C70纳米/亚微米棒的高压相变研究

通过溶剂挥发法获得了准一维C70纳米/亚微米棒状晶体,直径为～500nm, 长度为～10μm,呈六方密堆(hcp)结构. 利用金刚石对顶砧(DAC)高压装置,采用同步辐射能量色散X光能量色散衍射方法(EDXD)和高压拉曼光谱,研究了压力对C70纳米/亚微米棒结构的影响, 实验中最高压力为26.1GPa. 结果表明, 在准静水压条件下,在23.3—26.1GPa压力范围内, hcp结构的C70纳米/亚微米棒发生了由hcp结构向非晶化的相变,相变压力比体材料高约5GPa, 该相变是不可逆相变, 而且该相变是由于C70在高压下笼状结构被破坏所导致的.     

紫外激光和压力共同作用下C60-peapod的聚合相变研究

采用气相扩散方法将C60分子填充到单壁碳纳米管(SWNTs)中,制备出高填充比率的豆荚形纳米材料C60@SWNT,又称为peapod.用金刚石对顶砧(DAC)装置获得高压,在高压下同时利用紫外激光处理样品,通过激光和压力的共同作用研究了C60分子在碳管内的聚合相变.在21.5 Gpa高压下,同时紫外激光(325 nm)照射30 min后,拉曼光谱表明C60分子在碳管内发生了聚合,形成一维链状O相聚合结构,且该相变是不可逆的.紫外激光的引入使样品发生O相聚合所需的压力值低于仅由压力诱导的聚合压力.     

Structural stability and electrical properties of AIB2-type MnB2 under high pressureStructural stability and electrical properties of AIB2-type MnB2 under high pressureStructural stability and electrical properties of AIB2-type MnB2 under high pressureStructural stability and electrical properties of AIB2-type MnB2 under high pressure

The structural stability and electrical properties of A1B2-type MnB2 were studied based on high pressure angle- dispersive x-ray diffraction, in situ electrical resistivity measured in a diamond anvil cell （DAC） and first-principles calcu- lations under high pressure. The x-ray diffraction results show that the structure of A1B2-type MnB2 remains stable up to 42.6 GPa. From the equation of state of MnB2, we obtained a bulk modulus value of 169.9~3.7 GPa with a fixed pressure derivative of 4, which indicates that A1B2-type MnB2 is a hard and incompressible material. The electrical resistance un- dergoes a transition at about 19.3 GPa, which can be explained by a transition of manganese 3d electrons from localization to delocalization under high pressure.     

High-pressure Raman study of solid hydrogen up to 300 GPa

The high-pressure behavior of solid hydrogen has been investigated by in situ Raman spectroscopy upon compression to 300 GPa at ambient temperature. The hydrogen vibron frequency begins to decrease after it initially increases with pressure up to 38 GPa. This softening behavior suggests the weakening of the intramolecular bond and the increased intermolecular interactions. Above 237 GPa, the vibron frequency softens very rapidly with pressure at a much higher rate than that of phase III, corresponding to transformation from phase III into phase IV. The phase transition sequence has been confirmed from phase I to phase III and then to phase IV at 208 and 237 GPa, respectively. Previous theoretical calculations lead to the proposal of an energetically favorable monoclinic C2/c structure for phase III and orthorhombic Pbcn structure for phase IV. Up to 304 GPa, solid hydrogen is not yet an alkali metal since the sample is still transparent.     

