共查询到20条相似文献,搜索用时 93 毫秒
1.
《Materials Today》2003,6(9):24-33
Hydrogen storage is a materials science challenge because, for all six storage methods currently being investigated, materials with either a strong interaction with hydrogen or without any reaction are needed. Besides conventional storage methods, i.e. high pressure gas cylinders and liquid hydrogen, the physisorption of hydrogen on materials with a high specific surface area, hydrogen intercalation in metals and complex hydrides, and storage of hydrogen based on metals and water are reviewed.The goal is to pack hydrogen as close as possible, i.e. to reach the highest volumetric density by using as little additional material as possible. Hydrogen storage implies the reduction of an enormous volume of hydrogen gas. At ambient temperature and atmospheric pressure, 1 kg of the gas has a volume of 11 m3. To increase hydrogen density, work must either be applied to compress the gas, the temperature decreased below the critical temperature, or the repulsion reduced by the interaction of hydrogen with another material. 相似文献
2.
R. G. Sharafutdinov A. E. Zarvin V. Zh. Madirbaev V. V. Gagachev G. G. Gartvich 《Technical Physics Letters》2005,31(8):641-643
Processes in a rarefied flow of methane activated by a high-energy electron beam have been studied as dependent on the gas
pressure and the electron energy and total current. The electron beam initiates reactions leading to the conversion of methane
into molecular hydrogen. The conversion coefficient has been determined as a function of the process parameters. By selecting
proper parameters, it is possible to provide for a high rate of the conversion reaction. 相似文献
3.
Summary The transonic flow near the throat of a converging-diverging nozzle of a gas with infinite electrical conductivity is considered. The magnetic fieldB is everywhere aligned with the velocityq so that the equations describing the flow are reducible to those of ordinary gasdynamics. Thus, it is possible to utilize the transonic similarity solution of Tomotika and Tamada [3] to study aligned field magnetohydrodynamic flow near a nozzle throat. Only transonic flows are considered, and the structures of sub- and supersonic flows with speeds greater and less than the Alfvén speed are investigated. 相似文献
4.
A. I. Shchedrin D. S. Levko V. Ya. Chernyak V. V. Yukhimenko V. V. Naumov 《Technical Physics Letters》2009,35(5):449-451
In search for an alternative fuel for internal combustion engines, we have studied the possibility of obtaining molecular
hydrogen via the conversion of air mixture with ethanol and water vapors in a new plasma reactor. It is shown that, in agreement
with experimental data, the H2 concentration is a linear function of the discharge current and decreases with increasing gas flow rate in the interelectrode
gap. It is established that the proposed approach provides higher molecular hydrogen concentrations as compared to those achieved
with other methods. 相似文献
5.
Hydrogen storage: The major technological barrier to the development of hydrogen fuel cell cars 总被引:2,自引:0,他引:2
In this paper, we review the current technology for the storage of hydrogen on board a fuel cell-propelled vehicle. Having outlined the technical specifications necessary to match the performance of hydrocarbon. fue1, we first outline the inherent difficulties with gas pressure and liquid hydrogen storage. We then outline the history of transition metal hydride storage, leading to the development of metal hydride batteries. A viable system, however, must involve lighter elements and be vacuum-tight. The first new system to get serious consideration is titanium-activated sodium alanate, followed by the lithium amide and borohydride systems that potentially overcome several of the disadvantages of alanates. Borohydrides can alternatively produce hydrogen by reaction with water in the presence of a catalyst but the product would have to be recycled via a chemical plant. Finally various possible ways of making magnesium hydride decompose and reform more readily are discussed. The alternative to lighter hydrides is the development of physisorption of molecular hydrogen on high surface area materials such as carbons, metal oxide frameworks, zeolites. Here the problem is that the surface binding energy is too low to work at anything above liquid nitrogen temperature. Recent investigations of the interaction mechanism are discussed which show that systems with stronger interactions will inevitably require a surface interaction that increases the molecular hydrogen-hydrogen distance. 相似文献
6.
The slowing of an ionized gas in a supersonic diffuser operating as a magnetohydrodynamic (MHD) generator is investigated
by numerical simulation. The calculation results, which reveal a significant dependence of the static pressure level and the
Mach number distribution in the exit cross section of the diffuser on the design of the electrode system, are presented.
Pis’ma Zh. Tekh. Fiz. 25, 1–8 (May 12, 1999) 相似文献
7.
Md. Shahjahan Kaisar Alam Sarkar S.W. Donne G.M. Evans 《Advanced Powder Technology》2010,21(4):412-418
In this study the flotation recovery of silica using air, and molecular and electrolytically-generated hydrogen was investigated. For comparison of air and molecular hydrogen recoveries, a laboratory Denver, type D12, flotation machine was used. For both gases, pH of the suspension, gas flow rate, concentration of collector and frother, solids concentration, particle size and speed of impeller were kept constant. Almost identical recoveries were obtained for both gases, suggesting that gas composition played no significant role in silica flotation. Electroflotation experiments were carried out using 12.6 μm mean diameter silica particles. While fine particles had very poor recovery in the Denver cell, greater than 70% recoveries were achieved in the electroflotation cell. This was thought to be the result of the very small (less than 40 μm) bubbles generated by the electroflotation process. A population-balance model, incorporating the hydrogen generation process, supported the conclusion that increased recovery for electroflotation, for very fine silica particles at least, was attributed to the reduced bubble size and not by the composition of the gas. 相似文献
8.
