纳米Sm2O3掺杂CeO2粉末的制备和性能表征

以Ce2(CO3)3和Sm2O3为原料, 用改进的氨水-双氧水沉淀法制备了CeO2和(CeO2)0.8为基质(Sm2O3)0.2的纳米粉末.对干燥后的氢氧化物进行了TG/DSC热分析, 约650 ℃时Ce(OH)4完全转变为CeO2.XRD分析表明, 650 ℃焙烧的粉末为萤石结构, 说明Sm2O3已固溶到CeO2中.经TEM测试, 粉体颗粒大小在5～10 nm之间, BET测试的平均颗粒尺寸为11.2 nm.由TEM照片还可以看出粉体具有良好的分散性, 且无硬团聚体存在.     

附载CeO2的纳米γ-Al2O3合成及其悬浮液的分散稳定研究

以异丙醇铝和六水硝酸亚铈为铈源和铝源,采用溶胶-凝胶法制备了前驱体,并将前驱体在800℃下空气中焙烧2 h得到附载CeO2的高纯纳米γ-Al2O3.样品经X射线衍射(XRD)、透射电镜(TEM)、比表面积(BET)、化学成分和杂质含量分析,结果表明:合成的粉末为由γ-Al2O3和CeO2组成的混合物相,两者均属立方晶系,其中γ-Al2O3空间群为O7H-FD3M,CeO2空间群为Fm3m;晶粒平均粒径为15.7 nm,颗粒平均粒径约60～80 nm,粒子呈类球形,比表面积为159.01 m2·g-1;粒子纯度不低于99.97%,CeO2含量为24.22%.红外光谱(IR)测试结果显示,有Al-O-Ce键生成,表明CeO2与Al2O3并非简单混合.进一步通过对其悬浮液体系Zeta电位和吸光度的测定,研究了不同pH值条件、分散剂种类和用量以及氧化剂对其悬浮液分散稳定性的影响;采用超声波分散法,选择硝酸、氢氧化钾溶液作为pH调节剂,异丙醇胺作为分散剂,过氧化氢作为氧化剂,成功制备了长期存放不沉降的附载CeO2的纳米γ-Al2O3CMP浆料,确定了配制的优化工艺条件.     

过渡金属离子掺杂Zn3(OH)2V2O7·2H2O的合成及其光催化性质

利用水热法合成了3d过渡金属离子掺杂Zn3(OH)2V2O7·2H2O的微米花结构,其分子式可表达为Zn3-3xM3x(OH)2V2O7·2H2O(其中M=Cu,Co,Ni,Mn;0.001≤x≤0.20)。应用XRD、SEM、TEM、UV-Vis DRS、EDX和BET等分析测试技术对产物进行了表征。结构和形貌分析结果显示过渡金属离子掺杂后产物仍保持Zn3(OH)2V2O7·2H2O的六方晶体结构,微米花由主晶面为(0001)的纳米片组装而成。紫外-可见漫反射光谱显示过渡金属离子掺杂后带边吸收红移,其中以Cu的掺杂产物Zn3-3xCu3x(OH)2V2O7·2H2O最为明显,带边吸收扩展到可见光区。首次对Zn3(OH)2V2O7·2H2O及其不同金属离子掺杂产物Zn3-3xM3x(OH)2V2O7·2H2O进行了可见光催化降解有机污染物的研究,结果显示与其它产物相比掺0.1at%Cu的Zn2.997Cu0.003(OH)2V2O7·2H2O对亚甲基蓝(MB)的可见光催化降解效果最好。对掺杂离子种类、掺杂离子浓度对产物可见光催化性质的影响也进行了考察。     

(Ag/Al2O3+Cu/Ce(x)/Al2O3)组合催化剂催化乙醇选择性还原NOx及其副产物的消除

制备了Cu/Ce(x)/Al2O3(x为Ce与Al的摩尔比)系列氧化催化剂,并考察了(Ag/Al2O3 Cu/Ce(x)/Al2O3)组合体系催化乙醇还原NOx以及氧化去除反应副产物(CO和未完全燃烧的碳氢化合物)的活性.在200～350℃温度区间,组合催化剂具有与Ag/Al2O3相似的NOx去除效率.随着Ce/Al比增加,氧化催化剂去除CO的活性逐渐提高.Cu/CeO2催化剂具有最好的氧化活性,但其对NOx的去除有较大影响.综合考虑NOx转化率以及CO和HC的去除效果,(Ag/Al2O3 Cu/Ce(0·15)/Al2O3)是最佳的催化剂组合体系.通过对此系列氧化催化剂的BET比表面积、XRD、H2-TPR以及XPS等表征结果的分析,发现Cu和Ce之间的相互作用是催化剂氧化CO能力提高的主要原因.     

