Superficial Physical Property And Functionalization Of SiO₂ Particles

SiO2 has been widely used in industry for its excellent chemical and thermal stability. It can be used to make optical fiber, crystal and other key components used in optoelectronic technology, it can also be used after reduction to various semiconductor devices used in verious kinds of electronic, automatic control make and measuremenal technologies. Refined, quartz and silica powders, white carbon and nano-SiO2 have been widely used for rubber reinforcement, UV shielding and electronic packaging materials. With the rapid development of information industry, silica powder has a bright future as IC packaging materials. Now, large-scale and supper-large scale integrated circuit demand increasingly high on packaging material, especially for the spherical shape of particle. Further study on the spherical SiO2 particles will broaden its application. In addition, SiO2 particle coated with functional surface has the appropriate light, color and other features whice will further expand its applications. Silicate-based luminescence materials has good chemical and thermal stability and has been concerned for a long time, which will occupy a very important position in the field of luminescent materials.This paper included two studies, one is SiO2 shaping and coating of luminescence materials one SiO2 surface:1) In the experiment, SiO2 particles was spheroidized by either chemical method or combined chemical and mechanical method at different temperatures with different solution concentration and time. The results showed that the best condition for chemical method of SiO2 shaping was in 2.5% KOH at 220℃for 24h, at this time some edges became smooth when further increasing the concentration of KOH, SiO2 particles initiated crack and displayed new sharp edges and corners. Simple chemical method only showed some effect on SiO2 shaping, After combining different concentrations of KOH, whice is milling of SiO2 particles the effect was much better than the previous method.2) The granular SiO2 was coated on the surface by hydrothermal method (using Mn2+ doped nano Zn2SiO4 with either KOH or NH3.H2O added respectively). The structure and surface morphotagy of the coating and the luminescence property before and after heat treated in ambient at different temperatures were analyzed. Meanwhile the formation mechanism of Zn2SiO4 crystal in the hydrothermal process was also investigated. XRD patterns showed that Zn2SiO4 film was obtained on the surface of SiO2 particles with KOH at the reaction temperature of 220℃for different reaction time. SEM analys showed that the shape of Zn2SiO4 is in the form of hexagonal prism. The coated layer of Zn2SiO4 was different under different reaction conditions. The photoluminescence measurements showed that the reaction products of Mn2+ doped nano-Zn2SiO4 coated on the surface of SiO2 particles have two photoluminescence spectrums. A set of spectrums was green light at 522nm observed with excitation band at 250nm and the other set wa blue light at 440nm with a wide excitation band from 340nm to 410nm. The former is obviously dued to Mn2+ ions exsisted in the crystal and the latter may come from the SiO2 matrix. When using NH3·H2O as a catalyst and a reaction temperature of 220℃with different time, the untreated samples only showed a 520nm green emission peak. After heat treatment, there was no significant change in light intensity, but all showed a wide band emission from 470nm to 520nm; At temperatures of 120℃, 160℃and 180℃and reaction time of 6d samples showed a blue emission peak with the wavelength of 470nm. At temperatures of 200℃and 220℃samples also showed a green emission peak at 520nm. This emission intensity after heat treatment had no significant change, but all showed a wideband emission from 470nm to 520nm.