Electrically Conductive Multiwall Carbon Nanotubes/Poly(vinyl alcohol) Composites with Aligned Porous Morphologies

Abstract

Electrically conductive multiwall carbon nanotubes (MWNTs)/poly(vinyl alcohol) (PVA) composites with aligned porous structure were obtained by a directional freezedrying process. The results show that the morphologies of the MWNTs/PVA composite can be tailored by adding different contents of MWNTs in the PVA matrix. Because of the aligned porous structure of the MWNTs/PVA composites, the conductivity property of MWNTs/PVA composite does not coincide absolutely with the universal percolation theory. In the aligned porous MWNTs/PVA composites, the existence of the micro-pores destroys the uniform distribution of the conductive network along the direction perpendicular to the aligned pores and results in a nonuniform distribution conductive network. When being used to monitor flowing vapors in pipes, compared with a film sensor with the thickness from several decades to hundreds of microns, the aligned porous conductive MWNTs/PVA composite with micron-sized pores should be a much better sensor.

Freeze casting – A review of processing, microstructure and properties via the open data repository, FreezeCasting.net

“…Dense composite materials may also be fabricated by infiltrating freeze-cast skeletons with a secondary phase. Thus far, ceramic/metal [52,[106][107][108][109][110][111][112][113][114][115][116][117][118][119], ceramic/polymer [120][121][122][123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138], metal/polymer [139][140][141][142][143], and metal/metal [144,145] composites have been demonstrated.…”

Facile preparation of carbon nanotube aerogels with controlled hierarchical microstructures and versatile performance

“…Therefore, the large ice crystals are formed at the beginning of freezing process, and some crystals grow continuously to be huge ice particles. The growth process will cease when the ice particles are restricted by compact CNT sheets (walls) between them [18,[26][27][28]. During lyophilization process, the huge ice particles are removed and the large pores (e.g., >100 μm) appear in CNT aerogels, while the small ice particles (existed inside CNT sheets in frozen CNT slurries) result in the formation of the nano-scale pores.…”

“…Therefore, the pores in the aerogels are relatively small. Subsequently, the well-known unidirectional freezing 3 method is developed to fabricate the CNT aerogels with highly ordered pores [18,[26][27][28][29][30][31][32][33]. In addition, the so-called critical-point-drying technique can prepare ultralight aerogel monoliths [12,14], but the preparation processes require complicated and/or strict conditions.…”

Regular Aligned Porous Waterborne Polyurethane Composite Obtained by a Directional Freeze-Drying Process

“…The directional freeze-drying process, based on freezing of water slurries and subsequent freezing-drying steps, has proved to be an easily-controlled route to fabricate aligned porous materials with two-dimensional surface patterns or three-dimensional monolithic structures [6,7]. This novel process does not involve any chemical reaction and can avoid potential complications associated with by-products or purification procedures [8][9][10]. Nowadays, the directional freeze-drying process has been used to prepare aligned porous materials such as chitosan/vacuum-stripped grapheme, poly (3,4-ethylenedioxythiophene), poly(styrenesulfonate), poly(vinyl alcohol), etc [4,11,12].…”