Publications

Results 84451–84475 of 96,771

Search results

Jump to search filters

Status of the Z Refurbishment project (ZR) at Sandia National Laboratories

Bloomquist, Douglas D.; McDaniel, Dillon H.; Weed, John W.; Faturos, Thomas V.; McKee, George R.; Tabor, Debra A.; Warner, Peggy J.

Sandia National Laboratories Z Refurbishment (ZR) Project formally began in August 2002 to increase the Z Accelerator's utilization by providing the capability to perform more shots, improve precision and pulse shape variability, increase delivered current, and accomplish the improvements with minimal disruption to Z's ongoing programs. A project overview was provided at the 14th International Pulsed Power Conference in 2003. This paper provides an update of the project including architectural changes over the past two years, timeframe for completion, and overall design and fabrication status.

More Details
TYPE Conference YEAR 2005
OSTI

Thermodynamic and structural characterization of Mg-Li-N-H storage system

Proposed for publication in the Journal of Alloys and Compounds.

Sickafoose, Shane S.

The Mg-Li-N-H system is a very promising hydrogen storage material due to its high capacity, reversibility and moderate operating conditions. Some of thermodynamic and structural properties for this system are characterized here. Pressure-composition isotherms are measured and presented in this paper for absorption-desorption at 220, 200 and 180 C. Powder X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis were carried out for samples at various degrees of hydrogenation. These results provide information about the structural changes during absorption/desorption. The mixture of (2LiNH{sub 2} + MgH{sub 2}) partially converts to (Mg(NH{sub 2}){sub 2} + 2LiH) when heated at 220 C and 100 bar of hydrogen without undergoing desorption. Based on two distinct parts which appear in all of the pressure-composition isotherms (180-220 C), two reactions taking place isothermally in hydrogen absorption/desorption are proposed for the material starting with (2LiNH{sub 2} + MgH{sub 2}) or (Mg(NH{sub 2}){sub 2} + 2LiH). These reactions include a single solid-phase reaction, corresponding to the sloping region for hydrogen weight percent (Hwt%) smaller than 1.5%, and a multiple-phase reaction, corresponding to a plateau region for Hwt.% > 1.5 in the isotherms. During hydrogen absorption/desorption, the single-solid-phase reaction corresponds to the forming/consuming of NH{sub 2} which is bonded to Li and the multiple-solid-phase reaction corresponds to forming/consuming Mg(NH{sub 2}){sub 2} and LiH. A mechanism for the sorption reactions has been proposed.

More Details
TYPE Journal Article YEAR 2005
OSTI

Bone response to 3-D periodic hydroxyapatite scaffolds with and without tailored microporosity to deliver bone morphogenetic protein 2

Proposed for publication in the Journal of Biomedical Materials Research.

Cesarano, Joseph C.; Dellinger, Jennifer D.

The in vivo bone response of 3D periodic hydroxyapatite (HA) scaffolds is investigated. Two groups of HA scaffolds (11 mm diameter x 3.5 mm thick) are fabricated by direct-write assembly of a concentrated HA ink. The scaffolds consist of cylindrical rods periodically arranged into four quadrants with varying separation distances between rods. In the first group, HA rods (250 {micro}m in diameter) are patterned to create pore channels, whose areal dimensions are 250 x 250 {micro}m{sup 2} in quadrant 1, 250 x 500 {micro}m{sup 2} in quadrants 2 and 4, and 500 x 500 {micro}m{sup 2} in quadrant 3. In the second group, HA rods (400 {micro}m in diameter) are patterned to create pore channels, whose areal dimensions of 500 x 500 {micro}m{sup 2} in quadrant 1, 500 x 750 {micro}m{sup 2} in quadrants 2 and 4, and 750 x 750 {micro}m{sup 2} in quadrant 3. Each group of scaffolds is partially densified by sintering at 1200 C prior to being implanted bilaterally in trephine defects of skeletally mature New Zealand White rabbits. Their tissue response is evaluated at 8 and 16 weeks using micro-computed tomography, histology, and scanning electron microscopy. New trabecular bone is conducted rapidly and efficiently across substantial distances within these patterned 3D HA scaffolds. Our observations suggest that HA rods are first coated with a layer of new bone followed by subsequent scaffold infilling via outward and inward radial growth of the coated regions. Direct-write assembly of 3D periodic scaffolds composed of micro-porous HA rods arrayed to produce macro-pores that are size-matched to trabecular bone may represent an optimal strategy for bone repair and replacement structures.

More Details
TYPE Journal Article YEAR 2005
OSTI
Results 84451–84475 of 96,771
Results 84451–84475 of 96,771