F. Hosseinabadi, S. M. Zebarjad, M. Mazinani, V. Kiani, H. R. Pourreza,
Volume 30, Issue 2 (Dec 2011)
Abstract
In this article, the role of nano-size calcium carbonate in penetration resistance of medium- density polyethylene (PE) was investigated through experiments. In order to study the penetration resistance of PE and its nanocomposites, perforation test was carried out. The results of tests showed that penetration resistance depends strongly on calcium carbonate amount. As a matter of fact, addition of CaCO3 to PE increases resistance against penetration as CaCO3 amount reaches to 5 percent of weight. Stereomicroscope was used to evaluate the damage and plastic zone around the perforated area in all the samples including neat polyethylene and its nanocomposites. The plastic zone was measured using an image analysis as an effective technique. The results of image analysis techniques proved that the addition of calcium carbonate to PE makes a damaged zone around the perforated area. The results of microscopic evaluations showed that the area of plastic zone rises as the amount of calcium carbonate increases up to 7.5 percent of weight. By increasing the amount of CaCO3, resistance against penetration decreases more and some micro cracks appear around the perforated area. For further clarification of the fracture mechanism of MDPE nanocomposites, scanning electron microscopy was employed. Fracture surface images showed that when calcium carbonate is higher than 5 percent of weight, agglomeration of nanoparticles occurs, resulting in lower resistance against penetration to the samples.
H. Hadian, M. Haddad Sabzevar , M. Mazinani,
Volume 39, Issue 4 (Journal of Advanced Materials-Winter 2021)
Abstract
In this research, effect of swarf addition on the microstructure of die cast aluminum A380 alloy and the possibility of altering the alloy structure in the metallic die has been studied. The microstructure mainly consists of the α-phase, eutectic, intermetallic compounds and porosity. Since the alloy solidifies under non-equilibrium conditions, the Scheil equation with exact amount of equilibrium distribution, analyzed by SEM-Line scan around an intermetallic phase at different mixing times as well as governing equations of thermal analysis, was used to calculate the solid weight fraction. Finally, using the thermal flux analysis in the crucible, a scientific prediction on the optimal amount of swarf addition, mixing time and temperature, was made. The shape factor at an optimum temperature of 590 °C was measured as 0.643. According to the optical microscope images of the die cast samples, the addition method (adding it to the floor or to the surface) and increasing the injection temperature have a significant effect on the solid weight fraction, morphology of the α-phases and final microstructure of the alloy.