V. A. Kagadei E. V. Nefyodtsev D. I. Proskurovsky S. V. Romanenko 《Technical Physics Letters》2003,29(11):897-900
Using one-or two-layer films of transition metals, it is possible to determine the atomic hydrogen flux density under reduced
gas pressure conditions (10−1–10−3 Pa). The method consists in monitoring a change in the film resistance caused by selective dissolution of atomic hydrogen
in the metal during exposure of the film in a mixed atomic-molecular flow, followed by determining a characteristic time τ
required for the hydrogen concentration in the film to reach 63% of the maximum possible level. The hydrogen flux density
is then calculated within the framework of a simple mathematical model of the film saturation with hydrogen described by a
relaxation law. The proposed method is characterized by a high selective sensitivity to atomic hydrogen. The atomic hydrogen
flux density in a mixed atomic-molecular flow can be determined in a range from 5×1013 to 1016 cm−2 s−1. 相似文献
9.
10.
G. A. Pozdnyakov 《Technical Physics Letters》2007,33(6):474-476
A pulsed gas-phase magnetohydrodynamic (MHD) disk accelerator with a radial initial gas flow and radial electric current direction is described. Some working regime parameters and characteristics of the accelerated natural gas flow are reported. MHD accelerators of this type can be used for the investigation of chemical kinetics. Another promising application is related to the development of supersonic gas-phase endothermal chemical reactors with gasdynamic control. 相似文献
11.
The process of hydrogen desorption from graphane (graphene sheet saturated by hydrogen adsorbed from both sides) has been
studied using the method of molecular dynamics. The temperature dependences of the time of desorption onset for various hydrogen
coverages on graphene are calculated and the corresponding activation energies in the Arrhenius equation are determined. It
is established that graphane exhibits a rather high thermal stability that makes possible its use in two-dimensional electronics
even at room temperature. For the same reason, graphane can hardly be considered as a promising hydrogen storage material
for fuel cells. 相似文献
12.
Yasushi Muranaka Hisao Yamashita Hiroshi Miyadera 《Journal of Materials Science》1991,26(12):3235-3243
A variety of diamond films were deposited using the microwave plasma of a CO-H2 system. Qualities of the synthesized films were correlated with the gas phase atomic hydrogen concentration monitored using optical emission spectroscopy. The amorphous components contained in the synthesized films were of a polyacetylene structure, which was possibly formed by the successive polymerization of C2H2 in the gas phase.Excess atomic hydrogen allowed highly crystallized diamond films to be deposited at high growth rates which included only a small amount of polyacetylene components. Two possible explanations for these results were proposed: the suppression of polyacetylene formation and the production of appropriate precursor (CH3) for diamond synthesis under the excess atomic hydrogen condition.Finally, the ratioI
H/I
Ar (whereI is the optical emission intensity) was suggested as a decisive parameter indicating the suitability of the plasma conditions for the growth of pure diamond with good crystallinity. 相似文献
13.
Spatial distributions of gas composition in rf glow discharge plasmas measured using a quartz sensor
A quartz sensor can detect changes in gas composition caused by plasma because the quartz sensor output depends on the total pressure, viscosity, and molecular weight of the gas. This simple mode of quartz sensor measurement was used to obtain spatial distributions of the gas composition changes in the plasmas between a chamber inner wall and a plasma electrode. These spatial distributions reflect gas phase reactions in the plasmas. For that reason, they are helpful to elucidate the reaction mechanisms occurring in the plasmas. Applying such quartz sensor measurements for hydrogen and argon-hydrogen plasmas, we found that the spatial distributions of the gas composition change, as measured using a quartz sensor, depend on source gases. The positions at which the quartz sensor output show the maximum gas composition change for hydrogen and argon-hydrogen plasmas were at the chamber inner wall and near the edge of the plasma electrodes that are the closest positions to the plasma glow. These results show that the gas composition change detected using the quartz sensor resulted from degassing from the chamber inner wall and the plasma electrodes. 相似文献
14.
A new "nanopumping" effect consisting of the activation of an axial gas flow inside a carbon nanotube by producing Rayleigh traveling waves on the nanotube surface is predicted. The driving force for the new effect is the friction between the gas particles and the nanotube walls. A molecular dynamics simulation of the new effect was carried out showing macroscopic flows of atomic and molecular hydrogen and helium gases in a carbon nanotube. 相似文献
15.
Hiroshi Nishikawa Masaaki Ibe Manabu Tanaka Tadashi Takemoto Masao Ushio 《Vacuum》2006,80(11-12):1311
A feasibility study has been conducted to determine whether steam plasma can be used for the treatment of carbonized wastes, such as the carbide of the hazardous waste. The gasification which was often called “water gas reaction” was studied to reduce the volume and weight of wastes and to produce the combustible gas like hydrogen from them by using steam plasma. In this study, the thermal plasma generated by DC plasma was used as a heat source, where steam was added to react with carbon. Graphite was used as a test piece instead of carbonized wastes. The weight of the test piece was measured before and after treatment to decide the weight reduction during the experiment. The gas produced in the reaction was analyzed. The result indicated that it is possible to reduce the weight of graphite and to produce the combustible gas from graphite by using the DC steam plasma. 相似文献
16.
