Abstract: This invention provides a hot forming mold made of xonotlite group materials such as xonotlite, or wollastonite made therefrom, which are known as a heat-resisting materials. By hot pressing these material to high bulk density e.g., 0.6 to 2.20, a mold suitable for use in hot forming, having increased sending strength and hardness can be efficiently made.Such molds are made by filter pressing an aqueous slurry of xonotlite, then drying the pressed product to remove moisture at a temperature less than about 700.degree. C., and then cutting out the mold for use in molding plastic, glass and the like. By heat treating this mold product at a temperature of about 700.degree. to 1200.degree. C. the mold so produced can be subjected to machining and can be used as a mold for superplastic forming aluminum, titanium and the like.

Abstract: A powder charging apparatus, in which a plasma electrode pair is disposed within an insulative tubular passage for transporting powder as carried by gas, a device for intermittently applying a D.C. voltage between that pair of plasma electrode is provided to form a space where mainly desired polarity ions drawn from the plasma electrode pair exist and another space where mainly opposite polarity ions exist, well dispersed powder is fed to the former space where mainly the desired polarity ions exist, and thereby stable and strong charging performances can be assured for a long term without adhesion and accumulation of the powder to and on either one of the pair of plasma electrodes; and an electrostatic powder painting apparatus containing this powder charging apparatus therein and having excellent penetrating performance and painting efficiency.