Showing papers on "Ceramic published in 1977"

Preparation of glasses and ceramics from metal-organic compounds

Abstract: The preparation of glass and ceramic systems from metal-organic compounds permits the mixing of the constituents at the molecular level. These mixes form clear glasses or sinter to dense bodies at temperatures considerably lower than the equivalent compositions prepared by classical methods. A significant recent development in this field has been the preparation of monolithic glass and ceramic material without the need of melting or high temperature sintering. Glass-forming reactions, previously achievable only by thermal means, can take place by chemical polymerization at room temperatures. Structural studies indicate that these materials are indeed amorphous or glassy in naturE. Thus, the often used description of glass as a “supercooled liquid” is, in the literal sense, inapplicable for these materials.

New prospects for a prolonged functional life‐span of artificial hip joints by using the material combination polyethylene/aluminium oxide ceramic/metal

Abstract: Investigations over the years have shown that the mirror-finished Al2O3 ceramic is a much more suitable frictional counterpart to ultrahigh molecular weight (UHMW) polyethylene than metal. Despite the extremely gread hardness difference between polyethylene and Al2O3 ceramic, a considerable lower wear rate is obtained for the polyethylene socked with this new low-friction material combination. The unexpectedly favorable tribological behavior of this ceramic material in contact with polyethylene may be attributed to the following factors: better values for corrosion resistance characteristics, wettability with liquids, surfact gloss, hardness, and scratch resistance of the ceramic material in comparison with those of the hitherto used metallic implant materials (AISI-316L steel or cast Co-Cr-Mo alloy). It appears that, by using this new combination of materials for the socket and the ball, it will be possible to prolong the service life of artificial hip joints considerably without having effecy any fundamental changes in the present design and implantation principle retaining the hitherto used anchorage shaft made of wrought Co-Ni-Cr-Mo-Ti alloy Protasul-10 of extremely high corrosion fatigue strength.

Directionally Solidified Ceramic Eutectics

Abstract: The aligned structures which result from the directional solidification (DS) of ceramic eutectics are of interest because of their potential for use in electronic devices and as structural materials. Techniques for growing DS ceramic eutectics are briefly discussed. The principles and controlling parameters of DS eutectic growth are described. The criteria for plane-front growth and the effect of growth rate on interlamellar or interfiber spacing are discussed. Examples of the effect of growth parameters on the alignment of the microstructure are given. Examples of the mechanical properties of directionally solidified oxide-oxide ceramics are also cited.

High-Level Waste Ceramics: Materials Considerations, Process Simulation, and Product Characterization

Abstract: A ceramic is one of the alternatives for solidification and storage of high-level wastes (HLW). The procedure for developing a tailor-made ceramic with HLW ions fixed in mutually compatible, refractory and leach-resistant crystalline phases has been developed. Cold engineering-scale evaluation of an early ceramic formulation at Pacific Northwest Laboratories (PNL) has resulted in a product that is easily crystallized and has more than adequate thermal stability and leaching resistance. When combined with the continuous pelletizing and coatings processes developed at PNL, the results to date demonstrate that the tailor-made ceramic and the multibarrier waste forms are very promising advanced alternatives to glass as an HLW solid. 5 figures, 3 tables.

Anchorage for highly stressed endoprostheses

Abstract: An implantable prosthesis anchorage which contains a non-porous outer coating in the regions which is positioned in contact with bone. The non-porous outer coating consists of (i) at least one bioactive resorbable ceramic material which is a calcium phosphate and (ii) at least one polymer which is mechanically and chemically stable in the body. The ceramic material is in particulate form having particle diameters between 0.5 and 1 mm. The ceramic material particles is incorporated in the polymer in such a way that resorption of the ceramic material leads to a polymer structure with continuous pores filled with living bone tissue. Bioactivating bonding residues of the ceramic material are left on the inner surfaces of the filled pores which were created by the resorption of the ceramic material.

