Metallic Nanoglasses Research Articles

A new class of non-crystalline materials: Nanogranular metallic glasses

Abstract Nanogranular metallic glasses (NGMGs) or metallic nanoglasses are assembly of metallic glass (MG) granules with a size typically ranging from a few to 100 nm interconnected by glass/glass interfaces. These materials can be synthesized by different techniques including inert gas condensation and physical vapor deposition. In comparison with conventional MGs produced by cooling of liquids, NGMGs show enhanced thermal stability, ferromagnetism with higher Curie temperature, better biocompatiblity and superior mechanical properties. This review aims to introduce such a new class of non-crystalline solids: NGMGs, emphasizing on the preparation methods and the unique properties of these materials. Meanwhile, an outlook on this subject is proposed for the possible future research topics in the field of nanoglasses.

Interfaces and interphases in nanoglasses: Surface segregation effects and their implications on structural properties

Metallic nanoglasses can be prepared by cold compaction of amorphous nanoparticles initially condensed in inert gas atmosphere. Experimentally, it has been found that a characteristic feature of nanoglasses is the occurrence of atomic density variations within the microstructure, that cannot be explained by interface induced topological variations in a chemically homogeneous material. Here we present molecular dynamics simulations, which reveal that compositional variations between glass-glass interfaces and the volume material can result from surface segregation effects already present in the primary particles. By comparing results for Pd80Si20 and Cu64Zr36 metallic glasses, we show that amorphous nanoparticles install an inhomogenous elemental equilibrium distribution in the gas phase before they undergo the glass transition into the solid state. A detailed analysis of planar interfaces generated by merging chemically equilibrated surfaces shows that glass-glass interfaces can be understood as interphases of different composition and short-range order, where the local topology, free volume and local composition are intimately linked.

Evidence of itinerant magnetism in a metallic nanoglass

Metallic nanoglasses are amorphous alloys which are prepared by consolidation of amorphous nanoparticles. The result is a unique two-component structure with comparable volume fractions, an interfacial component of nanometer-sized regions of reduced density, and a component in the cores of the nanoparticles. The magnetic properties of a Fe90Sc10 nanoglass and a rapidly quenched metallic glass as a reference have been investigated by means of Mössbauer spectroscopy and magnetic Compton scattering. The contribution of itinerant electrons to the magnetic moment in the interfaces is higher than in crystalline Fe and all known amorphous transition metal alloys. Consequently, the FeSc nanoglass represents a material with magnetic properties different from any known amorphous alloys.