Structural and Optical Properties of Barium Strontium Titanate (Ba0.5Sr0.5TiO3) Thin Films

Ferroelectric Barium Strontium Titanate (Ba_0.5Sr_0.5TiO₃) or BST thin films on quartz substrates have been prepared by using a modified sol gel processing technique. The starting materials are Barium 2-ethylhexanoate Ba[CH₃(CH₂)₃CH(C₂H₅)CO₂]_2, Strontium 2-ethylhexanoate Sr[CH₃(CH₂)₃CH(C₂H₅)CO₂]₂ and Titanium(IV) isopropoxide [TiOCH(CH₃)₂]₄. The precursors except [TiOCH(CH₃)₂]₄ were synthesized in the laboratory. Transparent and crack-free films were fabricated on quartz substrates by spin coating. The as-fired films were found to be amorphous, which crystallized to cubic phase after annealing at 550°C in air for 1 hr. In this paper we report the structural and optical properties of BST films prepared by the modified sol-gel process.

Communicated by Prof. E. C. Subbarao     

CH4/C2H6/C3H8在MOF-505@5GO上吸附相平衡和选择性

应用溶剂热法合成了不同氧化石墨烯（GO）负载量的MOF-505@GO复合材料,分别采用全自动表面积吸附仪、P-XRD、SEM和Raman对材料进行了性能表征,测定了CH₄、C₂H₆和C₃H₈在MOF-505@GO上的吸附等温线,并进行Langmuir-Freundlich方程拟合,依据IAST理论模型计算了C₂H₆/CH₄和C₃H₈/CH₄二元混合气在MOF-505@5GO上的吸附选择性。研究结果表明,随着GO负载量增大,MOF-505@GO复合材料的孔容及BET比表面积先增大后减小,当GO负载量为5%（质量）时,复合材料MOF-505@5GO的孔容及BET比表面积达到最大,当GO负载量进一步增大至8%（质量）和10%（质量）时,复合材料的孔容及BET比表面积逐渐降低。在0.1 MPa和298 K条件下,MOF-505@5GO对CH₄、C₂H₆和C₃H₈的吸附容量分别为0.88、4.81和5.17 mmol·g^-1,相比MOF-505分别提高了14.9%、30.7%和13.1%。MOF-505@5GO对C₂H₆/CH₄和C₃H₈/CH₄的吸附选择性分别为40.1和3056.1,其对C₂H₆/CH₄和C₃H₈/CH₄具有极高的吸附选择性。     

Calorimetric investigations of overcritical behaviour in (TEA)2CuCl4 crystals

The results of experimental investigation of molar heat capacity of [N(C₂H₅)₄]₂CuCl₄ - ferroelasto-ferroelectric crystals in a wide temperature range are presented. The typical anomaly for the first order phase transition of order-disorder type at 258 K and additional anomaly with maximum at 195 K has been observed. We suggest that the low temperature anomalies of physical properties of [N(C₂H₅)₄]₂CuCl₄ crystals can be attributed to over critical traces of isomorphous phase transitions (similar to that observed in liquid-gas system). Results of numerical analysis of phenomenological model of phase transition in [N(C₂H₅)₄]₂CuCl₄ crystals are presented and compared with the experimentally determined temperature dependence of the specific heat and entropy changes.     

A pillared-layer metal-organic framework for efficient separation of C3H8/C2H6/CH4 in natural gas

Metal-organic frameworks (MOFs) have great potentials as adsorbents for natural gas purification. However, the trade-off between selectivity and adsorption capacity remains a challenge. Herein, we report a pillared-layer metal-organic framework Ni(HBTC)(bipy) for efficiently separating the C₃H₈/C₂H₆/CH₄ mixture. The experimental results show that the adsorption capacity of C₃H₈ and C₂H₆ on Ni(HBTC)(bipy) are as high as 6.18 and 5.85 mmol·g^-1, while only 0.93 mmol·g^-1 for CH₄ at 298 K and 100 kPa. Especially, the adsorption capacity of C₃H₈ at 5 kPa can reach an unprecedented 4.52 mmol·g^-1 and for C₂H₆ it is 1.48 mmol·g^-1 at 10 kPa. The ideal adsorbed solution theory predicted C₃H₈/CH₄ selectivity is as high as 1857.0, superior to most of the reported materials. Breakthrough experiment results indicated that material could completely separate the C₃H₈/C₂H₆/CH₄ mixture. Therefore, Ni(HBTC)(bipy) is a promising material for separation of natural gas.     

