Engineering topics

Wang, J. J.

Publications and source records attributed to Wang, J. J..

At least 19 records

DOE OSTI2024

Design, construction, and operation of a 1-ton Water-based Liquid scintillator detector at Brookhaven National Laboratory

Water-based liquid scintillators (WbLS) are a new class of detector materials that provide efficient and tunable detection of both Cherenkov and scintillation light. A massive WbLS neutrino detector with suitable photosensor coverage for low intensity light detection could therefore reconstruct the momentum of an energetic charged particle and also have enhanced low-energy sensitivity. These materials are also better suited for metal doping broadening the potential scientific utility. Here, we recently constructed and commissioned a 1-ton WbLS detector with good photosensor coverage and a capable data acquisition and calibration system. We intend to use this flexible detector system as a testbed for WbLS R&D. In this paper we give an overview of the 1-ton system and provide some early results.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Constraining the Nature of the PDS 70 Protoplanets with VLTI/GRAVITY

We present K-band interferometric observations of the PDS 70 protoplanets along with their host star using VLTI/GRAVITY. We obtained K-band spectra and 100 μas precision astrometry of both PDS 70 b and c in two epochs, as well as spatially resolving the hot inner disk around the star. Rejecting unstable orbits, we found a nonzero eccentricity for PDS 70 b of 0.17 ± 0.06, a near-circular orbit for PDS 70 c, and an orbital configuration that is consistent with the planets migrating into a 2:1 mean motion resonance. Enforcing dynamical stability, we obtained a 95% upper limit on the mass of PDS 70 b of 10 M {sub Jup}, while the mass of PDS 70 c was unconstrained. The GRAVITY K-band spectra rules out pure blackbody models for the photospheres of both planets. Instead, the models with the most support from the data are planetary atmospheres that are dusty, but the nature of the dust is unclear. Any circumplanetary dust around these planets is not well constrained by the planets’ 1–5 μm spectral energy distributions (SEDs) and requires longer wavelength data to probe with SED analysis. However with VLTI/GRAVITY, we made the first observations of a circumplanetary environment with sub-astronomical-unit spatial resolution, placing an upper limit of 0.3 au on the size of a bright disk around PDS 70 b.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Gemini Planet Imager Spectroscopy of the Dusty Substellar Companion HD 206893 B

We present new near-infrared Gemini Planet Imager (GPI) spectroscopy of HD 206893 B, a substellar companion orbiting within the debris disk of its F5V star. The J, H, K1, and K2 spectra from GPI demonstrate the extraordinarily red colors of the object, confirming it as the reddest substellar object observed to date. The significant flux increase throughout the infrared presents a challenging atmosphere to model with existing grids. Best-fit values vary from 1200 to 1800 K for effective temperature and from 3.0 to 5.0 for log(g), depending on which individual wavelength band is fit and which model suite is applied. The extreme redness of the companion can be partially reconciled by invoking a high-altitude layer of submicron dust particles, similar to dereddening approaches applied to the peculiar red field L dwarf population. However, reconciling the HD 206893 B spectra with even those of the reddest low-gravity L dwarf spectra still requires the contribution of additional atmospheric dust, potentially due to the debris disk environment in which the companion resides. Orbit fitting from 4 yr of astrometric monitoring is consistent with a ∼30 yr period, an orbital inclination of 147°, and a semimajor axis of 10 au, well within the estimated disk inner radius of ∼50 au. As one of a very few substellar companions imaged interior to a circumstellar disk, the properties of this system offer important dynamical constraints on companion–disk interaction and provide a benchmark for substellar and planetary atmospheric study.

47 OTHER INSTRUMENTATION↗

DOE OSTI2019

Temperature dependence of structural, dynamical, and electronic properties of amorphous Bi 2 Te 3 : an ab initio study

