Atomic force microscopic micrographs of PE reveal the fibrillar morphology of the uniaxially oriented material. Microfibrils with diameters in the range 20-90 nm are aligned parallel to the extrusion direction. In the smaller scale images the oriented patterns were assigned to the individual polymer chains. The surface texture pattern shows chain overlapping as a result of the extrusion process. Parts of extended chains were also found. AFM responses of individual methylene groups have been resolved

Atomic force microscopy on polymers and polymer related compounds: 1. Cold-extruded polyethylene

Atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) have been used to investigate changes in topography and surface chemical functionality on PAN-based carbon fibres exposed to low-temperature, lowpower, oxygen plasmas. Unsized, type II, Cellion 6000 carbon fibres were treated in oxygen plasmas for 2–60 min at a power of ∼25 W. Increasing treatment time caused an increase in oxidation from surface alcohol(ether) to carbonyl and carboxyl species, but the total amount of oxidized carbon near the surface remained constant. SEM confirmed that treatments longer than 15 min resulted in pitting on the fibre surface, but even treatments of 60 min did not significantly reduce the overall fibre diameter. AFM showed surface morphology changes after oxygen plasma treatments for 2 and 15 min. 1 μm×1 μm AFM scans of untreated fibres showed processing grooves with a distribution of depths. Enlarged images along these grooves revealed that their walls were smooth. Oxygen plasma treatments of 2 min roughened fibre surfaces and created holes of the order of 50 nm evenly distributed with a spacing of 150 nm along the bottoms of the grooves. Treatment for 15 min smoothed the overall topography and resulted in smaller holes, of the order of 5–10 nm, with a spacing of < 50 nm. Calculated RMS roughnesses from the AFM data showed an initial increase in roughness with treatment, followed by a decrease to final values lower than those for untreated fibres.

AFM, SEM and XPS characterization of PAN-based carbon fibres etched in oxygen plasmas

Ordered structures observed by scanning tunnelling microscopy at atomic scale on carbon black surfaces

The creation of a new family of scanning probe techniques is one of the most exciting events in surface analysis in the last decade. The unique results have been achieved with the main representatives of these techniques—scanning tunneling microscopy (STM) and atomic force microscopy (AFM)-in the visualization of topographic and electronic features in the atomic scale. These new methods attracted many research teams. In a relatively short time, surfaces of different materials (metals, semiconductors, inorganic layered compounds, organic layers, single crystals, polymers, and biological objects) were examined by these techniques. This review is based on ambient conditions STM and AFM experiments conducted at the Materials Research Center of Freiburg University. Two main aspects of the results of imaging transition metal chalcogenides and halides, conductive organic salts, and polymers are emphasized. One is related to interpretation of the images, with the separation of the contributions of the el...

Surface Characterization of Materials at Ambient Conditions by Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)

Study of carbon fiber surfaces by scanning tunnelling microscopy, part i. carbon fibers from different precursors and after various heat treatment temperatures

The experimental results obtained by scanning tunneling microscopy (STM) studies of different carbon fibres are presented and discussed The comparative analysis of the STM images at scales from hundreds of nanometers down to atomic scale reveals the differences of surface features for carbon fibres processed from different precursors, polyacrylonitrile fibres and pitch The high temperature treatment of carbon fibres — the so-called graphitization process — as used to improve the stress modulus induces drastically increased ordering phenomena at the atomic level Structural information obtained by STM on the surface of the fibres as well as in their cross sectional areas is discussed in comparison with known results of diffraction studies STM appears to be the new powerfull technique for the detailed structural studies of surfaces of carbon fibres The perspectives of these studies are under discussion

J. B. Donnet

Papers

Characterization of surfaces of carbon fibres by scanning tunneling microscopy