室温固相合成掺杂ZnO纳米粉体制备ZnO压敏电阻

以金属离子盐和草酸为原料,采用室温固相化学反应合成掺杂ZnO前驱物,根据DSC-TG分析结果,将其在450℃热分解2 h,得到掺杂ZnO粉体,并用此粉体制备了片式ZnO压敏电阻。借助XRD、TEM、BET等检测手段对粉体产物的物相、形貌、粒度等进行了表征。研究了烧结温度对ZnO压敏电阻电性能的影响。结果表明,所制备的粉体为平均粒径24 nm左右、颗粒呈球状、分散性好的纤锌矿结构掺杂ZnO。在1 080℃烧结时,ZnO压敏电阻的综合电性能达到最佳,电位梯度为791.64 V/mm,非线性系数为24.36,漏电流为43μA。     

共沉淀法制备ZnO基纳米复合粉体及高压ZnO压敏电阻的电性能

以金属离子盐为原料,氨水、乙醇胺为沉淀剂,十二烷基苯磺酸钠、聚乙二醇2000为表面改性剂,采用共沉淀法制备ZnO基纳米复合粉体。以共沉淀法最佳工艺所得粉体制备高压ZnO压敏电阻。采用热重–差示扫描量热分析、X射线衍射、扫描电子显微镜、激光粒径分析对ZnO基复合前驱体及ZnO基纳米复合粉体进行表征,探讨了沉淀剂种类、溶液pH值、Zn2＋起始浓度和表面改性剂对粉体粒度的影响。结果表明：以氨水为沉淀剂、溶液体系pH值为6.0、Zn2＋浓度为1.0mol/L、聚乙二醇2000为表面改性剂时可制备出粒径分布窄、平均粒径为89nm的ZnO基复合粉体。用该粉体制备的高压ZnO压敏电阻的平均电位梯度为543V/mm,非线性系数为29.3,漏电流为49μA。通过共沉淀工艺,可制备出电性能优良的高压ZnO压敏电阻。     

自蔓延燃烧法合成ZnO粉体及其压敏电阻的制备

以硝酸锌、尿素以及其它添加剂为原料,通过自蔓延燃烧法一次性合成了ZnO压敏电阻用掺杂纳米粉体.用X射线衍射、扫描电镜、比表面测试、激光粒度分析等手段对所制备粉体的性能进行了表征.研究了反应物质量比对粉体性能的影响,以及煅烧温度对ZnO压敏电阻电性能的影响,并对自蔓延燃烧合成反应进行了初步探讨.结果表明:在点火温度为600℃,尿素/金属离子盐质量比为1∶1时,所制备的掺杂纳米ZnO粉体的综合性能最好.用此粉体制备的ZnO压敏电阻的电性能最佳,电位梯度为745.27V/mm,非线性系数为56.53,漏电流为6μA.     

烧结温度对锌硼玻璃掺杂氧化锌压敏陶瓷的影响

研究了不同烧结温度情况下,用固相法制备掺杂锌硼玻璃料ZnO压敏陶瓷,使用CJ1001型压敏电阻直流参数仪测量各样品的电位梯度E_(1 mA),漏电流IL和非线性系数α。结果表明,利用传统陶瓷制备工艺制备得到的锌硼玻璃料掺杂的氧化锌压敏陶瓷样品,以烧结温度1050℃保温时间为2 h所得到样品的电学性能最佳:电位梯度为566 V/mm;非线性系数为115;漏电流为2.6μΑ。     

纳米Bi_2O_3掺杂对ZnO压敏电阻片电学性能的影响

为获得电学性能优异、生产成本低的ZnO压敏电阻片,本文采用传统陶瓷烧结技术制备ZnO压敏电阻片,研究不同含量纳米Bi_2O_3掺杂对ZnO压敏电阻片的电位梯度、漏电流、非线性系数等电性能的影响。采用压敏电阻直流参数仪对ZnO压敏电阻片的电学性能进行表征。实验结果表明,随着纳米Bi_2O_3含量的增加,ZnO压敏电阻片的电位梯度先升高后降低,漏电流变化不显著,非线性系数先增大后减小。当掺杂纳米Bi_2O_3摩尔分数为0.80%时,ZnO压敏电阻片的电学性能最佳。     

