Thermal evolution of the first stage Cs(THF)1.75C24 graphitide,an example of segregation and decorrelation at low temperature

The thermal variation of the first stage ternary compound Cs(THF)_1.75C₂₄ has been investigated by powder neutron diffraction. Two phase transitions have been observed. The first one occurs at 248 K and can be interpreted as a three-dimensional segregation within the graphitic host. The second one starts at about 180 K and is continuous down to 50 K. This corresponds to a decorrelation of the graphen planes at low temperature. The origin of this transition could be the elastic constraint due to the kinks of the planes.     

Simultaneous observation of the triangular and honeycomb structures on highly oriented pyrolytic graphite at room temperature: An STM study

Scanning tunneling microscopy (STM) was used to study the surface structures of dry-prepared and di-chloroethane-treated HOPG samples. Both triangular and honeycomb structures were simultaneously observed with the same tip at room temperature around a strand (grain boundary) on the HOPG surface. This observation did not support the tip effect in STM imaging explanation for HOPG in literature. A general layer-sliding model was utilized to explain the experimental results: sliding of the HOPG topmost layer was used to explain the origins of the triangular and honeycomb structures, and molecule intercalation into inter-layer spacing between the first and second layers of HOPG induced inhomogeneous deformation of the HOPG topmost layer that accordingly generated the Moiré patterns of the HOPG sample in di-chloroethane.     

Ferroelectricity in antiferromagnetic phases of Eu1−xY xMnO3

This work reports an experimental investigation of the ferroelectric character of magnetic phases of the orthorhombic Eu_1−xY _xMnO₃ system at low temperatures. The temperature dependence of the polarization curves clearly reveals the existence of a re-entrant improper ferroelectric phase for x=0.2, 0.3 and 0.5. A ferroelectric phase is also stable for x=0.4, and we have no experimental evidence for its vanishing down to 7 K. From these and early results obtained using other experimental techniques, the corresponding (x,T) phase diagram was traced, yielding significant differences with regard to the ones previously reported.     

涂钼热解石墨管电热原子吸收测定痕量镓的研究

比较了不同基体改进剂 ,不同涂层对镓在热解石墨管中原子化的影响。研究了以硝酸镍为基体改进剂 ,以涂钼热解石墨管为原子化器镓的原子化机理 ,优化了各项参数 ,找到了一种测定复杂样品中痕量镓的新方法。方法特征量为 2 1 2× 1 0 -1 1 g ,检出限为 1 4× 1 0 -1 0 g ,RSD≤ 3 6 % (n =1 1 ) ,样品回收率 97 4 %～1 0 2 7%。     

Husimi Operator for Describing Probability Distribution of Electron States in Uniform Magnetic Field Studied by Virtue of Entangled State Representation

For the first time we introduce an operator Δ _h (γ,ε;κ) for studying Husimi distribution function in phase space (γ,ε) for electron’s states in uniform magnetic field, where κ is the Gaussian spatial width parameter. The marginal distributions of the Husimi function are Gaussian-broadened version of the Wigner marginal distributions. Using the Wigner operator in the entangled state 〈λ | representation we find that Δ _h (γ,ε;κ) is just a pure squeezed coherent state density operator | γ,ε〉 _{κ κ} 〈γ,ε |, which brings much convenience for studying Husimi distribution, so we name Δ _h (γ,ε;κ) the Husimi operator. We then derive Husimi operator’s normally ordered form that provides us with an operator version to examine various properties of the Husimi distribution. Work supported by the National Natural Science Foundation under the grant: 10775097.     

DISTRIBUTION OF RANDOM ELEMENTS SUBJECTED TO A FLEXIBLE BOUNDARY CONDITION

The probability distribution function of n random elements subjected to the flexible boundary condition is derived. The probability density is a descending curve and converges to a delta function as n tends to infinity. The distribution of the minimum value is discussed in context of ordered statistics.     

碳化物衍生碳与石墨的摩擦磨损性能比较

通过高温氯化处理工艺在SiC表面制备碳化物衍生碳涂层(CDC),考察并比较了SiC、石墨和CDC在空气中的摩擦磨损性能.结果表明:在本文试验条件下,CDC的摩擦磨损性能优于石墨,CDC的摩擦系数低于0.15;CDC在载荷5 N下的磨损率在10-15 m3/N量级,当载荷等于或低于30 N时磨损率在10-14 m3/N量级,远低于相同条件下石墨的磨损率,即使在40 N或 50 N下其磨损率仅与20 N下SiC和石墨的磨损率相当.CDC的纳米结构及涂层与基体界面组成和性能的变化是影响其摩擦磨损性能的主要因素.     

石墨对铜基自润滑材料高温摩擦磨损性能的影响

通过基体多元合金化和选用不同粒度的石墨颗粒,采用常规粉末冶金方法制备了铜基石墨固体自润滑材料,在大越式OAT-U型摩擦磨损试验机上考察了复合材料从室温到500℃温度条件下的摩擦磨损性能,利用扫描电子显微镜观察分析磨损表面形貌,进而探讨其摩擦磨损机理.结果表明:在室温条件下,石墨颗粒越小,则复合材料的摩擦系数越小,减摩自润滑效果越好;在室温至500℃条件下,选用合适的石墨粒度(0.3～0.5mm)和多元基体合金化,可使铜基石墨固体自润滑材料保持较好的自润滑特性.     

CO(υ)高振动激发态向C2H2的振动传能研究

用时间分辨富里叶红外发射谱研究了高振动激发态ＣＯ向Ｃ２Ｈ２的传能，得到了ＣＯ（ｖ＝１－３）各振动态布居及其随时间的变化。利用微分法解出弛豫微分方程组，获得ＣＯ（ｖ＝１－３）向Ｃ２Ｈ２的传能速率常数分别为：２．０±０．１，６．０±０．２和９．４±０．８（１０＾－１３ｃｍ＾３·ｍｏｌｅｃｕｌｅ＾－１·ｓ＾－１）。传能速率随着振动量子数的增加而迅速增加。ＣＯ的振动能应向Ｃ２Ｈ２的对称伸缩模ｖ２近共振Ｖ－     

氧化锌修饰铅笔芯电极电致化学发光法测定苯酚的研究

采用滴涂法将氧化锌纳米颗粒滴涂在自制铅笔芯电极上制成氧化锌修饰铅笔芯电极,当以过硫酸根为共反应剂时,该修饰电极在氢氧化钠溶液中具有良好的电致化学发光(ECL)行为,对其发光机理进行了考察。基于苯酚对该修饰电极的ECL具有抑制作用,建立了一种测量苯酚的新方法,当苯酚浓度为2×10-8~2×10-6mol/L时,发光强度与苯酚浓度的对数呈线性关系,检出限为1×10-8mol/L。该方法具有灵敏度高、方法简单、快速、稳定性好等优点,将其应用于工业废水中苯酚浓度的检测,回收率为96.5%~104.5%。