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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Lubrication with sputtered MoS2 films: Principles, operation, limitations

The present practices, limitations, and understanding of thin sputtered MoS2 films are reviewed. Sputtered MoS2 films can exhibit remarkable tribological properties such as ultralow friction coefficients (0.01) and enhanced wear lives (millions of cycles) when used in vacuum or dry air. To achieve these favorable tribological characteristics, the sputtering conditions during deposition must be optimized for adequate film adherence and appropriate structure (morphology) and composition.

Spalvins, T.↗
NASA NTRS1971

Lubrication with sputtered MoS2 films.

Sputtered MoS2 films (2000-6500 A) were deposited on highly polished metal surfaces. These films have a low coefficient of friction (0.03-0.04) at speeds of 40-80 rpm and loads of 250-1000 grams. At loads of 250 grams the wear lives are over 0.5 million cycles, but at 1000 gram loads, it decreases to 38,000 cycles. Friction experiments and tensile tests have indicated that sputtered films have a strong adherence to metal surfaces. Electron transmission, diffraction and scanning electron microscopy show that these films have an extremely small particle size, less than 30 A in diameter, and are very dense and free from observable pinholes. The high kinetic energy of these sputtered species, the submicroscopic particle size and the sputter-etched substrate surface is responsible for strong adhesion and cohesion of the sputtered film.

Spalvins, T.↗
NASA NTRS1971

Lubrication with sputtered MoS2 films.

Sputtered MoS2 films (2000-6500 A) were deposited on highly polished metal surfaces. These films have a low coefficient of friction (0.03-0.04) at speeds of 40-80 rpm and loads of 250-1000 grams. At loads of 250 grams, the wear lives are over 0.5 million cycles, but at 1000 gram loads, it decreases to 38,000 cycles. Friction experiments and tensile tests have indicated that sputtered films have a strong adherence to metal surfaces. Electron transmission, diffraction, and scanning electron microscopy show that these films have an extremely small particle size less than 30 A in diameter and are very dense and free from observable pinholes.

Spalvins, T.↗
NASA NTRS1972

Evidence of crystal structure in some sputtered MoS2 films.

Electron diffraction patterns and electron micrographs of molybdenum disulfide films sputtered on single-NaCl-crystal and electropolished-aluminum substrates are presented as evidence that crystalline MoS2 films can be sputtered onto various substrates in thicknesses up to 2 microns. Applied to Falex test pins and V-blocks, some of these films exhibited a wear life as long as 65 minutes at 1000 lb jaw load.

Lavik, M. T.↗
NASA NTRS1973

High field superconductivity in alkali metal intercalates of MoS2

In the search for better high temperature, high critical field superconductors, a class of materials was found which have layered structures and can be intercalated with various elements and compounds. Since a large number of compounds can be formed, intercalation provides a method of control of superconducting properties. They also provide the possible medium for excitonic superconductivity. Results of magnetic field studies are presented on alkali metal (Na, K, Rb, and Cs) intercalated MoS2 (2H polymorph).

Woollam, J. A.↗
NASA NTRS1975

Morphological growth of sputtered MoS2 films

Sputtered MoS2 films from 300 A to 20,000 A thick were deposited on metal and glass surfaces. The substrate effects such as surface temperature, finish, pretreatment and chemistry as they affect the film formation characteristics were investigated by optical, electron transmission, electron diffraction, and scanning electron microscopy. Substrate temperature and surface chemistry were found to be the prime variables as to the formation of a crystalline or amorphous film. The friction characteristics are strictly influenced by the type of film formed. Surface chemistry and surface pretreatment account for compound formation and corresponding grain growth, which directly affect the adhesion characteristics, resulting in poor adherence. The type of surface finish (topography) as related to scratches, impurities, inhomogeneities, etc., are favorable nucleation sites for the growth of isolated and complex nodules within the film, and various complex surface overgrowths on the film. These nodular growth features have progressively more undesirable effects on the film behavior as the film thickness increases.

