A study of interface-sustained ferromagnetism in 1/2(1-x)Ln2O3-xSrO/1/3Co3O4 nano-composite

The binary oxide composite, consisting of rock salt-type SrO and spinel Co3O4 nano-domains, exhibits soft ferromagnetic properties at ambient temperature. This ferromagnetism is originated from interface-induction, and the magnitude of the magnetic properties can be enhanced when the spinel phase of the composite is doped by a small amount of Ln2O3 (Ln = La, Nd, for instance). In this work, we study the composites of tri-oxide, 1/2(1-x)Ln2O3-xSrO/1/3Co3O4, where 0.01 < or =1-x < or = 0.6, by focusing on three areas: (i) generation of nano-composite dominant by interfacial phase via the pyrolysis of preceramic metallo-organic gel; (ii) influence of post-pyrolysis calcination and Ln2O3 content on the phase composition of the composite; and (iii) elucidation of different magnetic responses caused by the nature of Ln2O3 dissolved in the Co3O4 phase. The Ln(3+)-doped Co3O4 oxide displays only paramagnetic behavior at room temperature, but the ferromagnetic response is attained upon its mixing with SrO in nano-scale. The SrO phase plays the role in assisting Co3O4 phase with aligning unpaired electrons through interfacial induction.     

TiO2包覆对LiCO1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3MnO2的循环件能,采用浸渍-水解法对其进行TiO2包覆.用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流允放电测试研究包覆材料的结构和电化学性能.TiO2仅在材料表面形成包覆层,并未改变材料的结构.TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能,TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%,而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%.包覆后的材料在2.0C下循环12周后的容最没有衰减,而未包覆的材料容量保持率仅为94.4%.EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高.循环后材料的XRD和ICP-OES测试表明,包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.     

CoAl2O4包覆LiNi1/3Co1/3Mn1/3O2的电化学性能

通过共沉淀法制得类球形锂离子电池正极材料LiNi_1/3Co_1/3Mn_1/3O₂,并用非水相共沉法对其进行CoAl₂O₄包覆得到LNCMO(x). 采用X射线衍射（XRD）、扫描电子显微术（SEM）和透射电子显微术（TEM）测试材料的结构和观察材料形貌. 结果表明,CoAl₂O₄在材料表面形成8 nm均匀包覆层,未改变主体材料的结构. 电化学性能测试表明,1%（by mass）CoAl₂O₄包覆量的LiNi1/3Co1/3Mn1/3O2材料（LNCMO(1)）高充电电压（3.0 ~ 4.6 V,150 mA·g^-1）100周期循环放电容量保持率为93.7%（无包覆LNCMO(0)保持率为74.4%）;55 °C高温100周期循环容量保持率为77%（无包覆LNCMO(0)保持率17%）. XRD和电感耦合等离子体原子发射光谱（ICP-AES）测试表明,CoAl₂O₄包覆的LNCMO(x)材料可有效地减缓材料中Mn离子在电解液的溶解,提高材料结构稳定性和热稳定性.     

Layered manganese oxide with O2 structure,Li(2/3)+x(Ni1/3Mn2/3)O2 as cathode for Li-ion batteries

Using LiI as the reducing agent, the compound O2-Li_(2/3)+x(Ni_1/3Mn_2/3)O₂, x∼1/3 (O2(Li+x)) has been prepared from the O2-Li_2/3(Ni_1/3Mn_2/3)O₂ (O2(Li)). Cyclic voltammetry and voltage-capacity profiles of the O2(Li+x) phase are qualitatively different from that of O2(Li) phase. The first extraction capacity of O2(Li+x) at C/10 rate is 190 mAh/g corresponding to the removal of 2/3 mole of Li from the compound. At C/5 rate it delivers a reversible capacity of 158 mAh/g at 25 °C and 184 mAh/g at 50 °C (vs Li metal; voltage window 2.5–4.6 V). In Li-ion cells, with MCMB anode and O2(Li+x) as cathode, a discharge capacity of 140 mAh/g was obtained at C/5 rate in the voltage window 2.5–4.5 V (25 °C). The charge–discharge cycling performance and the cyclic voltammograms reveal that O2(Li) and O2(Li+x) do not convert to the spinel structure.     

