氢氧化铁溶胶制备条件对其电泳等性能的影响

In order to explore the optimum preparation conditions, effects of FeCl₃ dosage, hydrolysis temperature and dialysis time on the particle size, conductivity, pH and double layer potential (ζ) of Fe(OH)₃ sol were systematically studied. The ultraviolet-visible reflection spectrophotometry was used to track the particle size of Fe(OH)₃ sol. With the increase of FeCl₃ dosage, the particle size of the colloid increased, the reflectivity decreased and the reflection wavelength shifted to longer wavelength, which is in accordance with the quantum confinement effect theory. The excessive Cl^- would inhibit the conductivity, and the stability of Fe(OH)₃ sol with larger particle size would be worse. Because of the better synergistic effect of q/m and V/l under the action of electric field of 80 V with electrophoresis, the ζ of the Fe(OH)₃ sol prepared under the optimum conditions (c_FeCl3, 0.01 mol·L^-1; 100℃; dialysis time, 1 d) was 43.67 mV which was most close to the theoretical value of 44.00 mV.     

SBA-15的孔壁碳膜修饰对钴基催化剂结构与催化性能的影响

在惰性气体中焙烧SBA-15制得孔壁被碳修饰的SBA- 15C样品,以它和SBA-15为载体,采用等量浸渍法制备了负载型Co基催化剂,并运用X射线衍射、N2物理吸附、程序升温还原、NH3吸附量热等手段对样品进行了表征.结果表明,SBA- 15C仍保持原有的六方有序的中孔结构,但其孔壁经碳修饰后发生增厚,比表面积略有下降...     

后处理温度对ZrO2气凝胶超细粉织构和结构的影响

运用神效儿宝治疗小儿厌食症２１０例，总有效率为９５．２％，显效率为６２．４％。该药使用、携带方便、见效快，疗效短，无毒副作用。实验证明，该药能显著提高胃蛋白酶含量，减慢肠管推进性运动，提高动物耐疲劳、耐缺氧能力，提高巨噬细胞吞噬率及血清补Ｃ３含量，且无毒副。作用     

Influence of Preparation Conditions on the Catalytic Performance of MoNx/SBA-15 for Ammonia Decomposition

The influence of preparation conditions (e.g. H2-N2 ratios, final nitriding temperatures) on the performance of MoNx/SBA-15 catalysts for ammonia decomposition was investigated. The variation of catalytic activity with H2-N2 ratios may be attributed to the variation of surface compositions and particle sizes of the active components. The variation of nitriding temperatures leads to the formation of molybdenum nitride domains of varying compositions, which are responsible for the difference in their catalytic performance with respect to ammonia decomposition. At 923 K. ammonia could be completely decomposed using 15800 ml/h·gcat of GHSVNH,, which shows high performance for the catalytic decomposition of ammonia.     

Influence of Solvent Size on Structural Properties of Bottle-brush Polymers

We proposed a modified dissipative particle dynamics simulation model by which one can effectively avoid the bond-crossing problem, and investigated the effect of solvent size on the structural properties of bottle-brush polymers in dilute solution on the basis of this model. It was found that with the increase of solvent size, the radius of the gyration of the bottle-brush polymer decreases considerably in the athermal solvent but increases in the selective solvent favoring the backbone, respectively.     

焙烧条件对金催化剂的结构及其催化CO氧化性能的影响

采用共沉淀法和金属有机配合物固载法,分别制备了负载型金催化剂,并考察了焙烧条件对其催化CO氧化性能的影响。实验结果表明,焙烧温度和时间对催化剂的结构和活性的影响显著,不同的金属氧化物负载的金催化剂具有不同的最佳焙烧温度。DTA-TG分析结果确定了催化剂稳定结构的形成温度;XRD测试结果显示,在最佳焙烧条件下得到的催化剂,其载体为具有一定结晶度的金属氧化物。     

离子液体功能化有序介孔SBA-15孔壁定域化磷钨酸催化活性中心构建及其催化性能

采用溶胶-凝胶法合成了一种桥键嵌入型双咪唑离子液体功能化介孔硅基材料(Bis-PImBr-PMO-SBA-15),然后离子交换将Keggin型磷钨酸负载于其上,制备了PW-Bis-PImBr-PMO-SBA-15催化剂,并运用X射线衍射、N2吸附-脱附、透射电子显微镜、傅里叶变换红外光谱和热重分析等手段对其进行表征.结果表明,该催化剂具有SBA-15分子筛的有序六方孔道结构,且负载后的磷钨酸阴离子仍保持其完整的Keggin结构.在以水为溶剂,30%H2O2为氧化剂的苯甲醇氧化反应中,该催化剂表现出比均相的或负载于SBA-15表面的Keggin型HPW更高的催化活性,苯甲醇转化率和苯甲醛选择性分别可达95%和94%.离子液体的咪唑阳离子可调节磷钨酸阴离子的氧化-还原性能,从而有利于提高催化剂的催化活性..     