稀土氧化物对二次锌电极性能的影响

应用阴极极化法在锌电极上覆盖一层稀土氢氧化物膜La(OH)3或Ce(OH)3,并用循环伏安、动电位极化、定电位阴极极化实验研究其电化学性能.结果表明,La(OH)3或Ce(OH)3膜能抑制锌酸根离子的迁移,提高析氢过电位,降低腐蚀电流密度并能抑制枝晶生长.SEM观测显示,稀土氧化物La2O3或CeO2改变了锌沉积形态,进而提高了锌酸钙电极的充放电循环性能.     

RE(III)与2-羰基丙酸水杨酰腙配合物的合成、表征及热化学

用2-羰基丙酸水杨酰腙与轻稀土硝酸盐反应,合成了7种新的配合物.经元素分析、化学分析及X射线粉末衍射等手段确定了其组成为RE(C10H9N2O4)(C10H8N2O4)·nH2O(RE=La、Ce、Pr、Nd、Sm、Eu、Gd),用红外、紫外、荧光光谱分析对以上配合物的结构进行了表征;用微热量计测定了稀土芳酰腙配合物的溶解焓,发现其溶解焓数据不随稀土原子序数单调变化,而呈转折变化,可认为呈稀土的四分组现象的前两组.     

(ZrO2)0.86(Sm2O3)0.14纳米粉体的水热法合成及其烧结体的电性能

以湿化学法制得Zr(OH)4和Sm(OH)3的共沉淀为前驱体,在碱性介质中用水热法合成了(ZrO2)0.86(sm2O3)014及(ZrO2)0.88(Sm2O3)0.12纳米粉体.将纳米粉体在较低温度(1450℃)下烧结制得了致密的固体电解质陶瓷样品,比通常高温固相反应法采用的烧结温度(＞1600℃)降低了150℃以上.XRD测定结果表明,(ZrO2)0.86(Sm2O3)0.14纳米粉体及其烧结体均为立方相,但(ZrO2)0.88(Sm2O3)0.12纳米粉体为立方相,它的烧结体为立方相和单斜相的混合相.用交流阻抗谱法、氧浓差电池法及氧泵(氧的电化学透过)法研究了(ZrO2)0.86(Sm2O3)0.14陶瓷样品在600～1000℃下的离子导电特性.结果表明,该陶瓷样品在600～1000℃下氧离子迁移数为1,氧离子电导率的最大值为3.2×10-2 S·cm-1,是一个优良的氧离子导体;它的氧泵性能明显地优于YSZ.     

铈掺杂TiO2光催化剂的制备及其催化性能

以TiCl4为原料、Ce(NO3)3·6H2O为稀土掺杂剂,制备了不同掺杂量的Ce/TiO2粉体,并进行了DTA-TG,XRD,SEM和TEM表征.实验主要考察铈掺杂对TiO2粉体的表面形状和光催化活性的影响.结果表明,掺铈能明显改善样品的团聚状态,有利于样品比表面积的增大.SEM和TEM对500℃的焙烧样品表征结果,掺杂样品二次颗粒的成孔性远好于没有掺杂的纯样品.掺杂量从m(CeO2)=0.5%增加到m(CeO2)=8%,样品的比表面积增加了74m2·g-1;活性评价结果表明,掺杂铈可有效提高催化剂的光催化活性,其中m(CeO2)=1%的样品活性最好.     

