Preparation of porous glass films using phase separation phenomenon and growth behavior of phase-separated structure

We report the preparation of porous glass films on transparent conductive oxide-coated glass substrates using the phase separation phenomena and the growth behavior of the phase-separated structure. We confirmed that the etched glass films are composed of microscale pores, a three-dimensional porous framework of SiO₂-rich phase with widths of about 40–300 nm, and a thin surface layer of about 40–90 nm thick. The SiO₂-rich phase grew by diffusion-dominated growth and then viscous flow-dominated growth.     

热致相分离法聚合物膜形成机理与形貌控制

介绍了近年来热致相分离(TIPS)法聚合物多孔膜研究的新进展.从热力学角度总结了TIPS的成膜机理,相图是理解TIPS机理的重要工具;液滴生长和晶粒生长是研究制膜体系TIPS动力学的两个方面.膜形貌由热力学、动力学共同控制,聚合物分子量、稀释剂种类、溶液固含量、冷却速率、成核剂是控制膜结构的五个重要方面.     

Segregation and phase separation in thin films

Surface segregation and phase separation in binary AB systems have been calculated in a slab consisting of atomic planes perpendicular to the free surfaces. For strongly segregating systems, if the average concentration lies in the two phase region of the binary phase diagram, a phase separation from the surfaces develops and two layers of the A-rich phase cover the A-poor central phase in the slab (lamellar structure). Furthermore, there is an enrichment (segregation) of A atoms in the near surface layers of the upper phase. For weakly segregating systems there exists a critical concentration C_h. If T > T_h (T_h is the temperature on the miscibility gap at C_h), a similar phase separation and segregation has been observed as above. However, for T < T_h, two different phases can be in equilibrium in a columnar structure. The concentrations in their central layers, if the slab is thick enough, correspond to the compositions of the miscibility gap at the given temperature. At the same time, there is a strong segregation of A atoms in the A-poor phase, while, due to the stronger separation tendency, the minority B atoms will ‘separate’ at the surface, leading to a desegregation of A atoms in the A-rich phase.     

Preparation of porous microsphere-scaffolds by electrohydrodynamic forming and thermally induced phase separation

The availability of forming technologies able to mass produce porous polymeric microspheres with diameters ranging from 150 to 300 μm is significant for some biomedical applications where tissue augmentation is required. Moreover, appropriate assembly of microspheres into scaffolds is an important challenge to enable direct usage of the as-formed structures in treatments. This work reports the production of poly (glycolic-co-lactic acid) and poly (ε-caprolactone) microspheres under ambient conditions using one-step electrohydrodynamic jetting (traditionally known as atomisation) and thermally induced phase separation (TIPS). To ensure robust production for practical uses, this work presents 12 comprehensive parametric mode mappings of the diameter distribution profiles of the microspheres obtained over a broad range of key processing parameters and correlating of this with the material parameters of 5 different polymer solutions of various concentrations. Poly (glycolic-co-lactic acid) (PLGA) in Dimethyl carbonate (DMC), a low toxicity solvent with moderate conductivity and low dielectric constant, generated microspheres within the targeted diameter range of 150–300 μm. The fabrication of the microspheres suitable for formation of the scaffold structure is achieved by changing the collection method from distilled water to liquid nitrogen and lyophilisation in a freeze dryer.     

冷冻抽提相分离法制备聚乳酸多孔支架

为了制备结构和性能满足骨组织工程支架要求的聚乳酸(PLA)多孔支架材料,采用冷冻抽提相分离法,以1,4-二氧六环和水为混合溶剂,聚乙二醇(PEG)为致孔剂,制得一系列PLA多孔支架,探讨了溶剂组成、PLA浓度、PEG添加量对PLA多孔支架结构和性能的影响,结果表明添加PEG有利于形成多孔三维支架,随着PEG含量的增加,...     

Enhanced separation of Toluene and Xylene through surface modified porous carbon matrix

Aromatics that are present in the feed of the Claus sulfur recovery process are well known to poison the catalyst and hence continued efforts are being made within the scientific community to remove them. In this context, the present work attempts to develop superior adsorbents in comparison with contemporary adsorbents for removal of toluene and m-xylene. In a bid to improve adsorption properties, nitrogen-containing surface functional groups were successfully introduced onto porous carbon by minimizing pore damage while maximizing nitrogen content. The surface modified adsorbents were subjected to gas phase adsorption of toluene and m-xylene at 45°C to generate the adsorption isotherms. Toluene adsorption capacity for the modified adsorbent was observed to have increased by approximately 30% at pressure of about 20 mbar and m-xylene by about 10% at about 22 mbar. Several orders of magnitude increase in adsorption capacity was observed for both aromatics at pressures less than 10 mbar. Such high adsorption capacity have not been reported in literature and could potentially favorably alter the economics of aromatics removal in gas processing. Regenerability of nitrogen doped adsorbent was ensured through cyclic adsorption/desorption tests. The adsorption isotherms as well as the kinetics of adsorption were modelled.     

