Procedia Materials Science最新文献

In the present work, we carried out a systematic study of structure, UV-Vis Spectra and surface conductivity of pure Bi₂Te₃, pure Polyaniline (PANI) and Bi₂Te₃ (5%)-PANI (95%) composite. Bi₂Te₃ was synthesized by a method similar to solvothermal method, whereas, pure PANI and Bi₂Te₃-PANI composite were synthesized by a chemical oxidative method. The materials were structurally characterized and the electrical properties were investigated in the temperature range from room temperature to 100 °C. The electrical conductivity of the Bi₂Te₃-PANI composite is found to be higher than that of its pure constituents at all the temperatures. The enhancement in the surface conductivity may be due to the PANI generated ordered molecular arrangement of Bi₂Te₃ in the Bi₂Te₃-PANI composite, as confirmed from powder x-ray diffraction, UV–vis spectral analysis.

Synthesis of nanoparticles and ultrafine particles of zinc oxide with controlled morphology using microwave irradiation is carried out by various methods. The effect of type of precursor as well as the time and the microwave irradiation power on the structure and size of ZnO nanoparticles have been studied. Particles Studied by SEM, TEM images and XRD analyze. By increasing the time of synthesis from 10 to 15 minutes needle-shaped particles with a diameter of 50-150 nm can be achieved. While increasing the microwave power from 540 to 680 watts, flower-shaped particles are obtained. By replacing zinc nitrate with zinc acetate, at different power and time of irradiation, needle-shaped particles are obtained and diameter of needles is decreased.

In the existing world, where demand for portable battery operated devices is increasing, a major push is given towards low power methodologies for high speed applications. Symmetric circuits with regenerative feedback give opportunity to identify new structures that may be particularly useful. Regenerative feedback is usually used in Dynamic Comparators and rarely in non-clocked comparators. Dynamic Comparators are generally used in the design of high-speed Analog to Digital Converters and can easily be designed. The existing comparator requires high accuracy timing Clkb, maximum drive current and high power. To overcome the disadvantages of the existing comparator a new dynamic comparator has been proposed in this paper that uses low power and has less delay. For the performance verification, the design is simulated in Cadence gpdk 180 nm Technology at 1.8 Voltage Supply. Post Layout Simulation results in 180 nm CMOS technology shows that power consumption is reduced by 58% and delay time is reduced by 41%.

In this study, aluminium metal composites reinforced with Zirconium dioxide (ZrO₂) nano-particles in different of volume percentage are manufactured through accumulative roll bonding. The results indicate that with the application of 10 ARB cycles and the composite microstructure shows excellent ZrO₂ particle distribution in the Al matrices. The X-ray diffraction results also showed that nanostructured Al/ZrO₂ Nanocomposite with the average crystallite size of 48.6 nm was successfully achieved by employing 10 cycles of ARB process. According to the results of this study, the tensile, hardness, and elongation properties of the Al/ZrO₂ composite are determined for 0.50, 0.75 and 1 vol.% ZrO₂.

In the present study, nanostructured Fe-30 wt.% Mn alloys produced by mechanical alloying of Fe and Mn powders mixture. The phase composition and morphology of nanostructured powder were analyzed by X-ray diffraction and scanning electron microscopy. It was found that by milling time up to 10 h, crystallite size was decreased to 6 nm, on the contrary lattice strain was increased. Solid solubility levels were determined from changes in the lattice parameter values. The lattice parameter increases slightly from 0.28167 to 0.35776 nm. Increasing milling intensity by higher ball to powder mass ratio resulted in Fe-Mn alloy formation with smaller crystallite size. The SEM results showed that, plate like particles were formed in initial milling time and particles morphology was changed to equiaxed form in final stage of milling process.

Online, continuous two phase flow measurements is often necessary for analysis of the two phase flow particularly in oil and gas, nuclear energy and chemical processing industries. Reliable measurements of void fraction and flow pattern identification are important for accurate modeling of two phase systems. Void fraction is one of the most important parameters used to characterize two-phase flows. It is the key physical value for determining numerous other important parameters, such as the two-phase density and the two-phase viscosity, for obtaining the relative average velocity of the two phases and is of fundamental importance in models for predicting the flow pattern transitions, heat transfer and pressure drop. Experiments are performed in atmospheric vertical air-water flows for void fraction measurement between the pipe size of 12.5 mm diameter to 4.5 mm diameter to emphasize on developing the measuring techniques of two-phase flow void fraction by using ‘Conducting probe circuit’ which uses a ‘needle probe’ for measurement of void fraction in an air lift loop. The process involves the immersion of probe tip in two phase mixture in order to detect the two phases instantaneously present at the tip and the corresponding readings for the measurement of void fraction are obtained from the processing circuit.

Interlaminar shear properties of the fibre reinforced polymer composites are very important in many structured applications. Interlaminar shear strength (ILSS) of a unidirectional fibre reinforced polymer composite laminate is usually a limiting design characteristic. And also it has been reported that, the interlaminar shear strength of fibre reinforced polymer composites may be improved by the modification of the matrix. In this paper, diglycidyl ether of bisphenol A (DGEBA) / triethylene tetramine (TETA) system is used as the epoxy matrix. Alumina nanoparticles are employed to modify the epoxy matrix at various concentrations. Unmodified and modified epoxy resins are used along with unidirectional glass fibres for fabricating composite laminates by vacuum bagging process. The interlaminar shear strength of the glass fibre reinforced composites at different orientation of the laminate is investigated and the results indicate that introduction of the alumina nanoparticles up to 0.8 wt%, enhances the ILSS in all the direction of fibres, while addition up to 1.2 wt% decreases the ILSS. Also, the percentage of enhancement in the ILSS is found to be altered in different direction of fibre orientation. In particular, the addition of 0.8 wt% alumina nanoparticles leads to the 2.07%, 8.71% and 18.02% increase in the ILSS for the composite in the direction of 0^o, 45^o and 90^o fibre orientation respectively. These phenomena are explained in terms of agglomeration of nanoparticles and dominant properties of fibres and matrix in different angles of fibre orientations.

In current study, the effect of nanohydroxyapatite (nHA) content on microstructural and mechanical properties of hydroxyapatite scaffolds fabricated using the water-based freeze casting method has been investigated. In the experimental procedure, the solidified samples were prepared by hydroxyapatite slurries containing different concentration of nHA followed by sintering procedure at 1350 °C. The characteristics of the initial powders, microstructure, and mechanical strength of the scaffolds were assessed by X-ray diffraction, scanning electron microscopy, and mechanical strength test, respectively. The results showed that, increasing of nHA leading to decrease in pore size, increase in inter structural bridges, reduce in porosity and increase in compressive strength of the hydroxyapatite scaffolds, which is believed to be more effective in bone tissue engineering applications.

Recently application of nano/bio materials for enhanced oil recovery (EOR) has been examined by few researchers, but there exists ambiguous concepts about simultaneous injection of nanoparticles/biomaterials. Therefore, in this study the heavy oil displacement mechanisms using simultaneous injection of nanosilica/biosurfactant have been investigated in a glass micromodel. In order to better illustrate the influence of nano/bio material different flooding scenarios containing distilled water, nanosilica/distilled water, biosurfactant/distilled water and nanosilica/biosurfactant/distilled water have been conducted. Experimental results indicate that simultaneous presence of nanoparticles and bioproducts have synergy on each other and because of IFT reduction, improving the mobility ratio and increasing the injected fluid viscosity; the oil recovery can be achieved about 58%. Furthermore, nanoparticles can play as an inhibitor to avoid asphaltene precipitation.