High-pressure H2O Research Articles

Simulation of localized electron density enhancement caused by high-pressure H2O gas release in ionosphere

Based on the continuity and momentum equations, a self-consistent simulation model is developed for describing the localized electron density enhancement caused by high-pressure H2O gas release in the ionosphere. The chemical reaction and momentum exchange process between the neutral gas and ionospheric plasma species are considered in the theoretical simulation model. The finite element method is used to solve the simulation model for H2O gas release, and the expansion and ionospheric disturbance process at the early stage of high-pressure gas release are studied. It is shown that the space expansion of the released gas is mainly dominated by the pressure difference between the H2O gas and the ionospheric plasma at the early stage of release. Then the diffusion process becomes the dominant process of the space transport of H2O molecules. An electron depletion region forms near the center of the release region due to the chemical reaction and collision process with H2O molecules. Meanwhile, an electron density enhancement region forms on both sides along the magnetic field direction due to the electron snowplow effect. With the increase in the released mass of H2O gas, the intensity and duration of the electron density enhancement increase gradually. With the release position rising, it is found that the intensity of the electron density enhancement has a peak near 380 km and the duration increases slightly with the increasing release height.

Molecular dynamics, thermodynamics and experimental studies on the corrosion mechanism of T92 and TP347H steels in high-pressure CO2 and H2O at 600 °C

The corrosion mechanisms of T92 and TP347H heat-resistance steels in high-temperature and high-pressure (HTHP) CO2 and H2O environments were investigated by molecular dynamics, thermodynamics and experiments. In the initial corrosion stage, the combination ability of Cr with O and C was stronger than that of Fe with O and C, which caused oxygen and carbon absorption capacity of TP347H steel was higher than that of T92 steel. In HTHP H2O environment, the Fe3O4 oxides on T92 steel were coarsened and pulverized, which made the Fe3O4 oxides become loose. The volatile CrO2(OH)2 were formed on the surface of TP347H steel, which caused the coarsening of Cr2O3 oxides.

High-pressure H2O post-annealing for improving reliability of LTPS and a-IGZO thin-film transistors within a coplanar structure

Improving reliability of low-temperature polycrystalline silicon (LTPS) and amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs), components of low-temperature polycrystalline silicon and oxide (LTPO), is crucial for fabricating high-performance and high-stability LTPS and oxide semiconductor-based electronics and display products. However, improving the reliability of these TFTs simultaneously in a uniform and effective manner within a coplanar structure is challenging. In this work, high-pressure H2O post-annealing (H2O HPPA) as a post-treatment for LTPS and a-IGZO TFTs within a coplanar structure are proposed to improve the uniformity and stability of the electrical characteristics simultaneously. It was demonstrated that oxygen and hydrogen in the HPPA-passivated defect state at the channel/gate dielectric layer interfaces and bulk gate dielectric layers of LTPS and a-IGZO TFTs considerably improve the uniformity and stability of the electrical performance and morphologies of the interfaces. Thus, the distribution of electrical characteristics (mobility, threshold voltage, and subthreshold swing) in LTPS and a-IGZO TFTs was reduced by more than 2-fold, and the trap charge densities at their interfaces and bulk gate dielectric layers were reduced by approximately 1.6-fold. Furthermore, the threshold voltage shift was decreased in both LTPS and a-IGZO-TFTs fabricated with H2O HPPA under negative and positive bias temperature stresses, respectively. The proposed H2O HPPA method can effectively facilitate the industry-level application of LTPS and oxide semiconductor-based electronics and display electronics.

