分散聚合法制备含交联剂的单分散PMMA微球

用分散聚合的方法,在甲醇、乙醇体系中制备了含交联剂二甲基丙烯酸乙二醇酯(EGDMA)的PMMA微球,讨论了分散体系对粒径的影响.     

生物分子LB膜表面结构与物化性质的原子力显微镜分析

LB膜以其广泛的应用价值而备受关注,而其各种性质的表征是推动其应用的源动力,原子力显微镜以其优秀的时空分辨能力、力学操纵能力而在众多表面表征技术中显得尤为突出。文章在详细介绍原子力显微镜基本探测原理的基础上,全面总结了原子力显微镜技术在LB膜参量,如表面精细结构、静电荷分布、磁畴分布、膜分子间相互作用等分析中的应用,并探讨了该技术在膜表面表征中存在的技术问题,对膜参量表征技术的发展和应用前景进行了展望。     

X-ray Absorption Spectroscopy and Atomic Force Microscopy of Films Generated from Organosulfur Extreme-Pressure (EP) Oil Additives

This study examines the interaction of sulfur-based oil additives on steel. Sulfurized isobutylene, dialkyldithiocarbamate and sulfurized esters were the additives investigated in this report. For the first time, X-ray absorption near edge structure (XANES) spectroscopy has provided detailed insight into the chemistry of both the thermo-oxidative and tribochemical films generated from these additives. It was found that the chemical nature of these films was strongly dependent on the operating environment for the additives. The XANES revealed that thermally, all three S additives reacted very similarly with steel to form a film mainly comprised of iron sulfate at temperatures as low as 100 °C. The ample supply of diffused oxygen from the base oil along with oxide naturally present on the substrate allowed for the complete oxidation of the S from the decomposed additive to iron sulfate. Tribochemical films were comprised of different forms of sulfur than observed for the thermo-oxidative films. The moderate AW conditions yielded a mixture of both oxidized and reduced forms of sulfur, with pyrite, FeS₂, being the major constituent. Rubbing between the steel pin and the substrate partially depleted the oxide layer present, allowing the additive to interact intimately with the fresh substrate, yielding FeS₂. Under extreme-pressure conditions, complete removal of the oxide layer occurred with a drastic increase in the interfacial temperatures between the pin and v-block, allowing for the complete thermal decomposition of FeS₂ to FeS to occur. AFM imaging of the AW films revealed the presence of tiny smooth domains randomly oriented, which were completely different from the pad-like structures observed for AW films generated from a typical ashless thiophosphate additive. The inability of the sulfur-based additives to form large pad-like structures, which can ultimately support the load, resulted in poor AW protection to the metal.     

TMX2000型原子力显微镜(AFM)力的标定

根据针尖的形状和各项参数进行了TMX2000型原子力显微镜载荷、粘附力、法向力、横向力及其摩擦力的标定。其标定结果为载荷Fl=0.073×(Ilm-Il0)/Sn×N·m-1,横向力Ft=0.156×It/Sn×N·m-1,摩擦力Ff=0.078×(It -It-)/Sn×N·m-1     

Comparison of Two Methods of Methyl Group Grafting to the Silica Thin Film Surface and Its Tribological Properties Measured by Atomic Force Microscopy

Two different methods are used to modify silica surfaces and the results of the different modification methods on the frictional properties are presented in this paper. Methyl groups were introduced to the silica film directly during the synthesis step with the use of triethoxymethylsilane or by post-synthesis grafting from solution using trimethylchlorosilane. Atomic Force Microscopy (AFM) was used to compare the frictional behaviour of samples after modifiying the silica surface using the two methods. It was found, that depending on the presence of methyl groups on the surface or in bulk, the frictional properties are strongly influenced not only by methyl groups but also by elasticity of final material.     

Elastic Properties of Suspended Conducting GaAs/AlGaAs Nanostructures by Means of Atomic Force Microscopy

This paper demonstrates the applicability of nanoindentation technique using atomic-force microscope cantilever for studying the elastic properties of suspended semiconductor structures on the basis of relatively thick GaAs/AlGaAs membranes in the case when their stiffness significantly exceeds that of the cantilever of atomic-force microscope, which is confirmed by the agreement between the experimentally determined values of both relative and absolute stiffness measured at different points of the investigated structure with theoretical predictions.     

