ZnO/Ag纳米复合材料的制备及电学性能研究

在室温下,利用超声活化法将机械研磨13h的Zn粉在V(水)∶V(环己烷)=19∶1的分散体系中合成ZnO纳米颗粒悬浮液,然后通过光还原AgNO3制备出ZnO/Ag纳米复合材料。并用X射线粉末衍射仪(XRD)、透射电子显微镜(TEM)对ZnO/Ag复合颗粒表征,用扫描电子显微镜(SEM)和探针台I-V测试仪对ZnO/Ag复合薄膜表征和电学性能测试,通过XRD和TEM得出,超声合成的ZnO具有六方纤锌矿结构,长约20nm的短棒状;经光还原沉积在其表面的纳米Ag呈现面心立方结构,直径约为5nm。通过SEM和I-V伏安特性曲线得出,干燥温度对复合结构有较大影响,60℃干燥的复合薄膜比较致密均匀,导通电压大约2V左右,在100℃时开始转变为有氧化锌附着的枝状银网状复合物,导通电压在0.02V左右,通过控制干燥温度可改变复合薄膜中ZnO和Ag的结合方式以及相应的电学性能。     

声化学法制备均匀分散的ZnO纳米晶(英文)

采用超声化学方法制备ZnO纳米颗粒,透射电子显微镜(TEM)测试结果显示,合成出的ZnO纳米颗粒尺寸均匀,形状规则。而X-射线衍射(XRD)结果表明,提高反应温度可以促进ZnO的生长。因而,对于合成单一分散的ZnO纳米晶而言,声化学方法是一种非常简便的方法。     

纳米Zn/ZnO复合结构的光催化活性

采用干法室温振动研磨的方法制备纳米Zn粉,纳米Zn水解制备纳米Zn/ZnO复合结构。光催化实验证明在太阳光和紫外光照射时,纳米Zn/ZnO复合结构具有优良的光催化性能。TEM检测表明,经11h研磨的Zn粉粒度分布在10～20nm之间,纳米Zn水解反应生成的固相产品,纳米ZnO与未完全反应的纳米Zn构成棒状与片状共存的独特结构,XRD分析表明产物中仅含有Zn和ZnO两种物质;UV-Vis谱显示纳米Zn/ZnO复合体在可见光区的吸收强度明显高于纳米ZnO颗粒,颗粒尺寸减小引起激子吸收峰蓝移,与体相材料相比纳米颗粒有更高的光催化氧化-还原能力。     

空气中热氧化电沉积Zn纳米晶制备一维ZnO纳米针及其生长机制与场发射效应的研究

在金属基板表面电沉积一层金属Zn纳米晶，将该纳米晶置于高温炉中，通过热氧化法成功制备了一维ZnO纳米针。研究了不同的热氧化温度因素对一维ZnO纳米针的制备及其形貌的影响。在本方法中，一维ZnO纳米针材料对应于初始电沉积层的Zn纳米晶颗粒，这与其他方法中ZnO的生长机制不同，可以认为本方法的ZnO的生长遵从自催化扩散机制。同时，研究了一维ZnO纳米针薄膜的场发射效应。     

纳米氧化锌的溶剂热法合成及其光学性能

以醋酸锌为原料,以乙二胺一水为混合溶剂,利用溶剂热法低温快速制备出分散均匀的氧化锌(ZnO)纳米粒子.探讨了溶剂热条件如温度和时间对于ZnO纳米晶的形成及其形貌和光学性能的影响.X-射线粉末衍射和能量散射x-射线能谱分析表明,产物是纯的六方纤锌矿结构的ZnO.透射电镜形貌观察显示,产物为均匀纳米粒子,直径为20～30 nm.所合成粉体紫外可见光谱表明,其紫外吸收大约为2.98eV,计算其直接带隙宽度为3.10eV.光致发光光谱显示ZnO纳米粒子具有良好的结晶性和光学性质.     