Bismuth telluride (Bi 2 Te 3 ) has garnered significant interest in thermoelectric applications and three-dimensional topological insulators due to its unique electronic, transport, and thermal properties. Bi 2 Te 3 and Sb 2 Te 3 chalcogenide compounds have the same crystal structure. While Sb 2 Te 3 has been shown to be a prototypical phase change memory (PCM) compound along the pseudobinary tie-line of Ge-Sb-Te alloys, whether Bi 2 Te 3 can also exhibit PCM functionality is still not well established. In this work, a systematic study on the structural, dynamical, and electronic properties of amorphous Bi 2 Te 3 during the quenching process has been performed by using ab initio molecular dynamics simulations. Pair correlation function, coordination number, bond-angle distribution functions, and a novel atomistic cluster alignment method are used to explore the structural characteristics of Bi 2 Te 3 as a function of temperature. Our study shows that there are many distorted octahedral clusters in amorphous Bi 2 Te 3 . In comparison with the local structures in Sb 2 Te 3 , we found that the degree of distortion of the octahedrons in the Bi 2 Te 3 system is smaller than that in Sb 2 Te 3 system. Moreover, the changes in the dynamical properties of Bi 2 Te 3 from liquid to glassy state are also explored. The approximate range of liquid-to-glass transition temperature is determined to be between 673 and 723 K. The electronic properties of Bi2Te 3 and Sb 2 Te 3 are also analysed by density-of-states and Bader charge calculations, both of them in glass state are semiconductors. Our studies provide useful insights into the local structure and dynamical properties of Bi 2 Te 3 at the atomistic level during the fast cooling process, and suggest that the compound can be a candidate for PCM materials.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Bergman-type medium range order in amorphous Zr77Rh23 alloy studied by ab initio molecular dynamics simulations

In recent years, some arguments about the existence of medium-range order (MRO) in the Zr-Rh system have been put forward. However, research on the structural features of the Zr-Rh binary alloy at the atomic level is still lacking. This study uses ab initio molecular dynamics simulations to systematically study the local structures of Zr77Rh23 from the liquid to the glassy states. Pair correlation function (PCF), coordination number (CN), Honeycutt–Anderson(HA) index, bond-angle distribution functions, and the Voronoi tessellation method are used to reveal a clear icosahedral-like configuration in the amorphous Zr77Rh23 alloy. It is noteworthy that the splitting in the second peak of the partial PDF implies the existence of a medium range order (MRO) in the Zr77Rh23 system. We obtain the local order in three-dimensional atomic density distributions by using a new atomistic cluster alignment (ACA) method. Interestingly, a Bergman-type MRO is observed in the glassy Zr77Rh23. Furthermore, the spatial distribution and connections of icosahedral-like clusters are shown to further demonstrate the MRO network. Our findings shed light on the nature of atomic local structures of amorphous Zr77Rh23 alloy and have important implications to understanding the formation of various MROs in metallic glasses.

Guo, Y. R.↗

DOE OSTI2019

Kinetic control of tunable multi-state switching in ferroelectric thin films

Deterministic creation of multiple ferroelectric states with intermediate values of polarization remains challenging due to the inherent bi-stability of ferroelectric switching. In this work we show the ability to select any desired intermediate polarization value via control of the switching pathway in (111)-oriented PbZr 0.2 Ti 0.8 O 3 films. Such switching phenomena are driven by kinetic control of the volume fraction of two geometrically different domain structures which are generated by two distinct switching pathways: one direct, bipolar-like switching and another multi-step switching process with the formation of a thermodynamically-stable intermediate twinning structure. Such control of switching pathways is enabled by the competition between elastic and electrostatic energies which favors different types of ferroelastic switching that can occur. As a whole, our work reflects an alternative approach that transcends the inherent bi-stability of ferroelectrics to create non-volatile, deterministic, and repeatedly obtainable multi-state polarization without compromising other important properties, and holds promise for non-volatile multi-state functional applications.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Epitaxial Growth and Band Alignment of p-NiO/n-Fe2O3 Heterojunction on Al2O3(0001)

Fe2O3 is one of the promising oxide semiconductors as photoanodes for photoelectrochemical water splitting, but its efficiency is still limited by the short diffusion length of photo-excited carriers. Using the internal electric field formed at a p-n heterojunction (HJ) is an efficient strategy to mitigate such limitation. Accordingly, the interfacial atomic structure and band alignment are the most crucial parameters for efficiency optimization. In this work, we report on the epitaxial growth and determination of the band energy alignment of NiO/Fe2O3 p-n heterojunction grown on Al2O3(0001) substrate by pulsed laser deposition. We show that high crystalline quality NiO(111) thin films can be grown on Fe2O3(0001) with epitaxial relationships of [1 ¯11]NiO||[0001 ¯ ]Fe2O3(out-of-plane), [1 ¯1 ¯0]NiO||[011 ¯0]Fe2O3 and [1 ¯12 ¯ ]NiO||[21 ¯1 ¯0]Fe2O3(in-plane). The rotation of NiO hexagons by 30° can effectively reduce the lattice mismatch from ~17.4% to ~1.58%. High resolution X-ray photoelectron spectroscopy reveals that valence and conduction band offset of NiO/Fe2O3 heterojunction are 0.7 eV and 2.3 eV with an upward band bending potential of 0.23 eV for Fe2O3 and a downward band bending potential of 0.32 eV for NiO, respectively. This kind of interfacial band alignment not only facilitates the charge separation, but lowers the overpotentials for oxygen evolution reaction.

