Preparation and functionalization of mesoporous silica spheres as packing materials for HPLC

This paper presents the integrated results of a series of new methods for preparing mesoporous silica spheres as high-performance liquid chromatography （HPLC） packing materials. The separation performance of the mesoporous spheres materials has also been determined. Micrometer- sized silica spheres with uniform spherical morphologies and ordered mesostructures were first successfully synthesized by the method employing a water-soluble polymer-assisted assembly. Then the templates for getting ordered mesoporous materials with high-density silanol groups were removed by using hydrothermal oxidation. Finally the silica spheres were functionalized with C8 alkyl groups by surface modification under hydrothermal conditions. The resultant functionalized silica spheres were demonstrated to be excellent oacking materials for HPLC.     

Preparation and Li^＋ storage properties of hierarchical hollow porous carbon spheres

Hollow ordered porous carbon spheres （HOPCS） with a hierarchical structure were prepared by templating with hollow ordered mesoporous silica spheres （HOMSS）. Scanning electron microscopy （SEM） and transmission electron microscopy （TEM） showed that HOPCS exhibited a spherical hollow morphology. High-resolution TEM, small angle X-ray diffraction （SAXRD） and N2 sorption measurements confirmed that HOPCS inversely replicated the unconnected hexagonal-stacked pore structure of HOMSS, and possessed ordered porosity. HOPCS exhibited a higher storage capacity for Li^＋ ion battery （LIB） of 527.6 mA h/g, and good cycling performance. A large capacity loss during the first discharge-charge cycle was found attributed to the high content of micropores. The cycling performance was derived from the hierarchical structure.     

Preparation and Li+ storage properties of hierarchical hollow porous carbon spheres

Hollow ordered porous carbon spheres (HOPCS) with a hierarchical structure were prepared by templating with hollow ordered mesoporous silica spheres (HOMSS). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that HOPCS exhibited a spherical hollow morphology. High-resolution TEM, small angle X-ray diffraction (SAXRD) and N₂ sorption measurements confirmed that HOPCS inversely replicated the unconnected hexagonal-stacked pore structure of HOMSS, and possessed ordered porosity. HOPCS exhibited a higher storage capacity for Li⁺ ion battery (LIB) of 527.6 mA h/g, and good cycling performance. A large capacity loss during the first discharge–charge cycle was found attributed to the high content of micropores. The cycling performance was derived from the hierarchical structure.     

SYNTHESIS AND COATING OF ORDERED MESOPOROUS SILICA

1,3,5-trimethyl benzene (TMB) was used as organic swelling agent in O/W emulsions to template ultra-large mesoporous materials using the hydrothermal method. The silicas with well-defined mesopores and hydrothermally robust framework were characterized by X-ray diffraction, transmission electron microscopy and BET surface area analysis. The influence of the quantity of TMB during preparation was studied. It has been found that the TMB/CTAB ratio must be controlled for producing high pore volume materials. Polysulfone (PSU), as the usual extraction agent, was coated on the silicas with the solvent evaporation method to produce a solid separation medium. The adsorptivity and the surface area of the coated MCM were determined: 10% PSU coated MCM adsorbed twice as much phenol as the uncoated material, reaching 0.5 mg/g silica. It was found that the surface area of the coated material decreased rapidly with an increase of the PSU Ioadina.     

等径圆球组简单压缩下的宏观应力-应变关系

应用虚功原理推导出规则排列等径因球颗粒在赫兹接触规律下简单压缩时宏观应力应变关系，并与TRUBAL程序离散元法模拟结果做了比较．比较发现规则排列模拟结果和理论结果是一致的．进一步模拟研究了随机排列，给出了等径圆球随机排列宏观应力应变关系拟合公式．     

POROUS SILICA NANO-TUBE AS HOST FOR ENZYME IMMOBILIZATION

With their hollow morphology and large openings, the as-synthesized porous silica nano-tubes (NTPS), prepared through a sol-gel routine by using nano-sized needle-shaped CaCO3 particles as templates, were used as host for enzyme immobilization. Bioimmobilization study showed that enzyme molecules could not only be adsorbed on the external surface of NTPS but also entrapped in their inner hollow cores, leading to higher enzyme loading capacities of NTPS (more than 350 mg/g silica) in a shorter time, as compared to common porous silica (less than 50 mg/g) and most conventional mesoporous silica materials (less than 100 mg/g).     

Mesoporous composite of LiFePO4 and carbon microspheres as positive-electrode materials for lithium-ion batteries

Mesoporous LiFePO4/C microspheres consisting of LiFePO4 nanoparticles are successfully fabricated by an eco-friendly hydrothermal approach combined with high-temperature calcinations using cost-effective LiOH and Fe3＋ salts as raw materials.In this strategy,pure mesoporous LiFePO4 microspheres,which are composed of LiFePO4 nanoparticles,were uniformly coated with carbon（1.5nm）.Benefiting from this unique architecture,these mesoporous LiFePO4/C microspheres can be closely packed,having high tap density.The initial discharge capacity of LiFePO4/C microspheres as positive-electrode materials for lithium-ion batteries could reach 165.3 mAh/g at 0.1 C rate,which is notably close to the theoretical capacity of LiFePO4 due to the large BET surface area,which provides for a large electrochemically available surface for the active material and electrolyte.The material also exhibits high rate capability（100 mAh/g at 8 C） and good cycling stability（capacity retention of 92.2%after 400 cycles at 8 C rate）.     

STRUCTURE CONTROL IN HYDROXYAPATITE SYNTHESIS BY HYDROTHERMAL REACTION AND ORGANIC MODULATORS

Properties of materials are determined not only by their composition, but also by their structure. It is, therefore, of great significance to develop the ability of tailoring the structure of materials according to the requirements of intended applications. In this work a novel glutamic acid-assisted hydrothermal process was developed to synthesize apatite crystals with controllable morphologies. Varied morphologies from whisk broom, fibers, mushroom, prickly spheres, to dandelion were produced through modulating both the formation of a transitory phase and its transformation into the final phase.     

转动驱动圆角立方体颗粒有序堆积的离散元模拟

宏观颗粒体系的有序堆积研究可以为热系统中微观粒子的自组装提供研究模型,也有助于工业生产中提高颗粒材料的填充率.实验发现圆筒中的圆角立方体颗粒受容器往复旋转剪切作用会实现有序堆积.为探究旋转圆筒中立方体颗粒有序堆积过程的内部结构演化过程和动力学机理,采用超二次曲面方程构造了圆角立方体颗粒,基于离散元方法对旋转剪切作用下圆...     

Steady water flow through unsaturated aggregated porous materials

The three-dimensional steady water flow through unsaturated aggregated porous materials composed of simple cubic open packed and tetrahedral close packed assemblies of uniform porous spheres is investigated with electric analogues and numerical computations. Water around the spheres is considered to be discontinuous with flow restricted through isolated annular water lenses held by surface tension forces around the contact points between spheres. It is found that the conductance of individual spheres depends only on the size of the water lenses and is independent of the radius of the sphere. For a simple cubic packing the conductance for small lens radii is given by Weber’s formula for flow from an electrified disc into an infinite medium. It follows that the bulk hydraulic conductivity of these assemblies of porous spheres is also independent of aggregate size over a range of water contents. This independence is also shown in measurements of hydraulic conductivity of aggregates of diatomaceous earth that show a convergence to a single relationship between conductivity and water content when there is no longer continuity of water in the macropore space. The effect of the three-dimensional flow through aggregates on solute leaching is demonstrated by considering the numerical results of the stream-tube pattern in a sphere.