回转曲面的可展切曲面

论文系统地提出了构造回转曲面的可展切曲面及它们间映射分析的理论与方法,建立了回转曲面可展切柱面和可展切锥面的数学模型以及曲面间的映射关系。根据回转曲面及其可展切曲面间微分长度比的理论分析,推出了映射中极值映射曲线和等距映射曲线的微分方程,通过整体和局部的变形分析,可以准确地掌握回转曲面与其可展切曲面间映射中的变形情况。     

Surface diffusion

A short review of field emission methods, namely shadowing and fluctuation, for measuring the mobility of adsorbed species on metal surfaces is presented and some results are given.     

Surface characterization

The biocompatibility of commercially pure titanium and its alloys is closely related to their surface properties, with both the composition of the protecting oxide film and the surface topography playing an important role. Surfaces of commercially pure titanium and of the two alloys Ti–6Al–7Nb and Ti–6Al–4V (wt %) have been investigated following three different pretreatments: polishing, nitric acid passivation and pickling in nitric acid–hydrogen fluoride. Nitric acid treatment is found to substantially reduce the concentration of surface contaminants present after polishing. The natural 4–6 nm thick oxide layer on commercially pure titanium is composed of titanium oxide in different oxidation states (TiO2, Ti2O3 and TiO), while for the alloys, aluminium and niobium or vanadium are additionally present in oxidized form (Al2O3, Nb2O5 or V-oxides). The concentrations of the alloying elements at the surface are shown to be strongly dependent on the pretreatment process. While pickling increases the surface roughness of both commercially pure titanium and the alloys, different mechanisms appear to be involved. In the case of commercially pure titanium, the dissolution rate depends on grain orientation, whereas in the case of the two alloys, selective -phase dissolution and enrichment of the -phase appears to occur. © 1999 Kluwer Academic Publishers     

水镁石粉体表面改性及表面能测算

水镁石粉体是聚合物的常用填料,但水镁石极性较大,与基材的相容性也较差,因此必须通过表面改性,降低水镁石粉体表面能,增强亲油疏水性,从而增加与聚合物之间的相容性,而阴离子表面活性剂是合适的改性剂之一。水镁石粉体改性后的表面性能,可以用固体表面能数值的变化来表征,本文选择丙三醇、水、1-溴代萘为探针液体,用直接测定法与Washburn方程间接计算法获得了改性前后水镁石的接触角,通过Lifshitz-van der Waals acid base三参数法计算其表面能。研究结果表明,不同的阴离子基团中,羧酸类、磷酸较之磺酸类硫酸类改性效果有明显优势,表面能的碱分量γ-S和酸分量γ＋S降为0;随着改性剂中非极性链烃的碳原子个数增加,表面能非极性分量γLSW下降很多,最终导致总表面能下降,接触角增加,疏水性增强。     

表面活性剂动态表面张力的测定

平衡法测定的是静止表面的表面张力，但若两相界不断更新，则溶质面表面的扩散和吸附未必能达到平衡本文介绍的动态表面张力的测定试验，就是基於测定到达平衡表面张力的时间。     

钢结构表面应力超声表面波检测技术研究

研究了表面波在金属材料表面的传播速度和表面应力之间的关系,简化了表面波二维平面应力的声弹性关系公式.设计了表面波应力测量的实验系统,对工程中常用的Q235钢表面波声弹性系数进行了标定,实现了一维表面应力的表面波无损检测,且实验精度满足工程检测需要.     

Surface Modification of a-Fe Metal Particles by Chemical Surface Coating

The structure of a-Fe metal magnetic recording particles coated with silane coupling agents have been studied by TEM, FT-IR, EXAFS, Mossbauer. The results show that a close, uniform, firm and ultra thin layer, which is beneficial to the magnetic and chemical stability, has been formed by the cross-linked chemical bond Si-O-Si. And the organic molecule has chemically bonded to the particle surface, which has greatly affected the surface Fe atom electronic structure. Furthermore, the covalent bond between metal particle surface and organic molecule has obvious effect on the near edge structure of the surface Fe atoms.     

