铅锌矿尾料中氧化锌的提取和纯化

利用酸法提取铅锌矿尾料中氧化锌,研究表明,在搅拌转速一定,温度为80℃、硝酸的浓度为3mol/L、液固质量比为5∶1时,铅锌矿尾料中氧化锌的产率能达到62.7%。产品中氧化锌的相对纯度可达99.5%。碱法提取氧化锌,氢氧化钠的浓度为9mol/L时,氧化锌的产率为27.6%。对于浸出液的回收利用则是用浸出液和硝酸配比,再对铅锌矿尾料进行浸出,从而使废液循环利用。     

Preparation of indium oxide powders by microwave plasma dehydration of indium hydroxide powders

Indium oxide was prepared from the dehydration of indium hydroxide using atmospheric-pressure microwave air plasma. Compared with the conventional thermal plasma processing that was performed with the vapor phase reaction, the solid-state reaction was attempted in this study because microwave plasma has an intermediate temperature that is comparable to the melting temperature of inorganic materials and between those of the electric furnace and the thermal plasma. The results were compared with those with the electric furnace and the thermal plasma. With both the microwave plasma and the electric furnace, the macro-morphologies of the raw material were maintained, which indicates successful dehydration. However, the micro-morphologies differed. The product of the microwave plasma had a smooth surface, whereas the product of the electric furnace had a cracked and rough surface. The cracks were regarded as the results of the poor diffusion of the dissociated water. In the microwave plasma, the high temperature and the fast heating rate enhanced the diffusion and controlled the formation of cracks. With the application of the thermal plasma, the nanoparticles were prepared due to the vaporization of the dehydrated material. Thus, the microwave plasma is considered applicable to the solid-state reaction accompanying degassing, without a change in the microstructure of the raw material.     

Investigation of the possibility of copper recovery from the flotation tailings by acid leaching

The flotation tailings pond of the Bor Copper Mine poses a great ecological problem not only for the town of Bor but also for the surrounding soils and watercourses. Since the old flotation tailings contain about 0.2% of copper on the average, we investigated their leaching with sulphuric acid in the absence and presence of an oxidant. The aim was to determine the leaching kinetics of copper and iron as affected by various factors such as: the pH value of the leach solution, stirring speed, pulp density, particle size, concentration of ferric ions, temperature and time for leaching. The average copper and iron recovery obtained was from 60% to 70% and from 2% to 3%, respectively. These results indicate that the old flotation tailings pond represents an important source of secondary raw material for the extraction of copper and that it should be valorized rather than land reclamation. At the end of the paper, a mechanism of dissolution of copper and iron minerals from the tailings was described.     

Synthesis, characterization, and photocatalytic activities of titanate nanotubes surface-decorated by zinc oxide nanoparticles

Nanoscaled zinc oxide (ZnO) particles with different amounts are coated on titanate nanotubes (TNTs) by a facile chemical method at room temperature. The characterizations of XPS, TEM, XRD and UV-vis spectra confirm that pure hexagonal wurtzite ZnO nanoparticles with an average size of about 9nm are distributed on the surfaces of TNTs evenly and attached strongly. The photocatalytic activities of the ZnO-TNTs nanocomposite are superior to those of P25, ZnO, TNTs and ZnO-anatase TiO2 (TNP) nanocomposite in the oxidation of rhodamine B under UV light irradiation. A comparison of the photocatalytic activities between different catalysts is discussed. Furthermore, we also find that the ZnO-TNT nanocomposite shows very favorable recycle use potential, because they have a high sedimentation rate and their photocatalytic activity is only slightly decreased even after five times of repeated uses.     

不同Sol-Gel前躯体体系制备纳米ZnO粉体的研究

为研究不同溶胶前躯体体系对制备纳米ZnO粉体粒径大小的影响,采用溶胶-凝胶法分别研究了硬脂酸体系、草酸体系、高分子网络体系制备纳米ZnO粉体,并利用TG-DTA、XRD、TEM对其结构、形貌和粒径进行了表征.在3种体系中,高分子网络体系所得粉体粒径最小,粒径在30～40nm,粒径大小均匀,团聚较少.硬脂酸体系得到ZnO粉末粒径较小,范围分布在30～50nm,分散性较好.草酸体系制得ZnO粉末粒径相对较大,在40～60nm,有轻微团聚.     

