在NaCl和HTAB共存条件下甲基纤维素溶液凝胶化行为

利用流变仪研究了甲基纤维素(MC)溶液在NaCl、十六烷基三甲基溴化铵(HTAB)以及两者共存下MC溶液的凝胶化行为,发现其凝胶化温度随着NaCl浓度的增加而下降,随着HTAB浓度的增加而上升;但是MC/NaCl的凝胶化温度保持不变,与HTAB浓度 无关,而MC/HTAB溶液的凝胶化温度则随着NaCl浓度的增加而下降．以上的实验结果表明,在NaCl存在下,HTAB将被诱导形成胶束,因此MC/NaCl的凝胶化温度保持不变;反之,当NaCl不存在时,HTAB将优先吸附到MC上而不会在溶液中形成胶束,尽管其浓度     

SrS相变和弹性性质的第一原理计算

利用平面波赝势密度泛函方法和准谐德拜模型研究了SrS从NaCl结构到CsCl结构的相变以及弹性性质.在零温下,我们计算的相变压强为17.9 GPa,这与实验值和其他作者的计算值符合很好.研究还表明:相变压强随温度增加而非线性地增加,然而力学不稳性的压强随温度增加而线性地增加.     

First-Principle Calculations for Transition Phase and Elastic Properties of SrS

The transition phase and elastic properties of SrS from NaCl structure （B1） to CsCl structure （B2） are investigated by ab initio plane-wave pseudopotential density functional theory method and by the quasi-harmonic Debye model. The transition pressure varies non-linearly with temperature, and the pressure of the mechanical instability increases linearly with increasing temperature. It is shown that the B1 structure SrS is a most elastically anisotropic minerat any pressure. The Debye temperature, the heat capacity, thermal expansion and Gruneisen parameter over a wide range of pressures and temperatures are also obtained.     

液体表面张力系数、声波在液体中传播速度与液体浓度关系的研究

通过实验的手段研究了氯化钠与蔗糖溶液的表面张力系数及声波在其中的传播速度与浓度关系,发现随着浓度的增加,表面张力系数与液体中的声波传播速度近似于线性变化。然而,两种液体中两个物理量的变化快慢不同,氯化钠溶液明显比蔗糖溶液变化快;从分子动理论角度,对此现象作了圆满的解释,说明两个物理量之间有着较密切的关联,也研究了温度变化时,两个物理量的变化情况。     

FTIR光谱的海水入侵区水-岩(土)间氟迁移机理分析

滨海地区饮水型氟中毒和海水入侵十分普遍。海水入侵引起地下水性质的改变对岩（土）氟迁移具有潜在影响，但尚未有直接模拟实验证实，其氟迁移机理也不明确。用淡水和海（卤）水混合及配制溶液模拟海水入侵过程，对含水砂层沉积物进行静态水-岩（土）氟迁移模拟实验，对比分析沉积物FTIR特征，探讨海水入侵对岩（土）氟迁移影响规律及机理。结果表明，含水砂层沉积物氟迁移量大小顺序为：海水＞1∶1淡海＞淡水；卤水＞1∶1淡卤＞淡水，随海（卤）水混入程度增加，含水砂层沉积物岩（土）氟迁移能力增强。氟迁移能力随NaCl和NaHCO₃浓度增加而增加，随CaCl₂浓度增加而降低。对含水砂层沉积物傅里叶红外吸收光谱（FTIR）分析表明，随NaCl和NaHCO₃浓度增加，NaCl溶液中沉积物Si-O-Si键伸缩振动峰强度明显增强，氟磷灰石弯曲振动峰减弱，O-H键特征峰变化不明显，而NaHCO₃溶液中沉积物羟基磷灰石弯曲振动峰和Si-O-Si键伸缩振动峰强度变化不明显，O-H键特征峰强度变化明显，表明NaHCO₃溶液主要通过OH-与F-离子交换，而NaCl溶液是通过Si-O-Si键中Si-O置换来影响岩（土）氟迁移。随CaCl₂浓度增加，Si-O-Si键伸缩振动峰强度明显减弱，氟磷灰石弯曲振动峰强度增强，表明Ca2+强烈地抑制岩（土）氟析出。同时，随NaCl和NaHCO₃浓度增加和CaCl₂浓度减少，Si-F特征峰强度减弱，Si-O-Si键弯曲振动峰向低波数偏移。由于大气CO₂混入，1 mol·L-1 CaCl₂作用沉积物出现1 460和1 420 cm-1碳酸根特征峰。由于碳酸根沉积作用，1 mol·L-1的NaHCO₃作用的沉积物在1 460 cm-1处峰强度增强，且在875 cm-1出现新峰，但是在淡海卤水和NaCl溶液作用的沉积物中无碳酸根特征峰，表明含水砂层中无萤石（CaF₂）溶解作用。海水入侵引起的偏碱性、高钠低钙的环境促进岩（土）氟迁移释放，是滨海地区高氟地下水重要动力。     

