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Metallic Multilayers: Structures, Growth and Properties

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (10 July 2022) | Viewed by 13914

Special Issue Editors


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Guest Editor
Karlsruhe Institute of Technology, Institute for Applied Materials (IAM-AWP), Campus North, Eggenstein-Leopoldshafen, Germany
Interests: surface engineering; thin film physics; physical vapour deposition

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Guest Editor
Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM), Eggenstein-Leopoldshafen, Germany
Interests: reactive materials; self-sustaining reactions; phase transformations; diffusion; metallic multilayers; nanocalorimetry; differential scanning calorimetry; X-ray diffraction
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Special Issue Information

Dear Colleagues,

During the past two decades, metallic multilayers have been developed as modern engineering materials with alternating layers of two different metals or alloys. The realization that periodic stacking of metals with nano- and micro-scale thin films leads to materials exhibiting unprecedented properties and functionalities that cannot be achieved by the individual constituents initiated research activities toward a comprehensive understanding of the underlying mechanisms. This research revealed, for example, that metallic multilayers are excellent model materials for exploring the fundamentals of phase transformations and self-sustaining reactions relevant for these properties, creating a demand for detailed studies of length scale effects from the nanometer up to the micrometer scale. For the latter studies, thin film synthesis became crucial for multilayer research due to its capabilities for precise microstructure and interface tailoring.

This Special Issue aims to provide a state-of-the-art survey of the latest developments in the field of metallic multilayers that are comprised of metallic elements, multicomponent complex alloys, high-entropy alloys, shape memory alloys, or Heusler alloys. Materials such as ceramics, polymers, 2D materials, and their composites are not included. All synthesis methods for designing nano- and micro-scale multilayer films are considered. The scientific scope of the Special Issue encompasses the following topics:

  1. Correlation between microstructure and properties. Multilayers with specific mechanical, tribological, caloric, optical, electronic, biological, biomedical, or other functional properties are the focus. Studies exploring effects of the multilayer synthesis are welcome, as are those elucidating the influence of the multilayer structure. 
  2. Phase transitions. Many applications harness or suffer from phase transitions that might be thermally and/or mechanically induced. Hence, transformational behavior is crucial and advanced approaches for its characterization, such as thermal analysis in combination with structural characterization, are considered
  3. The multilayer performance on system level. Contributions should shed light on the multilayer behavior in applications such as protective (or even self-healing) and functional coating.
  4. Reports on the latest experimental observations and computational and simulation approaches are desired, as well as regular scientific contributions and review articles in the field.

Along this scope, we intend to provide a comprehensive overview of the current activities in the field.

Dr. Michael Stüber
Dr. Karsten Woll
Guest Editors

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Keywords

  • metallic multilayers
  • microstructure
  • properties
  • functional coatings
  • phase transformation, slef-propagating reactions
  • thin film synthesis
  • simulation

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Published Papers (4 papers)

