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借助原位液槽原子力显微镜(insituAFM)的观察,通过Cd2+,Pb2+替代方解石最外层晶格Ca2+生长模式的实验研究,探讨了Cd2+与Pb2+作用下方解石表面溶解与结晶行为。在液体反应槽中,分别将含不饱和Cd2+与Pb2+溶液流经方解石{101_4}解理面,结果发现:(1)Cd2+的存在不影响方解石沿<4_41>晶向台阶的溶解,而Pb2+的存在则强烈阻碍了方解石沿<441>+晶向台阶的溶解;(2)停止输入溶液含Cd2+,Pb2+溶液后,随着方解石表面与溶液达到平衡,溶解过程逐渐转变为结晶过程。结果显示在Cd2+存在时,单分子生长层具有方解石原有的定向性,而在Pb2+存在时的生长则不具任何定向性。尽管有此差异,但(Ca,Cd)CO3和(Ca,Pb)CO3固溶体都受控于单分子层外延生长这一结晶机理。含Cd2+和Pb2+溶液对方解石溶解动力学的作用与选择性吸附的阳离子半径大小、吸附复合体的几何形状及其结晶学取向有关。Cd2+离子倾向于优先进入更狭小的<4_41>-晶向的微台阶上,而Pb2+则倾向于形成扭曲的八面体络合物吸附在更开阔的<4_41>+晶向台阶上。因此,Pb2+存在下方解石表面生长方向无序可认为是白铅矿和方解石结构差异的原因。
With the help of the in situ liquid-liquid atomic force microscope (insitu AFM), the surface dissolution and crystallization behavior of calcite under Cd2 + and Pb2 + interaction were studied by using Cd2 + and Pb2 + instead of the Ca2 + growth mode in the outermost layer of calcite. The results show that: (1) The presence of Cd2 + does not affect the dissolution of calcite along the <4_41> crystal to the step, whereas the Pb2 + (2) stop the input solution containing Cd2 +, Pb2 + solution, with the calcite surface and solution to achieve equilibrium, the dissolution process gradually transformed into the crystallization process. The results show that in the presence of Cd2 +, the monolayer growth layer has the original orientation of calcite, while the growth in the presence of Pb2 + does not have any orientation. Despite this difference, both (Ca, Cd) CO3 and (Ca, Pb) CO3 solid solutions are controlled by the crystal mechanism of monolayer epitaxial growth. The effect of Cd2 + and Pb2 + containing solutions on the dissolution kinetics of calcite is related to the size of the cation radius of the selective adsorption, the geometry of the adsorption complex and its crystallographic orientation. Cd2 + ions tend to preferentially enter the narrower <4_41> - crystallographic microlevels, whereas Pb2 + tends to form distorted octahedral complexes adsorbed on the more open <4_41> + crystallographic steps. Therefore, disordering the growth direction of calcite surface in the presence of Pb2 + can be considered as the reason for the structural differences between lead and calcite.