A new technology for processing niobite ore found in Jiangxi province

A new process is proposed for refining niobite ore that is found in Jiangxi province of China. Niobite, also known as columbite or niobite–tantalite, is a mineral that contains tantalum and niobium. The separation process includes two-stage grinding, gravity concentration, magnetic separation, and flotation. The tantalum/niobium concentrate obtained had a grade of Ta₂O₅ 18.28%, Nb₂O₅ 41.62% at a recovery rate of Ta₂O₅ 49.08%, Nb₂O₅ 70.77%. Other minerals occurring along with the niobite, such as zinnwaldite, feldspar, and quartz, were also recovered to comprehensively utilize this ore.     

Synthesis and performance of mesoporous phosphotungstic acid/alumina composite as a novel oxidative desulfurization catalyst

A series of mesoporous phosphotungstic acid/alumina composites （HPW/Al_2O_3） with various HPW contents were synthesized by evaporation-induced self-assembly method. These composites were characterized by nitrogen adsorption-desorption, TEM, FTIR, and UV-vis, and were tested as catalysts in oxidation desulfurization of model fuel composed of dibenzothiophene （DBT） and hydrocarbon, using H202 as the oxidant. These composites exhibited high activity in catalytic oxidation of DBT in model fuel and good reusing ability. The best performance was achieved by using the mesoporous HPW/Al_2O_3 with 15wt% HPW content, which resulted in a DBT conversion of 98% after 2 h reaction at 343 K, and it did not show significant activity degradation after 3 recycles. Characterization results showed that the mesoporous structure of alumina and the Keggin structure of HPW were preserved in the formed composite. These results suggested that HPW/ Al_2O_3 could be a promising catalyst in oxidative desulfurization process.     

Adsorption of NO and NH3 over CuO/γ-Al2O3 catalyst

The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH₃ and NO on CuO/γ-Al₂O₃ catalysts plays an important role in the reaction. Performance of the CuO/γ-Al₂O₃ catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350 °C. Comprehensive tests were carried out to study the adsorption behavior of NH₃ and NO over the catalysts. The desorption experiments prove that NH₃ and NO are adsorbed on CuO/γ-Al₂O₃ catalysts. The adsorption behaviors of NH₃ and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results show that NH₃ could be strongly adsorbed on the catalysts, resulting in coordinated NH₃ and NH₄⁺ NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The interaction of NH₃ and NO molecules with the Cu²⁺ present on the CuAl₂O₄ (100) surface was investigated by using a periodic density functional theory. The results show that the adsorption of all the molecules on the Cu²⁺ site is energetically favorable, whereas NO bound is stronger than that of NH₃ with the adsorption site, and key information about the structural and energetic properties was also addressed.     

Preparation, characterization and dielectric properties of Sr5RTi3Ta7O30 (R=Pr and Eu) ferroelectric ceramics

Polycrystalline samples of Sr₅PrTi₃Ta₇O₃₀ (SPTT) and Sr₅EuTi₃Ta₇O₃₀ (SETT) compounds were prepared by high-temperature solid-state reaction method and their formation, structure and dielectric properties were studied. They are found to be ferroelectric phase of filled tetragonal tungsten bronze (TB) structure at room temperature and undergoes diffuse type of ferroelectric-paraelectric phase transition around 34 °C and 31 °C, respectively. At 1 MHz SPTT exhibits high dielectric constants of 177 and low dielectric losses of 3.5×10⁻⁴ and SETT has high dielectric constants of 125 and low dielectric losses of 2.4×10⁻³.     

Self-assembly of Ag-TiO2 nanoparticles: Synthesis, characterization and catalytic application

The formation of Ag clusters on titanium oxide (TiO2) nanoparticles was achieved by self-assembly process and calcination. The obtained nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and ultraviolet visible spectroscopy (UV-Vis), and conventional techniques (XRD, TEM and UV-Vis) were used to identify Ag particles on the TiO2 surfaces. The results show that Ag-TiO2 particles can be applied to improve catalytic activity of the epoxidation of styrene oxides. Styrene oxide is the main product of catalytic reaction with H2O2 as the oxidant by using Ag-TiO2 nanoparticles as catalysts. High catalytic activitity of styrene oxide can be obtainable at 80 ℃. The reaction temperature, reaction time, the molar ratio of H2O2/styrene and solvent affect greatly the catalytic epoxidation of styrene.     

