Thermolysis of the polyyne C8H2 in hexane and methanol: Experimental and theoretical study

The mean lifetimes of polyyne C₈H₂ in hexane were determined at 50, 60, 80, and 100 °C and in methanol at 60 °C. The reactions are second order at all temperatures: ln k₂ = 20.5 ± 1.5-10303 ± 520T⁻¹ and the corresponding activation energy is 85.7 ± 6.3 kJ mol⁻¹ (7164 cm⁻¹). Extrapolation suggests that solutions at 1 mM concentration are significantly unstable at room temperature. Quantum chemical calculations show that polyynes C_mH₂ + C_nH₂ (m + n = 16) could be products, but these were not detected. Alternatively, C₁₆H₂ isomers could form. IR spectra of the solid residues from hexane and methanol solutions were obtained.     

Application of pulse discharge sintering (PDS) technique to rapid synthesis of Ti3SiC2 from Ti/Si/C powders

To synthesize Ti₃SiC₂ samples, pulse discharge sintering (PDS) technique was utilized to sinter elemental powders of Ti/Si/C with stoichiometric and off-stoichiometric ratios in a temperature range of 1200–1500 °C. The results showed that high purity Ti₃SiC₂ could not be obtained from the Ti/Si/C powder with molar ratio of 3:1:2, and Ti₃SiC₂ preferred to form at relatively low sintering temperature for a short time. When 5Ti/2Si/3C and 3Ti/1.5Si/2C powders were sintered for 15 min, the TiC content was respectively decreased to 6.4 and 10 wt.% at 1250–1300 °C. The corresponding relative density of the samples sintered from 5Ti/2Si/3C powder was calculated to be as high as 99% at the temperature above 1300 °C. It is suggested that low-temperature rapid synthesis of Ti₃SiC₂ would be possible through the PDS technique, provided that the composition of the starting powders should be adjusted to be off-stoichiometric ratio from 3:1:2.     

大直径浅圆仓缩尺模型试验研究

大直径浅圆仓在生产过程中,由于仓底的偏心卸料使筒仓仓壁产生不均受力,会给筒仓结构的使用带来安全隐患。通过对浅圆仓缩尺模型试验,模拟筒仓生产过程的卸料状况,并对筒仓仓壁及仓底廊道顶部进行压力测试,将测试结果与理论计算进行对比,从而得出偏心卸料与静载状态的超压系数,为大直径浅圆仓设计提供依据。     

直接和间接电合成制备出的高铁酸钾的物理和电化学性能

K2FeO4 powders were synthesized by the ex-situ and in-situ electrochemical methods, respectively, and characterized by infrared spectrum （IR）, scanning electron microscopy （SEM）, X-ray powder diffraction （XRD） and BET. Their electrochemical performances were investigated by means of galvanostatic discharge and electrochemical impedance spectroscopy （EIS）. The results of physical characterization showed that the two samples have simi- lar structural features, but their surface morphologies and oriented growth of the crystals are different, which results in smaller specific surface area and lower solubility of the ex-situ electrosynthesized K2FeO4 sample. The results of discharge experiments indicated that the ex-situ electrosythesized K2FeO4 electrode has much larger discharge capacity and lower electrode polarization than the in-situ electrosynthesized K2FeO4 electrode. It was found from the results of EIS that lower electrochemical polarization might be responsible for the improvement on the discharge performance of the ex-situ electrosynthesized K2FeO4 electrode.     

Charge/discharge characteristics of sulfur composite cathode materials in rechargeable lithium batteries

The charge and discharge characteristics of lithium batteries with sulfur composite cathodes have been investigated. The sulfur composites showed novel electrochemical characteristics. The analysis of the differential capacity indicated that the discharge process showed two voltage plateaus of 2.10 V and 1.88 V, and the charge process also presented two voltage plateaus of 2.22 V and 2.36 V. The overcharge test showed that the composite cannot be charged over 4.0 V, the voltage always stopped at about 3.9 V during charging, indicating that the composite presented the intrinsic safety for the overcharge of lithium batteries. The overcharge can cause serious safety problem for the conventional Li-ion batteries. The overcharge test also showed that the batteries with sulfur composite were destroyed when the upper cut-off voltage was over 3.6 V. However, the composite presented good reversible capacity after it was deep discharged even to 0 V. It showed stable cycleability and high cycling capacity of 1000 mAh g⁻¹ when cycling between 0.1 V and 3.0 V, indicative of the different characteristic from the conventional oxide cathode materials. The prototype polymer battery with the composite cathode material presented the energy density of 246 Wh kg⁻¹ and 401 Wh L⁻¹.     

