Transparent ceramics production

A glaze is defined as a thin layer on the surface of a ceramic product,either glassy or partially crystalline. Its main function is to render impermeable the surface of a porous body, to permit application of decoration techniques, and in some cases to improve the technological properties. In contrast to enamels, to which glazes are related by their naturp as well as function, a lower degree of opacity is usually required and transparent glazes are frequently employed. 

Besides, according to the definition of T, the transmission of transparent ceramics can never be 100 %. It is also necessary to mention that 7 in Eqs. (1.3) and (1.4) is calculated by assuming that the reflection occurs on a theoretically perfect surface. Because theoretically perfect surface is an ideal assumption, real ceramics inevitably have a certain value of roughness. Therefore, technical roughness gives rise to additional loss—another mechanism which decreases the real in-line transmission of products depending on the quality of surface preparation [7]. 

Serantoni M, Piancastelli A, Costa AL, Esposito L (2012) Improvements in the production of Yb YAG transparent ceramic mabaials spray drying optimisation. Opt Mater 34 995-1001... 

Chemical decomposition is usually observed in solid reactions, such as carbonate, hydroxides, nitrate, acetate, oxalates, alkoxides and so on, when they are heated at a certain temperature. The decomposition leads to the formation of a new solid product, together with one or more gaseous phases, which is usually used to produce powders of simple oxides in most cases and complex oxides sometimes. Although this method has not been widely reported for the synthesis of transparent ceramic powders, it could be a potential technique for such a purpose, due to its various advantages, such as simple processing, inexpensive raw materials, and capability of large scale production. In fact, the calcination step involved in most wet-chemical processing routes, especially chemical precipitation or co-precipita-tion, is chemical decomposition, either from carbonates or hydroxides, as discussed later. 

Since then, HP became a widely used technique to prepare transparent spinel ceramics. For example, HP process was used to fabricate MgAl204 transparent ceramics, with a nearly 100 % densification [44]. Spinel powders for the production of transparent polyciystalline ceramic windows were produced by using both the traditional ceramic solid-state reaction and solgel methods. Among them, the powders produced from the reaction of organomagnesium compounds with surface modified boehmite precursors were best to produce high-quality transparent spinel ceramics. The powder synthesis method allowed fine control over the particle size. 

Transparent fused silica can be formed at a temperature of 1200°C and a pressure of 13.8 MPa (2000 psi) from silica powder consisting of 15 nm ultimate particles (92) or by electric arc fusion of pure silica sand having low iron and alkali metal contents. The cooled product is ground to the desired particle size. Fused sihca is primarily manufactured by C-E Minerals, Minco, and Precision Electro Minerals in the United States by Chuo Denko, Denki Kagaku Kogyo, NKK, Showa Denko, and Toshiba Ceramics in Japan. Based on 1988 data and projected growth, an estimated 135,000 metric tons of fused siUca were used in 1994 as a sacrificial component or investment casting in the manufacture of metals and as a component in refractory materials (62). 

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