生物大分子超微结构研究中的原子力显微术

原子力显微镜作为第三代显微探测工具,具有原子级的空间分辨率,其样品制备方法简单易行,可在离体的近生理条件下直接观测生物样品及其动态变化过程,能够对样品进行力学操纵,在观察生物大分子的结构和生物力学特性上具有显著的优势。本文尝试从蛋白质、核酸、多糖的超微结构和力学特性的研究角度入手,期望向读者展现出原子力显微镜在大分子生物学研究中的应用前景。     

原子力显微技术在生命科学中的应用概况

从原子力显微技术自发明以来应用于生命科学领域的文章量来概述其应用和发展情况；同时，分成生物大分子、超分子聚集体和细胞三类，总结了原子力显微技术应用于生命科学的大部分研究对象，并简单介绍了其应用的发展规律。     

用力-距离曲线标定原子力显微镜力测量系数的研究

推导出根据原子力显微镜测量得到的电压信号计算法向力和横向力的公式,然后研究用力-距离曲线标定公式中测量系数的方法,并用几种不同的探针和试样测试和确定所用原子力显微镜的测量系数。从测量的结果可以看到,不同探针和试样的测量值较为接近,表明该方法可行。当原子力显微镜测量系统的光路对称时,用本方法标定测量系数较为简单和准确。     

基于纳米压痕技术和AFM的单晶铝硬度测试实验研究

利用纳米压痕技术对单晶铝作压痕试验,获得载荷-压深的加载和卸载曲线。根据O liver-Pharr方法求出压头与测试材料之间接触表面的投影面积Ac和硬度值Hop。再利用原子显微镜(atom ic force m icroscopy,AFM)得到压痕的真实三维形貌图。结合M atlab对压痕进行分析,得到压痕的真实残余面积Aresidual,并计算出其硬度Hresidual。通过对两组单晶铝的硬度数据进行比较分析:在微纳米尺度下,两种方法计算得到的压痕硬度都存在压痕尺寸效应,Hresidual的压痕尺寸效应比Hop要更明显。     

Chemical and Physical Analysis of Reaction Films Formed by Molybdenum Dialkyl-Dithiocarbamate Friction Modifier Additive Using Raman and Atomic Force Microscopy

In order to improve the fuel economy of engines it is now common to include in modern engine oils small quantities of soluble, molybdenum-based friction-reducing additives. These additives are generally believed to form MoS₂ in rubbed contacts and thereby reduce friction in boundary lubrication conditions. This paper describes the application of Raman and atomic force microscopy to study the reaction films formed in rubbing contacts by simple solutions of molybdenum dialkyl-dithiocarbamate additive. Raman microanalysis shows that MoS₂ is present in the wear scars produced whenever this molybdenum additive effectively reduces friction. In reciprocating friction tests, the MoS₂ is unevenly distributed in the wear scar, with more in the centre of the stroke than at the reversal points. This explains the experimentally observed influence of stroke length on friction. Atomic and lateral force microscopy show that when the additive effectively reduces friction, tiny, discrete, flake-like low friction domains are present in the wear scar. These are typically 10–25 nm in diameter and 1–2 nm thick and are believed to represent MoS₂ nanocrystals as have been previously reported in the literature using high-resolution TEM. Coupled topography and lateral force measurements shows that these nanocrystals are present only on the high spots of the rubbed surface.     

Atomic Force Microscopy and Thermo-Rheological Characterisation of Lubricating Greases

In this work, non-perturbed microstructures of several commercial and model lubricating greases, differing in nature and concentration of the thickener agent, were examined using the atomic force microscopy (AFM) technique. Grease microstructure mainly depends on the nature of the thickener employed and, also, on thickener concentration and viscosity of the base oil. Thermal-induced changes in the viscoelastic response of lubricating greases have been investigated by using different rheological techniques in a temperature range of 0–175 °C. Small-amplitude oscillatory shear (SAOS) measurements were carried out to determine the mechanical spectra of the different samples studied. Lubricating grease rheological thermal susceptibility was analysed by following the evolution of the plateau modulus with temperature. SAOS functions dramatically decrease, in most cases, above a characteristic temperature, which depends on nature and/or concentration of the thickener used and therefore on grease microstructure. The thermo-mechanical reversibility of grease microstructure has been studied by carrying out triple-step-shear stress tests (shear stresses inside and outside of the linear viscoelasticity range), at different temperatures. The degree of lubricating grease non-reversible structural breakdown, which increases with temperature, depends on the shear stress applied above the linear viscoelasticity limits.     

