Abstract: The present invention is directed to polycrystalline diamond and cubic boron nitride (CBN) composite compacts and a method of making the same under high temperature/high pressure (HP/HT) processing conditions, and more particularly to HP/HT polycrystalline composite compacts having reduced abrasive layer stresses. The method of the invention involves making a metal carbide supported polycrystalline composite compact under conditions of high pressure and high temperature (HP/HT) in an HP/HT apparatus by the following steps:(a) placing within an enclosure a mass of abrasive particles, a first mass of metal carbide support material adjacent said abrasive particles, and a second mass of metal carbide support material adjacent said first mass with a layer of brazing filler alloy having a liquidus above about 700.degree. C.

Abstract: Disclosed is a process for preparing sintered polycrystalline CBN/ceramic conjoint masses in an HP/HT process which comprises subjecting a mixture of GBN and one or more of a ceramic material or metal which reacts with BN to form a ceramic material, to HP/HT conditions for inducing conversion of said GBN to CBN, inducing conversion of any of said metal to its corresponding metal ceramic, and forming said CBN/ceramic conjoint mass.

Abstract: Multigrain abrasive compacts and processes for making the same are provided which comprise fine granules of cubic boron nitride or diamond bound by a sintered matrix derived from a coating on the granules. The coating comprises one or more layers of an active coating material which chemically bonds to the underlying surface. These compacts are obtained by coating fine granules of cubic boron nitride or diamond with the active coating material and sintering the coated particles with or without a powdered metal or alloy. The compacts can be obtained utilizing a short sintering step with relatively low pressures and temperatures. In certain embodiments, the use of high pressure, high temperature equipment can be voided. These compacts have improved breakdown characteristics due to the nature of the coated particles incorporated therein. The process provided is well suited for the use of diamond powder obtained from chemical vapor deposition processes.

Abstract: The present invention provides methods for forming cubic boron nitride from large particle ideal structure hexagonal boron nitride. Large particles provide improved packing density within the high pressure, high temperature equipment utilized, providing higher yields from conversion processes which utilize a catalyst and those which do not. This large particle ideal structure HBN can be used with conventional high pressure, high temperature processes to provide CBN particulates, composites and compacts.

Abstract: Multigrain abrasive particles and articles made therefrom are provided wherein the particles comprise fine granules of cubic boron nitride or diamond bound by a sintered matrix of one or more layers of active coating material that is chemically bonded to the underlying surface. These particles are obtained by sintering the coated granules under relatively mild conditions in comparison to those necessary to form monocrystalline abrasive particles of a similar size. In certain embodiments, the use of high pressure, high temperature equipment can be avoided. The particles have improved breakdown characteristics which can be controlled through a selection of the coating thickness, the type of coating and the size of the fine granules to be bonded. The process is well suited for the use of diamond powder produced from chemical vapor deposition processes.

Abstract: Broadly, the present invention is directed to a high pressure/high temperature (HP/HT) process for making polycrystalline CBN composite masses from graphitic boron nitride (GBN) in the substantial absence of catalytically-active material. The present invention specifically comprises subjecting a mixture of different structural forms of GBN to simultaneous conversion of each for making a CBN/CBN composite mass. Pyrolytic boron nitride/hexagonal boron nitride (PBN/HBN) mixtures are ideally suited for conversion into the inventive CBN/CBN composite masses of the present invention.

Abstract: A process for preparing sintered polycrystalline CBN/ceramic conjoint masses comprises forming a mixture of GBN and one or more of a ceramic material or metal which reacts with BN to form a ceramic material, subjecting said mixture to a high pressure and a high temperature conditons for inducing conversion of said GBN to CBN and inducing conversion of any of said metal to its corresponding metal ceramic, and forming said CBN/ceramic conjoint mass. The mixture of GBN and ceramic material or metal can be formed by a process selected from the group consisting of chemical vapor deposition, sol gel techniques, polymer pyrolysis techniques, and combustion synthesis.

Abstract: Abrasive particles and articles made from cubic boron nitride derived from coated hexagonal boron nitride which is substantially free of oxides and volatile contaminants. Polycrystalline CBN is prepared from HBN by removing oxide from the surface of HBN particles to form HBN particles having a substantially oxide-free surface. The HBN particles having a substantially oxide-free surface are coated with an agent which is capable of preventing re-oxidation of the surface of the HBN particles to form coated HBN particles in a substantially oxide-free state. The coated HBN particles in a substantially oxide-free state are then converted to a polycrystalline CBN by direct conversion of HBN to CBN. Coating agents include metals, metal carbides, metal nitrides and metal borides. A preferred coating agent is titanium carbide.

