水热法制备碱式硫酸镁/氢氧化镁改性膨胀石墨

Preparation of magnesium hydroxide sulfate/magnesium hydroxide modified expanded graphite by hydrothermal method

为了提高低碳耐火材料用膨胀石墨的抗氧化性和分散性,以MgSO_(4)、NH_(4)OH和表面活性剂十二烷基苯磺酸钠(SDBS)、聚乙二醇(PEG)、聚丙烯酸钠(PAAS)为原料,采用水热法对膨胀石墨进行改性,主要研究了NH_(4)OH加入量(n(NH_(4)OH)∶n(MgSO_(4))分别为3∶1、2∶1和1∶1)和表面活性剂种类对水热生成的改性物质的相组成和显微结构的影响,以及对改性膨胀石墨的抗氧化性和沉降性的影响。结果表明,(1)加入不同表面活性剂水热生成的改性物质的种类不同,改性膨胀石墨的抗氧化性和沉降性也随之不同:加入SDBS生成晶须状碱式硫酸镁,加入PEG生成片状氢氧化镁,加入PAAS生成晶须状碱式硫酸镁和片状氢氧化镁;(2)加入不同种类表面活性剂制备的改性膨胀石墨的抗氧化性和沉降性均好于原膨胀石墨的,但均以加入PEG制备的改性膨胀石墨的为最佳。

This work aims at improving the oxidation resistance and dispersion of expanded graphite for low carbon refractories.Expanded graphite was modified by the hydrothermal method using MgSO_(4),NH_(4)OH and surfactants:sodium dodecyl benzene sulfonate(SDBS),polyethylene glycol(PEG),and sodium polyacrylate(PAAS)as starting materials.The effects of the NH_(4)OH addition(NH_(4)OH and MgSO_(4) mole ratios of 3∶1,2∶1 and 1∶1)and surfactants on the phase composition,the microstructure,the oxidation resistance and the sedimentation property of modified expanded graphite were discussed.The results reveal that:(1)different surfactants result in different phase composition of the hydrothermal products,and the prepared modified expanded graphites have different oxidation resisitance and sedimentation property:whisker-like magnesium hydroxide sulfate is generated with the SDBS addition;flake magnesium hydroxide is generated with the PEG addition;both whisker-like magnesium hydroxide sulfate and flake magnesium hydroxide are generated with the PAAS addition;(2)the modified expanded graphites all have improved oxidation resistance and sedimentation property than the original expanded graphite;the modified expanded graphite prepared with PEG is the optimal.