质子化g-C3N4/β-SiC复合材料的制备及光催化降解茜素红性能

分别采用热解法和溶胶-凝胶-碳热还原法合成了石墨相氮化碳(g-C₃N₄)和纳米级碳化硅(β-SiC), 通过浸渍-热处理法将两者复合并通过浓盐酸质子化, 分别制备了g-C₃N₄/β-SiC和质子化g-C₃N₄/β-SiC(P-g-C₃N₄/β-SiC)复合光催化剂. 利用X射线衍射(XRD)、 扫描电子显微镜(SEM)、 高分辨透射电子显微镜(HRTEM)、 傅里叶变换红外光谱(FTIR)、 X射线光电子能谱(XPS)、 紫外-可见漫反射光谱(UV-Vis-DRS)和光致发光光谱(PL)等对样品进行了表征. 结果表明, P-g-C₃N₄/β-SiC复合材料的比表面积增大, 光生电子-空穴对的复合几率降低, 光催化性能明显提高. 在光催化降解染料茜素红(ARS)研究中, 样品的可见光催化活性顺序为P-g-C₃N₄/β-SiC>g-C₃N₄/β-SiC>P-g-C₃N₄>g-C₃N₄>β-SiC. 其中P-g-C₃N₄/β-SiC在60 min内对ARS的降解效率高达99.9%, 符合准一阶动力学模型, 速率常数为0.0967 min ^-1, 且循环使用9次后, 光催化降解效率仍保持97.5%以上.     

高尔夫球状球霰石的简易制备研究

碳酸钙材料在合成过程中的形貌和物相组成控制对其应用极为重要.本文利用乙二醇和水的混合溶液,通过简单的混合沉淀法快速合成了高尔夫球状球霰石.利用X-射线衍射(XRD)、场发射扫描电镜(FESEM)以及傅里叶变换红外光谱(FI-IR)等手段对获得的样品进行了表征.结果表明,在室温下反应产物能够保持高尔夫球形貌但较高温度下样品为无规则形貌,不同温度下反应产物都发生了部分相转变.     

UV-O3照射处理对柔性染料敏化光阳极性能的影响

分别从UV-O3照射ITO-PEN基板和低温烧结后光阳极薄膜两个角度,采用XRD、SEM、接触角测量仪等手段,系统的分析了UV-O3照射处理对光阳极光电性能的影响.研究表明:UV-O3照射处理能够改善基板表面的亲水性,提高了浆料在ITO-PEN基板表面的涂覆均匀性;同时UV-O3照射处理还可以有效的去除低温烧结后光阳极TiO2薄膜中残余的有机物,改善了光阳极TiO2薄膜的导电性及其内部不同粒径TiO2纳米颗粒之间的连接性,使电池的短路电流密度得到了提升,最终使得电池的光电转化效率由5.30;提高到了5.71;.     

倾斜度及温度震荡频率对三维多孔介质方腔自然对流换热的影响

对三维多孔介质倾斜方腔内非稳态自然对流换热进行数值研究.腔体右壁面(X=1)保持恒温T₀,左壁面(X=0)基于温度T₀按正弦规律变化,其他所有壁面保持绝热.采用Brinkman扩展达西模型及SIMPLE算法模拟方腔内的流动.方腔沿y轴转动倾角α1的变化范围为0°~90°,沿x轴转动倾角α2的变化范围为0°~45°,无量纲温度震荡频率f的变化范围为5π~90π.详细研究倾角和温度震荡频率对三维方腔自然对流换热的影响.计算结果表明:当倾角α1=46°,α2=45°及温度震荡频率f=45π时,方腔内的换热最强.     

Accurate evaluation of lowest band gaps in ternary locally resonant phononic crystals

Based on a better understanding of the lattice vibration modes, two simple spring--mass models are constructed in order to evaluate the frequencies on both the lower and upper edges of the lowest locally resonant band gaps of the ternary locally resonant phononic crystals. The parameters of the models are given in a reasonable way based on the physical insight into the band gap mechanism. Both the lumped-mass methods and our models are used in the study of the influences of structural and the material parameters on frequencies on both edges of the lowest gaps in the ternary locally resonant phononic crystals. The analytical evaluations with our models and the theoretical predictions with the lumped-mass method are in good agreement with each other. The newly proposed heuristic models are helpful for a better understanding of the locally resonant band gap mechanism, as well as more accurate evaluation of the band edge frequencies.     

Segregations and desorptions of Ge atoms in nanocomposite Si_(1-x)Ge_x films during high-temperature annealing

Nanocomposite Si_(1-x)Gex films are deposited by dual-source jet-type inductively coupled plasma chemical vapor deposition(jet-ICPCVD).The segregations and desorptions of Ge atoms,which dominate the structural evolutions of the films during high-temperature annealing,are investigated.When the annealing temperature(Ta)is 900~℃,the nanocomposite Si_(1-x)Gex films are well crystallized,and nanocrystals(NCs)with the core-shell structure form in the films.After being annealed at 1000~℃(above the melting point of bulk Ge),Ge atoms accumulate on the surfaces of Ge-rich films,whereas pits appear on films with lower Ge content,resulting from desorption.Meanwhile,voids are observed in the films.A cone-like structure involving the percolation of the homogeneous clusters and the crystallization of NCs enhances Ge segregation.     

基于NI ELVIS和LabVIEW的动态杨氏模量实验系统设计

设计了基于NI ELVIS平台和LabVIEW虚拟仪器的动态杨氏模量实验系统。该系统在NI ELVIS平台基础上采用虚拟信号发生器和虚拟示波器代替YM-2型信号发生器和传统示波器,有效提高了试样棒共振频率测量的精度,实现了测量信号的实时显示、采集、存储和自动化测量。实践表明,该系统的搭建和测试有助于学生更好地理解和掌握实验,提高实践创新能力。     

精确稀疏扩展信息滤波的多机器人SLAM研究

在机器人同时定位与地图创建(SLAM)问题中,多机器人SLAM成为目前机器人学中的研究热点.因此,基于精确稀疏扩展信息滤波算法(ESEIF)的多机器人SLAM问题,根据多机器人的运动模型和观测模型分别对多机器人位姿估计及环境特征点进行观测,并依据阈值划分观测特征点,以完成机器人的观测更新,同时边缘化机器人位姿并进行重定位.实验仿真数据表明:多机器人的位姿精度良好,观测更新阶段时间基本上恒定,与地图特征点数量无关,体现了ESEIF算法在研究多机器人SLAM问题的有效性.     

Spectral broadening induced by intense ultra-short pulse in 4H–SiC crystals

We report the observation of spectral broadening induced by 200 femtosecond laser pulses with the repetition rate of 1 kHz at the wavelength of 532 nm in semi-insulating 4H–SiC single crystals.It is demonstrated that the full width at half maximum of output spectrum increases linearly with the light propagation length and the peak power density,reaching a maximum 870 cm~(-1)on a crystal of 19 mm long under an incident laser with a peak power density of 60.1 GW/cm~2.Such spectral broadening can be well explained by the self-phase modulation model which correlates time-dependent phase change of pulses to intensity-dependent refractive index.The nonlinear refractive index n_2 is estimated to be1.88×10~(-15)cm~2/W.The intensity-dependent refractive index is probably due to both the nonlinear optical polarizability of the bound electrons and the increase of free electrons induced by the two-photon absorption process.Super continuum spectra could arise as crystals are long enough to induce the self-focusing effect.The results show that SiC crystals may find applications in spectral broadening of high power lasers.