Limits...
High-speed roll-to-roll manufacturing of graphene using a concentric tube CVD reactor.

Polsen ES, McNerny DQ, Viswanath B, Pattinson SW, John Hart A - Sci Rep (2015)

Bottom Line: We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD.We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions.We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, 2350 Hayward St., Ann Arbor, MI 48109, USA.

ABSTRACT
We present the design of a concentric tube (CT) reactor for roll-to-roll chemical vapor deposition (CVD) on flexible substrates, and its application to continuous production of graphene on copper foil. In the CTCVD reactor, the thin foil substrate is helically wrapped around the inner tube, and translates through the gap between the concentric tubes. We use a bench-scale prototype machine to synthesize graphene on copper substrates at translation speeds varying from 25 mm/min to 500 mm/min, and investigate the influence of process parameters on the uniformity and coverage of graphene on a continuously moving foil. At lower speeds, high-quality monolayer graphene is formed; at higher speeds, rapid nucleation of small graphene domains is observed, yet coalescence is prevented by the limited residence time in the CTCVD system. We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD. We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions. We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

No MeSH data available.


Computational fluid dynamics (CFD) model of gas flow within the CTCVD reactor. a) Cross-section diagram of the flow paths within the concentric tube arrangement and colormap of C2H4 mass fraction during steady operation. b) Profiles of average gas velocity in the gap between the tubes and average temperature versus position along the flow direction. c) Mass fraction of He, H2, and C2H4 along the flow direction, showing the abrupt change upon injection of C2H4 through the inner tube, and the rapid stabilization <1 cm downstream of this point (x = 0.38 m). Data is from CFD simulations run at a system pressure of 760 torr.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4440526&req=5

f2: Computational fluid dynamics (CFD) model of gas flow within the CTCVD reactor. a) Cross-section diagram of the flow paths within the concentric tube arrangement and colormap of C2H4 mass fraction during steady operation. b) Profiles of average gas velocity in the gap between the tubes and average temperature versus position along the flow direction. c) Mass fraction of He, H2, and C2H4 along the flow direction, showing the abrupt change upon injection of C2H4 through the inner tube, and the rapid stabilization <1 cm downstream of this point (x = 0.38 m). Data is from CFD simulations run at a system pressure of 760 torr.

Mentions: A further attractive feature of the CTCVD design is the ability to create two sequential treatment zones (Fig. 2a) via the injection of the precursor gas through the inner tube. For example, a first gas mixture such as He/H2 is supplied to the upstream chamber, and flows into the gap between the tubes; and a second gas mixture including the precursor is directly fed to the inner tube. The inner tube is custom-made with radial holes and a blockage adjacent to the holes; these direct the second gas mixture to enter the annular gap, creating the second gas treatment zone without changing the local temperature profile. The flow dynamics in the CTCVD system with downstream injection were studied using computational fluid dynamics (CFD) simulations, at system pressures of 10–3 and 760 torr. The mixing of C2H4 upon injection from the inner tube is visualized in Fig. 2a, where the tube gap is 4.5 mm. The injection of the precursor into the annular gap increases the average gas velocity from 0.024 m/s to 0.048 m/s (Fig. 2b), and the velocity and chemistry of the gas mixture are stable to within 99% of their final values at a point 10 mm downstream of the injection holes (Fig. 2b,c). The rapid deceleration and acceleration of the gases at the injection location is due to the gas flow through the inner tube holes impinging on the inner wall of the outer tube. The injection causes slight backward flow of the carbon precursor due to diffusive mixing and impingement of the gas on the inner wall of the outer tube, but a net forward velocity is maintained.


High-speed roll-to-roll manufacturing of graphene using a concentric tube CVD reactor.

Polsen ES, McNerny DQ, Viswanath B, Pattinson SW, John Hart A - Sci Rep (2015)

Computational fluid dynamics (CFD) model of gas flow within the CTCVD reactor. a) Cross-section diagram of the flow paths within the concentric tube arrangement and colormap of C2H4 mass fraction during steady operation. b) Profiles of average gas velocity in the gap between the tubes and average temperature versus position along the flow direction. c) Mass fraction of He, H2, and C2H4 along the flow direction, showing the abrupt change upon injection of C2H4 through the inner tube, and the rapid stabilization <1 cm downstream of this point (x = 0.38 m). Data is from CFD simulations run at a system pressure of 760 torr.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440526&req=5

f2: Computational fluid dynamics (CFD) model of gas flow within the CTCVD reactor. a) Cross-section diagram of the flow paths within the concentric tube arrangement and colormap of C2H4 mass fraction during steady operation. b) Profiles of average gas velocity in the gap between the tubes and average temperature versus position along the flow direction. c) Mass fraction of He, H2, and C2H4 along the flow direction, showing the abrupt change upon injection of C2H4 through the inner tube, and the rapid stabilization <1 cm downstream of this point (x = 0.38 m). Data is from CFD simulations run at a system pressure of 760 torr.
Mentions: A further attractive feature of the CTCVD design is the ability to create two sequential treatment zones (Fig. 2a) via the injection of the precursor gas through the inner tube. For example, a first gas mixture such as He/H2 is supplied to the upstream chamber, and flows into the gap between the tubes; and a second gas mixture including the precursor is directly fed to the inner tube. The inner tube is custom-made with radial holes and a blockage adjacent to the holes; these direct the second gas mixture to enter the annular gap, creating the second gas treatment zone without changing the local temperature profile. The flow dynamics in the CTCVD system with downstream injection were studied using computational fluid dynamics (CFD) simulations, at system pressures of 10–3 and 760 torr. The mixing of C2H4 upon injection from the inner tube is visualized in Fig. 2a, where the tube gap is 4.5 mm. The injection of the precursor into the annular gap increases the average gas velocity from 0.024 m/s to 0.048 m/s (Fig. 2b), and the velocity and chemistry of the gas mixture are stable to within 99% of their final values at a point 10 mm downstream of the injection holes (Fig. 2b,c). The rapid deceleration and acceleration of the gases at the injection location is due to the gas flow through the inner tube holes impinging on the inner wall of the outer tube. The injection causes slight backward flow of the carbon precursor due to diffusive mixing and impingement of the gas on the inner wall of the outer tube, but a net forward velocity is maintained.

Bottom Line: We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD.We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions.We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, 2350 Hayward St., Ann Arbor, MI 48109, USA.

ABSTRACT
We present the design of a concentric tube (CT) reactor for roll-to-roll chemical vapor deposition (CVD) on flexible substrates, and its application to continuous production of graphene on copper foil. In the CTCVD reactor, the thin foil substrate is helically wrapped around the inner tube, and translates through the gap between the concentric tubes. We use a bench-scale prototype machine to synthesize graphene on copper substrates at translation speeds varying from 25 mm/min to 500 mm/min, and investigate the influence of process parameters on the uniformity and coverage of graphene on a continuously moving foil. At lower speeds, high-quality monolayer graphene is formed; at higher speeds, rapid nucleation of small graphene domains is observed, yet coalescence is prevented by the limited residence time in the CTCVD system. We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD. We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions. We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing.

No MeSH data available.