Journal of Materials Science and Engineering A 2 (5) (2012) 402-409

Effect of the Density to the Electrical Conductivity of

Carbon-Carbon Composite Made of the Mixture of

Organic Waste Carbon

Agus Edy Pramono1, Anne Zulfia2 and Johny Wahyuadi Soedarsono2

1. Mechanical Engineering Department, Politeknik Negeri Jakarta, Kampus Baru UI, Depok 16425, Indonesia

2. Departement of Metallurgy and Material Engineering, Universitas Indonesia, Kampus Baru UI, Depok 16424, Indonesia

Received: March 22, 2012 / Accepted: April 01, 2012 / Published: May 10, 2012. Abstract: This paper reveals the results of research about the electric conductivity of carbon-carbon composites made of a mixture of carbon particles of coal waste and coconut shell waste carbon. This study experimentally was initiated by mixing coal waste carbon powder and coconut shells waste carbon powder in the composition ratio of 60/40, 70/30 and 80/30 %weight, the mesh particle size was of 100, 150, 200 and 250, mixed with coal tar pitch with ratio of 70:30% in weight at a temperature of 100 °C, compacted in a hot of 100 °C with the pressure of 778.75 bar, compacted in a hot of 100 °C with the pressure of 778.75 bar, processed in the pyrolysis at temperatures of 500 °C. Four-point probe test results showed that the higher the percentage of carbon content of coal powder in the composite had increased the electrical conductivity of carbon-carbon composites. The larger the densities increase the electrical conductivity value of the composite. The highest electrical conductivity value is 3.40 Siemens/m was shown by the composites with the density of 2 gram/cm3, and this composite was made of the composition ratio of 80:20 %weighting and a particle size of 150 meshes.

Key words: Electrical conductivity, carbon-carbon composite, coconut shell waste carbon, coal waste carbon.

1. Introduction

This paper reveals the results of research of the

electrical conductivity properties on carbon-carbon

composites made of a mixture of coal waste particles

carbon and coconut shell waste carbon. The mixture of

carbon particles were used as reinforcement particles in

the composite. Coal tar pitch was used as the

composites adhesive matrix. These engineering

materials can be used as a machine rubbing component

as well as delivering electric power, such as brush

carbon in an electric generator, or electrically

conductive contactor on the pantograph of an electric

trains. For comparative study, the following is a review

based on the journals reference. Comparison of journal

reference indicated the value of density of 1.43 to 1.57

Corresponding author: Agus Edy Pramono, lecturer,

research field: carbon composite. E-mail: aepram@yahoo.com.

gram/cm3, [1]; engineering studies and characterization

of carbon-carbon composite materials based on

coconut shell waste as reinforcement in a matrix of coal

tar pitch obtained the maximum density value of 1.45

gram/cm3 [2]; composites made with thermosetting

resins as matrix precursor of low density passed from

1.55 gram/cm3 to 1.75 gram/cm3 and micro-porosity

were well distributed, on the contrary they were made

with a pitch as matrix precursor, after densification

showed that the density of 1.8-2.0 gram/cm3 with some

meso pores [3]; final density of all samples which were

prepared from PAN-based carbon fiber type of

non-woven sheet was 1.73-1.75 gram/cm3 [4]; Four

pitches (coal tar pitch commercial, water-blown pitch

and two heat-treated coal tar pitch) and four granular

carbon (graphite, anthracite, green petroleum coke and

foundry coke) were used for the preparation of carbon

composites to be tested as carbon brake shoe. This

DAVID PUBLISHING

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Effect of the Density to the Electrical Conductivity of Carbon-Carbon Composite Made of the Mixture of Organic Waste Carbon

