Interdependence of carbon nanotubes agglomerations, its structural integrity and the mechanical properties of reinforced nickel aluminide composites

Spark plasma sintered NiAl-CNTs intermetallic composites were fabricated via two different ball milling processes. One comprising of an exclusive low energy ball milling (LEBM), and the other comprising of a two-stage milling, typically a prolonged LEBM with a short term high energy ball milling (HEBM). The differently milled powders were consolidated, and the resulting composites characterized. This was done to determine the individual effects of agglomerations vis-à-vis the structural integrity of the nanotubes. The composites were extensively characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy (RS), scanning electron microscopy (SEM) and nanoindentation techniques. The uniform dispersion of slightly impaired CNTs led to better mechanical properties as compared to the in-homogenous dispersion of higher structural integrity CNTs in the NiAl intermetallic matrices. Results showed that the sample with a two-stage milling exhibited superior mechanical properties in terms of hardness, elastic modulus and fracture toughness with 422.79 Hv, 50.5 GPa and 9 MPa√m respectively.