The SrB4O7:Sm2+ optical sensor and the pressure homogeneization through thermal cycles in diamond anvil cells

Abstract

Preliminary results, up to 550 kbar, on a thermal-cycling relaxation process of the 4.Methanol-1.Ethanol pressure-transmitting medium, are presented. The homogeneization is monitored by linewidth measurements of the ⁵D₀-⁷F₀ emission line of SrB₄O₇:Sm²⁺, recently proposed as an “almost ideal” high pressure calibrant. Above 100 kbar at 20°C, the line broadens linearly with increaisng pressure. Upon heating, at a fixed pressure, the linewidth is reduced to a minimum (“hydrostatic”) value provided a sufficient temperature is reached and this narrowing is irreversible upon cooling. For T=300°C this relaxation is observed for P (250 kbar, incomplete at 340 kbar and not observed at 550 kbar.     

High pressure,high temperature them determination of triple point in CdSe

Abstract

Thermal investigation of melting in gas pressures (Nz) up to 17 kbar was used to determine p-T phase diagram of CdSe. The method, based on measurements of temperature gradient in the container wall during heating and cooling, allowed to obtain the temperature of fusion. The pressure dependence of the melting temperature was given for both low and high pressure phases. The triple point coordinates, equal to 10.90 kbar and 1221 °C confirm earlier measurements of Jayaraman et a1.     

流体静压力下快离子导体Rb4Cu16I7Cl13离子电导的研究

在流体静压力为0.5—11.6kbar,温度-80—80℃范围内,测量了Rb₄Cu₁₆I₇Cl₁₃多晶粉末“松散”样品和“致密”样品的离子电导。“松散”样品电导与压力的关系表明,在4.0—5.0kbar附近,电导存在极大值;“致密”样品电导随压力单调下降。在一定压力下,“致密”样品电导率随温度变化的趋势与常压结果相同,压力对Rb₄Cu₁₆I₇Cl_关键词：     

Lutetium: High pressure polymorph and compression

The effect of pressure on the lattice parameters of the h.c.p. phase of Lu has been studied up to 230 kbar at 23 ± 3°C by means of X-ray diffraction employing a diamond-anvil cell. The data fitted to the Birch equation yield an isothermal bulk modulus of 460 ± 20 kbar with a pressure derivative of 2.8 ± 0.5. The axial ratio $\text{(}\text{c}\text{a}\text{)}$ decreases nonlinearly with increasing pressure, the decrease being 2.4 per cent at 230 kbar. When the pressure exceeds 230 kbar, Lu transforms reversibly from the h.c.p. phase to the Sm-type structure. The transition occurs with increasing pressure in the range of 230 ± 5 kbar. The lattice parameters of the Sm-type structure at about 231 kbar are a = 3.176 ± 0.006 Å and c = 21.77 ± 0.04 Å, and the volume change is $\text{?0.21}\text{cm}{}^3\text{mole}$ or ?1.6 per cent of the volume of the h.c.p. phase.     

Optical absorption edge of GaS under hydrostatic pressure

The pressure variation of the optical edge of GaS has been measured. The direct exciton has been studied up to 6 kbar at 77 K and the indirect edge up to 40 kbar at 300 K. The exciton is shown to have a coefficient of ?2 ± 0.5 × 10^?6eV/bar and the indirect edge of ?ll ± 1.5× 10^?6eV/bar. A discussion of the values of the pressure coefficients for direct and indirect transitions in gallium chalcogenides is given.     

Hydrostatic pressure effects on oxygen-related irradiation-produced defects in silicon

