扫描隧道显微交易针尖与铅（110）样品间“连颈”自动变细过程的实验研究

近期的实验表明跳触现象很可能是摩擦的起源。所谓跳触就是当针尖和平的表面距离很近时二者会突然接触从而形成“连颈”。在用扫描隧道显微镜研究这现象的过程中，利用电导随时间的演变曲线，我们发一扫描隧道显微镜针尖和铅样品表面间的这种连颈在被拉伸到一定程度后，会彼发变细直到拉断。     

扫描隧道显微镜针尖与铅(110)样品间“连颈”自动变细过程的实验研究

近期的实验表明跳触现象（jumpto contact）很可能是摩擦的起源．所谓跳触就是当针尖和平的表面距离很近时二者会突然接触从而形成“连颈”．在用扫描隧道显微镜研究这种现象的过程中，利用电导随时间的演变曲线，我们发现扫描隧道显微镜针尖和铅（110）样品表面间的这种连颈在被拉伸到一定程度后，会自发变细直到拉断．环境温度和表面清洁度对这种自发变细过程的显著影响表明这种过程是由连颈表面铅原子的扩散引起的     

几种微构件材料的表面能及纳观黏附行为研究

对微机电系统（MEMS）中几种常用构件材料的表面能及其主要影响因素进行了探讨,并与材料表面的纳观黏附性能进行了分析比较.用Owens二液法计算出硅基材料的表面能在60—75 mJ/m²之间,它们之间总表面能的差异主要归结为表面能极性分量的差异,表面粗糙度的存在使表观表面能有所偏高.施加自组装分子膜后的表面能大为降低,粗糙度的存在可以使其表面能进一步减小.纳观黏附力和表面能之间有一定的对应关系.另外,在研究中发现表面粗糙度对纳观黏附行为的影响较小. 关键词： MEMS 表面能 纳观黏附 粗糙度     

3ω法加热/测温膜中温度波解析及其在微/纳米薄膜导热系数测量中的应用

给出了3ω法测试系统中描述薄膜表面加热/测温膜中温度波动的级数形式解，并将复数温度波动的实部和虚部分开表示.利用该解分析了交流加热频率、加热膜宽度和材料热物性的组合参数对加热膜温度波动幅度的影响.并根据此解对测量原理的数学模型进行了修正，建立了相应的3ω测试系统，首先测定了厚度为500 nm SiO₂薄膜的导热系数，验证了实验系统的合理性.加大了测试频率，利用级数模型在高频段直接得到SiO₂薄膜的导热系数，结合低频段的数据同时确定了Si基体的导热系数.利用级数解分析测试了激光晶体Nd:YAG〈111〉面上多层ZrO₂/SiO₂增透膜的导热系数，测试的ZrO₂薄膜的导热系数比体材料小.进行了不确定度分析.结果表明，提出的分析方法可以有效研究微器件表面薄膜结构的导热性能. 关键词： ω法')" href="#">3ω法 微/纳米薄膜 导热系数 微尺度加热膜     

硅基二氧化硅厚膜材料的快速生长

采用火焰水解法在Si片上快速淀积SiO₂厚膜材料,材料膜厚达到40μm以上,生长速率达8μm/min.然后将该材料分别在真空中/空气气氛中高温致密化处理,获得了各种形态的二氧化硅厚膜材料,包括平整度好、光滑透明的玻璃态SiO₂厚膜材料.并利用XRD、电子显微镜等仪器对SiO₂膜的表面和膜厚进行了测试分析.     

感应耦合等离子体刻蚀p-GaN的表面特性

研究了p-GaN材料经感应耦合等离子体(ICP)刻蚀后的表面特性，并用不同的方法对刻蚀表面进行处理.利用原子力显微镜(AFM)和X射线光电子能谱(XPS)对刻蚀样品进行分析，并在样品表面制作Ni/Au电极，进行欧姆接触特性的测试.实验结果表明了NaOH溶液处理表面对改善材料表面和欧姆接触特性是比较有效的.     

