Effect of buffer layer on thermochromic performances of VO2 films fabricated by magnetron sputtering

As a well-developed industrial fabricating method, magnetron sputtering technique has its distinct advantages for the large-scale production. In order to investigate the effect of buffer layer on the formation and thermochromic performances of VO₂ films, using RF magnetron sputtering method, we fabricated three kinds of buffer layers SiO₂, TiO₂ and SnO₂ on soda lime float-glass. Then according to the reactive DC magnetron sputtering method, VO₂ films were deposited. Due to the restriction of heat treatment temperature when using soda lime float-glass as substrates, dense rutile phase TiO₂ cannot be formed, leading to the formation of vanadium oxide compounds containing Na ions. When using SnO₂ as buffer layer, we found that relatively high pure VO₂ can be deposited more easily. In addition, compared with the effect of SiO₂ buffer layer, we observed an enhanced visible transparency, a decreased infrared emissivity, which should be mainly originated from the modified morphology and/or the hetero-structured VO₂/SnO₂ interface.     

Vibrational computations beyond the harmonic approximation: performances of the B3LYP density functional for semirigid molecules

The performances of the B3LYP density functional in the computation of harmonic and anharmonic frequencies were tested using 14 standard basis sets of double and triple zeta quality for a set of semirigid molecules containing from 4 to 12 atoms. The quality of the results is assessed by comparison with the most reliable computations available in the literature. The study reveals that the relatively cheap 6-31+G(d,p) basis set performs a very good job for harmonic frequency calculations and that B3LYP anharmonicities are in close agreement with the reference values irrespective of the basis set used. On these grounds "hybrid force fields" are proposed to achieve the best compromise between computer time and quality of the results.     

纳米Co-Sn金属间化合物的合成、表征及电化学吸放锂行为

用溶剂热法合成了三种纳米尺寸的Co-Sn金属间化合物, 即CoSn2、CoSn和Co3Sn2, 并研究了它们作为锂离子二次电池新型负极材料的电化学性能. 合成的粉末经过了X射线衍射(XRD), 透射电镜(TEM)和场发射扫描电镜(FESEM)的表征. 研究发现, 这三种金属间化合物均显示出较高的充放电稳定性. 由于低的锂离子扩散速率, 在嵌锂过程中锂离子不能深入到晶粒内部, 导致它们的电化学活性较低, 尤其是Co3Sn2, 其首次充电容量仅为 93 mAh•g−1.     

Searching for high performance asymmetrically substituted teterazine energetic materials based on 3-hydrazino-6-(1H-1,2,3,4-tetrazol-5-ylimino)-s-tetrazine

Tetrazine compounds are promising candidates of high performance energetic materials (EMs). For the purpose of exploring high performance asymmetrically substituted teterazine explosives, 3-hydrazino-6-(1H-1,2,3,4-tetrazol-5-ylimino)-s-tetrazine was selected as the precursor and a series of teterazine EMs were prepared based on three synthetic strategies. All the obtained compounds were fully characterized and the crystal structures of seven compounds were further confirmed by single crystal X-ray diffraction. The thermal dynamics and thermal safety parameters, the detonation properties and impact sensitivities were also obtained. The results revealed that compounds 15–17 show excellent energetic properties (detonation velocities > 9000 m·s^?1, detonation pressures > 30 GPa) and have impact sensitivities (8–12 J) that comparable or lower than RDX. Compounds 9–13 are insensitive to impact and have detonation velocities range from 8452 to 8775 m·s^?1. These compounds can be good candidates of high performance secondary explosives or insensitive EMs.     

Effect of carbon black on the mechanical performances of magnetorheological elastomers

Several magnetorheological elastomer (MRE) samples, with different weight percentages of carbon black, were fabricated under a constant magnetic field. Their microstructures were observed by using an environmental scanning electron microscope (SEM), and their mechanical performance including magnetorheological (MR) effect, damping ratio and tensile strength were measured with a dynamic mechanical analyzer (DMA) system and an electronic tensile machine. The experimental results demonstrate that carbon black plays a significant role in improving the mechanical performance of MR elastomers. Besides the merits of high MR effect and good tensile strength, the damping ratio of such materials is much reduced. This is expected to solve a big problem in the application of MR elastomers in practical devices, such as in adaptive tuned vibration absorbers.     

