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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

SU-E-T-495: Neutron Induced Electronics Failure Rate Analysis for a Single Room Proton Accelerator

Purpose: To determine the failure rate as a function of neutron dose of the range modulator's servo motor controller system (SMCS) while shielded with Borated Polyethylene (BPE) and unshielded in a single room proton accelerator. Methods: Two experimental setups were constructed using two servo motor controllers and two motors. Each SMCS was then placed 30 cm from the end of the plugged proton accelerator applicator. The motor was then turned on and observed from outside of the vault while being irradiated to known neutron doses determined from bubble detector measurements. Anytime the motor deviated from the programmed motion a failure was recorded along with the delivered dose. The experiment was repeated using 9 cm of BPE shielding surrounding the SMCS. Results: Ten SMCS failures were recorded in each experiment. The dose per monitor unit for the unshielded SMCS was 0.0211 mSv/MU and 0.0144 mSv/MU for the shielded SMCS. The mean dose to produce a failure for the unshielded SMCS was 63.5 ± 58.3 mSv versus 17.0 ±12.2 mSv for the shielded. The mean number of MUs between failures were 2297 ± 1891 MU for the unshielded SMCS and 2122 ± 1523 MU for the shielded. A Wilcoxon Signed Ranked test showed the dose between failures were significantly different (P value = 0.044) while the number of MUs between failures were not (P value = 1.000). Statistical analysis determined a SMCS neutron dose of 5.3 mSv produces a 5% chance of failure. Depending on the workload and location of the SMCS, this failure rate could impede clinical workflow. Conclusion: BPE shielding was shown to not reduce the average failure of the SMCS and relocation of the system outside of the accelerator vault was required to lower the failure rate enough to avoid impeding clinical work flow.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2015

SU-E-T-239: Design and Evaluation of a Nozzle Shielding System in Passively Scattered Proton Therapy

Purpose: To design, implement and evaluate a shielding system that will reduce out-of-field dose experienced by the patient and associated electronic systems in passively scattered proton therapy treatment. Methods: A multi-stage neutron shielding system was retrofitted to the Gantry 1 treatment nozzle at Loma Linda University Medical Center. The system uses multiple borated polyethylene plates staged after the primary beam modifying devices to attenuate and absorb neutrons produced by such devices. This arrangement locates increasing levels of shielding between the sources of secondary particles in the nozzle and the patient. Additionally, the design of this shielding structure allows it to be easily retrofitted to an existing proton nozzle system without impacting design or treatment beam characteristics. The effectiveness of the shielding was evaluated both through experimental measurements and Geant4 Monte Carlo simulations. Results: Measurements were completed with Landauer Luxel+ dosimeters that use optically stimulated luminescence and CR-39 to detect fast neutrons, thermal neutrons, protons, photons and beta particles. Measurements of a 250 MeV proton beam indicated that the shielding system reduced out-of-field dose to the patient by almost half with dose equivalent values at 50 and 40 cm from the field edge decreasing from 0.965 and 1.262 mSv/Gy to 0.596 and 0.777 mSv/Gy respectively. The installation of the multi-stage shielding system also reduced dose equivalent experienced by electronic systems installed in the treatment room by up to 80%. Geant4 simulations were also used to evaluate the neutron fluence at various positions in the treatment room as well as provide information on microdosimetry spectra within the patient and treatment room. Conclusion: The shielding system described above proved to be an effective an inexpensive method of reducing out-of-field doses to the patient and electronic systems and can be easily retrofitted to existing passive scattering nozzles.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Synthesis, crystal structure refinement, and nonlinear-optical properties of CaB{sub 3}O{sub 5}(OH): Comparative crystal chemistry of calcium triborates

Calcium triborate CaB{sub 3}O5(OH) obtained by hydrothermal synthesis in the Ca(OH){sub 2}–H{sub 3}BO{sub 3}–Na{sub 2}CO{sub 3}–KCl system is studied by single-crystal X-ray diffraction. The parameters of the orthorhombic unit cell are as follows: a = 13.490(1), b = 6.9576(3), and c = 4.3930(2) Å; V = 412.32(3) Å{sup 3} and space group Pna2{sub 1}. The structure is refined in the anisotropic approximation of the atomic displacement parameters to R = 4.28% using 972 vertical bar F vertical bar > 4σ(F). It is confirmed that the crystal structure of Ca triborate CaB{sub 3}O{sub 5}(OH) is identical to that described earlier. The hydrogen atom is localized. An SHG signal stronger than that of the quartz standard is registered. The phase transition of calcium triborate into calciborite is found on heating. The comparative crystal-chemical analysis of a series of borates with the general chemical formula 2CaO · 3B{sub 2}O{sub 3} · nH{sub 2}O (n = 0–13) with the constant CaO: B{sub 2}O{sub 3}= 2: 3 ratio and variable content of water is performed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Kinetics of tunneling electron transfer between antimorphous defects in optical crystals with mobile cations

