained at 500 °C in air for 150 hrs, indicating a service durability of ~ 25 years. Also, the directional and hemispherical emissivity is not compromised during annealing at 500 °C in air and in vacuum for 12 hrs. It is noteworthy to mention that the recently conducted high temperature testing (30 cycles at 450°C) in simulated solar field environment at Sandia National Laboratory establishes excellent thermal shock resistance property of the coating. In summary, a broad spectrum of ceramic combinations as tandem absorber coatings was investigated, and attempts were made to demonstrate the governing physical phenomena to explain the origin of spectral selectivity of ceramic absorbers. This dissertation will also provide guidelines to develop multilayer ceramic absorber coating for high temperature photo-thermal conversion systems.
Części książek na temat "Ceramic absorber coating"
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Mark, James E., Dale W. Schaefer i Gui Lin. "Composites". W The Polysiloxanes. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780195181739.003.0011.
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A relatively new area that involves silicon-containing materials is the synthesis of “ultrastructure” materials (i.e., materials in which structure can be controlled at the level of 100 Å). An example is the “sol-gel” hydrolysis of alkoxysilanes (organosilicates) to give silica, SiO2. The reaction is complicated, involving polymerization and branching, but the overall reaction may be written . . . Si(OR4 + 2H2O → SiO2 + 4ROH (9.1) . . . where the Si(OR)4 organometallic species is typically tetraethoxysilane such as tetraethylorthosilicate (TEOS, with R being C2H5). In this application, the precursor compound is hydrolyzed and then condensed to yield branched polymers. Eventually a continuous swollen gel is formed. The gel is dried at moderately low temperatures to remove volatile species, and then it is fired into a porous ceramic object that can then be densified and machined into a final ceramic part. The production of ceramics by this novel route triggered interest in the ceramics community because of advantages over the conventional powder-processing approach to ceramics. Advantages include (i) the higher purity of the starting materials, (ii) the relatively low temperatures required, (iii) the possibility of controlling the ultrastructure to reduce the microscopic flaws that lead to failure, (iv) the ease with which ceramic coatings can be formed, and (v) the ease with which ceramic alloys can be prepared (e.g., by hydrolyzing solutions of both silicates and titanates). The sol-gel approach has been used to form ceramic-like phases in a variety of polymers. Poly(dimethylsiloxane) (PDMS) is the most popular. PDMS is relatively weak and stands to benefit most from reinforcement. PDMS is easily absorbs the precursor materials generally used in the solgel process. Nearly monodisperse silica microparticles can be obtained using siloxane elastomer mixtures. In some cases, the PDMS has been part of a copolymer, with ureas, imides, amideimides, and dianilines. In other approaches, the particle surface is modified, for example, with a polysiloxane. Siloxane/silica nanocomposites have also been used as “culture-stone-protective materials.” Sol-gel hydrolysis and condensation can be carried out within a polymeric matrix to generate particles of the ceramic material, typically with an average diameter of a few hundred angstroms.
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Pradeepkumar, Maurya Sandeep, i Md Imteyaz Ahmad. "CuInxGa1-xS2 absorber material for thin-film solar cells". W Advanced Ceramic Coatings for Emerging Applications, 239–61. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-323-99624-2.00009-7.
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Das, Rajib, Vibhav Ambardekar i Partha Pratim Bandyopadhyay. "Titanium Dioxide and Its Applications in Mechanical, Electrical, Optical, and Biomedical Fields". W Titanium Dioxide [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98805.
