The United States of America As Represented by the United States

Thermal Technology, Inc.

University of California

Danny C Halverson

Richard L Landingham

Zuhair A Munir

Beverly Y Lum

George M Johnston

Garth W Billings

Joseph B Holt

Ilhan A Aksay

Stephen D Dunmead

Aleksander J Pyzik

Neutron absorbing refractory B.sub.4 C-Gd and Gd.sub.2 O.sub.3 -Gd cermets, B.sub.4 C-Gd and Gd.sub.2 O.sub.3 -Gd metal-matrix composites, and B.sub.4 C-Gd.sub.2 O.sub.3 ceramic-ceramic composites can be manufactured by applying fundamental thermodynamic and kinetic guidelines as processing principals. Three steps are involved in the fabrication of these new compositions of matter. First, the starting materials are consolidated into a compacted porous green body. Next, the green body is densified using the appropriate method depending on the class of material sought: cermet, metal-matrix composite, or ceramic-ceramic composite. Finally, either during the densification process or by subsequent heat treatment, new phase evolution is obtained via interfacial chemical reactions occurring in the microstructures. The existence of a new phase has been identified in B.sub.4 C-Gd and B.sub.4 C-Gd.sub.2 O.sub.3 composites.

High neutron absorbing refractory compositions of matter and methods for

Neutron absorbing refractory B.sub.4 C--Gd and Gd.sub.2 O.sub.3 --Gd cermets, B.sub.4 C--Gd and Gd.sub.2 O.sub.3 --Gd metal-matrix composites, and B.sub.4 C--Gd.sub.2 O.sub.3 ceramic-ceramic composites can be manufactured by applying fundamental thermodynamic and kinetic guidelines as processing principals. Three steps are involved in the fabrication of these new compositions of matter. First, the starting materials are consolidated into a compacted porous green body. Next, the green body is densified using the appropriate method depending on the class of material sought: cermet, metal-matrix composite, or ceramic-ceramic composite. Finally, either during the densification process or by subsequent heat treatment, new phase evolution is obtained via interfacial chemical reactions occurring in the microstructures. The existence of a new phase has been identified in B.sub.4 C--Gd and B.sub.4 C--Gd.sub.2 O.sub.3 composites.

High neutron-absorbing refractory compositions of matter and methods for

A self-sustaining combustion synthesis process for producing hard, tough, lightweight, low exothermic potential product (LEPP)/high exothermic potential product (HEPP) composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the LEPP and HEPP reactants. For lightweight products the composition must be relatively rich in the LEPP component. LEPP rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.

Combustion synthesis of low exothermic component rich composites

Ceramic-metal composites (cermets) are made by a combination of self-propagating high temperature combustion synthesis and molten metal infiltration. Solid-gas, solid-solid and solid-liquid reactions of a powder compact produce a porous ceramic body which is infiltrated by molten metal to produce a composite body of higher density. AlN-Al and many other materials can be produced.

Cermet materials prepared by combustion synthesis and metal infiltration

A self-sustaining combustion synthesis process for producing hard, tough, lightweight B.sub.4 C/TiB.sub.2 composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the B.sub.4 C and TiB.sub.2 reactants. For lightweight products the composition must be relatively rich in the B.sub.4 C component. B.sub.4 C-rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.

Combustion synthesis of boride and other composites

A chemical pretreatment method is used to produce boron carbide-, boron-, and boride-reactive metal composites by an infiltration process. The boron carbide or other starting constituents, in powder form, are immersed in various alcohols, or other chemical agents, to change the surface chemistry of the starting constituents. The chemically treated starting constituents are consolidated into a porous ceramic precursor which is then infiltrated by molten aluminum or other metal by heating to wetting conditions. Chemical treatment of the starting constituents allows infiltration to full density. The infiltrated precursor is further heat treated to produce a tailorable microstructure. The process at low cost produces composites with improved characteristics, including increased toughness, strength.

Infiltration processing of boron carbide-, boron-, and boride-reactive

Hard, tough, lightweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidation step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modulus of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi.sqroot.in. These composites and methods can be used to form a variety of structural elements.

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Modesto, CA, United States of America

Danny C Halverson