气相色谱-负离子化学源-质谱法分析禽蛋食品中10种多溴联苯和多溴联苯醚残留

建立了气相色谱-负离子化学源-质谱法(GC-NCI-MS)同时分析禽蛋食品中10种多溴联苯(PBBs)和多溴联苯醚(PBDEs)残留的分析方法。禽蛋食品用正己烷超声提取、浓硫酸酸化、中性和酸性硅胶层析柱净化和正己烷洗脱后,以PCB209为内标物,采用GC-NCI-MS的选择离子监测方式(SIM)分析;同时探讨了目标物PBDE100 NCI-MS特征离子的断裂机理。当禽蛋食品空白的加标质量浓度为5(3.5)和50(35)μg/kg时,加标回收率为75.2%～107%,相对标准偏差为2.3%～8.8%,方法检测限为0.14～0.39μg/kg,线性范围为1～250μg/kg,相关系数皆大于0.9991,方法已用于禽蛋食品中10种痕量PPBs和PBDEs残留的同时分析。     

Temperature-Dependent Characteristics of GaN Schottky Barrier Diodes with TiN and Ni Anodes

The effect of temperature on the characteristics of gallium nitride (GaN) Schottky barrier diodes (SBDs) with TiN and Ni anodes is evaluated. With increasing the temperature from 25 to 175℃, reduction of the turn-on voltage and increase of the leakage current are observed for both GaN SBDs with TiN and Ni anodes. The performance after thermal treatment shows much better stability for SBDs with Ti N anode, while those with Ni anode change due to more interface states. It is found that the leakage currents of the GaN SBDs with TiN anode are in accord with the thermionic emission model whereas those of the GaN SBDs with Ni anode are much higher than the model. The Silvaco TCAD simulation results show that phonon-assisted tunneling caused by interface states may lead to the instability of electrical properties after thermal treatment, which dominates the leakage currents for GaN SBDs with Ni anode. Compared with GaN SBDs with Ni anode, GaN SBDs with TiN anode are beneficial to the application in microwave power rectification fields due to lower turn-on voltage and better thermal stability.     

应变对橡胶材料导热系数的影响

材料的导热系数通常极大地依赖于其微观结构。应力/应变是改变材料内部结构的一种有效手段,本文通过实验研究了天然橡胶在不同拉伸状态下的导热系数变化。搭建了基于Angstrom方法的热导率测量平台,并进行了标准样品的测试。通过对橡胶的测试,发现对于橡胶这类交联材料,虽然由于交联作用拉伸倍数受到较大的限制,但在低倍拉伸的条件下依然可以有效的提高定向的热导率。     

Timing properties and pulse shape discrimination of LAB-based liquid scintillator

Linear Alkyl Benzene (LAB) is a promising liquid scintillator solvent in neutrino experiments because it has many appealing properties. The timing properties of LAB-based liquid scintillator have been studied through ultraviolet and ionization excitation in this study. The decay time of LAB, PPO and bis-MSB is found to be 48.6 ns, 1.55 ns and 1.5 ns, respectively. A model can describe the absorption and re-emission process between PPO and bis-MSB perfectly. The energy transfer time between LAB and PPO with different concentrations can be obtained via another model. We also show that the LAB-based liquid scintillator has good (n, γ) and (α, γ) discrimination power.     

季阳离子基团对聚吡咯膜伏安特性的影响

在含有相同阴离子与不同阳离子基团的电解质溶液中用电位阶跃技术制备了聚吡咯(PPy)膜，用循环伏安法于空白溶液中研究了膜的电化学行为。研究结果表明随着阳离子基团增大，制膜时消耗的电量减小，膜的氧化还原电流下降，阴极和阳极峰电位分别向更负和更正的方向移动。扫描电镜显示阳离子基团对PPy膜的沉积过程和形态结构产生了一定的影响。