Low-temperature magnetic behavior of perovskite compounds PbFe(1/2)Ta(1/2)O3 and PbFe(1/2)Nb(1/2)O3

The isostructural perovskite compounds PbFe(1/2)Ta(1/2)O3 and PbFe(1/2)Nb(1/2)O3 have been known for long time, and they are part of the important class of materials called multiferroic, where ferroelasticity, ferroelectricity, and ferromagnetism coexist. In the literature regarding PbFe(1/2)Ta(1/2)O3 and PbFe(1/2)Nb(1/2)O3, an "anomaly" of their low-temperature magnetic behavior has not always been reported. Moreover, both the origin of this behavior, and the cause for which it was not always observed, were never completely explained. In this paper, the magnetic behavior of the two compounds at low temperature has been extensively studied and explained as the occurring of a spin-glasslike transition.     

湿化学法合成LiNi_(1/3)Mn_(1/3)Co_(1/3)O_2及其表征(英文)

利用琥珀酸为鳌合剂的湿化学法成功合成了一系列锂离子电池正极材料LiNi1/3Mn1/3Co1/3O2,在合成过程中改变琥珀酸与金属离子摩尔比(R)并研究了这一参数对合成LiNi1/3Mn1/3Co1/3O2材料物理及电化学性质的影响.采用热重、X射线衍射、Rietveld精修、扫描电镜以及超导量子干涉仪对反应机理、材料的结构、形貌以及磁学性质进行了详细表征.得到最佳合成条件为R=1,此时LiNi1/3Mn1/3Co1/3O2的阳离子混排度最低.此外,通过Rietveld精修得到该材料阳离子混排度的结果与通过磁学方法得到的结果定量相符,如对于在R=1条件下合成的样品,Rietveld精修结果显示其阳离子混排度为1.85%,而超导量子干涉仪的测试结果为1.80%.当充放电区间为3.0-4.3V,电流密度为0.2C(1C=160mA·g-1)时,该样品的首次放电容量为161mAh·g-1,库仑效率为93.1%,经过50次循环后,容量保持率可达91.3%.     

Über die Alkaliselenoarsenate(III) KAsSe3 · H2O,RbAsSe3 · 1/2 H2O und CsAsSe3 · 1/2 H2O

On the Alkali Selenoarsenates(III) KAsSe₃ · H₂O, RbAsSe₃ · 1/2 H₂O, and CsAsSe₃ · 1/2 H₂O The alkali selenoarsenates(III) KAsSe₃ · H₂O, RbAsSe₃ · 1/2 H₂O, and CsAsSe₃ · 1/2 H₂O have been prepared by hydrothermal reaction of the respective alkali carbonate with As₂Se₃ at a temperature of 135°C. Their X-ray structural analyses demonstrated that the compounds contain polyselenoarsenate(III) anions (AsSe₃^?)_n, in wich the basic units are ψ-AsSe₃ tetrahedra, which are linked together through Se? Se bonds into infinite zweier single chains. The Rb and Cs salts are isotypic.     

