Isovalent substitution of vanadium in LiFePO4: Evolution of monoclinic α-Li3Fe2(PO4)3 phase

Structural and electrochemical characterization of a melt spun AB 5-type alloy

Studies on improvement of hydrogen storage capacity of AB 5 type:MmNi 4.6Fe 0.4 alloy

The substitution of vanadium by chromium in thallium pentavanadium octasulfide. Part 1: Anisotropic metal atom interactions. A single crystal X-ray study

Effect of boron-doping on thermoelectric properties of rutile-type titanium dioxide sintered materials

The removal mechanism of vanadium addition on nitrogen pores in 30Cr15Mo1N ingot is systematically investigated through statistical analysis and theoretical calculation. The nitrogen solubility is obtained by the thermodynamic model, and the nitrogen content is obtained by combining the ProCAST software and the C–K model. Then, according to the formula of critical nucleation radius and growth rate of nitrogen bubbles, the variation of critical nucleation radius and growth rate of nitrogen bubbles with different vanadium contents is calculated. As the vanadium content increases, the number and mean area of nitrogen pores decrease. In comparison to the 0 V ingot, the number of nitrogen pores decreases in the 0.2 V ingot, but there is an increase in the number of large‐sized nitrogen pores (>3000 μm in diameter). When the vanadium content increases to 0.4, the nitrogen pores are completely removed. The results demonstrate that increasing vanadium content can remove nitrogen pores. Since the solidification mode remains unchanged with increasing vanadium content, increasing the vanadium content cannot remove nitrogen pores by changing the solidification mode of the 30Cr15Mo1N ingots. Therefore, increasing the vanadium content removes the nitrogen pores mainly by inhibiting the nucleation of nitrogen bubbles and promoting nitrogen bubble overflow in 30Cr15Mo1N ingots.

The different dilatometric curves of continuous cooling transformation with the different cooling rates were determined by means of Gleeble-2000 thermal simulation machine. The CCT curve of BVRE heavy rail steel was obtained by measuring the dilatometric curves and metallographic analysis. And the effects and mechanisms of vanadium on the phase transformation and microstructure of BVRE heavy rail steel were investigated. It is found that, the BVRE heavy rail steel only takes place pearlite and martensite transformation during continuous cooling. The CCT curve of BVRE heavy rail steel is moved to lower right with increasing vanadium content, which indicates that vanadium can obviously improve the stability of super cooled austenite and delay the pearlite transformation. When the content of vanadium is increased from 0.052% to 0.12%, the shortest incubation time of pearlite transformation is increased from 30s to 59s. When the cooling rate ≤ 5 ·s-1, with increasing vanadium content, both starting and finishing temperatures of pearlite transformation are decreased at different extent, meanwhile the pearlite is refined and the pearlite percentage is notably decreased. When the cooling rate is 2 ·s-1, the pearlite percentage is decreased from 65.7% to 35.9% with increasing vanadium content. When the content of vanadium is increased from 0.052% to 0.12%, the critical cooling rate of quenching is decreased from 13 ·s-1 to 7 ·s-1, thus the hardenability of BVRE heavy rail steel is improved.

The spin crossover compounds [FeL2](BF4)2, L=2,6-di(3-methylpyrazol-1-yl)pyrazine and [FeL2](ClO4)2 have very unusual two stage spin transitions which are initially steep and then become more gradual. A detailed variable temperature single crystal X-ray diffraction study has shown that the course of the spin transition is controlled by an order-disorder transition in the counter anions. The high and low spin states both crystallise in the tetragonal space group I4, the structures of the high and low spin states are presented at 290 and 30 K, respectively. The title compounds are shown to undergo LIESST (Light Induced Excited Spin State Trapping) under irradiation with either red or green laser light with wavelengths of 632.8 and 532.06 nm, respectively, at 30 K. The cell parameters for the tetragonal photo-induced metastable high spin state at this temperature are a= 9.169(6), c= 17.77(1) A for [FeL2](ClO4)2 with an increase in unit cell volume of 21 A3, and a= 9.11(1), c= 17.75(2) A and an increase in volume of 42.8 A3 for [FeL2](BF4)2.