PANI/Ce(OH)3-Pr2O3·3H2O/NanoG复合材料制备与表征

开发了反胶束模板-原位聚合纳米复合法制备聚苯胺(PANI)/Ce(OH)3-Pr2O3·3H2O/石墨纳米薄片(NanoG)纳米复合材料的方法.膨胀石墨在乙醇水溶液中经超声处理制得石墨纳米薄片,以苯胺的氯仿溶液为油相,稀土金属离子Pr3+、Ce3+水溶液为水相,依靠表面活性剂十六烷基三甲基溴化铵(CTAB)自组装形成的反胶束为模板-制备PANI/Ge(OH)3-Pr2O3·3H2O/NanoG复合材料.利用红外光谱(FTIR)、扫描电镜(SEM)、透射电镜(TEM)和 X-射线衍射(XRD)对该复合材料进行了表征和分析,研究了其导电性能和热性能.结果表明,PANI/Ce(OH)3-Pr2O3·3H2O/NanoG复合材料各相分散均匀,稀土纳米粒子在体系中以棒状的形态分布.热重分析表明,该复合材料的热稳定性明显提高;导电性研究说明,石墨纳米薄片的特殊的结构(较大的径厚比)对其在聚合物基体中形成导电网络具有重要作用;PANI/Pr2O3-Ce(OH)3/NanoG纳米复合材料的渗滤阀值低于1.0wt%.     

自发氧化还原法制备Co3O4/CeO2纳米复合材料及其CO催化氧化反应结构优化

采用简单的自发氧化还原法合成了Co3O4/CeO2纳米复合材料,采用透射电子显微镜(TEM)\,X射线衍射(XRD)及X射线光电子能谱(XPS)等分析手段对样品进行了表征,并探究了反应参数对其催化CO氧化反应活性的影响.结果表明,Co/Ce摩尔比、pH值、反应温度和煅烧温度均显著影响Co3O4/CeO2纳米复合材料的催化性能;性能最优的样品用于催化CO氧化反应在140℃时即可实现100%的转化率,并且在循环测试中其催化活性保持不变,显示出良好的稳定性.     

Thermal Decomposition of CF3C(O)O2NO2, CClF2C(O)O2NO2, CCl2FC(O)O2NO2, and CCl3C(O)O2NO2

Haloacetyl, peroxynitrates are intermediates in the atmospheric degradation of a number of haloethanes. In this work, thermal decomposition rate constants of CF₃C(O)O₂NO₂, CClF₂C(O)O₂NO₂, CCl₂FC(O)O₂NO₂, and CCl₃C(O)O₂NO₂ have been determined in a temperature controlled 420 l reaction chamber. Peroxynitrates (RO₂NO₂) were prepared in situ by photolysis of RH/Cl₂/O₂/NO₂/N₂ mixtures (R = CF₃CO, CClF₂CO, CCl₂FCO, and CCl₃CO). Thermal decomposition was initiated by addition of NO, and relative RO₂NO₂ concentrations were measured as a function of time by long-path IR absorption using an FTIR spectrometer. First-order decomposition rate constants were determined at atmospheric pressure (M = N₂) as a function of temperature and, in the case of CF₃C(O)O₂NO₂ and CCl₃C(O)O₂NO₂, also as a function of total pressure. Extrapolation of the measured rate constants to the temperatures and pressures of the upper troposphere yields thermal lifetimes of several thousands of years for all of these peroxynitrates. Thus, the chloro(fluoro)acetyl peroxynitrates may play a role as temporary reservoirs of Cl, their lifetimes in the upper troposphere being limited by their (unknown) photolysis rates. Results on the thermal decomposition of CClF₂CH₂O₂NO₂ and CCl₂FCH₂O₂NO₂ are also reported, showing that the atmospheric lifetimes of these peroxynitrates are very short in the lower troposphere and increase to a maximum of several days close to the tropopause. The ratio of the rate constants for the reactions of CF₃C(O)O₂ radicals with NO₂ and NO was determined to be 0.64 ± 0.13 (2σ) at 315 K and a total pressure of 1000 mbar (M = N₂). © 1994 John Wiley & Sons, Inc.     

NaMn6(P2O7)2(P3O10) and KCd6(P2O7)2(P3O10)

The crystal structures of two new diphosphates, sodium hexamanganese bis­(diphosphate) triphosphate, NaMn₆(P₂O₇)₂(P₃O₁₀), and potassium hexacadmium bis­(diphosphate) triphosphate, KCd₆(P₂O₇)₂(P₃O₁₀), confirm the rigidity of the M₆(P₂O₇)₂(P₃O₁₀) matrix (M is Mn or Cd) and the relatively fixed dimensions of the tunnels extending in the a direction of the unit cell. The compounds are isomorphous; the P₂O₇^4? anion and the alkali metal cations lie on mirror planes. Bond‐valence analysis of the bonding details of the atoms found within the tunnels permits a prediction of the conductivity.     

