Estimation of the dimensions of nano-capillaries from gas adsorption data

A new approach is presented to determine the dimensions of cylindrical nanopores from adsorption measurements.     

Effect of Pluronic F127 on the pore structure of macrocellular biodegradable polylactide foams

Thermally induced phase separation technique was utilized to fabricate biodegradable poly(l ‐lactic acid) (PLLA) macrocellular foams which were capable of being applied in tissue engineering. The block copolymer Pluronic F127 composed of (polyethyleneoxide)‐(polypropyleneoxide)‐(polyethyleneoxide) [(PEO)‐(PPO)‐(PEO)] was used as a porogen. Water/dioxane mixtures with different volume ratios were used as solvents. The addition of Pluronic F127 could induce an appearance of large pores (50–200 μm) besides small pores (10–20 μm) or a change from a solid–liquid phase separation to a liquid–liquid phase separation. The role of Pluronic F127 depends on the water/dioxane ratios in the PLLA/dioxane/water system. The X‐ray diffraction patterns and porosity measurement results showed that Pluronic F127 was crystallized and existed on the pore wall. The effect of Pluronic F127 on changing pore structure is attributed to the occurrence of the interaction of the lipophilic PPO blocks in Pluronic F127 with PLLA clews, consequently, this results in PLLA aggregation and early phase separation on cooling. Copyright © 2004 John Wiley & Sons, Ltd.     

Axial dispersion in a liquid fluidized bed of particles akin to immobilized enzymes

The axial dispersion of a liquid fluidized bed of controlled pore silica (CPS) particles has been determined by the pulse tracer method. The CPS used was the same as for enzyme immobilization, having an average diameter of 0.436 mm and mean pore size of 37.5 nm. The fluidization liquid is α-amylase liquefied manioc starch, 30% w/v, 45°C pH=4.5. Nominal bed porosities tested were 0.7 and 0.8. The results show that the axial dispersion coefficient increases with greater superficial liquid velocities. Various available correlations tested disagree with each other to a large extent and are unable to represent collected experimental data.     

Numerical Study of Pore Sizes Distribution in Gels

We introduce a new numerical technique for the calculation of the pore size distribution in two-dimensional disordered systems. Our method is based on a triangulation technique which allows a closer measurement of pores surface without any morphological hypothesis.In this work, we focus our calculations in simulated gels. Such materials are modeled in two different conditions: by means of the Diffusion-Limited and Reaction-Limited Cluster-cluster Aggregation algorithms, DLCA and RLCA, respectively. In both situations, when the particles concentration decreases, the average pores size increases. The more compact cluster in RLCA, compared with DLCA, is consistent with the pore size distribution we have calculated. The simulated mean pore size is quantitatively in agreement with experimental data from literature.     

新型醋酸乙烯酯／二乙烯苯共聚物的研究（Ⅱ）──醇解物的制备、结构及其性能

新型醋酸乙烯酯／二乙烯苯共聚物的研究（Ⅱ）──醇解物的制备、结构及其性能吴向东，郭贤权，何炳林（南开大学高分子化学研究所，天津，３０００７１）关键词皂化反应，醇解物，芳香族氨基酸，孔结构参数，吸附性能氨基酸失衡是指肝性脑病患者血液中芳香族氨基酸的浓度...     

Sorption of petrochemicals from aqueous solutions on thermally activated schungite rock

Thermal oxidative treatment enhances the activity of a schungite rock in the sorption of petrochemicals from aqueous solutions. The effect of the thermal oxidative activation on the content and distribution of carbon in the rock and the dependence of the sorption activity on the texture of sorbents were studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2233–2238, October, 2005.     

Double Pore Silica Gel Monolith Applied to Liquid Chromatography

Silica gels retaining double pore structure in the size ranges of micrometer and nanometer have been applied to the rod-shaped monolithic column for liquid chromatography. The macropore structure was designed by controlling the phase separation process induced by the hydrolysis and polycondensation of alkoxysilane, whereas the mesopore structure was tailored by the solvent exchange treatments on wet gels. The size exclusion chromatograms on polystyrene standards exhibited almost similar features for octadecyl-modified rod and conventional packed beads columns. The dependence of plate height on the velocity of mobile phase determined for amylbenzene was by far weaker in the rod column than in the packed beads column, suggesting that additional geometrical factors should be considered in describing the separation mechanism in the rod column.     

模拟混凝土孔溶液中钢筋钝化膜生长动力学及孔蚀过程的研究

用恒电位电流衰减法及激光扫描光电化学显微技术研究了在于ＰＨ＝１２．５及１３．８的模拟混凝土孔溶液中钢筋钝化化膜的生长动力学及相应的破坏过程，实验结果表明，钢筋钝化膜的生长过程存在两个主要阶段，各阶段膜厚均与生长时间存在正比对数关系，但当ｔ＜３０秒和ｔ＞３０秒时，膜的生长表出出不同的动力学特征，在钝化发生点蚀前，钝化膜的微区光电流一定的预兆，腐蚀抑制剂ＮａＮＯ２影响膜的生长过程及膜厚，能提高钢筋的抗     

TG and DSC investigation of the dehydration of the extra large pore aluminophosphate molecular sieve VPI-5 and related materials

The dehydration of a series of VPI-5 and H3 samples, synthesized under various conditions, as well as the solid state transformation of VPI-5 to AlPO₄-8 have been investigated using combined TG-DTG-DSC and high-resolution solid state³¹P-NMR. The TG curves show a quasi-continuous release of water, the total loss being characteristic for each sample. Complete dehydration is achieved when the samples are heated from 20°C to about 150°C at various beating rates. Besides the main dehydration effect, several weak endothermic peaks are observed. These generally non-reproducible modulated peaks, recorded at high heating rates, are presumably due to the interactions of the water molecules leaving the channels of VPI-5 with the randomly positioned fragments stemming from the destruction of the water triple helix assemblage. The non-isothermal kinetic parameters of the dehydration have been evaluated from the TG and DTG curves recorded at low heating rates. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Synthesis of SBA-15/carbon composite with an ink-bottle-like pore structure by a novel pulse CVD technique

A novel and easy post modification method, pulse chemical vapor deposition (pulse CVD), was developed to tailor the pore-opening of SBA-15 while largely keeping its surface area and pore volume. By using acetylene as carbon precursor and nitrogen as carrier gas, the pore-mouth of SBA-15 was effectively reduced from 8.1 nm to 5.1 nm within 5 min while maintaining the pore body at 8.1 nm. This ink-bottle-structured SBA-15/carbon composite only losses 12% BET specific surface area and 16% total pore volume, respectively. The SBA-15/carbon composite is highly hexagonally ordered and has similar particle morphology as the original SBA-15. The effect of three pore modification factors—the number of cycles of pulse CVD, the ratio of acetylene/nitrogen and the feeding time of carbon precursor, on the final pore structure of the SBA-15/carbon composite is also studied.