电感耦合等离子体原子发射光谱法测定水中总磷的方法研究

目前,越来越多的磷进入水中,严重影响着生态环境和人类身体健康,但磷的传统分析方法操作复杂,需外加多种试剂。采用电感耦合等离子体原子发射光谱法(ICP-AES)测定水中总磷,对仪器工作条件进行了探讨。结果表明仪器最佳工作条件如下：分析谱线为213.617 nm,射频功率为1 300 W,雾化器流速为0.5 L·min-1,观测高度为15 mm,蠕动泵泵速为1.2 mL·min-1,观测方式为径向。在仪器的最佳工作条件下,对本方法测定磷的检出限,精密度,回收率进行了研究。结果表明仪器检出限为0.028 mg·L-1,方法检出限为0.084 mg·L-1,精密度在0.6%~3.9%之间,回收率为102.3%~103.0%。此外,本方法与磷钼蓝分光光度法进行了对比,分析结果基本一致。该方法快捷简便,具有较好的精密度和回收率,适于实际样品的分析。     

两级溴化锂气泡泵的泵起时间及其影响因素的实验研究

为了进一步提高能源利用效率和实现其空冷化,在双效溴化锂吸收式制冷系统中利用两级气泡泵代替溴化锂吸收制冷系统中传统的机械溶液泵。本文重点对两级溴化锂气泡泵的泵起时间及其影响因素做相关的实验研究,并得出以下的主要研究结果:1)对于不同的管径,两级气泡泵的泵起时间随着加热功率、浸没高度、工质浓度的变化趋势是基本一致的;2)加热功率越大越有利于气泡泵的泵起;3)随着浸没高度的增大气泡泵的泵起时间逐渐减小;4)工质浓度的增大也会使气泡泵的泵起时间增大,但当溴化锂溶液浓度大于54%后影响不明显;5)一级气泡泵的气液成分及中间溶液的闪发一定程度上影响两级气泡泵的泵起时间,因而造成局部区域与上述规律的偏离。     

Raman Investigation of Sodium Titanate Nanotubes under Hydrostatic Pressures up to 26.9GPa

High pressure behavior of sodium titanate nanotubes （Na2Ti2O5） is investigated by Raman spectroscopy in a diamond anvil cell （DAC） at room temperature. The two pressure-induced irreversible phase transitions are observed under the given pressure. One occurs at about 4.2 GPa accompanied with a new Raman peak emerging at 834 cm-1 which results from the lattice distortion of the Ti-O network in titanate nanotubes. It can be can be assigned to Ti-O lattice vibrations within lepidocrocite-type （H0.7Ti1.825V0.175O4＆#12539;H2O）TiO6 octahedral host layers with V being vacancy. The structure of the nanotubes transforms to orthorhombic lepidocrocite structure. Another amorphous phase transition occurs at 16.7 GPa. This phase transition is induced by the collapse of titanate nanotubes. All the Raman bands shift toward higher wavenumbers with a pressure dependence ranging from 1.58-5.6 cm-1/GPa.     

有限长单壁碳纳米管的受压频移

使用第一原理密度泛函计算方法，我们研究了(5,5)有限长单壁碳纳米管（FSWNT）在气相条件下，结构的变化对振动模式（红外强度和拉曼活性）的影响. 我们得到了与无限长单壁碳纳米管（SWNT）有差异的拉曼频谱，发现了A1g, E1g 和 E2g的不同频移特征，并对其原因进行了解释. 当结构压缩到1.5 时，我们得到了一个双管的FSWNT结构，它也具有一个呼吸模（409.26 cm-1），而释放“压力”之后，FSWNT不同于SWNT之处在于其不能恢复到理想的D5d对称性结构，我们得到了一个新的具有C2h对称性的稳定的两端半封闭的FSWNT，其也具有一个明确的呼吸模（365.01 cm-1）. 并且，我们发现了稳定的D5d和C2h对称性结构的不同的电子布居特征.     

有机芳香烃掺杂控制C_(60)微/纳米晶形貌和发光

C60高度的分子对称性使其能带间的电子跃迁被禁止,导致其发光很弱。为了提高C60纳米晶的发光强度,采用挥发C60的芳香烃饱和溶液的方法,一步合成了芳香烃溶剂化的C60纳米晶。实验结果表明,有机溶剂的掺杂在不同程度上增强了C60纳米晶的发光,其原因可能是溶剂的掺杂破坏了C60的高度的分子对称性。