Nonmonotonic Coupled Dissolution-Precipitation Reactions at the Mineral–Water Interface

Dissolution is inherent to fluid-mineral systems. Yet its impact on minerals reacting with electrolytes is overlooked. Here, a novel nonmonotonic behavior for the surface interactions of carbonates (calcite and Mg-calcite) with organic acids is reported. Applying a bioinspired approach, Mg-calcite sensors via amorphous precursors, avoiding any preconditioning with functional groups are synthesized. A quartz crystal microbalance is used to study the mass changes of the mineral on contact with organic acids under varying ionic conditions, temperatures, and flow velocities. Supported by confocal Raman microscopy and potentiometric titrations, nonmonotonous mass developments are found as a function of Ca²⁺ concentration and flowrate, and attributed to three coupled chemical reactions: i) carbonate dissolution via Ca²⁺ ion complexation with organic molecules, and the formation of organo-calcium compounds as ii) a surface phase at the mineral–water interface, and iii) particles in the bulk fluid. These processes depend on local ion contents and the precipitation onset (i.e., saturation index) of organo-calcium salts, both of which substantially differ in the bulk fluid and in the fluid boundary layer at mineral interfaces. This continuum between dissolution and precipitation provides a conceptual framework to address reactions at mineral interfacial across disciplines including biomineralization, ocean acidification and reservoir geochemistry.     

Co-酞菁和Cu-酞菁在Au(111)表面吸附行为的比较

利用扫描隧道显微术并结合理论计算研究了金属co-酞菁和cu-酞菁分子在Au（111）表面上的吸附行为的差异。结果显示,由于这两种分子与衬底电荷转移的差异,引起了分子间相互作用不同,使得两种分子在Au（111）表面表现出不同的吸附组装结构。分子一衬底相互作用与分子间库仑排斥作用两种机制的竞争是造成其组装结构差异的原因。     

Spontaneous Current Oscillations during Hard Anodization of Aluminum under Potentiostatic Conditions

Nanoporous anodic aluminum oxide is prepared by hard anodization of aluminum under potentiostatic conditions using 0.3 M H₂C₂O₄. Under unstirred electrolyte condition, spontaneous current oscillations are observed. The amplitude and period of these current oscillations are observed to increase with anodization time. As a consequence of the oscillatory behavior, the resulting anodic alumina exhibits modulated pore structures, in which the diameter contrast and the length of pore modulation increase with the amplitude and the period of current oscillations, respectively, and the current peak profile determines the internal geometry of oxide nanopores. The mechanism responsible for the oscillatory behavior is suggested to be a diffusion‐controlled anodic oxidation of aluminum.     

淀粉类多糖在方解石和萤石表面吸附特性及作用机理

通过吸附试验，Ｘ－射线光电子能谱（ＸＰＳ）和俄歇电子能谱（ＡＥＳ）、浮选试验、系统地研究了糊精在萤石和方解石表面作用行为，结果发现，方解石经糊精作用前后ＣａＬＭＭ俄歇参数变化值为０．８０ｅＶ，变化显著，这说明糊精与方解石表面作用为化学键合；而萤石经糊精处理前后ＣａＬＭＭ俄歇参数变化值为－０．２０ｅＶ，变化不明显，说明糊精与萤石表面化学作用很弱，更接近物理作用－氢键作用；浮选试验结果证实了测试结果可     

真空集热型太阳能固体吸附式制冷的理论研究

为提高太阳能吸附制冷系统的集热性能。提出了采用真空集热管式吸附床的太阳能固体吸附制冷系统,并对选择吸收式和直接吸热式的真空集热制冷系统分别进行了理论分析与计算模拟。这两种系统均具有较高的制冷性能,前者宜以沸石-水为制冷工质对,而后者则宜采用活性碳-甲醇工质对。分析了工作参数对这两种真空集热型制冷系统的影响,并对系统结构进行了优化研究。     

BaX分子筛吸附C8芳烃作用机理

采用正则系综蒙特卡洛方法模拟等量4种C₈芳烃分子分别在SiFAU和BaX分子筛上的吸附行为,并结合量子化学计算和波函数分析,基于分子筛组成和结构、C₈芳烃分子结构和电子分布特征进行吸附机理研究。蒙特卡洛模拟结果表明：4种C₈芳烃分子的密度分布主要在分子筛超笼内,吸附能分布近似为正态分布,吸附状态多样化;SiFAU上吸附位随机且范围广,但对二甲苯无选择性;BaX上吸附位集中在超笼内的Ba附近,平均吸附热由高到低的顺序为对二甲苯、乙苯、邻二甲苯、间二甲苯,与BaX分子筛对C₈芳烃吸附选择性的实验结果顺序一致。波函数分析结果表明,4种C₈芳烃分子静电势分布相似,芳环区域静电势为负,静电势极小值点偏离于取代基方向。考虑乙苯侧链柔顺性,将C₈芳烃分子的负静电势面积与其在BaX分子筛上的平均吸附能进行关联,阐明电子分布特征对吸附性能的影响。     

基于构造差异的页岩孔隙结构与吸附能力表征

运用场发射扫描电镜(FE-SEM)和N2/CO2等温吸附方法,文中对黔北地区不同构造区五峰组—龙马溪组页岩的孔隙特征进行表征,并且基于构造差异深入分析了其孔隙结构及甲烷吸附能力.研究表明:相比于高陡构造区,低缓构造区孔径以双峰分布为主,并且发育较多的微裂隙有机质孔隙、与黏土矿物紧密结合的有机质孔隙以及粒间孔隙,而刚性矿...     

萨尔马法在大广坝抗震稳定分析中的应用

本文用萨尔马法和我国抗震规范法两种方法，分析了大广坝土坝抗震稳定性，萨尔马法可算出临界加速度，不能直接算出安全系数，本文进一步发展，可算出安全系数，并与抗震规范法算出的结果作了对比，经过大量的计算，发现了萨尔马法所存在的某些局限性，并对其原因进行了初步探讨，对改进的抗震规范法提出了实施的办法，以考虑地震孔隙水压力升高强度降低的影响。     

Experimental study of NiO electrical conductivity changes under low oxygen pressures

The electrical conductivity of NiO was measured at 740°C in an oxygen pressure range of 10^–2 –1.3 Torr. By means of continuous recording, longtime experiments were performed. The results show that for any admittance of oxygen, the electrical conductivity initially increased and then decreased to its initial value. For pressures higher than 0.1 Torr the decrease of the signal was reduced and the time required to attain the initial value sometimes reached several days. These results suggest that the electrical conductivity changes may be considered as a transitory phenomenon connected to attaining gassolid equilibrium.