添加Sb2O5,ZnO和玻璃对(Zr0.7Sn0.3)TiO4陶瓷高频介电性能的影响

用氧化物混合方法制备了主晶相为(Zr0.7Sn0.3)TiO4的高频陶瓷材料.添加Sb2O5,ZnO和玻璃有效降低了陶瓷的烧成温度和介质损耗.添加0.5%Sb2O5(摩尔分数),1.5%ZnO(质量分数)和3.0%玻璃(质量分数)的陶瓷组成在1 150℃烧结,在测试频率l MHz下的介电性能为:介电常数ε≈38,损耗角正切tanδ＝0.6×10-4,介电常数温度系数αe＝0±30×10-6/℃,体电阻率pv≥1013Ω.cm.用此种陶瓷材料可在中温烧结制成多层陶瓷电容器(multilayer ceramic capacitor,MLCC).     

添加剂对Ba(Zn1/3Nb2/3)O3-Sr(Zn1/3Nb2/3)O3陶瓷介电性能的影响

研究了MnCO3,BaZrO3对0.35Ba(Zn1/3Nb2/3)O3(BZN)-0.65Sr(Zn1/3Nb2/3)O3(SZN)陶瓷介电性能的影响.研究表明:添加MnCO3,BaZrO3时,对陶瓷的烧结均起促进作用,增大介电常数.加入1%(质量分数)的MnCO3可使陶瓷具有较小的介质损耗,同时MnCO3对陶瓷的介电常数温度系数具有正向调整作用.加入BaZrO3后通过生成液相而减少了第二相Ba5Nb4O15,BaNb2O6的生成.所制备的(0.35BZN0.65SZN)+0.1%MnCO3陶瓷的εr≈43.6,αe≈-8×10-6/K,tanδ＝0.6×10-4,且烧结温度低于1 300℃.     

添加CuO对Ca(Sm0.5Nb0.5)O3陶瓷烧结和微波介电性能的影响

采用传统高温固相反应法制备了掺杂不同量烧结助剂CuO的Ca(Sm0.5Nb0.5)O3微波介质陶瓷,研究了CuO对Ca(Sm0.5Nb0.5)O3陶瓷的烧结性、结构及微波介电性能的影响. 结果表明：添加CuO能有效促进Ca(Sm0.5Nb0.5)O3陶瓷晶粒致密化,降低烧结温度约200℃. 添加1.5%(w) CuO, 1350℃保温4 h烧结的Ca(Sm0.5Nb0.5)O3陶瓷的介电性能较优,相对介电常数er=23.98,品质因素与频率乘积Q′f=27754.5 GHz,谐振频率温度系数tf=-2.7′10-6 ℃-1.     

Bi2O3及MnO2掺杂对[(Pb,Ca) La](Fe,Nb)O3介质陶瓷结构及微波性能的影响

研究了Bi2O3及MnO2掺杂量对[(Pb0.5Ca0.5)0.92La0.08](Fe0.5Nb0.5)O3陶瓷结构及介电性能的影响.结果表明Bi2O3及MnO2均是良好的烧结助剂,可降低体系的烧结温度60～100 ℃,同时提高陶瓷的密度.XRD图谱证明当MnO2的质量分数≤2%时,陶瓷为钙钛矿相及焦绿石相,表明Mn4+进入主相晶格,而Bi2O3的掺杂会使体系中出现未知第三相.随MnO2的增加,陶瓷的介电常数先增加后减小,同时使品质因数及谐振频率温度系数的单调下降.Bi2O3的掺杂则会使陶瓷介电常数及谐振频率温度系数升高,而品质因数下降.Bi2O3及MnO2的联合掺杂比单一掺杂更有效地降低了陶瓷的烧结温度,达100～140 ℃,且在低温烧结条件下有比单一掺杂时更好的微波介电性能.其中当Bi2O3和MnO2的质量比k=1,2种添加物总质量分数w=1%,烧结条件为1 050 ℃,保温4 h,陶瓷的相对介电常数εr,品质因数(Q)与谐振频率(f)的乘积Qf以及谐振频率温度系数分别为91.1, 4 870 GHz和18.5×10-6/℃.     

