Polymer‐Derived SiOC Nanotubes and Nanorods via a Template Approach

Abstract

The synthesis of silicon‐based ceramic nanowires and nanotubes produced by liquid infiltration of commercially available silicon‐based polymers, namely polysilazane (CerasetTM, polyureasilazane), polysilazane VL20 (Kion Coop.) and polycarbosilane (Starfire Systems SP‐MatrixTM) in alumina templates with defined pore channels is reported. After polymer infiltration, pyrolysis of the preceramic polymer at 1000–1100 °C in Ar atmosphere followed by dissolution of the alumina templates, ceramic nanowires and nanotubes were obtained. In the case of the polymeric ceramic precursor polysilazane, nanorods were formed only if an oligomeric fraction was distilled off from the polymer precursor prior to infiltration of the template. In contrast, the formation of nanotubes was found after infiltration of the untreated (crude) preceramic polymer. Despite the fact that the preceramic polymers contain silicon, carbon and nitrogen and no oxygen as constituting elements, the final ceramic nanostructures obtained were analysed consistantly by various techniques to contain oxygen and only limited amounts of carbon and nitrogen after pyrolysis consistent with a composition as silicon oxycarbide (SiOC). This behaviour strongly indicates that the porous alumina template may significantly influence the pyrolysis process of the precursors thus affecting the chemical composition of the final ceramic products. It is a central result of our study that the alumina templates are not inert under the reaction conditions employed instead acting as a reaction partner at the high temperatures employed during pyrolysis. Taking this into account, reaction of otherwise inert amorphous alumina with inorganic polymers at elevated temperatures could lead to a directed synthesis of new ceramic compositions.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

SiOCN Functionalized Carbon Nanotube Gas Sensors for Elevated Temperature Applications

“…The response is reversible and returns to its original conductance after cooling. This reversible increase in conductance with temperature change is an indication of semiconductive behavior and the similar trends are reported for semiconductive CNT thin films . The second thermal cycle (from 50°C to 400°C) caused a sudden increase in conductance after 250°C and reached a value more than twice that of the starting conductance at 400°C.…”

Evidence for electrohydrodynamic convection as a source of spontaneous self-ordering in porous anodic alumina films

“…A considerable part of contemporary research in nanotechnology is linked to self-organized materials, such as porous anodic aluminium oxide (PAOX) layers. 1 For instance, porous alumina membranes can be used in nanofluidic systems, [2][3][4] for the template synthesis of rod-like nanostructures, 5 or even as nanoreactors, which can regulate the degree of polymerization by the spatial confinement effect. 6 For all these applications, the facile adjustment of both the structural parameters and the nonstoichiometric chemical composition of PAOX would be highly desirable.…”

Conceptual Progress for Explaining and Predicting Self-Organization on Anodized Aluminum Surfaces

“…Self-organized PAA architectures have recently received growing interest in many innovative research areas, such as nano-optics and nanophotonics [ 21 , 22 , 23 , 24 ], surface-sensitive optical spectroscopy [ 25 , 26 , 27 , 28 , 29 , 30 ], biological and chemical sensors [ 31 , 32 ], nanofluidic devices [ 33 ], nanoreactors [ 34 ], biotechnology and biomedicine [ 35 , 36 , 37 , 38 , 39 ], or environmental decontamination [ 40 ]. They also frequently serve as templates for nanotechnology, e.g., for the synthesis of highly uniform rod-like or planar porous nanomaterials that cannot be achieved directly by the electrochemical method (readers who need a quick familiarization with the morphology and composition of PAA templates that have uniform cylindrical pores may turn to Figure S1 in the Supplementary Materials file ) [ 1 , 41 , 42 , 43 ]. Moreover, the fabrication of self-organized PAA with controllable size and arrangement of pores in many instances offers a cost-effective alternative to conventional nanolitographic approaches.…”