A_2BO_4型复合氧化物Dy_(0.5)Sr_(1.5)Mn_(1-x)Ni_xO_4(0≤x≤1)的Rietveld分析和CO氧化催化活性

X射线衍射Rietveld分析和微反分析表明,A位含Dy的A_2BO_4型过渡金属稀土复合氧化物Dy_(0.5)Sr_(1.5)Mn_(1-x)Ni_xO_4(0≤x≤1),是空间群为I4/mmm的四方相K_2NiF_4型结构,A位和B位约有3%至7%的占位无序缺位.健价计算表明,B位Mn的平均价态在3.73至3.77之间,Ni在2.84至2.96之间.对CO氧化催化活性顺序为X=0.2>0.4>0.6>0.8>1. 0.X=0.2的样品,在空速5000h~(-1),463K时,CO转化率达80%.     

钴掺杂Sr1.5La0.5MnO4的合成及高温电化学性能研究

采用EDTA-柠檬酸法合成了中温固体氧化物燃料电池阴极材料Sr_(1.5)La_(0.5)Mn_(1-x)Co_xO_4(SLMCOx),并利用粉末X射线衍射(XRD)、X射线光电子能谱(XPS)以及电化学交流阻抗谱(EIS)进行表征。结果表明,该材料与Ce0.9Gd0.1O1.95(CGO)在1 200℃烧结12 h不发生化学反应。随着Co掺入量的增加,氧化物中Mn~(3+)和Co~(2+)含量增多,晶格氧含量降低,晶格畸变率增大。交流阻抗谱(EIS)测试结果显示,钴的掺杂明显降低电极的极化电阻,其中Sr_(1.5)La_(0.5)Mn_(0.7)Co_(0.3)O_4阴极在700℃空气中的极化电阻为0.62Ω·cm~2,明显小于Sr_(1.5)La_(0.5)MnO_4阴极在750℃的极化电阻(1.5Ω·cm~2),表明钴掺杂的Sr_(1.5)La_(0.5)Mn_(1-x)CoxO_4是一种潜在的IT-SOFC阴极材料。     

Dy_(2)O_(3),Cu_(2)O在LiF-DyF_(3)熔盐体系的溶解度研究EI北大核心CSCD

以LiF-DyF_(3)为熔盐,电解Dy_(2)O_(3),Cu_(2)O制备Dy-Cu合金过程中,明确Dy_(2)O_(3),Cu_(2)O溶解度是制定合理加料制度、提高电解效率的关键。采用等温饱和法研究了Dy_(2)O_(3),Cu_(2)O溶解平衡时间,考察了温度、DyF_(3)浓度对单一氧化物(Dy_(2)O_(3)或Cu_(2)O)及混合氧化物(Dy_(2)O_(3)与Cu_(2)O)溶解度的影响,通过最小二乘法对溶解度数据进行了拟合,建立了温度、DyF_(3)浓度与Dy_(2)O_(3),Cu_(2)O溶解度之间的数学回归方程。研究结果表明,Dy_(2)O_(3),Cu_(2)O在LiF-DyF_(3)熔盐中溶解平衡的时间分别为110,120 min,溶解反应为吸热反应。相同温度下,随熔盐中DyF_(3)浓度增大,Dy_(2)O_(3)的溶解度逐渐增大,Cu_(2)O溶解度变化较小;在温度为910~1030℃,熔盐中DyF_(3)浓度为15%~40%(摩尔分数)时,Dy_(2)O_(3),Cu_(2)O溶解度分别为0.55%~3.45%,0.39%~0.52%。     

LiAl_xMn_(2-x)O_4的制备及其在酸介质中的稳定性

采用沉淀法合成了系列掺Al尖晶石氧化物LiAl_xMn_(2-x)O_4(x=0,0.3,0.5,0.7,1.0)。通过X射线衍射(XRD)、能量色散谱(EDS)和扫描电子显微镜(SEM)等方法对其结构、成分和形貌进行了表征,并通过酸浸实验考察了不同组成和不同焙烧温度的LiAl_xMn_(2-x)O_4在弱酸性介质中的稳定性。结果表明当x为0.5,合成温度为850℃时,Al能最大程度地纳入尖晶石晶格,形成结晶致密、成分均匀的产物。同时,LiAl_(0.5)Mn_(1.5)O_4能较大程度地抑制Mn在弱酸条件下的溶出,而具有较低的Al溶出率和较高的Li溶出率。酸浸后LiAl_(0.5)Mn_(1.5)O_4仍保持尖晶石结构且形貌完整。     

