BaFe2O4/BaSO4复合光催化剂的制备及降解罗丹明B废水的活性研究

采用化学法、传统溶胶凝胶法和低温烧结技术合成了BaSO₄、BaFe₂O₄和BaSO₄/BaFe₂O₄复合物光催化剂。X射线粉末衍射和傅里叶红外光谱分析表明,BaSO₄和BaFe₂O₄复合后未改变主晶格相的结构。表面形貌分析发现,BaSO₄颗粒细小均匀,BaFe₂O₄颗粒较大且形貌不规则;当二者复合后颗粒尺寸变化较为明显。紫外可见吸收谱分析表明,5%BaSO₄/BaFe₂O₄复合物光催化剂具有强的紫外可见光吸收能力;BaSO₄、BaFe₂O₄、5%BaSO₄/BaFe₂O₄和10%BaSO₄/BaFe₂O₄复合物光催化剂的E_g值分别为3.23、2.89、2.74、2.26 eV。光催化结果表明,5%BaSO₄/BaFe₂O₄光催化剂在降解罗丹明B染料方面比其他几种催化剂显示出了更高的光催化活性。光催化机理分析发现,空穴、羟基自由基和超氧自由基在染料降解过程中扮演了至关重要的角色。     

聚乙二醇4000对硫酸钡微粒形貌的调控作用

以水溶性高聚物聚乙二醇4000（PEG4000）为分散剂,研究了反应方式、聚乙二醇浓度、钡离子与硫酸根物质的量比等因素对硫酸钡微粒形貌和晶体结构的影响,通过扫描电镜（SEM）、透射电镜（TEM）、X射线粉末衍射（XRD）等手段对合成样品的形貌和结构进行了表征。结果表明,反应体系经陈化和回流过程,均有利于硫酸钡微粒“溶解与再生长过程”的发生,易于得到较大尺寸的硫酸钡微粒;随着聚乙二醇浓度的增加,所得硫酸钡晶体的形貌呈现从十字花形经片状向棒状结构的显著变化,且在合适聚乙二醇浓度时可以得到具有良好光泽性能的片状硫酸钡单晶结构。钡离子与硫酸根物质的量比的改变也能影响硫酸钡微粒的形貌而得到新颖的“鱼骨刺”形的纳米结构。     

微通道反应器合成纳米BaSO4颗粒及其在干片多功能层上的应用

以BaCl₂和Na₂SO₄为原料，采用微通道反应器制备得到立方形纳米BaSO₄颗粒，并通过SEM、XRD对其进行表征。考察了不同反应方式及微通道反应器结构、反应物体积流量、反应物浓度、反应温度、体积流量比对纳米BaSO₄颗粒大小和形貌的影响。实验结果表明：25℃下，体积流量为2.5 ml/min，反应物浓度为0.1 mol/L，体积流量比为5是应用于淀粉酶医用干片多功能层的纳米BaSO₄颗粒合成的最佳反应条件。与直接沉淀法相比，微通道反应器内制备出的纳米BaSO₄颗粒形貌规整，最终得到产物粒径为25～55 nm。将所制备的BaSO₄多功能层应用到淀粉酶医用干片中，颜色梯度明显，经反射光密度仪检测，信号值依次减小，且信号值变化曲线重复性、稳定性较好，说明制备的BaSO₄颗粒可应用于淀粉酶体外诊断试剂中多功能层上。     

超重力液相沉淀法制备纳米铁酸钴

针对磁力搅拌器制备纳米材料时存在粒径分布宽、分散不均匀的问题,采用撞击流-旋转填料床结合化学共沉淀法,以Fe（NO₃）₃·9H₂O、Co（NO₃）₂·6H₂O、NaOH为原料制备CoFe₂O₄纳米颗粒。研究了转速、液体流量、NaOH浓度以及晶化时间对CoFe₂O₄纳米颗粒粒径的影响;并与磁力搅拌器制备的CoFe₂O₄纳米颗粒在磁性能方面进行了对比。采用X射线衍射仪（XRD）、傅里叶红外光谱仪（FTIR）、透射电镜（TEM）、纳米粒度仪及振动样品磁强计（VSM）对产物的粒径形貌及磁性能进行表征。结果表明：CoFe₂O₄纳米颗粒的粒径随转速、液体流量和NaOH浓度的增加而减小,但随晶化时间的增加而增大。最佳工艺条件为：转速900r/min,液体流量60L/h,NaOH浓度3mol/L,晶化时间6h。此条件下制备的CoFe₂O₄纳米颗粒的粒径约为20nm,饱和磁化强度为75.43emu/g,较磁力搅拌器提高40%。     

