Nd扩渗BaTiO_3陶瓷的电性能与XPS研究

采用气相法对钛酸钡陶瓷扩渗Nd元素,经Nd扩渗BaTiO3陶瓷的电性能发生了十分显著的变化。通过正交实验,确定了最佳扩渗条件,当Nd的浓度为2%,扩渗时间为4h,扩渗温度为860℃时,BaTiO3陶瓷的导电性最好,其室温电阻率从4 3×109Ω·m下降为37 45Ω·m,而且随着温度升高,交流电导逐渐增大,导电性更强。Nd扩渗使BaTiO3陶瓷的介电常数增加,而介电损耗降低,BaTiO3陶瓷的介电性能得到了显著改善。经Nd扩渗BaTiO3陶瓷的介电常数随着温度的变化呈明显的PTC效应,其居里温度降低为118 1℃。经XPS测试分析,给出了Nd扩渗BaTiO3陶瓷体系中各元素结合能位置的峰值,并表明Nd扩渗BaTiO3陶瓷中Nd,Ba,Ti都存在变价,因而导致了BaTiO3陶瓷导电性的增强。     

B2O3-Bi2O3-ZnO-Al2O3玻璃助烧剂对BaTiO3陶瓷烧结条件、晶体结构和介电性能的影响

通过调节B₂O₃‐Bi₂O₃‐ZnO‐Al₂O₃(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO₃)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明：添加适量的BBZA玻璃能够有效地将BaTiO₃陶瓷烧结温度由1350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO₃的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO₃陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO₃晶粒表面。优化的BaTiO₃陶瓷制备条件如下：BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO₃陶瓷介电常数达到1364,介电损耗低至1.2%。     

Nd扩渗BaTiO3陶瓷的电性能与XPS研究

采用气相法对钛酸钡陶瓷扩渗Nd元素, 经Nd扩渗BaTiO3陶瓷的电性能发生了十分显著的变化. 通过正交实验, 确定了最佳扩渗条件, 当Nd的浓度为2%, 扩渗时间为4 h, 扩渗温度为860 ℃时, BaTiO3陶瓷的导电性最好,其室温电阻率从4.3×109 Ω*m下降为37.45 Ω*m, 而且随着温度升高, 交流电导逐渐增大, 导电性更强. Nd扩渗使BaTiO3陶瓷的介电常数增加, 而介电损耗降低, BaTiO3陶瓷的介电性能得到了显著改善. 经Nd扩渗BaTiO3陶瓷的介电常数随着温度的变化呈明显的PTC效应, 其居里温度降低为118.1 ℃. 经XPS测试分析, 给出了Nd扩渗BaTiO3陶瓷体系中各元素结合能位置的峰值, 并表明 Nd扩渗BaTiO3陶瓷中Nd, Ba, Ti都存在变价, 因而导致了BaTiO3陶瓷导电性的增强.     

低温合成四方相BaTiO3及其压电催化性能

基于淀粉糊化机制低温合成了四方相BaTiO₃粉体。采用扫描电子显微镜、透射电子显微镜、X射线衍射、傅里叶变换红外光谱、紫外可见吸收光谱、X射线光电子能谱对合成粉体的形貌、物相进行表征;在超声条件下,以系列典型染料为降解对象测试BaTiO₃压电催化性能。结果显示,煅烧温度为600℃时即可获得四方相BaTiO₃粉体,且随着温度的提升,结晶度逐渐增加;当煅烧温度为700℃时,合成的BaTiO₃粉体尺寸分布均匀,分散度良好,呈现类立方体状;在超声驱动下,BaTiO₃降解罗丹明B、刚果红、甲基橙染料时均展现出良好的效果,反应速率常数分别为1.090×10^-2、1.113×10^-2、1.084×10^-2 min^-1,并以降解刚果红为对象揭示其压电催化的机理,即空穴和超氧自由基是降解过程中的主要反应物质。     