Photoelectrochemical Water Splitting, Oxide Semico↗

DOE OSTI2018

Detection of N-glycolylneuraminic acid biomarkers in sera from patients with ovarian cancer using an engineered N-glycolylneuraminic acid-specific lectin SubB2M

Highlights: • N-glycolylneuraminic acid (Neu5Gc) has been proposed as cancer biomarker. • A Neu5Gc-specific lectin, SubB2M, was used to detect Neu5Gc in patient sera. • Serum from ovarian cancer patients has significantly elevated Neu5Gc levels. • Late stage ovarian cancer patients have uniformly elevated levels of Neu5Gc-glycans. N-glycolylneuraminic acid (Neu5Gc)-containing glycans are a prominent form of aberrant glycosylation found in human tumor cells and have been proposed as cancer biomarkers. The B subunit of the subtilase cytotoxin (SubB) produced by Shiga toxigenic Escherichia coli recognises Neu5Gc containing glycans. We have previously engineered this lectin, SubB2M, for greater specificity and enhanced recognition of Neu5Gc-containing glycans. Here we further explore the utility of SubB2M to detect Neu5Gc tumor biomarkers in sera from patients with ovarian cancer. Using surface plasmon resonance (SPR) we show that SubB2M can detect the established ovarian cancer biomarker, CA125, in a highly sensitive and specific fashion in the context of human serum. These studies established conditions for screening serum samples from patients with ovarian cancer for Neu5Gc glycans. We found that serum from patients with all stages of ovarian cancer had significantly elevated mean levels of Neu5Gc glycans compared to normal controls. Serum from patients with late stage disease (stages IIIC, IV) had uniformly elevated levels of Neu5Gc glycans. Detection of Neu5Gc-glycans using SubB2M has the potential to be used as a diagnostic ovarian cancer biomarker, as well as a tool for monitoring treatment and disease progression in late stage disease.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2018

Pressure induced short-range structural changes in supercooled liquid Ge 2 Sb 2 Te 5

Phase-change material such as Ge 2 Sb 2 Te 5 is usually utilized to store data due to the pronounced contrast in optical and electrical properties between crystalline and amorphous phases. As the density differs in the two phases, it is necessary to explore the influence of pressure on the structures of Ge 2 Sb 2 Te 5 , especially for the supercooled liquid which is an inevitable state in the formation of the two phases. The short-range structures in supercooled liquid Ge 2 Sb 2 Te 5 under compression have been investigated by using ab initio molecular dynamics simulation. The supercooled liquid eventually changes to a solid with an increase in pressure. During the process, tetrahedrons decrease slightly, revealing that tetrahedral structures are insensitive to the pressure. Octahedrons increase as the pressure is less than 3.7 GPa and then decrease, suggesting that a moderate pressure can promote the formation of octahedrons. The body-centered-cubic, face-centered-cubic and hexagonal closed-packed structures are observed at 9.9 GPa and then increase gradually. Additionally, it is noticed that Sb- and Te-centered clusters prefer Ge-centered clusters to forming the high-coordinated short-range structures during the compression process. Here our research makes us aware of the effects of pressure on short-range structures in supercooled liquid, which is of great importance in the application of phase-change materials.

