TY - JOUR

T1 - Graphene nanoplatelet (GNPs) doped carbon nanofiber (CNF) system

T2 - Effect of GNPs on the graphitic structure of creep stress and non-creep stress stabilized polyacrylonitrile (PAN)

AU - Ali, Ahmad B.

AU - Renz, Franz

AU - Koch, Julian

AU - Tegenkamp, Christoph

AU - Sindelar, Ralf

N1 - Funding information: Acknowledgments: The authors are grateful to Hannover School for Nanotechnology (HSN) and Deutsche Forschungsgemeinschaft (DFG) for their financial support under grant number, 21-78904-63-7/16, by Niedersächsisches Ministerium für Wissenschaft und Kultur (Ministry of Science and Culture of Lower Saxony/Germany).

PY - 2020/2/18

Y1 - 2020/2/18

N2 - Improving the graphitic structure in carbon nanofibers (CNFs) is important for exploiting their potential in mechanical, electrical and electrochemical applications. Typically, the synthesis of carbon fibers with a highly graphitized structure demands a high temperature of almost 2500° C. Furthermore, to achieve an improved graphitic structure, the stabilization of a precursor fiber has to be assisted by the presence of tension in order to enhance the molecular orientation. Keeping this in view, herein we report on the fabrication of graphene nanoplatelets (GNPs) doped carbon nanofibers using electrospinning followed by oxidative stabilization and carbonization. The effect of doping GNPs on the graphitic structure was investigated by carbonizing them at various temperatures (1000° C, 1200° C, 1500° C and 1700° C). Additionally, a stabilization was achieved with and without constant creep stress (only shrinkage stress) for both pristine and doped precursor nanofibers, which were eventually carbonized at 1700° C. Our findings reveal that the GNPs doping results in improving the graphitic structure of polyacrylonitrile (PAN). Further, in addition to the templating effect during the nucleation and growth of graphitic crystals, the GNPs encapsulated in the PAN nanofiber matrix act in-situ as micro clamp units performing the anchoring function by preventing the loss of molecular orientation during the stabilization stage, when no external tension is applied to nanofiber mats. The templating effect of the entire graphitization process is reflected by an increased electrical conductivity along the fibers. Simultaneously, the electrical anisotropy is reduced, i.e., the GNPs provide effective pathways with improved conductivity acting like bridges between the nanofibers resulting in an improved conductivity across the fiber direction compared to the pristine PAN system.

AB - Improving the graphitic structure in carbon nanofibers (CNFs) is important for exploiting their potential in mechanical, electrical and electrochemical applications. Typically, the synthesis of carbon fibers with a highly graphitized structure demands a high temperature of almost 2500° C. Furthermore, to achieve an improved graphitic structure, the stabilization of a precursor fiber has to be assisted by the presence of tension in order to enhance the molecular orientation. Keeping this in view, herein we report on the fabrication of graphene nanoplatelets (GNPs) doped carbon nanofibers using electrospinning followed by oxidative stabilization and carbonization. The effect of doping GNPs on the graphitic structure was investigated by carbonizing them at various temperatures (1000° C, 1200° C, 1500° C and 1700° C). Additionally, a stabilization was achieved with and without constant creep stress (only shrinkage stress) for both pristine and doped precursor nanofibers, which were eventually carbonized at 1700° C. Our findings reveal that the GNPs doping results in improving the graphitic structure of polyacrylonitrile (PAN). Further, in addition to the templating effect during the nucleation and growth of graphitic crystals, the GNPs encapsulated in the PAN nanofiber matrix act in-situ as micro clamp units performing the anchoring function by preventing the loss of molecular orientation during the stabilization stage, when no external tension is applied to nanofiber mats. The templating effect of the entire graphitization process is reflected by an increased electrical conductivity along the fibers. Simultaneously, the electrical anisotropy is reduced, i.e., the GNPs provide effective pathways with improved conductivity acting like bridges between the nanofibers resulting in an improved conductivity across the fiber direction compared to the pristine PAN system.

KW - Carbonization

KW - Creep stress

KW - Electrical anisotropy

KW - Graphene nanoplatelets

KW - Graphitization

KW - Polyacrylonitrile

KW - Shrinkage stress

KW - Stabilization

UR - http://www.scopus.com/inward/record.url?scp=85079733513&partnerID=8YFLogxK

U2 - 10.3390/nano10020351

DO - 10.3390/nano10020351

M3 - Article

AN - SCOPUS:85079733513

VL - 10

JO - Nanomaterials

JF - Nanomaterials

SN - 2079-4991

IS - 2

M1 - 351

ER -