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NASA NTRS1979

Method of purifying metallurgical grade silicon employing reduced pressure atmospheric control

A method in which a quartz tube is charged with chunks of metallurgical grade silicon and/or a mixture of such chunks and high purity quartz sand, and impurities from a class including aluminum, boron, as well as certain transition metals including nickel, iron, and manganese is described. The tube is then evacuated and heated to a temperature within a range of 800 C to 1400 C. A stream of gas comprising a reactant, such as silicon tetrafluoride, is continuously delivered at low pressures through the charge for causing a metathetical reaction of impurities of the silicon and the reactant to occur for forming a volatile halide and leaving a residue of silicon of an improved purity. The reactant which included carbon monoxide gas and impurities such as iron and nickel react to form volatile carbonyls.

Ingle, W. M.↗

NASA NTRS1979

Eolian sedimentation on earth and Mars - Some comparisons

Eolian sediments on earth are mostly formed from quartz. The quartz particles originally came from a granitic source. With respect to eolian sediments on Mars, it appears that an entirely different set of criteria must apply, but some critical parameters can be usefully compared. Impact experiments with basalt in eolian abrasion devices suggest that basalt sand-sized particles fragment rapidly to produce silt and clay-sized detritus. Cohesive forces must be more effective on Mars since the gravitational contribution to the bond/weight ratio is lower. Compared to the terrestrial situation, both larger and smaller particles can be expected to make significant contributions to eolian sediments on Mars. The low gravity and the high speed of moving particles and the relative weak rock material of which they are composed will allow large-scale fine particle production.

Smalley, I. J.↗

NASA NTRS1980

Evaluation of multispectral middle infrared aircraft images for lithologic mapping in the East Tintic Mountains, Utah

Six channels of multispectral middle infrared (8 to 14 micron) aircraft scanner data were acquired over the East Tintic mining district, Utah. This area has high relief and moderate vegetation and consists mainly of Tertiary silicic igneous rocks and Paleozoic quartzite and carbonate rocks that have been locally hydrothermally altered. These digital-image data were computer processed to create a color-composite image based on principal component transformations. Color differences in this image are related to the spectral differences in the surface material and allow discrimination of several rock types, depending primarily on their silica content. When combined with a visible and near infrared color-composite image from a previous flight, with limited field checking, it is possible to discriminate quartzite, carbonate rocks, quartz latitic and quartz monzonitic rocks, latitic and monzonitic rocks, silicified altered rocks, argillized altered rocks, and vegetation.

Kahle, A. B.↗

NASA NTRS1981

The radiolysis and radioracemization of amino acids on silica surfaces

Results are presented of experiments on the radioracemization of amino acids in the presence of silica surfaces such as may have been found on the prebiotic earth. L-leucine and a DL-leucine mixture deposited on samples of 1-quartz and an amorphous silica preparation (Syloid 63) was subjected to Co-60 gamma-ray irradiation, then analyzed by gas chromatography to determine the radiolysis and racemization rates. The quartz surface is found to have a marginal efficacy in enhancing radiolysis when compared with a crystalline L-leucine control, although enhancing radioracemization symmetrically by a factor of two. Both the radiolysis and radioracemization of L-leucine and DL-leucine on a Syloid-63 silica surface are observed to increase with increasing radiation dose, and to be substantially greater than in the crystalline controls. Additional experiments with the nonprotein amino acid isovaline deposited on Syloid 63 confirm the greater radiolysis susceptibility of amino acids deposited on silica with respect to the crystalline state, although racemization is not observed. The observations suggest that the presence of a silica surface would have a deleterious effect on any mechanism for the origin of molecular chirality relying on stereoselective beta-radiolysis.