负载型TiO2/SBA-15的制备及其光催化还原CO2性能

以羧基改性的SBA-15(COOH/SBA-15)和钛酸四丁酯(TB)为原料,利用COOH/SBA-15表面上高分散的大量羧基将TB锚定,通过溶剂热处理得到高分散负载型TiO2/SBA-15催化剂.产物经XRD,Raman,FT-IR,TEM,N2吸脱附和UV-Vis表征,结果显示:所制备的TiO2/SBA-15催化剂为比表面大、结晶度较高的锐钛矿TiO2,TiO2均匀分散于SBA-15表面,此外,COOH/SBA-15有效抑制了TiO2晶粒的长大.以光催化还原CO2为探针反应,考察了TiO2/SBA-15催化剂在紫外光照射下的光催化性能.结果表明:相比于后处理浸渍法制备的光催化剂,本文制备的TiO2/SBA-15催化剂表现出了高的光催化还原CO2活性,主要产物为甲醇,且TiO2最佳负载量为16.5%,并对相关反应机理做了探讨.     

Influence of mesoporous structure type on the controlled delivery of drugs: release of ibuprofen from MCM-48, SBA-15 and functionalized SBA-15

Ordered mesoporous materials exhibit potential features to be used as controlled drug delivery systems, including their wide range of chemical compositions and their outstanding textural and structural properties. Therefore, it is possible to control the drug release kinetics by tailoring such parameters. In this paper, mesoporous materials such as MCM-48 and SBA-15, which present different pore sizes (3.7 and 8.8 nm) and structural characteristics (3D-bicontinuous cubic and 2D-hexagonal, respectively) have been synthesized to evaluate their application as drug delivery system and to determine their influence on release kinetic of ibuprofen. Moreover, a chemical modification of the SBA-15 mesoporous material with octadecyltrimethoxysilane has also been performed to study its influence on the release rate of ibuprofen. The structural characteristics (3D cubic and 2D hexagonal pore system) do not affect the release kinetic profiles of ibuprofen. On the contrary, the pore size affects highly to the release kinetic profiles from first-order kinetic to zero-order kinetic for MCM-48 and SBA-15, respectively. Moreover, the importance of surface functionalization was demonstrate through the very fast delivery of ibuprofen from SBA-15 mesoporous materials functionalized with octadecyl chains.     

Effects of Morphology and Structural Characteristics of Ordered SBA-15 Mesoporous Silica on Release of Ibuprofen

Three kinds of highly ordered SBA-15 mesoporous materials with different pore sizes and morphologies denoted as LPS-SBA-15 (stick-like with pore size 7.28 nm), CPS-SBA-15 (stick-like with pore size 5.96 nm) and T-SBA-15 (tablet-like with pore size 4.64 nm) have been prepared, characterized and employed as carrier materials. The release behaviors of the ibuprofen in a simulated body fluid from these mesoporous silica materials were studied. The influences of pore size and exterior morphologies of mesoporous silica on the release behaviors of ibuprofen have been investigated. It has been found that the release becomes fast with increasing of pore size and slow with extending of transport pathway, and that the release rate of ibuprofen from the three kinds of SBA-15 is LPS-SBA-15 > T-SBA-15 > CPS-SBA-15. The results show that the inner structure as well as the exterior morphologies of SBA-15 mesoporous silica can seriously affect the release behaviors of ibuprofen.     

