Polymer Stamp-Based Mechanical Exfoliation of Thin High-Quality Pyrolytic Graphite Sheets

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
David Hahn ◽  
Buddhika Jayasena ◽  
Zhigang Jiang ◽  
Shreyes N. Melkote
Keyword(s):  
High Frequency ◽  
Pyrolytic Graphite ◽  
Plane Shear ◽  
Pdms Stamp ◽  
Mechanical Exfoliation ◽  
Morphological Variations ◽  
Surface Areas ◽  
Highly Ordered Pyrolytic Graphite ◽  
Thermally Conductive ◽  
Graphite Sheets

This paper reports on a polymer stamp-based mechanical exfoliation method for producing thin (<1 μm) graphite sheets from a highly ordered pyrolytic graphite (HOPG) source by tailoring key exfoliation process parameters, utilizing in-plane shear oscillation during exfoliation, and controlling the thickness of a polydimethylsiloxane (PDMS) stamp. Experiments on the effect of high frequency in-plane shear oscillation and the effect of PDMS stamp thickness are designed to reduce the thickness of exfoliated layers and to minimize surface morphological variations. Results show that the exfoliated sheets consist of a range of layer thicknesses, surface areas, and surface morphological features. The exfoliated HOPG sheets are also found to be thinner, more electrically and thermally conductive, and of higher quality than commercially available pyrolytic graphite sheets.

Formation of Carbon Nanoscrolls During Wedge-Based Mechanical Exfoliation of HOPG

2014 ◽  
Vol 2 (1) ◽  
Author(s):  
B. Jayasena ◽  
S. Subbiah ◽  
C. D. Reddy
Keyword(s):  
Pyrolytic Graphite ◽  
Molecular Simulations ◽  
Fine Tuning ◽  
Mechanical Exfoliation ◽  
Highly Ordered Pyrolytic Graphite ◽  
Potential Applications ◽  
Literature Evidence ◽  
Carbon Nanoscrolls ◽  
Edge Defects ◽  
Moving Wedge

Carbon nanoscrolls (CNS) of various forms are observed when highly ordered pyrolytic graphite (HOPG) is mechanically exfoliated using a wedge. We present two hypothesis of how such scrolls form. The first hypothesis is based on microscopy evidence of pre-existing folds in layer edges of the HOPG. The second hypothesis is based on the literature evidence that graphene sheets when subject to deformation can result in defects on the torn edges. The sample preparation process can induce such defects in the HOPG layers. We show using molecular simulations that the interaction of the moving wedge with certain fold geometries can trigger scroll formation, confirming the first hypothesis. To test the second hypothesis, we show using molecular simulations, that layers with edge defects, upon interacting with the moving wedge, can also form scrolls. In reality, both these factors could simultaneously cause scrolls to form. Opportunities exist in fine-tuning this wedge-based mechanical exfoliation process to synthesize CNS for use in potential applications.

High Rake Angle Orthogonal Machining of Highly Ordered Pyrolytic Graphite Parallel to the Basal Plane

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
B. Jayasena ◽  
S. Subbiah ◽  
C. D. Reddy
Keyword(s):  
Basal Plane ◽  
Pyrolytic Graphite ◽  
Rake Angle ◽  
Machining Process ◽  
Dynamic Simulations ◽  
Kink Bands ◽  
Orthogonal Machining ◽  
Highly Ordered Pyrolytic Graphite ◽  
Graphite Sheets

High rake angle orthogonal machining of highly ordered pyrolytic graphite (HOPG) parallel to the basal plane was carried out to synthesize few layers of graphene. The quality of the graphite sheets was found to be an alliance of any pre-existing defects in the HOPG and the nature of the machining process itself. Presence of pre-existing defects such as kinks and discontinuous layers were observed during the lateral examination of HOPG structure prior to machining. Evidence of flat, folded, and rolled structures were found in exfoliated graphite sheets in addition to defects such as two types of kink bands. Multiple spikes in measured cutting forces were seen during machining due to disturbances in tool movement. Molecular dynamic simulations were carried out to support the argument that specific pre-existing defects such as discontinuous layers cause the marked disturbances during machining.

scholarly journals Scanning Tunneling Microscope Investigation of Self-Assembled Rosette Nanotubes on Highly Ordered Pyrolytic Graphite

2010 ◽  
Vol 16 (S2) ◽  
pp. 470-471 ◽  
Author(s):  
J-Y Cho ◽  
G Borzsonyi ◽  
H Fenniri
Keyword(s):  
Scanning Tunneling Microscope ◽  
Pyrolytic Graphite ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Microscope Investigation ◽  
Rosette Nanotubes ◽  
Highly Ordered Pyrolytic Graphite ◽  
Self Assembled

