| Normal glass fibers are widely used in fiberglass industry. In recent years, to meet the demands of the military industry, high strength glass fibers are being developed and entering the production stage. However, large amounts of waste fiber become a trouble for the enterprises. This work aims at using the waste for the preparation of sintered glass ceramics and spheroid proppants. Based on the composition of S-type high strength glass fibers a series of magnesium aluminum silicate glasses have been prepared. The influence of addition of other oxides on glass property and crystallization, sintering and spheroidization has been studied. This work can help to accumulate experimental data for the actual reutilization of the waste glass fibers.CeO2, TiO2, Li2 O, CaF2, CaO, ZnO was added into MgO-Al2O3-SiO2 glass containg different amounts of Na2 O. The density and Vicker hardness of the samples were measured.DTA, XRD,SEM and TEM were used to investigate the phase tansformation and crystallization of the glasses. The results indicate that CaO and ZnO increase the density and decrease the Vicker hardness. However, the hardness of the glass containing both CaO and ZnO is larger than the glass only contains CaO. The density and Vicker hardness of the glass first increases then decreases with Na2 O. It is also observed that the addition of CaO, ZnO and Na2 O decrease the viscosity and the glass transition temperature. The heat treatment of the glass containing 3% Na2 O leads to the formation of lithium aluminum silicate, spinel and titanium dioxide. With the increase of Na2 O, a new phase of anorthite sodian forms, and the spinel and TiO2 crystal phases changes to zinc magnesium spinel and magnesium titanium oxide.The magnesium aluminum silicate glass with good crystallization behavior was used for the sintering experiment. The results indicate that with the increase of the molding pressure and the decrease of the particle size, the sintered samples show improved mechanical properties. Glass powders with a wide distribution of particle size favors the formation of sintered samples with high mechanic properties. Sintering temperature and crystallization during the sintering affect the mechanical properties of sintered samples. With the increase of sintering temperature, crystallization retards the sintering, giving products with decreasingproperties.Spheroidization experiments show that small particles can be easily spheroidized. Both crystallization and glass melting rate affect the roundness and sphericity of the obtained particles. The glass containing 9%Na2O, 3% NaCl and 1% Ca F2 has a suitable viscosity and no crystallization after heat treatment, thus the galss powder can be well spheroidized with sphericity and the roundness of 0.9. However, the compressive test breakage rate is 28%, the acid solubility is 10.56%. The product can only be used as proppants at low pressure. In addition, the isolation agent MgO used in the spheroidization is about 50 wt %. Too much MgO will leave residue in the glass spheroidized sample and difficult to separate. A low amount of MgO does not benefit the spheroidization. |
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