Effect of Rare Earth Upon As-Cast Microstructure and High Temperature Performance of ZA40 Alloy
In testing comparison, this study is made on the modification effect of 0.05 wt.% La-rich rare earth (RE) upon as-cast microstructure, mechanical properties of materials at high temperatures (100, 150, 200°C) and wear resistance under different temperatures (100and 200°C) of ZA40 alloy containing Si. The addition of RE shows that it can not only effectively refine Al-rich and Cu-rich phase, but also reduce the amount of needle-like eutectic silicon, and then make the size of massive primary silicon phase smaller. Thus, there are the improvement of strength, ductility and wear resistance of materials at high temperature. The analyses are also conducted on the mechanism of underlying RE elements.
Effects of stabilizing heat treatment on microstructures and creep behavior of Zn–10Al–2Cu–0.02Ti alloy
Abstract The microstructures of as-extruded and stabilizing heat-treated Zn–10Al–2Cu–0.02Ti alloys were observed by scanning electron microscopy, transmission electron microscopy, electron probe microanalysis and X-ray diffraction analysis techniques. The change in structure after heat treatment and its effects on room temperature creep behavior were investigated by creep experiments at constant stress and slow strain rate tensile tests. The results show that after stabilizing heat treatment ((350 °C, 30 min, water-cooling)+(100 °C, 12 h, air-cooling)), the amount of α+η lamellar structure decreases, while the amount of cellular and granular structure increases. The heat-treated Zn–10Al–2Cu–0.02Ti alloy exhibits better creep resistance than the as-extruded alloy, and the rate of steady state creep decreases by 96.9% after stabilizing heat treatment.
Improved Skin Penetration Using In Situ Nanoparticulate Diclofenac Diethylamine in Hydrogel Systems: In Vitro and In Vivo Studies
Delivering diclofenac diethylamine transdermally by means of a hydrogel is an approach to reduce or avoid systemic toxicity of the drug while providing local action for a prolonged period. In the present investigation, a process was developed to produce nanosize particles (about 10 nm) of diclofenac diethylamine in situ during the development of hydrogel, using simple mixing technique. Hydrogel was developed with polyvinyl alcohol (PVA) (5.8% w/w) and carbopol 71G (1.5% w/w). The formulations were evaluated on the basis of field emission scanning electron microscopy, texture analysis, and the assessment of various physiochemical properties. Viscosity (163–165 cps for hydrogel containing microsize drug particles and 171–173 cps for hydrogel containing nanosize drug particles, respectively) and swelling index (varied between 0.62 and 0.68) data favor the hydrogels for satisfactory topical applications. The measured hardness of the different hydrogels was uniform indicating a uniform spreadability. Data of in vitro skin (cadaver) permeation for 10 h showed that the enhancement ratios of the flux of the formulation containing nanosize drug (without the permeation enhancer) were 9.72 and 1.30 compared to the formulation containing microsized drug and the marketed formulations, respectively. In vivo plasma level of the drug increased predominantly for the hydrogel containing nanosize drug-clusters. The study depicts a simple technique for preparing hydrogel containing nanosize diclofenac diethylamine particles in situ, which can be commercially viable. The study also shows the advantage of the experimental transdermal hydrogel with nanosize drug particles over the hydrogel with microsize drug particles.