Lanxides

Alternatively, tows of fibers can be passed through a Hquid metal bath, where the individual fibers are wet by the molten metal, wiped of excess metal, and a composite wine is produced. A bundle of such wines can be consoHdated by extmsion to make a composite. Another pressureless Hquid metal infiltration process of making MMCs is the Prim ex process (Lanxide), which can be used with certain reactive metal alloys such as Al—Mg to iafiltrate ceramic preforms. For an Al—Mg alloy, the process takes place between 750—1000°C ia a nitrogen-rich atmosphere (2). Typical infiltration rates are less than 25 cm/h. 

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

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. Fibres or other reinforcing materials can be placed in the path of the oxidation reaction and so incorporated in 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 Du Pont 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. 

Lanxide process (a) infiltration of preform (b) wicking of liquid metal along grain boundaries (reproduced by permission of Woodhead Publishing Limited)74. 

Fareed, A.S., Sonuparlak, B., Lee, C.T., Fortini, A.J., Schiroky, G.H. (1990), Mechanical properties of 2-D Nicalon fiber-reinforced LANXIDE aluminum oxide and aluminum nitride matrix composites , Ceram. Eng. Sci. Proc., 11(7-8), 782-794. 

C. A. Anderson, P. Barron-Antolin, A. S. Fareed, and G. H. Schiroky, Properties of Fiber-Reinforced Lanxide Alumina Matrix Composites, in Whisker- and Fiber-Toughened Ceramics, eds. R. A. Bradley, D. E. Clark, D. C. Larsen, and J. O. Stiegler, ASM, Materials Park, PA, 1988, p. 209. 

A. W. Urquhart, Novel reinforced ceramics and metals A review of Lanxide s composite technologies. Mater. Sci. Eng. A44, 75-82 (1991). 

William B. Johnson (85), Lanxide Corporation, Newark, Delaware 19714... 

New types of ceramic composites with high thermal shock resistance have recently been developed that show some promise for gas turbine applications. These composites consist of a ceramic matrix reinforced by ceramic fibers or platelets inside the matrix. The fibers pull out of the matrix during fracture to resist crack propagation. Such composites can be readily fabricated using a new process developed by Lanxide Corporation [18]. The process uses directed oxidation reactions of molten metals to grow a ceramic matrix around a reinforcing material. 

The Lanxide process, developed by the Lanxide Corporation, involves the formation of a ceramic matrix by the reaction between a molten metal and a gas, e.g., molten aluminum reacting with oxygen to form alumina. Growth... 

FIGURE 20.18 Illustration of the Lanxide process for making a shaped CMC. 

Newkirk, M.S., A.W. Urquhart, H.R. Zwicker, and E. Breval. 1986. Formation of Lanxide ceramic composite materials. Journal of Materials Research 1(1) 81-89. ... 

One approach for fabricating fiber reinforced ceramic matrix composites is the directed oxidation of metals, a process first introduced by Lanxide Corporation [1, 2] and later used successfully to produce turbine engine and aerospace components. Rights to the DIMOX technology, as it was identified, were ultimately acquired by Power Systems Composites, L.L.C., a subsidiary of the Power Systems business of the General Electric Company. 

A portion of the technical development work leading to the results described was supported by the Defense Advanced Research Projects Agency through the Office of Naval Research. Oxide fiber composites were partially funded by the Department of Energy as part of the CFCC program. Additional funding was provided by the DuPont Company and Lanxide Corporation in support of the DuPont Lanxide Composites Inc. joint venture. 

The author respectfully acknowledges the many stimulating discussions held with various colleagues at Lanxide, DuPont Lanxide Composites and Power Systems Composites, LLC. Williams International and the University of Michigan generated some of the data presented. The permission to use these data from all parties concerned is gratefully acknowledged. 

M.S. Newkirk, H.D. Lesher, D.R. White, C.R. Kennedy, A.W. Urquhart, and T.D. Claar, Preparation of Lanxide Ceramic Matrix Composites Matrix Formation by the Directed Oxidation of Molten Metals, Ceram. Eng. Sci. Proc., 8 [7-8] 879-85 (1987). 

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