低温固态反应制备纳米Ba_(1-y)Sr_yTi_(1-x)Zr_xO_3介电材料及性能研究

将TiCl4的水解产物与固体Ba(OH)2按摩尔比1∶1混合,混合物经室温研磨、100℃烘干,得到钛酸钡纳米晶;按相同工艺掺杂,合成了一系列Ba1-ySryTi1-xZrxO3(0x≤0.3,0y≤0.4)固溶体;采用X射线衍射分析了产物的晶体结构,采用透射电镜观察了其形貌;并测定了系列固溶体的室温介电常数、介电损失.结果表明,所制备的Ba1-ySryTi1-xZrxO3为完全互溶取代固溶体,由平均粒径70 nm的球形微粒组成.经低温固态反应掺入适量锆、锶后,BaTi O3的室温介电常数由3 000提高到20 000左右.     

1200 ℃合成Mn3O4-Fe2O3体系的物相关系、结构和阳离子分布

在空气气氛中1200℃温度下合成了Mn3O4-Fe2O3体系的各类样品,并将其快速淬火到室温.X射线粉末衍射(XRD)分析表明这样得到的该体系样品存在三个固溶体Mn3-3xFe3xO4(0.00≤x≤0.278),Mn3-3xFe3xO4(0.291≤x≤0.667)和Mn2-2xFe2xO3(0.89≤x≤1.00).X射线粉末衍射数据的结构精修显示它们分别具有I41/amd空间群的黑锰矿结构、Fd3m空间群的尖晶石结构和R3c空间群的赤铁矿结构.各固溶体之间都存在两相共存的区域.57Fe穆斯堡尔谱数据显示Fe在各个物相中都是Fe3+,在黑锰矿和尖晶石中存在两种结晶学环境不同的Fe3+,而在赤铁矿中只存在一种Fe3+.结合X射线光电子能谱(XPS)的数据,可以认为黑锰矿和尖晶石中的阳离子分布可以用分子式Mn12-+xFex3+[Mnx2+Fex3+Mn32-+3x]O4表示,而赤铁矿为Mn23-+2xFe23x+O3.     

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.     

镁掺杂对In2O3电导和气敏性能的影响

用共沉淀法制备了Mg2+掺杂的In2O3纳米粉,研究了镁掺杂对In2O3电导和气敏性能的影响.结果表明:MgO和In2O3间可形成有限固溶体In2-xMgxO3(0≤x≤0.40);MgIn×电离的空穴对材料导带电子的湮灭,使掺镁纳米粉的电导变得很小;n(Mg2+):n(In3+)=1:2共沉淀物于900℃下热处理4 h,用所得的纳米粉制作的传感器在320～370℃下,对45μmol/L C2H5OH的灵敏度达102.5,为相同浓度干扰气体Petrol的12倍多.     

Pt/γ-Al2O3/CexZr1-xO2催化剂低温催化燃烧去除饮食油烟

以CexZr1-xO2固溶体做载体, 制备了系列Pt/γ-Al2O3/CexZr1-xO2催化剂(x=1, 0.75, 0.5, 0.25, 0). 应用Brunauer-Emmet-Teller (BET)比表面积分析、X射线衍射(XRD)和H2程序升温还原(H2-TPR)等手段对催化剂进行相关表征, 并系统研究了催化剂在饮食油烟催化燃烧中的催化活性. BET结果表明催化剂的比表面积随Ce/Zr摩尔比的减小而减小. XRD结果表明贵金属Pt很好地分散在氧化铝和CexZr1-xO2固溶体上. H2-TPR结果发现催化剂Pt/γ-Al2O3/Ce0.5Zr0.5O2的还原峰面积最大且氧离子的流动性最好. 催化活性研究结果表明Pt负载在CexZr1-xO2固溶体上有利于油烟的催化燃烧, 降低了反应温度. 随着CexZr1-xO2固溶体中Ce/Zr摩尔比的变化, 催化剂的活性顺序为Pt/γ-Al2O3/Ce0.5Zr0.5O2>Pt/γ-Al2O3/Ce0.25Zr0.75O2>Pt/γ-Al2O3/Ce0.75Zr0.25O2>Pt/γ-Al2O3/CeO2>Pt/γ-Al2O3/ZrO2.     

