Ceramic thermal spray materials

Ceramic or cermet thermal spray materials deposited by plasma spraying, detonation gun (D-gun), or high-velocity oxyfuel processes... 

Spherical particles proved to be superior in several applications owing to their favorable properties. Thus, they are used in thermal spraying for their excellent flowabil-ity, in powder metallurgy because of their excellent reproducibility in manufacturing parts with controlled porosity and as a filler material, as well. Metal microspheres can be easily produced by melt atomization. Similar method in the case of ceramics is impractical. Micron-sized ceramic particles, however, can be smelted by thermal plasmas that provide exceptional conditions for spheroidization due to its high temperature. In terms of purity and residence time of the particles in the hot temperature core, RF plasmas provide better conditions as compared to arc plasmas. 

Fehringer, G. et al.. Proton-conducting ceramics as electrode/electrolyte materials for SOFCs preparation, mechanical and thermal-mechanical properties of thermal sprayed coatings, material combination and stacks, J. Eur. Ceram. Soc., 24, 705-715 (2004). 

Nowadays, many advanced techniques are available in the ceramic industry to coat a solid layer onto a solid surface or to make ceramic materials with special properties [99-1 IS], such as spin-coating [99], chemical vapor deposition [100-106], and chemical vapor infiltration [106-109], thermal spray [110-112], plastic spray [113], and spray-coating [114]. The deposition can be caused by conventional heating, by laser beam, or by microwave heating. 

Knowles JC, Gross K, Berndt CC, Bonfield W (1996) Stmctural changes of thermally sprayed hydroxylapatite investigated by Rietveld Analysis. Biomaterials 17 639-645 Kobayashi T, Nakamura S, Yamashita K (2001) Enhanced osteobonding by negative surface charges of electrically polarized hydroxylapatite. J Biomed Mater Res 57 477-484 Kokubo T (1998) Apatite formation on surfaces of ceramics, metals and polymers in body enviromnent. Acta Materi a 46 2519-27... 

A ceramic bond coat is almost exclusively used to modify a surface for adhesive bonding. The ceramics include, but are not limited to, alumina, zirconia, titania, spinels, carbides and combinations of these materials." The thermally sprayed bond coatings provide a rough surface on the order of 8 p,m R that has a three-dimensional morphology. Arc-plasma is traditionally used for deposition of the ceramics for these applications. 

Coatings, ranging from 0.01 mm to greater than 1.5-mm thick, can be thermally sprayed onto a wide variety of substrates, such as metals, ceramics and plastics including fibre-reinforced composites. The wide variety of coating materials that can be deposited include ... 

Successful procedures for the artifact-free preparation of porous ceramics can only be developed and applied when the ceramographic specialist has sufficient knowledge of the microstructure that can be expected, as well as the production, treatment, and mechanical properties of the material at hand. The ceramographic specialist must also acquire an understanding of the type of surface treatment involved in each of the preparation steps. Basic information on the subject of porosity can be found in Salmong-Scholze. The interaction between pores and pull-outs is treated by Telle et al. (1995). Leistner and others have reported on the preparation of thermally sprayed coatings. 

Figure 11. Comparisons of Ka /Kit of plasma sprayed ZrO 8wt%Y203 thermal barrier coatings with other advanced monolithic ceramics and brittle materials at ambient temperature, (a) Comparison with previous studies . (b) Comparison with data compiled by Munz and Fett. ...

Jadhav A, Padture NP, Wu F, Jordan EH, Cell M. Thick ceramic thermal barrier coatings with high durability deposited using solution-precursor plasma spray. Materials... 

The following tribological data under dry ftiction were compared with homologous results issued fiom the tribological data base TRIBOCOLLECT of thermally sprayed coatings [6,8], self-mated ceramics, ceramic composites [9] and steels as well as mated with stationary specimen in alumina. The tribological characteristics of these materials are summarized in [10]. 

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