Ionic liquid salt bridge based on tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide for stable liquid junction potentials in highly diluted aqueous electrolyte solutions

A moderately hydrophobic ionic liquid, tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide ([TBMOEP⁺][C₂C₂N⁻]), shows a very stable liquid junction potential upon contact with an aqueous solution whose ionic strength is as low as 1 μmol dm⁻³. The stability with the maximum excursion of the potential within ±0.5 mV for 30 min is very promising for accurate determination of pH and other single ion activities potentiometrically.     

Influence of accelerated ageing on the physico-mechanical properties of alkali-treated industrial hemp fibre reinforced poly(lactic acid) (PLA) composites

30 wt% aligned untreated long hemp fibre/PLA (AUL) and aligned alkali treated long hemp fibre/PLA (AAL) composites were produced by film stacking and subjected to accelerated ageing. Accelerated ageing was carried out using UV irradiation and water spray at 50 °C for four different time intervals (250, 500, 750 and 1000 h). After accelerated ageing, tensile strength (TS), flexural strength, Young's modulus (YM), flexural modulus and mode I fracture toughness (K_Ic) were found to decrease and impact strength (IS) was found to increase for both AUL and AAL composites. AUL composites had greatest overall reduction in mechanical properties than that for AAL composites upon exposure to accelerated ageing environment. FTIR analysis and crystallinity contents of the accelerated aged composites support the results of the deterioration of mechanical properties upon exposure to accelerated ageing environment.     

金属有机化合物中金属-配体键能的研究进展

介绍了金属有机物质热力学研究的进展,概述了过渡金属-配体键能的基本概念、估测方式、实验和理论研究方法.收集了已测得的第三副族到第八族所有中性金属有机络合物金属-配体σ-单键绝对键焓的实验值.对第三副族及锕系元素,收集了钪-氢、钪-碳、钍-氢、钍-碳、钍-氮、钍-氧、钍-硫、钍-氯、铀-氢、铀-碳、铀-硅、铀-氧、铀-氯、铀-溴、铀-碘、钐-氢、钐-碳、钐-硅、钐-氮、钐-磷、钐-氧、钐-硫、钐-氯、钐-溴和钐-碘键的键焓.对第四副族元素,收集了钛-碳、锆-氢、锆-碳、锆-硅、锆-氮、锆-氧、锆-氯、锆-碘、铪-氢、铪-碳键的键焓.对第五副族元素,收集了钒-氢、钽-碳键的键焓.对第六副族元素,收集了铬-氢、铬-碳、铬-硅、铬-氮、铬-氙、钼-氢、钼-碳、钼-硅、钼-氮、钼-磷、钼-氯、钼-溴、钼-碘、钼-氙、钨-氢、钨-碳、钨-硅、钨-氮、钨-氩、钨-氪、钨-氙键的键焓.对第七副族元素,收集了锰-氢、锰-碳、锰-硅、锰-氧、锰-硫、锰-氯、锰-溴、锰-碘、锝-氯、锝-溴、锝-碘、铼-氢、铼-碳、铼-氯、铼-溴、铼-碘键的键焓.对第八族元素,收集了铁-氢、铁-碳、铁-氮、铁-氩、铁-氪、铁-氙、钌-氢、钌-碳、钌-磷、锇-氢、锇-碳、钴-氢、钴-碳、铑-氢、铑-碳、铱-氢、铱-碳、铱-氯、铱-溴、铱-碘、镍-碳、镍-硫、钯-碳、铂-氢、铂-碳键的键焓.但未包括平均键焓值.此外,还收集了铁-氢、铁-碳、铁-氮、铁-磷、铁-羰基、铁-亚硝基、铁-氧分子、铁-硼、铁-铝、铁-镓、铁-铟、铁-铊键的理论计算值以及金属有机片断和离子的键焓.     

