JOURNAL OF ADVANCED MATERIALS AND TECHNOLOGIES
Year:2018 | Volume:7 | Issue:2 |Papers Count:7

Substitution of Mg2 + in ferrite nanoparticles improves properties such as chemical stability, corrosion resistance, magnetic anisotropy, and optical-magnetic properties. In this study Co-Mg-Ferrite single phase is synthesized using mechanical alloying as a simple and inexpensive method. XRD and SEM were used for characterizing the samples. Shape of powder particles after milling was irregular and their size was was in the range of 5-48 nm. XRD results revealed that after 30 hours of milling and sintering at temperatures above 700oC, single phase Co-Mg-ferrite is produced. Grain size of the sintered products is 33 to 85 nm and the lattice strain is 0. 88 to 0. 75%. Increasing the sintering temperature from 700º C to 1100º C resulted in improved magnetic properties. Magnetic permeability increased with increasing sintering temperature due to structural changes. Paramagnetic properties in samples sintered below 1000º C are dominant while sintering at 1100º C produced a strong ferromagnetic state giving a well-formed sigmoid-shape hysteresis loop.

In this work, commercial pure aluminum was subjected to friction stir processing (FSP) up to six passes, then, mechanical properties, electrical conductivity, and microstructure analysis of the processed samples were compared with the initial condition. Better yield strength, ultimate tensile strength, and hardness are achieved after imposing the process. Also, strengthening rate is reduced at the subsequent passes. It was found that hardness magnitude is decreased mildly by getting away from the center. Although material formability is reduced after the first pass, it is grown a little by adding the pass number. The microstructure analysis indicated that application of one pass FSP changes considerably grain size of the annealed aluminum and leads to extreme decrease of the high-angle grain boundaries density which plays the main role in the reduction of electrical conductivity. Addition of FSP pass number leads to increment of dislocations density, transformation of low-angle to high-angle grain boundaries, and the further intersection of shear micro bands, causing improvement of sample formability and electrical conductivity compared to the first pass. Therefore, this process has the capability for fabrication of pure aluminum with improved mechanical properties and acceptable electrical conductivity.

The aim of this research is to synthesize and study the microstructure and mechanical properties of biodegradable Mg-Zn scaffolds for orthopedic applications. For this purpose, Mg-Zn scaffolds containing 3 and 5 wt. % Zn were prepared using 15, 25 and 35 Vol% of urea by powder metallurgy and were subjected to heat treatment at different temperatures of 500, 550, 565, and 580 ° C to determine the optimum sintering temperature. Then, the chemical composition, microstructure and mechanical properties of the scaffolds were investigated. According to the results, the average diameter of macro-pores and micro-pores in the scaffolds are about 400-200 and less than 100 μ m, respectively. The results showed that the compressive strength of Mg-Zn scaffolds increases with decreasing porosity amount. In fact, the porosity in the sample reduces the mechanical strength of the scaffold due to the stress concentrating areas and the reduction of the effective surface of scaffold against external stresses. Also, by increasing the Zn content, the strength of the Mg-Zn scaffold increases through the strength of the solid solution and dispersion strengthening. However, in all of the made scaffolds, the compressive strength is in the range of compressive strength of the human body's bone. The results of the SEM micrographs also showed that, by adding Zn, the intermetallic compounds Mg7Zn3 and MgZn could be formed. The results of polarization test showed that, by adding 5 wt. % of Zn in comparison with samples containing 3 wt%, due to the formation of more intermetallic compounds, the corrosion resistance decreased. According to the results of cytotoxicity measurement, the cell viability of scaffolds containing 3 wt% Zn was higher than those containing 5 wt% Zn.

