Influence Of A New Mineralization Agent And Additives Onproperties Of Silica Brick

In this dissertation, the quartz sand and waste silica brick are used as the main raw materials, sulfite cellulose liquor and a small amount of bentonite are used as binding agents, and the suspension of lime with manganese ore tailings was used as mineralization agent to prepare silica brick samples. In addition, 100 mesh and 1000 mesh silicon carbide powder are used as additives. The prepared samples were fired at 1430 ℃for 20 hours. After that, the bulk density, apparent porosity, compressive strength and refractoriness under load as well as other physical properties of the fired samples were measured. The effects of the manganese ore tailings as a new mineralization agent and silicon carbide powders with two kinds of particle size as additives on the physical properties of silica brick are investigated. At the same time, the mineralogical composition and microstructure of the fired samples were analyzed by X-ray powder diffraction(XRD) and scanning electron microscopy(SEM), respectively. As a result, the effects of the manganese ore tailings and the two kinds of silicon carbide powder on the mineralogical constitution and microstructure of silica bricks are also probed in this study. The some experimental results are enumerated as follows:(1) The silica bricks with eminent properties could be absolutely made by substituting the new mineralization agent(lime milk + manganese ore tailings) for the traditional mineralization agent(lime milk + iron oxide scrap).(2) When using(lime milk + manganese ore tailings) as mineralization agent, with the increase of addition amount of the manganese ore tailings, the content of tridymite in the silica brick samples increased, whereas the content of cristobalite and residual quartz decreased correspondingly. At the same time, the physical properties at room temperature and refractoriness under load of the fired samples were gradually improved at first, and then got worse. When the addition amount of manganese ore tailings is 0.9%, the physical properties of the sample was the best and better than that of the sample prepared by using(lime milk + iron oxide scrap) as mineralization agent.(3) The SEM observations showed that the increasing manganese ore tailings led to the increase of glass phase in the samples and also made the distribution of the glass phase more homogeneous and structure of the samples denser. Moreover, the sample added with 0.9% of manganese ore tailing was possessed of better microstructure than the one added with the traditional mineralization agent.(4) The particle size of silicon carbide additives played an important role on the physical properties, mineralogical composition and microstructure of the silica brick specimens. The results of SEM observation showed that the samples added with silicon carbide had a denser structure than the one without silicon carbide, whereas the samples added with 1000 mesh silicon carbide powder had denser structure than the ones added with 100 mesh silicon carbide powder, which revealed the former had higher sintering degree than the latter. However, the content of glass phase in the specimens added with two kinds of particle size of silicon carbide powder was nearly similar to each other. For the specimens added with the same amount of silicon carbide powder, the sample added with finer silicon carbide powder was in possession of larger bulk density, higher cold compressive strength and refractoriness under load as well as lower apparent porosity than the one added with coarse silicon carbide powder.(5) As far as influence of addition amount of silicon carbide powder on physical properties of the samples is concerned, regardless of fineness of silicon carbide, with the increase of added silicon carbide powder, the bulk density, cold compressive strength and refractoriness under load of the samples were gradually enhanced and apparent porosity of the samples was decreased on the whole. Compared with the sample without silicon carbide powder, the bulk density and cold compressive strength of samples added with silicon carbide powder were improved remarkably.(6) Though the detecting results of XRD indicated that no silicon carbide existed in the sample added with silicon carbide and fired at 1430 ℃for 20 hours, some silicon carbide particles were found in the samples by SEM photographs. However, the phenomenon was not be observed in the samples added with 1000 mesh of silicon carbide powder.