▪ Abstract The synthesis of the two currently used superhard materials, diamond and cubic boron nitride, is briefly described with indications of the factors influencing the quality of the crystals obtained. The physics of hardness is discussed and the importance of covalent bonding and fixed atomic positions in the crystal structure, which determine high hardness values, is outlined. The materials investigated to date are described and new potentially superhard materials are presented. No material that is thermodynamically stable under ambient conditions and composed of light (small) atoms will have a hardness greater than that of diamond. Materials with hardness values similar to that of cubic boron nitride (cBN) can be obtained. However, increasing the capabilities of the high-pressure devices could lead to the production of better quality cBN compacts without binders.

Synthesis and Design of Superhard Materials

An articulating surgical instrument is shown, which comprises a shaft and an end effector. The shaft has a longitudinal axis, and the end effector is operationally coupled, preferably mechanically coupled, to the shaft at an articulation pivot. The instrument also comprises a first band, and in some embodiments, a second band, each operationally connected to the end effector and extending through at least a portion of the shaft. An articulation control applies a force in a direction substantially transverse to the longitudinal axis, wherein the force, when applied in one direction, is translated through the first band to the end effector to effect rotation of the end effector relative to the shaft about the articulation pivot in a first rotational direction, and when the force is applied in the opposite direction, is translated through the second band to the end effector to effect rotation of the end effector relative to the shaft about the articulation pivot in a second rotational direction.

Surgical instrument having an articulating end effector

An overview of the machinability of aeroengine alloys

The elastic constant tensor of an inorganic compound provides a complete description of the response of the material to external stresses in the elastic limit. It thus provides fundamental insight into the nature of the bonding in the material, and it is known to correlate with many mechanical properties. Despite the importance of the elastic constant tensor, it has been measured for a very small fraction of all known inorganic compounds, a situation that limits the ability of materials scientists to develop new materials with targeted mechanical responses. To address this deficiency, we present here the largest database of calculated elastic properties for inorganic compounds to date. The database currently contains full elastic information for 1,181 inorganic compounds, and this number is growing steadily. The methods used to develop the database are described, as are results of tests that establish the accuracy of the data. In addition, we document the database format and describe the different ways it can be accessed and analyzed in efforts related to materials discovery and design.

/pdf/charting-the-complete-elastic-properties-of-inorganic-540nz2xj01.pdf

Charting the complete elastic properties of inorganic crystalline compounds

Elastic constants versus melting temperature in metals

The elastic constants of single crystal tungsten monocarbide were determined using highfrequency (20 to 50 mHz) ultrasonic pulse-echo measurements. The measured values from this study are a full order of magnitude lower than the previously reported values estimated from X-ray elastic constants. The elastic modulus of polycrystalline tungsten carbide was also measured to verify the accuracy of the ultrasonic method used.

Single crystal elastic constants of tungsten monocarbide

A mass of diamond crystals contacting a mass of elemental silicon are confined within a pressure-transmitting medium. The resulting charge assembly is subjected to a pressure of at least 25 kilobars causing application of isostatic pressure to the contacting masses which dimensionally stabilizes them and increases the density of the mass of diamond crystals. The resulting pressure-maintained charge assembly is heated to a temperature sufficient to melt the silicon and at which no significant graphitization of the diamond occurs whereby the silicon is infiltrated through the interstices between the diamond crystals producing, upon cooling, an adherently bonded integral body.

Silicon carbide and silicon bonded polycrystalline diamond body and method of making it

Wear characteristics of various hard materials for machining sic-reinforced aluminum alloy

A polycrystalline diamond body infiltrated by a silicon atom-containing metal (e.g., silicon alloy) is bonded to a substrate comprising cemented carbide with a barrier of refractory material extending between the diamonds cemented together with silicon atom-containing binder and the substrate substantially precluding migration of the cementing medium (e.g., cobalt) from the carbide substrate into contact with the silicon atom-containing bonding medium in the diamond body. The process comprises subjecting a mass of diamond powder, a quantity of silicon atom-containing metal binder material, a cemented carbide body and a barrier made of material selected from the group consisting of tantalum, vanadium, molybdenum, zirconium, tungsten and alloys thereof to the simultaneous application of elevated temperature and pressure.

Polycrystalline diamond and cemented carbide substrate and synthesizing process therefor

A mass of diamond crystals in contact with a mass of eutectiferous silicon-rich alloy and a silicon carbide ceramic substrate are disposed in a container and placed within a pressure transmitting powder medium. Pressure is applied to the powder medium resulting in substantially isostatic pressure being applied to the container and its contents sufficient to dimensionally stabilize the container and its contents. The resulting shaped substantially isostatic system of powder-enveloped container is hot-pressed whereby fluid eutectiferous silicon-rich alloy is produced and infiltrated through the interstices between the diamond crystals and contacts the contacting face of the silicon carbide substrate sufficiently producing, upon cooling, an adherently bonded integral composite.

Polycrystalline diamond body/silicon carbide substrate composite

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