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Characterisation of highly ordered pyrolytic graphite with covalently attached ferritin by electron probe microanalysis

The Analyst ◽  
1988 ◽  
Vol 113 (2) ◽  
pp. 341 ◽  
Author(s):  
Robert F. Antrim ◽  
Alexander M. Yacynych ◽  
Henry J. Wieck ◽  
George W. Luther
Keyword(s):  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Pyrolytic Graphite ◽  
Highly Ordered Pyrolytic Graphite

scholarly journals Covalent Modification of Highly Ordered Pyrolytic Graphite with a Stable Organic Free Radical by Using Diazonium Chemistry

2016 ◽  
Vol 23 (6) ◽  
pp. 1415-1421 ◽  
Author(s):  
Gonca Seber ◽  
Alexander V. Rudnev ◽  
Andrea Droghetti ◽  
Ivan Rungger ◽  
Jaume Veciana ◽  
...  
Keyword(s):  
Free Radical ◽  
Pyrolytic Graphite ◽  
Covalent Modification ◽  
Highly Ordered Pyrolytic Graphite ◽  
Organic Free Radical

Wedge Radius Effects in Mechanical Exfoliation of HOPG: A Molecular Simulation Study

2014 ◽  
Author(s):  
B. Jayasena ◽  
S. Subbiah ◽  
C. D. Reddy
Keyword(s):  
Molecular Dynamics ◽  
Pyrolytic Graphite ◽  
Single Layer ◽  
Layered Material ◽  
Critical Depth ◽  
Graphene Layers ◽  
Highly Ordered Pyrolytic Graphite ◽  
Single Sheet ◽  
Dynamics Simulations ◽  
Atomically Flat

We study the effects of wedge bluntness in mechanically exfoliating graphene layers from highly ordered pyrolytic graphite (HOPG), a layered material. Molecular dynamics simulations show that the layer initiation modes strongly depend on the wedge radius. Force and specific energy signatures are also markedly affected by the radius. Cleaving with a larger wedge radius causes buckling ahead of the wedge; larger the radius more the buckling. A critical depth of insertion of 1.6 A° is seen necessary to cleave a single layer; this is also found to be independent of wedge radius. Hence, with accurate positioning on an atomically flat HOPG surface it is possible to mechanically cleave, using a wedge, a single sheet of graphene even with a blunt wedge.

scholarly journals High Frequency Plant Regeneration of Musa paradisiaca cv. Karibale Monthan

2015 ◽  
Vol 3 (2) ◽  
pp. 202-209 ◽  
Author(s):  
R. Shashi Kumar ◽  
V. Krishna ◽  
. Venkatesh
Keyword(s):  
Plant Regeneration ◽  
High Frequency ◽  
Synergetic Effect ◽  
Multiple Shoot ◽  
Coconut Water ◽  
Morphological Variations ◽  
Musa Paradisiaca ◽  
Shoot Initiation

High frequency plant regeneration protocol has been standardized from banana cultivar Musa paradisiaca cv. Karibale Monthan, an endemic cultivar of Malnad region of Karnataka. The fruits are used as glomerular protective to solve kidney problems. To minimize the microbial contamination and to promote healthy growth, explants were treated with 70 % absolute alcohol for 6 min, 0.1 % Mercuric chloride for 10 min and 0.2 % for 10 min, 1 % Sodium hypochlorite for 15 min, 0.1 % Cefotaxime for 5 min and 0.05 % Gentamicin for 5 min. The high frequency shoot initiation (93.33 %) was recorded at 5 mg/l BAP. The synergetic effect of BAP (4 to 6 mg/l), TDZ (0.1 to 1.2 mg/l) and coconut water (0.1 to 0.9 ml/l) induced multiple shoot buds and it was optimized at the concentration of 5 mg/l BAP, 0.5 mg/l TDZ and 0.5 ml/l coconut water with 15.90 ± 1.66 frequency of shoots per propagule. Supplementation of 1.0 mg/l IBA induced 5.33 ± 1.21 numbers of roots with a mean root length of 7.50 ± 1.87 roots. The 99% of plantlets with distinct roots and shoots were successfully acclimatized in the green house and transferred to the field to evaluate the agro-morphological variations. The weight of the bunch (kg), number of hands in a bunch, number of fingers in a hand, length of the finger (cm), girth of the finger (cm) and girth of the pseudostem (cm) exhibited by in vitro plants were higher than the in vivo plants.Int J Appl Sci Biotechnol, Vol 3(2): 202-209 DOI: http://dx.doi.org/10.3126/ijasbt.v3i2.12536 

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