权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Enhanced Magnetic Cooling through Optimising Local Interactions

通过优化局部相互作用增强磁冷却

基本信息

批准号：
EP/T027886/1
负责人：
Paul James Saines
金额：
$ 53.05万
依托单位：
University of Kent
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FT027886%2F1
关键词：
Enhanced Magnetic Cooling through Optimising

项目摘要

Refrigeration is central to modern society by making hot climates habitable, preserving food, and facilitating medical scanners and quantum computing. Over a tenth of Britain's electricity is estimated to go to cooling, at a cost of over £5 billion a year, with nearly 12 million (m) people globally employed in refrigeration related industries. Cryogenic refrigeration, which provides temperatures close to absolute zero, is becoming a major industry; the research council STFC have predicted that contributions to the UK economy from cryogenic refrigeration will increase from £324m to £3300m in the decade to 2025. Solid state cooling based on caloric materials promises higher energy efficiencies than current technologies based on fluid refrigerants and do not suffer from inevitable escape of their active components as gases, such as scarce liquid helium used for cryogenic applications. Caloric refrigerants rely on a change in entropy, a measure of the universe's tendency to disorder, in response to external stimuli such as applied magnetic and electric fields or pressure. Practical caloric cooling requires new materials that exhibit the maximum change in their entropy for readily achievable external stimuli. In magnetocalorics, the cooling process is driven by applied magnetic fields. This has advantages, including high cyclability compared to other calorics as materials do not tend to deteriorate when exposed to magnetic fields. Magnetocalorics have been known for over a century, but their use has mostly been restricted to refrigeration at ultra-low temperatures, measured in milli-kelvins, and with very large magnetic fields, limiting their application. Developing magnetocalorics that work at higher temperatures and under lower magnetic fields will enable magnetisation based cryogenic cooling to be more used much more widely. We can systematically optimise new magnetocalorics for desired cryogenic temperatures by tuning interactions in these materials. This achieves large entropy changes for small magnetic field changes at key operating temperatures. While this approach is well known for magnetocalorics for near room temperature cooling its importance when optimising magnetocalorics for cryogenic cooling has only been shown recently. Enhanced cryogenic magnetocalorics will have greater efficiency than alternative cooling technologies enabling us to greatly decrease dependence on liquid helium, which is increasingly expensive and prone to supply disruptions. Realising the best magnetocalorics requires an interdisciplinary approach that combines chemistry and physics; this is well matched by our team's expertise in materials synthesis, structural and physical properties characterisation and prototype testing.Magnetocalorics with strong interactions within chains of magnetic ions and weaker competing interactions between chains appear particularly suited to replace liquid helium. We will take advantage of this recent discovery by developing framework magnetocalorics, a new class of materials that enable enormous freedom to optimise properties due to their very flexible compositions and structures. We will systematically investigate how these magnetocalorics are best optimised for use above 4 K by tuning the extent of competing interactions between units with strong magnetic coupling and modifying the dimensionality of the strongly coupled units. These magnetocalorics will be optimised further by changing the magnetic ions incorporated to directly tune their magnetic interactions. The best magnetocalorics to emerge from this screening process will then be assessed to determine their maximum cooling capacity and power. This key information will enable us to establish their utility in practical cooling devices, which will be demonstrated by incorporation into a prototype magnetocaloric refrigerator. Understanding gained from this project will enable development of precise design rules for tailored magnetocalorics.

制冷是现代社会的核心，使炎热的气候适合居住，保存食物，促进医疗扫描仪和量子计算。据估计，英国超过十分之一的电力用于制冷，每年的成本超过50亿英镑，全球有近1200万人从事制冷相关行业。提供接近绝对零度的温度的低温制冷正在成为一个主要产业;研究理事会STFC预测，到2025年的十年内，低温制冷对英国经济的贡献将从3.24亿英镑增加到3.3亿英镑。基于热材料的固态冷却承诺比基于流体制冷剂的当前技术更高的能量效率，并且不会遭受其活性组分不可避免地作为气体逸出，例如用于低温应用的稀缺液氦。热量制冷剂依赖于熵的变化，熵是衡量宇宙无序趋势的一种指标，它会对外部刺激做出反应，如施加的磁场和电场或压力。实际的热量冷却需要新材料，这些材料在容易实现的外部刺激下表现出最大的熵变化。在磁热学中，冷却过程由施加的磁场驱动。这具有优势，包括与其他热量相比的高循环性，因为材料在暴露于磁场时不会劣化。磁热效应已经存在了超过世纪，但是它们的使用主要局限于以毫开尔文测量的超低温下的制冷，并且具有非常大的磁场，这限制了它们的应用。开发在更高温度和更低磁场下工作的磁热技术将使基于磁化的低温冷却得到更广泛的应用。我们可以通过调整这些材料中的相互作用来系统地优化新的磁热材料以获得所需的低温温度。这在关键操作温度下实现了小磁场变化的大熵变化。虽然这种方法是众所周知的磁热近室温冷却的重要性时，优化磁热低温冷却最近才被证明。增强的低温磁热技术将比替代冷却技术具有更高的效率，使我们能够大大减少对液氦的依赖，液氦越来越昂贵，而且容易出现供应中断。实现最佳的磁热效应需要化学和物理相结合的跨学科方法;这与我们团队在材料合成、结构和物理特性表征以及原型测试方面的专业知识非常匹配。磁热效应在磁性离子链内具有强相互作用，而链间竞争相互作用较弱，似乎特别适合取代液氦。我们将利用这一最新发现，开发框架磁热材料，这是一类新材料，由于其非常灵活的组成和结构，可以极大地自由优化性能。我们将系统地研究这些磁热是如何最好地优化使用以上4 K通过调整强磁耦合单元之间的竞争相互作用的程度，并修改强耦合单元的维数。这些磁热将通过改变磁性离子来进一步优化，以直接调整它们的磁相互作用。然后将评估从这个筛选过程中出现的最佳磁热器，以确定它们的最大冷却能力和功率。这些关键信息将使我们能够建立它们在实际冷却装置中的实用性，这将通过将其并入原型磁热制冷机来证明。从这个项目中获得的理解将使定制磁热器的精确设计规则的发展。