Solvation pressure in chloroform

Molecular dynamics (MD) simulations of chloroform vapor and liquid at normal temperature and pressure and liquid under hydrostatic pressure are presented, giving bond lengths and vibrational frequencies as functions of pressure. The change in bond lengths between vapor and liquid at normal temperature and pressure is consistent with a pressure equivalent to the cohesive energy density (CED) of the liquid, supporting the solvation pressure model which predicts that solvated molecules or nanoparticles experience a pressure equal to the CED of the liquid. Experimental data for certain Raman frequencies of chloroform in the vapor phase, in the liquid, and in the liquid under pressure are presented and compared to MD. Results for C-Cl vibrational modes are in general agreement with the solvation pressure model whereas frequencies associated with the C-H bond are not. The results demonstrate that masking interactions exist in the real liquid that can be reduced or eliminated in simplified simulations.     

CGC using a programmable electronic pressure controller

Capillary gas chromatographic separations were performed with an electronic pressure control system developed to provide precise closed-loop control of inlet pressure through the use of a solid state micro-machined pressure sensor and electronically controlled proportional valve. The closed-loop control of the electronic system provided better precision than the open-loop control achieved by manual pressure regulation. Closed-loop control can perform pressure programming, which can be combined with temperature programming to optimize separations. The pressure sensor monitors the integrity of the flow system and singals the controller to reduce flow in the presence of a sudden loss of system pressure.     

N,N-二丁基甲酰胺的制备-二正丁胺存在下二氧化碳催化氢化反应的研究

研究了在二正丁胺存在下RuCl3/DPPE催化二氧化碳氢化反应, 探讨了N,N-二正丁基甲酰胺的制备新途径, 考察了温度、溶剂、二氧化碳及氢气压力等对催化氢化反应的影响, 产物的结构及量用核磁共振波谱、气相色谱分析测定. 反应的催化效率随温度的升高(120 ℃)先上升后降低; 在4 MPa二氧化碳压力下催化效率随氢气的压力升高而升高; 在4 MPa氢气压力下, 催化效率随二氧化碳压力的升高(6 MPa)先升高后降低, 在10 MPa氢气压力下, 催化效率随二氧化碳的压力升高而升高. 二氧化碳压力的非线性效应可能是由于二丁胺与二氧化碳反应, 导致二丁胺对甲酸的稳定化效应随二丁胺的量的变化而变化的结果, 该假设得到对照实验的验证.     

黑膜厚度与膜表面张力关系的研究

用微干涉测量技术直接测定楔压等温线,研究了电解质浓度对阳离子表面活性剂TTAB在浓度大于cmc时形成黑膜厚度的影响及膜表面张力与溶液表面张力之间的差别.结果显示,黑膜厚度取决于楔压和电解质浓度,随着楔压的增加,液膜厚度减少至一定程度后几乎保持不变,表明黑膜类型的转化是阶跃式的,而电解质屏蔽了液膜两个表面电荷层间的排斥作用,故电解质浓度增加,液膜厚度变小.由楔压等温线得出的膜表面张力的结果说明一般黑膜的表面张力与溶液的表面张力并无明显差别.     

Melting of icosahedral nickel clusters under hydrostatic pressure

The thermal stabilities and melting behavior of icosahedral nickel clusters under hydrostatic pressure have been studied by constant‐pressure molecular dynamics simulation. The potential energy and Lindemann index are calculated. The overall melting temperature exhibits a strong dependence on pressure. The Lindemann index of solid structure before melting varies slowly and is almost independent of pressure. However, after the clusters melt completely, the Lindemann index at the overall melting point strongly depends on pressure. The overall melting temperature is found to be increasing nonlinearly with increasing pressure, while the volume change during melting decreases linearly with increasing pressure. Under a high pressure and temperature environment, similar angular distributions were found between liquid and solid structures, indicating the existence of a converging local structure. © 2014 Wiley Periodicals, Inc.     