Influence of the Synthetic Conditions on the Structural and Electrochemical Properties of Carbon Nano‐Onions

Thermal annealing of nanodiamonds with diameters of a few nanometers (in an inert atmosphere and at temperatures in the range: 1500–1800 °C) leads to the formation of carbon nano‐onions (CNOs) with diameters between 5 and 6 nm, which correspond to nanostructures with six to eight graphitic layers. The resulting spherical CNO structures were thermally modified under different atmospheres and characterized by SEM, TEM, thermogravimetric analysis and spectroscopic (Raman and diffuse reflectance infrared Fourier transform/FTIR) spectroscopy. The electrochemical properties of the CNOs prepared under different conditions were determined and compared. The results reveal that the CNOs show different structures with predominant spherical “small” carbon nano‐onions. The aim of this article is to investigate the impact of the CNO′s synthesis conditions on the resulting structures and study the effect of further thermal modifications on the sizes, shapes and homogeneity of these carbon nanostructures.     

Iron Oxide Supported on Al2O3 Catalyst for Methane Decomposition Reaction: Effect of MgO Additive and Calcination Temperature

Production of hydrogen is a challenging task and have significant impact in the recent scenario. The alumina supported iron oxide nanoparticle synthesized using non‐ionic surfactant Triton‐X was found very effective for steady production of hydrogen through methane decomposition reaction. The high surface area, easily reducible catalyst calcined at 500 °C and 800 °C temperature showed steady activity towards methane decomposition reaction. At a higher reaction temperature there was catalyst deactivation. The doping of MgO facilitated particle growth rendering the poor catalytic activity. The TPR study showed that reducibility of TPR was difficult in presence of MgO additive. The formation of Fe? Mg? Al solid solution confirmed by XRD study was found mainly responsible for the lower catalytic activity. The bamboo‐shaped carbon nanotube formed from 20 % Fe/Al₂O₃ catalyst which is mainly because of the poor wetting property of quasi‐liquid metal and carbon nanotube.     

Kinetic Studies of Donor–Acceptor Cyclopropanes: The Influence of Structural and Electronic Properties on the Reactivity

The kinetics of (3+2) cycloaddition reactions of 18 different donor–acceptor cyclopropanes with the same aldehyde were studied by in situ NMR spectroscopy. Increasing the electron density of the donor residue accelerates the reaction by a factor of up to 50 compared to the standard system (donor group=phenyl), whereas electron‐withdrawing substituents slow down the reaction by a factor up to 660. This behavior is in agreement with the Hammett substituent parameter σ. The obtained rate constants from the (3+2) cycloadditions correlate well with data from additionally studied (3+n) cycloadditions with a nitrone (n=3) and an isobenzofuran (n=4). A comparison of the kinetic data with the bond lengths in the cyclopropane (obtained by X‐ray diffraction and computation), or the ¹H and ¹³C NMR shifts, revealed no correlation. However, the computed relaxed force constants of donor–acceptor cyclopropanes proved to be a good indicator for the reactivity of the three‐membered ring.     

Effect of surface acidity and pore size of Al-substituted plugs-containing SBA-15 and MCM-41 silicas on the polymerization of THF

We reported here the simultaneous influence of surface acidity and pore size of Al-substituted hexagonal mesoporous silicas(Al-doped plugs-containing SBA-15 and Al-doped MCM-41) on polymerization of THF.These materials were directly synthesized by introduced aluminum isopropoxide into reaction mixture including surfactant and siliceous precursor.Al-doped plugs-containing SBA-15(denotes as PAS) samples not only possess typical two-step desorption isotherms,which implied PAS materials generated plugs in their mesochannel,but also exhibit larger pore size and thicker wall than that of Al-doped MCM-41(denotes as ACM), which implied PAS would have a great advantage on catalytic reaction involving large molecular(e.g.polymer of THF) in industrial point of view.To investigate catalytic activity of PAS and ACM with moderate acidic sites the polymerization of THF in the presence of acetic anhydride was carried out.The results showed PAS exhibiting good performance on polymerization of THF.Such result could be related to the large pore size and moderate acidic sites.     

Effect of Calcination Temperature on the Structural,Thermodynamic, and Optical Properties of MoO3 Nanoparticles

Temperature dependence of the structural, thermodynamic, and optical properties of MoO₃ nanoparticles synthesized using sol–gel and sonication methods were studied. MoO₃ nanoparticles showed variation in crystallite shape from hexagonal to orthorhombic and crystallite size in the range 3.05–5.21 nm with bandgap in the range 4.11–4.36 eV with change in the calcination temperature and the method of synthesis. Rietveld refinement of the X‐ray diffraction (XRD) data confirmed the crystallite phase transition with space group PE and Pbnm with change in the lattice parameter ratio. Activation energy was calculated using XRD and TGA–DSC (thermogravimetry–differential thermal analysis) data and was found to be close to 4 kJ/mol. The bandgap fluctuation was due to the size dependence of the blue shift, which indicates strong quantum confinement due to the Bohr radius effect. Optical parameters such as the extinction coefficient, refractive index, optical conductivity, dielectric functions, and Urbach energy were calculated and found to depend on electron–phonon interactions.     

