No abstract

No abstract

Graphene has proved its significant role as a reinforcement material in improving the strength of polymers as well as metal matrix composites due to its excellent mechanical properties. In addition, graphene is also shown to block dislocation motion in a nanolayered metal-graphene composites resulting in ultra high strength. In the present paper, we demonstrate the synthesis of very hard Cu-Graphene composite foils by a simple, scalable and economical pulse reverse electrodeposition method with a well designed pulse profile. Optimization of pulse parameters and current density resulted in composite foils with well dispersed graphene, exhibiting a high hardness of ~2.5 GPa and an increased elastic modulus of ~137 GPa while exhibiting an electrical conductivity comparable to that of pure Cu. The pulse parameters are designed in such a way to have finer grain size of Cu matrix as well as uniform dispersion of graphene throughout the matrix, contributing to high hardness and modulus. Annealing of these nanocomposite foils at 300°C, neither causes grain growth of the Cu matrix nor deteriorates the mechanical properties, indicating the role of graphene as an excellent reinforcement material as well as a grain growth inhibitor.

No abstract

Dense β‐Si4Al2O2N6 ceramics were obtained from α‐Si3N4, α‐Al2O3, AlN, and Y2O3 upon sintering (for 4 h at 1675°C) green bodies consolidated by an aqueous gelcasting and a conventional dry‐powder processing route. The as‐purchased AlN powder was treated with H3PO4 and Al(H2PO4)3 and dispersed in aqueous‐organic premix solution along with α‐Si3N4, α‐Al2O3, and Y2O3 powder with the help of a commercial amino alcohol‐based cationic (Dolapix A88) dispersing agent to obtain suspensions with 45–50 vol% solids loading for gelcasting purpose. The gelcat β‐Si4Al2O2N6 exhibited superior hardness (1423±6 Hv), fracture toughness (3.95±0.3 MPa·m1/2), and coefficient of thermal expansion (3.798 × 10−6/°C between 30° and 1000°C) in comparison with the ceramic consolidated by conventional dry‐powder pressing route, which exhibited only 1317±5 Hv, 3.30±0.2 MPa·m1/2 and 3.532 × 10−6/°C between 30° and 700°C.

No abstract

No abstract

No abstract