大直径W1/O/W2乳粒的稳定性

在准静态条件和旋转流体场中采用乳液微封装技术制备约2 mm的大直径W1/O/W2乳粒,研究了有机相浓度和水溶性聚合物浓度对W1/O/W2乳粒稳定性的影响。从乳粒受力和变形的角度,探索了旋转流体场对W1/O/W2乳粒动力学稳定性的增强作用机制。研究表明：无论是在准静态条件下还是旋转流场中,乳粒稳定性都随聚苯乙烯浓度单一上升,随聚乙烯醇浓度呈现先上升后下降的趋势;相对于准静态条件,旋转流体场在一定条件下对大直径W1/O/W2乳粒的动力学稳定具有明显增强作用。     

Au/Al2O3催化剂的UV-Vis谱研究

研究了十六烷基三甲基溴化铵 (CTAB) /正己醇 /水体系的W/O微乳体系中 ,几种主要实验参数对用NaBH4还原氯金酸溶液制得的金纳米粒子大小的影响。实验结果表明 :微乳体系中水与表面活性剂的摩尔比rw 在所研究的范围内对金粒子大小影响不大 ,而氯金酸溶液的浓度对金粒子大小影响较大。通过优化制备条件 ,用两种不同的方法制备了Au/Al2 O3 催化剂 ,并用紫外 可见光谱、透射电镜 (TEM)和X射线衍射(XRD)对其进行表征 ,初步考察了不同制备方法对催化剂中活性组分Au粒大小的影响     

电场作用下S修饰C24N24从CO2/N2混合气体中选择性吸附CO2的第一性原理计算

在燃烧后气体中选择性捕获CO₂,对减缓因CO₂浓度过高引发的环境问题具有十分重要的意义.本文采用第一性原理计算的方法,研究了外加电场作用下S修饰C₂₄N₂₄富勒烯(S@C₂₄N₂₄)对CO₂的选择性吸附性能.首先研究了S@C₂₄N₂₄的结构和性质,发现其具有良好的稳定性.其次,研究了无电场时S@C₂₄N₂₄对CO₂的吸附行为,发现其吸附为弱的物理吸附.另外,进一步研究了外加电场作用下S@C₂₄N₂₄对CO₂的吸附行为.结果表明,结合距离(CO₂与S)和CO₂的键角(O=C=O)随电场的增大而减小;当电场增加到0.018 a.u.时,物理吸附转变为化学吸附.关闭电场时,化学吸附又转化为物理吸附.此外,即使在相同的电场条件...     

氧离子导体La2Mo2-xMxO9(M=Cr,W)的理论研究

采用第一性原理方法研究了高温β-La₂Mo₂O₉中Mo被Cr或W取代后晶体的结构性质和高温相稳定性.研究发现Cr和W分别倾向于占据具有4配位数和5配位数的Mo位.W取代体系晶胞参数相对取代浓度非线性变化.该非线性变化与W离子取代位置配位数降低以及体系内La—O和Mo(W)—O平均键长非线性变化有关.内聚能计算表明W取代Mo后能够有效稳定高温相结构,降低相变温度.La₄Mo₃W₁关键词： 氧离子导体 第一性原理 晶体结构 相稳定性     

钒掺杂W18O49纳米线的室温p型电导与NO2敏感性能

钨氧化物纳米线在高灵敏度低功耗气体传感器中极具应用潜力, 且通过掺杂改性可进一步显著改善其敏感性能. 本文以WCl₆为钨源, NH₄VO₃为掺杂剂, 采用溶剂热法合成了钒掺杂的W₁₈O₄₉纳米线. 利用扫描电镜、透射电镜、X射线衍射、X射线光电子能谱仪表征了纳米线的微结构, 并利用静态气敏性能测试系统评价了掺杂纳米线的NO₂敏感性能. 研究结果表明: 五价钒离子受主掺杂进入氧化钨晶格结构, 抑制了纳米线沿轴向的生长并导致了纳米线束的二次集聚; 室温下, 钒掺杂W₁₈O₄₉纳米线接触NO₂气体后表现出反常的p型响应特性; 随工作温度逐渐升高至约110 ℃时, 发生从p型到n型的电导特性转变; 该掺杂纳米线气敏元件对浓度低至80 ppb (1 ppb=10^-9) 的NO₂气体具有明显的室温敏感响应和良好的响应稳定性. 分析并探讨了钒掺杂W₁₈O₄₉纳米线的高室温敏感特性及其p-n电导转型机理, 认为钒掺杂W₁₈O₄₉纳米线在室温下的良好敏感响应及反常p型导电性与掺杂纳米线表面高密度非稳表面态诱导的低温气体强吸附有关. 关键词： 氧化钨 纳米线 气体传感器 室温灵敏度     