贝壳粉/ZnO复合材料的制备及其在聚脲涂料中的应用

以贝壳粉为载体采用共沉淀法制备了贝壳粉/ZnO复合材料,采用XRD、FT-IR、SEM分析手段对所制备的复合材料进行了表征。将合成的贝壳粉/ZnO复合材料作为填料,以质量分数为2%的比例添加到聚脲涂料中,研究其对涂层性能的影响。结果表明:负载的ZnO颗粒呈椭球形并与载体紧密结合,粒径约为50 nm,贝壳粉/ZnO复合材料粒径约为500 nm,贝壳粉/ZnO复合材料的加入使聚脲涂料具有更优异的物理性能和耐久性能。     

高能球磨对Pr_6O_(11)和Y_2O_3掺杂ZnO压敏电阻微观结构和电学性能的影响

利用高能球磨法制备Pr6O11、Y2O3掺杂ZnO压敏电阻,并对球磨时间对微观结构、物相组成及电学性能的影响进行了研究和分析。高能球磨有利于微观组织的均匀化和晶粒的细化,从而提高了电学性能。当球磨时间从0到10 h时,烧结后的ZnO晶粒尺寸变化从8.7到4.0μm,坯体烧结密度变化从5.40到5.62 g/cm3。最佳的制备工艺为球磨时间为7.5 h,烧结温度为1100℃,其对应的电学性能分别为:电位梯度(V1mA)是542 V/mm,漏电流(IL)是2.88μA,非线性系数(α)是47。     

粉体粒度对BaTiO_3陶瓷结构与电性能的影响

以采用共沉淀法制备的钛酸钡(BaTiO3)粉体为原料制备陶瓷。并利用XRD、DSC、SEM等分析手段对陶瓷材料的物相、相转变、显微结构进行表征,和利用电容测量仪、粒度分析仪等对陶瓷材料的电性能及粉体的粒度进行测试。研究了粒度对BaTiO3陶瓷微观结构和介电性能的影响。结果表明:随着预烧温度的提高,粉体的粒度增大,其陶瓷烧成温度也相应提高,并获得了优良的介温性能,粉体粒径为360nm的BaTiO3粉体经1290℃烧结后居里峰介电常数达到8119。     

一种合成ZnO压敏电阻陶瓷主料的新方法

以Zn(NO3)2为原料,采用NaOH为沉淀剂,制备氧化锌压敏电阻陶瓷主料ZnO。结果显示制备的ZnO均为纳米级,并通过调节控制酸碱度pH值、反应温度、反应溶液的浓度等,探索了实验的最佳条件。为今后采用共沉淀法制备氧化锌压敏电阻陶瓷复合粉体奠定了扎实的基础。     

CaO-ZrO2纳米粉体的制备和表征

采用醇-水法和柠檬酸络合法制备了CaO-ZrO2粉体,用XRD和TEM等手段对粉体的结构和形貌进行了表征.结果表明:醇-水法所得粉体的粒径在70nm左右,基本无团聚体存在;至800℃时,晶粒已经发育完好,与固相法相比,其合成温度降低了600℃左右;晶型结构为四方晶型,无单斜相存在.而柠檬酸络合法所得粉体中含有大量单斜相.将醇-水法所得粉体加入到BaTiO3中,进行烧结实验,与固相法合成的CaO-ZrO2粉体相比,它使BaTiO3的烧结温度降低了20℃左右.     

