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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Nuclear Data Sheets for A = 42

The experimental data are evaluated for known nuclides of mass number A = 42 (Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr). Detailed evaluated level properties and related information are presented, including adopted values of level and γ–ray energies, decay data (energies, intensities and placement of radiations), and other spectroscopic data. This work supersedes earlier full evaluations of A = 42 published by B. Singh, J.A. Cameron – Nucl.Data Sheets 92, 1 (2001) and P.M. Endt – Nucl. Phys. A521, 1 (1990); Errata and Addenda Nucl. Phys. A529, 763 (1991); Errata Nucl. Phys. A564, 609 (1993) (also P.M. Endt – Nucl. Phys. A633, 1 (1998) update). No excited states are known in {sup 42}Al, {sup 42}P, {sup 42}V and {sup 42}Cr, and structure information for {sup 42}Si and {sup 42}S is quite limited. There are no decay schemes available for the decay of {sup 42}Al, {sup 42}Si, {sup 42}P, {sup 42}V and {sup 42}Cr, while the decay schemes of {sup 42}Cl and {sup 42}Ti are incomplete in view of scarcity of data, and large gap between their Q–values and the highest energy levels populated in corresponding daughter nuclei. Structures of {sup 42}Ca, {sup 42}K, {sup 42}Sc and {sup 42}Ar nuclides remain the most extensively studied via many different nuclear reactions and decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Efficiency, Power Loss, and Power Factor Measurement of Quadrupole Magnet Power Supplies at the Spallation Neutron Source

The linear accelerator (LINAC) quadrupole magnets are powered by 42 silicon-controlled rectifier (SCR) based power supplies at the Spallation Neutron Source (SNS) facility of Oak Ridge National Laboratory. These 35V, 525A power supplies are bulky, inefficient and require both air and water cooling. The reliability of the SNS facility is impacted due to water leaks internal to power supplies and current readback issues associated with their unique control system interface, resulting in multiple downtime events. Hence, an alternate solution is necessary for the continued reliable operation of the SNS. To mitigate the above-mentioned problems, this paper proposes the use of off-the-shelf Switch Mode Power Supplies (SMPS) rated for 20V, 500A with serial control interface. These SMPS are air-cooled, more efficient and more compact owing to their switching speeds of approximately 160 kHz. The performance enhancements of the SMPS in comparison with the existing SCR power supply are discussed in detail in this paper. The features of the SMPS, along with experimental results for both power supplies, like efficiency, power losses and stability, are presented. Ongoing work is also discussed.

Harave, Sudarshan↗
DOE OSTI2019

Native Void Space for Maximum Volumetric Capacity in Silicon-Based Anodes

Volumetric energy density is considered a primary factor in developing high-energy batteries. Despite its significance, less efforts have been devoted to its improvement. Silicon-based materials have emerged as next-generation anodes for lithium-ion batteries due to their high specific capacity. However, their volumetric capacities are limited by the volume expansion rate of silicon, which restricts mass loading in the electrodes. To address this challenge, we introduce porous silicon templated from earth-abundant minerals with native internal voids, capable of alleviating volumetric expansion during repeated cycles. In situ transmission electron microscopy analysis allows the precise determination of the expansion rate of silicon, thus presenting an analytical model for finding the optimal content in silicon/graphite composites. The inner pores in silicon reduce problems associated with its expansion and allow higher silicon loading of 42% beyond the conventional limitations of 13–14%. Consequently, the anode designed in this work can deliver a volumetric capacity of 978 mAh cc–1. Thus, suppressing volume expansion with natural abundant template-assisted materials opens new avenues for cost-effective fabrication of high volumetric capacity batteries.

Yeom, Su Jeong↗
NASA NTRS2009

Effect of Oxygen Concentration on Autogenous Ignition Temperature and Pneumatic Impact Ignitability of Nonmetallic Materials

Extensive test data exist on the ignitability of nonmetallic materials in pure oxygen, but these characteristics are not as well understood for lesser oxygen concentrations. In this study, autogenous ignition temperature testing and pneumatic impact testing were used to better understand the effects of oxygen concentration on ignition of nonmetallic materials. Tests were performed using oxygen concentrations of 21, 34, 45, and 100 %. The following materials were tested: PTFE Teflon(Registered Trademark), Buna-N, Silicone, Zytel(Registered Trademark) 42, Viton(registered Trademark) A, and Vespel(Registered Trademark) SP-21.

Smith, Sarah↗
DOE OSTI2020

Boron-hyperdoped silicon for the selective oxidative dehydrogenation of propane to propylene

Boron containing catalysts have great potential in the oxidative dehydrogenation of propane. Herein, a series of 15, 25 and 42 at% boron-hyperdoped silicon catalysts synthesized by laser pyrolysis was studied. Here, boron-hyperdoped silicon samples showed >6 times higher propylene productivity than commercial h-BN at 450 °C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Inserting a Low-Refractive-Index Dielectric Rear Reflector into PERC Cells: Challenges and Opportunities

One of the simplest and most effective ways to reduce the operating temperature of photovoltaic systems in the field is to reflect unusable, 'sub-bandgap' light with energies below the cell absorber's bandgap energy. In this work, low-refractive index SiO2 nanoparticle films inserted between c-Si wafers and metal electrodes significantly increase the reflectance of sub-bandgap light in fabricated test structures. These films are then integrated into the standard PERC fabrication sequence, revealing that the reflection benefits remains after some processing steps but are lost in certain conditions. The SiO2 nanoparticle films are easily ablated during laser contact opening, but are undesirably etched during post-laser cleaning. After Al metallization, the fully fabricated devices show enhanced sub-bandgap reflection when annealed at moderate temperatures, but energy-dispersive X-ray spectroscopy shows that high-temperature firing causes unwanted Al penetration into the SiO2 nanoparticle film, compromising reflection.

