Study on the Preparation, Structure Controlling and Application of Nanosized Zirconia

Abstract: In this dissertation, a series of new preparing methods, phase transformation control,and its application were studied, and the principal contents and results of thedissertation are discussed as follows:A homogenous sol was prepared using ZrOCl_2·8H_2O and H_2C_2O_4·2H_2O as rawmaterials, and spherical ZrO_2 nanoparticles were prepared by this sol and distillingtechnology, using n-butanol as templating agent, the results indicate that the propertiesof this product are better than those prepared using traditional technology. UsingZrOCl_2·8H_2O and NH_3·H_2O as raw materials, we also prepared spherical ZrO_2nanoparticles with good properties by the modified precipitating method, usingPEG-butanol network as template. In addition, the crystal form can be adjustedeffectively by controlling the calcination conditions. Based on the above researchresults, we prepare nanosized MgO and Y_2O_3 particles using above PEG-butanoltechnology. MgO nanoparticles with an average size of 30 nm were obtained usingmagnesitun chloride and NaOH aqueous solution as the raw materials. The resultsindicate that this kind of nanosized MgO powders have a uniform particle sizedistribution and a good dispersibility. A novel structural nanosized Y_2O_3 powders witha specific surface area of 160 m~2/g were successfully synthesized using YCl_3 aqueoussolution and ammonia as raw materials and Polyethylene Glycol as dispersant. Thestudy results indicate that this product was a kind tousy structure with a low density of0.05 g/cm~3. Furthermore, the catalytic effects of MgO and Y_2O_3 nanosized powderson the decomposition of Ammonia Perchlorate were investigated, respectively. Theresults suggest that they all have intense catalytic activity on the thermaldecomposition of Ammonia Perchlorate.For the first time, a brand new water-in-oil type microemulsion system(water/span80/Triton X-100/n-hexyl alcohol/n-octane) was studied. This workindicates that such micro emulsion system has two distinct advantages: on one hand,significant improvement on the solubilization capability has been observed (As highas 50 vol.% water content can be achieved in our case comparing with the maximum value around 30 vol.% as in previous reported ones); on the other hand, the cloudypoint in this system can be manipulated in a wide temperature range by simplyadjusting the content of Triton X-100. Taking these advantages into account, we havesuccessfully prepared nanosized zirconia utilizing this system; the results revealedthat the calcination conditions were essential for the crystal growth of nanosizedzirconia. Furthermore, the Raman active-modes with nanometer character wereobserved in the Raman spectra of this kind zirconia made by this microemulsiontechnology. In addition, an important phenomenon, which the order-structure ofmonoclinic phase (m-phase) (-111) direction was firstly come into being, was foundin the phase transformation of ZrO_2 from tetragonal phase (t-phase) to monoclinicphase.For the first time, an oil-in-water type microemulsion system of n-Octane/Tween80/Triton X-100/n-Hexyl alcohol/Water was successfully prepared, and its formationmechanism was detail studied. The relationship between the content of n-Octane andthe system cloudy point was also studied, the results showed that the cloudy pointwould increase with the rising of the environment temperature. In addition, ananosized hollow sphere with an average pore size of 7.5 nm was obtained using theabove microemulsion system as template. Its formation mechanism was studied andthe results indicated that component of the hollow structure was ZrOC_2O_4nanocrystallines.Alkaline earth metal oxides and rare earth metal oxides were used to control thecrystal form of ZrO_2, using oxalic acid sol distilling and modified precipitatingmethod, respectively. To obtain the t-phase ZrO_2, which structure can remain to roomtemperature, the lowest molar ratio of metal ionic to Zr~(4+) was studied. An importantphenomenon, which the order-structure of m-phase (-111) direction was firstly comeinto being, was found in the phase transformation of ZrO_2 from t-phase to m-phase;the second order-structure was (111) direction of m-phase. These two order-structuresare connection with the MP2 and MP8 Raman active-mode of m-phase ZrO_2. Theresults suggest that the phase transformation of ZrO_2 from t-phase to m-phase ismartensite phase transformation induced by the formation of (-111) and (111) of m-phase order-structures. Furthermore, The Raman active-modes with nanometercharacteristic were observed in the Raman spectra of the modified ZrO_2. Comparingwith pure zirconia, there are red shifts on the Raman shifts, this suggest that modifiedZrO_2 has more intense nanometer character.The application of nanosized ZrO_2 powders on the heat-resistance coating ofsodium water glass system was detail studied, the results showed that this kindinorganic coating could resist the high temperature below 1000℃, and theheat-resistance experiments showed that the property of the high-temperature coatingwas very good and could be used in industry…
Key words: nanosized zirconia; soft-template; structural control; inorganic coating

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