磁场对(C4H9NH3)2(CH3NH3)Pb2I7钙钛矿发光特性调控的研究

(C₄H₉NH₃)₂(CH₃NH₃)Pb₂I₇是一种Ruddlesden-Popper相钙钛矿材料，具有层状结构，层间通过van der Waals力结合，因此可以通过机械剥离的方法，获得其二维薄层。二维(C₄H₉NH₃)₂(CH₃NH₃)Pb₂I₇内束缚激子会自发复合从而表现出强的荧光，其圆极化率、峰位均受磁场调控。在外磁场中，荧光圆极化率与磁场呈线性关系，激子中电子和空穴之间的朗德因子差Δg约为0.43。束缚激子在磁场中受抗磁效应影响，致使其发光峰随磁场增加而红移。     

低碳烷烃烯烃在超微孔柔性Cu(Qc)2上的吸附行为

采用实验研究与分子模拟相结合的方法研究了低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附热力学、动力学和吸附分离机理。用常温合成方法制备了超微孔金属-有机骨架材料Cu(Qc)₂,测定了低碳烷烃烯烃（CH₄/C₂H₄/C₂H₆/C₃H₆/C₃H₈）在Cu(Qc)₂上的吸附相平衡和吸附动力学。使用Materials Studio中的Fortcite模块模拟低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附机理以及材料的结构形变。结果表明Cu(Qc)₂具有优良的C₂H₆ /C₂H₄吸附选择性和吸附动力学,而对C₃H₈ /C₃H₆的吸附选择性很低。273 K和0.1 MPa下,C₂H₆/C₂H₄在Cu(Qc)₂上的IAST选择性达4.6。298 K和0.05 MPa下C₂H₆/C₂H₄在Cu(Qc)₂上的扩散时间常数分别达1.42×10^-3和1.48×10^-3_{s^-1,扩散活化能分别为16.62 和16.43 kJ/mol。应用装填Cu(Qc)2的固定床可在常温条件下实现C2H6 /C2H4二元混合气的完全分离。模拟结果显示Cu(Qc)2为二维堆叠结构,材料会由于吸附不同分子而发生不同程度的结构形变。甲烷易从变大的层间扩散脱附,导致其在材料上的吸附量很低;C2H6/C2H4两者都能稳定吸附在层中的孔道中,其分离推动力主要来源于两种气体在材料上明显的吸附热差异;C3H8/C3H6会分别吸附在两种不同的环境,吸附热差异小导致Cu(Qc)2对C3H8 /C3H6的吸附选择性低。}     

C2H6/C3H8影响CH4爆炸极限参数及动力学特性研究

为研究C₂H₆/C₃H₈对甲烷爆炸极限参数及动力学特性的影响,采用标准的可燃气体爆炸极限测定装置测定了不同配比的C₂H₆/C₃H₈混合气体对甲烷爆炸极限的影响规律,同时得出了氮气惰化条件下甲烷爆炸临界参数的变化规律。此外,利用Chemkin软件模拟了C₂H₆/C₃H₈混合气体对甲烷爆炸过程中中间产物浓度的影响情况,并进行了敏感性分析。结果表明,C₂H₆/C₃H₈的存在降低了甲烷的爆炸上下限,增大了甲烷的爆炸危险度;在氮气惰化过程中甲烷的爆炸上限下降,爆炸下限上升,最终爆炸上下限重合,重合点处甲烷浓度和氮气临界浓度均随C₂H₆/C₃H₈的添加而逐渐减小;此外,C₂H₆/C₃H₈混合气体使甲烷爆炸过程中CO和·H的生成量逐渐增大,而CO₂、·O和·OH的生成量则有下降趋势,通过对爆炸过程中甲烷体积的敏感性分析,发现C₂H₆/C₃H₈的存在在某种程度上促进了甲烷爆炸。对比不同配比的C₂H₆/C₃H₈混合气体,发现C₃H₈含量越高,其对甲烷爆炸过程中相关参数的影响越大,这可为工矿企业的安全生产提供一定的理论依据。     

(CH3CH[NH3]CH2NH3)1/2·ZnPO4, a zincophosphate analogue of aluminosilicate zeolite thomsonite

The synthesis and structure of (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, an organically templated zincophosphate (ZnPO) analogue of aluminosilicate zeolite thomsonite (THO), are described. The ZnPO framework is built up from an alternating, vertex-sharing, network of ZnO₄ and PO₄ groups (d_av(Zn–O)=1.944 (8) Å, d_av(P–O)=1.535 (9) Å, θ_av(Zn–O–P)=130.5°) involving distinctive 4=1 secondary building units. The 1,2-diammonium propane cations are highly disordered in the [0 0 1] 8-ring channels. Crystal data: (CH₃CH[NH₃]CH₂NH₃)_1/2·ZnPO₄, M_r=198.42, orthorhombic, space group Pncn (no. 52), a=14.119 (6) Å, b=14.136 (5) Å, c=12.985 (5) Å, V=2591 (3) ų, Z=10, R(F)=0.057, R_w(F)=0.061 (for a twinned crystal).     

