Synthesis and dielectric relaxation behavior of 55B2O3–15SiO2– 30Na2O: WO3 glass system

55 B₂O₃ – 15 SiO₂ – 30 Na₂O: x WO₃, (x ranging from 0 to 5 wt%) glass composites were prepared according to the melt-quenching procedure. The prepared samples were characterized via X-ray diffraction and broad band dielectric spectroscopy (viz., dielectric constant (ε₁), tanδ and AC conductivity (σ_AC) over a wide range of frequency and temperature). No sharp peaks were shown in the XRD pattern and is evidence of the amorphous nature of the samples. It turns out that the values of ε₁ and ε₂ are increasing at higher temperatures particularly at lower frequencies. The energy barrier height, W_M values decreased as 0.27, 0.25 and 0.22 while showed value of 0.29 eV for 5.0 wt% WO₃. In the dielectric modulus plots, two relaxation processes are found especially on the higher temperature side. It also shifted a higher frequency with increasing temperature. The values of exponent s have been found to lie between 0.48 and 0.74, which confirms that the conduction mechanism in the glass samples follows the correlated barrier hopping model. By calculating the activation energy associated with the relaxation processes and DC conductivity, it was found that the values are close, which indicates that the same charges contribute to the two processes.     

Effect of Ultrasound on the Production Reaction Kinetics of Sodium Thiosulfate

It is known that the production reaction of sodium thiosulfate which consists of the reaction of Na₂SO₃ with sulfur is considerably slow. Ultrasound energy was used to increase the conversion fraction of sulfur and to accelerate the production reaction of Na₂S₂O₃, and the effect of ultrasonic energy on the reaction kinetics was investigated. The particle size, reaction temperature, concentration of Na₂SO₃ solution and amplitude of ultrasound power were chosen as parameters. The experiments were performed in the absence and presence of ultrasound. Considering the results the reaction is chemically controlled first order and the activation energy is equal to 42 kJ/mol in both cases. The results indicated that the ultrasound energy increased the reaction speed but it did not vary the activation energy. The effect of ultrasound is on the pre‐exponential factor A. Finally, an empirical relation is given which relates the rate constant to ultrasound power.     

Increasing the conversion fraction of sulfur to sodium thiosulfate with the ultrasound energy

The usage of ultrasound has gained popularity in the recent years. Ultrasonic processing means blasting liquids, usually water, with very intense sound at high frequency, producing very well mixed powerful chemical and physical reactions. This paper deals with the investigation of the effect of ultrasonic energy on the conversion fraction of sulfur in the production reaction of sodium thiosulfate which was obtained from sulfur and Na₂SO₃ solution. Concentration of Na₂SO₃ solution parameter was chosen as the constant parameter. The experiments were performed with various amplitudes of ultrasound power and in the absence and presence of ultrasound energy in various temperatures with various particle sizes. The results indicate that the conversion fraction values increase in the presence of ultrasound energy and increase at high amplitude values.     

Adsorption of cationic polyacrylamide onto sepiolite

The adsorption of PAM onto sepiolite from aqueous solutions has been investigated systematically as a function of some parameters such as calcination temperature of sepiolite, pH, ionic strength and temperature. The adsorption of cationic polyacrylamide (PAM) increases with pH from 5.50 to 11.00, temperature from 25 to 55 degrees C and ionic strength from 0 to 0.1molL(-1). The sepiolite sample calcined at 200 degrees C has a higher adsorption capacity than the other calcined samples. Adsorption isotherms of PAM onto sepiolite have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The physical properties of this adsorbent are consistent with the parameters obtained from the isotherm equations. The zeta potentials of sepiolite suspensions have been measured in aqueous solutions of NaCl and different PAM concentrations and pH. From the experimental results: (i) pH strongly alters the zeta potential of sepiolite, (ii) sepiolite has an isoelectric point at about pH 6.6 in water and about pH 8 in 250mgL(-1) PAM concentration, (iii) PAM changes the interface charge from negative to positive for sepiolite. Effect of temperature on adsorption has been quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy. The dimensionless separation factor (R(L)) has shown that sepiolite can be used for adsorption of PAM from aqueous solutions.     

An evaluation of the alternative transport fuel policies for Turkey

The search for alternative fuels and new fuel resources is a top priority for Turkey, as is the case in the majority of countries throughout the world. The fuel policies pursued by governmental or civil authorities are of key importance in the success of alternative fuel use, especially for widespread and efficient use. Following the 1973 petroleum crisis, many users in Turkey, especially in transportation sector, searched for alternative fuels and forms of transportation. Gasoline engines were replaced with diesel engines between the mid-1970s and mid-1980s. In addition, natural gas was introduced to the Turkish market for heating in the early 1990s. Liquid petroleum gas was put into use in the mid-1990s, and bio-diesel was introduced into the market for transportation in 2003. However, after long periods of indifference governmental action, guidance and fuel policies were so weak that they did not make sense. Entrepreneurs and users experienced great economical losses and lost confidence in future attempts to search for other possible alternatives. In the present study, we will look at the history of alternative fuel use in the recent past and investigate the alternative engine fuel potential of Turkey, as well as introduce possible future policies based on experience.     

Wear and friction behavior of metal impregnated microporous carbon composites

Metal-matrix composites have been prepared by pressure-infiltration casting of copper-base alloy melts into microporous carbon preforms. The carbon preforms contained varying proportions of amorphous carbon and graphite. Load dependence of the wear and friction behavior of the composite pins has been examined under ambient conditions against cast-iron plates, using a pin-on-plate reciprocating wear tester. The wear resistance of the composite is significantly improved, as compared with the base alloy. Contrary to the normally expected behavior, the addition of graphite to the amorphous carbon does not reduce the friction coefficient, especially at high loads. The wear and friction behavior of the composites is very sensitive to the size and distribution of the microstructural constituents.