High Pressure and High Temperature Studies on Manganese Oxides

High pressure and high temperature quench experiments on f -MnO 2 , Mn 2 O 3 and sol gel derived manganese oxides have been carried out to identify any new phases to which the materials may transform under high pressure and high temperature conditions. Results of ESR, DTA and TGA investigations on sol gel derived manganese oxide have shown it to be hausmannite Mn 3 O 4 , instead of n -Mn 2 O 3 as reported earlier in the literature. The sol gel derived manganese oxide transforms to n -Mn 2 O 3 when heated above 700°C. Sol gel derived Mn 3 O 4 , when quenched from 5 GPa and temperature range 800-1200°C, gives a mixture of Mn 3 O 4 (hausmannite) and a phase having CaMn 2 O 4 (marokite)-type structure. f -MnO 2 undergoes partial amorphization when pressure-quenched from 8 GPa at room temperature. The high pressure and high temperature quench experiments up to 5 GPa and 700°C showed that the decomposition temperature of f -MnO 2 increases with pressure. The new phase reported by Liu (1976) from diamond-anvil cell (DAC) experiments on pyrolusite MnO 2 is identified to be a low-density polymorph f -MnO 2 . This unusual result of formation of low-density f -MnO 2 , having an open structure at high pressure and high temperature, is probably due to quenching of a non-equilibrium phase in Liu's (1976) laser-heated DAC experiment.     

Increasing Preservation Efficiency and Product Quality through Control of Temperature Distributions in High Pressure Applications

The effectiveness of HP sterilisation is a function of both temperature and pressure. As during pressurisation the product temperature increases, heat transfer to the colder HPP vessel wall occurs and the product fraction near the vessel wall will be colder than the product in the middle of the vessel. The effect of the temperature distribution in the vessel on the inactivation of Bacillus stearothermophilus has been examined. A mathematical model has been built, in which both thermodynamics and inactivation kinetics are integrated. Heat transfer is based on a Finite Element simulation, inactivation kinetics are based on first order kinetics. Based on this model and experiments the effect of an homogeneous temperature distribution on inactivation is demonstrated.     

New materials from high pressure experiments: Challenges and opportunities

Recent improvements in high pressure techniques have led to new scientific discoveries in fields ranging from Earth and Planetary Science, to fundamental physics and biology. Here we examine the possibilities for development of new technologically-important materials based on high pressure research.     

B-C-N Compound Synthesized Under High Temperature and High Pressure

Crystalline hexagonal B(N 1 m x C x ) and cubic B-C-N compounds have been synthesized from a precursor produced from melamine and boric acid by application of high temperature and high pressure. The synthesized products were characterized by X-ray diffraction. The lattice parameters for the hexagonal crystal are a=2.506 Å, c=6.657 Å, and that for the cubic crystal is a=3.596 Å. The X-ray photoelectron spectra of the B-C-N compound indicate the presence of B-N, C-N, C-C, and B-C bonds, which suggests that boron, carbon, and nitrogen atoms all bond with one another and that the B-C-N crystal is a compound in which the three kinds of atoms are mixed atomically. The composition of the B-C-N compound is B 0.47 C 0.23 N 0.30 . A strong absorption band at 1000～1120 cm m 1 attributable to the cubic B-C-N phase is observed in the infrared spectrum. The photoluminescence spectrum of hexagonal B-C-N powder measured at room temperature features a broad peak centered at 374 nm, corresponding to the band-edge emission of h-B-C-N, and is similar to that of w-GaN.     

High Pressure Theoretical Studies of Actinide Dioxides

Actinide dioxides (ThO 2 , UO 2 , Pu 2 etc.) compounds have the CaF 2 -type structure at ambient pressure and temperature. Under high pressure, they exist in the PbCl 2 -type structure, belonging to space group Pnma [1]. We have studied crystal structures under high pressure in actinide dioxides by means of first-principles self-consistent total-energy calculations with the non-local Perdew, Burke and Ernzerhof (PBE) exchange correlation using the full-potential linear-muffin-tin-orbital (FPLMTO) method. The atomic equilibrium volume, bulk modulus and transition pressure for actinide dioxides were calculated, covering the full pressure range for which the mentioned experiments have been done [2].     

High Temperature-High Pressure Structural Studies of Cerium

Energy dispersive X-ray-diffraction with the large volume press MAX 80 at HASYLAB/DESY is used in the present study for the determination of the p - V - T -relations around the critical point of the f - n -phase transition in Cerium. Furthermore the f - l -phase boundary is studied experimentally to remove the last question marks from the phase diagram of Cerium in the accessible region of pressure and temperature.     