Pump with porus ceramic tube

Abstract: In a pump for use in a hot chamber type die casting machine wherein corrosive molten metal particularly aluminum or alloys thereof is injected into a metal mould through a goose neck shaped passage, a porous ceramic tube having a porosity of 10 to 40% and acting as the goose neck shaped passage is cast in the main body of the pump. The porous ceramic tube comprises sintered zircon or porous graphite.

Refractive index and surface layers of ceramic (Pb,La)(Zr,Ti)O 3 compounds

Abstract: Refractive indexes of the (Pb,La)(Zr,Ti)O(3) system are determined by minimum deviation for eight ceramic compounds over the 400-750-nm wavelength range and for two compounds over the 25-150 degrees C temperature range. The index of one compound (10/65/35) is reported to 2600 nm. Ellipsometric measurements show the presence of a low-index surface layer on these ceramics. Such layers, whose origin is not determined, have influenced previous index measurements based on reflection techniques.

Low temperature fired ceramic capacitors

Abstract: A multi-layer ceramic capacitor is characterized by a ceramic composition including barium titanate and lithium fluoride as essential ingredients resulting in the capability of sintering the composition at temperatures below 1100° C. As a consequence, the electrodes for the capacitor can be formulated from pure silver or a silver palladium composition in which the major component is silver thereby decreasing the expense of such capacitors as compared to those requiring platinum, gold, or mixtures of these precious metals and/or similar precious metals in making up the electrodes.

Submicron beta silicon carbide powder and sintered articles of high density prepared therefrom

Abstract: Shaped silicon carbide ceramic articles of high density, e.g., at least 90 percent of theoretical, are produced by cold pressing and sintering boron-containing high purity, submicron beta silicon carbide powder. The silicon carbide powder is produced preferably by gas phase reaction of silicon halide, e.g., silicon tetrachloride, carbon source reactant, e.g., halogenated hydrocarbon, and boron source reactant, e.g., boron trichloride, with a hydrogen plasma.

Process for producing sintered silicon carbide ceramic body

Abstract: Pressureless sintering of silicon carbide to produce ceramic bodies having 75% and greater theoretical densities, can be accomplished 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 2500° C.

Bioglass coated A1203 ceramics

Abstract: A method of coating a Al2 O3 ceramic surface with a biologically active glass comprising contacting a glass and ceramic having different thermal coefficients of expansion at a temperature sufficient to bond the glass to the ceramic surface by ion diffusion, cooling the coated substrate to a temperature sufficient to produce thermo-mechanical stress induced interconnected micro-cracks in the glass coating and overcoating said micro-cracked glass coating with at least one additional coating of biologically active glass. The invention includes a product of manufacture comprising a compacted Al2 O3 ceramic surface coated with at least two layers of biologically active glass characterized in that the first layer of glass has interconnected thermo-mechanical stress induced micro-cracks therein.

Method of producing a ceramic product

Abstract: A method of producing a ceramic product which comprises the step of forming a powder mixture consisting essentially of a first component consisting of compounds containing the elements silicon, aluminum, oxygen and nitrogen in proportion such that the ratio of the total number of silicon and aluminum atoms to the total number of oxygen and nitrogen atoms lies in the range 0.735 to 0.77 and such that said compounds react together during the subsequent sintering process to produce a single phase ceramic material obeying the general formula: Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where z is between 0.38 and 1.5, and between 0.1 and 10% by weight of a second component in the form of an oxide of at least one of the further elements yttrium, scandium, cerium, lanthanum and the metals of the lanthanide series. The mixture is then sintered in a protective environment at a temperature between 1600° C and 2000° C and for a time, decreasing with increasing temperature, of at least 10 minutes to at least 5 hours so as to produce a ceramic material containing at least 80% by volume of said single phase ceramic material together with a second phase containing said at least one further element.

[Resorbable calcium phosphate ceramics under load (author's transl)].

