Aluminate glass fibers

For example, in bulk appHcations as thermal insulation, synthetic mineral fibers (glass or slag fibers) have adequately replaced natural asbestos fibers. In sprayed insulation coatings, asbestos fibers have been replaced, for example, by vermicuhte. As replacement for asbestos textiles, clothing made from aramid fibers or aluminized glass fibers is being offered (see High PERFORMANCE FIBERS). 

Electrically conductive pipes are less well known. These pipes are used to prevent electrostatic hazards in oil tanker applications. The pipe for this purpose was developed using glass fiber for reinforcement and carbon fiber to obtain conductivity. There are also methods of production of such pipe where aluminized glass fiber is mixed with reinforcing glass fiber. 

Silicate glass fibers, which command by far the largest sales volume in the market, are derived from the liquid phase, a viscous melt. Ultrapure silica fibers are either derived from a melt, which is downdrawn from a preform, or they are dry spun from a viscous solution. While a high melt or solution viscosity seems to be a generai prerequisite for fiber formation, it is possible to form glass fibers, such as YAG or aluminate glass fibers, from melts. 

Aluminate - glass fiber endless solid one comm. liquid/melt 4.3.3... 

Continuous glassy metal ribbons can be formed with high quench rates from their inviscid melts by a rapid solidification process [60] that is akin to a generic bushing process (Figure 3, top left), except that the extruded ribbon must be rapidly cooled on the surface of a cold quench wheel. Continuous aluminate glass fibers and metal wires [10-12] and continuous amorphous YAG fibers [73] can be melt spun from inviscid melts by increasing the jet lifetime... 

Quaternary calcium aluminate glass fibers were also downdrawn from preforms on a laboratory [9] and a development unit [41], Downdrawing is a valid, but costly, method for fiberizing fragile melts. In addition, only one of >500 compositions could be fiberized on a conventional melt fiberizing unit [17], This process is not suitable for fragile melts. 

Quaternary calcium aluminate glass fibers made by updrawing from a supercooled fragile melt offer superior mechanical properties and sapphire-like infrared transmission spectra. 

Their resistance to aikaline media exceeds that of commercially available AR silicate glass fibers (Chapter 6) having a zirconia content of up to 15% [20]. Hydroxyl-free quaternary calcium aluminate glass fibers (Figure 9), e.g., non-silica fibers containing 46.2% AI2O3 -36.0% CaO - 4.0% MgO -13.8% BaO, afford sapphire-like infrared transmission properties. 

In processes with conventional quench rates of 10 K/s, the inviscid liquid (melt) or resulting jet is carefully under- or supercooled to its narrow fiber forming range (log 2.5 to log 3.0 poise). Three types of fibers have been made by variants of this process continuous optical yttrium aluminum garnet (YAG) glass fibers, continuous aluminate glass fibers and steel fibers. 

Figure 12. Straight fiber and frozen Rayieigh waves. The straight cyiindrical fiber represents an inviscid meit spun caidum aluminate glass fiber that had been surface stabilized with particulate carbon. The frozen Rayleigh wave strudure represents a caidum aluminate fiber that was not surface stabilized and solidified while it was in the process of breaking up into droplets and shot...

Continuous binary calcium aluminate glass fibers can also be formed by inviscid melt spinning. In this case, carbon particles which are formed by the decomposition of propane enter into the surface of the molten jet and raise its surface viscosity, a process that lengthens the lifetime of the jet and prevents its breakup. 

Table Vm. Properties of inviscid melt spun calcium aluminate glass fibers [11]...

Inviscid melt spun calcium aluminate glass fibers have low strength (0.5-1.1 GPa) and moduli (46-58 GPa). Low strength and low stiffness can be attributed to the random structure frozen into the fibers during rapid solidification. As a result, they are not likely to become composite reinforcing fibers, despite their excellent alkali resistance which they share with quaternary calcium-aluminate fibers [9]. 

Continuous aluminate glass fibers are formed in the presence of propane, but not in its absence. A viable mechanism of jet stabilization must therefore explain (1) the function of carbon which enters into the surface or skin of the molten jet, (2) the function of carbides and carbonates which are instantly formed in the molten jet surface, and (3) the increase in tetrahedral from octahedral coordination of aluminum atoms in the surface [51] before the fiber solidifies and secondary overgrowth with carbon can occur. 

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