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Particle charge distributions in the effluent of a flow-through atmospheric pressure low temperature plasma
Atmospheric pressure low-temperature plasmas are often utilized to perform particle synthesis, treatment, and removal. It is well-known that dust particles are highly negatively charged in these plasmas; however, little is known about dust particle charging behavior as particles leave the plasma volume and pass through the spatial afterglow region. In this work, monodisperse particles of various sizes and work functions were introduced into an atmospheric pressure radiofrequency capacitively coupled flow-through plasma. Dust particle electrical mobility distributions downstream of the flow-through plasma were measured utilizing a differential mobility analyzer in conjunction with a condensation particle counter at various gas flow velocities. Charge distributions were determined from the measured electrical mobility distributions. Experiments confirm that particles become less negatively charged, and even net-positively charged after leaving the plasma volume, with a distribution that follows a shifted Boltzmann charge distribution. Additionally, particle charge in the effluent of the flow-through plasma is negligibly dependent on work function but highly size and flow velocity dependent. Larger particles were shown to have a higher magnitude of charge under all studied conditions; however, particle polarity was switchable by varying gas flow velocity. The charging dynamics were simulated utilizing a constant number Monte Carlo model that accounts for electron temperature decay and the transition from ambipolar to free diffusion of electrons and ions in the spatial afterglow. Simulation results also suggest that, at the same flow velocity, larger particles obtain a greater magnitude of charge, negative or positive. Furthermore, the decrease in electron mobility and the difference between ion and electron convective loss rates create an ion-rich region in the plasma effluent that promotes ion–particle collisions and drives particle charge removal and even reversal of polarity. Larger particles more favorably collide with energetic species in these environments, which results in higher charge states.
Anharmonicity-induced first-order isostructural phase transition of zirconium under pressure
We have performed a detailed x-ray diffraction structural study of Zr under pressure and unambiguously identify the existence of a first-order isostructural bcc-to-bcc phase transition near 58 GPa. First-principles quantum molecular dynamics calculations support the existence of this phase transition, in excellent agreement with experimental results, triggered by anharmonic effects. Lastly, our results highlight the potential ubiquity of anharmonically driven isostructural transitions within the periodic table under pressure and call for follow-up experimental and theoretical studies.
Estimates of Ta strength at ultrahigh pressures and strain rates using thin-film graded-density impactors
In this paper, we present results from an experimental technique used to estimate the strength of Ta at extreme pressures (150 GPa) and strain rates (10 7 s -1 ). A graded-density impactor (GDI) was fabricated using sputter deposition to produce an approximately 40-μm-thick film containing alternating layers of Al and Cu. The thicknesses of the respective layers are adjusted to give an effective density gradient through the film. The GDIs were launched with a 2-stage light gas gun, and shock-ramp-release velocity profiles were measured over timescales of ~10 ns. Results are presented for the direct impact of the film onto LiF windows, which allows for a dynamic characterization of the GDI, as well as from impact onto thin (~40μm) sputtered Ta samples backed by a LiF window. The measurements were coupled with mesoscale numerical simulations to infer the strength of Ta, and the results agree well with other high-pressure platforms, particularly when strain-rate, microstructural, and thermodynamic-path differences are considered.
Pressure-Induced Confined Metal from the Mott Insulator Sr 3 Ir 2 O 7
The spin-orbit Mott insulator Sr 3 Ir 2 O 7 provides a fascinating playground to explore insulator-metal transition driven by intertwined charge, spin, and lattice degrees of freedom. Here, we report high-pressure electric resistance and resonant inelastic x-ray scattering measurements on single-crystal Sr 3 Ir 2 O 7 up to 63-65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa, showing metallicity in the ab plane but an insulating behavior along the c axis. Such an unusual phenomenon resembles the strange metal phase in cuprate superconductors. Since there is no sign of the collapse of spin-orbit or Coulomb interactions in x-ray measurements, this novel insulator-metal transition is potentially driven by a first-order structural change at nearby pressures. Our discovery points to a new approach for synthesizing functional materials.
Cost-Effective Additive Manufacturing of Ambient Pressure-Dried Silica Aerogel
The conventional manufacturing processes for aerogel insulation materials mostly rely on the supercritical drying, which suffers from issues of massive energy consumption, high-cost equipment, and prolonged processing time. Considering the large market demand for the aerogel insulation material in the next decade, a cost-effective and scalable fabrication technique is highly desired. In this paper, a direct ink writing (DIW) method is used to three-dimensionally fabricate the silica aerogel insulation material, followed by room-temperature and ambient pressure drying. Compared with the supercritical drying and freeze-drying techniques, the reported method significantly reduces the fabrication time and costs. The cost-effective DIW technique offers the capability to print complex hollow internal structures, coupled with the porous aerogel structure, it is found to be beneficial for the thermal insulation property. In this work, the addition of fiber to the ink assures the durability of the fabricated product, without sacrificing the thermal insulation performance. The foam ink preparation methods and the printability are demonstrated in this paper, along with the printing of complex three-dimensional geometries. The thermal insulation performance of the printed objects is characterized, and the mechanical properties were also examined. The proposed approach is found to have a 56% reduction in the processing time. The printed silica aerogels exhibit a low thermal conductivity of 0.053 W m –1 K –1 .
