This study focused on synthesizing nanopowders of Co and Al 2 O 3 from Co 3 O 4 and Al powders and fabricating nanocrystalline Al 2 O 3 reinforced Co composite to improve its mechanical properties. Nanopowders of Co and Al 2 O 3 were synthesized from Co 3 O 4 and Al by highenergy ball milling. A highly dense nanostructured 2.25CoAl 2 O 3 composite was consolidated by high-frequency induction heated sintering method within 3 min from the mechanically synthesized powders (2.25CoAl 2 O 3 ) under the 80 MPa pressure. The advantage of this process is that it allows for very quick densification to near theoretical density and prohibits grain growth in nanostructured materials. The grain sizes of Co and Al 2 O 3 in the composite were calculated. And the average hardness and fracture toughness values of nanostuctured CoAl 2 O 3 composite were investigated.

Nano-powders of 5Ni 0.6 Fe 0.4 and Al 2 O 3 were synthesized from 3NiO and 2FeAl powders by high energy ball milling. Nanocrystalline 5Ni 0.6 Fe 0.4 -Al 2 O 3 composite was consolidated by pulsed current activated sintering method within 2 min from mechanically alloyed powders of Al 2 O 3 and 5Ni 0.6 Fe 0.4 . The average hardness and fracture toughness values obtained were 990 kg/mm 2 and 7.5 MPa·m 1/2 , respectively.

Nanopowders of MoSi2 and Si3N4 were synthesized from Mo2N and Si by high ball milling. Dense nanostructured 8MoSi2-Si3N4 composite was consolidated by high frequency induction heated sintering (HFIHS) method within two minutes from mechanically synthesized powders of MoSi2 and Si3N4. Highly dense 8MoSi2-Si3N4 composite with a relative density of up to 97 % was produced under simultaneous application of 80 MPa pressure and the induced current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated.

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