Abstract: Disclosed is a method for making re-sintered polycrystalline CBN compact which comprises placing sintered boron-rich polycrystalline CBN particles in a high temperature/high pressure apparatus and subjecting said boron-rich CBN particles to a pressure and a temperature adequate to re-sinter said particles, the temperature being below the reconversion temperature of CBN, for a time sufficient to re-sinter the polycrystalline CBN particles therein. The boron-rich polycrystalline CBN particles in the HP/HT apparatus contain no impurity which would interfere with the sintering process (CBN sintering inhibiting impurities) and no sintering aid material.

Abstract: Optical windows for hostile environments have been made from diamond and adamantine boron nitride compacts. The compact windows can comprise a single layer of large crystals bonded in a matrix. For example, they are made by exposing a sample of diamond (425-1700 micron) in a diamond and graphite matrix to high pressure-high temperature conditions (e.g., 50 Kbar at 1400.degree. C. to 85 Kbar at 1800.degree. C.).A typical boron nitride reaction zone assembly (cell) is shown in FIG. 1, in which carbon heater tube 1 is surrounded by tantalum foil sleeve 2. The sample of pyrolytic boron nitride 3 is disposed between carbon discs 5, tantalum foil discs 4 and hot pressed boron nitride plugs 6.The optical windows produced are capable of transmitting infrared light and visible light.

Abstract: Boron rich cubic boron nitride suitable for use in electroplating processes (e.g. nickel plating) has been made by an acid leaching process. Boron rich aggregated cubic boron nitride grinding grits are leached in a mixture of nitric and sulfuric acids, the following conditions being typical;(a) volume ratio of 67% nitric acid to 98% sulfuric acid of 10:20;(b) temperature of 250.degree. C; and(c) for a time of 1 hour.The process removes sufficient free surface boron to reduce the conductivity at the surface, resulting in an abrasive which does not overplate.FIG. 1 is a photomicrograph of a typical plated surface containing the improved CBN grinding grit of this invention, and FIG. 3 is an X-ray diffraction pattern characteristic of this new product.

Abstract: Cubic boron nitride has been made from powdered hexagonal boron nitride by a process which comprises vacuum firing of the HBN and conversion by high pressure-high temperature processing at 55-80 kilobars and 1600.degree. C. to the reconversion temperature.The high pressure reaction cell has a special design which prevents the entrance of impurities into the sample. This cell, referring to FIG. 2, comprises, for example, a carbon tube (8) enclosing concentric titanium sleeve (9). Within the cylinder defined by the tube and sleeve are: the HBN sample (4), carbon filler (3), shielding tantalum foil discs (2) and carbon end plugs (10).The vacuum firing is done at pressures of 10.sup.-5 --10.sup.-10 mm Hg, 1400.degree.-1900.degree. C., for 5 minutes--4 hours, and is believed to form a thin, free-boron coating on the HBN particles.The process works on both pyrolytic (turbostratic) and graphitic hexagonal boron nitride.

Abstract: Hard boron nitride particles of wurtzite and zincblende crystal structure of larger than 50 microns particle size are formed by subjecting recrystallized pyrolytic boron nitride to dynamic shock treatment to create pressures and temperatures in which the stable form of boron nitride has a wurtzite or zincblende crystal structure.

Abstract: Hard boron nitride particles of wurtzite and zincblende crystal structure of larger than 50 microns particle size are formed by subjecting recrystallized pyrolytic boron nitride to dynamic shock treatment to create pressures and temperatures in which the stable form of boron nitride has a wurtzite or zincblende crystal structure.

Abstract: A process for making a sintered polycrystalline cubic boron nitride (CBN) compact by direct conversion of a pyrolytic, preferably substrate nucleated, boron nitride (PBN). Direct conversion takes place by subjecting the PBN to temperatures and pressures within the CBN stable region. The crystallites of the compact produced by this process are preferentially oriented. Also, such compacts have a high thermal conductivity between about 2 watts/cm.degree. K. and 9 watts/cm.degree. K. and thus are useful as a heat sink for electronic devices. The size of the CBN crystallites of the compact may be between about 1.times.10.sup.3 A to 1.times.10.sup.5 A.

Abstract: Soft hexagonal boron nitride crystals of 200-600 microns platelet size are produced from crystals of less than fifty microns particle size by mixing the small crystals with Li.sub.3 N, simultaneously heating and pressurizing said mixture to a temperature and pressure in a restricted region of the graphitic (hexagonal) boron nitride (GBN) stable region of the pressure-temperature (P-T) phase diagram of boron nitride, cooling and depressurizing said mixture, and separating off the water soluble material present in the mixture to leave a residue of large crystals of boron nitride.