Search

Inverse opal zirconia is useful in many ways because of their ability to combine several chemical and physical properties. In this research, polystyrene template was fabricated by self-assembly method and inverse opal zirconia was prepared by colloidal crystal-templating method. The process of preparation of inverse opal zirconia as well as effects on morphology and phase of as-prepared inverse opal zirconia were studied. The results showed precursor ratio of zirconium acetate and methanol, mass ratio of polystyrene templates and precursor and dipping times had remarkable influence on morphology of inverse opal zirconia. When the precursor ratio was 1:1; the mass ratio was 1:15 and dipped once, much better morphology of inverse opal zirconia was obtained. The mass ratio, sintering temperature and holding time had significant effect on crystallization of zirconia. Pure phase zirconia could be obtained when sintered at 600 oC, holding time was 2h and the mass ratio was 1:1. A distinguished single stop band in the visible region of the spectrum and unique structural color were observed in inverse opal zirconia, which will make this material promising candidate for novel pigment.

Activated pores in the glass-alumina composite during isothermal sintering at 710?C by colloidal processing were extracted by the threshold conversion of the micrograph obtained with a field emission scanning microscope. The relative ratio of the activated pores in the final stage of sintering to that in the initial stage of sintering was calculated. The kinetics equation of the evolution of the activated pores during isothermal sintering was established. The pores evolution confirms the viscous flow of the glass matrix, indicating the validity of the predominant liquid-phase sintering of the composite.

The Bi2O3-SiO2 (BS) glass-ceramics were prepared by melt-quench technique, and the crystallization kinetics and phase transformation behavior were investigated in accordance with Kissinger and Johson-Mehl-Avrami equation, DSC, XRD and SEM. The results show that in the heat treatment process (or termed as re-crystallizing process) Bi2SiO5 and Bi4Si3O12 crystals were found consequently. Respectively, the crystallization activation energies of the two crystals are Ep1=14.8kJ/mol and Ep2=34.1kJ/mol. And the average crystallization index of n1=1.73 and n2=1.38 suggested volume nucleation, one-dimensional growth and surface nucleation, one-dimensional growth from surface to the inside respectively. The meta-stable needle-like Bi2SiO5 crystals are easily to be transformed into stable prismatic Bi4Si3O12 crystals. By quenching the melt and hold in 850?C for 1h, the homogenous single Bi4Si3O12 crystals were found in the polycrystalline phase of the BS glassceramics system.

The sintering mechanism of glass-alumina functionally graded materials (G-A FGMs) at 710?C prepared by a novel rapid prototyping manufacturing (RP&M) technology was studied. An integrated kinetics equation was established for the initial 20 minutes. Linear shrinkage is due to the integrated working of both viscous flow of the glass particles and gravitation of the effective activated alumina grain boundaries towards the equilibrium state. The driving force for gravitation of the activated alumina grain boundaries originates from the coactions of passive flow of the alumina particles during viscous flow of the glass particles and the compressive stress formed during cooling. In the middle 10 minutes, the sintering process follows the solution-precipitation mechanism. Confirmed by Scanning Electron Microscope (SEM) and the line scanning Energy Dispersive Spectrum (EDS), a layer of Si-Al eutectic of about 1.04?m on the alumina surface is formed. Then the alkali and alkali earth ions in the glass phase diffuse through this layer and precipitate on the surface. Additionally, the dissolved Al ions can easily transport through the eutectic layer and precipitate in the glass matrix due to the effect of Si in the glass matrix.