Micro-friction of diazoresin/polyacrylic acid self-assembly films in water with atomic force microscopy

Ultrathin films composed of diazoresin（DR）and polyacrylic acid（PAA）were fabricated.The surface morphology of the films in water was measured using an atomic force microscopy（AFM）.The self-assembly technique makes the surface rather flat and uniform.The friction force and its dependence on the velocity differ from the surface charge of the thin films.The friction force of repulsive DR/PAA film increases linearly with velocity and has lower values than that of attractive DR film over the full range of velocity.As the velocity increases,the attractive friction of DR film first decreases to a minimum at a velocity of 2 line/s and then increases all the way.When the surface is repulsive to the friction substrate,the friction of thin films that is determined by hydrated lubrication of polymer chains that is ultralubricated;when it is adhesive to the friction substrate,the friction is mainly contributed from the elastic deformation of adsorbed polymer chains in the low velocity region and from viscous sliding in the presence of hydrated-layer lubrication of the polymer chains in the higher velocity region.     

有机溶剂对纳滤膜结构及透过特性的影响

观察了两种纳滤膜(NF-SH,MPF-44)的稳定性,并利用原子力电镜技术(AFM)观察膜的活性表面结构,发现有机溶剂导致膜结构发生显变化。观测在溶剂中的传递通量以及溶质截留率发现,影响NF-SH膜的通量的主要因素是膜本身的结构;对MPF-44膜,影响膜通量的主要因素是溶剂性质。对于这两种纳滤膜影响截留率的主要因素都是溶剂与溶质的相互作用。     

AFM对TiN薄膜和聚酰亚胺微观结构的分析

论述了一种高精度的原子力显微镜AFM．IPC-208B型机在分子形态学方面的应用．以磁控溅射获得的TiN薄膜和普通的聚酰亚胺纤维为例,从原子力显微镜测得的三维图上探析该TiN薄膜的优先生长面及其在优先生长面上的原子排布和聚酰亚胺的表面形态．这种实验不仅鉴定了测试材料的微观形态,也充分肯定了该原子力显微镜原子量级的精度及其在微观结构领域的潜在发展,为该机应用于微加工领域奠定了基础．     

Flaking and degradation of polyurethane coatings after 2 years of outdoor exposure in Lhasa

The exposure of a high gloss polyurethane aircraft topcoat system with polyurethane intermediate coating and epoxy primer to strong ultraviolet radiation in Lhasa, Tibet was studied by using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance Fourier-transform infrared (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). Micro-flakes were found to form on the topcoat surface after exposure and the size and quantity of the flakes increased with the increase of the exposure time. The magnitude of micro-bulges and the topcoat roughness increased after a long exposure to sunlight. Flakes and micro-bulges resulted in the loss of the topcoat gloss. ATR-FTIR and XPS analysis indicated that chain scissions of the polyurea C==O group and the polyurethane C―O―C and CO―NH groups occurred, and the degradation products of NH and carbonyl groups formed due to the exposure. The breaking of the chemical structure of the polyurethane resulted in a decrease in its elasticity and in the adhesion of the flakes to its surface.     

Research on the reconstruction of fast and accurate AFM probe model

The AFM image will be distorted due to the tip-broadening effect. It may be mathematically represented as the effect of the tip’s convolution on the real image. As a result, the true geometry of the sample surface can not be obtained. If the tip shape could be known accurately, such distortion can be eliminated with the adoption of disconvolution operation. It is of practical significance in the accurate reconstruction of the AFM image. Among the current tip modeling algorithms, the blind tip estimation algorithm based on mathematical morphology is widely applied. However, it takes much time and has difficulties in defining the optimal noise threshold. In view of the above problems, this paper proposes a new blind tip evaluation method to accelerate the speed of blind tip modeling calculation and realize the accurate reconstruction of the AFM image. The simulation and the experimental results demonstrate the feasibility and effectiveness of the above research method.     

求解一类非线性方程组的Newton-PLHSS方法

基于倾向一侧的对称／反对称分裂(LHSS)迭代方法,提出了一类求解Jacobi矩阵在解x*处为大型稀疏非埃尔米特矩阵的非线性方程组的Newton PLHSS方法,给出了这类不精确牛顿法的两种局部收敛性定理。数值结果验证了该方法的正确性和有效性。     

基于AFM推动的纳米棒建模与操作

研究了AFM推动作用下纳米棒的运动情况,引入了与速度相关的黏滞摩擦力,建立了纳米棒体的运动学模型.在运动学模型的基础上,针对AFM单探针及纳米环境操作不确定性问题,对AFM探针操作参数的设置进行了讨论,提出了虚拟纳米手Z字形稳定操作策略.仿真及实验结果表明:纳米棒的运动学模型能够实时预测推动操作后棒体的瞬心位置,虚拟纳米手Z字形操作策略能够将棒体的位置误差限制在规定误差范围内,实现了纳米棒的稳定、定姿态操作.     

H4SiW6Mo6O40／SiO2在H2O2催化氧化环己酮合成己二酸中的应用

采用溶胶一凝胶法制备了二氧化硅负载硅钨钼酸催化剂．以二氧化硅负载硅钨钼酸（H4SiW6M06040／SiO2）为催化剂,30％H202为氧源,催化氧化环己酮合成己二酸．探讨H4SiW6Mo6O40／SiO2对氧化反应的催化活性,较系统地研究了二氧化硅负载硅钨钼酸用量、反应温度、H。02用量、反应时间等因素对产物收率的影响．实验表明：H4SiW6Mo6O40／SiO2是合成己二酸的良好催化剂;在n（环日酮）：n（H2O2）：n（H4SiW6Mo6O40／SiO2）=100：198：0．124,反应温度为110℃,反应时间3．5h的最佳条件下,己二酸的收率可达86．7％．     

Recent development of peptide self-assembly

Amino acids are the building blocks to build peptides and proteins. Recent development in peptide synthesis has however enabled us to mimic this natural process by preparing various long and short peptides possessing different conformations and biological functions. The self-assembly of short designed peptides into molecular nanostructures is becoming a growing interest in nanobiotechnology. Self-assembled peptides exhibit several attractive features for applications in tissue regeneration, drug delivery, biological surface engineering as well as in food science, cosmetic industry and antibiotics. The aim of this review is to introduce the readers to a number of representative studies on peptide self-assembly.     

纳米压痕过程温度影响的分子动力学研究

建立了基于AFM的单晶铜薄膜纳米压痕过程的三维分子动力学模型,采用Morse势函数计算试件原子与压头原子之间,试件原子之间的相互作用关系.研究了不同温度的纳米压痕过翟中试件变形区域大小、系统能量变化.结果显示单晶铜薄膜的纳米压痕的力学机理是非晶态产生的变形.温度对纳米压痕过程有显著的影响.压痕过程中试件材料变形区域面积随着温度的增高而增加.不同温度下的系统势能-步长曲线的变化趋势基本相同,但是系统势能值随着温度的增加而减小.