Showing papers on "Ceramic published in 1978"

Ceramic Processing before Firing

Abstract: Provides a systematic scientific basis for understanding and controlling the processing of powders and ceramic bodies. Applies a wide range of analytical tools for characterizing agglomerate features throughout the processing steps. Contains electron and optical micrographs and discusses the improvement of product reliability, reduction of costs, and energy and environmental concerns.

Processing of crystalline ceramics

Abstract: Keynote Address.- Some Considerations in the State of the Art in Processing Crystalline Ceramics.- I: Fine Particle Science, Technology and Characterization.- Physical and Chemical Parameters Controlling the Homogeneity of Fine Grained Powders and Sintering Materials.- Ultrafine Powders of Oxide and Non-Oxide Ceramic Materials and Their Sinterability.- Handling and Green Forming of Fine Powders.- The Potential of Fine Particle Technology Applied to Ceramic Raw Materials.- Particle Size and Permeability in Slip Casting.- Chemical Processing for Ceramics (and Polymers).- Ceramics Sintered Directly from Sol-Gels.- Characterization of Ceramic Microprocessing.- Packing and Sintering Relations for Binary Powders.- Stress and Density Distributions in the Compaction of Powders.- Pore Morphography in Ceramic Processing.- II: Solid State Sintering and Grain Growth.- Fundamentals of the Sintering of Ceramics.- Current Paradigms in Powder Processing.- Some Effects of Aggregates and Agglomerates in the Fabrication of Fine Grained Ceramics.- The Sintering of Conductive Rutile: A Model System for Sintering Electronic Ceramics.- Sintering of Mullite.- Rate Controlled Sintering as a Processing Method.- A Multiple-Lognormal Model of a Normal Grain Growth.- III: Liquid Phase Sintering And Post-Firing Technology.- Rearrangement During Liquid Phase Sintering of Ceramics.- Reactivity of Alumina Substrates with High Lead Glasses.- Influence of the Processing Parameters on the Properties of Rapid Fired Porcelain.- Strengthening of Lime-Stabilized Zirconia by Post Sintering Heat Treatments.- Strain and Surface Energy Effects in Ceramic Processes.- Dynamic and Material Parameters in Brittle Fracture in Ceramics.- Processing Induced Sources of Mechanical Failure in Ceramics.- IV: Dielectric and Magnetic Ceramics.- Processing of High Density Piezoelectric Ceramic Compositions.- The Role of ZrO2 Powders in Microstructural Development of PZT Ceramics.- Novel Uses of Gravimetry in the Processing of Crystalline Ceramics.- Deformation Processing of Magnetic Hexaferrites for Hc Maximization Through Grain Growth Control.- Processing and Magnetic Properties of Low-Loss and High-Stability Mn-Zn Ferrites.- Relationship Between Processing Conditions, Oxygen Stoichiometry and Strength of MnZn Ferrites.- Sintering of High Density Ferrites.- V: Energy Related Ceramics I: Fast Ion Conductors MHD, Nuclear and Refractory Ceramics.- Processing and Characterization of Polycrystalline ?"-Alumina Ceramic Electrolytes.- Microstructural Control During Sintering of ?"-Alumina Compositions Through Ceramic Processing Modification.- Transient Eutectics in Sintering of Sodium Beta Alumina.- Microstructural Evolution During the Processing of Sodium ?-Alumina.- Fabrication and Performance of MHD Electrodes.- Fabrication and Property Control of LaCrO3 Based Oxides.- Strontium Containing Perovskites and Related Conductive Electronic Ceramics.- Hot Pressed Composite Ceramic MHD Electrode Development.- Processing Variables Affecting the Thermomechanical Degradation of Monolithic Refractory Concretes.- UO2-Gd2O3 Sintering Behavior.- Processing Requirements for Property Optimization of EU2O3-W Cermets for Fast Reactor Neutron Absorber Applications.- Ceramic Processing of Boron Nitride Insulators.- VI: Energy Related Ceramics II: Non-Oxide Ceramics.- Grain Boundary Engineering in Non-Oxide Ceramics.- The Fabrication of Dense Nitrogen Ceramics.- Ceramics in the Si-Al-O-N System Fabricated by Conventional Powder Processing and Sintering Techniques.- Polytypism in Magnesium Sialons.- Dense Silicon Nitride Ceramics: Fabrication and Interrelations with Properties.- High-Pressure Hot-Pressing of Silicon Nitride Powders.- The Structure of Grain Boundaries in Silicon Nitride Based Alloys.- Evolution of Microstructure in Polycrystalline Silicon Carbide.- Thermal Gradient Deposition of SiC Diffusion Tracers.- Contributors.