基于数字图像相关法的Mg含量对Al合金Protein-Le Chatelier效应影响的实验研究

利用数字图像相关法研究了常温与恒定应变率(5.00×10~(-3)s~(-1))下Mg含量(质量分数)分别为2.30%,4.57%,6.10%及6.91%四种Al-Mg合金Portevin-Le Chatelier(PLC)效应的宏观变形行为.实验发现,Mg含量的增加导致强化效果的增强;低Mg含量(2.30%)合金中锯齿跌落幅值基本保持不变,而在高Mg含量(4.57%,6.10%,6.91%)合金中随应变增加而增加.锯齿跌落幅值随Mg含量增加而逐渐增大,在高Mg含量合金中趋于饱和.宏观局域变形带的观察结果表明PLC带宽不随Mg含量或者应变改变而变化,带内变形量随着Mg含量或者应变的增加而逐渐增大.此外,在低Mg含量合金的加载曲线后段(应变约为0.3时)观测到了特殊的周期性的衰减锯齿,相应的时域PLC带演化表明加载曲线的周期性转变大锯齿对应着空间上PLC带的转向,幅度逐渐减小的振荡对应着PLC带的传播,且在转向前后PLC带均向上连续传播.     

Measurement of surface resistivity/conductivity of metallic alloys in aqueous solutions by optical interferometry techniques

Optical interferometry techniques were used for the first time to measure the surface resistivity/conductivity of the pure aluminium (in seawater at room temperature), UNS No.304 stainless steel (in seawater at room temperature), and pure copper (in tap water at room temperature) without any physical contact. This was achieved by applying an electrical potential across the alloys and measuring the current density flow across the alloys, during the cyclic polarization test of the alloys in different solutions. In the mean time, optical interferometry techniques such as holographic interferometry were used in situ to measure the orthogonal surface displacement of the alloys, as a result of the applied electrical potential. In addition, a mathematical model was derived in order to correlate the ratio of the electrical potential to the current density flow (electrical potential/electronic current flow = resistance) and to the surface (orthogonal) displacement of the metallic samples. In other words, a proportionality constant (surface resistivity or conductivity = 1/surface resistivity) between the measured electrical resistance and the surface displacement (by the optical interferometry techniques) was obtained. Consequently the surface resistivity (ρ) and conductivity (σ) of the pure aluminium (in seawater at room temperature), UNS No.304 stainless steel (in seawater at room temperature), and pure copper (in tap water at room temperature) were obtained. Also, electrical resistivity values (ρ) from other source were used for comparison sake with the calculated values of this investigation. This study revealed that the measured value of the resistivity for the pure aluminium (7.7 × 10¹⁰ Ω cm in seawater at room temperature) is in good agreement with the one found in literature for the aluminium oxide, 85% Al₂O₃ (5 × 10¹⁰ Ω cm in air at temperature 30 °C). Unfortunately, there is no measured value for the resistivity of cupric oxide (CuO), cuprous oxide (Cu₂O), or even the oxide of the UNS No.304 stainless steel in literature comparing those values with the measured values in this study.     

Raman spectra of phase a at various pressures and temperatures

Variations of the Raman spectra of phase A (Mg₇Si₂O₁₄H₆) were investigated up to about 400 kbar at room temperature and in the range 80–853 K at atmospheric pressure. Phase A appears to undergo a reversible phase transition around 180 kbar at room temperature, and it becomes amorphous above 813 K at atmospheric pressure. The Raman frequencies of the two strong OH bands of phase A decrease linearly with increasing pressure, but increase non-linearly with increasing temperature. The frequencies of the other Raman bands of phase A increase non-linearly with increasing pressure but decrease both linearly and non-linearly with increasing temperature within the experimental uncertainties and the range investigated. The trends of the pressure and temperature effects on the Raman frequencies of phase A parallel those observed in the hydrous β-phase, but nonlinear behaviour was not observed in the latter.     

A brief study on the mixture rules of the acoustic non-linearity parameter B/A in binary biological mixtures

Using the improved thermodynamic method, the acoustic non-linearity parameter B/A of binary biological mixtures — such as pig blood, sheep blood and bovine blood — is measured in order to test the mixture rules proposed by Apfel and Sehgal. The results show that the B/A values of the above-mentioned blood decrease with an increasing volume fraction of water. The B/A value varies linearly with the volume fraction of protein. It is also shown that, treated as a binary mixture, the blood obeys the trend that the B/A value varies with the volume of water. This is in agreement with the rules proposed by Apfel and Sehgal. However, the measured B/A value is not exactly equal to that of the mixture rules.     

