Theses and Dissertations

Weiqi Leng

Issuing Body

Mississippi State University

Advisor

Barnes, H. Michael

Committee Member

Zhang, Jilei

Committee Member

Nikolic, Dragica Jeremic

Committee Member

Hassan, El Barbary M.

Date of Degree

8-14-2015

Document Type

Dissertation - Open Access

Major

Forest Resources

Degree Name

Doctor of Philosophy

College

College of Forest Resources

Department

Department of Sustainable Bioproducts

Abstract

In this project, the synthesis of carbon encapsulated copper nanoparticles using sustainable bioproducts as raw material was systematically studied. The synthesis mechanism, process parameters, and functionalization of carbon encapsulated copper nanoparticles were well established. In a preliminary study, carbon encapsulated copper nanoparticles were successfully synthesized at 1000 ºC, 1h, 20 ºC/min, and 1800 sccm argon gas flow rate using BCL-DI lignin as the carbon source. Carbon encapsulated copper nanoparticles were mainly located at defect sites. Copper was found not tightly encapsulated by graphene shells. The carbon encapsulated copper nanoparticles were uniformly distributed. The conversion of copper ions into copper atoms occurred at above 300 ºC, with the company of decomposition of BCL-DI lignin into CO, CO2, and hydrocarbon gases. The growth of graphene layers was proposed to start above 300 ºC. TEM images illustrated the onset of growth of graphene at the edge of the surface at 400 ºC, and the formation of graphene bands at 500 ºC. Copper catalyst continued to facilitate the decomposition of lignin functional groups at 600 ºC. Further increasing the temperature retarded the degradation of lignin, while assisted the reconstruction of the defective sites of the graphene layers, producing higher quality products. Plastic film phase of lignin dominated on the synthesis of carbon encapsulated copper nanoparticles, while gaseous phase had little impact. The orthogonal experiment revealed that temperature played the most important role in the growth of graphene: high temperature was preferred in order to obtain less defective sites. The optimum synthesis parameters were suggested as 1000 °C, 30 min duration time, 20 °C/min temperature rising ramp, and 1200 sccm argon gas flow rate. Post heat treatment was proved to be a feasible way to improve the crystallinity of graphite. Amorphous carbon was removed or converted into crystalline graphite under heat and oxygen. FTIR spectra confirmed the covalent linkages between carbon encapsulated copper nanoparticles and N-methyl-2-pyrrolidone and polyvinylpyrrolidone, indicating a successful functionalization. This study has presented a homogeneous carbon encapsulated copper nanoparticles solution in water and ethanol, and paved ways for further functionalization of CECNs.

URI

https://hdl.handle.net/11668/20007

Comments

Graphene||synthesis||mechanism||functionalization

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