By use of reduced and carburized starting powder with a composition of SKH57, and vanadium carbide (VC) powder, tool steels having higher VC content than that in SKH57 were vacuum-sintered, HIP-ed and finally heat-treated. The mechanical properties such as hardness and transverse-rupture strength (σm) at room temperature were studied in detail mainly as a function of vanadium (or VC) contents in the range from 3.5 to 18.5 mass%V.The hardness and σm increased and decreased with increasing vanadium or VC content, respectively. As for the σm, it was found that the value of about 4.8 GPa of SKH57 dropped to that of 3.0 GPa, according to the increase in vanadium content from 3.5 to 18.5 mass%. It was noted that σm was controlled by the size of structural defect, that is, the segregated area of MC type carbides influenced mainly by the vanadium content, excepting the carbide structure, sintering and quenching temperatures, etc. The discussion as for the reason why such a structural defect as a fracture source develops in sintered tool steels, has been given.

In this study, molecular dynamics simulations were employed to study the interaction between dislocations with Fe-V precipitate with different vanadium concentrations. Increasing the vanadium concentration in the precipitate results in a strong interaction between the dislocations and the precipitate, and the dislocation line bows out more as a result of increasing the energy of the dislocation line, and the critical stress needed for depinning the dislocations increases. However, at a low vanadium concentration (1:3 atomic ratio) the dislocations cut through the precipitate without changing the speed. An increasing vanadium concentration not only affects the dislocation shape and movement speed, but also affects the configuration of the junction between the a/2[111] and a/2[100] dislocations, and the void formation after the cutting process. The formation of strong junctions and a high number of voids locks the a/2[111] dislocation motion, and increases the strength of the alloy. The results of the radial distribution function before and after the cutting process show that the structure of the precipitate changes from crystalline to amorphous, and the degree of amorphization decreases with an increasing vanadium concentration.

Vanadium-substituted mesoporous molecular sieves (MCM-41) were prepared and the effects of water concentration, anti-foaming agent addition, pH adjustment, and Si/surfactant mole ratio were investigated. The hydrothermal and mechanical stability were tested for the pH-adjusted sample (Si/surfactant = 3.67 and 7.34). Catalysts were characterized by XRD, N2 physisorption, ICP, and 51V NMR. The acidic properties of synthesized V−MCM-41 were also examined by in-situ FTIR and TPD after pyridine adsorption. The increase of water concentration in the synthesis solution did not affect the physical properties of the resulting samples. The anti-foaming agent was very effective in improving the reproducibility of sample structure. The degree of vanadium substitution in the silica framework was increased with increasing water concentration and surfactant chain length. All of the incorporated vanadium was tetrahedrally coordinated in the silica framework. When the pH of the synthesis solution for V−MCM-41 was adjusted to 11 (Si/surf. = 7.34), the hydrothermal and mechanical stability were enhanced. The vanadium-substituted MCM-41 formed Lewis and Brönsted acid sites. Brönsted acid sites increased with increasing vanadium content, but the density of Lewis acid sites was constant for all samples. It is hypothesized that there is formed a constant and saturated density of isolated tetrahedral coordinated vanadium, and these make weak Lewis acid sites. Brönsted acid sites can be formed by a combination of incorporated vanadium with a hydroxyl group of a free silanol and/or a hydroxyl group produced by dissociation of water when the sample was pretreated at high temperature.

A series of vanadium substituted potassium hexagonal tungsten bronzes KxVyW1-yO3 (K-HTB) were prepared by conventional solid state method at 800 °C with compositions of x = 0.30 and 0.00 ? y ? 0.15. A mixture of K-HTB and non bronze phases with y ? 0.20 was observed. The proportion of this non bronze phase increases with increasing vanadium content. The non bronze phases in the mixture could not be indexed yet. In contrast, a very small amount of vanadium can be substituted in potassium tetragonal tungsten bronzes (K-TTB) at 800 °C with x = 0.50 and 0.00 ? y ? 0.02, however at 700 °C vanadium substituted K-TTB can be prepared with 0.00 ? y ? 0.05. Further substitution of vanadium in K-TTB decomposes to K-HTB and non-bronze phases. Keywords: Tungsten bronzes; Vanadium substituted bronze; Bronzoids. © 2012 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v4i2.9349 J. Sci. Res. 4 (2), 507-514 (2012)