Abstract

Hydrostatic pressure has been used as a variable to investigate the E_c-0.164 eV acceptor level for the oxygen-vacancy (O—V) defect in γ-ray irradiated Si, and the annealing/formation of oxygen-related defects in neutron-irradiated Si. The acceptor level is found by deep level transient spectroscopy to move closer to the conduction band and away from the valence band at rates of 3.9 meV/kbar and 2.4 meV/kbar, respectively, i.e., the level moves higher in the gap. There is also a relatively large inward (outward) breathing mode lattice relaxation (4.6±1.2 ų/electron) accompanying electron emission (capture) from this level. Both results reflect the antibonding nature of the level and are qualitatively consistent with the Watkins—Corbett model for the O—V defect. The annealing rate was found by infrared absorption to increase with pressure for the O—V defect at 350°C with a derived activation volume of ?4.5 ų/defect, where the negative sign implies inward relaxation (contraction) on annealing. Pressure has relatively little effect on annealing of the C—Si—O C(3) defect which is interstitial in nature, but strongly favors the formation of the dioxygen (2 oxygen atoms per vacancy, i.e., O₂—V) defect. The intensity of the O₂—V band after annealing at 20 kbar is 5 times higher than that following similar annealing at 0 kbar. Additionally, this intensity at 20 kbar is higher than that achievable by any isochronal or isothermal annealing steps at 0 kbar. These annealing/formation results are discussed qualitatively in terms of models for the various defects.     

The use of the high pressure hydrothermal method for tailored synthesis of zeolites without structure directing agents. Instance: Synthesis of natural zeolites with 5-1 building units

Abstract

The synthetic counterparts of natural alumosilicate zeolites containing 5-1 structural building units have been synthesized by simulating the natural hydrothermal formation conditions. Synthetic glasses of the respective zeolite composition were used as starting materials, while distilled water under hydrothermal conditions was used as pressure and reaction medium. No structure directing agents, additional solutions or sol-gel material has been employed.

The experience of former investigations on the tailored synthesis of alumosilicate zeolites showed, that 220°C is the expected temperature of maximum gain. Synthesis time was always 60 d. Synthesis pressure for mazzite (MAZ), mordenite (MOR), fer-rierite (FER), epistilbite (EPI) and dachiardite PAC) was 1 kbar while bikitaite (BIK) could only be synthesized at 2 kbar pressure.

The results of the investigations on hand show, that this process can be applied for the tailored synthesis of zeolites with completely new properties (e.g., semiconducting frameworks).     

Phase transformations in equiatomic alloy TiZr at pressure up to 70 kbar

The effect of pressure on the α ? β and ω ? β transformations in the equiatomic alloy TiZr is studied by the differential thermal analysis (DTA) and calorimetric technique. The α-β equilibrium at atmospheric pressure occurs at a temperature of 579°C, and the heat of transition ΔH is 40.9±2.0 J/g. As the pressure increases up to 28 kbar, the temperature of the α-β equilibrium linearly decreases, dT/dP=?2.2±0.3 K/kbar. In the pressure range 28–48 kbar, the β-phase undergoes a transition to the two-phase (α + ω) state upon cooling to room temperature. At pressures above the triple point with the coordinates P=49±3 kbar and T=460±30°C, the cooling of the β-phase gives rise to only the hexagonal ω-phase with the unit cell parameters a=4.843 Å, c=2.988 Å, and c/a=0.617 under normal conditions. The slope of the ω-β equilibrium boundary is positive at pressures up to 70 kbar, dT/dP≈0.46 K/kbar. The ω → α transformation at atmospheric pressure proceeds in the temperature range T=425–470°C with the enthalpy of transition ΔH=2.8 J/g.     

Features of magnetic phase transitions in iron-manganese arsenides of the type Fe a−x MnxAs (a≈1.6)

This paper discusses how temperature/pressure processing affects the cascade of magnetic phase transitions in the alloy Fe_0.5Mn_1.1As with a C38 tetragonal crystal lattice. It shows that after various temperature/pressure treatment regimes (quenching of the sample from 800 °C under pressures of 30–60 kbar) no transition to the low-temperature phase is observed, as a result of which the ferrimagnetic phase extends to liquid-nitrogen temperatures. These results are analyzed on the basis of a qualitative model that takes into account the competition of ferromagnetic and antiferromagnetic interactions within and between nonequivalent crystallographic subsystems. Fiz. Tverd. Tela (St. Petersburg) 39, 889–893 (May 1997)     

High pressure neutron-scattering experiments on phospholipid model biomembranes

Abstract

By use of neutron small-angle scattering (SANS) the structural properties of saturated and unsaturated phosphatidylcholine model biomembrane systems have been investigated in the temperature range from 0°C to 70°C and at pressures up to 3.5 kbar. The effect of chemical constitution of the hydrocarbon chains of the lipids and the effect of cholesterol on the thermotropic and barotropic phase behaviour is discussed.     

