Fatih Sevim

Kinetic analysis of thermal decomposition of boric acid from thermogravimetric data

The kinetic parameters of the thermal decomposition of boric acid have been investigated by using TGA data. Suzuki and Coats-Redfern methods have been applied for the kinetic investigation. It was determined that decomposition kinetics of boric acid occurred in two steps and both regions suitably fit a first-order kinetic model. According to Coats-Redfern method, the activation energy and frequency factor were found as 79.85 kJ·mol-1 and 3.82x 104 min-1 for region I and 4.79 kJ·mol-1 and 4.045 x 10-5 min-1 for region II, respectively. The activation energies and frequency factors were found as 4.45 kJ·mol-1 and 4.08 x108 min-1 for the Suzuki method.

A kinetic study of the cementation of copper from sulphate solutions onto a rotating aluminum disc

Abstract The cementation kinetics of copper deposition from sulphate solutions onto aluminum was studied using a rotating disc electrode system. The effect of temperature, Cu++ ion concentration, rotational speed of the aluminum disc and pH was investigated. The activation energy was found to be 14.1 kJ mol−1, confirming that the rate of reaction was controlled by diffusion.

Calcination Kinetic of Magnesite from Thermogravimetric Data

The kinetic parameters of the thermal decomposition of magnesite were investigated using TGA data. For the kinetic analysis, the Coats–Redfern and Suzuki methods were separately applied. It was observed that the process fitted a first-order kinetic model and the values of the activation energies decreased with decreasing particle size, which can be attributed to the increasing particle internal resistance to the escape of CO 2 as the grain size increased. According to Coats–Redfern and Suzuki methods, the activation energy values, respectively, for the range of were found to be 236.25-278.37 and 255.52–302.21 kJ mol −1 respectively, for the range of particle size fraction used.

Flash calcination of a magnesite ore in a free-fall reactor and leaching of magnesia

Abstract Flash calcination of a magnesite ore in a free-fall reactor and leaching of calcined magnesite with aqueous carbon dioxide were investigated. The effect of temperature and particle size on the weight loss were observed in the calcination experiments. The maximum weight loss was obtained as 43.2% for the particles of −100 + 140 mesh at the calcination temperature of 850°C. In leaching experiments; leaching temperature and time, particle size, stirring speed, and solid/liquid ratio were selected as variables. The dissolution fraction of magnesium increases with the increase in the leaching time, temperature and to a lesser degree stirring speed. The dissolution also increases with decreasing solid/liquid ratio and particle size. A thermal gravimetric method was used to measure activation energy, preexponential factor and rate constants for the thermal decompositon of the magnesite ore. The activation energy and preexponential factor were calculated as 39.4 kcal mol−1 and 3.5×106 s−1, respectively. The rate constants were found to vary between 1.2×104 and 1.3×10−2 s−1 in the temperature range of 823 to 1023 K.

Synthesis and Characterization of Nanofibres of 2ZnO·3B2O3·5H2O Ceramic Composite Using the Sol-Gel Processing and the Electrospinning Techniques

2ZnO.3B2O3.nH2O (Zinc borate) having the industrially important composite and used as flame retardant, anti-smoke and semiconductor in the electronic circuits was examined different crystal structures. In this study, nanofibers of PVA /zinc nitrate/ boric acid composite were prepared by using sol-gel processing and electrospinning technique. By high temperature calcinations of the above precursor fibers, nanofibers of 2ZnO.3B2O3.5H2O composite with diameters of 110 nm could be successfully obtained. The products have been characterized by X-ray powder diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), scanning electron microscopy (SEM) and FT-IR (Fourier transform-infrared spectroscopy). The effects of experimental conditions on the products were investigated.