La0.7K0.3Ni0.9Cu0.1O3钙钛矿的制备及催化碳烟性能的研究

采用溶胶凝胶法制备了一系列La1-xKxNi1-yMyO3(M=Cu,Co,Mn)钙钛矿复合氧化物催化剂,并利用O2-TPO测试该系列催化剂催化氧化碳烟的性能。通过XRD、H2-TPR、XPS对其进行了表征,结果表明,所制备催化剂均为六方晶系钙钛矿结构。着重考察了A位K掺杂量和B位掺杂元素及其掺杂量对催化碳烟性能的影响。结果表明:当K掺杂量x=0.3时,产生更多氧空位,增加了表面吸附氧数量,同时提高了B位Ni的价态;B位Cu掺杂量y=0.1时,表面吸附氧数量增加,Ni 3+含量增大,从而提高了催化剂的活性。La0.7K0.3Ni0.9Cu0.1O3催化剂与碳烟紧密接触下,Ti、Tm分别为268.1℃和272.8℃。     

PbS插层K4Nb6O17复合物的制备及其光催化制氢活性

采用固相法合成层状半导体K4Nb6O17,通过层间离子交换反应、胺插入反应以及硫化反应制备了纳米PbS插层的K4Nb6O17复合光催化剂(记作K4Nb6O17/PbS).利用X射线衍射(XRD),场发射扫描电镜(SEM),X射线荧光光谱仪(XRF),紫外可见漫反射(UV-Vis)和分子荧光光谱(PL)等技术对其进行表征.考察了催化剂在Na2SO3和Na2S为牺牲剂的光催化制氢活性.结果表明,PbS的插层拓展了K4Nb6O17对可见光的响应,催化制氢活性也有明显提高.在紫外光和可见光下3 h产氢量分别达到123.94和0.66 mmol/(g cat).最后讨论了插层复合催化剂光生电荷转移的机理.     

K4Nb6O17光催化分解水产氢活性的研究

通过高温固相反应法合成了层状K4Nb6O17,采用X射线衍射、比表面积测定、扫描电镜等对K4Nb6O17进行了结构和形貌表征.在I-为电子给体、RuO2为助催化剂的情况下研究了RuO2的负载量、I-离子浓度和溶液pH值对K4Nb6O17光催化分解水产氢活性的影响.研究结果表明,表面负载RuO2可以显著提高K4Nb6O17光催化产氢速度.当I-浓度为15mmol/L,pH=9,RuO2负载量为0.7%时,约400nm紫外光辐射下K4Nb6O17光催化产氢的活性最佳,氢气生成的速度为798.9μmol/L·h.     

固相法合成La2Ni0.5M0.5O4+δ(M=Co,Cu)材料及电性能

使用金属氧化物La2O3,NiO,CuO和Co2O3作为原料,固相反应法能够合成出具有K2NiF4型结构单一相的、且晶粒尺寸在35～50nm范围的La2Ni0.5M0.5O4 δ(M=Co,Cu)粉料,用XRD、SEM和直流四极探针电导测试法研究了合成La2Ni0.5M0.5O4 δ(M=Co,Cu)粉料的煅烧工艺条件和掺杂元素对电性能的影响以及粉料的颗粒形貌.随着煅烧温度的升高和保温时间的延长,晶粒尺寸在不断长大;合成的粉料在1300℃烧结5h后所有样品的电导率在空气条件下于100～800℃范围内都在增加.掺杂C0或Cu后的材料La2NiO4 δ的电导率均有增加,但掺杂Co后材料电导率要大于掺杂Cu的电导率.为此确定La2Ni0.5M0.5O4 δ(M=Co,Cu)类粉料固相法合成的适宜煅烧条件为1400℃下保温时间14h.     