Improvement of the corrosion resistance capability by the electropolishing (EP) is one of the most importance process surface modification. In this paper, the effects of two variables perchloric acid concentration and bath temperature on the electropolishing process and the corrosion resistance performance of the Inconel 718 alloy were studied. Evaluation of microstructure and surface roughness quality before and after electropolishing process by the scanning electron microscopy (SEM) and surface roughness test were used, respectively. In order to determine voltage range and current electropolishing to I-V curves were used. The results showed that, obtain to uniform surface and without pores can be achieved only under the conditions has the electrolyte composition as 10 vol% H2O-70 vol% CH3COOH-20 vol% HClO4 and bath temperature is 15 ° C. Electropolishing rate in the above conditions at the grain boundaries and inside the grains came close together and lead to a smooth and uniform surfaces. The minimum surface roughness after electropolishing on the above condition amount 0. 026 μ m obtained. The results of the TOEFL polarization test in a solution of 0. 5M H2SO4 + 0. 01M KSCN indicated, electropolishing Inconel 718 alloy reduces the corrosion current density and become more Noble in potential (Ecorr). Electropolished samples under optimized conditions has exhibited the highest resistance to corrosion. The reason improving in the corrosion resistance Inconel 718 alloy by electropolishing that was attributed to the formation of very uniform oxide layer on surface and microstructure free of cavities.

bioactive glasses are widely employed in repair and treatment of bone defects and also as an appropriate replacement for the ossicles in middle ear owing to their bonding ability to hard and soft tissues. In this research, the molecular dynamics package (GROMACS) was used to study the structure of bioactive glass synthesized by sol-gel method. To create related hydroxyl groups, the bioactive glass system was modeled. Then, a thermal cycle at temperature of 298-923 K with a constant rate was applied to the studied system and several parameters such as the internal structure, penetration coefficient, density and molecular weight, number of hydrogen bonding, bond length and bond angles were evaluated. Finally, the radial distribution functions were analyzed to study the structure of the bioactive glass, and the effect of the synthesis method on the bioactive glasses was also determined. The evaluation of the molecules density and simulation results of the bond angles and lengths indicated that materials are tend to be placed in the optimal condition and sustainable system. Due to the higher molecular weight of P2O5 and its lesser movement throughout the box, SiO2 and CaO species played more important role in the uniform distribution of materials through the system. By determining the diffusion coefficient and molecules distribution via radial distribution function method in the simulation box, it was concluded that the system components had a fairly uniform distribution and there was an acceptable and logical distance between atoms in almost every molecule.

The aim of this research is to synthesize and study on a nanoemulsion bio-organic pesticide for higher efficiency and reducing chemical pesticide use. In this research, Persian Cumin essential oil were used, which can be applied as bio-organic pesticide and they are biocompatible, harmless to human beings and also animals; do not cause environmental pollution and agricultural products. Then various parameters of surfactant concentration, essential oil percentage, and sonication time were studied in order to prepare nanoemulsion systems. In order to study on physical stability of different nanoemulsion formulations, optical clarity, viscosity, pH and conductivity were measured. The size and morphology of nanoemulsion formulations were then analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The results showed that the nanoemulsions in concentration ranges of 1 to 5 % were stable (study during 14 months) and the mean droplets size of synthesized nanoemulsios was about 15 nm. Pesticide experiments showed that contact toxicity LC50 of synthesized nanoemulsion against Aphis gossypii was obtained 3461. 91 ppm, which demonstrated a significant increase in pesticide activity with increasing essential oil concentration.

In this research, synthesis and evaluation of aluminium nitrate on the conductivity of hydrogel nanocomposite had been studied using acrylic acid monomer and single-walled carbon nanotubes. For this purpose, the water-based acrylic acid-based monomer was synthesized with optimal amounts to achieve a high-water absorption capacity of a hydrogel. The polymerization reaction was carried out in an aqueous medium by ammonium persulfate as initiator and methylene bisacrylamide as cross-linker. The hypothetical mechanism proposed for the formation of the hydrogel and its structure was confirmed by SEM and FTIR instruments. Then water absorption and swelling behavior in buffer solutions were examined. The results show that the synthesized hydrogels in water absorption capacity and conductance and electrical conductivity of single-walled carbon nanotube has increased by the addition of aluminium nitrate and sodium phosphate, conductivity is improved and 19. 60m/S. the next step, the swelling rate of the hydrogel was investigated in buffer solutions of 4 and 9 that in the basic medium was 0. 921 /g.