Effect of Acid Activation-Hydrophilic-Modified Sepiolite on Comprehensive Properties of Oil-Well Cement

In this paper, sepiolite was treated by acid activation, coupling agent treatment, and sulfonation modification. The purpose of this study was to explore the changes in the fluidity and mechanical properties of sepiolite cement slurry before and after modification. Therefore, the comprehensive properties of unmodified sepiolite fiber (HPS) and acid activation-coupling agent treatment-sulfonated sepiolite fiber (S-O-H-HPS) in oil-well cement slurry were evaluated. FT-IR and microscopic mechanism of cement paste fracture surface before and after sepiolite modification were analyzed. The results showed that HPS can effectively improve the toughness of cement paste, but when the content of HPS was more than 1%, the fluidity of cement paste deteriorated sharply and the compressive strength decreased gradually. The addition of S-O-H-HPS can significantly improve the fluidity and stability of HPS slurry. Without affecting the compressive strength, it can effectively improve the flexural strength and impact strength and reduce the elastic modulus of cement paste. The mechanism analysis showed that S-O-H-HPS can not only form network structure in cement paste but also improve the toughness of cement paste by forming a bridge. This also explains why the strength of S-O-H-HPS cement paste does not decrease significantly with the increase of S-O-H-HPS.

Preparation of Refractory Fiber Cardboard for Building Insulation

A kind of refractory fiber cardboard functioning as building insulation materials was developed. To improve the cardboard abilities to bear high temperature, sepiolite and alumino-silicate fibers were chosen as the raw materials for making refractory fiber carboard. In addition, inorganic adhesives and PVA fiber were used as bonding agents to enhance the physical strength of cardboard. The effect of bonding agents amount on tensile strength of the cardboard were investigated. When choosing inorganic adhesives and PVA fibers as the adhesives, the optimum condition is that amount of aluminum sol and PVA fibers is 30%and 3%-4% by weight, respectively; The best technical conditions for making the refractory fiber cardboard were determined. When the mass ratio of alumino-silicate fibers, sepiolite fiber, PVA fibers is 90: 6: 4, the physical strength of refractory fiber cardboard can be up to 1.556N·m/g. When the bulk density of the cardboard is 305.8kg/m3, the thermal conductivity of insulation cardboard at 200°C is very low, which is only 0.065W/m·K.

Preparation and Characterization of Sepiolite Nanofibers by Microwave Chemical Methods

The sepiolite samples were defibered by using microwave chemical technique, and then different sepiolite samples were obtained with different treatment process. The effect of reaction time on the defibering for sepiolite fiber bundles was studied systematically. Through characterization by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), it was found that the defibered sepiolite samples had an average diameter of about 100 nm and length greater than 20μm. The defibering effect of sepiolite samples as prepared reached optimum at the reaction time of 13 min, and the structural stability of sepiolite was kept after defibering treatment.