title: Size-Dependent Brittle-to-Ductile Transition in Silica Glass Nanofibers.
abstract: Silica (SiO2) glass, an essential material in human civilization, possesses excellent formability near its glass-transition temperature (Tg > 1100 °C). However, bulk SiO2 glass is very brittle at room temperature. Here we show a surprising brittle-to-ductile transition of SiO2 glass nanofibers at room temperature as its diameter reduces below 18 nm, accompanied by ultrahigh fracture strength. Large tensile plastic elongation up to 18% can be achieved at low strain rate. The unexpected ductility is due to a free surface affected zone in the nanofibers, with enhanced ionic mobility compared to the bulk that improves ductility by producing more bond-switching events per irreversible bond loss under tensile stress. Our discovery is fundamentally important for understanding the damage tolerance of small-scale amorphous structures.
authors.affiliation: Department of Mechanical Engineering & Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Junhang
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Mechanical Engineering & Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Jiangwei
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Nuclear Science and Engineering and Department of Materials Science and Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.|Department of Materials Science and Engineering, Institute I, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) , 91058 Erlangen, Germany.
authors.forename: Erik
authors.initials: E
authors.lastname: Bitzek
authors.forename: Jian Yu
authors.initials: JY
authors.lastname: Huang
authors.affiliation: Department of Mechanical Engineering & Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: He
authors.initials: H
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University , Hangzhou 310027, China.
authors.forename: Limin
authors.initials: L
authors.lastname: Tong
authors.affiliation: State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University , Hangzhou 310027, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Department of Nuclear Science and Engineering and Department of Materials Science and Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors.forename: Ju
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Mechanical Engineering & Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Scott X
authors.initials: SX
authors.lastname: Mao
mesh_terms: D005898:Glass / Q000737:chemistry*; D006801:Humans; D057139:Nanofibers / Q000737:chemistry*; D044367:Phase Transition; D012822:Silicon Dioxide / Q000737:chemistry*; D013696:Temperature; D013718:Tensile Strength
chemical_list: D012822:Silicon Dioxide
keywords: Brittle-to-ductile transition; glass surface; in situ transmission electron microscopy; plasticity; silica glass