Study on the relationship between Fe3O4 fouling and NiFe2O4 oxide layer in the secondary circuit of nuclear steam generator

Fouling is one of the most significant problem in the steam generator (SG) of pressurized water reactor (PWR) nuclear power plant (NPP). To figure out the deposition process, through changing the Fe2+concentration and temperature in the simulated configurations (523 K–603 K), adsorption mechanism of fouling Fe3O4 on steam generator (SG) tube in secondary circuit of pressurized water reactor (PWR) nuclear power plant was investigated by molecular dynamic simulation. The ion concentration distribution, the mean square displacement (MSD), the radial distribution function (RDF), and the energy change before and after adsorption were compared. The influence of the change of temperature and Fe2+ concentration on the corrosion of the SG tube was discussed. Due to the negative surface charge of NiFe2O4, the Fe2+ in the solution did not bond with OH−, but agglomerated with high-pressure high-temperature H2O in the form of triangular bipyramid and octahedron. The diffusion coefficient of OH− increases linearly with the increase of temperature (from 15.28 × 10−5 cm2/s to 18.59 × 10−5 cm2/s) and concentration (from 14.40 × 10−5 cm2/s to 16.06 × 10−5 cm2/s). While the diffusion coefficient of Fe2+reduces, the diffusion coefficient of H2O changes. Simultaneously, Fe3O4 fouling formed on the surface of NiFe2O4 dense oxide layer due to the ion adsorption and interface charges. This work can provide an atomic-scale basis for fouling inhibition in the SG of PWR nuclear power plant.

Abstract 13551: RhoA Mediates Pressure-Induced Endothelial Hyperpermeability

Pulmonary edema is a severe complication of heart failure. It is often caused by the abrupt increase in lung pulmonary capillary pressure that leads to endothelial barrier instability and disruption. The mechanisms whereby high pressure causes pulmonary edema is unresolved. However, eNOS uncoupling and downstream protein nitration may play a role. We have previously shown that eNOS uncoupling, leading to RhoA activation, is key to the development of pulmonary edema in a model of hypertensive heart failure. Herein, we sought to determine if RhoA activation plays a role in pressure-induced pulmonary edema and the molecular mechanisms that govern this process. Human lung microvascular endothelial cells (HLMEC) were exposed to 0cm (control) or 30cm (high pressure) H 2 O pressure for 5 to 60 minutes. Phosphorylation of eNOS at T495 and PKCα activation were assessed by Western blot, RhoA activation and nitration was assessed by ELISA and dot blot assays and endothelial barrier stability was assessed by VE-cadherin staining. The effects of pressure on barrier function were assessed by transendothelial electrical resistance (TEER). High hydrostatic pressure induced PKCα activation (1.42±0.2 vs 0.8±0.05 control, p=0.029; N=5) and the phosphorylation of eNOS at T495 (1.6±0.1 vs 0.62±0.08 control; p=0.0319; N=3), which was used as a correlation to eNOS uncoupling. This was associated with increased RhoA activity (0.009±0.001 vs. 0.005±0.001 control; p=0.0247; N=5), RhoA nitration (2.1±0.4 vs 1.0±0.02 control, p=0.0511; N=4) and VE-cadherin internalization. HLMEC exposed to control and high pressure conditions were transferred to gold electrodes (ECIS assay) to monitor TEER as indices of barrier recovery. High pressure caused a delay in barrier recovery and a decrease in the maximum TEER after 24 hours (0.952±0.16 vs 1.55±.019 control; p=0.0412; N=4). Fasudil, a Rho inhibitor, mitigated the effects of pressure on barrier recovery (1.996±0.79 vs 0.968±0.44 pressure; p<0.0001; N=4). Altogether, these findings suggest that pressure induces endothelial barrier disruption via PKCα-mediated eNOS uncoupling and subsequent activation of RhoA. This may be important in conditions in which pulmonary pressure can increase abruptly, including heart failure.

3D characterization of individual grains of coexisting high-pressure H2O ice phases by time-domain Brillouin scattering

