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The use of dye-laser-resonance-absorption photography and resonant holographic interferometry techniques enables the analysis of expansion of KrF excimer laser beam-induced laser ablation plumes in gas, vacuum and plasma environments. The ablation plumes expand more rapidly in plasma than in other environments. The expansion velocity of the plumes in gas varies with gas pressure, and the 3 times 10 to the power of 14 value of the total number of Al neutral atoms indicates a surface etch rate of approximately 1 mn per pulse.

Pulsed laser deposition of beta-FeSi(2) films on Si(111) substrates leads to both FeSi and beta-FeSi2 at high deposition rates and low substrate temperature and only beta-FeSi2 at low deposition rates and high substrate temperature. Interfacial roughness and silicide film microstructure change with thickness of the film. The dependence of epitaxial orientation of the films on initial film composition indicates that pulsed laser deposition provides a Fe-rich growth medium for films.

Short-range order in amorphous carbon thin films containing silicon and hydrogen (Si-aC:H) was characterized using radial distribution functions (RDFs). RDFs describe the average number of neighbors located a distance r away from an arbitrary atom in the sample. Two methods in the transmission electron microscope (TEM) were used in this study to obtain RDFs: energy-filtered convergent-beam electron diffraction (EFCBED) and extended electron energy-loss fine structure (EXELFS) analyses. Four Si-aC:H film samples were prepared in cross section for TEM using a focused ion beam system. Both EFCBED and EXELFS techniques were used to study the same samples. RDF interpretation included estimation and comparison of near-neighbor distances, average bond angles, and coordination numbers as a function of sample composition. Key RDF characteristics were correlated to thin film material properties. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Experiments are reported in which two configurations for ablation-plasma-ion-implantation (APII) are characterized by diagnostics and compared. Thin film analysis showed excellent adhesion with smoother films for an accelerating voltage of -3.2 kV, higher voltages (-7.7 kV) roughened the film.

Mechanical systems that operate in agricultural, construc-tion, and mining and mineral processing applications typically operate in debris-containing and thin-film lubrication environ-ments. Consequently, the lives of rolling element bearings in these applications are often limited by surface fatigue aris-ing from thin-film lubrication, damage from the debris, false brinelling, and scuffing. Traditional approaches utilizing spe-cialized heat treatments and lubricant additives can sometimes delay the onset of early raceway fatigue, but even in these cases the actual bearing life is still usually less than that for which the bearing was designed. Bearings with a highly durable W-aC:H coating applied to the rolling elements are shown to have sig-nificantly longer fatigue lives in debris-containing and thin-film lubrication environments and are highly resistant to wear from false brinelling and scuffing. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid rolling element bearings are being considered for use in flight critical aerospace applications. The following work was undertaken to lay the foundation for future work that would permit the recommendation of appropriate quantities of lubrication for these advanced bearing systems. This was accomplished by focusing on the tribological performance of M50/M50 (or AISI M-50) and M50/Si3N4 interfaces with minimum quantities of lubrication at two levels of speed and slide-to-roll ratio (SRR). Ball-on-ring tribological testing was conducted with stepped reductions of lubricant pump rate into the tribological contacts at initial lambda values of approximately 1.7 and 2.5, as calculated from the Hamrock and Dowson film thickness equation and surface finish measurements. Experiments were conducted with 5% and 45% slide-to-roll ratio (or SRR). Starting from these high initial lambda levels, the lubricant flow rate into the contact was reduced until severe damage occurred. Tests were then suspended due to excessive traction (traction coefficient greater than 0.2). The results of this work are in agreement with the starved lubrication literature and the bearing test literature. They provide some solid insight into the minimum quantity of lubrication recommended for M50/M50 and M50/Si3N4 interfaces. In all of the tests conducted there was a clear trend that higher speed and increased sliding both require an increased supply of lubricant to the contact. The M50/M50 interface needed an order of magnitude higher lubricant pump rate into the contact for adequate lubrication as compared to the M50/Si3N4 interface in the initial lambda∼1.7 experiments. At lambda∼2.5 with 5% SRR, the M50/M50 interface needed three times the lubricant pump rate that the M50/Si3N4 interface needed. However, both M50/M50 and M50/Si3N4 needed a similar amount of lubricant at lambda∼2.5 with 45% SRR, in which the interfaces were severely damaged due to the extreme test conditions. These tribological test results are interpreted with an analysis of the wear morphology and surface chemistry of the test articles. [Copyright &y& Elsevier]