Micropore formation mechanism in iridium coating after high‐temperature treatment

Noble metal iridium is of great interest for high‐temperature applications and extreme environments. A high (110)‐oriented iridium coating was prepared by a double glow plasma process on the surface of niobium substrate. The morphology and composition of the coating were determined by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy, respectively. The phase of the coating was identified by X‐ray diffraction analysis. The misorientation angle distributions of grains on the surface and cross section of the coating were characterized by electron backscatter diffraction system. The uniform and pure iridium coating consisted of the submicrometer‐sized columnar grains with high‐angle boundary. The mean misorientation angles on the surface and cross section of the coating were 38.6° and 45.6°, respectively. After high‐temperature treatment, the coating was composed of equiaxed grains with distinct grain boundaries. Micropores appeared on the fracture surface of the coating. The micropore formation mechanism in Ir coating after high‐temperature treatment was investigated. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparative Studies of the Micropore Size Distributions of an Alumina Pillared Montmorillonite and a Molecular Sieve Carbon

The aim of this work is to applicate and to compare various analysis methods for the characterization of the microporous structure from nitrogen adsorption at 77 K of an alumina pillared montmorillonite and a molecular sieve carbon. The adsorption potential distribution (X(A)), the Horvath-Kawazoe (HK) method, the Jaroniec-Gadkare-Choma (JGC) one and a numerical algorithm for the reconstruction of the micropore size distribution (MPSD) from the adsorption equilibrium isotherm have been applied. Comparison of all distributions revealed that the molecular sieve carbon shows smaller micropores and smaller structural hetereogeneity than the alumina pillared montmorillonite.     

Predicting isotherms in micropores for different molecules and temperatures from a known isotherm by improved Horvath-Kawazoe equations

Our improved Horvath-Kawazoe (H-K) equations (by considering the isotherm nonlinearity) for three pore geometries are first summarized. These equations apply to adsorption in microporous materials at subcritical temperatures. From a known isotherm at a given temperature, these equations are used to predict isotherms of the same adsorbate molecules at other temperatures, and also to predict isotherms for other adsorbate molecules at the same (or any subcritical) temperature. A reasonable agreement is obtained between predictions and experimental data. Since the H-K formulation only involves dispersion forces, it underpredicts for gas-solid systems in which other forces also exist. The N₂-zeolite system is one of these systems.     

New equation of adsorption for the calculation of parameters of microporous structure

A new equation describing the equilibrium adsorption of vapors of substances with different physicochemical properties was obtained on the basis of the lognormal distribution of pore volume within the theory of volume filling of micropores. Unlike the existing equations, this equation is more general since it is not related to a specific geometrical model of pores. Adsorption isotherms described by this equation for active carbons with wide pore-size distributions have smaller mean square deviations than those calculated using the Dubinin-Stoeckli equation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1931–1933, October, 1995.This study was financially supported by the Russian Foundation for Basic Research (Project No. 94-03-09550).     

Density of He adsorbed in micropores at 4.2K

The density of He adsorbed in the cylindrical micropores of zeolites NaY and KL has been determined by He adsorption at 4.2K. He adsorption isotherms were then compared with N₂ adsorption isotherms at 77K. Crystallographic considerations of the micropore volumes gave the density of the He adsorbed layer, which is necessary for assessment of ultramicroporosity of less-crystalline microporous solids, such as activated carbons. The determined density of He adsorbed in the cylindrical micropores of the zeolite was in the range 0.22 to 0.26 gml^–1, greater than that of He adsorbed on a flat surface (0.202 gml^–1). A value for the density of He between 0.20 to 0.22 gml^–1 is recommended for evaluation of ultramicroporosity of a slit-shaped microporous system such as activated carbon.     

微孔对单壁纳米碳管储氢性能的影响

用巨正则蒙特卡罗分子模拟方法研究了单壁纳米碳管中的微孔即单壁纳米碳管基本孔-内管腔和管间孔对单壁纳米碳管储氢性能的影响.与低温下氮气吸附实验结果的比较发现单壁纳米碳管的内管腔是吸附的主要位置.分析单壁纳米碳管内管腔中吸附势的叠加和利用效率，发现管径为2nm左右时单壁纳米碳管内管腔的储氢容量最高.当单壁纳米碳管阵列的管间距增加时，单壁纳米碳管的管间孔也会成为有效的氢吸附位. 关键词： Monte Carlo方法 单壁纳米碳管 储氢 微孔     

测量多孔粉体扩散系数和孔分布的实验装置

多孔粉体在介孔和微孔范围内的表征需要专业的实验仪器,这限定了对该类材料全面的表征只能在大型实验室中进行.本文提出了一种改进的BET测量装置,其核心部件是高精度的压差传感器,这种设备让小型实验室也可以测量多孔粉体的内扩散系数和孔分布.使用数值解析方法和蒙特卡罗模拟方法分析了测量扩散系数实验的数据.