CeO2-MOx (M=La3+, Ca2+)改性Pd/γ-Al2O3催化甲烷燃烧性能

采用沉积-沉淀法制备了固溶体CeO2-MOx(M=La3+, Ca2+)改性的Pd/γ-Al2O3催化剂, 利用XRD、Raman和XPS对催化剂进行了表征. 结果表明, 金属(M)离子进入CeO2的晶格, 形成CeO2-MOx固溶体, Raman谱上463 cm-1处对应于Ce—O键的F2g对称伸缩振动强度降低. 其中, 样品Pd/γ-Al2O3-CeO2-CaO在615 cm-1处出现一小峰, 样品Pd/γ-Al2O3-CeO2-La2O3在320 cm-1处出现的肩峰, 都表明固溶体CeO2-MOx的形成使O2-亚晶格结构对称性降低. XPS分析表明, 固溶体改性的Pd/γ-Al2O3催化剂中Pd 的3d5/2结合能比正常价态的PdO的结合能高出0.5-0.6 eV, 形成了一种高度离子化的, 与载体具有强相互作用的Pd物种. 催化甲烷燃烧实验证明, 固溶体CeO2-MOx(M=La3+, Ca2+)改性的Pd/γ-Al2O3催化剂的低温活性和稳定性均高于未经改性的Pd/γ-Al2O3催化剂和仅用CeO2改性的Pd/γ-Al2O3催化剂, 在空速为50000 h-1时, 可使1%CH4-99%空气(体积分数)混合气中甲烷的10%转化温度降至254 ℃, 转化率100%时的转化温度降至340 ℃.     

Ba~1~-~xCa~xSn~yTi~1~-~yO~3纳米材料的、合成结构与性能

采用常压水相法,在100℃以下制备了一系列Ba~1~-~xCa~xSn~yTi~1~-~yO~3固溶体纳米粉末(0≤x≤0.5,0≤y≤0.3),经XRD物相分析和d-间距-组成图证明,产品为立方晶系的完全互溶取代固溶体,结果符合Vegard定律。TEM形貌观察,粒子为均匀球形,平均粒径70nm。通过制陶实验,分别测定了该系列固溶体的室温介电常数以及介电常数随温度的变化,结果发现,用软化学方法在BaTiO~3中掺入适量钙和锡,由于掺杂离子均匀进入母体晶格,引起T~c降低,室温介电常数达9800,经BaTiO~3纯相提高6倍,而介电损失却降低50%。     

微乳法制备Au/Fe2O3水煤气变换反应催化剂Ⅱ.催化剂的表征

 采用XRD,BET,H2-TPR,TEM和XPS等方法对微乳法制备的Au/Fe2O3催化剂进行了表征,研究了不同制备方法对催化剂结构及性能的影响. 结果表明,在辛烷基酚基聚氧乙烯醚(10)(Triton X-100)体系中,Au/Fe2O3催化剂在低温区的活性物种为单质金和氧化态金,在高温区的活性物种中可能含有Au-FeOx固溶体. 金粒径小于10 nm,且高度分散于载体表面. 氧化态金的含量及金的粒径和分散度是影响Au/Fe2O3催化水煤气变换反应活性的主要因素. Au/Fe2O3催化剂中Au-FeOx固溶体的缺陷数目越多,则其高温催化活性越高.     

