Abstract: A method for treating workpieces that consist of porous carbon material with liquid silicon with the formation of silicon carbide, comprising the steps: Preheating porous carbon workpieces under inert gas to the selected operating temperature TB1, feeding liquid silicon to the porous carbon workpieces at an operating pressure pB2 and an operating temperature TB2, and impregnating the porous carbon workpieces with liquid silicon, reaction of the liquid silicon in the workpiece at a temperature TB3 with the formation of silicon carbide that consists of carbon and silicon, gassing the workpiece with inert gas and cooling from the operating temperature TB3 to the conditioning temperature Tk, cooling the workpieces to room temperature, the temperature TB3 being greater than or equal to the temperature TB2, and the workpiece in step d of the method no longer being in contact with liquid silicon outside of the workpiece.

Abstract: Method for treatment of workpieces of porous carbon material with liquid silicon with the formation of silicon carbide, comprising the following steps: preheating of porous carbon workpieces under an inert gas to a selected operating temperature TB1, delivery of liquid silicon to the porous carbon workpieces at an operating pressure pB2 and an operating temperature TB2 and impregnation of the porous carbon workpieces with liquid silicon, reaction of the liquid silicon in the workpiece at a temperature TB3 with formation of silicon carbide from carbon and silicon, gassing of the workpieces with inert gas, and cooling from the operating temperature TB3 to a conditioning temperature Tk, cooling of workpieces to room temperature, in step c the delivery of silicon and transport of the workpieces taking place over preferably cylindrical rolls which are porous at least in the exterior region and which are pivoted, and their speed of rotation determining the residence time for the delivery of silicon in step c, and t

Abstract: Graphite electrodes for the production of aluminum by carbothermic reduction of alumina are either submerged in the molten bath in the low temperature compartment or they are horizontally arranged in the side walls of the high temperature compartment. The electrodes are manufactured by using a mixture of coke particles covering the complete particle size range between 25 ?m to 3 mm and by using an intensive mixer to effectively wet all coke particles with pitch. The electrodes have a flexural strength of at least 20 N/mm2. By using a complete range (continuum) of particle sizes in conjunction with an intensive mixer, the geometric packing of the particles is significantly improved, hence the material density is increased and thus a higher mechanical strength as well as improved electrical conductivity in comparison to conventional graphite electrodes is achieved.

Abstract: A graphite electrode for an electrothermic reduction furnace is formed from anode grade coke and graphitized at a graphitization temperature below 2700° C. The resulting electrode is particularly suited for carbothermal reduction of alumina. It has an iron content of about 0.05% by weight, a specific electrical resistivity of above 5 ?Ohm·m, and a thermal conductivity of less than 150 W/m·K. The graphite electrode is manufactured by first mixing calcined anode coke with a coal-tar pitch binder, and a green electrode is formed from the mixture at a temperature close to the softening point of the pitch binder. The green electrode is then baked to carbonize the pitch binder to solid coke. The resultant carbonized electrode, after further optional processing is then graphitized at a temperature below 2700° C. for a time sufficient to cause the carbon atoms in the carbonized electrode to organize into the crystalline structure of graphite.

Abstract: An inner lining for the steel shell of a carbothermic reduction furnace for the production of alumina has a base layer of graphite and a coating layer of refractory material. The refractory material is corundum (Al2O3) bound by Sialon (Si.Al.O.N). The lining structure provides protection against the molten slag and it is not attacked by the CO-rich melt furnace atmosphere. Further, the lining does not contaminate the melt and it provides an effective heat dissipation system in case of a power shut-off.

Abstract: A method for producing aluminum and a method for producing a graphite electrode for a carbothermic reduction furnace, in which aluminum is produced by carbothermic reduction of alumina, render the graphite electrode substantially gas-impermeable. The graphite electrode is consumed during furnace operation and electrode columns connected by graphite pins are fed continuously fed in from the top into the furnace. The coating of the electrode withstands a temperature of up to 300° C. and more over a period of several hours without oxidation. Since the coating enters the furnace compartment at least partially, it is configured so that it will not contaminate the hot melt. That is, the chemistry of the coating materials is similar to the ingredients of the overall reaction or, at a minimum, the amount of foreign elements is very low. The coating is provided so that it does not increase the electrical contact resistance at the connection between the electrode columns and the electrode holding clamps.

