No abstract

Aluminum nitride (AlN) powders manufactured via three major commercial processes, namely, chemical vapor deposition from triethyl aluminum, carbothermal reduction and nitridation of alumina, and direct nitridation of aluminum, were exposed to moist air at room temperature to investigate the degradation mechanism and kinetics. In the degradation, the powders were initially hydrolyzed to amorphous aluminum oxyhydroxide, which subsequently transformed into mixtures of crystallized aluminum trihydroxide (Al(OH) 3 ) polymorphs, i.e., bayerite, nordstrandite, and gibbsite, forming agglomerates around the unreacted AlN. The data were fitted by using the unreacted-core model. Three stages were found in the degradation: the stage of an induction period at the beginning, followed by a stage of fast hydrolysis with the chemical reaction being rate controlling, and finally, with gradual closing of pores in the structure of Al(OH) 3 around AlN, changing to a stage of slow hydrolysis that was controlled by mass diffusion through Al(OH) 3 . The existence of an induction period was attributed to slow hydrolysis of the surface oxide/oxyhydroxide layer. The powder produced by the carbothermal process showed the longest induction period, which was attributed to its surface structure being different from other powders. 937J ournal

No abstract

A light diffuser film based on hollow silica nanoparticles as fillers was facilely fabricated by coating suspension of the particles in a UV-curable acrylate monomer solution on a cleaned glass substrate. The amount of the particles in the films was varied from 5 to 20 vol%. The optical properties and the light diffusing ability of the films were then studied and further compared to those of the cleaned glass. The result revealed that the films become opaque when the amount of the particles increases. The increment of the particles also leads to the formation of aggregated particles with a larger size and homogeneous dispersion as the FE-SEM images had been presented. Although the films exhibit the opacity, their total transmittance is still high and close to the cleaned glass transmittance. Moreover, the improved diffuse transmittance of the films is obtained from the increased amount of the particles. The increment of the particles also provides the different scattered light image sizes with a homogeneous light resulting in a distinct light diffusing ability. Those results indicated that the films based on the hollow silica nanoparticles as fillers are probably applied for light diffuser films in the LCD industry.

No abstract