Fleming Rafael Oliveira, Gonçalves Sofia, Davarpanah Amin, Radulov Iliya, Pfeuffer Lukas, Beckmann Benedikt, Skokov Konstantin, Ren Yang, Li Tianyi, Evans John, Amaral João, Almeida Rafael, Lopes Armandina, Oliveira Gonçalo, Araújo João Pedro, Apolinário Arlete, Belo João Horta
Institute of Physics of Advanced Materials, Nanotechnology and Nanophotonics (IFIMUP), Departamento de Física e Astronomia da Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
Institute of Material Science, Technical University of Darmstadt, 64287 Darmstadt, Germany.
ACS Appl Mater Interfaces. 2022 Sep 28;14(38):43498-43507. doi: 10.1021/acsami.2c11586. Epub 2022 Sep 13.
Zero thermal expansion (ZTE) composites are typically designed by combining positive thermal expansion (PTE) with negative thermal expansion (NTE) materials acting as compensators and have many diverse applications, including in high-precision instrumentation and biomedical devices. La(Fe,Si)13-based compounds display several remarkable properties, such as giant magnetocaloric effect and very large NTE at room temperature. Both are linked via strong magnetovolume coupling, which leads to sharp magnetic and volume changes occurring simultaneously across first-order phase transitions; the abrupt nature of these changes makes them unsuitable as thermal expansion compensators. To make these materials more useful practically, the mechanisms controlling the temperature over which this transition occurs and the magnitude of contraction need to be controlled. In this work, ball-milling was used to decrease particles and crystallite sizes and increase the strain in LaFeMnSiH alloys. Such size and strain tuning effectively broadened the temperature over which this transition occurs. The material's NTE operational temperature window was expanded, and its peak was suppressed by up to 85%. This work demonstrates that induced strain is the key mechanism controlling these materials' phase transitions. This allows the optimization of their thermal expansion toward room-temperature ZTE applications.
零热膨胀（ZTE）复合材料通常是通过将正热膨胀（PTE）材料与作为补偿器的负热膨胀（NTE）材料相结合来设计的，并且有许多不同的应用，包括在高精度仪器和生物医学设备中。基于La(Fe,Si)13的化合物表现出几种显著的特性，如巨大的磁热效应和室温下非常大的负热膨胀。两者都通过强磁体积耦合联系在一起，这导致在一级相变过程中同时发生急剧的磁性和体积变化；这些变化的突然性使其不适宜作为热膨胀补偿器。为了使这些材料在实际中更有用，需要控制控制这种转变发生的温度以及收缩幅度的机制。在这项工作中，球磨被用于减小LaFeMnSiH合金中的颗粒和微晶尺寸并增加应变。这种尺寸和应变调整有效地拓宽了发生这种转变的温度范围。该材料的负热膨胀工作温度窗口被扩大，并且其峰值被抑制高达85%。这项工作表明，诱导应变是控制这些材料相变的关键机制。这使得它们能够朝着室温零热膨胀应用优化其热膨胀性能。
