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In this paper a review of the thermodynamic, electrical and structural properties of liquid alkali-tellurium alloys is presented with a special emphasis on the interplay between these properties. The thermodynamic properties indic...
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In this paper a review of the thermodynamic, electrical and structural properties of liquid alkali-tellurium alloys is presented with a special emphasis on the interplay between these properties. The thermodynamic properties indicate ordering of the solutions at compositions corresponding to about 12, 50, and 67 atom% of alkali atoms. The electrical conductivity and thermopower data confirm that these liquids are true semiconductors. The neutron diffraction patterns coupled with the above information indicate that in the case of liquid K(sub 0.12)Te(sub 0.88) the measured structure is dominated by the Te-Te contribution, and is remarkably similar to that of pure liquid tellurium, while the equiatomic alloy K(sub 0.50)Te(sub 0.50) is shown to contain mostly Te pairs which are identified with Zintl ions, Te(sub 2)(sup 2(minus)).
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Today's cryogenic coolers that operate down to 77 K suffer from several problems. Their most serious difficulties are significant noise levels, excessive vibration and poor reliability. Thermoelectric coolers do not suffer any of ...
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Today's cryogenic coolers that operate down to 77 K suffer from several problems. Their most serious difficulties are significant noise levels, excessive vibration and poor reliability. Thermoelectric coolers do not suffer any of these concerns. However, thermoelectric coolers are not presently capable of cooling to temperatures as low as 77 K. Development of thermoelectric materials capable of extending cooler performance to these temperatures would open up potential applications such as cryogenic cooling of infrared detectors and CCDs as well as removing heat from Joule-Thomson refrigerators. Presently, the best thermoelectric materials over the temperature range 200 K to 450 K and the most practical below 200 K, are solid solutions of Bi2Te3, Sb2Te3 and/or Bi2Se3. These alloys yield a peak dimensionless figure of merit, ZT, of approximately one near 300 K. These materials often require doping in order to optimize the carrier concentration and figure of merit, Z. As reported by Ravich and Vedernikov, certain impurities can also be added to improve thermoelectric properties through a selective scattering mechanism.
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Liquid-junction photoelectrochemical cells can be used either for the direct conversion of solar energy to electricity or to generate stored chemical species available for later electrochemical discharge. The objective of this pro...
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Liquid-junction photoelectrochemical cells can be used either for the direct conversion of solar energy to electricity or to generate stored chemical species available for later electrochemical discharge. The objective of this program is to identify experimental approaches for electrochemical photovoltaic cells that not only show promise of high power-conversion efficiencies but also have the potential to achieve long life and the capacity for energy storage. The work is organized as follows: (1) selection of high-efficiency semiconductor photoelectrode/electrolyte systems; (2) development of long-life electrochemical photovoltaic cells; (3) development of an all solid-state electrochemical photovoltaic cell with in-situ storage; and (4) demonstration of laboratory-size photoelectrochemical cell with redox storage. This program is directed toward identifying a suitable match between the proposed semiconductor and the redox species present in aqueous, nonaqueous, and solid electrolytes for achieving the necessary performance and semiconductor stability requirements. Emphasis is on aqueous electrolyte-based systems where fast kinetics are favored. The proposed systems will be compatible with convenient storage of the electroactive species generated and their later electrochemical discharge in a redox cell. (ERA citation 06:005919)
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A brief summary of work accomplished in thermal conductivity measurements of Si, InSb, NaxW03, Bi2Te3, Bi8Te7S5, and Mg2Sn above room temperature and Si, InSb, and EuO below room temperature is presented together with a list of pu...
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A brief summary of work accomplished in thermal conductivity measurements of Si, InSb, NaxW03, Bi2Te3, Bi8Te7S5, and Mg2Sn above room temperature and Si, InSb, and EuO below room temperature is presented together with a list of publications and reports. (Author)
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Gamma spectral analysis of measurements made on Special Nuclear Materials (SNM) provides identification and sometimes quantification of the SNM present. Different radiation detection technologies have been used for measurement of ...
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Gamma spectral analysis of measurements made on Special Nuclear Materials (SNM) provides identification and sometimes quantification of the SNM present. Different radiation detection technologies have been used for measurement of SNM. Selection of one of these for a particular application depends on the information that can be obtained using that detector and on the support needed to use the detection technology, especially if it is to be applied at sites where limited support is available. In some cases, detector selection may be determined by a need to limit the information available from measurements due to international treaty requirements. There are many studies of system capabilities in SNM measurement. Most of these used either scintillator or high-resolution (HPGe) detectors embedded in a unique electronics and software combination. Their respective developers claimed good results for their instrument. Unfortunately, the packaging often obscured the question of what can be obtained from various detector technologies. While instrumentation and analysis is important, a study comparing only detector characteristics would serve as a starting point for development of systems for SMN measurement. Our detector study consisted of measurements on shielded and unshielded high-enriched uranium and Plutonium sources using detectors: NaI(Tl), Cadmium Zinc Telluride (CZT), Mercuric Iodide (HgI2), and two HPGe detectors, one with liquid nitrogen cooling and one with electromechanical cooling. Measurements were made simultaneously using all detectors. As expected, all detectors are suitable for SNM measurements in cases where one radionuclide, such as 235U, is the dominant constituent, but only the high-resolution detectors are suitable for isotopic composition determinations using standard spectroscopic analysis. Room temperature semiconductor detectors (CZT, HgI2) can provide limited isotopic information.
