J. Charles Barbour

In Situ Ultrahigh Vacuum Friction Measurement and Wear Track Analysis of Ion Implanted 304 Stainless Steel

The dual ion implantation of Ti and C into 304 stainless steel has been found to reduce friction and wear in uhv. The implantation treatment producting this result, 4.6 x 10/sup 17/ Ti/cm/sup 2/ (180 keV) followed by 2.0 x 10/sup 17/ C/cm/sup 2/ (50 keV), produced TiC precipitates dispersed in an amorphous surface layer. Friction and wear track compositions were measured in situ with a scanning Auger microprobe without removing the pin from the track. This treatment decreased the friction coefficient from 1.2 to 0.6 to 0.8 and the wear track width from 342 ..mu..m after 1000 cycles. Relative to unimplanted 304, wear tracks formed in uhv and air on implanted 304 had more N and less C, with O and the metallic elements similar in concentration, in addition to the presence of Ti. Friction coefficients measured in air were less than those in uhv; track composition suggests that oxides or adsorbed moisture (and perhaps hydrocarbons) helped lower the friction in air. 22 refs., 3 figs., 1 tab.

Effect of homopolymer host chain relaxations on the translational diffusion of a diblock copolymer

The effect of the dynamics of polystyrene (PS) host chains on the overall translational diffusion of a diblock copolymer of polystyrene and polymethacrylate (ps-b-pmma) of degree of polymerization, N c = 262, was investigated. Measurements of the diffusion coefficient of the diblock copolymer, D ps-pmma , into PS hosts of varying molecular weight, P. were performed using forward recoil spectrometry. These diffusion coefficients were orders of magnitude less than those of PS chains of the same degree of polymerization diffusing into the same environments. While D ps-pmma (PS) was independent of P for P > 2 x 10 5 , it increased for P < 2 x 10 5 . These results are interpreted in light of constraint release models.