Improvement of Wear Resistance in Alumina Matrix Composites Reinforced with Carbon Nanotubes

Abstract

Alumina matrix composites reinforced with carbon nanotubes (CNTs) fabricated by CNT purification, mixing, compaction, and sintering processes, and the effects of the CNT addition on wear resistance were investigated in relation to the relative density, hardness, and fracture toughness. Wear resistance and fracture toughness were measured by the dry sliding wear test method and the indentation fracture test method, respectively. Zero to~3 vol pct of CNTs were homogeneously distributed in the composites, although some pores existed. The wear resistance and fracture toughness increased with an increasing CNT fraction, but the composite specimen containing 3.0 vol pct of CNTs hardly showed an increase over the specimen containing 2.25 vol pct of CNTs. Observations of worn surfaces revealed that the wear mechanism involved both the abrasive and delamination wear modes in the specimens containing 0 tõ 0.75 vol pct of CNTs, whereas the surface was worn largely in an abrasive wear mode in the specimens containing 1.5 to~3.0 vol pct of CNTs. This was because CNTs helped to change the delamination wear mode to the abrasive wear mode by preventing crack initiation and propagation at alumina grains. The fracture toughness increase provided beneficial effects in the resistance to crack initiation and propagation, the reduction in delamination wear on the worn surface, and the consequent improvement in wear resistance. Because the effect of the porosity increase due to the CNT addition unfavorably affected the improvement of wear resistance and fracture toughness in the specimen containing 3.0 vol pct of CNTs, the appropriate level of CNT fraction was 1.5 to~2.25 vol pct.

Multi-walled carbon nanotube–Al2O3 composites: Covalent or non-covalent functionalization for mechanical reinforcement

“…The calculated microhardness values (Table 1) are the average of 10 measurements. The Vickers microhardness of the composites (17.8-19.8 GPa) is lower than that of the Al 2 O 3 sample (21.3 GPa), in good agreement with earlier results [13,14]. The transverse fracture strength (r f ) was measured by the three-point bending method on eight specimens with dimensions of about 1.8 Â 1.8 Â 18 mm 3 .…”

Effect of Composite Alumina and Carbon Nanotubes on Cell Viability In Vitro

“…Recently, several studies have proven that composite materials from aluminum oxide and multiple wall carbon nanotubes (MWCNT) improve mechanical properties of these ceramic materials, increasing up to 10% in flexural strength, if comparing with monolithic aluminum oxide [6]. Additionally, the enhanced aluminum oxide matrix with carbon nanotubes which is purified by acid treatment shows better wearing resistance compared with ceramic materials without enhancement [7].…”