原子吸收光谱法研究纳米纤维膜对Cr(Ⅵ)的吸附性能

利用静电纺丝技术制备了醋酸纤维素和聚乙烯吡咯烷酮纳米纤维膜.此纤维膜材料经水和NaOH处理后,除去了聚乙烯吡咯烷酮,脱乙酰化后进一步在表面接枝氨基(-NH2).用红外光谱图和扫描电镜图表征了合成的功能化纳米纤维膜,然后将胺基化纳米纤维膜用于Cr(Ⅵ)离子的吸附研究,重点用火焰原子吸收光谱法分析了溶液酸度和吸附时间对吸附容量的影响;同时通过Langmuir、弗兰德列希等吸附模型和一级、二级动力学方程对吸附行为进行线性拟合,发现改性后的纳米纤维膜材料对Cr(Ⅵ)离子的最大吸附量为55.55mg/g;符合二级动力学模型,化学吸附是主要的吸附方式.     

天然超疏水生物表面研究的新进展

文章简要地论述了表面浸润性的基本理论，介绍了几种天然超疏水生物表面最新的研究进展，包括荷叶、蝉翼、水稻叶以及水黾腿，特别介绍了作者的研究小组利用从壁虎脚高黏附力获得的灵感仿生制备出一种对水滴具有高黏附的超疏水阵列聚苯乙烯纳米管材料，最后对超疏水材料的研究趋势作了展望。     

双波段激光防护多层反射膜的设计

利用TFCalc膜系设计软件,从理论上对激光防护多层反射膜的光学性能进行了分析。计算了各个膜系的理论投射率曲线。分析了各个因素(如膜系结构、膜层奇偶性、起膜材料)对膜层光学性质的影响。并设计了以ZrO2和SiO2为膜层材料,聚碳酸酯(PC)为基体材料,可以同时防护532nm和1064nm波长激光的1∶2型多层反射薄膜。在532nm和1064nm处的理论透过率都达到了0.01%(光学密度D=4)。并在PC镜片表面镀上23层1∶5型激光反射膜,对理论设计进行验证。对其在400nm~1200nm波长范围内的光学性能进行了测试,测试结果与理论计算值基本吻合。     

用表面等离子体共振原理检测湿度环境（英文）

采用Kretschmann结构激发表面等离子体,利用多孔陶瓷材料SiO2作感湿材料,当外界环境的相对湿度变化时,引起感湿层SiO2的折射率发生相应变化,导致表面等离子体共振角发生偏移.采用有限元法对传感系统在不同感湿层折射率下的反射谱进行了模拟分析,并根据反射谱的共振半峰宽和共振峰深度对金膜的厚度进行优化.研究结果表明:金膜的最佳厚度为55nm,反射谱的共振角偏移量与感湿层折射率变化呈线性关系,湿度检测的分辨率高达0.37%RΗ,灵敏度达到0.03°/%RH.该研究对基于表面等离子体共振原理的湿度传感器的研制与应用具有一定意义.     

二氧化硅及其硅烷自组装膜微观摩擦力与粘着力的研究(Ⅱ)粘着力的实验与分析

使用原子力/摩擦力显微镜,在5%—99%相对湿度范围,研究了二氧化硅和二氧化硅基体上十八烷基三甲氧基硅烷自组装膜(简称OTE SAM/SiO₂)表面粘着力随湿度的变化规律.实验表明,二氧化硅表面的粘着力随湿度的增大先逐渐增大,然后急剧减小.相反,OTE SAM/SiO₂由于其良好的斥水性,表面的粘着力随湿度的增大基本不变.着重从基本界面力,即表面张力、范德瓦耳斯力和基本键合力的形成与变化,分析了二氧化硅表面粘着力随湿度的增大先增后减的原因,探讨了粘着力的产生机理 关键词： 固体表面的物理性能 分子膜 纳米摩擦学     