Bonner, W. A.↗

NASA NTRS1983

LDR segmented mirror technology assessment study

In the mid-1990s, NASA plans to orbit a giant telescope, whose aperture may be as great as 30 meters, for infrared and sub-millimeter astronomy. Its primary mirror will be deployed or assembled in orbit from a mosaic of possibly hundreds of mirror segments. Each segment must be shaped to precise curvature tolerances so that diffraction-limited performance will be achieved at 30 micron (nominal operating wavelength). All panels must lie within 1 micron on a theoretical surface described by the optical precipitation of the telescope's primary mirror. To attain diffraction-limited performance, the issues of alignment and/or position sensing, position control of micron tolerances, and structural, thermal, and mechanical considerations for stowing, deploying, and erecting the reflector must be resolved. Radius of curvature precision influences panel size, shape, material, and type of construction. Two superior material choices emerged: fused quartz (sufficiently homogeneous with respect to thermal expansivity to permit a thin shell substrate to be drape molded between graphite dies to a precise enough off-axis asphere for optical finishing on the as-received a segment) and a Pyrex or Duran (less expensive than quartz and formable at lower temperatures). The optimal reflector panel size is between 1-1/2 and 2 meters. Making one, two-meter mirror every two weeks requires new approaches to manufacturing off-axis parabolic or aspheric segments (drape molding on precision dies and subsequent finishing on a nonrotationally symmetric dependent machine). Proof-of-concept developmental programs were identified to prove the feasibility of the materials and manufacturing ideas.

Krim, M.↗

NASA NTRS1983

Results from a 'small box' realtime molecular contamination monitor on STS-3

On the basis of early estimates of the Shuttle induced environment, Scialdone (1979) concluded that in the vicinity of the cargo, the cargo would have the largest influence on the environment. As a contamination control device, realtime monitors can indicate safe operational periods for sensitive attached payloads. It was, therefore, decided to develop the OSS-1/Contamination Monitor Package (CMP) experiment which was seen as a forerunner of an operational monitor. A description of the CMP is provided, taking into account four actively temperature controlled quartz crystal microbalances (TQCM). The TQCM temperatures could be varied from -60 C to +80 C. The sensor consisted of a matched pair of quartz crystals. The crystals were designated as a sensor and reference crystal. Results obtained during the STS-3 mission are discussed. These results show the feasibility and advantages of a small real-time contamination monitor.

Triolo, J.↗

NASA NTRS1982

Gravity-driven convection studies in compound semiconductor crystal growth by physical vapor transport

Experimental results are summarized, and it is pointed out that gravity-driven convection can alter the diffusive-advective mass transport behavior in the growth of crystals by physical vapor transport. Specially designed and constructed transparent furnaces are described which are being used to study the effects of gravity in the crystal growth of the compound semiconductors PbTe and CdTe. The theory underlying vapor transport behavior is reviewed, with attention given to the vapor-solid behavior of compound materials, to one-dimensional mass transport, and to gravity-induced (natural) convection. In the transparent furnaces, the quartz capillary tube mounted along the axis of the main quartz ampoule is used to measure the temperature at the growth surface (vapor-solid crystal interface) and the source, as well as the complete temperature profile along the axis of the tube. The light-pipe works to remove heat from the growth end of the ampoule by radiative heat transfer. The ampoules are sealed after being evacuated to the low 10 to the -8th torr range with a cryogenic vacuum pump.

Zoutendyk, J. A.↗

NASA NTRS1983

S-band SBAW microwave source, phase 2

Results of aging experiments on 1.072 GHz SBAW oscillators are discussed as well as the design, fabrication and test of 2.143 GHz SBAW delay lines. Two design approaches were implemented. The third harmonic transducer on 36 deg rotated Y cut quartz proved to be the most useful design, whereas the fifth harmonic transducer on - 50 5 deg rotated Y cut quartz suffered from high insertion loss and poor sidelobe rejection. The construction and characterization of the 2 GHz SBAW oscillator are described. Phase noise, frequency dependence on temperature, and 6-month aging were measured. Some SAW and SBAW oscillators were compared as were both the 1 and 2 GHz oscillators. The 2 GHz SBAW oscillator showed significant improvement in phase noise and temperature stability over the 2 GHz SAW oscillator developed in previous NASA programs. A technique to produce SBAW delay lines of different frequencies from a single mask is examined. The delay lines were incorporated into oscillator circuits to demonstrate the ability to select the frequency output of the SBAW oscillator.

