Here, we demonstrate the potential utility of using chemical modification to reorganize metastable nanoparticles into nanostructured nanoparticles without coincidentally inducing extensive necking/sintering. The motivation for this effort derives from the concept that chemical reduction in a single component in a mixed-metal nanoparticle will create segregated islands of a second immiscible phase. Given the very high chemical energies inherent in nanoparticles, the formation of even smaller islands of a second phase can be anticipated to lead to extremely high interfacial energies that may drive these islands to diffuse to cores or surfaces to form core-shell structures that minimize such interfacial energies. Thus, ammonolysis of (TiO₂)_0.43(Al₂O₃)_0.57 composition nanopowders where both elements are approximately uniformly mixed at atomic length scales, under selected conditions (1000°C) for various periods of time at constant NH₃ flow rates leads primarily to the reduction in the Ti species to form TiN or TiON which then appears to diffuse to the surface of the particles. The final products consist of Al₂O₃@TiON core-shell nanopowders that remain mostly unaggregated pointing to a new mechanism for modifying nanopowder chemistries and physical properties.

中文翻译：

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纳米粉及其内部的化学改性：通过在NH3中氮化纳米（TiO2）0.43（Al2O3）0.57粉末来合成核壳Al2O3 @ TiON纳米粉

在这里，我们证明了使用化学修饰将亚稳态纳米颗粒重组为纳米结构纳米颗粒的潜在效用，而不会同时引起广泛的颈缩/烧结。进行这项工作的动机来自这样一种概念，即化学还原混合金属纳米粒子中单个成分会产生第二个不混溶相的隔离岛。考虑到纳米粒子固有的非常高的化学能，预计第二相甚至更小的岛的形成会导致极高的界面能，该界面能可驱使这些岛扩散到核或表面以形成核壳结构，从而最大程度地减少这种现象。界面能。因此，（TiO ₂）_0.43（Al ₂ O₃）_0.57组成的纳米粉，其中两种元素在选定的条件下（1000°C）在恒定的NH ₃流速下在不同的时间段内以原子长度尺度近似均匀地混合，这主要导致Ti物种的减少，从而形成TiN或TiON然后似乎扩散到粒子的表面。最终产品由Al ₂ O ₃ @TiON核壳纳米粉组成，这些纳米粉几乎没有聚集，这指出了一种改变纳米粉化学性质和物理性质的新机制。