高温高压下电解质溶液谱学研究的进展

高温高压下电解质溶液研究在理论和工业应用上都具有重要的意义，拉曼光谱、红外光谱、紫外可见光谱、中子和X射线衍射、以及X射线吸收精细结构方法都已经用于它的研究。随着温度升高，溶液的结构发生了变化，离子的缔合度增加，内层配位水的数目减少，出现了离子的多核簇组成。除了静态结构的研究外，也用拉曼光谱进行溶液的动力学探讨。水热金刚石压腔装置是高温高压电解质溶液研究的一个重要的进步，在水热金刚石压腔装置中，拉曼光谱和X射线吸收精细结构两种方法具有重要的应用潜力。     

A New High Pressure - Low Temperature Process for the Synthesis and the Crystal Growth of Gallium Nitride

Gallium nitride can be synthesized by a solvothermal route using ammonia as solvent and a nitriding additive (such as hydrazine hydrochloride NH 2 NH 3 Cl or sodium azide NaN 3 ) encapsulated in melt gallium as chemical reagents. The involved temperature and pressure are respectively 600 °C and 150 MPa. The synthesized products are then characterized by X-Ray Diffraction and Scanning Electron Microscopy. The synthesis parameters influence the powder morphology and purity.     

Magnetic Transitions in Fe 3 Pt Invar Alloy Under High Pressure and Temperature Studied by Inelastic X-ray Scattering

The magnetic properties of the Invar alloy Fe 72 Pt 28 have been investigated by X-ray emission spectroscopy as a function of temperature up to 900 K and pressure up to 25 GPa. With increasing temperature and pressure, the amplitude of the Fe local moment, deduced from the Fe K g line satellite intensity, is reduced. Both the temperature and pressure dependence are interpreted in terms of transitions from a high-spin state to a low-spin state. This behavior provides a microscopic picture of the Fe magnetism in Invar alloys in agreement with the 2 n state model.     

Solid and Liquid AgI at High Pressure and High Temperature: A X-ray Absorption Spectroscopy Study

We report about recent X-ray absorption spectroscopy (XAS) measurements on solid and liquid AgI under high pressure. The structural behaviour of AgI has been investigated to pressures P～4.3 GPa at room temperature and to P～1.8 GPa at 1100 K. The high temperature/high pressure conditions have been obtained by means of a large-volume press of the Paris-Edinburgh type, coupled with a 10 mm boron/epoxy biconical gasket. The absorption spectra have been collected in transmission mode, both at the K-edge of Ag and I, and the samples have been characterized in situ by energy scanning X-ray diffraction at fixed angles. Our XAS results for solid AgI are compatible with previous X-ray diffraction measurements. For liquid AgI, we observe a slight change in the intensity and a shift in the frequency of the XAS oscillations with respect to what obtained in the case of the ambient pressure liquid.     

High Pressure Studies on the Optical and Electronic Properties of Para -Terphenyl

Based on X-ray powder diffraction experiments of p -terphenyl that yield pressure dependent lattice parameters, we performed geometry optimizations of all structural degrees of freedom including bond lengths and bond angles as well as molecular orientation using ab initio bandstructure methods. For these optimized structures we calculated the dielectric tensors. Upon increasing pressure we find a spectral red shift of the lowest energy absorption feature that is significantly smaller than that of the second peak at higher energies. We attribute this effect to intermolecular interactions that affect the bands involved in the second transition more than the bands giving raise to the first transition. This picture is confirmed by quantum chemical calculations for single molecules with the internal geometry extracted from the optimized structures.     

New Members of the RuSr 2 RECu 2 O 8 Family of Phases (RE=Rare Earth) Obtained at High Pressure and Temperature

At room pressure, Sm, Eu and Gd seem to be the only RE elements that accept to enter into the structure of RuSr 2 GdCu 2 O 8 . However high pressure and high temperatures allow one to replace gadolinium by other lanthanide cations. We have been successful in replacing Gd by Y, La, Pr, Nd, Tb, Dy, Ho and Er. X-ray diffraction patterns fitted by the Rietveld method show that the average crystal structure of RuSr 2 RECu 2 O 8 is tetragonal with P 4/ mmm space group symmetry. Micro-Raman experiments have been performed on RuSr 2 GdCu 2 O 8 samples synthesized at both high and room pressure; the resulting spectra are consistent with the same structure, since there are no major changes in the low-frequency range.     

High Pressure Instrumentation: Low and Negative Pressures

Much work on semiconductors, soft solids and biological materials does not require the megabar capability of the diamond anvil cell; a few accurate kbar being all that may be required. Work in this range poses its own challenges, to make the experiments routine, safe and reliable, and well-calibrated. We contrast diamond anvil cells working at what for them is very low pressure, with traditional bombs working at what for them is dangerously high pressure. We describe our preferred solution, a single-diamond cell, and demonstrate its use with Raman data from ethanol under low pressure. Negative hydrostatic pressure cannot be obtained by traditional methods. However, we present data showing the Raman spectrum of ethanol apparently at the negative pressure of m 3 kbar.     

