有机溶剂对镧和钇ICP光谱信号的增敏机理研究

本文考察了有机溶剂（乙酸丁酯）及有机试剂（PMBP）引入ICP－AES对稀土元素镧和钇光谱信号的影响。实验结果表明，有机溶剂的引入明显增大了待测物的传质效率，从而导致分析灵敏度的改善。与水相相比，有机相的引入对ICP激发温度未产生明显影响，但使线对强度比（LogI^ /I)增强，有利于待测物的电离。     

Solvothermal synthesis and characterisation of La1−xAxMnO3 nanoparticles

The synthesis of La_1−xA_xMnO₃ (A=Ca, Sr, Ba) nanoparticles in nonaqueous solvents has been studied. For this solvothermal procedure benzyl alcohol and acetophenone were chosen as reaction media. After this treatment in mild conditions a precipitate was obtained, which, however, can be annealed to the crystalline perovskite structure. Our results show that acetophenone is more suited to obtain the clean pervoskite phase than benzyl alcohol.     

NiO/La2O3催化剂上甲烷催化部分氧化制合成气的研究

采用浸渍法制备了一系列不同N i含量的N iO/La2O3催化剂,并利用XRD、BET对催化剂结构进行了表征,采用常压下固定床石英管反应器考察了催化剂对甲烷部分氧化制合成气的反应性能和催化剂的稳定性,其甲烷转化率与反应温度、N i含量以及空速有关.结果表明,N i含量为30%的N iO/La2O3催化剂具有良好的催化活性,800℃时甲烷的转化率为88%,CO选择性可达83%,100 h的连续测试显示N iO/La2O3具有良好的稳定性.     

LaB6-ZrB2共晶复合材料的组织特征及控制

用电弧炉和电子束悬浮区熔炉法制备了ＬａＢ６ＺｒＢ２共晶复合材料，并用ＳＥＭ和ＴＥＭ方法对其显微组织进行了研究。结果表明，ＬａＢ６ＺｒＢ２形成纤维状共晶组织，控制凝固条件可得到定向排列的组织，ＬａＢ６基体上均匀分布着直径为０２～１２μｍ的ＺｒＢ２纤维，纤维长度可达１００μｍ以上。对于固液界面为平面生长的试样，其结晶学取向关系为［００１］ＬａＢ６∥［００１］ＺｒＢ２，（１１０）ＬａＢ６∥（０１０）ＺｒＢ２。     

氯化铯和氯化镧溶剂体系及四类新化合物的合成

研究了四元体系ＣｓＣｌ－ＬａＣｌ３－ＨＣｌ－Ｈ２Ｏ（２５℃、「ＨＣｌ」＝１３％（ｗｔ），２３％（ｗｔ）和ＣｓＣｌ－ＬａＣｌ３－ＨＡｃ－Ｈ２Ｏ（３０℃，「ＨＡｃ」＝４２％（ｗｔ））的平衡态的溶度数据，并给出制了相应的溶度图，共得到了ＣｓＣｌ．ＬａＣｌ３．４Ｈ２Ｏ、２ＣｓＣｌ．ＬａＣｌ３．２Ｈ２Ｏ和３ＣｓＣｌ．ＬａＣｌ３．３Ｈ２Ｏ３种化合物。对得到的新相进行了热分析，Ｘ射线粉末衍射及偏光性质的测定，依     

Study of transition metal oxide doped LaGaO3 as electrode materials for LSGM-based solid oxide fuel cells

Transition metal oxide doped lanthanum gallates, La_0.9Sr_0.1Ga_0.8M_0.2O₃ (where M=Co, Mn, Cr, Fe, or V), are studied as mixed ionic-electronic conductors (MIECs) for electrode applications. The electrochemical properties of these materials in air and in H₂ are characterized using impedance spectroscopy, open cell voltage measurement, and gas permeation measurement. Three single cells based on La_0.9Sr_0.1Ga_0.8 Mg_0.2O₃ (LSGM) electrolyte (1.13 to 1.65 mm thick) but with different electrode materials are studied under identical conditions to characterize the effectiveness of the lanthanum gallate-based MIECs for electrode applications. At 800 °C, a single cell using La_0.9Sr_0.1- Ga_0.8Co_0.2O₃ as the cathode and La_0.9Sr_0.1Ga_0.8Mn_0.2O₃ as the anode shows a maximum power density of 88 mW/cm², which is better than that of a cell using Pt as both electrodes (20 mW/cm²) and that of a cell using La_0.6Sr_0.4CoO₃ (LSC) as the cathode and CeO₂-Ni as the anode (61 mW/cm²) under identical conditions. The performance of LSGM-based fuel cells with MIEC electrodes may be further improved by reducing the electrolyte thickness and by optimizing the microstructures of the electrodes through processing. Received: 9 January 1998 / Accepted: 1 May 1998     

Extending framework based on the linear coordination polymers: Alternative chains containing lanthanum ion and acrylic acid ligand

One-dimensional alternative chains of two lanthanum complexes: [La(L¹)₃(CH₃OH)(H₂O)₂]·5H₂O (L¹=anion of α-cyano-4-hydroxycinnamic acid ) 1 and [La(L²)₃(H₂O)₂]·3H₂O (L²=anion of trans-3-(4-methyl-benzoyl)-acrylic acid) 2 were synthesized and structurally characterized by single-crystal X-ray diffraction, element analysis, IR and thermogravimetric analysis. The crystal structure data are as follows for 1: C₃₁H₃₆LaN₃O₁₇, triclinic, P-1, , , , α=72.7960(10)°, β=83.3820(10)°, γ=67.1650(10)º, Z=2, R₁=0.0377, wR₂=0.0746; for 2: C₃₃H₃₇LaO₁₄, triclinic, P-1, , , , α=81.145(2)°, β=87.591(2)°, γ=67.345(5)°, Z=2, R₁=0.0869, wR₂=0.220. 1 is a rare example of the alternative chain constructed by syn-syn and anti-syn coordination mode of carboxylato ligand arranged along the chain alternatively. La(III) ions in 2 are linked by two η³-O bridges and four bridges (two η²-O and two η³-O) alternatively. Both of the linear coordination polymers grow into two- and three-dimensional networks by packing through extending hydrogen-bond network directed by ligands.     

Multiple-magnetic field 139La NMR and density functional theory investigation of the solid lanthanum(III) halides

Results from a solid-state ¹³⁹La NMR spectroscopic investigation of the anhydrous lanthanum(III) halides (LaX₃; X=F, Cl, Br, I) at applied magnetic fields of 7.0, 9.4, 11.7, 14.1, and 17.6 T are presented and highlight the advantages of working at high applied magnetic field strengths. The ¹³⁹La quadrupolar coupling constants are found to range from 15.55 to 24.0 MHz for LaCl₃ and LaI₃, respectively. The lanthanum isotropic chemical shifts exhibit an inverse halogen dependence with values ranging from −135 ppm for LaF₃ to 700 ppm for LaI₃, which represents nearly half of the total lanthanum chemical shift range. The spans of the magnetic shielding tensors also vary widely, from 35 to 650 ppm for the solid LaF₃ through LaI₃. DFT calculations of the ¹³⁹La electric field gradient and magnetic shielding tensors have been performed and provide a qualitative interpretation of the trends observed experimentally.