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Amorphous silicon thin films obtained from hydrofluosilicic acid using the electrodeposition method are analysed for structure and morphology. The chemical nature of the films is discussed using the data from IR spectroscopy. The electrical resistivity of these films is very high, of the order of 10(12)-10(13) OMEGA cm, under the present experimental conditions. X-ray diffraction spectra revealed that the films are not crystalline in nature. At low concentrations of the electrolyte, scanning electron microscopy photographs exhibited some microstructure with crystalline order of about 100 angstrom, At high concentrations, the structure of the films changed widely to be homogeneous.

Infrared spectra of 13 samples of amorphous silicon bonded with hydrogen, fluorine and carbon, prepared by electrodeposition using a mixture of ethylene glycol and fluosilicic acid were analysed in the wave number region 4000-400 cm-1 with a Fourier transform infrared spectrometer. Strong absorption peaks were observed at 1000 cm-1 due to the SiF(x) stretching mode. Small peaks were seen around 2300 and 640 cm-1 due to SiH stretching and wagging modes of absorption. The number of bonded hydrogen atoms in the film deposited at 0.05 M, 50 mA cm-2 was calculated to be 6.2579 x 10(21) and 1.2302 x 10(20) atm cm-3 using integrated absorption of the CH and SiH stretching modes, respectively. The absorption coefficient around the SiF(x) stretch region was found to vary from 1300-2500 cm-1 as the molarity of the electrolyte was increased. Binding energy shifts in X-ray photoelectron spectrum were used as a cross check to confirm the silicon bonding with carbon, hydrogen, oxygen and fluorine atoms. The absence of columnar growth in SEM photographs indicates no polysilane formation in the films.

The end effects phenomenon is investigated in a MHD channel with finitely segmented electrode walls when the applied magnetic field decays as a sinusoidal function at the entrance and is constant inside the channel. the governing equations to determine the electric potential are solved numerically by the successive overrelaxation method. the normal current distribution and the electrical efficiency are calculated for various types of electrode spacing. It is found that the leakage currents are more for the case when the electrode length is greater than the insulator length, and the end losses are less.

Finite-difference analysis of the heat transfer in the developing flow of an annulus bounded by two concentric and rotating cylinders is carried out. The two cylinders are assumed to be at unequal temperatures. Numerical results for temperature profiles, mixing-cup temperature θm and the Nusselt number Nu are derived for different values of Re2/Ta (Re = axial Reynolds number; Ta = Taylor number), θ (ratio of the angular velocities of two cylinders) and N (ratio of the two radii). Temperature profiles are shown graphically, whereas the numerical values of θm and Nu are listed in tables. The effects of these parameters are discussed.