Fe_3O_4具有很强的磁性,利用简单的磁选工艺将普通粉煤灰中的铁氧化物(Fe_(1-δ)O)吸取出来,可得Fe_3O_4含量较高的磁选粉煤灰.Fe_3O_4在常温下的电导率为2.5×10~4Ω~(-1)·m~(-1),和沥青基碳纤维的电导率为同一数量级.利用磁选粉煤灰作为导电材料可以制备出具有良好导电性能和力学性能且成本低廉的导电砂浆.随着磁选粉煤灰掺量的增加,粉煤灰颗粒互相接触并逐渐形成局部导电网络,使电子和空穴可通过隧道效应跃过水泥基体阻隔所形成的势垒进行传导;当磁选粉煤灰掺量超过"渗滤阈值"后,砂浆的导电性明显增强,与掺加细集料的碳纤维导电砂浆的导电性接近.
Ferroferric oxide has very strong magnetic.The iron oxide in normal fly ash can be extracted by the simple magnetic separation technique,and then the magnetic separation fly ash,which contains higher ferroferric oxide,will be obtained.The conductivity of ferroferric oxide is 2.5×10~4Ω~(-1)·m~(-1) at normal temperature,which is close to the conductivity of pitch-based carbon fiber. The magnetic separation fly ash can be used as conductive materials to prepare conductive mortar which has favorable conductivity,excellent mechanical properties and lower price.Fly ash particles contact each other and form local conductive net gradually,so electrons and hole get across the barrier of cement matrix to conduct through tunneling effect. When the content of magnetic separation fly ash is beyond percolation threshold,the electrical conductivity of mortar enhances remarkably,being close to the conductivity of carbon fiber mortar.
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