复合金属氧化物Mg_(1.5)Mn_(0.5)Ti_(0.75)O_4的锂离子交换性能研究

具有尖晶石型结构的化合物能够在插入大量替代离子改变自身锂和氧化学计量数的同时保持结构的稳定性,这种特性能够被用于离子交换研究,用来满足提取锂的需求。通过检测尖晶石型复合金属氧化物的饱和交换能力、分配系数等,可以确定其具体特性。本文利用共沉淀/固相反应热结晶方法,合成尖晶石型复合金属氧化物Mg_(1.5)Mn_(0.5)Ti_(0.75)O_4。实验结果表明,经酸化的Mg_(1.5)Mn_(0.5)Ti_(0.75)O_4,其Mg~(2+)的抽出比率高达72%,Mn~(4+)和Ti~(4+)的溶解比率低于8.2%。实验分析表明,无机离子交换剂Mg_(1.5)Mn_(0.5)Ti_(0.75)O_4对Li~+有较好的离子筛效应,离子选择性较好,酸化后的样品对Li~+的离子交换能力高达10.6mmol·g~(-1)。     

THE PREPARATION,STRUCTURE AND PROPERTES OF Sr_(0.5)Ca(0.5)CuO_2

Sr_(0.5)Ca_(0.5)CuO_2 has been synthesized by the solid state reaction.Thecompound crystallizes in an orthorhombic unit cell,space group D_(2h)~(17)-Cmcmwith a=3.444 ,b=16.11 ,c=3.868 .It decomposes shove 1038℃.Sr_(0.5)Ca_(0.5)CuO_2 is s black p-type semiconductor with resistivity 53Ω.cmat room tempersture.     

N_2O分解催化剂Co-Al尖晶石型复合氧化物制备参数的优化

以柠檬酸为配合剂,用溶胶-凝胶法制备了一组不同组成的Co-Al复合氧化物(CoAl_2O_4、CoCo0.5Al1.5O4、CoCoAlO_4、CoCo_(1.5)Al_(0.5)O_4、Co_3O_4),用于催化分解N_2O.用N_2物理吸附、X射线衍射(XRD)、扫描电镜(SEM)、H2程序升温还原(H2-TPR)、X射线光电子能谱(XPS)等技术对催化剂进行了结构表征,考察了复合氧化物组成、母液pH值、配合剂用量等制备参数对催化剂活性的影响.结果表明:用Al取代Co_3O_4中部分Co制备Co-Al复合氧化物,提高了催化剂的比表面积和催化活性,其中组成为CoCo_(1.5)Al_(0.5)O_4、母液pH=2、柠檬酸/金属离子(摩尔比)为1的催化剂活性较高.在CoCo_(1.5)Al_(0.5)O_4表面浸渍K2CO3溶液制得K改性催化剂,弱化了钴-氧化学键,提高了催化活性.其中0.02K/CoCo1.5Al0.5O4催化剂在有氧有水气氛400℃连续反应50h,N_2O转化率达97.1%.     

LiF-DyF_3-Cu_2O-Dy_2O_3熔盐体系的粘度特性研究

熔体粘度对熔盐电解过程中金属与熔盐的有效分离、炉膛及电极寿命等具有显着影响。因此,运用旋转法对制取Dy-Cu合金的LiF-DyF_3-Dy_2O_3-Cu_2O熔盐体系粘度进行了研究。考察了温度、单一氧化物(Dy_2O_3或Cu_2O)及混合氧化物(Dy_2O_3与Cu_2O)添加对熔盐体系粘度的影响。同时,通过Arrehnius公式验证了熔盐粘度与温度的关系,计算并分析了粘度活化能的变化规律。研究结果表明:在温度为910～1030℃范围内, LiF-DyF_3熔盐体系的粘度均随着温度的升高及单一氧化物(Dy_2O_3或Cu_2O)添加量的增大而降低,随熔盐中Cu_2O与Dy_2O_3质量比的增大而升高;粘度活化能随单一氧化物(Dy_2O_3或Cu_2O)添加量的增大而增大。熔盐电解制备Dy-Cu合金适宜温度为970～1000℃,W_((Cu_2O))+W_((Dy_2O_3))=2.0%(质量分数)且W_((Cu_2O))∶W_((Dy_2O_3))比值为1∶0.5。     