添加Sb_2O_5,ZnO和玻璃对(Zr_(0.7)Sn_(0.3))Ti_4陶瓷高频介电性能的影响

用氧化物混合方法制备了主晶相为 (Zr0 .7Sn0 .3)TiO4的高频陶瓷材料。添加Sb2 O5,ZnO和玻璃有效降低了陶瓷的烧成温度和介质损耗。添加 0 .5 %Sb2 O5(摩尔分数 ) ,1.5 %ZnO(质量分数 )和 3.0 %玻璃 (质量分数 )的陶瓷组成在 115 0℃烧结 ,在测试频率 1MHz下的介电性能为 :介电常数ε≈ 38,损耗角正切tanδ=0 .6× 10 - 4 ,介电常数温度系数αε=0± 30× 10 - 6 /℃ ,体电阻率 ρv≥ 10 1 3Ω·cm。用此种陶瓷材料可在中温烧结制成多层陶瓷电容器 (multilayerceramiccapacitor,MLCC)     

BiVO4掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7陶瓷介电性能的影响

采用传统陶瓷工艺制备了BiVO4掺杂的(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7(bismuth zincate niobate,BZN)介质陶瓷,用X射线衍射、扫描电镜以及电感-电容-电阻测试仪等对其烧结特性、相结构及介电性能进行了系统研究.结果表明BiVO4掺杂能显著降低BZN的烧结温度,由1 000℃降至850℃,同时可优化频率温度系数τf,由-450×10-6/℃变为-254×10-6/℃.BiVO4的掺杂量为5%,烧结温度为900℃时,BZN陶瓷具有较好的介电性能介电常数ε=153,品质因数Q=2 100,频率温度系数τf=-350×10-6/℃.     

V2O5掺杂对(Bi1.5Zn1.0Nb1.5)O7介质陶瓷性能的影响

采用传统的固相反应法制备陶瓷试样,借助XRD,SEM和LCR测试仪,研究了V2O5掺杂对(Bi1.5Zn1.0Nb1.5)O7介质陶瓷的烧结特性和介电性能的影响.结果表明,掺杂适量V2O5后试样的烧结温度明显降低,相结构仍为立方焦绿石单相,且具有良好的介电性能:介电常数(εr)为135～154,介电损耗(tan δ)为0.0033～0.0007,频率温度系数(τf)为-442～-387(2MHz).     

底电极与组分对Ba1-xSrxTiO3薄膜结构与介电性能影响的研究

以Pt与La0.5Sr0.5CoO3为电极,采用溶胶-凝胶法分别沉积Sr/Ba比不同的Ba1-xSrxTiO3薄膜,研究结果表明:沉积在两种电极上的Ba1-xSrxTiO3薄膜,随着Sr/Ba比的增加,Ba1-xSrxTiO3薄膜的介电常数呈先增大后减小的趋势,当Sr含量为50%即为Ba0.5Sr0.5TiO3且频率为1 kHz时,薄膜具有最大的介电常数,分别是80,95和最小的介质损耗,分别是0.15,0.1.介电常数随着频率的升高呈下降趋势,介质损耗则成上升趋势.沉积La0.5Sr0.5CoO3电极上的Ba1-xSrxTiO3薄膜比Pt电极上的Ba1-xSrxTiO3薄膜具有更高的介电常数和低的介质损耗.     

