水基氧化石墨烯悬浮液的等温结晶过程与过冷度实验研究

Experimental study on isothermal crystallization and supercooling degree of aqueous graphene oxide suspensions

为研究水基氧化石墨烯悬浮液的浓度对其凝固过程和过冷度的影响,测试并得到了0 ～ 1000 mg/kg的不同浓度水基氧化石墨烯悬浮液的等温结晶曲线.结果表明,氧化石墨烯纳米颗粒的添加不仅能提高悬浮液的导热系数,亦可起到结晶成核剂的效果从而降低悬浮液的过冷度.随着浓度的增加,悬浮液的过冷度呈逐步减小的趋势,当浓度为750 mg/kg时悬浮液的过冷度较纯水可降低3℃以上,而当浓度增大到1000 mg/kg时悬浮液的过冷现象消失.此外,还采用T-history法对等温结晶曲线进行了分析并计算得到了有过冷工况下悬浮液的凝固潜热,发现少量氧化石墨烯的添加对水悬浮液的凝固潜热几乎没有影响.

In an effort to investigate the effect of concentration of an aqueous graphene oxide suspension on its solidification and supercooling degree, aqueous graphene oxide suspensions of various concentrations from 0 to 1000 mg/kg were tested to obtain their isothermal crystallization curves. The results showed that the addition of graphene oxide nanoparti- cles is not only able to increase the thermal conductivity of the suspensions but also serves as the nucleation agents that reduce their supercooling degree. The supercooling degree of the suspensions was shown to gradually reduce with increasing the concentration. The maximum reduction of the supercooling degree, as compared to that of pure water, was found to be greater than 3℃ for the 750 mg/kg suspension, whereas the supercooling phenomenon disappeared when the concentration was increased to 1000 mg/kg. In addition, the T-history method was employed to analyze the isothermal crystallization curves. The latent heats of solidification of the suspensions were thus determined for cases with supercooling. It was shown that the addition of the minute amounts of graphene oxide nanoparticles has negligible influ- ence on the latents heat of solidification of the aqueous suspensions.