403

produced carbon composite density from 2.9 gram/cm3

to 3.6 gram/cm3 [5]; in studies of LDPE composites

filled with basalt materials of 10%-70% weight

produced density 0.94-1.81 gram/cm3 [6]; by filling in

isostatic graphite polypropylene (IPP) in the study of

polymer matrix composite density was obtained

0.98-1.67 gram/cm3 [7]; Hot compaction process

produced density of 1.43 gram/cm3, 1.434 gram/cm3

and 1.448 gram/cm3. Increasing the temperature of the

hot compaction process was proven to increase the

density [8]. The used conductive amplifier was

exfoliated nano-platelets graphite, carbon black,

carbon fibers developed vapor and polyacrylonitrile

carbon fiber. Composites were made using melt mixing

followed by injection molding [9]. To increase the

sensitivity of the electrical conductivity of conductive

polymers, zeolite Y (Si/Al = 5.1, 30, 60 and 80) were

added to the conductive polymer matrix. The

sensitivity of the electrical conductivity of the

composite sensor increased linearly with increasing

ratio of Si/Al: with a value of 0.201, 1.37, 2.80 and 3.18,

respectively [10]. A conductive polymer (polyaniline

(Pani)) which was incorporated in the presence of pulp

fibers were distributed in the polymerization reaction

to produced Pani composite fiber/pulp, which was then

shaped into conductive sheets of paper. The paper

surfaces were investigated using SEM and electrical

conductivity and measurements of electron vortex

character was done. The maximum conductivity value

of this study was 1.9 × 10-2 S/cm [11]; surface

resistivity of the lowest was recorded for the fabric

woven from yarns with a number of wrappers 4.5

coil/cm; the surface resistance was 28.7 Ω/sq. [12];

Vegetation fire that burns under high voltage

transmission lines to reduce blast over voltage by an

increase in electrical conductivity of air and

temperature. Analyzer determined the electrical

conductivity ranged from 0.0058 mho/m to 0.0079

mho/m to the fire with a maximum temperature of

1,240 K. [13]. The research of adhesive based epoxy

yielded the electric conductivity of 2.0 × 10-3-1.67 ×

10-4 S/cm [14]. The research of electric resistance

measurement of carbon fibrous polymer matrix

composite yielded the electric conductivity of 0.001-20

(Ω·mm)-1. [15]. Based on above study of journal, then

the problems that can be revealed in this research is

how the influence of physical properties of density on

electrical conductivity of carbon-carbon composites?

2. Experiment

This research had been carried out experimentally by

following the flow diagram in Fig. 1:

Coconut shells organic waste was carbonized. This

process was carried out by continuous vacuum furnace

technology. Carbonization process was carried out at a

temperature of 900 °C. Coconut shell carbon was

ground in the disc/ball mill machine. The carbon

powder of coconut shell waste of the mill results was

sifted to achieve the mesh size of 100, 150, 200 and

250, sieving was carried out in vibration filter machine.

Material of coal waste powders was milled in the

disc/ball mill machine. Carbon powder of coal waste of

milling results was sieved to achieve mesh size of 100,

150, 200 and 250, sieving was carried out in vibration

filter machine. Carbon powder of coal waste from each

mesh size was weighted by the percentage of 60%,

70% and 80% weight of the total weight of the

reinforcing powder of pre-form sample. Carbon

powder of coconut shell waste from each mesh size

was weighted by the percentage of 40%, 30% and 20%

weight of the total weight of the pre-form sample

reinforcing powder. Coal waste carbon powder and

coconut shells waste carbon powder from each mesh

size were mixed into reinforcing powder with the

composition ratio of 60/40, 70/30 and 80/20 %weight.

The mixture of reinforcing powder carbon was 70%

weights of pre-form sample, 30% weight of the

pre-form sample was adhesive matrix of coal tar pitch.

Coal tar pitch matrix was weighted of 30% weight of

pre-forms. Powder mixture of 70% reinforcing carbon

was mixed with adhesive matrix of coal tar pitch of

30% by heating 100 °C. A mixture of the reinforcing

Effect of the Density to the Electrical Conductivity of Carbon-Carbon Composite Made of the Mixture of Organic Waste Carbon

404

Fig. 1 Flowchart of research.

particles and adhesive matrix of coal tar pitch was

further solidified in the mold with a pressure of 778.75

bars, heated of 100 °C and held at that temperature for

30 min. The pre-form sample was processed in curing

pyrolysis in oxygen impermeable vacuum furnace at

the temperatures of 500 °C and held for 15 min.

3. Results and Discussion

3.1 Characterization of Composite Materials

All used materials in manufacture of carbon-carbon

composites were characterized through the ultimate

test, as shown in Table 1, while the thermogravimetry

analysis results were presented in Fig. 2.

3.2 FTIR Test Results

Infrared vibration energy absorbed by the molecules

bond in the carbon-carbon composite with the

composition ratio of CC:CSC of 60/40, 70/30 and

80/20 %weight, for particle size of 100 mesh is shown

at Fig. 3.