吡啶基离子液体+有机盐双水相体系相图的测定及盐析性能研究

测定了离子液体N-乙基吡啶四氟硼酸盐([EPy]BF₄)+有机盐[丁二酸钠（CH₂COONa)₂/柠檬酸铵C₆H₅O₇(NH₄)₃/柠檬酸钠C₆H₅O₇Na₃] +水双水相体系在303.15、308.15和313.15 K下的双节线及系线数据。基于相图中的杠杆定律通过质量法研究双水相体系的系线,并用Othmer-Tobias方程、Bancroft方程等经验方程以及NRTL活度系数模型对数据进行关联。采用有效排除体积和Setschenow-type的拟合参数深入研究三种有机盐的盐析能力。结果表明,双节线的三个经验式拟合效果良好,但较多参数的经验式会导致部分参数失去意义;双水相体系的系线满足经验方程,数据可靠性较好,且均方根偏差表明系线数据很好地符合NRTL模型;低温更有利于该双水相体系的形成;三种盐都能和[EPy]BF₄离子液体形成双水相体系,且C₆H₅O₇Na₃的盐析能力更优。本文提供的数据为离子液体的回收循环利用提供了理论参考依据。     

[(C2H5)3NH]Cl/ZnCl2离子液体催化合成维生素E

维生素E合成过程中催化剂用量大、损失严重且不能循环使用, 后处理过程产生大量废液导致严重的环境问题。实验合成了几种Lewis酸性离子液体, 并应用于维生素E合成。研究发现, [(C₂H₅)₃NH]Cl/ZnCl₂离子液体催化合成维生素E效果最好, 该离子液体中无机阴离子起主要催化作用, 季铵阳离子易与异植物醇的羟基形成氢键, 能使异植物醇与主环发生定向缩合反应。采用FT-IR研究了[(C₂H₅)₃NH]Cl/ZnCl₂离子液体结构和酸性, 并系统考察了其对维生素E合成的影响。随着ZnCl₂摩尔分数增加, 离子液体的Lewis酸性增强。在ZnCl₂摩尔分数为0.66的[(C₂H₅)₃NH]Cl/ZnCl₂离子液体催化作用下, 维生素E的产率可达到87.4%, 该离子液体重复使用5次, 催化性能没有明显下降。     

Zeolite synthesis in the presence of flexible diquaternary alkylammonium ions (C2H5)3N(CH2)nN(C2H5)3 with n=3–10 as structure-directing agents

The use of flexible diquaternary alkylammonium ions (C₂H₅)₃N⁺(CH₂)_nN⁺(C₂H₅)₃ (Et₆-diquat-n with n=3–10) as structure-directing agents for zeolite synthesis in the presence of alkali metal cation is described. Among the organic structure-directing agents studied here, a considerable diversity in the phase selectivity was observed only for the Et₆-diquat-5 ion: this cation can produce five different zeolite structures (i.e., P1, SSZ-16, SUZ-4, ZSM-57, and mordenite), depending on the oxide composition of synthesis mixtures. Analysis of the variable-temperature ¹H CRAMPS NMR spectra obtained from the Et₆-diquat-5 molecules in these five zeolites reveals that the host–guest interactions occurring within the respective materials maintain in a manner different from one another even at 160 °C at which the zeolite hosts crystallize.     

Boosting selective C2H2/CH4, C2H4/CH4 and CO2/CH4 adsorption performance via 1,2,3-triazole functionalized triazine-based porous organic polymers