Preparation and properties of SrBi2.2 Ta2O9 thin film

SrBi_2.2 Ta₂O₉ (SBT) thin film with thickness of 2 μm was successfully prepared by sol-gel method, using strontium acetate semihydrate [Sr(CH₃ COO)₂ · 1/2H₂O] and bismth subnitrate [BiO(NO₃)], and tantalum ethoxide [Ta(OCH₂CH₃)₅] as source materials, glacial acetic and ethylene glycol as solvents. The X-ray diffraction (XRD) and transmission electron microscope(TEM) results indicate that SBT layer-perovskite phase obtained has to be single phase, SBT thin film is formed after being annealed at 800 °C for for 1 min. The typical hysteresis loop of SBT thin film on Pt/Ti/SiO₂/Si is obtained, and the measured polarization value of the SBT thin film is 4. 2 μ/C/cm². Foundation item: Project (HIT. 2001. 67) supported by the Scientific Research Foundation of Harbin Institute of Technology; project (50172012) supported by the National Natural Science Foundation of China     

N掺杂Co3O4纳米片的制备以及活化过一硫酸盐的性能研究

采用牺牲模板法合成N掺杂Co₃O₄纳米片（N-Co NS）,通过透射电子显微镜（TEM）、原子力显微镜（AFM）和光电子能谱（XPS）对制备材料的形貌结构、化学组成进行分析,并通过催化活化过一硫酸盐（PMS）降解水中双酚A （BPA）来探究催化剂的催化性能.实验结果表明与Co₃O₄纳米颗粒（Co NP）、Co₃O₄纳米片（Co NS）相比,N-Co NS表现出了较高的催化性能.在PMS浓度为2 mmol·L^-1、BPA初始质量浓度为50 mg·L^-1的反应条件下,N-Co NS在10 min内完全降解水中的BPA,表明N掺杂和二维纳米片结构有利于催化剂性能的提升.通过pH及离子影响实验证实N-Co NS在复杂水化学环境中仍具有较高的活性.此外结合自由基捕获实验和电子顺磁共振（EPR）测试证实反应体系中产生了高氧化活性的羟基自由基和硫酸根自由基.     

The microstructure and properties of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramic system

The microstructure and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3(x=0,0.04,0.08,0.12,0.16) ceramic system were investigated.The Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics were prepared by the traditional solid-state reaction method and were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and Raman spectrometer.The sintering ability and dielectric properties of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 were found to be improved with the doping of Mn4+ and W6+ ions.The densification temperature of Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramics decreased from 1 080 ℃ to 1 000 ℃ when x increased from 0 to 0.16.Ag(Nb0.8Ta0.2)1-x(Mn0.5W0.5)xO3 ceramic was found to have the best dielectric properties when x=0.08,larger permittivity(■=547) and smaller dielectric loss(tan■=0.00156).     

