this work, we have used the diamond-like carbon (DLC) also known as hydrogenated amorphous carbon (a-C:H), silicon doped DLC (a-C:H:Si) thin films deposited by the plasma enhanced chemical vapour deposition (PECVD) process on silicon substrate and studied their structural, electrical and electronic properties. The DLCs films were prepared at different applied bias voltage (Vb) starting from 100V to 600V; whereas the silicon is doped with DLC thin films using tetramethysilane (TMS) as a precursor at different standard centimetre cube per minute (sccm). In addition nitrogen doped amorphous carbon (a-C:Nx) thin films prepared by pulsed laser deposition (PLD) process and studied their different properties. Different nitrogen concentration (at.%) of a-C:Nx thin films were deposited on silicon substrate using nitrogen-gas as a precursor. The thicknesses of all thin films were ~15015 nm controlled and monitored during deposition process. Raman spectroscopy of these thin films was measured by using two different laser excitation wavelengths viz 488 nm and 647 nm respectively. The microstructure and electronic properties of these samples were investigated by Raman spectroscopy and the electrical property was studied by current-voltage (I-V) characteristics. Finally, a correlation among the electrical properties, electronic properties and micro-structure properties were established based on their sp3 and sp2 concentration in the thin film structure.

Thesis (Ph.D.)--Ohio University, November, 2005. / Includes bibliographical references (leaves 182-196)

The mechanical alloying (MA) process and hot isostatic pressing (HIP) were used to synthesize bulk amorphous Ni-Ti alloy as an alternative to the traditional methods of casting multi-component metallic alloys. Samples milled cryogenically for 10 hours provided a homogeneous lamella structure with spacing of 30-110 nm. X-ray diffraction and transmission electron microscopy studies indicated that there were alloying and amorphous phase within the layers of the MA powder prior to annealing or HIPing. The amount of amorphous phase increased with time when the milled powder was annealed at a constant temperature and with temperature when annealing time was held constant. The microhardness of the powder correspondingly increased with the amount of amorphous formed in the powders. The HIPing of the MA powder produced a close to 100% amorphous compact with some dispersion of nanocrystals in the amorphous matrix. However, densification was not achieved. / Master of Science

Fe78_C.,r xSiioBj2 and Fe77S. xCr-,S i7S. Bjs (with x values ranging from 0 to 8) glassy metallic alloys have been produced in the form of both wires and ribbons using the rotating water bath melt spinning process and chill block melt spinning process, respectively. It was found that the Fe77.5C.,r,, ,S ii. 5B15s eries had better amorphousw ire forming ability than the Fe7g_XCrXSiloBs1e2ri es. However, in ribbon form, both series showed good castability as amorphous alloys. Selected mechanical properties of the glassy samples have been compared with those of high tensile steel wire. Both thermal and mechanical properties were found to be composition-dependent, especially on the Cr content, with the Fe77.X5.C rrSi7.5B1s5e ries wires being thermally more stable and strongert han their Fe7gX. CrrSiloB12c ounterparts. A new bend type fatigue testing machine that uses two pulleys (DP) has been developed to perform tests on the basis of tension-compression loading cycles. The results have been compared with those obtained by using an existing single pulley (SP) machine that performs only tensile-tensile loading cycles. Although the DP machine can impose compressive to tensile bend stresses at different constant mean stress, it was observed that, for low stress ranges and large constant mean stresses the machine performed equivalent bend tests to those using the SP machine. The fatigue performance of amorphous wires was improved on substituting Fe by Cr and on decreasing the constant mean stress. The high tensile (HT) steel wire apparently had better fatigue performance than amorphous wires in terms of stress range; however, when the results were expressed in terms of strain range, the fatigue performance of amorphous wires was slightly better than HT steel wires, as had been demonstrated in previous studies. It was observed that, when the DP machine performed compressive to tensile bending stress cycles, the fracture surfaces differed from those observed in the SP machine. Under tensile to tensile conditions, the fracture surfaces observed for samples tested in the DP machine were similar to those tested in the SP machine. Fracture mechanics analysis of the results suggests that embrittlement is occurring ahead of growing fatigue cracks in these amorphous wires.

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