Engineering topics

Wang, W. S.

Publications and source records attributed to Wang, W. S..

13 records

NASA NTRS1999

Melt Growth of a Nonlinear Optical Crystal Triethylphosphine Sulfide using Modified Bridgman-Stockbarger Technique

Bulk single crystals of triethylphosphine sulfide (C2H5)3P(S), a potential nonlinear optical organic material has been grown from melt using Bridgman- Stockbarger method. Commercially available material triethylphosphine sulfide procured from Johnson Matthey was purified by physical vapor transport using low pressure sublimaton (about 30 mTorr). Modified Bridgman-Stockbarger technique is characterized by the smallest possible quantity of product in the melt for a short period of time. The temperature gradient was chosen to be about 10 C/cm and the ampoule was lowering rate was chosen to be 0.2-0.3 mm/h. For various growth conditions, several single crystal of triethylphosphine sulfide have been grown with sizes 10X10X15mm(exp 3). The second harmonic generation (SHG) efficiency was measured and has been found to be comparable to phase matched potassium dihydrogen phosphate crystals. Further characterization of the grown single crystals is in progress and the results will be presented at the symposium.

Curry, K.↗

NASA NTRS1998

Bulk Crystal Growth of Nonlinear Optical Organic Materials Using Inverted Vertical Gradient Freeze Method

A new process for producing large bulk single crystals of benzil (C6H5COCOC6H5) is reported in this paper. Good quality crystals have been successfully grown using this approach to crystal growth. This method seems to be very promising for other thermally stable NLO organic materials also. The entire contents vycor crucible 1.5 inch in diameter and 2 inch deep was converted to single crystal. Purity of the starting growth material is also an important factor in the final quality of the grown crystals. The entire crystal can be very easily taken out of the crucible by simple maneuvering. Initial characterization of the grown crystals indicated that the crystals are as good as other crystals grown by conventional Bridgman Stockbarger technique.

Choi, J.↗

NASA NTRS1998

Growth of Bulk Single Crystals of Dicyanovinyl-Ansiole and its Derivatives for Nonlinear Optical Applications

Bulk single crystals of a series of thermally stable nonlinear optical organic materials, Dicyanovinyl-anisole (DIVA) and their methoxy derivatives, have been successfully grown using the Bridgman-Stockbarger technique. The growth conditions are chosen to be temperature gradient of 5 to 10 C/cm and lowering rate of 0.1 to 0.3 mm/h. Single crystals of DIVA and its derivatives, of 8 x 8 x 50 cu mm in size, have been grown while maintaining a flat solid-liquid growth interface.

Gebre, T.↗

NASA NTRS1998

Solution Growth of a Novel Nonlinear Optical Material: L-Histidine Tetrafluoroborate

Single crystals of L-Histidine tetrafluoroborate (L-HFB), a semiorganic nonlinear optical (NLO) material have been successfully grown by the temperature lowering and evaporation methods in our laboratory. Solubility curves of L-HFB have been determined in different solvents, such as water, ethanol and acetone. The solubility of L-HFB is very low in acetone, and ethanol, therefore, it is not feasible to grow L-HFB single crystals using these solvents. Good quality single crystals of a novel nonlinear optical material L-HFB have been grown from aqueous solution. Effects of seed orientation on morphologies of L-HFB crystals were studied. The advantages and disadvantage of both the evaporation and the temperature lowering techniques are compared. The single crystals in size 20 x 20 x 10 cubic mm were grown with deionized water as solvent in two weeks with an approximate growth rate of 1.4mm/day. The transmission range for these crystals has been found to be from 250 nm to 1500 nm.

Aggarwal, M. D.↗

NASA NTRS1996

A Simple Inexpensive Bridgman-Stockbarger Crystal Growth System for Organic Materials

Direct observation of solid-liquid interface is important for the directional solidification to determine the desired interface shape by controlling the growth parameters. To grow good quality single crystals of novel organic nonlinear optical materials, a simple inexpensive Bridgman-Stockbarger (BS) crystal growth system has been designed and fabricated. Two immiscible liquids have been utilized to create two zones for this crystal growth system. Bulk single crystals of benzil derivative and n-salicylidene-aniline have been successfully grown in this system. The optimum lowering rate has been found to be 0.1 mm/h for the flat interface. Results on the crystal growth and other parameters of the grown crystals are presented.

Choi, J.↗

NASA NTRS1994

Growing Organic Crystals By The Czochralski Method

Apparatus grows high-quality single crystals of organic compounds by Czochralski method. In Czochralski process, growing crystal lifted from middle of molten material without touching walls. Because of low melting temperatures of organic crystals, glass vessels usable. Traditional method for inorganic semiconductors adapted to optically nonlinear organic materials.

Shields, Angela↗

NASA NTRS1992

A versatile low-cost Czochralski crystal growth system for nonlinear optical organic materials

A versatile low-cost Czochralski system for pulling crystals from melt has been described. It is designed for low melting, transparent, and nonlinear optical materials. One of the most important novel feature of this crystal growth system is that the entire growth process including the solid-liquid interface can be viewed from any direction. Another is the use of an after-heater to reduce excess heat loss from the surface of the melt.

Aggarwal, M. D.↗

NASA NTRS1981

Low temperature latching solenoid

A magnetically latching solenoid includes a pull-in coil and a delatching coil. Each of the coils is constructed with a combination of wire materials, including material of low temperature coefficient of resistivity to enable the solenoid to be operated at cryogenic temperatures while maintaining sufficient coil resistance. An armature is spring-based toward a first position, that may extend beyond the field of force of a permanent magnet. When voltage is temporarily applied across the pull-in magnet, the induced electromagnetic forces overcome the spring force and pulls the armature to a second position within the field of the permanent magnet, which latches the armature in the pulled-in position. Application of voltage across the delatching coil induces electromagnetic force which at least partially temporarily nullifies the field of the permanent magnet at the armature, thereby delatching the armature and allowing the spring to move the armature to the first position.

Wang, W. S.↗

NASA NTRS1979

Latching solenoid for cryogenic valves

Pull-in and Delatching Coils of cryogenic solenoid contain copper and low-resistance, low-temperature-coefficient alloy to limit current at low temperatures.

Wang, W. S.↗

NASA NTRS1979

Low-leakage low-temperature valve

Valve was originally designed to handle liquid nitrogen tetroxide and mononethyl hydrazine. It successfully survived leakage at temperature as low as minus 95.5 C. It seals tightly against cold fluids, even after thousands of opening-and-closing cycles.

Wang, W. S.↗

NASA NTRS1972

Two-stage coaxial gas compressor

Compressor raises pressure of gases from low ambient supply during space experiments by a system of low weight, size, and power input. Dc rotary-torque motor and ball-screw drive shaft activate first and second stage of compressor, utilizing inertia forces to operate check valves.

Wang, W. S.↗

NASA NTRS1972

Miniature high pressure regulator

Metal bellows, capable of suppling required spring rate and operational stability, replaced diaphragms, sliding seals, and springs in design of small gas regulator.

Wright, H. W., Jr.↗

NASA NTRS1971

Gas chromatograph sample-transfer valve

Slide-type gate valve incorporates sampling volume and transfer passageway for guiding a metered quantity of gas from pressurized test cell to gas chromatograph. Gate is moved by pneumatic bellows-type actuator.

Wang, W. S.↗