氧化锌纳米棒微球的水热制备及其气敏性质研究

以Zn粉为原料,采用水热法制备了由氧化锌纳米棒自组装而成的氧化锌纳米棒微球和氧化锌亚微米棒,对氧化锌纳米棒微球进行了镍掺杂,用x射线衍射仪和扫描电镜对产物的结构和微观形貌进行了表征,探讨了反应机理,并测试了其气敏性质.研究发现,氧化锌纳米棒微球具有良好的气敏性质,对酒精和汽油具有较高的灵敏度,镍的掺杂明显提高了氧化锌纳米棒微球在酒精和汽油之间的选择性.     

均匀沉淀法制备纳米氧化锌的研究

以硝酸锌、尿素为原料, 采用均匀沉淀法制备纳米氧化锌粉末. 以TEM和BET等方法对产物进行了表征, 发现可获得50nm左右的纳米氧化锌, 粒子 的比表面积为25.6m²/g; XRD分析表明, 产物为六方晶系; 通过XRD、IR和TG-DSC分析, 确定了纳米氧化锌的形成机理.     

氨水对纳米氧化锌的影响

以六水硝酸锌为锌源,氨水为沉淀剂,聚乙二醇为分散剂,直接制备了纳米氧化锌.利用X射线衍射(XRD)和透射电子显微镜(TEM)对纳米氧化锌的晶体结构、尺寸和形貌进行了表征.结果表明,在氨水的质量分数为19％,温度为60℃的条件下合成的纳米氧化锌属于六方纤维矿单晶结构,呈棒状形貌,直径约为72nm,长径比约为8.5.讨论了氨水作用下纳米氧化锌的形成机理以及氨水浓度对产物形态和纳米氧化锌收率的影响.     

真空限氧法制备纳米氧化锌及其动力学

以热镀锌渣为原料、以空气为氧源,采用真空限氧法制备了纳米氧化锌.用热重法测定了不同系统压力条件下锌蒸气的氧化动力学曲线,用扫描电镜研究了氧化产物ZnO的形貌.结果表明:采用真空限氧法制备的纳米氧化锌晶体为六方纤锌矿结构,纯度≥99.98％;当氧化反应遵守抛物线规律时,纳米氧化锌的形貌主要为颗粒状、无定形、四针状或单针状;当氧化反应遵守直线规律时,产物主要为短小的四针状或单针状;在锌氧化反应前期和后期分别受收缩球状模型R3和三维扩散模型D4控制,表观活化能分别为101.3～ 122.1 kJ/mol和111.2～143.4 kJ/mol.     

聚合物包覆热分解法制备纳米氧化锌的工艺研究

采用聚合物包覆热分解法化学工艺制备了纳米氧化锌,对其工艺进行系统的比较研究,对所得粉体进行XRD与SEM表征。发现利用该工艺所得粉体为六方晶系纤锌矿结构（空间群为P63mc）的纳米氧化锌。该方法制备的氧化锌衍射峰尖锐,表明此种方法合成的氧化锌结晶程度高。所得的氧化锌粉体XRD图谱中没有杂质衍射峰,说明产物纯度都很高。产品SEM表征结果显示了此工艺产物在形貌方面的高度一致性——为菊花状氧化锌纳米杆团簇,对产物形貌形成的原因做了探讨。     

一维纳米结构氧化锌的水热法制备及紫外光敏特性研究

在陶瓷衬底上制作叉指状金电极,采用低温水热法生长一维纳米结构氧化锌,制得氧化锌紫外光电导型探测器.探讨了反应溶液的浓度对氧化锌纳米结构形貌及紫外光电导特性的影响.X射线衍射分析表明,产物为六方纤锌矿结构的ZnO.扫描电镜观察显示.产物为一维纳米结构,因反应溶液浓度的不同直径介于80～500nm.光电测试表明,一维纳米结构氧化锌的紫外光电导特性受其表面形貌的影响显著.     

不同形貌纳米ZnO的合成及其光催化性能研究

以Zn(NO3)2·6H2O和NH4HCO3为原料,采用直接沉淀法制备了不同形貌和微观结构的纳米氧化锌。详细研究了反应终点pH值及沉淀前驱物的后处理方式等对粉体的晶体结构、形貌、粒径分布和团聚状况的影响。通过调节反应条件可分别获得网络状或颗粒状纳米氧化锌;光催化降解实验结果表明,网络状纳米氧化锌的光催化性能优于纳米颗粒状产物,而且该网络状和颗粒状纳米氧化锌的光催化活性均明显优于商品光催化剂P25。     

