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Eingeladener Vortrag
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In der vorliegenden Arbeit wurden mittels eines Rasterkraftmikroskopes (Scanning Force Microscope, SFM) nanomechanische Experimente zur Charakterisierung des Grenzbereiches (Interphase) zwischen einer polymeren Matrix und anorganischen Verstärkungskomponenten durchgeführt. Ziel der Untersuchungen war es, mit Hilfe einer sinusförmigen Modulation der Auflagekraft zwischen SFM-Spitze und Probe innerhalb der polymerseitigen Interphase vorhandene Steifigkeitsgradienten zu detektieren sowie ihren Verlauf zu charakterisieren. Es konnte gezeigt werden, dass die Steifigkeitsmessung im SFM die Möglichkeit bietet, Grenzphasen über die lokalen Änderungen im Elastizitätsmodul quantitativ zu charakterisieren.
Laser ablation of single-crystalline indium phosphide (InP) was performed in air by means of linearly polarized Ti:sapphire femtosecond-pulses (800 nm, 130 fs, 10 Hz). As a result of the first laser pulses, several morphological changes (crater formation, rim formation, ripple structures and cones) were observed. These effects were explored using force modulation microscopy (FMM), a technique based on scanning force microscopy (SFM), allowing the simultaneous imaging of both topography and local stiffness at a high lateral resolution. The first laser pulse induces the formation of a protruding rim (height <20 nm, width ~300 nm) bordering the ablated crater. A Fourier-analysis of the multi-pulse generated topographies reveals the formation of wavelength-sized periodic ripples (modulation depth <100 nm) with an orientation perpendicular to that of the electric field vector of the laser radiation. Besides these morphological alterations, also material modifications were observed in the irradiated regions by means of the FFM technique. Within the ablated craters, local stiffness variations were found revealing an inhomogeneous material composition/structure as a consequence of the femtosecond pulse laser treatment.
Investigation of interphases between thermoplastic and thermosetting polymers - an AFM approach
(2002)
Beyond measuring the topography of surfaces, scanning force microscopy (SFM) has proved to be valuable both for mapping of various materials properties and for modifying surfaces via lithography techniques. Thus, SFM has gained relevance as a surface analysis technique as well as a tool for nanoscale engineering purposes. Different kinds of tip-sample interactions are exploitable, e.g. mechanical, thermal and electrical ones. Owing to its versatility, SFM has found plenty of applications in polymer science. Among others, the examples reported on in this review article encompass issues related to commodity polymers, various polymer-based composites, polymer blends, or ferroelectric polymers. For instance, stiffness imaging is elucidated as a technique for detecting interphases occurring in composites with inorganic fillers. The described applications are mainly related to mechanical and electrical tip-sample interactions. The respective fundamentals are outlined as well as some aspects of the measurement of materials contrasts. The presented techniques of nano-scale modification are a dynamical sort of plowing lithography and electrical poling, both performed by means of SFM-probes.