Ba0.98Bi0.02(Ti0.9Zr0.1)1-xCuxO3陶瓷的介电性能、弛豫行为与结晶化学特性

采用固相合成法, Bi3+作施主掺杂A位, Cu₂₊作受主掺杂B位, 制备了Ba_0.98Bi_0.02(Ti_0.9Zr_0.1)_1-xCu_xO₃(x=0, 0.01, 0.02, 0.03)陶瓷样品。借助XRD、LCR等研究了该陶瓷的结构与介电性能。结果表明:当x=0.03时, 陶瓷样品出现第二相。通过GULP模拟, 缺陷偶极子的稳定性从低到高依次为:[2Bi_Ba^·+V_Ba"]、[2Bi_Ba^·+Cu_Ti/Zr"]、[Cu_Ti/Zr"+V_O^··], 结合实验可知:介电弛豫程度与晶体中缺陷偶极子的存在形式相关, 其中x=0.01时, 晶体中以[2Bi_Ba^·+Cu_Ti/Zr"]为主。随Cu₂₊掺杂量的增加, 介电常数增加, 介电常数与B位键价和呈反比变化、与八面体BO₆的体积呈正比变化。     

Bi2O3掺杂对Ag(Nb0.8Ta0.2)O3陶瓷结构和介电性能的影响

本文研究了Bi₂O₃掺杂对Ag(Nb_0.8Ta_0.2)O₃陶瓷的结构和介电性能的影响。X射线衍射(XRD)结果表明,Bi₂O₃的掺杂可以使陶瓷中Ag⁺被还原并析出,且银析出的量随Bi₂O₃掺杂量的增加而不断增加,这可能源自于Bi³⁺对Ag⁺的取代。在一定范围内增大Bi₂O₃掺杂量可提高Ag(Nb_0.8Ta_0.2)O₃陶瓷的室温介电常数,降低介电损耗,并使温度系数向负值方向移动。当Bi₂O₃的掺杂量约为3.5wt%时,样品具有较大的介电常数(ε=672)和较小的介电损耗(tanδ=7.3×10^-4)。     

均匀共沉淀法制备钛酸钡-钡铁氧体核-壳结构粒子

用均匀共沉淀法制备了钛酸钡-钡铁氧体核-壳粒子, 研究了沉淀反应温度、尿素/金属离子摩尔比值(R)和BaTiO₃浓度对核-壳粒子形貌和结构的影响, 探讨了钛酸钡-钡铁氧体核-壳粒子在焙烧时的形成过程及其磁性能. 采用透射电子显微镜(TEM)、X射线衍射(XRD)分析仪对钛酸钡-钡铁氧体前驱物核-壳粒子及钛酸钡-钡铁氧体核-壳粒子的形貌和结构进行了表征, 采用振动样品磁强计(VSM)研究了钛酸钡-钡铁氧体核-壳粒子的磁性能. 结果表明: 当沉淀反应温度为100 °C, R为180, BaTiO₃浓度为2.5 g·L^-1时, 金属离子沉淀完全, 得到的钛酸钡-钡铁氧体前驱物核-壳粒子包覆层均匀、完整、光滑, 厚度约为10 nm. 过高的温度和R值都会导致大量独立颗粒杂质的生成; 随着BaTiO₃浓度的增大, 包覆层厚度有减小的趋势. 当焙烧温度为900 °C时, 壳层中开始形成BaFe₁₂O₁₉相, 其形成过程为晶态的α-Fe₂O₃和BaCO₃首先生成中间相BaFe₂O₄, 然后由BaFe₂O₄和α-Fe₂O₃反应得到最终的BaFe₁₂O₁₉. 当焙烧温度为1000 °C时, 壳层完全转化为BaFe₁₂O₁₉相. 随着焙烧温度从900 °C升高到1000 °C, 所得BaTiO₃-BaFe₁₂O₁₉核-壳粒子的饱和磁化强度从16.5 A·m²·kg^-1增加到39.5 A·m²·kg^-1, 矫顽力从340 kA·m^-1略微降低到316 kA·m^-1.     

稀土气相扩渗BaTiO3基PTC陶瓷的NTCR效应

采用稀土气相扩渗法制备了La改性的BaTiO3基PTC陶瓷,并对其室温电阻率的变化及温-阻效应进行了研究.结果表明,BaTiO3基PTC陶瓷经La气相扩渗后,室温电阻率从2.7×109Ω.m下降到220Ω.m,在25-500℃范围内,电阻率随温度升高单调递减,从220Ω.m降至5.8Ω.m,产生了明显的NTCR效应.结合XRD,SEM,EDAX以及介电性能测试结果分析了La气相扩渗BaTiO3基PTC陶瓷NTCR效应的形成机理,建立了NTCR效应的物理结构模型.     

