Showing 3 results for Physical Properties
S. A. Hosseini, G. Afkhami, A. Tabibi and A. Sadeghi,
Volume 23, Issue 1 (7-2004)
Abstract
Physical properties of cotton yarns are affected by the characteristics of cotton fibers such as fineness, length, maturity and strength. This relationship has been worked out by means of multivariable regression and stepwise method for an open-end spun (NeC 20) cotton yarn. Moreover, with the help of linear programming, it was made possible to determine the percentage of different cottons in the blend with the aim of reducing the yarn price to a minimum while keeping the yarn quality to a certain level.
A. Amiri Moghaddam, M. Kalantar,
Volume 36, Issue 1 (6-2017)
Abstract
The aim of this investigation is obtaining WC-Co composite powder from WO3 and Co3O4 by in-situ and carbothermic reduction method using activated carbon as a reducing agent. In this study, cobalt and tungsten oxide powders with 17% carbon (30% more than stoichiometric value) were mixed by ball-milling under atmosphere of argon for 20 hours. Differential Thermal Analysis (DTA) and Thermal Gravimetric Analysis (TGA) results on powder mixture show complete reducing of oxides at 1050°C and forming cobalt carbide and tungsten carbide. Compact samples underwent carbothermic reduction at 1050 °C for different times of 1, 2 and 4 hours with protective layer of alumina and carbon powder mixture with ratio of 1:1. Based on X-Ray Diffraction (XRD) analyses, the best holding time in furnace is 4 hours, in which tungsten reduction and carbonization is completed. XRD evaluation of reduced compacted samples in three conditions of atmosphere protective layer of alumina and carbon powder mixture with ratio of 1:1, protective foil of refractory steel and argon, shows that unreduced oxides and extra phases are present in argon atmosphere and protective foil of steel but not in alumina and carbon mixture layer. The measurement results of physical and mechanical properties on the sintered composite sample in heating rate of 5 °C /min to temperature 1500 °C and the holding time of 2 hours under a shielding layer of alumina and carbon shows obtaining the optimal properties (Pr=80%, KIC=8.1 MPa , MHV=15.67GPa) comparable to that of advanced and costly methods.
S. Daneshvar E Asl, S. K. Sadrnezhaad,
Volume 36, Issue 3 (11-2017)
Abstract
TiO2/MWCNT nanocomposite thin films containing different percentages of multi-walled carbon nanotubes were coated on fluorinated tin oxide substrates by sol-gel dip coating method. Results of X-ray diffraction analysis indicated that the crystal structure of the coatings was anatase TiO2. It was also understood that the size of crystallites reduced with CNT but structural properties and equilibrium phase remain intact. Field emission scanning electron microscope images showed that CNTs dispersed uniformly among 45 nm spherical TiO2 particles of close relations. These images also showed that CNT promoted cracks on the coated surface. Results of the UV-Vis spectroscopy showed that the visible light range adsorption increased with CNT and the absorption edge did not significantly differ with the pure TiO2 layers.. Results of the photoluminescence spectroscopy revealed that the presence of CNT could reduce the pair electron–electron holes recombination which is considered totally undesirable.
