Crystallization of Celecoxib in Microemulsion Media

Celecoxib belongs to a new NSAID family specifically inhibiting cyclooxygenase‐2 (COX‐2). The present formulations require high dosage since the transmembrane transport fluctuates and is very difficult to control. We solubilized celecoxib in micelles of nonionic microemulsions and hydrophilic surfactant. The supersaturated solubilized drug was precipitated from the nano‐droplets to form a new solid structure with improved dissolution properties. The selected microemulsion systems loaded with celecoxib were characterized by SAXS, SD‐NMR, viscosity, and electrical conductivity techniques. Precipitation was conducted from W/O as well as from O/W U‐type microemulsions. The crystals obtained by the precipitation were characterized by x‐ray powder scattering, differential scanning calorimetry, FTIR measurements, and microscopic scans.     

八甲基环四硅氧烷一氯代物微乳液聚合及其消泡性能

八甲基环四硅氧烷一氯代物;有机硅微乳液;微乳液聚合;消泡性能     

Blocking Ability and Flow Characteristics of Nitrogen Foam Stabilized with Clay Particles in Porous Media

Particles-stabilized foams have received more attention in recent years due to their specific characteristics and advantages in contrast to conventional foams which were stabilized with surfactants. However, the rheology of particles-stabilized foam in consolidated cores was rarely studied. To investigate the feasibility of the particles-stabilized foam application in enhanced oil recovery, the blocking ability and flowing characteristics of foam stabilized with clay particles were investigated by using experimental cores. To do this, the foam resistance factor was studied as an index in this article. The effects of foam quality (gas velocity divided by total velocity), injection rate of foam, and the permeability of cores on the blocking ability of foams were investigated. Results showed that the blocking ability reached the peak value at the foam quality of 0.74. This indicated effective blocking ability as conventional foams performed in porous media. Moreover, the foams block the channels more effectively in high permeability cores, compared with low permeability ones. Finally, foams displayed shear-thinning property in porous media as injection rate increased.      

超细二氧化硅粉体的制备

超细二氧化硅粉体的制备李中军＊刘长让王雪清ａ赵秦生（郑州大学化学化工学院，物理系ａ郑州４５００５２）（中南工业大学长沙）关键词溶胶－凝胶法，ＳｉＯ２超细粉，粉体制备１９９７－０９－２３收稿，１９９８－０３－０２修回溶胶－凝胶工艺是液相法制备超细ＳｉＯ...     

Interactions of Pyrene-Labeled Silica Particles

Silica spheres were prepared by the St?ber method, and the method of labeling with pyrene, using aminopropylysilane as the linking agent, was optimized. Excimers between particles were formed when high concentrations of label were used. Both surfactant and polyelectrolyte addition were able to cause floc formation when added to suspensions of the silica, but only the surfactant changed the I(1)/I(3) ratio and diminished excimer formation. Copyright 2000 Academic Press.     

Esterification of Octanoic Acid with Octanol in Microemulsion and Emulsion System

The esterification of octanoic acid with octanol in microemulsion and emulsion system is studied. In the presence of 5–10% dodecylbenzene-sulfonic acid (DBSA), which is a surfactant-type catalyst, high conversion of esterification can be given both in microemulsion and in emulsion system. Compared with emulsion system, single-phase microemulsion is a more effective reaction system for esterification, with the advantages of comparatively little influence by the amount of water, no need of hard stirring, and stable state when laid long. The esterification of other fatty acids and alcohols in this reaction system were also accomplished in favorable conversion.     

Sorption Modification of Fine Silica with Polyvinylpyrrolidone

The interaction of fine silica with polyvinylpyrrolidone in aqueous medium was studied by IR spectroscopy.     

微乳液法制备超细包裹型铁粉

应用Ｗ／Ｏ型微乳流法制备了纳米量级包裹型超细铁粉,由ＸＲＤ、ＳＥＭ、ＴＥＭ和ＩＲ谱测试表明：它属于表面活性剂包裹型超细微粒。平均粒径约１２０ｎｍ,微粒的密度为３．００ｇ／ｃｍ＾３。比饱和磁化强度σｓ＝９２．４Ａｍ＾２／ｋｇ,矫顽力Ｈｅ＝４３（Ｏｅ）,剩磁ｒ＝３．８９Ａｍ＾２／ｋｇ。将其用于制备磁流变液（ＭＲＦ）,具有良好的磁流变（ＭＲ）性能和优良的沉降稳定性。     

