ORALS

SESSION: ManufacturingTuePM2-R4 High Strain-Rate Phenomena / Treatment under Shock Loading–I	Mamalis International Symposium on Advanced Manufacturing of Advanced Materials and Structures with Sustainable Industrial Applications
Tue Nov, 6 2018 / Room: Sao Conrado (50/2nd)
Session Chairs: Manos Maragakis; Session Monitor: TBA

16:20: [ManufacturingTuePM210]
Preparation of Graphene Nanosheets by Shock Waves
Pengwan Chen¹ ; Xin Gao¹ ; Hao Yin² ; Chunxiao Xu¹ ; Qiang Zhou¹ ; ¹Beijing Institute of Technology, Beijing, China; ²Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang, China;
Paper Id: 159 [Abstract]

Shock wave action of high temperature, high pressure and high strain rate lasting for very short time (~10^-6 s) will cause a series of catastrophic changes of material chemical and physical properties, and herein both detonation-driven high velocity flyer impact loading and electrical explosion technique were employed to induce shock wave for the synthesis of high-quality graphene materials. Using solid CO₂ (dry ice) as the carbon source [1], few layer graphene nanosheets were successfully synthesized by reduction of CO₂ with calcium hydride through detonation-driven flyer impact. Furthermore, by adding ammonium nitrate to the reaction system, nitrogen-doped graphene materials were formed in this one-step shock-wave treatment. Similarly, a few layers of graphene and nitrogen-doped graphene materials were also prepared through the reaction of calcium carbonate and magnesium [2], and the shock pressure and temperature are two important factors affecting the synthesis of few layer graphene nanosheets. Besides that, electrical explosion exfoliation of crystalline flake graphite suspension was achieved to synthesize graphene sheets. Meanwhile, graphite nanosheets, few-layer graphene, and especially, mono-layer graphene with good crystallinity were also produced by electrical explosion of high-purity graphite sticks in distilled water at room temperature [3]. Delicate control of energy injection is critical for graphene nanosheets formation, whereas mono-layer graphene was produced under the charging voltage of 22.5-23.5 kV. The recovered samples were characterized using various techniques such as transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, atomic force microscope, and X-ray photoelectron spectroscopy. Therein, the nitrogen-doped graphene was demonstrated to act as a metal-free electrode with an efficient electrocatalytic activity toward oxygen reduction reaction in alkaline solution. This work provides a simple but innovative route for producing graphene nanosheets.

References:
[1] P. Chen, C. Xu, H. Yin, X. Gao, L. Qu, Carbon 115 (2017) 471-476.
[2] H. Yin, P. Chen, C. Xu, X. Gao, Q. Zhou, Y. Zhao, L. Qu, Carbon 94 (2015) 928-935.
[3] X. Gao, C. Xu, H. Yin, X. Wang, Q. Song, P. Chen, Nanoscale 9 (2017) 10639-10646.

SESSION: AdvancedMaterialsTuePM3-R6	4th Intl. Symp. on New and Advanced Materials and Technologies for Energy, Environment and Sustainable Development
Tue Nov, 6 2018 / Room: Guaratiba (60/2nd)
Session Chairs: Pengwan Chen; Werner Urland; Session Monitor: TBA

18:05: [AdvancedMaterialsTuePM314] Keynote
Shock Induced Elemental Doping of Materials
Pengwan Chen¹ ; Xin Gao¹ ; Chunxiao Xu¹ ; Jianjun Liu² ; Xiang Gao¹ ; ¹Beijing Institute of Technology, Beijing, China; ²State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China;
Paper Id: 421 [Abstract]

Shock wave action generates high temperature, high pressure, and high strain rate that last for a very short time (~10^-6 s), which may cause a series of catastrophic changes to the chemical and physical properties of materials. Shock induced doping is a new method to realize elemental doping in specific materials. Two types of shock-induced doping are realized in our experiments; one is pressure-induced diffusion doping, the other is in-situ doping through shock-induced chemical reaction. Shock wave action has been successfully utilized for enhancing certain properties of materials by elemental doping. This work provides a simple but efficient route for elemental doping of materials. In this work, elemental doped TiO₂ nanopowders are synthesized through shock induced doping method. A shock-loading apparatus is designed for generating shock wave and recovering the doped powders, consisting of a sample container, a flyer, and a cylindrical explosive container with an explosive and a detonator. A mixture of dopants and TiO₂ powder is filled in the sample container and impacted by a detonation-driven high-velocity flyer, leading to the doping of N, S, B, Ga in TiO₂powder under high temperature and high pressure. The characterizations of recovered samples confirm the presence of elemental doping. The visible light photocatalytic activity and photo-electrochemistry of shock doped TiO₂ are tested. N-doped graphene nanopowders are synthesized using the mixture of carbon source, strong reductant and nitrogen source through shock waves. Under the impact action of detonation-driven high-velocity flyer, the carbon source is reduced to form carbon atoms with the decomposition of nitrogen source under high temperature and pressure. Subsequently, as the formation of graphene nanosheets occurs from carbon atom deposition, the nitrogen atoms are doped in the formed graphene nanosheets. The nitrogen-doped graphene demonstrates and acts as a metal-free electrode with an efficient electrocatalytic activity toward oxygen reduction reaction in alkaline solution.