Exploring novel silicon-containing polymers---From preceramic polymers to conducting polymers with nonlinear optical properties (open access)

Exploring novel silicon-containing polymers---From preceramic polymers to conducting polymers with nonlinear optical properties

Several new types of silicon-containing preceramic polymers, i.e., poly(diorganosilacetylene) and poly(diorganosilvinylene) have been synthesized with molecular weights from 10,000 to 120,000. These polymers could be thermally converted to SiC with a moderate to high char yields. Ready solubility and good processability made these types of polymers attractive in their applications to ceramics. The thermal polymerization of diethynyldiphenyl-silane, which was reported in 1968 to afford poly(diphenylsilyldiacetylene) via dehydrogenation, was reinvestigated. Spectroscopic studies showed that the polymer had a structure of polyacetylene type not diacetylene. Diphenyldiethynylgermane and a series of diorganodiethynylsilances were synthesized. These could be polymerized in the presence of MoCl{sub 5} or WCl{sub 6} to afford a soluble, violet material with Mw as high as 108,000. 100 refs., 56 figs., 16 tabs.
Date: October 7, 1991
Creator: Pang, Yi.
System: The UNT Digital Library
A miniature inexpensive, oxygen sensing element (open access)

A miniature inexpensive, oxygen sensing element

An exhaustive study was conducted to determine the feasibility of Nernst-type oxygen sensors based on ceramics containing Bi{sub 2}O{sub 3}. The basic sensor design consisted of a ceramic sensing module sealed into a metal tube. The module accommodated an internal heater and thermocouple. Thermal-expansion-matched metals, adhesives, and seals were researched and developed, consistent with sequential firings during sensor assembly. Significant effort was devoted to heater design/testing and to materials' compatibility with Pt electrodes. A systematic approach was taken to develop all sensor components which led to several design modifications. Prototype sensors were constructed and exhaustively tested. It is concluded that development of Nerst-type oxygen sensors based on Bi{sub 2}O{sub 3} will require much further effort and application of specialized technologies. However, during the course of this 3-year program much progress was reported in the literature on amperometric-type oxygen sensors, and a minor effort was devoted here to this type of sensor based on Bi{sub 2}O{sub 3}. These studies were made on Bi{sub 2}O{sub 3}-based ceramic samples in a multilayer-capacitor-type geometry and amperometric-type oxygen sensing was demonstrated at very low temperatures ({approximately} 160{degree}C). A central advantage here is that these types of sensors can be mass-produced very inexpensively ({approximately} 20--50 cents …
Date: October 7, 1991
Creator: Arenz, R. W.
System: The UNT Digital Library
Influence of faults on groundwater flow and transport at YuccaMountain, Nevada (open access)

Influence of faults on groundwater flow and transport at YuccaMountain, Nevada

Numerical simulations of groundwater flow at Yucca Mountain, Nevada are used to investigate how faults influence groundwater flow pathways and regional-scale macrodispersion. The 3-D model has a unique grid block discretization that facilitates the accurate representation of the complex geologic structure present in faulted formations. Each hydrogeologic layer is discretized into a single layer of irregular and dipping grid blocks, and faults are discretized such that they are laterally continuous and varied in displacement varies along strike. In addition, the presence of altered fault zones is explicitly modeled, as appropriate. Simulations show that upward head gradients can be readily explained by the geometry of hydrogeologic layers, the variability of layer permeabilities, and the presence of permeable fault zones or faults with displacement only, not necessarily by upwelling from a deep aquifer. Large-scale macrodispersion results from the vertical and lateral diversion of flow near the contact of high- and low-permeability layers at faults, and from upward flow within high-permeability fault zones. Conversely, large-scale channeling can occur as a result of groundwater flow into areas with minimal fault displacement. Contaminants originating at the water table can flow in a direction significantly different from that of the water table gradient, and isolated zones …
Date: October 7, 1999
Creator: Cohen, Andrew J.B. & Sitar, Nicholas
System: The UNT Digital Library
Trace gas emission data bases for atmospheric chemistry studies (open access)