双微乳液法制备纳米硫酸钡颗粒

在水溶液/TritonX-100/正己醇/环己烷组成的反相微乳液中,以氯化钡和硫酸钠为原料,通过沉淀反应,制备出类球形BaSO₄纳米颗粒,并通过XRD、SEM、TEM、FTIR对其进行表征。考察了三种反应方式、水/TritonX-100摩尔比（R）、反应物浓度以及助表面活性剂/表面活性剂摩尔比（P）对纳米BaSO₄颗粒大小和形貌的影响。同时考察了R对微乳液液滴大小和粒径分布的影响,并通过动态光散射技术（DLS）对微乳液液滴进行测定。实验结果表明：室温条件下,采用双微乳液法,R=17.97,P在2.11～4.22之间是纳米BaSO₄颗粒合成的最佳反应条件,反应物浓度对BaSO₄颗粒的大小和形貌几乎没有影响。在该反应条件下,合成出的类球形BaSO₄粒径为18～22 nm,产率可达87.5%。     

Preparation and characterization of transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency

Transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency were reported in this paper. First, zinc oxide (ZnO) precursor was synthesized via the homogeneous precipitation method and ZnO nanoparticles were then made by calcination of the precursor at different temperature. The structural properties of the as-prepared ZnO nanoparticles were studied in detail using thermogravimetry (TGA), differential thermal analysis (DTA), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and transmission electron microscopy (TEM), respectively. Transparent ZnO/epoxy nanocomposites were subsequently prepared from transparent epoxy (EP-400) and as-prepared ZnO nanoparticles via in situ polymerization. Optical properties of ZnO/epoxy nanocomposites, namely visible light transparency and UV light shielding efficiency, were studied using an ultraviolet-visible (UV-vis) spectrophotometer. The optical properties of the as-obtained nanocomposites were shown to depend on ZnO particle size and content. The nanocomposite containing a very low content (0.07% in weight) of ZnO nanoparticles with an average particle size of 26.7 nm after calcination at 350 °C possessed the most optimal optical properties, namely high-visible light transparency and high-UV light shielding efficiency, that are desirable for many important applications.     

High-gravity-assisted synthesis of aqueous nanodispersions of organic fluorescent dyes for counterfeit labeling

Organic fluorescent dyes have attracted wide interest because of their high photoluminescence quantum efficiencies. However, there are several application limitations arising from their hydrophobicity, poor dispersity and large particle sizes. These problems can be improved by preparing nanoparticles with a small size. Herein, we present a continuous approach to efficiently prepare an aqueous nanodispersion of water-insoluble organic fluorescent dye Nile red (NR) with monodispersed and uniform nanoparticles (35 nm) by high-gravity antisolvent precipitation in a rotating packed bed (RPB). In contrast, NR nanodispersions prepared using a traditional batch stirred tank (ST) had a broad size distribution (20–150 nm). Due to its small size effect and good dispersity in water, the RPB nanodispersion displayed significantly increased saturation solubility and much stronger fluorescent intensity compared to raw NR, and was obviously superior to the ST counterpart. Furthermore, NR nanodispersions were mixed with ink to draw fluorescent patterns on paper for counterfeit labeling.     

撞击流反应器制备纳米四氧化三铁的研究

在浸没式循环撞击流反应器中,以氨水为沉淀剂,用七水合硫酸亚铁和六水合三氯化铁为原料,采用共沉淀法制备了纳米四氧化三铁粒子。考察了搅拌转速、亚铁与三价铁物质的量比、反应温度和溶液pH对所得纳米四氧化三铁的分散性和粒径的影响。采用傅里叶红外光谱仪、透射电镜、X射线衍射仪等对制得的纳米粒子的结构和性能进行了表征。结果表明：用撞击流反应器制备纳米四氧化三铁粒子的最佳工艺条件：亚铁与三价铁物质的量比为1 ∶1,反应温度为40 ℃,搅拌转速为1 600 r/min,以氨水作沉淀剂,最佳pH控制在11.0左右。在上述条件下,可以制备出分散性好、纯度高、平均粒径为10 nm的四氧化三铁粒子。     

