Effect of initial preform geometry and friction on the cold deformation behaviour of sintered titanium carbide composite steel

Cold upsetting experiments were carried on sintered titanium carbide composite steel preforms in order to assess their deformation characteristics. The effect of aspect ratio and frictional constraints on deformation behaviour have been investigated thoroughly. Cylindrical compacts with different aspect ratios were prepared, sintered and upset forged at room temperature. The above cold deformation work was carried out using 1.0 MN capacity Universal Testing Machine. Cold deformation experiments were carried out in several steps. Dimensions such as height, contact, and bulged diameters and densities were measured for each test. In general, each compact was subjected to an incremental compressive loading in steps of 0.005 MN until fine cracks appeared on its free surface. Effect of various upsetting parameters, namely, axial strain, axial stress, Poisson’s ratio on the densification has been studied.     

Evidence of photoluminescence quenching in poly(3-hexylthiophene-2,5-diyl) due to injected charge carriers

Photoluminescence spectra of poly(3-hexylthiophene-2,5-diyl) (P3HT) has been studied in forward and reverse bias direction in an indium tin oxide (ITO)/P3HT/Al Schottky device. It has been observed that photoluminescence quenching is relatively higher in forward direction and the quenching pattern gets reversed when a thin insulating layer of poly(4-vinylphenol) is coated on ITO. The observed behavior of photoluminescence quenching pattern has been explained on the basis of interaction of the injected charge carriers with the excitons generated in the bulk of P3HT together with the interaction of excitons with the applied electric field.     

Extractive separation of copper and nickel from copper bleed stream by solvent extraction route

Bleed stream from electro refining step of copper smelter was processed to recover the metals as high value products such as copper and nickel powders or salts. The process consists of partial decopperisation of the bleed stream followed by crystallization of a mixed salt of copper and nickel sulphate, leaching of the mixed salt, removal of iron, solvent extraction for the separation of copper and nickel and winning the solution to produce metal powders. After partial decopperisation of copper bleed stream, the resultant solution was subjected to crystallization which produces composite crystals with the chemical composition of 8.4–12.5% Cu, 13.7–14.38% Ni and 1–2 ppm of Fe as impurity. This mixed salt was leached with water and was treated for iron precipitation. The purified solution was subjected to solvent extraction using two solvents namely LIX 84 or Cyanex 272. A 20% LIX 84 in kerosene extracted 99.9% copper and 0.059% nickel at a pH of 2.5, similarly a 5% Cyanex 272 in kerosene extracted 98.06% copper and 0.51% nickel at a pH of 4.85. LIX 84 was used for metal separation in the mixer-settler unit and a flow sheet was developed using this solvent. The pure solutions of copper after stripping it from the loaded organic and nickel left in the raffinate were further electrolysed to produce pure copper (99.9%) and nickel (99.8%) powders, alternatively pure sulphate salts could also be crystallized. Since it is well known that Cyanex 272 is used for the separation of cobalt and nickel, a few experiments were performed on the extraction of copper by using Cyanex 272. A complete study is yet to be done to develop a flow sheet by using this solvent.     

Effect of geometric work-hardening and matrix work-hardening on new constitutive relationship for aluminium–alumina P/M composite during cold upsetting

The densification and strain hardening behaviour during cold deformation of sintered aluminum–3.5% alumina powder metallurgy preforms were investigated by constitutive model and experimental data obtained with no and with subsequent annealing. The mechanisms most likely involved in the constitutive model, namely, densification and strain hardening were studied. The effect of geometric and matrix work hardening on the various constants involved in the constitutive model, namely, instantaneous density coefficient, instantaneous strain hardening index, instantaneous strain rate sensitivity and instantaneous strength coefficient were discussed in detail.     

Clarification of Stevia extract by ultrafiltration: Selection criteria of the membrane and effects of operating conditions

Clarification of pre-treated Stevia extract using ultrafiltration is presented in this study. Performance of four different ultrafiltration membranes, namely 5, 10, 30 and 100 kDa were investigated in terms of permeate flux and permeate quality, mainly the recovery of Stevioside in the permeate. In this regard, the 30 kDa membrane was found to be most suitable. A systematic set of experiments under steady state were conducted to analyze the effects of the operating conditions, transmembrane pressure drop and stirrer speed on the permeate flux and permeate quality. Steady state was reached in between 8 and 16 min depending on the operating conditions. Steady state was reached earlier at higher stirring speed. A simple resistance in series model was used to quantify the fouling resistance. Membrane resistance was found to be negligible compared to the fouling resistance. It was a strong function of the stirrer speed but remained almost invariant with transmembrane pressure drop. The steady state permeate flux increased with pressure drop as well as the stirrer speed. 45% average recovery of Stevioside was obtained during stirred steady state experiments at lower operating pressures (276 and 414 kPa). At higher operating pressures, recovery of Stevioside in the permeate decreased remarkably.     

Adsorption effect of Zn+2 and Co+2 on the antibacterial properties of SiC-porcelain ceramics

This investigation reports the adsorption effect of Cobalt and Zinc ions on the antibacterial properties of Silicon Carbide (SiC) added fired Porcelain based ceramics against Escherichia coli and Staphylococcus aureus. Incorporation of SiC in porcelain composition shows decrease in bulk density and increase in apparent porosity gradually upto 15 weight percent addition. The bulk density and apparent porosity of 15 wt% SiC added porcelain are 2.01 g/cm³ and 24.03%, respectively. Phase and microstructural charecterization reveals that fine grained interlocked mullite network with little unconverted quartz and carborandum are uniformly distributed in the microstructure. Co⁺² and Zn⁺² adsorption on exposed surface is calculated to be ~0.42 mg/cm² and Inductively coupled mass plasma spectroscopy (ICP-MS) shows that 1641.41 ppm of Co⁺² and 1936.37 ppm of Zn⁺² are leached in water from adsorbed surface. This is the first report where, transition metal specific antibacterial efficacy of SiC added porcelain-based ceramics are investigated. This report reveals that both Co⁺² and Zn⁺² adsorption results in antibacterial efficacy against E coli and S aureus and Co⁺² adsorption is superior to (zone of inhibition is ~1.3 cm more depending on bacteria and sample specifications) Zn⁺² adsorption.     

Influence of residual stress on performance of AlN thin film based piezoelectric MEMS accelerometer structure

Microsystem Technologies - The presence of residual stress is inevitable and major constraint for MEMS devices as they induce deformation, fracture, fatigue and micro structural changes in the...