دانلود رایگان مقاله روش و نوع تلفیق شدت نفوذ اکسید گرافیت نتیجه خواص گرافن

Abstract

Graphene is the one of the most intensively studied materials for its unique mechanical, electrical and thermal properties. The aim of this study is to compare the significant differences between individual graphenes prepared using different graphite oxides as starting materials. Graphene was prepared by chemical and thermal reduction of five different graphite oxides, which were prepared according to Brodie, Hofmann, Hummers, Staudenmaier and Tour method. Due to the significant differences in the composition of graphite oxide used for synthesis significant differences can be also observed in graphene prepared by chemical and thermal reduction of starting material. The synthesized graphene materials were characterized in detail using different chemical and structural analytical methods. Significant level of unintentional nitrogen doping was observed on chemically reduced graphite oxide synthesized by permanganate methods. Also the degree of exfoliation and the corresponding structural properties were strongly dependant on the degree of oxidation of the starting graphite oxide. Finding the best synthesis procedure of graphene with desirable properties is essential to optimize technologies in large scale production of graphene for its utilization in industrial applications.

4. Conclusions

The influence of oxidation methods on the properties of chemically and thermally reduced graphene was investigated in detail. Five main methods for the synthesis of graphite oxide using chlorate and permanganate oxidation procedures were selected for the investigation. Our findings show several significant differences in the graphenes prepared by chlorate and permanganate methods. In general, the properties like surface area, morphology and remaining oxygen functionalities are controlled not only by the degree of oxidation, but also by the composition of oxygen functionalities and the method of reduction. In general the thermal reduction methods yield significantly higher degree of exfoliation and lower concentration of oxygen functionalities. Differences between the individual samples are significantly lower in such graphenes in comparison with various graphenes prepared by chemical reduction. This mainly originates from incomparably lower concentration of oxygen functionalities and much higher C/O ratio indicating the degree of reduction. The exfoliation of chemically reduced graphene is significantly higher for the samples originating from graphite oxide prepared by permanganate routes compared to chlorate methods, showing the importance of proper selection of the starting graphite oxide for various applications. The main exception from all trends is the graphene prepared from graphite oxidized by Staudenmaier method. The low degree of oxidation led to a markedly lower degree of exfoliation and subsequently to high differences in the observed properties such as surface area, stability towards oxidation and others. Interestingly, all graphenes have comparable HET rate represented by the value of peak-to-peak separation value using hexakyanoferrate redox probe. Our findings showed large variability in structure, composition and properties of graphene obtained from graphite oxide prepared by various oxidation methods. These findings must be considered for the proper selection of graphene for different applications of graphene in industrial processes.