Effect of Various Synthesis methods on the Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2

Layered LiNi1/3Co1/3Mn1/3O2 has the isostructure of α-NaFeO2 and shows high rate capacity with stable cycleability. Furthermore, the thermal behavior of this material is milder than that of lithium nickel oxide and lithium cobalt oxide. In addition, it is expected to be stable at elevated temperatures. Therefore LiNi1/3Co1/3Mn1/3O2 may be the most promising cathode materials of lithium-ion secondary battery.In this research, LiNi1/3Co1/3Mn1/3O2 was prepared by solid-state reaction, sol-gel method and mixed hydroxide method. The influences of synthesis method on the physical and electrochemical properties of LiNi1/3Co1/3Mn1/3O2 were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), charge/discharge cycling cyclic voltammetry and differential scanning calorimetry (DSC). XPS studies show that the predominant oxidation states of Ni, Co and Mn in the LiNi1/3Co1/3Mn1/3O2 compound are 2+, 3+ and 4+. From the voltage profile and cyclic voltammetry, the redox processes occurring at ～3.8V and ～4.5V are assigned to the Ni2+/Ni3+ and Co3+/Co4+ couples, respectively. Different preparation methods result in the difference in morphology (shape, particle size and specific surface area) and electrochemical behaviors. A sample prepared by solid-state reaction has the worst electrochemical performance among these three methods. Sample synthesized by mixed hydroxide method displays the better rate capacity than that prepared by sol-gel method, while the capacity retention of sample prepared by sol-gel method is superior to that synthesized by mixed hydroxide method.     

Quenching of I(2P1/2) by O3 and O(3P)

Oxygen-iodine lasers that utilize electrical or microwave discharges to produce singlet oxygen are currently being developed. The discharge generators differ from conventional chemical singlet oxygen generators in that they produce significant amounts of atomic oxygen. Post-discharge chemistry includes channels that lead to the formation of ozone. Consequently, removal of I(2P1/2) by O atoms and O3 may impact the efficiency of discharge driven iodine lasers. In the present study, we have measured the rate constants for quenching of I(2P1/2) by O(3P) atoms and O3 using pulsed laser photolysis techniques. The rate constant for quenching by O3, (1.8 +/- 0.4) x 10(-12) cm3 s-1, was found to be a factor of 5 smaller than the literature value. The rate constant for quenching by O(3P) was (1.2 +/- 0.2) x 10(-11) cm3 s-1.     

Y2O3包覆LiCo1/3Ni1/3Mn1/3O2的电化学性能

通过在硝酸钇水溶液浸渍并焙烧的简单工艺, 在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3. 采用X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析. 结果表明, Y2O3包覆并没有改变LiCo1/3Ni1/3Mn1/3O2的晶体结构, 只存在于LiCo1/3Ni1/3Mn1/3O2的表面; 与未包覆的材料相比, Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量. CV测试表明, 包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应.     

LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的低温性能及动力学分析

通过高温烧结制备了锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2,并用XRD、SEM和恒流充放电对材料的结构、形貌和低温电性能进行了表征,通过线性极化、GITT和EIS等手段研究分析了低温下LiNi1/3Co1/3Mn1/3O2性能变差的原因.结果表明,-20℃时,LiNi1/3Co1/3Mn1/3O2材料的0.1、0.2、1和5 C倍率放电比容量依次为25℃时同倍率下放电比容量的83.2%、68.4%、57.2%和34.1%,放电中值电压比25℃时依次降低了0.049、0.125、0.364和0.531 V.低温充放电过程表现出明显的极化现象,其中最显著的极化来自锂离子穿过活性物质/电解液界面过程以及电荷转移过程,而非锂离子在电极材料内部的扩散过程.     

Size-manipulable synthesis of single-crystalline BaMnO3 and BaTi1/2Mn1/2O3 nanorods/nanowires

We report a size-manipulable synthesis of single-crystalline nanorods/nanowires of barium manganite (BaMnO(3)) and barium titanium manganite (BaTi(1/2)Mn(1/2)O(3)) by using the composite-hydroxide-mediated approach. The synthesis cleanly yields nanorods with a hexagonal perovskite structure. Typical nanorods have widths ranging between 50 and 100 nm, and the lengths can be easily controlled by time and temperature or by adding a small amount of water during the synthesis process. Resistance measurement shows that a phase transition happened at 58 K on BaMnO(3). The photoluminescence spectrum of BaTi(1/2)Mn(1/2)O(3) presents two emission peaks at wavelengths of 465 and 593 nm, corresponding to blue and green fluorescence. The ability to synthesize nanorod manganites of a desired length should enable detailed investigations of the size-dependent evolution of magnetism, magnetoresistance, nanoscale phase separation, and realization of a nanodevice of magnetic sensors.     

