Anoop Nagar

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 <

Circulatory system for unmanned air vehicles

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.

Membrane purification system

We have built a platform circulatory system by fabricating channels whose dimensions and layout are analogous to a fractal system where the reactants (fluids) are carried from a central reservoir, through progressively smaller channels ultimately with a width of 100 microns as they interface with the cellular structure. The construction of the macro/micro channel platform has been carried out using the direct write/solid freeform photo fabrication hybrid platform developed by the principle investigator. The interaction of reactants is controlled at the cellular level depending upon the fractional change in structural properties to be performed. The macro/micro channel system is metallized with copper, nickel and gold to enable to allow electrochemical transformations on demand. The circulatory system has been used to increase the modulus of a beam by polymerizing monomers to high modulus polymers with a view towards repairing structural damage. The metallized channels have been used to alter the electromagnetic absorption of a structure via electrochemical switching between conducting, semiconducting and insulating states. The electromagnetic characteristics have also been altered by replacing the dopant anions with anions of significantly altered stereoelectronic characteristics by taking advantage of the circulatory system.