聚醚环酰胺固体推进剂用键合剂的合成及使用性能

以丙三醇、环氧乙烷、环氧丙烷、氯化亚砜、异氰脲酸等为原料,合成了聚醚环酰胺键合剂。将其应用到推进剂(GAP/HMX/Al/AP)配方中,对成型后的推进剂进行力学性能测试和断面电子显微镜分析。结果表明,此类键合剂可以改善与推进剂中氧化剂的界面粘结性能,有效地提高成型后的推进剂在不同温度下的最大延伸率,但对抗拉伸强度的提高作用不明显。     

高体分SiC_p/Al复合材料螺纹性能的测试

从SiCp/Al复合材料性能分析着手,讨论了预置件法、焊接法和粘接法等在空间遥感器研制中常用的联接方法的优缺点,提出了在高体积分数(体分)SiCp/Al复合材料上直接加工螺纹,并加装钢丝螺套的方法来改善螺纹联接性能。对在某高体分SiCp/Al复合材料上加工的M4、M5螺纹进行了拉伸测试,结果表明:加装钢丝螺套前,复合材料螺纹有被拉脱现象;加装钢丝螺套后,M4螺纹、螺杆在3 000～4 000 N被拉断;M5螺纹、螺杆在8 000～9 000 N被拉断,测试后两种规格的螺纹状态良好,可以满足实际应用对该材料拉伸强度的要求,其已应用于工程项目中。     

Investigation of crystallographic sites of Eu in La2BaZnO5 by site-selective laser-excitation spectroscopy

La₂BaZnO₅:Eu³⁺ (0.05 mol%) was prepared by a solid-state reaction at high temperature. X-ray powder diffraction analysis confirmed the formation of single phase La₂BaZnO₅. Luminescence properties of La₂BaZnO₅:Eu³⁺ are investigated by site-selective laser-excitation and emission spectroscopy at 18 K. Two different crystallographic sites for Eu³⁺ corresponding to the La³⁺ and Ba²⁺ sites are identified from the ⁷F₀→⁵D₀ excitation spectra obtained by monitoring the ⁵D₀→⁷F_J (J=1, 2, …, 6) emissions. It is found that Eu³⁺ substituted for the Ba²⁺ ion experiences stronger crystal-field strength than Eu³⁺ substituted for the La³⁺ ion. Energy transfer between the two crystallographic Eu³⁺ centers is investigated by luminescence decay curves at 18 K.     

Optical properties in a two-dimensional quantum ring: Confinement potential and Aharonov-Bohm effect

Optical properties of a two-dimensional quantum ring with pseudopotential in the presence of an external magnetic field and magnetic flux have been theoretically investigated. Our results show that both of the pseudopotential and magnetic field can affect the third non-linear susceptibility and oscillator strength. In addition, we found that the oscillator strength and the absolute value of the resonant peak of the linear, non-linear and total absorption coefficient demonstrates the Aharonov-Bohm oscillation with magnetic flux, moreover, changes in confinement potential can influence the Aharonov-Bohm oscillation in peak while the resonant peak value of the linear, non-linear and total refractive index changes decreases as magnetic flux increases.     

高体分SiC_p/Al复合材料螺纹性能的测试

从SiCp/Al复合材料性能分析着手,讨论了预置件法、焊接法和粘接法等在空间遥感器研制中常用的联接方法的优缺点,提出了在高体积分数（体分）SiCp/Al复合材料上直接加工螺纹,并加装钢丝螺套的方法来改善螺纹联接性能。对在某高体分SiCp/Al复合材料上加工的M4、M5螺纹进行了拉伸测试,结果表明：加装钢丝螺套前,复合材料螺纹有被拉脱现象;加装钢丝螺套后,M4螺纹、螺杆在3 000～4 000 N被拉断;M5螺纹、螺杆在8 000～9 000 N被拉断,测试后两种规格的螺纹状态良好,可以满足实际应用对该材料拉伸强度的要求,其已应用于工程项目中。     

囚禁弱相互作用玻色气体的势场优化准则

根据Thomas-Fermi近似,在基于最小动量态上玻色-爱因斯坦凝聚的前提下,研究了囚禁弱相互作用玻色气体势场的最优化问题.导出了指数吸引势阱中有效势场和粒子数极限判据,粒子数给定时,可由此判据求出所需势场强度;势场强度给定时,可由此判据求出粒子数极限.根据吸引相互作用系统的稳定性以及求出的排斥相互作用的最大粒子数极限,结合有效势场判据,分别给出了囚禁吸引和排斥相互作用玻色气体时,势场强度的最佳取值范围. 关键词： 玻色-爱因斯坦凝聚 弱相互作用 粒子数极限 势场强度