Ethanol sensor based on ZnO and Au-doped ZnO nanowires

ZnO nanowires and Au-doped ZnO nanowires were prepared by oxidation reaction. The oxidation was performed by heating zinc powder and a mixture of zinc and 1 wt% gold powder which was pressed into a tube shape at 600 °C for 24 h. The ethanol sensors based on ZnO nanowires were simply fabricated by applying silver electrode at each end of the tube and inserting a coil heater into the tube. The ethanol sensing properties of ZnO nanowires were observed from the resistance change under ethanol vapor atmosphere. By considering the sensitivity and response time, the optimum operating temperature of the ethanol sensor was found to be 240 °C. Also, it was found that the sensitivity of the sensor based on Au-doped ZnO nanowires exhibits higher value than that of the sensor based on undoped ZnO nanowires.     

Structural change of Cu/ZnO by reduction of ZnO in Cu/ZnO with methanol

The reducibility of ZnO was investigated in the temperature range of 523–623 K in a stream of a reducing agent such as H₂, CO, and methanol. ZnO was reduced only in the presence of copper in the vicinity of ZnO with CO and methanol, but it was not reduced with H₂. Methanol was a stronger reducing agent in the reduction of ZnO than CO, while CO was stronger in the reduction of CuO than methanol. Two types of brass were observed resulting from the reduction of ZnO in the Cu/ZnO sample by XRD. Zanghengite brass started to be formed at 573 K in addition to α-brass which was observed at the temperature above 523 K in the temperature range of 523–623 K during the ZnO reduction with methanol. The carbon monoxide chemisorption showed that the copper surface areas decreased during the reduction of ZnO with methanol. This revised version was published online in July 2006 with corrections to the Cover Date.     

Growth of vertically aligned ZnO nanorods using textured ZnO films

A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells.

PACS

61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)     

One-step solution synthesis of urchin-like ZnO superstructures from ZnO rods

The urchin-like ZnO superstructures have been directly prepared by the assistance of poly (acrylic acid) (PAA, M_w 5000) under a one-step solution-based process. X-ray diffraction (XRD) patterns indicate that the crystal structure of the special ZnO urchins is hexagonal. The results of Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) tests show that the urchins are composed of rods and the average aspect ratio of them is about 10 with a length of about 1.5 μm. Selected area electron diffraction (SAED) pattern reveals that the rods are single crystal in nature, which preferentially grow up along the 〈0001〉 direction. Furthermore, the sizes and aspect ratios of the rods can be easily controlled by regulating the concentration of ZnSO₄ solution. It is believed that the process of crystallization, including nucleation and crystal growth, happens along PAA chains resulting in the production of rods and assembly of them into superstructures.     

Gas Sensing Characteristics of Porous ZnO and Pt/ZnO Ceramics

Changes in resistivity and chemical changes in reducing gases were measured for porous zinc oxide ceramics with and without a platinum catalyst at 300° and 400°C to examine the gas sensing mechanism and the effect of platinum additions. Reducing gases were oxidized to CO₂ and Hz₂ on the sensor surfaces. Platinum addition promoted the oxidation of reducing gases but did not lead to an increase in the resistivity change at 400°C. The reaction sequences for the gas sensing process are proposed, taking into account partially oxidized intermediates of hydrocarbons and oxidation on platinum without an electron transfer process.     

Dispersivity of modified ZnO and characterization of polyurethane/ZnO composites

The properties of inorganic nanoparticles/polymer composites depend on the dispersivity of nanoparticles in a polymer matrix. The effect of surface modification on the dispersivity of ZnO nanoparticles in a polyurethane (PU) resin matrix was investigated. The nanocomposites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis, and X‐ray diffraction. The scanning electron micrographs show that ZnO nanoparticles (CDI–SA–APS–ZnO), which were modified by aminopropyltriethoxysilane (APS) and activated stearic acid (SA) by N,N′‐carbonyldiimidazole (CDI), can be homogeneously dispersed and had been encapsulated in the PU phase. The interfacial compatibility between ZnO nanoparticles and PU matrix was significantly improved by hydrophobically modifying ZnO nanoparticles with APS and SA. The tensile strength and elongation at break of PU/CDI–SA–APS–ZnO nanocomposites increased by 82 and 64% respectively, compared with the pure PU material. The thermal stability and ultraviolet‐shielding properties were also improved by incorporating ZnO nanoparticles into the PU matrix. POLYM. COMPOS., 35:237–244, 2014. © 2013 Society of Plastics Engineers     

