关于材料表面微纳米颗粒对材料功能性影响的判定新方法

Common material properties （e.g. hardness, tensile modulus ａnd strength, poisson?s ratio） are well known. On the other hand, properties of thin layers ａnd micro volumina can differ significant from those data, in particular for micro/nano-particle systems. AFM ａnd FFM methods work with excellent lateral, topographic ａnd force resolution but often do not provide testing-situations close to practical applications, e.g. high pressure flat contact within micro wear ａnd micro friction investigations. Optimization of friction/wear-properties of multi micro-area contact especially of relevance on curved ａnd topographically structured surfaces need access to measurement technique, that covers the gap between micro ａnd nano scale. The results presented here are done with the UST （Universal Surface Tester） to determine the influence of incorporation of micro/nano-particles ａnd their distribution on micro echanical ａnd functional properties of polymer materials close to the surface.
1. COMPOSITE MATERIALS
During the last decade there was an increase in the usage of composite materials even for consumer products. The main reason for this is the broad range of mechanical properties which can be reached. Tailor-made properties are possible for nearly each application. In a lot of cases carbon is used as the appropriate filler. Carbon black is used for rubber whereas carbon fibres are used for optimizing mechanical properties like the young’s modulus, tear strength ａnd wear resistance. Even the dynamical properties of composite
materials are better.
2. NANO- AND MICROCOMPOSITE MATERIALS
Another increase in properties is possible by usage of micro- or nanoparticles. For example carbon shows a whole family of unusual sp?-hybridized modifications like fullerenes [1] ａnd carbon nano tubes [2]. Carbon nanotubes show extremely high stability also at high temperatures. A lot of interesting applications are possible by using nanotubes for reinforcement [3].
Table 1 shows the properties of typical fibres in comparison to carbon nanotubes [4].
“Table 1. Typical Properties of fibres.”
Property carbon fibre carbon nanotube
Young’s Modulus （GPa） 230 1000
Tear strength （GPa） 4 30
Length/Diameter ratio 《100 》1000
3. SURFACE PROPERTIES
As mentioned micro- ａnd nano particles are used for reinforcement of the material. In a lot of cases the bulk properties like modulus are not so important. Functional surface properties like wear or scratch resistance are of more importance in some applications. Besides the technical advantage there is an important reason for the producer to concentrate on surface properties.
The appearance of a surface let a customer judge the value of the product. Therefore it is necessary to improve the surface resistance over time. Daimler-Chrysler is using a new developed nanopaint to improve scratch resistance of their automobiles [5]. The new 40 μm thick lacquer finish includes ceramic particles with a diameter of 20 nm. Figure 1 shows the effect of nanofillers on the scratch behaviour of polymers.

Fig. 1. Scratch on an epoxy with ａnd without nanofillers [6].
The use of lacquer or special coatings improve the surface properties like elasticity, hardness, friction without using a big amount of material. environmental resistance ａnd chemo mechanical resistance are also improved.

4. MICRO STRUCTURE ANALYSIS （MISTAN?）
All measurements are done with an Universal Surface Tester （UST?） which is a new ａnd patented measuring ａnd testing device for continuously determining the deformation behaviour of a material in a region near its surface. The UST yields measured values of : permanent, plastic, elastic, viscoelastic ａnd total deformation, micro hardness, hardness structure, abrasion ａnd scratch resistance, creeping ａnd relaxation, roughness, haptic ａnd softness, cutting ａnd piercing resistance, thickness ａnd structure of layers ａnd of microfriction. All this values are obtained with a high precision with only one single instrument. Whereas existing procedures, e.g. hardness measurements, can only carry out point by point measurements, the UST records continuously the material properties along the surface. If required, the roughness parameters are determined from the surface profiles according to the DIN or ISO standards depending on the used tip geometry ａnd the applied forces. Since the results include formation of every single deform