Process for producing hollow spherical particles and sponge-like particles composed therefrom

A process for making a molded article, comprising the steps of:

• (a) providing metallized lightweight spherical bodies from cores of a foamed polymer with a metallic coating of a thickness of 5 to 20 microns;
• (b) coating said metallized lightweight spherical bodies with a dispersion of at least one particulate material selected from the group which consists of metals, metal oxides, ceramics and refractories to a dispersion coating thickness of 15 to 500 microns;
• (c) drying the dispersion coating on said metallized lightweight spherical bodies to form a dry layer of said material thereon;
• (d) vibrating the metallized lightweight spherical bodies with said dry layers of said material thereon into a mold having a shape corresponding to that of said article;
• (e) heating said metallized lightweight spherical bodies with said dry layer of said material thereon in said mold to a temperature of about 400.degree. C. to pyrolyze said polymer cores and form hollow bodies essentially consisting of said metallic coatings and said dry layers of said material thereon;
• and
• (f) subjecting said hollow bodies essentially consisting of said metallic coatings and said dry layers of said material thereon in said mold to a sintering temperature of 900.degree. C. to 1400.degree. C. for a period sufficient to sinter the material of the respective layer and the respective layer to the respective metallic coating, thereby forming hollow spherical particles and to sinter said hollow spherical particles together into said article.