氨法浸出氧化锌烟尘制取活性氧化锌

为实现冶锌废渣中锌资源的再利用,以商洛炼锌厂冶锌过程中产生的氧化锌烟尘为原料,采用氨法浸出-微波蒸氨-火法焙解工艺制得粒度分布均匀的球状活性氧化锌.对锌的浸出工艺及氧化锌前驱体的热解工艺进行研究,并利用TG/DTA、XRD、SEM等测试手段对产品进行结构及物相表征.研究表明,氨法浸出过程中总氨浓度为8 mol/L、pH为10.0、液固比为4∶1、浸出温度为40℃时,锌的浸出率最高可达92.05%.浸出液经两段净化除杂后,80℃下蒸氨25 min时,制得前驱体碱式碳酸锌.在400℃焙解120 min制得平均粒径约为3μm,六方晶系的球状活性氧化锌.此法对设备要求不高,生产成本低,工艺流程短,具有较强的实用性.     

Preparation and characterization of lithium nickel cobalt oxide powders via a wet chemistry processing

Nickel-rich phases of the solid solutions, LiNi_1−yCo_yO₂ (y=0.1, 0.2, 0.3), were synthesized by a sol–gel method with citric acid as a chelating agent. Various initial conditions were studied in order to find the optimal conditions for the synthesis of LiNi_0.8Co_0.2O₂. The discharge capacity for the compound synthesized under an optimal synthesis condition of 800 °C for 12 h was found to be 187 mAh g⁻¹ in the 1st cycle and it was 176 mAh g⁻¹ after 10 cycles. The other nickel-rich phases, namely, LiNi_0.9Co_0.1O₂ and LiNi_0.7Co_0.3O₂ showed 1st-cycle discharge capacities of 144 and 163 mAh g⁻¹, respectively. The corresponding capacity values were 140 and 159 mAh g⁻¹ in the 10th cycle. Excess lithium stoichiometric phases, Li_xNi_0.8Co_0.2O₂, where x=1.10, 1.15 and 1.20, resulted in decreased capacity. Structural and electrochemical properties of the synthesized compounds were compared with those of a commercial LiNi_0.8Co_0.2O₂ sample. The effect of calcination temperature and duration, excess lithium stoichiometry and divalent strontium doping in LiNi_0.8Co_0.2O₂ are described. Doping with strontium improved both the capacity and cycling performance of LiNi_0.8Co_0.2O₂.     

化学共沉淀法制备纳米ITO粉体及结构表征

以InCl3·5H2O和SnCl4·5H2O为原料,在掺杂浓度In2O3与SnO2的质量比为9∶1的条件下,采用化学共沉淀法合成了纳米ITO粉体。利用TEM、XRD、IR、粒度分布仪等实验手段对粉体的形貌、物相、粒度进行了表征,讨论了煅烧温度对粉体物相和粒度的影响。研究结果表明:当煅烧温度>300℃时,可以获得立方In2O3结构的球形纳米ITO粉体。     

溶剂热法制备不同微米结构的氧化亚铜

以乙酸铜为原料,采用溶剂热法合成了球形直径约为2~3μm和八面体粒径大小约为4μm的氧化亚铜颗粒。通过选用不同的还原剂如三乙醇胺和乙二醇,系统研究了不同反应体系中如反应温度、溶剂、原料配比和添加表面活性剂十六烷基三甲基溴化铵(CTAB)对微米结构氧化亚铜晶型与形貌的影响,选出制备氧化亚铜八面体和球形的最佳条件,并初步探讨了氧化亚铜微米颗粒的生长机理。     

A novel approach for the synthesis of nanocrystalline zinc oxide powders by room temperature co-precipitation method

A single step co-precipitation route has been employed for the first time in the preparation of ZnO nanoparticles using ammonium hydroxide and zinc nitrate tetrahydrate. The X-ray diffraction analysis revealed that the synthesized powder has the hexagonal (wurtzite) structure. The as-prepared ZnO powder was well crystalline, without any calcination. This is a promising result compared to those mentioned in the literature, in which crystallization of ZnO nanoparticles was detected at > 300 °C. The average crystallite size of the as-prepared ZnO nanopowder is 20-40 nm. The nanocrystalline ZnO could be sintered to ~ 95% of the theoretical density at 1300 °C in 4 h.     

分步插层法制备硝酸盐-硫酸-GIC

通过硫酸、硝酸或硝酸盐分步插层的方法,成功制备了硝酸/硝酸盐-硫酸-GIC三元石墨层间化合物.采用XRD、SEM和EDS对GIC的结构进行了研究.结果表明:与直接插层法相比,分步插层法有利于插层物质的插层反应,充分扩大石墨层间距,形成低阶石墨层间化合物,使膨胀效果更优,膨胀体积高达450mL/g以上;膨胀后GIC的孔结构均匀,层壁较薄,片层结构清晰,膨胀充分.同时,分步插层法能够降低实验操作的危险性,污染小,反应易于控制.     