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We have measured electron and ion emission under high vacuum conditions from several semiconductor and insulator surfaces excited by the first and third harmonics of a 1.06 mu m Nd laser. The dependence of this emission on laser f...
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We have measured electron and ion emission under high vacuum conditions from several semiconductor and insulator surfaces excited by the first and third harmonics of a 1.06 mu m Nd laser. The dependence of this emission on laser fluence and wavelength is consistent with a multiphoton excitation process. The dependence on laser pulse length implies, however, that other processes, either diffusive, thermal or thermomechanical, are also involved. Additional information is provided by the temporal and spatial distribution of the charge emission. The most extensive results have been obtained with single crystals of ZnS, for which nearly equal magnitudes of negative and positive charge emission are observed. The results suggest the possibility that the observed charge emission results primarily from the ejection of neutral atoms and molecules from the surface, followed by selective multiphoton ionization of one or more of the neutral species. The irreversible surface modification implied by the observed emission may be the precursor to observable surface damage. Detailed studies of the properties of the emitted particles may be very useful in developing a basic understanding of the damage mechanisms. 6 refs., 4 figs. (ERA citation 11:055152)
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The report investigates the effect of various ambient gases on the electrical properties of PbSe epitaxial films evaporated onto NaCl substrate. Hall coefficient, electrical conductivity, and magnetoresistance measurements were ma...
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The report investigates the effect of various ambient gases on the electrical properties of PbSe epitaxial films evaporated onto NaCl substrate. Hall coefficient, electrical conductivity, and magnetoresistance measurements were made as a function of film temperature and ambient gas uptake by the film. Ambient gas uptake kinetic measurements were also made. The nature and relative amount of ambients could be determined via a residual gas analyzer. Atomic hydrogen (H) was produced by interacting a hot filament with hydrogen gas, hydrocarbon diffusion pump oil, or alcohol, and was found to make freshly-evaporated films with 'clean' surfaces and air-exposed films n-type. H uptake by the films is inadequately described by the surface model.
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The conventional two-oscillator model together with the assumption of an abrupt interface has been used to fit far-infrared reflection and transmission data for the epitaxial-substrate systems PbSe on NaCl, Pb(0.79)Sn(0.21)Te on P...
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The conventional two-oscillator model together with the assumption of an abrupt interface has been used to fit far-infrared reflection and transmission data for the epitaxial-substrate systems PbSe on NaCl, Pb(0.79)Sn(0.21)Te on Pb(0.79)Sn(0.21)Te, and InAs on semi-insulating GaAs. The model worked well for the first system but failed for the other two. These results suggest, as Tennant and Cape found for PbSnTe, that interface effects appear in far-infrared data. The interface phenomena appear to involve free-carrier mixing across the interface in the PbSnTe system and both carrier and lattice mixing in InAs-GaAs. The joint measurement of reflection and transmission was found especially helpful in analyzing interface behavior. A new high-power pumped far-infrared laser spectrometer was used to make the transmission measurements. The design and spectroscopic application of a submillimeter-far-infrared (FIR) optically pumped tunable laser are described. Driven by 15-25 W of power from a cw CO2 laser, the FIR system gave milliwatts of power between 96 and 1217 micrometers. The pumped media were methyl alcohol and 1,1-difluoroethylene. The laser spectrometer was used to measure the transmission of liquid H2O, the bulk semiconductor GaAs, the epitaxial semiconductor InAs, and the high-temperature superconductor V3Si. In general, the laser system gave vastly improved signal-to-noise ratios, reduced stray light problems, and increased penetration power relative to more conventional FIR spectrometers.
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Zinc telluride films were fabricated by sputtering onto glass substrates using argon as the sputtering gas and ion exchange waveguides were made by exchanging the sodium atoms of a glass substrate for the silver atoms of a silver ...
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Zinc telluride films were fabricated by sputtering onto glass substrates using argon as the sputtering gas and ion exchange waveguides were made by exchanging the sodium atoms of a glass substrate for the silver atoms of a silver nitrate bath. Guided light techniques were than applied to both the zinc telluride films and the ion exchange waveguides in order to determine the modes of propagation. The waveguide modes were determined in the ion exchange waveguides but there were not any modes of propagation observed in the zinc telluride films. The determination of the modes of propagation for the ion exchange waveguides allowed their characterization to be done. (Author)
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The acid-dependent chemistry of sulfur was investigated. The behavior of oxides, selenides and tellurides were compared with sulfides. A detailed electrochemical study of selenium was undertaken. The electrochemistry of various mo...
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The acid-dependent chemistry of sulfur was investigated. The behavior of oxides, selenides and tellurides were compared with sulfides. A detailed electrochemical study of selenium was undertaken. The electrochemistry of various molybdenum species were also studied.
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