Time-domain Brillouin scattering (TDBS) uses ultrashort laser pulses to (i) generate coherent acoustic pulses of picoseconds duration in a solid sample and (ii) follow their propagation in order to image material inhomogeneities with the axial resolution that can be deeply sub-optical, to nm-scale, and the lateral one down to the optical diffraction limit (half the optical wavelength of the probe laser). TDBS permits highly resolved 3D-imaging of grains in polycrystalline transparent samples with unlimited lateral sizes and thicknesses of at least 10 μm also when samples are orientationally textured and/or located in devices permitting access along one direction and from one side only. This optical technique presents, accordingly, clear advantages compared to any x-ray based computed tomography (neither back-projection algorithm nor multiple viewpoints of the sample are needed) and classical spectroscopic methods. Here, we applied TDBS to the 3D-imaging of a sample of polycrystalline water ice containing two high-pressure phases. The imaging, accomplished via a simultaneous detection of quasi-longitudinal and quasi-shear waves, provided shape, coordinates, phase content, and crystallographic orientation of resolved crystallites in a common coordinate system. Monitoring of acoustic pulses simultaneously propagating in two neighboring grains provided a new tool for the localization of grain boundaries.

Modelling of CO <sub>2</sub> and H <sub>2</sub>O Interaction During Adsorption Cycles on Hydrotalcite for SEWGS Applications

Sorption Enhanced Water Gas Shift (SEWGS) is an intensified pre-combustion capture process, based on a potassium promoted Mg/Al-hydrotalcite sorbent. The technology has demonstrated low energy requirements and high capture performances in real industrial settings within the Iron and Steel sector. Reactor modelling is an essential tool to develop energy and cost-efficient SEWGS units. The TNO developed model captures the fundamentals of the gas-solid thermodynamic and kinetic interactions, to accurately predict the multi-column behaviour, allowing for unit sizing and quantification of the energy requirements. The updated interaction model consists of Langmuir interaction for CO2, a competitive interaction site for CO2 and H2O, an exchange site where either CO2 or H2O is adsorbed and a pore condensation for high-pressure H2O. The updated model is validated against single column and multi-column operation with simulated blast furnace gas.

Improvement of negative bias temperature instability of LTPS TFTs by high pressure H2O annealing

In this study, high pressure H2O annealing (HPA) was performed to improve the reliability of low temperature poly-Si thin film transistors (LTPS TFTs) fabricated on a polyimide (PI) substrate. Due to the low heat resistance of the PI substrate, the pressure was high to reduce the temperature of the heat treatment. HPA was performed at 130 °C and 0.3 Mpa in an H2O ambient for 2 h. After HPA treatment, the threshold voltage (VT) shifted to the positive direction from −2.27 V to −1.75 V, and the hysteresis (ΔVT) decreased from 0.67 V to 0.24 V. The density of states (DOS) measurement shows that the interface trap decreased after HPA processing, hence, it is assumed that stability for bias stress has improved. Before and after HPA, the VT shift for negative bias temperature instability (NBTI) stress was 1.19 V and 0.2 V, respectively. After HPA treatment, ΔVT decreased significantly for bias stress. It seems that the decomposed oxygen from H2O diffused to the gate insulator and combined with Si to reduce the oxygen vacancy. The strength of the gate insulator improved after HPA.

Selective Fragmentation through C–N Bond Cleavage of Carbon Nitride Framework for Enhanced Photocatalytic Hydrogen Production

A simple, practical approach for the structural modification of bulk g-C3N4 employing high-pressure NH3 and H2O formed by the polycondensation of urea is reported. The high-pressure processes the p...

Efficient organic/polycrystalline silicon hybrid solar cells

We firstly investigated efficient poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS)/n-type polycrystalline silicon (p-Si) heterojunction solar cells fabricated by chemical mist deposition (CMD) using a high-pressure H2O-vapor-treated p-Si prior to organic film deposition. High-pressure H2O vapor treatment of the p-Si efficiently suppressed grain boundary defects and improved carrier transport at the PEDOT:PSS/p-Si interface. Furthermore, compared to spin coated devices, the CMD devices demonstrated a more uniform photovoltaic performance. The power conversion efficiency of the PEDOT:PSS/p-Si heterojunction solar cells was 9.7% with a short-circuit current density of 33.5mA/cm2, an open-circuit voltage of 0.54V, and a fill factor of 0.53. These findings suggest that CMD with a negatively charged mist precursor provides uniform adhesion of PEDOT:PSS on p-Si, resulting in increased photovoltaic performance.

Equations of state of ice VI and ice VII at high pressure and high temperature.