14 SOLAR ENERGY↗
NASA NTRS1980

Effects of varying oxygen partial pressure on molten silicon-ceramic substrate interactions

The silicon sessile drop contact angle was measured on hot pressed silicon nitride, silicon nitride coated on hot pressed silicon nitride, silicon carbon coated on graphite, and on Sialon to determine the degree to which silicon wets these substances. The post-sessile drop experiment samples were sectioned and photomicrographs were taken of the silicon-substrate interface to observe the degree of surface dissolution and degradation. Of these materials, silicon did not form a true sessile drop on the SiC on graphite due to infiltration of the silicon through the SiC coating, nor on the Sialon due to the formation of a more-or-less rigid coating on the liquid silicon. The most wetting was obtained on the coated Si3N4 with a value of 42 deg. The oxygen concentrations in a silicon ribbon furnace and in a sessile drop furnace were measured using the protable thoria-yttria solid solution electrolyte oxygen sensor. Oxygen partial pressures of 10 to the minus 7 power atm and 10 to the minus 8 power atm were obtained at the two facilities. These measurements are believed to represent nonequilibrium conditions.

Ownby, D. P.↗
DOE OSTI2019

Evaluation of Carrier Trapping in SiNx Towards Ion Migration Measurements

Sodium ion migration has been implicated in potential induced degradation of the shunting type. The kinetics of sodium migration in silicon nitride can be investigated using a simple capacitance-voltage characterization technique. However, we show that the charge trapping strongly affects the measurement and must be taken into consideration in the experimental approach. Furthermore, we perform a systematic analysis of charge carrier trapping in silicon nitride, allowing us to correct trapping effects that otherwise prevent sodium signal detection. We extract trapping and detrapping time constants both on the order of several hours. This shows that trapping cannot be ignored as it occurs relatively quickly and is constantly evolving in time. Accurate determination of sodium behavior in dielectric layers will facilitate robust co-optimization of these layers for optical, passivation, and barrier properties.

42 ENGINEERING↗
DOE OSTI2022

Medium Voltage Integrated Drive and Motor

The objective of this program was to design, build, and test a medium voltage (4,160VAC) high speed permanent magnet machine (HSPMM) and variable speed drive (VSD) that incorporates next generation 10kV silicon carbide (SiC) modules. The use of a HSPMM allows for high efficiency, small footprint, maintenance free operation while the SiC modules enable higher voltage operating conditions, improved efficiency, and small footprint.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2017

Superacid-Treated Silicon Surfaces: Extending the Limit of Carrier Lifetime for Photovoltaic Applications

Minimizing carrier recombination at interfaces is of extreme importance in the development of high-efficiency photovoltaic devices and for bulk material characterization. Here, we investigate a temporary room temperature superacid-based passivation scheme, which provides surface recombination velocities below 1 cm/s, thus placing our passivation scheme amongst state-of-the-art dielectric films. Application of the technique to high-quality float-zone silicon allows the currently accepted intrinsic carrier lifetime limit to be reached and calls its current parameterization into doubt for 1 Ω·cm n-type wafers. The passivation also enables lifetimes up to 65 ms to be measured in high-resistivity Czochralski silicon, which, to our knowledge, is the highest ever measured in Czochralski-grown material. The passivation strategies developed in this work will help diagnose bulk lifetime degradation under solar cell processing conditions and also help quantify the electronic quality of new passivation schemes.

42 ENGINEERING↗
DOE OSTI2023

Synchronous micromechanically resonant programmable photonic circuits

Abstract Programmable photonic integrated circuits (PICs) are emerging as powerful tools for control of light, with applications in quantum information processing, optical range finding, and artificial intelligence. Low-power implementations of these PICs involve micromechanical structures driven capacitively or piezoelectrically but are often limited in modulation bandwidth by mechanical resonances and high operating voltages. Here we introduce a synchronous, micromechanically resonant design architecture for programmable PICs and a proof-of-principle 1×8 photonic switch using piezoelectric optical phase shifters. Our design purposefully exploits high-frequency mechanical resonances and optically broadband components for larger modulation responses on the order of the mechanical quality factor Q m while maintaining fast switching speeds. We experimentally show switching cycles of all 8 channels spaced by approximately 11 ns and operating at 4.6 dB average modulation enhancement. Future advances in micromechanical devices with high Q m , which can exceed 10000, should enable an improved series of low-voltage and high-speed programmable PICs.

42 ENGINEERING↗
DOE OSTI2020

Methodology of Low Inductance Busbar Design for Three-Level Converters

Three-level (3L) converters are more susceptible to parasitics compared with two-level converters because of their complicated structure with multiple switching loops. In this article, the methodology of busbar layout design for 3L converters based on the magnetic cancellation effect is presented. The methodology can fit for 3L converters with symmetric and asymmetric configurations. A detailed design example is provided for a high-power 3L-active neutral point clamped (ANPC) converter, which includes the module selection, busbar layout, and dc-link capacitor placement. The loop inductance of the busbar is verified with simulation, impedance measurements, and converter experiments. Furthermore, the results match with each other, and the inductances of short and long loops are 6.5 and 17.5 nH, respectively, which are significantly lower than the busbars of NPC-type converters in other references.

42 ENGINEERING↗