The Research Of Controllable Synthesis And Characterization Of Nano Ceria With Specific Exposures

Nano CeO2materials have excellent properties than bulk material in polishes,catalysts, ultraviolet ABForption and ion conductivity, thus widely used in micro-circuitpolishing, air purification, and solid oxide fuel cells, and many other fields. Therefore,controllable preparation of CeO2nano-materials is a major significance in the synthesisfield. Specific exposure of CeO2Nano-crystals has greatly effect to the catalytic activity.Controllable synthesize of CeO2Nano-Crystal have started to attract great passion ofresearchers. Hydrothermal method is an effective method of achieving controllablesynthesize of CeO2nano-materials. However in an actual hot water preparation process,the reagent of choice is blind. There is an urgent need for predictive experimentalreagents to control the morphology of products.The main purpose of this paper is to establish a mineralizer filtering mechanism, soas to achieve the controlled synthesis of nano-materials. Furthermore nano-structure ofceria with different exposure surfaces was characterized, providing theoreticalexplanations for their catalytic properties.At present, the extensive use of first-principles to do theory research in materialsscience filed in particular the atomic structure and electronic properties ofsemiconductor materials.This paper integrated the preparation of Nano material with the first-principles,established atomic adsorption model of specific surface ceria, and based onfirst-principles to calculate the surface energy by the elements adsorption to the ceriaspecific of exposed. In addition, we respectively established the filter mechanism ofmineralizer to control the ceria with the different exposed surface, and optimized thetechnology parameter to synthesis nano ceria. Verified the feasibility of controllablesynthesis of nano ceria with specific exposures, which prepared by the filter mechanismof mineralizer agent established by adsorption atomic mode. Additional, the sampleswere characterized by using such as XRD, SEM, TEM, STEM technology, finally theUV-VIS properties were tested. The main results are as follows:（1） The nano-rods prepared with cerium nitrate hexahydrate and sodium phosphateare thicker and shorter with diameter of³0nm and length of¹00nm, and thoseprepared with cerium acetate hydrate and dibasic sodium phosphate are thinner andlonger with¹0nm in diameter and⁴00nm in length. Microstructural analyses reveal that the two species of nano-rods have the low-energy {111} surfaces and grow alongthe <112> direction. The CeO2nano-rods show well properties of ultraviolet shielding.Three kinds of hybrid architectures with two different types of ceria nanoparticles, thenano-rods and nano-octahedrons were synthesized, within one step via a facile yetefficient hydrothermal process. We demonstrate that morphology of the synthesizedCeO₂nanomaterials can be manipulated via tuning the type and concentration of themineralizer. The synthesis mechanism and chemical evolution of the harvestednanomaterials are also discussed in light of the role played by the mineralizer. Such asimple method to synthesize the functional nano-crystallites with tunable morphologyby tailoring the concentration of mineralizer alone should be applicable to other types ofnanomaterials and significant for a wide range of applications. And we also synthesizedof two types of CeO2nano-rods via the facile and efficient hydrothermal process freefrom any surfactant and template. The synthesized nano-rods are chemically identifiedas CeO2with the standard fluorite structure but their morphologies are different.（2）The affection of the surface energy of ceria （111） surfaces by the differentnon-metals adsorption by first-principles. The surface energy could be reduced, whenF, B,C,Si,P,S, adsorbed while its surface energy rising by H, N,O, Cl,Br,Iadsorption. Thus we could select the mineralizer containing F, B,C,Si,P, S elementsto stabilize oxidation cerium of （111） surface, thus established filter mechanism ofmineralizer. Uses nitric acid cerium as cerium source, selected NaF and NH4Accontaining f and c element as mineralizer agent, through adjusted synthesis parameter.The nono-octahedrons were synthesized successfully by mineralizer NH4Ac whichcontaining c element. To determine chemical composition of the prepared samples, wefirst conducted XRD analysis, the diffraction peaks of the sample stem from the oxideCeO2only, no other impurities. SEM displayed the sample have better dispersibility, thesize of the nano octahedrons was uniform of. From TEM characterization, the exposuresof the Nano ceria were all {111}, and some particles have defects, STEM observationalso shown many defects of nano-ceria surface. As to the mineralizer containing anionreact with Ce3+to produce insoluble cerium, could use them to prepare the nano CeO2under very low concentrations. Nano-ceria octahedral has strong UV adsorption, alsohave20nm blue-shift relative to bulk material. The ultraviolet shielding properties ofCeO2nano-octahedrons were significantly inferior to nano-rods.（3）The affection of the surface energy of ceria （001） surfaces by the differentnon-metals and metals adsorption by first-principles. The surface energy could be reduced, when Sr， La，Mg，Na，Ba，K， Y， Ca metal elements adsorbed while itsdramatically rise by Be adsorption. The surface of （001） plane adsorbed F，B，C，Si，P，S，OH，Cl，Br non-metal elements could reduce surface energy, while adsorbed H，N，O， I were opposite. Based on the principle of the mineralizer of selection, filtermechanism of mineralizer was established. Uses nitric acid cerium as cerium source,selected KOH as mineralizer agent. The nono-cubes were synthesized successfully viaadjusting synthesis parameter. To determine chemical composition of the preparedsamples, we first conducted XRD analysis, the diffraction peaks of the sample stemfrom the oxide CeO2only, no other impurities. SEM presented the sample have betterdispersibility, the size of the nano octahedrons was uniform of. From TEMcharacterization, the exposures of the Nano ceria were all {001}, no defect wasobserved, STEM observation also shown many restructure of nano-ceria surface.Temperature may affect the crystallinity of nano-cube. The ultraviolet shieldingproperties of CeO2nano-cubes were significantly superior to nano-ceria octahedronsand nano-rods. Compared to bulk material, the strongest UV ABForption wave lengththe CeO2nano-cube had22nm blue-shift...