高效凝胶过滤色谱填料KH-s-GFC300的合成与评价

以碱溶法制备的高孔隙度硅胶为基质,与γ-环氧丙基丙氧基三甲氧基硅烷配基进行共价键合,经过酸性水解,使其转化为二醇基,制成了高效亲水凝胶色谱填料。键合反应中采用70 ℃回流冷凝管,使生成的甲醇可顺利地排到体系外,促使反应向有利于键合的方向进行,以获得较高的配基密度。研究表明,水解反应条件与配基密度以及柱效密切相关。当配基密度为2.6~3.5 μmol/m2时,才能显示出较高的柱效。蛋白质分离实验结果显示,此填料的相对分子质量排阻极限为300000,牛血清白蛋白的回收率为99％。     

Studies of heterogeneity properties of selected high-temperature superconductor surfaces

Nitrogen adsorption measured at 77 K was used to characterize the surface heterogeneity of high-temperature superconductor surfaces. Properties relating to adsorption and porosity of the solids (adsorption capacity, specific surface area, radii and volume of the pores, pore-size distribution function) were determined from nitrogen adsorption–desorption isotherms and atomic force microscopy (AFM) for a series of oxide superconductors. It is shown that the adsorption isotherms of all samples are S-shaped and belong to type II according to the IUPAC classification. On the basis of the nitrogen adsorption isotherms and AFM data, fractal dimensions were determined and correlations found with adsorption and porosity parameters.     

Microporosity of a Guanidinium Organodisulfonate Hydrogen‐Bonded Framework

Guanidinium organosulfonates (GSs) are a large and well‐explored archetypal family of hydrogen‐bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4‐benzenedisulfonate ( p ‐G₂BDS ). p ‐G₂BDS is obtained from its acetone solvate, AcMe@ G₂BDS , by single‐crystal‐to‐single‐crystal (SC‐SC) desolvation, and exhibits a Type I low‐temperature/pressure N₂ sorption isotherm (SA_BET=408.7(2) m² g^?1, 77 K). SC‐SC sorption of N₂, CO₂, Xe, and AcMe by p ‐G₂BDS is explored under various conditions and X‐ray diffraction provides a measurement of the high‐pressure, room temperature Xe and CO₂ sorption isotherms. Though p ‐G₂BDS is formally metastable relative to the “collapsed”, nonporous polymorph, np ‐G₂BDS , a sample of p ‐G₂BDS survived for almost two decades under ambient conditions. np ‐G₂BDS reverts to zCO₂@ p ‐G₂BDS or yXe@ p ‐G₂BDS (y,z=variable) when pressure of CO₂ or Xe, respectively, is applied.     

烧结金属纤维板大空间自然对流实验研究

实验研究了烧结金属纤维板在大空间下的自然对流换热,分析了倾角、孔隙率、纤维丝经、Ra数和金属纤维导热系数对换热性能的影响.实验结果表明:存在最优的角度(60°左右)使烧结金属纤维板的自然对流换热性能最好,但倾斜角度对烧结金属纤维板的换热影响没有光板显著;加热面的平均Nu数随着纤维直径和孔隙率的增加均先增加后减小;在实验...     

透明激光陶瓷散射损耗分析

 为了定量分析激光陶瓷中散射损耗对其透过率的影响,通过建立气孔尺寸分布模型,引入第二相体积比概念,并结合Mie散射、瑞利散射和全散射积分等理论,讨论了激光陶瓷中气孔、晶界第二相和表面粗糙度等引起的散射损耗对激光陶瓷透光性能的影响。研究结果表明：气孔率的大小将明显影响陶瓷透过率,且气孔尺寸分布决定了透过率包络的变化趋势;晶界和表面散射对透过率的影响主要集中在短波长处;在气孔率较低情况下,晶界第二相的存在是导致短波长处透过率急剧降低的主要因素。     

Growth of ZIF-8 MOF Films with Tunable Porosity by using Poly (1-vinylimidazole) Brushes as 3D Primers