一种在线监测的ATR探头的设计

生物过程是一个复杂的系统,在反应过程中,会产生固态、液态、气态的过程反应物,且具有生物活性,想要准确的掌握过程反应物的种类与含量,必须对生物过程进行实时在线的监测,才能够获得准确的数据。生物过程的原位在线分析依赖于高性能的衰减全反射探头,衰减全反射技术是在线分析系统中实现原位在线测量的有力手段。通过分析衰减全反射技术的基本原理与特点,设计了一种成本低、光通量高、具有标准生物过程传感器接口的中红外衰减全反射探头,能够直接插入到生物反应器中,对生物过程反应物进行无损、零延迟的监测。实验结果表明,在线式ATR探头具有较宽的光谱范围,所采集光谱具有较高的信噪比,能够应用在生物过程的在线定量分析之中。     

High Pressure Processing at Subzero Temperature: Effect on Spoilage Microbiota of Poultry

Mechanically recovered poultry meat (MRPM) was treated at 350 and 450 MPa for 5 and 15 min at m 20 °C and then stored at 2 °C. Counts of mesophilic, psychrotrophic and lactic acid bacteria were determined at 1, 4 and 15 days of storage. Initial counts were ca. 7 log CFU/g for the three populations. High pressure induced lethalities of ca. 1.5 log CFU/g for mesophiles and psychrotrophs and, in some cases, ca. 2.5 log CFU/g for lactic acid bacteria. At 4 days, counts in pressurized samples increased less for mesophiles and psychrotrophs ( h 0.5 CFU/g) than for lactic acid bacteria ( S 1 log CFU/g). At 15 days, counts of the three populations were ca. 9 log CFU/g in all samples. High pressure processing at subzero temperature does not extend shelf-life of MRPM.     

生物材料红外波段消光性能分析

对制备的三种消光材料真菌An0429孢子,真菌Bb0919孢子以及真菌Cx0507孢子的红外波段消光性能进行了测试分析。静态测试采用压片法得到三种生物材料的镜面反射光谱,然后根据Krames-Kronig(K-K)关系对三种生物材料红外波段的复折射率进行了计算。由Mie理论计算得到三种生物材料红外波段的静态质量消光系数,并与几种无机非金属材料进行了对比。搭建烟幕箱实验平台,对三种生物材料3~5 μm波段动态质量消光系数进行了测试分析,得到三种消光材料的动态质量消光系数分别为1.257,1.065以及1.009 m2·g-1。测试分析结果表明,三种生物材料的红外波段消光性能优于常见的无机材料,其生产周期短,生产成本低,生产过程无毒,对环境友好等优点,使得生物消光材料具有较好的应用前景。     

生物材料低温保存设备的研究

介绍了生物材料低温保存设备的工作过程和装置结构,并对主要部件冷却室的结构和制作原理进行了分析,同时对控制系统及冷冻速率进行讨论。     

红外辐射材料的制备与光谱研究

本文开展了红外辐射材料ＺｒＯ２、Ａｌ２Ｏ３及其复合氧化物ＺｒＯ２－Ａｌ２Ｏ３的纳米材料制备方法研究,对其开展了ＦＴＩＲ,ＮＩＲ ＦＴ－Ｒａｍａｎ、ＸＲＤ和红外发射光谱研究,研究表明复合氧化物具有较好的红外发射性能。在构效关系的研究基础上,探讨其实际应用价值。     

High Pressure Study of Dynamics in Tetraphenyltin

Measurements of proton NMR relaxation times as well as inelastic and elastic neutron scattering of tetraphenyltin (C 6 H 5 ) 4 Sn as a function of temperature and pressure were performed in the work. It allowed to determine activation volume j V * for a small amplitude reorientation/oscillation of the phenyl rings. The values of activation volume is very small and the ratio of j V */ V M ( V M is molar volume) is less than 1%.     

白硅钙石的高温高压拉曼光谱研究

利用活塞圆筒装置在1.2 GPa,1 473 K的条件下合成了白硅钙石。采用外加热装置和金刚石压腔结合拉曼光谱分析技术,采集了白硅钙石298,353,463,543,663,773以及873 K温度区间的常压及1 atm～14.36 GPa(常温)压力区间的拉曼谱图。扫描电镜下,该研究合成的样品为结构一致的单一相,颗粒大小为10～20 μm。电子探针分析结果表明,样品的组成为Ca_7.03(2)Mg_0.98(2)Si_3.94(2)O₁₆,该组分完全吻合白硅钙石理论组分。Raman分析结果表明,高温时白硅钙石的拉曼谱图中具有29个振动峰。随着温度的升高,部分振动峰出现了合并或者弱化消失的现象。该现象尤其以800～1 200 cm-1范围内的909,927和950 cm-1振动峰峰位最为明显,这些振动峰分别在873,773以及873 K时弱化消失。据此,白硅钙石的结构在实验温压范围内稳定,且随着温度和压力的升高,其拉曼振动峰峰位分别呈现往低频和高频方向线性飘移的趋势。除此之外,根据高温和高压拉曼实验的结果,分别计算了白硅钙石拉曼振动峰峰位的等压mode-Grüneisen参数和等温mode-Grüneisen参数,其算术平均值分别为1.47(2)和0.45(3)。最后结合高温和高压拉曼实验的结果,计算了白硅钙石的非谐系数,结果表明,Si-O振动模式对于非谐效应的贡献要小于其他振动模式。