The experimental data on the transient optical absorption of wide-band-gap optical crystals of lithium borates Li{sub 2}B{sub 4}O{sub 7}, LiB{sub 3}O{sub 5}, and Li{sub 6}Gd(BO{sub 3}){sub 3} and potassium (KH{sub 2}PO{sub 4} (KDP)) and ammonium (NH{sub 4}H{sub 2}PO{sub 4} (ADP)) dihydrogen phosphates in the visible and ultraviolet spectral regions are analyzed using the theory of diffusion-controlled tunneling recombination. A nanosecond pulsed radiation action on these crystals is shown to form defect pairs, such as polaron-type hole centers and electron centers based on interstitial cations. The relaxation kinetics of these centers over a wide time range of 10{sup -8}-10 s is described by a proposed model of tunneling electron transfer between antimorphous defects in the cation sublattice under the thermally stimulated mobility of recombination partners. The numerical values of the kinetic parameters are determined and the time dependences of the reaction rate constants are calculated for all crystals under study. As a result, the dynamics of change in the optical properties of these crystals under a pulsed radiation action can be simulated.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A technique for searching for the 2K capture in {sup 124}Xe with a copper proportional counter

An experimental technique for searching for the 2K capture in {sup 124}Xe with a large low-background copper proportional counter is described. Such an experiment is conducted at the Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Sciences. The experimental setup is located in the Low-Background Deep-Level Laboratory at a depth of 4900 m.w.e., where the flux of muons of cosmic rays is suppressed by a factor of 10{sup 7} relative to that at the Earth’s surface. The setup incorporates a proportional counter and low-background shielding (18 cm of copper, 15 cm of lead, and 8 cm of borated polyethylene). The results of processing the data obtained in 5 months of live measurement time are presented. A new limit on the half-life of {sup 124}Xe with respect to the 2K capture is set at the level of 2.5 × 10{sup 21} years.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Photoelastic Properties of Potassium Sulfate Crystals

The spectral dependences of the absolute piezooptic coefficients of potassium sulfate crystals are studied. It is established that their dispersion dependence is insignificant. The matrix of elastooptic coefficients p{sub in} of these crystals is filled using the elastic stiffness coefficients and the absolute piezooptic coefficients. The coefficient of acoustooptical efficiency M{sub 2} is calculated. It is shown that, considering the maximum values, it is more than an order of magnitude higher than that of quartz and strontium borate crystals. Potassium sulfate crystals are proposed for use for acoustooptic modulation of ultraviolet radiation, taking into account the short-wavelength limit of their transparent region (~170 nm).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Mixed polyanion glass cathodes: Effect of polyanion content

Mixed polyanion glass cathodes in lithium-ion batteries have very high capacities (200-500 mAh/g), but currently these materials have fundamental problems with 1 st -cycle irreversible loss, cycling efficiency, and capacity fade. It is well established that polyanion substitutions into glasses can dramatically affect their physical properties, but the effect of polyanion content on the electrochemical performance has not been previously established. The proper amount of lithium and borate substitution in copper phosphate/vanadate glasses was shown to nearly eliminate 1 st -cycle irreversible loss and improve cycling efficiency. As a result, Raman and IR spectroscopy were used to identify polyanions that correlated with electrochemical performance changes.

25 ENERGY STORAGE↗
DOE OSTI2012

Oxide Melt Solution Calorimetry of Fe2+ -bearing Oxides and Application to the Magnetite - Maghemite (Fe3O4-Fe8/3O4) system

