Crystallization in pores
Crystallization in pores
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DOI：
10.1016/s0008-8846(99)00002-2
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发表时间：
1999-08-01
影响因子：
11.4
通讯作者：
Scherer, GW
中科院分区：
文献类型：
--
作者：
Scherer, GW
本综述讨论了多孔材料内结晶的热力学以及影响应力发展和开裂的因素。结晶的最大驱动力与在溶液中生长的晶体的过饱和度以及从熔体中生长的晶体的过冷有关。然而，孔壁上产生的应力取决于其他因素，包括孔径、孔壁与晶体之间界面的能量 (gamma(cs)) 以及（对于针状晶体）晶体的屈服应力或屈曲强度。生长的晶体将粒子推向很远的距离这一事实表明 gamma(cs) 通常很大。如果 gamma(cs) 很小，晶体将倾向于在孔壁上成核而不是将它们推开，并且晶体将在没有阻力的情况下通过孔网络传播。即使结晶压力很大，单个孔隙中存在的应力也不会导致失效，因为它作用的体积太小。为了发生断裂，晶体必须传播通过足够大的网络区域，以便应力场可以与控制强度的大缺陷相互作用。在混凝土中，这种规模的生长需要足够的驱动力，以允许晶体穿过与突破半径一样小的孔隙（突破半径是进入控制物体渗透性的较大孔隙渗透网络的入口尺寸）。 (C) 1999 Elsevier Science Ltd. 保留所有权利。
This review discusses the thermodynamics of crystallization within porous materials and the factors that influence stress development and cracking. The maximum driving force for crystallization is related to the supersaturation for crystals growing in solution, and to the undercooling for crystals growing from a melt. However, the stresses generated on the pore walls depend on other factors, including the pore size, the energy (gamma(cs)) of the interface between the pore wall and the crystal, and (for acicular crystals) the yield stress or buckling strength of the crystal. The fact that growing crystals push particles over large distances indicates that gamma(cs) is often large. If gamma(cs) were small, crystals would tend to nucleate on pore walls rather than pushing them away, and the crystals would propagate through the pore network without resistance. Even when the crystallization pressure is large, the stress existing in a single pore cannot cause failure because it acts on too small a volume. For fracture to occur, the crystals must propagate through a region of the network large enough that the stress field can interact with the large flaws that control the strength. In concrete, growth on this scale requires that the driving force be sufficient to permit the crystals to pass through pores as small as the breakthrough radius (which is the size of the entry into the percolating network of larger pores that controls the permeability of the body). (C) 1999 Elsevier Science Ltd. All rights reserved.