E. Ganjeh, H. Khorsand,
Volume 31, Issue 1 (Jun 2012)
Abstract
The fracture surfaces of PM Cr-Mo steels intensively depends on pores structure, densification, diffusion of alloying elements, contact area between particles (sinter necks), microstructural homogeneity, and type of applied load. Also, knowing about element distribution in PM parts to evaluate what places are good for crack growth, nucleation and coalescenc is important. In this investigation, fracture surfaces and crack growth mechanism for element distribution environments of cracks were studied under the three point bending (TPB) test. In this work, crack growth mechanism in Cr-Mo PM parts with three different densities (6.7, 7 and 7.2 g/cm3), were evaluated accurately. Crack walk occurred in some places that had more alloying elements, particularity molybdenum. In addition, crack route was obtained from among the sharpened porosities and martensite/bainite structures.
S. Khorsand, K. Raeissi, F. Ashrafizadeh,
Volume 34, Issue 4 (Journal of Advanced Materials-winter 2016)
Abstract
Super-hydrophobic nickel and nickel-cobalt alloy coatings with micro-nano structure were successfully electrodeposited on copper substrates with one and two steps electrodeposition. Surface morphology, wettability and corrosion
resistance were characterized by scanning electron microscopy, water contact angle measurements, electrochemical impedanc spectroscopy (EIS) and potentiodynamic polarization curves. The results showed that the wettability of the micro-nano Ni and Ni-Co films varied from super-hydrophilicity to super-hydrophobicity by exposure of the surface to air at room temperature. The corrosion results revealed the positive effect of hydrophobicity on corrosion resistance of Ni coating (~10 times) and Ni-Co coating (~100 times) in comparison with their fresh coatings. The results showed that super-hydrophobic nickel coating had higher corrosion resistance than super-hydrophobic nickel-cobalt coating.
M. Ghorbani, H. Khorsand,
Volume 40, Issue 2 (Journal of Advanced Materials-Summer 2021)
Abstract
Strontium hexaferrite M-type nanoparticles doped with La and Cu (SrFe12-xCuxO19-Sr1-xLaxFe12-xCuxO19) with different mole fractions (x=0.1-0.2-0.3-0.4-0.5) synthesized by self-combustion sol-gel technique. Firstly, a gel of metal nitrates with the above-mentioned mole fractions were fabricated and the obtained powder was cured at 950°C. Microstructural properties and the morphology of the compounds were investigated by employing X-ray diffraction (XRD) and scanning electron microscopy (SEM). Also, in order to investigate the magnetic properties, Vibrating Sample Magnetometer (VSM) was used. SEM images revealed that the particles had an average size of about 100 nm. Cu2+ ions were substituted with Fe3+ ions within the crystalline sites of SrFe12O19 structure. It was shown that the lattice parameter (a) remained approximately unchanged with an increase in Cu-dopped while the lattice parameter (c) decreased with increasing the mole fraction (x). By using VSM hysteresis diagrams, it was observed that the saturated magnetization and coercive force increased with the addition of La; this was attributed to the variation in the distribution of ions and the shape anisotropy of the nanoparticles. These significant changes in the magnetic properties were for the sample with the composition of Sr1-xLaxFe12-xCuxO19 and SrFe12-xCuxO19, for the x=0.1 and x=0.5, respectively.
