| Nano-ceria is a kind of new composite with higher chemical activity, better redox activity and much more coordination numbers. It is characterized by the advantages of both common nano-materials and rare earth materials. Nano-ceria prepared by detonation method has a huge specific surface area, lots of structural defects and surface oxygen-containing functional groups. Nano-ceria is endowed with a great potential with those special characters as a sort of new materials. This thesis studied the agent formulations, purification process, and characters of agent to prepare nano-ceria. Meanwhile crystal forms, particle size, morphology, ultraviolate absorption properties of nano-ceria were studied. The main conclusions are as below:1. Based on the principle of oxygen balance, special agent used to prepare nano-ceria was prepared in which aqueous solution of Ce(NO3)3·6H2O and NH4NO3acted as the oxidant, paraffin acted as the combustible agent, Span-80acted as the emulsifier, hollow resin microspheres acted as the sensitizer and urea acted as the additive. Seven formulas of special agents were designed by changing contents of Ce(NO3)3-6H20, adding urea, or changing shearing force of emulsion.2. The preparation technology of special agent was studied. The best heating temperature to prepare aqueous solution was studied by condsidering dissolution time and process safety. The best heating temperature to prepare oil phase solution was studied by considering molten time and process safety. Then the best emulsification temperature was studied according to emulsification effect and the best sensitization temperature was studied accroding to sensitization effect. The results indicated that the best heating temperature of aqueous solution and oil phase solution was about130℃, the best emulsification temperature was130℃and rotational speed of emulsifying machine was about2700r/min. Emulsion base should be sensitized immediately after the emulsion process. It’s inadvisable to place it for a long time. Seven kinds of special agents were developed according to these conditions.3. The physicochemical properties and detonation properties of seven special agents were studied. The density and the explosion velocity of the special agents were mensurated. Detonation pressure, explosion heat, explosion temperature and detonation let of the special agents were calculated theoretically. The results showed that the agents have detonator sensitivity; the density of emulsion explosives was1.08～1.20g·cm-3; the storage life was three months; the detonation velocity was above4000m/s; the detonation pressure was5.11 GPa or above; the explosion heat was about580kcal/kg; the explosion temperature was above2000K; the detonation let was750L-kg"1or above.4. The morphology, size and crystal type of ceria particles were tested with X-ray diffraction (XRD) and transmission electron microscope (TEM). And the yield of ceria was studied. Considering particle size, particle appearance, dispersion and crystal type of ceria, the best formula of special agent to prepare nano-ceria was given, which was cerous nitrate hexahydrate with mass fraction by52.88%, ammonium nitrate with mass fraction by39.51%, paraffin with mass fraction by4.97%, Span-80with mass fraction by1.95%and resin-microballon with mass fraction by0.7%. The rotational speed of emulsifying machine was2700r/min.5. The purification process of ceria was studied by the pickling method. A set of orthogonal test was designed. The optimum parameters of purification process were obtained. The parameters were as follows:the pickling time was12h; water to nitric ratio acid was5/1; volum of nitric acid was6mL; the pickling temperature was90℃. The purity of ceria powder was up to99.95%by this method.6. The influences imposed by heat treatment temperature on the particle size and crystal type were studied. Samples with different calcinations temperature were characterized with X-ray diffraction (XRD) and transmission electron microscope (TEM). The results indicated that the best calcinations temperature of ceria powder was600℃.7. Test results showed that the crystal form of nano-cerium oxide particles prepared by detonation method was cubic, the particles were spherical by morphology and particle size of nanosized ceria was20nm-50nm. This method had some advantages, including low cost, short production circle and simple technical process.8. By means of ultraviolet spectrophotometer and BET specific surface test, the nano-ceria was characterized. Test results showed that nano-ceria prepared by detonation mehthod had good UV absorption performance and the absorption wavelength was350nm-220nm. According to IUPAC classification based on BET test, the nitrogen adsorption-desorption curve was type Ⅱ. Shape of most pores inner the particles were tapered and the specific surface area was up to28.5m2/g. |
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