三元体系La(CIO_4)_3-BAPHDCA-H_2O(30℃)的相平衡研究及La(BAPHDCA)_2·(CIO_4)_3·4H_2O的合成和表征

在30℃时采用等温溶度法研究了三元体系La(ClO_4)_3-BAPHDC-H_2O(BAPHDCA,N,N′-二安替比林-1,6-己二酰胺)的相平衡,绘制了体系的溶度图及饱和溶液的折光指数-组成图,发现并制备了未见文献报道的固液异组成三元化合物La(BAPHDCA)_2(ClO_4)_3·4H_2O.通过化学分析、元素分析、IR光谱、TG-DTG及X射线粉末衍射分析等对其进行了物理化学表征.     

Regioselective Exohedral Functionalization of La@C82 and its 1,2,3,4,5‐Pentamethylcyclopentadiene and Adamantylidene Adducts

The first regioselective functionalization of La@C₈₂ by two different groups has been performed. Bis‐adducts of La@C₈₂ with Cp* and adamantylidene were synthesized by using two different routes and characterized. Spectroscopic analysis and theoretical calculations reveal that the addition position is controlled by the charge density and p‐orbital axis vector value of the fullerene cage.     

LaCl3对硝态氮供应下小麦根系生长的影响

选择石麦15、衡观35两个品种小麦为供试作物,进行营养液培养,研究不同浓度硝态氮供应下Ca2+通道阻断剂LaCl3对小麦苗期根系形态特征的影响。结果表明:添加Ca2+通道阻断剂LaCl3后,3种浓度硝态氮处理的小麦根系初生根长度、侧根长度、根系总长度、侧根平均长度均较不添加LaCl3处理显著变短;直径(>0.45 mm)范围内根系所占比例增加。不施用硝态氮条件下,与不添加LaCl3处理相比,LaCl3处理对小麦植株地上部NO3-含量变化不大,但一级侧根数量明显减少,2.5和50.0 mmol.L-1硝态氮施用时,LaCl3处理侧根分布密度增加,衡观35较石麦15更明显。结论初步认为:Ca2+通道阻断剂LaCl3施用,影响小麦根系生长发育:根系伸长受抑,根系变粗,若施用硝态氮,侧根数量分布增加。     

Crystal structure of lanthanum bismuth silicate Bi2−xLaxSiO5 (x∼0.1)

A melting and glass recrystallization route was carried out to stabilize a new tetragonal form of Bi₂SiO₅ with bismuth partially substituted by lanthanum. The crystal structure of Bi_2−xLa_xSiO₅ (x∼0.1) was determined from powder X-ray and neutron diffraction data (space group I4/mmm, , c=15.227(1) Å, V=224.18 Å³, Z=2; reliability factors: R_Bragg=5.65%, R_p=14.6%, R_wp=16.8%, R_exp=8.3%, χ²=8.3 (X-ray) and R_Bragg=2.40%, R_p=8.1%, R_wp=7.5%, R_exp=4.2%, χ²=3.3 (neutrons); 11 structural parameters refined).The main effect of lanthanum substitution is to introduce, by removing randomly some bismuth 6s² lone pairs, a structural disorder in the surroundings of (Bi₂O₂)²⁺ layers, that is in the (SiO₃)²⁻ pyroxene files arrangement. It results in a symmetry increase relatively to the parent compound Bi₂SiO₅, which is orthorhombic. The two structures are compared.     

Effect of LaFeO3 Decoration and Ozone Treatment on Thermal Stability of Au/Al2O3 for CO Oxidation

The 1.1%Au/LaFeO_x/Al₂O₃ catalysts were prepared by the iso-volume impregnation method and activated with H₂ or O₃. The catalytic performance for CO oxidation at room temperature was investigated by accelerated deactivation tests in 1.0% CO reactant stream at 550 °C. The introduction of La and Fe enhanced the thermal stability of Au/Al₂O₃ with a decrease in initial activity, probably due to the formation of LaFeO₃ perovskite on the Al₂O₃ surface. The 1.1%Au/2%LaFeO₃/Al₂O₃ catalyst activated by H₂ can transform 65% CO into CO₂ at room temperature after pretreatment in 1.0% CO reactant stream at 550 °C for 2 h, whereas 1.1%Au/Al₂O₃ activated by H₂ totally loses its activity. O₃ activation can always make 1.1%Au/LaFeO₃/Al₂O₃ more active than that of H₂ activation during the pretreatment process in 1.0% CO. After pretreatment for 10 h, 1.1%Au/2%LaFeO₃/Al₂O₃ activated by O₃ still shows 40% conversion of 1.0% CO at room temperature, whereas those activated by H₂ become inactive completely. The better thermal stability of the catalysts activated by O₃ may be due to that O₃ activation leads to the formation of partially oxidized state of Au in Au/FLA-O₃, which may reinforce the interaction between the metal and support.     