Abstract: A method for treating workpieces that consist of porous carbon material with liquid silicon with the formation of silicon carbide, comprising the steps: Preheating porous carbon workpieces under inert gas to the selected operating temperature TB1, feeding liquid silicon to the porous carbon workpieces at an operating pressure pB2 and an operating temperature TB2, and impregnating the porous carbon workpieces with liquid silicon, reaction of the liquid silicon in the workpiece at a temperature TB3 with the formation of silicon carbide that consists of carbon and silicon, gassing the workpiece with inert gas and cooling from the operating temperature TB3 to the conditioning temperature Tk, cooling the workpieces to room temperature, the temperature TB3 being greater than or equal to the temperature TB2, and the workpiece in step d of the method no longer being in contact with liquid silicon outside of the workpiece.

Abstract: A glass powder or a glass-ceramic powder is provided that includes multicomponent glasses with at least three elements, where the glass powder or a glass-ceramic powder has a mean particle size of less than 1 ?m. In some embodiments, the mean particle size is less than 0.1 ?m, while in other embodiments the mean particle size is less than 10 nm.

Abstract: Process for producing bodies from ceramic materials using silicon carbide, comprising the steps: configuration of fiber-reinforced porous bodies (1, 5) that consist of carbon on a base (2) that is inert relative to liquid silicon, the bodies having cavities (3) that are accessible from the exterior or surface recesses (3?), and the cavities (3) being closed at the bottom in the porous bodies or the surface recesses (3?) together with the base (2) forming a reservoir that is sealed at the bottom; heating the configuration by introduction of energy to melt the silicon (6) that is present in the reservoir; and infiltrating the melted silicon in the bodies (1, 5) and reaction of the silicon with the carbon to form silicon carbide; and use of the thus produced bodies as brake disks and as clutch driving disks.

Abstract: Graphite electrodes for the production of aluminum by carbothermic reduction of alumina are either submerged in the molten bath in the low temperature compartment or they are horizontally arranged in the side walls of the high temperature compartment. The electrodes are manufactured by using a mixture of coke particles covering the complete particle size range between 25 ?m to 3 mm and by using an intensive mixer to effectively wet all coke particles with pitch. The electrodes have a flexural strength of at least 20 N/mm2. By using a complete range (continuum) of particle sizes in conjunction with an intensive mixer, the geometric packing of the particles is significantly improved, hence the material density is increased and thus a higher mechanical strength as well as improved electrical conductivity in comparison to conventional graphite electrodes is achieved.

Abstract: A graphite electrode for an electrothermic reduction furnace is formed from anode grade coke and graphitized at a graphitization temperature below 2700° C. The resulting electrode is particularly suited for carbothermal reduction of alumina. It has an iron content of about 0.05% by weight, a specific electrical resistivity of above 5 ?Ohm·m, and a thermal conductivity of less than 150 W/m·K. The graphite electrode is manufactured by first mixing calcined anode coke with a coal-tar pitch binder, and a green electrode is formed from the mixture at a temperature close to the softening point of the pitch binder. The green electrode is then baked to carbonize the pitch binder to solid coke. The resultant carbonized electrode, after further optional processing is then graphitized at a temperature below 2700° C. for a time sufficient to cause the carbon atoms in the carbonized electrode to organize into the crystalline structure of graphite.

Abstract: A graphite electrode for an electrothermic reduction furnace in which aluminum is produced by carbothermic reduction of alumina is rendered substantially gas-impermeable. The graphite electrode is consumed during furnace operation and electrode columns connected by graphite pins are fed continuously fed in from the top into the furnace. The coating of the electrode withstands a temperature of up to 300° C. and more over a period of several hours without oxidation. Since the coating enters the furnace compartment at least partially, it is configured so that it will not contaminate the hot melt. That is, the chemistry of the coating materials is similar to 1o the ingredients of the overall reaction or, at a minimum, the amount of foreign elements is very low. The coating is provided so that it does not increase the electrical contact resistance at the connection between the electrode columns and the electrode holding clamps. Where the electrode inlet area is cooled by water, the coating is insoluble in water.

