High-temperature spark plasma sintering of h-BN composites reinforced with carbon nanotubes, carbon fibers, and graphene nanoplates

In this study, two h-BN-based composites reinforced with carbon fibers (CF) and carbon fibers/carbon nanotubes (CNTs)/graphene nanoplates (GNPs) have been produced successfully through a high-temperature spark plasma sintering. ۱ wt% short carbon fibers (length of ۵ mm) with ۰.۱ wt% of CNTs and also ۰.۱ wt% of GNPs as hybrid composite were mixed through a simple mixing method including a high energy sonicating and stirring on the hot plate in ethanol media until drying. Moreover, the h-BN/۱ wt% CF composite was mixed with a similar method to compare the impacts of CNTs and GNPs addition on the mechanical properties and microstructure of the h-BN/CF composite. The high-temperature spark plasma sintering processes were performed at vacuum conditions of almost ۲۰–۲۵ MPa with a starting pressure of ۱۰ and a final applied pressure of ۵۰ MPa at a maximum temperature of ۱۹۰۰ °C. Both prepared samples showed near full densification of higher than ۹۸.۱% of the theoretical density determined by Archimedes’ principle. Investigation of the crystalline phases by XRD represented only related peaks to h-BN. The FESEM images indicated an almost uniform distribution of reinforcement in the h-BN matrix. Furthermore, the polished surface of the provided samples showed only the pulled-out carbon fibers effects while the fracture surfaces confirmed the presence of CF and its tunneling effects. The obtained mechanical properties revealed ۲۷۳±۱۲ MPa of bending strength, ۱.۳۲±۰.۱ GPa of Vickers hardness, and ۴.۷۹±۰.۲ MPa.m۰.۵ fracture toughness for the prepared hybrid composite.In this study, two h-BN-based composites reinforced with carbon fibers (CF) and carbon fibers/carbon nanotubes (CNTs)/graphene nanoplates (GNPs) have been produced successfully through a high-temperature spark plasma sintering. ۱ wt% short carbon fibers (length of ۵ mm) with ۰.۱ wt% of CNTs and also ۰.۱ wt% of GNPs as hybrid composite were mixed through a simple mixing method including a high energy sonicating and stirring on the hot plate in ethanol media until drying. Moreover, the h-BN/۱ wt% CF composite was mixed with a similar method to compare the impacts of CNTs and GNPs addition on the mechanical properties and microstructure of the h-BN/CF composite. The high-temperature spark plasma sintering processes were performed at vacuum conditions of almost ۲۰–۲۵ MPa with a starting pressure of ۱۰ and a final applied pressure of ۵۰ MPa at a maximum temperature of ۱۹۰۰ °C. Both prepared samples showed near full densification of higher than ۹۸.۱% of the theoretical density determined by Archimedes’ principle. Investigation of the crystalline phases by XRD represented only related peaks to h-BN. The FESEM images indicated an almost uniform distribution of reinforcement in the h-BN matrix. Furthermore, the polished surface of the provided samples showed only the pulled-out carbon fibers effects while the fracture surfaces confirmed the presence of CF and its tunneling effects. The obtained mechanical properties revealed ۲۷۳±۱۲ MPa of bending strength, ۱.۳۲±۰.۱ GPa of Vickers hardness, and ۴.۷۹±۰.۲ MPa.m۰.۵ fracture toughness for the prepared hybrid composite.

کلیدواژه ها:

Hexagonal boron nitride ، CNTs ، Carbon fiber ، GNPs ، Spark plasma sintering