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Ceramics and Composites
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
A cermet is simply a mixture of ceramics and metals, a special case of composite materials. The intent is to combine the high strength of ceramics with the high fracture toughness of metals. A good example is WC-Co. Adding 5%–10% cobalt (a tough metal) to tungsten carbide (a strong and wear-resistant ceramic) results in a tough material with excellent wear resistance under high stress. This material is known as cemented carbide and is used in cutting tools.
Solar water heating
Published in John Twidell, Renewable Energy Resources, 2021
In summarizing the classification and properties of different types of selective surfaces, Bermel et al. (2012), utilizing Kennedy (2002), consider that there are six classes of selective solar absorbers. These are (a) intrinsic absorbers, (b) semiconductor–metal tandems, (c) multilayer tandems, (d) ceramic–metal composites (known as cermets), (e) textured absorbers, and (f) photonic crystals. They conclude ‘cermets are generally considered the best for practical collectors. However photonic crystals have great potential, since they can be used to optimize selectivity with respect to the wavelength, angle of incidence, and polarization of the incoming insolation.’
Sputter Deposited Nanostructured Coatings as Solar Selective Absorbers
Published in Sam Zhang, Jyh-Ming Ting, Wan-Yu Wu, Functional Thin Films Technology, 2021
Cermet is a metal–dielectric composite. The “cer” stands for ceramics and the “met” stands for metals. A cermet consists of metal nanoparticles (NPs) homogeneously distributed in a dielectric ceramic matrix. The optical performance of the dielectric ceramic is enhanced due to the light scattering from the metal NPs. These films are transparent in the IR band region but have high absorption in the UV and visible band. Moreover, the enhancement of the absorptance is also contributed by surface plasmon resonance from the NPs. The cermet concept offers a high degree of flexibility, and the solar selectivity can be optimized by proper choice of constituents, thin film thickness, nanoparticle concentration, nanoparticle size, and orientation [10]. For the cermet absorbers, conventional black materials, such as Au-MgO and Cr-Cr2O3 (as known as the black chrome) were used in the beginning. Popular dielectric matrix materials also include carbon and aluminum oxide (Al2O3). This led to the introduction of Ni-Al2O3 and Mo-Al2O3 cermet. In addition to oxide, AlN was also commonly used for its stability.
Experimental Study on the Influence of Gas-Solid Heat Transfer in a Mesoscale Counterflow Combustor
Published in Combustion Science and Technology, 2023
Patryk P. Radyjowski, Janet L. Ellzey
The experimental reactors were fabricated using in-direct laser sintering with metal infiltration. This method produces a metal-infilled ceramic material, called cermet, that has properties of both materials. The process is described in detail in a previous study that focused on a straight channel reactor (Radyjowski, Schoegl and Ellzey, 2021). It enabled creating a set of reactors in shapes that modified only a limited set of parameters. Two geometries were created that changed the RA/V from the straight channel base case: a divergent channel and a split-channel design. The discussion of all geometries is provided in Core design. The split-channel reactor increases the heat exchange by introducing a fin in the middle of the normal channel, increasing the available surface area. Dimensions and channel shape were chosen such that the wall surface area was increased by 50% while preserving the flow area. This change necessitated the introduction of diverging and converging sections upstream and downstream of the fin, respectively. A different approach has to be used to reduce the RA/V since the straight channel layout already approaches the minimum. Instead, the width increases in the diverging channel design, which locally decreases the flow velocity and reduces RA/V.
Plutonium-238 Production Program Results, Implications, and Projections from Irradiation and Examination of Initial NpO2 Test Targets for Improved Production
Published in Nuclear Technology, 2022
Emory D. Collins, Robert N. Morris, Joel L. McDuffee, Padhraic L. Mulligan, Jeffrey S. Delashmitt, Steven R. Sherman, Raymond J. Vedder, Robert M. Wham
The targets are irradiated currently in nine HFIR reflector positions,2 and each position contains an array of seven targets. The operating schedule time for the HFIR is typically seven cycles per year. Even though the conversion of 237Np to 238Pu is greater for the three-cycles of irradiation, the isotopic purity of the 238Pu produced is not as good. More importantly, the number of targets that can be irradiated each year is greater for two-cycle irradiation and therefore the annual yield of HS PuO2 is greater. Improvements in cermet target performance are planned in the future. Even so, the yield will not be enough to meet the production goal in the HFIR; thus, the production will need to be supplemented by irradiations in the ATR.
Binder-jetting of TiCN-based cermets
Published in Powder Metallurgy, 2022
Christian Berger, Johannes Pötschke, Manfred Fries, Tassilo Moritz, Alexander Michaelis
Cermets are composites containing a ceramic hard phase, mostly Titanium Carbonitride (Ti(C, N) or also TiCN), a metallic binder phase most often Nickel (Ni) or Cobalt (Co) and additives like molybdenum carbide (Mo2C) or tungsten carbide (WC) [1,2]. Here the hard phase Ti(C,N) is a solid solution and common in the modification of 50/50 or 70/30 in terms of titanium carbide to titanium nitride ratio [3]. This solid solution in combination with a metallic binder phase and the additives leads to composites with a high hardness, a good fracture toughness and a high chemical resistance. Owing to these properties, cermets are mainly used as tools in the area of drilling, shaping and milling of mostly metals, but also wood-based composites [4]. Furthermore, also in the area of shaping, wear applications as well as in forming larger and most often complex geometries are used.