Refractory production routes

The preparation of ferrovanadium by this route is carried out batchwise in refractory-lined open reactors, with vanadium pentoxide, aluminum powder, iron scrap and lime or fluorspar constituting the charge. The reactions once initiated, proceed briskly to completion. The reaction heat is sufficient to melt the ferrovanadium and the alumina-lime/fluor-spar slag, which readily separate due to density difference. The aluminothermic ferroalloy product contains practically no carbon. 

Zirconium oxides are extensively used in many fields (such as ceramic, refractory, sensor and catalysis) due to their properties[l]. Many methods have been developed for the production of such materials[2]. Among them. Rapid Thermolysis Approach (RTA) is a safe, simple and instantaneous route. Kingsley firstly reported the preparation of alumina and related oxides by RTA[3]. However, the samples derived showed a relative low BET surface area. ZrOj so-produced has been shown to be highly active towards CO oxidation and methane combustion. In order to have a full understanding of so-derived zirconia, the preparation of zirconia is in the first instance investigated in the present work. 

Aluminates are refractory materials and their synthesis often simply involves solid-state growth of mixtures of purified oxides. Alternative synthesis routes are also used in specialist applications, for example in production of materials with controlled porosity and these invariably involve sol-gel methods. For glasses, one notable, commercially important method of production is container-less synthesis, which is necessary because of the non-Arrhenius (fragile) viscosity of aluminate liquids. 

Polymer pyrolysis to form advanced ceramics allows the production of highly covalent refractory components (fibers, films, membranes, foams, joints, monolithic bodies, ceramic matrix composites) that are difficult to fabricate via the traditional powder processing route [1-4]. Yajima was the first to demonstrate the feasibility of producing high-strength SiC-based fibers from pyrolysis of polycarbosilane [5]. In this process, a thermoplastic pre-ceramic polymer is first shaped into the desired form, cross-linked into a pre-ceramic network and finally converted into a ceramic material by a pyrolysis process in a controlled atmosphere (Fig. 1). A common feature of the polymer route is the formation of intermediates called amorphous covalent ceramics (ACC) [6]. These are formed after removal of the organic components and before crystallization that occurs at higher temperatures. 

The refractories may corrode and there may be difficulties to complete the reaction. Therefore this process may be seen as less satisfactory to produce a high-quality product. Metasilicate produced by this route may bear a considerable proportion of insoluble material such as unreacted sand, natural impurities in sand, and refractory particles [1,7]. 

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