Provided is an alumina particle for use as a filler for resin compositions, which can improve the thermal conductivity of the resin composition over conventional resin compositions. It is an alumina particle having a particle diameter D50 of more than 100 ?m at a cumulative value of 50% from the fine particle side in the cumulative particle size distribution, and having an ?-alumina rate of 90% or more; wherein the ?-alumina is a monocrystalline alumina. The alumina particle preferably has a Na content of 800 ppm or less. In addition, the alumina particle preferably has a particle diameter D10 of 70 to 135 ?m at a cumulative value of 10% from the fine particle side in the cumulative particle size distribution.

Provided is an alumina particle for use as a filler for resin compositions, which can improve the thermal conductivity of the resin composition over conventional resin compositions. It is an alumina particle having a particle diameter D50 of more than 100 ?m at a cumulative value of 50% from the fine particle side in the cumulative particle size distribution, and having an ?-alumina rate of 90% or more; wherein the ?-alumina is a monocrystalline alumina. The alumina particle preferably has a Na content of 800 ppm or less. In addition, the alumina particle preferably has a particle diameter D10 of 70 to 135 ?m at a cumulative value of 10% from the fine particle side in the cumulative particle size distribution.

A production apparatus for fine particles includes a vacuum chamber, a material supply device, a plurality of electrodes arranged and a collection device connecting to the other end of the vacuum chamber and collecting fine particles, which generates plasma and produces fine particles from the material particles, in which a first electrode arrangement region on the material supply port's side and a second electrode arrangement region apart from the first electrode arrangement region to the collection device's side which respectively cross a direction in which the material flows between the vicinity of the material supply port and the collection device are provided in the intermediate part of the vacuum chamber, and both the first electrode arrangement region and the second electrode arrangement region are provided with a plurality of electrodes respectively to form the electrodes in multi-stages.

The disclosure relates to methods for making a ceramic or glass-ceramic, the methods comprising spray-drying a mixture comprising batch materials to form agglomerated particles; bringing the agglomerated particles into contact with a plasma for a residence time sufficient to form fused particles; and annealing the fused particles at a temperature and for a time sufficient to form ceramic or glass-ceramic particles. Fused glass particles, ceramic or glass-ceramic particles, and ceramic or glass-ceramic articles, such as ceramic honeycombs, made by these methods are also disclosed herein.

A production apparatus for fine particles includes a vacuum chamber, a material supply device, a plurality of electrodes arranged and a collection device connecting to the other end of the vacuum chamber and collecting fine particles, which generates plasma and produces fine particles from the material particles, in which a first electrode arrangement region on the material supply port's side and a second electrode arrangement region apart from the first electrode arrangement region to the collection device's side which respectively cross a direction in which the material flows between the vicinity of the material supply port and the collection device are provided in the intermediate part of the vacuum chamber, and both the first electrode arrangement region and the second electrode arrangement region are provided with a plurality of electrodes respectively to form the electrodes in multi-stages.

The present disclosure provides a transparent alumina-based plate, and a hot-pressing method to make the transparent alumina-based plate from platelet alumina. Alumina powder with a platelet morphology was hot-pressed to transparency with pre-load pressures of about 0-8 MPa, maximum temperatures of about 1750-1825? C., maximum pressures of about 2.5-80 MPa, and isothermal hold times of 1-7 hours. A novel alumina-based plate has been prepared, wherein the plate has a thickness of 2-5 mm, an in-line transmission of at least 60-75% for a light with a wavelength range of 645-2500 nm, an in-line transmission variance of <15% over the wavelength range of 645-2500 nm, and a relative density of 99.00-99.95%.

The present disclosure provides a transparent alumina-based plate, and a hot-pressing method to make the transparent alumina-based plate from platelet alumina. Alumina powder with a platelet morphology was hot-pressed to transparency with pre-load pressures of about 0-8 MPa, maximum temperatures of about 1750-1825? C., maximum pressures of about 2.5-80 MPa, and isothermal hold times of 1-7 hours. A novel alumina-based plate has been prepared, wherein the plate has a thickness of 2-5 mm, an in-line transmission of at least 60-75% for a light with a wavelength range of 645-2500 nm, an in-line transmission variance of <15% over the wavelength range of 645-2500 nm, and a relative density of 99.00-99.95%.

The present disclosure provides a transparent alumina-based plate, and a hot-pressing method to make the transparent alumina-based plate from platelet alumina. Alumina powder with a platelet morphology was hot-pressed to transparency with pre-load pressures of about 0-8 MPa, maximum temperatures of about 1750-1825? C., maximum pressures of about 2.5-80 MPa, and isothermal hold times of 1-7 hours. A novel alumina-based plate has been prepared, wherein the plate has a thickness of 2-5 mm, an in-line transmission of at least 60-75% for a light with a wavelength range of 645-2500 nm, an in-line transmission variance of <15% over the wavelength range of 645-2500 nm, and a relative density of 99.00-99.95%.

The present disclosure provides a transparent alumina-based plate, and a hot-pressing method to make the transparent alumina-based plate from platelet alumina. Alumina powder with a platelet morphology was hot-pressed to transparency with pre-load pressures of about 0-8 MPa, maximum temperatures of about 1750-1825? C., maximum pressures of about 2.5-80 MPa, and isothermal hold times of 1-7 hours. A novel alumina-based plate has been prepared, wherein the plate has a thickness of 2-5 mm, an in-line transmission of at least 60-75% for a light with a wavelength range of 645-2500 nm, an in-line transmission variance of <15% over the wavelength range of 645-2500 nm, and a relative density of 99.00-99.95%.

The present invention relates to temperature-treated polycrystalline porous Al.sub.2O.sub.3 bodies comprising an amount of aluminum oxide of more than 97% by weight, an amount of other oxide alloying components of a total of less than 3% by weight, a macroporosity of between 5 and 30% by volume, wherein the Al.sub.2O.sub.3 bodies are composed of a plurality of Al.sub.2O.sub.3 primary crystals comprising a crystallite size of between 20 and 100 m.