“超重力+”法可控制备透明纳米分散体及应用

纳米颗粒的分散是纳米材料应用的核心难题之一。新一代纳米材料——单分散纳米颗粒材料分散在溶剂中可形成具有良好透明性或明显丁达尔效应的纳米分散体，较传统纳米粉体材料更易于分散，展现出更优异的纳米效应及应用性能，是国际前沿研究方向。其中，低成本规模化可控制备高固含量、高稳定、高透明的纳米分散体仍面临巨大挑战。针对此问题，本文作者课题组面向终端工程应用需求，提出基于颗粒表面主动设计和修饰调控表面特性，利用超重力强化分子混合结晶过程的方法，有机耦合表面改性-分离过程，率先提出了超重力反应结晶-改性分离耦合的新方法，即“超重力+”法制备透明纳米分散体。本文总结了近年来本文作者课题组在透明纳米分散体“超重力+”法可控制备与应用方面的成果，并对下一步研究方向进行了展望。     

Particle Adhesion in Model Systems: 16. Barium Sulfate Particles on Glass and Protein Surfaces

The adhesion phenomena of monodispersed barium sulfate (BaSO₄) particles on gelatin-coated glass beads were evaluated using the packed column technique and compared with the same system in the absence of the protein.

Multilayer deposition was observed with the uncoated glass beads at pH 4, 5 and 6, while at pH 9, which is above the isoelectric point (pH ∼ 6) of BaSO₄ particles, monolayer deposition took place, even though the BaSO₄ particles and glass beads bore the same sign of charge. At pH = 10, no uptake was observed on the glass beads, but the addition of 10^-4 mol dm^-3 BaCl₂ induced multilayer deposition due to the adsorption of the Ba²⁺ cation on BaSO₄ particles, which causes a reversal of their charge to positive.

The formation of multilayers was found to occur over a much wider pH range on the gelatin coated glass beads.

BaSO₄ particles deposited in multilayers could not be removed from either glass beads or gelatin-coated glass beads by rinsing the loaded column with solutions of pH 11.5, but could be detached from monolayers on glass beads only.     

Numerical study on particle size distribution in the process of preparing ultrafine particles by reactive precipitation

Based on the population balance and mass balance in a reactive precipitation process, a numerical simulation model was developed to predict the particle size distribution (PSD) in the reactive precipitation process. The precipitation system of BaCl₂ with Na₂SO₄ to prepare BaSO₄ in aqueous solution was adopted to obtain ultrafine particles in a stirred precipitation reactor and the particle size distribution and the morphology of the particle were observed under transmission electron microscope. It was illustrated by the experimental observation of the micrographs of BaSO₄ particles obtained that apparent agglomeration occurred between the particles, which phenomenon must be taken into consideration in PSD modeling. The population balance equation was calculated by discretization method to obtain particle number and particle size distribution. By implementing the model, the reactive precipitation process in a batch reactor including reaction, nucleation, growth and agglomeration was simulated. The simulation results were validated by the experimental data of BaSO₄ precipitation. Further analysis was endeavored to explore the effects of some important factors such as the supersaturation degree and agglomeration on the evolution of the volume-based characteristic particle size and the variance of volume-based characteristic size of the particles. It was depicted that particle size and particle size distribution are controlled by the supersaturation degree and agglomeration between the particles. Stemming from the analysis in the context, the disciplinarian of the influences of these factors and the method for controlling particle size distribution were presented for the reactive precipitation process.     

Preparation of a porous nanocrystalline TiO2 layer by deposition of hydrothermally synthesized nanoparticles

In this work, a porous nanocrystalline anatase TiO₂ layer is prepared by tape casting a viscous dispersion of nanoparticles. Phase pure anatase titanium dioxide nanoparticles with a particle size of 10–20 nm are prepared by a very simple low temperature (100 °C) hydrothermal synthesis route in a pressure vessel, using only water as the medium and Ti(IV)-isopropoxide as starting material without additives. The size, shape and phase composition of the particles are studied by means of X-ray diffraction and transmission electron microscopy. A dispersion of the as-prepared nanoparticles with a narrow particle size distribution, confirmed by photon correlation spectroscopy, is prepared. After increasing the viscosity of this dispersion by addition of hydroxypropyl cellulose, anatase titanium dioxide layers are tape cast on a transparent conducting metal oxide substrate. Pores are induced by burning out the organic additive at 450 °C. The morphology and the final phase composition of the deposited TiO₂ layers are examined by X-ray diffraction and scanning electron microscopy.     