Zn0.98Nd0.02O室温拉曼特性和伏安特性

通过固相反应工艺制备了Zn0.98Nd0.02O纳米颗粒,射频磁控溅射技术在Si(111)衬底上制备了Zn0.98Nd0.02O薄膜。应用XRD、AFM以及拉曼光谱等手段,分析了Zn0.98Nd0.02O纳米颗粒与薄膜的结构,并测试了Zn0.98Nd0.02O薄膜的室温伏安特性。表明Nd掺杂没有改变ZnO纤锌矿结构,Zn0.98Nd0.02O颗粒为纳米多晶粉末态,其薄膜为沿(100)、(101)方向生长的纳米多晶结构,表面形貌粗糙。拉曼光谱分析表明,Zn0.98Nd0.02O颗粒的局部应力增大,晶格畸变缺陷增加,缺陷态比较复杂,导致拉曼峰发生频移。Zn0.98Nd0.02O薄膜的室温I-V曲线表明了Zn0.98Nd0.02O薄膜的非线性导电特性。其非线性导电特性源于,薄膜中的载流子受外加电场在薄膜中所产生热激发进入导带导电,环境光中能量高于ZnO带隙的光子引起的光电导效应,以及薄膜中纳米粒子间的隧穿导电。在光辐照作用下,提高了薄膜内浅施主缺陷浓度,降低了薄膜的表面电阻率,增强了Zn0.98Nd0.02O薄膜的导电能力。     

一种制备ZnO纳米颗粒的新方法

提出了一种制备ZnO纳米颗粒的新方法。在金属钠的液氨溶液中还原硝酸锌,所形成的金属Zn自然氧化而制得ZnO颗粒。为了研究表面修饰对产物形貌、粒径和性能的影响,制备了十二烷基磺酸钠（SDS）修饰的ZnO纳米颗粒。采用X射线粉末衍射仪（XRD）、透射电子显微镜（TEM）、傅立叶变换红外光谱仪（FT-IR）、热重及差热分析仪（TG-DTA）等手段对产物进行了表征。结果表明采用该方法可制得具有六方纤锌矿结构的ZnO颗粒,未修饰ZnO颗粒团聚较为严重;修饰的ZnO纳米颗粒呈棒状,分散较好。红外和热分析表明SDS修饰在了ZnO纳米颗粒表面。测试了所制备ZnO颗粒的紫外可见吸收（UV-Vis）和光致发光（PL）谱,均出现了ZnO的特征谱带。提出的方法也适用于制备其它金属或氧化物纳米材料。     

制备室温纳米ZnO脱硫剂方法的研究

为了提高ZnO脱硫剂的室温硫容及脱硫精度,对直接沉淀法进行了工艺改进,并利用动态实验以及XRD和XPS等表征手段对纳米ZnO脱硫剂进行了结构和效能分析.研究表明,通过在沉淀反应后添加Na2CO3溶液,解决了直接沉淀法阴离子难洗涤、颗粒易团聚、粒径分布不均等缺点,制备出粒径只有8.00 nm、颗粒均匀分散性好的纳米ZnO脱硫剂,其室温脱硫活性是同条件下其他方法制备纳米ZnO脱硫剂脱硫活性的5～10倍,且其脱硫产物中有不同于ZnS中的晶格硫的新硫物种产生.     

染料包覆胶态银纳米粒子掺杂的有机复合膜的制备与光吸收特性

为避免传统的湿化学法制备纳米掺杂复合材料中热处理给材料性能带来的负面影响,提出了一种简易可行的工艺方法:通过胶体化学法制备出稳定的胶态银纳米粒子分散系,以它为纳米粒子来源,使有机染料罗丹名6G(R6G)分子包覆到银纳米胶粒表面,将该胶体分散系均匀掺杂到明胶溶液中,制备出染料包覆胶态银纳米粒子掺杂的有机复合膜.本工作成功地制备出无机/有机活性基元掺杂的三元系复合膜,实现了染料分子对金属纳米粒子完全意义上包覆的设想和对活性基元的室温包埋工艺.电镜(TEM)观测了复合膜的显微结构,对复合膜的UV-Vis吸收光谱进行了测量.给出了一种包覆掺杂的结构模型,并用该模型成功地解释了实验结果.     

镍 -纳米氧化铝复合电镀液的制备及影响因素研究

性质均匀稳定的镍/纳米颗粒复合镀液是制备镍/纳米复合镀层的物质和工艺基础.在瓦特镀镍溶液中加入纳米Al2O3粉末,混合液静置10 h后,因颗粒沉淀而产生不同程度的分层,通过比色法研究了分散剂、分散形式、镀液pH值对纳米Al2O3粉末在镀液中均匀稳定分散的影响.结果表明,在镀液中加入适量的聚羧酸铵、柠檬酸三铵或十六烷基三甲基溴化铵分散剂,并通过超声分散,可得到稳定分散10 h以上的复合电镀液.原子力显微镜分析表明,复合镀液中纳米颗粒的平均尺寸为63 nm,略大于其原料颗粒的尺寸(40 nm),大部分的纳米颗粒在复合镀液中能实现高度分散.     

