Abstract: Cold formed and sintered titanium diboride shapes of high density are prepared by grinding particulate carbothermic titanium diboride in a mill having non-contaminating grinding media in the presence of an inert, substantially oxygen-free liquid grinding aid to form finely-divided titanium diboride powder having a surface area of at least about 3 square meters per gram, cold forming the finely-divided titanium diboride powder into a desired shape and sintering the shape to produce a titanium diboride article having a density of at least 95 percent of the theoretical density of titanium diboride.

Abstract: Submicron carbon-containing titanium diboride powder and other hard, refractory metal boride powders, such as zirconium diboride and hafnium diboride powders, are prepared by vapor phase reaction of the corresponding metal halide, e.g., titanium halide, vaporous carbon source, and boron source reactants in the presence of hydrogen in a reaction zone and in the substantial absence of oxygen, either combined or elemental. In a preferred embodiment, the metal halide, e.g., titanium tetrachloride, carbon source, e.g., halogenated hydrocarbon, and boron source, e.g., boron trichloride, reactants are mixed with a hot stream of hydrogen produced by heating hydrogen in a plasma heater. The reaction zone is maintained at metal boride forming temperatures and submicron solid, carbon-containing metal boride powder is removed promptly from the reactor and permitted to cool. The preponderant number of metal boride particles comprising the powder product have a particle size in the range of between 0.05 and 0.7 microns.

Abstract: A method is described for controllably heating an electrolytic cell used for the production of metal, e.g., aluminum, from a compound of the metal, e.g., alumina, to a desired temperature. The method is especially applicable to electrolytic cells which have refractory hard metal articles, e.g., Group 4b metal diboride articles, as internal elements of the cell. The electrolytic cell is brought to the desired temperature, e.g., substantially operating temperature, from ambient temperature by placing a resistance heater having a positive change in resistivity with temperature within the cell and passing current through the heater. Typically, a plurality of heaters is used. In one embodiment, the heaters are placed close to but spaced from the refractory hard metal articles. The heaters are usually connected in parallel to a source of electrical power and in a preferred embodiment are in electrical contact with the cathode and anode of the electrolytic cell.

Abstract: A method is described for heating an electrolytic cell used for the production of metal, e.g., aluminum, by electrolysis of a molten electrolyte which contains solid electrolyte between adjacent surfaces of the anode and cathode of the cell. In the described method, holes are drilled in the solid electrolyte, e.g., to the floor of the cell, to provide space for supporting blocks. The holes are spaced a predetermined distance apart to position at least one anode between them. Supporting blocks with a length sufficient to extend from the floor to at least the level of the solid electrolyte beneath the anode are placed in the holes and a resistance heater, preferably one having a positive change in resistivity with temperature, is disposed between the supporting blocks at least one of which is electrically conductive.

Abstract: Refractory metal diboride articles having an overall density of 50-90 percent of theoretical and a matrix of near theoretical density, e.g., 95-99 percent are described. They may be made by cold pressing and sintering an intimate mixture of submicron Group IVb metal diboride powder and finely divided solid hydrocarbon, e.g., microcrystalline petroleum wax. The hydrocarbon remains particulate in the cold pressed piece but is driven out by heat at the beginning of the sintering operation, thereby leaving voids which remain as gross pores surrounded by a dense matrix in the sintered article. Submicron boride powders capable of forming the dense matrix contain a minor proportion of a sintering or densifying aid such as carbon or a metal carbide such as titanium carbide, tungsten carbide, or boron carbide. The articles so produced are lighter in weight than non-porous articles of the same size, have high electrical conductivity and, by virtue of the dense matrix, have excellent resistance to chemical attack.