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51.
A new approach
is presented to determine the dimensions of cylindrical nanopores from adsorption
measurements. 相似文献
52.
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. 相似文献
53.
Zanin Gisella M. Neitzel Ivo De Moraes Flavio F. 《Applied biochemistry and biotechnology》1993,(1):477-489
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. 相似文献
54.
55.
Juan Primera Anwar Hasmy Thierry Woignier 《Journal of Sol-Gel Science and Technology》2003,26(1-3):671-675
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. 相似文献
56.
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... 相似文献
57.
The concentration sensitivity of a thermal conductivity detector (TCD) depends, among other factors, on the amount of sample mixture in the detector's sensing cell. Since the cell volume has to be appropriately matched with column diameter, it makes the concentration sensitivity of a TCD dependent on column diameter and, therefore, on the speed of gas chromatography. Through reduction of column diameter, higher speed tends to lead to a reduction in the concentration sensitivity of the cell. The factor which the most directly affects the concentration sensitivity of a TCD cell is the heat power conducted through the cell. The higher the power, the greater the sensitivity. The limit of detection of a TCD depends on the concentration-sensitivity of its cell and on the level of statistical errors in the measurement. The errors increase with increasing analysis speed. As the column diameter is reduced, the errors cause additional worsening (on top of the decrease in concentration sensitivity) of the detection limit, dynamic range, and other performance characteristics of the TCD. 相似文献
58.
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. 相似文献
59.
Double Pore Silica Gel Monolith Applied to Liquid Chromatography 总被引:2,自引:0,他引:2
K. Nakanishi H. Minakuchi N. Soga N. Tanaka 《Journal of Sol-Gel Science and Technology》1997,8(1-3):547-552
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. 相似文献
60.
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 相似文献