Abstract: In this study the effect of zirconia (ZrO2) nanoparticles (40 nm) in reinforcing A356 aluminum alloys as a base metal matrix were investigated. Zirconia nanopowders were stirred in the A356 matrix with different fraction ratios ranging from (0, 1, 2, 3, 5%) by weight at variable stirring speeds ranging from (270, 800, 1500, 2150 r.p.m) at a mushy zone (600°C) and liquid state (700°C) using a constant stirring time for one minute. The microstructure revealed the change of grains from dendritic to spherical shape with increasing stirring speed. The Scanning Electron Microscopy of the fractured surface revealed the presence of nanoparticles at the interdendritic spacing of the fracture surface and was confirmed with EDX analysis of these particles.The results of the study showed that the mechanical properties (strength, elongation and hardness) using ZrO2 as reinforcements were increased at the following parameters: 1500 r.p.m stirring speed in semi-solid state (600oC) and adding 3 wt.% of ZrO2.
Abstract: Thin hard coatings are widely used in the protection of cutting tools, dies and molds to prolong their wear resistance and lifetime. Superior properties of different coatings can be combined with multilayer design, and especially a higher microhardness can be obtained by nanocomposite structures. In this study, a multilayer design composing of TiAlSiN, TiSiN and TiAlN layers was applied on carbide cutting tools. The top TiAlSiN layer has a nanocomposite structure of crystalline fcc-TiAlN and amorphous Si3N4 phases. The multilayer nanocomposite TiAlSiN/TiSiN/TiAlN coating was deposited on the carbide cutting tool using an industrial magnetron sputtering system. Wear behavior of the coated tools was investigated in the milling of hardened AISI D2 steel (~55 HRc). The changes in tool wear and surface roughness as a function of cutting distance were recorded. Wear mechanisms and types were investigated using optical and scanning electron microscopy in combination with energy dispersive spectroscopy. It was found that the multilayer nanocomposite TiAlSiN/TiSiN/TiAlN coating provides at least 1.2 times higher wear resistance and a longer lifetime than single layer TiN and TiAlN coatings. Main wear mechanisms are abrasion and adhesion of the workpiece material on the cutting edge. As a result, wear types are notch wear and build-up-edge formation.
Abstract: The current tendency in electronics is the reduction of size while continuously increasing the power consumption due to new functionalities and applications. Both aspects generate a heat increment. Consequently, dissipating the heat to the environment is necessary in order to avoid component overheating. [1,2]. The most efficient way to achieve it is to allow the heat to flow from the hot component to a heat sink. In order to improve the efficiency of this process, thermal resistance between both components must be reduced which is usually done by using a thermal interface material (TIM) between both surfaces [3-5]. This material should fill the gaps created due to the microscopic roughness of both surfaces and it must have good thermal conductivity . These air filled gaps result in a very high contact resistance between joined parts, as the air thermal conductivity is very low .
Abstract: The main aim of this work is to analyze the various heat transport mechanisms and their roles in efficiency enhancement of a thin-film solar cell due to embedded metallic nanoparticles at the rear of the cell, from both electrical and thermal aspects. The nanoparticles present deep inside the cell reflect incident radiation which then increases the optical path length for enhanced electricity generation. The increase in the optical path length also tends to induce additional but undesirable thermal heating which reduces the performance of the cells. The relationship between the improved conversion efficiency and the thermal effect is the crucial factor of maximizing the performance of thin-film solar cells and has yet to be explored. An accurate theoretical/numerical modeling is warranted in this case. Here, we present an analysis of combined light propagation and preliminary phonon transport in the cell to study solar-energy deposition and the associated thermal gradient.
Abstract: Zinc oxide (ZnO) with different nanoparticle (NP) sizes was prepared and synthesized by using the sol-gel method with organic precursor, followed by the characterization of the ZnO nanoparticle by using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) to identify the effect of nanoparticle sizes of ZnO on the viscosity of the nanofluid. The impact of nanoparticle sizes on EOR was investigated. Results showed both viscosity and interfacial tension (IFT) increased with the nanoparticle size.
