In this study, the metastable zone width of potassium tetraborate tetrahydrate was determined for four different temperatures and cooling rates. The induction period of potassium tetraborate tetrahydrate in aqueous solution was examined according to polythermal method by using visual observation. The induction period, which changes inversely proportional to the nucleation rate has been used to determine the interfacial tension between the potassium tetraborate tetrahydrate and aqueous solution. By using interfacial tension, the nucleation parameters such as Gibbs free energy change for the formation of critical nucleus, ∆G*, free energy of formation, ∆G, radius of critical nucleus, r and number of molecules in the critical nucleus, i* has been calculated. The effect of Li + and Ca 2+ impurities on metastable zone width has been studied. The metastable zone width of aqueous solution of potassium tetraborate tetrahydrate decreases with increasing impurity concentrations. The equilibrium saturation concentration change is high in the presence of Ca 2+ ions while it is low in the presence of Li + ions.

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SUMMARYSodium borohydride (NaBH 4 ) reacts with water to produce 4 mol of hydrogen per mol of compound at room temperature. Under certain conditions, it was found that 6 mol of hydrogen per mol of sodium borohydride was produced in the presence of electrical field created by DC voltages, whereas 4 mol of hydrogen was produced in the presence of catalyst per mole of sodium borohydride. Electrical field created by alternative current with three different waves (sin, square and triangle type) increases the hydrolysis of sodium borohydride. It was found that hydrogen produced from sodium borohydride by applying an electrical field can be effectively used for both increasing the electrolysis of water and hydrolysis of sodium borohydride. The hydrolysis reaction was carried out at temperature of 20, 30, 40 and 601C in the presence of electrical field created by AC voltages square wave. The experimental data were fitted to the kinetic models of zero-order, first-order and nth-order. The results indicate that the first-order and nth-order model give a reasonable description of the hydrogen generation rate at the temperature higher than 301C. Reaction rate constant at different temperatures were determined from experimental data, and activation energy was found to be 50.20 and 52.28 kJ mol À1for first-order and nth-order, respectively.

3-dodecylthiophene (3-dth) was electropolymerized onto platinum wire (Pt) in acetonitrile (ACN) containing different percentages of boron trifluoride diethyl etherate (BFEE) by using cyclic voltammetry (CV). The oxidation potential of the monomer was decreased by adding BFEE in ACN. The monomer was oxidized in pure BFEE at 0.78 V. The thickness of the film was reached to maximum value for 40% BFEE. Electrochemical impedance spectroscopy (EIS) measurements and Equivalent Circuit Modeling (ECM) were performed on the Pt/Poly (3-dth)/electrolyte system. The specific capacitance (C sp ) value increased while the charge transfer resistance (R ct ) value decreased with the increasing of concentration of BFEE. R ct value was 62.68 cm 2 for 100% BFEE. The highest C sp , 0.007 μFcm −2 , and double layer capacitances (C dl ), 269 μFcm −2 , were obtained for the film obtained in 100% BFEE. The inclusion of BFEE in the polymer structure was confirmed by Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR). Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to investigate the polymer film deposited onto substrate in terms of morphology. The pore resistance (R p ) value was decreased with increasing the concentration of BFEE. As result of this the roughness of the polymer surface was decreased due to the decreasing of porous structure.