硬脂酸法制备层状K2La1.8Nb0.2Ti3O10

采用硬脂酸法在相对较低的温度下掺杂Nb制备了K2La1.8Nb0.2Ti3O10层状化合物.通过X射线衍射、透射电子显微镜、紫外-可见吸收光谱、拉曼光谱对产物进行了表征.结果表明,通过硬脂酸法在800℃可获得超细K2La1.8Nb0.2Ti3O10,颗粒尺寸为100～250 nm,经过Nb掺杂后的产物仍然保持层状结构,层间距约1.5nm.紫外-可见光谱表明掺杂前后的产物在紫外区均有较明显的吸收,但经Nb掺杂后的K2La1.8Nb0.2Ti3O10吸光度明显增强.     

层状半导体K_4Nb_6O_(17)光催化研究进展

阐述了半导体光催化分解水的基本原理,介绍了新型光催化剂K4Nb6O17的结构及制备方法,对K4Nb6O17的金属负载、离子掺杂以及插层复合等改性方法进行综述,并就K4Nb6O17作为光催化剂的前景进行了展望。     

元素(Ce、Co、La、Sn)掺杂对V-Mo/TiO2催化剂脱硝活性的影响

采用浸渍法制备了一系列V-Mo/TiO2催化剂,考察了钒含量、钼含量及元素(Ce、Co、La、Sn)掺杂对催化剂脱硝活性的影响,并利用XRD、BET、H2-TPR、NH3-TPD及XPS等方法对催化剂的理化性能及结构进行了表征.结果显示,钒最佳含量为3％,钼最佳含量为6％.将Ce、La、Co、Sn掺杂到3％V2 O5-6％MoO3/TiO2中,催化剂的脱硝效率明显提高,其中,3％V2 O5-6％MoO3-1％SnO2/TiO2催化剂表现出最佳的脱硝活性,在180℃具有良好的脱硝稳定性,在引入10％(体积分数)H2 O和0.03％(体积分数)SO2后,表现出良好的抗SO2/H2 O的性能.这主要是由于引入的金属元素以氧化物或钒酸盐形式存在,并与活性组分钒物种有很强的相互作用,抑制了TiO2晶粒的长大,起到了细化TiO2粒径的作用,增加了催化剂表面的弱酸性位点,同时,表面活性氧及还原态的V4+、Mo4+物种数量有了大幅提升,增大了催化剂的还原程度,有利于催化还原反应的进行.     

β-FeSi2基热电材料的研究进展

介绍了β-FeSi2合金的基本特性和制备方法.评述了目前通过不同的元素掺杂可制得N型或P型β-FeSi2基半导体材料以及在热电性能方面取得的重要大进展.其中掺杂Co,B元素可得到N型β-FeSi2基半导体材料,且掺杂Co,在850 K最大ZT值为0.4;而掺杂B,高于800 K时Z值是未掺杂3～6倍,在667 K最大Z值为1.18×10-4 K-1.掺杂Mn,Cu,Al可获得P型β-FeSi2基半导体材料,掺杂Mn在873 K时最大Z值达2×10-4 K-1;掺杂Cu可缩短β相的生成时间;掺杂Al,在743 K获得的最大Z值为1.55×10-4 K-1.指出通过结构优化、组分调整,进一步提高β-FeSi2基合金的热电性能.     

油水自组装制备Ag@AgCl/K_4Nb_6O_(17)及其光催化降解有机污染物的研究

在高温固相法制备K4Nb6O17的基础上,采用油水自组装合成复合光催化剂Ag@Ag Cl/K4Nb6O17,利用XRD、SEM、TEM、EDX、UV-Vis、PL、BET等多种手段对复合光催化剂的微观结构、形貌和性能进行了表征,并研究了可见光下降解亚甲基蓝(MB)的催化性能。研究表明,Ag@Ag Cl的粒径约为20 nm,均匀分散在二维层状结构K4Nb6O17的表面上;贵金属Ag纳米粒子的表面等离子体效应显著,对可见光的吸收范围从400 nm拓展到800 nm;Ag@Ag Cl(25%(质量分数))/K4Nb6O17在可见光照射60 min对亚甲基蓝的降解率为88.2%,远远高于单体Ag@Ag Cl和K4Nb6O17的活性。循环实验证明催化剂具有较好的稳定性,同时对苯酚和罗丹明B(Rh B)也具有一定的催化降解活性。淬灭实验表明自由基和空穴均为活性物种,并在此基础上提出降解机理。     