Ti, F复合掺杂改进LiNi1/3Co1/3Mn1/3O2正极材料的电化学性能

采用复合离子掺杂技术对LiNi1/3Co1/3Mn1/3O2进行改性, 并对材料的结构及电化学性能进行了考察.     

Kinetics of O2(a1Deltag) and I(2P1/2) in the photochemistry of N2O/I2 mixtures

The recent demonstration of a discharge-driven oxygen-iodine laser has generated renewed interest in the kinetics of iodine interacting with electronically excited O2 and atomic O. Kinetic measurements that are of relevance to the laser have been carried out using 193 nm pulsed laser photolysis of N2O/I2/CO2 mixtures. Singlet oxygen was generated in this system by the reaction O(1D)+N2O-->O2(a1Deltag, X3Sigma-g)+N2. The fraction of electronically excited O2 produced by this channel was shown to be >0.9. The secondary photochemistry of the N2O/I2/CO2 system was characterized by monitoring the time histories of I(2P1/2), I2, IO, and O2(a). Kinetic modeling of these data was used to determine the rate constant for the deactivation of I(2P1/2) by O(3P) (k=(1.2+/-0.1)x10(-11) cm3 s(-1)). Quenching of I(2P1/2) by O(3P) is suppressed in the discharge-driven laser by using NO2 to scavenge the O atoms. The reaction O(3P)+NO2-->O2+NO is sufficiently exothermic for the production of O2(a), and it has been speculated that this channel may be significant in the laser excitation kinetics. Photolysis of NO2 was used to probe this reaction. O2(a) was not detected, and an upper bound of <0.1 for its production in the reaction of O(3P) or O(1D) with NO2 was established.     

Au/Mn2O3/Al2O3催化剂的制备及其deNOx活性

由于燃煤烟气、汽车尾气的过度排放 ,大气中ＮＯｘ(其中ＮＯ占 90 %以上 )浓度已呈上升趋势。ＮＯ在阳光作用下 ,易形成光化学烟雾 ,危害人体的呼吸系统。ＮＯ还是破坏大气臭氧层和形成酸雨的前驱气体之一 ,破坏生态环境。催化分解和催化还原法是消除ＮＯ(ｄｅＮＯｘ)的主要方法。但由于实际环境中ＮＯ往往与某一种或几种还原性气体 (如ＣＯ、低碳烃 )共存 ,所以催化还原法是人们公认的有应用前景的ｄｅＮＯｘ 方法[1 ] 。近十几年来 ,国内外研究较多的ｄｅＮＯｘ 催化剂是Ｃｕ ＺＳＭ 5 ,其催化活性除受原料气中氧含量的影响外 ,很大程度上…     

Comparative Study of CuO Species on CuO/Al2O3, CuO/CeO-Al2O3 andCuO/La2O-Al2O3 Catalysts for CO Oxidation

CuO/Al2O3, CuO/CeO2-Al2O3, and CuO/La2O3-Al2O3 (denoted as Cu/Al, Cu/CeAl, and Cu/LaAl) catalysts were prepared by an impregnation method. CuO species and CuO/Al2O3 thermal solid-solid interaction were characterized by in situ XRD, Raman spectroscopy and H2-TPR techniques. For the Cu/Al catalyst, a CuAl2O4 phase exists between the CuO and Al2O3 layer and the CuO phase exists on the surface in both highly dispersed and bulk forms. For the Cu/CeAl catalyst, there is highly dispersed and bulk CuO on the surface, but most of the CuO has transferred into the internal layer of CeO2 as bulk CuO and CuAl2O4. For the Cu/LaAl catalyst, only bulk CuO is present on the surface of the catalyst and no CuAl2O4 is formed. The catalytic activity order for CO oxidation is Cu/CeAl>Cu/Al>Cu/LaAl. The highly dispersed CuO on the catalyst surface may be the active phase for CO oxidation. The results show that the addition of CeO2 not only promotes both the transference of CuO and the formation of CuAl2O4 but also favors the CO oxidation due to the association of highly dispersed CuO with CeO2, while La2O3 hinders the transference of CuO and the formation of CuAl2O4.     