Abstract: Due to the geographical location and technological limitation, various novel enhanced oil recovery (EOR) methods has been proposed to recover the remaining oil from a depleted oil reservoir. Research on application of nanoparticles either on its own or coupled with other stimulating agents has been growing enormously and some of them have shown a promising future. In high temperature and high pressure reservoirs, thermal degradation will cause failure to the conventional chemicals. In this work, temperature-stable YIG magnetic nanoparticles with an electromagnetic wave has been proposed as a new candidate for reservoir stimulating agent. The purpose of nanoparticle injection is to increase the sweep efficiency in the reservoir by increasing the viscosity of displacing fluid. In this research, Yttrium iron garnet (YIG) nanoparticles have been injected into a waterflooded oil saturated porous medium to recover the remaining oil in the presence of an electromagnetic wave. At the sintering temperature 1200°C, a mixture of hematite and YIG was obtained, suggesting a higher temperature for single phase YIG. From VSM analysis, the average magnetic saturation, coercivity and remanence are 18.17 emu/g, 21.73 Oe and 2.38 emu/g, respectively. 1.0 wt% of YIG nanofluid was prepared and subsequently injected into the pre-saturated porous medium in the presence of square electromagnetic wave of 13.6 MHz. As much as 43.64% of the remaining oil in place (ROIP) was recovered following the injection of 2 pore volume of YIG nanofluid.
Abstract: Recently, the incidence of American Cutaneous Leishmaniasis (ACL) has been grown in Latin America, especially in Brazil, where from 1980 to 2005, 605,062 cases were recorded. The drug glucantime®, whose active principle is the meglumine antimoniate (or meglumine antimonate) is used in the treatment of leishmaniasis. Its toxicity is due mainly to the presence of antimony in its structure. Therefore, it is crucial to determine the safe dose levels of this drug in the treatment. Drug delivery systems have been currently the focus of many studies due to its effectiveness in treating diseases proved to be superior compared to conventional methods. Drug delivery systems can avoid overdosing by decreasing the amount of drug intake, which results in a better therapeutic effect in addition to reducing the risks of plasma concentration reaching toxic levels. Synthetic nanomaterials have been receiving great attention due to their potential applications in pharmaceutical technology as well as the possibility of controlling their particle size and composition, which allows a better performance in drug release. Pseudoboehmite is a synthetic aluminum compound precursor of alumina  and a polymorph of boehmite, with active groups in its structure , making it an excellent adsorbent material. In this work, pseudoboehmite was prepared by using the sol-gel process for being used as an excipient. The incorporation of pseudoboehmite in glucantime® was performed in the processing of tablets. Both pseudoboehmite and the tablets were characterized via X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG), and scanning electron microscopy (SEM) using secondary electron detector and EDS detector. The release profile was obtained by UV/Vis spectroscopy for in vitro simulation. No reaction between the drug and the excipient was observed.
Abstract: In the present study we report on the microwave conductivity of Fe and Mg based nanocomposites. They consist of an epoxy resin matrix reinforced with coarse Fe, mechanically milled Fe and mechanically milled Mg powders. Mechanically milled powders were obtained by high energy ball milling. The morphology of the obtained powders was characterized using Scanning Electron Microscopy (SEM). Electromagnetic scattering parameters were measured within a rectangular X-band metallic wave guide. Electromagnetic parameters were calculated using the Nicolson-Ross-Weir (NRW) algorithm. Microwave conductivity and associated skin depth spectra of the nanocomposites under study are deduced.
Abstract: In this paper, the separation of sulphuric acid from a suspension of cellulose nanocrystal by manual shaking is described. Cellulose nanocrystals are prepared from acid hydrolysis of cotton using 64 wt% sulphuric acid at ca. 45 °C for 45 minutes. After the hydrolysis was complete, water was added to dilute the mixture to a resulting concentration of 30 wt% of the acid. This mixture was shaken rigorously in a closed container and after 48 hours, separation occurs such that cellulose nanocrystals float, with the bubbles introduced by the shaking, to give clear acid solution at the bottom. This shaking-floating process is repeatable for several cycles after the acid was removed from the bottom and more water was added. Using this simple process, the total acid recovery of > 90% has been achieved, and the concentration of all the acid recovered combined was 17.5 wt%. This work demonstrates a method that allows energy efficient and up-scalable separation of cellulose nanocrystals from the acidic suspension from which it was extracted.