微乳液反应法制备草酸铜均匀微粒

在Ｔｒｉｔｏｎ ｘ－１００－ｎ－Ｃ６Ｈ１３ＯＨ／ｃ－Ｃ６Ｈ１２／水溶液（硝酸铜或草酸）体系Ｗ／Ｏ微乳液中，通过变换草酸和硝酸铜溶液的速度、温度和ｐＨ值而获得超细、方形的、管状的以及网络状的多种形态粒子，特别是制备得到方形和管状两种均匀胶体粒子。研究了影响粒子形态和大小的因素。     

Formation of Water-Soluble Dye-Doped Silica Particles

Formation mechanism of dye-doped silica particles less than 1 µm in diameters by the Stöber method was investigated. With increasing the content of dyes such as water-soluble porphyrin (TTMAPP) and laser dye (Nile blue), these dye-doped silica particles showed the similar tendency to the following characters: (1) Particle size increased, passed through the maximum at the dye content corresponds to the isoelectric point, and then followed by decrease; (2) Ratio of dimer and monomer of the incorporated dye decreased. In aqueous solution positively charged dyes showed good affinity with negatively charged SiO₂ primary particles from the early stage of the formation. Zeta potential of doped-silica particles was measured against nominal dye content: from non-doped to highly doped particles, their surface charge changed from negative to positive. The similar influence caused by positively charged dyes on the particle formation was also observed by Ca²⁺ doping.     

由硅溶胶生长单分散颗粒的研究

针对现行单分散二氧化硅颗粒制备方法的粒径预见性差、步骤繁琐、收率低等问题，研究了一种用硅溶胶作为种子，在氨、水和乙醇的混合溶液中通过水解正硅酸乙酯（ＴＥＯＳ）生长出单分散颗粒的简便方法。该方法仅在初始的悬浮液中滴加ＴＥＯＳ即可使种子正常生长，无须补充氨水以修正体系浓度的变化。最终的分散相浓度可达１０％（质量分数）。可选择生长的粒径范围在１微米以内并可精确控制。所得颗粒粒径分布偏差于Ｓｔｏｂｅｒ方法     

Sorption of Cobalt on Modified Silica Gel Materials

Various silica gel materials were chemically modified with imidazole, diaza-18-crown-6 (DA18C6) and dibenzod-18-crown-6 (DB18C6). The degree of functionalization of the covalently attached molecule was calculated from C, H, N analysis and ranged between 0.270 and 0.552 mmol/g (for sorbents with imidazole) and between 0.043 and 0.062 mmol/g (for sorbents with DA18C6 and DB18C6). The degree of functionalization depends on the reflux time and silica gel matrix used. Experimental sorption capacity ranged between 0.038 and 0.228 mmol/g (for sorbents with imidazole) and between 0.019 and 0.050 mmol/g (for sorbents with DA18C6 and DB18C6). Synthesized hexagonal mesoporous silica matrix MCM-41 with uniform pore diameter <40 Å was used too. Change of pore diameters of silica gel support to larger pores should have a positive influence on access of cobalt ion to sorption centers to increase of sorption capacity of sorbents. The sorption kinetics of cobalt and the influence of cobalt concentration, pH of various kinds of silica gel matrix with immobilized imidazole group in static conditions on sorption were measured. The sorption of cobalt in various conditions (pH, contact time of phases) with constant liquid-solid ratio (V/m = 50 ml/g) was studied. The distribution coefficients ranged between 200 and 50 000 ml/g (for imidazole), 85 and 120 ml/g (for DB18C6) and between 230 and 500 ml/g (for DA18C6) according to silica gel matrix used and according to the method of sorbent preparation. pH plays important role in the sorption of cobalt on prepared sorbents with immobilized crown ethers due to protonization of crown ethers. Protons significantly competes to sorption of cobalt in acidic solutions. The influence of presence of other heavy or toxic metals (Hg(II), Cd(II), Mn(II), Zn(II), Cu(II), Fe(III), Cr(III), Al(III) and the influence of sodium and potassium on sorption Co(II) from aqueous solutions was investigated. Sorption of cobalt decreases in order Hg > Cu > Cd > Zn, Fe > Mn > Al, Cr. The presence of sodium and potassium ions at concentration 0.05 mol/l significantly influences on the sorption of cobalt with sorbent with immobilized DB18C6 functional group.     