基于光纤光栅的高压固体压力传感器研究

固体内部压力是国防科技领域需重点监测的参数之一,目前使用较多的测压设备均存在电磁干扰严重、可靠性及准确性差等缺陷.针对以上不足,本研究设计了光纤光栅耐高压固体压力传感器.采用平面薄板作为弹性承压膜片,利用压力作用下的挠度,拉动压力敏感光栅产生轴向位移,实现压力传感.根据测压范围,对其结构进行理论计算,并进行有限元仿真,验证了本设计的可行性.在恒温条件下,进行了压力校准实验,并通过处于同一温度场的温补光栅进行温度补偿,修正应变光栅的温漂.实验结果表明,构建的承压光栅(FBG)压力传感器可以进行压力传感,测压上限可达50 MPa,线性度为99.2%.     

Supercritical fluid chromatography with a slurry-packed capillary column

A versatile system with a slurry-packed capillary column was developed for supercritical fluid chromatography, which is capable of programming both inlet and outlet pressure independently, as well as using a restrictor to apply back pressure. This system revealed the relationships between pressure drop, flow rate, and linear velocity in pressure-programmed supercritical fluid chromatography. In the restrictor system, both the pressure drop and the flow rate increased almost linearly with inlet pressure, while under conditions of constant pressure drop characteristic behavior was observed which depended on the density-viscosity relationships of supercritical fluid. Resolution in the separation of polysiloxane oligomers was found to be increased by increasing the ratio of pressure drop to pressure-programming rate, although the sensitivity decreased due to the increase in peak volume. The system controlling both inlet and outlet pressure has distinct advantages over the restrictor system controlling both inlet and outlet pressure has distinct advantages over the restrictor system in practical in practical operations.     

阿托伐他汀联合缬沙坦对慢性肾炎的临床疗效分析

目的研究阿托伐他汀联合缬沙坦对慢性肾炎的临床疗效。方法以2014年1月—2016年6月慢性肾炎患者90例随机分为两组。单一药物组采用缬沙坦治疗,联合用药组采用阿托伐他汀联合缬沙坦治疗。比较两组患者慢性肾炎治疗总有效率;治疗前和治疗后患者肾功能指标、舒张压、收缩压的差异。结果联合用药组患者慢性肾炎治疗总有效率高于单一药物组,P0.05;治疗前两组肾功能指标、舒张压、收缩压比较无显著差异,P0.05;治疗后联合用药组肾功能指标、舒张压、收缩压改善幅度更大,P0.05。结论阿托伐他汀联合缬沙坦对慢性肾炎的临床疗效确切,可有效改善患者血压和肾功能,值得推广应用。     

Pressure effects on the fluorescence from naphthalene vapour

The fluorescence lifetimes and yields of naphthalene vapour have been measured at low pressure as a function of exciting wavelength and of the pressure of added foreign gases. The lifetimes and yields increase with pressure for short wavelength excitation (< 305 nm) and decrease with increasing pressure for excitation > 305 nm. The pressure dependence of the naphthalene S 1 state at low excitation energies is interpreted in terms of collisionally induced vibrational redistribution.     

Ginzburg number and phase behavior of binary polymer blends in pressure fields

In some polymer blends the temperature and pressure dependence of thermal composition fluctuations have been measured with small angle neutron scattering. The Ginzburg number Gi, the Flory‐Huggins parameter Γ, and the phase boundaries were determined for pressure fields up to 150 MPa. In polymer blends the compressibility leads to a strongly increased Gi which could be appreciably larger than in low molecular liquids and which decreases with increasing pressure fields. Usually, the phase boundaries of UCST as well as of LCST blends shift with pressure to higher temperatures. One blend having PDMS as one component, however, shows an abnormal decrease of the phase boundaries with increasing pressure. The Clausius‐Clapeyron equation correctly predict from the experimentally determined Γ and Gi the observed pressure dependence of the phase boundaries.     

