Addition/Correction www.acsami.org
Correction to Hydrothermal-Assisted Cold Sintering Process: A New Guidance for Low Temperature Ceramic Sintering Hanzheng Guo,* Jing Guo, Amanda Baker, and Clive A. Randall* ACS Appl. Mater. Interfaces 2016, 8 (32), 20909−20915. DOI: 10.1021/acsami.6b07481
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he authors add a reference to this work, as cited below.1 The authors regret that this related paper was not brought to the attention of the editors and reviewers when the ACS Applied Materials & Interfaces paper was under review. The oversight was brought to attention by readers after both papers were published. We publish this correction to make the scientific differences clear to the readers of both journals. The statement below is aimed at aiding comparison of the content and lessons learned from the two works. The presented correction statement does not affect the results and conclusions for either article, but should guide the interested reader to different material selection approaches and rationales for other systems that can utilize the cold sintering approaches, especially when properties are affected by size effects. For both articles (A1: ACS Nano, DOI: 10.1021/ acsnano.6b03800; A2: ACS Appl. Mater. Interfaces, DOI: 10.1021/acsami.6b07481), BaTiO3 nanoparticles (NPs) are employed as starting powders because of their high chemical activity and high surface energy, which is beneficial for ceramic densification through hydrothermal reactions. In both cases, significantly enhanced densification was reported at an ultralow temperature of 180 °C. However, the difference between the two articles is as follows. For the article A2, the material employed is pure 50 nm sized BaTiO3 NPs with cubic crystal symmetry and highly crystalline surfaces; the topic throughout the entire article focuses on hydrothermal chemical reactions, and the hydrothermal synthesis mechanisms are thoroughly discussed. This method is demonstrated to be available for BaTiO3 NPs rather than coarse BaTiO3 ceramic powders. In contrast, for article A1, a unique design is proposed using a “bimodal particle size composite”, which is composed of a combination of 50 nm(cubic)/400 nm(tetragonal) BaTiO3 powders. The emphasis of A1 is the thermodynamics of how to utilize NPs to achieve dense ceramics composed of submicrometer-sized coarse particles. Compared to the ceramics produced by pure NPs in A2, those prepared using the bimodal particle mixture in A1 show superior property with enhanced dielectric permittivity at intermediate annealing temperatures. The focus of article A1 is that the NPs are used as a sintering aid to effectively modify the thermodynamic environment through hierarchical particle distributions. It is important to note that in article A1, it has not been possible to densify pure 400 nm BaTiO3 powders under the reported conditions without the addition of NPs. The discussion in A1 focuses on the quantification analysis of the microstructures and thermodynamics, considering surface energy modifications. The bimodal particle size composite in A1 has been regarded as a very important concept, and not only for BaTiO3, but it also provides important lessons in other cases where nanograin © XXXX American Chemical Society
sizes limited performance. The bimodal particle approach teaches us about the design of microstructure in previously unrealized ways. We note here that similar strategies have merit in many other systems, such as MgO. In summary, A2 demonstrates cold sintering is possible in NPs of BaTiO3 and explores the hydrothermal processes involved, whereas A1 shows that cold sintering is possible in mixture of BaTiO3 NPs with coarse BaTiO3 particles and discusses underlying thermodynamic considerations.
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REFERENCES
(1) Guo, H.; Baker, A.; Guo, J.; Randall, C. A. Protocol for UltralowTemperature Ceramic Sintering: An Integration of Nanotechnology and the Cold Sintering Process. ACS Nano 2016, 10, 10606−10614.
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DOI: 10.1021/acsami.6b12137 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