无载体手性固定相拆分对映体

本文介绍了无载体纤维素三—(4—甲基苯甲酸酯)手性固定相对外消旋药物酮洛芬的拆分且就不同的柱尺寸及装填方式作了比较。为了反映无载体手性固定相的拆分能力,还将无载体柱与有载体柱、自制柱与日本柱作了比较。结果表明:无载体手性固定相对外消旋药物是有拆分能力的,只是其能力低于有载体的。若无载体手性固定相能与高新分离技术(如模拟移动床)相结合,将有望实现外消旋药物的低成本拆分。     

Enhancement of charge-transport characteristics in polymeric films using polymer brushes

We show that charge-transporting polymer chains in the brush conformation can be synthesized from a variety of substrates of interest, displaying a high degree of stretching and showing up to a 3 orders of magnitude increase in current density normal to the substrate as compared with a spin-coated film. These nanostructured polymeric films may prove to be suitable for electronic devices based on molecular semiconductors as current fabrication techniques often provide little control over film structure.     

Large-scale synthesis of CuS hexaplates in mixed solvents using a solvothermal method

Large-scale covellite CuS hexaplates were successfully synthesized by the 200 °C solvothermal reactions of CuCl₂.2H₂O and (NH₄)₂S in C₂H₅OH-H₂O mixed solvents containing HCOOH as a pH stabilizer, including different amounts and molecular weights (MWs) of polyethylene glycol (PEG). By using XRD and SAED, CuS (hcp) was detected. XRD peaks of the product, synthesized in a solution containing 5 g PEG6000 and 1.5 ml HCOOH for 5 h, are in accordance with those of the simulation and database. The (110) peak shows the preferential growth, corresponding to the hexaplates, characterized using SEM, TEM and HRTEM. CuS hexaplates with the (100) and (010) lattice planes at an angle of 120° were detected on the flat surface, and the (002) lattice plane on the edge. UV-vis absorption edge was detected at 610 nm (2.03 eV), and the PL emission at 361 nm (3.43 eV). Phase and morphology formations were also explained according to the experimental results.     

Enhanced transport properties of assembled CdSe quantum dot through slow evaporation with mixed solvents

CdSe quantum dots (QDs) were assembled into uniform aligned packed sheets over large area in a mixture of toluene/acetonitrile solvents through slow evaporation, and preferential evaporation of the solvent led to self-assembly under conditions of continuously decreasing solvent quality. Depending on the volume ratio of acetonitrile, the CdSe QDs formed different packing type and coverage. This simple method of depositing assembled CdSe QDs makes it possible to study the novel transport properties of CdSe QDs. The related transport results showed that the increase in photocurrent with hydrazine and post annealing treatment are due to increased QDs surface passivation and decreased QDs spacing.     

基于相分离制备高分子微孔材料的新探索

对制备聚合物微孔膜的相分离法进行了评述.简介了课题组几种基于相分离制备聚合物微孔材料的新探索,包括热致相分离,冷冻诱导相分离,聚合致相分离,基板诱导共混聚合物的有规相分离.     

Magnetic-field-induced phase separation via spinodal decomposition in epitaxial manganese ferrite thin films

In this study, we report about the occurrence of phase separation through spinodal decomposition (SD) in spinel manganese ferrite (Mn ferrite) thin films grown by Dynamic Aurora pulsed laser deposition. The driving force behind this SD in Mn ferrite films is considered to be an ion-impingement-enhanced diffusion that is induced by the application of magnetic field during film growth. The phase separation to Mn-rich and Fe-rich phases in Mn ferrite films is confirmed from the Bragg’s peak splitting and the appearance of the patterned checkerboard-like domain in the surface. In the cross-sectional microstructure analysis, the distribution of Mn and Fe-signals alternately changes along the lateral (x and y) directions, while it is almost homogeneous in the z-direction. The result suggests that columnar-type phase separation occurs by the up-hill diffusion only along the in-plane directions. The propagation of a quasi-sinusoidal compositional wave in the lateral directions is confirmed from spatially resolved chemical composition analysis, which strongly demonstrates the occurrence of phase separation via SD. It is also found that the composition of Mn-rich and Fe-rich phases in phase-separated Mn ferrite thin films deposited at higher growth temperature and in situ magnetic field does not depend on the corresponding average film composition.     

