Papers by Author: Tolou Shokuhfar

Abstract: Aluminum-titanate (tialite) based ceramics have found widespread applications due to their good thermal shock resistance and low thermal expansion. Tialite is presently used in automotive industry, thermal processing technology, metallurgy and glass industry. Eutectoid decomposition in to the initial oxides and low mechanical strength limit the well-known properties of aluminum-titanate. In the present work, good stabilizing behavior was achieved by addition of talc in micron size and appropriates properties were obtained by adding nano boehmite and colloidal silica that results mullite phase formation. The effect of mullite phase in the densification of tialite has been studied. XRD, DTA and SEM have been used to characterize the influence of these additives on phase transformation, sintering process and microstructure.

Abstract: In this research work, a high-energy ball mill has been applied to prepare an Al/SiC nanocomposite. The formation mechanism of the nanocomposite was investigated. This nanocomposite contained the nanocrystalline characteristics. Crystallite size, lattice strain and particle size of the nanocomposite as a function of milling time were determined. SEM micrographs showed that the nanocomposite powders agglomerated after milling. The particle size analysis confirmed the agglomeration of the nanocomposite particles. TEM observations showed that the SiC particles were in the nanometer size and these particles embedded in the Al matrix, and the nanocomposite produced in the final stage of mechanical alloying. In addition, a simple model checked for the refinement of the crystallite and the particle size of nanocomposite.

Abstract: Monodispersed nanometer-sized particles proved to be very important and advantageous in many industrial applications. One of the notable groups of these particles is silica (SiO2) nanoparticles which are widely utilized in developing numerous products such as electrical and thermal insulators, humidity sensors, varnish, etc. Since the quality of some of these products depends highly on the purity and size distribution of the silica particles, it is necessary to produce silica nanoparticles of narrow size distribution and very high purity. In this research silica nanoparticles, with a relatively narrow size distribution, have been synthesized via the hydrolysis reaction of tetraethoxisilane (TEOS) in the solution of deionized water and ethanol (C2H5OH), and in the presence of ammonia (NH3) as a catalyst. The nature, morphology and the size of the silica particles has been studied using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray diffraction. Results indicate that the morphology, structure and the diameter of silica particles depend strongly on the molar ratios of the reactants.