Showing papers on "Ceramic published in 1979"

Ceramic filters for diesel exhaust particulates

Abstract: Diesel exhaust particulates are efficiently trapped by incineration cleanable ceramic monolith porous wall filter elements A number of arrangements for high efficiency elements having high filtration area in compact units are disclosed

Non-vitreous ceramic metal oxide microcapsules and process for making same

Abstract: Shaped and fired, porous or impermeable nonvitreous ceramic microcapsules of metal oxide, preferably transparent and polycrystalline, are made by a non-melt process comprising the liquid-liquid extraction of aqueous metal oxide precursor with a dehydrating liquid having a limited water solubility, and drying and firing the resulting gelled microcapsules. For example, an aqueous titania sol is added to an agitated body of n-butanol to form a dispersion of droplets of said sol and water is rapidly extracted from the droplets to form gelled microcapsules; the latter are recovered by filtration, dried, and fired to convert them into transparent, sealed or heat-sealable, non-vitreous ceramic, spherical microcapsules of polycrystalline titania. The microcapsules can be used as fillers for plastic and other composites or filled with a selected solid, liquid or gas for purpose of storing, transporting, or facilitating the use of the same.

Fabrication of front surface matched ultrasonic transducer array

Abstract: A slab of piezoelectric ceramic plated on all surfaces is bonded to quarter wavelength impedance matching layers of glass and plastic. The top surface of the ceramic is slotted and parallel cuts orthogonal to the slots are made through the ceramic and into the glass to delineate an array of elements each with a signal electrode between slots and a wrap-around ground electrode. After making ground connections and flying lead connections to the signal electrodes, the matching layers are fully cut through from the front. A covering or wear plate is attached to the front surface and a relatively large mass of acoustic damping material covers the backs of the elements.

Implantable bone replacement materials based on calcium phosphate ceramic material in a matrix and process for the production thereof

Abstract: An implantable bone replacement material (body) based on completely or partially resorbable particles incorporated in a matrix material. The particles are composed of bioactive sintered calcium phosphate ceramic material having a CaO:P2 O5 composition ratio between 3:1 and 4:1. The replacement material (body) consists of a metal containing calcium phosphate ceramic material in the form of a monolayer of particles in the peripheral areas of the material (body) which serve as interfaces to the body tissue. The metal is compatible with body tissue. The ceramic particles have a size range between about 500 μm and a few millimeters. The calcium phosphate particles are located so that they lie exposed on the upper surface of the material (body). Other embodiments and processes are also disclosed.

Application of Transmission Electron Microscopy to Radiation Damage in Ceramics

Abstract: Ceramics are becoming increasingly important in many radiation environments. In addition to refractory fissionable fuels, electrical insulators will be needed for instrumentation in breeder reactor systems and will be widely applied in all fusion reactor concepts, including first-wall coatings, blanket gaps, injectors, divertors, magnet insulation, and windows. These applications require mechanically stable (and in some cases transparent) dielectric solids which must maintain electrical as well as mechanical integrity under severe radiation fields. Refractory ceramic materials of low atomic number will be increasingly useful in structural applications as well because they resist activation and contribute less objectionable sputter contaminants. Ceramic solids are also likely to be increasingly utilized as repository media for active nuclear wastes. The irradiation behavior of these nonmetallic materials is critical and at present poorly understood, but transmission electron microscopy is beginning to reveal significant similarities, as well as substantial differences, in their behavior as compared to that of better-characterized metallic solids.

Sintered alpha silicon carbide ceramic body having equiaxed microstructure

Abstract: Pressureless sintered silicon carbide ceramic bodies, having an equiaxed microstructure and an alpha crystalline habit can be produced by firing shaped bodies, containing finely divided silicon carbide, boron source such as boron carbide, carbon source such as phenolic resin and a temporary binder, at a sintering temperature of from about 1900° C. to about 2250° C., depending on the sintering atmosphere, under conditions such that a coating of carbon source is maintained on the finely divided silicon carbide, and sufficient boron is maintained within the shaped body during firing. Boron can be maintained within the shaped body by various techniques, such as the use of a "seasoned boat" or graphite container for the body being sintered, which has been saturated with boron by exposure to boron at or about the temperature of sintering. There is also disclosed a process for producing a sintered silicon carbide ceramic body, with or without the equiaxed crystal microstructure, from silicon carbide powders of alpha or beta crystal structure, or amorphous noncrystalline silicon carbide, or mixtures thereof.