Absorption peaks of infrared spectrum energy was

occurred at the same wave numbers for all composition

ratio, in such a way at that wave numbers shown the

possible of the same molecules bond for all composition

Table 1 Ultimate test results of composite materials.

No Material Material code

Parameter analysis (%) Density

Carbon Hydrogen Nitrogen Sulfur Oxygen Ash gram/cm3

1 Coal CC 72.31 3.39 1.36 1.70 0 0 1.633

2 Coconut shell CSC 99.27 0.16 0.62 0.05 0 1.64 1.3794

3 Coal tar pitch CTP 84.99 5.91 1.32 0.61 5.03 2.14 1.02

Effect of the Density to the Electrical Conductivity of Carbon-Carbon Composite Made of the Mixture of Organic Waste Carbon

405

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90Time [min]

0

10

20

30

40

50

60

70

80

90

100

%TGA

0

100

200

300

400

500

600

700

800

900

CTemp

CC

CSC

CTP

TGA test result of coal carbon, coconut shell carbon and coal tar pitch

Fig. 2 The graph of TGA test results.

Fig. 3 The graph of FTIR test results.

Effect of the Density to the Electrical Conductivity of Carbon-Carbon Composite Made of the Mixture of Organic Waste Carbon

406

ratio of the carbon-carbon composite. At about of contiguous wave number, each of composition ratios of CC:CSC absorbed the different percentage of infrared spectrum energy. The more the percentage of coal powder content, the higher the absorbed energy of infrared spectrum by each molecules bond in the carbon-carbon composite, as shown in Table 2.

3.3 Density Test Results

Changes in the composition ratio of CC:CSC changed the density of the composite, the higher the carbon content of coal, the higher the density of the composite. It is revealed in Fig. 4.

Increased density values for the greater percentage of coal carbon content was also supported by the density test results of each carbon particle materials. It is revealed in Table 1.

The highest density of carbon-carbon composites was produced by the composition ratio of 80:20 on

150 mesh particle size, i.e., 1.93 gram/cm3. This carbon-carbon composite contain 80% carbon weight of coal, resulting in higher densities than the composite with the composition ratio of 70:30 and 60:40. The lightest carbon-carbon composites were shown by the composition ratio of 60:40 on 100 mesh particle size, i.e., 1.65 gram/cm3. This carbon-carbon composite contains 40% weight of coconut shell carbon, resulting in a lower density than the composite with the composition ratio of 80:20 and 70:30, as shown in Fig. 5.

3.4 Electrical Conductivity Test Results

Conductivity test was conducted by two point probes to measure the electrical conductivity of carbon-carbon composites. Measurements were performed on electrical resistance, distance of electric current flows and cross-sectional area where the electrical current was flowing in the composite.

Table 2 Absorption of infrared spectrum energy by molecules bond.

No Molecules bond [16]

CC:CSC = 60:40 CC:CSC = 70:30 CC:CSC = 80:20 Wave numbers (cm-1)

Absorbed energy (%)

Wave numbers (cm-1)

Absorbed energy (%)

Wave numbers (cm-1)

Absorbed energy (%)

1 C≡C 2,303.01 10 2,303.01 17 2,308.79 40 2 C–C 894.97 7 883.40 14 869.90 20 3 C–H 2,885.51 7 3,005.10 12.5 2,991.59 30 4 651.94 15 650.01 17 648.08 20 5

O–H

3,730.33 11 3,734.19 17.5 3,732.26 42 6 1,512.19 7.5 1,583.56 13.5 1,606.70 30 7 1,462.04 6 1,514.12 14 1,514.12 31 8 1,315.45 12 1,294.24 17 1,292.31 33

Fig. 4 The relationship of density vs. composition ratio, for 100, 150, 200 and 250 mesh.

Fig. 5 The relationship of particle size mesh vs. density vs. composition ratio.

Effect of the Density to the Electrical Conductivity of Carbon-Carbon Composite Made of the Mixture of Organic Waste Carbon

407

Furthermore, resistance static or was calculated by

the following equation:

) (.

ml

AR

where is the static resistance in Ω·m, results of

calculations. R is the electrical resistivity in Ω,

measurement results. A cross-sectional area in m2,

results of calculations. l distance of currents flow in m,

measurement results. The electrical conductivity of the

composite was determined by the following equation:

)(1 1 m

or by unit (siemens/m)

The results of electrical resistance measurement and

calculation of electrical conductivity can be explained

in the following charts and information. Changes in

composition percentage ratio of CC:CSC affected on

the magnitude of the electrical conductivity of

carbon-carbon composites.

