Scientists at the CSIC and at the Jožef Stefan Institute have developed a method to combine at the nanoscale cellulose nanofibers with ceramic nanoparticles such as alumina and zirconia, resulting in mechanically strong and highly electro-conductive ceramic materials that can be subjected to different types of machining, such as green machiningm or electro-discharge machining.
Machined green body (left) and electro-discharge machined ceramic after sintering (right)Nanocellulose is a material with a huge potential in a variety of technological fields due to its properties like optical transparency, low specific weight, and mechanical strength. In addition, nanocellulose is a versatile precursor to nanocarbons with multiple applications.
The process developed by the scientists consists in the preparation of homogeneous aqueous slurries of ceramic nanoparticles and hydrophilic cellulose nanofibers, which remain homogeneously dispersed in the ceramic matrix after pressing, resulting in fiber-reinforced, strong ceramic green bodies, which can be easily machined.
Upon sintering the cellulose, nanofibers convert to carbon fibers within the consolidated ceramic matrix and infer high electric conductivity to the ceramic. The content of conducting carbon in the ceramic is very low, which guarantees the preservation of the good mechanical properties of the ceramic.
It is the first time that ceramic nanocomposites made of nanocellulose and ceramic nanoparticles are produced as a stable gel which can be transformed into strong (Hv=20 GPa) and electro-conductive ceramics (400 S/m).
These ceramics can be used as resistors, electrodes, heating elements, resonators, or as molds machined by non-conventional shaping techniques such as electro-discharge machining or green body machining.
The use of natural, hydrophilic nanofibers instead of synthetic, hydrophobic carbon fillers like carbon nanotubes or carbon black allows for aqueous processing. Nanoscale dimensions of the cellulose nanofibers and the good mixing with ceramic nanoparticles slurries leads to extremely low percolation thresholds for electrical conductivity. Machinable green bodies and highly conducting sintered ceramics are obtained.
Contact:
Marisa Carrascoso Arranz
Deputy Vice-Presidency
for Knowledge Transfer- CSIC
Tel.: +34 915681533
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