Preparation Of Zirconia Micro / Nano Materials

Zirconia is a technologically important material due to its thermal and chemical stability,and excellent mechanical properties,such as high strength and fracture toughness,high melting point, low thermal conductivity,and high corrosion resistance.Its catalytic properties are especially promising because zirconia has both acidic and basic properties as well as a high thermal stability. These unique mechanical and electronic properties of ZrO₂ ceramics have led to their widespread applications in the fields of structural materials,thermal barrier coatings,oxygen-sensor,fuel cell, catalyst and catalytic support,a possible high dielectric contant material for very large scale integrated circuits,and as a gate dielectric in metal oxide-semiconductor(MOS) dvices.In the present work,novel methods for the synthesis of hollow ZrO₂ microspheres,rosette-like NH₄Zr₂F₉, and ZrO₂ precusor nanowires have been developed.(1) Hollow ZrO₂ microspheres with mesoporous shells have been synthesized by a novel hydrothermal reaction of zirconium oxychloride in the presence of urea,hydrochloric acid and ethanol.The morphology and shell thickness of the hollow microspheres can be controlled by varying synthesis conditions.After calcinations at high temperature the morphologies of the hollow microspheres are essentially preserved.The Pt catalyst supported on the hollow,calcined ZrO₂ microspheres exhibits more excellent catalytic performance in CO oxidation than those on ZrO₂ powders derived from conventional precipitation methods.(2) Single-crystalline,rosette-like ammonium flurorzirconate(NH₄Zr₂F₉) aggregates have been synthesized via a novel reaction route by using zirconium oxychloride,urea, 1-butyl-3-methylimidazolium tetrafluoroborate(BMImBF₄) and hydrochloric acid in ethanol solution.The as-synthesized NH₄Zr₂F₉ can be changed from rosette-like aggregates to hexagonal plates by varying synthesis conditions.After calcination at high temperature the rosette-like NH₄Zr₂F₉ aggregates can be converted into monoclinic phase ZrO₂ with similar morphology.(3) Uniform zirconia precursor nanowires with a dimension on the scale of 25μm in length and 50 nm in width have been successfully synthesized through a solvent hydrothermal method in the presence of an ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate.The morphology of as prepared nanowires was characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),powder X-ray diffraction,infrared spectroscopy(FT-IR),and differential scanning calorimetry-thermogravimetric(TGA-DSC) measurement,etc..The mechanism of the nanowires formation was proposed.