添加剂对Ba(Zn_(1/3)Nb_(2/3))O_3-Sr(Zn_(1/3)Nb_(2/3))O_3陶瓷介电性能的影响

研究了MnCO3,BaZrO3对 0 .35Ba(Zn1 /3Nb2 /3)O3(BZN) -0 .65Sr(Zn1 /3Nb2 /3)O3(SZN)陶瓷介电性能的影响。研究表明 :添加MnCO3,BaZrO3时 ,对陶瓷的烧结均起促进作用 ,增大介电常数。加入 1% (质量分数 )的MnCO3可使陶瓷具有较小的介质损耗 ,同时MnCO3对陶瓷的介电常数温度系数具有正向调整作用。加入BaZrO3后通过生成液相而减少了第二相Ba5Nb4O1 5,BaNb2 O6 的生成。所制备的 ( 0 .35BZN -0 .65SZN) 0 .1%MnCO3陶瓷的εr≈ 43.6,αε≈ -8× 10 - 6 /K ,tanδ =0 .6× 10 - 4 ,且烧结温度低于 130 0℃。     

Ni替代Nb对Bi1.5ZnNb1.5O7陶瓷介电性能的影响

以分析纯级原料,按照一定比例混合,利用固相反应制备Bi1.5ZnNb1.5O7陶瓷.研究结果表明:Ni掺杂样品能够有效地降低烧结温度至960℃;样品相结构保持立方焦绿石相;随着Ni3+替代量的增加,介质材料的介电常数及介电损耗逐渐增大;在-195～150℃的温度范围内,介电常数存在明显的弛豫现象,随Ni3+的掺杂量增加,逐渐向高温方向移动,在1 MHz下其峰值温度为:-98.1℃,-97.7℃,-97.1℃,-94.2℃.     

钕-铝系稀土色料的研制

通过钕-铝系列色料合成实验,分析不同配比及不同矿化剂等对色料呈色效果的影响,确定最佳工艺方法。对实验结果进行XRD及色度分析,确定其主晶相为钕酸铝,试样的明度均在70以上,色彩鲜艳亮丽。     

Phase equilibrium in binary La2O3-Dy2O3 and ternary CeO2-La2O3-Dy2O3 systems

Cerium oxide doped with oxides of rare earth elements is a multifunctional material, a wide range of uses which is associated with its unique physicochemical properties. Phase diagrams of multicomponent systems are the physicochemical basis for the creation of new materials with improved characteristics.In this work, phase equilibria in ternary CeO₂–La₂O₃–Dy₂O₃ and binary La₂O₃–Dy₂O₃ systems in the whole concentration range were studied. No new phases have been identified in these systems. An isothermal section of the phase diagram of the CeO₂–La₂O₃–Dy₂O₃ system at a temperature of 1500 °С is constructed. No new phases have been detected in the system. It was found that in the studied ternary system solid solutions are formed on the basis of (F) modification of CeO₂ with structure of fluorite type, monoclinic (B), cubic (C) and hexagonal (A) modifications of Ln₂O₃.In the La₂O₃–Dy₂O₃ binary system (1500–1100 °С) three types of solid solutions are formed: based on hexagonal modification A-La₂O₃, monoclinic modification B-Dy₂O₃ and cubic modification C-Dy₂O₃ separated by two-phase fields (A+B) and (B+C), respectively. The boundaries of the regions of homogeneity of solid solutions based on A-La₂O₃ are determined by compositions containing 35–40, 20–25, 15–20 mol% Dy₂O₃ at 1500, 1250, 1100 °C, respectively. From the obtained data it follows that the solubility of Dy₂O₃ in the hexagonal modification of lanthanum oxide is 39 mol% at 1500 °C, 23 mol. % at 1250 °C and 16 mol% at 1100 °C. The limits of existence of solid solutions based on monoclinic B-modification are determined by compositions containing 30–35, 65–60 (1250 °С), 35–40, 55–60 (1100 °С) 40–45, 70–75 (1500 °C) mol% Dy₂O₃.In the studied system, with a decrease in temperature from 1500° to 1100°C, there is a decrease in the solubility of La₂O₃ in the crystal lattice of cubic solid solutions of C-type from 16 to 10 mol%.     

