A suspension of nanodiamond aggregates according to the present invention is a suspension of detonation nanodiamond aggregates. The suspension has such a pH and an electric conductivity as to meet one of conditions (1) and (2) as follows. (1) The suspension has a pH of 4 to 7 and an electric conductivity of 50 μS/cm or less per weight percent of the solids concentration of the suspension; and (2) the suspension has a pH of 8 to 10.5 and has an electric conductivity of 300 μS/cm or less per weight percent of the solids concentration of the suspension.

Luminescent diamond is made by subjecting a volume of diamond grains to high-pressure/high-temperature conditions with or without a catalyst to cause the grains to undergo plastic deformation to produce nitrogen vacancy defects in the diamond grains, increasing the luminescent activity/intensity of the resulting diamond material. The consolidated diamond material may be further treated to further increase luminescent activity/intensity, which treatment may comprise reducing the consolidated diamond material to diamond particles, heat treatment in vacuum, and air heat treatment, which reducing process further increases luminescent activity/intensity. The resulting luminescent diamond particles display a level of luminescence intensity greater than that of conventional luminescent nanodiamond, and may be functionalized for use in biological applications.

Luminescent diamond is made by subjecting a volume of diamond grains to high-pressure/high-temperature conditions with or without a catalyst to cause the grains to undergo plastic deformation to produce nitrogen vacancy defects in the diamond grains, increasing the luminescent activity/intensity of the resulting diamond material. The consolidated diamond material may be further treated to further increase luminescent activity/intensity, which treatment may comprise reducing the consolidated diamond material to diamond particles, heat treatment in vacuum, and air heat treatment, which reducing process further increases luminescent activity/intensity. The resulting luminescent diamond particles display a level of luminescence intensity greater than that of conventional luminescent nanodiamond, and may be functionalized for use in biological applications.

A high-pressure high-temperature, HPHT, diamond tool piece and a method of producing an HPHT diamond tool piece. At least a portion of the HPHT diamond tool piece comprises an aggregated nitrogen centre to C-nitrogen centre ratio of greater than 30%. The method includes irradiating an HPHT diamond material to introduce vacancies in the diamond crystal lattice, annealing the HPHT diamond material such that at least a portion of the HPHT diamond material comprises an aggregated nitrogen centre to C-nitrogen centre ratio of greater than 30%, and processing the HPHT diamond material to form an HPHT diamond tool piece.

A high-pressure high-temperature, HPHT, diamond tool piece and a method of producing an HPHT diamond tool piece. At least a portion of the HPHT diamond tool piece comprises an aggregated nitrogen centre to C-nitrogen centre ratio of greater than 30%. The method includes irradiating an HPHT diamond material to introduce vacancies in the diamond crystal lattice, annealing the HPHT diamond material such that at least a portion of the HPHT diamond material comprises an aggregated nitrogen centre to C-nitrogen centre ratio of greater than 30%, and processing the HPHT diamond material to form an HPHT diamond tool piece.

The present invention relates to a method for preparing a carbon-based particle/copper composite material in which carbon-based particles such as graphite and copper are mixed, the method including mixing a solution of a polymer organic compound having a main chain of carbon and a copper precursor in a solvent, with a dispersion solution of carbon-based particles in a first dispersion medium to produce a mixture, adding a first reducing agent to the mixture to form composite particles in which copper (I) oxide particles are attached to the surface of the carbon-based particles, and sintering the composite particles under a non-oxidizing atmosphere. According to the preparing method, a composition material is obtained, in which carbon-based particles and copper are well mixed.

A method of forming a polycrystalline diamond comprises derivatizing a nanodiamond to form functional groups, and combining the derivatized nanodiamond with a microdiamond having an average particle size greater than that of the derivatized nanodiamond, and a metal solvent-catalyst. A polycrystalline diamond compact is prepared by adhering the polycrystalline diamond to a support, and an article such as a cutting tool may be prepared from the polycrystalline diamond compact.

A mild, acid- and alkali-free purification method of detonation nanodiamond material from water-insoluble metal-containing impurities and product obtained thereof. The products thus obtained include nanodiamond and diamond-containing detonation blend. The method is implemented by an impact treatment of the detonation nanodiamond material with aqueous or water organic solutions of chelating agents in concentrations 0.5-20 wt. % at elevated temperature, wherein the weight-percent ratio of the detonation nanodiamond material to an undiluted chelating agent is substantially 1 to 0.2. Impact treatment of the detonation nanodiamond material in chelating agent solution may include boiling, ultrasonication, cavitational disintegration, and harsh treatment in sealed chamber at temperatures of up to about 300° C. and high pressure. The method provides at least 5-fold reduction of metal-containing impurities in the resulting product, wherein the content of such elements as chromium and iron is reduced to negligible amounts.

A nanodiamond according to the present invention has acidic functional groups, contains the acidic functional groups in a number density of 1 or more per square nanometer in the nanodiamond surface, and has a specific surface area of 150 m.sup.2/g or more. Particles of the nanodiamond preferably have a D50 (median diameter) of 9 nm or less. The nanodiamond is preferably derived from a nanodiamond synthesized by a detonation technique (in particular, an air-cooling detonation technique).

A sensor system is based on diamonds with a high density of NV centers. The description includes a) methods for producing the necessary diamonds of high NV center density, b) characteristics of such diamonds, c) sensing elements for utilizing the fluorescence radiation of such diamonds, d) sensing elements for utilizing the photocurrent of such diamonds, e) systems for evaluating these quantities, f) reduced noise systems for evaluating these systems, g) enclosures for using such systems in automatic placement equipment, g) methods for testing these systems, and h) a musical instrument as an example of an ultimate application of all these devices and methods.