计时电量法求NiCl2(bpy)3在DMF中的扩散系数和速率常数

讨论了NiCl₂(bpy)₃(bpy：2,2-联吡啶)在DMF中的电化学行为. 控制电位使电极过程处于扩散控制下, 采用计时电量法求得了29 ℃时NiCl₂(bpy)₃在DMF中的扩散系数为5.99×10^－6 cm²•s^-1, 不同温度下的扩散系数随温度升高而增大. 选择合适的电极电位, 使电极过程处于扩散和电化学混合控制下, 采用计时电量法求得了不同电极电位下的反应速率常数k_f, 以及不同温度下的标准速率常数k⁰, 求得了表观活化能为14.4 kJ•mol^-1.     

低温烧结NaBi(WO4)2陶瓷的介电性能

采用固相合成法制备了（WO₄）₂（NBW）陶瓷，研究了NBW陶瓷的相结构、形貌、烧结特性和微波介电性能。NBW陶瓷在625~800℃烧结1~4 h能够致密化。X射线衍射表明在625~800℃烧结2 h的NBW陶瓷均为四方晶系白钨矿结构的单相陶瓷。随着烧结温度的提高，NBW陶瓷的介电常数、品质因数（Qf值）先增加后降低，谐振频率温度系数逐渐降低。经650℃烧结2 h获得的NBW陶瓷的介电常数为14.36，Qf值为16 503 GHz，谐振频率温度系数为-1.055×10-5℃^-1。NBW陶瓷与银共烧反应生成Ag₂W₂O₇相，而与Au、Al共烧具备化学兼容性。     

Near infrared study of aqueous rare-earth ethylsulfates

The near infrared spectra of aqueous solutions of the ethylsulfates of La, Nd, Gd, Tb, Er, Yb, Lu, Y, and Na have been determined from about 0.2 mol-dm^–3 to nearly saturation. The extinction coefficients of water have been calculated taking into account the absorption of ethylslfate anions determined in separate experiments. Their values appeared to be nearly the same as that of pure water. The relative contents of free OH groups in 0.5 and 0.7M solutions have been estimated from the absorbances at 1160 nm. They were lower in solutions of the heavy rare-earth ethylsulfates (Tb, Er, Yb, Lu) than in equimolar solutions of the lighter ones (La, Nd), confirming our previous view that secondary hydration of the heavy trivalent rare-earth cations is distinctly stronger than that of the lighter ones. A comparison of the spectra of these aqueous ethylsulfates with those of perchlorates shows that the structure-breaking ability of the C₂H₅SO ₄ ^– ion is much smaller than that of perchlorate anion.     

Microstructures of Some Bi-W-Nb-O Phases

Microstructures of three Bi-W-Nb-O phases have been examined by using high-resolution transmission electron microscopy. Bi₁₇W₂Nb₃O₃₉ and Bi₁₇WNb₃O₃₆ have incommensurate superstructures derived from the defect fluorite-type δ-Bi₂O₃ and can be regarded as intermediate phases between the type II solid solutions in the Bi-Nb-O and Bi-W-O systems. Bi₈W₂Nb₂O₂₃ has a Bi₂WO₆-like subunit cell with a stepped superstructure. Formation mechanisms of various superstructures are discussed.     

Reactivity of Binary Mixtures of La(III) Oxide and Cu(II) Oxalate or Nitrate and Synthesis of La(III) Cuprate

Reactivity of mixtures of La(III) oxide and Cu(II) oxalate/nitrate in hydrated as well as anhydrous state was studied using TG, DTA and XRD. Cu(II) oxide formed in the endothermic decomposition of mixture containing hydrated Cu(II) nitrate and La(III) oxide could not form La₂CuO₄ while Cu(II) oxide formed in the exothermic decomposition of mixture containing hydrated/anhydrous Cu(II) oxalate and La(III) oxide reacts with La(III) oxide and develops the phases CuLaO₃ and La₂CuO₄. The maximum reactivity with respect to the formation of La₂CuO₄phase was observed in mixture containing anhydrous Cu(II) oxalate. This revised version was published online in July 2006 with corrections to the Cover Date.     