36 MATERIALS SCIENCE↗

DOE OSTI2018

The local structural differences in amorphous Ge-Sb-Te alloys

Chalcogenide alloys in pseudobinary line between Sb 2 Te 3 and GeTe are extensively utilied in phase change memories for optical and electronic contrast between crystalline and amorphous phases. Different from the crystalline structure, the understanding of amorphous structures is still insufficient due to disorder and distortion. By employing first-principle molecular dynamics simulations and atomistic cluster alignment analysis, the short-range orders and the associated distortions of amorphous Sb 2 Te 3 , Ge 1 Sb 2 Te 4 , Ge 2 Sb 2 Te 5 , Ge 3 Sb 2 Te 6 and GeTe are investigated to explore the origin of nature difference. The results reveal that Gesingle bondGe and Sbsingle bondSb bonds present a notable competitive mechanism with GeTe content. The GeTe content has a great influence on Ge- and Te-centered short-range orders but little influence on the structures of Sb-centered clusters, especially for the octahedral sites and unidentified structures. The tetrahedrons in Ge-centered clusters of each alloy show a close proportion, but the fraction of tetrahedrons in total clusters increases with the increasing GeTe content due to the increase in the ratio of Ge atom. As for the distortions of clusters, the distorted tetrahedrons in Ge 2 Sb 2 Te 5 are closest to the standard tetrahedron, the Peierls distortion of Ge-centered 6-fold octahedron reduces with an increase in GeTe content whereas that of Sb-centered 6-fold octahedron shows a little change. Also, it is found that GeTe content can inhibit the formation of nanocavity but contribute to the formation of the odd rings. Our findings deepens the understanding of amorphous structures, which can promote the design and application of phase-change materials.

36 MATERIALS SCIENCE↗

NASA NTRS2018

Electrostatic Precipitation for Cleaning Mars Atmospheric ISRU Intakes

Future Mars ISRU atmospheric intakes are estimated to ingest several hundred grams of dust over their lifetime. The Electrostatics and Surface Physics Laboratory at NASA's Kennedy Space Center is developing a dust removal system based on a mature terrestrial technology - electrostatic precipitation. In this technology, a high voltage and grounded collection electrode create a corona discharge which charges particles in a dust-laden flow. The resulting electric field between the high voltage and collection electrodes drive the charged particles toward the collection electrode. This paper presents the design of the electrostatic precipitator and preliminary results.

Precipitator↗

DOE OSTI2018

Evolution of short- and medium-range order in the melt-quenching amorphization of Ge 2 Sb 2 Te 5

Phase-change memory takes advantage of the fast phase transition between amorphous and crystalline phases of phase-change materials (e.g.,Ge 2 Sb 2 Te 5 or GST). To date, while the “SET” process (crystallization of GST glass) has been intensively studied, studies on the “RESET” process (melt-quenching amorphization of GST) are still limited. Here, we explore the structural changes of GST upon rapid cooling by ab initio molecular dynamics simulations and atomistic cluster alignment (ACA) analysis. Different from other methods which only focus on the nearest bonding atoms, the ACA method can study both the short- and medium-range order clusters containing atoms beyond the first-neighboring shell and enables us to explore the changes of cluster structures in a larger scale. The results reveal that low-coordinated octahedral clusters tend to become high-coordinated ones, and Ge-centered octahedral structures change to tetrahedrons whereas Sb-centered tetrahedrons transform to octahedral structures during the amorphization process. Interestingly, tetrahedrons show aggregation in liquid and supercooled liquid in contrast to 6-fold octahedrons which present notable aggregation in amorphous GST. Furthermore, our study showed that wrong bonds (Ge–Ge, Sb–Sb, Ge–Sb and Te–Te bonds) can promote the formation of large rings, and irreducible rings tend to separate into smaller and larger rings as the temperature is decreased. Our conclusions provide useful insights into the formation process and the structure of amorphous GST, which is valuable for facilitating the application of phase change materials.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Structural signature and transition dynamics of Sb 2 Te 3 melt upon fast cooling

Crystalline Sb 2 Te 3 is widely studied due to its important applications in memory materials and topological insulators. The liquid and amorphous structures of this compound as well as the dynamics upon quenching, however, are yet to be fully understood. In this paper, we have systematically studied the dynamical properties and local structure of Sb 2 Te 3 at different temperatures using ab initio molecular dynamics simulations. The calculated structure factors agree well with the experimental results. The atomic number density and mean-squared displacement as a function of temperature clearly indicate three states as the temperature decreases, namely, melt, undercooled liquid and glass state, respectively. By analyzing the chemical environments and bond-angle distribution functions, we demonstrate that the most probable short-range motifs in the Sb 2 Te 3 system are defective octahedrons, and they are connected with each other via four-fold rings. Finally, this interesting structural feature may be responsible for the high fragility and easy phase transition upon glass forming that is applied in memory devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager

Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the Gemini Planet Imager, we discovered a planet orbiting the ~20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10 –6 and an effective temperature of 600 to 750 kelvin. For this age and luminosity, “hot-start” formation models indicate a mass twice that of Jupiter. As a result, this planet also has a sufficiently low luminosity to be consistent with the “cold-start” core-accretion process that may have formed Jupiter.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

