Fabrication Of Zirconia Fibers/Films And Their Formation Mechanism Study

Zirconia （ZrO₂） fibers have many features such as high melting point （2600℃）, high-temperature resistance （2200℃）, low heat-conductivity and resistance, and anti-corrosion in acid and alkali solution as well. Therefore, it has been widely used in many areas such as an insulating material, a structural ceramic, catalyst or catalytic support, and battery separators. However, the big problem for this material is how to make it. Because ZrO₂ has very high melting-point, it is difficult to obtain ZrO₂ fibers by traditional melting spinning method. In this thesis, organic polymer fibers were used as the templates to prepare the ZrO₂ fibers and cloths. The method includes two steps: （1） impregnating viscose fibers or cloths with zirconium salt solutions; （2） heating the impregnated viscose materials under controlled condition to remove the organic materials and oxidize zirconium salt into zirconia. The process of impregnating and heating, the structure and properties of ZrO₂ fibers and cloths, the effects of preparing conditions on the fibers’ properties have been investigated. In addition, Models on the impregnating dynamic process and the alkaline absorbing dynamic process have also been developed. Following is the main results we obtained:（1） Rayon is the suitable template materials for preparing ZrO₂ fibers. The physical form and shape of ZrO₂ products is essentially the same as and is mainly determined by the physical form of the starting materials （e.g. rayon）, although considerable reduction in size takes place.（2） Pre-swetling of rayon in water prior to immersion is preferably employed to increase both the rate and extent of salt imbibition. The increasing of immersion time, immersion temperature or Zr⁴⁺ concentration is benefit for the salt imbibition.（3） In the process of heat treatment, the important factor is to avoid ignition and burning of the organic portion of the impregnated materials. At higher heating rate, there exist many holes on the surface of ZrO₂ fibers which could be used as the absorption materials. At lower heating rate, we can obtain the products with smooth surface and with higher mechanical properties.（4） For zirconia cloths, the impregnated rayon cloths undergo shrinkage during the heat treatment. The shrinkage of 40％-70％in dimension takes place in our work.（5） The prepared ZrO₂ cloths have good tolerance in acid and alkali solution. Its surface resistance in 31％KOH solution and the biggest force loading are about 0.003Ω·cm² and up to 168g, respectively.（6）The developed model of impregnating dynamic could effectively predict the zirconium ions’ impregnating behavior. The model for describing the electrolyte-absorption process in zirconia cloths has also been developed successfully. The prediction values are very close to the experimental data, which means the validity of the models.Ni Wenjing（Material Science）Supervised by: Wang Huaping...