发泡温度对常压自发泡煤基泡沫炭结构和机械强度的影响

Effects of foaming temperature on structure and mechanical strength of coalbasedcarbon foam prepared by selffoaming technique under ambient pressure

  • 摘要: 煤的材料化是实现其低碳高值化利用的重要途径之一,煤基泡沫炭因其独特的物化性能 具有良好的应用前景。 以强黏结性焦煤为原料,采用常压自发泡法,在塑性区间内不同发泡温度条 件下制得以开孔结构为主的无定型煤基泡沫炭;利用 SEM、XRD、全自动压汞仪和真密度分析仪等 手段表征了泡沫炭的微观形貌、泡孔结构和微晶结构,并采用电子压力试验机测定了泡沫炭的机械 强度,分析了发泡温度对泡沫炭结构和性能的影响。 结果表明,发泡温度不同引起原料煤热分解以 及胶质体流动性行为变化,导致制备过程中煤样的发泡程度不同,进而对泡沫炭生料( NCF) 的泡孔 结构及碳骨架结构产生影响,使得在最大流动度对应的温度(480 °C)作为发泡温度时所得 NCF- 480开孔率最高(70.89%)、体积密度最小(0.460 g/cm3),但其碳骨架结构相对致密导致其机械强 度提高,抗压强度和抗折强度分别达到 1.63 MPa 和 1.11 MPa。 经高温炭化,炭化泡沫炭( CCF) 的 孔径减小,开孔率和体积密度增大,同时缩聚反应使碳骨架更加致密,导致其机械强度明显提高。 其中,CCF-490 的平均孔径、开孔率以及体积密度均处于中间值且孔径差异较小,其机械性能表现 最为优异,抗压强度和抗折强度分别达到 8.52 MPa 和 5.14 MPa。 合成的具有良好结构性能的煤基 泡沫炭材料表现出优异的应用前景,同时也为煤炭的材料化高附加值利用提供了新思路。

     

    Abstract: The materialization of coal is one of the important ways to realize its lowcarbon and high valueadded utilization. Coalbased carbon foam has good application prospects due to the unique physical and chemical properties. Herein,the coking coal as the precursor was adopted to prepare the amorphous coalbased carbon foam with an opencell structure through the selffoaming technique under ambient pressure by selecting different foaming temperature in the plastic interval. The microscopic morphology,cell structure and crystal structure of carbon foams were characterized by SEM,XRD,a mercury porosimeter and a helium gas displacement pycnometry system;the mechanical strength of the carbon foam was measured by electronic universal testing machine,and by analyzing the effects of foaming temperature on the structure and the performance of the final products was deeply investigated. The results showed that the changes in the thermal decomposition of raw coal and the fluidity behavior of the metaplast caused by the different foaming temperature,resulted in different degrees of foaming of coal samples during the preparation process,which would affect the cell and carbon skeleton structures of the green carbon foam(NCF). Combined with these changes,when the foam temperature at 480 ℃ corresponding to the maximum fluidity was selected and then the obtained NCF-480 had the highest open porosity(70.89%),the smallest bulk density(0.460 g/cm3)but the relatively dense carbon framework structure,which jointly lead to its better mechanical strength. Its compressive strength and flexural strength reached 1.63 MPa and 1.11 MPa,respectively. After hightemperature carbonization,the pore size of the obtained carbonized carbon forms(CCF)reduced,while their open porosity and bulk density increased. Meanwhile,their carbon skeletons became more compact under the polycondensation reaction. These changes resulted in a significant increase in its mechanical strength compared with NCF samples. Among them,the CCF-490 sample had a benign structural balance with the middle value of average pore diameter,open porosity and bulk density,and small differences of its pore size,which made its mechanical performance best with compressive strength of 8.52 MPa and flexural strength of 5.14 MPa,respectively. This study not only synthesizes coalbased carbon foam materials with good structural properties,showing excellent application prospects,but also provides a new idea for the materialization and high valueadded utilization of coal.

     

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