Abstract: Provided is polycrystalline diamond having a diamond single phase as basic composition, in which the polycrystalline diamond includes a plurality of crystal grains and contains boron, hydrogen, oxygen, and the remainder including carbon and trace impurities; the boron is dispersed in the crystal grains at an atomic level, and greater than or equal to 90 atomic % of the boron is present in an isolated substitutional type; hydrogen and oxygen are present in an isolated substitutional type or an interstitial type in the crystal grains; each of the crystal grains has a grain size of less than or equal to 500 nm; and the polycrystalline diamond has a surface covered with a protective film.

Abstract: A diamond polycrystal includes diamond grains, the diamond polycrystal including a cubic diamond and a 6H type hexagonal diamond, wherein the cubic diamond and the 6H type hexagonal diamond exist in the same or different diamond grains, and a ratio Ab1/Ab2 is more than or equal to 0.4 and less than or equal to 1, Ab1 representing a maximum value of absorption in a range of more than or equal to 1200 cm?1 and less than or equal to 1300 cm?1 in an infrared absorption spectrum, Ab2 representing a maximum value of absorption in a range of more than or equal to 1900 cm?1 and less than or equal to 2100 cm?1.

Abstract: A diamond polycrystal is a diamond polycrystal basically composed of a diamond single phase, wherein the diamond polycrystal is composed of a plurality of diamond grains having an average grain size of less than or equal to 30 nm, and the diamond polycrystal has a carbon dangling bond density of more than or equal to 10 ppm.

Abstract: 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 ?? (cm?1) of a peak in a primary Raman scattering spectrum of the synthetic single crystal diamond and the Raman shift ? (cm?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): ??????0.10??(1).

Abstract: Provided is polycrystalline diamond having a diamond single phase as basic composition, in which the polycrystalline diamond includes a plurality of crystal grains and contains boron, at least either of nitrogen and silicon, and a remainder including carbon and trace impurities; the boron is dispersed in the crystal grains at an atomic level, and greater than or equal to 90 atomic % of the boron is present in an isolated substitutional type; the nitrogen and the silicon are present in an isolated substitutional type or an interstitial type in the crystal grains; each of the crystal grains has a grain size of less than or equal to 500 nm; and the polycrystalline diamond has a surface covered with a protective film.

Abstract: In a diamond polycrystal, a value of a ratio (d?/d) of d? to d is less than or equal to 0.98 in a Vickers hardness test performed under a condition defined in JIS Z 2244:2009, where the d represents a length of a diagonal line of a first Vickers indentation formed in a surface of the diamond polycrystal when a Vickers indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the d? represents a length of a diagonal line of a second Vickers indentation remaining in the surface of the diamond polycrystal after releasing the test load.

Abstract: In a diamond polycrystal, a value of a ratio (a?/a) of a? to a is less than or equal to 0.99 in a Knoop hardness test performed under a condition defined in JIS Z 2251:2009, where the a represents a length of a longer diagonal line of a first Knoop indentation formed in a surface of the diamond polycrystal when a Knoop indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the a? represents a length of a longer diagonal line of a second Knoop indentation remaining in the surface of the diamond polycrystal after releasing the test load.

Abstract: An indenter is made of polycrystalline diamond and has a tip having a spherical surface with a radius of 10 to 2000 ?m.

Abstract: A diamond polycrystal includes diamond grains, the diamond polycrystal including a cubic diamond and a 6H type hexagonal diamond, wherein the cubic diamond and the 6H type hexagonal diamond exist in the same or different diamond grains, and a ratio Ab1/Ab2 is more than or equal to 0.4 and less than or equal to 1, Ab1 representing a maximum value of absorption in a range of more than or equal to 1200 cm?1 and less than or equal to 1300 cm?1 in an infrared absorption spectrum, Ab2 representing a maximum value of absorption in a range of more than or equal to 1900 cm?1 and less than or equal to 2100 cm?1.

Abstract: Nano polycrystalline diamond is composed of carbon, an element of different type which is an element other than carbon and is added to be dispersed in carbon at an atomic level, and an inevitable impurity. The polycrystalline diamond has a crystal grain size not greater than 500 nm. The polycrystalline diamond can be fabricated by subjecting graphite in which the element of different type which is an element other than carbon has been added to be dispersed in carbon at an atomic level to heat treatment within high-pressure press equipment.

