氧化铝微滤膜孔径的影响因素及控制

首次发现膜泡压孔径随膜厚增加而减小;随烧结温度升高,膜孔道实际几何孔径基本上不变,泡压孔径增大;膜孔径的控制方法为：根据孔径要求选择适当的微粉,通过控制膜厚准确控制膜孔径。     

金属橡胶过滤材料孔径分布特性研究

孔径分布是金属橡胶过滤材料重要的孔隙特征,它对过滤器的过滤精度和截留效率起着决定性作用,采用压汞法对金属橡胶滤材的孔径分布进行研究,结果表明在孔隙体积构成中,一部分狭窄范围内的孔隙总是占有多数,金属橡胶滤材孔径分布规律为正态分布。     

Pore structures of multi-walled carbon nanotubes activated by air, CO2 and KOH

Multi-walled carbon nanotubes (MWNTs) synthesized by the catalytic decomposition of benzene were activated by KOH, CO₂ or air. The adsorption isotherms of the activated MWNTs were analyzed and their pore size distributions were obtained. The results showed that the specific surface areas of the MWNTs activated by KOH, CO₂ and air were increased to 785 m²/g, 429 m²/g and 270 m²/g, respectively. The MWNTs activated by KOH were rich in micropores and mesopores, especially high mesopores having volumes up to 1.04 cm³/g. The CO₂-activated MWNTs also had many micropores while the air-activated MWNTs had a much smaller micropore volume. The morphologies of the activated MWNTs were examined by transmission electron microscopy and high resolution transmission electron microscopy, and the activation mechanisms were discussed.     

Lognormal Simulation of Pore Size Distributions in Cementitious Materials

The pore size distributions in cement pastes and mortars, over the range of pore sizes determined by high-pressure mercury intrusion porosimetry (MIP), can be described in terms of a multimodal distribution by using lognormal simulation. The pore size distribution may be regarded as a mixture of lognormal distributions. Such a mixture is defined by a compound density function: p ( x ) =Σ f_i p ( x , μ _i , σ _i ), Σ f_i = 1, where x is the pore diameter, f_i , is the weighting factor of the i ^th lognormal subdistribution of pore sizes, p ( x , μ _i , σ _i ), and μ _i and σ _i are the location parameter and the shape parameter of the i ^th subdistribution, respectively. It may indicate that different origins and formation mechanisms exist for pores in different size ranges in cementitious materials. A graphical method is proposed to estimate the parameters for the compound distribution. Applications of this model to prediction of permeability are discussed.     

炭分子筛的孔径分布研究

采用容积法测定了CO2在两种炭分子筛（CMS-200A、CMS-200B）上的吸附等温线,温度为273K、相对压力为0.000001～0.9。通过HK模型和D-R方程对吸附平衡数据进行分析,计算得到了两种炭分子筛的孔径分布。结果表明：两者的孔径分布主要在0.35～0.8nm之间,CMS-200B的平均孔径略大于CMS-200A。HK模型和D-R方程两种方法均可以反映出两种炭分子筛孔径分布的差异,且计算得到的结论是一致的。     

添加剂对气凝胶孔径分布的影响

以稻壳灰为硅源,在适宜的凝胶形成条件下,加入不同添加剂(羟基类和酰胺类有机物),通过溶胶-凝胶、溶剂置换过程及超临界二氧化碳干燥工艺制备了硅气凝胶. 结果表明,丙三醇、乙二醇添加量为15%~20%时调控作用显著,凝胶孔洞变小且分布更均匀,比表面积增大、平均孔径减小;聚乙二醇使凝胶化时间缩短,孔径分布较均匀;二甲基甲酰胺、甲酰胺调控效果最显著,所得样品孔径集中分布于20~40 nm,比表面积均在750 m2/g以上. 聚乙烯吡咯烷酮可加快缩聚速率,使小孔比例大幅增加,网络结构致密.     

Effect of Attapulgite Pore Size Distribution on Soybean Oil Bleaching

The pore size distribution and specific surface area of the attapulgite was a crucial parameter for the uptake of pigments of oil. Bleaching of the soybean oil with three attapulgites with different pore size distribution, which were assigned a, b, and c, respectively was investigated. The specific surface area and the pore size distribution of the attapulgites were characterized. The Freundlich isotherm analysis was used to evaluate the sorption capacity of the three attapulgite. Sample b gave the highest surface area and sample c the lowest. Sample b exhibited a wider pore distribution (8–65 Å) whereas samples a and c had more micropores smaller than 15 Å. Sample a, in contrast to samples b and c, was characterized by some larger pores (100–170 Å). The sorption capacity followed the sequence: attapulgite sample c > attapulgite sample a > attapulgite sample b. The sorption capacity was decided by the pore size distribution. The more pores with a distribution range 8–32 Å (i.e., close to the diameter of the pigments), the more pigments removed. The attapulgite sample c, which had most pores (8–32 Å) was the best.     