Analytical optimization of some parameters of a Laser-Induced Breakdown Spectroscopy experiment

Laser-Induced Breakdown Spectroscopy (LIBS) experiments are performed on standard metallic samples, in air at atmospheric pressure, using a Nd:YAG laser at 1064 nm and a fiber located close to the plasma to collect its emission. This configuration is chosen because it is representative of many LIBS setups. The influence of several experimental parameters is studied in order to optimize the analytical performances: signal-to-background ratio (SBR), line intensity and repeatability. Temporal parameters of the detector are adjusted for each measurement to maximize the SBR. The signal is found to linearly depend on the pulse energy over our range of investigation. This behavior is related to the increase of the number of vaporized atoms when the pulse energy increases. Complementary measurements of plasma dimensions support our conclusions. We show the existence of an optimum fluence on the sample that gives the highest signal and the lowest relative standard deviation (RSD), and which does not depend on the pulse energy. Finally we demonstrate that ablation is much more efficient using a laser beam with a high numerical aperture, other experimental parameters being unchanged, because of a less pronounced laser shielding by the plasma. Analytical consequences of this result are discussed.     

水热法合成球花状二硫化钼及其电化学性能

采用二水钼酸钠(Na_2MoO_4·2H_2O)和硫脲(CS(NH_2)_2)分别作为钼源和硫源,通过水热合成法获得球花状二硫化钼,其较佳的水热条件为:180℃下反应48 h,钼硫原子比为1∶4,反应物浓度为0.001 mol·L-1,在100 m L反应釜中的填充体积为90 m L。采用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)、对样品的物相和形貌进行了表征,并利用低温氮吸附BET模型测试了样品的比表面积。结果表明,合成的二硫化钼结晶性良好,平均粒径约为1μm,比表面积约为87 m2·g-1,分布均匀且无明显团聚。通过循环伏安(CV)曲线、恒电流充放电曲线(GCD)、阻抗谱图(EIS)表征其电化学性能,测试表明:在3 mol·L-1 KOH水相电解液中,单电极比电容可达130.6 F·g-1(扫速为5 m V·s-1)和110.9 F·g-1(电流密度为0.1 A·g-1),界面转移电阻Rct为0.33Ω;循环1 000圈后比电容损失为14.7%。说明采用该水热法合成的二硫化钼可以成为超级电容器电极的理想材料。     

Nd3+掺杂Lu2O3透明陶瓷的制备和光学性能

通过化学途径合成了Nd3+掺杂的氧化镥纳米晶粉体,研究了工艺条件对粉体性能及透明陶瓷光学性能的影响,通过优化工艺参数,获得了品粒均匀、尺寸在30 nm的高质量的Nd:Lu2O3纳米晶粉体.采用复合溶液法合成的粉体,经等静压成型、流动H2气氛及1880℃/ 8 h烧结后制备出光学透明性好的Nd:Lu2O3透明陶瓷,其在1080nm波长处的实测折射率为1.908,直线透过率超过75;,发射截面(σem)达到6.5×10-20cm2.     

阻燃剂对镍钴锰三元材料体系电化学性能的影响

测试了不同浓度的电解液阻燃添加剂对镍钴锰三元材料（LiNi_0.4Co_0.2Mn_0.4O₂）作为正极的锂离子电池电化学性能的影响. 实验结果表明,当阻燃剂浓度增加时,电池的放电容量下降,电化学反应电阻和锂离子扩散阻力都有所增加,但加入阻燃添加剂的锂离子电池,当充放电的电流相对比较小的时候,循环性能相比于不含阻燃剂的有所提高,循环稳定性得到了改善. 在0.5C倍率电流下,不含阻燃剂时容量保持率为89%,而当阻燃剂含量增至10%后保持率达到94.21%. 当充放电电流为1C时,未使用阻燃剂时容量保持率约为92.22%,当阻燃剂的浓度为10%时容量保持率为93.01%. 在2C倍率下,不含阻燃剂时容量保持率为87.92%. 阻燃剂浓度为10%时,容量保持率有所提升,达到92.16%. 与基础电解液相比,选用含有10%阻燃剂的电解液可使容量保持率提高5%左右,相比于其他浓度,包含10%阻燃剂的电池循环性能也最为稳定.     

Li1+xMn2O4的溶胶-凝胶法合成及其电化学性能

锂离子电池;锂锰氧化物;尖晶石结构;Li1+xMn2O4的溶胶-凝胶法合成及其电化学性能