Evaluation techniques for the friction behavior of gold sliding contacts operating in high- purity environments
Gold sliding electric contacts friction behavior, studying adsorbed gas lubrication in ultrahigh purity environments
Glaeser, W. A.↗
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The optical properties of platinum and gold in the vacuum ultraviolet
The optical constants of platinum and gold thin films have been determined in the spectral region of 40 to 200 nm by reflection measurements. The highly polarized continuum of synchrotron radiation emitted by the 240-MeV electron storage ring at the Physical Sciences Laboratory of the University of Wisconsin was used as a light source for the spectrum below 120 nm, while a windowless discharge lamp coupled to a normal incidence monochromator provided a source for the longer wavelengths. Optical constants were determined by a computer program based on iterative solutions to the Fresnel equations for reflection as a function of the angle of incidence.
Linton, R. C.↗
The solar abundance of gold.
Thirteen spectral scans (in the direction of increasing and decreasing wavelength) obtained with a new double-band pass monochromator system put into operation with the Michigan spectrometer at the Snow telescope at Mount Wilson are interpreted by the method of spectral synthesis. The intensity profile of the 3122.79 line, attributable to gold, is interpreted, and a representation of the solar spectrum in the neighborhood of the AU 3122.79 line is given in tabular form.
Ross, J. E.↗
The Cyclic Mechanical and Fatigue Properties of Ferroanelastic Beta Prime Gold Cadmium
The fatigue behavior of beta prime Au1.05Cd0.95 alloy was investigated and found to be exceptional for certain orientations with lives of 10,000 to 1,000,000 cycles at total strain amplitudes above 0.05 not uncommon. Fatigue lives were influenced principally by the stress level which controlled the amount of plastic deformation, and stress fatigue resistance was low compared with most metals. Failure always exhibited brittle characteristics. An algorithm was devised to predict mechanical behavior from the twin system orientations and was found in good agreement with experiment for longitudinal strains above 0.04. The cyclic mechanical properties were examined, and a model for the behavior was proposed utilizing previous theories of the restoring force and the Peierls-Nabarro stress for twinning and new concepts. Gold-cadmium was found to have certain strain fatigue resistant applications, particularly in electronics where the alloy's high electrical conductivity is utilized.
Karz, R. S.↗
Measurements of the acoustical parameters of rock powders and the Gold-Soter lunar model.
We are measuring the low frequency velocities and damping factors of acoustic waves in rock powders in vacuo with a view to understanding the lunar seismic signals. Our results combined with those of others, when extrapolated to lunar conditions, lend support to the Gold-Soter model of the outer moon in which the lunar surface is covered with a fine rock powder to a depth of at least 4 km.
Jones, B. W.↗
Discourse following award of Kepler Gold Medal
Kuiper briefly reviews Kepler's contributions to the field of planetary astronomy and physics, along with references to his own background in the study of stars, planets, and the solar system. He mentions his participation in NASA programs related to planetary astronomy. He concludes his remarks with thanks for being honored by the award of the Kepler Gold Medal.
Kuiper, G. P.↗
Nuclei growth kinetics during the nucleation of gold on UHV-cleaved mica substrates
Measurements of crystalline sizes during nucleation of gold on mica surfaces cleaved in ultra-high vacuum (UHV) reveal the presence of symmetric, sharply peaked distributions which flatten and broaden with increasing nucleation time. When the number density of nuclei increases, the growth rate is suppressed. The time taken to reach a given size increases with increasing temperature when the nuclei are growing as isolated particles. When the nuclei are spaced so far that their diffusion fields overlap, then the time taken to reach a given size decreases with increasing temperature.
Elliot, A. G.↗
Sputtered gold mask for deep chemical etching of silicon
Sputtered mask resists chemical attack from acid and has adherence to withstand prolonged submergence in etch solution without lifting from silicon surface. Even under prolonged etch conditions with significant undercutting, gold mask maintained excellent adhesion to silicon surface and imperviousness to acid.
Pisciotta, B. P.↗
Oxygen reduction of several gold alloys in 1-molar potassium hydroxide
With rotated disk-and-ring equipment, polarograms and other electrochemical measurements were made of oxygen reduction in 1-molar potassium hydroxide on an equiatomic gold-copper (Au-Cu) alloy and a Au-Cu alloy doped with either indium (In) or cobalt (Co) and on Au doped with either nickel (Ni) or platinum (Pt). The results were compared with those for pure Au and pure Pt. The two-electron reaction dominated on all Au alloys as it did on Au. The polarographic results at lower polarization potentials were compared, assuming exclusively a two-step reduction. A qualified ranking of cathodic electrocatalytic activity on the freshly polished reduced disks was indicated: anodized Au Au-Cu-In Au-Cu Au-Cu-Co is equivalent or equal to Au-Pt Au-Ni. Aging in distilled water improved the electrocatalytic efficiency of Au-Cu-Co, Au-Cu, and (to a lesser extent) Au-Cu-In.
Miller, R. O.↗
In situ investigation of the mobility of small gold clusters on cleaved MgO surfaces
The mobility of small clusters of gold (about 10 A in diameter) on electron-beam-cleaved MgO surfaces was studied by in situ transmission electron microscopy under controlled vacuum and temperature conditions. During the first 10 min following a deposition at room temperature, over 10 per cent of the crystallites moved over short distances (about 20 A) discontinuously, with a velocity greater than 150 A/sec. Eighty per cent of the mobility events were characterized by the avoidance of proximity of other crystallites, and this was tentatively explained as the result of repulsive elastic forces between the interacting crystallites.
