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41.
The product from reaction of lanthanum chloride seven-hydrate with salicylic acid and 8-hydroxyquinoline, La(C7H5O3)2·(C9H6NO), was characterized by IR, elemental analysis, molar conductance, and thermogravimetric analysis. The standard molar enthalpies of solution of [LaCl3·7H2O (s)], [2C7H6O3 (s)], [C9H7NO (s)] and [La(C7H5O3)2·(C9H6NO) (s)] in a mixed solvent of absolute ethyl alcohol, dimethyl formamide (DMF) and perchloric acid were determined by calorimetry to be [LaCl3·7H2O (s), 298.15 K] = −96.45 ± 0.18 kJ mol−1, [2C7H6O3 (s), 298.15 K] = 14.99 ± 0.17 kJ mol−1, [C9H7NO (s), 298.15 K] = −3.86 ± 0.06 kJ mol−1 and [La(C7H5O3)2·(C9H6NO) (s), 298.15 K] = −117.78 ± 0.11 kJ mol−1. The enthalpy change of the reaction
(1) 相似文献
42.
CO2选择性氧化甲烷制C2烃催化剂La2O3/ZnO的氧化还原和CO2吸附性能 总被引:6,自引:0,他引:6
La2O3/ZnO催化剂体系在以二氧化碳作为氧化剂的甲烷氧化偶联反应中具有很高的C2烃选择性和稳定性.采用CO2-TPD-MS和TPR技术考察了La2O3/ZnO对CO2的吸附性质及其氧化还原行为.结果表明:(1)La2O3/ZnO催化剂体系存在着强、弱两种碱中心,其中弱碱中心数量随样品中La2O3含量增加而减少,强碱中心强度随样品中La2O3含量增加而增强.(2)由于组分相互作用,高温下,La2O3/ZnO易产生晶格氧空位,使之对CO2的吸附增强,吸附后的CO2与晶格氧作用形成立方晶型La2O2CO3.(3)La2O3/ZnO表面的La3+和Zn2+可以部分被还原,由于组分间的相互作用,使得二者的还原都较单一组分存在时更难.(4)H2-CO2-H2氧化还原循环实验表明,La2O3/ZnO表面被部分还原后,CO2可以将部分被还原的表面再氧化.在此基础上对La2O3/ZnO催化剂上甲烷与CO2转化为C2烃的机制也进行了讨论. 相似文献
43.
La2O(CN2)2 was synthesized from a 1:1:2 molar reaction mixture of LaCl3, LaOCl, and Li2(CN2) at 650 °C. Well developed single crystals were grown from a LiCl‐KCl flux. The crystal structure was refined as monoclinic (space group C2/c, Z = 2, a = 13.530(2) Å, b = 6.250(1) Å, c = 6.1017(9) Å, β = 104.81(2)°) from single crystal X‐ray diffraction data. The La3+ and (CN2)2— ions in the crystal structure of La2O(CN2)2 can be compared to Fe3+ and S22— ions in the cubic pyrite structure, being arranged like in a distorted NaCl type structure with their centers of gravity. In addition, the O2— ions in La2O(CN2)2 are occupying 1/4 of the tetrahedral voids formed by the arrangement of metal ions. 相似文献
44.
Highly fluorescent LaPO4:Ce/Tb@LaPO4@SiO2 (core/shell/Si) nanorods(NRs) were fabricated with an average length 100 nm by co-precipitation process at low temperature. X-ray diffraction (XRD), Transmission electron microscopy (TEM), energy dispersive X-ray analysis, Fourier transform infrared, optical absorption and photoluminescence spectral techniques were applied to investigate the crystal structure, phase purity, morphology, surface chemistry and optical properties of the as-prepared samples. XRD results confirmed the formation of highly crystalline with single phase, monoclinic type structure. TEM image illustrates the poly-dispersed, narrow size distributed, irregular size rod-shaped nanostructures, with mean diameters of 20 nm and average lengths up to 140 nm. FTIR spectral analysis confirmed the silica surface modification. The comparative emission spectral study shows highest luminescence intensity of core/shell NRs, due to a reduction in nonradiative transition rate. The emission intensity enhancement proves that growing of an inert LaPO4 layer on the surface of luminescent core-NRs was an effective way to suppress surface related quenching mechanism. These well crystalline, highly aqueous soluble along with extraordinary colloidal stability core/shell/Si NRs were extremely suitable material in fluorescent bio-labeling applications. 相似文献
45.
以三氧化二镧为原料, 经过醇化, 制备了三(月桂硫醇)镧及三(巯基乙酸异辛酯)镧, 并对合成方法进行了优化. 采用热失重分析、FTIR光谱、感应耦合等离子色谱、元素分析和1H NMR对目标产物进行了表征. 确定合成稀土异丙醇盐最佳反应条件为: 反应温度80 ℃, 反应时间2 h; 合成三(月桂硫醇)镧的反应条件为反应温度110 ℃, 反应时间2 h, 月桂硫醇的摩尔分数过量24%; 合成三(巯基乙酸异辛酯)镧的反应条件为反应温度60 ℃, 反应时间2 h, 月桂硫醇过量32%. 相似文献
46.