La_(0.5)Pr_(0.5)Ni_(0.7)Co_(0.3)O_3在乙醇水蒸气重整中催化性能研究

用共沉淀法制备了La_(0.5)Pr_(0.5)Ni_(0.7)Co_(0.3)O_3钙钛矿氧化物催化剂,用XRD、SEM、TPR、TG等对La_(0.5)Pr_(0.5)Ni_(0.7)Co_(0.3)O_3钙钛矿氧化物的晶相结构、还原性能及反应50 h后的La_(0.5)Pr_(0.5)Ni_(0.7)Co_(0.3)O_3钙钛矿氧化物表面积碳情况进行了分析,同时用微反色谱装置在不同的反应温度条件下的La_(0.5)Pr_(0.5)Ni_(0.7)Co_(0.3)O_3钙钛矿氧化物的初活性、氢气平均选择性和积碳性能进行了探讨。结果表明,La_(0.5)Pr_(0.5)Ni_(0.7)Co_(0.3)O_3钙钛矿氧化物在乙醇水蒸气重整反应中具有较好的低温初活性和氢气的选择性,乙醇的平均转化率和氢气的选择性随着反应温度的升高而增大。当温度大于550℃时,转化率增幅不大,氢气的平均选择性在600℃时有所下降。反应温度升高催化剂的积碳量有所增多,积碳主要是不定型碳。     

SBA-15表面改性及其对介孔La_(0.8)Sr_(0.2)CoO_3钙钛矿型催化剂结构和性能的影响（英文）

本文通过改进的水热法制备了孔径较大的有序介孔SBA-15,其孔径(Dp)为10.1 nm,并采用浓盐酸、三甲基氯硅烷(TMCS)和3-氨丙基三乙氧基硅烷(APTES)对SBA-15表面进行了羟基、甲基和氨基改性处理。以嫁接不同表面官能团的SBA-15为模板,合成了一系列菱方晶系钙钛矿型介孔La_(0.8)Sr_(0.2)CoO_3氧化物,系统地研究了模板SBA-15的表面性能对La_(0.8)Sr_(0.2)CoO_3氧化物结构和性能的影响。X射线衍射(XRD)图谱表明,外表面引入―CH_3,内表面羟基化和引入―NH_2的模板有利于合成结晶度较高的、物相单一的钙钛矿结构氧化物。小角XRD图谱、高分辨率透射电子显微镜(HRTEM)图像以及N2吸附测试结果表明,所制备的催化剂为介孔结构。CO氧化的催化活性测试表明,采用表面改性的模板合成的La_(0.8)Sr_(0.2)CoO_3氧化物表现出较高的催化活性和稳定性,在140℃时可以实现CO的完全转化,连续使用100 h后催化剂的催化活性几乎没有下降。X射线光电子能谱(XPS)、H_2程序升温还原(H_2-TPR)和O_2程序升温脱附(O_2-TPD)测试结果表明,催化剂表面丰富的吸附氧物种,高价态的Co离子,钙钛矿结构中Sr在表面富集,及优良的低温氧化还原性是催化活性提高的主要原因。     

K_2NiF_4型结构的A_（2－x）Sr_xBO_4（A＝La，Dy，B＝Mn，Fe，Co，Ni）希土复合氧化物的合成

以典型的轻希土镧和重希上镝及碱土金属锶作为Ａ位离子，以过渡金属锰、铁、钴、镍作为Ｂ位离子，合成了Ｋ２ＮｉＦ４型结构的Ａ２－ｘＳｒｘＢＯ４希土复合氧化物．采用粉末Ｘ射线衍射技术考察了反应条件等因素对生成Ｋ２ＮｉＦ４型四方（Ｔ）结构相的影响．实验结果表明，四方结构的形成不仅与几何因素有关，而且与各组分的物理化学性质有关．各个不同的组成，生成四方相的温度范围也有所不同．适当地提高反应温度以及延长灼烧时间总是有利于高结晶态的Ｋ２ＮｉＦ４型结构相的形成．值得注意的是，过高的合成反应温度反而会引起四方结构的不稳定性以致破坏．     

Mn_(1-x)(Li,Ti)_xCo_2O_4尖晶石型复合氧化物的制备、表征与催化性能

用柠檬酸配位燃烧法合成了Mn1-x(Li,Ti)xCo2O4系列尖晶石型复合氧化物催化剂,使用FTIR和XRD方法对催化剂结构进行表征,通过程序升温氧化反应(TPO)技术对这些催化剂在模拟柴油机尾气条件下进行同时消除NOx和柴油碳黑反应的活性评价。结果表明,掺杂Li或Ti后的Mn1-x(Li,Ti)xCo2O4系列催化剂仍然保持了完整的尖晶石型复合氧化物结构,这些催化剂对同时消除柴油机尾气中的碳黑颗粒和NOx具有良好的催化性能,其中Li或Ti的掺杂量为x=0.05较佳,结合碳黑燃烧与NOx还原总的催化效果,Mn0.95Li0.05Co2O4具有最好的催化活性。     

