Flaky alumina particles including mullite in a surface layer of the flaky alumina particles. A method for producing flaky alumina particles including forming a mixture by mixing together an aluminum compound that contains elemental aluminum, a molybdenum compound that contains elemental molybdenum, and silicon or a silicon compound that contains elemental silicon, the aluminum compound being in an amount greater than or equal to 50 mass %, calculated as Al.sub.2O.sub.3, the molybdenum compound being in an amount less than or equal to 40 mass %, calculated as MoO.sub.3, the silicon or the silicon compound being in an amount of 0.5 mass % or greater and less than 10 mass %, calculated as SiO.sub.2, relative to a total mass of the flaky alumina particles taken as 100 mass %; and firing the mixture.

An abrasive grain is disclosed and may include a body. The body may define a length (l), a height (h), and a width (w). In a particular aspect, the length is greater than or equal to the height and the height is greater than or equal to the width. Further, in a particular aspect, the body may include a primary aspect ratio defined by the ratio of length:height of at least about 2:1. The body may also include an upright orientation probability of at least about 50%.

The present invention provides alumina particles having a fixed card-house structure formed of three or more flat plate-like alumina particles and having an average particle diameter of 3 to 1000 m. Also, there is provided alumina particles having an average particle diameter of 3 to 1000 m and having a fixed card-house structure in which the three or more flat plate-like alumina are aggregated to be crossed each other at two or more plurality of positions, and the plane directions of the flat plates crossed each other are in a state of disordered arrangement.

An abrasive grain is disclosed and may include an elongated body. The body may define a length (l), a width (w), and a height (h), where the length is the longest dimension. The elongated body may have a first end face, a second end face, and a side surface extending between the first end face and the second end face. The body can include a twist along an axis body.

An abrasive grain is disclosed and may include an elongated body. The body may define a length (l), a width (w), and a height (h), where the length is the longest dimension. The elongated body may have a first end face, a second end face, and a side surface extending between the first end face and the second end face. The body can include a twist along an axis body.

Flaky alumina particles including mullite in a surface layer of the flaky alumina particles. A method for producing flaky alumina particles including forming a mixture by mixing together an aluminum compound that contains elemental aluminum, a molybdenum compound that contains elemental molybdenum, and silicon or a silicon compound that contains elemental silicon, the aluminum compound being in an amount greater than or equal to 50 mass %, calculated as Al.sub.2O.sub.3, the molybdenum compound being in an amount less than or equal to 40 mass %, calculated as MoO.sub.3, the silicon or the silicon compound being in an amount of 0.5 mass % or greater and less than 10 mass %, calculated as SiO.sub.2, relative to a total mass of the flaky alumina particles taken as 100 mass %; and firing the mixture.

Flaky alumina particles including mullite in a surface layer of the flaky alumina particles. A method for producing flaky alumina particles including forming a mixture by mixing together an aluminum compound that contains elemental aluminum, a molybdenum compound that contains elemental molybdenum, and silicon or a silicon compound that contains elemental silicon, the aluminum compound being in an amount greater than or equal to 50 mass %, calculated as Al.sub.2O.sub.3, the molybdenum compound being in an amount less than or equal to 40 mass %, calculated as MoO.sub.3, the silicon or the silicon compound being in an amount of 0.5 mass % or greater and less than 10 mass %, calculated as SiO.sub.2, relative to a total mass of the flaky alumina particles taken as 100 mass %; and firing the mixture.

To provide plate-like alumina particles that are less likely to wear apparatuses. Plate-like alumina particles containing germanium or a germanium compound. The plate-like alumina particles preferably have a molar ratio of Ge to Al, [Ge]/[Al], of 0.08 or more as determined in an XPS analysis. The plate-like alumina particles preferably contain the germanium or germanium compound in a surface layer. The plate-like alumina particles preferably have a density of 3.7 g/cm.sup.3 or more and 4.1 g/cm.sup.3 or less. The plate-like alumina particles preferably have a molar ratio of Ge to Al, [Ge]/[Al], of 0.08 or less as determined in an XRF analysis.

An abrasive grain is disclosed and may include a body. The body may define a length (l), a height (h), and a width (w). In a particular aspect, the length is greater than or equal to the height and the height is greater than or equal to the width. Further, in a particular aspect, the body may include a primary aspect ratio defined by the ratio of length:height of at least about 2:1. The body may also include an upright orientation probability of at least about 50%.

An abrasive grain is disclosed and may include a body. The body may define a length (l), a height (h), and a width (w). In a particular aspect, the length is greater than or equal to the height and the height is greater than or equal to the width. Further, in a particular aspect, the body may include a primary aspect ratio defined by the ratio of length:height of at least about 2:1. The body may also include an upright orientation probability of at least about 50%.