Field of the Invention

The present invention relates to a process of fabricating graphene using galvanising
dross, sulphuric acid and graphite.
Background of the invention
Graphene is a monolayer of carbon with a two-dimensional honeycomb lattice, and
has many peculiar properties like (a) high mobility of charge carriers unique
transport performance (b) high mechanical strength and (c) high thermal
conductivity. These properties render graphene a suitable candidate for many
technological applications such as graphene based electronics, composite materials,
molecular gas sensors, and energy storage and conversion. All of these applications
demand huge production of high quality graphene materials. So far, many methods
have been developed to produce graphene.
These comprises: (i) Micromechanical cleavage. This methodology can only produce
a very limited quantity of graphene sheets for fundamental research. (ii) Epitaxial
growth via ultra-high vacuum graphitization. This allows fabrication of patterned
graphene structure, which is desirable for electronics. However, the combination of
high cost and small wafer size limits its application. (iii) Chemical synthesis through
oxidation of graphite, which involves oxidation of graphite to graphite oxide,
exfoliation of graphite oxide to graphene oxide sheets, and chemical or thermal

reduction to grapheme, the process introducing defects in graphene sheets. (iv)
Chemical vapor deposition (CVD) growth of graphene either on a substrate or
substrate free. (v) Solvothermal synthesis combined with pyrolysis and liquid phase
exfoliation of graphite.
Structurally, Graphene is a flat monolayer of carbon atoms tightly packed into a
two-dimensional (2D) honeycomb lattice, and is a basic building block for graphitic
materials of all other dimensionalities. It can be wrapped up into 3D fullerenes,
rolled into 1D nanotubes or stacked into 3D graphite. Graphene planes get well
separated in intercalated graphite compounds. In 2004, physicists at the University
of Manchester and the Institute for Microelectronics Technology, Chernogolovka,
Russia, first isolated individual graphene planes by using adhesive tape, and
measured electronic properties of the obtained flakes which showed the unique
properties of the graphene. In 2008, graphene produced by exfoliation was one of
the most expensive materials on Earth, with a sample that can be placed at the
cross section of a human hair costing more than $1,000 as of April 2008 (about
$100,000,000/cm2). Since then, exfoliation procedures have been scaled up, and
now companies sell graphene in large quantities. On the other hand, the price of
epitaxial graphene on SiC is dominated by the substrate price, which is

approximately $100/cm2 as of 2009. Even cheaper grapheme is reported to have
been produced by transfer from nickel by Korean researchers, with wafer sizes up to
30 inches (760 mm).
Drawing method: In 2004, the Manchester group obtained graphene by micro-
mechanical alleviation of graphite. They used adhesive tape to repeatedly split
graphite crystals into increasingly thinner pieces. The tape with attached optically
transparent flakes was dissolved in acetone, and, after a few further steps, the
flakes including monolayers were sedimented on a silicon wafer. Individual atomic
planes were then hunted in an optical microscope.
Graphite oxide reduction: Graphite oxide reduction was probably historically the first
method of graphene synthesis. Graphite oxide exfoliation can be achieved by rapid
heating and yields highly dispersed carbon powder with a few percent of graphene
flakes. Reduction of graphite oxide monolayer films e.g. by hydrazine, annealing in
argon/hydrogen was reported to yield graphene films.
From graphite by sonication: The method consists of dispersing graphite in a liquid
medium that is then sonicated. Non exfoliated graphite is eventually separated from
graphene by centrifugation.
Laser scribing method: Maher F. El-Kady, Veronica Strong, Sergey Dubin and
Richard B. Kaner from the University of California, Los Angeles, discovered an
efficient and low cost way to produce graphene. Applying a layer of graphite oxide
film to a DVD disc and burning it in a DVD writer resulted in a thin graphene film

with high electrical conductivity and specific surface area besides being highly
resistant and malleable.
As described above, there had been a number of methods established in state of art
describing manufacturing of graphene. However, there is still need for a method that
is easy to execute and is not expensive. Further, the method should ensure that
manufactured graphene can be extracted easily.
Considerable amount of dross is produced during operations of a continuous
galvanising line. Dross is a skimmed product which floats on the top surface of the
bath of molten zinc alloy [8]. This unwanted dross causes substantial economic loss
to the galvanizing process.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to develop a process of fabricating
graphene using galvanising dross, sulphuric acid and graphite.
Another object of the invention is to propose a process of fabricating graphene using
galvanising dross, sulphuric acid and graphite from graphite through chemical
synthesis.
A further object of the invention is to propose a process of fabricating graphene
using galvanising dross, sulphuric acid and graphite, wherein the produced
grapheme nano sheets are stable in aqueous solution and can be easily isolated as
monolayer or multilayer graphene sheets.

