A composite polycrystal contains polycrystalline diamond formed of diamond grains that are directly bonded mutually, and compressed graphite dispersed in the polycrystalline diamond.

A double-tube connection structure for detonation synthesis, a detonation synthesis device and an application thereof are provided. The double-tube connection structure for detonation synthesis includes a drive tube, a sample tube, fixing components, and end plugs provided at ports of the sample tube. The drive tube is sleeved outside the sample tube, cavities are provided between the drive tube and the sample tube, and between the drive tube and the end plug. The fixing components are provided on two ends of the drive tube and the sample tube. After detonation, a detonation wave is transferred from top to bottom. Under the action of the detonation wave, the drive tube performs convergent sliding motion towards the sample tube, and covers outsides of the sample tube, and the top end plug and the bottom end plug of the sample tube. A detonation synthesis device includes the double-tube connection structure for detonation synthesis.

A synthetic single crystal diamond containing 100 ppm or more and 1500 ppm or less of nitrogen atoms, in which the synthetic single crystal diamond contains aggregates each composed of one vacancy and two to four nitrogen atoms present adjacent to the vacancy, a ratio b/a of a length b of a short diagonal line to a length a of a long diagonal line of diagonal lines of a Knoop indentation in a <110> direction in a {001} plane of the synthetic single crystal diamond is 0.08 or less, and the Knoop indentation is formed by measuring Knoop hardness in the <100> direction in the {001} plane of the synthetic single crystal diamond according to JIS Z 2251: 2009 under conditions of a temperature of 23° C.±5° C. and a test load of 4.9 N.

Provided is a synthetic single crystal diamond containing nitrogen atoms at a concentration of more than 600 ppm and 1500 ppm or less. The Raman shift λ′ (cm.sup.−1) of a peak in a primary Raman scattering spectrum of the synthetic single crystal diamond and the Raman shift λ (cm.sup.−1) of a peak in a primary Raman scattering spectrum of a synthetic type IIa single crystal diamond containing nitrogen atoms at a content of 1 ppm or less satisfy the following expression (1):
λ′−λ≥−0.10  (1).

[Technical Problem]To provide diamond grits with enhanced friability, and method for the production comprising in combination internal microcracks within the diamond particle and surface irregularities, with or without a layer of non-diamond carbon covering the particle surface.

[Solution to Problem]

The diamond grits of the invention consist of diamond particles synthesized by a static ultrahigh pressure-high temperature process, comprising both microcracks generated within the particles due to the effect of heating, and surface irregularities formed on the particles by oxidizing etching at elevated temperatures.

The production method comprises providing a starting volume of diamond particles, from a synthesizing process in a static ultrahigh pressure-high temperature process, subjecting said diamond particles to a heating process in intimate contact with an oxidizing etchant at a temperature of 800° C. or higher, generating thus microcracks within the diamond particles and also causing to corrode the particle surface thus forming increased surface irregularities, and recovering the treated diamond particles.

The present invention is to provide a method for producing nanodiamonds doped with a Group 14 element, the method comprising: detonating by exploding an explosive composition containing at least one explosive and at least one Group 14 element compound in a sealed container to obtain nanodiamonds doped with at least one Group 14 element selected from the group consisting of Si, Ge, Sn, and Pb, and removing the Group 14 element and/or oxide thereof by subjecting the nanodiamonds doped with a Group 14 element to an alkali treatment.

An apparatus for the manufacture of synthetic diamonds includes a pressure vessel having a chamber therein, and a body located in the chamber. The pressure vessel and the body are formed of materials having different coefficients of expansion. The coefficient of expansion of the body is greater than the coefficient of expansion of the pressure vessel. The pressure vessel is formed from a material having a melting point in excess of 1327° C. and capable of withstanding a pressure of at least 4.4 Gpa at a temperature of at least 1327° C. The chamber is configured to receive the body, and a carbon source, the apparatus further comprising a heating means configured to heat at least the body to a temperature at least of 1327° C. The coefficient of expansion of the body is selected such that upon heating thereof to at least 1327° C. the pressure exerted on the carbon source is at least 4.4 Gpa.

A synthetic block for optimizing the performance of diamonds and gemstones is provided, including: a sealing material, a thermal insulation material, conductive materials, and a heating material. The conductive materials are provided at both ends of the sealing material. The heating material abuts between the conductive materials, and a high-temperature and high-pressure area is formed inside the heating material. The thermal insulation material includes a first thermal insulation tube and a second thermal insulation tube that are sequentially telescoped the conductive materials. The first thermal insulation tube abuts on an outer wall of the heating material, the second thermal insulation tube is provided between the sealing material and the first thermal insulation tube, a height of the second thermal insulation tube is greater than that of the first thermal insulation tube, and the synthetic block is square.

Nano polycrystalline diamond is composed of carbon and a plurality of impurities other than carbon. A concentration of each of the plurality of impurities is not higher than 0.01 mass %, and the nano polycrystalline diamond has a crystal grain size (a maximum length) not greater than 500 nm. The nano polycrystalline diamond can be fabricated by preparing graphite in which a concentration of an impurity is not higher than 0.01 mass % and converting graphite to diamond by applying an ultra-high pressure and a high temperature to graphite.

A superabrasive material and method of making the superabrasive material are provided. The superabrasive material may comprise a superabrasive crystal having an irregular surface. The superabrasive material further comprises a plurality of structure defects within the superabrasive crystal. The plurality of structure defects may cause micro-chipping when used as grinding materials.