Abstract: Bhimal fibres are quite a newer kind of bio-degradable fibres. They have never been heard before in literatures from the view point of their utility as engineering material. These fibres have been utilized for investigation of their properties. Characterization of this fibre is essential to determine its properties for further use as reinforcing fibre in polymeric, bio-degradable and other kinds of matrix. With this objective, the fabrication method and other mechanical properties of Bhimal-reinforced-PVA biocomposite have been discussed. The stress-strain curves and load-deflection characteristics are obtained. The tensile, compressive, flexure and impact strengths have been calculated. The results are shown in tables and graphs. The results obtained are compared with other existing natural fibre biocomposites. From the observations, it has been concluded that the tensile strength of Bhimal-reinforced-PVA biocomposite is higher than other natural fibre composites. Hence these can be used as reinforcement to produce much lighter weight biocomposites.
Abstract: Has successfully created an optimum composite of rPP/DVB/PP-AA/comBen+ZB based on the mechanical and fuel resistance properties. The starting material recycled PP (rPP), PP modified acrylic acid (AA) as coupling agent (PP-AA), crosslinker divinylbenzene (DVB), 20 phr of commercial bentonite (comBen) and 5 phr of zinc borate (ZB), was reactivelly processed in xylene. Composites analysis using XRD presented that the bentonite had been exfoliated inside of PP matrix. Test results showed that both of tensile strength (TS) and young's modulus (YM) of rPP/DVB/PP-AA/comBen+ZB composites following ASTM D638 was increased. The testing results of burning rate (BR) of composite rPP/DVB/PP-AA/comBen+ZB according to ASTM D635 decreased. The presence of bentonite as a natural fire retardant and ZB as fire retardant additive on composite rPP/DVB/PP-AA/comBen+ZB able to increase mechanical properties and also improving the flammability resistance.
Abstract: Nanocomposites attracted the attention of scientists due to their superior mechanical, thermal, chemical and electrical properties. This research studied the impact of adding carbon nanotubes (CNTs) to the woven Kevlar laminated composites on the high and low speed impact characteristics. Different percentages of CNTs were added to the woven Kevlar-Vinylester composite materials. An in-house developed drop weight testing apparatus was utilized for the low speed impact testing. Two different concentrations of the CNTs were added to a 15-layer woven Kevlar laminates, 0.32 wt% and 0.8 wt%. The results showed that: The 0.32 wt % CNT sample enhanced the interlaminar strength of the composite without enhancing the energy absorption capacity whereas, the 0.8 wt % CNT sample did not improve the impact resistance of the Kevlar composite.For the high speed impact tests, a bulletproof vest was prepared using woven Kevlar, resin, and CNTs at 1.5 w% percentage. The ballistic shooting was carried out by a professional shooter using a 30 caliber and 9 mm bullets for the tests. The CNT bulletproof sample bounced back the 30 caliber copper alloy bullet with no penetration.
Abstract: Thin Film layers of metal are often prepared by magnetron sputtering technique for electronic, optical and micro/nanoelectromechanical systems. Usually, experimental work is a common way to find out the optimum deposition conditions and correlate between the thin film properties and the deposition parameters. However, experimental methods are very exhaustive, time and cost-consuming. A good simulation model which can provide the optimum operating conditions to avoid exhaustive experiments and reduce time and cost is highly recommended. Therefore, the present paper is focusing on the development of a computer simulation model of the deposition process in the magnetron sputtering system since such type of models is not well established yet. Monte Carlo (MC) simulation model has been developed to study the effects of deposition parameters on the deposition rate and thin film thickness uniformity. Titanium (Ti) samples were used as the target whereas argon (Ar) was the ambient inert gas. MC simulation has successfully predicted the optimum deposition rate and thickness of Ti thin films on the plastic substrate. The model also depicted the performance of magnetron deposition due to change of processing parameters. Comparison between the simulation and experimental results proved the validity of the proposed model.
Abstract: Copper nitride thin films were prepared by reactive radio frequency magnetron sputtering at different sputtering pressures with fixed nitrogen to argon ratio. The influences of sputtering pressure on the structure, optical band gap, and surface morphology of films were investigated. The results show that the preferential orientation of polycrystalline Cu3N thin films changes from  to  when the sputtering pressure increases. Meanwhile, the optical band gap (Eg) of Cu3N thin films increases with the sputtering pressure. The surface morphology of Cu3N thin film deposited at high sputtering pressure becomes smoother than that of Cu3N thin film deposited at low sputtering pressure.
