Hydrothermal Synthesis Of NASICON-type Zirconium Phosphate Crystals And Their Characteristics Of Ion-exchange Assembly

The NASICON-type (Sodium Super Ionic Conductor) zirconiumphosphates, a kind of compounds having high temperature stability, chemicalstability and radiation stability, can form firmly structure with two thirds ofthe metals ions of the periodic table. Due to its exceptional structure, theNASICON-type zirconium phosphates exhibit excellent properties of ionicconduction, low thermal expansion and capability of ion exchange, etc. As aresult, they are one kind of outstanding carriers for antimicrobial, catalysts,nuclear radwaste and so on.The existing methods for preparation of NASICON-type zirconiumphosphates have a number of drawbacks, i.e., the requirement of complicatedprocedure, high reaction temperature, long reaction time and impure crystals.This thesis presents research on preparation of pure NASICON-typezirconium phosphates via the facile hydrothermal method by using oxalic acidas mineralizing agent, ZrOCl₂ as zirconium root and H3PO4 or NaH₂PO₄/NH₄H₂PO₄ as phosphorus root. The mechanism of hydrothermal synthesis wasinvestigated. It was shown from the results that compatible addition ofmineralizing reagent can reduce the hydrothermal temperature and shorten itsduration.There are some reports about the application of NASICON-typezirconium phosphates as carrier of antimicrobial and catalysts, but basicdatum are still lacks for supporting their application. In this thesis, thebehavior of ion exchange, immobilization and leachability in solution withAg⁺ by NASICON-type zirconium phosphates were conducted. The resultsshowed that NASICON-type zirconium phosphates were a kind of goodexchanging materials for Ag⁺, and this immobilized materials had controllableleaching performance. Besides, new approach for disposal of nuclear radwastesuch as Sr isotope was explored by NASICON-type zirconium phosphates attemperature of 200℃ in an autoclave. The results indicated that this methodcould remove Sr2+ in the solution on suitable conditions and NASICON-typezirconium phosphates carrying Sr2+ have low leaching rate.The thin films with special structure have unique functions.Hydrothermal synthesis of zirconic films with different morphologies wastested on the substrate of Zr at different conditions in this thesis. It was foundfrom primary experiments that the phosphate film with sheet nano-clusterstructure had significant performance of exchanging assembly with Ag+, andthis film exhibited obvious photo-current response after exchanging assembly.