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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Nuclear Data Sheets for A = 33

The experimental data are evaluated for known nuclides of mass number A=33 (Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K). Detailed evaluated level properties and related information are presented, including adopted values of level and {gamma}-ray energies, decay data (energies, intensities and placement of radiations), and other spectroscopic data. This work supersedes earlier full evaluations of A=33 published by 1990En08 (also 1998En04 update) and 1978En02. Experimental studies for the identification of the {sup 33}Ne and {sup 33}K nuclides have not met with success as yet. Values of S(n) and S(p) from systematics for {sup 33}Ne and {sup 33}K, respectively suggest that these nuclei are likely to be unstable to particle emission. The radioactive decay schemes of {sup 33}Na and {sup 33}Al seem incomplete in view of large Q values and known excitations much below than allowed by the Q values. The {sup 33}S and {sup 33}Cl nuclides remain as the most extensively studied from many different reactions and decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Final Report: Use of Graphite Foam as a Thermal Performance Enhancement of Heavy Hybrid Propulsion Systems

Oak Ridge National Laboratory's graphite foam has the potential to be used as a heat exchanger for the Army's Future Combat System Manned Ground Vehicle and thus has the potential to improve its thermal performance. The computational fluid dynamics (CFD) program FLOW3D was used to develop a new CFD model for the graphite foam to be used in the development of a proper heat exchanger. The program was calibrated by first measuring the properties of the solid foams and determining the parameters to be used in the CFD model. Then the model was used to predict within 5% error the performance of finned foam heat sinks. In addition, the f factors and j factors commonly used to predict pressure drop and heat transfer were calculated for both the solid and finned structures. There was some evidence that corrugating the foams would yield higher j/f ratios than state of the art heat exchangers, confirming previously measured data. Because the results show that the CFD model was validated, it is recommended that the funding for Phases 2 through 5 be approved for the design of both the finned heat exchanger using tubes and round fin structures and the solid foam design using corrugated foams. It was found that the new CFD model using FLOW3D can predict both solid foam heat transfer and finned foam heat transfer with the validated model parameters. In addition, it was found that the finned foam structures exhibited j/f ratios that indicate that significant heat transfer is occurring within the fin structures due to aerodynamically induced flow, which is not present in solid aluminum fin structures. It is possible that the foam surfaces can act as turbulators that increase heat transfer without affecting pressure drop, like the vortex generators seen in state of the art heat exchangers. These numbers indicate that the foam can be engineered into an excellent heat exchanger. It was also found that corrugating the solid foams would increase the j/f ratio dramatically, allowing the solid foams to compete directly with standard heat exchangers. Although corrugated L1 foam samples have not been produced (attempts are under way), it is possible that their j/f ratio can be even higher than those of the finned structures.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2012

Production of Diesel Engine Turbocharger Turbine from Low Cost Titanium Powder

Turbochargers in commercial turbo-diesel engines are multi-material systems where usually the compressor rotor is made of aluminum or titanium based material and the turbine rotor is made of either a nickel based superalloy or titanium, designed to operate under the harsh exhaust gas conditions. The use of cast titanium in the turbine section has been used by Cummins Turbo Technologies since 1997. Having the benefit of a lower mass than the superalloy based turbines; higher turbine speeds in a more compact design can be achieved with titanium. In an effort to improve the cost model, and develop an industrial supply of titanium componentry that is more stable than the traditional aerospace based supply chain, the Contractor has developed component manufacturing schemes that use economical Armstrong titanium and titanium alloy powders and MgR-HDH powders. Those manufacturing schemes can be applied to compressor and turbine rotor components for diesel engine applications with the potential of providing a reliable supply of titanium componentry with a cost and performance advantage over cast titanium.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2011

An Energy Based Fatigue Life Prediction Framework for In-Service Structural Components

An energy based fatigue life prediction framework has been developed for calculation of remaining fatigue life of in service gas turbine materials. The purpose of the life prediction framework is to account aging effect caused by cyclic loadings on fatigue strength of gas turbine engines structural components which are usually designed for very long life. Previous studies indicate the total strain energy dissipated during a monotonic fracture process and a cyclic process is a material property that can be determined by measuring the area underneath the monotonic true stress-strain curve and the sum of the area within each hysteresis loop in the cyclic process, respectively. The energy-based fatigue life prediction framework consists of the following entities: (1) development of a testing procedure to achieve plastic energy dissipation per life cycle and (2) incorporation of an energy-based fatigue life calculation scheme to determine the remaining fatigue life of in-service gas turbine materials. The accuracy of the remaining fatigue life prediction method was verified by comparison between model approximation and experimental results of Aluminum 6061-T6. The comparison shows promising agreement, thus validating the capability of the framework to produce accurate fatigue life prediction.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2012

