A silicon nitride sintered body includes at least one black portion with a major axis of 10 μm or more in a field of view with a unit area of 5 mm×5 mm, when observing an arbitrary cross-section of the silicon nitride sintered body using a metallurgical microscope. A major axis of the black portion is Preferably 500 μm or less. The number of the black portion within the field of view with a unit area of 5 mm×5 mm is preferably 2 or more and 10 or less. A segregation portion of Fe is preferably included in the black portion.

Provided is a MgAl.sub.2O.sub.4 sintered body, which includes a relative density of the MgAl.sub.2O.sub.4 sintered body being 90% or higher, and an L* value in a L*a*b* color system being 90 or more. A method of producing a MgAl.sub.2O.sub.4 sintered body is characterized by that a MgAl.sub.2O.sub.4 powder is hot pressed at 1150 to 1300° C., and is thereafter subjected to atmospheric sintering at 1350° C. or higher. Embodiments of the present invention address the issue of providing a high density and white MgAl.sub.2O.sub.4 sintered body and a sputtering target using the sintered body, and a method of producing a MgAl.sub.2O.sub.4 sintered body.

[Problem]

A technique for improving translucency in order to prepare a zirconia sintered body having high translucency without using special equipment, has been required.

[Solution]

To provide A sintering method for a dental zirconia calcined body containing 5.5 mol % to 7.0 mol % of a stabilizer, wherein the method satisfies the following (a) to (c). (a) an average rate of temperature increase in the section from room temperature to 1300° C. is 9° C./min or more. (b) an average rate of temperature increase in the section from 1300° C. to 1400° C. is 0.6° C./min or more and 3° C./min or less. (c) an average rate of temperature increase in the section from 1400° C. to the maximum temperature of the sintering process is 0.5° C./min or more and 2.5° C./min or less.

A cubic boron nitride sintered body including cubic boron nitride and a binder phase, wherein a content of the cubic boron nitride is 40 volume % or more and 70 volume % or less; a content of the binder phase is 30 volume % or more and 60 volume % or less; an average particle size of the cubic boron nitride is 0.1 μm or more and 3.0 μm or less; the binder phase contains TiN and/or TiCN, and TiB.sub.2 and contains substantially no AIN and/or Al.sub.2O.sub.3, the binder phase has a TiB.sub.2 (101) plane that shows a maximum peak position (2θ) in X-ray diffraction of 44.2° or more; and I.sub.2/I.sub.1 is 0.10 or more and 0.55 or less, where denotes an X-ray diffraction intensity of a (111) plane of the cubic boron nitride and I.sub.2 denotes an X-ray diffraction intensity of a (101) plane of TiB.sub.2 of the binder phase.

Shaped ceramic abrasive particles include a first surface having a perimeter having a perimeter comprising at least first and second edges. A first region of the perimeter includes the second edge and extends inwardly and terminates at two corners defining first and second acute interior angles. The perimeter has at most four corners that define acute interior angles. A second surface is disposed opposite, and not contacting, the first surface. A peripheral surface is disposed between and connects the first and second surfaces. The peripheral surface has a first predetermined shape. Methods of making the shaped ceramic abrasive particles, and abrasive articles including them are also disclosed.

Antiballistic armour plate includes a ceramic body including a hard material, provided, on its inner face, with a back energy-dissipating coating. The ceramic body is monolithic. The constituent material of the ceramic body includes grains of ceramic material having a Vickers hardness that is higher than 15 GPa, and a matrix binding the grains, the matrix including a silicon nitride phase and/or a silicon oxynitride phase, the matrix representing between 5 and 40% by weight of the constituent material of the ceramic body. The maximum equivalent diameter of the grains of ceramic material is smaller than or equal to 800 micrometres. The constituent material of the ceramic body has an open porosity that is higher than 5% and lower than 14%. The metallic silicon content in the material, expressed per mm of thickness of the body, is lower than 0.5% by weight.

A method for making ceramic composites via sintering a mixture of alumina and oil fly ash. The alumina is in the form of nanoparticles and/or microparticles. The oil fly ash may be treated with an acid prior to the sintering. The composite may comprise graphite carbon derived from oil fly ash dispersed in an alumina matrix. The density, mechanical performance (e.g. Vickers hardness, fracture toughness), and thermal properties (e.g. thermal expansion, thermal conductivity) of the ceramic composites prepared by the method are also specified.

A refractory object may include a zircon body that is intentionally doped with a dopant including an alkaline earth element and aluminum. The refractory object can have an improved creep deformation rate. In an embodiment, the refractory object can have a creep deformation rate of not greater than about 1.8 E-5 h.sup.−1 at a temperature of 1350° C. and a stress of 2 MPa. In another embodiment, the zircon body may include an amorphous phase including an alkaline earth metal element.

The present invention aims to provide a scintillator which has a short fluorescence decay time, whose fluorescence intensity after a period of time following radiation irradiation is low, and which shows largely improved light-transmittance. A scintillator represented by the following General Formula (1), the scintillator including Zr, having a Zr content of not less than 1500 ppm by mass therein, and being a block of a sintered body. Q.sub.xM.sub.yO.sub.3z:A . . . (1) (wherein in General Formula (1), Q includes at least one or more kinds of divalent metallic elements; M includes at least Hf; and x, y, and z independently satisfy 0.5≤x≤1.5, 0.5≤y≤1.5, and 0.7≤z≤1.5, respectively).

Shaped ceramic abrasive particles include a first surface having a perimeter having a perimeter comprising at least first and second edges. A first region of the perimeter includes the second edge and extends inwardly and terminates at two corners defining first and second acute interior angles. The perimeter has at most four corners that define acute interior angles. A second surface is disposed opposite, and not contacting, the first surface. A peripheral surface is disposed between and connects the first and second surfaces. The peripheral surface has a first predetermined shape. Methods of making the shaped ceramic abrasive particles, and abrasive articles including them are also disclosed.