Showing 3 results for Tafreshi
M. Sheikhzadeh, K. Matin, M. G. Tafreshi,
Volume 26, Issue 1 (7-2007)
Abstract
The aim of this research is to design a controlling loop that eliminates the irregularities in yarn tension during the winding process. In order to achieve this, we employed a relative feedback industrial control system. The yarn tension sensor measures the tension. Its output is analyzed in the automatic controlling unit. This unit adjusts the tension level according to feedback signals, thus adjusting the yarn tension to the desired value. The yarn package wound using this system will additionally experience the least yarn tension variations.
M. Tafreshi, S. R. Allahkaram, S. Mahdavi,
Volume 37, Issue 3 (Journal of Advanced Materials-Fall 2018)
Abstract
In this research, Zn-Ni and Zn-Ni/PTFE coatings were electrodeposited from sulfate-based electrolytes. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to investigate the corrosion properties of the coatings. Hardness and tribological behavior of the coatings were examined by the Vickers microhardness testing machine and the pin-on-disc method, respectively. Chemical composition and morphology of the as-deposited and worn surfaces of the coatings were studied by a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). According to the results, the corrosion current density of the Zn-Ni film was about 30% of that of the composite coating. Hardness of the alloy film was partially decreased by the incorporation of Polytetrafluoroethylene (PTFE) particles. However, the wear loss and coefficient of friction of the Zn-Ni/PTFE coating were, respectively, about 43% and 57% of those of the Zn-Ni film. Moreover, wear mechanism was changed from plastic deformation and adhesive wear to slight abrasion by the co-deposition of PTFE particles.
S. Solgi, M. Jafar Tafreshi, M. Sasani Qhamsari,
Volume 38, Issue 1 (Journal of Advanced Materials-Spring 2019)
Abstract
The synthesis of calcium tetraborate was investigated in a temperature ranging from 800℃ to 900℃ using the solid-state reaction method. The synthesis was done using ammonium tetraborate tetrahydrate as the source of boron. At temperatures of 800 ℃ and 880 ℃, the mixed phases from different compounds were formed. At the optimum temperature of 840℃, the mixed phase was only composed of meta and tetraborate phases. A 2wt% excess of ammonium tetraborate tetrahydrate led to the calcium tetraborate phase formation. X-ray diffraction analysis (XRD) confirmed the monoclinic structure at the optimum temperature of 840℃ and by 2wt% excess of ammonium tetraborate tetrahydrate. Formation of BO3 and BO4 units composition and morphology of the prepared sample were studied by Field emission scanning electron microscopy (FE-SEM). The stoichiometry of the prepared powders was almost the same as the theoretical amounts, and powder particles exhibited some monoclinic characteristics.