High-pressure H2O polymorphs among which ice VI and ice VII are abundant in the interiors of large icy satellites and exo-planets. Knowledge of the elastic properties of these pure H2O ices at high-temperature and high-pressure is thus crucial to decipher the internal structure of icy bodies. In this study we assess for the first time the pressure-volume-temperature (PVT) relations of both polycrystalline pure ice VI and ice VII at high pressures and temperatures from 1 to 9 GPa and 300 to 450 K, respectively, by using in situ synchrotron X-ray diffraction. The PVT data are adjusted to a second-order Birch-Murnaghan equation of state and give V0 = 14.17(2) cm(3) mol(-1), K0 = 14.05(23) GPa, and α0 = 14.6(14) × 10(-5) K(-1) for ice VI and V0 = 12.49(1) cm(3) mol(-1), K0 = 20.15(16) GPa, and α0 = 11.6(5) × 10(-5) K(-1) for ice VII.

THE EFFECT OF TEMPERATURE EVOLUTION ON THE INTERIOR STRUCTURE OF H2O-RICH PLANETS

For most planets in the range of radii from 1 to 4 R⊕, water is a major component of the interior composition. At high pressure H2O can be solid, but for larger planets, like Neptune, the temperature can be too high for this. Mass and age play a role in determining the transition between solid and fluid (and mixed) water-rich super-Earth. We use the latest high-pressure and ultra-high-pressure phase diagrams of H2O, and by comparing them with the interior adiabats of various planet models, the temperature evolution of the planet interior is shown, especially for the state of H2O. It turns out that the bulk of H2O in a planet's interior may exist in various states such as plasma, superionic, ionic, Ice VII, Ice X, etc., depending on the size, age, and cooling rate of the planet. Different regions of the mass–radius phase space are also identified to correspond to different planet structures. In general, super-Earth-size planets (isolated or without significant parent star irradiation effects) older than about 3 Gyr would be mostly solid.

Crystallization of Amorphous Silicon Thin Films by Microwave Heating

ABSTRACTWe report crystallization of amorphous silicon (a-Si) thin films and improvement of thin film transistors (TFTs) characteristics using 2.45 GHz microwave heating assisted with carbon powders. Undoped 50-nm-thick a-Si films were formed on quartz substrates and heated by microwave irradiation for 2, 3, and 4 min. Raman scattering spectra revealed that the crystalline volume ratio increased to 0.42 for the 4-min heated sample. The dark and photo electrical conductivities measured by Air mass 1.5 at 100 mW/cm2 were 2.6x10-6 and 5.2x10-6 S/cm in the case of 4-min microwave heating followed by 1.3x106-Pa-H2O vapor heat treatment at 260°C for 3 h. N channel polycrystalline silicon TFTs characteristics were improved by the combination of microwave heating with high-pressure H2O vapor heat treatment. The threshold voltage decreased from 5.3 to 4.2 V and the effective carrier mobility increased from 18 to 25 cm2/Vs.

Isotopic differentiation and sublattice melting in dense dynamic ice

The isotopes of hydrogen provide a unique exploratory laboratory for examining the role of zero point energy (ZPE) in determining the structural and dynamic features of the crystalline ices of water. There are two critical regions of high pressure: (i) near 1 TPa and (ii) near the predicted onset of metallization at around 5 TPa. At the lower pressure of the two, we see the expected small isotopic effects on phase transitions. Near metallization, however, the effects are much greater, leading to a situation where tritiated ice could skip almost entirely a phase available to the other isotopomers. For the higher pressure ices, we investigate in some detail the enthalpics of a dynamic proton sublattice, with the corresponding structures being quite ionic. The resistance toward diffusion of single protons in the ground state structures of high-pressure H2O is found to be large, in fact to the point that the ZPE reservoir cannot overcome these. However, the barriers toward a three-dimensional coherent or concerted motion of protons can be much lower, and the ensuing consequences are explored.

