Spray ceramics

Sintered and sprayed ceramic anodes have been developed for cathodic protection applications. The ceramic anodes are composed of a group of materials classified as ferrites with iron oxide as the principal component. The electrochemical properties of divalent metal oxide ferrites in the composition range 0- lA/O-0-9Fe2O3 where M represents a divalent metal, e.g. Mg, Zn, Mn, Co or Ni, have been examined by Wakabayashi and Akoi" . They found that nickel ferrite exhibited the lowest consumption rate in 3% NaCl (of 1 56 g A y at 500 Am and that an increase in the NiO content to 40mol 7o, i.e. O NiO-O-bFejO, reduced the dissolution rate to 0-4gA y at the expense of an increase in the material resistivity from 0-02 to 0-3 ohm cm. 

Usually, as the coated web emerges from the last zone of the oven it passes a bank of infra-red heaters (which maintain the temperature) and through a simple direct emboss nip fitted with a plain embossing roller. This treatment helps to smooth minor imperfections in the surface and gives a matt finish preparatory to printing. The roller is of steel with surface grit-blasted or (better) with a sprayed ceramic surface and water-cooled internally. 

Due to the high rates of general corrosion in this testing, specimen examination for localized corrosion was not conducted. Thermally sprayed ceramic coalings were simultaneously tested with the alloys shown in Table 11. The... 

Common causes of porosity of plasma-sprayed ceramic coatings include (Heimann, 2008) ... 

Measurement of the porosity of plasma-sprayed ceramic coatings can be accomplished by a wide variety of methods that can be divided into those yielding as a result a simple number, the porosity or pore volume related to the total volume of the coating in cm3 g-1, and those that yield a pore size distribution function. In many cases, the former methods are sufficient to characterise the porosity of a coating. 

Li, C.J. and Wang, W.Z. (2004) Quantitative characterization of lamellar microstructure of plasma-sprayed ceramic coatings through visualization of void distribution. Mater. Sci. Eng., A, 386, 10-19. 

B., and Krishnamurthy, R. (2007) Study on influence of porosity, pore size, spatial and topological distribution of pores on microhardness of as plasma sprayed ceramic coatings. Mater. Sci. Eng., A, 445—446, 269-274. 

Sprayed ceramic coatings can be made chemically active by selection of the spray parameters, which result in metastable phases within the coating. Ceramic bond coats are useful for difficult to bond materials such as ceramic components, including carbide-containing parts and refractory metals. These materials may be used in combination with a metallic bond coat on metallic substrates to mitigate stress differentials between the metallic substrate and the ceramic bond coat due to thermal or mechanical stress. 

Pajares, A., Wei, L., Lawn, B.R., Padture, N.P., Bemdt, C.C., 1996. Mechanical characterization of plasma-sprayed ceramic coatings on metal substrates by contact testing. Mater. Sci. Eng. A 208, 158-165. 

Tomota, T., Miyamoto, N., and Koyama, H. (1988) Formation of Thermal Spraying Ceramic Layer, Patent JP 63 169371, A. 

E. Wessel, R.W. Steinbrech, Crack propagation in plasma sprayed ceramic. Key Engineering Ma terials, Vol. 223 (2002) 55 60... 

A. Pajares, L. Wei, B. R. Lawn, N. P. Padture, C. C. Berndt, Mechanical Characterization of Plasma Sprayed Ceramic Coatings on Metal Substrates by Contact Testing, Materials Science and Engineering., A208 158 165 (1996). 

Thermally sprayed ceramics, for example, chromium oxide, alumina, preferably sealed... 

Thermally sprayed ceramics or cermets, for example, WC-Co, alumina, chromium oxide, and so forth, for maximum wear resistance. If corrosion is likely, a corrosion barrier is required under the hard coating. 

Liu Z-G, Zhang W-H, Ouyang J-H, Zhou Y. Novel double-ceramic-layer (Lao gEuo2)2Zr207/YSZ thermal barrier coatings deposited by plasma spraying. Ceramics International. 2014 40 11277-11282. 

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