Abstract: An inner lining for the steel shell of a carbothermic reduction furnace for the production of alumina has a base layer of graphite and a coating layer of refractory material. The refractory material is corundum (Al2O3) bound by Sialon (Si.Al.O.N). The lining structure provides protection against the molten slag and it is not attacked by the CO-rich melt furnace atmosphere. Further, the lining does not contaminate the melt and it provides an effective heat dissipation system in case of a power shut-off.

Abstract: A method rebakes and graphitizes pitch-impregnated carbon bodies in an encapsulated Castner-type lengthwise graphitization furnace in one step. A furnace shell is constructed of element modules and can carry out the method. A furnace utilizes the furnace shell. The oxygen content in the interior of the furnace is kept below 4% by volume. The method is carried out under atmospheric pressure or at pressures that differ only slightly from the atmospheric pressure.

Abstract: A method rebakes and graphitizes pitch-impregnated carbon bodies in an encapsulated Castner-type lengthwise graphitization furnace in one step. A furnace shell is constructed of element modules and can carry out the method. A furnace utilizes the furnace shell. The oxygen content in the interior of the furnace is kept below 4% by volume. The method is carried out under atmospheric pressure or at pressures that differ only slightly from the atmospheric pressure.

Abstract: The invention relates to a process for the chromatographic separation of fullerenes using a nonpolar aromatic solvent as eluant. Coke, anthracite and/or graphite are used as support material. The nonpolar solvent is the main constituent of the eluant.

Abstract: Disclosed is a barium-free glass of good x-ray absorption, which has a composition (in wt.-% on the oxide basis) of SiO.sub.2 50-75; ZrO.sub.2 5-30; Li.sub.2 O 0-5; Na.sub.2 O 0-25; K.sub.2 O 0-25; .SIGMA. alkali oxides 0-25. Preferred is a dental glass of the composition of SiO.sub.2 55-70; ZrO.sub.2 10-25; Li.sub.2 O 0-15; Na.sub.2 O 10-25; K.sub.2 O 0-15; .SIGMA. alkaloids 15-25. The glass can furthermore contain also up to 3 wt.-% of fluorine, up to 5 wt.-% of MgO, up to 5 wt.-% of TiO.sub.2, and in each case up to 10 wt.-% of the oxides Al.sub.2 O.sub.3, GeO.sub.2, P.sub.2 O.sub.5, La.sub.2 O.sub.3, Y.sub.2 O.sub.3, Ta.sub.2 O.sub.3, Gd.sub.2 O.sub.3, ZnO and Nb.sub.2 O.sub.5. The glass finds its use in powder form with an average particle size of .ltoreq.10 .mu.m as filler for dental composites for filling teeth.

Abstract: For the preparation of high purity glass powder having a mean particle size of .ltoreq.10 .mu.m, glass powder having a larger particle size up to 300 .mu.m is ground to the desired particle size in a stirred mill with glass grinding elements in the presence of a grinding liquid comprising water or preferably a mixture of at least 50% by weight of water and at least one water-soluble, oxygen-containing organic compound having 1 to 5 carbon atoms in the molecule, e.g., tert.-butyl alcohol; the ground slurry is then frozen, and the solvent is subsequently removed from the frozen slurry by freeze-drying. A resultant glass powder with a mean particle size d.sub.50 of 0.5 to 2 .mu.m is particularly suitable as a filler for synthetic resins in the dental sector.

Abstract: A glass sealant comprises a mixture of about 70-90% of a solder glass powder of a low-melting lead-borate glass with a transformation temperature of 330.degree. C. or lower, 1-20% by weight of cordierite powder, and 1-25% by weight of mullite powder, with the combined content of cordierite and mullite powder being from about 10-30%. The lead-borate glass comprises from about 82-88% by weight of PbO, 12-17% by weight of B.sub.2 O.sub.3, 0-1% by weight of SiO.sub.2, and 0-1% by weight of Al.sub.2 O.sub.3. Both the cordierite and mullite powder are preferably synthetically produced to reduce the .alpha.-radiation. The synthetically produced cordierite powder preferably still contains up to about 9% by weight of a non-crystalline vitreous phase. The grain size of the powders is preferably under 100 microns. This glass sealant has well-balanced properties relative to thermal expansion, melting temperature, dielectric constant, loss angle, mechanical strength, thermal shock resistance, and chemical resistance.