Jianer Bao

Impedance Study of the Synergistic Effects of Coal Contaminants: Is Cl a Contaminant or a Performance Stabilizer?

Impedance spectroscopy and current-voltage measurements were used to study the synergistic effects of the coal gas contaminants As, P, S, and Cl at the parts per million level on the performance of the anode-supported Ni-yttria-stabilized zirconia (YSZ)/YSZ/ lanthanum strontium manganese solid oxide fuel cells (SOFCs) at 750°C. Three semicircles were differentiated in cell impedance spectra. The results indicate that the effects of the contaminants are synergistic, can be destructive or constructive, and are not a simple addition of individual contaminants. Adding H 2 S to As and P accelerated the performance degradation. The addition of H 2 S also increased the charge-transfer resistance, whereas the removal of H 2 S resulted in a substantial ohmic resistance increase. The presence of Cl could mitigate or prevent performance loss from an attack by As and P. Impedance spectra show that the presence of Cl species protected the electronic percolation and slowed the rate of the charge-transfer resistance increase. Therefore, the tolerance limit of SOFCs for each contaminant could be significantly increased with Cl species in the gas stream. It is speculated that Cl species could react with nickel phosphides and Ni-P alloy to form NiCl(g), resulting in the restructuring of the catalyst surface.

Production of low-cost solar-grade silicon by reduction of SiF 4 gas with sodium: Technical and industrial developmental status

To meet increasing demand for electrical power using solar photovoltaics, millions of tons of solar-grade silicon costing <

Progress report on an experiment to clarify collimated x-ray emission in Karabut’s experiment

20/kg will be needed. Low-cost solar-grade silicon can be mass produced by burning Na metal in an atmosphere of pure SiF4 gas—an exothermic, fast, and complete reaction. SRI International routinely uses reactors that can produce at rates >20 metric tons per year (mty), and has licensed the technology to several companies. The Si product is completely separated from the by-product NaF by leaching or melt separation. With the direct use of industrially available Na, B and P levels in the Si product are <1 ppm. Using purified Na results in Si with dopant levels as low as 20 ppb. Experimental ingots grown have resistivity of 1 to 30 Ω·cm, with >100 Ω·cm when purified reactants were used. The purity, electronic parameters, and solar cell efficiency of 15% indicate that this silicon is of solar grade and can be a key contributor in developing solar power markets.

A New Activated Carbon for CO2 Capture from Coal-Fired Boiler Flue Gas

Karabut has reported collimated x-ray emission in a high-current density glow discharge experiment, a result which has for some years remain unexplained. A model has been proposed to account for the emission based on the up-conversion of vibrational quanta to produce excitation of the 1565 eV excited state in 201Hg. To test this idea, we are developing an experiment in which a Cu foil is vibrated. Evidence for charge emission is described; and preliminary x-ray measurements discussed.

Effect of various coal contaminants on the performance of solid oxide fuel cells: Part I. Accelerated testing

With the current environmental interest in controlling greenhouse gases, there is a new focus on materials that can discriminate between gas molecules by capturing those gases that must be curtailed and releasing those that pose no adverse effects to the atmosphere. Although zeolites can be applied to such tasks, molecular sieve (MS) carbons have an additional advantage in their ability to both adsorb and desorb molecules cyclically with comparatively little energy demand. ATMIs BrightBlack™ MS carbons have been extensively characterized using a variety of techniques and modified for the task of selectively adsorbing CO2 from a synthetic flue gas in a laboratory and a pilot plant falling-bed adsorber system. The integrated falling-bed adsorber system was then moved to a field test location to capture CO2 from flue gas from a coal-fired stoker boiler. In a 7000-cycle test, the carbon captured CO2 at 90% efficiency, generating product CO2 gas with purity greater than 95%.