Apparatus and method for bending glass sheets

Abstract: Sheet glass is heated during conveyance within a furance housing having a fixed roof and vertically movable side doors that define side slots through which ends of conveyor rolls project outwardly to be supported and frictionally driven by continuous drive loops slidably driven over external support surfaces that extend alongside the side slots. A vacuum holder of the apparatus is positioned within the furnace housing above the conveyor and has a downwardly facing surface with spaced openings in which a vacuum is drawn to receive a glass sheet from the conveyor and support the sheet above the conveyor. The holder surface is disclosed as being both planar and curved and as having a porous cover of ceramic fibers so as to distribute the vacuum and prevent marring of the glass as it is supported. A greater vacuum is drawn to initially support the glass and a lesser vacuum is subsequently drawn to prevent glass deformation at the spaced openings. Vertically movable auxiliary lifters positioned between the rolls or vertical movement of the vacuum holder facilitates glass pickup. Sensing of the glass position along the conveyor and operation of a locator cooperatively provide accurate positioning of the glass on the holder surface without requiring the conveyor to be stopped prior to the holder operation. A carrier mold ring moves under the supported glass and the vacuum is then terminated so the glass drops onto the ring and bends under the bias of gravity in a manner that allows thin glass to be accurately bent. Subsequently the mold ring is moved from the furnace to a quench unit between upper and lower blastheads that temper the bent glass. Increased air is then supplied to the lower blasthead relative to the upper blasthead to lift the glass sheet off the ring and allow return of the ring to the furnace.

Base metal electrode capacitor and method of making the same

Abstract: A monolithic ceramic capacitor with base metal electrodes fired in an atmosphere of oxygen at low partial pressure in which the reaction between the electrodes and the ceramic prevents conversion of the ceramic into the semiconductive state. The base metal is a transition metal or a transition metal alloy, preferably nickel. The method is usable with any green ceramic without changing the firing temperature. The only change required is from the normal oxygen partial pressure in the kiln open to the atmosphere to an atmosphere of much lower oxygen partial pressure.

Ceramic insulated engine pistons

Abstract: Internal combustion engine pistons are provided with aluminum bodies with highly insulative ceramic inserts cast in place in the upper combustion chamber defining wall. In each of the disclosed embodiments, the ceramic insert has tapered edges to dovetail the insert in place. A fibrous ceramic cushioning layer applied around the insert edge before casting distributes cooling stresses and allows limited relative expansion and contraction of the aluminum body and ceramic insert without overstressing either of the members. Other features are also included.

Porous ceramic carriers for controlled release of proteins, polypeptide hormones, and other substances within human and/or other mamillian species and method

Abstract: The product and process of making an in-vivo body implant pharmaceutical carrier of a resorbable ceramic crystalline structure of interconnecting pores capable of the critical controlled time release of pharmaceutical preparations such as proteins, polypeptides, hormones, and other small molecular weight active materials. The ceramic is comprised of aluminum oxide (Al2 O3), calcium oxide (CaO), and phosphorous pentoxide (P2 O5) in a controlled weight percent mixture. In the process of making, the mixture is calcined. The calcined mixture is again ground and sieved through screens of two different mesh sizes to obtain desired sizes and mixed with a binder. This mixture is compressed and sintered at a predetermined temperature. The particle sizes of the sieved calcined compound and the sintering temperatures are interrelated to provide a ceramic of a desired pore size for the controlled release of the pharmaceutical.

Liquid contact relays driven by piezoelectric membrane - pref. of polyvinylidene fluoride film for high sensitivity at low power

Abstract: Commutators for switching electrical or optical circuits by movement of conductive or transparent liquids derive their motion from variations in the geometry of a membrane which is a piezo-electric element. Slight variations in the length and hence curvature of the membrane in a reservoir is amplified by causing relatively large shifts of a liquid surface or interface level in a capillary system with lateral branches for the circuit connections. The membrane may be film made of oriented organic polymeric material, pref. polyvinylidene fluoride produced under conditions which enhance the phase content. Alternatively the piezoelectric switch motor may be a quartz or ceramic crystal. Suitable for switches or relays or voltage protection devices of relatively compact size, esp. for use in telephone exchange junctions etc. where the low power requirement of individual switches reduces the heat dissipation problem from large numbers of switches contained in a small volume.

