In situ silica reinforcement was applied to the acrylonitrile—butadiene rubber (NBR) vulcanizates. The amount of in situ silica introduced in the NBR vulcanizates was limited due to the high polarity of NBR. The presence of γ-mercaptopropyltrimethoxysilane (γ-MPS) in the NBR vulcanizate increased the conversion of TEOS in the sol-gel reaction and resulted in the higher amount of in situ silica, compared to the system without γ-MPS. The obtained silica was very fine and dispersed very homogeneously. In situ sol-gel reaction of TEOS in the NBR vulcanizates mixed with a conventional silica (VN-3) was also carried out. The reinforcement efficiency in this system increased with the increase of the amount of mechanically mixed conventional silica. Interestingly, the hysteresis loss decreased by the in situ filling of silica.
In situ silica reinforcement for the acrylonitrile-butadiene rubber (NBR) vulcanizates, which were premixed with a conventional silica (VN-3) and γ-mercaptopropyltrimethoxysilane (γ-MPS), was achieved by the sol-gel reaction of tetraethoxysilane (TEOS) using ethylenediamine. It was observed that the reinforcement efficiency tended to increase with the increase of mechanically premixed conventional silica. From the observations of transmission electron microscopy and scanning electron microscopy, the simultaneous use of VN-3 and γ-MPS was found to promote the formation of large silica particles and clusters with a relatively good dispersion by the sol-gel reaction of TEOS in the NBR vulcanizate. The results of hysteresis measurements supported this promotion. It was considered to be due to the surface modification of VN-3 by the sol-gel reaction of TEOS and the presence of γ-MPS which worked as a dispersion agent for silica particles. The relationship between the mechanical properties and the morphology of the in situ silica filled vulcanizates is discussed.
Ring structures inside voids in the SiO2 layer on a Si(100) substrate, which are concentrically formed by repeating thermal annealing in vacuum, have been investigated by scanning electron microscopy and atomic force microscopy. We demonstrate that slight exposure of the surface to volatile organic compounds during a cooling process significantly affects the formation of the ring structures. This result clearly shows that the key to ring-structure formation is surface adsorption of carbon atoms, which probably suppresses surface migration of silicon atoms. Our research provides a novel technique for the fabrication of nanostructured semiconductors for such applications as quantum effect devices.
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