过渡金属(Mn2+、Ni2+、Fe3+、Cu2+)掺杂ZnO基稀磁半导体的制备及性质

利用溶液腐蚀法制备了Mn2+、Ni2+、Fe3+、Cu2+离子掺杂的ZnO基稀磁半导体。XRD表明掺杂后的ZnO仍然保持单一的纤锌矿结构,没有任何杂质相产生。由紫外-可见光反射谱可知掺杂后吸收边发生了红移。掺杂前ZnO的带隙为3.20eV,对样品分别掺入Mn、Ni、Fe和Cu后的带隙分别为3.19eV、3.15eV、3.08eV和3.17eV。掺杂后样品的室温PL谱除了紫外发射峰外,对于Mn掺杂的样品还在蓝光区域出现了2个分别位于424nm和443nm的发射峰,Fe掺杂的样品出现了一个位于468nm的微弱发射峰,Cu掺杂的样品出现了位于469nm及535nm的很宽的发射峰。室温磁滞回线显示掺杂后样品有明显的铁磁性,掺入Mn、Ni、Fe和Cu样品的剩余磁化强度(Ms)分别为0.3902×10-3emu/cm3、0.454emu/cm3、0.372emu/cm3和0.962×10-3emu/cm3,矫顽力分别为47Oe、115.92Oe、99.33Oe和23Oe。经分析室温铁磁性来源于缺陷调制的Mn2+-Mn2+长程铁磁交换相互作用。     

Specific Features of Anodic Dissolution of Copper in H2SO4 + H2O and H2SO4 + CuSO4 + H2O Systems

We investigate anodic dissolution of copper in H₂SO₄ + H₂O and H₂SO₄ + H₂O + CuSO₄ systems, which model solutions for the electrochemical production of copper (+2) sulfate. Ultimate densities of anodic current in the temperature range 20–80°C for a voltage up to 8 V were found. We show that a concentration of copper ions ( Cu²⁺) of 1.5–2.0 moles/liter in the anolyte is the limiting one in the electrochemical production of solutions of copper (+2) sulfate.     

Characterization of various Eu2+ sites in Ca2SiO4:Eu2+ and Ba2SiO4:Eu2+ by high-pressure spectroscopy

Photoluminescence of Ba₂SiO₄ and Ca₂SiO₄ activated with Eu²⁺ was investigated at various temperatures (from 10 K to 300 K) and pressures (from ambient to 200 kbar). At ambient pressure and room temperature, under UV excitation both phosphors yielded a green emission band with maxima at 505 nm and 510 nm for Ba₂SiO₄ and Ca₂SiO₄, respectively. The energies of these bands depended on pressure; the pressure shifts were ?12:55 cm^?1/kbar for Ba₂SiO₄:Eu²⁺; and ?5:59 cm^?1/kbar for Ca₂SiO₄:Eu²⁺. In the case of Ca₂SiO₄:Eu²⁺, we observed additional broadband emission at lower energies with a maximum at 610 nm (orange band). The orange and green emission in Ca₂SiO₄:Eu²⁺ had different excitation spectra: the green band could be excited at wavelengths shorter than 470 nm, whereas the orange band — at wavelengths shorter than 520 nm. The pressure caused a red shift of orange emission of 7.83 cm^?1/kbar. The emission peaked at 510 nm was attributed to the 4f⁶5d→4f⁷(⁸S₇₌₂) transition of Eu²⁺ in the β — Ca₂SiO₄:Eu²⁺ phase, whereas the emission peaked at 610 nm — to the γ — Ca₂SiO₄:Eu²⁺ phase. The emission of Ba₂SiO₄:Eu²⁺ peaked at 505 nm was attributed to the 4f⁶5d→ 4f⁷(⁸S_7/2) transition of Eu²⁺ in the β — Ba₂SiO₄ phase.     

