Research On Structure And Devitrification Behaviour Of Aluminoborosilicate Glass Fibre With Low Dielectric Constant

In recent years, with the rapid development of China’s electronic information industry, communication equipments are proposed for the demands of high-speed, high-frequency and miniaturization. Printed circuit boards and radomes are key parts of the transmission devices, and low dielectric constant glass fiber is an indispensable part of these in their reinforcements when acting as their reinforcements.The object which was studied in this paper is low dielectric constant glass, whose application background was phenomenon of phase separation and crystallization that might be encountered when drawing glass fiber. Fixing the remaining components in the glass, molar ratio of divalent oxides and Ca O and the amounts of Ti O2 was changed. The serial number was setted as kn(n = 1, 2, 3, 4) =(MO /(MO + Ca O))(MO is Mg O, Sr O, Ba O, Zn O). The structure and devitrification behavior of low dielectric constant glass fiber were investigated by the methods such as(MAS)NMR, FTIR, DSC, gradient temperature crystallization furnace, XRD and SEM ect.The main results were as followed:With increase of k1, the glass network structure was depolymerized gradually, the content of [BO4], [Al O4] and Q4( [Si O4] that contains four bridging oxygen)decreased, [BO3] gradually increased;The thermal stability decreased;The range and hihgest value of temperature of devitrification which was mainly caused by phase separation increased;When k1 was smaller, morphology of phase separation looked like communicating honeycomb, whose mechanism is called Spinodal Decomposition or Metastable Phase separation.Along with changes in composition and heat treatment, the phase that is rich for alkaline earth metal ions and boron clustered and formed droplet phases whose diameter is about 1μm, stable Phase separation.With increase of k2, the content of [BO4], [Al O4] and Q4 increased slightly in the glass structure, the glass network structure becomed a little more stable. The range and highest temperature of devitrification which is mainly caused by phase separation decreased.With increase of k3, the glass structure was more stable, the content of [BO4] decreased after the increase in the glass structure due to "boron anomaly" phenomenon. [Al O4],Q4,bridging oxygen gradually increased. Ba O could enhance network structure of glass, and the enhancing effect is greater compared to Sr O. The range and highest temperature of devitrification decreased, which is mainly caused by phase separation.With increase of k4, the content of [BO4], [Al O4] and Q4 in the glass reduced, while the number non-bridging oxygen increased, which meaned that Zn O had damage to the glass network, and the change was greater Compared with the Mg group.Its density, range and highest temperature of devitrification decreased increased. Devitrification is mainly caused by Phase separation when the content of Zn O and the heat treatment temperature is small, however with the addition of Zn O and heat treatment temperature and holding time becomed bigger, crystal would be found in the devitrification glass. The main phase was aluminum zinc oxide(Al2Zn O4), and the second phase was aluminum borate(Al8B4O33).Ti O2 had the function of weakening the structure of glass and promoting phase separation and crystallization. With the addition of Ti O2, the content of [BO4], [Al O4] and Q4 was gradually reduced, three-coordinated boron [BO3] increased, which meaned that stability of the glass structure reduced. Its density increases, range and highest temperature devitrification greatly increased. The phase separation and crystallization becomed easier, the main crystal phase was rutile titanium oxide crystals that looked like lath about 1μm, and the second phase was granulated aluminum borate(Al18B4O33) crystals.