重入自旋玻璃尖晶石系统CoxZn1-x(FeyCr1-y)2O4中的微波磁共振

研究了具有重入自旋玻璃转变的尖晶石系统Co_xZn_1-x(Fe_yCr_1-y)₂O₄(0.4≤x≤0.8,y=O.5,0.8)中的微波磁共振,获得了共振线型、共振线宽、共振场、g因子、积累强度等共振参数与温度的依赖关系,并研究了磁性离子Co²⁺的浓度对共振线宽的影响。采用自旋成团效应及局域混乱场模型讨论了这些实验现象的机制,认为在一定条件下自旋团的形成、发展 关键词：     

水包油乳液的流变特性和黏度实验研究

采用超声波乳化法制备了不同类型的水包油乳液,对其粒径、流变特性、黏度等物性进行了表征。结果表明:O/W乳液的粒径随超声处理时间的延长而逐渐变小,油的浓度对粒径的影响较小,导热油乳液比橄榄油乳液具有更大的粒径。实验制备的不同质量分数、不同粒径、不同乳化剂含量的O/W乳液均可视为牛顿流体,这些O/W乳液的黏度随温度升高而减小,随着粒径的减小、油和乳化剂浓度的增大而增加。基于实验数据,采用多元非线性回归分析法和人工神经网络法为O/W乳液建立了新的黏度模型,这些模型考虑了流体的热物理性质、油浓度、油滴尺寸和温度的影响。     

超声场对钛基PbO2电极电化学氧化Cr3+过程电流效率的影响

本文研究了超声场对Ti／SnO2 Sb2O3／PbO2电极电化学氧化Cr3 过程的影响,探讨了在不同的操作电流密度、反应温度、硫酸浓度及Cr3 浓度下,超声场对硫酸介质中Cr3 电化学氧化生成Cr2O72-过程中的电流效率的影响,并用扫描电镜对有无超声场时不同反应时间下的电极形貌进行了分析。实验结果表明:在相同的反应条件下,有超声场作用时Cr3 电化学氧化过程的电流效率明显高于无超声场时的电流效率。扫描电镜测定发现,有超声场作用时不同反应时间下电极的形貌有明显的变化。     

Eu3+掺杂Gd2W2O9和Gd2（WO4）3纳米荧光粉发光性质研究

采用共沉淀法制备了不同Eu3+掺杂浓度的Gd2W2O9和Gd2(WO4)3纳米发光材料.通过对纳米材料样品的X射线衍射谱(XRD)和场发射扫描电镜(FE-SEM)照片的观察和分析,对样品的结构和形貌进行了表征.测量了各样品的发射光谱、激发光谱,计算了各样品的部分J-O参数和Eu3+5D0能级量子效率,绘制了不同基质中Eu3+发光的浓度猝灭曲线,对Eu3+掺杂的Gd2W2O9和Gd2(WO4)3纳米发光材料的光致发光性质进行了研究.实验结果证明,与较常见的Gd2(WO4)3:Eu一样,Gd2W2O9:Eu中Eu3+5D0→7F2跃迁的红色发光也能被395nm和465nm激发光有效激发,具有近紫外(蓝光)相对激发效率高,猝灭浓度大的优点,有潜力成为高效的近紫外(蓝光)激发白光LED用红色荧光粉材料.     