A consistent methodology for obtaining enthalpy of formation of Fe{sup 2+}-containing binary and multicomponent oxides using high temperature oxide melt solution calorimetry has been developed. The enthalpies of wuestite (FeO) and magnetite (Fe{sub 3}O{sub 4}) oxidation to hematite (Fe{sub 2}O{sub 3}) were measured using oxidative drop solution calorimetry in which the final product is dissolved ferric oxide. Two methods were applied: drop solution calorimetry at 1073 K in lead borate solvent and at 973 K in sodium molybdate, each under both oxygen flowing over and bubbling through the solvent, giving consistent results in agreement with literature values. The enthalpies of formation of all three iron oxides from the elements were obtained using a thermodynamic cycle involving the directly measured oxidative dissolution enthalpy of iron metal in sodium molybdate at 973 K and gave excellent consistency with literature data. The methodology was then applied to the magnetite - maghemite system. The enthalpy of mixing of the Fe{sub 3}O{sub 4}-Fe{sub 8/3}O{sub 4} spinel solid solution is exothermic and, 2 represented by a subregular (Margules) formalism, {Delta}H{sub mix} = x(1-x)(-63.36 {+-} 8.60(1-x) + 17.65 {+-} 6.40x) kJ/mol, where x is the mole fraction of magnetite. The entropies of mixing of the solid solution were calculated for different assumptions about the distribution of cations, charges, and vacancies in these defect spinels. The different models lead to only small differences in the entropy of mixing. Calculated free energies of mixing show no evidence for a solvus in the magnetite - maghemite system.

58 GEOSCIENCES↗
DOE OSTI2011

CHARACTERIZATION OF DWPF MELTER OFF-GAS QUENCHER SAMPLE

The Savannah River National Laboratory (SRNL) recently received a deposit sample from the Melter Primary Off Gas System (POG) of the Defense Waste Processing Facility (DWPF). This sample was composed of material that had been collected while the quencher was in operation January 27, 2011 through March 31, 2011. DWPF requested, through a technical assistance request, characterization of the melter off-gas deposits by x-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis. The purpose of the Melter Off-Gas System is to reduce the amount of radioactive particles and mercury in the gases vented to the atmosphere. Gases emitted from the melter pass through the primary film cooler, quencher, Off-Gas Condensate Tank (OGCT), Steam Atomized Scrubbers (SAS), a condenser, a high efficiency mist eliminator, and a high efficiency particulate air filter, before being vented to the Process Vessel Vent System. The film coolers cool the gases leaving the melter vapor space from {approx}750 C to {approx}375 C, by introducing air and steam to the flow. In the next step, the quencher cools the gas to about 60 C by bringing the condensate from the OGCT in contact with the effluent (Figure 1). Most of the steam in the effluent is then condensed and the melter vapor space pressure is reduced. The purpose of the OGCT is to collect and store the condensate formed during the melter operation. Condensate from the OGCT is circulated to the SAS and atomized with steam. This atomized condensate is mixed with the off-gas to wet and join the particulate which is then removed in the cyclone. The next stage incorporates a chilled water condenser which separates the vapors and elemental mercury from the off-gas steam. Primary off-gas deposit samples from the DWPF melter have previously been analyzed. In 2003, samples from just past the film cooler, from the inlet of the quencher and inside the quencher were analyzed at SRNL. It was determined that the samples were a mixture of sludge and glass frit. The major component was Si along with Fe, Al, and other elements in the radioactive waste being processed. The deposits analyzed also contained U-235 fission products and actinide elements. Prior to that, deposits in the off-gas system in the DWPF nonradioactive half scale melter and the one-tenth scale integrated DWPF melter system were analyzed and determined to be mixtures of alkali rich chlorides, sulfates, borates, and fluorides entrained with iron oxides, spinels and frit particles formed by vapor-phase transport and condensation. Additional work was performed in 2007 in which researchers similarly found the deposits to be a combination of sludge and frit particles.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

XRD, Electron Microscopy and Vibrational Spectroscopy Characterization of Simulated SB6 HLW Glasses - 13028

Sample glasses have been made using SB6 high level waste (HLW) simulant (high in both Al and Fe) with 12 different frit compositions at a constant waste loading of 36 wt.%. As follows from X-ray diffraction (XRD) and optical and scanning electron microscopy (SEM) data, all the samples are composed of primarily glass and minor concentration of spinel phases which form both isometric grains and fine cubic (∼1 μm) crystals. Infrared spectroscopy (IR) spectra of all the glasses within the range of 400-1600 cm{sup -1} consist of the bands due to stretching and bending modes in silicon-oxygen, boron-oxygen, aluminum-oxygen and iron-oxygen structural groups. Raman spectra showed that for the spectra of all the glasses within the range of 850-1200 cm{sup -1} the best fit is achieved by suggestion of overlapping of three major components with maxima at 911-936 cm{sup -1}, 988-996 cm{sup -1} and 1020-1045 cm{sup -1}. The structural network is primarily composed of metasilicate chains and rings with embedded AlO{sub 4} and FeO{sub 4} tetrahedra. Major BO{sub 4} tetrahedra and BO{sub 3} triangles form complex borate units and are present as separate constituents. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Low Melting Temperature Glass for Immobilisation of Contaminated Zeolitic Ion Exchangers from Fukushima - 16494