Nitrogen-rich porous organic polymers have shown great potentials in gas adsorption/separation, photocatalysis, electrochemistry, sensing and so on. Herein, 1,2,3-triazole functionalized triazine-based porous organic polymers (TT-POPs) have been synthesized by the copper-catalyzed azide-alkyne cycloaddition (Cu-AAC) polymerization reactions of 1,3,5-tris(4-azidophenyl)-triazine with 1,4-diacetylene benzene and 1,3,5-triacetylenebenzene, respectively. The characterizations of N₂ adsorption at 77 K show TT-POPs possess permanent porosity with BET surface areas of 666 m²·g^-1 (TT-POP-1) and 406 m²·g^-1 (TT-POP-2). The adsorption capacities of TT-POPs for CO₂, CH₄, C₂H₂ and C₂H₄, as well as the selective separation abilities of CO₂/N₂, CO₂/CH₄, C₂H₂/CH₄ and C₂H₄/CH₄ were evaluated. The gas selective separation ratio of TT-POPs was calculated by the ideal adsorbed solution theory (IAST) method, wherein the selective separation ratios of C₂H₂/CH₄ and C₂H₄/CH₄ of TT-POP-2 was 48.4 and 13.6 (298 K, 0.1 MPa), which is comparable to other adsorbents (5.6-120.6 for C₂H₂/CH₄, 10-26 for C₂H₄/CH₄). This work shows that the 1,2,3-triazole functionalized triazine-based porous organic polymer has a good application prospect in natural gas purification.     

高弹性自愈水凝胶(C3H5O)1CB[7]/PAA的制备及性能

用丙烯氧基七元瓜环（（C₃H₅O）₁CB[7]）替代传统的交联剂N,N-亚甲基双丙烯酰胺（BIS）制备了新型丙烯氧基七元瓜环/聚丙烯酸凝胶（（C₃H₅O）₁CB[7]/PAA gel）,该凝胶具有高弹性和自愈性。采用IR和¹H NMR技术对其结构进行表征,研究了该水凝胶的溶胀、力学性能,宏观观察了其自愈性能。结果表明：（C₃H₅O）₁CB[7]/PAA gel的网络形成作用力主要是多重氢键;在丙烯酸（AA）17.2%,水82.1%,（C₃H₅O）₁CB[7]0.33%,过硫酸钾（KPS）0.33%时该水凝胶具有良好的自愈性及力学性能,其最大伸长量为105.6 cm,为原长的86倍,弹性模量0.39 kPa,平衡溶胀率是600%。该水凝胶有望成为一种潜在的生物组织工程材料。     

[C16H33N(CH3)3]3[PO4(WO3)4]催化脂肪酸甲酯环氧化性能

在无酸、无溶剂条件下,以[C₁₆H₃₃N(CH₃)₃]₃[PO₄(WO₃)₄]为反应控制相转移催化剂,研究各因素对脂肪酸甲酯(FAME)环氧化反应的影响。结果表明,水相pH对环氧化反应的影响最大,反应适宜pH为4;适宜反应条件为过氧化氢与脂肪酸甲酯中双键摩尔比为1.05:1,反应温度50～60℃,反应时间5 h。在此反应条件下催化剂循环5次不失活,产品环氧值大于4.0%,碘值小于5 g I·(100 g)^-1。并通过元素分析与红外光谱,研究了催化剂在反应过程中的变化,认为磷钨杂多阴离子的分解是导致催化剂失活的关键原因。     

Dielectric dispersion in [N(C2H5)4]2ZnCl4 single crystal

Temperature dependence of the complex dielectric permittivity of [N(C₂H₅)₄]₂ZnCl₄ crystal was measured in the frequency range 300 Hz / MHz. Jump-wise changes in the real and imaginary components of ε* were observed for the three crystallographic directions at the phase transition temperature. The dielectric dispersion clearly apparent in the high-temperature phase, rapidly disappears at the phase transition. The anomalous changes in the dielectric permittivity are related to vibrations of the tetraethylammonium ion. The activation energy of these vibrations amounts to 40 kJ/mol.     

温度对MOF-74(Ni)吸附分离丙烯丙烷机理和选择性的影响

采用水热法成功制备了MOF-74(Ni),使用PXRD、孔径分析对材料进行了表征,测定了材料在不同温度下的C₃H₆和C₃H₈吸附等温线,应用程序升温脱附技术估算了脱附活化能,并使用IAST理论预测了材料对C₃H₆/C₃H₈二元体系的吸附选择性。讨论了温度对吸附机理和吸附选择性的影响。结果显示,MOF-74(Ni)的BET比表面积高达1306 m²·g^-1。在298 K下,C₃H₆的吸附量高达7.4 mmol·g^-1。随着温度升高,C₃H₈的吸附量大幅降低,而C₃H₆的吸附量下降程度较小,导致材料对C₃H₆/C₃H₈吸附选择性升高。当温度为328K时,MOF-74(Ni)对C₃H₆/C₃H₈二元气体混合物的吸附选择接近12。程序升温脱附的实验结果显示,C₃H₆在MOF-74(Ni)上的脱附活化能大于C₃H₈,分别为68.92 kJ·mol^-1和50.80 kJ·mol^-1。C₃H₆是通过与MOF-74(Ni)的不饱和金属位点Ni²⁺以p络合作用方式吸附,作用力较强,而C₃H₈与Ni²⁺之间的作用力较弱。根据吸附机理不同的特点,适当提高温度,将有助于提高MOF-74(Ni)吸附分离C₃H₆/C₃H₈混合物体系的吸附选择性。     

