应用于扫描探针显微镜的石英音叉机械模型研究

石英音叉作为力传感器广泛地应用于各种扫描探针显微镜,主要涉及石英音叉的同相振动和反相振动两种振动模式.通过实验方法和有限元仿真方法对石英音叉的两种振动模式进行研究,发现石英音叉的双臂之间以及双臂与音叉的基部之间都存在耦合作用,双臂之间的耦合使音叉的反相共振频率升高,双臂与基部之间的耦合使音叉的同相共振频率降低.针对两种振动模式的动态特性建立了石英音叉的机械模型并进行合理简化.简化模型是一个四弹簧三质点系统,计算了简化模型的参数.通过一个音叉臂等效质量变化与音叉反相共振频率变化之间的定量关系证明了简化机械模 关键词： 扫描探针显微镜 石英音叉 振动模式 机械模型     

ITO上AuPd合金和Au阵列图案的制备及电催化活性的SECM表征

利用电化学湿法印章技术在氧化铟锡(ITO)导电玻璃上制备AuPd合金和Au的双组分阵列图案. 采用具有微浮雕图案的琼脂糖印章存储足够多的溶液,并通过控制电沉积的时间来控制图案厚度. 应用场发射扫描电子显微镜(FE-SEM),X射线能谱分析(EDX)和原子力显微镜(AFM)分别对ITO表面上的AuPd合金和Au的形貌和组分进行表征,并通过循环伏安(CV)技术和扫描电化学显微镜(SECM)研究比较了Au和AuPd合金的催化活性. 利用扫描电化学显微镜(SECM)的针尖产生-基底收集(TG-SC)模式和氧化还原竞争(RC)模式,发现Au电极对二茂铁甲醇氧化物(FcMeOH⁺)电催化还原能力高于AuPd合金电极,而在AuPd合金上催化还原H₂O₂的能力显著高于Au.     

线性扫描伏安法测定辣椒制品中苏丹红Ⅰ含量

基于苏丹红Ⅰ分子中的-C=C-和-N=N-基团的电活性,在悬汞电极上还原产生还原波,其还原峰高与苏丹红的浓度呈线性关系。据此提出用线性扫描伏安法测定辣椒制品中苏丹红Ⅰ的含量。试验中用悬汞电极为工作电极,饱和甘汞电极为参比电极,铂微电极为对电极,饱和硼砂缓冲溶液(pH 9.2)为支持电解质,并以丙酮作为样品的溶剂,记录在-1 050mV处还原峰电流ip。测得苏丹红Ⅰ的质量浓度在0.1~1.4mg·L-1范围内与其峰高呈线性关系,检出限(3s/k)为9.8μg·L-1。用标准加入法进行回收试验,测得回收率在88.0%~98.4%之间,测定值的相对标准偏差(n=5)在0.72%~5.4%之间。     

Fabrication of hollow silica microspheres utilizing a hydrothermal approach

Hollow silica microspheres(HSMSs) have been successfully fabricated via a facile hydrothermal route using D-glucose as the sacrificial template and sodium silicate powder as the silica precursor.The resulting silica hollow particles were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and infrared spectroscopy(IR).The surface area was determined using the BET method.SEM and TEM images exhibited micro-sized silica hollow particles with a size of ~1.5μm.     

Synthesis and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 as a concentration-gradient cathode material for lithium batteries

A well-ordered and spherical LiNi0.6Co0.2Mn0.2O2 cathode material was successfully synthesized from Ni and Mn concentration-gradient precursors via co-precipitation. The crystal structure, morphology and electrochemical properties of LiNi0.6Co0.2Mn0.2O2 were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and charge-discharge tests. The material delivered an initial discharge capacity of 174.3 mAh/g at 180 mA/g （1 C rate） between 2.8 and 4.3 V and more than 93.1% of that was retained after 100 cycles. In addition, it also exhibited excellent rate capability, high cut-off voltage and temperature performance.     

Coking-resistant Ni-ZrO2/A1203 catalyst for CO methanation

Highly coke-resisting ZrO2-decorated Ni/A1203 catalysts for CO methanation were prepared by a two-step process. The support was first loaded with NiO by impregnating method and then modified with ZrO2 by deposition-precipitation method （IM-DP）. Nitrogen adsorption- desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetdc analysis, H2 temperature- programmed reduction and desorption, NH3 temperature-programmed desorption, and zeta potential analysis were employed to characterize the samples. The results revealed that, compared with the catalysts with the same composition prepared by co-impregnation （CI） and sequential impregnation （SI） methods, the Ni/A1203 catalyst prepared by IM-DP showed much enhanced catalytic performance for syngas methanation under the condition of atmospheric pressure and a high weight hourly space velocity of 120000 mL.g-1 .h-1. In a 80 h life time test under the condition of 300-600 ~C and 3.0 MPa, this catalyst showed high stability and resistance to coking, and the amount of deposited carbon was only 0.4 wt%. On the contrary, the deposited carbon over the catalyst without ZrO2 reached 1.5 wt% after a 60 h life time test. The improved catalytic performance was attributed to the selective deposition of ZrO2 nanoparticles on the surface of NiO rather than A1203, which could he well controlled via changing the electrostatic interaction in the DP procedure. This unique structure could enhance the dissociation of CO2 and generate surface oxygen intermediates, thus preventing carbon deposition on the Ni particles in syngas methanation.     

多壁碳纳米管修饰玻碳电极测定铜离子

以多壁碳纳米管(MWCNTs)修饰玻碳电极为工作电极,采用阳极溶出线性扫描法研究了铜离子的电化学测定方法。探讨了MWCNTs修饰层数、富集电位、富集时间、溶液pH、支持电解质对峰电流的影响。实验表明,铜离子浓度在1.0×10-8~1.0×10-5mol·L-1范围内与峰电流呈良好的线性关系,检测限为2.0×10-9mol·L-1,且该电极具有良好的稳定性和抗干扰能力。     

Phase Behavior of Liquid Crystals Formed in [C12mim]CI/H2O and [C12mim] Cl/Alcohols Systems

Phase behaviors of different binary systems involving 1-dodecyl-3-methylimidazolium chlo- ride （[C12mim]Cl） and H20, [C12mim]Cl and different alcohols （1-butanol, 1-pentanol, 1- hexanol and 1-octanol） are investigated at 25 ℃. Hexagonal liquid crystal phase （H1） is identified in [C12mim]Cl/H2O system, and lamellar liquid-crystalline （Lα） phase is found in [C12mim]Cl/alcohols systems by using polarized optical microscopy and small-angle X-ray scattering techniques. The formation of such phases is considered as a synergetic result of the solvatophobic force and the hydrogen-bonded network comprising an imidazoliuin ring, chloride ion and water （or alcohols）, which can be confirmed by Fourier transform infrared spectra. It is noticeable that in [C12mim]Cl/1-octanol system, the lattice spacings of lamellar phase increase with increasing C12mimCl concentration, which is opposite to the results of [C12mim]Cl/H2O system. This may result mainly from stronger static repulsion among hydrophilic headgroups of imidazolium salts arranged in the bilayers of lamellar structures. Further measurements by differential scanning calorimetry indicate that the lamellar phase is stable within a wide temperature range above room temperature. However, the lattice spacings decrease with the increase of temperature, which may. be due to the softening of the hydrocarbon chain of [C12mim]Cl molecules. In different alcohols systems, it is found that the lamellar lyotropic liquid crystal structure is easier to be formed when the carbon chain length becomes longer.