Thermal behaviour and vibrational spectra of (NH4)3Ga(C2O4)3 · 3H2O and (NH4)3Al(C2O4)3 · 3H2O

The IR and Raman spectra and the thermal behaviour of the isomorphous compounds (NH₄)₃Ga(C₂O₄)₃·3H₂O and (NH₄)₃Al(C₂O₄)₃·3H₂O were investigated. Detailed stoichiometries, sustained by TG, DTA and IR spectroscopic analyses, were found in both cases. Different results, associated with the different polarizing powers of the metal cations, were obtained. The first evidence was found of the formation of basic gallium carbonates.     

Spectroscopic properties of Er(3+)/Yb(3+) co-doped Bi(2)O(3)-B(2)O(3)-GeO(2) glasses

Er(3+)/Yb(3+) co-doped 60Bi(2)O(3)-(40 - x)B(2)O(3)-xGeO(2) (BBG; x=0, 5, 10, 15 mol%) glasses that are suitable for fiber lasers, amplifiers have been fabricated and characterized. The absorption spectra, emission spectra, and lifetime of the (4)I(13/2) level and quantum efficiency of Er(3+):(4)I(13/2) --> (4)I(15/2) transition were measured and calculated. With the substitution of GeO(2) for B(2)O(3), both Delta lambda(eff) and sigma(e) decrease from 75 to 71 nm and 9.88 to 8.12 x 10(-21) cm(2), respectively. The measured lifetime of the (4)I(13/2) level and quantum efficiency of Er(3+):(4)I(13/2) --> (4)I(15/2) transition increase from 1.18 to 1.5 ms and 36.2% to 43.2%, respectively. The emission spectra of Er(3+):(4)I(13/2) --> (4)I(15/2) transition was also analyzed using a peak-fit routine, and an equivalent four-level system was proposed to estimate the stark splitting for the (4)I(15/2) and (4)I(13/2) levels of Er(3+) in the BBG glasses. The results indicate that the (4)I(13/2) --> (4)I(15/2) emission of Er(3+) can be exhibit a considerable broadening due to a significant enhance the peak A, and D emission.     

Spectroscopic properties of Dy(3+) ions in NaF-B(2)O(3)-Al(2)O(3) glasses

This paper reports the optical properties of Dy(3+) in sodium fluoroborate glasses of the type XNaF.(89-X)B(2)O(3).10 Al(2)O(3).1Dy(2)O(3) (where X=8, 12, 16, 20 and 24). Judd-Ofelt intensity parameters (Omega(2), Omega(4), Omega(6)) are derived from the absorption spectra. The Judd-Ofelt theory has been applied to interpret the local environment of Dy(3+) ions and bond covalency of RE-O bond. These parameters have been used to calculate radiative transition probabilities (A(rad)), lifetimes (tau(R)) and branching ratios (beta(R)) for the excited level (4)F(9/2). The predicted values of tau(R) are compared with the measured values for (4)F(9/2) level for five glass compositions (Glass (A-E)). The stimulated emission cross-section sigma(lambda(P)) are also evaluated for the (4)F(9/2)-->(6)H(J) (J=11/2, 13/2, and 15/2) transitions.     

Die IR-Spektren von [Cr(O2)2(NH3)3] und K3[Cr(O2)2(CN)3]

The infrared spectra of the title compounds are reported and discussed. The influence of the peroxide groups on the bond properties of the other ligands and some characteristics of the metal—peroxide interactions are analyzed.     

Ga2O3-La2O3-Yb2O3-Er2O3(HO2O3)体系光谱性质的研究

根据稀土离子能级的特点,对Ga2O3-La2O3-Yb2O3-Er2O3(HO2O3)体系的光谱性质进行了探讨,发现它们有二类发光性质:Stokes发光和反Stokes发光,研究了发光强度和发射波长与掺杂离子的依赖关系,观察到由能量的共振转移引起的荧光浓度猝灭现象,并取得了最大发光强度时的掺杂离子浓度和一些规律性结果.