Stimulation of aldosterone secretion by increases in extracellular potassium concentration is associated with increases in the volume of the adrenal glomerulosa cell. Because increases in cell volume have been associated with increases in aldosterone secretion, the effect of preventing the potassium-induced increase in cell volume by removal of chloride from the medium on the response of dispersed bovine glomerulosa cells grown in primary culture was determined. Totally replacing the chloride ion with the methylsulfate ion prevented the increase in cell volume and significantly suppressed the increase in aldosterone secretion normally associated with increasing [K] to 10 mM. In the absence of Cl-, the increase in cytosolic calcium concentration ([Ca2+]c) normally induced by increasing the [K] to 10 mM was also significantly suppressed. The replacement of 10 mM methylsulfate by Cl- restored the potassium-induced increase in both cell volume and aldosterone secretion to values not different from those found in the presence of 108 mM Cl-. The potassium-induced increase in cell volume was dependent also on the presence of extracellular calcium. Thus a component of the glomerulosa cell response to an increase in [K] may be caused by a chloride-dependent increase in cell volume that is triggered by the initial depolarization-induced increase in [Ca2+]c. The increase in cell volume enhances the increase in [Ca2+]c and amplifies the increase in aldosterone secretion.

A primary element of copper is dispersed with a secondary element (vanadium) by stir casting technique. This alloy is melted in a furnace and the percentage of Vanadium is added in Cu as 0%, 0.5%, 1.0%, 1.5% & 2% respectively. The metal matrix composite is characterised by x-ray diffraction, Optical micrograph, Energy Dispersive x-ray, Fourier Transform Infrared Spectroscopy and Fractography. It is found that by the addition of vanadium the grain size is getting reduced and the strength of the metal matrix increases. There is also a improvement in the hardness with the increase in vanadium content. Pin on-disc setup is used for wear study and it is found that there is an increase in wear resistance for the increase in vanadium content. The results observed from experiments that vanadium will act as a reliable reinforcement material for the enhancement of properties in copper matrix composites.

The effects of chromium and vanadium additions on the microstructure, hardness and wear resistance of high-vanadium alloy steel (containing 5–10 wt-% V and 2–10 wt-% Cr) were studied by means of optical microscopy, scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), Vickers hardness and Rockwell-hardness tester & M-200 ring block wear tester. Researching results showed that the solidification structure of high-vanadium wear-resistant alloy steel was mainly consisted α-Fe (martensite), vanadium carbide (VC), M3C and M7C3. Vanadium is mainly distributed over VC, and certain amount of vanadium exists in the matrix and M7C3 type eutectic carbide. Chromium is mainly distributed over the M7C3, and the matrix also contains a small quantity of chromium. It is found that the content of VC increases with the increase of vanadium content when carbon and chromium contents are constant. The change of micro- and macro-hardness was not obvious with the increase of vanadium content. The content of M7C3 type eutectic carbides increases gradually with the increase of chromium content when carbon and vanadium contents are constant. The micro- and macro-hardness increases with the increase of chromium content. The increase of vanadium content brings to the increase of wear resistance of alloy steel when carbon and chromium contents are constant. The change of chromium content had no obvious effect on wear resistance of high-vanadium alloy steel when carbon and vanadium contents. The increase of vanadium content brings to the increase of wear resistance of alloy steel when carbon and chromium contents are constant. The wear resistance of as-cast high-vanadium alloy steel is the best when the content of vanadium and chromium is 10 wt-% and 5 wt-% respectively.

The relation between the phase transition temperature and unit cell volume in the (K1‐xCsx)2ZnCl4 mixed crystals was studied. The phase transition temperature of A2BX4 family is dependent on the size of cation and anion (FABRY and PEREZ‐MATO). That is, the transition temperature of crystal decreases with increasing unit cell volume. In this study we investigated this property of mixed crystals with the increasing mixture ratio. From the current study, we obtained the result that in the mixed crystals (K1‐xCsx)2ZnCl4, the increase of x induces the increase of unit cell volume, so that TI decreases with increasing unit cell volume. In order to determine the distribution of the substituted Cs+, using the near IR and UV spectrophotometer, we investigated both the band gap energy and the type of transition.