Ceramic faced structures and methods for manufacture thereof

Abstract: CERAMIC FACED STRUCTURES AND METHODS FOR MANUFACTURE THEREOF ABSTRACT OF THE DISCLOSURE A method of adhering a ceramic facing material to an underlying substrate is disclosed. Substrates to which the concepts apply include unsupported low modulus, porous wire pads as well as low modulus, porous wire pads backed by a solid metallic form. The ceramic application techniques employed are centered around the impregnation of the regions of the pad to be ceramic coated with an underlayment coating, such as MCrAlY material. Deep penetration of the underlayment material into the pad is achieved with a high velocity, spraying process. Ceramic material is applied over the underlayment material by conventional spraying techniques. Articles of manufacture which are suited to fabrica-tion in accordance with the concepts disclosed herein include, but are not limited to, outer air seals, combustion chambers, and airfoils of gas turbine engines.

Bone implant embodying a composite high and low density fired ceramic construction

Abstract: A composite high and low density fired ceramic article is employed as a bone implant. High density ceramic material forms the core or structural member of the composite. An integral inner portion of ceramic material having interconnected porosity encourages the growth of new bone marrow. An integral outer portion of porous ceramic material provides a means for bone and tissue attachment.

Investigations with bioactivated polymethylmethacrylates.

Abstract: Compound bone cement on a PMMA base with an additive of bioactive glass ceramic particles in different portions and different particle sizes are tested in animal experiments. The tissue reactions to extracorporal polymerized specimens and to in situ polymerized specimens are observed. The experiments with an implantation period up to six months demonstrate a tight bonding between the newly formed osseous tissue and the glass ceramic particles at the interface. The inflammatory reactions in the vicinity of the implant are small. It is the objective of the investigations to improve the adherance of the bone cement at the interface to achieve a more durable anchorage of bone cement in the tissue.

Gas component detector

Abstract: A gas component detector has a detector element of a metal oxide held on one end of a ceramic body. The detector element is exposed to the gases to be detected and the electrical resistance value thereof is varied depending on the component of the gases. An electrical signal representing an electrical resistance value of the detector element is delivered through a pair of electrodes connected to the detector element and further through a pair of sub-lead-lines connected to the electrodes. The pairs of electrodes and sub-lead-lines are inserted in a pair of penetrating holes of the ceramic body after the electrodes and sub-lead-lines have been welded to each other. The ceramic body is inserted in a metal tube and the ceramic body and the metal tube are fixed to each other either by a tight surface contact or an adhesive. The openings of the pair of penetrating holes of the ceramic body at the opposite end with respect to the detector element are closed by a sealing material of an electrically insulating metal oxide.

Composite ceramic/metallic turbine blade and method of making same

Abstract: A composite, ceramic/metallic fabricated blade unit for an axial flow rotor includes an elongated metallic support member having an airfoil-shaped strut, one end of which is connected to a dovetail root for attachment to the rotor disc, while the opposite end thereof includes an end cap of generally airfoil-shape The circumferential undercut extending between the end cap and the blade root is clad with an airfoil-shaped ceramic member such that the cross-section of the ceramic member substantially corresponds to the airfoil-shaped cross-section of the end cap, whereby the resulting composite ceramic/metallic blade has a smooth, exterior airfoil surface The metallic support member has a longitudinally extending opening through which coolant is passed during the fabrication of the blade Simultaneously, ceramic material is applied and bonded to the outer surface of the elongated airfoil-shaped strut portion, with the internal cooling of the metallic strut during the processing operation allowing the metal to withstand the processing temperature of the ceramic material

High-Resolution Techniques and Application to Nonoxide Ceramics

Abstract: The microstructure of ceramic materials can be observed directly at the atomic level by using high-resolution electron microscopy. These techniques are described in detail and the new information that they reveal about ceramic microstructures is illustrated with examples of hot-pressed silicon nitrides, sintered silicon sarbide, and a “sialon” system.

Diesel exhaust particulate traps

Abstract: Related arrangements of diesel exhaust particulate traps are disclosed wherein particulate filter elements are formed from porous ceramic monoliths made of high temperature ceramic and containing passage defining micronic pores intercepted by high temperature ceramic fibers retained in the ceramic substrate and extending into the passages to provide surfaces for separating particulates from the gases passed through the element.

Heat-resistant electrically insulated wires and a method for preparing the same

Abstract: A heat-resistant electrically insulated wire has a composite coating layer of a mixture of an inorganic fine powder and an inorganic polymer on a conductor and the composite coating layer has a resinous overcoat layer thereon. The composite coating layer has not artificially been fired, but is adapted to be converted into a ceramic layer when exposed to elevated temperatures during use.