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Titanium dioxide (TiO2), owing to its non-toxicity, chemical stability, and low cost, is one of the most valuable ceramic materials. TiO2 derived coatings not only act like a ceramic protective shield for the metallic substrate but also provide cathodic protection to the metals against the corrosive solution under Ultraviolet (UV) illumination. Being biocompatible, TiO2 coatings are widely used as an implant material. The acid treatment of TiO2 promotes the attachment of cells and bone tissue integration with the implant. In this chapter, the applications of TiO2 as a corrosion inhibitor and bioactive material are briefly discussed. The semiconducting nature and high refractive index of TiO2 conferred UV shielding properties, allowing it to absorb or reflect UV rays. Several studies showed that a high ultraviolet protection factor (UPF) was achieved by incorporating TiO2 in the sunscreens (to protect the human skin) and textile fibers (to minimize its photochemical degradation). The rutile phase of TiO2 offers high whiteness, and opacity owing to its tendency to scatter light. These properties enable TiO2 to be used as a pigment a brief review of which is also addressed in this chapter. Since TiO2 exhibits high hardness and fracture toughness, the wear rate of composite is considerably reduced by adding TiO2. On interacting with gases like hydrogen at elevated temperatures, the electrical resistance of TiO2 changes to some different value. The change in resistance can be utilized in detecting various gases that enables TiO2 to be used as a gas sensor for monitoring different gases. This chapter attempts to provide a comprehensive review of applications of TiO2 as an anti-corrosion, wear-resistant material in the mechanical field, a UV absorber, pigment in the optical sector, a bioactive material in the biomedical field, and a gas sensor in the electrical domain.
Streszczenia konferencji na temat "Ceramic absorber coating"
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Khivsara, S. D., Rathindra Nath Das, T. L. Thyagaraj, Shriya Dhar, V. Srinivasan i P. Dutta. "Development of a Ceramic Pressurized Volumetric Solar Receiver for Supercritical CO2 Brayton Cycle". W ASME 2014 8th International Conference on Energy Sustainability collocated with the ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/es2014-6482.
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Recently, the supercritical CO2 (s-CO2) Brayton cycle has been identified as a promising candidate for solar-thermal energy conversion due to its potentially high thermal efficiency (50%, for turbine inlet temperatures of ∼ 1000K). Realization of such a system requires development of solar receivers which can raise the temperature of s-CO2 by over 200K, to a receiver outlet temperature of 1000K. Volumetric receivers are an attractive alternative to tubular receivers due to their geometry, functionality and reduced thermal losses. A concept of a ceramic pressurized volumetric receiver for s-CO2 has been developed in this work. Computational Fluid Dynamics (CFD) analysis along with a Discrete Ordinate Method (DOM) radiation heat transfer model has been carried out, and the results for temperature distribution in the receiver and the resulting thermal efficiency are presented. We address issues regarding material selection for the absorber structure, window, coating, receiver body and insulation. A modular small scale prototype with 0.5 kWth solar heat input has been designed. The design of a s-CO2 loop for testing this receiver module is also presented in this work.
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Real, Daniel, i Nico Hotz. "Novel Non-Concentrated Solar Collector for Solar-Powered Chemical Reactions". W ASME 2013 7th International Conference on Energy Sustainability collocated with the ASME 2013 Heat Transfer Summer Conference and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/es2013-18382.
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The purpose of this study is the proof that non-concentrating solar-thermal collectors can supply the thermal energy needed to power endothermic chemical reactions such as steam reforming of alcoholic (bio-) fuels. Traditional steam reformers require the combustion of up to 50% of the primary fuel to enable the endothermic reforming reaction. Our goal is to use a selective solar absorber coating on top of a collector-reactor surrounded by vacuum insulation. For methanol reforming, a reaction temperature of 220–250°C is required for effective methanol-to-hydrogen conversion. A multilayer absorber coating (TiNOX) is used, as well as a turbomolecular pump to reach ultra-high. The collector-reactor is made of copper tubes and plates and a Cu/ZnO/Al2O3 catalyst is integrated in a porous ceramic structure towards the end of the reactor tube. The device is tested under 1000 W/m2 solar irradiation (using an ABB class solar simulator, air mass 1.5). Numerical and experimental results show that convective and conductive heat losses are eliminated at vacuum pressures of <10−4 Torr. By reducing radiative losses through chemical polishing of the non-absorbing surfaces, the methanol-water mixture can be effectively heated to 240–250°C and converted to hydrogen-rich gas mixture. For liquid methanol-water inlet flow rates up to 1 ml/min per m2 of solar collector area can be converted to hydrogen with a methanol conversion rate above 90%. This study will present the design and fabrication of the solar collector-reactor, its testing and optimization, and its integration into an entire hydrogen-fed Polymer Electrolyte Membrane fuel cell system.
