Ductility observed in flash-sintered yttria-stabilized zirconia
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” straight on the substrate, forming orderly distributed arrays, as suggested by liquid-crystal theory. These vertical arrays were maintained after the C12E6 surfactants were removed. This structure contains abundant inter-sheet slits that serve as ion-movement “expressways” to allow quick ion diffusion. Electrochemical testing revealed that the vertically aligned Ti3C2Tx nanosheets are capable of being charged rapidly. Cyclic voltammetry tests showed that the 200-µmthick film electrode lost little of its chargestorage capacity at a fast charging rate of 1000 mV s–1. This behavior was observed in electrodes that were 40–320 µm thick. The control sample, the same Ti3C2Tx nanosheets but stacked parallel to the substrate, abruptly lost its charge-storage capability starting at an intermediate rate of 10 mV s–1, even though the thickness was only 35 µm. The results unambiguously
highlight the advantage of the vertical arrangement in retaining the fast chargestorage characteristic of MXene-based supercapacitor electrodes. “It is amazing that simply making MXenes ‘stand up’ leads to such a big difference,” says Yat Li of the University of California, Santa Cruz. “This work shows an innovative method of controlling the alignment of electrochemically active materials to achieve ultrafast directional ion diffusion in thick electrodes,” he says. Li was not involved in this study. This method may encourage a plethora of future work. Gogotsi says, “Alignment of mechanically strong and electrically conductive MXene layers may lead to manufacturing of MXene fibers, membranes, coatings, and other forms with unique and anisotropic properties for various applications beyond energy storage.” Tianyu Liu
transformation that grants it limited ductility as crack propagation is slowed. However, further increases in ductility remain elusive as ceramics lack the ability to support a high-enough dislocation density. In a recent issue of Nature Communications (doi:10.1038/s41467-018-04333-2), Jaehun Cho, Qiang Li, Haiyan Wang, and Xinghang Zhang of Purdue University and
their colleagues detail their study of flashsintered YSZ with improved ductility. Ductility observed in flash Flash sintering is a rapid densification sintered yttria-stabilized zirconia process that results in nano-sized grains: eramics have many important highheat is increasingly applied to a sample temperature industrial applications at a constant rate, under a moderate exbut are exemplars of brittle failure. Yttriaternal electric field. When flash sintering stabilized zirconia (YSZ) is a ceramic that was developed by Rishi Raj’s group at undergoes a stress-induced phase the University of Colorado Boulder a few years ago, this process seemed promising as a way to limit the grain Increasing strain Increasing strain 25˚C 400˚C growth of ceramics g a b c d e f h upon sintering, which e=0 e = 5% e = 8% e = 9% e=0 e = 4% e = 6% e = 10% is one of the standard ways of increasing ductility in metals—following the well-known Hall–Petch relation (doi:10.1111/j.1551i 4.0 2916.2010.0
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