A comparison of ice VII formed in the H2O, NaCl–H2O, and CH3OH–H2O systems: Implications for H2O-rich planets

High-pressure H2O polymorphs, namely ice VI, ice VII, and ice X, are hypothesized to make up a considerable portion of the interiors of large icy satellites and select extra-solar planets. The incorporation of foreign ions or molecules into these high-pressure phases is possible through ocean–ice interaction, rock–ice interaction at depth, or processes that occurred during accretion. Recent research concerning the effects charged ions have on ice VII has shown that these ions notably affect the structure of ice VII (Frank et al., 2006; Klotz et al., 2009). This study was designed to determine the effects of a molecular impurity on ice VII and compare those effects to both pure H2O ice and ice with an ionic impurity. Ice samples were formed in this study via compression in a diamond anvil cell from either H2O, a 1.60mol% NaCl aqueous solution, a 1.60mol% CH3OH aqueous solution, or a 5.00mol% CH3OH aqueous solution and were compressed up to 71GPa at room temperature. Ice formed from pure H2O had no impurities whereas ices formed in the NaCl–H2O and CH3OH–H2O systems contained the impurities Na+ and Cl− and CH3OH, respectively. Pressure–volume relations were observed in situ by using synchrotron based X-ray diffraction and were used to determine the equations of state for ices formed in the H2O, NaCl–H2O and CH3OH–H2O systems. The data illustrate that ice VII formed from a NaCl-bearing aqueous solution exhibited a depressed volume when compared to that of H2O-only ice VII at any given pressure, whereas ice VII formed from CH3OH-bearing aqueous solutions showed an opposite trend, with an increase in volume relative to that of pure ice VII. The ices within planetary bodies will most likely have both ionic and molecular impurities and the trends outlined in this study can be used to improve density profiles of H2O-rich planetary bodies.

Heat treatment of amorphous silicon p-i-n solar cells with high-pressure H2O vapor

We report improvement in characteristics of hydrogenated amorphous silicon (a-Si:H ) p-i-n structured solar cells by high-pressure H2O vapor heat treatment. a-Si:H p-i-n solar cells were formed on glass substrates coated with textured SnO2 layer. P-, i-, and n-type a-Si:H layers were subsequently formed by plasma enhanced chemical vapor deposition. Finally an indium-tin-oxide layer was coated on the n-type a-Si:H surface. Heat treatment at 210°C with 2×105 Pa H2O vapor for 1h was applied to the a-Si:H p-i-n solar cells. Electrical characteristics were measured when samples were kept in dark and illuminated with light of AM 1.5 at 100mW/cm2. The heat treatment with H2O vapor increased fill factor (FF) and the conversion efficiency from 0.54 and 7.7% (initial) to 0.57 and 8.4%, respectively. Marked improvement in solar cell characteristics was also observed in the case of a poor a-Si:H p-i-n solar cell. FF and the conversion efficiency were increased from 0.29 and 3.2% (initial) to 0.56 and 7.7%, respectively.

Surface Passivation of Crystalline Silicon by Combination of Amorphous Silicon Deposition with High-Pressure H2O Vapor Heat Treatment

A high minority carrier effective lifetime τeff of crystalline silicon was achieved by hydrogenated amorphous silicon (a-Si:H) films formed by a combination of plasma-enhanced chemical vapor deposition at 150 °C with high-pressure H2O vapor heat treatment. τeff was 1.6×10-4, 3.0×10-4, and 1.15×10-3 s for n-type silicon substrates coated with 3-, 10-, and 50-nm-thick a-Si:H films treated with 1.0×106 Pa H2O vapor heat treatment between 180 and 300 °C for 1 h. Light-induced passivation enhancement was demonstrated when 620-nm light was illuminated at the 50-nm-thick a-Si:H surface. τeff increased from 8.5×10-4 to 1.15×10-3 s probably caused by field effect passivation induced by hole trapping at the SiOx formed by H2O vapor heat treatment for 1 h. On the other hand, τeff was further increased to 1.2×10-3 s by 1.0×106 Pa H2O vapor heat treatment at 300 °C for 3 h for the sample formed with the 50-nm-thick a-Si:H film. However, no increase in τeff was observed by light illumination at the a-Si:H surface, probably because the SiOx clusters became stable and had no hole trapping property.