Fourier transform Raman spectroscopy at high pressures: Preliminary results of sulphur to 56 kbar

The feasibility of obtaining Fourier transform (FT) Raman spectra at high pressure in a diamond anvil cell has been investigated. By using a high pressure cell in conjunction with a micro-FT-Raman system, FT-Raman spectra with good signal-to-noise ratios have been measured for sulphur to 56 kbar. In general, the internal modes show significant increases with pressure. No phase transition was observed throughout the pressure range studied.     

Al-Ni-Y三元共晶合金高压凝固组织

利用光学显微镜,扫描电镜,X射线衍射仪对不同压力(2,4,6 GPa)下凝固的Al-1Ni-3Y(%,原子分数)共晶合金组织形貌和相组成进行研究,并且与常压条件下合金凝固组织进行对比。实验结果表明,与常压凝固相比,在超高压力条件下凝固的合金的显微组织形貌发生了很大的改变,但是合金的相组成没有发生变化。常压凝固的合金具有共晶团组织,而高压下凝固的合金具有枝晶状亚共晶组织。高压凝固合金显微组织中出现了大量的初生α-Al相,这表明高压条件下凝固的合金共晶点发生偏移,使得常压共晶成分的合金在高压下变成亚共晶成分合金。同时,共晶组织的形貌发生了很大变化,常压下凝固的合金的组织为Al3Y相与α-Al相形成的菊花状的二元共晶和Al23Ni6Y4相与α-Al相形成的层片状的二元共晶,而高压下这两种共晶组织逐渐转化为离异共晶组织。随着压力的增大,共晶第二相的体积分数减小,α-Al的晶格常数增加。     

应用超临界CO2制备微孔聚丙烯的微孔形貌

研究了应用超临界CO2技术制备微孔聚丙烯时发泡条件和聚丙烯(PP)的熔体强度对微孔形貌的影响。结果表明:在一定的饱和压力下,随着温度的升高,PP的变形能力改善,有利于泡孔的长大。随着饱和压力的增加,PP的熔点降低,升高压力和升高温度具有一定的等同作用。由于CO2在PP内分散的不同,高压低温时得到的泡孔比高温低压时得到的泡孔要规整。降压速率对泡孔形貌的影响因饱和压力的大小而异,饱和压力较高时随着降压速率的提高,孔密度增加,泡孔形貌经历了一个从球体到多面体转变的过程。由于PP熔体强度较低,在发泡温度和PP熔点之间非常接近时,CO2气体容易冲破孔壁而使泡孔呈开孔结构。     

Electronic structure study of the high-pressure vibrational spectrum of FeS2 pyrite

Plane-wave density functional calculations are used to investigate the pressure dependence of the geometry and Gamma-point phonons of FeS(2) pyrite up to 150 GPa. The linear response method is employed to calculate the vibrational properties. Raman-active modes are in excellent agreement with the experimental data available up to 50 GPa,(1) and we predict the evolution with pressure of the IR-active modes for which no high-pressure spectroscopic data have been reported so far. Over the wide pressure range investigated here, all vibrational frequencies depend nonlinearly on pressure; their pressure dependence is quantified by determining the full set of mode Grüneisen parameters and their pressure derivatives.     

High-pressure reactions. II. γ-Ray polymerization of acrylamide

The post-irradiation effect of high pressure on the γ-ray-initiated solid-state polymerization of acrylamide has been described. Polymer conversion was found to increase significantly with applied pressure. The molecular weight of polymer increases with pressure.     

热解压力对生物质焦结构及气化反应性能的影响

利用加压固定床反应器、吸附仪、X射线衍射仪、元素分析仪、电感耦合等离子原子发射光谱仪等考察了热解压力对生物质半焦(以下简称半焦)产率、物化结构、元素组成的影响规律。同时,利用热天平对不同热解压力下所制半焦的气化行为进行了考察。结果表明,随热解压力升高,半焦产率增大,当压力升至1.0 MPa后,半焦产率基本不变;半焦中C元素含量随热解压力的升高而增加,而H元素含量和BET比表面积则减小;此外,随热解压力升高,玉米秸秆焦和锯末焦的石墨化程度增强,而稻壳焦的石墨化程度则基本不受热解压力影响。气化反应的研究表明,玉米秸秆焦及锯末焦的平均气化反应速率随热解压力的提高而减小,而稻壳焦的平均气化反应速率基本不受热解压力的影响。热解压力对半焦BET比表面积及碳微晶结构的影响规律与气化反应速率变化规律的对比研究表明,热解压力引起半焦微晶结构的变化是造成热解压力对半焦气化反应速率影响的主要原因。     

