Research On The Exfoliation And Reflocculation Reactions Of The Inorganic Layered Materials

Functional nanomaterial and technology is one of the most important research fields, which is also very close to application. Recently, the functional inorganic layered materials are received high attention in preparation, property, applications, and so on. A series of functional ions and groups could be inserted into the interlayer of inorganic layered materials, and many functional nanomaterials with novel properties have been prepared. Meanwhile, inorganic layered materials could be exfoliated into their single nanosheets under some appropriate condition. The exfoliated nanosheets have a molecular thickness and single crystal characteristic, which can be used as the basic unit for reassembling new functional nanomaterials.Based on the special structure and wide application prospect of the inorganic layered materials, the inorganic layered materials with different electricities were chosen as the precursors, and the guest ions and molecules with different sizes were intercalated into the interlayer of inorganic layered materials. The guest-intercalated materials can be exfoliated their nanosheets with different electricities. By using agglomeration or reassembly technologies, a series of the functional nanomaterials with novel properties were prepared and the variation and effecting factors of the reassembling process of metal chalcogenides layers were also researched. The prepared nanohybrids are expected to show potential applications, such as ion-exchange, adsorption, energy storage, separation, catalysis, etc. This thesis mainly consists of two parts that were the review and experiments. The sorts, structural characters, synthesis methods, applications and development foreground of the layered inorganic materials were reviewed; and the main research work and purpose were described in the review part. The exfoliation condition and variation factors on the layered manganese oxide, layered titanate and molybdenum disulfide were studied in the experimental parts, respectively. An alternate stacking layered nanohybrid was synthesized based on the reassembling condition of the nanosheets with the same charge. The main research contents were introduced as follows:(1) Research on the exfoliation behavior of the layered manganese oxide. Firstly, the layered manganese oxide was prepared by using oxidation-sedimentation under hydrothermal condition; and its composition and structure were analysized. When the molar of tetramethylammonium ions was 5 times of the ion-exchange capacity of layered manganese oxide, the layered manganese oxide was soaked in the tetramethylammonium hydroxide solution. The obtained suspension solution was treated for 20 min with the help of the ultrasonic treatment; the layered manganese oxide was exfoliated into MnO₂ single nanosheet. The sonochemistry treatment technology was a fast and simple exfoliation method for layered manganese oxide.In addition, layered titanate was synthesized by solid state reaction and the obtained material was systematically characterized. When the molar of tetrabuthylammonium ions was 5 times of the ion-exchange capacity of layered titanate, the layered titanate was soaked in the tetrabuthylammonium hydroxide solution. The obtained suspension solution was treated for 20 min with the help of the ultrasonic treatment; the layered titanate was successfully exfoliated into TiO₂ single nanosheet.(2) Research on the exfoliation behavior of molybdenum disulfide. LiMoS₂ was firstly prepared by ultrasonic treatment of molybdenum disulfide with n-butyllithium. Sample LiMoS₂ was treated with a HNO₃ solution (pH=4) under ultrasonic, single MoS₂ nanosheets with negative charge were obtained, which was resulted by Mo³⁺ and OH^- adsorbed on the layer surface. On the other hand, single MoS₂ nanosheets with positive charges was obtained when the sample LiMoS₂ was mixed with a HNO₃ solution (pH=1) under ultrasonic treatment, which was caused by adsorbing H⁺ ions on the surface of the nanosheets.(3) Research on the synthesis of MnO₂/MoS₂ alternate stacking layered nanohybrid. The exfoliated suspension of layered manganese oxide (TMA/MnO₂) was obtained by soaking H-type layered manganese oxide in a tetramethylammonium hydroxide under ultrasonic treatment. LiMoS₂ was prepared by ultrasonic treatment of molybdenum disulfide with n-butyllithium. When a Mn/Mo molar ratio was close to 1, a mixed solution of LiMoS₂ and HNO₃ (pH=4) was added to the TMA/MnO₂ suspension, followed by ultrasonic treatment for 2 hours, the alternate stacking layered nanohybrid (MnO₂/MoS₂) was prepared. Basis on the pH variation of the exfoliated MoS₂ suspension, the formation mechanism of MnO₂/MoS₂ alternate stacking layered nanohybrid was also discussed.(4) Research on the synthesis of TiO₂/MoS₂ alternate stacking layered nanohybrid. The exfoliated suspension of layered titanate (TiO₂ exf) was obtained by soaking H-type layered titanate in a tetrabuthylammonium hydroxide under ultrasonic treatment. LiMoS₂ was prepared by ultrasonic treatment of molybdenum disulfide with n-butyllithium. Sample LiMoS₂ was immersed in a HNO₃ solution (pH=4) and sonicated for 2 h, the exfoliated MoS₂ suspension was centrifuged and washed several times to ensure the complete removal of LiOH. When a Ti/Mo molar ratio was close to 15, the exfoliated MoS₂ suspension and the exfoliated TiO₂ suspension were mixed, followed by stirring for 6 days, the alternate stacking layered nanohybrid (TiO₂/MoS₂) was prepared. Basis on the variation of the Mo/Ti molar ratios and the deposit times of the exfoliated MoS₂ suspension, the optimum formation conditions of TiO₂/MoS₂ alternate stacking layered nanohybrid were studied.TEM, XRD, SEM, and TGA-DSC were employed to characterize the obtained samples at different stages.