Metois, J. J.↗
Adhesion and friction of iron and gold in contact with elemental semiconductors
Adhesion and friction experiments were conducted with single crystals of iron and gold in contact with single crystals of germanium and silicon. Surfaces were examined in the sputter cleaned state and in the presence of oxygen and a lubricant. All experiments were conducted at room temperature with loads of 1 to 50 grams, and sliding friction was at a sliding velocity of 0.7 mm/min. Results indicate that the friction nature of metals in contact with semiconductors is sensitive to orientation, that strong adhesion of metals to both germanium and silicon occurs, and that friction is lower with silicon than with germanium for the same orientation. Surface effects are highly sensitive to environment. Silicon, for example, behaves in an entirely brittle manner in the clean state, but in the presence of a lubricant the surface deforms plastically.
Buckley, D. H.↗
Morphology of gold and copper ion-plated coatings
Copper and gold films (0.2 to 2 microns thick) were ion plated onto polished 304-stainless-steel, glass, mica surfaces. These coatings were examined by SEM for defects in their morphological growth. Three types of defects were distinguished: nodular growth, abnormal or runaway growth, and spits. The cause for each type of defect was investigated. Nodular growth is due to inherent substrate microdefects, abnormal or runaway growth is due to external surface inclusions, and spits are due to nonuniform evaporation (ejection of droplets). All these defects induce stresses and produce porosity in the coatings and thus weaken their mechanical properties. During surface rubbing, large nodules are pulled out, leaving vacancies in the coatings.
Spalvins, T.↗
Friction and transfer of copper, silver, and gold to iron in the presence of various adsorbed surface films
Sliding friction experiments were conducted with the noble metals copper, silver, and gold and two binary alloys of these metals contacting iron in the presence of various adsorbates including, oxygen, methyl mercaptan, and methyl chloride. A pin on disk specimen configuration was used with a load of 100 grams, sliding velocity of 60 mm/min; at 25 C with the surfaces saturated with the adsorbates. Auger emission spectroscopy was used to monitor surface films. Results of the experiments indicate that friction and transfer characteristics are highly specific with respect to both the noble metal and surface film present. With all three metals and films transfer of the noble metal to iron occurred very rapidly. With all metals and films transfer of the noble metal to iron continuously increased with repeated passes except for silver and copper sliding on iron sulfide.
Buckley, D. H.↗
A structural analysis of small vapor-deposited 'multiply twinned' gold particles
High resolution selected zone dark field, Bragg reflection imaging and weak beam dark field techniques of transmission electron microscopy were used to determine the structure of small gold particles vapor deposited on NaCl substrates. Attention was focused on the analysis of those particles in the 50-150 A range that have pentagonal or hexagonal bright field profiles. These particles have been previously described as multiply twinned crystallites composed of face-centered cubic tetrahedra. The experimental evidence of the present studies can be interpreted on the assumption that the particle structure is a regular icosahedron or decahedron for the hexagonal or the pentagonal particles respectively. The icosahedron is a multiply twinned rhombohedral crystal and the decahedron is a multiply twinned body-centered orthorhombic crystal, each of which constitutes a slight distortion from the face-centered cubic structure.
Yang, C. Y.↗
Post-breakdown bulk oscillations in gold-doped silicon p/+/-i-n/+/ double-injection diodes
Experimental results on postbreakdown bulk oscillations in n-type gold-doped phosphorus-compensated p(+)-i-n(+) double-injection diodes is presented. It is suggested that changes observed in the postbreakdown oscillation frequency and amplitude are due to changes in the prebreakdown characteristics. An empirical relationship for the frequency of oscillation is derived. It is concluded that the postbreakdown oscillations are drift-related, although their exact mechanism is not known.
Mantha, B.↗
Fabrication of Thick Gold Strip Lines
Ion-beam etching and masking techniques fabricate micron-sized gold strip lines. Fabricated by use of argon ion-beam milling.
Gee, C. M.↗
Magnetron Sputtered Gold Contacts on N-gaas
Direct current planar magnetron sputtering was used to deposit gold Schottky barrier electrical contacts on n-type GaAs of varying doping densities. The electrical character of the contact was determined from current voltage and electron beam induced voltage data. Without reducing the surface concentration of carbon and oxide, the contacts were found to be rectifying. There is evidence that energetic neutral particles reflected from the magnetron target strike the GaAs and cause interfacial damage similar to that observed for ion sputtering. Particle irradiation of the surface during contact deposition is discussed.
Buonaquisti, A. D.↗
An integrtated approach to the use of Landsat TM data for gold exploration in west central Nevada
This paper represents an integration of several Landsat TM image processing techniques with other data to discriminate the lithologies and associated areas of hydrothermal alteration in the vicinity of the Paradise Peak gold mine in west central Nevada. A microprocessor-based image processing system and an IDIMS system were used to analyze data from a 512 X 512 window of a Landsat-5 TM scene collected on June 30, 1984. Image processing techniques included simple band composites, band ratio composites, principal components composites, and baseline-based composites. These techniques were chosen based on their ability to discriminate the spectral characteristics of the products of hydrothermal alteration as well as of the associated regional lithologies. The simple band composite, ratio composite, two principal components composites, and the baseline-based composites separately can define the principal areas of alteration. Combined, they provide a very powerful exploration tool.
Mouat, D. A.↗