TiO2包覆对LiCo1/3Ni1/3Mn1/3O2材料的表面改性

为了提高材料LiCo1/3Ni1/3Mn1/3O2的循环性能, 采用浸渍-水解法对其进行TiO2包覆. 用X射线衍射(XRD)、电化学交流阻抗谱(EIS)、电感耦合等离子体发射光谱(ICP-OES)和恒流充放电测试研究包覆材料的结构和电化学性能. TiO2仅在材料表面形成包覆层, 并未改变材料的结构. TiO2包覆能提高材料LiCo1/3Ni1/3Mn1/3O2的倍率性能和循环性能, TiO2包覆后的材料在5.0C(1.0C=160 mA·g-1)下的放电容量达到0.2C下的66.0%, 而包覆前的材料在5.0C下的放电容量仅为其0.2C下的31.5%. 包覆后的材料在2.0C下循环12周后的容量没有衰减, 而未包覆的材料容量保持率仅为94.4%. EIS测试表明包覆材料性能的提高是由于循环过程中材料的界面稳定性得到了提高. 循环后材料的XRD和ICP-OES测试表明, 包覆层能提高材料LiCo1/3Ni1/3Mn1/3O2的结构稳定性.     

First-principles calculations of 17O nuclear magnetic resonance chemical shielding in Pb(Zr(1/2)Ti(1/2))O3 and Pb(Mg(1/3)Nb(2/3))O3: linear dependence on transition-metal/oxygen bond lengths

First-principles density functional theory oxygen chemical shift tensors were calculated for A(B,B')O(3) perovskite alloys Pb(Zr(1/2)Ti(1/2))O(3) (PZT) and Pb(Mg(1/3)Nb(2/3))O(3) (PMN). Quantum chemistry methods for embedded clusters and the gauge including projector augmented waves (GIPAW) method [C. J. Pickard and F. Mauri, Phys. Rev. B 63, 245101 (2001)] for periodic boundary conditions were used. Results from both methods are in good agreement for PZT and prototypical perovskites. PMN results were obtained using only GIPAW. Both isotropic δ(iso) and axial δ(ax) chemical shifts were found to vary approximately linearly as a function of the nearest-distance transition-metal/oxygen bond length, r(s). Using these results, we argue against Ti clustering in PZT, as conjectured from recent (17)O NMR magic-angle-spinning measurements. Our findings indicate that (17)O NMR measurements, coupled with first-principles calculations, can be an important probe of local structure in complex perovskite solid solutions.     