Trace gas emission data bases for atmospheric chemistry studies

Global data bases of trace gas emissions to the atmosphere have been compiled for the use in atmospheric chemistry studies. The resolution provided is a 1{degree} latitude by 1{degree} longitude. A series of 3 data bases has been provided. The first is an inventory of emissions of NO{sub x} from fossil fuel combustion, while the second is an inventory of SO{sub 2} emissions from the same anthropogenic source. The third database includes a global inventory of the emissions of NO{sub x} from terrestrial biomass burning and is given seasonally for the globe. The units of emission for the inventories are given as the mass in metric tons of N for the NO{sub x} inventories and metric tons of S for the SO{sub 2} inventory for each 1{degree} {times} 1{degree} grid. The emissions are expected to represent the emissions for the year 1980. The biomass burning source is given for 2 seasons where XXXXjul represents an ascii file containing the cumulated emissions for the months from April to September, and XXXXjan represents October to March. The grid for these data bases, (i,j) arrays, is (360,180), which represents 1 degree (lon,lat) resolution. The Table shows a description of each data base and …
Date: October 7, 1991
Creator: Dignon, J.
System: The UNT Digital Library
Reactor Restart Division trend analysis report, second quarter 1991 (open access)

Reactor Restart Division trend analysis report, second quarter 1991

This document provides a trend analysis for the Savannah River Reactor Restart Program. The data contained in this report is comprised of Nonconformance Report (NCR), Surveillance Reports, and Corrective Action Reports (CAR). The data trended now includes six quarters and provides the capability of looking at changing patterns in the various performance categories over time.
Date: October 7, 1991
Creator: Castles, R.B.
System: The UNT Digital Library
Electrochemical processing of nitrate waste solutions (open access)

Electrochemical processing of nitrate waste solutions

The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F[sup [minus]] ions from the synthetic mix migrating across the cation …
Date: October 7, 1992
Creator: Genders, D.; Weinberg, N. & Hartsough, D. (Electrosynthesis Co., Inc., Cheektowaga, NY (United States))
System: The UNT Digital Library
Reactor Restart Division trend analysis report, second quarter 1991 (open access)

Reactor Restart Division trend analysis report, second quarter 1991

This document provides a trend analysis for the Savannah River Reactor Restart Program. The data contained in this report is comprised of Nonconformance Report (NCR), Surveillance Reports, and Corrective Action Reports (CAR). The data trended now includes six quarters and provides the capability of looking at changing patterns in the various performance categories over time.
Date: October 7, 1991
Creator: Castles, R. B.
System: The UNT Digital Library
The Savannah River Site`s Groundwater Monitoring Program: Second quarter 1992 (open access)

The Savannah River Site`s Groundwater Monitoring Program: Second quarter 1992

The Environmental Protection Department/Environmental Monitoring Section (EPD/EMS) administers the Savannah River Site`s (SRS) Groundwater Monitoring Program. During second quarter 1992, EPD/EMS conducted extensive sampling of monitoring wells. EPD/EMS established two sets of criteria to assist in the management of sample results. The flagging criteria do not define contamination levels; instead, they aid personnel in sample scheduling, interpretation of data, and trend identification. Since 1991, the flagging criteria have been based on the federal Environmental Protection Agency (EPA) drinking water standards and on method detection limits. A detailed explanation of the current flagging criteria is presented in the Flagging Criteria section of this document. Analytical results from second quarter 1992 are listed in this report.
Date: October 7, 1992
Creator: Rogers, C. D.
System: The UNT Digital Library
PXAMS -- Projectile X ray AMS: X ray yields and applications (open access)

