Fibers directed metal oxidation

Lanxide A process for making composites of metals with oxides. A molten metal reacts with an adjacent oxidant and is progressively drawn through its own oxidation product so as to yield a ceramic-metal composite. Fibers or other reinforcing materials can be placed in the path of the oxidation reaction and so be incorporated into the final product. The Lanxide Corporation was founded in 1983 in Newark, DE, to exploit this invention. In 1990 it formed a joint venture with DuPont to make electronic components by this process. Variations are Dimox (directed metal oxidation), for making ceramic metal composites, and Primex (pressureless infiltration by metal), for making metal matrix composites. 

With the analysis embodied in Fig. 12, the formation of carbon fiber reinforced Si3N4 matrix materials by directed metal oxidation of molten silicon can also be described. To avoid fiber degradation during processing, the fiber should, ideally, be thermodynamically stable with respect to... 

Fig. 14. Micrograph of a C-fiber reinforced Si3N4 matrix composite prepared by directed metal oxidation. From Johnson [52],...

A variety of CMC systems have been developed and fabricated in the past. These have included aluminum oxide, aluminum nitride and sihcon nitride matrix composites [3-5]. The reinforcement has predominantly consisted of silicon carbide based fibers. Oxide based fibers have also been evaluated over the years as and when they have become available. This chapter reviews the development effort of silicon carbide reinforced aluminum oxide matrix composites fabricated via directed metal oxidation and compares them with those reinforced with oxide fibers. 

The generic process for fabrication of fiber-reinforced aluminum oxide matrix composites by directed metal oxidation includes preforming, fiber-matrix interface coating, matrix growth and removal of residual aluminum. A flow chart with the various processing steps is shown in Fig, 1. 

A.S. Fareed, G.H. Schiroky, andC.R. Kennedy, Development ofBN/SiCFiberCoatings for Fiber-Reinforced Alumina Matrix Corrposites Fabricated by Directed Metal Oxidation, CerattL Eng. Sd. Proc., 14 [9-10] 794-801(1993). 

A.S. Fareed, Ceramic Matrix Composite Fabrication and Processing Directed Metal Oxidation, Handbook on Continuous Fiber Reinforced Ceramic Matrix Composites, ed. R.L. Lehman, S.K. El-Rahaiby Jr and J.B. Wachtman, Jr., ClAC/ACers, 301-324 (1995). 

G.H. Schiroky, A.S. Fareed, B. Sonuparlak, C.T. Lee, and B. Sorenson, Fabrication and Properties of Fiber-Reinforced Ceramic Composites Made by Directed Metal Oxidation, pp. 151-163, in Flight-Vehicle Materials, Structures and Dynamics - Assessment and Future Directions, Vol. 3, S.R. Levine Jr, ed, ASME, New York, 1992. 

Farced, A. S., Schiroky, G. H., and Kennedy, C. R. (1993). Development of BN/SiC duplex fiber coatings for fiber-reinforced aluminia matrix composites fabricated by directed metal oxidation. Ceram. Eng. Sci. Proc. 18 794-801. 

Figure 1.6 Optical micrograph of an AI2O3/AI matrix reinforced with SiC fibers produced by directed metal oxidation. (From Ref 15.)...

Dyes are also classified on the basis of their application. The water-soluble dyes which are the salts of sulfonic acid or phenolic compounds are named acid dyes] those which are the salts of amino compounds are called basic. If the dyeing is accomplished without use of mordants the dyes are called direct. Dyes which require the use of metallic oxides, tannin, and other substances to give fast shades are called mordant dyes. The water-insoluble dyes are known as vat dyes. The insoluble colored substance is reduced in a fermentation vat or by hydrosulfite to a soluble form which is applied to the fiber then oxidized by air to the insoluble color. Finally ingrain dyes are produced by performing one or more of the chemical reactions used for the preparation of the dye directly on the fiber. 

TABLE rV. Selected Properties of Oxide Fibers Used to Fabricate CMCs Via Directed Metal... 

Insolubilization. Insolubilization of compounds within textiles parallels the history of humanity the direct dyeing techniques for cotton were highly advanced in the Bronze Age. With the exception of fiber-reactive dyes discussed earlier, other cotton dyes, ie, vat and sulfur, are insolubilized within the fiber after an oxidization step. Insoluble metal oxides have been used to flameproof cotton, and zirconium compounds have been insolubilized on cotton to render the fabric microbial resistant (135) or mildew resistant (136) via a mineral dyeing process (see Textile Finishing). 

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