纳米氧化锌的制备及抗菌性能研究

目的 研究以乙酸锌和氢氧化钠为原料,利用水热合成法制备纳米氧化锌的最佳工艺条件及抗菌性能。方法 以纳米氧化锌的粒径和形貌为评价指标,讨论合成条件对产物的影响;基于单因素设计响应面实验,以抑菌圈直径为响应值,分析抑菌效果较好的纳米氧化锌的制备条件。结果 在水热温度为111.14 ℃,反应时间为10 h,乙酸锌浓度为0.02 mol/L时制备的纳米氧化锌的抗菌效果最好,大肠杆菌的抑菌圈直径为（17.265±0.011）mm。结论 水热温度、水热时间和前驱体浓度会影响纳米氧化锌的粒径和形貌;水热温度和前驱体浓度是影响纳米氧化锌抑菌性的显著因素,水热时间是非显著因素。     

聚乙烯醇为助剂水热法制备氧化锌纳米棒

一维结构的纳米氧化锌具有独特的电子和光电性能,在众多领域有着广阔的应用前景,故而对其合成方法的研究十分重要.本文中以聚乙烯醇作为修饰剂,通过水热法在较低的反应温度下制备了一维氧化锌纳米棒.分别用透射电镜、选区电子衍射和X射线衍射对产物形貌与结构进行了表征.研究发现,以聚乙烯醇为助剂在120℃反应24h可制备出具有六方结构的氧化锌纳米棒,其直径为50～80nm、长度为1～2μm.实验表明,聚乙烯醇在一维结构合成过程中起到关键作用,以Zn(0H)2为水热反应前驱体可制备出品质较高的一维氧化锌纳米棒.     

以木质素基磷酸酯季铵盐为模板剂直接沉淀法制备纳米氧化锌的研究

利用制浆造纸废料碱木质素制备了木质素基磷酸酯季铵盐两性表面活性剂,以此表面活性剂为结构导向剂,采用直接沉淀法一步制备了纳米氧化锌材料,XRD、EDS和SAED分析结果表明,产物为高结晶度的多晶六方纤维锌矿氧化锌,粒径在30nm左右;SEM和TEM分析可知,所合成的纳米氧化锌为具有粒子-片层-粒子三级结构的纳米材料,氧化锌主要沿着[101]和[100]晶面生长。同时对所制备的纳米氧化锌进行了紫外光催化降解亚甲基蓝的研究,实验结果显示,该纳米氧化锌有较好的光催化活性。     

Electronic structure and formation mechanism of complex Ti-Nb oxide

Two-layer thin film specimens of Nb₂O₅ and TiO₂ were deposited on optical-grade quartz and n-type single crystalline silicon substrates with (100) crystallographic orientation by a magnetron deposition source under high vacuum. All samples were subjected to 1-5 h of resistive heating at ultra high vacuum, and in situ X-ray diffraction measurements (XRD) were made in the temperature range of 300-1373 K. Analysis of the XRD data confirmed the growth of TiNbO₄ during cooling of the two-layered specimens which had been previously heated to 1373 K. Optical measurements revealed a band gap value of 3.78 eV for the direct transition and 3.29 eV for the indirect one. The samples had a transmittance of 85% in the visible range. Electrophysical measurements in high vacuum established the electroresistivity vs. temperature dependence in the range of 300-773 K, from 7.3 ? 10^− 1 to 3.9 ? 10^− 2 Ω cm, respectively. X-ray photoelectron spectroscopy measurements were used to examine the chemical shift for Nb 3d, with a value of − 1.1 eV in comparison with Nb⁵⁺ and matched to Nb⁴⁺[1], while the Ti lines correspond to Ti⁴⁺[2].     

Optical properties of thin films of mixed Ni-W oxide made by reactive DC magnetron sputtering

Thin films of Ni_xW_1 − x oxides with x = 0.05, 0.19, 0.43 and 0.90 were studied. Films with thicknesses in the range 125-250 nm were deposited on silicon wafers at room temperature by reactive DC magnetron co-sputtering from targets of Ni and W. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopic ellipsometry (SE). XRD spectra and SEM micrographs showed that all films were amorphous and possessed a columnar structure. The ellipsometric angles Ψ and Δ of as-deposited films were measured by a rotating analyzer ellipsometer in the UV-visible-near infrared range (0.63-6.18 eV) and by an infrared Fourier transform rotating compensator ellipsometer in the 500-5200 cm⁻¹ wavenumber range. SE measurements were performed at angles of incidence of from 50 ° to 70 °. Parametric models were used to extract thicknesses of the thin films and overlayers of Ni_xW_1 − x oxide at different compositions, band gaps and optical constants. Features in the optical spectra of the Ni_xW_1 − x oxides were compared with previous data on tungsten oxide, nickel oxide and nickel tungstate.     

High k dielectrics for low temperature electronics

In this work the electrical and structural properties of two high k materials as hafnium oxide (HfO₂) and tantalum oxide (Ta₂O₅) produced at room temperature are exploited. Aiming low temperature processing two techniques were employed: r.f. sputtering and electron beam evaporation.The sputtered HfO₂ films present a nanocrystalline structure when deposited at room temperature. The same does not happen for the evaporated films, which are essentially amorphous. The density and the electrical performance of both sputtered and evaporated films are improved after annealing them at 200 °C. On the other hand, the Ta₂O₅ samples deposited at room temperature are always amorphous, independently of the technique used. The density and electrical performance are not so sensitive to the annealing process. The set of data obtained show that these dielectrics processed at temperatures below 200 °C present promising properties aiming to produce devices at low temperature with improved interface properties and reduced leakage currents.     