氯氧化铋/氧化亚铜复合材料的制备及其可见光催化性能

通过水热法成功制备了BiOCl/Cu₂O 复合材料, 是一种良好的可见光响应的光催化剂。通过X 射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-vis) 和电化学阻抗谱(EIS) 等分析方法对BiOCl/Cu₂O 复合材料进行表征分析。以酸性橙(AO7) 为目标污染物进行光催化降解实验, 探究了BiOCl/Cu₂O 复合材料的光催化性能和降解机制。XRD 结果表明, 随着BiOCl 含量的增多, BiOCl 的衍射强度逐渐上升。SEM 结果表明, BiOCl 小纳米片附着在相对较大的八面体Cu₂O 表面形成复合结构。通过UV-vis 和EIS 分析结果可知, 复合材料的带隙相较于Cu₂O 略微增大但其阻抗明显变小。降解实验结果表明, 质量比为3 : 5 的BiOCl/Cu₂O 复合材料在90 min时的可见光催化降解率(56.8%) 明显高于Cu₂O 的降解率(26.3%), 其降解速率常数(0.009 3 min^-1) 是纯Cu₂O(0.003 3 min^-1) 的2.8 倍。自由基捕获实验表明BiOCl/Cu₂O 复合材料光催化过程中起主要作用的活性物种是超氧自由基(·O_{2^- )。6 次循环降解实验后光催化剂BiOCl/Cu2O(3 : 5) 对AO7 的降解率仍可达到48.3%。BiOCl 与Cu2O形成的异质结构在一定程度上降低了表面转移电阻, 加快了光催化过程中光生电子的转移速率, 提高了光生电子和空穴的分离率, 增强了光催化效果。}     

水热辅助溶胶凝胶法制备纳米钛酸锌及其光催化性能

采用水热辅助的溶胶凝胶法制备纳米钛酸锌（ZnTiO₃）光催化剂,以罗丹明B为目标降解物,运用动力学模型分析罗丹明B（RhB）初始浓度对降解效果的影响。通过SEM、XRD、XPS、UV-Vis DRS对ZnTiO₃进行表征,并使用自由基捕获试验分析其降解机理。结果表明,ZnTiO₃为纯六方相,形貌为类球形,粒径50 nm左右。在催化剂用量为1 g/L、RhB初始浓度为5 mg/L、pH值为3的条件下,光催化反应150 min后,RhB降解率为93.2%。其动力学方程为k=0.132C₀^-1.253。ZnTiO₃光催化剂降解过程中,·OH、h⁺、·O₂^-均起到催化作用,产生·OH、h⁺的量相近且多于·O₂^-,说明·OH、h⁺在催化反应中起主要作用。     

Electrochemical preparation of V<Subscript>2</Subscript>O<Subscript>3</Subscript> from NaVO<Subscript>3</Subscript> and its reduction mechanism

Vanadium trioxide (V₂O₃) was directly prepared by NaVO₃ electrolysis in NaCl molten salts. Electrolysis products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The existing state and electrochemical behavior of NaVO₃ were also studied. The results indicated that V₂O₃ can be obtained from NaVO₃. VC and C were also formed at high cell voltage, high temperature, and long electrolysis time. During electrolysis, NaVO₃ was dissociated to Na⁺ and VO₃ ^? in NaCl molten salt. NaVO₃ was initially electro- reduced to V₂O₃ on cathode and Na₂O was released simultaneously. Na₂CO₃ was formed due to the reaction between Na₂O and CO₂. The production of C was ascribed to the electro-reduction of CO₃ ^2?. VC was produced due to the reaction between C and V₂O₃.     

污泥基催化剂强化臭氧深度处理煤制气废水中试性能

为解决煤制气废水生化处理后出水仍含有大量有毒和难降解污染物,对环境产生严重污染的问题,以污水污泥为原料制备污泥基活性炭,采用浸渍法将其负载过渡金属锰和铁的氧化物(主要为Mn_3O_4和Fe_3O_4,负载量分别为15.52%和7.45%),制备比表面积分别为327.5和339.1 m~2/g的臭氧催化剂.中试实验结果表明,催化剂的使用显著提高臭氧氧化废水污染物的效能,处理后出水COD、TOC、总酚和氨氮质量浓度分别为41~43,19~20,0.6~0.9和4.3~4.5 mg/L,均达到城镇污水处理厂污染物排放一级A标准;在最佳的臭氧投加量18 g/h条件下,催化剂的使用将臭氧利用率提高40%,达1.24 mg/mg(以COD计),显著降低工艺运行成本;相比新鲜的催化剂,连续50次的催化臭氧氧化运行,COD去除率仅下降5.2%.催化剂具有良好的稳定性,制备成本仅为5 000元/t.制备的臭氧催化剂具有性能高效稳定、经济节约和可持续发展的技术优势,适用于强化臭氧深度处理煤制气废水.     

