Abstract: The present invention is to produce an aluminum nitride powder which is turned into a sintered body at a temperature of not more than 1600° C., thereby obtaining a sintered aluminum nitride in which the density and thermal conductivity are high and which can be properly used as a substrate material. Using a vapor phase reaction apparatus shown in FIG. 1, ammonia gas was fed from a reactor 2 heated at from 300 to 500° C. and maintained at that temperature by a heating section 1 via a feeding tube 4 while being regulated by a flow regulator 3. At the same time, while being regulated by the flow regulator 5, nitrogen gas containing an organic aluminum compound is fed via a feeding tube 6 to obtain an aluminum nitride powder. The aluminum nitride powder is subjected to a heat treatment at from 1100 to 1500° C. in a reducing gas atmosphere and/or an inert gas atmosphere to obtain an aggregate aluminum nitride powder.

Abstract: The present invention is to produce an aluminum nitride powder which is turned into a sintered body at a temperature of not more than 1600° C., thereby obtaining a sintered aluminum nitride in which the density and thermal conductivity are high and which can be properly used as a substrate material. Using a vapor phase reaction apparatus shown in FIG. 1, ammonia gas was fed from a reactor 2 heated at from 300 to 500° C. and maintained at that temperature by a heating section 1 via a feeding tube 4 while being regulated by a flow regulator 3. At the same time, while being regulated by the flow regulator 5, nitrogen gas containing an organic aluminum compound is fed via a feeding tube 6 to obtain an aluminum nitride powder. The aluminum nitride powder is subjected to a heat treatment at from 1100 to 1500° C. in a reducing gas atmosphere and/or an inert gas atmosphere to obtain an aggregate aluminum nitride powder.

Abstract: A laser irradiation nozzle free from clogging, adhesion of metal oxides, directional gas blowing, and oxidation occurring on the weld; yet capable of providing sound bead morphology and a stable weld depth on a workpiece. Accordingly, the laser irradiation nozzle comprises a conical outside nozzle and a conical inside nozzle being arranged as such to give a concentric ring-shaped top, having an assist gas outlet being established between the inside and the outside nozzles, wherein, the distance h between the laser beam focal position on the workpiece and said irradiation nozzle is controlled to a predetermined value, and the ratio of the cross sectional area of the assist gas outlet being as defined between the outside and the inside nozzles to the cross sectional area of the inside concentrical ring defined by the outer diameter of said ring on the nozzle top is also controlled to a predetermined value.