CO is a toxic and detrimental air pollutant. It not only affects human beings but also vegetation and indirectly increases global warming. An estimate has shown that vehicular exhaust contributes about 64% of the CO pollution in developed countries. Due to the exponentially increasing number of automobiles on roads, CO concentrations have reached an alarming level in urban areas and regulatory measures had been adopted to curb the menace of vehicular pollution. To control vehicular exhaust pollution, end-of-pipe-technology using noble metals catalytic converters are recommended. The increasing prices of noble metals with the increasing number of vehicles motivates the investigation of material concepts to reduce the precious metal content in automotive catalysts or to find a substitute for noble metals. Among non-noble metals, copper chromite is found to be most promising and exhibits comparable activity for CO oxidation to that of precious metals. Further, low cost, easy availability and advance synthesi...

A Review on CO Oxidation Over Copper Chromite Catalyst

This invention is directed to lithium disilicate (Li 2 Si 2 O 5 ) based glass-ceramics comprising silica, lithium oxide, alumina, potassium oxide and phosphorus pentoxide. The glass-ceramics are useful in the fabrication of single and multi-unit dental restorations (e.g. anterior bridges) made by heat pressing into refractory investment molds produced using lost wax techniques. The glass-ceramics have good pressability, i.e., the ability to be formed into dental articles by heat-pressing using commercially available equipment. In accordance with one embodiment directed to the process of making the glass-ceramics, the compositions herein are melted at about 1200 ° to about 1600 ° C., thereafter cast into steel molds in the shape of cylindrical blanks (pellets), or alternately, cooled to the crystallization temperature. The resulting glass blank are heat-treated to form glass-ceramic blanks via a one or two step heat-treatment cycle preferably in the temperature range of about 400 ° to about 1100 ° C. The resulting glass-ceramic pressable pellets and/or blanks of desired shapes, sizes and structures are later pressed into dental restorations. Alternatively, instead of forming into pressable pellets or blanks, the pulverized powder is used to form a dental restoration using the refractory die technique or platinum foil technique.

Lithium disilicate glass ceramics

This invention is directed to lithium disilicate (Li2 Si2 O) based glass-ceramics comprising silica, lithium oxide, alumina, phosphorus pentoxide, and optionally potassium oxide or tantalum oxide. The glass-ceramics are useful in the fabrication of single and multi-unit dental restorations (e.g. anterior bridges) made by heat pressing into refractory investment molds produced using lost wax techniques. The glass-ceramics have good pressability, i.e., the ability to be formed into dental articles by heat-pressing using commercially available equipment. In accordance with an embodiment directed to the process of making the glass-ceramics, the starting compositions are melted at about 1200° to about 1600 °C, thereafter quenched (e.g., water quenched or roller quenched) or cast into steel molds, or alternately, cooled to the crystallization temperature. The resulting glass is heat-treated to form a glass-ceramic via a one or two step heat-treatment cycle preferably in the temperature range of about 400° to about 1100 °C. The resulting glass ceramics are then pulverized into powder and used to form pressable pellets and/or blanks of desired shapes, sizes and structures which are later pressed into dental restorations.

Pressable lithium disilicate glass ceramics

A silica-based coating for, and a method for coating glass, metal, ceramic, and plastic surfaces by forming single cross-linked O-Si-O polymer chains. The coating generally comprises a binder and a filler. The binder is a mixture of silica-based polymers, colloidal silica, and metal oxide particles in an aqueous suspension. It includes four main ingredients: an alkali metal silicate; silica gel; a cross-linking agent such as methyltrimethoxysilane or tetraethoxysilane; and water. After curing, the binder forms an amorphous layer that binds the fillers to the surface. The protective coating is formed at room temperature, without the addition of energy in any form. The fillers are chosen to provide the coating with mechanical strength, abrasion resistance, and increased corrosion resistance. Fillers may also be chosen to modify the coating's dielectric constant, to improve the coating's surface lubricity, and to alter the coating's thermal coefficient of expansion. Typical fillers include clay, wollastonite, nepheline syenite, talc, flint, ceramic fibers, metallic fibers, ceramic microspheres, glass microspheres, cerium dioxide, and dichromium trioxide.

Room temperature curable surface coatings and method of producing and applying same

Metal products having improved properties and processes for preparing the metal products are provided. In an embodiment, the present disclosure provides for a metal product comprising a metal surface, an oxide layer and a glass layer. The glass layer is provided by coating a stable aqueous silicate or borosilicate solution onto the metal surface and curing the aqueous solution to produce a glass layer. The metal products have surface characteristics that outperform current anodized metal surfaces.

Protective coatings for metals

A composite base metal oxide catalyst of improved high temperature stability is provided by prereacting a selected base metal oxide catalyst or its precursor compounds with a selected refractory high-surface-area spinel or its precursor compounds to form a crystalline solid solution of the catalyst and the spinel. This solid solution has the properties of good catalytic activity and high temperature structural and surface area stability. An example of such a composite catalyst is CuCr2O4 in solid solution with NiAl2O4.

Thermally stable composite base metal oxide catalysts

The present invention relates to a method for hydrating fine-dimensioned alkali metal-containing silicate glass bodies so as to impart the property of thermoplasticity thereto. More particularly, this invention contemplates contacting fine-dimensioned alkali metal silicate glass bodies with an aqueous solution at elevated temperatures and pressures to develop at least a surface layer thereon having a water content ranging up to about 36% by weight, said aqueous solution having a pH less than 6 as measured at room temperature. The hydrated bodies can approach certain properties of high-polymer organic plastics and exhibit the capability of being thermoplastically formed at relatively low temperatures.

Hydration of silicate glasses in aqueous solutions

This invention relates to the production of chemically durable inorganic silicate coatings which are homogeneous, easy to apply, and exhibit essentially infinite shelf life. More specifically, this invention relates to the preparation of such coatings by incorporating a metal oxide (M x O y ) wherein Y:X is at least 1.5, into a true aqueous solution of an alkali metal silicate, at least about 50% by weight of said alkali metal consisting of potassium, which will dry in air, i.e., be non-hygroscopic. Thereafter, upon drying and curing, a crystal phase precipitates in situ within the solution causing polymerization of the silica at the crystal interfaces and subsequently throughout the solution, thus yielding a durable coating consisting essentially of a crystal phase homogeneously dispersed in a silicate glassy matrix.

Larry E. Campbell

Papers

Thermally stable composite base metal oxide catalysts

Hydration of silicate glasses in aqueous solutions

Method for making chemically durable silicate coatings