Tailored Materials for High Efficiency CIDI Engines

The overall goal of the project, Tailored Materials for High Efficiency Compression Ignition Direct Injection (CIDI) Engines, is to enable the implementation of new combustion strategies, such as homogeneous charge compression ignition (HCCI), that have the potential to significantly increase the energy efficiency of current diesel engines and decrease fuel consumption and environmental emissions. These strategies, however, are increasing the demands on conventional engine materials, either from increases in peak cylinder pressure (PCP) or from increases in the temperature of operation. The specific objective of this project is to investigate the application of a new material processing technology, friction stir processing (FSP), to improve the thermal and mechanical properties of engine components. The concept is to modify the surfaces of conventional, low-cost engine materials. The project focused primarily on FSP in aluminum materials that are compositional analogs to the typical piston and head alloys seen in small- to mid-sized CIDI engines. Investigations have been primarily of two types over the duration of this project: (1) FSP of a cast hypoeutectic Al-Si-Mg (A356/357) alloy with no introduction of any new components, and (2) FSP of Al-Cu-Ni alloys (Alloy 339) by physically stirring-in various quantities of carbon nanotubes/nanofibers or carbon fibers. Experimental work to date on aluminum systems has shown significant increases in fatigue lifetime and stress-level performance in aluminum-silicon alloys using friction processing alone, but work to demonstrate the addition of carbon nanotubes and fibers into aluminum substrates has shown mixed results due primarily to the difficulty in achieving porosity-free, homogeneous distributions of the particulate. A limited effort to understand the effects of FSP on steel materials was also undertaken during the course of this project. Processed regions were created in high-strength, low-alloyed steels up to 0.5 in. deep that showed significant grain refinement and homogeneous microstructures favorable to increased fracture toughness and fatigue performance. The final tasks of the project demonstrated that the FSP concept can be applied to a relevant part geometry by fabricating diesel piston crowns with FSP regions applied selectively to the edge of the bowl rim. This area of the piston typically suffers from conditions at high PCP that cause severe thermal fatigue issues. It is expected that, given the data from coupon testing, the durability of pistons modified by FSP will allow much higher fatigue lifetime and potentially also greater resistance to elevated stress-level effects on fatigue.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2015

Transverse piezoelectric coefficient measurement of flexible lead zirconate titanate thin films

Highly flexible lead zirconate titanate, Pb(Zr,Ti)O{sub 3} (PZT), thin films have been realized by modified sol-gel process. The transverse piezoelectric coefficient d{sub 31} was determined from the tip displacement of bending-mode actuators made of PZT cantilever deposited onto bare or RuO{sub 2} coated aluminium substrate (16 μm thick). The influence of the thickness of ruthenium dioxide RuO{sub 2} and PZT layers was investigated for Pb(Zr{sub 0.57}Ti{sub 0.43})O{sub 3}. The modification of Zr/Ti ratio from 40/60 to 60/40 was done for 3 μm thick PZT thin films onto aluminium (Al) and Al/RuO{sub 2} substrates. A laser vibrometer was used to measure the beam displacement under controlled electric field. The experimental results were fitted in order to find the piezoelectric coefficient. Very large tip deflections of about 1 mm under low voltage (∼8 V) were measured for every cantilevers at the resonance frequency (∼180 Hz). For a given Zr/Ti ratio of 58/42, it was found that the addition of a 40 nm thick RuO{sub 2} interfacial layer between the aluminium substrate and the PZT layer induces a remarkable increase of the d{sub 31} coefficient by a factor of 2.7, thus corresponding to a maximal d{sub 31} value of 33 pC/N. These results make the recently developed PZT/Al thin films very attractive for both low frequency bending mode actuating applications and vibrating energy harvesting.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Characterisation of Ga-coated and Ga-brazed aluminium

