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In the bulk polycrystalline ceramic–carbon nanotube ( CNT ) composites developed to date, reinforcing CNT s have been present just at the matrix grain boundaries, with the grain interiors being nearly completely devoid of CNT ; thus severely limiting the improvements achieved in fracture and wear properties. Against this backdrop, bulk polycrystalline Al 2 O 3 ‐based composites, having multi‐walled CNT s ( MWCNT s) present within the matrix grain interiors (not just at grain boundaries), have been developed in this work for the first time.

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Abstract

In the bulk polycrystalline ceramic–carbon nanotube ( CNT ) composites developed to date, reinforcing CNT s have been present just at the matrix grain boundaries, with the grain interiors being nearly completely devoid of CNT ; thus severely limiting the improvements achieved in fracture and wear properties. Against this backdrop, bulk polycrystalline Al 2 O 3 ‐based composites, having multi‐walled CNT s ( MWCNT s) present within the matrix grain interiors (not just at grain boundaries), have been developed in this work for the first time. Such microstructure development has been rendered possible by an innovative, but facile, wet‐chemical synthesis route (sans ball‐milling) involving incorporation of well‐dispersed MWCNT s directly into matrix sol, followed by rapid gelation (within a few seconds) and sintering (inclusive of crystallization step). Intragranular MWCNT reinforcements (in “sol–gelled” composites) led to significant improvements in indentation‐induced crack propagation resistances and abrasive wear resistances, as compared to “conventionally” prepared Al 2 O 3 – MWCNT composites (i.e., “ball‐milled” counterpart) having the same contents of MWCNT , but present only at grain boundaries. Wear rates recorded with the “sol–gelled” Al 2 O 3 ‐2.5 vol% MWCNT are lower than those for monolithic Al 2 O 3 and “ball‐milled” counterpart by ~95% and ~90%, respectively. Such improvements, as never achieved before, are a consequence of reinforcing the matrix grain interiors with MWCNT s.

Key findings

  • In the bulk polycrystalline ceramic–carbon nanotube (CNT) composites developed to date, reinforcing CNTs have been present just at the matrix grain boundaries, with the grain interiors being nearly completely devoid of CNT; thus severely limiting the improvements achieved in fracture and wear properties.
  • 5 vol%MWCNT are lower than those for monolithic Al₂O₃ and “ball‐milled” counterpart by ~95% and ~90%, respectively.
  • Such improvements, as never achieved before, are a consequence of reinforcing the matrix grain interiors with MWCNTs.

Keywords

CrystalliteComposite materialBall millCarbon nanotubeGrain boundaryNanotube

Identifiers

DOI
10.1111/jace.14425
Journal
Journal of the American Ceramic Society
Year
2016