Influence of dioxin reduction on chemical composition of sintering exhaust gas with adding urea

With the addition of urea as an inhibitor, four groups of reducing dioxin emission experiments in sintering pot were conducted. The results show that, adding 0.05%, 0.1% and 0.5% (mass fraction) urea, the emission concentrations of dioxin are 0.287, 0.258 and 0.217 ng-TEQ/m³, respectively. The dioxin emission rates drop substantially compared to 0.777 ng-TEQ/m³ free of urea. With an increase of the urea content, the concentration of SO₂ emission reduces sharply. (NH₄)₂SO₄, formed by the reaction of SO₂ and NH₃, goes into the dust and part of NH3 is released before reaction with the emission of exhaust gas. The NO _x emission presents an increasing trend because the reaction of NH₃ and O₂ at high temperature produces NO _x . Based on the consideration of factors such as the effect of reducing dioxin emission, and the chemical composition of exhaust gas, 0.05% is the optimum adding content of urea.     

Luminescent properties of BaO-La2O3-B2O3 glasses with dopant

The luminescent properties of glasses synthesized in air atmosphere by conventional high temperature process were stud{ed. The emissions spectra of Eu^2 and Eu^3 were observed in BaO-La2O3-B2O3-Eu2O3 glasses.The results show that the broad emission peaks at 430 nm correspond to 5d→4f emission transition of Eu^2 , the sharp emission peaks at 592, 616, 650 and 250 nm correspond to 5^D0→1Fj(j=1--4) emission transition of Eu^3 ,respectively, which indicates that the BaO-La2O3a-B2O3-Eu2O3 glass can convert ultraviolet and green omponents of sunlight into blue and red light so as to increase the intensity of blue and red light, respectively. The luminescent in--tensity of Eu^2 increases with increasing the molar ratio of Tb^3 in BaO-La2O3-B2O3-Eu2O3a-Tb4O3 glasses, whereas the luminescent intensity of Eua^3 decreases. So the luminescent intensity of Eu(Ⅲ,Ⅱ) is influenced by Tb^3 .These phenomena can be explained by electron transfer mechanism; Eu^3 (4f6) Tb^3 (4f^8)→Eu^2 (4f′) Tb^4 (4f′). Taking advantage of the luminescent properties of BaO-La2O3-B2O3-Eu2O3 glasses, light-conversion glass for agriculture can be produced.     

Preparation and characterization of V-K catalysts supported on porous α-alumina ceramic substrate for diesel soot oxidation

The V-K catalysts were produced on porous α-alumina substrate by a solution impregnation route and the compositions and catalytic activities for soot oxidation were studied by XRD, TG/DTG, DSC and TPR. According to the catalytic activity studies, the catalytic activity of the crystalline phases is in the order: KNO₃+KVO₃>K₃V₅O₁₄+KVO₃. The appearance of excessive KHCO₃ phase will lead to the deterioration of catalytic activity when the catalysts contain higher KNO₃ content. It is also found that when the K:V molar ratio is higher than 1:1, the prepared catalysts show a strong CO₂ absorption characteristic and this behavior will become gradually significant with the increasing of K:V molar ratio. Considerable amount of absorbed CO₂ are strongly bonded to the crystal lattice with onset desorption temperature of 200 °C.     

The structure and properties of Ag(Nb0.8Ta0.2)O3 ceramic doped with MnNb2O6

The influences of doping of MnNb2O6 on the structure and dielectric properties of Ag(Nb0.8Ta0.2)O3 were illustrated. Ag(Nb0.8Ta0.2)O3 samples doped with different amount of preformed MnNb2O6 (1 mol%, 2 mol%, 3 mol%, 4 mol%, 6 mol%, 8 mol%) were prepared by traditional solid-state reaction method and characterized by XRD, SEM and EDS, and the dielectric properties of samples were compared. The experiment results indicated that when the doping amount of MnNb2O6 was greater than 3 mol%, second phase appeared because of the solid solution limit. The permittivity of the Ag(Nb0.8Ta0.2)O3 samples doped with MnNb2O6 firstly increased and then decreased with the sintering temperature, while the dielectric loss decreased first, and then increased slightly. 1 100 ℃ seems to be the most proper sintering temperature for most of the samples. When the amount of MnNb2O6 is about 3 mol%, the samples have the best dielectric properties, larger permittivity and smaller dielectric loss.     

