离子液体C3MIBF4和C5MIBF4溶解焓的研究

在298.15 K下利用等温环境溶解反应热量计测定了离子液体C₃MIBF₄(四氟硼酸1-甲基-3-丙基咪唑)和C₅MIBF₄(四氟硼酸1-甲基-3-戊基咪唑)不同浓度水溶液的摩尔溶解焓(Δ_sH_m). 借助Pitzer电解质溶液理论, 得到了它们的标准摩尔溶解焓 和Pitzer焓参数: 和 , 并计算了表观相对摩尔焓. 根据Glasser理论计算了离子液体晶格能, 进而估算了离子液体C₅MIBF₄和C₃MIBF₄中正离子的水化焓分别为－171 kJ•mol^－1 (C₅MI^＋)和－207 kJ•mol^－1 (C₃MI^＋).     

二甲基亚砜-水混合溶液的等效介电常数特异性研究

在2.45 GHz下利用微扰谐振腔法测量二甲基亚砜(DMSO)-水(H₂O)混合溶液的等效介电常数过程中, 发现混合溶液等效介电常数虚部大于其中任一组分的介电常数虚部的特异现象. 分析表明, 这种特异性现象的发生主要是由于DMSO与H₂O混合后溶液的高频摩擦项大于混合前引起的. 因此, 经典混合物介电常数公式需要进行适当修正才能较好地适用于这类特异性问题计算.     

固溶体结构对Ca_(2-x)Sr_xZn_4Ti_(15)O_(36)∶Pr~(3+)发光性质的影响

0引言在绿色和蓝色长余辉发光材料达到应用程度之后,耐候性红色长余辉发光材料成为人们研究的重点。Eu3 、Sm3 激活的硫氧化物[1￣3]、Eu2 铝锶复合硫氧化物[4]和Y2O3∶Eu3 [5]等耐热耐水性红色长余辉材料被相继发现。Pr3 离子掺杂的碱土金属钛酸盐(M TiO3∶Pr,M=M g,Ca,Sr,Ba)是一种新型的红色长余辉发光材料。这种发光材料在615nm附近有很好的单色性红光发射。碱土金属钛酸盐基质化学性能稳定,已开始应用于场发射显示器(FE D)[6,7]。碱土金属钛酸盐是A BO3型化合物,具有钙钛矿结构。B all[8]曾通过在CaTiO3中掺入不同量的Sr2 …     

Synthesis and Crystal Structure of 1,2-Bis-（p-nitrophenylsulfonamido）-4,5-dinitrobenzene

The title compound, 1,2-bis-(p-nitro-phenylsulfonamido)-4,5-dinitrobenzene, was synthesized and characterized by elemental analysis, IR and 1H NMR. A pale yellow prism crystal of C23H26N8O13S2 (Mr = 686.64) was obtained in DMF solution and determined by single-crystal X-ray diffraction method. It crystallizes in triclinic system, space group P1 with a = 10.346(4), b = 12.210(5), c = 12.976(5) , α = 108.220(8), β = 99.482(4), γ = 95.490(4)°, V = 1516.7(10) 3, Z = 2, Dc = 1.504 g/cm3, F(000) = 712, μ = 0.254, Mr = 686.64, the final R = 0.0561 and wR = 0.1487. One sulfonamido group of the title compound is deprotoned and forms N(3)=C(13). The crystal involves N,N-dimethylamine from the decomposition of DMF and the proton is transferred to N,N- dimethylamine. It is a strong proof for the characterization of deprotoned recognition compound by X-ray single-crystal structure.     

Growth and Spectral Properties of Yb^3＋-doped Ba3Gd（BO3）3 Crystal

Crystal of Yb3+-doped Ba3Gd(BO3)3 has been grown by the Czochralski method. The spectroscopic characterizations have been investigated at room temperature. The Yb3+:Ba3Gd(BO3)3 crystal exhibits broad absorption at 976nm with FWHM of 7nm and large overall spitting of 2F7/2 manifold (823cm-1). The absorption and emission cross sections are 5.09×10-21cm2 at 976nm and 0.97×10-21cm2 at 1040nm,respectively. The fluorescence lifetime is 2.84 ms.     