Catalytic converter mounting arrangement for reducing bypass leakage

Abstract: Arrangement for resiliently mounting a ceramic monolithic type catalytic converter element in a metal housing with a blanket of knit wire mesh material includes at least one circumferential band of high temperature intumescent material containing ceramic fibers positioned within the wire mesh blanket which prevents virtually all bypass leakage around the element and substantially reduces the temperature of the wire mesh.

Discoidal monolithic ceramic capacitor

Abstract: A discoidal monolithic ceramic capacitor being terminated at a hole in the center and at the outer periphery thereof, includes concentric annular electrodes buried in a discoidal ceramic body and arranged to provide series connected equal value sub-capacitors to reduce dielectric stress and permit operation at high voltages. Misregistration of the concentric annular electrodes in one plane with respect to those in another plane may occur in manufacturing without disturbing the balance in the equal sub-capacitor values and thus even distribution of voltage stress in the ceramic dielectric.

Intumescent fire retardant composites

Abstract: The disclosure relates to flexible heat expanding, fire retardant composite materials comprising an intumescent component in granular form, an organic binder component such as an elastomer, an organic char-forming component and fillers such as clay, silica, synthetic organic staple fibers or inorganic fiberglass or ceramic fibers. These composites, when subjected to heat at about 110° C., can intumesce up to ten times their original volume.

Metal-ceramic turbine shroud and method of making the same

Abstract: A turbine shroud includes a ceramic sealing layer secured to a metal substrate. In one form, the metal substrate includes a plurality of pegs extending therefrom. Intermediate bonding layers are disposed on the peg-metal substrate structure. A ceramic sealing layer of zirconium oxide with about 20 weight percentage magnesium oxide is disposed, e.g., plasma sprayed, on the intermediate bonding layers. The ceramic sealing layer includes an ordered pattern of very fine cracks therein which reduce the thermal stress in the ceramic sealing layer. A method of constructing a turbine shroud structure is also disclosed.

Cordierite, alumina, silica porous ceramic bodies coated with an activated alumina layer

Abstract: A ceramic porous body useful as a filtering material for molten metal is disclosed. The ceramic porous body, consisting essentially of cordierite, alumina and silica, is formed by covering surfaces of cell strands of a ceramic porous body skeleton having a bulk specific gravity of 0.25-0.55 with 3-40% by weight per the weight of the skeleton of an activated alumina layer and has an average diameter of interconnected voids of 0.3-5.0 mm, a pressure loss of 0.3-30.0 mm as a water-gauge pressure when passing air through the body of 1 cm thick at a rate of 1 m/sec., a microsurface area of not less than 10 m 2 /g and a porosity of 75-95%.

Molten metal filter

Abstract: The present invention provides a highly efficient, ceramic foam material for filtering molten metal which is characterized by improved strength reliability. The filter of the present invention is prepared by impregnating an organic foam material with an aqueous ceramic slurry containing ceramic fibers. In accordance with the present invention it has been found that it is possible to prepare a low cost, porous ceramic filtration medium having improved strength reliability.

Method for producing a thermal stress-resistant, rotary regenerator type ceramic heat exchanger

Abstract: A thermal stress-resistant rotary regenerator type ceramic heat exchanger comprising a plurality of ceramic honeycomb structural matrix segments bonded by a ceramic binder is produced by extruding a plurality of ceramic honeycomb structural matrix segments, firing the segments, bonding the segments with one another by application of a ceramic binder, said ceramic binder after the subsequent sintering having substantially the same mineral composition as said ceramic matrix segments and the thickness of 0.1 to 6 mm, and a difference in thermal expansion being not greater than 0.1% at 800° C. relative to the ceramic matrix segments, drying the bonded segments, and firing the dried bonded segments.

Device for high thermal stress connection between a part made of a ceramic material and a part made of a metallic material

Abstract: An improvement in a high thermal stress connection between a rotationally symmetrical component made of ceramic material and a component made of metallic material is provided in which a connecting part which is elastic and radially and axially resilient connects the ceramic part and the metallic part by means of high temperature soldering. The stresses normally produced by differential expansion of the ceramic part and the metallic part are substantially absorbed by elastic deformation of the connecting part.