Abstract: Shape memory alloys have a peculiar property to return to a previously defined shape or dimension when they are subjected to variation of temperature. Shape memory effect is facilitated by martensitic transformation governed by changes in the crystalline structure of the material. Martensitic transformations are first order lattice-distorting phase transformations and occur with the cooperative movement of atoms by means of lattice invariant shears in the materials on cooling from high temperature parent phase region.
The material cycles between the deformed and original shapes on cooling and heating in reversible shape memory effect. Thermal induced martensite occurs as twinned martensite, and the twinned martensite structures turn into detwinned structures by deforming the material in the martensitic condition. Deformation of shape memory alloys in martensitic state proceeds through a martensite variant reorientation. The deformed material recovers the original shape on first heating over the austenite finish temperature in reversible and irreversible shape memory cases.
Meanwhile, the parent phase structure returns to the twinned structure in irreversible shape memory effect on cooling below to martensite finish temperature and to the detwinned structure in reversible shape memory effect. Therefore, the twinning and detwinning processes have great importance in the shape memory behaviour of the materials.
Copper based alloys exhibit this property in metastable β-phase region, which has bcc-based structures at high temperature parent phase field, and these structures martensitically turn into layered complex structures with lattice twinning following two ordered reactions on cooling.
Abstract: Non-oriented silicon iron (NO Fe-Si) alloys are soft magnetic materials used in the construction of medium and high power rotating machines. To obtain efficiency higher than 95%, it is necessary to promote a new design of their magnetic circuits and/or alternative cutting technologies. There were tested steel samples of fully processed non-oriented silicon iron (NO FeSi) grades, M400-65A and M800-65A, with an area of 300 × 30 mm2. The magnetic properties were measured with a single strip tester in the range of frequency from 10 ÷ 200 Hz at 1 T peak magnetic polarization. The sheet cutting technologies, involved in this study, are mechanical, laser, water-jetting and electro-erosion.
Abstract: PbS crystals of different morphologies and sizes were prepared by the reaction of lead acetate (Pb (CH3COO)2) and thiourea (CH4N2S) using cetyltrimethylammonium bromide (CTAB) as surfactant through hydrothermal and microwave methods. In hydrothermal process, reaction was carried out for different reaction time. The samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and UV-VIS-NIR spectroscopy. The results demonstrate that the reaction method and reaction time play important role on the evolution of morphologies and sizes of PbS micro/nanocrystals.
Abstract: Shape memory alloys (SMAs) are now widely used in many industrial and engineering applications e.g. in aircrafts, space vehicles, robotics and actuators. However the available literature reveals that little or no work is published on the machinability of these alloys. In this paper, the effect of the main cutting parameters namely: cutting speed, depth of cut and feed rate on the surface quality of the machined surface of the Cu-Zn-Al shape memory alloy both in the cast and after direct extrusion using a CNC milling is investigated. The cutting speed was varied from 750 to 2000 rpm , the depth of cut was varied from 1 to 4 mm and the feed rate was varied from 100 to 250 mm/min. Furthermore, the general microstructure, the mechanical behavior and hardness of the Cu-Zn-Al shape memory alloy both in the cast and after direct extrusion are determined and discussed. It was found that the best achieved surface quality in this SMA, machined within the different investigated cutting conditions is 0.13 microns at cutting speed of 750 rpm, 1 mm depth of cut and 150 mm/min. feed rate, which is better than the surface quality achieved in other materials at the same cutting conditions.
Abstract: In this paper, we propose a physics-based analytical model of novel InAlN/GaN High Electron Mobility Transistor (HEMT) by considering the quasi-triangular quantum well with minimal empirical parameters. The derived model is compared for different short and long gate length devices. The results are calibrated and verified with experimental data over a full range for gate and drain applied voltages. Significant improvement in ns, drain Current, and transconductance are observed for InAlN HEMT making it suitable for nanoscale and microwave analysis in circuit design. Therefore, the proposed model can deal directly with device/physical parameters, and it can be expressed by a very small number of model parameters.