Nucleation of Hematite: A Nonclassical Mechanism

Hematite (α-Fe₂O₃) is thermodynamically stable under ambient conditions, of vast geological importance, and widely used in applications, for example, as corrosion protection and as a pigment. It forms at elevated temperatures, whereas room-temperature reactions typically yield metastable akaganéite or ferrihydrite. The mechanistic key changes underlying this observation were explored in the present study. The entropic contribution to the prenucleation hydrolysis reaction categorically implies the presence of prenucleation clusters (PNCs) as fundamental precursors. The formation of hematite is then due to a change in the reaction mechanism above approximately 50 °C, whereby the reaction limitation towards oxolation in phase-separated clusters is overcome. A model that rationalizes the occurrence of hematite, akaganéite, and ferrihydrite based on the chemistry of olation PNCs is proposed. Supersaturation and the temperature dependence of olation and oxolation rates from monomeric precursors are irrelevant in this nonclassical mechanism.     

基于相空间重构的PHM数据处理算法研究

采集数据的非线性特性极大地限制了故障预测与健康管理技术(PHM)在飞机自主保障能力中的应用,提出了一种基于相空间重构的数据处理方法;首先,对PHM技术进行了系统研究,并对数据处理进行了分析;然后,根据数据处理的特点,分别采用自相关法、复自相关法、FNN法和C-C法计算相关的延迟时间及嵌入维数;最后,通过仿真对比分析以上几种方法得到的延迟时间与嵌入维数;结果表明作为一种联合计算延迟时间和嵌入维数的数据处理方法,C-C法可以同时计算延迟时间τ为3和嵌入维数m为6。     

Ba2SbInO6双钙钛矿的水热合成和表征

利用水热晶化法制备了Ba₂SbInO₆纯相，并通过XRD、SEM、IR、XPS和ICP等方法，对产物的物相、形貌、结构和组成进行了表征。初步结构表征结果表明，产物可能为B位离子无序排列的立方钙钛矿结构，空间群为Pm3m，晶胞参数为a=0.4132 mm。产物粉末呈现立方晶型，粒度约为0.5～2 μm。     

Nonlinear Coupled Mathematical Model for Solid Deformation and Gas Seepage in Fractured Media

Based on detailed investigation into the interactional physical mechanism of solid deformations and gas seepage in rock matrix and fracture, a nonlinear coupled mathematical model of solid deformation and gas seepage is put forward and the FEM model is built up to carry out numerical analysis. The coupled interaction laws between solid deformations and gas seepage in rock matrix and fractures has been emphasized in the model, which is a vital progress for coupled mathematical model of solid deformation and gas seepage of rock mass media. As an example, the methane extraction in fractured coal seam has been numerically simulated. By analyzing the simulation results, the law of methane migration and exchange in rock matrix and fractures is interpreted.     

Retarding the Shuttling Ions in the Electrochromic TiO2 with Extensive Crystallographic Imperfections

To understand the role of structure imperfections on the performance of electrochromic transition metal oxide (ETMO) is challenging for the design of efficient smart windows. Herein, we investigate the performance evolution with tunable crystallographic imperfections for rutile TiO₂ nanowire film (TNF). Structure imperfections, originating mainly from the copious oxygen deficiency, are apt to cumulatively retard the shuttling ions, resulting in the response rate for raw TNF being less than the half that of TNF annealed at 500 °C. We describe ion accommodation sites as a convolution of normal site and abnormal site, in which the normal site performs reversible coloration but the abnormal site contributes only to charge storage, which gives a rationale for the non-linear coloration and rate capability loss. These findings give a clear picture of the ion shuttling process, which is insightful for enhancing the electrochromic performance via structure reprogramming.     

电感耦合等离子体发射光谱(ICP-OES)法测定含硼聚乙烯核屏蔽材料中的硼

含硼聚乙烯作为一种广泛应用的核屏蔽材料，准确掌握其中硼含量对于辐射防护屏蔽工程设计和屏蔽效果目标计算具有重要的意义。本文采用碳酸钠950 ℃熔融试样，以50%的盐酸溶液浸提熔融块，利用全程序空白试验溶液作为打底液配制校准系列曲线溶液作线性校准，建立了电感耦合等离子体发射光谱法（ICP-OES）测定含硼聚乙烯核屏蔽材料中硼量的方法。试样测试溶液与线性校准系列溶液中大量钠离子基体相匹配，有效消除试样溶液与工作曲线溶液因离子强度、黏度等物理因素引起的非光谱干扰对测定结果准确度的影响；选用15%的王水冲洗进样系统，有效消减了硼在测定过程中存在的记忆效应问题；测试不同含量水平的试样，方法精密度（RSD，n=6）为0.7%～1.6%；以方法比对和加标回收方式验证本方法的准确度，与化学容量滴定法分析测试结果无显著性差异，相对误差为-1.6%～1.9%；回收率为99.0%～102%。该方法操作简便，能够快速准确的为工艺生产、屏蔽工程设计计算等提供可靠的分析数据。