钴镁铝类水滑石液相选择性催化苯甲醇氧化合成苯甲醛

采用共沉淀法制备了不同Co₂AlMg_x(x=0.5、1、1.5和2)原子比的类水滑石,用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、表面孔吸附(BET)及电感耦合等离子光谱(ICP)等技术手段表征了催化剂的结构、组成和比表面积,并考察了其催化苯甲醇选择氧化制苯甲醛的性能。 结果表明,随着Mg含量的增加,催化剂的碱性增强,苯甲醛的选择性提高。 在优化条件:苯甲醇0.02 mol,催化剂Co₂AlMg₁类水滑石100 mg,过氧化氢叔丁醇0.04 mol,溶剂乙腈8 mL,反应温度60 ℃,反应时间9 h下,苯甲醇的转化率为39.5%,苯甲醛的选择性达到89.2%。 催化剂重复使用5次后其活性与选择性未见明显降低,表明催化剂具有较好的稳定性。     

Study on actuating voltage and switching time of a MOEMS optical switch

The micro-opto-electro-mechanical systems (MOEMS) optical switch with slant lower electrode and with torsion beam on silicon is designed and analyzed theoretically. Based on the torsion dynamics theory, the technique and relative formula are presented for the first time for analyzing the actuating voltage and the switch time. The optimized results of the structural parameters are compared between this technique and the finite element modeling (FEM). Finally, the difference between the experimental results and theoretical data is discussed.     

Controlled Al-doped single-crystalline silicon nitride nanowires synthesized via pyrolysis of polymer precursors

Al-doped single-crystalline Si(3)N(4) nanowires were synthesized by catalyst-assisted pyrolysis of polymeric precursors. The doping levels can be controlled by tailoring the Al concentration in the precursors. It is found that the Al concentration has a significant effect on the shape, sizes, and phase compositions of the synthesized Si(3)N(4) low-dimensional nanomaterials. The photoluminescence measurements revealed that the Al dopants have a profound effect on the emission behavior. The current study provides a simple way to realize the controlled doping in Si(3)N(4) nanomaterials, which could be useful for applications in optoelectronic nanodevices.     

具有内部相移的分布反馈半导体激光器电路模型

以耦合波方程为基础,经过适当的近似处理,给出一个比较简单的适用于有内部相移的单模分布反馈半导体激光器电路模型。该模型可用于直流、交流和瞬态分析。适于在开发光电集成回路电路级模拟软件中采用,亦可加入到现有电路模拟软件中。     

采用CCD技术的微型光机电系统光开关测试方法

在研制基于微型光机电系统技术的光电器件过程中,需要精确测定器件在给定驱动条件下的运动情况。在对制作完成的光开关进行性能测试时,由于微型光机电系统光开关的几何尺寸的限制,如果要准确测定光开关微反射镜的运动位移。将会有一定的困难。提出了一种采用线阵CCD技术的光学测量方法,实现了对光开关悬臂梁在驱动电压作用下的旋转角度的精确测量。通过理论推导得到了悬臂梁扭转角度与可测量物理量的关系．通过求解方程得到了各个物理量的数值选择对于测量结果的影响,并且给定了测量时各个物理量的参考值。通过实验测量,误差小于10％,表明这是一种具有实际意义的测量方案。     

Design of thermo-optic tunable optical filter based on Si/Air DBR and polymer Fabry–Perot microcavity in SOI

An integrated tunable optical filter (TOF) based on thermo-optic effect in silicon on insulator (SOI) rib waveguide is designed and simulated. The device is comprised of two high refractivity contrast Si/Air stacks, functioning as high reflectivity of DBRs (distributed Bragg reflectors) and separating by a variable refractive index polymer Fabry–Perot (F–P) cavity. The designed device exhibits Q = 24077, FWHM = 0.065 nm and finesse = 566. Wavelength tuning is achieved through thermal modulation of refractive variation of the cavity. As the cavity polymer is heated, the refractive index of the cavity decreases. When the temperature of cavity polymer changes within 105, the central wavelength gets a continuous 35 nm shift from 1530 nm to 1565 nm, which can operate the whole C-band in the WDM (wavelength division multiplexing) networks. Moreover, by calculating, the tuning sensitivity is about 0.33 nm/°C. Owing to the compact size and excellent characteristics of integration, the proposed component has a promising utilization in spectroscopy and optical communication.     

金属卟啉催化烷烃选择性氧化反应的研究进展

金属卟啉作为一种仿生催化剂,能够实现在温和条件下对分子氧的催化活化,在催化烷烃氧化反应中显现出巨大的潜力.本文总结了金属卟啉结构对烷烃选择性氧化结果的影响,并介绍了近期金属卟啉催化剂应用于烷烃氧化反应的研究进展,最后探讨了金属卟啉催化剂在催化烷烃选择性氧化反应中存在的问题及发展前景.     

An efficient aerobic oxidative phosphonation of a-amino CH bonds over CoNiFe hydrotalcite

An efficient and convenient heterogeneous catalytic procedure has been developed for the phosphonation of a-amino CH bonds with various dialkyl phosphites and diarylphosphine oxides using molecular oxygen as a sustainable oxidant over CoNiFe hydrotalcite. The catalytic system could tolerate various tetrahydroquinoline derivatives, and the corresponding a-amino phosphonic compounds could be obtained in good to excellent yields. Synergistic effect might exist in the oxidative phosphonation under the catalysis of CoNiFe hydrotalcite.     

Fabrication of Si3N4/SiC nanocomposites toughened by in-situ formed low-dimensional nanostructures

We report the fabrication of Si₃N₄/SiC nano/nano-composite reinforced by single-crystal low-dimensional nanostructures via spark plasma sintering of nanocomposite powders containing in-situ formed Si₃N₄ nanowires/nanobelts. The fabricated nanocomposite is analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and selective area electron diffraction. The results show that the in-situ formed Si₃N₄ nanowires/nanobelts are uniformly distributed within the matrix. Such a nanocomposite could exhibit improved mechanical properties, due to the superior mechanical properties and uniform distribution of the nano-reinforcements.     

四种材料构成的超晶格能带结构的研究

本文对由AIAs,AIyGl-yAs、AIxGal-xAs和GaAs四种材料构成的超晶格价带的自旋劈裂进行了研究.通过改变材料组分和层厚,发现当超晶格单胞对其中心点是不对称结构时,对应的自旋向上和自徒向下的子带产生劈裂,而且劈裂主要发生在重空穴带和轻空穴带相互作用较强的地方.