High silica fibers

High temperature textiles consisting of continuous filaments of amorphous silica in a variety of forms are available conunerdally. These can he used to replace asbestos-based high temperature textiles because of the health hazards associated with asbestos fiber. These high silica fibers are used for a variety of high temperature thermal insulation products for example, welding curtains. 

Quartz fibers are made from natural quartz crystals by softening quartz rods in an oxy-hydrogen flame and drawing rods into filaments. Because high purity quartz crystals are rare, the cost of quartz fibers is considerable higher than that of glass fiber and high silica fibers. 

Figure 15. Strength retention of commercial silica yams at elevated temperatures. Sil and QSA fibers are derived from the liquid phase. Silfa Is a pure silica yam made from a viscous waterglass solution. Q A is an ultrapure silica fiber made from a high viscosity melt. Asahl, Nextel and Refrasil are derived from solid phase precursor fibers. Asahi is an ultrapure silica fiber, Nextel is an alumlnate fiber, and both are derived from a sol-gel precursor fiber. Refrasil is a high silica fiber It is derived from borosllicate E-glass by add leaching. Redrawn from product information supplied by Ametek Corporation in Wilmington, DE...

High silica fibers by leaching of borosllicate fibers... 

It is clear that processing must address both loss (with impurities in the parts per billion range) and fiber structure designed to minimize dispersion. Figure 4 shows the window of transparency for high silica fiber. At short wavelengths, loss is bounded by ultraviolet... 

Figure 21. Demonstration of high strength and sharp distribution of tenacity of silica fibers protected and controlled compared to those from conventional...

Initial attempts to prepare Cf metal using metallothermic reduction methods (Section II,A) were less than successful due to the high vapor pressure of Cf metal 28, 46). Reduction of californium oxide with La metal (Section II,B) and collection of the product Cf metal on a fused silica fiber (in the apparatus shown schematically in Fig. 15), were found to give metal with usable X-ray diffraction patterns (5). Later, the same method was used to collect Cf metal both on a fused silica fiber for X-ray diffraction analysis and on an electron microscopy grid for electron diffraction analysis 56). As more Cf became available, preparations via this method were carried out on 0.4-1.0-mg samples of californium oxide (55), using fibers of quartz. Be, or C (suitable for direct X-ray diffraction analysis) to collect the product Cf metal. 

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