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1.
D. Gournis A. Lappas M. A. Karakassides D. Többens A. Moukarika 《Physics and Chemistry of Minerals》2008,35(1):49-58
Neutron powder diffraction measurements on lithium and cesium saturated montmorillonite samples before and after heat treatment
at 300°C are studied, in order to undertake a complete refinement of crystal structure and unravel the migration mechanism
for the interlayer cations of Li or Cs. Rietveld analysis of the corresponding diffraction patterns finds that montmorillonite
crystallizes in the C2/m space group with unit cell dimensions consistent with the size of the specific interlayer cation. We show that thermal treatment
affects the two types of samples in a different way. This is with respect to their unit cell dimensions and the migration
of Li from the 2b to the 2c clay lattice site, in constrast to the Cs positioning which remains effectively unchanged. 相似文献
2.
Simplified evaluation for swelling characteristics of bentonites 总被引：9，自引：0，他引：9
Bentonite is currently planned to be used as buffer and backfill materials for repositories of high-level nuclear waste because these materials must have the swelling characteristics to seal the waste. In the design for buffer and backfill materials, we must choose the adequate bentonite among many kinds of bentonite in the world. The database of the swelling characteristics of various bentonites and its evaluation will be available when we will select the adequate bentonite. For this purpose, this study performed the laboratory tests on the swelling pressure and swelling deformation of four kinds of bentonite produced in Japan and the United States. These bentonites have different physicochemical properties. This study investigated the characteristics of swelling pressure and swelling deformation from the viewpoint of the physicochemical properties of each bentonite. Furthermore, this study also proposed the simplified evaluation of swelling characteristics of various bentonites on the basis of microscopic analysis. 相似文献
3.
A natural montmorillonite containing radiation-induced defects was studied with Electron Paramagnetic Resonance (EPR) spectroscopy (X- and Q-band). A first dominant native defect, namely native defect 1, is identified. It gives rise to an orthorhombic spectrum with gx= 2.004 ± 0.005 gy= 2.010 ± 0.003, gz= 2.065 ± 0.002. Simulation of the EPR spectrum at X- and Q-band reveals a second native defect with isotropic spectrum at g= 2.019 ± 0.005. Both are electron holes trapped on oxygen atoms of the structure. The native defect 1 is located on an oxygen-silicon bond or a non-bonding orbital parallel to the c* axis. These defects are annealed at 500°C and the half-life determined for native defect 1 is circa 3,000 years. Irradiations with beta rays produced two additional hole centers of lower stability and distinct EPR parameters. Artificial irradiations show that montmorillonite can be used as a dosimeter in a large dose range. 相似文献
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经水化的蒙脱石,具有特殊的性能.本文通过经纯水水化的蒙脱石和未经纯水水化的蒙脱石,在浓Nil_4Cl溶液中的行为及对溶液电导率的影响,说明蒙脱石经纯水水化,在其表面形成较厚的水化膜,在浓NH_4Cl溶液中不易被NH_4~(+)离子“剥离”掉,表现出具有特殊的胶体性能. 相似文献
7.
蒙脱石层间域的性质及其环境意义 总被引：28，自引：0，他引：28
蒙脱石矿物是土壤中比表面积大、分布很广的一种粘土矿物,也是土壤中主要的活性组分之一。蒙脱石层间域是一个特殊的化学反应场所。系统地评述了无机、有机阳离子、农药分子在蒙脱石层间域中的吸附、脱附、氧化还原、催化降解等反应机理,并指出它们的环境化学行为对环境的影响和意义。 相似文献
8.
Grumusols (Vertisols), though having a uniformly high clay content with depth, commonly exhibit a coarsening upward in the sand fraction, either of skeletal grains or of nodules. The non-uniform way in which the wetting front advances in swelling clay soils, with preferred advance and swelling around the coarse grains, produces upward directional forces and uplifting of the grains, thus producing the observed textural differentiation in the coarse fraction. From observations of slickenside distribution in the profile, and using published data on the ratio of lateral to vertical stresses and swelling pressure distribution with depth, a concept of optimum depth for slickensides is developed. Generally at 150–200cm, below the depth of cracking, this depth depends in part on climatic conditions. Below the optimal depth increased overburden pressure and smaller moisture variations restrain the extent of swelling and deformation, above it drying produces cracks and obliterates large slickensides, though a strong bimasepic microfabric remains. The extent of intrapedonic turbation was estimated from measurements of the volume of cracks and of surface material falling into the cracks. It indicates a turnover time of several hundred to a few thousand of years. This agrees with the known increase of radiocarbon ages of organic matter (MRT) with depth which in Vertisols (Grumusols) is only slightly slower than in non-turbating Udolls (Chernozems) and Udalfs (Lessivés). The moderate rate of homogenization due to intrapedonic turbation does not prevent the development of a normal organic carbon profile and it is slower than the upswelling of coarse grains by upward directional forces. The development of shear planes and slickenside structures is a rapid process and not dependent on turbation. 相似文献
9.
总结分析了PVC／蒙脱石（粘）土纳米复合材料的研究进展，并对其应用进行综述。采用熔融插层、悬浮聚合及乳液聚合等方法可以制备PVC／蒙脱石（粘）土纳米复合材料，并被应用到工程材料、阻隔性材料、功能性材料等领域。PVC／蒙脱石（粘）土纳米复合材料与传统的复合材料相比，表现出了更优越的综合性能，且比传统的复合材料轻，具有高强度、高模量、高耐热性、低吸湿性、高尺寸稳定性、阻隔性能好，性能全而超过了PVC树脂。PVC／蒙脱石（粘）土纳米复合材料不仅具有良好的加工性能，与普通的玻璃纤维增强和矿物增强PVC相比，具有密度低、耐磨性好、综合性能优等特性。 相似文献
10.
Four smectites with different total Fe contents (two nontronites, one ferruginous smectite, and one montmorillonite) were
reduced to obtain a range of Fe(II)/Fe(III) ratios and their magnetic properties measured with a SQUID (superconducting quantum
interference device) as a function of applied magnetic field strength at 5 K and as a function of temperature in a field of
0.1 T. The unaltered nontronite and ferruginous smectite specimens showed antiferromagnetic coupling, whereas the coupling
in the reduced samples was ferromagnetic; the paramagnetic Curie temperature increased with increasing Fe(II) content. Data
collected after cooling samples in both the presence and absence of an external magnetic field of 0.1 T showed that at low
temperatures the reduced (ferromagnetic) nontronite and ferruginous smectite samples exhibit a memory effect of previous magnetic
field exposure consistent with superparamagnetic or spin glass behavior. The superparamagnetic/ferromagnetic transition temperature,
T
f
, increased linearly with increasing Fe(II) content for each of the nontronites, but the relationship between T
f
and Fe(II) content differed for different clays, thus demonstrating that T
f
is sensitive to isomorphous substitutions in the clay structure. The montmorillonite was paramagnetic in both oxidized and
reduced forms.
Received: 23 March 1999 / Revised, accepted: 27 August 1999 相似文献