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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Use of LEED, Auger emission spectroscopy and field ion microscopy in microstructural studies

Surface research tools such as LEED, Auger emission spectroscopy analysis, and field ion microscopy are discussed. Examples of their use in studying adhesion, friction, wear, and lubrication presented. These tools have provided considerable insight into the basic nature of solid surface interactions. The transfer of metals from one surface to another at the atomic level has been observed and studied with each of these devices. The field ion microscope has been used to study polymer-metal interactions and Auger analysis to study the mechanism of polymer adhesion to metals. LEED and Auger analysis have identified surface segregation of alloying elements and indicated the influence of these elements in metallic adhesion. LEED and Auger analysis have assisted in adsorption studies in determining the structural arrangement and quantity of adsorbed species present in making an understanding of the influence of these species on adhesion possible. These devices are assisting in the furtherance of understanding of the fundamental mechanism involved in the adhesion, friction, wear, and lubrication processes.

Ferrante, J.↗
NASA NTRS1972

Adhesion and transfer of PTFE to metals studied by auger emission spectroscopy

The adhesion and transfer of polytetrafluoroethylene (PTFE) to metals in ultrahigh vacuum has been studied using Auger emission spectroscopy. The transfer was effected both by compressive static contact and by sliding contact. The transfer observed after static contact was independent of the chemical constitution of the substrate. Electron induced desorption of the fluorine in the transferred PTFE showed that the fluorine had no chemical interaction with the metal substrate. The coefficient of friction on metals was independent of the chemical constitution of the substrate. However, sliding PTFE on soft metals such as aluminum, generated wear fragments that lodged in the PTFE and machined the substrate.

Pepper, S. V.↗
NASA NTRS1972

Metallic transfer between metals in sliding contact examined by auger emission spectroscopy

Metallic transfer between polycrystalline metals in sliding contact was examined. Hemispherical riders of iron, nickel, and cobalt were slid on tungsten, tantalum, niobium, and molybdenum disks in ultrahigh vacuum. Auger emission spectroscopy was used to monitor the elemental composition of the disk surfaces. Iron, nickel, and cobalt transferred to tungsten, whereas only cobalt transferred to tantalum, niobium, and molybdenum. The results of this investigation are discussed in terms of the cohesive energy and strain hardening characteristics of the specimen materials.

Pepper, S. V.↗
NASA NTRS1972

Use of LEED, Auger emission spectroscopy and field ion microscopy in microstructural studies.

The studies reported were conducted to gain a fundamental understanding of adhesion and dynamic friction on an atomic or microscopic level. Fundamental aspects of low energy electron diffraction (LEED), Auger emission spectroscopy (AES), and field ion microscopy (FIM) are discussed. Typical results of studies conducted are considered, giving attention to LEED-AES experiments, pin and disk experiments, and field ion microscope investigations.

Ferrante, J.↗
NASA NTRS1972

Adhesion and transfer of polytetrafluorethylene to metals studied by Auger emission spectroscopy

The adhesion and transfer of polytetrafluoroethylene (PTFE) to metals in ultrahigh vacuum were studied. The transfer was effected both by compressive static contact and by sliding contact. The transfer observed after static contact was independent of the chemical constitution of the substrate. Electron-induced desorption of the fluorine in the transferred PTFE showed that the fluorine had no chemical interaction with the metal substrate. The coefficient of friction on metals was independent of the chemical constitution of the substrate. However, sliding PTFE on soft metals, such as aluminum, generated wear fragments that lodged in the PTFE and machined the substrate.

Pepper, S. V.↗
NASA NTRS1972

Adhesion of metals to a clean iron surface studied with LEED and Auger emission spectroscopy.

Discussion of the results of adhesion experiments conducted with various metals contacting a clean iron surface. The metals included gold, silver, nickel, platinum, lead, tantalum, aluminum, and cobalt. Some of the metals were examined with oxygen present on their surface as well as in the clean state. The results indicate that, with the various metals contacting iron, the cohesively weaker will adhere and transfer to the cohesively stronger. The chemical activity of the metal also influenced the adhesive forces measured. With oxygen present on the metal surface, the adhesive forces measured could be correlated with the binding energy of the metal to oxygen.