微通道反应器中反应沉淀过程的工艺研究

采用Y型和线型微通道反应器,成功制备出平均粒径为35～110nm、无因次方差为0.2～0.3的纳米BaSO4颗粒:同时利用TEM、BET及XRD分别对微反应器和普通反应釜合成的硫酸钡粉体性质进行了表征.实验结果表明,反应物流量增大,混合效率提高,平均粒径及方差下降;初始浓度或体积流量比增加,粒径下降:在相同的工艺条件下,通过较大尺寸Y型微反应器制备的颗粒粒径及方差略大于小尺寸Y型合成的,而线型微反应器合成的产物粒子粒径最小.     

纳米γ-氧化铁的制备及其吸附性能研究

以硝酸铁和十二烷基三甲基溴化铵为原料,采用固相法制备了γ-氧化铁纳米粒子。通过X射线衍射、氮气吸附-脱附、磁性测试等手段对γ-氧化铁样品进行了表征。研究了γ-氧化铁对有机染料直接耐酸大红4BS的吸附性能。结果表明,制备的γ-氧化铁样品为γ-氧化铁纳米粒子,平均晶粒尺寸为18.5 nm;γ-氧化铁的比表面积为83.2 m ²/g,孔容为0.25 cm ³/g,最可几孔径为3.8 nm,属于介孔范围;γ-氧化铁的最大饱和磁化强度为63.7 A·m ²/kg;介孔γ-氧化铁对直接耐酸大红4BS的吸附过程符合准二级吸附动力学模型;γ-氧化铁对直接耐酸大红4BS的吸附符合Langmuir吸附等温式,极限吸附量为113.3 mg/g;将γ-氧化铁脱附处理后可重复使用。     

微通道中原位分散技术可控制备氧化铜纳米流体及复合薄膜前体

疏水纳米颗粒分散于有机体系中形成的纳米分散体,具有独特的理化性质和重要的应用价值。其中,纳米颗粒的单分散性、均匀性和稳定性是决定纳米分散体性能的关键。以CuO纳米分散体作为纳米流体和复合薄膜前体这一典型体系为研究对象,通过设计平板型微通道实现了CuO纳米分散体制备过程中的液滴聚并和改性CuO纳米颗粒的原位分散。制备了颗粒体积分数达2%、平均粒径约30 nm的CuO-基础油纳米流体,该纳米流体具有良好的稳定性和达到0.184 W·m^-1·K^-1的较高热导率;制备的CuO-PDMS（聚二甲基硅氧烷）复合薄膜具有较强的抗菌性能和颗粒复合层稳定性。通过系统性实验研究,证明了原位分散方法在强化改性颗粒高效分散中的重要作用,确定了颗粒性能及分散行为对分散体性能的影响规律。     

Preparation of a Monodispersed Suspension of Barium Titanate Nanoparticles and Electrophoretic Deposition of Thin Films

A transparent and stable monodispersed suspension of nanocrystalline barium titanate was prepared by dispersing a piece of BaTiO₃ gel into a mixed solvent of 2-methoxyethanol and acethylacetone. The results of high-resolution transmission electron microscopy (HR-TEM) and size analyzer confirmed that the BaTiO₃ nanoparticles in the suspension had an average size of ∼10 nm with a narrow size distribution. Crystal structure characterization via TEM and X-ray diffraction indicated BaTiO₃ nanocrystallites to be a perovskite cubic phase. BaTiO₃ thin films of controlled thickness from 100 nm to several micrometers were electrophoretic deposited compactly on Pt/Ti/SiO₂/Si substrates. The deposited thin film had uniform nanostructure with a very smooth surface.     

Preparation of Aqueous Nanodispersions of Disperse Dye by High-Gravity Technology and Spray Drying

Disperse dyes are poorly water-soluble and difficult to stably disperse in an aqueous medium, which greatly limits their application in dyeing synthetic fibers. Micronization can solve this problem. Herein, a facile way to prepare stable aqueous nanodispersions of disperse dye (C.I. disperse yellow 54) is presented by combining high-gravity antisolvent precipitation in a rotating packed bed (RPB) with spray drying. The as-prepared product had an average particle size of 120 nm, which could be readily redispersed in water. Compared with raw dye, the wettability and dispersibility of disperse dye nanoparticles were remarkably improved. Furthermore, the dyeing properties of the nanodispersions were obviously better than those of the commercial dye, which was micronized by ball milling.     

