Alumina/Silica Fibers

Expanded alumina silica fiber blanket with a minimum density of 6 Ib/fC (96 kg/m )... 

Fig. 3. Effect of density on thermal conductivity. A, 48-mg/cm3 silica fiber B, 96-mg/cm3 silica fiber C, 128-mg/cm3 alumina—silica fiber D, 192-mg/cm3...

Figure 6.8 Schematic of the Sumitomo process for making an (alumina+ silica) fiber.

Horikiri, S., K. Tsuji, Y. Abe, A. Fukui, and E. Ichiki. 1978. Process for producing alumina fiber or alumina-silica fiber. U.S. PATENT 4,101,615, 1978 July 18. 

The Nextel 720 contains the same alumina to silica ratio as in the Altex fiber, that is around 85% wt AI2O3 and 15 % wt Si02- The fiber has a circular cross section and a diameter of 12 im. The sol-gel route and higher processing temperatures have induced the growth of alumina rich mullite and alpha alumina. Unlike other alumina-silica fibers the Nextel... 

As shown in Figure 5 of Chapter 4, the modulus increases as the alumina content of the fibers increases. For a given composition, the stiffness of alumina-silica fibers produced by the sol-gel route depends on the residual porosity and hence the processing conditions. For example, the modulus of alumina fibers with a 96 AbOrSiOz (wt.%) composition increases from 110 GPa for the highly porous r -transition alumina fiber, to 280-300 GPa for the dense 5-AI2O3 fiber prepared at higher temperature. 

Various ceramic oxides are used for making ceramic fibers, among them pure alumina fibers and alumina-silica fibers are the most common. The former were commercialized by ICl Ltd. under the trade name SaffW extensively used in high temperature insulation to replace asbestos and glass fiber felts that pose occupational safety issues, while alumina-silica fibers were commercialized by 3M under the trade name Nextel . Various processing routes can be used to manufacture ceramic oxide fibers, the most common being ... 

Saffil alumina-silica fibers have excellent thermal insulation behavior and resilience up to 1600°C. Their diameter is small, about 3 p.m. 

I would like to give an overview of inorganic fibers technology, then discuss the developments and keys structural feat ires of alumina and alumina/silica fibers and new products based on inorganic fibers. The development of inorganic fiber reinforced materials requires a systems approach to tailor the fiber structure to be compatible with the matrix and assure component fabricability and performance. 

Figure 28 compares the perfomance of alumina-silica fiber-reinforced aluminum matrix composites vith competitive ceramics and imreinforced aluminum alloys. Inorganic fiber reinforced metal matrix composites appear to have the best combination of properties for piston insert applications. 

The materials used for the launders - alumina silica fiber materials with coatings, fused silica, wollastonite, LCCs and MCCs, heat insulation castables - only partly satisfy the above-listed requirements. 

Many articles used at casting of aluminium are called casting tooling. They are small (sometimes 1-2 kg, others are 10-20 kg), and the consumption of the cast house may be within tens to hundreds of items per year. Stoppers, glasses, sieves, siphons, plugs, funnels, terminal boxes, and the like should be thermal shock-resistant and shouldn t interact with Al. At a certain time, all these articles were made from asbestos-containing materials. Currently, they are made from wollas-tonite and from alumina silica fiber compositions, sometimes with impregnation. 

---