温度相关的微波频率下氯化钠水溶液介电特性

针对NaCl水溶液(0.001–0.5 mol/L)介电特性, 实验调查了频率(200–6.25 GHz), 温度(293–353 K)、 浓度相关复介电常数. 结果表明: 频率增大的过程中虚部呈逐渐减小的趋势, 高温使离子扰动增大, 破坏了溶液内部水分子四面体结构和氢键构象而使介电常数实部减小. 与纯水相比, 溶液的损耗角正切在高温353 K低频区下降明显. 同时发现2.45和5.8 GHz的复介电常数随温度变化的温度窗效应, 温度窗效应导致微波加热时耗散功率的振荡变化, 温度分布不均匀现象在实验中得以证实. 关键词： 微波 复介电常数 介电特性 高温探头     

生物媒质中非线性声学参量B/A的研究

本文用插入取代法测量和研究了猪全血、牛全血、牛奶和各种分子量的聚乙二醇水溶液等多种液态生物样品中的非线性声学参量B/A值。聚乙二醇水溶液的B/A值随浓度线性增加,并呈现与分子量无明显依赖关系的特性。 关键词：     

生物媒质非线性效应的超声研究

本文利用比较法测定了若干种生物样品水溶液的非线性声学参数B/A值及其与溶液浓度的依赖关系,葡萄糖、蔗糖、乙二醇水溶液的B/A值均呈现随浓度线性增加的依赖关系,新鲜猪全血的B/A值在26℃时为5.8,文中还计算了乙二醇水溶液的内压强P_*与浓度的关系。     

Theoretical study of the structural phase transition and elastic properties of HfN under high pressures

The effect of hydrostatic pressure on the structures of HfN at 0 K was investigated by using the projector augmented wave (PAW) within the Perdew–Burke–Ernzerhof (PBE) form of the generalized gradient approximation (GGA). The transition pressure between NaCl (B1) and CsCl (B2) structures is predicted to be 277.3 GPa. This value is consistent with that reported by Kroll, while in contrast to the results obtained by Ojha et al. and Meenaatci et al. Moreover, the elastic properties of B1-HfN and B2-HfN under high pressures are successfully obtained. It is found that the elastic constants, bulk modulus B, shear modulus G, compressional and shear wave velocities increase monotonically with increasing pressure. The Debye temperature Θ calculated from the elastic constants of HfN is in good agreement with the experimental values. The anisotropies of B1-HfN and B2-HfN at zero pressure have also been discussed.     

Elemental depth imaging of solutions for monitoring corrosion process of steel sheet by confocal micro X‐ray fluorescence

Non‐destructive and non‐contact analysis has been in demand on numerous occasions. Confocal micro X‐ray fluorescence analysis enables depth‐selective elemental analysis of solid samples in the laboratory. In this paper, we applied this technique for imaging elemental distributions in solutions. A low‐carbon steel sheet was placed in artificial seawater (NaCl: 3.5 mass%), and the corrosion process in the solution was observed. A depth image of Fe Kα intensity in the NaCl solution was obtained by using this technique. The Fe Kα intensity in the solution was measured with corrosion time by sequential line analysis at a fixed lateral position. The corrosion of Fe from the steel sheet, the migration of Fe ions in solution, and their condensation near a polymer window were successfully monitored. Copyright © 2014 John Wiley & Sons, Ltd.     

NaCl-H2O和NaCl-KCl-H2O溶液低温相变过程的原位XRD研究

应用原位X射线衍射法对盐湖卤水体系的两个子体系--NaCl-H₂O和NaCl-KCl-H₂O溶液在低温条件下进行扫描,获得了实验条件下体系的衍射图谱,得到了溶液低温相变过程的信息。图谱解析结果表明：含NaCl 26.25%的溶液在-20~-25℃范围内析出了冰、NaCl、低水合氯化钠和二水氯化钠,含NaCl 25.70%的溶液没有发生相变;对于NaCl-KCl-H₂O体系,含NaCl 20.03%和KCl 10.19%的溶液在0~-25 ℃范围内析出了氯化钾和氯化钠,含NaCl 22.40%和KCl 7.28%的溶液在-10~-25 ℃范围内只有氯化钾析出,含NaCl 21.90%和KCl 6.46%的溶液没有发生相变。实验结果显示：这两个水盐体系低温相变过程析出盐的种类与相图结果有差异,原因在于两者的状态不同;体系中二水氯化钠的析出需要经过氯化钠与水的化合过程,该过程是分步进行的;实验体系在低温条件下发生相变受结晶因素控制,温度只是其中一个因素,体系相变发生与否是结晶因素综合影响的结果。     

Heat capacity and entropy of two electrons quantum dot in a magnetic field with parabolic interaction

