13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Electrification of Glass by Fracture Li Xie,*, Dewen Sun, Jun Zhou Key Laboratory of Mechanics on Western Disaster and Environment, Ministry of Education, PRC, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu * Corresponding author: xieli@lzu.edu.cn Abstract In 1883, Faraday found that some crystals can be electrified by deformation and cleavage and many researchers reported that the brittle materials such as rock can also be electrified. Nowadays, a new technology was developed to forecast earthquake and collapse of mine well by detecting the electrification of rock. In the paper, we set up an instrument to measure the electrification of the broken glass. We observed the electrification of glass by fracture and the charges carried by the broken glass were measured. It was found that the amount of charges was directly proportional to the broken area of glass and the maximum surface charge density can be reached up to 0.5 C/m2. By SEM observation of broken surface, we can infer the charges distribute near initial nick. Keywords Electrification of fracture; Glass slab; Surface charge density 1. Introduction The study on electrification of fracture is not only to develop a new technology to ensure the security of mine wells [1-2], but also to be inferred an electrification mechanism of sand particles in wind-blown sand flux [3]. The fist study on the charge fracture date back to 1883, and Faraday found that some crystals can be electrified due to cleavage and deformation [4]. From then on, many researchers found that the rock can be electrified during the deformation and break. Kornfeld measured the charges and the electric field of the lithium fluoride crystal cleft by a sapphire chisel. He found that in the vast majority of cases, the field of one part of a specimen was positive over the entire extension of the cleavage, whereas the field of the other part of the specimen was negative. He thought the electrification of cleft lithium fluoride resulted from the presence of an intrinsic charge. Many researchers measured the electrification of broken rock, and inferred the charging mechanism, such as triboelectrification, electrification of electron escaping of broken surface [5-12]. Triboelectrification has been known for millennia[13] which means two materials surfaces are contacted (especially rubbed) and separated and the electrical charges can be transferred [13]. Nowadays, researchers like use the term contact electrification to name the charge transfer phenomena after two materials surfaces contact, because subsequent studies found that the contacted surfaces can be electrified if they are contacted and then separated, not necessarily rubbed. The current researches of contact electrification focus on electrification mechanism, that is what kind of charge is transferred, how to transfer charge and what is the drive force to transfer charge [14], which involve physics, chemistry and so on and interests many researchers on the electrification mechanism of chemically identical material. However, the electrification of fracture may be different from the contact electrification, because the electrification of fracture results from the break of material, which means that the part
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