Abstract: An exhaust emission control device includes a single filter assembly composed of a pair of side plates respectively formed in an L-letter shape in cross-section and integrally assembled in a square framework having inlet and outlet openings, and a plurality of ceramic filter elements aligned in parallel within the square framework and clamped by the side plates. The filter elements are each made of porous ceramic material and have a thin-walled cellular structure square in cross-section formed with a plurality of axially extending passages separated from each other by thin partition walls, wherein a first group of the passages are closed at their one ends in a checked pattern and opened at their other ends to introduce therein exhaust gases to be purified, while a second group of the passages are opened at their one ends to discharge purified gases therefrom and closed at their other ends in a checked pattern.

Abstract: A porous structure consisting of one or more packings each consisting of honeycomb blocks arranged in a first direction in the plane of the packing perpendicular to the nominal direction of fluid flow through the structure. Each block includes partition walls which define channels inclined to the nominal direction and provided in parallel rows arranged in the first direction. The walls include intersections by which the channels of each row are spaced apart from each other in a second direction perpendicular to the first direction. The walls define a pair of voids between the adjacent channels of each row, at least one of the voids constituting part of the channels of the adjacent rows. Perforations are formed through the walls in a direction intersecting the rows of channels, for fluid communications between the adjacent channels of each row and adjacent rows.

Abstract: A porous structure through which at least one fluid flows, consisting of a plurality of honeycomb blocks each of which has partition walls defining a multiplicity of parallel channels. The plurality of honeycomb blocks adjacently located in stacked packings, the stacked packings being superposed on each other such that the parallel channels formed in honeycomb blocks in two superposed stacked packings communicate with each other. The parallel channels in one of the honeycomb blocks are inclined with respect to the parallel channels in the corresponding honeycomb blocks such that the honeycomb blocks cooperate to form a multiplicity of zigzag fluid passages extending through the porous structure.

Abstract: A packing material for a packed tower through which fluids to be processed are adapted to flow in contact with each other. The packing material comprises a packing block of honeycomb structure comprising partition walls defining a multiplicity of channels which are formed in parallel to each other as fluid passages through the packing block. The packing block includes plural plane sides in which said channels are open at opposite ends thereof. At least one of these plane sides is non-orthogonal or inclined to a line of extension of the channels. This at least one non-orthogonal plane side may have a larger surface area than the rest of the plane sides of the packing block. The packing block is preferably a polyhedron having not less than eight planes sides each as viewed in elevation, so that said channels are open in non-orthogonal relation with at least two of the plane sides of the polyhedron.

Abstract: A silicon nitride base sintered body having high strength and high density is formed by a normal sintering, namely by sintering without pressure. The sintered body is produced of silicon nitride and the metal oxides yttrium oxide and cerium oxide.A silicon nitride base sintered body having yet a higher strength and higher density can be produced by heating yttrium oxide and cerium oxide together for forming Y.sub.2 O.sub.3.2CeO.sub.2 before sintering.

Abstract: A silicon nitride based ceramic is formed of silicon nitride and at least two metal oxides of such a type that when the metal oxides are heated separately they form a spinel. Combination of said metal oxides and said silicon nitride as fine powders and sintering same at a specified temperature for a specified period of time results in a silicon nitride based ceramic having improved mechanical and chemical properties.

Abstract: A silicon nitride based ceramic is formed of silicon nitride and at least two metal oxides of such a type that when the metal oxides are heated separately they form a spinel. Combination of said metal oxides and said silicon nitride as fine powders and sintering same at a specified temperature for a specified period of time results in a silicon nitride based ceramic having improved mechanical and chemical properties.

Abstract: A resistor built-in spark plug comprising an insulator formed therein with an axially extending bore, a terminal nut fitted in an upper end portion of the bore, a center electrode fitted in a lower end portion of the bore, a resistor arranged in a central portion of the bore, one copper-glass electrode interposed between the resistor and the terminal nut, and another copper-glass electrode interposed between the resistor and the center electrode, such resistor being made by firing (calcining) and solidifying a resistor powder mixture consisting of 30 to 10 volume % of a principal resistor component containing tin oxide, 35 to 85 volume % of insulating ceramic filler powder of a higher electric resistivity than the principal resistor component which is selected from the group consisting of quartz glass, alumina, zircon, zirconia, silica (SiO.sub.2) and .beta.-spodumene, and 35 to 5 volume % of glass powder having a softening temperature in a range between 300.degree. and 600.degree. C.

Abstract: A resistor built-in spark plug comprises an insulator formed with an axially extending inner hole, a stem fitted in the upper part of said hole in said insulator, a center electrode fitted in the lower part of said hole, a resistor disposed in the central part of said hole, and copper-glass electrode layers disposed between said resistor and said stem and between said resistor and said center electrode. Said resistor is made by firing and solidifying powder of resistor mixture consisting of 75 to 38 volume percent of main resistor component containing tin oxide and 25 to 62 volume percent of glass powder with softening temperature of 300.degree. to 600.degree.C. Said copper-glass electrode layers are made by firing and solidifying a mixture of copper powder and glass powder with the softening temperature of above 530.degree.C and more than 30.degree.C higher than the softening point of glass in the resistor portion.

Abstract: A silicon nitride based ceramic is formed of silicon nitride and at least two metal oxides of such a type that when the metal oxides are heated separately they form a spinel. Combination of said metal oxides and said silicon nitride as fine powders and sintering same at a specified temperature for a specified period of time results in a silicon nitride based ceramic having improved mechanical and chemical properties.