Abstract: A heater for a gas sensor has a first thermistor element and a second thermistor element arranged in an electrically parallel configuration. Each thermistor element may be deposited onto a substrate such that the first thermistor element extends about a perimeter of the substrate and the second thermistor element extends across a portion of the substrate intermediate the perimeter of the substrate. The thermistor elements are preferably fabricated of materials having differing thermal coefficients of resistivity. A method of heating the gas sensor includes disposing the two thermistor elements in an electrically parallel configuration over a surface of the substrate and passing an electric current through the elements.

Abstract: A heater pattern for a heater of a gas sensor in which a temperature profile is manipulated utilizes a thermistor element arranged in an electrically serial configuration and disposed on a substrate. The thermistor element is arranged so as to define an edge pattern extending about a perimeter of the substrate and a center pattern serially connected to the edge pattern. The center pattern extends over a portion of the substrate that is intermediate the perimeter of the substrate. In a preferred embodiment, the thermistor element is screen printed onto the substrate to a thickness of about 5 microns to about 50 microns, and preferably to a thickness of about 10 microns to about 40 microns. The edge and center patterns are furthermore preferably formed of materials having differing coefficients of thermal resistivity, e.g., platinum and platinum/palladium blends.

Abstract: A heater for a gas sensor has a first thermistor element and a second thermistor element arranged in an electrically parallel configuration. Each thermistor element may be deposited onto a substrate such that the first thermistor element extends about a perimeter of the substrate and the second thermistor element extends across a portion of the substrate intermediate the perimeter of the substrate. The thermistor elements are preferably fabricated of materials having differing thermal coefficients of resistivity. A method of heating the gas sensor includes disposing the two thermistor elements in an electrically parallel configuration over a surface of the substrate and passing an electric current through the elements.

Abstract: A catalyst for treatment of exhaust emissions from diesel engines includes a washcoat layer with a catalytically active metal. The washcoat layer has refractory oxide particles with catalytically active metal particles dispersed thereon, and colloidal silica disposed in a thin layer over the refractory oxide and metal particles. The refractory oxide particles and colloidal silica are each characterized by respective surface charges at a selected pH to cause the colloid to form the layer over the refractory oxide and metal particles. Preferably, the pH is selected to provide opposite and attractive surface charges between the colloidal silica and the refractory oxide particles. Preferably, the metal particles are at least one of the group consisting essentially of platinum, palladium, rhodium, ruthenium, copper and chromium.