Investigation of yttria-doped alumina nanocomposites reinforced by multi-walled carbon nanotubes

Magnesia tuned multi-walled carbon nanotubes–reinforced alumina nanocomposites

“…A further drop in the grain size by 5 and 28% was observed in the case of the PL-sintered nanocomposites tuned with 300 and 600 ppm MgO, respectively, as shown in Fig. 6e and f. In this context, it may be assumed that the MWCNTs are not present at all of the Al 2 O 3 grain boundaries to act as a pinning agent, because some studies showed that MWCNTs could be dispersed homogenous only up to very low levels (2 wt.%) [20]. Therefore, grain refinement in the tuned nanocomposites is probably due to the precipitates of magnesium-aluminate-spinel phase (MgAl 2 O 4 ) that were present throughout the microstructure and formed thermodynamically from the MgOAl 2 O 3 system through phase transformation process [19].…”

“…Studies on the MWCNT-reinforced ceramics described that an adequate dispersion is attainable for up to 2 wt.% MWCNT reinforcement with further additions always resulting in poor quality nanocomposites, due to severe MWCNT agglomeration [12,16,20]. Keeping this in view, a wet chemistry route was adopted to disperse MWCNTs homogenously into the Al 2 O 3 matrix as described elsewhere [14].…”

“…For example, small amounts (b 1000 ppm) of Y 2 O 3 doping into monolithic Al 2 O 3 and ZrO 2 -reinforced Al 2 O 3 nanocomposites have shown notable improvements, resulting in high densities, defect-free microstructures and enhanced mechanical properties [19]. A recent study on the Y 2 O 3 tuned Al 2 O 3 -CNT nanocomposites reported a higher (N 99%) density, fivefold grain refinement and toughness enhancement of 40%, compared with the reference monolithic Al 2 O 3 [20]. Similarly, small amounts of MgO (300 ppm) have been reported to reduce the effective sintering temperatures and restrict grain growth of Al 2 O 3 reinforced with 5 vol.% silicon carbide (SiC) [21,22].…”

“…In this perspective, microstructural modification of pure Al 2 O 3 and Al 2 O 3 -based composites containing rare-earth metal oxides such as magnesia (MgO), cerium oxide (Ce 2 O 3 ), lithia (Li 2 O) and yttria (Y 2 O 3 ) is an effective practice [17][18][19][20]. For example, small amounts (b 1000 ppm) of Y 2 O 3 doping into monolithic Al 2 O 3 and ZrO 2 -reinforced Al 2 O 3 nanocomposites have shown notable improvements, resulting in high densities, defect-free microstructures and enhanced mechanical properties [19].…”

Preparation and Catalytic Activity of M2O3/CNTs (M = Y, Nd, Sm) Nanocomposites by Solvothermal Process

“…Rare-earth oxide (M 2 O 3 ) nanoparticles have received considerable attention because of their applications in various fields, such as advanced ceramics, superconducting materials, luminescence materials, oxygen sensor, and catalysis [1][2][3][4]. In the past years, all kinds of one-dimensional and twodimensional rare-earth nanostructures, such as rods, wires, tubes, and plates, have been synthesized by numerous groups [5,6].…”