This work reports on a novel and versatile approach to control the structure of metal–organic framework (MOFs) films by using polymeric brushes as 3D primers, suitable for triggering heterogeneous MOF nucleation. As a proof-of-concept, this work explores the use of poly(1-vinylimidazole) brushes primer obtained via surface-initiated atom transfer radical polymerization (SI-ATRP) for the synthesis of Zn-based ZIF-8 MOF films. By modifying the grafting density of the brushes, smooth porous films were obtained featuring inherently hydrophobic microporosity arising from ZIF-8 structure, and an additional constructional interparticle mesoporosity, which can be employed for differential adsorption of targeted adsorbates. It was found that the grafting density modulates the constructional porosity of the films obtained; higher grafting densities result in more compact structures, while lower grafting density generates increasingly inhomogeneous films with a higher proportion of interparticle constructional porosity.     

Light Emission and Scanning Electron Microscopic Characterization of Porous Silicon

Optical emission resulting from sputtered species during ion bombardment of porous and oxidized porous silicon targets has been studied. Samples were bombarded with 5‐keV Kr⁺ ions at an incidence angle of 70 degrees, and the light emitted was analyzed over the wavelength range 200–300 nm. The surface morphology was investigated, and the micrographs revealed grooves parallel to the plane of incidence when the porosity was surprisingly observed in the grooves under each pore. The results are discussed as a function of the incidence angle and the porosity of the silicon targets.     

基于微结构参数建模的多孔硅绝热层热导率研究

多孔硅由于具有较低的热导率,因而可以将其作为半导体器件中的绝热层.与其他从边界散射等复杂微观热传导机制出发建模研究多孔硅的热导率不同,将多孔硅热导率影响机制更表观地归结到孔洞的存在和分布等结构因素上,把整个多孔硅视为由硅连续材料介质和孔洞连续介质通过串联和并联组合成的复合微结构,给予其低热导率一个更为易于理解和简化的解释.进一步把孔隙率对等效热导率的影响分解为两个不同的部分,即纵向部分和横向部分,半定量地给出不同的孔洞结构和分布下孔隙率与等效热导率的关系.与实验数据进行对比后验证了模型的有效性.继而从结构的角度说明了多孔硅热导率较低的原因.     

Glass bead grafting with poly(carboxylic acid) polymers and maleic anhydride copolymers

Glass beads were etched with acids and bases to increase the surface porosity and the number of silanol groups that could be used for grafting materials to the surfaces. The pretreated glass beads were functionalized using 3‐aminopropyltriethoxysilane (APS) coupling agent and then further chemically modified by reacting the carboxyl groups of carboxylic acid polymers with the amino groups of the pregrafted APS. Several carboxylic acid polymers and poly(maleic anhydride) copolymers, such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), poly(styrene‐alt‐maleic anhydride) (PSMA), and poly(ethylene‐alt‐maleic anhydride) (PEMA) were grafted onto the bead surface. The chemical modifications were investigated and characterized by FT‐IR spectroscopy, particle size analysis, and tensiometry for contact angle and porosity changes. The amount of APS and the different polymer grafted on the surface was determined from thermal gravimetric analysis and elemental analysis data. Spectroscopic studies and elemental analysis data showed that carboxylic acid polymers and maleic anhydride copolymers were chemically attached to the glass bead surface. The improved surface properties of surface modified glass beads were determined by measuring water and hexane penetration rates and contact angle. Contact angles increased and porosity decreased as the molecular weights of the polymer increased. The contact angles increased with the hydrophobicity of the attached polymer. The surface morphology was examined by scanning electron microscopy (SEM) and showed an increase in roughness for etched glass beads. Copyright © 2007 John Wiley & Sons, Ltd.     

硫辅助合成高孔隙率大孔氮化硼材料

采用硫粉辅助的方法合成了具有一定有序孔洞结构的三维大孔氮化硼材料,具有高比表面积(230 m2.g-1)和高孔隙率(85.6%),并呈现开孔结构。在未加入硫粉的情况下则只形成完全无序的三维大孔氮化硼,并且比表面积和孔隙率分别降至122m2.g-1和73.7%。热重测试表明两种产品均具有良好的抗氧化性能。本文还对这种大孔材料的形成过程和硫粉的作用进行了初步的探讨。