Ag/C包覆对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响

运用共沉淀和元素化学沉积相结合的方法,制备出了具有Ag/C 包覆层的层状富锂固溶体材料Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂. 通过X 射线衍射（XRD）、场发射扫描电子显微镜（SEM）、透射电子显微镜（TEM）、恒流充放电、循环伏安（CV）,电化学阻抗谱（EIS）和X 射线能量散射谱（EDS）方法,研究了Ag/C 包覆层对Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂电化学性能的影响. 结果表明,Ag/C 包覆层的厚度约为25 nm,Ag/C 包覆在保持了固溶体材料α-NaFeO₂ 六方层状晶体结构的前提下,显著地改善了Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ 的电化学性能. 在2.0-4.8 V（vs Li/Li⁺）的电压范围内,首次放电（0.05C）容量由242.6 mAh·g^-1提高到272.4 mAh·g^-1,库仑效率由67.6%升高到77.4%;在0.2C倍率下,30 次循环后,Ag/C 包覆的电极材料容量为222.6 mAh·g^-1,比未包覆电极材料的容量高出14.45%;包覆后的电极材料在1C下的容量仍为0.05C下的81.3%. 循环伏安及电化学交流阻抗谱研究表明,Ag/C包覆层抑制了材料在充放电过程中氧的损失,有效降低了Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂颗粒的界面膜电阻与电化学反应电阻.     

Study of intermolecular interactions in aqueous solutions by millimeter spectroscopy

The absorption of millimeter electromagnetic radiation (v=1.4, 1.71, and 5 cm⁻¹) by aqueous solutions of glycine (pH 6.1–6.2) in the concentration range of 0.5–2.5 mol L⁻¹ was measured. It was found that the absorbing ability of the water present in the solutions, is higher than that of pure water. This phenomenon is explained by the presence of a center of negative hydration in the structure of the glycine zwitterion, which results in an increase in the rotational mobility of water molecules immobilized in the hydrate shell of the glycine zwitterion. For Part 5, see Ref. 1. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1305–1307, July, 1997.     

Solvent effects on hydrogen bond formation

Enthalpies of solution have been used to calculate transfer enthalpies for phenol, pyridine, and DMSO between the solvent cyclohexane and the solvents CCl₄, benzene, and CHCl₃. By use of model compounds, enthalpies due to interactions with phenol, pyridine, and DMSO have been determined. These enthalpies are used to calculate the effect of solvation relative to cyclohexane on hydrogen bonded complexes in CCl₄ and benzene solvents. Correlations with enthalpies due to interactions and frequency shifts for the hydroxyl stretch in these solvents have also been made.     

XRD and Si MAS-NMR spectroscopy across the β-Lu2Si2O7-β-Y2Si2O7 solid solution

Samples in the system Lu_2−xY_xSi₂O₇ (0?x?2) have been synthesized following the sol-gel method and calcined to 1300 °C, a temperature at which the β-polymorph is known to be the stable phase for the end-members Lu₂Si₂O₇ and Y₂Si₂O₇. The XRD patterns of all the compositions studied are compatible with the structure of the β-polymorph. Unit cell parameters are calculated as a function of composition from XRD patterns. They show a linear change with increasing Y content, which indicates a solid solubility of β-Y₂Si₂O₇ in β-Lu₂Si₂O₇ at 1300 °C. ²⁹Si MAS NMR spectra of the different members of the system agree with the XRD results, showing a linear decrease of the ²⁹Si chemical shift with increasing Y content. Finally, a correlation reported in the literature to predict ²⁹Si chemical shifts in silicates is applied here to obtain the theoretical variation in ²⁹Si chemical shift values in the system Lu₂Si₂O₇-Y₂Si₂O₇ and the results compare favorably with the values obtained experimentally.     

Pt/CexZr1-xO2 催化剂在含硫合成气中催化水煤气变换反应活性

 采用浸渍法制备了 Pt/Ce_xZr_1-xO₂ 催化剂, 通过 X 射线衍射和程序升温还原等方法对催化剂进行了表征, 并在固定床反应器中评价了催化剂在合成气和含硫合成气中的水煤气变换活性. 结果表明, 铈锆固溶体的氧化还原能力强于 CeO₂, Zr 的掺杂明显改善了 CeO₂ 的孔道结构, 其担载的 Pt 催化剂具有更高的金属分散度, 因而活性更高. 两种催化剂在含硫合成气中的催化活性较无硫合成气中的均有所降低, 且 H₂S 浓度越大, 催化剂活性下降越多, 但这种因吸附硫而引起的失活是可逆的, 即催化剂重新暴露在无 H₂S 重整气的还原性气氛下活性能基本恢复.