Ceramic orthodontic bracket

Abstract: Ceramic orthodontic brackets are disclosed. The brackets are fabricated from high alumina ceramic materials and, in preferred embodiments, have holes or grooves on the back or rear surfaces thereof to improve adhesion to the teeth. Light wire brackets are also disclosed which is substantially wider than prior art light wire brackets, but which comprise means defining a substantially point contact for an arch wire.

Rigid electro-optic device using a transparent ferroelectric ceramic element

Abstract: A rigidly bonded electro-optic phase retardation device comprising a transparent, electrically induced ferroelectric ceramic element bonded with a rigid adhesive in sandwich-like configuration between transparent sheet elements, such as glass, or polarizer elements is described. The electro-optic phase retardation device, provided with means for applying an electric field across at least a portion of the induced ferroelectric ceramic element, can be utilized as a birefringent optical device for controllable modulation of polarized light passing through the device. The device is bonded with an adhesive material, such as a cross-linked unsaturated polyester, effective to provide a rigid boundary between the ceramic material and the sheet elements thereof and exhibits rapid optical response speed in the switching from a field-induced birefringent mode to an isotropic zero-field condition. The device is thus suited to application in welding plates, glasses, goggles, helmets and similar devices for controlling the transmission of light radiations to the wearer's eyes, particularly in the prevention of flashblindness.

The fracture toughness of ceramics

Abstract: Recently proposed approaches for enhancing the toughness of ceramics have been examined. Several approaches have been demonstrated to produce appreciable increases in toughness, including (a) controlled microfracture, (b) coherent precipitation, (c) ductile second phase networks, and (d) stress induced phase transformations. The relative merits and limitations of each approach, and the important prerequisites for optimum toughening, have been discussed.

Multi-purpose ceramic element

Abstract: A ceramic sponge made from plastic is described. Because of the ease of cutting the plastic in various shapes before converting to ceramic several unique applications are possible. In case of a column packing better contact between liquid and gas is made. For an auto catalytic converter better contact between gas and catalyst is realized. By cutting in other ways a filter to remove solids is made, permitting longer use before clogging, also a scrubber to remove particulates. A rotary ceramic filter is described; it is also a composite of fibers and ceramic which retains small particulates without excessive pressure drop upon passage of fluid through the filter. An acid resistant collector plate for an electrostatic precipitation is described.

Tool Wear in Cutting Carbon-fiber-reinforced Plastics : The Effect of Physical Properties of Tool Materials

Abstract: A turning (facing) test on glass-fiber-reinforced-plastics was performed with several tool materials, e.g., sintered carbides, cermets and ceramics, and the wear patterns and wear land growth rate were analyzed to clarify the relationship between physical (mechanical) properties and flank wear of cutting tools. The main results are obtained as follows: (1) When cutting speed is increased, the rate of wear on the nose in every tool material starts to increase remarkably at a certain speed, i.e., a critical speed. (2) Thermal conductivity coefficient versus critical speed curve is approximately linear when plotted on log-log coordinates. The higher the thermal conductivity coefficient of tool material, the higher the critical speed becomes. There also seems to exist an influence of the compressive strength and thermal expansion coefficient of tool materials on its performance in high speed cutting of GFRP.

Uniaxial-stress effects in a 95/5 lead zirconate titanate ceramic

Abstract: The response of a lead zirconate titanate ceramic to statically applied uniaxial stresses in the range 0–0.4 GPa has been investigated. The material studied was a niobium‐doped composition with the chemical formula Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3. Properties measured as a function of stress include electrical charge release from poled specimens, ferroelectric hysteresis‐loop behavior, macroscopic strains, and ultrasonic velocities. Data from the experiments exhibit anomalous behavior at low‐stress levels (0.05–0.2 GPa). Comparison with similar data obtained under conditions of hydrostatic pressure indicate that the anomalies observed in the uniaxial‐stress experiments are caused by domain‐reorientation processes rather than by the ferroelectric to antiferroelectric phase transition. This transition occurs at 0.32 GPa under hydrostatic‐pressure conditions, but no evidence for it is seen in the uniaxial‐stress measurements to 0.4 GPa. The relationship of the present results to other uniaxial‐stress studies...

