Preparation Of Glass-ceramics Produced From Industrial Slag

With the rapid development of industry, plenty of slag was ejected into environment. In order to dispose solid waste effectively and to find some way to reuse them, blast-furnace slag and chrome residue were tried to be used as main material, mixed with other reagents, such as SiO₂, Al₂O₃ and TiO₂, to produce glass-ceramics in this article. Mixtures with different composition were melted under high temperature, melted liquid was rapidly cooled into parent glass, parent glass changed into glass-ceramics after heat treatment. In preparation of glass-ceramics produced from blast-furnace slag, nucleation and crystallization temperature range were determined according to DTA curves of parent glass. Parent glass with different composition was treated under cross heat treatment system to get glass-ceramics. By SEM and XRD analysis, the best material composition and best heat treatment were determined. Crystallization activation energy of parent glass with different content of TiO₂ (used as nucleation-agent) was calculated, glass-ceramics with different content of TiO₂ was analyzed by IR to see phase separation and crystallization condition. In preparation of glass-ceramics produced from chrome residue, the best composition of material, nucleation temperature and nucleation time were decided by DSC curve, crystallization temperature and crystallization time were determined by XRD analysis. Total Cr concentration in lixivium of chrome residue, parent glass and glass-ceramics was measured to show how glass-ceramics fix up Cr.The experiment results showed: In preparation of glass-ceramics with blast-fumace slag, Sample S₁ and S₂ had only a little crystal, crystal in S₁ is uniform, and crystal in S₂ is like branch. S₃ sample treated under 760℃ for nucleation, and 990℃ for crystallization had plenty of uniform crystal, and its main crystal phase was diopside, S₃ sample was composed of blast-furnace slag 25.0g, SiO₂8.0g, Al₂O₃5.0g, MgO1.5g, Na₂CO₃1.6g, TiO₂0.8g. With the content of TiO₂ in mixture increased, crystallization activation energy first decreased, then increased. When the content of TiO₂ was 3.1%, crystallization activation energy was minimum, values with 3 different methods calculating were 135.7, 143.9, 151.7 kJ/mol. IR spectra showed that samples with 3% and 4% TiO₂ had obvious phase separation peaks between 1100～900cm～(-1), which meant there were plenty of crystal in samples. XRD analysis showed that when the content of TiO₂ was 3% and 4%, the formed glass-ceramics had crystal phases of diopside as main phase and rutile as subordinate crystal phase. In preparation of glass-ceramics with chrome residue, the 2# sample was the best component of material, 2# sample was composed of chrome residue25g, SiO₂30g, Al₂O₃3g, TiO₂2g, Na₂SO₄2g, and its best heat treatment system was to preserve temperature for one hour under 750℃ for nucleation and to preserve temperature for two hours under 920 ℃ for crystallization. The glass-ceramics samples were analyzed by SEM and XRD, the XRD analysis results showed that the formed glass-ceramics had the crystal phases of diopside as main phase and chromite as subordinate crystal phase. The total Cr concentration in lixivium of chrome residue, parent glass and glass-ceramics showed that glass-ceramics can fix up Cr in chrome residue, prevent Cr from leaking out to pollute the environment.