Flow phenomena of superfluid helium through a porous plug phase separator

A porous plug, which separates vapour from superfluid helium (He II), is an indispensable component for space cryogenics. Precise measurement of the temperature distribution inside a number of porous plugs has been successfully carried out to reveal the actual flow phenomena of superfluid helium and the vapour flow through the plugs. It was found that He II flows ideally through the upstream portion of the porous plug, thus the London equation can be applied there. Superfluid helium turns into vapour near the exit of the porous plug. The flow of the normal component of He II remained laminar in the cases examined in the experiment. The liquid-vapour phase boundary was formed just at the exit of the porous plug and moved toward the upstream side as the mass flow rate increased. A thermodynamic consideration of He II phase separation using a porous plug is also presented in this Paper.     

密差分相式液膜法提取L-苯丙氨酸

采用密差分相液膜分离技术，以P204为载体，H2SO4为反萃剂，以初始浓度15．28g/L的L－苯丙氨酸水溶液提取5次后，浓度降至1．92g/L，反萃相中L－苯丙氨酸浓度达54．35g/L，膜溶胀和破裂均较小，过程不需要制乳和破乳；对反萃剂也进行了后处理。     

Aiding mixed convection through a vertical anisotropic porous channel with oblique principal axes

In this paper, an analytical study is carried out on the mixed convection in parallel-plate vertical porous channels with an anisotropic permeability whose principal axes are oriented in a direction which is oblique to the gravity vector. The channel walls are assumed to be isothermal and the flow fully developed at the entrance is upward, so that natural convection aids the forced flow. In the formulation of the problem, use is made of the generalized Brinkman-extended Darcy model which allows the no-slip boundary condition on solid wall, to be satisfied. The flow reversal and the limiting cases of low and high porosity media for natural and forced convection are considered. The effects of varying the anisotropic permeability ratio and the orientation angle of the principal axes on the flow and the heat transfer are investigated.     

Atomic force microscopy studies of lateral phase separation in mixed monolayers of dipalmitoylphosphatidylcholine and dilauroylphosphatidylcholine

Atomic force microscopy imaging of dipalmitoylphosphatidylcholine (DPPC)/dilauroylphosphatidylcholine (DLPC) monolayers deposited onto alkanethiol modified-gold surfaces by the Langmuir–Schaefer technique was used to investigate domain formation in a binary system where phase separation arises from a difference in the alkyl chain lengths of the lipids. We have established how the condensed domain structure (shape and size) in DPPC/DLPC monolayers depends on the surface pressure and lipid composition. The mixed monolayers exhibit a positive deviation from an ideal mixing behavior at surface pressures of 32 mN/m. Lateral compression to pressures greater than the liquid-expanded-to-liquid-condensed (LE-to-LC) phase transition pressure of the mixed monolayer (8–16 mN/m) induces extensive separation into condensed DPPC-rich domains and a fluid DLPC matrix. The condensed structures observed at a few milliNeutons per meter above the LE-to-LC transition pressure resemble those reported for pure DPPC monolayers in the LE/LC co-existence region. At a bilayer equivalence pressure of 32 mN/m and 20 °C, condensed domains exist between x_DPPC 0.25 and 0.80, analogous to aqueous DPPC/DLPC dispersions. Compression from 32 to 40 mN/m results in either a striking distortion of the DPPC domain shape or a break-up of the microscopic DPPC domains into a network of nanoscopic islands (at higher DPPC mol fractions), possibly reflecting a critical mixing behavior. The results of this study provide a fundamental framework for understanding and controlling the formation of lateral domain structures in mixed phospholipid monolayers.     

Two-dimensional phase separation and surface-reconstruction driven atomic ordering in mixed III–V layers

In mixed III–V layers atomic species having different covalent tetrahedral radii are not distributed at random on their respective sublattices. Two types of deviation from randomness are observed: (i) phase separation, and (ii) atomic ordering. Phase separation is two-dimensional in nature, occurs on the surface while the layer is growing and is driven by surface thermodynamics. In contrast, atomic ordering is induced by subsurface stresses associated with (2×4) and (2×3) reconstructions of group V terminated (001) surfaces. These stresses bias the occupation of sites by atomic species differing in their tetrahedral radii and this feature leads to the evolution of double and triple period superlattices on ( 11)_B, (1 1)_B, and (111)_A, (11 )_A planes respectively.