Multifunktionale zellulosebasierte Fasern, Grenzschichten und Verbundwerkstoffe
Final Report Abstract
In this project, we mainly developed two processes to prepare multifunctional materials based on cellulose and carbon nanotubes: one is dip coating process for cellulose-coated fibres or fabrics and their corresponding cellulose fibre/polymer composites; another one is solution blending process for cellulose/CNT composites including films and aerogels. Both of them were simple and efficient. Especially, the blending process was carried out in a new and environmentally friendly way by dissolving cellulose and dispersing CNTs homogeneously in aqueous alkaline/urea solution, which provided a novel platform for preparation of functional cellulose-carbon nanotube composites. Through these processes we had successfully distributed the MWCNTs both on the surface of cellulose and into the matrix of cellulose materials. A series of functional materials based on cellulose and CNTs with different forms and different structures, including one-dimensional (1D, such as cellulose-coated fibres), two-dimensional (2D, such as cellulose/CNT films) and even three-dimensional (3D, such as cellulose/CNT aerogels), were thus prepared. Based on systematic investigation of these produced materials, we found that the cellulose-based materials with different distribution of CNT networks would exhibit different properties and applications. The interconnected MWCNT networks formed on the fibre surfaces via dip coating process had good electrical conductivity. The ultra-thin features of them and the hydrophilic feature of cellulose fibres provided high sensitivity to various local changes on the micro scale. Single MWCNT-cellulose fibres exhibited good sensing abilities towards varies environmental stimuli such as tensile strain, temperature, environmental humidity. Especially, they were demonstrated to be used as highly sensitive, well reversible and reproducible sensor for water, with a sensitivity of 100 - 8000%. The MWCNT-cellulose fibres with high resistance can even serve as simple and efficient electrochemical water “switches”. Moreover, these functional fibres exhibited good sensitivity to electrolytes aqueous solution. Our work also demonstrated that the composites fabricated using the MWCNT-cellulose fabrics exhibited controllable anisotropic electrical properties and significantly high dielectric constants. The MWCNT-cellulose fibres could be used as embedded sensors or surface-mount strain gauges to monitor crack initiation/propagation and strain/stress in different composite structures and their interphases, respectively. By using solution blending process, cellulose/CNT composites were also prepared by dispersing CNTs into cellulose matrixes. Uniform dispersion of CNTs, in combination with favourable CNT-cellulose matrix interaction, causes a better ductility and higher toughness of the composite materials, as well as an enhanced thermal stability. The CNT network formed within the cellulose matrix introduced good conductivity and also led to impressive multifunctional sensing abilities towards various environmental stimuli (tensile strain, temperature, environmental humidity, etc.). Especially, the fractional resistance of the composite films exhibits highly linear and repeatable correlation to tensile strain. The useful linear strain range for these composite films is 7 - 13 % strain with the value of GF in the range of 0.6 - 1.2. This unique characteristic indicates their excellent sensing ability as strain gages. Furthermore, these electrically conductive films composed of CNTs and cellulose could also serve as unique sensors for liquids. They exhibited rapid response and high sensitivity for liquid water, with a relative electrical resistance change of 5500 - 500. This unique performance is well reproducible, highly stable even for long-term use. Since the swelling behaviour of cellulose is varied in different liquids, it is possible to distinguish water from other solvents. Thus, these probes can be widely used in many fields such as detection of water leakages and water content determination. Furthermore, cellulose/CNT composite aerogels with both nanostructured solid networks and nanoporous networks showed good sensitivity to ambient pressure, which provides the potential applications for detection of gases or various organic vapours. Due to their unique characteristics and excellent sensing abilities, therefore, materials based on cellulose and CNTs have great opportunities to be further developed and used in many fields as smart and functional materials.
Publications
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Multi-functional multi-walled carbon nanotubejute fibres and composites. Carbon, 2011, 49, 2683–2692
Zhuang R, Doan, T T L, Liu J, Zhang J, Gao S, Mäder E
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Electrically conductive aerogels composed of cellulose and carbon nanotubes. J. Mater. Chem. A, 2013, 1, 9714–9720
Qi H, Mäder E, Liu J
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Multifunctional films composed of carbon nanotubes and cellulose regenerated from alkaline–urea solution. J. Mater. Chem. A, 2013, 1, 2161-2168
Qi H, Liu J, Gao S, Mäder E
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Unique water sensors based on carbon nanotube-cellulose composites. Sens. Actuator B-Chem., 2013, 185, 225–230
Qi H, Mäder E, Liu J
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Cellulose fibres with carbon nanotube networks for water sensing. J. Mater. Chem. A, 2014, 2, 5541–5547
Qi H, Liu J, Deng Y. Gao S, Mäder E