High-pressure water vapor treatment for poly-crystalline germanium thin films

We have investigated the high-pressure water (H2O) vapor treatment for poly-crystalline Ge (poly-Ge) thin films, which were prepared by solid phase crystallization. The optical-absorption coefficients of poly-Ge were reduced by the treatment, suggesting that the grain-boundary defects were successfully passivated. But the poly-Ge films were sometimes damaged by the treatment in higher pressure and temperature. Compromised conditions should be pursued between the effective passivation and avoiding the damage. The rapid cooling after the treatment promotes defect passivation but causes structural distortion. The results show that the high-pressure H2O vapor treatment is an effective method for the defect passivation of poly-Ge films.

Passivation of Silicon Surfaces by Formation of Thin Silicon Oxide Films Formed by Combination of Induction-Coupled Remote Oxygen Plasma with High Pressure H2O Vapor Heat Treatment

ABSTRACTWe report formation of thin silicon oxide films on the silicon surfaces by combination of oxygen radical and high pressure H2O vapor heat treatment for passivation of silicon surfaces at a low temperature. Oxygen plasma was generated by 13.56 MHz radio frequency induction-coupled remote plasma with mixed gases of O2 and Ar at 2 sccm, 2x10-2 Pa and at a power of 50 W. Oxygen radical was produced from the plasma via a metal mesh closing plasma in the reactor. The top surfaces of 20 Wcm n-type silicon substrates with the rear surface coated by thermally grown SiO2 layers were exposed by oxygen radical from 1 to 5 min to oxidize the silicon surface. The samples were subsequently annealed with 9.0x105 Pa H2O vapor heat treatment at 260oC for 3 h. The effective minority carrier lifetime estimated using photo-induced carrier microwave absorption system in the case of 635 nm light illumination at 1.5 mW/cm2 to the top surface increased from 1.3x10-4 to 5.1x10-4s as the oxygen radical treatment duration increased from 1 to 5 min. The recombination velocity decreased from 380 to 90 cm/s. 500 kHz capacitance response with bias gate voltages characteristics of metal oxide semiconductor structure resulted in the effective oxide thicknesses (EOT) ranging from 1.3 to 1.7 nm. These results indicate a capability of thin oxide formation and effective passivation of silicon surfaces at a low temperature.

Formation of Aluminum Oxide Films on Silicon Surface by Aluminum Evaporation in Oxygen Gas Atmosphere

ABSTRACTWe report formation of thin aluminum oxide AlOx films on the silicon surface by a simple method of Al metal evaporation in oxygen gas atmosphere. 520 μm thick 30-Ωcm p-type-silicon substrates with a top bare surface and a rear surface coated with 100 nm thick thermally grown SiO2 layers were prepared. AlOx films were formed on the top surfaces by Al metal evaporation up to 20 s in oxygen gas atmosphere at 0.8 Pa with a flow rate of 3 sccm. Samples were subsequently annealed with 9.0x105 Pa H2O vapor at 260°C for 3 h. Measurement of capacitance response to a modulation voltage at 500 kHz as a function of bias gate voltages C-V revealed that AlOx films had the effective oxide thickness ranging from 2.0 and 2.6 nm were formed. C-V measurements also revealed that negative fixed charges were accumulated with a density of 5x1012 cm-2 in AlOx films. Photo-induced carrier microwave absorption measurement resulted in a high minority carrier effective lifetime τeff of 3.6x10-4 s comparable to that of 4.1x10-4 s for thermally grown SiO2 passivation. Field effect passivation was probably caused by negative charges in AlOx so that the surface recombination velocity decreased to 70 cm/s. X-ray reflectivity analysis indicated that the interfacial layer like SiOx was formed between AlOx and Si substrate. High pressure H2O vapor heat annealing caused increase in the density and decrease in the thickness of AlOx layers, although it increased the density and thickness of the interfacial SiOx layer thickness. H2O vapor treatment is effective to improve the quality of nanometer thick AlOxlayer.