Thermal insulation containing silica aerogel and alumina

Abstract: A material having good thermal insulation properties can be made from an intimate mixture of a microporous silica aerogel, a ceramic fibre material and optionally an opacifier. According to the invention alumina is added to those mixtures, e.g. in the form of alumina particles or alumina fibres constituting all or part of the ceramic fibre material. The resulting materials have a reduced tendency to sinter and consequently shrink at high temperatures.

Process for producing polycrystalline cubic aluminum oxynitride

Abstract: A structural ceramic material comprising single phase polycrystalline cubic aluminum oxynitride preferably with at least 97% of theoretical density which displays transparency and isotropic optical, thermal and electrical properties, an infrared cutoff at about 5.2 microns wavelength, and which shows no chemical or physical property change after heating in air (atmosphere) at 1100° C.

The Formation of High-temperature Materials by Direct High-frequency Fusion in a Cold Container

Abstract: A new technology of the formation of high-temperature non-metallic crystals, glasses, and fused ceramic materials is described. It is based on the method of direct induction fusion in a cold container. An account is given of the physical foundations of the technology and the technological apparatus is described. The possibilities and advantages of the new technology in the synthesis of pure high-temperature compounds in melts, in the growing of single crystals of oxide compounds, and in the preparation of high-temperature glasses and polycrystalline fused ceramics are demonstrated. The properties of the new materials are described. The bibliography includes 83 references.

Process for injection molding sinterable carbide 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.

Method of manufacturing multilayer ceramic board

Abstract: In a method of manufacture of a multilayer ceramic board, a conductor land is formed and baked on a first substrate. A second substrate on which the wiring pattern is formed is then electrically connected to the first substrate via the land. An error in the substrate due to shrinkage at the time of sintering is thereby compensated by the conductor land. This assures the formation of a highly accurate wiring pattern on the sintered substrate surface, despite shrinkage of the ceramic during sintering of the raw sheets of ceramic.

Ceramic honeycomb composite structure, catalyst supported thereby and method of producing the same

Abstract: A ceramic honeycomb composite structure adapted to be used as a catalyst support comprises a ceramic honeycomb body and ceramic layers integrally provided thereon having surfaces including therein microscopic holes, a sum of volumes of the holes 5 microns or more being at least 0.1 cm3 /g to ensure a sufficient catalyst-supporting property and achieve a high mechanical strength of the structure. On the layers of the structure are provided active material layers onto which a catalytic component is applied to enable it to be used as a catalyst. A ceramic material is extruded through a die to form the ceramic honeycomb body to which is applied ceramic grains and then the body with the grains is dried and sintered to complete the composite structure.

Hermetic electrical feedthrough for aluminum housing and method of making same

Abstract: A leak-tight joint between a Kovar ceramic feed-through and an aluminum housing is obtained by electron beam welding a short length of the outside surface of the Kovar cylindrical shell of the feedthrough to a region of nickel deposited on a thin wall cylindrical tube of aluminum formed in the aluminum housing.

Gold-to-alumina solid state reaction bonding

Abstract: This paper describes methods by which strong vacuum-tight bonds between gold and alumina can be fabricated in an air atmosphere. Temperature was found to be a sensitive factor in bond formation; the higher the temperature, the stronger the bond, provided that the temperature remained below the melting point of gold. Intimate contact between the bonding gold and alumina surfaces during formation of the bond was also an important consideration. This was achieved by using an optically flat and polished ceramic surface and applying a low pressure of about 1 MPa to the bonding couple. Further enhancement of the contact can be achieved by depositing an additional thin layer of gold onto the ceramic surface by evaporation or by other means, and by thorough cleaning by high temperature heat treatment prior to bonding. Good bonding occurs in the range of 1 to 100 h. Bond strengths as high as 80 MPa were achieved.

Effect of SiC content and orientation on the properties of Si/SiC ceramic composite

Abstract: Silicon/silicon carbide ceramic composites are made by infiltrating carbonaceous material with liquid silicon to form SiC crystallites dispersed in a silicon matrix. The present study was conducted to determine the effects on the room temperature properties of density, elastic modulus, strength, and fracture toughness by varying the amount and distribution of the SiC crystallites. Most of the work involved uniaxially aligned SiC crystals of varying volume fraction tested both longitudinally and transversely to the converted fibre axis.