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

doi:10.3969/j.issn.1001-1935.2021.06.001

Abstract

Abstract:

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 MgSO₄,NH₄OH and surfactants:sodium dodecyl benzene sulfonate (SDBS),polyethylene glycol (PEG),and sodium polyacrylate (PAAS) as starting materials.The effects of the NH₄OH addition (NH₄OH and MgSO₄ 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.

Key words: expanded graphite, modification, hydrothermal method, oxidation resistance, dispersion, surfactants

摘要：

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MgSO₄、NH₄OH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NH₄OH加入量(n(NH₄OH)∶n(MgSO₄)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。

关键词: 膨胀石墨, 改性, 水热法, 抗氧化性, 分散性, 表面活性剂

CLC Number:

TQ175.3+2

Duan Hongjuan, Cai Weijie, Zhang Hao, Li Faliang, Zhang Haijun. Preparation of magnesium hydroxide sulfate/magnesium hydroxide modified expanded graphite by hydrothermal method[J]. Refractories, 2021, 55(6): 461-465.

段红娟, 蔡伟杰, 张浩, 李发亮, 张海军. 水热法制备碱式硫酸镁/氢氧化镁改性膨胀石墨[J]. 耐火材料, 2021, 55(6): 461-465.

Figures/Tables 8

Fig.1 SEM photograph of expanded graphite

Fig.2 TG-DTA curve of expanded graphite in air

Fig.3 XRD patterns of modified expanded graphite with different NH4OH additions

Fig.4 SEM photographs of modified expanded graphite with different NH4OH additions

Fig.5 XRD patterns of modified expanded graphite with di-fferent surfactants

Fig.6 SEM photographs of modified expanded graphite with different surfactants

Fig.7 Oxidation rate of modified expanded graphite without or with different surfactants

Fig.8 Sedimentation photo of modified expanded graphite with different surfactants

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