High stress abrasive wear behavior of sillimanite-reinforced Al-alloy matrix composite: A factorial design approach

An attempt has been made to explore the possibility of using a natural mineral, namely sillimanite, as dispersoid for synthesizing aluminum alloy composite by solidification technique. The abrasive wear behavior of this composite has been studied through factorial design of experiments. The wear behavior of the composite (Y _composite) and the alloy (Y _alloy) is expressed in terms of the coded values of different experimental parameters like applied load (x ₁), abrasive size (x ₂), and sliding distance (x ₃) by the following linear regression equations:

Optimization study of adsorption parameters for removal of phenol on gastropod shell dust using response surface methodology

Phenolics have recently been of great concern because of the extreme toxicity and persistence in the environment. This study explores the possibility of using gastropod shell dust (GPSD) to remove phenol from aqueous solutions. The removal of phenol was investigated in batch mode. The influence of different experimental parameters—initial pH, adsorbent dose, initial concentration, contact time, stirring rate, temperature, and their interaction during phenol adsorption—were determined by response surface methodology based on three-level four-factorial Box–Behnken design. Optimized values of initial phenol concentration, pH, adsorbent dose, and contact time were found as 10.16 mg/L, 4.22, 0.50 g/L, and 33.47 min, respectively. The experimental equilibrium data were tested by four widely used isotherm models namely, Langmuir and Freundlich, D–R, and Temkin. It was found that adsorption of phenol on gastropod shell dust correlated with the Langmuir isotherm model, implying monolayer coverage of phenol onto the surface of the adsorbent. The maximum adsorption capacity was found to be 56.89 mg g^?1 at 333 K. Regeneration study revealed that about 92 % phenol can be regenerate within 90 min from the spent GPSD. Kinetics of the adsorption process was tested by pseudo-first-order, pseudo-second-order kinetics, and intra-particle diffusion mechanism. Pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order model. Intra-particle diffusion was not the sole rate-controlling factor. The activation energy of the adsorption process (E _a) was found to be 2.68 kJ mol^?1, indicating physisorption nature of phenol adsorption onto gastropod shell dust. A thermodynamic study showed spontaneous nature and feasibility of the adsorption process. A negative enthalpy (ΔH°) value indicated that the adsorption process was exothermic. The results revealed that gastropod shell dust can be used as an effective and low-cost adsorbent to remove phenol from aqueous solutions.     

Technical note The effect of rate of decay of rain path profile on microwave communication

The attenuation of radio waves due to rain can be predicted with a good degree of accuracy, provided the rain rate characteristics over the entire path of propagation are known. The attenuation due to rain is usually deduced on the basis of point rain rate, which can lead to inaccuracy in the estimation of attenuation. We use the concept of rate of decay of rain path profile to estimate the attenuation due to rain. The attenuation has been deduced at 11GHz and 13.4 GHz for 56 elevation angle by using the theory of decay rate of rain path profile, its controlling factor, gamma, and rain rate distribution over Delhi, a tropical station in India. The theoretically-estimated attenuation is compared with observed values, as well as with values obtained using the International Radio Consultative Committee (CCIR) method. The CCIR model is found to overestimate the attenuation.     

Evolution of microstructure and texture in an ultrafine-grained Al6082 alloy during severe plastic deformation

The evolution of microstructure and texture in Al6082 precipitation-hardened alloy during equal-channel angular pressing (ECAP) was studied. It was found that although the dislocation density and the subgrain size saturated after 1 pass, the size of grains bounded by high angle boundaries reached its minimum value only after 4 passes. Furthermore, the grain orientation distribution changes between 4 and 8 passes, indicating the development of grain boundary structure even after the saturation of the parameters of the microstructure. As a result of this evolution, the initial texture of the commercial alloy was diminished after 8 passes and the grain orientation distribution became to be close to random case.     

In situ nanocrystalline Fe–Si coating by mechanical alloying

A new approach for deposition of in situ nanocrystalline Fe–Si alloy coating on mild steel substrate by mechanical milling has been proposed. The thickness of nanocrystalline coating was a function of milling time and speed. Milling speed of 200 rpm was the optimum condition for development of uniform, hard, adherent and dense 200–300 μm thick nanocrystalline coating. A possible mechanism, consisting of three steps like repeated impact, cold welding and delamination, has been proposed for the formation of coating. These coatings have resulted in the increase of the hardness to almost double the value before coating.     

Studies on Hg(II) ion retention properties of cross-linked graft copolymer of acrylic acid and its analytical application

The effects of different parameters such as time, concentration, pH and temperature, on metal ion retention properties of the polymer have been investigated. Metal ion adsorption kinetics, isotherms and thermodynamics have been studied. A plausible mechanism for mercury ion retention has been suggested. Mercuric ion has been isolated quantitatively from various synthetic mixture containing metal ions (Ni²⁺, Cd²⁺, Pb²⁺ and Zn²⁺).     

Effect of heating mode on sintering of tungsten

Microwave heating is recognized for its various advantages, such as time and energy saving, very rapid heating rates, considerably reduced processing cycle time and temperature, fine microstructures and improved properties. The present paper investigates the feasibility of consolidating tungsten powders through microwave sintering. A comparative analysis has also been attempted between the sintering response of pure tungsten powder compact in a microwave and conventional furnace.     

Comparative Study on the Properties of Galvanically Deposited Nano- and Microcrystalline Thin Films of PbSe

Thin films of PbSe having both nano- and microstructures have been deposited on transparent conducting oxide (TCO)-coated glass substrates electrochemically, from an aqueous solution of Pb(OAc)₂, ethylenediamine tetraacetic acid (EDTA), and SeO₂. A Pb strip acted as the sacrificial anode, while the TCO glass was the cathode. No external bias was applied. The formation of PbSe was pH sensitive, and pH ~3 was found to be optimum for film deposition. Films grown at room temperature (25°C) were nanocrystalline (~25 nm), while those deposited at 80°C were microcrystalline (~150 nm). Films were characterized by x-ray diffraction studies, field-emission scanning electron microscope image analysis, infrared spectral analysis, and by both alternating-current (a.c.) and direct-current (d.c.) electrical measurements. A blue-shift was observed for the nanocrystalline films. Film resistivity and junction properties were obtained from electrical measurements.     

Microstructure and growth of ZnTe films

The microstructure and growth of ZnTe films deposited onto glass and freshly cleaved NaCl substrates are carefully studied by a TEM. Effect of different stimulator on the grain growth is also described.