Glass fibers zirconia

A layer with a high specific surface area could be developed on woven glass fiber supports by leaching the nonsilica components out of commercial fabrics in acidic solution [54,62], This treatment created mesoporosity and specific surface areas between 5 and 275 m2 g, depending on the temperature and the contact time with HCI solution. In some cases, the surface of porous glass fibers was modified by titania, zirconia, or alumina to increase the thermomechanical stability and to vary the surface reactivity. The modification was made by impregnation of the porous glass fibers with aqueous solutions of the appropriate salts and subsequent calcinations in air. 

Inorganic membranes, usually appUed when high temperatures or chemically active mixtures are involved, are made of ceramics [171,172], zirconia-coated graphite [173],silica-zirconia [174],zeolites [168], or porous glass [175] among others [176]. Ceramic membranes are steam sterilizable and offer a higher mechanical stability [134], thus they may be preferably used in aseptic fermentations, since some hollow fibers are only chemically sterilizable and not very suitable for reuse. Composite materials, in which glass fiber filters are used as support for the polymerization of acrylamide monomers, were developed for the hydrolysis of penicillin G in an electrically immobilized enzyme reactor. By careful adjustment of the isoelectric point of amphoteric membranes, the product of interest (6-aminopenicillanic acid) was retained in an adequate chamber, adjacent to the reaction chamber, while the main contaminant (phenyl acetic acid), was collected in a third chamber [120]. 

Table IV summarizes the effect of various oxides on the resulting fiber properties [30-31]. The addition of increasing amounts of alumina, beryllia, yttria or nitride has already been discussed in Chapter 4.1.2. These modifiers tend to increase the modulus or stiffness of a glass fiber. In addition, alumina and baria tend to increase the density, alumina and strontia tend to increase the refractive index, and zinc oxide and zirconia tend to increase the alkali resistance of a fiber.

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. 

Oxide fibers include glass fibers, mullite fibers, zirconia fibers and alumina fibers. Of these, a-alumina-based fibers have been used intensively for ceramic matrix composites. Fiber FP, manufactured by Du Pont in 1979, was the first wholly a-alumina fiber produced [34]. At present, Almax (Mitsui Mining Material Co. Ltd., Japan) and Nextel 610 (3M Co., USA) are commercially available a-alumina fibers. Almax contains 99.5% alumina and has an elastic modulus of 330 GPa, and Nextel 610 has a tensile strength of 2.4 GPa and an elastic modulus of 380 GPa [35]. 

Epoxy resin reinforced with 60 vol.% zirconia glass fibers 2004 45 1426 ... 

Many other methods of strengthening are based on formation of composites by inclusion of fibers or whiskers or by crystallization to form glass-ceramics. Phase separation may also affect strength by altering crack propagation mechanisms. Transformation toughening has also been attained by formation of a small concentration of zirconia crystals in glasses. 

Titanium fiber reinforced bioactive glass Zirconia reinforced A-W glass-ceramic Calcium phosphate particle reinforced polyethylene Calcium phosphate fiber and particle reinforced bone cement... 

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