Preparation and sedimentation behavior of conductive polymeric nanoparticles

A facile route to prepare Fe₃O₄/polypyrrole (PPY) core-shell magnetic nanoparticles was developed. Fe₃O₄ nanoparticles were first prepared by a chemical co-precipitation method, and then Fe₃O₄/PPY core-shell magnetic composite nanoparticles were prepared by in-situ polymerization of pyrrole in the presence of Fe₃O₄ nanoparticles. The obtained nanoparticles were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and laser particle size analyzer. The images indicate that the size of Fe₃O₄ particles is about 10 nanometers, and the particles are completely covered by PPY. The Fe₃O₄/PPY core-shell magnetic composite nanoparticles are about 100 nanometers and there are several Fe₃O₄ particles in one composite nanoparticle. The yield of the composite nanoparticles was about 50%. The sedimentation behavior of Fe₃O₄/PPY core-shell magnetic nanoparticles in electrolyte and soluble polymer solutions was characterized. The experimental results indicate that the sedimentation of particles can be controlled by adjusting electrolyte concentration, solvable polymers and by applying a foreign field. This result is useful in preparing gradient materials and improving the stability of suspensions.     

Preparation of Protein-Stabilized β-Carotene Nanodispersions by Emulsification–Evaporation Method

This work was initiated to prepare protein-stabilized β-carotene nanodispersions using emulsification–evaporation. A pre-mix of the aqueous phase composed of a protein and hexane containing β-carotene was subjected to high-pressure homogenization using a microfluidizer. Hexane in the resulting emulsion was evaporated under reduced pressures, causing crystallization and precipitation of β-carotene inside the droplets and formation of β-carotene nanoparticles. Sodium caseinate (SC) was the most effective emulsifier among selected proteins in preparing the nanodispersion, with a monomodal β-carotene particle-size distribution and a 17-nm mean particle size. The results were confirmed by transmission-electron microscopy analysis. SC-stabilized nanodispersion also had considerably high ζ-potential (−27 mV at pH 7), suggesting that the nanodispersion was stable against particle aggregation. Increasing the SC concentration decreased the mean particle size and improved the polydispersity of the nanodispersions. Nanodispersions prepared with higher β-carotene concentrations and higher organic-phase ratios resulted in larger β-carotene particles. Although increased microfluidization pressure did not decrease particle size, it did improve the polydispersity of the nanodispersions. Repeating the microfluidization process at 140 MPa caused the nanodispersions to become polydisperse, indicating the loss of emulsifying capacity of SC due to protein denaturation.     

硫酸铅在硼硅酸盐玻璃熔体中的溶解特性

针对高硫、高钠的高放废液玻璃固化过程中Na₂SO₄极易分解和分相的问题,本文提出在模拟高放废液中加入适量Pb(NO₃)₂溶液将Na₂SO₄转变成PbSO₄,再利用熔融法制备硼硅酸盐玻璃固化体。首次采用在钢铁材料中广泛应用的高温激光共聚焦显微镜原位观察PbSO₄在玻璃熔体中的溶解特性,并探究不同温度(800～1 150 ℃)下PbSO₄与硼硅酸盐玻璃混合熔制后的热稳定性以及玻璃体中的硫含量。结果表明:在硼硅酸盐玻璃中掺入6%(质量分数,以SO₃计)PbSO₄的样品在800 ℃和900 ℃为均匀的玻璃陶瓷,其中800 ℃时主要含SiO₂及少量BaSO₄、PbSO₄晶体,900 ℃时SiO₂晶体减少,BaSO₄晶体增多,PbSO₄消失并出现CaMgSi₂O₆晶体;样品在1 000 ℃时玻璃表面开始出现由PbO、BaSO₄、LiNaSO₄晶体组成的白色分相,在1 000～1 100 ℃时圆形PbO晶体逐渐长大,BaSO₄晶体由块状变为条状;样品在800～1 000 ℃时玻璃体中的硫含量基本保持不变,随着温度进一步升高硫含量迅速下降。