金属醇盐法制备Ta2O5气凝胶

以乙醇钽为前驱物,采用金属醇盐溶胶-凝胶技术,获得了Ta2O5湿凝胶,分析了不同条件下的溶胶-凝胶过程,并初步探讨了凝胶过程机理。Ta2O5的溶胶-凝胶过程主要受到水量、催化剂用量及钽源浓度等因素的影响：体系在强酸性条件下凝胶,且随着酸性的增强,体系凝胶时间明显缩短;当水量较少时,凝胶时间随水量的增加而增加,但当水量增加到一定程度时,体系凝胶时间基本不变;实验证明,通过增大溶剂用量,体系凝胶时间延长,气凝胶理论密度降低。通过对溶胶-凝胶过程的控制,结合超临界干燥技术,获得了密度低至44 mg/cm3的Ta2O5气凝胶样品。     

Effect of ultrasonic power on the stability of low-molecular-weight oyster peptides functional-nutrition W1/O/W2 double emulsion

Ultrasonic-assisted treatment is an eco-friendly and cost-effective emulsification method, and the acoustic cavitation effect produced by ultrasonic equipment is conducive to the formation of stable emulsion. However, its effect on the underlying stability of low-molecular-weight oyster peptides (LOPs) functional-nutrition W₁/O/W₂ double emulsion has not been reported. The effects of different ultrasonic power (50, 75, 100, 125, and 150 W) on the stability of double emulsions and the ability to mask the fishy odor of LOPs were investigated. Low ultrasonic power (50 W and 75 W) treatment failed to form a well-stabilized double emulsion, and excessive ultrasound treatment (150 W) destroyed its structure. At an ultrasonic power of 125 W, smaller particle-sized double emulsion was formed with more uniform distribution, more whiteness, and a lower viscosity coefficient. Meanwhile, the cavitation effect generated by 125 W ultrasonic power improved storage, and oxidative stabilities, emulsifying properties of double emulsion by reducing the droplet size and improved sensorial acceptability by masking the undesirable flavor of LOPs. The structure of the double emulsion was further confirmed by optical microscopy and confocal laser scanning microscopy. The ultrasonic-assisted treatment is of potential value for the industrial application of double emulsion in functional-nutrition foods.     

聚-α-甲基苯乙烯空心微球制备过程中的缺损研究

基于二次乳化技术产生W1/O/W2双重乳液,采用乳液微封装技术制备聚--甲基苯乙烯(PAMS)空心微球,研究了部分工艺参数对PAMS微球缺损形态和比例的影响。实验结果表明:薄壁微球的低强度导致了微球表面缺损。当微球壁厚一定时,有3个因素影响缺损微球比例:W2相中聚乙烯醇质量分数、CaCl2质量分数和O/W2的相比,当它们分别为1.0%,1.5%,0.01时,薄壁(2 m)微球的缺损比例低于40%,球壳内也无气泡存在。     

聚-α-甲基苯乙烯空心微球制备过程中的缺损研究

基于二次乳化技术产生W1/O/W2双重乳液,采用乳液微封装技术制备聚--甲基苯乙烯(PAMS)空心微球,研究了部分工艺参数对PAMS微球缺损形态和比例的影响。实验结果表明：薄壁微球的低强度导致了微球表面缺损。当微球壁厚一定时,有3个因素影响缺损微球比例：W2相中聚乙烯醇质量分数、CaCl2质量分数和O/W2的相比,当它们分别为1.0%,1.5%,0.01时,薄壁(2 m)微球的缺损比例低于40%,球壳内也无气泡存在。     

空气放电非平衡等离子体的模拟计算

基于空气放电非平衡等离子体动力学,对空气放电进行了数值计算,分析了放电后等离子体中的主要粒子（N2(v6),N2(A3),O2(a1),O和O3）数密度随起始温度、电子数密度和约化场强的变化趋势。计算结果表明,随着初始温度的升高,空气放电产生的粒子数密度增加。温度为300 K时,放电产生的O原子数密度最大值约为4.90×7 cm-3,而当温度升高到400 K和500 K时,O原子数密度的最大值则相应地增加到5.2×1010 cm-3和5.51×1010 cm-3。约化场强的影响与温度类似,其中氮气的振动激发态N2(v6)数密度随约化场强的变化幅度不明显。电子数密度增加,粒子数密度大幅增加,氮分子的激发态N2(A3)粒子数密度与电子数密度保持严格的线性关系。     

Polystyrene/Fe3O4 magnetic emulsion and nanocomposite prepared by ultrasonically initiated miniemulsion polymerization

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation.     