两相不相容共混体系的亚微形态及其影响因素

本文讨论了“海岛”两相分散、分散相纤维化、分散相层化等三种亚微形态的形成条件以及与共混物组成、组份粘度比、加工工艺和增容剂之间的关系。     

相分散-交联在聚合物共混中的协同作用

以聚氯乙烯／聚乙烯共混物为例，论述了相分散－交联在不相容聚合物共混中的协同作用。     

漆酚甲醛缩聚物水基分散体系的相反转乳化

用复合表面活性剂将漆酚缩甲醛聚合物乳化为水包油型的稳定水基乳液。系统研究了乳化剂种类、乳化剂用量、H LB值和乳化温度等对相反转乳化过程的影响,并用乳液体系电导率变化和黏度变化表征了相反转乳化过程。实验结果表明,复合乳化剂吐温-20/司班-20乳化效果最好;高乳化剂用量和低乳化温度有利于水包油乳液的形成;当水和油的质量比(R)为1.05时,体系开始发生相反转,至R=1.4时,体系由油包水型转化为水包油型。相反转乳液粒径小,分布均匀。     

Phase and Dispersion of Cylindrical Surface Waves

Most theoretical and experimental work on surface waves does not take into account dispersion. When propagating along a flat planar half space, surface waves are known as Rayleigh waves and are not dispersive. When the radii of curvature are large, surface waves behave like Rayleigh waves. However, when the radii are small, dispersion becomes a contributing factor. Experimental measurements indicate that along with dispersion, there appears to be a strong phase shift effect as the wave propagates along the circumferential path of cylindrical specimens. The phase shift effect is observed even under conditions where dispersion is not detected. Classical theories provide the velocity-frequency equations, which represent the dispersion relationships, for surface waves. An alternate theoretical approach is discussed in this article that demonstrates the phase-dispersion relationship for cylindrical surface waves. Experimental data support the theoretical conclusions and indicate phase shift is directly related to the radius of curvature to an extent much more sensitive than dispersion.     

高强Al-Mg-Si-Cu铝合金的时效工艺研究

目的 研究时效工艺参数对高强Al-Mg-Si-Cu铝合金微观组织和力学性能的影响规律,以得到Al-Mg-Si-Cu铝合金时效后最优的性能和微观组织。方法 在不同时效处理工艺参数条件下,通过对Al-Mg-Si-Cu铝合金时效处理后的硬度、电导率、室温力学性能进行测试与对比分析,并结合微观组织观察实验,分析了不同时效温度及时效时间对Al-Mg-Si-Cu铝合金时效强化相及力学性能的影响规律。结果 在不同时效温度条件下,经不同时效时间的时效处理后,Al-Mg-Si-Cu铝合金的电导率随时效温度的升高和时间的延长而增大,当时效温度为170、180、190 ℃时,硬度和力学性能在时效时间为16、12、8 h时达到峰值。同时,当时效时间为8、12、16 h时,Al-Mg-Si-Cu铝合金的时效强化相分别是β''相、β''相和Q''相;在峰值时效和过时效工况下,Al-Mg-Si-Cu铝合金的析出相均存在Q''相,该相对合金的强度具有明显的贡献。在过时效阶段,Al-Mg-Si-Cu铝合金强化相明显初化,力学性能和硬度均有明显降低。结论 经淬火处理+180 ℃/12 h时效处理后,高强Al-Mg-Si-Cu铝合金的力学性能最优,抗拉强度和屈服强度分别为404 MPa和388 MPa,硬度为136HV。     

Characteristics of TM Surface Waves in a Nonlinear Antiferromagnet–Semiconductor–Superconductor Waveguide Structure

The frequency characteristics of the transverse magnetic (TM) surface waves at mid-infrared frequencies in a layered system, consisting of YBa₂Cu₃O_7–x superconductor film bounded by a nonlinear antiferromagnet (FeF₂) cover and a resonant semiconductor plasma (In_0.53Ga_0.47As) substrate, are fully described. The permeability tensor of the antiferromagnet crystal, for the absence of an applied Zeeman field, has a nonlinear response to the intense rf field. The complex wave number of TM wave is computed by solving the dispersion equation in order to determine the effects of the superconductor and resonant semiconductor on the dispersion characteristics for both the reduced phase and reduced attenuation constants as a function of the temperature and frequency. The power flow through the waveguide structure has also been investigated. We have found that superconductors have the ability to reduce the propagation losses. We have also found that the reduced attenuation constant is highly dependent on the temperature of the superconductor.     