Fe2+/H2O2体系O2生成路径

掌握Fe²⁺/H₂O₂体系O₂的生成路径,可为避免H₂O₂无效分解,开发经济高效的Fe²⁺/H₂O₂体系利用技术指明方向。采用添加自由基捕获剂的方法,探究Fe²⁺/H₂O₂体系内各种自由基对O₂生成速率的影响,进而确定O₂的生成路径。结果表明:Fe²⁺/H₂O₂体系内不会产生大量O₂^-·,O₂^-·不是生成O₂的主要反应物质;O₂^-·被全部捕获后,体系中仍产生大量O₂^-·,但此时无O₂生成,证明生成O₂的反应由·OH和HO₂·两种自由基直接参与。分析认为反应·OH+HO₂·-H₂O+O₂是体系内O₂生成的主要路径。控制Fe²⁺/H₂O₂体系定向生成·OH,抑制HO₂·的产生,是提高Fe²⁺/H₂O₂体系中H₂O₂利用率的有效手段。     

Polycrystalline In2O3 and In2O3/Y2O3 photoanodes

Single crystal In₂O₃ shows promise as a photoanode for the decomposition of water. Because of various difficulties in the preparation of the single crystal material, two simple techniques were developed for the preparation of polycrystalline In₂O₃ anodes. One method involves the thermal decomposition of the nitrate while the other utilizes the chemical vapour deposition technique. Voltammograms and photoresponse spectra of these anodes are compared to the single crystal material. Among other observations, it is noted that the quantum efficiencies of the thermally decomposed films are comparable to the single crystal material. It is also shown that the on-set potential can be shifted to more negative values by forming the mixed oxide In₂O₃/Y₂O₃.     

Na2O-Al2O3-Fe2O3系烧结过程中铝、铁的反应行为

以Al2O3, Fe2O3和Na2CO3为原料,对Na2O-Al2O3-Fe2O3系烧结过程中的反应行为进行了详细研究. 基于溶出率与时间、温度的关系,证明Na2O×Al2O3和Na2O×Fe2O3的生成反应动力学都服从Zhuralev-Lesokin-Tempelman模型,表观活化能分别为186.59和80.92 kJ/mol,表明Na2O×Fe2O3比Na2O×Al2O3在动力学上更易形成;Al2O3易与Na2O×Fe2O3反应形成Na2O×Al2O3和Fe2O3,在1273 K烧结30 min,所得熟料Al2O3溶出率达98.51%;Fe2O3对Na2O×Al2O3的形成有双重作用,在1273 K下可加速Na2O×Al2O3的形成,超过1323 K,促使Na2O×Al2O3分解成Na2O和b-Al2O3,且随着温度升高或时间延长,分解程度增高,从而导致熟料中Al2O3溶出率显著降低.     

H2O2 / O3, H2O2 / UV And H2O2 / Fe2+ Processes For The Oxidation Of Hazardous Wastes

Activated hydrogen peroxide produces very reactive OH-radicals which destroy hazardous contaminants in water. The principles and different methods of activation are described. Results from laboratory studies show the numerous applications of this new technology. A successful scaleup of laboratory tests to an industrial level is discussed. Finally, a cost estimate for treating different types of water with hydrogen peroxide is presented.     

Propylene metathesis over Re2O7/Al2O3-B2O3 catalysts

A series of alumina aluminum borate (AAB) with various Al/B molar ratios were prepared by the coprecipitation method. The supported rhenium oxide catalysts with various contents of Re₂O₇ were also prepared by the impregnation method with perrhenic acid. The catalytic activity and stability of Re₂O₇/AAB catalysts for the reaction of propylene metathesis were tested in a fixed-bed microreactor. It was found that Re₂O₇/AAB is more active, stable and regenerable than Re₂O₇/Al₂O₃ for propylene metathesis. The optimum Al/B molar ratio was found to be in the range of 4–10.     

Barium aluminate hydrates—VI. 2BaO.Al2O3.5H2O and 2BaO.Al2O3.H2O

The compound 2BaO.Al₂O₃.5H₂O has been synthesised and studied by infra-red, X-ray and thermal analytical techniques. The compound of approximate formula 2BaO.Al₂O₃.H₂O forms as a dehydration product. The results are interpreted in terms of the known structure.