弹性波CT技术在码头加固效果检测中的应用

青岛港是我国北方一个很重要的港口码头,但由于年久失修,码头的使用出现安全隐患。经多种修补方案比较,最终采用垂直注浆加固方案。为了检测码头高压注浆加固处理效果,采用弹性波CT方法并结合岩芯波速测试及强度试验对其进行检测。本文简要叙述了弹性波CT法的原理与测试方法,探讨了该法在灌浆效果检测中的应用。试验证实,弹性波CT技术在探测水下高压注浆效果检测方面有其独特的效果。     

Molecular dynamics simulation of the pressure-induced phase transition in BaFCl

The structural phase transition in BaFCl under high-pressure up to 30 v GPa has been studied using molecular dynamics (MD) method. It was found that BaFCl transforms from a tetragonal structure to a monoclinic structure in the upstroke process and then the tetragonal structure is recovered upon releasing the pressure. The atomistic mechanisms of the transformation have been examined using the pair-correlation functions and the coordination numbers for the lattices with or without vacancies in the MD cell. It was also demonstrated that the Cl atoms between the adjacent weakly bonded Cl layers shift in the compressed direction and move to positions with a 2-fold coordination number at a nearest-neighbour site after the transition.     

Pressure-Induced Charge Delocalization in Manganites Studied by Means of Infrared Spectroscopy

Infrared absorption spectra of the La 0.75 Ca 0.25 MnO 3 manganite have been collected over the spectral range 600-1100 cm m 1 along isobaric paths at P =0,2,4, and 7 GPa in the 240-320 K temperature range. The pressure dependence of the insulator-to-metal transition temperature T IM has been determined from the spectra analysis and the first PT phase diagram of a manganite in the high-pressure regime is presented and discussed.     

2-d data collection in high pressure powder diffraction studies-applications to semiconductors

Abstract

Using angle-dispersive diffraction techniques and synchrotron radiation, we have made a detailed re-examination of the high-pressure behaviour of a number of core II-VI, III-V and group IV semiconductors. Despite much previous work on these materials, the good resolution afforded by angle-dispersive techniques, and the high-sensitivity of the image-plate area detector have yielded many new results which reveal that the accepted structural systematics have to be modified quite substantially. In this paper, we summarise the newly emerging structural systematics, and use the results to show how access to full 2-d powder patterns has proved essential in determining correct crystal structures.     

Interaction of micellar casein and i-Carrageenan: Influence of high pressure

The effect of high-pressure treatment (HPT) (up to 950 MPa) on the rheological properties of a mixed system of i-Carrageenan (i-Car) + skim milk powder (SMP), expressed in terms of its micellar casein (MC) content, has been investigated. In the presence and absence of ionic calcium, with or without initial thermal processing, no significant effect has been found on the rheology or gelation/melting temperatures of pure i-Car even under harsh HPT conditions. But, in mixed systems, containing varying amounts of i-Car (up to 1 wt.%) and MC (up to 8 wt.%), substantial changes have been detected. Most significantly, at the higher molar ratios of MC, and particularly at the higher pressures (>400 MPa), the dispersions were not thermoreversible in gelation anymore, probably due to the strong interactions of disrupted casein micelles with i-Car molecules, as well as due to the formation of a dominant proteinaceous network.     

Noncatalytic organic rearrangement using supercritical water

Abstract

Significant acceleration of Beckmam and pinacol rearrangements can be achieved by using supercritical water (scH₂O), especially just near the critical point even in the absence of any acid catalysts. A high-pressure, high-temperature flow reactor system with FTlR operable at 500°C and 50 MPa was suaxssfdy developed, wherein the non-catalytic Beckmam and pinacol rearrangements using scH₂O were carried out and monitored. It has been demonstrated that scH₂0 itself acts very effectively in the place of conventional acid catalysts for both the rearrangements. The rate of the pinacol rearrangement using scH₂O is 28,200-fold rate of that in 0.871 M HCl solution at 46.7 MPa under distillation conditions. The high rate of reaction may be attributed to a great increase in the local proton concentration around the organic reactants.     