双乳液液滴形变及破碎特性

本文基于VOF（Volume of Fluid）相界面追踪方法,建立了不可压缩W₁/O/W₂双乳液液滴动力学模型并进行了数值求解,模拟了双板平行剪切流条件下液滴在流场中的稳定变形与破碎过程。研究结果表明:液滴的稳定变形程度随着毛细数的增大而加剧,且双乳液内液滴的变形程度要明显小于液滴整体变形程度;液滴雷诺数为0.05时,存在一个0 57～0.58之间的临界毛细数,当液滴毛细数小于临界毛细数时,液滴只发生稳定变形,反之则发生破碎。     

Ultrasound-assisted multilayer Pickering emulsion fabricated by WPI-EGCG covalent conjugates for encapsulating probiotics in colon-targeted release

This study demonstrated the influences of ultrasound-assisted multilayer Pickering double emulsion capsules on the pasteurization and gastrointestinal digestive viability of probiotic (L. plantarum) strain liquid. Firstly, the role of ultrasonic homogenization on the morphology of W₁/O/W₂ double emulsions were studied. The double emulsion formed by ultrasonic intensity at 285 W had a single and narrow distribution with smallest droplet size. The double emulsion particles were then coated with chitosan(Chi), alginate (Alg), and CaCl₂(Ca). The multilayer emulsion after pasteurization and gastrointestinal digestion both had the highest viability at 5 coating layers, but its particle size (108.65 μm) exceeded the limit of human oral sensory (80 μm). It could be noted that the deposition of 3–4 layers of coating had similar activity after pasteurization/GIT digestion. And droplets with 3 layers of coating were the minimum and most available formulation for encapsulated probiotics (L. plantarum). Hence, the results suggest that the use of ultrasound-assisted multilayer emulsions encapsulated with probiotics in granular food and pharmaceutical applications is a promising strategy.     

Electro-hydrodynamic behavior and interface instability of double emulsion droplets under high electric field

Dynamics of multiphase flow under high voltage has attracted extensive research interests due to its wide industrial applications. In this paper, numerical solution of electro-hydrodynamic behavior and interface instability of double emulsion droplet is presented. Level set method and leaky dielectric model coupled with Navier-Stokes equation are used to solve the electro-hydrodynamic problem. The method is validated against the theoretical analysis and the simulation results of the other researchers. Double emulsion droplet with inner droplet (core) and outer droplet (shell) phases immersed in continuous phase is subjected to high electric field. Shell/continuous and core/shell interfaces of the droplet undergo prolate-oblate or oblate-prolate deformation depending on the extent of the penetration of electric potential and sense of charge distribution at the interfaces. The deformation of the shell deviates from theory at larger volume fraction of core for oblate-prolate case whereas it follows theory for prolate-oblate case. The interfaces showing oblate-prolate deformation split at the poles whereas, for prolate-oblate, they split away along the equator. The re-union of the interfaces under high electric field results with production of daughter droplet at the core. The large decrease in critical electric field for oblate-prolate case shows their less interface stability at larger volume fraction of core. When the core is eccentric, the electric field drives it towards the shell center or to the shell/continuous interface depending on electrical parameters. The study is beneficial in understanding the electro-hydrodynamic behavior of emulsion droplets and efficient design of related industrial processes.     

Ultrasound-assisted production of palm oil-based isotonic W/O/W multiple nanoemulsion encapsulating both hydrophobic tocotrienols and hydrophilic caffeic acid with enhanced stability using oil-based Sucragel

In this work, the effects of thickeners and tonicity towards producing stable palm oil-based water-in-oil-in-water (W/O/W) multiple nanoemulsion using ultrasound and microfluidizer were investigated. Palm oil, Sucragel, polyglycerol polyricinoleate, Tween 80, Xanthan gum, and NaCl were used. W/O/W was formed under the optimized conditions of ultrasound at 40% amplitude and for 180 s of irradiation time, whereas for the microfluidizer, the optimized conditions were 350 bar and 8 cycles. This is the first work that successfully utilized Sucragel (oil-based thickener) in imparting enhanced stability in W/O/W. W/O/W with isotonic stabilization produced the lowest change in the mean droplet diameter (MDD), NaCl concentration, and water content by 1.5%, 2.6%, and 0.4%, respectively, due to reduced water movement. The final optimized W/O/W possessed MDD and dispersity index of 175.5 ± 9.8 and 0.232 ± 0.012, respectively. The future direction of formulating stable W/O/W would be by employing oil phase thickeners and isotonicity. The observed ~12 times lesser energy consumed by ultrasound than microfluidizer to generate a comparable droplet size of ~235 nm, further confirms its potential in generating the droplets energy-efficiently.