Laser-induced breakdown spectroscopy of carbon in helium and nitrogen at high pressure

This work is devoted to the study of the gas pressure effect on the laser-induced breakdown spectroscopy signal intensity of carbon. Experiments are performed, using a 1064 nm Nd:YAG laser, with carbon solid samples placed inside a high pressure chamber filled with helium or nitrogen, the gas pressure varying from 1 to 80 atm. The signal intensity of the carbon line (247.86 nm) decreases with increasing pressure. As the plasma size strongly decreases with pressure, two collection optical setups are used, showing different raw results. To take into account the plasma size evolution with pressure, calculated corrections are applied to the collected light intensity. Carbon line emission is measured and corrected as a function of pressure in both gases. At 1 atm, the emission line is found to be greater in helium than in nitrogen by a factor of approximately 3, whereas the intensities in the two gases become close to each other at 80 atm.     

Pressure effect on positronium reactions in organic solutions

The reaction rate constants of positronium (Ps) atoms with a series of nitrobenzene derivatives and nitromethane in toluene solutions have been determined as a function of external pressure up to 1000 kg cm⁻² (about 1000 atm). The rate constants for relatively weak Ps acceptors such as p-nitroanisole, 1,3-dimethyl-2-nitrobenzene and nitromethane increased considerably with external pressure, while those for relatively strong Ps acceptors like p-dinitrobenzene or nitrobenzene either decreased or changed little with external pressure. Comparison of the experimental results on pressure effects with those on temperature effects revealed that the application of external pressure suppresses the thermal decomposition of Ps complexes which are unstable at room temperature. The effect on a solvent of the Ps reaction was also studied by determining the reactivities of Ps atoms with nitrobenzene in various solvents as a function of external pressure.     

Pressure tensor for electrostatic interaction calculated by fast multipole method with periodic boundary condition

A microscopic expression of the pressure tensor using the fast multipole method (FMM) with periodic boundary conditions has been derived. The pressure tensor calculated using this expression has been compared with that obtained using the Ewald method with high accuracy. The precision of the pressure tensor can be controlled as a function of expansion order p of FMM. Using the calculated pressure tensor, the constant pressure molecular dynamics calculation with fully fluctuating cell can be performed for anisotropic systems such as crystals, metals, liquid crystals, glasses, polymers, lipid bilayers, and interfacial regions between two phases. © 2018 Wiley Periodicals, Inc.     

聚合物在压力下的流动诱导结晶

流动诱导聚合物结晶研究很少在压力场下开展,其原因是压力下流动诱导聚合物结晶对实验设备要求较高。然而,实际加工中不仅存在流动场,还有压力场。为此,作者课题组利用自制的装置对压力下流动诱导聚合物结晶开展了系统研究,发现其结晶行为与常压的流动诱导结晶有较大差别。等规聚丙烯(iPP)在压力和剪切场下可形成独特取向球形晶体形态。在短时间内(30min),iPP片晶可快速增厚,形成熔点接近平衡熔点的厚片晶(近180℃),其原因是在压力和流动场协同作用下,片晶增厚活化能快速减小。同时,从研究结果也获得了添加β成核剂的iPP体系在压力和流动场下形成β晶的窗口条件。对聚乳酸(PLA)的研究也发现了相似的片晶快速增厚规律。另外,在压力和流动场下,可直接从PLA熔体中获得可增韧PLA的β晶。研究成果为实际加工中的聚合物形态结构调控提供了理论和实验依据。