Micrometer-Scale Kirkendall Effect in the Formation of High-Temperature-Resistant Cr₂O₃/Al₂O₃ Solid Solution Hollow Fibers

Abstract

The Kirkendall effect in the formation of hollow structures mainly focuses on nanoscaled metal−metal reactions; few have been performed to fabricate micrometerscale ceramic hollow structures due to the diffusion difficulty.Here, through introduction of the liquid mesophase to accelerate the diffusion rates, we identify that a micrometerscale ceramic hollowing process could be achieved via the Kirkendall effect. The formation mechanism of the Cr 2 O 3 / Al 2 O 3 solid solution hollow fibers is analyzed. The small Kirkendall voids appear at the interface between Cr 2 O 3 and Al 2 O 3 via a bulk diffusion process. Then, the core material diffuses along the pore surface through the liquid mesophase, which leads to the depletion of the center matter and forms the hollow structures. The introduction of the liquid mesophase is the key factor in the formation of Cr 2 O 3 /Al 2 O 3 hollow fibers. The as-fabricated Cr 2 O 3 /Al 2 O 3 hollow fibers have a pore size of 8 μm and a shell thickness of 2 μm. The hollow structure remains well after being heat-treated at 1400 °C for 100 h in air, which indicates that the hollow fibers have excellent high temperature resistance. This method confirms that micrometer-scale ceramic hollow fibers can be fabricated in a simple and low-cost method using commercial raw materials without pollutant emissions. We expect that our findings could offer new perspectives in fabricating micrometer-scale ceramic hollow structures, such as hollow sphere, tube, and heterotypic structures.

Methods to Generate Structurally Hierarchical Architectures in Nanoporous Coinage Metals

“…The Kirkendall effect was first introduced in 1947 to generate pores in alloys. However, the methodology was not accepted by many due to the impairment of mechanical properties of the alloy [62,63]. Recently, synthesis of Kirkendall effect-based hollow 3D structures was achieved.…”

Hollow structures Prussian blue, its analogs, and their derivatives: Synthesis and electrochemical energy‐related applications

“…A hollow structure can also be synthesized according to the Kirkendall effect. [29][30][31] The formation mechanism is based on the different diffusion rate of ions in the multi-component system. The synthesis of cobalt oxide and cobalt sulfide hollow nanocrystals based on the Kirkendall effect was first reported in 2004.…”

Tailoring hollow structure within NiCoP nanowire arrays via nanoscale Kirkendall diffusion to enhance hydrogen evolution reaction

“…Many methods have been developed to synthesize the hollow nanostructured materials, such as using silica as the template [23]. Among these synthetic methods, the template-free method based on the Kirkendall effect which is the drive of the formation of pores near the interface of dissimilar materials during the inter-diffusion of different atom species showing an imbalance of diffusivities, is a facile and economic synthetic procedure compared to the templated methods due to the free-templated [24][25][26]. Several hollow structured TMPs have been reported, which could be synthesized via the Kirkendall effect in aqueous solution.…”

“…For instance, hollow structured CoP nanoparticles were synthesized by using trioctylphosphine as the source of phosphorous in the mixture of Co nanoparticles, octadecene and oleylamine [24]. In addition, the method was also adopted to synthesize other hollow materials such as hollow structured Cr 2 O 3 /Al 2 O 3 nanotubes [25] and core-shell Fe@CoFe 2 O 4 particles [26]. Although hollow structured and 1D nano-sized materials have many advantages over materials with other morphologies [27][28][29], 1D hollow structured TMP containing two transitional metals have not been reported to be synthesized based on the Kirkendall effect in the gas-solid reaction due to the slow diffusion under such conditions.…”