Buckley, D. H.↗
NASA NTRS1979

Auger electron emission due to incident particle in Ar(+), Ne(+) and Na(+) collisions with different solid targets

The L23 Auger spectra of Ar, Ne and Na from Ar(+)-Ti, Ne(+)-Mg, Ne-A1, Na(+)-Be, Na(+)-Mg and Na(+)-A1 collisions were obtained. For Ar, L23 MM Auger electrons are emitted from the fast moving incident projectiles and a Doppler broadened structure is observed. The Ne and Na Auger spectra are due to Auger transitions with single or double 2p vancancies in the initial state of the implanted Ne atoms or surface trapped Na atoms.

Benazeth, C.↗
NASA NTRS1981

Application of surface analysis to solve problems of wear

Results are presented for the use of surface analytical tools including field ion microscopy, Auger emission spectroscopy analysis (AES), cylindrical mirror Auger analysis and X-ray photoelectron spectroscopy (XPS). Data from the field ion microscope reveal adhesive transfer (wear) at the atomic level with the formation of surface compounds not found in the bulk, and AES reveals that this transfer will occur even in the presence of surface oxides. Both AES and XPS reveal that in abrasive wear with silicon carbide and diamond contacting the transition metals, the surface and the abrasive undergo a chemical or structural change which effects wear. With silicon carbide, silicon volatilizes leaving behind a pseudo-graphitic surface and the surface of diamond is observed to graphitize.

Buckley, D. H.↗
NASA NTRS1980

Changes in surface chemistry of silicon carbide (0001) surface with temperature and their effect on friction

Friction studies were conducted with a silicon carbide (0001) surface contacting polycrystalline iron. The surface of silicon carbide was pretreated: (1) by bombarding it with argon ions for 30 minutes at a pressure of 1.3 pascals; (2) by heating it at 800 C for 3 hours in vacuum at a pressure of 10 to the minus eighth power pascal; or (3) by heating it at 1500 C for 3 hours in a vacuum of 10 to the minus eighth power pascal. Auger emission spectroscopy was used to determine the presence of silicon and carbon and the form of the carbon. The surfaces of silicon carbide bombarded with argon ions or preheated to 800 C revealed the main Si peak and a carbide type of C peak in the Auger spectra. The surfaces preheated to 1500 C revealed only a graphite type of C peak in the Auger spectra, and the Si peak had diminished to a barely perceptible amount. The surfaces of silicon carbide preheated to 800 C gave a 1.5 to 3 times higher coefficient of friction than did the surfaces of silicon carbide preheated to 1500 C. The coefficient of friction was lower in the 11(-2)0 direction than in the 10(-1)0 direction; that is, it was lower in the preferred crystallographic slip direction.

Miyoshi, K.↗
NASA NTRS1979

Metal-dielectric interactions

Metal direlectric surface interactions and dielectric films on metal substrates were investigated. Since interfacial interaction depends so heavily on the nature of the surfaces, analytical surface tools such as Auger emission spectroscopy, X-ray photoelectron spectroscopy and field ion microscopy were used to assist in surface and interfacial characterization. The results indicate that with metals contacting certain glasses in the clean state interfacial, bonding produces fractures in the glasses while when a film such as water is present, fractures occur in the metal near the interface. Friction forces were used to measure the interfacial bond strengths. Studies with metals contacting polymers using field ion microscopy revealed that strong bonding forces could develop being between a metal and polymer surface with polymer transferring to the metal surface in various ways depending upon the forces applied to the surface in contact. With the deposition of refractory carbides, silicides and borides onto metal and alloy substrates the presence of oxides at the interface or active gases in the deposition plasma were shown to alter interfacial properties and chemistry. Auger ion depth profile analysis indicated the chemical composition at the interface and this could be related to the mechanical, friction, and wear behavior of the coating.

Buckley, D. H.↗
NASA NTRS1972

Investigation of low-Z Coster-Kronig transitions by means of Auger and photoelectron spectroscopy

Experimental intensity ratios of Auger transitions for Co, Ni, Cu, and Zn as well as the relative L sub 2 and L sub 3 level widths of Cu and Zn, derived from their photoelectron spectra, are presented. Evidence is presented that a great deal of vacancy reorganization took place following photoionization and prior to Auger emission. These reorganizations are assumed to be due to Coster-Kronig transitions f sub 23. These results are compared with theoretical calculations and agree with predicted discontinuity at Z = 30 where f sub 23 transitions become energetically impossible.

Yin, L. I.↗