PXAMS -- Projectile X ray AMS: X ray yields and applications

Characteristic x rays have recently been explored as a method for the detection and identification of ions in accelerator mass spectrometry (AMS). After analysis in the AMS spectrometer, the ions stop in an appropriately chosen target and the induced x rays identify the ions by atomic number. For the application of AMS to higher mass isotopes, characteristic x rays allow significantly better discrimination of competing atomic isobars than is possible using energy loss detectors. Characteristic x rays also show promise as a convenient component in hybrid detection systems. Measurements of x ray yields are presented for Si, Fe, Ni, Se, Mo, and Pd ions of 0.5--2 MeV/AMU. The yields rise by more than a factor of 10 over this energy range, and approach 1 x-ray per incident ion at 2 MeV/AMU for the lighter ions. Preliminary work on the application of PXAMS to the detection of {sup 79}Se is described.
Date: October 7, 1994
Creator: McAninch, J. E.; Bench, G. S.; Freeman, S. P. H. T.; Roberts, M. L.; Southon, J. R.; Vogel, J. S. et al.
System: The UNT Digital Library
Spool assembly support analysis (open access)

Spool assembly support analysis

This document provides the wind/seismic analysis and evaluation for the pump pit spool assemblies. Hand calculations were used for the analysis. UBC, AISC, and load factors were used in this evaluation. The results show that the actual loads are under the allowable loads and all requirements are met.
Date: October 7, 1994
Creator: Norman, B. F.
System: The UNT Digital Library
Thermodynamic analysis of actinide volatilities for the thermal processor units in the ITTS study (open access)

Thermodynamic analysis of actinide volatilities for the thermal processor units in the ITTS study

Available thermodynamic data for volatilization of U and Pu gaseous species under oxidizing conditions are tabulated: UO{sub 3}, UO{sub 2}(OH){sub 2}, UO{sub 2}F{sub 2}, PuO{sub 3}, PuO{sub 2}(OH){sub 2}. Results of a thermodynamic analysis of U, Pu, and Am volatilities in the secondary combustor, plasma arc process, and vitrifier are given.
Date: October 7, 1993
Creator: Krikorian, O. H.
System: The UNT Digital Library
Characterization of 618-11 solid waste burial ground, disposed waste, and description of the waste generating facilities (open access)

Characterization of 618-11 solid waste burial ground, disposed waste, and description of the waste generating facilities

The 618-11 (Wye or 318-11) burial ground received transuranic (TRTJ) and mixed fission solid waste from March 9, 1962, through October 2, 1962. It was then closed for 11 months so additional burial facilities could be added. The burial ground was reopened on September 16, 1963, and continued operating until it was closed permanently on December 31, 1967. The burial ground received wastes from all of the 300 Area radioactive material handling facilities. The purpose of this document is to characterize the 618-11 solid waste burial ground by describing the site, burial practices, the disposed wastes, and the waste generating facilities. This document provides information showing that kilogram quantities of plutonium were disposed to the drum storage units and caissons, making them transuranic (TRU). Also, kilogram quantities of plutonium and other TRU wastes were disposed to the three trenches, which were previously thought to contain non-TRU wastes. The site burial facilities (trenches, caissons, and drum storage units) should be classified as TRU and the site plutonium inventory maintained at five kilograms. Other fissile wastes were also disposed to the site. Additionally, thousands of curies of mixed fission products were also disposed to the trenches, caissons, and drum storage units. Most …
Date: October 7, 1997
Creator: Hladek, K. L.
System: The UNT Digital Library
Obstruction of Justice Under Federal Law: An Abbreviated Sketch (open access)

Obstruction of Justice Under Federal Law: An Abbreviated Sketch

This report focuses on selected aspects of the general obstruction of justice provisions found in 18 U.S.C. 1503, 1505, and 1512. It is essentially a replica, without footnotes or citations, of CRS Report 98-832, Obstruction of Justice Under Federal Law: A Review of Some of the Elements.
Date: October 7, 1998
Creator: Doyle, Charles
System: The UNT Digital Library
Electrochemical processing of nitrate waste solutions. Phase 2, Final report (open access)

Electrochemical processing of nitrate waste solutions. Phase 2, Final report

The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F{sup {minus}} ions from the synthetic mix migrating across the cation …
Date: October 7, 1992
Creator: Genders, D.; Weinberg, N. & Hartsough, D.
System: The UNT Digital Library
Engineering Basis Document Review for Waste Feed Delivery from Single Shell Tanks (SST) (open access)

Engineering Basis Document Review for Waste Feed Delivery from Single Shell Tanks (SST)