Summary of the invention
Hot dip galvanisation waste i.e. Dross is used to produce hydrogen. This hydrogen is
used in situ reduction of exfoliated graphene oxide to graphene.
Dross is intermetallic compound of mainly zinc, iron and aluminium. Figure 10-
shows EDAX analysis carried out on the dross. In the oxidising media like dil H2S04
according to standard reduction potential zinc will oxidise first then iron and at last
aluminium. In the present invention graphene is generated from graphite comprising
the steps of:
Oxidation of graphite to graphene oxide to increase the interlayer distance and
weaken the interaction between the layers;
Exfoliation of graphite oxide by ultrasonification; and
Reduction of the exfoliated GO by utilisation of dross generated during galvanisation.
Graphite → Graphene oxide (GO) → Exfoliated GO
Graphene
Process of in situ utilisation of hydrogen generated by Dross reacting with sulphuric
acid to generate the graphene is the essence of this invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS AND TABLES
Figure 1 Transmission electron microscope image of the graphene generated from
Experiment 1
Figure 2 Transmission electron microscope image of the graphene generated from
Experiment 2
Figure 3 Transmission electron microscope image of the graphene generated from
Experiment 3
Figure 4 Transmission electron microscope image of the graphene generated from
Experiment 4
Figure 5 Raman spectra of the graphene generated by experiment 1
Figure 6 Raman spectra of the graphene generated by experiment 2
Figure 7 Raman spectra of the graphene generated by experiment 3
Figure 8 Raman spectra of the graphene generated by experiment 4
Figure 9 XRD pattern of typical dross generated in continuous galvanizing line
Figure 10- shows EDAX analysis carried out on the dross
Table-1- shows the results of EDAX analysis exhibiting strong peaks of AI,Zn, and Fe.

Detail Description of the invention
Graphite has a unique role in different industries due to its various physical and
chemical characteristics. It is a crystalline form of carbon and a good conductor of
heat and electricity and a good lubricant. Natural graphite is found into two
commercial varieties: (i) flaky or crystalline and (ii) amorphous graphite.
Graphite-like nanoplatelets have recently attracted attention as viable and
inexpensive filler in composite materials that can be used in many engineering
applications, given the excellent in-plane mechanical, structural, thermal, and
electrical properties of graphite. These excellent properties may be relevant at the
nanoscale if graphite can be exfoliated into thin nanoplatelets, and even down to the
single graphene sheet level.
Graphene Oxide (GO) is produced by the oxidative treatment of graphite via one of
three principal methods developed by Hummers method [10].
It still retains a layered structure, but is much lighter in color than graphite due to
the loss of electronic conjugation brought about by the oxidation. According to the
most recent studies, GO consists of oxidized graphene sheets (or "graphene oxide
sheets') having their basal planes decorated mostly with epoxide and hydroxyl
groups, in addition to carbonyl and carboxyl groups located presumably at the edges
(Lerf-Klinowski model).

These oxygen functionalities render the graphene oxide layers of GO hydrophilic and
water molecules can readily intercalate into the interlayer galleries. GO can therefore
be also thought of as a graphite-type intercalation compound with both covalently
bound oxygen and non-covalently bound water between the carbon layers. Indeed,
rapid heating of GO results in its expansion and delamination caused by rapid
evaporation of the intercalated water and evolution of gases produced by thermal
pyrolysis of the oxygen-containing functional groups. Such thermal treatment has
recently been suggested to be capable of producing individual functionalized
graphene sheets.
By nature, GO is electrically insulating and thus cannot be used, without further
processing, as a conductive nanomaterial. In addition, the presence of the oxygen
functional groups makes GO thermally unstable, as it undergoes pyrolysis at
elevated temperatures. Notably, it has been demonstrated that the electrical
conductivity of GO (and presumably its thermal stability as well) can be restored
close to the level of graphite by chemical reduction. Such reductions of GO,
however, have not been studied in great detail.
Given our interest in the preparation of graphene-based materials, we set out to
develop a general and reproducible approach for the preparation of graphene sheets
from graphite. We decided to use graphite oxide (GO) as one possible route for
meeting this challenge.

The basic strategy of the inventive process involved complete exfoliation of GO into
individual GO sheets followed by their in-situ reduction to produce individual
graphene-like sheets. Hereinafter is described a detailed process for reduction of
exfoliated GO sheets with galvanising dross and the characterization of the resulting
material. In particular, the present inventors established that GO can be completely
exfoliated into individual graphene oxide sheets and that chemical reduction of such
sheets can furnish graphene-like sheets.
In the dross typically three phases were observed. In dross the zinc oxide phase
encapsulating large amounts of the galvanising zinc alloy in which an aluminium-
iron-zinc alloy occurs as dispersed inclusions.(fig 9 ,10 and tablel). The chemical
reduction of exfoliated graphene oxide sheets with several reducing agents were
examined and found dross to be a good one in producing very thin graphene-like
sheets, consistent with previous reports. High-resolution micrograph also provided
us with evidence of thin sheets.
Raman spectroscopy has been a powerful tool to characterize graphene. Higher 2D
to G peak intensity ratio and lower D to G peak intensity ratio signify the good
quality of graphene [11]. The inventors from the experiments found highest 2D to G
peak intensity ratio and lowest D to G peak intensity ratio for graphene samples
prepared using dross (see Tab.2). Moreover TEM measurements also indicate good
quality of graphene prepared by dross compared to other used metals.