Calculation of quasi binary and quasiternary oxynitride systems — III

Abstract: A data base is being developed for calculation of quasi-binary and quasi-ternary phase diagrams of ceramic systems. Initially the base was restricted to the following oxides: Cr2O3, MgO, Fe2O3, Fe3O4, FeO, Al2O3, CaO and SiO2. Lattice Stability, Solution and Compound Phase Parameters were derived covering the liquid, spinel, corundum, periclase, crystobalite, tridymite and quartz phases which appear in the binary systems composed of these oxides. These parameters were selected in accordance with the observed thermochemical properties and phase diagrams of these binary systems. The usefulness of this analytical description was illustrated by computing isothermal sections for ternary systems composed of these oxides. The above mentioned data base has now been expanded to cover combinations of the oxides with silicon nitride, Si3N4, and aluminum nitride, A1N thus permitting computation of oxynitride SIALON ceramic systems which are of current practical interest. The current analysis provides isothermal sections in the Si3N4-Al2O3-A1N and SiO2-A12O3-Si3N4 systmes as well as computed values for the free energy of formation of the beta sialons in the Si3N4-A12O3-A1N system and the X phase in the SiO2-Al2O3-Si3N4 system. The former results are compared with independent calculations reported by Doerner et.al. at CALPHAD VIII and published in the current issue of the CALPHAD Journal.

Statistics and grain size in zinc oxide varistors

Abstract: A ZnO varistor is a ceramic with grains of various sizes. Therefore, some of the electrical breakdown characteristics of the ceramic reflect variations in the voltage impressed upon a grain, rather than the breakdown characteristics of an average grain boundary. It is found that the mean breakdown voltage per grain in the ceramic is less than that of an isolated grain boundary because there are chains of long grains through the ceramic; the density of such chains is finite even in a thick sample. The maximum value of the coefficient of nonlinearity αmax, which measures the rapidity of breakdown, is found to be characteristic of the grain boundaries when αmax is moderate, that is, if αmax <50. The high values of αmax observed at low temperatures appear to be limited by statistical effects rather than being representative of the boundaries.

Element and method for connecting ceramic and metallic parts

Abstract: Disclosed are means and method for forming elastic connection between ceramic and metallic structural elements. The means comprises a ceramic structural element; a metallic structural element having thermal and elastic properties different from those of the ceramic structural element; and a connecting element connecting the ceramic and metallic structural elements and comprising an insulating resilient body of ceramic material having a thermal conductivity of between about 0.02 and 0.25 W/cmK at a temperature difference between the ceramic and metallic structural elements of from about 100 to 1500 Centigrade degrees, an elastic modulus of between about 5000 and 150,000 N/mm2 and being substantially free of plastic deformation.

Application of Transmission Electron Microscopy to the Study of Deformation in Ceramic Oxides

Abstract: Slip systems, dislocation reactions, and dislocation dissociations are reviewed in relation to the crystal structures of ceramic oxides. Techniques of deformation and transmission electron microscopy (TEM) are described. The impact of TEM on the understanding of deformation in oxides is discussed by relating the observed dislocation substructures to the mechanical properties in several oxide systems. Important information can be obtained on dislocation glide and climb processes in relation to work hardening, recovery, and creep. Yielding and the brittle-to-ductile transition temperature are discussed in terms of the magnitude of the Burgers vector in various crystal structures and the influence of dissociation reactions and diffusion. Examples include oxides with close-packed anions such as MgO, MgAl2O4 BeO, A12O3, TiO2, and Mg2SiO4, and other oxides such as Cu2O, UO2, and SiO2.

Low firing monolithic ceramic capacitor with high dielectric constant

Abstract: The ceramic body of a monolithic ceramic capacitor consists of a granular barium titanate phase and a relatively low temperature melting intergranular phase. The body is capable of exhibiting a very high dielectric constant, e.g., over 5000, a Curie temperature of near 25° C., and may be fired to maturity at 1150° C. or lower and contain low cost buried electrodes. These properties obtain from a narrow range of compositions for which charge balance and large/small cation stoichiometry in the total formulation are found to be very critical. Cd, Zn, Cu, Li and Na are found to enter the grains as large acceptor cations on Ba sites and may be charge compensated by the small donor cations of charge +5, Bi, Sb, Nb and Ta or by the small donor cations of charge +6, W and Mo, on the Ti sites. At least 0.3 mole percent of glass-former cations are desirable for establishing a low melting flux during sintering but more than 2.2 mole percent glass-formers tends to reduce the dielectric constant.

Method for producing a catalyst and a carrier therefor

Abstract: A method is provided for producing a catalyst and a carrier therefor in the form of sheet or honeycomb. The method comprises: beating a heat-resistant fiber such as asbesto fiber in water to form a slurry; mixing the slurry with a catalytically active agent, a carrier material therefor and/or their precursors to fix such materials in the fiber, thus forming a stock; and forming the stock into a sheet and drying the same. The sheet thus obtained may be formed into a honeycomb structure with an improved adhesive.