Department of Physics and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, Germany.
Nanotechnology. 2011 Apr 1;22(13):135601. doi: 10.1088/0957-4484/22/13/135601. Epub 2011 Feb 22.
Nanocrystalline bulk materials are desirable for many applications as they combine mechanical strength and specific electronic transport properties. Our bottom-up approach starts with tailored nanoparticles. Compaction and thermal treatment are crucial, but usually the final stage sintering is accompanied by rapid grain growth which spoils nanocrystallinity. For electrically conducting nanoparticles, field activated sintering techniques overcome this problem. Small grain sizes have been maintained in spite of consolidation. Nevertheless, the underlying principles, which are of high practical importance, have not been fully elucidated yet. In this combined experimental and theoretical work, we show how the developing microstructure during sintering correlates with the percolation paths of the current through the powder using highly doped silicon nanoparticles as a model system. It is possible to achieve a nanocrystalline bulk material and a homogeneous microstructure. For this, not only the generation of current paths due to compaction, but also the disintegration due to Joule heating is required. The observed density fluctuations on the micrometer scale are attributed to the heat profile of the simulated powder networks.
纳米晶块体材料在许多应用中都是理想的，因为它们结合了机械强度和特定的电子输运性能。我们的自下而上的方法从定制的纳米粒子开始。压实和热处理是至关重要的，但通常最终的烧结阶段伴随着快速的晶粒生长，这会破坏纳米晶度。对于导电的纳米粒子，场激活烧结技术克服了这个问题。尽管进行了固结，但仍保持了较小的晶粒尺寸。然而，尚未完全阐明这些具有高度实际重要性的基本原理。在这项结合了实验和理论的工作中，我们展示了在烧结过程中，使用高度掺杂的硅纳米粒子作为模型系统，如何通过粉末的电流渗滤路径与正在发展的微观结构相关联。有可能获得纳米晶块体材料和均匀的微观结构。为此，不仅需要压实产生电流路径，还需要焦耳加热引起的解体。在微米尺度上观察到的密度波动归因于模拟粉末网络的热分布。