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Hotz, Nico. "Non-Concentrated Solar Collector for Solarthermal Chemical Reactions". W ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65433.
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The purpose of this study is the proof that non-concentrating solar-thermal collectors can supply the thermal energy needed to power endothermic chemical reactions such as steam reforming of alcoholic (bio-) fuels. Traditional steam reformers require the combustion of up to 50% of the primary fuel to enable the endothermic reforming reaction. Our goal is to use a selective solar absorber coating on top of a collector-reactor surrounded by vacuum insulation. For methanol reforming, a reaction temperature of 220–250°C is required for effective methanol-to-hydrogen conversion. A multilayer absorber coating (TiNOX) is used, as well as a turbomolecular pump to reach ultra-high. The collector-reactor is made of copper tubes and plates and a Cu/ZnO/Al2O3 catalyst is integrated in a porous ceramic structure towards the end of the reactor tube. The device is tested under 1000 W/m2 solar irradiation (using an ABB class solar simulator, air mass 1.5). Numerical and experimental results show that convective and conductive heat losses are eliminated at vacuum pressures of <10−4 Torr. By reducing radiative losses through chemical polishing of the non-absorbing surfaces, the methanol-water mixture can be effectively heated to 240–250°C and converted to hydrogen-rich gas mixture. For liquid methanol-water inlet flow rates up to 1 ml/min per m2 of solar collector area can be converted to hydrogen with a methanol conversion rate above 90%. This study will present the design and fabrication of the solar collector-reactor, its testing and optimization, and its integration into an entire hydrogen-fed Polymer Electrolyte Membrane fuel cell system.
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Bobzin, K., W. Wietheger i E. Burbaum. "The Effect of Water Absorption in Ceramic Coatings on High Frequency ac Resistance". W ITSC2021, redaktorzy F. Azarmi, X. Chen, J. Cizek, C. Cojocaru, B. Jodoin, H. Koivuluoto, Y. C. Lau i in. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.itsc2021p0315.
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Abstract Thermally sprayed ceramic coatings can be used for wear protection as well as thermal and electrical insulation. When exposed to environments with high humidity, the water absorption of the ceramic coating has a tremendous impact on the electrical insulation. In thermally sprayed ceramic coatings, water can easily be absorbed by the porous microstructure of the coating. A general result of the water absorption is the reduction of the dc resistivity. However, in the high frequency regime of ac loads, contrary results were observed for sealed Al2O3 coatings on steel substrates. Specimens exposed to high air humidity have shown an increased ac resistance compared to dry specimens if frequencies above 1 MHz are considered. To analyse this phenomenon, a novel measurement technique was developed to investigate the influence of the water absorption of detached ceramic coatings on the ac resistivity at high frequencies. Moreover, the water absorption of the ceramic is measured gravimetrically. To ensure the results are also applicable to ceramic coatings on substrates, the morphology of the coating was analysed using electron microscopy and compared to reference specimens deposited on steel substrates from [1].
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Müller, P., M. Floristán, A. Killinger, R. Gadow, A. Cardella i C. Li. "Development and Characterization of Oxide Ceramic APS Coatings for Microwave Absorption". W ITSC2011, redaktorzy B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima i A. McDonald. DVS Media GmbH, 2011. http://dx.doi.org/10.31399/asm.cp.itsc2011p0879.
