Zirconium silicate refractories

Zirconium-silicate refractories have found successful application in certain parts of glass furnaces, in particular those for borosilicate and fluoride glasses (tank, feeder, throat). Refractories based on Cr203 have recently been employed at the critical points of glass tanks. This oxide show s the best resistance to glass-contact corrosion but its application is limited by its colouring effect. 

Zirconia. Zircon (zirconium silicate), the most widely occurring zirconium-bearing mineral, is dispersed in various igneous rocks and in zircon sands. The main deposits are in New South Wales, Australia Travancore, India and Florida in the United States. Zircon can be used as such in zircon refractories or as a raw material to produce zirconia. The zircon structure becomes unstable after about 1650°C, depending on its purity, and decomposes into Zr02 and Si02 rather than melting (see Zirconiumand zirconium compounds). 

Zirconia. Zircon (zirconium silicate), the most widely occurring zirconium-bearing mineral, is dispersed in various igneous rocks and in zircon sands, Zircon can be used as such in zircon refractories or as a raw material to produce zirconia, ZrC>2. 

The range of materials used as refractories is very wide and includes such substances as the fireclays and kaolins, quartzites, bauxites, schist, magnesite, dolomite, graphite, carborundum, fused alumina, chromite, magnesium aluminate, magnesium silicate, zirconium oxide, zirconium silicate, boron nitride, and others. 

Special Refractories.— Under certain conditions refractories of special qualities may be employed such as zirconium oxide, zirconium silicate, chromite, fused silica, boron nitride, aluminum nitride, lime, beryllium oxide, cerium dioxide, thoria, asbestos and various synthetic combinations. 

Experimental arrangement for studying a heterogeneous reaction between zirconium silicate (ZS) refractory (1) and oxidic melt (2). The zirconia electrode (3) is used as a reference electrode for the platinum electrode (4) measuring the oxygen fugacity of the melt, for the ZS crucible (1), and for a short-circuit with ZS, via platinum contact (3). 

Cederqvist studied 17 different tool materials to friction stir weld 50 mm thick copper (Ref 33), and the first material evaluations were for use as the tool pin. Tungsten carbide-cobalt pins provided the initial welding parameter development, but tool life issues (due to large spindle eccentricities) made this tool material impractical for production. Likewise, eccentricity issues caused PCBN, alumino-silicate, and yttria-stabilized zirconium oxide pins to fail within the plunge or dwell sequence of the friction stir welds. A majority of e pins manufactured from refractory metals (four molybdenum-base and three tungsten-base) did not have dimensional... 

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