摘要:
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.
摘要:
Low-density composites are produced consisting chiefly of boron carbide and aluminum, or aluminum alloy, and minor amounts of ceramic material. The method allows control of the rate of reaction between boron carbide and metal so that the final components of the composite, and hence the mechanical properties, are controlled. The invention includes modification of the carbon content of the boron carbide composition, dispersion of boron carbide and formation of a compact, infiltration of the compact by aluminum or aluminum alloy, and heat treatments. The invention produces low-density boron carbide-aluminum composites with a homogeneous microstructure possessing desired mechanical properties.
摘要:
A porous discriminating layer is formed on a ceramic support having at least one porous wall by (a) establishing a flow of a gas stream containing agglomerates of particles and (b) calcining said deposited layer to form the discriminating layer. At least a portion of the particles are of a sinter-resistant material or a sinter-resistant material precursor. The particles have a size from 0.01 to 5 microns and the agglomerates have a size of from 10 to 200 microns. This method is an inexpensive and effective route to forming a discriminating layer onto the porous wall.
摘要:
An improved ceramic honeycomb structure is comprised of at least two separate smaller ceramic honeycombs that have been adhered together by a cement layer comprised of a cement layer has at least two regions of differing porosity or cement layer where the ratio of toughness/Young's modulus is at least about 0.1 MPa·m1/2/GPa.
摘要:
A skin is applied to a ceramic honeycomb. The skin is formed by applying a skin-forming composition and drying it. The skin-forming composition includes a carrier liquid, colloidal silica and/or colloidal alumina, and an inorganic filler. The filler includes an inorganic fiber. The filler may contain low aspect ratio particles that have the same or nearly the same CTE as the inorganic fiber. The filler may include a small proportion of a low aspect ratio filler particle that has a different CTE than the inorganic fiber.
摘要:
A ceramic honeycomb structure comprised of at least two separate smaller ceramic honeycombs that have been adhered together by a cement comprised of inorganic fibers and a binding phase wherein the smaller honey-combs and fibers are bonded together by the binding phase which is comprised of an silicate, aluminate or alumino-silicate. The fibers have a multi-modal size distribution in which some fibers have lengths of up to 1000 micons and other fibers have lengths in excess of 1 mm. The cement composition may be made in the absence of other inorganic and organic additives while achieving a shear thinning cement, for example, by mixing oppositely charged inorganic binders in water together so as to make a useful cement composition for applying to the smaller honeycombs to be cemented.
摘要:
A porous mullite composition is made by Forming a mixture of one or more precursor compounds having the elements present in mullite (e.g., clay, alumina, silica) and a property enhancing compound. The property enhancing compound is a compound having an element selected from the group consisting of Mg, Ca, Fe, Na, K, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, B, Y, Sc, La and combination thereof. The mixture is shaped and to form a porous green shape which is heated under an atmosphere having a fluorine containing gas to a temperature sufficient to form a mullite composition comprised substantially of acicular mullite grains that are essentially chemically bound.
摘要:
A concrete article comprised of concrete having therein a reinforcing polymer that has a surface comprised of a thermoplastic hydroxy-functionalized polyether or polyester. The concrete article is made by mixing concrete, water and a reinforcing polymer that has a surface comprised of a thermoplastic hydroxy-functionalized polyether or polyester and curing said concrete mixture forming the concrete article.
摘要:
A method for preparing a concrete article comprised of concrete having therein a reinforcing fiber, where at least about 50 percent of the reinforcing fibers are frayed only at an end or ends of the reinforcing fibers, may be made by mixing concrete, water and a reinforcing fiber for a sufficient time to fray the ends of at least 50 percent of the fibers and curing the mixture to form the concrete article. The fiber may be a reinforcing fiber comprised of at least two filaments bonded together and the filaments being comprised of a polymeric core and a polymeric sheath comprised of a fusing-fraying polymer, such that the reinforcing fiber, when mixed with inorganic particulates, frays predominately only at an end or ends of the fiber
摘要:
A ceramic-metal composite that is tough and stiff has been prepared and is comprised of an inert ceramic (e.g., alumina) embedded and dispersed in a matrix comprised of a metal (e.g., aluminum), a reactive ceramic (e.g., boron carbide) and a reactive ceramic-metal reaction product (e.g., AlB2, Al4BC, Al3B48C2, AlB12, Al4C3, AlB24C4 or mixtures thereof) wherein grains of the inert ceramic have an average grain size greater than or equal to the average grain size of grains of the reactive ceramic. The ceramic-metal composite may be prepared by forming a mixture comprised of an inert ceramic powder (e.g., alumina) and a reactive ceramic powder (e.g., boron carbide), the inert ceramic powder having an average particle size equal to or greater than the average particle size of the reactive ceramic powder, forming the mixture into a porous body and consolidating the porous body in the presence of a metal (e.g., aluminum) to form the ceramic-metal composite.