由硅溶胶生长单分散颗粒的研究

针对现行单分散二氧化硅颗粒制备方法的粒径预见性差、步骤繁琐、收率低等问题，研究了一种用硅溶胶作为种子，在氨、水和乙醇的混合溶液中通过水解正硅酸乙酯（TEOS）生长出单分散颗粒的简便方法．该方法仅在初始的悬浮液中滴加TEOS即可使种子正常生长，无须补充氨水以修正体系浓度的变化．最终的分散相浓度可达10％（质量分数）．可选择生长的粒径范围在1微米以内并可精确控制．所得颗粒粒径分布偏差优于Stber方法．讨论了种子数密度、生长环境和TEOS滴加速度对生长最终颗粒粒径分布偏差的影响     

柴油乳状液与微乳液的制备及节能效果研究

研究了用非离子表面活性剂制备含水柴油乳状液和微乳液伯条件，测定了掺水柴油在不同燃料条件下的放热量，结果表明，在供氧充分的条件下，水的掺入对燃烧热无贡献，若在大气中燃烧，掺水柴油以喷燃方式进料，一般掺水量以１０－２０％（Ｗ／Ｗ）时燃烧效率较高，若水中含有某些金属离子，掺水量达３０％，仍有较高的热效率，柴油微乳液的稳定性虽比柴油乳状液好，但只要两者的水量相同，燃烧时的放热是相同。     

Effects upon Nitrogen Sorption Analysis in Aerogels

Nitrogen sorption at 77 K is a standard technique for the characterization of mesoporosity. However, it seemed to be unable to detect the full, theoretically expected pore volume in high-porosity aerogels. Investigating this problem, we found that if only the sample is sufficiently equilibrated upon sorption, the full pore volume is detected regardless of its porosity. As insufficient equilibration also effects the pore size distribution deduced from the isotherm, highly erroneous results can be avoided if complete equilibration upon each sorption step is assured. For compliant aerogels the effect of sample deformation during analysis has to be taken into account. Copyright 2001 Academic Press.     

Synthesis of Strontium Ferrite Ultrafine Particles Using Microemulsion Processing

The strontium ferrite ultrafine particles have been prepared using the microemulsion processing. The mixed hydroxide precursor was obtained via the coprecipitation of Sr(2+) and Fe(3+) in a water-in-oil microemulsion of water/CTAB/n-butanol/isooctane. According to the investigation on the thermochemical properties by TGA/DTA and the phase analysis by XRD, it was shown that the precursor could yield pure strontium ferrite after calcination at 700 degrees C for 5 h while using an appropriate molar ratio of Sr/Fe in microemulsions. From TEM measurement, the diameters of the precursor and calcined particles were 3.8+/-0.7 and 50-100 nm, respectively. The magnetic properties characterized by a SQUID magnetometer showed that the saturation magnetization, remanent magnetization, coercivity, and squareness ratio were 55 emu/g, 28 emu/g, 492 Oe, and 0.51, respectively. The magnetization was also observed to increase with the decrease of temperature at 5-400 K. Compared with those reported earlier, the quite low coercivity implies the potential application of final product in the high-density perpendicular recording media. Copyright 2001 Academic Press.     

无溶剂及微乳液体系中脂肪酶催化红花油水解的动力学

 在无溶剂及二(2-乙基己基)丁二酸酯磺酸钠(AOT)/异辛烷/磷酸盐缓冲液微乳液体系中,研究了黑曲霉脂肪酶催化红花油水解反应的动力学. 结果表明,无溶剂及微乳液体系中反应的活化能分别为32.205和7.391 kJ/mol. 酶在无溶剂体系中的热稳定性高于微乳液中. 无溶剂及微乳液体系中的表观米氏常数分别为0.135和0.101 mol/L. 在两种体系中,乙醇对水解反应的抑制作用均为竞争性可逆抑制,且均在底物浓度大于0.819 mol/L时出现底物抑制现象. 结合胶团催化理论和酯键水解机理对两种体系中酶水解性能的差异进行了解释.     

O／W微乳液中聚吡咯超微粒子的制备

选择合适的ＳＤＢＳ／吡咯／Ｈ２Ｏ三组分Ｏ／Ｗ微乳液与吡咯单体共存的两相体系，以单体相为单体源，在Ｏ／Ｗ三组分微乳液中进行了吡咯聚合，所得聚吡咯粒子大小仅为２～３ｎｍ，分布较均匀，且具有较好的导电性能．     

Surface Characterisation of Cerium-Doped Silica Coatings Obtained by Sol-Gel

The chemical composition of cerium-doped silica coatings prepared via sol-gel were studied using X-ray photoelectron spectroscopy (XPS) in conjunction with Ar⁺-ion sputtering, Rutherford back-scattering spectroscopy (RBS) and photoluminescence (PL) spectroscopy. XPS results showed that cerium was incorporated in the silica network as Ce(III). The absence of PL emissions from Ce(III) was explained by a clustering of the ions producing a quenching of the luminescence. XPS combined with Ar⁺ and RBS showed that the distribution of Ce is not uniform across the coating, showing a maximum concentration in an inner layer of the coating.