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Research

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14 pages, 3984 KiB  
Article
An Overview of Nano Multilayers as Model Systems for Developing Nanoscale Microstructures
by Chelsea D. Appleget, Juan Sebastian Riano and Andrea M. Hodge
Materials 2022, 15(1), 382; https://doi.org/10.3390/ma15010382 - 5 Jan 2022
Cited by 5 | Viewed by 2426
Abstract
The microstructural transformations of binary nanometallic multilayers (NMMs) to equiaxed nanostructured materials were explored by characterizing a variety of nanoscale multilayer films. Four material systems of multilayer films, Hf-Ti, Ta-Hf, W-Cr, and Mo-Au, were synthesized by magnetron sputtering, heat treated at 1000 °C, [...] Read more.
The microstructural transformations of binary nanometallic multilayers (NMMs) to equiaxed nanostructured materials were explored by characterizing a variety of nanoscale multilayer films. Four material systems of multilayer films, Hf-Ti, Ta-Hf, W-Cr, and Mo-Au, were synthesized by magnetron sputtering, heat treated at 1000 °C, and subsequently characterized by transmission electron microscopy. Binary systems were selected based on thermodynamic models predicting stable nanograin formation with similar global compositions around 20–30 at.%. All NMMs maintained nanocrystalline grain sizes after evolution into an equiaxed structure, where the systems with highly mobile incoherent interfaces or higher energy interfaces showed a more significant increase in grain size. Furthermore, varying segregation behaviors were observed, including grain boundary (GB) segregation, precipitation, and intermetallic formation depending on the material system selected. The pathway to tailored microstructures was found to be governed by key mechanisms and factors as determined by a film’s initial characteristics, including global and local composition, interface energy, layer structure, and material selection. This work presents a global evaluation of NMM systems and demonstrates their utility as foundation materials to promote tailored nanomaterials. Full article
(This article belongs to the Special Issue Metallic Multilayers: Structures, Growth and Properties)
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15 pages, 2615 KiB  
Article
Influence of Initial Temperature and Convective Heat Loss on the Self-Propagating Reaction in Al/Ni Multilayer Foils
by Mostafa Baloochi, Deepshikha Shekhawat, Sascha Sebastian Riegler, Sebastian Matthes, Marcus Glaser, Peter Schaaf, Jean Pierre Bergmann, Isabella Gallino and Jörg Pezoldt
Materials 2021, 14(24), 7815; https://doi.org/10.3390/ma14247815 - 17 Dec 2021
Cited by 15 | Viewed by 2639
Abstract
A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, [...] Read more.
A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, these Al/Ni multilayer foils were fabricated by the magnetron sputtering technique with a 1:1 atomic ratio. Heat of reaction of the fabricated foils was determined employing Differential Scanning Calorimetry (DSC). Self-propagating reaction was initiated by an electrical spark on the surface of the foils. The movement of the reaction front was recorded with a high-speed camera. Activation energy is fitted with these velocity data from the high-speed camera to adjust the numerical model. Calculated reaction front temperature of the self-propagating reaction was compared with the temperature obtained by time-resolved pyrometer measurements. X-ray diffraction results confirmed that all reactants reacted and formed a B2 NiAl phase. Finally, it is predicted that (1) increasing thermal conductivity of the final product increases the reaction front velocity; (2) effect of heat convection losses on reaction characteristics is insignificant, e.g., the foils can maintain their characteristics in water; and (3) with increasing initial temperature of the foils, the reaction front velocity and the reaction temperature increased. Full article
(This article belongs to the Special Issue Metallic Multilayers: Structures, Growth and Properties)
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13 pages, 754 KiB  
Article
Influence of Impurities on the Front Velocity of Sputter Deposited Al/CuO Thermite Multilayers
by Altangerel Dulmaa and Diederik Depla
Materials 2021, 14(23), 7224; https://doi.org/10.3390/ma14237224 - 26 Nov 2021
Cited by 2 | Viewed by 1899
Abstract
CuO and Al thin films were successively deposited using direct current (reactive) magnetron sputter deposition. A multilayer of five bilayers was deposited on glass, which can be ignited by heating a Ti resistive thin film. The velocity of the reaction front which propagates [...] Read more.
CuO and Al thin films were successively deposited using direct current (reactive) magnetron sputter deposition. A multilayer of five bilayers was deposited on glass, which can be ignited by heating a Ti resistive thin film. The velocity of the reaction front which propagates along the multilayer was optically determined using a high-speed camera. During the deposition of the aluminum layers, air was intentionally leaked into the vacuum chamber to introduce impurities in the film. Depositions at different impurity/metal flux ratios were performed. The front velocity reaches a value of approximately 20 m/s at low flux ratios but drops to approximately 7 m/s at flux ratios between 0.6 and 1. The drop is rather abrupt as the front velocity stays constant above flux ratios larger than 1. This behavior is explained based on the hindrance of the oxygen transport from the oxidizer (CuO) to the fuel (Al). Full article
(This article belongs to the Special Issue Metallic Multilayers: Structures, Growth and Properties)
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Review

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25 pages, 4242 KiB  
Review
Materials Engineering for Flexible Metallic Thin Film Applications
by Megan J. Cordill, Patrice Kreiml and Christian Mitterer
Materials 2022, 15(3), 926; https://doi.org/10.3390/ma15030926 - 25 Jan 2022
Cited by 40 | Viewed by 5945
Abstract
More and more flexible, bendable, and stretchable sensors and displays are becoming a reality. While complex engineering and fabrication methods exist to manufacture flexible thin film systems, materials engineering through advanced metallic thin film deposition methods can also be utilized to create robust [...] Read more.
More and more flexible, bendable, and stretchable sensors and displays are becoming a reality. While complex engineering and fabrication methods exist to manufacture flexible thin film systems, materials engineering through advanced metallic thin film deposition methods can also be utilized to create robust and long-lasting flexible devices. In this review, materials engineering concepts as well as electro-mechanical testing aspects will be discussed for metallic films. Through the use of residual stress, film thickness, or microstructure tailoring, all controlled by the film deposition parameters, long-lasting flexible film systems in terms of increased fracture or deformation strains, electrical or mechanical reliability, can be generated. These topics, as well as concrete examples, will be discussed. One objective of this work is to provide a toolbox with sustainable and scalable methods to create robust metal thin films for flexible, bendable, and stretchable applications. Full article
(This article belongs to the Special Issue Metallic Multilayers: Structures, Growth and Properties)
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