碱化插层二维过渡金属碳化物的制备及其对铀酰离子的电化学检测

二维过渡金属碳化物(MXenes)具有良好的电化学性能与辐照稳定性, 其在放射性核素电化学检测领域有潜在应用价值。本研究通过碱活化的方式处理碳化钛型MXene(Ti₃C₂T_x), 随后将钾插层的Ti₃C₂T_x(K-Ti₃C₂T_x)负载到玻碳电极(GCE)上得到K-Ti₃C₂T_x/GCE修饰电极。采用XRD、SEM、XPS等手段分别对Ti₃C₂T_x和K-Ti₃C₂T_x进行分析表征, 并进一步研究了K-Ti₃C₂T_x/GCE对痕量铀酰离子(UO₂²⁺)的电化学检测性能。循环伏安(CV)实验结果表明, 相比于GCE电极, K-Ti₃C₂T_x/GCE修饰电极对UO₂²⁺的电化学响应显著增强。进一步使用差分脉冲伏安法(DPV)扫描, 发现pH=4.0时, K-Ti₃C₂T_x/GCE修饰电极对UO₂²⁺在铀浓度0.5~10 mg/L范围内呈现良好的线性检测关系, 本方法的检测限为0.083 mg/L(S/N=3), 稳定性和重复性好。     

Dual application of Ti-catalyzed Li-RHC composite for H2 purification and CO methanation

2LiH + MgB₂ composite doped with TiO₂ (Li-RHC-Ti) is employed with a two-fold purpose: hydrogen purification under a H₂–CO (0.1 mol%) mixture and CO methanation. Upon dynamic cycling under CO–H₂ mixture, hydrogen release curves display a quite stable amount of pure hydrogen of about 10 wt%, short release times of around 60 min, and minor degradation. Gas analysis by Fourier transform infrared spectroscopy (FTIR) after a thermal dehydrogenation process of MgH₂ and LiBH₄ under CO evidence the conversion of CO to CH₄. Li-RHC-Ti dehydrogenated under CO shows the simultaneous formation of CH₄, CH₃OH, and B(CH₃)₃ in the gas phase. X-ray powder diffraction (XRPD) and FTIR characterizations of the solid phases of Li-RHC-Ti after both H₂–CO mixture and CO interactions demonstrate the formation of MgO, LiBO_2, and HCOO⁻ species. Li-RHC-Ti acts as a hydrogen source and promoter for the CO conversion. Reaction pathways are proposed based on experimental results and equilibrium composition calculations.     

氡子体未结合态份额的变化规律研究

氡及其子体对公众的辐射照射占天然辐射照射的一半以上,而室内氡子体未结合态份额是影响氡子体剂量转换系数的重要参数。为探究氡子体未结合态份额的变化及受室内外环境因素的影响规律,本研究采用自行开发的累积式氡子体未结合态份额采样装置,在北京大学技物楼室内外环境中开展了氡子体未结合态份额的年变化测量,并利用商用连续式氡子体测量仪测量了室内氡子体未结合态份额的日变化。实测结果表明：在室内和室外不同环境中,氡子体未结合态份额的年平均值分别为8.8%(6.4%～12.5%）和9.7%(4.9%～12.8%);室内环境中氡子体未结合态份额相对稳定;室外环境中氡子体未结合态份额受环境因素影响大,波动较大;关于日变化,虽然室内平衡当量氡子体浓度呈现出明显的上午高下午低的日变化规律,但没有观察到未结合态份额有规律性的日变化。     

智能气体识别仪的研究

智能气体识别仪用以识别气体种类,它具有学习识别多种气体的功能。本文介绍了仪器的工作原理、特点及仪器的硬件和软件构成。     

现代化工仿真技术的发展与应用

化工生产过程普遍存在间歇过程多、自动化程度低、工艺复杂、条件苛刻、危险性高等特点。传统的过程研究及开发手段风险大、周期长,需要消耗大量的人力、物力、财力。而利用现代仿真技术建立一套虚拟生产系统,人们可在没有危险的情况下从事相关科研工作;节省实际研究中所需的高额成本;动态搭建并分析反应流程,优化工艺参数,加快整个化工生产研究的进程;与搭建的流程进行人机交互,实时观察各相关设备的工作状态和反应现象;可人为设置故障点,或改变工艺参数, 为应急演练和操作培训提供一种新的思路和实践;为开展化工流程模拟、仿真培训与生产过程可视化监控提供有效的支持。本文介绍了最近国内外在现代化工仿真技术领域取得的进展并探讨了其未来的发展趋势。     

Pole-placement self-tuning control of nonlinear Hammerstein system and its application to pH process control

By taking advantage of the separation characteristics of nonlinear gain and dynamic sector inside a Hammerstein model, a novel pole placement self tuning control scheme for nonlinear Hammerstein system was put forward based on the linear system pole placement self tuning control algorithm. And the nonlinear Hammerstein system pole placement self tuning control (NL-PP-STC) algorithm was presented in detail. The identification ability of its parameter estimation algorithm of NL-PP-STC was analyzed, which was always identifiable in closed loop. Two particular problems including the selection of poles and the on-line estimation of model parameters, which may be met in applications of NL-PP-STC to real process control, were discussed. The control simulation of a strong nonlinear pH neutralization process was carried out and good control performance was achieved.     

Polystyrene microsphere-based lanthanide luminescent chemosensor for detection of organophosphate pesticides

Fluorescent microspheres of polystyrene-based Eu(Ⅲ) complexes were prepared from TentaGel resin,2,6-bisbenzimidazolylpyri-dine and europium nitrate. The microspheres were characterized by FTIR spectroscopy, elemental analysis, XPS measurements and fluores-cence spectroscopy. Characteristic red emission under irradiation of365nm light from a hand-held UV lamp was observed for the micro-spheres either in a solution or solid-state.Fluorescent quenching was observed when the microspheres were exposed to a trace amount of di-ethyl chlorophosphate (DCP)in the dispersion. The material and property can be potentially used to fabricate chemosensor in the detection of organophosphates.     

红外光谱法气体定量分析研究进展

对近几年红外光谱法在气体定量分析中的应用进行了概述。利用人工神经网络、支持向量学机等化学计量法可解决混合气体吸收谱线严重重叠和非线性的问题,从而实现红外光谱法对混合气体的定量分析。同时随着红外光谱法研究的进展,利用傅里叶变换红外光谱遥测技术可实现对大气污染物的定性定量分析。     

Experiment and Analysis on the Treatment of Gaseous Benzene Using Pulsed Corona Discharge Plasma

An experiment and analysis on removal of gaseous benzene by pulse corona inducedplasma is presented in this article. Important parameters effecting removal efficiency have been investigated, such as pulse peak voltage, pulse frequency, gas inlet concentration, gas flow rate and reactor temperature. The result shows that the removal efficiency increases with the increase in pulse peak voltage, pulse frequency and reactor temperature, but decreases in the rise of gas inlet concentration and gas flow rate. On the condition of Vp = 36 kV, f = 80 Hz, C = 1440 mg/m^3 and Q = 640 ml/min, the largest removal efficiency is 98%. Finally, the reacted products are qualitatively analysed and the reaction processes are deduced in combination with plasma-chemistry theory.