Advantages of a wet process for the production of Ti matrix composite
reinforced with carbon nano materials by powder metallurgy route
Department of Composite Materials Processing, JWRI, Osaka University

Abstract
A titanium matrix composite reinforced with different carbon nano materials i.e. carbon nanotubes, acetylene black and carbon black was fabricated by spark plasma
sintering (SPS) and hot extrusion. Carbon nano materials were added for the in-situ formation of TiC fine dispersoids during the SPS process. Fine Ti powders were coatedwith carbon materials by a wet process using a zwitterionic solution containing 0.5wt.% of carbon materials. The coated Ti powders were consolidated by hot extrusion. The
mechanical properties of the composites were remarkably improved by adding a small amount of carbon nano materials. The increases in the yield stress of the extruded fine
Ti was 50.7%, 41.2% and 64.2%, while the tensile strength increases 24.8%, 22.5% and 35.7% for the carbon nanotubes, acetylene black and carbon black reinforcement,
respectively, compared to those of extruded pure Ti with no reinforcement.

Separation Mechanism of Bundled CNTs
Zwitterionic surfactants

Hydrophilic group(Plus and Minus charge)+100

Weight Change, %Zwitterionicsurfactant

Self-rearrangement

Un-bundled CNTs

Bundled CNTs

-Bundled CNTs

Dipole/Dipole
attraction

Hydroprobic group(Neutral charge)

Carbon nanotube

80
Carbon black60
40

Dried solid zwitterionic20

Acetylene black0
The neutral charge of hydrophobicgroup will attract to the surface ofcarbon nano particles, while theelectrostatic interaction between
positive and negative charges ofhydrophilic group is attracted together.

ElectrostaticforceNeutralization0

Dispersed in Zwitterionic

200300400500600700a)

1000

Acetylene blackb)

CNT

Determination of debiding temperature
by TG analysis

Agglomerated in WaterResults

Coating carbon nano materials
Ti powders
Wet processing

100

Temperature, oC

Un-bundled CNTs disperse
in Zwitterionic surfactant

Carbon black

Carbon nanotube

Stress , MPa

800

Debinding process: 600oC, 60minc)

Carbon blackd)

Acetylene black600
As extruded Ti

400
200

Bundled CNTs

00
Individually and uniformly dispersed
CNT on the Ti powder surface

CNTs dispersion inZwitterionicsolution10●●● Ti●■ TiC

Grain sizeµm

TiC sizeµm

YS
MPaTSMPa

ef%

HV

●

Chemical analysis (wt.%)
CON

Incremental stress
per 0.1wt.% ofCarbon, MPaYSTS

Ti/CNTs
Ti/Acetylene black

5.8
8.1

1.9
2.1

683 [20]640 [28]808 [11]793 [12]27.2 [10.4]
28.8 [16.5]

306
286

0.245
0.121

0.35
0.33

0.01100.0070

98.7
171.6

69.1
133.9

Ti/Carbon black

5.8

3.0

744 [14]878 [18]

29.3 [12.0]

340

0.162

0.38

0.0092

194.0

154.0

Ti without reinforcement4.1-

453 [25]647 [19]37.3 [1.7]2610.012

0.210.0100--[ ] : Maximum – Minimum value.

Conclusion

Intensity (a.u.)

Extruded Ti samples

3040

Stress-strain curves for P/M extruded titanium composites reinforced
with in situ formed TiC particles.

Ti powder coated by a) CNTs, b) acetylene black and c)
carbon black particles via a wet process, compared to that
mixed with CNTs by a planetary ball millMechanical properties and chemical analysis results of the extruded Ti/TiC composites

2030
Elongation, %●■■■Acetylene black■■■Carbon black

■3540

●CNT

45TiC●●

50556065

7075

Diffraction angle, 2θ
XRD patterns of the extruded Ti composite
reinforced with carbon nano materials

80

Microstructure of extruded Ti
composite reinforced with CNTs
revealed the distribution of in situ
formed TiC particles throughout theTi matrix

A wet process, the zwitterionic surfactant solution containing CNTs, acetylene black and carbon black particles, was used to coat the Ti powders. The
coated Ti powders revealed a good distribution of non-agglomerated carbon reinforcing phases on the surfaces. Consequently, the in situ formed TiCparticles were highly distributed throughout the Ti matrix, resulting in the increased mechanical properties. Furthermore, the effect of grain size, oxygenand nitrogen contents did not significantly improve the mechanical properties of the extruded Ti composites materials.