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Full-Text Articles in Physics

Photoemission Study Of Ce-Catalyzed Oxidation Of W(110) And W(111), C. Gu, C. G. Olson, David W. Lynch Oct 1993

Photoemission Study Of Ce-Catalyzed Oxidation Of W(110) And W(111), C. Gu, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

Different catalytic oxidation effects of Ce on W(110) and W(111) were observed with photo- emission spectroscopy. On Ce-covered W(110), the top W layer is quickly oxidized to a surface monoxide at room temperature. Oxidation is almost halted after the completion of one monolayer of WO. On Ce/W(111), instead of WO, WO3 grows on the surface under the same conditions. The monolayer suboxide formation found on Ce/W(110) and Ce/Ta(110) (as reported earlier) is a direct consequence of the most densely packed structure of the bcc (110) surfaces. The more effective oxidation promotion ...


Molecular-Motion Analysis Of 5cb In Pdlcs Using Solid-State C-13 Nmr Relaxation Spectroscopy, Karen L. Buchert, Jack L. Koenig, Shi-Qing Wang, John L. West Jul 1993

Molecular-Motion Analysis Of 5cb In Pdlcs Using Solid-State C-13 Nmr Relaxation Spectroscopy, Karen L. Buchert, Jack L. Koenig, Shi-Qing Wang, John L. West

Chemistry & Biochemistry Publications

In samples of polymer-dispersed liquid crystals (PDLCs), submicron droplets of liquid crystal reside within a polymer matrix. By the use of the cross polarization technique for solid-state C-13 NMR spectroscopy, the NMR spectrum of the liquid crystal can be obtained without interference from the polymer spectrum, even though the two materials have some similar chemical structures. Both C-13 T1 and C-13 T1 rho relaxation experiments were performed on a PDLC system of 5CB in epoxy as a function of 5CB domain size. The C-13 T1 relaxation constants and the localized motions they measure showed no significant change over the liquid ...


Analysis Of Polymer-Dispersed Liquid Crystals By Infrared Spectroscopy, Coleen A. Mcfarland, Jack L. Koenig, John L. West Mar 1993

Analysis Of Polymer-Dispersed Liquid Crystals By Infrared Spectroscopy, Coleen A. Mcfarland, Jack L. Koenig, John L. West

Chemistry & Biochemistry Publications

FT-IR microspectroscopy is used to compare the polymer and liquid crystal droplet regions within polymer-dispersed liquid crystal (PDLC) films. Thermoplastic polymer matrix PDLCs contain a higher amount of liquid crystal within the polymer regions than do thermoset polymer matrix films. IR functional group images of a droplet show characteristic textures corresponding to the visual images of the same droplet. The textures in the IR images change with IR polarization and with an applied electric field. Analysis by conventional IR spectroscopy shows that the C=N and the pentyl CH2 groups require an equivalent voltage to switch in the IR ...