Source record↗

NASA NTRS1984

Hubble space telescope component qualification utilizing a residual gas analyzer

An approach is described for integrating an automated residual gas analyzer (RGA) into the thermal vacuum outgas process. The RGA has the capability of detailed analysis over a 200 amu range with monitoring of each peak as the test progresses. The NASA criterion of either a 50% reduction of each peak over 44 amu or less than an 0.1% amplitude of the 28 amu base peak for all amu's above 44 amu is satisfied. A computer sorts, reports which peaks do not satisfy the criterion, and reports test completion. The computer plots amplitudes of all the peaks from 1 amu through 200 amu for each scan. This RGA real time approach is unique in that it provides sufficient detail to highlight a problem as it occurs. By comparison, a quartz crystal microbalance (QCM) or a thermoelectric quartz crystal microbalance (TQCM) indicates to the operator when changes occur, but not what has happened. Optical witness samples indicate whether a test was satisfactory within a few days after the test was completed.

Westfall, A. H.↗

NASA NTRS1984

Quantum efficiency measurements for several waveshifter coatings in the extreme vacuum ultraviolet

Quantum efficiency measurements are given for coronene and liumogen coatings designed to enhance UV sensitivity for silicon charge coupled device imaging detectors. Coatings on quartz and on UDT PIN 10DP photodiodes were tested. The wavelength range extended from 153.7 to 50.0 nm in the vacuum ultraviolet. Similar measurements were made for coronene, liumogen, and stilbene-3 laser dye films on quartz disks relative to sodium salicylate. Sodium salicylate and coronene are the most efficient waveshifters down to 50 nm so far observed. Coronene's fairly constant quantum efficiency over such a wide wavelength range into the far VUV makes it a useful waveshifter for UV and VUV applications.

Butner, C. L.↗

NASA NTRS1985

Thermal Shock-Resistant Composite Crucible

Heating rates of 350 degrees F per minute have not caused cracking. Surrounding inner crucible is annulus of loosely packed alumina powder, which serves as compressible insulating material. Second annulus consisting of section of fused-quartz tubing surrounds and retains alumina powder. Quartz tube held in place by refractory cement helps to contain alumina powder. Small holes in upper ring of cement allow alumina powder to outgas during operation in vacuum. Originally intended for use in Chill Block Melt Spinning (CBMS) apparatus, crucible adaptable to other operations involving rapid self-induction heating of metallic charges.

Geringer, H. J.↗

NASA NTRS1984

Silicon film solar cell process

The most promising way to reduce the cost of silicon in solar cells while still maintaining performance is to utilize thin films (10 to 20 microns thick) of crystalline silicon. The method of solution growth is being employed to grow thin polycrystalline films of silicon on dissimilar substrates. The initial results indicate that, using tin as the solvent, this growth process only requires operating temperatures in the range of 800 C to 1000 C. Growth rates in the range of 0.4 to 2.0 microns per minute and grain sizes in the range of 20 to 100 microns were achieved on both quartz and coated steel substrates. Typically, an aspect ratio of two to three between the width and the Si grain thickness is seen. Uniform coverage of Si growth on quartz over a 2.5 x 2.5 cm area was observed.

Hall, R. B.↗

NASA NTRS1985

Reusable thermal cycling clamp

A reusable metal clamp for retaining a fused quartz ampoule during temperature cycling in the range of 20 deg C to 1000 deg C is described. A compressible graphite foil having a high radial coefficient of thermal expansion is interposed between the fused quartz ampoule and metal clamp to maintain a snug fit between these components at all temperature levels in the cycle.

Debnam, W. J., Jr.↗

NASA NTRS1986

Temperature-Sensitive Oscillator

Ingestible thermometer consists of oscillator with temperature-dependent frequency. Device is quartz-crystal oscillator, frequency of which changes in proportion to change in temperature. Temperature-Sensitive Oscillator with nearly linear temperature coefficient of frequency obtained by using high-speed, high-gain, programable operational amplifier such as OP-32 to produce temperature-varying reflected capacitance across quartz crystal. New, small, inexpensive, low-power, temperature-sension circuit suitable for use as ingestible thermometer for measuring internal body temperature.