室温固态反应制备纳米Ba1－xSrxTiO3固溶体及其结构与介电性能研究

采用室温固态反应合成了一系列Ba_1－xSr_xTiO₃固溶体纳米粉末(0≤x≤1.0). 经XRD物相分析和d-间距-组成图证明, 产品为立方晶系的完全互溶取代固溶体. TEM形貌观察, 粒子基本为球形, 平均粒径40 nm. 该方法具有产率高, 无需溶剂, 对环境无污染等优点. 通过制陶实验, 分别测定了该系列固溶体的室温介电常数、介电损失以及介电常数随温度的变化. 结果发现, 采用室温固态反应在BaTiO₃中掺入适量锶, 由于掺杂离子均匀进入母体晶格, 引起居里点降低, 室温介电常数达11000以上, 介电损耗由BaTiO₃纯相的0.03 (3%)降为0.008 (0.8%). 纳米粉体的烧结温度为1180 ℃, 比传统微米级粉体的烧结温度降低100～150 ℃.     

La0.8Sr0.2-xCaxCo0.9Fe0.1O3-δ的合成与电性能

利用X射线衍射 (XRD)、差热 热重 (DSC/TG)与直流四探针测试分析方法研究了少量Ca取代LaCoO3 中部分La的合成过程及对其电导率的作用。采用固相反应合成的La0 .8Sr0 .2 -xCaxCo0 .9Fe0 .1 O3 -δ(LSCCF ,0≤x≤ 0 1)氧化物为单一钙钛矿相 ,其烧结过程可以分为 3个阶段 :即反应原料的变化 ;LaCoO3 基氧化物的生成 ;LSCCF固溶体的形成。LSCCF复合掺杂材料电导率的最大值都超过了 10 0S·cm- 1 ,其导电机制可以用p型小极子的绝热空隙理论来解释     

Die Kristallstruktur des W3CoB3 und der dazu isotypen Phasen Mo3CoB3, Mo3NiB3 und W3NiB3

Zusammenfassung Mo₃CoB₃, Mo₃NiB₃, W₃CoB₃ und W₃NiB₃ kristallisieren in einem eigenen Typ (W₃CoB₃-Struktur). Das trigonal prismatische Bauelement [T ₆B]^* ist zu Ketten vereinigt, wobei B₃-Gruppen entstehen. Die Phasen sind vermutlich Bor-reicher als obiger Formel entspricht.

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The crystal structure of W₃CoB₃ and the isotypic phases Mo₃CoB₃, Mo₃NiB₃, and W₃NiB₃

Mo₃CoB₃, Mo₃NiB₃, W₃CoB₃, and W₃NiB₃ were found to possess a new type of crystal structure (W₃CoB₃-structure type). Trigonal prismatic groups [T ₆B]^* are linked together forming chains in such a way that B₃-groups occur. These borides do probably exist with a larger amount of boron as to compared with the formula.

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γ-Nitro-γ-butyrolacton

γ-Nitro-γ-butyrolactone By oxidation of 3-(1-nitro-2-oxocyclohexyl)propanal ( 1 ) with KMnO₄, besides 3-(1′-nitro-2′-oxocyclohexyl)pripionic acid ( 2 ), the complete hydrolysis product 4-oxononanedioic acid ( 4 ) and the oxidized semi-hydrolysis product 5-(2-nitro-5-oxotetrahydro-2-furyl)pentanoic acid ( 3 ) were formed. The crystalline 3 decomposes at r.t. forming 4 and nitrous gases; its structure was established by X-ray determination.     

Synthesis of γγγ-trifluorocarbonyl compounds

γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF₃-CH₂-) on the -methylene group of a ketone.     

K3SbSe3, Rb3SbSe3 und Cs3SbSe3 – Synthese und Kristallstruktur

K₃SbSe₃, Rb₃SbSe₃, and Cs₃SbSe₃ – Synthesis and Crystal Structure The compounds K₃SbSe₃, Rb₃SbSe₃ and Cs₃SbSe₃ were synthesized by heating mixtures of Sb₂O₃ and an alkalicarbonate in a stream of hydrogen saturated by selenium in a temperature range between 750 °C and 800 °C. The compounds crystallize isostructural with Na₃AsS₃. A comparison of atomic distances and bond angles with those of the isostructural arsenic and bismuth compounds shows the effect of lone pairs.     

