Arthur D. Little, Inc.

Ceres Electronics Corporation

Wilson P Menashi

Joseph F Wenckus

Roger A Castonguay

John S Haggerty

Edwin C Moxon

Martin L Cohen

Peter C VonThuna

Natural diamonds can be distinguished from simulated diamonds in seconds by merely touching a hand held probe to the gems. The tip of the probe includes a rounded gem contacting head of high thermal conductivity and low thermal mass. The head is preferably of gold-coated copper. It is supported on a high thermal resistivity neck extending from a large spring biased thermal mass. The head supports a thermistor heater element and a thermistor temperature sensing element within an annular space. Pulses of power are cyclically applied to the heater element to produce a predetermined amount of heat flow from the probe through the sample gem. The resulting change in temperature of the contacting head is determined by sensing the change in resistance of the sensing thermistor and weighting that change by the sensed thermistor resistance. The weighting function is carried out by a gain-controlled amplifier. The change-in-temperature signal controls a meter and LEDs which indicate whether the gem is natural or simulated.

Method and device for distinguishing material by thermal conductivity

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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Lexington, MA, United States of America

Wilson P Menashi