High-pressure synthesis and structural characterization of three new polyphosphides, α-SrP3, BaP8, and LaP5

Three novel metal polyphosphides, α-SrP₃, BaP₈, and LaP₅, were prepared in BN crucibles by the reaction of the respective stoichiometric mixtures under a high pressure of 3 GPa at 950-1000°C. Their crystal structures were determined from single-crystal X-ray data (α-SrP₃: space group C2/m, a=9.199(6) Å, b=7.288(3) Å, c=5.690(3) Å, β=113.45(4)°, Z=4, R₁/wR₂=0.0684/0.1180 for 471 observed reflections and 22 variables; BaP₈: space group P−1, a=6.762(2) Å, b=7.233(2) Å, c=8.567(2) Å, α=86.32(2)°, β=84.31(2)°, γ=70.40(2)°, Z=2, R₁/wR₂=0.0476/0.1255 for 2702 observed reflections and 82 variables; LaP₅: space group P2₁/m, a=4.885(1) Å, b=9.673(3) Å, c=5.577(2) Å, β=105.32(2)°, Z=2, R₁/wR₂=0.0391/0.1034 for 1272 observed reflections and 31 variables). α-SrP₃ is isostructural with SrAs₃ and the crystal structure consists of two-dimensional puckered polyanionic layers _∞²[P₃]²⁻ that stack along the c-axis yielding channels occupied by Sr²⁺ counterions. BaP₈ crystallizes in a new structure type which contains a three-dimensional infinite polyanionic framework _∞³[P₃]²⁻, with large channels hosting the barium cations. LaP₅ is a layered compound containing _∞²[P₅]³⁻ polyanionic layers separated by La³⁺ ions. All three compounds exhibit expected diamagnetic behaviors.     

High-pressure synthesis and crystal structure analysis of NaMn2O4 with the calcium ferrite-type structure

Single crystals of a new sodium manganese oxide, NaMn₂O₄, were synthesized for the first time using a high-temperature and high-pressure technique. The NaMn₂O₄ single crystal is black, has a needle shape, and crystallizes in the orthorhombic calcium ferrite-type structure, space group Pnam with , , , , and Z=4. The structure was determined from a single-crystal X-ray study and refined to the conventional values R=0.041 and wR=0.034 for 1190 observed reflections. The framework structure is built up from edge-sharing chains of MnO₆ octahedra that condense to form one-dimensional tunnels in which the sodium atoms are located. The Mn-O bond distance and bond valence analyses revealed the manganese valence Mn³⁺/Mn⁴⁺ ordering in the two “double rutile” chains of NaMn₂O₄.     

High-pressure synthesis, crystal structures, and characterization of CdVO3−δ and solid solutions CdVO3-NaVO3

CdVO_3−δ and solid solutions of Cd_1−xNa_xVO₃ with the GdFeO₃-type perovskite structure were prepared using a high-pressure (6 GPa) and high-temperature technique. No significant oxygen and cation deficiency was found in CdVO₃. Cd_1−xNa_xVO₃ are formed in the compositional range of 0?x?0.2. CdVO₃ and Cd_1−xNa_xVO₃ demonstrate metallic conductivity and Pauli paramagnetism between 2 and 300 K. A large electronic contribution to the specific heat (γ=13.4 and ) for CdVO₃ and Cd_0.8Na_0.2VO₃, respectively) was observed at low temperatures due to the strongly correlated electrons. Crystal structures of CdVO₃ and Cd_0.8Na_0.2VO₃ were refined by X-ray powder diffraction: space group Pnma; Z=4; , , and for CdVO₃ and , , and for Cd_0.8Na_0.2VO₃.     

Structural and magnetic properties of high-pressure/high-temperature synthesized (Sr1-xRx)CoO3 (R=Y and Ho) perovskites

Polycrystalline perovskite cobalt oxides Sr_1-xR_xCoO₃ (R=Y and Ho; 0?x?1) were prepared by high-pressure/high-temperature technique. X-ray powder patterns of the Y-system indicated cubic perovskite form for 0?x?0.5, and orthorhombic perovskite form for x=0.8 and 1.0, while coexisting of the two phases for x=0.6. The cubic perovskite samples had metallic electric resistivities while the orthorhombic ones with semiconducting or insulating nature. The parent compound SrCoO₃ showed a ferromagnetic transition at 266 K. With the Y substitution, the transition temperature increased slightly to ∼275 K at x=0.1, then decreased rapidly to ∼60 K for x=0.6. The YCoO₃ (x=1) sample showed non-magnetic behavior. The Ho-substituted system showed quite similar structural, transport and magnetic properties to those of the Y-system.