Emission spectra of gas discharges resulted from dipole allowed transitions between triplet states of the hydrogen molecule are placed in the near ultraviolet, visible and near infrared wavelength ranges. This makes them attractive for use in spectral diagnostics of gas discharges. An improved collisional-radiative model is used for analysis of applicability of optical emission spectroscopy based on the emission of triplet states of molecular hydrogen for diagnostics of non-equilibrium microwave plasma. 相似文献
17.
Zechao Yang Christian Lotze Martina Corso Sebastian Baum Katharina J. Franke Jos I. Pascual 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(12)
Molecular recognition is a crucial driving force for molecular self‐assembly. In many cases molecules arrange in the lowest energy configuration following a lock‐and‐key principle. When molecular flexibility comes into play, the induced‐fit effect may govern the self‐assembly. Here, the self‐assembly of dicyanovinyl‐hexathiophene (DCV6T) molecules, a prototype specie for highly efficient organic solar cells, on Au(111) by using low‐temperature scanning tunneling microscopy and atomic force microscopy is investigated. DCV6T molecules assemble on the surface forming either islands or chains. In the islands the molecules are straight—the lowest energy configuration in gas phase—and expose the dicyano moieties to form hydrogen bonds with neighbor molecules. In contrast, the structure of DCV6T molecules in the chain assemblies deviates significantly from their gas‐phase analogues. The seemingly energetically unfavorable bent geometry is enforced by hydrogen‐bonding intermolecular interactions. Density functional theory calculations of molecular dimers quantitatively demonstrate that the deformation of individual molecules optimizes the intermolecular bonding structure. The intermolecular bonding energy thus drives the chain structure formation, which is an expression of the induced‐fit effect. 相似文献
18.
Hydrogen solubility in molten aluminium at different temperatures from 973–1123 K, has been measured using Sieverts' method.
Inert gas (helium or argon) was used as a reference gas to calibrate the measurement system of the Sieverts' apparatus. The
measured hydrogen solubility was found to vary with the reference gases. Helium was detected to be soluble in liquid aluminium.
When helium is used as the reference gas, its solubility resulted in lower measured hydrogen solubility than that when argon
was used to calibrate the measurement system of the apparatus. Argon gas was therefore considered as an appropriate reference
gas when Sieverts' method is used to measure the hydrogen solubility in liquid aluminium. The hydrogen solubility, S, in liquid aluminium as a function of melt temperature, T, determined in the present investigation is expressed as log S = (−2980/T) + 3.07. 相似文献
19.
《Vacuum》1999,52(1-2):169-181
Boron Nitride coatings have been deposited by plasma-assisted chemical vapour deposition (PACVD) from BCl3/N2/H2/Ar gas mixtures in a hot wall capacitively coupled radio-frequency (13.56 MHz) reactor. The nature of active species in the plasma during deposition was determined by Optical Emission Spectroscopy (OES) and Mass Spectrometry (MS). The plasma characterisation was performed as follows: first, an Ar/H2 plasma was studied in order to understand the influence of molecular hydrogen in the discharge mixture. Then the two precursors N2 and BCl3 were added and the new gas mixture studied. Finally the deposition plasma was investigated. These characterisations were correlated to the microstructure and c-BN concentrations determined by Scanning Electron Microscopy (SEM) and Fourier Transformed Infrared Spectroscopy (FTIR).The study demonstrates the major role of atomic hydrogen on the possible mechanisms leading to BN deposition:—the introduction of hydrogen in Ar/N2 controls the nature of the NHx (from N to NH3) species in the gas phase. These results are correlated to the relative amount of NH groups in the films,—by a modification of the excitation state of the plasma (ne, Te) the introduction of H2 can increase the dissociation rate of the boron precursor BCl3 and, reacting with chlorine, leads to the formation of HCl. This corresponds to an increase in the growth rate of the coatings.Finally, BN samples containing 5% of cubic phase were treated by Ar, Ar/H2 and Ar/Cl2 plasmas. These post treatments demonstrated that ion assisted preferential etching of h-BN by H or Cl atoms could be used to obtain large concentrations of c-BN coatings and possibly offer a new route for deposition of low stress cubic boron nitride. 相似文献
20.
Low-temperature hydrogen plasma has been investigated under the conditions of electron cyclotron resonance by emission spectroscopy. The molecular distribution functions over the low rotational and vibrational levels of the hydrogen molecule in the d3Πu- triplet state have been measured. The translational, rotational, and vibrational temperatures of the ground and excited triplet states of the hydrogen molecule are determined. The obtained translational and vibrational temperatures indicate that low-temperature hydrogen plasma under the conditions of electron cyclotron resonance is a more efficient source of vibrationally excited hydrogen molecules in comparison with the other gas discharges. 相似文献