AFM针尖"突跳"研究

为了研究原子力显微镜（AFM）“突跳”现象的产生机理，基于经典弹性理论和Lennard-Jones势能定律建立了AFM针尖与样品纳米接触的弹性模型。给出了在AFM针尖逐渐趋近样品表面的过程中，AFM针尖与样品间的粘着力、样品表面的轮廓曲线和样品表面的变形量随AFM针尖与样品表面间距的变化规律。分析了AFM“突跳”现象的产生机理和影响因素。研究表明，AFM“突跳”现象主要是由样品表面在粘着引力的作用下产生拉伸变形并与AFM针尖“突跳”接触引起的。     

Nanoscale Fabrication of the Ferroelectric Polymer Poly(vinylidene Fluoride with Trifluoroethylene) P(VDF‐TrFE) 75:25 Thin Films by Atomic Force Microscope Nanolithography

Thin films of an organic ferroelectric system, poly(vinylidene fluoride with trifluoroethylene) P(VDF‐TrFE, Kureha Corporation, Tokyo, Japan) 75:25 layers, have been deposited on highly ordered pyrolytic graphite and silicon dioxide by the horizontal Schaefer method of Langmuir–Blodgett techniques. It is possible to “shave” or mechanically displace small regions of the polymer film by using atomic force microscope nanolithography techniques such as nanoshaving, leaving swaths of the surface cut to a depth of 4 nm and 12 nm exposing the substrate. The results of fabricating stripes by nanoshaving two holes close to each other show a limit to the material “stripe” widths of an average of 153.29 nm and 177.67 nm that can be produced. Due to the lack of adhesion between the substrates and the polymer P(VDF‐TrFE) film, smaller “stripes” of P(VDF‐TrFE) cannot be produced, and it can be shown by the sequencing of nanoshaved regions that “stripes” of thin films can be removed. SCANNING 34: 404‐409, 2012. © 2012 Wiley Periodicals, Inc.     

Studies on ZDDP Anti-Wear Films Formed Under Different Conditions by XANES Spectroscopy,Atomic Force Microscopy and 31P NMR

Antiwear (AW) films, generated from a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive, were studied as a function of formation temperature, load and rubbing time. The surface morphology of these films was investigated using atomic force microscopy (AFM), and surface roughness calculated for the observed differing surface morphologies. The morphology of the films is heterogeneous for all the tested conditions, but the surface roughness is dependent on the rubbing condition. X-ray absorption near edge structure (XANES) spectroscopy has been used to characterize the chemistry of these films, and the intensity of the phosphorus K-edge was also used to monitor their thickness. The thickness of these films is in the range of 10–90 nm depending on the running conditions. Phosphorus L-edge spectra show that these films have a similar chemical nature with variable polyphosphate chain-lengths. 31P NMR was used to study the decomposition of ZDDP in the residual oils. The spectra show that the primary and secondary ZDDP react differently under the various conditions. The tribological characteristics of these AW films were probed by measuring the coefficients of friction (μ) and the wear scar width (WSW) of the counter faces. μ is highly related to the applied load and the results of WSW measurements show that the wear performance is related to all the tested parameters, temperature, load and rubbing time.     

基于AFM的振幅曲线研究探针一样品间的相互作用

在原子力显微镜(Atomic Force Microscope, AFM)的拍击工作模式(Tapping Mode)下,探针的振幅受探针-样品间作用力的影响.该作用力与两者的间距密切相关,以探针-样品间作用力的平衡位置为界,将探针-样品间距划分为引力作用区域和斥力作用区域.本文中通过实验得到了探针的振幅随探针-样品间距变化的关系曲线--振幅曲线,详细讨论了振幅曲线与探针-样品间作用力的关系;并通过计算机模拟验证了振幅随探针-样品间距的变化关系.结果表明研究软样品时应该尽可能选取引力作用区域,以避免测量对样品的影响.     

