Superior Mechanical and Magnetic Performance of Highly Anisotropic Sendust‐Flake Composites Freeze Cast in a Uniform Magnetic Field
Year: 2020
Type: article
Abstract: Despite extensive research, the manufacture in the bulk of high‐performance flake‐based magnetic composites with a highly aligned, nacre‐like structure remains challenging. Many challenges can be overcome by freeze casting in an externally applied, uniform magnetic field, which causes both the flakes and the composite walls of the cellular solid to align parallel to the B‐field lines. When appropriately sized, the flakes experience a second alignment parallel to the freezing direction because of a shear flow that occurs due to both the volumetric expansion of the ice phase and mold contraction during the directional solidification. The resulting orthotropic structure of the freeze‐cast magnetic composite is reflected in orthotropic mechanical and magnetic properties of the material. The magnetic composites manufactured by magnetic‐field assisted freeze casting outperform by a factor of 2–4 in terms of stiffness, strength, and toughness materials that are processed in the absence of a magnetic field and do not exhibit a monodomain architecture. Because of the highly aligned microstructure, it is possible to compact the initially lamellar composite with 90% porosity to at least 80% strain. The results presented in this study illustrate the tremendous potential for magnetic freeze casting of magnetic composites for use in power conversion.
Source: Advanced Functional Materials
Institutions: Dartmouth College, Northeastern University, University of Freiburg
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $5,000
Awards: G1830523874, Phase I IUCRC at Dartmouth College: Center for Integrated Power Management Circuits and Systems - Power One IC, G421379376, Collaborative Research: Modeling-Based Design of Freeze-Cast Hybrid Materials, DARTMOUTH S CONTRIBUTION TO THE TEAM EFFORT OF THE COLLABORATIVE NASA PROJECT ENTITLED STRUCTURE-PROPERTY-PROCESSING CORRELATIONS IN FREEZE-CAST BIOMIMETIC MATERIALS WILL BE TO INVESTIGATE AND DETERMINE WITH CUSTOM-DESIGNED FREEZING STAGES ANALYTICAL TOOLS AND CONTRIBUTIONS TO THE MODELING EFFORT THE KINETICS OF THE ICE-PHASE GROWTH AND THE MECHANISMS BY WHICH THE GROWING ICE-CRYSTALS THUS ICE PHASE TEMPLATES THE POLYMER PHASE DURING ITS TRANSITION FROM A SOLUTION TO A GLASSY SOLID. THE WATER-BASED SYSTEM WILL BE COMPARED WITH MODEL SYSTEMS SUCH AS THAT OF TBA-WATER: (I) WITH LIGHT MICROSCOPY PERPENDICULAR TO THE MOVING FREEZING FRONT WE WISH TO OBSERVE THE FORMATION OF MULLINS- SEKERKA INSTABILITIES AND THEIR SUBSEQUENT REORGANIZATION INTO AN ARRAY OF CELLS OR DENDRITES AS A FUNCTION OF POLYMER CONCENTRATION AND COOLING RATES WHICH IS EQUAL TO THE PRODUCT OF VELOCITY AND THERMAL GRADIENT IN DIRECTIONAL SOLIDIFICATION; (II) WITH CONFOCAL MICROSCOPY PARALLEL TO THE FREEZING FRONT WE WISH TO OBSERVE AND DETERMINE UNDER WHICH EXACT PROCESSING CONDITIONS SUCH AS POLYMER CONCENTRATION AND COOLING RATE THE DIFFERENT STRUCTURES FORM ON EARTH IN PREPARATION OF EXPERIMENTS USING THE REFURBISHED PFMI IN SPACE. FINALLY THE RESULTS OF THE EXPERIMENTAL AND THEORETICAL WORK WILL BE TRANSLATED INTO STRUCTURE-PROPERTY-PROCESSING CORRELATIONS FOR HIGHLY POROUS FREEZE-CAST MATERIALS (POLYMER CERAMIC METAL AND COMPOSITE) MADE ON EARTH SO THAT THEY CAN BE APPLIED IN THE DEVELOPMENT OF NEW AND IMPROVED FREEZE-CAST MATERIALS THAT ARE STRONG TOUGH AND LIGHTWEIGHT AND CAN BE CUSTOM-DESIGNED FOR A GIVEN APPLICATION. THE WORK EFFORT WILL PARALLEL THE FUNDING AND PHASE IN DURING YEARS 1 AND 2., G7854435144, G7940003770, Cancer Center Support Grant
OpenAlex ID: W3108135579