Surface Acidity of Aluminum Phosphate and Its Catalytic Performance in Benzene Alkylation with Long Chain Olefin

The acidic properties of aluminum phosphate (AlPO₄-5) solid acid catalyst were characterized by temperature programmed desorption (TPD) of ammonia (NH₃), n-propylamine (n-C₃H₇NH₂), iso-propylamine [(CH₃)₂CHNH₂] and n-dipropylamine [(C₃H₇)₂NH] separately, and its catalytic performance in benzene alkylation with long chain olefin was studied in a fixed-bed reactor. The characterized acid amount of catalyst increased with the basicity of adsorbates. With increase of the activation temperature of catalyst, the acid amount characterized by NH₃-TPD decreased, however, it increased when characterized by TPD using three other adsorbates. The desorption kinetics of TPD process and the deactivation kinetics of catalyst were investigated. The acidity and catalytic performance of catalyst was also correlated. The results showed that the acid amount and strength are well correlated with the activity and stability using NH₃ as adsorbate, respectively, which indicated NH₃ was a better basic adsorbate. It was also found that the catalyst with higher acid amount and lower acid strength on the surface exhibited the better catalytic performance and stability.     

Water-soluble niobium peroxo complexes as precursors for the preparation of Nb-based oxide catalysts

In the frame of research aimed at developing new synthetic procedures of multimetallic Nb-based catalysts, peroxo complexes of niobium(V) of general formula A^I₃[Nb(O₂)₄] and A^I₃[Nb(O₂)_x(H_yL)]·nH₂O (A^I: NH₄⁺, CN₃H₆⁺ (gu); L: oxalate, tartrate, citrate) have been prepared and characterized on the basis of elemental and thermal analysis, FTIR and ¹³C-NMR spectra. The crystal structure of (gu)₃[Nb(O₂)₄] and (gu)₃[Nb(O₂)₂(C₂O₄)₂]·2H₂O have been determined. The application of the obtained Nb complexes as precursors for the preparation of silica-supported Nb–Mo–O catalysts has been demonstrated. Combining Nb peroxo-carboxylato compounds with analogous Mo(VI) compounds in a silica-impregnation method carried out in aqueous medium leads to the formation of the supported Nb₂Mo₃O₁₄ phase.     

Polymerization of methyl methacrylate catalyzed by mono-/bis-salicylaldiminato nickel(II) complexes and methylaluminoxane

Two types of salicylaldiminato-based nickel complexes, mono-ligated Ni(II) complexes ([O-C₆H₄-o- C(H)=N-Ar]Ni(PPh₃)(Ph) (5), [O-(3,5-Br₂)C₆H₂-o-C(H)=N-Ar]Ni(PPh₃)(Ph) (6), [O-(3-t-Bu)C₆H₃-o-C(H)=N-Ar]Ni(PPh₃)(Ph) (7)) and bis-ligated Ni(II) complexes ([O-(3,5-Br₂)C₆H₂-o-C(H)=N-Ar]₂Ni (8), [O-(3,5-Br₂)C₆H₂-o-C(H)=N-2-C₆H₄(PhO)]₂Ni (9), Ar=2,6-C₆H₃(i-Pr)₂) were synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), mass spectrography (MS) and elemental analysis (EA). In the presence of methylaluminoxane (MAO) as cocatalyst, all the nickel complexes exhibited high activities for the polymerization of methyl methacrylate (MMA) and syndiotactic-rich poly(methyl methacrylate) (PMMA) was obtained. The complexes with less bulky substituents on salicylaldiminato framework possessed higher activities, while with the same salicylaldiminato, the mono-ligated nickel complexes showed higher catalytic activity than bis-ligated ones.     

Raman spectra of (NH4)4H2(SeO4)3 superionic single crystal

Raman spectra of (NH₄)₄H₂(SeO₄)₃ protonic conductor were studied at room temperature using a 1064 nm - excited Fourier transform (FT) - Raman spectroscopy. A tentative assignment of the external and internal vibrations is proposed.