Micro thermoplastic forming of a Pd-based metallic glass:theory and applications

Metallic glasses（MGs）are considered as the ideal materials for miniature fabrication because of their excellent micro thermoplastic forming ability in the supercooled liquid region.The understanding and controlling of micro filling process are fundamental for miniature fabrication and their applications,yet presently remain unresolved issues.A universal kinetic equation was proposed to describe the filling kinetics of viscous metallic glass supercooled liquid in micro molds with general cross sectional shapes by using a Pdbased MG as the modeling material and a series of potential applications based on the micro thermoplastic forming of the MG were developed.

Precise Thermoplastic Processing of Graphene Oxide Layered Solid by Polymer Intercalation

The processing capability is vital for the wide applications of materials to forge structures as-demand.Graphene-based macroscopic materials have shown excellent mechanical and functional properties.However,different from usual polymers and metals,graphene solids exhibit limited deformability and processibility for precise forming.Here,we present a precise thermoplastic forming of graphene materials by polymer intercalation from graphene oxide(GO)precursor.The intercalated polymer enables the thermoplasticity of GO solids by thermally activated motion of polymer chains.We detect a critical minimum containing of intercalated polymer that can expand the interlayer spacing exceeding 1.4 nm to activate thermoplasticity,which becomes the criteria for thermal plastic forming of GO solids.By thermoplastic forming,the flat GO-composite films are forged to Gaussian curved shapes and imprinted to have surface relief patterns with size precision down to 360 nm.The plastic-formed structures maintain the structural integration with outstanding electrical(3.07×10^(5) S m^(−1))and thermal conductivity(745.65 W m^(−1) K^(−1))after removal of polymers.The thermoplastic strategy greatly extends the forming capability of GO materials and other layered materials and promises versatile structural designs for more broad applications.

Thermoplastic micro-formability of TiZrHfNiCuBe high entropy metallic glass

High entropy metallic glasses（MGs） have attracted tremendous attentions owing to high entropy that benefits the probing of new MG-forming systems. However, the micro-formability of high entropy MGs is lack of investigation in comparison with these conventional MG counterparts, which is crucial to the development of this kind of metallic alloys. In this work, the thermoplastic mciro-formability of TiZrHfNiCuBe high entropy MG was systemically investigated. Time-Temperature-Transformation（TTT）curve was first constructed based on isothermal crystallization experiments, which provides thermoplastic processing time of the supercooled high entropy MGs. By comparison with the deformation map,Newtonian flow was found beneficial to the thermoplastic formability. While the thermoplastic forming becomes arduous with reducing mould size to tens micrometer, because of the strong supercooled TiZrHfNiCuBe high entropy MG（fragility = 27）. Fortunately, the micro-formability of TiZrHfNiCuBe high entropy MG could be improved by vibration loading, as demonstrated by finite-element-method simulation. Our findings not only systemically evaluate the thermoplastic micro-formability of high entropy MG, but also provide fundamental understanding of the phenomenon.

Area-Specific Positioning of Metallic Glass Nanowires on Si Substrate

This paper presents a novel technique to fabricate metallic nanowires in selective areas on a Si substrate.Thermoplastic drawing of viscous metallic glass from cavities etched in Si can produce metallic nanowires.The length and diameter of nanowires can be controlled by adjusting the drawing conditions without changing the Si mold.A thin metal shadow mask is stacked above the Si mold during thermoplastic drawing to fabricate the nanowires only in specific locations.The mask restricts the flow of metallic glass to predefined shapes on the mask,resulting in the formation of nanowires in selected areas on Si.An Al foil-based mask made by a benchtop vinyl cutter is used to demonstrate the proof-of-concept.Even a simple Al foil mask enables the positioning of metallic nanowires in selective areas as small as 200μm on Si.The precision of the vinyl cutter limits the smallest dimensions of the patterned areas,which can be further improved by using laser-fabricated stencil masks.Results show that a single row of metallic glass nanowires can be patterned on Si using selective thermoplastic drawing.Controllable positioning of metallic nanowires on substrates can enable new applications and characterization techniques for nanostructures.