DETERMINATION OF THE PORE STRUCTURE OF POROUS MATERIALS USING ELECTRICAL CONDUCTANCE

A new method for determining the pore structure of porous materials has been developed. The methodology combines the plastic ice model for solid-liquid phase transitions of pore water with relationships between conductance and temperature, and conductance and pore structure. With these relationships and measurements of the electrical conductance and the corresponding temperature of a saturated porous material subjected to a cycle of capillary freezing and melting, a pore size distribution is obtainable.

Baaed on this methodology a conductometric phase transition poroai-meter was constructed. The pore size distribution of porous Vycor glass was measured using this porosimeter. The modal neck and body radii measured by thia method are 28 and 55 angstroms respectively. These results are comparable to those obtained using other techniques. The modal neck and body radii measured on the same sample by mercury porosimetry are 30 and 85 angstroms and by phase transition porosimetry, 27 and 49 angstroms, respectively.     

Environmental challenges and developmental angst: Mimarlık and the early environmental discourse in Turkish architecture

This paper seeks to examine and contextualise the emergence of environmental thought in Mimarl?k, a Turkish architecture magazine, within the period starting with its inception in 1963 until the military coup in 1980. In Mimarl?k this brief phase marks the introduction of the basic terms and concepts of environmental discourse. More interestingly, though, it demonstrates the influence of a developmental discourse on the uptake of environmentalism and environmental problems by Turkish writers. In line with the anti-imperialist tendencies of the Turkish left movement in the 1960s and 1970s, environmentalism was dismissed mostly as a ‘Western’ construct or a tool of ‘imperial domination’. As a result, the architectural discourse of the 1970s in Mimarl?k paid relatively little attention to the political opportunities the environmental emphasis could bring or to the imagining of a radically different architecture.     

Enhanced thermoelectric properties induced by chemical pressure in Ca3Co4O9

We report the investigation of boron substitution on structural, electrical, thermal, and thermoelectric properties of Ca_3−xB_xCo₄O₉ (x=0, 0.5, 0.75, and 1) in the temperature range between 300 K and 5 K. X-ray diffraction studies show that the Ca₃Co₄O₉ phase is successfully preserved as the majority phase in the x=0.5 sample despite the small size of boron ions. Electrical transport measurements confirm that B³⁺ substitution for Ca²⁺ causes an increase in resistivity due to the decrease in carrier concentration. x=0.5 sample is found to have a Seebeck coefficient of 181 μV/K at room temperature which is ~1.5 times higher than that of the pure Ca₃Co₄O₉. Our results indicate that the chemical pressure due to the large ionic radii difference between B³⁺ (0.27 Å) and Ca²⁺ (1 Å) enhances the thermoelectric properties as long as the unique crystal structure of Ca₃Co₄O₉ is preserved.     

Capturing and using CO2 as feedstock with chemical looping and hydrothermal technologies

Chemical looping technology for capturing and hydrothermal processes for conversion of carbon are discussed with focused and critical assessments. The fluidized and stationary reactor systems using solid, including biomass, and gaseous fuels are considered in chemical looping combustion, gasification, and reforming processes. Sustainability is emphasized generally in energy technology and in two chemical looping simulation case studies using coal and natural gas. Conversion of captured carbon to formic acid, methanol, and other chemicals is also discussed in circulating and stationary reactors in hydrothermal processes. This review provides analyses of the major chemical looping technologies for CO₂ capture and hydrothermal processes for carbon conversion so that the appropriate clean energy technology can be selected for a particular process. Combined chemical looping and hydrothermal processes may be feasible and sustainable in carbon capture and conversion and may lead to clean energy technologies using coal, natural gas, and biomass. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of alcohols on citric acid production by Aspergillus niger A-9 entrapped in polyacrylamide gels

In this study, the production of citric acid has been achieved by using Aspergillus niger conidiaspores, entrapped in polyacrylamide gels, and the factors that affect this production have been investigated. On citric acid production the effect of starting sucrose concentration (100–180 g/l), the initial nitrogen concentration (0–0.3 g/l), the effect of the methanol concentration in 100 ml feeding medium (0–6 ml), and finally the effect of ethanol concentration (0–6 ml) in 100 ml feeding medium were studied and optimum experimental conditions were determined. As a result of the experiments, the starting nitrogen concentration (0.05 g/l) and the starting sucrose concentration (140 g/l) were optimized and maximum citric acid production was observed for the given conditions. On the other hand, the maximum citric acid production was observed by the addition of 4.0 ml methanol and 3.0 ml ethanol.