水热碳化制备碳微球及其在Al2O3–SiC–C浇注料中的应用

Preparation of Carbon Spheres by Hydrothermal Carbonization and Its Application in Al2O3–SiC–C Castable

以淀粉为碳源,采用水热碳化法制备了粒径均匀、分散性良好的碳微球。研究了反应温度、淀粉浓度和反应时间对合成碳微球显微形貌和粒径大小的影响;用所制备的碳微球替代球形沥青制备了Al2O3–SiC–C浇注料,研究了碳微球替代量对浇注料流动性和常温力学性能的影响。结果表明：所合成的碳微球为无定形碳。随着反应温度的升高和淀粉浓度的增加,碳微球的粒径呈增大趋势。水热时间对碳微球粒径的影响较小,但过长的水热时间会导致碳微球团聚现象严重。水热温度为180℃、反应时间为12 h及淀粉浓度为0.5 mol/L时所制备的碳微球分散度好且粒径均匀,其平均粒径约为1.3μm。在相同加水量的条件下,当碳微球替代沥青的量为50%（质量分数）时,所制备浇注料的流动值提高了15 mm,其抗折和耐压强度分别从6.7及29.2 MPa增加至7.6和48.0 MPa。

Monodispersed carbon spheres （CS） were prepared via a hydrothermal carbonization method using starch as a starting material. The effect of process parameters （i. e., reaction temperature, reaction time and starch concentration） on the microstucture and particle size distribution of CS was investigated. Moreover, the substitution of ball pitch with CS on the preparation of Al2O3-SiC-C castable was discussed. The self-flow value and physical properties of CS containing castable were also analyzed. The results show that the CS is amorphous. The size and dispersion of the prepared CS can be easily controlled by the process parameters. The particle size of the prepared CS increases with increasing the reaction temperature and the starch concentration. The reaction time has a slight effect on the particle size of the prepared CS. However, a longer soaking time can result in the aggregation of the CS. The monodispersed CS with an average diameter of 1.3 μm is obtained at the reaction temperature of 180 ℃, reaction time of 12 h and starch concentration of 0.5 mol/L. At the same amount of water, the self-flow value of the Al2O3-SiC-C castable containing 50% （mass fraction） CS is 15 mm higher than that of the castable only containing ball pitch when the substitution quantity of CS is 50% （in mass fraction）. The flexural strength and compressive strength of as-prepared CS containing castable increase from 6.7 and 29.2 MPa for the castable containing only ball pitch to 7.6 and 48.0 MPa, respectively.