The clean-up of the Fukushima Daiichi site continues to generate large volumes of spent adsorbents which need to be disposed of permanently, one of the candidates is a low temperature immobilisation process to avoid volatilising radioactive Cs and Sr species. To this end an immobilisation process with a maximum temperature of 600 deg. C was developed by sintering model waste with glass frit to form a dense Glass Composite Material (GCM) wasteform. A zeolitic model wasteform, chabazite, was sintered with two lead-based glass compositions, lead borosilicate (PBS) and a lead borate (PB) glass composition, at a maximum temperature of 600 deg. C. Full encapsulation of the zeolitic wasteform was achieved for waste-loadings up to 40 wt.% in PBS and 30 wt.% in PB in all cases, with both GCM systems showing foaming. PBS GCM formation was successful at a maximum of 600 deg. C, while the PB GCM formation was shown to be possible at a maximum temperature of 550 deg. C. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Selectivity, Kinetics, and Efficiency of Reversible Anion Exchange with TcO 4 - in a Supertetrahedral Cationic Framework

[ThB5O6(OH)6][BO(OH)2]·2.5H2O (Notre Dame Thorium Borate-1, NDTB-1) is an inorganic supertetrahedral cationic framework material that is derived from boric acid flux reactions. NDTB-1 exhibits facile single crystal to single crystal anion exchange with a variety of common anions such as Cl-, Br-, NO3-, IO3-, ClO4-, MnO4-, and CrO42-. More importantly, NDTB-1 is selective for the removal of TcO4- from nuclear waste streams even though there are large excesses of competing anions such as Cl-, NO3-, and NO2-. Competing anion exchange experiments and magic-angle spinning (MAS)-NMR spectroscopy of anion-exchanged NDTB-1 demonstrate that this unprecedented selectivity originates from the ability of NDTB-1 to trap TcO4- within cavities, whereas others remain mobile within channels in the material. The exchange kinetics of TcO4- in NDTB-1 are second-order with the rate constant k2 of 0.059 s-1 M-1. The anion exchange capacity of NDTB-1 for TcO4- is 162.2 mg g-1 (0.5421 mol mol-1) with a maximum distribution coefficient Kd of 1.0534 × 104 mL g-1. Finally, it is demonstrated that the exchange for TcO4- in NDTB-1 is reversible. TcO4- trapped in NDTB-1 can be exchanged out using higher-charged anions with a similar size such as PO43- and SeO42-, and therefore the material can be easily recycled and reused.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Revealing the Electrophilic‐Attack Doping Mechanism for Efficient and Universal p‐Doping of Organic Semiconductors

Abstract Doping is of great importance to tailor the electrical properties of semiconductors. However, the present doping methodologies for organic semiconductors (OSCs) are either inefficient or can only apply to some OSCs conditionally, seriously limiting their general applications. Herein, a novel p‐doping mechanism is revealed by investigating the interactions between the dopant trityl tetrakis(pentafluorophenyl) borate (TrTPFB) and poly(3‐hexylthiophene) (P3HT). It is found that electrophilic attack of the trityl cations on thiophenes results in the formation of tritylated thiophenium ions, which subsequently induce electron transfer from neighboring P3HT chains to realize p‐doping. This unique p‐doping mechanism enables TrTPFB to p‐dope various OSCs including those with high ionization energy (IE ≈ 5.8 eV). Moreover, this doping mechanism endows TrTPFB with strong doping capability, leading to doping efficiency of over 80% in P3HT. The discovery and elucidation of this novel doping mechanism not only points out that strong electrophiles are a class of efficient p‐dopants for OSCs, but also provides new opportunities toward highly efficient doping of various OSCs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

High Voltage Operation of Ni-Rich NMC Cathodes Enabled by Stable Electrode/Electrolyte Interphases

