Abbas Saeed Hakeem

Spark plasma sintering of metals and metal matrix nanocomposites: a review

Metal matrix nanocomposites (MMNCs) are thosemetal matrix composites where the reinforcement is of nanometer dimensions, typically less than 100nm in size. Also, it is possible to have both the matrix and reinforcement phases of nanometer dimensions. The improvement in mechanical properties of MMNCs is attributed to the size and strength of the reinforcement as well as to the fine grain size of the matrix. Spark plasma sintering has been used extensively over the past years to consolidate wide range of materials including nanocomposites and was shown to be effective noneconventional sintering method for obtaining fully dense materials with preserved nanostructure features. The objective of this work is to briefly present the spark plasma sintering process and review published work on spark-plasma-sintered metals and metal matrix nanocomposites.

Age Hardening Behavior of Carbon Nanotube Reinforced Aluminum Nanocomposites

In the present work, age hardening behavior of CNT reinforced Al6061 and Al2124 nanocomposites, prepared by ball milling and spark plasma sintering, was investigated. The effect of CNT content, annealing time and temperature on the age hardening behavior of the nanocomposites was evaluated and compared to the monolithic alloys prepared and age hardened under the same conditions. It was found that CNTs have a negative influence on the age hardening of the alloys. The alloys displayed standard age hardening behavior i.e. a sharp increase in hardness during initial aging followed by a steady decrease in hardness. Whereas the nanocomposites did not only display initial softening during aging but also showed reduced age hardening efficiency. The hardening efficiency was found to decrease with increasing CNT content. The complicated behavior of nanocomposites was explained in terms of dislocation recovery, large thermal mismatch between matrix and CNTs and bulk microstructure of the composites.

Thermal effect of ceramic nanofiller aluminium nitride on polyethylene properties

Ethylene polymerization was done to form polyethylene nano-composite with nanoaluminum nitride using zirconocene catalysts. Results show that the catalytic activity is maximum at a filler loading of 15 mg nanoaluminum nitride. Differential scanning calorimeter (DSC) and X-ray diffraction (XRD) results show that percentage crystallinity was also marginally higher at this amount of filler. Thermal behavior of polyethylene nanocomposites (0, 15, 30, and 45) mg was studied by DSC and thermal gravimetric analyzer (TGA). Morphology of the component with 15 mg aluminium nitride is more fibrous as compared to 0mg aluminium nitride and higher filler loading as shown by SEM images. In order to understand combustibility behavior, tests were performed on microcalorimeter. Its results showed decrease in combustibility in polyethylene nanocomposites as the filler loading increases.

Effect of Consolidation Mechanism on the Properties of Nanostructured WC-6, 9, 12 wt%Co Hardmetals

The development of nanostructured materials has been exploited in enormous applications nowadays owing to the remarkable properties possessed by these advanced materials. Among these materials, tungsten carbide (WC)-based alloys, which have been widely used in a range of industrial applications including cutting and drilling tools, wear resistant components in wire drawing, and wear resistant surfaces in various equipments and dies. These alloys are processed using variety of techniques in which powder metallurgy has been widely adopted. The key challenge lies in retaining the nanostructure of WC-based powders after the consolidation stage that is used to obtain dense parts following powder metallurgy processing. In the present study, the densification parameters, microstructural development and mechanical behavior of WC containing 6, 9 and 12wt. %Co powders in the range of nm to µm size of WC particles were investigated. Two types of consolidation techniques were considered i.e., spark plasma sintering (SPS) and microwave sintering (MW) for a comparative analysis as well as to explore the best suitable process that will minimize grain growth. The consolidated (sintered) samples are characterized by X-ray diffraction, scanning electron microscopy, and hardness measurement.