Surface Supported Gold–Organic Hybrids: On‐Surface Synthesis and Surface Directed Orientation

The surface‐assisted synthesis of gold–organic hybrids on Au (111) and Au (100) surfaces is repotred by thermally initiated dehalogenation of chloro‐substituted perylene‐3,4,9,10‐tetracarboxylic acid bisimides (PBIs). Structures and surface‐directed alignment of the Au–PBI chains are investigated by scanning tunnelling microscopy in ultra high vacuum conditions. Using dichloro‐PBI as a model system, the mechanism for the formation of Au–PBI dimer is revealed with scanning tunnelling microscopy studies and density functional theory calculations. A PBI radical generated from the homolytic C‐Cl bond dissociation can covalently bind a surface gold atom and partially pull it out of the surface to form stable PBI‐Au hybrid species, which also gives rise to the surface‐directed alignment of the Au–PBI chains on reconstructed Au (100) surfaces.     

圆锥面作为辅助面求作球体切平面

球体切平面作图方法在工程图学中较少研究,论文就单球、双球和三球体公切平面(在各种约定条件下)的形成原理,空间走向、表达形式以及数量作了详尽地分析,提出了利用圆锥面作为辅助面求作球体切平面的方法。对单球、双球和三球切平面作图方法采用了一题两解的办法,并对两种作法进行比较和分析,从而得出正确的结论。     

超声冲击诱发表面纳米化及其对表面完整性的影响

采用不同超声冲击参数处理SMA490BW钢,研究了冲击后试样在低、高倍下的微观组织特征、残余应力及硬度分布等表面完整性能的变化。实验结果表明,经过超声冲击表面处理后,样品表面层晶粒细化为纳米晶,平均晶粒尺寸约为30nm;并在试样表层引入残余压应力,数值最大约为255.5MPa;超声冲击对SMA490BW钢表面能够起到明显的强化作用,与未经处理的试样相比,处理后试样表面硬度最大提高了约66.7%。超声冲击强化处理改善SMA490BW钢的表面完整性的效果与冲击电流、冲击时间之间的关系不遵循单调变化规律,超声冲击参数为20min/1.5A时,试样具有较好的表面完整性,冲击影响层深度约为320μm。     

甲基修饰二氧化硅膜的表面自由能与表面结构

以正硅酸乙酯(TEOS),甲基三乙氧基硅烷(MTES)为硅源,硝酸为催化剂,制备了甲基修饰的二氧化硅膜,研究了MTES改性二氧化硅膜的表面润湿性与表面结构的关系以及MTES改性二氧化硅膜的吸水率.用已知表面张力的液体测定接触角,按扩展的Fowkes式计算试样的表面张力γs及其三组分值γsd(色散力)、γsp(偶极矩力)和γsb(氢键力),用热重分析(TG)法测定二氧化硅膜的吸水率.结果表明,随着MTES/TEOS摩尔比增大,二氧化硅膜的表面自由能显著减小,表面润湿性降低,主要是表面张力中氢键力组分的贡献.X射线光电子能谱分析表明,这是由于二氧化硅颗粒表面Si-CH3基团增加而Si-O和O-H基团减小所致.随着MTES/TEOS摩尔比增大,二氧化硅膜的吸水率降低,疏水性二氧化硅膜的MTES/TEOS摩尔比应大于0.8.     

三维表面偏斜度与陡度的规律研究

使用ADE公司的非接触式表面三维形貌仪对粗糙度标准样板进行系统测试,研究分析了三维表面偏斜度与陡度的规律。结果表明：三维表面偏斜度、陡度与表面的摩擦磨损性能有重要的对应关系,它们是表面微观结构形状的描述,与表面的精度无直接关系;对应不同结构的表面,三维表面偏斜度与陡度在数值上出现了一定的规律性,随机性较强的表面的工作性能明显优于周期性较强的表面,这给我们更加准确地根据零件的使用要求选择不同的加工方法或选择表面结构类型提供了依据;三维表面偏斜度与陡度明显优于二维,三维参数取点于整个区域,更能反映表面微观的特征,测量值更加稳定、可靠。     

Surface spin-valve effect

We report an observation of spin-valve-like hysteresis within a few atomic layers at a ferromagnetic interface. We use phonon spectroscopy of nanometer-sized point contacts as an in situ probe to study the mechanism of the effect. Distinctive energy phonon peaks for contacts with dissimilar nonmagnetic outer electrodes allow localizing the observed spin switching to the top or bottom interfaces for nanometer thin ferromagnetic layers. The mechanism consistent with our data is energetically distinct atomically thin surface spin layers that can form current- or field-driven surface spin-valves within a single ferromagnetic film.     

镯面和一般复曲率面的光线追迹

本文讨论镯面和一般复曲率面的光线追迹;指出一般文献的疏漏;提出解决办法。