Synthesis Technology Of Functional Inorganic Materials Via Wet Chemical Routes

In recent years,the researchers discover that the properties of materials are related not only with the size of the crystal but also with the morphologies such as the dimension,the exposed planes and the surface structures.All of these factors may play a key role in the properties of materials such as electronic,optical,magnetic,acoustic,thermal and mechanical properties. For example,compared with bulks materials,one-dimensional nanoscale materials,with their possible quantum-confinement effects and anisotropy,exhibit distinct chemical and thermal properties.Hollow nano/microcrystals,with their large surface areas,may have great advantages in the catalyst and transformation of medicine.In this dissertation,systematic explorations have been carried out on new synthetic strategies of functional inorganic nano/micromaterial(Nb₂O₅,Mg₂B₂O₅) and their structure fabrication based on chemical solution method.The main points can be summarized as follows:A general chemical strategy based on coordination-assisted preferential etching process to fabricating Nb₂O₅(orthorhombic) hollow tubes by a two-step process has been reported.Nb₂O₅ rods serviced as precursors are synthesized by a simple hydrothermal method and the diameter of rods can be tuned by varying the synthetic conditions.The orthorhombic Nb₂O₅ tubes are then obtained by a coordination-assisted preferential etching reaction of the precursors.The controlled interior structure of Nb₂O₅ tubes can also be achieved by tuning reaction time.The orthorhombic Nb₂O₅ hollow spheres are fabricated through the sacrificial template route.As we know,the formation of the nanocrystals involves two steps:nucleation of an initial 'seed' and growth.So the diameters of the niobic acid spheres are tuned by controlling the concentration of ammonia.The porous(NH₄)₃Nb(O₂)₂F₄ are also be prepared by precipitation at room temperature.Magnesium borates with controlled compositions and morphologies are successfully fabricated through a two-step synthetic process.Without any organic additive or catalyst, MgBO₂(OH) nanorods and Mg₇B₄O₁₃·7H₂O hollow spheres can be prepared by controlling the concentration of hydroxide ions in hydrothermal condition.Hydroxide ions used here not only act as precipitator but also as shape-directing agent to change the relative specific surface energies of various planes and eventually influence the nucleation and growth of crystal. Mg₂B₂O₅ and Mg₃B₂O₆ with corresponding morphology can be obtained through a simple heat treatment process of MgBO₂(OH) and Mg₇B₄O₁₃·7H₂O precursors at 700℃for 2 h under air atmosphere...