Experiments
A. Graphite of 99% purity is oxidised by standard hummer method to become
graphene oxide.
B. Graphene oxide is being ultrasonicated using a ultrasonic probe (500-800W,
20kHz) for continuously 1-4 h to become exfoliated graphene oxide.
C. These Exfoliated graphene oxide (llitre solution) after washing with deionised
water (2litre) and methanol (1 Litre) separated in powder form.
Experiment 1
1. 2-10 gms of exfoliated graphene oxide is dispersed in 100 ml of deionised water.
Then 4-15 gms of dross was added to the above solution and 20ml of 1-10M H2SO4
was added.
2. After 6-20 hrs graphene was found on the surface of the liquid because graphene
has low density.
Experiment 2
1. 2-10 gms of exfoliated graphene oxide is dispersed in 100 ml of deionised water.
Then 4-15 gms of Zinc was added to the above solution and 20ml of 1-10M H2SO4
was added.
2. After 6-20 hrs graphene was found on the surface of the liquid because graphene
has low density.

Experiment 3
1. 2-10 gms of exfoliated graphene oxide is dispersed in 100 ml of deionised water.
Then 4-15 gms of aluminium was added to the above solution and 20ml of 1-10M
H2SO4 was added.
2. After 6-20 hrs graphene was found on the surface of the liquid because graphene
has low density.
Experiment 4
1. 2-10 gms of exfoliated iron is dispersed in 100 ml of deionised water. Then 4-15
gms of iron was added to the above solution and 20ml of 1-10M H2SO4 was added.
2. After 6-20 hrs graphene was found on the surface of the liquid because graphene
has low density.
Reference
1. Sung Ryong Kim, Md. Khaled Parvez, Manish Chhowalla, Chemical Physics Letters
483 (2009) 124-127
2. Dmitriy A. Dikin, Sasha Stankovich, Eric J. Zimney, Richard D. Piner, Geoffrey H.
B.Dommett,Guennadi Evmenenko, SonBinh T. Nguyen3 & Rodney S. Ruoff Vol
448|26 July 2007| doi:10.1038/nature06016
3. Sasha Stankovich, Dmitriy A. Dikin, Richard D. Piner, Kevin A. Kohlhaas, Alfred
Kleinhammes, Yuanyuan Jia, Yue Wu, SonBinh T. Nguyen, Rodney S. Ruoff Carbon
45 (2007) 1558-1565

4. Hemtej Gullapalli , Arava Leela Mohana Reddy , Stephen Kilpatrick , Madan
Dubey, and Pulickel M. Ajayan small 2011,7, No. 12, 1697-1700
5. Cecilia Mattevi, Goki Eda, Stefano Agnoli, Steve Miller, K. Andre Mkhoyan, Ozgur
Celik, Daniel Mastrogiovanni, Gaetano Granozzi, Eric Garfunkel, and Manish
Chhowalla Adv. Funct. Mater. 2009, 19, 2577-2583
6. Konstantin N. Kudin,t Bulent Ozbas, Hannes C. Schniepp,Robert K.
Prud'homme,Ilhan A. Aksay,and Roberto Car Nano Lett., Vol. 8, No. 1, 2008
7. Gopichand Nandamuri, Sergei Roumimov, and Raj Solanki APPLIED PHYSICS
LETTERS 96, 154101 _2010_
8. US patent 4221591 (1979) inventors: John C. Hogan, Alan F. Gibson,
9. Guoxiu Wang, Bei Wang, Jinsoo Park, Ying Wang, Bing Sun and Jane Yao C A R B
ON 47(2009)3242-3 246

10. William S. Hummers Jr., and Richard E. Offeman, J. American Chemical Society,
Vol 80 (1958), pages 1339-1339 .
11. LM. Malarda, M.A. Pimentaa, G. Dresselhaus, M.S. Dresselhaus, Physics Reports,
473 (2009) 51-87

WE CLAIM:

1. A method for preparing graphene sheet, comprising:
treating graphene oxide with 20 kHz ultrasonic waves for 1 to 4 hours;
dispersing the graphene oxide with deionised water;
adding continuous galvanizing line dross to the dispersed graphene
oxide, concentration of the continuous galvanizing line dross in the
mixture being in the range of 4-20 weight%; and
mixing said mixture of graphene oxide and the continuous galvanizing
line top dross with 1-10 molar sulphuric acid solution.
2. The method as claimed in claim 1, wherein the graphene oxide is produced by
hummer method using graphite of 99% purity.
3. The method as claimed in claim 1 further comprising the step of treating the
ultrasonicated graphene oxide with a solution of deionised water and
methanol.
4. The method as claimed in claim 1, wherein the galvanizing dross is comprised
of Zn (15-97%), AI(l-60%), and Fe (1-40%) percentage by weight.

5. The method as claimed in claim 1, wherein the graphene oxide is converted
to graphene sheet at temperature range 20-80°C.
6. The method as claimed in claim 1, wherein the continuous galvanizing line
dross is top dross.