Pore Size Reduction and Performance Upgrade of Silica Membranes with an Ambient Temperature C-ALD Post-Treatment Method

An ambient temperature C-ALD (with NH₃ as catalyst) method was employed to modify sol-gel silica membranes, in order to reduce their pore size and upgrade their gas separation performance. Membranes were characterized before and after modification in terms of permeance and permselectivity with the use of He and N₂, as gas separation indicators. The application of the proposed method significantly improved the permselectivity of the membranes accompanied with a minor permeance reduction. The process temperature renders it ideal for application in commercial membrane modules which utilize economic, current available, sealing technologies. The performance of the C-ALD modified silica membranes in various gas separation applications was further examined, indicating that they are potential candidates for H₂ separation in various chemical processes. Finally, the stability of the C-ALD modified silica membranes in H₂O was studied, indicating some performance loss during the first hours of the membrane's exposure to a H₂O atmosphere, which nevertheless remained high and steady then on.     

颗粒粒径和膜孔径对陶瓷膜微滤微米级颗粒悬浮液的影响

通过测定颗粒悬浮液通过陶瓷微滤膜时的参透通量及污染阻力,确定了陶瓷膜处理微米级颗粒悬浮液时,颗粒粒径和膜孔径对微滤过程的影响和膜污染机理,获得了微米级颗粒悬浮液微滤过程中膜孔径的选择方法。     

玻璃基TiO_2膜的孔径尺寸对其光催化性能的影响

通过在溶胶—凝胶溶液中加入聚乙烯乙二醇有机聚合物 ,利用平板玻璃作衬底 ,制备了多孔 Ti O2 薄膜。扫描电镜观察表明 ,一定的热处理条件下 ,有机聚合物可以显著地改变 Ti O2 薄膜的孔径尺寸。光催化结果显示 :当 Ti O2 膜的孔径尺寸在 15 0～ 2 5 0 nm时 ,它的光催化性能较好。     

Effect of Calcination Conditions on Crystalline Structure and Pore Size Distribution for a Mesoporous Alumina

In this article, a mesoporous commercial alumina was calcined in the temperature range of 600°C–1200°C. The effect of several parameters such as calcination temperature, calcination time, heating rate, and calcination steps on phase transformation and crystal size was experimentally investigated. The characterization of the commercial mesoporous alumina and samples calcined at 1000°C, 1040°C, 1070°C, 1100°C, and 1200°C by single-step and multi-step calcination was performed using XRD and N₂ adsorption/desorption techniques. For the commercial mesoporous alumina, TG/DTA analysis was also performed. Experimental results showed that mostly pure α-Al₂O₃ was obtained at 1100°C.     

大孔容孔径氧化铝的合成研究

采用中和成胶法,以偏铝酸钠、硫酸铝等为原料,考察了成胶温度、成胶p H值、助剂等条件对合成氧化铝产品性能的影响。结果表明:升高成胶温度,氧化铝产品的结晶度随之增高,比表面积呈先增大后减小的趋势,孔容、孔径增大,在成胶温度为70℃时产品的最可几孔径最大。随成胶pH的升高,氧化铝产品的比表面积逐渐减小,pH=7时以小孔为主,pH=8时孔容增至最大,孔分布向大孔方向偏移,继续增高p H值孔容和大孔比例均减小。在成胶体系中引入2%的P、F、Si作为助剂均可有效提高氧化铝的孔径,助剂F和Si会使氧化铝的比表面积和孔容有所减少,而P会显著提高氧化铝的比表面积和孔容。加入0.2%~1%的B_2O_3作为助剂后,产品的孔径分布向大孔方向显著偏移。     

Application of Pore Size Analyzers in Study of Chinese Angelica Slices Drying

The objective of this article is to study the influence of pore size and distribution in plant tissue on drying behavior of plant materials using Chinese Angelica slices as an example. By using an automatic mercury injection apparatus and automatic surface area–porosity analyzer, the study compares the pore size distribution inside the matrix of a sample dried by 200 W microwave and 60°C hot air. The study also characterizes the matrix microstructure by scanning electronic microscopy (SEM) and discusses the drying dynamics of the sample, as well as the rehydration property of the dried sample. This work may be helpful for further investigation of the optimization of drying technology focused on micromechanisms and the quality of dried products.     