This work is devoted to the brazing of aluminium using liquid gallium. Gallium was deposited on aluminium samples at {approx} 50 Degree-Sign C using a liquid gallium 'polishing' technique. Brazing was undertaken for 30 min at 500 Degree-Sign C in air. EDS (Energy Dispersive X-ray Spectroscopy) and AES (Auger Electron Spectroscopy) characterisation of Ga-coated samples has shown that the Ga surface layer thickness is of ten (or a few tens of) nanometres. Furthermore, aluminium oxide layer (Al{sub 2}O{sub 3}) was shown to be 'descaled' during Ga deposition, which ensures good conditions for further brazing. Cross-section examination of Ga-coated samples shows that liquid gallium penetrates into the aluminium grain boundaries during deposition. The thickness of the grain boundary gallium film was measured using an original EDS technique and is found to be of a few tens of nanometres. The depth of gallium grain boundary penetration is about 300 {mu}m at the deposition temperature. The fracture stress of the brazed joints was measured from tensile tests and was determined to be 33 MPa. Cross-section examination of brazed joints shows that gallium has fully dissolved into the bulk and that the joint is really autogenous. - Highlights: Black-Right-Pointing-Pointer Aluminium can be brazed using liquid gallium deposited by a 'polishing' technique. Black-Right-Pointing-Pointer The aluminium oxide layer is 'descaled' during liquid Ga 'polishing' deposition. Black-Right-Pointing-Pointer EDS can be used for determination of surface and grain boundary Ga film thickness. Black-Right-Pointing-Pointer The surface and grain boundary Ga film thickness is of a few tens of nm. Black-Right-Pointing-Pointer Surface and grain boundary gallium dissolves in the bulk during brazing.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Pulsed DC magnetron sputtered piezoelectric thin film aluminum nitride – Technology and piezoelectric properties

Pulsed DC magnetron sputtered aluminum nitride (AlN) thin films are prepared on several seed layers and at different sputtering conditions. The piezoelectric c-axis (002) orientation of the AlN is analyzed with X-ray diffraction method. The transverse piezoelectric coefficient d{sub 31} is determined with a Laser-Doppler-Vibrometer at cantilevers and membranes by analytical calculations and finite element method. Additionally, thin film AlN on bulk silicon is used to characterize the longitudinal piezoelectric charge coefficient d{sub 33}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} laser ceramics: Influence of the size of yttrium oxide particles on sintering

The influence of the size of Y{sub 2}O{sub 3} powder particles on the structure formation and densification of Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} laser ceramics has been studied. It is shown that the use of 50- and 100-nm yttrium oxide particles makes it possible to synthesize single-phase yttrium aluminum garnet at temperatures of 1200 and 1500°C, respectively, whereas in the case of 5000-nm yttrium oxide particles 2-h exposure at a temperature of 1500°C yields only 80 wt % of the Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} phase. Bulk swelling of pressed samples during sintering of 2.94Y{sub 2}O{sub 3}-0.06Nd{sub 2}O{sub 3}-5Al{sub 2}O{sub 3} powders with the size ratio of the initial particles R(Al{sub 2}O{sub 3}/Y{sub 2}O{sub 3}) ∼ 5 is observed. The application of different-sized powders (R ∼ 2.5) provides quantitative ratios between phases in the 3Y{sub 2}O{sub 3}-5Al{sub 2}O{sub 3} system at which shrinkage in a temperature range of 20–1500°C is dominant. Laser ceramics 0–2 at % Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} have been obtained by the solid-phase sintering of oxide powders (R ∼ 2.5). The slope efficiency for 1 at % Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} laser ceramics is found to be 33%.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Lasing in a Tm : Yb{sub 3}Al{sub 5}O{sub 12} crystal pumped at 1.678 μm

The Yb{sub 3}Al{sub 5}O{sub 12} (YbAG) crystal is proposed as a matrix of Tm{sup 3+}-doped laser elements for two-micron lasers. A Tm : YbAG crystal of high optical quality is grown by the Czochralski method and its spectral and luminescent characteristics are studied. The luminescence decay time for the upper laser level {sup 3}F{sub 4} is measured to be 4.7 ms. Lasing in this crystal pumped by a 1.678-μm fibre laser is obtained at a wavelength of 2.02 μm for the first time. The total and slope efficiencies of the laser at room temperature and an output power up to 330 mW reach 33% and 41%, respectively. (lasers)

36 MATERIALS SCIENCE↗
DOE OSTI2012

Piezoelectric material for use in a nuclear reactor core

In radiation environments ultrasonic nondestructive evaluation has great potential for improving reactor safety and furthering the understanding of radiation effects and materials. In both nuclear power plants and materials test reactors, elevated temperatures and high levels of radiation present challenges to ultrasonic NDE methodologies. The challenges are primarily due to the degradation of the ultrasonic sensors utilized. We present results from the operation of a ultrasonic piezoelectric transducer, composed of bulk single crystal AlN, in a nuclear reactor core for over 120 MWHrs. The transducer was coupled to an aluminum cylinder and operated in pulse echo mode throughout the irradiation. In addition to the pulse echo testing impedance data were obtained. Further, the piezoelectric coefficient d{sub 33} was measured prior to irradiation and found to be 5.5 pC/N which is unchanged from as-grown samples, and in fact higher than the measured d{sub 33} for many as-grown samples.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