Magnetic and dielectric properties of InFe2O4, InFeCuO4, and InGaCuO4

The magnetic and dielectric properties of InFe2O4, InFeCuO4, and InGaCuO4 have been investigated. All these materials are isostructural with RFe2O4 (R = Y, Ho-Lu), which shows ferroelectricity due to iron-valence ordering. InFe2O4 exhibits ferrimagnetic ordering at T(C) approximately 242 K and a dielectric constant (epsilon) of approximately 10,000 at around room temperature. These properties resemble those of RFe2O4; the origins of the magnetic and dielectric phenomena are likely common in InFe2O4 and RFe2O4. From measurements of the other two materials, we found that both T(C) and epsilon are decreased in the order of InFe2O4, InFeCuO4, and InGaCuO4. This result strongly supports the previously reported explanation based on an electron transfer between the Fe-site ions for the corresponding rare-earth systems. Therefore, we propose that the dielectric properties of the oxides isostructural with RFe2O4 are plausibly governed by electron transfer; this situation is different from that of ordinary ferroelectrics and dielectrics, in which the displacement of cations and anions is important. In addition, InFeCuO4 and InGaCuO4 exhibit large epsilon values (epsilon > approximately 1500). In consideration of this property, we discuss the possible applications of these oxides.     

New Materials Derived from Ybco: CrSr2RECu2O8 (RE = La, Pr, Nd, Eu, Gd, Tb, Dy, Y, Ho, Er, Lu)

Eleven new oxides, derived from yttrium barium copper oxide by replacing the square-planar copper [Cu-O4] of the basal plane of the triple perovskite-based structure with octahedral Cr(IV), have been prepared at high pressure and temperature. Their crystal structures have been determined, and their complex microstructure has been established by means of high-resolution electron microscopy and electron diffraction. The materials have a general formula of CrSr2RECu2O8 (RE = La, Pr, Nd, Eu, Gd, Tb, Dy, Y, Ho, Er, and Lu); they are tetragonal, show the symmetry of space group P4/mmm, and do not appear to be superconducting.     

Molecular precursors for ferroelectric materials: synthesis and characterization of Bi2M2(mu-O)(sal)4(Hsal)4(OEt)2 and BiM4(mu-O)4(sal)4(Hsal)3(O(i)Pr)4 (sal = O2CC6H4O,Hsal = O2CC6H4OH) (M = Nb,Ta)

Reactions between triphenyl bismuth, salicylic acid, and niobium or tantalum ethoxide have been explored. Four new coordination complexes incorporating bismuth and the group 5 metals niobium or tantalum have been synthesized and characterized spectroscopically, by elemental analysis, and by single crystal X-ray diffraction. The new complexes are Bi(2)M(2)(mu-O)(sal)(4)(Hsal)(4)(OEt)(2) (1a, M = Nb; 1b, M = Ta) and BiM(4)(mu-O)(4)(sal)(4)(Hsal)(3)(O(i)Pr)(4) (sal = O(2)CC(6)H(4)-2-O, Hsal = O(2)CC(6)H(4)-2-OH) (2a, M = Nb; 2b, M = Ta). Complexes 1a and 1b are isomorphous, as are 2a and 2b. The thermal and hydrolytic decomposition of 1a has been explored by DT/TGA and powder X-ray diffraction, while scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the morphology and composition of the oxides. The heterobimetallic molecules are completely converted to the amorphous bimetallic oxide by heating to 500 degrees C in air. Decomposition of 1a or 1b at 650 degrees C produces the metastable high temperature form of BiNbO(4) as the major crystalline oxide phase. Heating samples of 1a to 850 degrees C favors conversion of the materials to the low temperature phase as well as disproportionation into Bi(5)Nb(3)O(15) and Nb(2)O(5). Thermal decomposition of 1a and 1b produces porous oxides, while hydrolytic decomposition of the complexes has been shown to produce nanometer scale bimetallic oxide particles. The potential of the complexes to act as single-source precursors for ferroelectric materials is considered.     

