Papers by Author: Yu Qin Liu

Abstract: A series of montmorillonite/alkylammonium complexes were prepared by the intercalation reaction between montmorillonite and Octadecyltrimethylammonium chloride (OTA). The effects of OTA dosage and intercalation duration on the structure and gelating properties of the complexes were investigated. And, the correlation between the structure of complexes and their gel viscosities were discussed. Results indicate that the OTA dosage and retention time have remarkable influence on the structure and gelating properties of montmorillonite/alkylammonium complexes, and the gelating properties also relates to the arrangement of the alkylammonium molecules in the interlayers of montmorillonite. Along with the increase of the OTA dosage under the same retentation time, both the d001 value of the montmorillonite/alkylammonium complexes and the adsorption amount of OTA increase to some extent, and the layer structure of the complex tends to show an interstratification structure. However, maximum gel viscosity of the complex was obtained at a moderate OTA dosage of 1.1~1.3CEC. Along with the increase of the retentation time, the adsorption amount of the OTA shows little variations, but the interlayer structure of the complex prepared under longer retention time tends to form a stable monolayer structure from an unstable interstratification structure under shorter retention time, and the gel viscosity of the complex increases gradually to the maximum value.

Abstract: The structure and thermal property of organomontmorillonite (OM) were studied by X-ray diffraction (XRD), differential thermal analysis (DTA), and thermalgravimetric analysis (TGA).Based on the thermal property of OM, a new method for quantitative characterization of the alkyl-ammonium adsorbed in the layers was established, and the influence of adsorption amount on the viscosity of OM gel was examined. Changes in the basal spacing of OMs and Na-montmorillonite (Na-mont) indicated that alky-ammonium ions intercalated into the montmorillonite layers. TGA results showed that OM and Na-mont had different thermal property, Na-mont held more free water in the layers. The intercalated alkyl-ammonium in OMs decomposed at the temperature of 230~480°C. Effective dosage (DOSeffective) has significant influence on the viscosity of OM gel. Under the optimal DOSeffective(1.1~1.3CEC), the alkyl-ammonium cations can fully cover the exchangeable site in the layers, then the “card-house” structure formed. Structure of the alkyl-ammonium cations determines the intercalation efficiency, the longer the carbon chain, the higher the intercalation efficiency. The intercalation efficiency has no evident correlativity with the viscosity; however, structure of the alkyl-ammonium cations determines their arrangement in the layers.

Abstract: Thixotropic gel can be formed in the organic solvents is one of the most important application characteristics of montmorillonite/octadecyl trimethy ammonium chloride complexes. The key factor influencing the formation of gel is the preparation technology, and the posterior disposal process is also an important affecting factor which should be paid more attention to. In the paper, the effects of washing, drying temperature, grind size, activators and the polarity of solvents on the gel viscosity of montmorillonite/octadecyl trimethy ammonium chloride complexes were systematically studied. The research shows that fully washing can elute the octadecyl trimethy ammonium chloride ions or molecula adsorbed on the layer and the edge of montmorillonite crystal, and improve viscosity of gel formed by the complexes. Controlling the drying temperature at the range of 90－100°C and ensuring the complexes with a little interlayer water are favorable for the gel formation of the complexes. When the granularity of the complexes is less than 0.074mm, particles in solvents can fully produce solvation action, solvent swells and strips, and then form the thixotropic organic gel. Using the 95% ethanol as the activator, when its dosage is 5 wt%, its activation effect is better. The stronger the polarity of the dispersing solvent is, the more favorable the formation of the organic gel with higher viscosity is.