Majid Jafari

A Novel Method for In Situ Synthesis of Nanostructure Hydroxyapatite–nylon 66 Composites in Tissue Engineering

An interfacial polymerization method for nylon 66 was adapted to produce nanostructured composites with nanohydroxyapatite (n-HA) via in situ polymerization. Nylon 66 was synthesized in n-HA slurry to increase homogeneity and biocompatibility. Synthesis powders was characterized by XRD, TEM, TGA, and FT-IR analysis. The results showed a uniform dispersion in composites, whereas needle-like, n-HA crystals dispersed in condensed polymer matrix. The samples were immersed in SBF for bioactivity tests in different periods, and results were monitored by SEM and EDX in terms of forming an apatite layer. The mechanical properties of the n-HA/nylon66 nanocomposites are discussed in terms of n-HA loading.

Investigating the Physical Properties of Sintered Alumina in the Presence of MgO Nanopowder

Magnesium oxide nanopowder is synthesized using magnesium nitrate hexahydrate and oxalic acid as precursors via the sol-gel method. In order to investigate the effect of magnesia nanopowders on the physical properties of sintered alumina, 0.1, 0.3, and 0.5 wt% of MgO are added to alumina. The prepared specimens were sintered at 1570°C for 4 hours under an inert atmosphere. The morphology and size of nanopowders were characterized by transmission electron microscope (TEM) and scanning electron microscope (SEM). Structural analysis was investigated by means of Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Outcomes show that by increasing the percentage of MgO, spinel phase (MgAl2O4) has been formed in the structure of alumina. During the sintering process, spinel phase diffused through the grain boundaries and pinned the grain boundaries which led to decrease in grain sizes. So, by decreasing the grain size, the physical properties of sintered alumina have improved.

Combination of Mechanical Activation and Silicothermal Reduction and Nitridation Process to Form X-Sialon by Using Andalusite Precursor

X-sialon formation by the combination of mechanical activation and silicothermal reduction and nitridation (SRN) process was investigated. The starting materials (andalusite, Si and alumina) were activated in a planetary mill and two kinds of milling cups and balls were utilized. Samples were characterized by XRD, SEM and DSC. Milling with steel equipment inhibited nitridation. This could be related to the formation of FeSi. Sialon formation proceeded when the milling was performed with a Teflon cup and alumina.

Synthesis and characterisation of NiWO4 nanopowders via simple molten salt route

Abstract A molten salt method employing NiCl2.2H2O and Na2WO4.2H2O as raw materials has been introduced to synthesise NiWO4 nanopowders. LiCl–KCl eutectic with a melting point of 353 °C was employed as the salt media. The displacement reaction (NiCl2.2H2O + Na2WO4.2H2O → NiWO4 + 2NaCl + 2H2O) occurred in the molten salt media during the synthesis. Characterisation of the as-synthesised powder was carried out using of X-ray diffraction, FTIR spectroscopy, Brunner–Emmett–Teller, transition electron microscopy (TEM) and photoluminescence. The results showed that temperature had a strong effect on the crystallite size of the synthesised nanopowders. TEM micrographs illustrated that the nanoparticles synthesised at 500 °C were mostly angular in shape with a grain size of <30 nm. The average activation energy (about 21.51 kJ/mol) of crystallite growth during synthesis indicated that crystallite growth during the synthesis occurred by means of an interfacial reaction.

Synthesis and Microstructural Characterization of Al2O3-SiO2-ZnO Composite

The present work deals with the preparation and characterization of Al2O3-SiO2-ZnO composite under mid-temperature conditions via sol-gel method. The structural features of all the samples were assessed by X-ray diffraction (XRD), specific surface area (BET), and scanning electron microscopy (SEM). The changes in the morphology and particle size of the as prepared composites were investigated. Al2O3-SiO2-ZnO composites with different amount of ZnO were prepared. The effect of temperature on the crystallization of Al2O3-SiO2-ZnO composites containing 70% ZnO was investigated. When the calcinations temperature increases up to 850°C, broad peaks of ZnAl2O4 with some impurities of Zn2SiO4 was appeared. From SEM images it was revealed that Naiad structure is formed when the calcinations temperature is 500°C.

Phase Analysis and Study of the Microstructure of Cordierite-Si3N4 Composite Synthesis by Nano- and Micro-Sized Silicon Particles

In this study the effect of in situ Si3N4 formation on the microstructure changes of cordierite-Si3N4 composite prepared using nano silicon powders, which obtained in a high energy planetary ball mill, and micro silicon powder was investigated. Different mixtures of the cordierite with nano and micro silicon powders were prepared and sintered in a tube furnace at different temperatures in a nitrogen atmosphere. Microstructural characteristics, thermal properties and phase analysis of these composites were carried out by using scanning electron microscopy (SEM), simultaneous thermal analysis (STA) and X-ray diffraction analysis (XRD). It was found that micro and nano silicon particles have different reaction characterizations with the nitrogen in the matrix of cordierite at various temperatures. Results showed that by using nano silicon powder the formation of silicon nitride bonding will be increased which could be related to the acceleration of nitride phase at temperatures lower than the temperature of liquid phase formation.