For alloy design of hydrogen permeable membrane, it is important to control pressure–composition–isotherm (PCT curve) in an appropriate manner in order to obtain high hydrogen permeability with ...strong resistance to hydrogen embrittlement. Based on this concept, V-based alloy membranes are designed under some given pressure conditions at a temperature in view of the partial molar enthalpy change, ΔH¯0.2, and entropy change, ΔS¯0.2, of hydrogen for hydrogen dissolution. It is demonstrated that the PCT curve can be controlled very precisely in view of ΔH¯0.2 and ΔS¯0.2. Also, the required membrane area to obtain 300 Nm3 h−1 of hydrogen flow is estimated. It is found that, in view of the membrane area, it is favorable to apply at least 400 kPa of hydrogen pressure at feed side.
•A concept for alloy design of H2 permeable membrane has been applied for V–Fe system.•In this concept, hydriding property must be controlled appropriately.•In view of the thermodynamic parameters, hydriding property can be controlled.•Correlation between membrane area and applicable hydrogen pressure is discussed.•A concept for scale up of the membrane area is obtained.
The hydrogen permeability of Pd–27mol%Ag alloy membrane has been analyzed in view of the new description of hydrogen permeation based on hydrogen chemical potential. The hydrogen flux is consistently ...proportional to the PCT factor, fPCT, which reflects the shape of the corresponding pressure–composition–isotherm (PCT curve), regardless of whether hydrogen solubility is expressed in a format of the Sievert's law or not. From the two points of the PCT factor, fPCT, and DBTC (the ductile-to-brittle transition hydrogen concentration), the concept for alloy design of non-Pd-based alloy membranes is obtained. As an example, V–9mol%Al alloy is designed for applied temperature and pressure condition. For this condition, this alloy membrane possesses excellent hydrogen permeability with strong resistance to hydrogen embrittlement.
•A new description of hydrogen permeation and its application are shown.•The hydrogen flux is proportional to the PCT factor consistently.•The concept for alloy design based on the new description is applied to V–Al system.•Designed alloy exhibits high hydrogen permeability without brittle fracture.•Hydriding property is essential to design the hydrogen permeable alloy membrane.
This paper presents a new correlative bioimaging technique using Y2O3:Tm, Yb and Y2O3:Er, Yb nanophosphors (NPs) as imaging probes that emit luminescence excited by both near-infrared (NIR) light and ...an electron beam. Under 980 nm NIR light irradiation, the Y2O3:Tm, Yb and Y2O3:Er, Yb NPs emitted NIR luminescence (NIRL) around 810 nm and 1530 nm, respectively, and cathodoluminescence at 455 nm and 660 nm under excitation of accelerated electrons, respectively. Multimodalities of the NPs were confirmed in correlative NIRL/CL imaging and their locations were visualized at the same observation area in both NIRL and CL images. Using CL microscopy, the NPs were visualized at the single-particle level and with multicolour. Multiscale NIRL/CL bioimaging was demonstrated through in vivo and in vitro NIRL deep-tissue observations, cellular NIRL imaging, and high-spatial resolution CL imaging of the NPs inside cells. The location of a cell sheet transplanted onto the back muscle fascia of a hairy rat was visualized through NIRL imaging of the Y2O3:Er, Yb NPs. Accurate positions of cells through the thickness (1.5 mm) of a tissue phantom were detected by NIRL from the Y2O3:Tm, Yb NPs. Further, locations of the two types of NPs inside cells were observed using CL microscopy.
▶ V–5
mol%W alloy possesses excellent hydrogen permeability together with strong resistance to hydrogen embrittlement. ▶ V-W alloy exhibits better mechanical properties than Nb-W alloy in hydrogen ...atmosphere at high temperature. ▶ Ductile-to-Brittle Transition hydrogen Concentration (DBTC) for pure V is determined to be about H/M
=
0.22. ▶ Vanadium is ductile even in hydrogen gas atmosphere when dissolved hydrogen concentration is less than DBTC. ▶ Alloying effects and temperature dependence on the hydrogen solubility of vanadium is clarified.
The alloying effects of tungsten on the hydrogen solubility and the hydrogen permeability are investigated for V-based hydrogen permeable membranes. The hydrogen solubility is found to decrease by the addition of tungsten into vanadium or by increasing the temperature. It is shown that the ductile fracture occurs for V–5
mol%W alloy even in the hydrogen pressures of 0.3
MPa at 773
K. It is also found that the mechanical properties (i.e., strength and ductility) of V-based alloy are better than that of Nb-based alloy in hydrogen atmosphere at high temperature. It is demonstrated that the V–5
mol%W alloy possess excellent hydrogen permeability without showing any hydrogen embrittlement when used under appropriate permeation conditions, i.e., temperature and hydrogen pressures.