Freezing the polarization of CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite films

Thin films of methylammonium lead halides, CH₃NH₃PbI₃ and CH₃NH₃PbI_3-xCl_x, were deposited onto symmetrical microstructured electrode arrays of gold or platinum on Si/SiO₂ wafers. Polarization studies were carried out on perovskite films under vacuum in the dark. For poling, a constant voltage was applied to the samples while the temperature was cycled between 295 K and 4 K. The measured current densities depending on the temperature showed distinct characteristics relating strongly to the crystal phase and the dielectric properties of the perovskite films. Voltage sweeps were carried out at different scan rates at specific temperature intervals after poling. The polarization of the films due to the migration of iodide vacancies in direction of the blocking perovskite/metal interface was frozen almost up to room temperature. Charge carriers were only able to cross the blocking barrier and contribute to the current where the ions have accumulated during poling. All J-V curves showed hysteresis: inverted and regular hysteresis at room temperature and below, respectively. Inverted hysteresis originates from the slow accumulation of ions at the blocking barrier, while regular hysteresis arises from a distortion in the adjacent crystals which will be discussed.     

Synthesis of some derivatives of 3-amino-3-desoxyerythrose and 3-amino-3-desoxy-D-3-erythrose

The synthesis of derivatives of 3-amino-3-deoxy-L-erythrose by LAH or LAD reduction of the oxime of 1,2-O-isopropylidene α-L -glycero-tetros-3-ulofuranose is described.     

K3BiSe3, Rb3BiSe3 und Cs3BiSe3 – Substitutionsvarianten des Th3P4-Typs

K₃BiSe₃, Rb₃BiSe₃, and Cs₃BiSe₃ – Derivatives of the Th₃P₄ Structure Type The compounds K₃BiSe₃, Rb₃BiSe₃, and Cs₃BiSe₃ were synthesized by heating mixtures of Bi₂O₃ and the respective alkalicarbonate in a stream of hydrogen saturated by selenium at 850°C. Thin crystals of the compounds appear red in transmitted light. They crystallize isostructural with Na₃AsS₃, space group P2₁3, lattice constants a = 9.771(5) Å, a = 10.161(3) Å, and a = 10.587(5) Å for K₃BiSe₃, Rb₃BiSe₃, and Cs₃BiSe₃, respectively. The Na₃AsS₃ structure type is a derivative of the Th₃P₄ structure type.     

Die Akzeptoreigenschaften von AsCl3, AsBr3, asJ3, SbCl3, SbBr3 und SbJ3

Zusammenfassung Es wurden die Enthalpien der Reaktionen von AsCl₃, AsBr₃, AsJ₃, SbCl₃, SbBr₃ und SbJ₃ mit Tributylphosphat, N,N-Dimethylacetamid und Hexamethylphosphorsäuretriamid bestimmt. Das Verhalten der Addukte bei Gegenwart eines Überschusses der Donoren wird beschrieben.

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Acceptor properties of AsCl₃, AsBr₃, AsI₃, SbCl₃, SbBr₃, and SbI₃

The enthalpies of the reactions of AsCl₃, AsBr₃, AsI₃, SbCl₃, SbBr₃ and SbI₃ with tributylphosphate, N,N-dimethylacetamide and hexamethylphosphoric acid triamide were measured. The behavior of the adducts in the presence of excess donor molecules is described.

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3x-pyrrolizin-3-ones

Condensation of pyrrole-2-dithiocarboxylates with CH acids containing ester groups, in the KOH-DMSO system, was used to prepare previously unknown 1-alkylthio-3H pyrrolizin-3-ones. The latter, treated with secondary amines, are readily converted to the corresponding 1-amino derivatives.     

3-H-pyrrolizin-3-ones

Previously unknown 1-alkylthio-3H-pyrrolizin-3-ones have been obtained by the condensation of pyrrole-2-dithiocarboxylates with CH acids containing ester groupings in the KOH-DMSO system. On treating the products with secondary amines they are readily converted into the corresponding 1-amino derivatives.Irkutsk Branch of the Russian Academy of Sciences, Irkutsk 664033. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 919–924, July, 1996. Original article submitted May 2, 1996.