Preparation of Graphene Sheet Contented Carbon Materialsfrom Biochars

• Main Authors: Liou, Yan-Jia, 劉晏嘉
• Other Authors: Huang, Wu-Jang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/a5bm6z

博士 === 國立屏東科技大學 === 環境工程與科學系所 === 102 === Graphene is a monolayer graphite and has higher electron mobility than silicon, high heat conduction and special optical properties. It can be a potentially new semiconductor material and could be applied in transparent conductive thin film, dye-sensitized solar cells, super capacitors and composites. Many graphene manufacturing methods have been proposed, such as chemical vapor deposition, chemical reduction of graphene oxide and the exfoliation method. However, these processes are complicated by a high cost and the difficulty of removing byproducts. Therefore, the market mechanisms of graphene have not yet been established. In this study, we would like to propose a feasible method to characterize graphene sheet content quantitatively in carbon materials and processes for preparing high graphene sheet content carbon material (GSCCM) from biochar. From our results, an empirical equation was found to calculate the graphene sheet content quantitatively in carbon-containing materials using an XRD spectrometer. Graphene sheet content, in a series of pyrolized biochar material powders, was calculated at a peak 2θ = 41° (d100) using XRD and resistivity measurement. The resistivity of ideal graphene powder was predicted to be 0.01 Ω‧cm, which was consistent with commercial reduced graphene oxide, and the highest graphene sheet content of GSCCMs from Elaeis biochar materials after CH3COOH impregnated through pyrolysis processes and catalytic pyrolized (added Na2O) is 83.86 and 82.88 %, respectively; its average conductivity is 84.690 and 78.895 S/cm, respectively. From SEM analysis, the formation of graphene sheet related with α-cellulose content of woody biomass materials, and that with the processes of GSCCMs added to some metal oxides as catalysts, the graphite spherical grains and cytoskeleton surface of wood cells were separated leaving some holes by Na2O catalyst at 1500 oC, and the size (~ 0.5 to 1 μm) of the holes was similar to the graphite spherical grains. We conjecture that the Na2O catalyst can cause the swelling of graphite spherical grains at high temperatures (above 1500 oC), and the phenomenon might have resulted from the sodium impregnation of α-cellulose. Therefore, we can produce carbon materials with adjustable hole sizes through the addition of metal oxides as catalysts. With the production of GSCCMs from pyrolized α-cellulose powder, the graphene sheet content is 93.01 %. The prepared GOPs from homemade graphene sheets contained carbon materials (GSCCMs) and evaluated the thermal properties of GSCCM derived GOPs. Results show that the GSCCM derived GOPs have high temperature phase transitions, and the average phase change enthalpy is 9.41 J/g, which is 2.87 times higher than graphite derived GOP. According to the industry reports, the cost of artificial graphite and graphene for the CVD process is 1,450 USD/ton and 28.57 USD/g, respectively. In this study, the yield of biochar and GSCCMs was 31.46 and 23.44 %, respectively. The production cost of GSCCMs was about 400 TND/ batch. Therefore, preparing GOP from GSCCMs could highly reduce the cost.