Processing of Zirconia

Carbothermal reduction. Thermal demixing by carbothermal reduction at temperatures 1750 °C generated by an electric arc is governed by the chemical reaction  

In a second processing step, the zirconia is purified by treating it with chlorine and hydrogen according to  

The zirconium chloride is subsequently converted to zirconia (see below). 

Direct chlorination. A variant of this process is the direct chlorination, which is conducted at temperatures between 800 and 1200 °C according to  

ZrSi04 + 4C + 4CI2 ZrCU T + SiCU T + 4COT ZrCU + H2O ZrOCl2 + 2HC1. 

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Further Stages of Sol-Gel Processing of Zirconia-Related Materials... 

Bender, B., Shadwell, D., Bulik, C., Incorvat, L. and Lewis III, D. (1986). Effect of fiber coating and composite processing on properties of zirconia-based matrix SiC fiber composites. Am. Ceram. Soc. Bull. 65, 363-369. 

Randon et al. reported on an alternative approach for the preparation of zirconia monoliths [96]. The sol-gel process is initiated by hydrolysis of an ethanolic zirconium alkoxide solution, on addition... 

Tetragonal zirconia was partly transformed into the cubic phase during the sintering process of the UAP (uniaxially pressed) and CIP-prepared green compacts, and was accompanied by the formation of a-TPC. The transformation tends to accelerate as the PSZ quantity increases. 

Ceramic foils are produced continuously by tape-casting methods. These ceramic tapes consist of an organic binder and oxide powder material, for example, zirconia, titania or alumina. If it is possible to integrate the production process of a micro structured reactor into such a continuous process, production costs would decrease strongly. An early approach used unstructured ceramic foils to build up a micro reactor [159], The reactor consisted essentially of two functional layers, a reaction layer and a heating layer (Figure 4.102). 

What precautions could be taken to prevent the take up of impurities when reducing the particle size of zirconia from 10 pm to 1 pm Describe the beneficial effects that addition of a deflocculating agent might be expected to have on the ball-milling process. 

In the NGASE operation both the anode gas (methane-steam) and cathode gas (hydrogen-steam) are reducing (low ), and thus both electrode materials must be capable of low Po stability. A Ni-based cermet electrode for both anode and cathode will be appropriate for this mode of operation. The authors have observed erosion of zirconia electrolyte at temperatures above 700°C under these conditions. This phenomenon may limit the usefulness of the NGASE process. 

Eguchi, K., Akasaka, N., Mitsuyasu, H., and Nonaka, Y., Process of solid state reaction between doped ceria and zirconia, Solid State Ionics, 2000, 135, 589-594. 

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