Abstract: Cylindrical implants with 45% by volume continuous open tubular pores were prepared from ceramic materials based on tricalcium and tetracalcium phosphate and used to replace 7 mm thick bone segments in the tibiae of dogs. The treated limbs of the experimental animals were fixed for 12 weeks, after which time the dogs were allowed to move freely so that the limbs were physiologically loaded. The histological examination showed that primary bone healing had taken place between the bone and the ceramic material. After 10 months the tricalcium-phosphate-based ceramic material was resorbed and replaced by bone tissue to a large extent. The ceramic material on the bases of tetracalcium phosphate on the other hand, had remained completely unchanged, and its pores were filled with lamellar bone tissue which was in direct contact with the implant without connective tissue. The bond between natural bone and implant was mechanically stable. The ceramic materials investigated were found to be tissue-compatible, and in our opinion they can be substituted for part of the bone transplants used today. Considering its varying strength properties, the tricalcium phosphate ceramic material can be used only in cases where no high stress is expected; the tetracalciumphosphate-based ceramic material, however, has a higher mechanical strength and can therefore be used also for larger permanent implants which have to bear high mechanical stress.

Bonding mechanism evidence in a ceramic–nonprecious alloy system

Abstract: Bonding between porcelain and dental ceramic alloys is thought to be dependent upon the establishment of a continous electron structure across the ceramicmetal interface (Pask, Proc. Procelain Enamel Inst., 33, 1, 1971). Such a structure most likely results from the compatibility of metal ions at the metal surface saturated in an oxide form with the complex oxide structure of the ceramic matrix. Reaction zone compounds are expected to play a prominent role in the strength of the ceramic–metal bonds but thus far none have been detected or identified. The present study was centered on the determination of possible adherence zone compounds in four composite ceramic–metal couples examined by x-ray energy analysis. Elemental analysis of four couples revealed the presence of a predominant AlCr interaction resulting from the formation of an AlCrO compound or mixed oxide complex. The Cr ions were supplied by the Cr2O3 oxide layer at the metal surface and the Al was provided by the initial bonding-agent coating.

Synthesis and Evaluation of Doped Y2O3-Stabilized ZrO2 for the Production of Hydrogen

Abstract: The preparation and characterization of single-phase sintered ceramic materials based on Y2O3-stabilized ZrO2 with oxides of Ti, Zn, Ce, Cr, Mn, and U/Fe as third-component additives are described. These materials were prepared for a process to produce high-purity hydrogen and were evaluated for this process via measurements of electrical conductivity, stability, and transport number. Compositions with oxides of Ce and Cr in Y2O3-stabilized ZrO2 are shown to be the most promising candidates.

Composition and process for injection molding ceramic materials

Abstract: Ceramic compositions that may be injection molded and subsequently sintered are described. A particulate ceramic material, such as silicon carbide, is coated with a mixture of thermoplastic resin and oils or waxes, and utilized as a feed material in an injection molding process. The molded product may subsequently be sintered at 2000° C. to 2200° C. to produce a hard, dense article.

Ceramic matrices for electronic devices and process for forming same

Abstract: Monolithic capacitors are produced by (1) providing on a plurality of thin leaves or sheets of suitable finely divided ceramic material bonded with a thermally-fugitive temporary bond, coatings comprising thin, selected patterns of pseudo-conductive material that consists essentially of thermally-fugitive material, one or more ceramic or metal granules, and a thermally-fugitive bond; (2) forming a consolidated stack from a plurality of the coated leaves or sheets; (3) firing the resulting body to remove the thermally-fugitive materials and sinter the ceramic material into a monolithic body in which there are thin cavities or open spaces which are interrupted only by one or more distinct ceramic or metal pillars, substantially all of which, when there are a plurality, are distinct and separated; (4) introducing conductive material, preferably metal, into the resulting cavities; and (5) providing suitable electrical connections to the resulting conductive layers. Alternative procedures for producing pillars in said thin spaces or cavities and an analogous procedure for forming multilayer ceramic circuit structures are described.