二氧化硅及其硅烷自组装膜微观摩擦力与粘着力的研究(Ⅰ)摩擦力的实验与分析

使用原子力/摩擦力显微镜在5%—99%的相对湿度范围,研究了二氧化硅和二氧化硅基体上十八烷基三甲氧基硅烷自组装膜(简称OTE SAM/SiO₂)表面摩擦力和粘着力随湿度的变化规律.实验表明OTE SAM/SiO₂不仅能明显改善二氧化硅基体表面的摩擦性能,而且在200nN(接触区Hertz压力约为0.8GPa)的载荷条件下表现出良好的抗磨性能.由于强的亲水性,二氧化硅表面的摩擦力随湿度的增大先逐渐增大,然后急剧减小.相反,OTE SAM/SiO_{2关键词： 固体表面的物理性能 分子膜 纳米摩擦学}     

Towards a Fundamental Understanding of the Mechanics of Crystal Agglomeration: A Microscopic and Molecular Approach

A novel experimental apparatus has been developed which enables the measurement of adhesion forces between two crystals suspended in a supersaturated solution and allowed to agglomerate over a fixed time period. The geometry of the crystal surfaces at the contact points and the dynamic development of the bond are captured on video and characterised using an image analysis technique. The experimental apparatus has been designed to allow control of supersaturation, orientation of crystal faces, distance between crystals, relative movement of crystals and contact time. The experimental results show that the agglomerate bond strength, expressed as the agglomerate adhesion force per unit contact area, increases with increasing supersaturation and is higher for faster growing faces than for slower growing faces. In addition, a qualitative comparison has been made between the measured force and a theoretical estimation of the interaction force between crystal faces, determined through molecular modelling. It is shown that the speed of approach of two opposing crystal faces is a key parameter in the nature of the subsequent bond, as is their atomic structure.     

Influence of relative humidity on the electrostatic charging of lactose powder mixed with salbutamol sulphate

In this study, electrostatic charging of lactose and its mixtures with salbutamol sulphate (SS) were studied as a function of relative humidity (RH). Powder adhesion onto a steel pipe surface was also investigated. The powders were charged by sliding in a steel pipe. Increase in RH decreased the charging of lactose and mixtures, but the effect on SS was not evident. Furthermore, the charge of the mixtures reversed from negative to positive as RH was increased and remained positive as the samples were again dried. Humidification also changed the adhesion behavior of the mixtures onto the pipe surface.     

Nanoscale analysis of degradation processes of cellulose fibers

Mapping the morphological and nano-mechanical properties of cellulose fibers within paper sheets or textile products at the nano-scale level by using atomic force microscopy is a challenging task due to the huge surface level variation of these materials. However this task is fundamental for applications in forensic or cultural heritage sciences and for the industrial characterization of materials. In order to correlate between nano-mechanical properties and local nanometer scale morphology of different layers of cellulose fibers, a new strategy to prepare samples of isolated cellulose fibers was designed. This approach is based on immobilizing isolated fibers onto glass slides chemically pretreated so as to promote cellulose adhesion. The experiments presented here aim at the nano-scale characterization of fibers in paper samples aged under different external agents (relative humidity, temperature) in such a way as to promote hydrolysis and oxidation of polymers. The observed variability of local mechanical properties of paper fibers was related to varying degrees of cellulose polymerization induced by artificial aging.     

Measurement of interaction force between RGD-peptide and Hela cell surface by optical tweezers

Since RGD peptides (R: arginine; G: glycine; D: aspartic acid) are found to promote cell adhesion, they are modified at numerous materials surface for medical applications such as drug delivery and regenerative medicine. Peptide-cell surface interactions play a key role in the above applications. In this letter, we study the adhesion force between the RGD-coated bead and Hela cell surface by optical tweezes. The adhesion is dominated by the binding of α5β1 and RGD-peptide with higher adhesion probability and stronger adhesion strength compared with the adhesion of bare bead and cell surface. The binding force for a single α5β1 -GRGDSP pair is determined to be 16.8 pN at a loading rate of 1.5 nN/s. The unstressed off-rate is 1.65 × 10-2s-1 and the distance of transition state for the rigid binding model is 3.0 nm.     