Hansjürgen Mattausch Dr. Manuel C. Schaloske Constantin Hoch Chong Zheng Arndt Simon 《无机化学与普通化学杂志》2008,634(3):491-497
Rare Earth Halides Ln4X5Z. Part 1: C and/or C2 in Ln4X5Z The compounds Ln4X5Cn (Ln = La, Ce, Pr; X = Br, I and 1.0 < n < 2.0) are prepared by the reaction of LnX3, Ln metal and graphite in sealed Ta‐ampoules at temperatures 850 °C < T < 1050 °C. They crystallize in the monoclinic space group C2/m. La4I5C1.5: a = 19.849(4) Å, b = 4.1410(8) Å, c = 8.956(2) Å, β = 103.86(3)°, La4I5C2.0: a = 19.907(4) Å, b = 4.1482(8) Å, c = 8.963(2) Å, β = 104.36(3)°, Ce4Br5C1.0: a = 18.306(5) Å, b = 3.9735(6) Å, c = 8.378(2) Å, β=104.91(2)°, Ce4Br5C1.5: a = 18.996(2) Å, b = 3.9310(3) Å, c = 8.282(7) Å, β = 106.74(1)°, Pr4Br5C1.3: a = 18.467(2) Å, b = 3.911(1) Å, c = 8.258(7) Å, β = 105.25(1)° and Pr4Br5C1.5: a = 19.044(2) Å, b = 3.9368(1) Å, c = 8.254(7) Å, β = 106.48(1)°. In the crystal structure the lanthanide metals are connected to Ln6‐octahedra centered by carbon atoms or C2‐groups. The Ln6‐octahedra are condensed via opposite edges to chains and surrounded by X atoms which interconnect the chains. A part n of isolated C‐atoms is substituted by 1‐n C2‐groups. The C‐C distances range between 1.26 and 1.40Å. In the ionic formulation (Ln3+)4(X?)5(C4?)n(C2m?)1?n·e? with 0 < n < 1 and m = 2, 4, 6 (C22?, C24? C26?), there are 1 < e? < 5 electrons centered in metal‐metal bonds. 相似文献
47.
The Lanthanumiodideethanide o‐La5I9(C2) – The Orthorhombic High Temperature Modification o‐La5I9(C2) is synthesized by reaction of LaI3, La metal and graphite powder in sealed Ta containers at 850 °C < T < 900 °C. It crystallizes in the orthorhombic space group Pbca with a = 8.0247(16) Å, b = 16.887(3) Å, c = 35.886(7) Å. o‐Ce5I9(C2) is isotypic with the lattice parameters a = 7.9284(4) Å, b = 16.714(1) Å, c = 35.530(3) Å. o‐La5I9(C2) transforms at 800 °C to the triclinic low temperature modification t‐La5I9(C2). The transformation is reversible. The La atoms form trigonal bipyramids centered by C2 groups. These units are connected by iodine atoms above the faces (f), edges (e) and corners according to La5(C2)I(f)iI(e)i?i2/2I(e)i?a7/2I(e)a?i7/2. The C‐C distance in the C2 unit is 1.45(2) Å. The crystals with greenish luster are moisture sensitive. 相似文献
48.
通过紫外-可见分光光度法测定了碳酸镧吸附前后溶液中的DNA含量,并计算了DNA的吸附率.通过X射线光电子能谱(XPS)与X射线衍射(XRD)分析了吸附DNA前后固相的变化.结果表明,碳酸镧对DNA有较强的吸附作用,且该过程对碳酸镧晶型未产生明显影响.通过对吸附条件的考察,发现DNA的吸附率随pH值升高而降低.最后通过磷酸二氢钾作为洗脱液将吸附的DNA回收,洗脱液中镧离子含量低于0.1×10~(-6)mol/L,对DNA的后期使用无污染. 相似文献
49.
The yet unknown intermetallic phase La5Al3Ni2 was obtained by partially crystallizing amorphous La50Al25Ni25 at 550 K (further heating above 600 K leads to irreversible disappearance of this phase), and its crystal structure was determined from X‐ray powder diffraction data. The crystal structure of the La5Al3Ni2 phase constitutes a new structure type (Cmcm, a = 14.231Å, b = 6.914Å, c = 10.460Å, oC40) and is built from [Al3Ni2] chains surrounded by La atoms. In the ternary system La‐Al‐Ni La5Al3Ni2 is located on the section La50Al50−nNin (0 ≤ n ≤ 50) with the binary compounds LaAl and LaNi as end members. Strikingly, also the crystal structures of the end members can be conceived as chain structures with Al and Ni chains surrounded by La, respectively. 相似文献
50.
Benedict Ita P. Murugavel V. Ponnambalam A. R. Raju 《Journal of Chemical Sciences》2003,115(5-6):519-524
Fine powders of lanthanum iron oxide, LaFeO3, have been prepared by solid state reaction as well as sol-gel synthesis and nebulized spray pyrolysis. Structures, morphologies
and magnetic susceptibility measurements of these powders have been examined. The powders prepared by all the three low-temperature
routes contain nearly spherical particles with an average diameter of 40 nm. These samples show a lower Neel temperature than
the powder prepared by solid state reaction besides showing much lower magnetic susceptibility at low temperatures.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献