Preparation of cobalt oxide nanoparticles and cobalt powders by solvothermal process and their characterization

Co₃O₄ nanoparticles and cobalt (fcc-Co) powders were successfully synthesized by solvothermal process from a single precursor. The reaction of Co(Ac)₂ with sodium dodecylbenzenesulfonate (SDBS) shows evident-dependent temperature effect. At 180 °C, Co(Ac)₂ reacts with SDBS to produce precursor CoCO₃ plate structures, which are assembled by small nanoparticles. At the temperature of 250 °C, the precursor CoCO₃ can be gradually decomposed to form Co₃O₄ nanoparticles with diameter of ca. 70 nm. While, at 250 °C, the reaction of Co(Ac)₂ with SDBS also produce precursor CoCO₃ nanoparticles/plates, but the CoCO₃ nanoparticles/plates would only decompose to give metal Co. In this process, SDBS acts as not only a surfactant but also a reagent. Magnetic measurements reveal that the as-prepared Co₃O₄ nanoparticles exhibit weak ferromagnetic properties and Co powders show ferromagnetic properties. In addition, a possible formation mechanism was elaborately discussed.     

氧化石墨烯与甲基丙烯酸和烯丙基磺酸钠共聚物的制备与性能

通过氧化和超声波作用制备了氧化石墨烯(GO)纳米相片层分散液,再与甲基丙烯酸(MAA)和烯丙基磺酸钠(SAS)进行自由基共聚反应制备了氧化石墨烯与甲基丙烯酸和烯丙基磺酸钠的共聚物P(GOMAA-SAS),各组分的质量比为m(MAA)∶m(SAS)∶m(GO)=13∶6∶1。FT-IR检测结果表明GO与单体之间发生了共聚反应,AFM检测结果表明共聚物中GO片层的厚度为4 nm、长宽在5~10 nm范围。应用结果表明用10%的P(GO-MAA-SAS)鞣制皮革的收缩温度为84℃,GO的鞣制作用与GO的纳米效应和与胶原纤维的键合作用及其二者之间的协同作用有关,研究结果 GO纳米片层可以鞣制皮革并且GO的分散状态是影响鞣制效果的主要因素。     

Preparation and photoluminescence of nanocrystalline Si-rich silicon oxide films by PECVD

Nanocrystalline Si-rich silicon oxide films were deposited using plasma enhanced chemical vapor deposition technique with the mixture of silane (SiH₄), nitrous oxide (N₂O) and hydrogen (H₂) as gas source on quartz glass substrate at the substrate temperature of 300 °C. The effect of the ratio N₂O/SiH₄ on the oxidation, microstructures and photoluminescence (PL) of the as-deposited Si-rich silicon oxide films was investigated with FTIR, XRD and HRTEM. The results reveal that with the increasing ratio of N₂O/SiH₄, more amounts of oxygen are incorporated in the as-deposited films and more nanosized silicon particles are embedded in the films, forming nanocrystalline Si-rich silicon oxide films. The quantum confinement effect or the cooperation of quantum confinement and luminescence center results in the nanocrystalline Si-rich silicon oxide films of higher PL intensity.     

Preparation and characterization of zero valent iron powders via transfer type reductor using iron oxide from the acid regeneration process

In this study, zero valent iron (ZVI) powders were generated by reducing iron oxide powders obtained from a pickling line in a transfer type reductor. The physical and chemical characteristic of the produced ZVI powders were analyzed by using instruments. Reaction activities of ZVI powders for decomposition of a methylene blue were evaluated. The mean size of ZVI powders increased and the specific surface area decreased with increasing reduction temperature due to sintering. The methylene blue decomposition rate increased with dose of ZVI powders. The ZVI powders generated by reducing iron oxide showed higher decomposition efficiencies than the commercial ZVI powders at all pH values tested in this study. Both non-commercial ZVIs showed a higher decomposition rate at a lower pH.     

Studies on structural and electrical properties of copper-doped zinc oxide powders prepared by a solid state method at high temperatures

Abstract

The synthesis, crystal structure and electrical conductivity properties of Cu-doped ZnO powders (in the range of 0.25 – 15 mole %) is reported. I-phase samples, which were indexed as single phase with a hexagonal (wurtzite) structure in the Cu-doped ZnO binary system, were determined by X-ray diffraction. The limit solubility of Cu in the ZnO lattice at this temperature is 5 mole % at 1000°C. The impurity phase was determined as CuO when compared with standard XRD data using the PDF program. We focused on single I-phase ZnO samples which synthesised at 1000°C because the limit solubility range is widest at this temperature. It was observed that the lattice parameters a increased and c decreased with Cu doping concentration. The morphology of the I-phase samples was analysed with a scanning electron microscope. The electrical conductivity of the pure ZnO and single I-phase samples were studied using the four-probe dc method at temperatures between 100 and 950°C in an air atmosphere. The electrical conductivity values of pure ZnO and 5 mole % Cu-doped ZnO samples at 100°C were 2 × 10^?6 and 1.4 × 10^?4 ohm^?1 cm^?1, and at 950°C they were 1.8 and 3.4 ohm^?1 cm^?1, respectively. In other words, the electrical conductivity slightly increased with Cu doping concentration. Also, it was observed that the activation energy of the I-phase samples was decreased with Cu doping concentration.     