This report provides the results of a review conducted on existing operating specifications and safety requirements and provides a summary of applicable design constraints on the Single-Shell Tank (SST) System. The SST System is required to transition from the current waste storage mission to support the Tank Waste Remediation System (TWRS) waste retrieval mission described in the Tank Waste Remediation System Mission Analysis Report (Acree 1998). The SST System is also required to support the Project Hanford Management Contract (PHMC) portions of the Waste Feed Delivery (WFD) mission. In Phase 1 the SST System will be required to retrieve waste from selected SSTs (tanks 241-C-102 and 241-C-104) for transfer to the Double-Shell Tank (DST) System (tanks 241-AZ-101,241-AY-102). The SST System will include all the systems, structures and components required to safely store, retrieve, and transfer waste in support of the TWRS mission. Operational Specification Documents (OSDs) govern operation of the existing SST System components. However, the system will be highly modified to support the TWRS mission. Therefore OSD requirements may not apply to the new system's design. This document describes the review of existing SST OSDs and provides the rationale for selecting or rejecting requirements as constraints on the SST …
Date: October 7, 1999
Creator: SMITH, D.F.
System: The UNT Digital Library
Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report (open access)

Hindered Diffusion of Asphaltenes at Elevated Temperature and Pressure Progress Report

During this time period, experiments were performed to study the diffusion controlled uptake of quinoline and a coal asphaltene into porous carbon catalyst pellets. Cyclohexane and toluene were used as solvents for quinoline and the coal asphaltene respectively. The experiments were performed at 27 C and 75 C, at a pressure of 250 psi (inert gas) for the quinoline/cyclohexane system. For the coal asphaltene/toluene system, experiments were performed at 27 C, also at a pressure of 250 psi. These experiments were performed in a 20 cm{sup 3} microautoclave, the use of which is advantageous since it is economical from both a chemical procurement and waste disposal standpoint due to the small quantities of solvents and catalysts used. A C++ program was written to simulate data using a mathematical model which incorporated both diffusional and adsorption mechanisms. The simulation results showed that the mathematical model satisfactorily fitted the adsorptive diffusion of quinoline and the coal asphaltene onto a porous activated carbon. For the quinoline/cyclohexane system, the adsorption constant decreased with an increase in temperature. The adsorption constant for the coal asphaltene/toluene system at 27 C was found to be much higher than that of the quinoline/cyclohexane system at the same temperature. …
Date: October 7, 1999
Creator: Guin, James A. & Ramakrishnan, Ganesh
System: The UNT Digital Library
K West Basin Integrated Water Treatment System (IWTS) E-F Annular Filter Vessel Accident Calculations (open access)

K West Basin Integrated Water Treatment System (IWTS) E-F Annular Filter Vessel Accident Calculations

Three bounding accidents postdated for the K West Basin integrated water treatment system are evaluated against applicable risk evaluation guidelines. The accidents are a spray leak during fuel retrieval, spray leak during backflushing, and a hydrogen explosion. Event trees and accident probabilities are estimated. In all cases, the unmitigated dose consequences are below the risk evaluation guidelines.
Date: October 7, 1999
Creator: RITTMANN, P.D.
System: The UNT Digital Library
DOE Integrated Safeguards and Security (DISS) historical document archival and retrieval analysis, requirements and recommendations (open access)

DOE Integrated Safeguards and Security (DISS) historical document archival and retrieval analysis, requirements and recommendations

The overall primary Objective of HDAR is to create a repository of historical personnel security documents and provide the functionality needed for archival and retrieval use by other software modules and application users of the DISS/ET system. The software product to be produced from this specification is the Historical Document Archival and Retrieval Subsystem The product will provide the functionality to capture, retrieve and manage documents currently contained in the personnel security folders in DOE Operations Offices vaults at various locations across the United States. The long-term plan for DISS/ET includes the requirement to allow for capture and storage of arbitrary, currently undefined, clearance-related documents that fall outside the scope of the ``cradle-to-grave`` electronic processing provided by DISS/ET. However, this requirement is not within the scope of the requirements specified in this document.
Date: October 7, 1994
Creator: Guyer, H.B. & McChesney, C.A.
System: The UNT Digital Library
Detection of explosive events by monitoring acoustically-induced geomagnetic perturbations (open access)

