Formation,growth and dissociation of clathrate hydrate crystals in liquid water in contact with a hydrophobic hydrate-forming liquid

Variations in macroscopic morphology of hydrate crystals formed to intervene between a liquid-water phase and a liquid-hydrochlorofluorocarbon (HCFC) phase have been observed. The HCFC used was R-141b (CH₃CCl₂F) which is known to form a structure II clathrate hydrate at temperatures lower than 281.5 K, the triple liquid-water/hydrate/liquid-R-141b equilibrium temperature T_tri, under the atmospheric pressure. Each experiment was commenced by immersing an R-141b drop in a quiescent pool of water, which was either an ordinary pure water having no prior contact with R-141b or a water presaturated with R-141b at a temperature higher than T_tri. With presaturated water held at a large subcooling (∼6.5 K) below T_tri, we have distinguished two stages of hydrate-crystal growth, which are greatly different from each other both in crystal-growth morphology and in time span. The primary stage is characterized by lateral growth of a thin, fine-grained polycrystalline layer along the surface of each R-141b drop for a period of several tens of seconds. The secondary stage begins typically with a delay of some 10 min and lasts for a few tens of hours; it is characterized by radial growth of plate-like crystals standing upright on the outer surface of the drop-enclosing hydrate shell formed in the primary stage, thereby protruding into the liquid-water phase. A subsequent temperature rise within the range below T_tri causes a dissolution of plate-like crystals, leaving the hydrate shell apparently unchanged. The second stage is never observable with pure water and/or at a small subcooling (≲2 K). A qualitative interpretation of these observations is presented.     

电感耦合等离子体质谱(ICP-MS)法工作参数对灵敏度和氧化物干扰的实验研究

电感耦合等离子体质谱仪作为无机元素分析最重要的仪器,在生产科研发挥着关键的作用。通过测定过程中改变电感耦合等离子体质谱仪的仪器工作条件实验,得出功率、雾化气流量、氦气流量和采样深度对灵敏度和氧化物的产率产生较大的影响,而改变扫描次数、驻留时间、冷却气流量和辅助气流量等条件,各元素的灵敏度和氧化物的产率基本无变化。采用氢氟酸-高氯酸-硫酸-硝酸-盐酸来消解样品,选择仪器的最佳条件,得出La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu和Y的方法检出限分别为0.01、0.01、0.003、0.02、0.004、0.002、0.004、0.001、0.004、0.001、0.003、0.001、0.002、0.001和0.03ng/g。三个标准物质的稀土元素方法精密度均小于6.0%,经多个标准物质进行验证,所测稀土元素相对误差基本都小于10%,满足多目标地球化学样品测试的精密度和准确度要求。     

ICP-MS测定元素活动态中金的分析方法研究

金的元素活动态是用来指示隐伏金矿床的有效方法,将各相态金完全提取、准确定量分析,可以清晰、明显的指示地壳深部金矿床的有效信息。金的元素活动态提取液经过王水处理后,采用泡塑吸附-硫脲解脱的方式将金分离富集,解脱溶液一般采用石墨炉原子吸收光谱法(GF-AAS)测定,该方法效率低、检出限高、精密度差,数据可信度降低。采用电感耦合等离子体质谱法(ICP-MS)测定可以有效避免GF-AAS法的缺点,实验采用低浓度的硫脲解脱液(0.2g/L),能够将1000ng的金完全解脱,低浓度的硫脲溶液也保证了仪器的长期稳定性;标准溶液采用和提取溶液一致的处理方法(王水分解+泡塑吸附+硫脲解脱),提高了测定结果的准确度。该方法得到了水溶态、粘土吸附态、有机结合态、铁锰氧化物态的检出限：0.012、0.006、0.006、0.014μg/kg,方法精密度：4.63%~18.17%,各相态加和结果和全量的相对误差的绝对值均小于4.94%,表明提取方法和分析方法准确可靠。     

沸石与酸性水溶液反应的动力学机制

利用连续搅拌筒反应器(CSTR)对天然沸石与酸性水溶液的反应动力学进行研究, 通过改变流速、 pH值等参数, 对反应速率进行计算和比较. 同时利用二次离子质谱(SIMS)、扫描电镜(SEM)对反应后的沸石表面进行分析研究. 实验结果表明, 沸石中的Si、Al、Na的释放速率在多数情况下不相同, 沸石的溶解为不一致溶解作用. 25 ℃、1.01×10⁵ Pa条件下, 硅的释放速率为：在pH=2.45溶液中反应时, -rSi=kS(aH+)1.25/ (aSi)0.60；在pH=3.26溶液中反应时, -rSi=kS(aH+)1.50/(aSi)0.25(S为矿物材料的表面积). SIMS研究显示, 天然沸石与酸性水溶液的反应中, 在沸石表面Si、Al、Na在100 nm的厚度范围内, 随着离表面距离的改变, 在近表面范围内Na、Al大量淋失, 有H⁺浸入. 此外, SEM分析结果显示, 天然沸石与纯水及酸性水溶液反应后, 表面形貌显著不同.     