A COMPREHENSIVE PHOTOMETRIC STUDY OF THE CONTACT BINARY GN BOO WITH POSSIBLE MAGNETIC ACTIVITIES

Multi-color photometric data of GN Boo observed from 2010 to 2013 are presented. The intrinsic variations of the light curves are remarkable, and their phenomena are probable evidence of stronger magnetic activities on the surfaces of the components. Based on all CCD times of minimum light, a secular increase superimposed on a cyclic oscillation is found. The orbital period increases at a rate of dP/dt = +1.74 × 10{sup −7} days yr{sup −1}, which can be explained by mass transfer from the less massive component to the more massive one. The period and amplitude of the cyclic variation are P = 9.5632 yr and A = 0.0046 days, respectively, which correspond to the previous published results. Using the 2010 version of the W–D code, five sets of photometric solutions were derived from our new data. The results imply that the stellar spot, the degree of fill-out, and the temperature difference ΔT between the components of GN Boo are variable. It is inferred that the magnetic activities perhaps influence the outer radius of the component, causing the temperature of the component star and the level of contact to change.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Photometric analysis of the overcontact binary CW Cas

New CCD photometric observations of overcontact binary CW Cas were carried out in 2004 and 2011. In particular, the light curve obtained in 2004 shows a remarkable O'Connell effect. Compared with light curves in different observing seasons, variations were found. These variations can be explained by dark spot activities on the surface of at least one component. Using the Wilson-Devinney code with a spot model, we find that the photometric solutions confirm CW Cas is a shallow W-subtype overcontact binary with a spotted massive component. Our new determined times of minimum light together with the others published in the literature were analyzed to find a change of orbital period. From the O – C curves, the period of the system shows a cyclic period change (P {sub 3} = 69.9 yr, A {sub 3} = 0.03196 days) superposed on the linear increase. The cyclic variation, if explained as the light-travel time effect, reveals the presence of a tertiary companion.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Three close binaries in different evolutionary stages in the old open cluster NGC 188

NGC 188 is a good laboratory for studying the formation and evolution of W UMa type contact binaries due to its rich populations of them. We present a detailed photometric study of three short-period close binaries, EP Cep, ES Cep, and V369 Cep, in the old open cluster NGC 188 based on our two-set photometric observations. We discovered that both EP Cep and ES Cep are shallow-contact binaries with continuously decreasing periods. The difference is in their mass ratios. EP Cep has an extremely low-mass ratio, q = 0.15, while ES Cep has a relatively high-mass ratio, q = 0.69, indicating that they lie in different evolutionary stages. ES Cep is likely a newly formed contact binary via a Case A mass transfer, while EP Cep is an evolved system and may be on the oscillations caused by the combined effect of the thermal relaxation oscillation and the variable angular momentum loss. For another system, V369 Cep, we found that it is a primary-filling near-contact binary. Both the semidetached configuration and the continuous decrease in the orbital period indicate that it is undergoing a mass transfer from the primary component to the secondary one. This conclusion is in agreement with the excess luminosity seen in the light curves on the ingress of the secondary minimum produced by the impact of the mass transfer. All of the results suggest that V369 Cep is evolving into contact, and a shallow-contact high-mass ratio system similar to ES Cep will be formed. Then, it will evolve into a low-mass ratio contact binary just like EP Cep, and finally merge into a rapidly rotating single star.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Effect of cryogenic treatment on the plastic property of Ti-6Al-4V titanium alloy

The effect of cryogenic treatment on the plastic property of Ti-6Al-4V plate was studied in the present work. After cryogenic treatment, the low temperature temper at 180 ▭ was conducted in one of the groups and the results were compared with that of the untreated and cryotreated ones. The SLX series program controlled cryogenic equipment was used for the cryogenic treatment. The tensile tests were conducted by universal tensile testing machine and parameters of elongation and area reduction were used to evaluate plastic property. The scanning electron microscope was used to study the morphology of microstructure and fracture surface. The results show that after cryogenic treatment alone the elongation increased 10.6% and the area reduction increased 13.5% while the strength reduced to a small extent. Cryogenic treatment followed with low temperature temper increased the elongation and area reduction just by the extent of 4.7% and 9.5%. It means that the additional low temperature temper after cryogenic is not beneficial to the tensile properties of Ti-6Al-4V alloy. The examination of microstructure by scanning electron microscopy revealed that cryogenic treatment reduced the content of β phase particles which is the main reason for the improvement in plasticity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