Lanthanum phenylphosphonate–based multilayered coating for reducing flammability and smoke production of flexible polyurethane foam

In the present work, lanthanum phenylphosphonate (LaPP)–based multilayered film was fabricated on the surface of flexible polyurethane (PU) foam by layer‐by‐layer self‐assembled method. The successful deposition of the coating was confirmed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX). Subsequently, the thermal decomposition and burning behavior of untreated and treated PU foams were investigated by thermogravimetric analysis (TGA) and cone calorimeter, respectively. The TGA results indicated that T_max2 of treated PU foams were increased by approximately 15°C to 20°C as compared with untreated PU foam. The peak heat release rate (PHRR) and total heat release (THR) of PU‐6 (with 19.5 wt% weight gain) were 188 kW/m² and 20.3 MJ/m², with reductions of 70% and 15% as compared with those of untreated PU foam, respectively. Meanwhile, the smoke production of treated PU foam was suppressed after the construction of LaPP‐based coating.     

La2O2S∶Mn2+荧光粉的微波合成及其荧光特性

Using La₂(SO₄)3 and the active carbon powder as reactants, La₂O₂S∶Mn²⁺ red phosphor was synthesized by microwave radiation method. The phosphor was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), laser-diffraction size analyzer and fluorospectrophotometer. The XRD analysis showed that the phosphor was pure phase La₂O₂S. The phosphor of La₂O₂S∶Mn²⁺ showed hexagonal crystal structure with diverse shapes, such as spherical and rod, with average particle size of 10.22 μm. The emission and excitation spectra of the phosphor were determined by fluorospectrophotometer and the results showed that the excitation spectrum of the phosphor under 600 nm emission wavelength was excitation bands between 250 nm and 350 nm with a peak value of 303 nm. Then ,when exicited under UV 303 nm, the phosphor showed broad band emission of 550~700 nm with a peak at 607 nm. In addition, the optimal effects were obtained for the phosphor preparation when the concentration of the activator Mn²⁺ was x_Mn=0.01, the ratio of C and O (n_C / n_O) in the reactants was 0.6∶1, and the time of reaction was about 1 h. La₂O₂S∶Mn²⁺ has strong absorption of UV spectrum and can emit bright red light.     

柠檬酸络合法制备La2CuO4纳米晶

以硝酸镧和硝酸铜为起始原料,柠檬酸为络合剂,采用溶胶-凝胶法制备了La₂CuO₄纳米晶。通过X射线衍射、场发射扫描电子显微镜、透射电子显微镜研究了柠檬酸的加入量对La₂CuO₄纳米粉体相组成、显微结构的影响,并采用Kissinger方法研究了La₂CuO₄纳米晶的合成活化能。结果表明：600 ℃煅烧保温2 h后,可获得单一物相的La₂CuO₄,晶粒为类钙钛矿型结构,晶粒尺寸为60~80 nm,分布集中;在制备过程中提高柠檬酸的加入量能够降低La₂CuO₄晶体的合成活化能,当柠檬酸与溶液中阳离子(La³⁺和Cu²⁺)的物质的量的比由1∶1增加至1.5∶1时,La₂CuO₄纳米晶的合成活化能由147.0 kJ·mol^-1降低到133.4 kJ·mol^-1。     

稀释剂对二（2—乙基己基）磷酸萃取镧（Ⅲ）的影响

二（２－乙基己基）磷酸从硝酸介质中对Ｌａ（Ⅲ）的萃取对不同稀释剂其平衡常数为；正己烷＞环己烷＞四氯化碳＞甲苯＞氯仿＞甲异丁酮，萃取平衡常数与稀释剂的极性参数Ｓ间呈线性关系。     

Pd-La/γ-Al2O3和Pd-La/MgAl2O4对2,6-二异丙基苯酚气相胺化反应的催化性能

 采用XRD,BET,吡啶吸附-IR,NH3-TPD和XPS等手段表征了Pd-La/γ-Al2O3和Pd-La/MgAl2O4负载型催化剂的物理性质和表面酸性,并对比研究了两种催化剂在2,6-二异丙基苯酚(DIPP)气相胺化制2,6-二异丙基苯胺(DIPA)反应中的催化性能. 结果表明,采用镁铝尖晶石载体大幅度提高了催化剂的活性、选择性和稳定性. 在Pd-La/MgAl2O4催化剂上,在n(NH3)/n(DIPP)=10,n(H2)/n(DIPP)=20,LHSV=0.3 h-1,θ=220 ℃和t=73 h的条件下,2,6-二异丙基苯酚转化率可达98.5%,2,6-二异丙基苯胺的选择性和收率分别可达88.9%和87.5%. 该催化剂连续运转400 h,反应到200 h时2,6-二异丙基苯胺的收率仍可达80%以上.