Preparation and characterization of submicron-cerium oxide by hypergravity coprecipitation method

Submicron-cerium oxide particles were synthesized by applying hypergravity using ammonium bicarbonate (precipitant) and cerium nitrate hexahydrate (precursor). The influence of the concentration, pH, dispersant loading, flow rate, rotation speed of the hypergravity rotating bed, calcination temperature, and time on the cerium oxide particle size were examined by zeta potential, solid–liquid contact angle, thermo-gravimetry–differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The cerium oxide particles were highly dispersed, with an average particle size of 200 nm. Calcining at 650 °C for 1.5 h afforded the smallest particles. The crystallite size and fraction crystallinity increased with prolonged calcination. Crystalline cerium dioxide grew along three crystal planes, forming a complete face-centered cube, affording high hardness and activity of the polishing powder. The optimal conditions were: cerium nitrate concentration: 0.7 mol/L, cerium nitrate/ammonium bicarbonate molar ratio: 1:3, dispersant mass fraction: 3%, cerium nitrate initial pH: 4–5; the precursor solution was adjusted to pH 9 with ammonia water. Hypergravity coprecipitation with 1.5 h calcination afforded submicron-sized cerium oxide with a uniform size distribution using ammonium bicarbonate in an industrially viable process. The simple and low-cost manufacturing process may enable the development of hypergravity-assisted chemical synthesis technology.     

Preparation and electrochemical properties of nickel oxide by molten-salt synthesis

Well-crystallized NiO nanoparticles with uniform morphology of hexagon plates were first fabricated by molten-salt synthesis method using NaCl as a flux at 1000 °C. The phase of the synthesized NiO powder was confirmed by comparing the obtained XRD pattern with the JCPDS standard. Transmission electron microscopy (TEM) image shows that the morphology of NiO particle is hexagon plate with particle size of 50-80 nm. NiO nanoparticles prepared by molten-salt synthesis method is homogenous and in high purity. The NiO sample has a better particle size distribution than that obtained from liquid precipitation and solid state reaction. The electrochemical behavior was investigated by chronopotentiometry and electrochemical impedance spectroscopy. The nickel oxide sample calcined at 1000 °C exhibited electrochemical supercapacitive behavior. The internal resistance measured at open circuit potential is only 0.5 Ω, which is smaller than that of the NiO prepared by other conventional precipitation. NiO prepared by molten-salt synthesis is a potential electrode material for supercapacitor.     

Preparation of zinc tin oxide films by reactive magnetron sputtering of Zn on liquid Sn

Zn is sputter-deposited on melted Sn films by radio-frequency magnetron sputtering in oxidizing plasma. The samples present an absorption cut-off wavelength close to the one of ZnO, and an optical transparency higher than 50% in the visible range. Ex-situ thermal annealing improves visible transparency and produces a slight blue-shift in the optical bandgap. X-ray diffraction patterns show typical spectra due to polycrystalline ZnO with evidence of the presence of crystalline SnO, before annealing, and Zn₂SnO₄, after annealing. Rutherford Backscattering studies reveal the existence of a ZnO layer on top of an O-rich (Zn, Sn)O thin film. After optimal thermal treatment, electrical characterization exhibits carrier concentrations of 10¹⁶-10¹⁷ cm⁻³ and mobilities of 20-80 cm² V⁻¹ s⁻¹ for the resulting (Zn, Sn)O n-type films.     

Photocatalytic oxidation of nitric oxide with immobilized titanium dioxide films synthesized by hydrothermal method

Gas-phase photocatalytic oxidation (PCO) of nitric oxide (NO) with immobilized TiO2 films was studied in this paper. The immobilized TiO2 films were synthesized by hydrothermal method. The characterization for the physicochemical properties of catalysts prepared under different hydrothermal conditions were carried out by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), Brunauer-Emmett-Teller measurements (BET) and scanning electron micrograph (SEM). It was found that the PCO efficiency of the catalyst was mainly depended on the hydrothermal conditions. The optimal values of hydrothermal temperature and hydrothermal time were 200 degrees C and 24 h, respectively. Furthermore, it was also known that the photocatalytic efficiency would decrease remarkably when the calcination temperature was over than 450 degrees C. Under the optimal conditions (hydrothermal condition: 200 degrees C for 24 h; calcination temperature: 450 degrees C), the photocatalytic efficiency of catalyst could reach 60% higher than that of Degussa P25.