Papers by Keyword: Hydrostatic Pressure

Abstract: We have studied single crystals with same La/Sr ratio but different initial Mn concentration, namely (La_0.85Sr_0.15)_0.93MnO₃ and (La_0.85Sr_0.15)_0.97MnO₃. We have observed, that the temperature of insulator-metal transition T_IM increases for both samples and the temperature of charge ordering T_CO increases for (La_0.85Sr_0.15)_0.93MnO₃ and decreases for (La_0.85Sr_0.15)_0.97MnO₃ with the external hydrostatic pressure in the range of 0.1 MPa - 1.3 GPa. After analysis of obtained dependence, we have concluded that (La_0.85Sr_0.15)_0.97MnO₃ sample has higher concentration of Mn vacancy. Thereby we suppose that growth of Mn vacancy concentration decreases transfer interaction of the conducting electrons and enhances charge ordering of Mn³⁺ and Mn⁴⁺ ions.

Abstract: A tensile/compressive-torsional biaxial testing system was employed and tensile/ compressive-torsional tests were performed for the hollow specimen, which was loaded and the austenized specimen was cooled so that pealrite transformation accompanied by transformation plasticity occurred and axial and torsional strain were measured. Furthermore, the elastic-plastic constitutive equation due to phase transformation based on the hydrostatic pressure dependent model was proposed, and the validity of this equation was discussed experimentally. The test results showed the transformation plasticity coefficient due to pearlitic transformation of S45C depends on the loading direction, and these behaviour can be appropriately expressed by the hydrostatic pressure dependent model than the isotropic model.

Abstract: The stability of submerged functionally graded (FG) cylindrical shell under hydrostatic pressure is examined in this paper. Based on the Flügges shell theory, the coupled frequency of submerged FG cylindrical shell is obtained, using wave propagation method and Newton method. Then the critical pressure of FG cylindrical shells is given by applying linear fitting method. Results are compared to known solutions, where these solutions exist. The effects of constituent materials, volume fraction, boundary condition and dimensions on the critical pressures of submerged FG cylindrical shell are illustrated by examples.

Abstract: In this paper, machining tests of silicon wafer under high hydrostatic pressure are reported. A lathe type machining tester was developed, and machining tests were conducted on the upper surface of silicon wafers whose crystal orientation was (001). Roughness of the finished surface was measured by using AFM, and the effect of hydrostatic pressure on roughness was studied. It was found that roughness decreases with increase of hydrostatic pressure. It was also found that the roughness depends on the cutting direction. The roughness is large when the cutting direction is parallel to the <100> direction, but it is small when the cutting direction is parallel to the <110> direction. Mechanism of effects of hydrostatic pressure and crystal orientation are discussed.

Abstract: In the fields of spintronics, extensive experiments and theoretical studies have been performed to discover materials that are ferromagnetic at room temperature. Many materials have attracted a great interest due to their potential applications in this area and their new physical properties. Our aim in this work is to study the electronic structure of Mn-doped Ge under pressure effect. We used the full-potential linearized augmented plane wave plus the local orbitals method based on the density functional theory within the generalized gradient approximation as parameterized by Perdew. Our calculations were ported on a 2x2x2 Germanium supercell where Ge atom in position (0, 0, 0) was substituted by Mn atom. The theoretical equilibrium lattice parameters are determined. The electronic band structures calculated at equilibrium show the half metallic character of Mn_xGe_1-x. The totat density of states demonstrate the half metallicity under pressure of Mn_xGe_1-x. In addition, the magnetic moment of the super-cell increases under pressure while the magnetic moment of Mn decreases with pressure increasing which is consistent with the available data.Keywords: spintronic, ferromagnetic, hydrostatic pressure, electronic properties, DFT.

Abstract: According to the physical principles of hydrostatics, we measure the gravitational acceleration by using the air specific heat ratio comprehensive instrument and an inverted test tube with a pressure sensor at the bottom of it. The experiment is simple and does not involve the measurement of time. The result is good.

Abstract: Improving machined surface integrity is one of the important issues in the precision machining. This study aims to develop a cutting tool, which enables to generate a local hydrostatic pressure field in the vicinity of the cutting point to suppress the extra plastic flow in the workpiece, because it is known that materials including metals never cause plastic flow and fracture no matter how much greater hydrostatic pressure field is given. In this paper, a simple cutting tool with planer jig is proposed and a molecular dynamics simulation of cutting is performed as the first step. As a result, it is confirmed that the reduction of the plastic deformation, mainly in the burr formation become remarkable with the proposed model due to the suppression of extra side plastic flow, and relatively high-hydrostatic stress field is formed in the vicinity of cutting point. However, it is also observed that relatively many dislocations are generated beneath the cutting groove.

Abstract: Using periodic density functional theory within the generalized-gradient approximation to electron exchange and correlation, we have studied S adsorption four-fold hollow site on Fe(100) in different hydrostatic pressure. We find that the adsorption height decreases with hydrostatic pressure increasing is non-monotonic. The adsorption energy decreases with an increase with pressure is monotonic and we have obtained density of states is almost unchanged, the adsorption energy change is mainly caused by lattice deformation in the hydrostatic pressure, and the adsorption energies increase linearly with pressure.

Abstract: A new type of cell (Hydrostatic horizontal cell (HHC)) developed for continuous electroplating of strip is described. The cell consists of upper frame, lower frame, upper anode, lower anode, liquid baffle, conductive roll, backup roll, edge mask and its control system etc. The upper and lower hydrostatic cavities are located at the middle of the cell. The HHC adopts an innovative operating principle to generate strong capability of using hydrostatic pressure to grip the strip and to correct the strip twist. It thereby remarkably decreases the running space height and the deviation-from-center error of the strip in the cell. It originally builds up the horizontal spray of electrolyte to both directions at the center of the cell. Consequently the gas exhausting ability of the cell and the electroplating efficiency are improved. The cell has improved overall technical performances over conventional horizontal cells, and it is capable to effectively prevent short circuiting between the strip and the anodes. In general, the advantages of HHC include stable operation, excellent coating quality, high current density, low power consumption, and simple as well as compact equipment.

Abstract: The galvanomagnetic properties in weak magnetic fields (4.2T300 K, B0.07 T) as well as Shubnikov-de Haas effect (T=4.2 K, B7 T) in the single crystal Pb_1-x-ySn_xV_yTe (x=0.20, y0.01) under hydrostatic compression up to 15 kbar have been investigated. It is shown that under pressure the decrease of activation energy of vanadium deep level, n-p-inversion of the conductivity type at low temperatures and insulator-metal transition take place. In the metallic phase sharp increase of the Hall mobility and appearance of Shubnikov-de Haas oscillations at helium temperature are observed. The pressure coefficient of vanadium level energy is determined and the diagram of the electronic structure rearrangement for Pb_1-x-ySn_xV_yTe under pressure is proposed.