The thermodynamic properties of two electrons in two dimensional parabolic GaAs quantum dot are studied where both the magnetic field and the e–e interaction are fully considered. The e–e interaction has been treated by a model potential which makes the Hamiltonian exactly solvable. The energy spectrum is used to calculate the canonical partition function, and then we obtain the thermodynamic properties; mean energy, heat capacity and entropy as a function of temperature (T) and magnetic field (B).A steep transition from zero to 4k_B is observed in the heat capacity as a function of temperature for small values of magnetic field and saturates within a small temperature range, also the heat capacity has a peak-like structure at low temperature, while for high magnetic field heat capacity develops a shoulder at 2k_B then it approaches the saturation value with further increase in temperature. The entropy increases with increasing temperature, but at higher temperature, it remains almost independent of the magnetic field. It is shown that, at low magnetic field values, the effect of magnetic field on heat capacity is tangible and it attains a constant value with further increase in magnetic field. Entropy is almost linearly proportional with increasing magnetic field strength.     

Electronic and magnetic properties of V- and Cr-doped zinc-blende AlN

The electronic and magnetic properties of the zinc-blende aluminum nitride doped with V and Cr are studied using the density functional theory (DFT), namely the KKR-CPA-PBE method. Pure AlN is found to be a wide band gap semiconductor, and doping V and Cr single impurities generate ferromagnetic half-metallic behavior. Moreover, the values of the formation energy reveal that these compounds are stable systems for all dopant concentrations. A self-consistent energy minimization scheme determines the ferromagnetic state as the stable magnetic state for V- and Cr-doping AlN. A double exchange mechanism is identified as the mechanism responsible for magnetism in our systems. When increasing doping impurities, the total magnetic moments increase linearly and the Curie temperature T_C, calculated using the mean-field approximation, shows a significant change. The present findings reveal Cr- and V-doped zinc-blende AlN as potential candidates for high Curie temperature ferromagnetic materials.     

Temperature-dependent capacitance–voltage biasing of the highly tunable TlGaTe2 crystals

The temperature effects on the capacitance–voltage characteristics as well as the room temperature capacitance–frequency characteristics of TlGaTe₂ crystals are investigated. A very wide range of linearly varying tunable capacitance from 6.0 μF to 60 pF was recorded. The capacitance–voltage characteristics, being recorded in the temperature range of 290–380 K, revealed a linear increase in the build in voltage associated with exponential decrease in the density of non-compensated ionized carriers with increasing temperature. The high temperature (up to 380 K) biasing ability, the linear tunability and the high dielectric constant values (∼10³) make the TlGaTe₂ crystals applicable in microelectronic components.     

Properties of aqueous NaCl solutions in external electromagnetic fields

Molecular dynamics simulations are performed to investigate the effects of an external electromagnetic field on aqueous NaCl electrolyte solutions at a temperature of 298 K. The simulations assume that the electromagnetic waves propagate in the x-axis direction with a frequency of 50, 100 or 200 GHz. The intensity of the electromagnetic field is assumed to vary in the range 0.1–0.3 V/Å. The simulations are conducted for two different NaCl solution concentrations, namely 1 m and 5 m (molality). The results indicate that as the intensity of the electromagnetic field is increased, the re-orientation of the water molecules becomes more pronounced and the diffusion coefficient of the aqueous NaCl solution increases. It is also shown that in both the low-concentration and high-concentration solutions, the diffusion coefficients of water molecules and ions increase as the frequency and intensity of the electromagnetic field increase.     

19F spectroscopy and relaxation behavior of trifluorovinyldichloroborane

The 19F NMR spectra and spin-lattice relaxation rate, R1, of trifluorovinyldichloroborane as shown in were studied as a function of temperature, T, and magnetic field, B. All logR1 vs 1/T plots show a minimum at 299K indicating the presence if dipolar relaxation at lower T and spin-rotation relaxation at higher T. The R1 values increase with increasing B due to chemical shift anisotropy relaxation. Estimates of the fluorine chemical shift values for F3 (cf. Fig. 1) suggest that there is pi character in the F-C bond. The other two C-F bonds are largely single bonded. No evidence was found for intermolecular exchange of the trifluorovinyl group. Two of the three fluorine atoms show large increases in their NMR linewidth with increasing temperature while the third shows only a small increase but the activation energy for the process is the same for all. The increase in linewidths is due to scalar coupling to the boron atoms. The boron linewidths were measured between 253 and 363K and decreased with increasing temperature. A plot of logR2, where R2 is the linewidth of the boron as a function of 1/T shows some curvature indicating a second relaxation mechanism. This is ascribed to spin-rotation but not enough data are available to be conclusive. In all cases there is a second small set of fluorine peaks that are due to 10B interactions separated from the 11B peaks by amounts varying from 1 to 4 ppm depending on the field and fluorine atom.