Measurement of the corrosion rate of aluminium in sodium hydroxide using holographic interferometry

The application of holographic interferometry to the measurement of the corrosion rate of aluminium in sodium hydroxide is investigated. Details of the fabrication of the corrosion cell and the experimental procedure are given. Thickness loss of aluminium was found for different dissolution times and compared with the conventional weight-loss method using a microbalance.

Position and Feed-Rate Control for Contouring Numerical-Control Systems

Numerical control (NC) for contouring operations requires precise control of position and feed rate for approximating the contour by linear moves of the cutter. A control scheme, for generating linear moves with desired slopes for the cutter, is described. This scheme provides for nine successive linear moves, and may be either expanded or implemented in succession, for approximating a contour.

High-Surface Step Density on Dendritic Pd Leads to Exceptional Catalytic Activity for Formic Acid Oxidation

Dendrite Pd with corrugated surfaces, obtained by a novel AC technique, exhibits an exceptionally high catalytic activity for the oxidation of formic acid because of the presence of a high density of surface steps. The formation of twinned dendrites leads to a predominance of exposed 111 facets with a high density of surface steps as evident from high resolution electron microscopy investigations. These surface sites provide active sites for the absorption of the formic acid molecules, thereby enhancing the reaction rate. Control experiments by varying the time of deposition reveal the formation of partially grown dendrites at shorter times indicating that the dendrites were formed by growth rather than particle attachment. Our deposition method opens up interesting possibilities to produce artisotropic nanostructures with corrugated surfaces by exploiting the perturbations involved in the growth process.

Continuity of plastic strain rate in stress relaxation tests

Stress relaxation testing is often utilised for determining whether athermal straining contributes to plastic flow; if plastic strain rate is continuous across the transition from tension to relaxation then plastic strain is fully thermally activated. This method was applied to an aged type 316 stainless steel tested in the temperature range 973–1123 K and to a high purity Al in the recrystallised annealed condition tested in the temperature range 274–417 K. The results indicated that plastic strain is thermally activated in these materials at these corresponding test temperatures. For Al, because of its high strain rate sensitivity, it was necessary to adopt a back extrapolation procedure to correct for the finite period that the crosshead requires to decelerate from the constant speed during tension to a dead stop for stress relaxation.

Effects of thermal annealing on the properties of zirconia films prepared by ion-assisted deposition

The effect of thermal annealing in the range 300–800 °C on the properties of zirconia films prepared by ion assisted deposition was studied. It was found that at low temperature the cubic phase is formed. This phase is stable up to 700 °C. All the films exhibit a monophasic monoclinic structure at 800 °C. The stress, estimated from X-ray patterns, shows a transition from tensile to compressive with increasing ion fluence. The refractive index and extinction coefficient do not seem to change appreciably up to 700 °C, showing a marked degradation thereafter. Single step annealing to the highest temperature was found to result in better stability than multistep annealing.

Epitaxial metallic LaNiO3 thin films grown by pulsed laser deposition

Epitaxial LaNiO3(LNO) thin films on LaAlO3(LAO), SrTiO3(STO), and YSZ are grown by pulsed laser deposition method at 350 mTorr oxygen partial pressure and 700 °C substrate temperature. As‐deposited LNO films are metallic down to 10 K. c‐axis oriented YBa2Cu3O7 (YBCO) films were grown on LNO/LAO as well as LNO/STO surfaces without affecting superconducting transition temperature of YBCO. Textured LNO thin films were grown on c‐axis oriented YBCO/STO and YBCO/YSZ . Transport measurements of these bilayer films showed that LNO is a good metallic contact material for YBCO.

Kinetics of ceric ion oxidation of naphthalene and its derivatives. Formation of the radical cation intermediate in the rate limiting step

Ceric ammonium sulfate, CAS, oxidizes naphthalene to 1,4-naphthoquinone in essentially quantitative yield in CH3CN-dil. H2SO4. Stoichiometric studies indicate that 6 mol of CAS are required for the oxidation of 1 mol of naphthalene to 1,4-naphthoquinone. Kinetic investigations reveal that the reaction takes place through initial formation of a 1:1 complex of naphthalene and cerium(IV) in an equilibrium step followed by slow decomposition of the complex to naphthalene radical cation. Kinetic results on the effects of acid strength, polarity of the medium, temperature and substituents are in accordance with this mechanism. Further conversion of the radical cation into 1,4-naphthoquinone takes place in fast steps involving a further 5 mol of cerium(IV) and 2 mol of H2O.