Tectonic setting discrimination and ~(40)Ar/~(39)Ar isotope geochronology of the Miba granite

The Miba granite is located in the juncture of Kang County in eastern Gansu Provinceand Lueyang County in Shanxi Province. It is considered to be the post-orogenic granite(POG-type) by major element discrimination method of Maniar. ~40Ar/~39Ar dating indicates that itsemplacement time is about 240-230 Ma and it is the result of the Indo-Sinian magmatism. In theearly Yanshan period (about 193.8 Ma), a thermal event resulted in the partial opening of the ar-gon isotope system of the biotite.     

不同结构烷基苯磺酸钠水溶液的泡沫性能及动态表面张力

研究了一系列直链三取代和支链双取代烷基苯磺酸钠水溶液的动态表面张力(DST)和泡沫性能, 考察了分子结构变化对烷基苯磺酸钠水溶液的DST和泡沫性能的影响. 探讨了动态表面张力参数(t*, n, R1/2)的变化规律及其与泡沫性能的关系. 结果表明, 随着取代烷基链长度增加, t*和n值增大, R1/2减小, 动态表面活性降低. 由于双取代支链烷基苯磺酸钠分子具有特殊的柔性长支链, 使得吸附膜排列紧密、膜弹性增大, 因而其泡沫稳定性明显优于多取代直链烷基苯磺酸钠的稳定性. 在气流法产生泡沫的过程中, 动态表面张力是控制起泡高度的关键因素.     

分子自组装法制备具有可控浸润性的铜表面

通过简单浸泡的方法在铜基底上制备出了具有微纳米复合结构的氧化铜, 再利用混合硫醇溶液[含HS(CH₂)₉CH₃和 HS(CH₂)₁₁OH]对浸泡后的表面进行修饰, 通过控制溶液中HS(CH₂)₁₁OH的浓度, 制备出一系列具有不同浸润性的铜表面, 实现表面从超疏水到超亲水的有效调控. 研究发现, 表面浸润的可控性源于表面复合结构与不同化学组成的协同作用, 微纳米复合结构的存在为表面浸润性的调节提供了必要的条件.     

聚氧乙烯醚类表面活性剂表面扩张粘弹性质研究

研究了非离子表面活性剂壬基苯酚聚氧乙烯醚NP-8, NP-10和NP-12水溶液的表面扩张粘弹性质, 考察了氧乙烯数的变化对表面吸附膜特性的影响. 研究结果表明, 三种表面活性剂的扩张弹性随着工作频率的增大而增大, 扩张粘性则在0.1~0.01 Hz范围内通过不明显的极大值; 扩张弹性和粘性随着浓度的增加在同一浓度处通过一个极大值; 氧乙烯数从8增加到12, 表面扩张弹性、粘性和相角的变化不大. 从发生在表面上和表面附近的微观弛豫过程的角度对实验结果进行了讨论.     

Pulsewave velocity measurement using a new real-time MR-method

A new, one-dimensional method for the measurement of pulsewave velocities using real-time magnetic resonance (MR) imaging is presented. The measurement sequence is essentially of a RACE-type (Real Time Acquisition and Evaluation) with interleaved acquisition in two not necessarily parallel slices. In each slice the blood flow velocity perpendicular to the slice orientation was monitored. From the relative time difference of blood flow activity and the slice distance, pulsewave velocities were calculated. With a time resolution of 13 ms an overall acquisition time of 3.3 s was achieved. A method for suppression of signal contributions from stationary tissue along the axis of projection is discussed on the basis of a simplified mathematical model. Preliminary volunteer studies show that pulsewave velocities in the range of 1–10 m/s can be measured with an uncertainty of about 0.6 m/s at a conventional 1.5 T imager with a gradient system of maximal 10 mT/m.