The effect of pressure on the superconducting transition temperature in TaSe3

The transition temperature of TaSe₃ is found to decrease for pressures up to 10 kbar at a rate -7.5 ± 0.3×10^-5 °K/bar. This unusually large decrease can only be explained by both a pressure induced lattice stiffening and a decrease in the Fermi level density of states.     

Internal friction in directed-crystallization (Cu-Sn)-Nb alloys

The distinctive features of the low-frequency internal friction Q ⁻¹(T) of (Cu-Sn)-Nb composites at high temperatures (up to 400°C) are investigated for strains in the range 10⁻⁵–10⁻⁴. Considerable hysteresis of Q ⁻¹(T) in the heating-cooling cycle is recorded, including the presence of a minimum at ∼175°C when the sample is heated to 400°C and two peaks P ₂ (at 280°C) and P ₁ (at ∼100°C) when the sample is cooled from 400°C. The activation energy of the anomalous internal friction background (up to 175°C), the oxygen diffusion parameters, and the oxygen concentration in the niobium fibers (all of which govern the peak P ₂) are calculated, and the value and temperature dependence of the yield point of the bronze matrix (which govern the peak P ₁) are estimated. Zh. Tekh. Fiz. 68, 114–117 (November 1998)     

Activation volumes of hydrolyses of maltose and maltotriose over an immobilized glucoamylase catalyst

Abstract

Initial rates of hydrolysis of maltose and maltotriose over an immobilized glucoamylase have been measured up to 127 MPa at 25±0.1°C. The observed rates have been analyzed showing the reaction pathways of both hydrolyses to be E+S?ES*?ES7ast;E+P, where E, S, P, ES*, and ES denote the enzyme, the substrate, the product, a substrate-subsite complex, and a substrate-active site complex, respectively. The apparent maximum rate r^mand the apparent Michaelis constant K^m as well as their respective pressure dependences in terms of the apparent activation volume Δ V_app ^# and the apparent volume of reaction Δ V_app have been evaluated. Small absolute values of Δ V_app ^num; and Δ V_app for both reactions have been discussed on the basis of the reaction mechanism.     

NMR Studies of Drugs. 1H and 13C NMR Chemical Shift Assignments in Etidocaine and Etidocaine Hydrochloride Determined by Two-Dimensional NMR Spectroscopy

¹H and ¹³C NMR chemical shift assignments were obtained for the local anesthetics etidocaine (1) and etidocaine hydrochloride (2) in CDCl₃ solution, as well as for 2 in D₂O solution. The COSY experiment was employed for proton-proton correlation, while onebond and long-range 2D heteronuclear techniques allowed the assignments of all ¹³C chemical shifts in each molecule. Etidocaine has a chiral carbon; etidocaine hydrochloride has, in addition to the natural chiral center, an acid-induced chirality at the protonated amine nitrogen, resulting in solvent-dependent diastereomers. Ten of the fourteen magnetically nonequivalent ¹³C nuclei of 2 exhibit doubled ¹³C resonance peaks (50.3 MHz, 20°C, CDCl₃ solution) due to the presence of the two diastereomers.     

Calibration of the R ruby fluorescence lines in the pressure range [0-1 GPa] and the temperature range [250-300 K]

Abstract

The pressure range [&1 GPa] and the temperature range [250–300 K] are commonly used in many science fields like biology, agro-chemistry, pharmacology, or geology. In this paper, the calibration of the ruby R lines of fluorescence is performed in these pressure and temperature ranges, using the melting curve of pure water. The linear shifts of ruby peaks are equal to ?0.140cm^?1/K and ?0.768cm^?1/kbar with R₁, and to ?0.137cm^?1/K and ?0.779 cm^?1/kbar with R₂. The accuracy of pressure measurements can be as good as ± 10MPa if the temperature is known with ±0.5 K. Such a precision is achieved if: (1) the position of each peak is determined using an inversion method; (2) daily shifts of the spectrometer are corrected before each acquisition; (3) peak positions of each ruby are known at ambient pressure and temperature.     