The higher the percentage of carbon content of coal

powder in the composite had increased the electrical

conductivity of carbon-carbon composites. This

happens to all types of composite particle sizes studied.

Fig. 6 shows these essentials.

The highest conductivity value was 3.40 Siemens/m,

shown by the composites with a particle size of 150

mesh and the composition ratio of 80:20, while the

lowest value was 0.07 Siemens/m, shown by the

composites with a particle size of 200 mesh and the

composition ratio of 60: 40, as shown in Fig. 7.

3.5 Density Relationship against Electrical

Conductivity

Electrical conductivity values were influenced by

the grade of density of carbon-carbon composites. The

higher density of carbon-carbon composites, the higher

value for electric conductivity of the composite. The

relationship of influences of the density value against

the conductivity of carbon-carbon composites with a

particle size of 100 mesh is shown in Fig. 8a. The graph

shows that the density value of 1.65 gram/cm3

generated electrical conductivity of 0.08 Siemens/m,

while when the density increased to 1.75 gram/cm3, the

Fig. 6 The relationship of conductivity vs. composition ratio, for 100, 150, 200 and 250 mesh.

Fig. 7 The relationship of particle size mesh vs. the conductivity vs. the ratio composition.

electrical conductivity value reached 2.87 Siemens/m.

The density value of 1.70 gram/cm3 generated

electrical conductivity of 0.24 siemens/m, then with a

density of 1.93 gram/cm3 generated electrical

conductivity of 3.40 Siemens/m, as shown in Fig. 8b.

The relationship between density and electrical

conductivity for carbon-carbon composites of the

particle size of 200 mesh is shown at Fig. 8c. This

graph shows the density value of 1.72 gram/cm3 which

generated electrical conductivity of 0.07 Siemens/m.

The higher the density values shown the increase of

electrical conductivity of carbon-carbon composites,

the density value of 1.78 gram/cm3 generated electrical

conductivity of 1.48 Siemens/m.

The influence of the density against the electrical

conductivity of carbon-carbon composites with a

particle size of 250 mesh is shown in Fig. 8d. Density

by 1.73 gram/cm3 generated electrical conductivity

0.27 Siemens/m, then the density value of 1.76

Effect of the Density to the Electrical Conductivity of Carbon-Carbon Composite Made of the Mixture of Organic Waste Carbon

408

gram/cm3 generated electrical conductivity of 2.95 Siemens/m.

Fig. 8 Relationship graph of density vs. electric conductivity.

3.6 Scanning Electron Microscopic Test

Fig. 9 shows the micro structure of carbon-carbon composite of composition ratio 60:40. The micro structure shows particle size of 39 µm and void size of 49 µm, as shown in Fig. 9a. Fig. 9b shows the particle size of 39 µm and void size of 49 µm, while Fig. 9c shows the particle size of 57 µm and void size of 35 µm,

Fig. 9 Micro structure of carbon-carbon composite.

(a)

(b)

(d)

(c)

(a)

(b)

(c)

(d)

Effect of the Density to the Electrical Conductivity of Carbon-Carbon Composite Made of the Mixture of Organic Waste Carbon

409

and Fig. 9d shows the particle size 87 m and void size

of 39 m.

4. Conclusions

The highest density of carbon-carbon composites

was produced by the composition ratio of 80:20 on 150

mesh particle sizes, i.e., 2 gram/cm3. The lightest

carbon-carbon composites are shown by the

composition ratio of 60:40 on 100 mesh particle size,

i.e., 1.65 gram/cm3.

The highest conductivity value is 3.40 Siemens/m, it

is shown by the composites with a particle size of 150

mesh and the composition ratio of 80:20, while the

lowest value is 0.07 Siemens/m, it is shown by the

composites with a particle size of 200 mesh and the

composition ratio of 60: 40.

Electrical conductivity values are influenced by the

grade of density of carbon-carbon composites. The

higher the density of carbon-carbon composites is, the

higher the value for conductivity of the composite is.

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