基于分子动力学的原子力显微镜表面成像

基于非接触式原子力显微镜针尖扫描成像机理,应用分子动力学方法采用非刚性针尖-表面原子团簇相互作用模型,模拟超低温环境下,非接触式原子力显微镜单晶硅针尖扫描单晶硅(111)-(7×7)表面成像过程.仿真计算采用两种原子间经验势函数描述针尖-表面原子间相互作用,两种晶向针尖末端模型都实现了对单晶硅(111)-(7×7)表面原子级分辨率仿真成像,在某些超原子级分辨率仿真图像中在单晶硅(111)-(7×7)表面Adatom原子位置出现了的双月牙峰形结构,模拟计算与成像试验文献中得到的图像基本一致.同时对采用确定的势函数及确定的晶向针尖末端,实现稳定成像的扫描针尖-表面距离进行讨论.扫描过程中针尖和被测表面形貌轻微改变,对扫描成像结果影响不大.     

Imaging and Measuring the Molecular Force of Lymphoma Pathological Cells Using Atomic Force Microscopy

Atomic force microscopy (AFM) provides a new technology to visualize the cellular topography and quantify the molecular interactions at nanometer spatial resolution. In this work, AFM was used to image the cellular topography and measure the molecular force of pathological cells from B‐cell lymphoma patients. After the fluorescence staining, cancer cells were recognized by their special morphological features and then the detailed topography was visualized by AFM imaging. The AFM images showed that cancer cells were much rougher than healthy cells. CD20 is a surface marker of B cells and rituximab is a monoclonal antibody against CD20. To measure the CD20‐rituximab interaction forces, the polyethylene glycol (PEG) linker was used to link rituximab onto the AFM tip and the verification experiments of the functionalized probe indicated that rituximab molecules were successfully linked onto the AFM tip. The CD20‐rituximab interaction forces were measured on about 20 pathological cells and the force measurement results indicated the CD20‐rituximab binding forces were mainly in the range of 110–120 pN and 130–140 pN. These results can improve our understanding of the topography and molecular force of lymphoma pathological cells. SCANNING 35:40‐46, 2013. © 2012 Wiley Periodicals, Inc.     

Friction and Adhesion Properties of Clean and Oxidized Al-Ni-Co Decagonal Quasicrystals: A UHV Atomic Force Microscopy/Scanning Tunneling Microscopy Study

The tribological properties of adhesion and friction between 10-fold Al-Ni-Co decagonal quasicrystals and conductive W₂C and TiN coated tips were studied in ultrahigh vacuum (UHV) with an atomic force microscope. Contacts between the tip and clean quasicrystals are dominated by strong adhesion forces, which result in irreversible deformations and material transfer. The irreversible adhesion was suppressed following an oxygen exposure of 10 Langmuir, which also reduced the adhesion force by a factor of two. An additional 2/3 reduction in adhesion force occurred after several 100 Langmuir exposure. A much larger decrease (by a factor 10) occurred by air-oxidation. The friction force decreased also with oxygen exposure although not as dramatically. A linear decrease by a factor two, was observed between the clean surface and the surface exposed to 200 Langmuir of oxygen. After that the friction force remained constant. Air-oxidation reduced friction by roughly another factor of two. In contrast with the clean surface, contacts with the air oxide substrate are well described by the Derjaguin-Müller-Toporov (DMT) model, while contacts with oxygen chemisorbed substrates are in the transition regime between Johnson-Kendall-Roberts (JKR) and DMT models.     

Quantifying Pathways and Friction of Nanoparticles During Controlled Manipulation by Contact-Mode Atomic Force Microscopy

Measuring interfacial friction during the manipulation of nanoparticles is becoming an increasingly important approach in nanotribology research. In this work, antimony and gold particles deposited on flat graphite surfaces have been translated by the tip of an atomic force microscope in contact mode along defined pathways. Two different manipulation techniques are discussed with respect to pathway control and friction quantification. The first technique includes pushing the particles from the side, which often results in a loss of the particle during translation due to unwanted sidewards motion. We analyze this phenomenon with an analytical model and find good agreement with experiments. An alternative approach is to move the particle while the tip remains on its top. We demonstrate that this approach allows better manipulation pathway control and that simultaneous interfacial friction measurements are in quantitative agreement with the first manipulation method.