Abstract: In a diamond polycrystal, a value of a ratio (a?/a) of a? to a is less than or equal to 0.99 in a Knoop hardness test performed under a condition defined in JIS Z 2251:2009, where the a represents a length of a longer diagonal line of a first Knoop indentation formed in a surface of the diamond polycrystal when a Knoop indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the a? represents a length of a longer diagonal line of a second Knoop indentation remaining in the surface of the diamond polycrystal after releasing the test load.

Abstract: In a diamond polycrystal, a value of a ratio (d?/d) of d? to d is less than or equal to 0.98 in a Vickers hardness test performed under a condition defined in JIS Z 2244:2009, where the d represents a length of a diagonal line of a first Vickers indentation formed in a surface of the diamond polycrystal when a Vickers indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the d? represents a length of a diagonal line of a second Vickers indentation remaining in the surface of the diamond polycrystal after releasing the test load.

Abstract: A synthetic single crystal diamond contains nitrogen atoms at a concentration of more than 600 ppm and 1500 ppm or less, and the nitrogen atoms do not include any isolated substitutional nitrogen atom.

Abstract: A diamond polycrystal is a diamond polycrystal basically composed of a diamond single phase, wherein the diamond polycrystal is composed of a plurality of diamond grains having an average grain size of less than or equal to 30 nm, and the diamond polycrystal has a carbon dangling bond density of more than or equal to 10 ppm.

Abstract: 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 ?? (cm?1) of a peak in a primary Raman scattering spectrum of the synthetic single crystal diamond and the Raman shift ? (cm?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): ??????0.10??(1).

Abstract: Provided is polycrystalline diamond having a diamond single phase as basic composition, in which the polycrystalline diamond includes a plurality of crystal grains and contains boron, at least either of nitrogen and silicon, and a remainder including carbon and trace impurities; the boron is dispersed in the crystal grains at an atomic level, and greater than or equal to 90 atomic % of the boron is present in an isolated substitutional type; the nitrogen and the silicon are present in an isolated substitutional type or an interstitial type in the crystal grains; each of the crystal grains has a grain size of less than or equal to 500 nm; and the polycrystalline diamond has a surface covered with a protective film.

Abstract: It is an object to provide a cubic boron nitride polycrystalline material excellent in toughness. A cubic boron nitride polycrystalline material containing fine cubic boron nitride which is granular, has a maximum grain size not greater than 100 nm, and has an average grain size not greater than 70 nm and at least one of plate-shaped cubic boron nitride in a form of a plate having an average major radius not smaller than 50 nm and not greater than 10000 nm and coarse cubic boron nitride which is granular, has a minimum grain size exceeding 100 nm, and has an average grain size not greater than 1000 nm is provided.

Abstract: The present diamond single crystal is a diamond single crystal containing nitrogen atoms, in which a concentration of the nitrogen atoms changes periodically along a crystal orientation of the diamond single crystal, and an arithmetic average value Aave, a maximum value Amax, and a minimum value Amin of the distance of one period along the crystal orientation satisfy the relationship expressed by the following equation (I): (Amax)/1.25?(Aave)?(Amin)/0.75??(I).

Abstract: A cubic boron nitride polycrystal includes cubic boron nitride, the cubic boron nitride having an average grain size of not more than 150 nm, the cubic boron nitride polycrystal having a crack generation load of not less than 25 N in a breaking strength test in which an R200 ?m diamond indenter is used to apply a load at a rate of 100 N/min.

Abstract: Provided is polycrystalline diamond having a diamond single phase as basic composition, in which the polycrystalline diamond includes a plurality of crystal grains and contains boron, hydrogen, oxygen, and the remainder including carbon and trace impurities; the boron is dispersed in the crystal grains at an atomic level, and greater than or equal to 90 atomic % of the boron is present in an isolated substitutional type; hydrogen and oxygen are present in an isolated substitutional type or an interstitial type in the crystal grains; each of the crystal grains has a grain size of less than or equal to 500 nm; and the polycrystalline diamond has a surface covered with a protective film.