School of Chemical Sciences University of Illinois at Urbana-Champaign 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
Adv Mater. 2010 Mar 12;22(10):1039-59. doi: 10.1002/adma.200904093.
Recent advances in nanostructured materials have been led by the development of new synthetic methods that provide control over size, morphology, and nano/microstructure. The utilization of high intensity ultrasound offers a facile, versatile synthetic tool for nanostructured materials that are often unavailable by conventional methods. The primary physical phenomena associated with ultrasound that are relevant to materials synthesis are cavitation and nebulization. Acoustic cavitation (the formation, growth, and implosive collapse of bubbles in a liquid) creates extreme conditions inside the collapsing bubble and serves as the origin of most sonochemical phenomena in liquids or liquid-solid slurries. Nebulization (the creation of mist from ultrasound passing through a liquid and impinging on a liquid-gas interface) is the basis for ultrasonic spray pyrolysis (USP) with subsequent reactions occurring in the heated droplets of the mist. In both cases, we have examples of phase-separated attoliter microreactors: for sonochemistry, it is a hot gas inside bubbles isolated from one another in a liquid, while for USP it is hot droplets isolated from one another in a gas. Cavitation-induced sonochemistry provides a unique interaction between energy and matter, with hot spots inside the bubbles of approximately 5000 K, pressures of approximately 1000 bar, heating and cooling rates of >10(10) K s(-1); these extraordinary conditions permit access to a range of chemical reaction space normally not accessible, which allows for the synthesis of a wide variety of unusual nanostructured materials. Complementary to cavitational chemistry, the microdroplet reactors created by USP facilitate the formation of a wide range of nanocomposites. In this review, we summarize the fundamental principles of both synthetic methods and recent development in the applications of ultrasound in nanostructured materials synthesis.
最近在纳米结构材料方面的进展是通过开发新的合成方法来实现的，这些方法可以控制尺寸、形态和纳米/微观结构。高强度超声的利用为纳米结构材料提供了一种简便、通用的合成工具，而这些材料通常无法通过传统方法获得。与材料合成相关的与超声有关的主要物理现象是空化和雾化。声空化（液体中气泡的形成、生长和内爆）在气泡内产生极端条件，并作为大多数声化学现象在液体或液-固悬浮液中的起源。雾化（超声通过液体并撞击气液界面而产生的雾）是超声喷雾热解（USP）的基础，随后的反应发生在雾的加热液滴中。在这两种情况下，我们都有相分离的 attoliter 微反应器的例子：对于声化学，它是在彼此隔离的气泡内的热气体，而对于 USP，它是在彼此隔离的热液滴在气体中。空化诱导的声化学提供了能量和物质之间的独特相互作用，气泡内的热点约为 5000 K，压力约为 1000 巴，加热和冷却速率>10(10) K s(-1)；这些非凡的条件允许进入通常无法进入的化学反应空间范围，从而可以合成各种不同寻常的纳米结构材料。与空化化学互补的是，USP 产生的微液滴反应器促进了广泛的纳米复合材料的形成。在这篇综述中，我们总结了这两种合成方法的基本原理以及超声在纳米结构材料合成中的应用的最新进展。