Improvement microwave dielectric properties of Zn2SnO4 ceramics by substituting Sn4+ with Si4+

The microwave dielectric properties of Zn₂(Sn_(1?x)Si_x)O₄ ceramics were examined with a view to their exploitation for mobile communication. The Zn₂(Sn_(1?x)Si_x)O₄ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Zn₂(Sn_(1?x)Si_x)O₄ ceramics revealed no significant variation of phase with sintering temperatures. A maximum density of 6.24 g/cm³ was obtained for Zn₂(Sn_0.93Si_0.07)O₄ ceramic, sintered at 1,175 °C for 4 h. Dielectric constant (? _r ) of 8.12, quality factor (Q × f) of 55,500 GHz, and temperature coefficient of resonant frequency (τ _f ) of ?119.3 ppm/°C were obtained for Zn₂(Sn_0.93Si_0.07)O₄ ceramics that were sintered at 1,175 °C for 4 h.     

Photo- and thermoluminescence of BaGa2S4:Eu2+ and BaGa2S4:Eu2+,Ce3+ crystals

Data are presented on the photo- and thermoluminescence of polycrystalline BaGa₂S₄:Eu²⁺ and BaGa₂S₄:Eu²⁺, Ce³⁺ at temperatures from 77 to 300 K. The broad photoluminescence band at 505 nm in BaGa₂S₄:Eu²⁺ is shown to be due to the 4f ⁶5d → 4f ⁷ transition. The broad emission bands at 460 and 510 nm in BaGa₂S₄:Ce³⁺ arise from the 5D (² D _3/2) → 4f ²(² F _5/2) and 5D (² D _3/2) → 4f ²(² F _7/2) transitions. Codoping of BaGa₂S₄ with Eu²⁺ and Ce³⁺ increases the luminescence efficiency owing to energy transfer from Ce³⁺ to Eu²⁺. The thermoluminescence data were used to evaluate the energies of the traps involved: 0.26, 0.31, 0.42, 0.57, and 0.64 eV in BaGa₂S₄:Eu²⁺ and 0.28, 0.32, 0.54, 0.61, and 0.65 eV in BaGa₂S₄:Eu²⁺, Ce³⁺. Original Russian Text ? A.N. Georgobiani, B.G. Tagiev, S.A. Abushov, O.B. Tagiev, Zheng Xu, Suling Zhao, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 2, pp. 151–155.     

Liquid phosphors POCl3-ZrCl4-235UO 2 2+ -Nd3+

Liquid phosphors POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ and POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ with concentrations of Nd³⁺ and UO ₂ ²⁺ of up to 0.75 and 0.12 M were prepared; the lifetime of the Nd³⁺ luminescence was up to 300 μs. The lifetime of the Nd³⁺ luminescence in POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions decreases with increasing neodymium concentration, and this decrease is more pronounced than that in POCl₃-ZrCl₄-Nd³⁺ solutions. At molar ratio [ZrCl₄]/[Nd³⁺] < 1.5, the luminescence lifetime sharply decreases with decreasing ZrCl₄ concentration. The intensity of the absorption bands of the OH groups observed in the near-IR range of the absorption spectra of POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions increases with increasing neodymium concentration. Upon storage of POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions for 2 years without contact with the environment, the intensity of the IR absorption bends of the OH groups gradually increases, whereas the lifetime of the Nd³⁺ luminescence decreases to 60-80 μs.     