Microstructural features of flow instability in α-titanium cylinders under high strain rate compression at 25°C to 400°C

Cylindrical specimens of commercial pure titanium have been compressed at strain rates in the range of 0.1 to 100 s-1 and temperatures in the range of 25-degrees-C to 400-degrees-C. At strain rates of 10 and 100 s-1, the specimens exhibited adiabatic shear bands. At lower strain rates, the material deformed in an inhomogeneous fashion. These material-related instabilities are examined in the light of the ''phenomenological model'' and the ''dynamic materials mode.'' It is found that the regime of adiabatic shear band formation is predicted by the phenomenological model, while the dynamic materials model is able to predict the inhomogeneous deformation zone. The criterion based on power partitioning is competent to predict the variations within the inhomogeneous deformation zone.

Novel mechanism for high speed growth of transparent and conducting tin oxide thin films by spray pyrolysis

A novel mechanism is proposed for efficient manipulation of transport forces acting on the droplets during spray pyrolytic deposition of thin films. A ‘‘burst mode’’ technique of spraying is used to adjust the deposition conditions so as to transport the droplets under the new mechanism. Transparent, conducting thin films of undoped tin oxide prepared by this method showed significant improvement in growth rate. The films are found to be of fairly good quality with optical transmission of 82% and sheet resistance of 35 Ω/☒. The films are chemically homogeneous and grow preferentially along 〈200〉 direction.

Adaptive Keeper Design for Dynamic Logic Circuits Using Rate Sensing Technique

The increasing variability in device leakage has made the design of keepers for wide OR structures a challenging task. The conventional feedback keepers (CONV) can no longer improve the performance of wide dynamic gates for the future technologies. In this paper, we propose an adaptive keeper technique called rate sensing keeper (RSK) that enables faster switching and tracks the variation across different process corners. It can switch upto 1.9x faster (for 20 legs) than CONV and can scale upto 32 legs as against 20 legs for CONV in a 130-nm 1.2-V process. The delay tracking is within 8% across the different process corners. We demonstrate the circuit operation of RSK using a 32 x 8 register file implemented in an industrial 130-nm 1.2-V CMOS process. The performance of individual dynamic logic gates are also evaluated on chip for various keeper techniques. We show that the RSK technique gives superior performance compared to the other alternatives such as Conditional Keeper (CKP) and current mirror-based keeper (LCR).

Nano structured carbon nitrides prepared by chemical vapour deposition

Nanostructured carbon nitride films were prepared by pyrolysis assisted chemical vapour deposition(CVD). A two zone furnace with a temperature profile having a uniform temperature over a length of 20 cm length has been designed and developed. The precursor Azabenzimidazole was taken in a quartz tube and evaporated at 400 degrees C. The dense vapours enter the pyrolysis zone kept at a desired temperature and deposit on the quartz substrates. The FTIR spectrum of the prepared samples shows peaks at 1272 cm(-1) (C-N stretching) and 1600 cm(-1) (C=N) confirms the bonding of nitrogen with carbon. Raman D and G peaks, are observed at 1360 cm(-1) and 1576 cm(-1) respectively. XPS core level spectra of C 1s and N 1s show the formation of pi bonding between carbon and nitrogen atoms. The size of the nano crystals estimated from the SEM images and XRD is similar to 100 nm. In some regions of the sample a maximum of 57 atom % of nitrogen has been observed.

Mass transfer and shear rate in baffled surface aerator

The scale up or scale down of the process variables in a surface aerator requires information about the shear rate prevailing in the system. In fact, the performance of surface aerator depends upon the shear rate. Shear rate affects the mass transfer operation needed by the surface aerator. Theoretical analysis of shear rate suggests a nonlinear behavior with rotational speed of the impeller, which has been shown in the present work. Present work also shows that in a geometrically similar system of baffled surface aerator, shear rate can be used as a governing parameter for scaling up or down the mass transfer phenomena.