Abstract
A novel building block material for the generation of non-brittle ceramic composites consisting of micron-sized alumina platelets homogeneously coated with multi-wall carbon nanotubes (MWCNTs) bound to their surface is described. The MWCNT phase is grown in situ from immobilised metal catalyst particles using chemical vapour deposition techniques. In-depth Raman and scanning electron microscope studies revealed that this approach solves the typical issue of MWCNT-agglomeration in ceramic matrices and paves the way to excellent control over MWCNT purity and concentration within the resulting composite material. Moreover, we show that the preparation of the catalyst is the most important factor for the generation of uniformly distributed MWCNTs of high-quality on these platelets. With these MWCNT-coated alumina building blocks, we have manufactured nacre-like biomimetic composites using spark plasma sintering. The resulting composites are electrically conductive and three-point bending tests show a transition from brittle/catastrophic failure to graceful failure, holding great promise towards multifunctional, tough and strong lightweight ceramic composite manufacturing.
Highlights
Ceramics exhibit extraordinary material properties such as chemical inertness, high temperature resistance, hardness and strength
It is well established that hydrogen can significantly increase multi-wall carbon nanotubes (MWCNTs) yield in chemical vapour deposition (CVD) when included in the carbon precursor mixture [51,52]
Scanning electron microscopy (SEM) images show that including hydrogen during synthesis enhances MWCNT growth by growing longer MWCNTs: This means that the catalyst is kept active for a longer time through either one or a combination of the mechanisms mentioned above
Summary
Ceramics exhibit extraordinary material properties such as chemical inertness, high temperature resistance, hardness and strength. Despite these attractive properties, ceramics are of limited use for advanced engineering solutions [1], especially where major load-bearing is required. Ceramics are of limited use for advanced engineering solutions [1], especially where major load-bearing is required The reason for this lies in the low fracture toughness and extreme brittleness of ceramics. Nature has provided a solution to this challenge; several biomaterials have evolved to combine fracture toughness with strength. For instance, has received much attention [4,5] as it combines both properties through its ‘brickand-mortar’ microstructure [6]. Nacre possesses a hierarchical structure consisting of a hard phase of aligned CaCO3 platelets
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