A cathodic arc with beam filter is employed for the deposition of hydrogen-free amorphous carbon films. A linear filter is used to prevent macroparticles and nonionized carbon atoms from reaching the substrate. The deposited films are characterized by their optical and mechanical behavior. Depending on the deposition conditions, optical band gaps in the range 2.1–2.4 eV are measured. Mechanical properties are investigated using the nanoindentation method and are shown to approach those of natural diamond. To our knowledge, the data obtained thus far reveal these films to be more diamondlike than those prepared using any other method for the deposition of nonhydrogenated amorphous diamond.
Viscosity of porous glasses has been derived from the elastic stress analysis, using the viscous analogy. Viscosity as a function of porosity has been estimated for spherical as well as for arbitrary pore geometry. Since the pore geometry changes during sintering, a shape factor that varies with pore geometry has been considered to predict the viscosityporosity relationship. Viscosity as a function of porosity was measured on cordierite-type glass by isothermal sinter-forging experiments and data showed good agreement with the anaylsis. Experimental data from literature on viscosity as a function of porosity on two other glasses also show good agreement with the analysis. [
The log d o g & data obtained from load relaxation experiments on Tic single crystals, at 900" to 14OO0C, were analyzed in terms of Hart's two-branch rheological model. The analysis verified the existence of a mechanical equation of state within the ranges of stress, strain rate, and temperature employed. Straight and clustered dislocations dominated the microstructure of samples at low temperatures, while well-developed cell structures dominated the microstructure of samples at high temperatures. The observed changes in log d o g . 4 curves and the dislocation structure both indicate that, in addition to the glide-controlled mechanisms, climb/cross-slip-controlled mechanisms contribute significantly to the plastic flow with increasing temperature.
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