Temperature and catalyst effects on the production of amorphous carbon nanotubes by a modified arc discharge

Large amounts of amorphous carbon nanotubes (ACNTs) were prepared with Co-Ni alloy powders as catalyst in hydrogen gas atmosphere by a modified arc discharging furnace which can control temperature during the electric arcing process. The experimental results indicate that the cooperative function of temperature and catalyst plays an important role in the soot production rate and the relative ACNT purity. When temperature increases from 25 °C to 700 °C, the soot production rate increases from around 1 g/h to 8 g/h, the best relative ACNT purity at 600 °C can reach up to 99% compared to the room temperature sample. Without catalyst, only plate graphite is formed at 25 °C and very few carbon nanotubes are found when temperature increases to 600 °C. TEM, SEM, HRTEM and XRD analysis showed that the as-prepared carbon nanotubes are almost amorphous. The soot production rate is 8 g/h and diameter range of amorphous carbon nanotubes is about 7-20 nm, respectively.     

大电流脉冲发生实验装置的研制

研制应用于高温超导脉冲特性研究的大电流脉冲实验装置,装置由充电回路、放电回路、测量系统、保护装置和控制回路组成.利用电容器储能,通过电感放电形成LC振荡回路,放电回路中利用二极管使通过试验样品的电流为单向脉冲电流,通过改变电容器储能电压、电感、电容参数,负载上可获得不同幅值、脉宽、频率的脉冲或振荡电流.装置试验达到要求,为超导装置失超与脉冲特性研究创造了实验条件.     

Surface performance of workpieces processed by electrical discharge machining in gas

The surface performance of workpieces processed by electrical discharge machining in gas(dry EDM)was studied in this paper.Firstly,the composition,micro hardness and recast layer of electrical discharge machined(EDMed)surface of 45 carbon steels in air were investigated through different test analysis methods.The results show that the workpiece surface EDMed in air contains a certain quantity of oxide,and oxidation occurs on the workpiece surface.Compared with the surface of workpieces processed in kerosene,fewer cracks exist on the dry EDMed workpiece surface,and the surface recast layer is thinner than that obtained by conventional EDM.The micro hardness of workpieces machined by dry EDM method is lower than that machined in kerosene,and higher than that of the matrix.In addition,experiments were conducted on the surface wear resistance of workpieces processed in air and kerosene using copper electrode and titanium alloy electrode.The results indicate that the surface wear resistance of workpieces processed in air can be improved,and it is related with tool material and dielectric.     

黑龙江省面污染源调查与污染物估算

根据黑龙江省水资源综合规划成果,提出面污染源负荷量的计算方法,并估算全省地表水面污染物产生量和入河量。     

高压脉冲电晕降解液相苯酚的实验研究

利用针-筒式反应器进行高压脉冲电晕放电降解液相苯酚的试验,研究Fe2+、脉冲电压峰值、脉冲频率、曝气及pH等对苯酚降解的影响.结果发现,苯酚降解率随着Fe2+添加量的增加先升高后降低,最佳Fe2+的添加量为0.015 mmol/L;提高脉冲电压峰值、脉冲频率、曝气体积流量和pH均可达到提高苯酚降解率的效果,其经济性、适应性最佳值如下：脉冲电压峰值为40 kV,脉冲频率为180 Hz,曝气O2的体积流量为6 L/min,此条件下苯酚降解率可达到84.8 %;偏碱性环境有利于苯酚的降解;曝气种类对苯酚降解率有较大影响,降解率由高到低依次是氩气、氧气、氮气.当曝气源为氩气时,苯酚的降解率可达到98.1 %.