Comparison of the Raman pressure shift and the Raman temperature shift of benzene and diamond with the ruby soale

Abstract

In order to serve as substitute for the pressure ruby scale at high temperature, the breathing mode of bemsens (990 cm^?1) and the first order Raman mode of diamond (1333 cm^?1) have been studied as a function of pressure and temperature in the range of 0–15 GPa and 25–400°C. The diamond and bensene Raman frequency shifts are shoft to be of valuable use as a pressure scale at high temperature. A further advantage of bensene is to remain a suitable pressure transmitting medium up to 350°C and 15 GP.     

High-pressure optical studies of Y2O3:Eu3+ nanoparticles

Abstract

The fluorescence spectra of Y₂O₃:Eu³⁺ nanoparticles have been measured under the pressure of up to 78 kbar at room temperature. In this pressure range, a red-shift of 0.02(1) nm/kbar^?1 is noticed for the 0–2 line (⁵D₀→⁷F₂ transition). This shift is explained by the change of negative charge of the surrounding ligands. Compatibility between measured and calculated values for the 0–2 line position was obtained. The luminescence decay curves of the ⁵D₀→⁷F₂ transition were studied up to 78 kbar and were found to behave exponentially for all pressures studied. The fluorescence lifetime τ for the 0–2 line (⁵D₀→⁷F₂ transition) slowly decreased with pressure. The pressure effect on τ for the 0–2 line (⁵D₀→⁷F₂ transition) was explained by a model which considers the pressure effect on the line position, inter-ionic distance, ion volume and polarizability, molecular volume and polarizability, molecular refractive index and the refractive index medium n _med of the surrounding hydrostatic medium. The fluorescence lifetime calculated by the present model is in close correspondence with the experimental values.     

Magnetic quantum oscillations in the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br

The interlayer magnetoresistance of the organic superconductor κ-(BEDT-TTF)₂Cu[N(CN)₂)Br is measured at ambient pressure and under pressures of up to 12.5 kbar. In addition to the slow Shubnikov-de Haas oscillations with a frequency of ≃150 T observed at P⩾5 kbar, rapid oscillations attributed to the magnetic breakdown orbit enveloping an area equal to 100% of the area of the Brillouin zone are found to emerge above B=20 T. The latter oscillations are observed at ambient pressure as well as under pressures of up to 9 kbar. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 190–194 (10 August 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Precision measurement of vector and tensor analyzing powers in elastic deuteron-proton scattering

High-precision vector and tensor analyzing powers of elastic deuteron-proton ( d + p) scattering have been measured at intermediate energies to investigate effects of three-nucleon forces. Angular distributions in the range of 70^°-120^° in the center-of mass frame for incident-deuteron energies E _d ^lab = 130 and 180 MeV were obtained using the RIKEN facility. The beam polarization was unambiguously determined by measuring the ^12C (d, α)^10B(2⁺) reaction at 0^°. Results of the measurements are compared with state-of-the-art three-nucleon calculations. The present modeling of nucleon-nucleon forces and its extension to the three-nucleon system is not sufficient to describe the high-precision data consistently and requires, therefore, further investigation.     

Positron annihilation in electron-irradiated n-type gap crystals

Abstract

The defects in n-GaP crystals irradiated by 2.3 MeV electrons up to 1 × 10¹⁹ cm^?2 at RT were studied by means of positron annihilation (angular correlation) and electrical property measurements. It was found that positrons are trapped in some radiation-induced vacancy-type defects (acceptors) but that the effect saturates at high electron fluences (D1 × 10¹⁸ cm^?2). The trapping rate in irradiated samples increases with temperature in the range 77–300 K. Post-irradiation isochronal annealing reveals the positron traps clustering at about 200–280°C. All positron sensitive radiation-induced defects disappear upon annealing up to 500°C.