电感耦合等离子体光谱法测定铜冶炼烟尘中锌

本实验介绍了电感耦合等离子体光谱法测定铜冶炼烟尘中锌含量的分析方法。针对样品碳,硅含量高的特点,有针对性的研究了样品的消解方法,确定采用盐酸、硝酸、氢氟酸、高氯酸对铜冶炼烟尘样品进行消解。同时进行了干扰试验,确定样品中高含量的铜,铅,砷等对样品测定结果没有影响。并对仪器的工作参数进行了优化。方法检出限为为0.011 mg/L,测定下限为0.019 mg/L,3个样品的相对标准偏差在0.54%~0.92%之间,加标回收率在96%~101.14%之间。该方法样品消解完全,流程短,操作简单,快速,测定准确度高,可以满足铜冶炼烟尘中锌含量的测定。     

Synthesis and characterization of gallium-based perovskitetype dense membrane with oxygen semipermeability

La0.15Sr0.85Ga0.3Fe0.7O3-δ(LSGFO) and La0.15Sr0.85Co0.3Fe0.7O3-δ(LSCFO) mixed oxygen-ion and electron conducting oxides were synthesized by using a combined EDTA and citrate complexing method, and the corresponding dense membranes were fabricated. The properties of the oxide powders and membranes were characterized with combined SEM, XRD, H2-TPR, O2-TPD techniques, mechanical strength and oxygen permeation measurement. The results showed that LSGFO had much higher thermochemical stability than LSCFO due to the higher valence stability of Ga3+. After the temperature-programmed reduction by 5% H2 in Ar from 20℃to 1020℃, the basic perovskite structure of LSGFO was successfully preserved. LSGFO also favors the oxygen vacancy formation better than LSCFO. Oxygen permeation measurement demonstrated that LSGFO had higher oxygen permeation flux than LSCFO, but they had similar activation energy for oxygen transportation, with a value of 110 and 117 kJ ?mol~(-1), respectively. The difference in oxygen permeation f     

α-Fe2O3掺杂对In2O3电导和气敏性能的影响

用化学共沉淀法制备了α Fe2O3掺杂的In2O3纳米晶微粉,研究了α Fe2O3掺杂对In2O3电导和气敏性能的影响. 结果表明, α Fe2O3和In2O3间可形成有限固溶体In2－xFexO3(0≤x≤0.40); Fe3＋对In2O3晶格中In3＋格位的部分取代,大大增强了阴阳离子间的结合力,导致材料中氧空位VO×数骤降、 自由电子的浓度变稀和电导下降. n(Fe3＋):n(In3＋)=5 :5的共沉淀粉于800 ℃下灼烧4 h所得的α Fe2O3掺杂In2O3传感器元件,对45 μmol•L－1 C2H5OH的灵敏度达54.0,为相同浓度干扰气体汽油的8倍多.     

Titania-supported mixed HPMoV polyoxometallates as precursors of hydrodesulfurization catalysts

HDS catalysts were prepared by loading H₃PMo₁₂O₄₀ or H₄PMo₁₁V₁O₄₀ polyoxometallates on TiO₂ (0.5 and 1.0 mmol (Mo+V)). Activity of the catalysts was tested in the HDS of thiophene. The activity of catalysts of low concentration was 2–3 times higher than the activity of those of high concentration. Temperature programmed reduction (TPR) and IR spectroscopy were used to determine the properties of the catalyst. TPR measurements proved that vanadium promotes and stabilizes HDS activity due to an increase in the Mo⁵⁺/Mo⁴⁺ ratio.     

Preparation of ZrO2-TiO2-CeO2 and Its Application in the Selective Catalytic Reduction of NO with NH3

TiO₂,ZrO₂-TiO₂,andZrO₂-TiO₂-CeO₂ were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature programmed desorption (NH₃-TPD), oxygen storage capacity (OSC), and temperature programmed reduction (H₂-TPR). The results showed that ZrO₂-TiO₂-CeO₂ exhibited large number of surface strong acid, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V₂O₅ and 9% (w)WO₃ for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O₂, and the results of catalytic activity showed that the catalyst used ZrO₂-TiO₂-CeO₂ as support yielded nearly 100% NO conversion at 275 °C at a gas hourly space velocity (GHSV) of 10000 h⁻¹, and it had the best catalytic activity and showed great potential for practical application.     

B2O3-Bi2O3-ZnO-Al2O3玻璃助烧剂对BaTiO3陶瓷烧结条件、晶体结构和介电性能的影响

通过调节B₂O₃-Bi₂O₃-ZnO-Al₂O₃(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO₃)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明：添加适量的BBZA玻璃能够有效地将BaTiO₃陶瓷烧结温度由1 350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO₃的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO₃陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO₃晶粒表面。优化的BaTiO₃陶瓷制备条件如下：BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO₃陶瓷介电常数达到1 364,介电损耗低至1.2%。