Method for making a monolithic ceramic capacitor employing a non-reducing dielectric ceramic composition

Abstract: Non-reducing dielectric ceramic compositions comprise solid solutions which are represented by the compositional formula: {(Ba.sub.1-x Ca.sub.x)O}.sub.m ·(Ti.sub.1-y Zr.sub.y)O.sub.2 wherein m, x and y have the following values: 1.005 ≦ m ≦ 1.03 0.02 ≦ x ≦ 0.22 O < y ≦ 0.20 The compositions possess high permittivity and small dielectric loss and maintain high insulation resistance even if fired in reducing atmospheres, thus making it possible to manufacture inexpensive but high reliable monolithic or multi-layer ceramic capacitors.

Process of constructing a ceramic catalyst support

Abstract: A method of producing a ceramic device having thin walls of microporous ceramic material, channels open at both ends, and a large exposed internal surface area. The method comprises preparation of a unique bilayer film and assembly of this film into a ceramic device by rolling it upon itself into a spiral cylinder or by arranging it in stacks of sheets. One layer of the film is composed of ceramic powder in an organic binder; the other of a material which may be removed by physical or chemical means.

Method of making multilayer module having optical channels therein

Abstract: A method for manufacturing a multilayer ceramic module structure is described which includes a ceramic body having a plurality of continuous glass channels within the body. The module transmits signals from point to point on the module and to points off of the module by allowing the movement of optical pulses through optical channels rather than the conventional electrical pulses and metal wiring. The method for fabricating the multilayer ceramic module includes providing a plurality of ceramic green sheets. The green sheets are then individually prepared for the circuit pattern plan for the module by opening via holes through certain locations of the various green sheets and forming grooves in other portions of the green sheets for a proper resulting pattern. A glass paste is applied to the green sheets to fill the grooves and the holes therein. The green sheets are then stacked and laminated by the use of suitable pressure. The laminated green sheets are then sintered to form a module package. During sintering, the ceramic fuses around the glass which also softens and fuses to form clear channels within the ceramic body. Glass must sinter fully at the sintering temperature of the ceramic without becoming so fluid that it would run out of the via and grooves into the interstices in the ceramic before the ceramic is fully sintered. This problem is overcome by selection of the ceramic and the glass so that the sintering temperature of the ceramic and the softening temperature of the glass paste are substantially the same.

Ceramic capacitor having a silver doped dielectric of (Pb,La)(Zr,Ti)O{HD 3 {B and glass

Abstract: The dielectric material of a ceramic capacitor contains a high temperature silver doped ceramic with a small proportion of a low temperature glass. The ceramic component consists essentially of a lead zirconate in which from 0.07 to 0.16 molar parts of the lead are replaced by lanthanum and in which from 0.10 to 0.40 molar parts of the zirconate are replaced by titanate. The capacitors may be fired in an air atmosphere without substantial loss of lead at temperatures as high as 2000 DEG F. Silver containing electrodes may be employed in a monolithic capacitor of this invention, the co-fired electrode advantageously causing a silver doping of the ceramic that in turn improves the stability of capacitance with temperature and applied voltage. Alternatively, the ceramic may be predoped with silver to achieve this result.

Eutectic die attachment method for integrated circuits

Abstract: A method is described for attaching sapphire, quartz, Spinel, etc. die to gold pads in a ceramic package. Because sapphire is not directly bondable to or alloyable with gold, while silicon is, silicon is either evaporated or deposited onto the backside of a sapphire or silicon-on-sapphire wafer. After the wafer has been scribed into die, the die are attached to the gold pads in the ceramic package using a gold-silicon preform as an intermediate layer.

Method of maintaining the strength of optical fibers

Abstract: The mechanical strength of an optical fiber is maintained by coating the er with an inorganic ceramic material that is impervious to both moisture and chemically corrosive environments. The ceramic coating is applied immediately after the fiber is drawn.

Resilient ceramic tile flooring

Abstract: A composite floor covering comprising a rubbery backing strip or layer in intimate contact with the floor, ceramic tiles placed over the backing layer and flexible grouting between the tiles.