Importance of Surface Area and Pore Size Distribution of Resin for Organic Toxicants Adsorption

Adsorption of benzoic acid and reactive brilliant blue 4 (RBB4) by hypercrosslinked resins and macroporous resins was examined. Micropore areas were much higher in the hypercrosslinked resins than macroporous resins while the pore volume and average pore diameter of macroporous resins were superior to the hypercrosslinked resins. The investigation showed that the pore size distributions of the resins significantly influenced the adsorption capacity of adsorbents. Adsorption of benzoic acid was dominated by BET surface area and the micropore area while the adsorption of RBB4 shifted to a pore-size-dominant process. The maximum mol adsorption capacities of benzoic acid were all higher than those of RBB4 by the resins, showing the influence of the molecular dimension on adsorption. The adsorption thermodynamic parameters were calculated and it revealed that the adsorption was an exothermic, spontaneous, and more ordered process. Adsorption kinetics and elution processes were also investigated for establishing the appropriate adsorption conditions for purifying wastewater containing benzoic acid or RBB4.     

干污泥表面形貌及孔隙分布规律

污泥干燥焚烧以回收其热能的资源化利用正受到越来越多的关注。污泥干燥过程中,孔隙的大小及其分布直接影响污泥中液体及气体的传递过程．进而影响干燥速率。为研究干污泥表面形貌及孔隙分布规律,采用扫描电子显微镜观测了干污泥表面形貌。利用动态氮吸附法测量了干污泥的孔隙大小。利用数理统计方法研究了孔隙分布规律,研究结果表明干污泥的孔隙分布服从对数正态分布。建立了孔隙分布模型,求解了5种干污泥的孔隙分布特征参数,模型计算值与实际测量值吻合较好,均方根误差小于18．2％,所建立的干污泥孔隙分布模型具有一定的通用性及准确性。     

多孔陶瓷孔径及其分布测定方法研究进展

孔径及其分布决定了多孔陶瓷的性能及应用,因此对其测定和定量表征非常重要。本文综述了多孔陶瓷孔径及孔径分布的常见测定方法,包括气泡法、压汞法、气体透过法、气体吸附法、气体渗透法、液-液法、悬浮液过滤法、X射线小角度散射法、核磁共振成像法、X射线断层扫描法以及电子显微镜图像分析法。比较了各种测试方法的优缺点,认为电子显微镜图像分析法是最直接有效的测定方法,并对多孔陶瓷的测试表征方法提出了展望。     

Influence of heating mode on drying behavior of capillary porous media: Pore scale modeling

Invasion percolation (IP) rules under non-isothermal conditions are applied to model the pore-scale events occurring during drying of capillary porous media, namely displacement of immiscible phases and cluster formation. A saturated two-dimensional network with a bimodal pore size distribution is dried by applying two different heat transfer boundary conditions; one corresponds to convective drying and the other to less resistive contact drying. Simulated macroscopic drying behavior is presented in conjunction with freely evolved microscopic temperature fields and phase distributions for both heating modes. Convective heating exhibits similar invasion patterns as those in isothermal simulations; both are dominated by the spatial distribution of pore radii. However, in contact heating, temperature dependency of surface tension produces significantly different invasion patterns.     

聚醚砜中空纤维血浆分离膜的孔径大小及分布

本文采用场致扫描电镜的显微观察法和膜对溶质的粒子筛分法测定聚醚砜中空纤维血浆分离膜的孔径大小及分布。通过显微镜观察统计得到膜的几何平均孔径为229nm,膜孔孔径分布在150nm,-350nm,筛分法测试得到膜的平均孔径为197nm。平均孔径大小约为200nm的聚醚砜中空纤维膜适合做血浆分离膜。     

竹炭粒径对竹活性炭的吸附性能与孔结构的影响

研究了竹炭粒径对KOH活化法制备的竹活性炭吸附性能和孔结构的影响。结果表明,竹炭粒径0.18~0.27 mm和0.55~0.88 mm时活化得率较高。竹活性炭碘吸附值和亚甲基蓝吸附值都随竹炭粒径的减小而先减小后增大,与活性炭的比表面积BET和总孔容积变化趋势相一致;苯酚吸附值随竹炭粒径的减小而先增大后减小。竹炭粒径对竹活性炭碘吸附值和苯酚吸附值的影响较小,0.11~0.15 mm粒径竹炭制备的活性炭的亚甲基蓝吸附值最大。0.18~0.27 mm和0.55~0.88 mm粒径竹炭制备的活性炭的平均孔径较小,说明0.18~0.88 mm粒径竹炭制备的活性炭的微孔率相对较高,有利于在低分子质量气体吸附方面的应用。因此,竹炭制备高性能活性炭的较佳粒径为0.18~0.88 mm。