Pt/Co3O4/3DOM Al2O3：甲苯燃烧的高效催化剂

与硫氧化物、氮氧化物、一氧化碳以及悬浮颗粒一样,大部分挥发性有机物(VOCs)污染大气环境.控制 VOCs排放有多种方法,其中催化氧化法是一种有效技术,关键在于获得高效催化剂.
　　近年来,负载过渡金属和贵金属催化剂因具有比单纯负载贵金属和单纯负载过渡金属氧化物更好的催化性能而备受关注.在负载贵金属催化剂中,高比表面积载体负载 Pt, Pd或 Rh催化剂得到广泛而深入的研究,尽管这些催化剂成本较高,但是其对 VOCs氧化反应显示了很高的低温催化活性.众所周知,催化活性取决于贵金属和 VOCs的种类,不同负载贵金属催化剂对特定反应会表现出不同的催化活性.负载 Pt催化剂对长链碳氢化合物和芳香族化合物氧化反应表现出更高的活性.相对于负载贵金属催化剂,负载过渡金属氧化物催化剂不仅具有良好的氧化活性,而且价格低廉.迄今已发现许多过渡金属氧化物(如 Co3O4, Cr2O3和 MnO2等)对典型 VOCs氧化反应具有催化活性,其中 Co3O4的催化活性尤为突出.研究表明, Co3O4的性质和分散度是决定其性能的关键因素,制备方法、载体性质和过渡金属氧化物负载量对 Co3O4的物化性质具有重要影响,而且在负载 Pt催化剂中添加金属氧化物能改善其催化性能.尽管多孔氧化铝是一种常用的载体材料,但目前尚无文献报道三维有序大孔-介孔氧化铝负载 Co3O4和 Pt纳米粒子催化剂的制备及其对甲苯氧化反应的催化性能.
　　本文采用聚甲基丙烯酸甲酯微球胶晶模板法、等体积浸渍法和聚乙烯醇保护的硼氢化钠还原法制备了三维有序大孔-介孔(3DOM Al2O3)负载 Co3O4和 Pt (xPt/yCo3O4/3DOM Al2O3, Pt的质量分数(x%)为0-1.4%, Co3O4的质量分数(y%)为0-9.2%)纳米催化剂.通过电感耦合等离子体原子发射光谱、X射线衍射、氮气吸附-脱附、扫描电子显微镜、透射电子显微镜、选区电子衍射、X射线光电子能谱及氢气程序升温还原等技术表征了催化剂的物化性质,利用固定床微型石英反应器评价了催化剂对甲苯氧化反应的催化活性.结果表明,xPt/yCo3O4/3DOMAl2O3催化剂具有多级孔结构(大孔孔径为180–200 nm,介孔孔径为4–6 nm),比表面积为94?102 m2/g.粒径为18.3 nm的 Co3O4纳米粒子和粒径为2.3?2.5 nm的 Pt纳米粒子均匀分散在3DOM Al2O3表面.在xPt/yCo3O4/3DOM Al2O3催化剂中,1.3Pt/8.9Co3O4/3DOM Al2O3拥有最高的 Oads浓度、最好的低温还原性和最高的甲苯氧化反应催化活性(当空速为20000mL g–1 h–1时,甲苯转化率达90%的反应温度为160oC).基于催化剂的活性数据和结构表征,我们认为,1.3Pt/8.9Co3O4/3DOM Al2O3优异的催化性能与其高分散的 Pt纳米粒子、高的 Oads浓度、好的低温还原性、Pt和 Co3O4纳米粒子间的强相互作用以及多级孔结构相关.     

Catalytic Combustion of Methane over CO1-xMgxO/Al2O3/FeCrAl Monolithic Catalysts

A series of CoxMgxO/Al2O3/FeCrAl catalysts （x=0-1） were prepared. The structures of the catalysts were characterized using XRD, SEM, and TPR analyses. The catalytic activity of the catalysts for methane combustion was evaluated in a continuous flow microreactor. The results indicated that the active washcoats adhered well on the FeCrAl foils. The phases in the catalysts were Co--xMgxO solid solutions, α-Al2O3, and γ-Al2O3. The surface particle size of the catalysts varied with variations in the molar ratios of Co to Mg. The Co component of the Co1_xMgxO/Al2O3/FeCrAl catalysts played an important role in the catalytic activity for methane combustion. In the Co1-xMgxO/AluO3/FeCrAl series catalyst （x=0.2-0.8）, the catalytic activity in terms of x was in the order of 0.5〉0.2〉0.8 under the experimental conditions. The presence of Mg in these catalysts could promote the thermal stability to a large extent. There were strong interactions between the Co1-xMgxO oxides and the AluO3/FeCrAl supports.