The Complexes of Rare Earth Elements with 2,5-Dihydroxybenzoic Acid Preparation, properties and thermal decomposition

The conditions of the formation of rare earth(III) 2,5-dihydroxybenzoates have been studied; their compositions and solubilities in water at 293 K have been determined. The IR spectra of the anhydrous complexes with the general formula Ln(C7H5O4)3 have been recorded and their thermal decompositions in static air determined. During heating the anhydrous complexes of Y, Pr-Lu decompose to the oxides Ln2O3, Pr6O11 and Tb4O7 with formation of the intermediate Ln2(C7H4O4)3. The lanthanum complex decomposes to the oxide in three steps forming La2(C7H4O4)3 and La2O2CO3 as intermediates and the Ce(III) complex decomposes directly to CeO2. The properties of rare earth 2,5- and 2,4-dihydroxybenzoates have been compared. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of Electron Donor–Acceptor Complex Formation of o-Chloranil With a Series of Phosphine Oxides and Tri- n-butyl Phosphate by the Absorption Spectrometric Method

Electron donor–acceptor (EDA) complex formation of o-chloranil with six different phosphine oxides and tri-n-butyl phosphate (TBP) has been studied in CCl ₄ solution by the UV-VIS absorption spectrophotometric technique. An absorption band due to a charge–transfer (CT) transition is observed in the visible region. Utilizing the CT transition energy, the electron affinity of o-chloranil in solution has been calculated. Degrees of charge transfer, and oscillator and transition dipole strengths have also been calculated for all of the investigated EDA complexes. Except for TBP, other phosphine oxides, viz., tri-n-octyl phosphine oxide, tri-n-butyl phosphine oxide, triphenyl phosphine, octyl(phenyl)-N,N-diisobutylcarbamoylphosphine oxide, octyl(phenyl)-N,N-dicyclohexylcarbamoylmethylphosphine oxide and octyl(phenyl)-N,N-diisopropylcarbamoylmethylphosphine oxide have been shown to form stable 1:1 EDA complexes with o-chloranil. The complex of TBP with o-chloranil decays slowly into a secondary product. Formation constants of the EDA complexes have been determined.     

Relativistic Jahn-Teller effects in the photoelectron spectra of tetrahedral P4, As4, Sb4, and Bi4

The group-V tetrahedral cluster cations P(4)(+), As(4)(+), Sb(4)(+), and Bi(4)(+) are known to exhibit exceptionally strong Jahn-Teller (JT) effects of electrostatic origin in their (2)E ground states and (2)T(2) excited states. It has been predicted that there exist, in addition, JT couplings of relativistic origin (arising from the spin-orbit (SO) operator) in (2)E and (2)T(2) states of tetrahedral systems, which should become relevant for the heavier elements. In the present work, the JT and SO couplings in the group-V tetramer cations have been analyzed with ab initio relativistic electronic structure calculations. The vibronic line spectra and the band shapes of the photoelectron spectra were simulated with time-dependent quantum wave-packet methods. The results provide insight into the interplay of electrostatic and relativistic JT couplings and SO splittings in the complex photoelectron spectra of these systems.     

Crystal refinement and magnetic structure of KNi4(PO4)3: a novel example of three interacting magnetic sub-lattices

KNi(4)(PO(4))(3) has been synthesised following a method previously reported by some of us and studied on the basis of magnetization and neutron powder diffraction (NPD) data. Magnetization measurements suggest the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) interactions: magnetization versus magnetic field curves present a remanent magnetization of around 2.15 micro(B) at T=2 K. The magnetic structure of the KNi(4)(PO(4))(3) has been determined at low temperature from the NPD data. These measurements show that there are three magnetic sub-lattices of Ni(2+) ions, which interact through common oxygen or phosphate groups, giving rise to FM and AFM couplings. The resulting interactions are FM in nature. Such a complex behaviour could provide an interesting model to analyse magnetic interactions in more condensed systems, such in mixed metal oxides.     

Li(+) ion conductivity in rock salt-structured nickel-doped Li(3)NbO(4)

Two mechanisms of doping Li(3)NbO(4), which has an ordered, rock salt superstructure, have been established. In the "stoichiometric mechanism", the overall cation-to-anion ratio is maintained at 1:1 by means of the substitution 3Li(+) + Nb(5+) --> 4Ni(2+). In the "vacancy mechanism", Li(+) ion vacancies are created by means of the substitution 2Li(+) --> Ni(2+). Solid solution ranges have been determined for both mechanisms and a partial phase diagram constructed for the stoichiometric join. On the vacancy join, the substitution mechanism has been confirmed by powder neutron diffraction; associated with lithium vacancy creation, a dramatic increase in Li(+) ion conductivity occurs with increasing Ni content, reaching a value of 5 x 10(-4) Omega(-1) cm(-1) at 300 degrees C for composition x= 0.1 in the formula Li(3-2x)Ni(x)NbO(4). This is the first example of high Li(+) ion conductivity in complex oxides with rock salt-related structures.