Properties of MWCNTs added Si3N4 composites processed from oxidized silicon nitride powders

Abstract

Si 3 N 4 /3 wt.% multi-walled carbon nanotubes (MWCNTs) composites were prepared from oxidized α-Si 3 N 4 powders and sintering additives by hot isostatic pressing (HIP). The Si 3 N 4 powders were oxidized at 1000°C in ambient air environment for 10 and 20 h and the powder mixture was sintered at 1700°C for 3 h under the pressure of 20 MPa in nitrogen. The relationship between oxidation, microstructure, tribology and mechanical properties was studied. The dispersion of MWCNTs was not optimal, as they were found mainly in the form of bundles between the β-Si 3 N 4 grains. Neither Si 2 N 2 O nor other oxide phase were observed after the sintering. This was probably caused by the presence of MWCNTs at the grain boundaries of the Si 3 N 4 grains causing reduction of oxide phases. The density, hardness, bending strengths and friction coefficient of the composites increased with the oxidation time of the Si 3 N 4 powder.

Silicon Nitride-Based Composites with the Addition of CNTs—A Review of Recent Progress, Challenges, and Future Prospects

“…Carbon may cause a mass loss in the sintered samples during sintering because of the reduction of SiO 2 . The damage to CNTs during the sintering process was observed by the researchers [15,42].…”

“…In the case of CNT-reinforced silicon nitride composites, a wide range of sintering additives of metal oxides or non-oxides were used. So far in the literature, these additives (TiO 2 , Y 2 O 3 , Al 2 O 3 , MgO, SiO 2 , AlN, HfO 2 and ZrO 2 ) were reported as sintering additives for the fabrication of CNT-reinforced silicon nitride composites [13,15,18,[42][43][44]. The most often used sintering additives were Y 2 O 3 , Al 2 O 3 and ZrO 2 .…”

Amorphous, Carbonated Calcium Phosphate and Biopolymer-Composite-Coated Si3N4/MWCNTs as Potential Novel Implant Materials

“…However, the pristine silicon nitride ceramic has an intrinsic brittleness, which can place some limitations on its applicability. In order to enhance the mechanical properties of silicon nitride ceramics to make them more reliable, the structure of the base Si 3 N 4 can be altered and adjusted by applying a second phase; for example, with carbon nanotubes (CNTs) [4,5]. A research work [5] thoroughly investigated how the CNT addition into the silicon nitride matrix affected its mechanical properties.…”

“…In order to enhance the mechanical properties of silicon nitride ceramics to make them more reliable, the structure of the base Si 3 N 4 can be altered and adjusted by applying a second phase; for example, with carbon nanotubes (CNTs) [4,5]. A research work [5] thoroughly investigated how the CNT addition into the silicon nitride matrix affected its mechanical properties. They concluded that the appropriate CNT content enhanced both the fracture toughness and the overall mechanical strength, and they revealed that the optimal carbon content was 3 wt%.…”