Fabrication of Fe2O3@polypyrrole nanotubes and the catalytic properties under the ultrasound

Fe₂O₃@polypyrrole nanotubes (Fe₂O₃@PPy nanotubes) have been successfully prepared by in-situ polymerization of the pyrrole on the surface of Fe₂O₃ nanotubes (Fe₂O₃-NTs), via using L-Lysine as modified surfactant. Hollow PPy nanotubes were also produced by dissolution of the Fe₂O₃ core from the core/shell composite nanotubes with 1 mol·L^?1 HCl. Scanning electron microscopy(SEM), transmission electron microscope (TEM), selective-area electron diffraction (SAED), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy(FT-IR) confirmed the formation of Fe₂O₃-NTs and Fe₂O₃@PPy core/shell nanotubes. Its catalytic properties were investigated under the ultrasound. The results of UV-vis spectroscopy (UV) demonstrated Rhodamine B (RhB) can be efficiently degraded by Fe₂O₃ @PPy nanotubes.     

Supporting of nickel(II) acenaphthenediimine with free amino group for ethylene polymerization

Bis (4-(4-amino-3, 5-diethylbenzyl)-2, 6-diethylphenylimino) acenaphthene] dichloronickel (NiLCl₂) was prepared and supported on SiO₂ modified by methyl trichlorsilane(S-1) and on SiO₂-MgCl₂/TiCl₄ (S-2) respectively. Two supported catalysts S-1 and S-2 used as catalysts for ethylene polymerization were studied and the influences of various polymerization conditions, including the polymerization temperature, cocatalysts, Al/Ni molar ratio on the catalytic activity, branching degree and branch length of PE were also investigated. The experimental results show that the supported catalysts exhibit higher catalytic activity for ethylene polymerization, the highest catalytic activity of S-1 using AlEt₂Cl as cocatalyst at 50°C, reaching 5.8×10⁵gPE/molNi··h, and needed lower Al/Ni molar ratio compared to homogeneous analogue.     

电合成过氧化氢电催化剂的设计及进展

过氧化氢（H₂O₂）是一种环境友好的高效氧化剂，被广泛应用于医疗、半导体芯片等行业.利用氧还原法（ORR）电化学合成过氧化氢替代传统蒽醌法极具潜力.为了实现这一工艺的商业化，开发具有高活性、高选择性和长期稳定性的2e^-ORR电催化剂迫在眉睫.本文系统地介绍了目前已有金属与非金属类催化剂的研究历程，特别强调表面基团调控策略，并解析了其对还原过程中间体键位结合强度及电子转移路径的影响.重点阐述电子和几何效应、配位杂原子掺杂和非金属基材料活性位点等关键问题，突出了适当的介观结构工程和动力学策略可进一步优化现有催化剂的催化活性和H₂O₂选择性.最后，指出了非金属催化剂活性中心的探索、电解质环境对催化剂的影响及较大输出功率工业设备的设计等方面的挑战，并对电催化合成过氧化氢领域的发展方向提出了展望.     

Structural and Dielectric Properties of Ba5RNiNb9O30 （R = La, Nd and Sm） ceramics

1 IntroductionSince the discovery of ferroelectricity and relatedproperties in BaTiO3,a large amount of research work onoxidesin search of novel materials for industrial applica-tions ,has been done .High performance dielectric ceram-ics are applied as key materials for resonators , discreteand multiplayer (MLC) capacitors ,andtemperature com-pensating capacitors . Some ferroelectric oxides are alsovery important due to the rapid progress in microwavetelecommunications ,satellite broadcastin…