Liquid luminophores POCl3-SiCl4-235UO 2 2+ -Nd3+

Samples of liquid luminophores POCl₃-SiCl₄-Nd³⁺, POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ , and POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ Nd³⁺ were prepared for the first time. The physicochemical properties and absorption spectra of the samples were compared. The solubility of Nd and U(VI) compounds in the POCl₃ SiCl₄ binary solvent was examined. The Nd³⁺ concentration attains a maximum of 0.3 mM when Nd and U(VI) trifluoroacetates are jointly dissolved at the [POCl₃]/[SiCl₄] molar ratio of 6 8. The shapes of the absorption band of the Nd ions at 860–900 nm, corresponding to the ⁴ I _9/2 → ⁴ F _3/2 electronic transition, differ significantly in POCl₃-SiCl₄-Nd³⁺ and POCl₃-SnCl₄-Nd³⁺ solutions, and in POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions the band shape also depends on the type of the Nd and U(VI) compounds introduced. The near-IR region of the absorption spectra of POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ and POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions contains absorption bands of the OH groups. The band intensity is analyzed in relation to the characteristics of the solutions. The Nd³⁺ luminescence lifetime τ in the luminophores synthesized was estimated at 70–20 μs.     

Microwave properties of the ceramic compositions M2+Ti4+ 1−x Me4+O3

The systems MgZr _x TiO₃, Mg_1?y Ca _y Ti_1?x Sn _x O₃, where Ti⁴⁺ is partially substituted by Zr⁴⁺ or Sn⁴⁺, and a series of compositions Mg (Ca_1.5Ta_0.2) _x Ti_1?x O₃, where Ti⁴⁺ is partially substituted by the four-valent cation (Ca_1.5Ta _0.2)⁴⁺, have been synthesized. For all compositions it was found that the permittivity ε_r and quality factor Q decreased monotonically with increasing substitution factor x. The measurements were carried out within the frequency range 9–11 GHz. At lower x, the quality factor had high values, so that such compositions could be used as microwave resonators with controllable parameters (for instance, for satellite television). The relationships between Q and x which have been obtained, together with the changes in density, are interpreted.     

Influence of Zn2+ and Si4+ codoping on luminescence properties of CaWO4:Eu3+ phosphor

The red afterglow phosphors of CaWO₄ doped with Eu³⁺, Zn²⁺ or (and) Si⁴⁺ were prepared by solid state reaction. All crystalline phases were identified by the X-ray powder diffraction (XRD). The photoluminescence spectra and decay curves as well as thermoluminecence (TL) curves of all samples were also investigated. In comparison to CaWO₄:Eu³⁺ phosphor, the luminescence and afterglow properties could be improved greatly after being doped with Zn²⁺ or (and) Si⁴⁺ ions.     

Adsorptive features of polyacrylamide-apatite composite for Pb2+, UO(2)2+ and Th4+

Micro-composite of polyacrylamide (PAA) and apatite (Apt) was prepared by direct polymerization of acrylamide in a suspension of Apt and characterized by means of FT-IR, XRD, SEM and BET analysis. The adsorptive features of PAA-Apt and Apt were then investigated for Pb(2+), UO(2)(2+) and Th(4+) in view of dependency on ion concentration, temperature, kinetics, ion selectivity and reusability. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. Apt in PAA-Apt had higher adsorption capacity (0.81, 1.27 and 0.69 mol kg(-1)) than bare Apt (0.28, 0.41 and 1.33 mol kg(-1)) for Pb(2+) and Th(4+), but not for UO(2)(2+). The affinity to PAA-Apt increased for Pb(2+) and UO(2)(2+) but not changed for Th(4+). The values of enthalpy and entropy changed were positive for all ions for both Apt and PAA-Apt. Free enthalpy change was DeltaG<0. Well compatibility of adsorption kinetics to the pseudo-second-order model predicated that the rate-controlling step was a chemical sorption. This was consistent with the free energy values derived from DR model. The reusability tests for Pb(2+) for five uses proved that the composite was reusable to provide a mean adsorption of 53.2+/-0.7% from 4x10(-3)M Pb(2+) solution and complete recovery of the adsorbed ion was possible (98+/-1%). The results of this investigation suggested that the use of Apt in the micro-composite form with PAA significantly enhanced the adsorptive features of Apt.