Facile Synthesis of SnO2 Nanotube Arrays by Using ZnO Nanorod Arrays as Sacrificial Templates

SnO2 nanotube arrays have been synthesized by means of a simple and low-cost method. The ZnO nanorod arrays prepared by aqueous chemical growth method were used as templates. By liquid phase deposition, SnO2 nanotubes were obtained with proper deposition time. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction were used to characterize the morphologies and structures of the products, and the formation mechanism was discussed according to the experimental results.     

All-solid-state reflectance-type electrochromic devices using iridium tin oxide film as counter electrode

We prepared an all-solid-state reflectance-type electrochromic device (ECD), consisting of the following five layers: Al/WO₃/Ta₂O₅/Ir_xSn_1 − xO₂/ITO. Using RF ion plating, we prepared a film containing dispersed iridium oxide in a tin oxide matrix; this film acts as the counter electrode in the all-solid-state ECD. Protons were used as coloration ions in the ECD. The size of the ECD was 150 cm², and the reflectance changed between more than 60% from 15%. The coloration and bleaching response times were less than a few seconds. We analyze the optical characteristics of the ECD, and report the results of a consecutive drive test and a high-temperature heat resistance test.     

Comparative study on early stages of film growth for transparent conductive oxide films deposited by dc magnetron sputtering

Early stages of film growth were investigated on three different kinds of representative transparent conductive oxide films including tin doped indium oxide (ITO), indium zinc oxide (IZO) and gallium doped zinc oxide (GZO) films deposited on unheated alkali free glass substrates by dc magnetron sputtering. The variations in sheet resistance, film coverage and average surface roughness showed clearly that ITO and GZO films possessed Volmer-Weber growth mode. In contrast, the evolution of islands is not clearly observed for IZO film. The nucleation density of IZO film is considered to be much higher than that of ITO and GZO films.     

纳米氧化物的合成新方法

以草酸和醋酸盐为原料,用低热固相化学反应合成出前驱配合物ＮｉＣ２Ｏ４·２Ｈ２Ｏ,ＣｕＣ２Ｏ４ 和ＺｎＣ２Ｏ４·２Ｈ２Ｏ,再分别在３５０℃,３００ ℃和４６０℃热分解２ｈ,得到纳米ＮｉＯ,ＣｕＯ和ＺｎＯ。用Ｘ－ 射线粉末衍射、透射电镜对产物的组成、大小、形貌进行表征。结果表明,纳米ＮｉＯ为球形立方晶系结构,平均粒径约为４０ｎｍ 左右;纳米ＣｕＯ为球形单斜晶系结构,平均粒径约为３０ｎｍ 左右;ＺｎＯ为粒度分布均匀的球形六角晶系结构,平均粒径约为２０ｎｍ 。     

Highly conductive, undoped ZnO thin films deposited by electron-cyclotron-resonance plasma sputtering on silica glass substrate

The electrical and optical properties of undoped ZnO films deposited by electron cyclotron resonance (ECR) plasma sputtering at room temperature were characterized. The lowest resistivity we achieved was 2.6 × 10^− 3 Ωcm with optical transmittance at visible wavelengths higher than 85%. The X-ray diffraction (002) peak was weak and the rocking curve was asymmetrical, indicating that oxygen vacancies prevented large crystalline domains from forming. At low argon-sputtering-gas pressure, carrier concentration and Hall mobility increased with increasing argon pressure. When the optimum pressure (40 mPa) was exceeded, however, Hall mobility and optical transmittance were severely reduced, which indicated that excess Zn atoms were populated at the interstitials of the network. Admitting only 0.67 mPa of O₂ gas during deposition deteriorated resistivity over 1 MΩcm due to high excitation efficiency in the ECR plasma. Deposition under a higher magnetic field produced lower resistivities.     

Microstructure and Mechanical Properties of ZrO2(2Y)-Toughened Al2O3 Ceramics Fabricated by Spark Plasma Sintering

Spark plasma sintering (SPS) has been performed for 5 min at 1500°C and 30 MPa using submicrometer-sized Al₂O₃/ZrO₂(2Y) composite powders in the Al₂O₃-rich region. Dense ZrO₂-toughened Al₂O₃ (ZTA) ceramics show excellent mechanical strength; the strength of 1620 MPa is achieved in the ZTA with 50 mol% ZrO₂. The grain size of Al₂O₃ in ZTA decreases from 1.5 to 0.6 m with increased ZrO₂ content. Almost all the ZrO₂ grains (0.3 m) are located in the boundaries of the Al₂O₃ grains. Mechanical properties are discussed, with an emphasis on the relation between t-/m-ZrO₂ ratios and microstructures of ZTA.