Detection of explosive events by monitoring acoustically-induced geomagnetic perturbations

The Black Thunder Coal Mine (BTCM) near Gillette, Wyoming was used as a test bed to determine the feasibility of detecting explosion-induced geomagnetic disturbances with ground-based induction magnetometers. Two magnetic observatories were fielded at distances of 50 km and 64 km geomagnetically north from the northernmost edge of BTCM. Each observatory consisted of three separate but mutually orthogonal magnetometers, Global Positioning System (GPS) timing, battery and solar power, a data acquisition and storage system, and a three-axis seismometer. Explosions with yields of 1 to 3 kT of TNT equivalent occur approximately every three weeks at BTCM. We hypothesize that explosion-induced acoustic waves propagate upward and interact collisionally with the ionosphere to produce ionospheric electron density (and concomitant current density) perturbations which act as sources for geomagnetic disturbances. These disturbances propagate through an ionospheric Alfven waveguide that we postulate to be leaky (due to the imperfectly conducting lower ionospheric boundary). Consequently, wave energy may be observed on the ground. We observed transient pulses, known as Q-bursts, with pulse widths about 0.5 s and with spectral energy dominated by the Schumann resonances. These resonances appear to be excited in the earth-ionosphere cavity by Alfven solitons that may have been generated by the …
Date: October 7, 1999
Creator: Lewis, J P; Rock, D R; Shaeffer, D L & Warshaw, S I
System: The UNT Digital Library
Radon Emanation from NORM-Contaminated Pipe Scale, Soil, and Sediment at Petroleum Industry Sites (open access)

Radon Emanation from NORM-Contaminated Pipe Scale, Soil, and Sediment at Petroleum Industry Sites

This report describes a study of radon (Rn) emanation from pipe scale and soil samples contaminated with naturally occurring radioactive material (NORM). Samples were collected at petroleum production sites in Oklahoma, Michigan, Kentucky, and Illinois. For comparison, data are also presented from preliminary studies conducted at sites in Texas and Wyoming. All samples collected were analyzed for their Rn emanation fraction, defined as the fraction of 222Rn produced that enters the interconnected pore space within a medium contaminated with 226Ra before the 222Rn undergoes radioactive decay. This measure represents one of the important parameters that determine the overall Rn activity flux from any solid medium. The goal of this project was to determine whether Rn emanation from pipe scale and soil is similar to emanation from uranium mill tailings.
Date: October 7, 1999
Creator: Rood, A.S. & White, G.J.
System: The UNT Digital Library
Addendum to the RCRA Assessment Report for Single-Shell Tank Waste Management Area S-SX at the Hanford Site (open access)

Addendum to the RCRA Assessment Report for Single-Shell Tank Waste Management Area S-SX at the Hanford Site

The initial Resource Conservation and Recovery Act (RCRA) groundwater quality assessment report for Waste Management Area S-SX (PNNL-11810) was issued in January 1998. The report stated a plan for conducting continued assessment would be developed after addressing Washington State Department of Ecology (Ecology) comments on initial findings in PNNL-11810. Comments from Ecology were received by US Department of Energy, Richland Operations Office (DOE-RL) on September 24, 1998. Shortly thereafter, Ecology and DOE began dispute resolution and related negotiations about tank farm vadose issues. This led to proposed new Tri-Party Agreement milestones covering a RCRA Facility Investigation-Corrective Measures Study (RFI/CMS) of the four single-shell tank farm waste management areas that were in assessment status (Waste Management Areas B-BX-BY, S-SX, T and TX-TY). The RCRA Facility Investigation includes both subsurface (vadose zone and groundwater) and surface (waste handling facilities and grounds) characterization. Many of the Ecology comments on PNNL-11810 are more appropriate for, and in many cases are superseded by, the RFI/CMS at Waste Management Area S-SX. The proposed Tri-Party Agreement milestone changes that specify the scope and schedule for the RFI/CMS work plans (Tri-Party Agreement change number M-45-98-0) were issued for public comment in February 1999. The Tri-Party Agreement narrative indicates …
Date: October 7, 1999
Creator: Chou, C. J. & Johnson, V. G.
System: The UNT Digital Library
Scale 4.4 Validation for the DFS System at SRS (open access)