Lithium (Li) metal battery (LMB) is one of the most promising candidates for the next generation energy storage systems. However, it is still a significant challenge to operate LMBs with high voltage cathode under high rate conditions. In this work, a LMB using nickel-rich layered cathode of LiNi0.76Mn0.14Co0.10O2 (NMC76) and an optimized electrolyte (0.6 M LiTFSI + 0.4 M LiBOB + 0.05 M LiPF6 dissolved in EC: EMC (4:6 by weight)) demonstrate excellent stability under a high charge cutoff voltage of 4.5 V. Remarkably, these Li||NMC76 cells can deliver a high discharge capacity of > 220 mAh g-1 (846 Wh kg-1) and retain more than 80% capacity after 1000 cycles under a high charge/discharge current rates of 2C/2C (1C = 200 mA g-1). These excellent electrochemical performances can be attributed to the highly enhanced structural/interfacial stability of both Ni-rich NMC76 cathode materials and Li metal anode using the optimized electrolyte.

Ni-rich NMC, cathode electrolyte interphase, dual ↗
DOE OSTI2018

Lithium–Iron (III) Fluoride Battery with Double Surface Protection

Abstract Lithium–metal fluoride batteries promise significantly higher energy density than the state‐of‐the‐art lithium‐ion batteries and lithium–sulfur batteries. Unfortunately, commercialization of metal fluoride cathodes is prevented by their high resistance, irreversible structural change, and rapid degradation. In this study, a substantial boost in metal fluoride (MF) cathode stability by designing nanostructure with two layers of protective shells—one deposited ex situ and the other in situ is demonstrated. Such methodology achieves over 90% capacity retention after 300 charge–discharge cycles, producing the first report on FeF 3 as a cathode material, where a very high capacity utilization in combination with excellent stability is approaching the level needed for practical applications of FeF 3 . The cathode solid electrolyte interphase (CEI) containing lithium oxalate and BF bond containing anions is found to effectively protect the cathode material from direct contact with electrolytes, thus greatly suppressing the dissolution of Fe. Quantum chemistry and molecular dynamics calculations provide unique insights into the mechanisms of CEI layer formation. As a result, this work not only demonstrates unprecedented performance, but also provides the reader with a better fundamental understanding of electrochemical behavior of MF cathodes and the positive impact observed with the application of a lithium bis(oxalato)borate salt in the electrolyte.

Zhao, Enbo↗
DOE OSTI2015

Dioxygen Activation by Non‐Adiabatic Oxidative Addition to a Single Metal Center

Abstract A chromium(I) dinitrogen complex reacts rapidly with O 2 to form the mononuclear dioxo complex [Tp t Bu,Me Cr V (O) 2 ] (Tp t Bu,Me =hydrotris(3‐ tert ‐butyl‐5‐methylpyrazolyl)borate), whereas the analogous reaction with sulfur stops at the persulfido complex [Tp t Bu,Me Cr III (S 2 )]. The transformation of the putative peroxo intermediate [Tp t Bu,Me Cr III (O 2 )] (S= 3 / 2 ) into [Tp t Bu,Me Cr V (O) 2 ] (S= 1 / 2 ) is spin‐forbidden. The minimum‐energy crossing point for the two potential energy surfaces has been identified. Although the dinuclear complex [(Tp t Bu,Me Cr) 2 (μ‐O) 2 ] exists, mechanistic experiments suggest that O 2 activation occurs on a single metal center, by an oxidative addition on the quartet surface followed by crossover to the doublet surface.

Akturk, Eser S.↗
DOE OSTI2015

Dioxygen activation by non-adiabatic oxidative addition to a single metal center [O 2 activation by non-adiabatic oxidative addition to a single metal center]

A chromium(I) dinitrogen complex reacts rapidly with O 2 to form the mononuclear dioxo complex [Tp tBu,Me Cr V (O) 2 ] (Tp tBu,Me =hydrotris(3- tert -butyl-5-methylpyrazolyl)borate), whereas the analogous reaction with sulfur stops at the persulfido complex [Tp tBu,Me Cr III (S 2 )]. The transformation of the putative peroxo intermediate [Tp tBu,Me Cr III (O 2 )] (S= 3 / 2 ) into [Tp tBu,Me Cr V (O) 2 ] (S= 1 / 2 ) is spin-forbidden. The minimum-energy crossing point for the two potential energy surfaces has been identified. Finally, although the dinuclear complex [(Tp tBu,Me Cr) 2 (μ-O) 2 ] exists, mechanistic experiments suggest that O 2 activation occurs on a single metal center, by an oxidative addition on the quartet surface followed by crossover to the doublet surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