Spalvins, T.↗
NASA NTRS1975

Morphological growth of sputtered MoS2 films

Sputtered MoS2 films from 300 A to 20,000 A thick were deposited on metal and glass surfaces. The substrate effects such as surface temperature, finish, pretreatment, and chemistry as they affect the film formation characteristics were investigated by optical, electron transmission, electron diffraction, and scanning electron microscopy. Substrate temperature and surface chemistry were found to be the prime variables as to the formation of a crystalline or amorphous film. The friction characteristics are strictly influenced by the type of film formed. Surface chemistry and surface pretreatment account for compound formation and corresponding grain growth, which directly affect the adhesion characteristics, resulting in poor adherence. Scratches, impurities, inhomogeneities, etc., are favorable nucleation sites for the growth of isolated and complex nodules within the film.

Spalvins, T.↗
NASA NTRS1976

Superconducting critical fields of alkali and alkaline-earth intercalates of MoS2

Results are reported for measurements of the critical-field anisotropy and temperature dependence of group-VIB semiconductor MoS2 intercalated with the alkali and alkaline-earth metals Na, K, Rb, Cs, and Sr. The temperature dependences are compared with present theories on the relation between critical field and transition temperature in the clean and dirty limits over the reduced-temperature range from 1 to 0.1. The critical-field anisotropy data are compared with predictions based on coupled-layers and thin-film ('independent-layers') models. It is found that the critical-field boundaries are steep in all cases, that the fields are greater than theoretical predictions at low temperatures, and that an unusual positive curvature in the temperature dependence appears which may be related to the high anisotropy of the layer structure. The results show that materials with the largest ionic intercalate atom diameters and hexagonal structures (K, Rb, and Cs compounds) have the highest critical temperatures, critical fields, and critical-boundary slopes; the critical fields of these materials are observed to exceed the paramagnetic limiting fields.

Woollam, J. A.↗
NASA NTRS1977

Physics and chemistry of MoS2 intercalation compounds

An investigation is made of the physics and chemistry of MoS2 intercalation compounds. These compounds may be separated into two groups according to their stoichiometry, structure and superconducting properties. The first group consists of Na, Ca, and Sr intercalates, and the second group consists of K, Rb, and Cs intercalates. Particular attention is given to the structure of the electronic energy band and to the normal state and superconducting properties of these compounds.

Woollam, J. A.↗
NASA NTRS1980

Tribological properties of sputtered MoS2 films in relation to film morphology

Thin sputter-deposited MoS2 films with thicknesses ranging from 2000 to 6000 A have shown excellent lubricating properties when sputtering parameters and substrate conditions are properly selected and controlled. The lubricating properties are strongly influenced by the crystalline-amorphous structure, morphology, and composition of the films. The coefficient of friction can range from 0.04 (which is effective lubrication) to 0.4 (no lubricating action).

Spalvins, T.↗
NASA NTRS1990

Influence of the deposition conditions on radiofrequency magnetron sputtered MoS2 films

By varying the radiofrequency (RF) power, the Ar pressure, and the potential on the substrates, MoS(x) films of various stoichiometry, density, adhesion, and morphology were produced. An increase of RF power increased the deposition rate and density of the MoS2 films as well as improved adhesion. However, the stoichiometry remained constant. An increase of Ar pressure increased the deposition rate but decreased the density, wheras both stoichiometry and adhesion were maximized at around 20 mtorr Ar pressure. Furthermore, a transition from compact film growth to columnar film growth was observed when the pressure was varied from 5 to 15 mtorr. Substoichiometric films were grown when a negative (bias) voltage was applied to the substrates.

Steinmann, Pierre A.↗
NASA NTRS2010

MoS2-Filled PEEK Composite as a Self-Lubricating Material for Aerospace Applications

At BAM, several projects were conducted in the past years dealing with the tribological properties of friction couples at cryogenic temperature and in vacuum environment. Promising candidates for vacuum application are MoS2-filled PEEK/PTFE composites, which showed a friction coefficient as low as 0.03 in high vacuum. To complete the tribological profile of these composites, further tests were performed in ultra-high vacuum (UHV) at room temperature. In this paper, friction and stick slip behavior, as well as outgassing characteristics during the test are presented.

Theiler, Geraldine↗