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Abstract Thermonuclear fusion is a promising source of clean energy for the future. Max-Planck-Institute für Plasmaphysik (IPP, Greifswald, Germany) is currently working on the new type of fusion reactor, the stellarator Wendelstein 7-X. The extreme operating conditions of fusion reactor devices have lead to an increasing interest in the field of high performance materials. The present work describes the development of coating systems acting as efficient absorbers for 140 GHz radiation, which is the microwave frequency to which the analyzed components of Wendelstein 7-X are subjected. Several types of oxide ceramic coatings were applied by Atmospheric Plasma Spraying. Different powders were used as feedstock material for the coating operation. The influence of the process parameters on the coating properties and microwave absorbing capability was analyzed. The coatings microstructure and mechanical properties were characterized in terms of porosity, microhardness, roughness, adhesion and residual stresses. XRD and SEM were carried out. It was found that thickness and microstructure of the coatings have a significant influence on microwave absorption behavior. For Al2O3/TiO2 coatings, absorption values over 90% were obtained. After optimization of the coating structure, the coating process was adapted to several real reactor components that will work in Wendelstein 7-X.
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Hollis, Kendall J., Marla I. Peters i Brian D. Bartram. "Plasma-Sprayed Ceramic Coatings for Molten Metal Environments". W ITSC2003, redaktorzy Basil R. Marple i Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p0153.
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Abstract Coating porosity is an important parameter to optimize for plasma-sprayed ceramics which are intended for service in molten metal environments. Too much porosity and the coatings may be infiltrated by the molten metal causing corrosive attack of the substrate or destruction of the coating upon solidification of the metal. Too little porosity and the coating may fail due to its inability to absorb thermal strains. This study describes the testing and analysis of tungsten rods coated with aluminum oxide, yttria-stabilized zirconia, yttrium oxide, and erbium oxide deposited by atmospheric plasma spraying. The samples were immersed in molten aluminum and analyzed after immersion. One of the ceramic materials used, yttrium oxide, was heat treated at 1000°C and 2000°C and analyzed by X-ray diffractography and mercury intrusion porosimetry. Slight changes in crystal structure and significant changes in porosity were observed after heat treatments.
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Amsellem, O., F. Pauchet, M. Jeandin i V. Guipont. "Interconnected Porosity Modification of Plasma Sprayed Alumina Coating Using Excimer Laser Surface Treatment". W ITSC 2012, redaktorzy R. S. Lima, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, A. McDonald i F. L. Toma. ASM International, 2012. http://dx.doi.org/10.31399/asm.cp.itsc2012p0521.
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Abstract Thermally sprayed ceramic coatings such as plasma-sprayed alumina exhibit a composite microstructure due to the presence of defects such as pores, interlamellar and intra-lamellar cracks. These second phase typed features influence the mechanical behaviour of the coating dramatically. In this study, an excimer laser surface treatment of plasma-sprayed alumina surface was developed for the optimization of component properties of a wireline tool used in the oil industry. In contrast to liquid phase treatment realized with CO2 or YAG laser, an excimer laser processing presents short wavelength which means that for ceramic materials, the energy is absorbed in a region of the surface. This condition leads to surface treatment free of cracks. Effect of laser operating parameters, i.e. wavelength, pulse number and power density, on microstructure and the sealing quality of the coating are discussed. First, surfaces and cross sections of the microstructures were studied using image analysis of scanning electron microscope (SEM). Surface roughness and coating ablation were characterized according to laser treatment. Then, three dimensional (3D) microstructures were obtained using X-ray microtomography to evaluate the 3D porosity after laser treatment. Finally, nanoindentation and Electrochemical Impedance Spectroscopy (EIS) were carried out to characterize respectively the mechanical and electrical properties of the modified coating microstructure. The excimer laser surface processing was shown to be an innovative process to control the insulating characteristics of plasma-sprayed alumina.
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Tufa, K. Y., i F. Gitzhofer. "Dc Plasma Sprayed Polymer Composite Coatings for Abrasion Resistant Protective Surfaces". W ITSC 1998, redaktor Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p0157.