Influence of photoinitiator and curing conditions on polymerization kinetics and gloss of UV-cured coatings

Polymerization kinetics and gloss of different formulations of coatings at different UV curing conditions were studied. The results showed that the photoinitiator type, its concentration, sample coating thickness, as well as the UV light intensity were the most significant factors affecting the polymerization course and the gloss of UV-cured films. The increasing concentration of the photoinitiator and the UV light intensity significantly decreased the gloss of the cured surface. The influence of the sample coating thickness on the kinetics and final gloss was also considerable.     

SBA-15分子筛羟基结构性质及其催化活性的理论研究

采用密度泛函方法对SBA-15分子筛簇模型化合物进行了计算模拟,重点研究了簇模型化合物羟基的几何构型和电子结构性质。从键级、前线分子轨道、静电势和质子化能等方面探讨了表面羟基的酸碱及氧化还原性质。分子筛模型化合物的静电势图显示SBA-15分子筛表面孤立羟基的H原子为分子筛表面的L酸性位,而氢键羟基的O原子则为分子筛表面的B碱性位。分子筛的前线分子轨道研究发现,表面羟基是分子筛表面的氧化还原活性位。计算得到的羟基SiO-H键级及形成的氢键键级分别在0.677 5～0.710 5和0.055 7～0.092 6范围,计算羟基OH的质子化能在1 471～1 589 kJ.mol-1范围。考察分子筛表面的质子化能显示未参与形成氢键的羟基H质子具有较强的B酸性。     

Influence of Adding Molybdenum on Structure and Performance of FexOy/SBA-15 Catalysts in Selective Oxidation of Propene

Mixed iron and molybdenum oxide catalysts supported on nanostructured silica, SBA-15, were synthesized with various Mo/Fe atomic ratios ranging from 0.07/1.0 to 0.57/1.0. Structural characterization of as-prepared Mo_xO_y_Fe_xO_y/SBA-15 samples was performed by nitrogen physisorption, X-ray diffraction, and DR-UV-Vis spectroscopy. Adding molybdenum resulted in a pronounced dispersion effect on supported iron oxidic species. Increasing atomic ratio up to 0.21Mo/1.0Fe was accompanied by decreasing species sizes. Strong interactions between iron and molybdenum during the synthesis resulted in the formation of Fe−O−Mo structure units, possibly Fe₂(MoO₄)₃-like species. Reducibility of Mo_xO_y_Fe_xO_y/SBA-15 catalysts was investigated by temperature-programmed reduction experiments with hydrogen as reducing agent. The lower reducibility obtained when adding molybdenum was ascribed to both dispersion and electronic effect of molybdenum. Catalytic performance of Mo_xO_y_Fe_xO_y/SBA-15 samples was studied in selective gas-phase oxidation of propene with O₂ as oxidant. Adding molybdenum resulted in an increased acrolein selectivity and a decreased selectivity towards total oxidation products.     

Effect of Dielectric Constant of Solvents on the Particle Size and Bandgap of La/SnO2‐TiO2 Nanoparticles and Their Catalytic Properties

Lanthanum (La) supported on tin oxide‐titanium oxide (SnO₂‐TiO₂ ) nanoparticles were prepared by a sol–gel method followed by a hydrothermal method. Effect of different solvents (ethyl acetate, benzyl alcohol, ethylene glycol) on the particle size and catalytic activity was investigated. The nanomaterial was characterized by transmission electron microscopy, powder X‐ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, and energy dispersive X‐ray. The catalytic and optical properties were studied using solid‐phase spectrophotometry and ultraviolet–visible spectroscopy, respectively. Gas chromatography‐mass spectrometry (GC‐MS) was used to detect the intermediates during the catalytic degradation of methylene blue. It was observed that with decrease in the dielectric constant (ε) of the solvent, the bandgap and particle size decrease and catalytic efficiency increases. Hence, the highest catalytic activity was observed with the solvent having the least dielectric constant.