Modeling of the rough spherical nanoparticles manipulation on a substrate based on the AFM nanorobot

In this paper, dynamic behavior of the rough spherical micro/nanoparticles during pulling/pushing on the flat substrate has been investigated and analyzed. For this purpose, at first, two hexagonal roughness models (George and Cooper) were studied and then evaluations for adhesion force were determined for rough particle manipulation on flat substrate. These two models were then changed by using of the Rabinovich theory. Evaluations were determined for contact adhesion force between rough particle and flat substrate; depth of penetration evaluations were determined by the Johnson–Kendall–Roberts contact mechanic theory and the Schwartz method and according to Cooper and George roughness models. Then, the novel contact theory was used to determine a dynamic model for rough micro/nanoparticle manipulation on flat substrate. Finally, simulation of particle dynamic behavior was implemented during pushing of rough spherical gold particles with radii of 50, 150, 400, 600, and 1,000 nm. Results derived from simulations of particles with several rates of roughness on flat substrate indicated that compared to results for flat particles, inherent roughness on particles might reduce the rate of critical force needed for sliding and rolling given particles. Given a fixed radius for roughness value and increased roughness height, evaluations for sliding and rolling critical forces showed greater reduction. Alternately, the rate of critical force was shown to reduce relative to an increased roughness radius. With respect to both models, based on the George roughness model, the predicted rate of adhesion force was greater than that determined in the Cooper roughness model, and as a result, the predicted rate of critical force based on the George roughness model was closer to the critical force value of flat particle.     

Les surfaces du verre : structure et physico-chimie

The surface of a silica glass sample can not be defined independently of its environment. Fracture under vacuum, exposure to the ambient, to controlled atmospheres or to variable relative humidity, create as many surfaces showing specific adsorption, grafting and adhesion properties.     

Electrostatic adhesion in food

Electrostatic adhesion is a significant force in painting and other industries. However, coating of food items uses powders and targets with properties that are far from ideal for electrostatic coating. In addition, the adhesion must last a long time in order to be useful. The goal of this study is to determine if electrostatic adhesion is significant in food coating. A range of food powders were coated onto different kinds of food samples electrostatically and nonelectrostatically and the adhesion measured. Electrostatic powder coating increased the adhesion of most food powders onto most food targets. Some correlation was found between effectiveness of the process and resistivity or oil content of the target, resistivity of the powder, and particle size. At low relative humidities, electrostatic adhesion lasted for several weeks, long enough to be valuable.     

Effects of natural environmental factors on delta13C of lichens

This preliminary study was designed to determine the extent to which the carbon isotope ratio in four species of lichens was influenced by such features as humidity, rainfall, radioactivity, and air quality. The sampling sites were selected to be at a great distance from any pollution. At the time of sampling, field data (temperature, relative humidity, average monthly precipitation, and radioactivity) were recorded. delta(13)C in whole lichen specimens were determined using standard mass spectrometric techniques with a standard deviation of+/-0.3 per thousand. We have found a weak but negative correlation between delta(13)C and relative humidity, and a positive correlation between delta(13)C and average monthly precipitation at the studied sites. The effects were minor, of the order of 1.5 per thousand for all the lichens. We have examined the correlation between (137)Cs activity concentration of the studied lichens and delta(13)C of these lichens, and we have suggested that fixation of radiocesium does not alter photosynthesis rate. There was a delta(13)C variation with the altitude gradient with less negative delta(13)C values at higher altitude. It is possible that this difference is caused by the ozone and occurred at the high elevations.