火花混搭形成多功能合金纳米颗粒
Sparking mashups to form multifunctional alloy nanoparticles
摘要：
由于动力学和热力学之间的无缝相互作用，合成非常规合金仍然具有挑战性。例如，高熵合金（HEAs）提出了一个全新的概念，可以探索相图中的未知区域。然而，传统的基于液-固相变的热力学理论阻碍了这一探索。在压力-温度相图上允许的气-固转变提供了形成任何期望的合金（例如，HEA）。在这里，我们报告了一种称为“火花混搭”的技术，该技术涉及快速淬火的蒸汽源，并诱导不受限制的混合，用于合金化55种不同类型的超小纳米颗粒（NPs），其成分可控。与湿化学中的前体进料不同，微秒长的振荡火花控制蒸汽组成，其最终保留在合金NP中。所得的NP范围从二元到HEAs，在室温下具有显著的热稳定性。我们表明，纳米尺寸效应确保了这种热稳定性，并模仿混合熵在HEAs中的作用。这一发现与传统的“越小越不稳定”的观点相矛盾，同时使迄今为止从未被合金化的元素组合成为可能。我们甚至通过在合金纳米颗粒中混合本体不混溶系统来打破可混溶性限制。作为强有力的例子，我们展示了合金纳米颗粒作为高性能燃料电池催化剂和三维（3D）纳米打印的构建块，以构建各种架构和组成的HEA纳米结构阵列。我们的研究结果形成了指导HEA-NP合成和将催化和3D打印推向新领域的新规则的基础。
英文摘要：
Synthesizing unconventional alloys remains challenging owing to seamless interactions between kinetics and thermodynamics. High entropy alloys (HEAs), for example, draw a fundamentally new concept to enable exploring unknown regions in phase diagrams. The exploration, however, is hindered by traditional metallurgies based on liquid-solid transformation. Vapor-solid transformation that is permissible on pressure-temperature phase diagrams, offers the most kinetically efficient pathway to form any desired alloy (e.g., HEA). Here, we report that a technique called "sparking mashups", which involves a rapidly quenched vapor source and induces unrestricted mixing for alloying 55 distinct types of ultrasmall nanoparticles (NPs) with controllable compositions. Unlike the precursor feed in wet chemistry, a microseconds-long oscillatory spark controls the vapour composition, which is eventually retained in the alloy NPs. The resulting NPs range from binary to HEAs with marked thermal stability at room temperature. We show that a nanosize-effect ensures such thermal stability and mimics the role of mixing entropy in HEAs. This discovery contradicts the traditional "smaller is less stable" view while enabling the elemental combinations that have never been alloyed to date. We even break the miscibility limits by mixing bulk-immiscible systems in alloy NPs. As powerful examples, we demonstrate the alloy NPs as both high-performance fuel-cell catalysts and building blocks for three-dimensional (3D) nanoprinting to construct HEA nanostructure arrays of various architectures and compositions. Our results form the basis of new rules for guiding HEA-NP synthesis and advancing catalysis and 3D printing to new frontiers.
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