Enhancement of solubility and oral bioavailability of manidipine by formation of ternary solid dispersion with d-α-tocopherol polyethylene glycol 1000 succinate and copovidone

Context: Low bioavailability of oral manidipine (MDP) is due to its low water solubility.

Objective: The objective of this study was to increase the solubility and bioavailability of MDP by fabricating ternary solid dispersion (tSD) with d-α-tocopherol polyethyleneglycol-1000-succinate and copovidone.

Methods: In this study, solid ternary phase diagram was applied in order to check the homogeneity of tSD prepared by melting and solidifying with dry ice. The physicochemical properties of different formulations were determined by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and hot stage microscopy. Their solubility, dissolution, stability and bioavailability were also investigated.

Results and discussion: The results demonstrated that tSD obtained from ternary phase diagram divided into homogeneous and non-homogeneous regions. In the homogenous region, the transparent characteristics of tSD was observed and considered as a glass solution, which have a higher MDP solubility than that in non-homogenous region. The hot stage microscopy, DSC and PXRD confirmed that solid dispersion was formed in which MDP was molecularly dispersed in the carriers, especially in the homogenous region of phase diagram. FTIR analysis demonstrated strong hydrogen bonding between amine groups of MDP and carbonyl groups of copovidone, which supported a higher solubility and dissolution of tSD. The pharmacokinetic study in Wistar rats showed that the tSD had the greatest effect on oral bioavailability. Immediate hypotensive effect of tSD was also observed in vivo.

Conclusions: The improvement of stability, dissolution and oral bioavailability of MDP could be achieved by using tSD technique.     

Theoretical foundation of cluster formation in supported liquid-phase catalysts

Despite the widespread use of supported liquid phase catalysts (SLPC) in industrial practice, the basic phenomenon of liquid dispersion which affects the diffusion rates of reaching components and gas-liquid interfacial area, is not well understood. The paper identifies the associated problems and formulates a model for the pore structure of real catalysts based on intersecting cylinders to study the effects of capillary forces. The formation of liquid clusters of dimensions larger than the pore dimensions and their subsequent effects on the performance of SLPC can be studied using this model. The model provides a basis for manipulating parameters that can reduce such cluster formation. This paper is dedicated to Dr L K Doraiswamy on his sixtieth birthday.     

Improved stability of solid dispersions of manidipine with polyethylene glycol 4000/copovidone blends: application of ternary phase diagram

Context: Manidipine (MDP) is generally used clinically as an antihypertensive agent; however, the bioavailability of orally administered MDP is limited due to their very low water solubility.

Objective: The objectives of this research were, therefore, to increase the solubility of MDP by the formation of ternary solid dispersions (tSD) with polyethylene glycol 4000 (PEG4000) and copovidone and to improve their stability.

Methods: Solid ternary phase diagram was constructed to find homogeneous solid dispersion region after melting and solidifying at low temperature with different quenching substances. The pulverized powder of solid dispersions was then determined, for their physicochemical properties, by differential scanning calorimetry, powder X-ray diffractometry, Fourier transform infrared (FTIR) spectroscopy and hot stage microscopy. The solubility and dissolution of MDP from the tSD were investigated. The physical stability of tSD was also determined under accelerated condition at 40?°C/75% relative humidity (RH) for 6 months.

Results and discussion: The results showed that MDP was molecularly dispersed in PEG4000 and copovidone when the tSD was created from homogeneous region of solid ternary phase diagram. FTIR results confirmed that strong hydrogen bonding was presented between MDP and copovidone, leading to a significant increase in the solubility and dissolution of MDP. After storage at accelerated condition (40?°C/75%RH) for 6 months, the tSD still showed a good appearance and high solubility.

Conclusion: The results of this study suggest that tSD prepared by melting has promising potential for oral administration and may be an efficacious approach for improving the therapeutic potential of MDP.     

Dispersion analysis of a non‐conforming finite element method for the Helmholtz and elastodynamic equations

We investigate the dispersive properties of a non‐conforming finite element method to solve the two‐dimensional Helmholtz and elastodynamics equations. The study is performed by deriving and analysing the dispersion relations and by evaluating the derived quantities, such as the dimensionless phase and group velocities. Also the phase difference between exact and numerical solutions is investigated. The studied method, which yields a linear spatial approximation, is shown to be less dispersive than a conforming bilinear finite element method in the two cases shown herein. Moreover, it almost halves the number of points per wavelength necessary to reach a given accuracy when calculating the mentioned velocities in both cases here presented. Copyright © 2003 John Wiley & Sons, Ltd.