| Glass-ceramics prepared by sintering process using industrial solid waste are often found to be uneven and porous with low crystallinity.To address this problem and achieve the resource utilization,the composition characteristics of industrial solid waste were analyzed in this thesis.It was found that most of the industrial solid waste contained a small amount of magnesium,ferrum or fluorine,which were difficult to be removed.The presence of these elements may affect the sintering behavior and product quality of glass-ceramics.However,the current researches on the influence of magnesium,ferrum or fluorine on the synergistic crystallization and sintering behavior of glass-ceramics,especially the researches on the influence of low element content or multi-element coexistence,are not clear and need to be studied systematically and deeply to establish the regularity,so as to provide scientific basis for the preparation of glass-ceramics from industrial solid waste.To this end,the effect mechanisms of MgO,Fe2O3 and CaF2 on the sintering performance,crystallization behavior,microstructure and properties of CaO-Al2O3-SiO2 or CaO-MgO-Al2O3-SiO2 glass-ceramics were studied using pure reagents in this thesis.The optimal compositions and technological parameters of glass-ceramics containing magnesium,ferrum or fluorine were determined.Based on the above research results,wollastonite and diopside glass-ceramics with excellent properties were prepared from blast furnace slag,bluestone powder and fluorite tailings.The complementary utilization of various industrial solid wastes has been realized.The results of this study can provide scientific basis and technical route for the preparation of glass-ceramics from industrial solid wastes containing Mg,Fe or F elements,and have important economic and social benefits for improving the comprehensive utilization ratio of wastes and performance of glass-ceramics,reducing production costs and protecting the environment.In this thesis,the effects of MgO on the sintering and crystallization behavior and properties of CaO-Al2O3-SiO2 system glass-ceramics were analyzed firstly from a single element of view.The results showed that the additon of MgO can promote the precipitation of the secondary crystalline phase-diopside(CaMgSi2O6)and suppress the precipitation of the main crystalline phase-wollastonite(CaSiO3).The crystalline of glass-ceramics will be transformed to diopside from wollastonite,which will lead an increase in the hardness,flexural strength and acid corrosion resistance of glass-ceramics,respectively.However,a further increase in MgO content will narrow the dense sintering temperature range and reduce the crystallinity of glass-ceramics.This is detrimental to obtain the glass-ceramics with smooth surface and high crystallinity.Therefore,the content of MgO in CaO-Al2O3-SiO2 system glass-ceramics should not exceed 3 wt.%.As the existence of MgO in glass-ceramics could make the crystalline transform to diopside from wollastonite,the mechanism of CaF2 on the diopside based glass-ceramics were studied in further.The results showed that the flexural strength of glass-ceramics with 2 wt.%CaF2 was nearly double higher than that without CaF2.But a further increase in CaF2 content would make the properties worse,which might be related to the fluorite phase precipitated independently.CaF2 could promote the crystallization and the rapid crystallization would hinder the sintering of glass particles.With increasing of heat-treatment temperature,the crystallized glass particles would generate plastic deformation,leading to a new amorphous phase formed in the sintering necks.The formation of new amorphous phase could be benefit for promoting the densification process.Therefore,the content of CaF2 should not be more than 2 wt.%in CaO-MgO-Al2O3-SiO2 system glass-ceramics.Moreover,in order to obtain good performances,the action of CaF2 on glass-ceramics should match with the proper process parameters.The increase of Fe2O3 content could promote the precipitation of the secondary crystal phase-hardystonite(Ca2ZnSi2O7)at lower temperature and narrow the heat treatment temperature range of CaO-Al2O3-SiO2 system glass-ceramics.With increasing of Fe2O3 content,the acid corrosion resistance of glass-ceramics was improved while the hardness,bending strength,water absorption rate and alkali corrosion resistance were reduced.In order to obtain glass-ceramics with smooth surface and good performance,the Fe2O3 content should be controlled below 3 wt.%.Due to the interaction between MgO and Fe2O3,the presence of Fe2O3 strengthened the tendency of MgO to promote the precipitation of diopside while MgO intensified the tendency of Fe2O3 to narrow the heat treatment temperature range.Therefore,the content of Fe2O3 and MgO in CaO-Al2O3-SiO2 system glass-ceramics should be less than 4 wt.%and 1.2 wt.%,respectively.Based on the above studies,wollastonite based and diopside based glass-ceramics were prepared by real blast furnace slag,bluestone powder and fluorite tailings.The results were entirely consistent with the above studies using pure reagents.Furtherly,the effects of the coexistence of MgO,Fe2O3 and CaF2 on the wollastonite based and diopside based glass-ceramics were studied.Among the glass-ceramic samples with cooperative utilization of the above three kinds of industrial solid wastes,the bending strength and hardness of wollastonite based glass-ceramics were 71.84 MPa and 596.70 HV,respectively.Their water absorption rate and acid or alkali corrosion resistance were less than 0.2%.Its comprehensive utilization ratio of industrial solid wastes was 80.10%.The bending strength and hardness of diopside based glass-ceramics were 104.77 MPa and 634.32 HV,respectively.Their water absorption rate and acid or alkali corrosion resistance were less than 0.2%.Its comprehensive utilization ratio of industrial solid wastes was 78.61%. |
PDF Full Text Request