黔西与湖南寒婆坳地区煤制石墨烯结构的演化特征

Evolutionary characteristics of coal based graphene structure in West Guizhou and Hanpo’ao,Hunan

石墨烯作为21世纪的战略性新兴材料,因其优异的性能受到广泛关注。研究表明煤可作为石墨烯碳源,并且煤的属性也影响石墨烯的结构特征,结合我国煤变质成因复杂、煤变质作用类型多样的特点,旨在研究不同变质作用背景对石墨烯结构的影响特征。采集黔西地区深成叠加热液变质作用6个煤样及寒婆坳地区岩浆热变质作用4个煤样,全部利用HCl-HF-HNO3酸洗方法进行处理后得到脱矿煤样,以排除矿物的影响;后使用中频感应石墨化炉对脱矿煤样进行2800℃高温处理后得到煤基石墨样品;最后利用改进的Hummers氧化还原法对煤基石墨进行氧化、超声剥离、还原处理,得到石墨烯样品;用于测试样品微晶尺寸、空间形态等信息的X射线衍射(XRD)对脱矿样、煤基石墨、石墨烯进行表征并得到相关结构参数,用于测试样品缺陷、完整性的拉曼光谱(Raman)对脱矿样、煤基石墨、石墨烯样品进行表征并得到相关参数,用于观察样品微观表面形貌的透射电镜(TEM)对石墨烯样品进行表征并得到图像。实验及表征结果:透射电镜(TEM)得到的图像表明2种变质类型的煤均可制备出3~5层的石墨烯层片。X射线衍射(XRD)和拉曼光谱(Raman)得到的相关参数表明煤的变质程度越高,对应的煤基石墨样品石墨化度越高,对应石墨烯样品的微晶结构片层越大、缺陷更少。以X射线衍射(XRD)、拉曼光谱(Raman)测试参数为依据,相对于岩浆热变质作用,深成叠加热液变质背景石墨烯样品的L_(c)、d_(002)以及峰位差G-D、I_(D)/I_(G)的变化随Ro,max的变化较大;而相对于深成叠加热液变质作用,岩浆热变质背景石墨烯样品的L_(a)和L_(a)/L_(c)变化随Ro,max的变化较大;说明在深成叠加热液变质作用背景下,煤的变质程度越高,越易得到堆砌性好、定向排列强、缺陷少的石墨烯样品,而在岩浆热变质作用条件下,煤的变质程度越高,越易获得横向尺寸大、“扁圆”空间形态的石墨烯样品。如今所进行的工作在后续还有拓展研究的空间,岩浆以及无岩浆对煤制石墨烯结构的影响有何不同,或者温度和压力是如何影响煤制石墨烯结构,这些问题需进一步研究以推进煤制石墨烯领域的科学发展。

As a strategic emerging material in the 21st century,graphene has attracted extensive attention due to its excellent performance.The research shows that coal can be used as the carbon source of graphene,and the properties of coal also affect the structural characteristics of graphene.Combined with the characteristics of complex coal metamorphic origin and diverse types of coal metamorphism in China,this paper aims to study the impact characteristics of different metamorphic backgrounds on the graphene structure.Six coal samples from the deep superimposed hydrothermal metamorphism in Western Guizhou and four coal samples from the magmatic thermal metamorphism in the Hanpo’ao area were collected,and all of them were treated with HCl-HF-HNO3acid washing method to obtain the demineralized coal samples to eliminate the influence of minerals.After that,the coal-based graphite sample was obtained after the demineralized coal sample was treated at 2800℃in a medium frequency induction graphitization furnace.At last,the improved Hummers redox method was used to oxidize,ultrasonic peel and reduce the coal-based graphite to obtain graphene samples.The X-ray diffraction(XRD)used to test the microcrystalline size,spatial morphology and other information of the sample was used to characterize the demineralized coal-based graphite and graphene and obtain relevant structural parameters.The Raman spectrum used to test the defect and integrity of the sample was used to characterize the demineralized,coal-based graphite and graphene samples and obtain relevant parameters.The transmission electron microscope(TEM)used to observe the micro surface morphology of the samples was used to characterize the graphene samples and obtain images.The results of experiment and characterization are as follows:the images obtained by transmission electron microscopy(TEM)show that 3-5 layers of graphene sheets can be prepared from two types of metamorphic coals.The relevant parameters obtained by the X-ray diffraction(XRD)and Raman spectroscopy(Raman)show that the higher the metamorphic degree of coal,the higher the graphitization degree of corresponding coal-based graphite sample,and the larger the microcrystalline structure lamella of corresponding graphene sample,with fewer defects.Based on the testing parameters of the X-ray diffraction(XRD)and Raman spectroscopy(Raman),relative to magmatic thermal metamorphism,the changes of L_(c),d_(002),G-D,I_(D)/IGof graphene samples in the metamorphic background of deep superimposed hydrothermal fluids vary greatly with Ro,max.Compared with the hydrothermal metamorphism,the variations of Laand La/Lcof graphene samples in the magmatic thermal metamorphic background vary greatly with Ro,max.It shows that under the background of hydrothermal metamorphism,the higher the metamorphic degree of coal is,the easier it is to obtain graphene samples with good stacking property,strong directional arrangement and few defects.Under the condition of magmatic thermal metamorphism,the higher the metamorphic degree of coal is,the easier it is to obtain graphene samples with large transverse size and“flat round”spatial morphology.There is a need for further research on the work carried out today.What are the different effects of magma and non-magma on the structure of coal based graphene,or how temperature and pressure affect the structure coal-based graphene?These issues need further research for promoting the scientific development in the field of coal-based graphene.