•The alloying effects on the mobility of hydrogen atom, B, in Nb have been investigated.•The analysis based on the new description of hydrogen permeation has been performed.•The mobility of hydrogen ...atom is expressed in a format of the Arrhenius equation.•The logarithm of the pre-exponential factor and the activation energy decrease linearly by alloying.•Ru, W and Mo in Nb enhance the hydrogen diffusivity at low temperature below Tint.
Hydrogen permeability of Nb-based alloy membranes have been analyzed in view of the new description of hydrogen permeation based on hydrogen chemical potential in order to investigate the alloying effects on the mobility of hydrogen atom, B. There is a liner relationship between the normalized hydrogen flux, J⋅L, and the PCT factor, fPCT. The mobility of hydrogen atom is expressed in a format of the Arrhenius equation. Then, the alloying effects on the activation energy, E, and the pre-exponential factor, B0, have been investigated. It is found that logarithm of the pre-exponential factor, lnB0, is proportional to the activation energy, E. In other words, when one factor decreases by alloying, the other factor also decreases linearly. As a result, the addition of ruthenium, tungsten and molybdenum into niobium enhances the hydrogen diffusivity at low temperature below the intersection temperature, Tint.
Local strain is introduced into the lattice around solute atom due to the size mismatch between solute and solvent atoms in alloy. In this study, local lattice strains are calculated for the first ...time in titanium alloys, using the plane-wave pseudopotential method. As an extreme case, the local lattice strain around a vacancy is also calculated in various bcc, fcc and hcp metals. It is found that the local strain energy is very high in both bcc Ti and bcc Fe, where the martensitic transformation takes place. From a series of calculations, it is shown that the magnitude of the strain energy stored in the local lattice is comparable to the thermal energy,
k
B
T
, where
k
B
is the Boltzmann constant and
T
is the absolute temperature. Therefore, the presence of local lattice strains in alloy could influence the phase stability that varies largely depending on temperatures. For example, the local lattice strain correlates with the martensitic transformation start temperature,
Ms
, in binary titanium alloys.
The alloying effects of iron and aluminum on the formation and decomposition temperatures of vanadium hydride, β phase, have been investigated by a series of in-situ X-ray diffraction measurements in ...hydrogen atmosphere. It is found that the addition of iron increases the formation temperature of β phase, while the addition of aluminum decreases the formation temperature drastically.
According to the first principal calculations, the addition of iron, chromium or nickel increases the hydrogen dissolution energy when hydrogen atom is inserted to the nearest neighbor site of alloying element. These results is considered to correspond to the increase in the plateau pressure of α–β phase transition by the addition of these alloying elements. The alloying effect on the change in the total energy upon hydrogen insertion into T-site is larger than O-site. As a result, the energy difference between T-site model and O-site model becomes small by the addition of these alloying elements, which will lead to increase the formation temperature of β phase. Aluminum in vanadium shows strong repulsive interaction with hydrogen so that hydrogen cannot occupy the nearest neighbor sites of aluminum energetically. Owing to this blocking effects, the formation temperature of β phase may decreases drastically by the addition of aluminum into vanadium.
•The addition of Fe into V increases the hydride formation temperature.•In contrast, the addition of Al into V decreases the formation temperature drastically.•The addition of at least 3.5 mol% Al into V will suppress the hydride formation under one atm of hydrogen even at room temperature.•Alloying effects on the phase stability of vanadium hydride are discussed based on a series of first principal calculations.
•The concept for alloy design of Nb-based hydrogen permeable membrane is applied to V-based alloy.•The addition of Mo into V–W alloy improves the resistance to hydrogen embrittlement.•V–5 mol%W–5 ...mol%Mo alloy membrane exhibits excellent hydrogen permeability at 673–773K.
The alloying effects of molybdenum (Mo) into V–W alloy on the solubility of hydrogen, the resistance to hydrogen embrittlement and the hydrogen permeability are investigated in a fundamental manner. It is found that the addition of Mo into V–W alloy decreases the hydrogen solubility. As a result, the applicable hydrogen pressures at the DBTC (the ductile-to-brittle transition hydrogen concentration, which is about 0.2 (H/M) for vanadium alloys) increases. In fact, about 0.15MPa (673K) to 0.6MPa (773K) of hydrogen pressures can be applied to V–5mol%W–5mol%Mo alloy membrane while keeping the hydrogen concentration less than or equal to the DBTC, which is about twice of hydrogen pressure applicable to V–5mol%W alloy. Thus, the addition of Mo into V–W alloy improves the resistance to hydrogen embrittlement. In addition, the alloying of Mo into V–W alloy also improves the hydrogen permeability. For instance, the hydrogen permeability of V–5mol%W–5mol%Mo alloy is about 4–5 times higher than that of Pd–25mass%Ag alloy at 673–773K.
PDF
