Sharif Digital Repository

In this paper, a new single cone-cap plasticity with an isotropic hardening rule is presented for powder materials. A general form is developed for the cap plasticity, which can be compared with some common double-surface plasticity models proposed for powders in literature. The constitutive elasto-plastic matrix and its components are derived based on the definition of yield surface, hardening parameter and nonlinear elastic behavior, as a function of relative density of powder. Different aspects of the model are illustrated and the procedure for determination of powder parameters is described. Finally, the applicability of the proposed model is demonstrated in numerical simulation of... 

We report a simple, inexpensive and one-step synthesis route of colloidal gold nanoparticles using arc discharge between titanium electrodes in HAuCl 4 solution achieving long-time stability. Gold nanoparticles of 8 nm diameter were formed during reduction of HAuCl4 in the plasma discharge zone. The resulting nanoparticles were characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Optical absorption spectroscopy of as prepared samples at 15 A arc current in HAuCl4 solution shows a surface plasmon resonance around 550 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal...