Abstract: A mullite composition is comprised substantially of mullite grains that are essentially chemically bound wherein the composition has at least two adjoining regions that have substantially different microstructures. The composition may be produced by forming a mixture of one or more precursor compounds having the elements present in mullite; shaping the mixture into a porous green shape applying a nucleation control agent to a portion of the porous green shape and then heating the porous green shape under an atmosphere and to a temperature sufficient to form the mullite composition.

Abstract: A mullite composition is comprised substantially of mullite grains that are essentially chemically bound wherein the composition has at least two adjoining regions that have substantially different microstructures. The composition may be produced by forming a mixture of one or more precursor compounds having the elements present in mullite; shaping the mixture into a porous green shape applying a nucleation control agent to a portion of the porous green shape and then heating the porous green shape under an atmosphere and to a temperature sufficient to form the mullite composition.

Abstract: A mullite composition is comprised substantially of mullite grains that are essentially chemically bound wherein the composition has at least two adjoining regions that have substantially different microstructures. The composition may be produced by forming a mixture of one or more precursor compounds having the elements present in mullite; shaping the mixture into a porous green shape applying a nucleation control agent to a portion of the porous green shape and then heating the porous green shape under an atmosphere and to a temperature sufficient to form the mullite composition.

Abstract: An aluminum nitride powder that has substantially no ammonia odor after exposure to atmospheric moisture is obtained by admixing the powder with a gettering compound that sublimes or decomposes at a temperature below 500.degree. C. The gettering compound is a C.sub.1 -C.sub.11 aliphatic carboxylic mono- or polyfunctional acid, an anhydride or an ester of such an acid or an anhydride of an aromatic carboxylic acid.

Abstract: A filter useful for separating contaminants from fluids includes a fused single crystal acicular ceramic support having a discriminating layer thereon, such as a sintered, porous alpha-alumina membrane, on at least part of the support. The support is preferably composed of a non-stoichiometric acicular mullite of about 76 percent by weight Al.sub.2 O.sub.3 and about 24 percent by weight SiO.sub.2. The support can be any one of a variety of shapes, but is conveniently elongated in form and preferably includes a plurality of parallel channels through it. The support may be in either a dead-end or cross-flow configuration. In the dead-end configuration, half of the channel holes at each end are plugged in a checkerboard arrangement with the holes open at one end and plugged at the other end. In the cross-flow configuration, all channels are connected by a series of shallow slits cut in the filter, and no end plugs are used.

Abstract: A cross-flow structure useful for filtering a fluid, for exchanging one or more constituents between two fluids, or for exchanging heat between two fluids, includes a body having porous partition walls defining at least one open channel extending entirely through it, and a portion of collecting fluid exiting the body through the porous partition walls, rather than through the open channel(s). The body is composed of a fused, interlocked, single crystal acicular ceramic material, preferably a non-stoichiometric acicular mullite of about 76 percent by weight Al.sub.2 O.sub.3 and about 24 percent by weight SiO.sub.2. The portion for collecting fluid exiting from the porous walls is preferably an impermeable coating, such as a glaze, substantially covering the exterior of the body, except for the areas where fluid enters the open channel(s) and exits the porous walls.

Abstract: A regenerable exhaust gas filter element for diesel engines includes an interlaced network of mullite crystals grown together forming a rigid porous body. Soot carried by exhaust gas from a diesel engine flowing through the filter is trapped in the porous body and thereafter burned off to regenerate the element. A network of mullite crystals in accordance with the invention is automatically interlaced and fused with one another to form the porous body of the filter element.

Abstract: A method comprising contacting an organic polymer viscosified halide ion-containing, aqueous solution with a sufficient amount of an in situ, electrochemically generated breaker suitable to reduce the viscosity of the solution.

Abstract: An anionic co-catalyst system is provided for the oxidation of organic compounds in aqueous solutions. After the solution is acidified, a nitrate ion source and at least one of either a bromide or an iodide ion source are introduced into the solution which is heated in the presence of an oxidizing agent.