Wall-pressure fluctuations and pressure- velocity correlations in a turbulent boundary layer
Wall pressure fluctuations & pressure-velocity correlations in turbulent boundary layers
A pressure telemeter for wind tunnel free flight pressure measurement
Pressure telemeter for wind tunnel free flight pressure measurement
Experimental evaluation of pressurant gas injectors during the pressurized discharge of liquid hydrogen
Effect of pressurant gas injectors during pressurized discharge of liquid hydrogen
Metabolic rates in pressurized pressure suits.
Metabolic rates in pressurized pressure suit, affecting heat balance of subjects metabolic heat with heat removed by environmental control
Pool boiling of methane between atmospheric pressure and the critical pressure.
Pool boiling of methane over pressure range from 1 atm to critical pressure in both nucleate and stable film boiling regimes
Concomitant ion effects on isotope ratio measurements with liquid sampling – atmospheric pressure glow discharge ion source Orbitrap mass spectrometry
RATIONALE: The field of highly accurate and precise isotope ratio (IR) analysis has been dominated by inductively coupled plasma and thermal ionization mass spectrometers. While these instruments are considered the gold standard for IR analysis, the International Atomic Energy Agency desires a field deployable instrument capable of accurately and precisely measuring U isotope ratios. METHODS: The proposed system interfaces the liquid sampling – atmospheric pressure glow discharge (LS-APGD) ion source with a high resolution Exactive Orbitrap mass spectrometer. With this experimental setup certified U isotope standards and unknown samples were analyzed. The accuracy and precision of the system were then determined. RESULTS: The LS-APGD /Exactive instrument measures a certified reference material of natural U (235U/238U = 0.007258) as 0.007041 with a relative standard deviation of 0.158% meeting the International Target Values for Uncertainty for the destructive analysis of U. Additionally, when three unknowns measured and compared to the results from an ICP multi collector instrument, there is no statistical difference between the two instruments. CONCLUSIONS: The LS-APGD / Orbitrap system, while still in the preliminary stages of development, offers highly accurate and precise IR analysis that suggest a paradigm shift in the world of IR analysis. Furthermore, the portability of the LS-APGD as an elemental ion source combined with the low overhead and small size of the Orbitrap suggest that the instrumentation is capable of being field deployable. With liquid sampling glow discharge-Orbitrap MS, isotope ratio and precision performance improves with rejection of concomitant ion species.
Pressure-induced phase transition and phonon softening in h-Lu0.6Sc0.4FeO3
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Superconducting Quantum Metamaterials from High Pressure Melt Infiltration of Metals into Block Copolymer Double Gyroid Derived Ceramic Templates
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Negative;#8208;Pressure;#8208;Induced Large Polarization in Nanosized PbTiO[subscript 3]
Abstract not provided
Effect of Pressure and Thermal Cycling on Long-Term Oxidation in CO 2 and Supercritical CO 2
Concentrating solar power plant designers are interested in supercritical CO 2 (sCO 2 ) for the power block to achieve > 50% electrical efficiency at > 700 °C. The goal of this project was to develop a long-term (> 100 kh) lifetime model for sCO 2 compatibility using 10–15 kh laboratory exposures. Three Ni-based alloys (625, 282 and 740H) and an advanced austenitic stainless steel were evaluated here in long-term exposures at 700–800 °C using 500-h cycles in laboratory air, 0.1 MPa industrial grade (IG) CO 2 and 30 MPa supercritical IG CO 2 and using 10-h cycles in 0.1 MPa IG CO 2 and O 2 . Mass change data and quantification of the oxide scale thickness and depth of internal attack after 1000–10,000 h exposures at 750 °C indicate that these materials are compatible with the sCO 2 environments with modeling used to predict long-term behavior. Comparison of the 0.1 and 30 MPa 500-h cycle results did not show a significant effect of pressure on the reaction, and no significant internal carburization was observed under these conditions, even for the stainless steel, suggesting that chromia scales may be better C diffusion barriers than expected. For the Ni-based alloys, thermal cycling to simulate the solar duty cycle did not result in scale spallation after 15 kh in 10-h cycles or 4 kh in 1-h cycles at 750 °C. However, the stainless steel specimens formed an Fe-rich oxide after ~ 1500-h cumulative exposure time in both 1- and 10-h cycles.
Highly efficient Cu-decorated iron oxide nanocatalyst for low pressure CO2 conversion
We report a nanoparticulate iron oxide based catalyst for CO2 conversion with high efficiency at low pressures and on the effect of the presence of copper on the catalyst’s restructuring and its catalytic performance. In situ X-ray scattering reveals the restructuring of the catalyst at the nanometer scale. In situ X-ray absorption near edge structure (XANES) shows the evolution of the composition and oxidation state of the iron and copper components under reaction conditions along with the promotional effect of copper on the chemical transformation of the iron component. X-ray diffraction (XRD), XANES and Raman spectroscopy proved that the starting nanocatalyst is composed of iron oxides differing in chemical nature (α-Fe2O3, Fe3O4, FeO(OH)) and dimensionality, while the catalyst after CO2 conversion was identified as a mixture of α-Fe, Fe3C, and traces of Fe5C2. The significant increase of the rate CO2 is turned over in the presence of copper nanoparticles indicates that Cu nanoparticles activate hydrogen, which after spilling over to the neighbouring iron sites, facilitate a more efficient conversion of carbon dioxide.
High-pressure vapor-phase hydrodeoxygenation of lignin-derived oxygenates to hydrocarbons by a PtMo bimetallic catalyst: Product selectivity, reaction pathway, and structural characterization
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