Materials of Future

Bulk Metallic Glasses:

It is known that amorphous metals can be produced by rapid cooling from the liquid rate. Until recently, the cooling rates achievable were on the order of 105-106 K/s, which limited the thickness of a fully amorphous alloy to fractions of a millimeter. The resulting ribbons and wires were used in transformer cores and magnetic sensors. The recent development of bulk metallic glasses (BMG's) has opened the door for use of these fascinating materials in structural applications. By developing certain Eutectic mixtures the cooling rate has come down to only 1-10 K/s, hence, amorphous castings up to a centimeter thick can be manufactured today.

For a Zr-Ti-Ni-Cu-Be bulk amorphous alloy, tensile strength of 2 GPa and fracture toughness values of ~20 MPa m^1/2 have been reported. With a density of 6.1 g/cm³, this BMG has a higher strength to weight ratio than steels and most of the titanium alloys. Though the alloy exhibits almost no plastic strain at failure, but typically shows up to 2.5% elastic strains. This ability to store large amount of energy per unit volume during elastic deformation makes the alloy an excellent candidate for making springs. In fact, it's first commercial application is as a golf club head!

Nanocomposites:

Nanocomposites refer to a group of composites where nano-sized particles/fibres are reinforced in polymeric or ceramic matrix to obtain extraordinarily high mechanical properties. Structurally the reinforcements may form a three dimensional, two dimensional or one dimensional network inside the composite. The most common of such composites are the lamellar nanocomposites which are again divided into two categories known as intercalated and exfoliated. Extensive researches are currently going on to understand the structure-function relationships in these nanocomposites. However, enormous improvement in elastic modulus, strength and damping are reported almost in all the cases.