Basaldella EI, Marco JF
Centro de Tecnología de Recursos Minerales y Cerámica, Cno. Centenario y 506, M.B. Gonnet, CC49 (1896), Argentina
J Colloid Interface Sci. 1999 Jul 15;215(2):339-344. doi: 10.1006/jcis.1999.6241.
The surface transformations induced on kaolinite by different thermal and mechanical treatments have been investigated by means of X-ray photoelectron spectroscopy (XPS), Bremsstrahlung induced Auger spectroscopy, and isoelectric point (IEP) measurements. Heating the kaolinite at temperatures between 500 and 750 degrees C results in the change of a substantial fraction of surface Al from octahedral to tetrahedral coordination, which we associate with the dehydroxylation of kaolinite. Heating at 900 and 980 degrees C brings about the development of an octahedral Al fraction which is associated with the formation of gamma-Al(2)O(3). The development of an Al tetrahedral component in the Al KLL spectra of the mechanically treated (ground) samples has been also observed. The Si/Al atomic ratio obtained by XPS in the thermally treated samples is the same as that shown by the original kaolinite. However, the XPS data show a clear reduction of the Si/Al atomic ratio in the mechanically treated samples, which suggests that the mechanical treatment has induced an Al enrichment of the kaolinite surface. The IEP values indicated a thermal transformation to metakaolinite and mullite with the increase of temperature (750 to 980 degrees C). The IEP change for the milled samples can be only explained by assuming a 30% kaolinite coating by the Al oxide neoformed by grinding. Copyright 1999 Academic Press.
通过X射线光电子能谱（XPS）、韧致辐射诱导俄歇能谱以及等电点（IEP）测量，研究了不同热机械处理对高岭土表面转变的影响。在500至750摄氏度之间加热高岭土，会导致相当一部分表面铝从八面体配位转变为四面体配位，我们认为这与高岭土的脱羟基作用有关。在900和980摄氏度下加热会促使八面体铝组分的形成，这与γ -Al₂O₃的形成有关。在机械处理（研磨）样品的Al KLL能谱中也观察到了四面体铝组分的出现。通过XPS在热处理样品中获得的Si/Al原子比与原始高岭土的相同。然而，XPS数据显示机械处理样品中的Si/Al原子比明显降低，这表明机械处理导致了高岭土表面铝的富集。IEP值表明随着温度升高（750至980摄氏度）会热转变为偏高岭土和莫来石。研磨样品的IEP变化只能通过假设研磨新形成的氧化铝对30%的高岭土进行包覆来解释。版权所有1999年学术出版社。