Comparison of ZnO and Ti-doped ZnO sensing membrane applied in electrolyte-insulator-semiconductor structure

In this paper, we demonstrate electrolyte-insulator-semiconductor devices for biochemical sensing applications prepared from ZnO and Ti-doped ZnO sensing membranes deposited on Si substrates by radio frequency sputtering. The structural, morphological, and compositional features of these deposited films with multitemperature annealing were studied using X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. Sensitivity, linearity, hysteresis, and drift rate were measured to determine the sensing and reliability performance of all fabricated devices. Compared to the ZnO electrolyte-insulator-semiconductor (EIS), the Ti-doped ZnO EIS sensor annealed at 700 °C exhibits a higher sensitivity of 57.56 mV/pH, lower hysteresis of 2.79 mV, and lower drift rate of 0.29 mV/h. For Ti-doped ZnO, sensitivities of 3.62 mV/mM and 6.42 mV/mM were obtained for urea and glucose sensing, respectively. The improvements are owing to Ti-doping, which produces a rougher sensing surface, a well-crystallized grain structure, and thinner silicate and SiO₂ at the silicon-oxide interface.     

超微细ZnO表面改性及PP/ZnO共混体系流变性能

研究了超微细ZnO的表面改性条件 ,并采用正交实验确定粉体改性中最重要的影响因素为偶联剂的用量。由于粉体的团聚 ,导致粉体表面活性点的封闭 ,因此实际偶联剂用量小于理论计算值。研究发现 ,粉体表面改性中的偶联剂用量对PP ZnO共混体系流变行为有较大的影响 ,当偶联剂用量适当时 ,共混体系的表观粘度趋于最小 ,过多或过少的偶联剂用量均导致共混体系表观粘度的增加     

Catalytic performance of ZnO nanoparticle in formation of LLDPE/ZnO nanocomposites

ZnO nanoparticle was used for preparing supported catalyst, which was applied in copolymerization of ethylene and 1-octene to obtain LLDPE/ZnO nanocomposite. There were two different impregnation methods (in situ and ex situ) in preparing the nano-ZnO supported catalyst. The investigation to compare both methods was conducted by employing various 1-octene initial concentrations in copolymerization. It was found that a heterogeneous catalytic system comprised a supported catalyst, prepared by in situ impregnation, provided higher catalytic activities and 1-octene incorporations compared to those of ex situ impregnation under similar condition perhaps due to closer similarity to a homogeneous system. For the ex situ impregnation, it was found that when zirconocene was directly impregnated onto the support, the catalytic activity decreased. This was due to zirconocene close vicinity to the supports and even deep into the support structure proved by XPS and TGA measurements. Therefore, it was more inaccessible to monomer attack and reducing the catalytic activity. The separate study on each catalytic system relating to the comonomer effect was also conducted by applying initial comonomer concentrations varied between 0 and 18?mmol. The increase in catalytic activity with increasing comonomer concentration can be considered as a positive comonomer effect, and the opposite was true for a negative comonomer effect. It was found that both positive and negative comonomer effects occurred in in situ impregnation and ex situ impregnation systems with Zn/(Al?+?Zr) support, whereas only positive comonomer effect was found in an ex situ impregnation system with Zn/Al support. This suggested that the comonomer effect was varied according to the nature of each system. The polymer properties, such as relative crystallinity and thermal properties were also investigated and found to alter with 1-octene concentration.