Arthur D. Little, Inc.

Ceres Electronics Corporation

Joseph F Wenckus

Wilson P Menashi

Roger A Castonguay

John S Haggerty

Martin L Cohen

Peter C VonThuna

A simulated diamond such as crystalline cubic zirconia, which has optical properties very similar to natural diamond and so is difficult to distinguish optically from natural diamond, is distinguished from natural diamond by measuring its thermal conductivity which is significantly different from the thermal conductivity of natural diamond, by measuring the temperature of a heated probe held against the simulated diamond as an indication of the simulated diamond thermal conductivity. In a preferred embodiment of the present invention, a controlled amount of heat energy is generated at the probe and thereafter, while the probe is held against the simulated diamond, the temperature of the probe is detected as a measure of relative thermal conductivity of the simulated diamond to the natural diamond.

Method and means of rapidly distinguishing a simulated diamond from

A cold crucible system is provided which is suitable for carrying out the process of 'skull' melting wherein highly refractory materials are melted by inductive heating in a manner to maintain the molten material in a shell of the material cool enough to act as a crucible. The cold crucible system incorporates a crucible formed as two separate halves held in a manner to define a narrow electrically insulating space between them. Each half section comprises a plurality of copper tubes forming half of a 'cage.' Each tube of the cage has a concentric smaller tube therein whereby there are defined in each tube an outer annular and a central inner fluid passage through which a fluid coolant is circulated. The system is formed as a module capable of being located within a controlled atmosphere chamber. The crucible system is readily adapted to Czochralski crystal growth, for use with a seed crystal to induce directional crystal growth by the Bridgeman technique and to centrifugal casting.

Cold crucible system

Apparatus for forming fibers of refractory materials. A melt volume is continuously formed on a feed rod of the material to be fiberized and a fiber drawn therefrom. The melt volume is formed by introducing the feed rod at a predetermined velocity into a heating zone. The fiber diameter is determined by the relative velocities at which the feed rod is moved and the fiber drawn, and by the fractional density of the feed rod material.

Apparatus for forming refractory fibers

Apparatus is provided for forming, by the Czochralski technique, single semiconductor crystals having essentially uniform diameters throughout their lengths. The apparatus includes means to monitor and control crystal diameter which takes advantage of the fact that the melt volume from which the crystal is pulled and the dielectric crucible containing the melt volume can be incorporated in a crucible assembly circuit in which the resistance varies with the melt volume level in the crucible. Determination of the difference between the measured resistance in the crucible assembly circuit and a programmed reference resistance produces a signal which is used to control one of two operational parameters--the rate at which the crystal is pulled or the temperature of the melt volume--to produce a uniform-diameter crystal.

Apparatus for forming semiconductor crystals of essentially uniform

Method and apparatus for forming fibers of refractory materials. A melt volume is continuously formed on a feed rod of the material to be fiberized and a fiber drawn therefrom. The melt volume is formed by introducing the feed rod at a predetermined velocity into a heating zone. The fiber diameter is determined by the relative velocities at which the feed rod is moved and the fiber drawn, and by the fractional density of the feed rod material.

Method for forming refractory fibers by laser energy

Apparatus for the melt synthesis of inorganic compounds from elemental reactants, at least one of which is highly volatile at the temperature of the reaction. An enclosure means defining a reaction chamber and a reservoir-closure means containing the volatile elemental reactant form the reaction vessel which is sealed by a combination mechanical-liquid seal which is of a character to permit diffusion by high-pressure gas through it. Heating means are provided to effect at least three heating regimes: (I) liquefaction of a liquid sealant, (II) formation and maintenance of a molten reaction mass, and (III) heating of the volatile elemental reactant to vaporize it.

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Needham, MA, United States of America

Joseph F Wenckus