Kleinberg, L. L.↗

NASA NTRS1983

HOST liner cyclic facilities

The HOST Liner Cyclic Program is utilizing two types of test apparatus, rectangular box rigs and a full annular rig. To date two quartz lamp cyclic box rigs have been tested and a third is to begin testing in late October 1983. The box rigs are used to evaluate 5x8 inch rectangular linear samples. A 21 inch diameter outer liner simulator is also being built up for testing beginning in April 1984. All rigs are atmospheric rigs. The first box rig, a three 6-kVA lamp installation, was operated under adverse conditions to determine feasibility of using quartz lamps for cyclic testing. This work was done in December 1981 and looked promising. The second box rig, again using three 6-kVA lamps, was operated to obtain instrumentation durability information and initial data input to a Finite Element Model. This limited test program was conducted in August 1983. Five test plates were run. Instrumentation consisted of strain gages, thermocouples and thermal paint. The strain gages were found to fail at 1200 F as expected though plates were heated to 1700 F. The third box rig, containing four 6-kVA lamps, is in build up for testing to begin in late October 1983. In addition to 33 percent greater power input, this rig has provision for 400 F backside line cooling air and a viewing port suitable for IR camera viewing. The casing is also water cooled for extended durability.

Schultz, D.↗

NASA NTRS1985

Initial development and performance evaluation of a process for formation of dense carbon by pyrolysis of methane

The three steps in pyrolytic carbon formation are: (1) gaseous hydrocarbon polymerization and aromatic formation; (2) gas-phase condensation and surface adsorption/impingement of polyaromatic hydrocarbon; and (3) final dehydration to carbon. The structure of the carbon in the various stages of formation is examined. The apparatuses and experimental procedures for the pyrolysis of methane in a 60 cm long quartz reactor tube at temperatures ranging from 1400-1600 K are described. The percentage of carbon converted and its density are calculated and tabularly presented. The results reveal that dense carbon formation is maximized and soot eliminated by this procedure. It is observed that conversion efficiency depends on the composition of the inlet gas and conversion increases with increasing temperature. Based on the experimental data a three-man carbon reactor subsystem (CRS) is developed; the functions of the Sabatier Methanation Reactor, two carbon formation reactors and fluid handling components of the CRS are analyzed. The CRS forms 16 kg of carbon at a rate of 0.8 kg/day for 20 days in a two percent volume density quartz wool packing at temperature of 1500-1600 K.

Noyes, G. P.↗

NASA NTRS1986

A new type of lamp and reflector for I.R. simulation

The lamps and reflectors used for infrared radiation simulation tests at ESTEC did not allow researchers to predict the intensity needed for test conditions with the desired accuracy. This was due to poor reproducibility of the polar diagrams, the unknown contribution of the radiation in the long wavelength range in vacuum, imperfections in the quartz bulbs, and misalignment of the lamp in the reflector. When using a 1000 W coiled spiral quartz lamp with a diffuse reflector, these shortcomings are overcome. Due to the good reproducibility, an overall accuracy within plus or minus 2 percent should be obtained.

Saenger, G.↗

NASA NTRS1987

Mapping hydrothermally altered rocks in the Northern Grapevine Mountains, Nevada and California with the airborne imaging spectrometer

Seven flightlines of Airborne Imaging Spectrometer (AIS) data were analyzed for an area of hydrothermally altered rocks. The data were reduced to reflectance relative to an average spectrum, and an automated procedure was used to produce a color coded image displaying absorption band information. Individual spectra were extracted from the AIS images to determine the detailed mineralogy. Two alteration types were mapped based upon mineralogy identified using the AIS data. The primary alteration type is quartz sericite pyrite alteration which occurs in northwest-trending zones in quartz monzonite porphyry. The AIS data allow identification of sericite (muscovite) based upon a strong absorption feature near 2.21 micron and weaker absorption features near 2.35 and 2.45 micron. The second alteration type occurs as a zone of argillic alteration associated with a granitic intrusion. Montmorillonite was identified based on a weak to moderate absorption feature near 2.2 micron and the absence of the two absorption features at longer wavelengths characteristic of sericite. Montmorillonite could be identified only where concentrations of sericite did not mask the montmorillonite spectrum.

Kruse, Fred A.↗