Scale 4.4 Validation for the DFS System at SRS

The document is a compilation of the work to date dealing with the validation of the CSAS25 sequence in SCALE 4.4. using the 27-group ENDF/B-IV and the 238-group ENDF/B-V cross section libraries, executed on the Digital Equipment Alpha Processors workstation cluster at WSMS. Revisions to this document will be made as new validation information is generated; therefore, this document should be used as the reference point for bias and bias uncertainties for SCALE 4.4-related work. This initial issue of the report (Revision 0) contains bias and bias uncertainty for plutonium and highly enriched uranium solutions and metal systems, including MTR type fuel.
Date: October 7, 1999
Creator: Blanchard, A.
System: The UNT Digital Library
Robustness and Flexibility in NCSX: Global Ideal MHD Stability and Energetic Particle Transport (open access)

Robustness and Flexibility in NCSX: Global Ideal MHD Stability and Energetic Particle Transport

Concerns about the flexibility and robustness of a compact quasiaxial stellarator design are addressed by studying the effects of varied pressure and iota profiles. For thirty related equilibrium configurations the global, ideal magnetohydrodynamic (MHD) stability is evaluated as well as energetic particle transport. It is found that tokamak intuition is useful to understanding the MHD stability, with pressure gradient driving terms and shear stabilization controlling both the N=0 and N=1 unstable modes. Global kink modes are generated by steeply peaked profiles and edge localized modes are found for plasmas with edge iota above 0.5. Energetic particle transport is not strongly dependent on these changes of pressure and iota profiles, although a weak inverse dependence on pressure peaking through the magnetic axis Shafranov shift is found. While good transport and MHD stability are not anticorrelated in these 30 equilibria, stability depends on a delicate balance of the pressure and shear stabilization forces.
Date: October 7, 1999
Creator: Diallo, A.; Fu, G. Y.; Johnson, J. L.; Redi, M. H. & others], W. A. Cooper
System: The UNT Digital Library
Structural studies of the metal-rich region in the ternary Ta-Nb-S system (open access)

Structural studies of the metal-rich region in the ternary Ta-Nb-S system

Six new solid solution type compounds have been prepared using high temperature techniques and characterized by means of single crystal x-ray techniques during a study of the metal-rich region of the ternary Ta-Nb-S system. The structures of Nb{sub x}Ta{sub 11-x}S{sub 4} are reminiscent of niobium-rich sulfides, rather than of tantalum-rich sulfides. The coordinations of sulfur are capped trigonal prismatic while the metal coordinations are capped distorted cubic prismatic for Nb{sub x}Ta{sub 11-x}S{sub 4}, and capped distorted cubic prismatic and pentagonal prismatic for Nb{sub 12-x}Ta{sub x}S{sub 4}. The structures of Nb{sub x}Ta{sub 5-x}S{sub 2} contain homoatomic layers sequenced S-M3-M2-M1-M2-M3-S (M is mixed Nb, Ta) generating six-layer sheets, respectively. Weak S-S interactions at 3.26 and 3.19{Angstrom} between sheets contrast with the M-M binding within and between the sheets in these two novel layered compounds. The former are presumably responsible for the observed graphitic slippage of the samples. Nb{sub 21-x}Ta{sub x}S{sub 8} and Nb{sub x}Ta{sub 2-x}S are isostructural with Nb{sub 21}S{sub 8} and Ta{sub 2}S, respectively. Extended Hueckel band calculations were carried out for two layered compounds, Nb{sub x}Ta{sub 5-x}S{sub 2} (x {approx} 1.72) and Nb{sub x}ta{sub 2-x}S (x {approx} 0.95). Based upon band calculations metallic properties can be expected for these two …
Date: October 7, 1991
Creator: Yao, Xiaoqiang.
System: The UNT Digital Library