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Abstract A high energy recovery of dc plasma torch has been developed and applied to the deposition of >10 mm thick polymer composites for abrasion resistant protective surfaces. The injection of low cost fillers such as alumina or silica in the hot plasma zone can absorb a lot of energy and cool down the plasma whereas polymer powder is injected downstream in a much cooler zone. Indeed, the energy absorbed by the fillers can then be transferred inside the polymer matrix coating allowing an energy recovery mechanism. The result is a composite polymer/ceramic with the following benefits: The shrinking phenomena due to the polymer recrystallisation is eliminated allowing a good coating adhesion, a high polymer/filler throughput can be achieved and the risk of the in-flight polymer combustion is largely reduced. The fillers addition decreases the overall cost of the coating and the type of filler can influence the composite properties. Abrasion resistant composites have been produced with alumina fillers. Medium density polyethylene (MDPE) sprayed with 45 wt % reinforcement as tested on the modified ASTM G-65 apparatus has shown abrasion resistance as good as ultra high molecular weight polyethylene (UHMWPE), which is one of the highest abrasion resistant polymer. In order to understand the abrasion resistance mechanisms, variables in the coating process such as: size of the fillers, polymer injection angles, polymer degradation and composite microstructure have been analyzed.
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Tapphorn, R., H. Gabel, L. Premuda, T. Crowe i K. Hashimoto. "Kinetic Metallization of Ceramic Armor Tiles". W ITSC 2012, redaktorzy R. S. Lima, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, A. McDonald i F. L. Toma. ASM International, 2012. http://dx.doi.org/10.31399/asm.cp.itsc2012p0500.
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Abstract Ceramic tiles are widely used as ballistic armor due to their ability to absorb high specific impact energy. However, ceramic materials often exhibit very low ductility and have a tendency to exhibit multiple fractures in spider-web patterns around the point of impact. One method used to introduce ductility is to encapsulate the tile in a metal jacket, or to provide a strongly adhered metallic backing plate. Aluminum and titanium metals are of primary interest to decrease the overall weight of the armor material system. The low temperature Kinetic Metallization (KM) process allows direct deposition of the metals onto the ceramic tiles. This is not possible with thermal spray processes due to the extreme mismatch in thermal expansion and adverse metallic-ceramic chemical reactions at high temperatures. Kinetic Metallization has been used to deposit aluminum and titanium coatings onto silicon carbide (SiC) and proprietary ceramic matrix composite (CMC) tiles. Ballistic testing of coated tiles has shown decreased fracturing of the armor material, leading to improved performance for subsequent impacts.
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Kawaharazuka, Fumihiro, i Noboru Uchida. "Study of Surface Insulation Structures to Reduce Cooling Loss in Heavy-Duty Diesel Engines". W WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2023. http://dx.doi.org/10.4271/2023-01-0948.
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<div class="section abstract"><div class="htmlview paragraph">Cooling loss reduction is essential to enable further increases in thermal efficiency of reciprocating internal combustion engines. Many in-cylinder cooling loss reduction studies have been carried out by applying various thermal barrier coatings to the piston and/or other in-cylinder surfaces, taking advantage of the lower thermal effusivity of ceramic materials. However, the end result was mostly minimal or in some cases, negative. In our previous study, significant cooling loss reduction was experimentally confirmed by utilizing a mirror-like polished stainless-steel thermal sprayed surface (HVOF: high velocity oxy-fuel) on a forged steel piston. This study firstly investigated an alternative insulating layer material to stainless-steel, along with effects of its thickness on heat transfer by a one-dimensional unsteady numerical model. Results showed that lower thermal effusivity doesn’t always reduce heat transfer, but increases nonuniformity of surface temperature. Next, a modified insulation structure composed of a thin aluminum coating overlayed by physical vapor deposition (PVD: physical vapor deposition) on a stainless-steel layer of both the piston and cylinder head, was tested in a heavy-duty single cylinder engine. Aluminum was initially selected due to its high reflectance, to reduce absorption of flame radiation, but selectively absorb it at soot deposits, where the flame interacts with the wall, and reduce local convection. Experimental results suggested that higher surface temperatures of exposed areas are caused by better heat conduction outward from hot spots during and after the combustion period, through the aluminum coating. Such surface temperature equalization could also result in further reduction of cycle-integrated heat transfer.</div></div>