Abstract: In this work, the preparation of nanostructured Al-4.5wt%Mg powder through the mechanical alloying (MA) process was evaluated. The X-ray diffraction (XRD) technique was used to calculate the crystallite size and microstrain. Scanning electron microscopy (SEM) was used not only to study the morphology of the powders but also to show the fact that the Mg powders were distributed during the MA process. Transmission electron microscopy (TEM) was also used to demonstrate whether the produced powders are nanostructured or not. XRD results showed that microstrain and crystallite size of milled powder (after 10 h milling at the ball-to-powder weight ratio (BPR) of 20:1) were ≈-0.34% and ≈20nm respectively. XRD and TEM results showed that Al12Mg17 has been formed during MA process. This means that during this process, mutual diffusion of Al and Mg has occurred.
Abstract: In the present article, α-Al2O3 nano powder was synthesized by a simple aqueous sol–gel method by using AlCl3 as precursor. It was shown that the gel calcined at 1000°C, 1100 °C and 1200 °C resulted in the formation of a crystalline α-Al2O3 nano powder. In continue TEOS and saccharose was used to prepare SiO2 xerogels containing carbon nano particles. The conversion of the gel to β-SiC nano powders was accomplished by carbothermal reduction at 1500°C for 1 h in argon atmosphere. In second pace alumina matrix composites with nano particles of 5 vol% SiC were prepared with the addition of TiO2 as sintering aid and densified by pressureless sintering method at 1600°C and 1630°C for 2 h in nitrogen atmosphere. Green pellets were obtained by uniaxial pressing of 137 MPa. Maximum density (97.3%) was achieved at 1630°C. Vickers hardness was 16.5 GPa after sintering at 1630°C. Scanning electron microscopy revealed that the SiC particles were well distributed throughout the composite matrix. The precursors and the resultant powders were characterized by X-ray diffraction (XRD), thermal analysis (STA) and scanning electron microscopy (SEM).
Abstract: LiFePO4/C nanocomposite was synthesized by the polyol process without any further heating as a post step and its properties were compared to LiFePO4 with no carbon. The X-ray diffraction patterns of all samples were indexed on the basis of the orthorhombic olivine-type structure. The field emission-SEM and TEM images of the nanocomposite showed agglomerated larger particles with rod type mixed with carbon nanoparticles. The initial discharge capacity of LiFePO4/C nanocomposite showed 166 mAh/g at a current density of 0.1 mA/cm2 in the voltage range of 2.5-4.2 V without capacity fading during the 20 cycles. Furthermore, the nanocomposite appeared more enhanced high rate performance, compared with the result of LiFePO4 with no carbon, due to the existence of conductive agents such as carbon which suppresses particle growth and exhibits improved electronic conductivity and lithium ion diffusivity, simultaneously.
Abstract: In the paper we present measurements of transport physical parameters such as thermal conductivity, diffusivity and specific heat capacity and dc electrical conductivity as well as the mechanical values E*, tg δ for rubber compounds filled by different ratio of silica - carbon black fillers. From presented results it is possible to see that proper filler concentration (rubber blend - silica - carbon black) rising all thermal parameters as well as mechanical properties represented by complex Young’s modulus and so, maintains the good mechanical parameters of the blend and finally it also lowers the electrical resistance. All trends are favourable for the improvement of useful rubber blends properties.
Abstract: The viscoelastic properties of composites multi walled carbon nanotube / epoxy at different weight fractions (0.1, 0.5 and 1wt %) were evaluated by performing dynamic mechanical thermal analysis (DMTA) test. The MWCNT/ epoxy composite were fabricated by sonication and a cast molding process. The results showed that addition of nanotubes to epoxy had a significant effect on the viscoelastic properties. However, the use of 0.5wt% increased the viscoelastic properties more significantly. Concerning viscoelastic modeling, the COLE-COLE diagram has been plotted by the result of DMTA tests. These results show a good agreement between the Perez model and the viscoelastic behavior of the composite.
Abstract: The main issue of the study is aluminum A356 alloy modification by TiC nanoparticles process. Nanoparticles of TiC were especially mechanochemically activated to remove the oxide layer on the particle surface in order to prevent its floating on the molten metal surface. Experimental results indicate that after T6 heat treatment the tensile strength of the modified alloy increased by 6.5%, yield strength increased by 9% and the elongation increased by 22%. A high resolution electron microscopy study shows that dislocation of the modified alloy concentrates near the grain boundary during the crystallization process, and these grain boundaries act as obstacles to dislocation motion. Based on these results, it was found that grain-size aluminum strengthening mechanism occurs in the nanoparticle carbide reinforcement process.
Abstract: In this study, a finite element model of a representative volume element that contains a hollow and filled single-walled Carbon nanotube (SWCNT) in two case studies was generated. It was assumed that the nanocomposites have geometric periodicity with respect to local length scale and the elastic properties can be represented by those of the representative volume element (RVE). Elastic properties in agreement with existing literature values for the Carbon nanotube and the matrix were assigned. Then for the two case studies, the tensile test was simulated to find the effect of the geometry, i.e. the volume fraction of matrix and SWCNT's properties variation, on the effective Young's modulus of the structure. In another approach, by applying perpendicular loading to the tube direction, the effect of matrix volume fraction on the transverse Young's modulus was studied. The investigations showed that for both RVEs with filled SWCNT and hollow SWCNT, the effective Young's modulus of the structure decreases approximately linear as the matrix volume fraction increases. The value of Young's modulus of the RVE with a filled Carbon nanotube was obtained to be higher than the RVE with the hollow Carbon nanotube. In addition, by increasing the tube diameter, the effective Young's modulus of the structure increases and the transverse Young's modulus decreases approximately linear for filled tubes but this parameter remains rather constant in the case of the hollow tube by increasing the matrix volume fraction.
Abstract: Nowadays, there are many ways to administer the huge variety of drugs that are on the market. A drug is a chemical substance, that when applied to a living creature, alters its body function. Many drugs are used daily, such as caffeine in coffee and aspirin for pain. A route of drug administration in pharmacology and toxicology is the path by which a drug is brought into contact with the body. The most critical issue is some drugs are not significantly absorbed into the bloodstream. There are thousands of questions on the drug diffusion in the bloodstream and the most common issue is how long will these micro particles drug be released from the tablet? Thus, to identify the rate of the drug release and to control the drug release in our body is important, where to meet the target and not to become a waste. The Computational Fluid Dynamics method was used to investigate the drug design and diffusion profiles with time during the process of degradation and diffusion in water.
Abstract: The research work presented here intends to contribute to the overall research effort towards nanofluids engineering and characterization. To accomplish the latter, multiwalled carbon nanotubes (MWCNTs) are added to an ethylene glycol (EG) based fluid. Different aspects concerning the nanofluids preparation and its thermal characterization will be addressed. The study considers and exploits the relative influence of CNTs concentration on EG based fluids, on the suspension effective thermal conductivity and viscosity. In order to guarantee a high-quality dispersion it was performed a chemical treatment on the MWCNTs followed by ultrasonication mixing. Furthermore, the ultrasonication mixing-time is optimized through the UV-vis spectrophotometer to ensure proper colloidal stability. The thermal conductivity is measured via transient hot-wire within a specified temperature range. Viscosity is assessed through a controlled stress rheometer. The results obtained clearly indicate an enhancement in thermal conductivity consistent with carbon nanotube loading. The same trend is observed for the viscosity, which decreases with temperature rise and its effect is nullified at higher shear rates.