AlN texturing and piezoelectricity on flexible substrates for sensor applications

We show that AlN-based piezocapacitors with relatively high piezoelectric coefficient (d{sub 33}) values (3–4 pC/N) can be fabricated on polyimide (PI) substrates at 160 °C or even at room temperature by sputtering processes. With respect to PI, a reduction of the piezoelectric performances was observed on polyethylene naphthalate (PEN). With the same approach, a d{sub 33} value as high as 8 pC/N was achieved on rigid substrates (SiO{sub 2}/Si). In all cases, a thin Al buffer layer was deposited, immediately before AlN, without breaking the vacuum in the deposition chamber, in order to preserve the interface from contaminations that would obstruct the optimal atomic stratification with the desired [0001] growth axis. The piezoelectric behavior was thus correlated to the degree of texturing of the AlN layer through the evaluation of the XRD texturing coefficients and to the morphology by means of AFM analyses. We show that a high level of roughness introduced by the PEN substrate, coupled with the effect of the substrate flexibility on the piezoelectric coefficient, reduces the impact of the AlN texturing on the d{sub 33} values.

36 MATERIALS SCIENCE↗
NASA NTRS2007

SEM-EDS Analyses of Small Craters in Stardust Aluminum Foils: Implications for the Wild-2 Dust Distribution

Aluminium foils were used on Stardust to stabilize the aerogel specimens in the modular collector tray. Part of these foils were fully exposed to the flux of cometary grains emanating from Wild 2. Because the exposed part of these foils had to be harvested before extraction of the aerogel, numerous foil strips some 1.7 mm wide and 13 or 33 mm long were generated during Stardusts's Preliminary Examination (PE). These strips are readily accommodated in their entirety in the sample chambers of modern SEMs, thus providing the opportunity to characterize in situ the size distribution and residue composition - employing EDS methods - of statistically more significant numbers of cometary dust particles compared to aerogel, the latter mandating extensive sample preparation. We describe here the analysis of nearly 300 impact craters and their implications for Wild 2 dust.

Borg, J.↗
DOE OSTI2015

Imaging of transient surface acoustic waves by full-field photorefractive interferometry

A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Oxidation of Advanced Steel Cladding Alloys in Extreme Environments

Accident tolerant claddings must withstand the loss of coolant for longer times than conventional zirconium-based reactor claddings. Advanced steel alloys (such as Alloy 33, APMT) offer enhanced resistance to high-temperature oxidation in steam environments due to the formation of protective oxide layers of chromia and/or alumina oxides on the surface of the alloy, which enhance their stability at high temperatures by acting as an effective diffusion barrier, so resulting in low rate of oxidation. These passivating oxide layers, resistant to accelerated oxidation, offer an improvement over the current designs by reducing the production of hydrogen gas, and by delaying the release of fission products into the environment. Hence, these alloys present a great opportunity to explore alternative cladding materials with better accident tolerance for commercial light water reactors. Alloy 33 and APMT showed enhanced resistance to corrosion under the normal operation and off-nominal conditions of light water reactors.

36 MATERIALS SCIENCE↗
NASA NTRS2004

T-shaped emitter metal heterojunction bipolar transistors for submillimeter wave applications

We report on the development of submillimeter wave transistors at JPL. The goal of the effort is to produce advance-reliable high frequency and high power amplifiers, voltage controlled oscillators, active multipliers, and high-speed mixed-signal circuits for space borne applications. The technology in development to achieve this is based on the Indium Phosphide (InP) Heterojunction Bipolar Transistor (HBT). The HBT is well suited for high speed, high power and uniform (across wafer) performance, due to the ability to tailor the material structure that electrons traverse through by well-controlled epitaxial growth methods. InP with its compatible lattice matched alloys such as indium gallium arsenide (InGaAs) and indium aluminium arsenide (InAlAs) provides for high electron velocities and high voltage breakdown capabilities. The epitaxial methods for this material system are fairly mature, however the implementation of high performance and reliable transistors are still under development by many laboratories. Our most recently fabricated, second generation mesa HBTs at JPL have extrapolated current gain cutoff frequency (FJ of 142GHz and power gain cutoff frequency (Fm,) of approximately 160GHz. This represents a 13% and 33% improvement of Ft and F, respectively, compared to the first generation mesa HBTs [l]. Analysis based on the University of California, Santa Barbara (UCSB) device model, RF device characteristics can be significantly improved by reducing base contact resistance and base metal contact width. We will describe our effort towards increasing transistor performance and yield.

transistor↗