Boron oxide fibers

Boron nitride fibers have been prepared in the laboratory by chemical vapor infiltration of boron oxide glass fibers with ammonia (Equation 8), a process that may alternatively be considered to be a nitridation of B2O3 precursor fibers [31]. The precursor fibers, in turn, are melt spun at a low temperature (480 C) from a viscous melt. Thus, the nitridation of a boron oxide fiber could alternatively be considered to be derived from a solid precursor fiber, a topic otherwise discussed in Chapters 8 to 12. In this process, the final step is the chemical conversion of a given precursor fiber at a high temperature in a highly reactive vapor phase environment. 

Economic Aspects and Uses. The principal producers in the United States are U.S. Borax and Chemical Corp., North American Chemicals Co., and American Borate Corp. Their combined aimual capacity in 1989 was reported to be 735,000 metric tons of equivalent boron oxide [1303-86-2], B2O2 (20). Of this toimage, 50% is exported. About 30% of boron compounds are used in glass fiber insulation. Another 30% is used in other type fibers and borosihcate glasses. Boron is also used in soaps and detergents, fire retardants, and agriculture (see Boron compounds). 

Bore skin fibers, 16 22 Boric acid, 4 249-255. See also Boron oxides, boric acid, and borates analysis, 4 255... 

Fiber glass - [GLASS] (Vol 12) - [REINFORCED PLASTICS] (Vol 21) -borate m pORON COMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vol 4) -borate m [BUILDING MATERIALS - SURVEY] (Vol 4) -for sound absorption [INSULATION, ACOUSTIC] (Vol 14) -use m ablative materials [ABLATIVE MATERIALS] (Vol 1) -use m conveying equipment [CONVEYING] (Vol 7) -use of oxygen for [OXYGEN] (Vol 17)... 

Fibers, glass - pORONCOMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vol 4)... 

Inorganics Oxides (glass, MgO, Si02, A1203) Hydroxides (Al(OH)3) Salts (CaC03, BaS04, CaS04, phosphates) Silicates (talc, mica, kaolin, woolastonite) Metals (boron, steel fibers)... 

The last quarter of the twentieth century saw tremendous advances in the processing of continuous, fine diameter ceramic fibers. Figure 6.4 provides a summary of some of the important synthetic ceramic fibers that are available commercially. We have included in Fig. 6.4 two elemental fibers, carbon and boron, while we have excluded the amorphous, silica-based glasses. Two main categories of synthetic ceramic fibers are oxide and nonoxides. A prime example of oxide fibers is alumina while that of nonoxide fibers is silicon carbide. An important subclass of oxide fibers are silica-based glass fibers and we devote a separate chapter to them because of their commercial importance (see chapter 7). There are also some borderline ceramic fibers such as the elemental boron and carbon fibers. Boron fiber is described in this chapter while carbon fiber is described separately, because of its commercial importance, in Chapter 8. 

A boron nitride fiber can be very competitive commercially with carbon fiber. It has about the same density (2.2 g/cm ) as the carbon fiber, but has greater oxidation resistance and excellent dielectric properties. A method of converting boric oxide precursor fibers into boron nitride fibers has been developed (Economy and Anderson, 1967). Melt spun boric oxide precursor fiber is nitrided with ammonia according to the following reaction ... 

Wider use of fiber-reinforced ceramic matrix composites for high temperature structural applications is hindered by several factors including (1) absence of a low cost, thermally stable fiber, (2) decrease in toughness caused by oxidation of the commonly used carbon and boron nitride fiber-matrix interface coatings, and (3) composite fabrication (consolidation) processes that are expensive or degrade the fiber. This chapter addresses how these shortcomings may be overcome by CVD and chemical vapor infiltration (CVI). Much of this chapter is based on recent experimental research at Georgia Tech. 

This chapter will describe the processing and properties of an oxide fiber reinforced ceramic matrix composite with a silicon oxycarbide matrix based on a PDC technology, introduced by AlliedSignal (now Honeywell International) under the trademark of Blackglas ceramic. The oxide fiber in this CMC system is the Nextel 312 fiber (3M, Inc.) that has been treated to form a boron nitride surface coating. The information that follows was primarily developed from Low Cost Ceramic Matrix Composites (LC ) program funded by DARPA from 1991-1997. 

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