Project leader:Daniel Kiener

Background

The ideal structural material should excel in both strength and toughness - a combination that represents the Holy Grail in materials science. Strength determines a material's resistance to deformation under stress, while toughness defines its ability to resist fracture through energy dissipation. These properties are mutually exclusive: While microstructural refinement to the nanometer scale dramatically enhances strength, it simultaneously causes a severe drop in ductility and damage tolerance. This inverse relationship has prevented the development of materials that combine both properties effectively, forcing engineers to compromise by using relatively soft metals in safety-critical applications such as airframes and pressure vessels. This fundamental limitation has tremendous economic implications.

Tungsten is a material with exceptional properties, having the highest melting point of any metal, outstanding thermal conductivity, and superior strength at elevated temperatures. It is a prime candidate for extreme environment applications, particularly as a plasma-facing material in nuclear fusion reactors. However, its inherent brittleness severely restricts component design and operating conditions, limiting its full potential in these demanding applications.

Our research group has previously demonstrated novel pathways to enhance toughness in nanostructured materials through various innovative approaches:

• Nanostructured metals with engineered grain boundary chemistry
• Nanocomposites incorporating ductile constituents
• High-strength nanoporous metals

The objective of this project is to translate these fundamental insights into economically viable nanostructured bulk tungsten materials. By synthesizing nanostructured tungsten with tailored interfaces using industrially scalable processes, we aim to demonstrate the feasibility of combining high strength with enhanced toughness in bulk materials. This advancement would be particularly valuable for applications in extreme environments where traditional materials reach their operational limits.

Research and technological objectives

• A viable synthesis route for nanograined tungsten powders and bulk nanostructured tungsten with potential for industrial scalability
• Engineering of interfaces to increase grain boundary cohesion and enhance mechanical properties
• Establishing structure-property relationships through chemical, microstructural and mechanical characterization
• Translation of laboratory-scale findings to industrial production

Novel methodologies

• Wet-chemical synthesis techniques for controlled production of nano-sized tungsten oxide particles
• High-temperature hydrogen reduction for production of nanosized tungsten powder
• Spark plasma sintering bulk nanostructured materials with modified interfacial chemistry
• Advanced in-situ micromechanical testing techniques performed in scanning electron microscopes
• Computer vision algorithms for automated tracking of deformation and crack propagation

Our approach combines innovative synthesis techniques with cutting-edge characterization methods to bridge the gap between fundamental materials science and industrial applications. By focusing on scalable processing routes and industrially relevant materials systems, this project aims to overcome one of the most persistent challenges in the design of structural materials.