Synthesis & Characterisation of CNT reinforced Al Nanocomposite

• By: Malik Tayyabwith co-member Muhammad Mutahir.

This work was conducted as a part of my final year project at NED University of Engineering & Technology during the year 2011 in Karachi, Pakistan.

This is a pdf file; since i created the presentation in ppt format(which is obiviously animated) therefore some things you might consider unclear. If you would like to have the ppt file or any other suggestion regarding this topic you can reach me through my email address: [email protected]

Group 2MM 07009 Muhammad MutahirMM07026 Malik Tayyab

Project Advisor Prof. Dr. Ashraf Ali Co-Project Advisor Asst. Prof. M. Sajid Ali Asghar

Department of Materials Engineering,NED University of Engineering & Technology.

A nanometer is one billionth of a meter.

Nanotechnology is the study of manipulating matter onan atomic and molecular scale.

Materials or structures possessing at least one dimensionsized from 1 to 100 nanometers.

Currently undergoing extensive development.It has not yet yielded significantly useful commercialproducts.

Malik TayyabMaterial Engineer

1. Data Storage Devices.2. Sensor units.3. Optical devices.4. Biomedical products.5. Computing and information

storage devices.6. Smart materials using Nano-

scale devices.


Smallest synthetic motor that's ever been made. A gold rotor, nanotube anchors and opposing stators are

simultaneously patterned around the nanotubes using electron beam lithography.


Bottom-up:

Products are manufactured oneatomic particle at a time.

Seek to have smaller (usuallymolecular) components built upinto more complex assemblies.

Top-down:

Every product begins with abulk material process and issubsequently refined down.

Top-down approaches seek tocreate Nano scale devices byusing larger, externallycontrolled ones to direct theirassembly.


Bottom Up Approach refers to the build up of amaterial from the bottom: Atom by Atom, Molecule byMolecule, or cluster –by-cluster

e.g. Polymer Synthesis


• Nano Buds• Nano Torus

i. Zero-Dimensional Nanostructures: Nanoparticles

ii. One-Dimensional Nanostructures: Nanowires and Nano rods

iii. Two-Dimensional Nanostructures: Thin Films

iv. Three-Dimensional Nanostructures: Special Hybrid Structures

Malik TayyabMalik TayyabMaterial Engineer

• Structural components with high strength to weight ratios

• Batteries with better power output

• Abrasion resistant coatings

• Automotive Parts Ball bearings made of CNT-Cu Nano composite.

Bicycle Crank set made of CNT-Al Nano composite.


• Nano composites differ from conventional compositematerials due to the exceptionally high surface to volumeratio of the reinforcing phase.

• Nano materials may have a significantly lower meltingpoint or phase transition temperature.

• Gravity plays no role whatsoever and inertial effects arebasically nonexistent because things are just so small.

All these and other similar factors give nanomaterials uniqueproperties like:Copper turns transparent from opaque.Gold becomes catalytic.Aluminium becomes combustible.


There are two main types of carbon nanotubes thatcan have high structural perfection.

• Single-walled nanotubes (SWNTs) consist of asingle graphite sheet seamlessly wrapped into acylindrical tube.

• Multi-walled nanotubes (MWNTs) comprise anarray of such nanotubes that are concentricallynested like rings of a tree trunk.

Arm chair or Metallic

Zig Zag

Chiral


Two techniques selected for production of Nano tubes:

• Arc Discharge Process• Flame Synthesis

Can be used for the production of both SWNTs and MWNTs.


The most common and perhaps easiest way to produce CNTs.

A technique that produces a complex mixture of components, and requires further purification - to separate the CNTs from the soot and the residual catalytic metals present in the crude product.

Applicable for production of both SWCNTs and MWCNTs.

Feed stock

Water in Water out

Gas inGas out

Pressure gauge

Anode

cathode


Sonication is the act of applying sound energy to agitate particles in a sample.• Temperature• Solvent(normally ethanol)• Vibrations• Operating time


CNTs produced by arc discharge at magnification 6000X.

CNTs produced by arc discharge at magnification 24000X


Flame SynthesisA wall-stagnation flow burner and its wall was made of catalystmaterial.The reactant gas used for the formation of the flame and thesynthesis of CNTs was ethylene/air premixed gas.

Malik TayyabMalik Tayyab

Material Engineer

MWNTs were used in this study with diameter 30 nm-40 nm.

Source Material Purity Level Mean Diameter

F.S. Corp. Aluminum Powder 99.9% 2.7 30 µm

Arc Discharge CNT >50-70% 1.95 N/A

Shenzhen Nanotech CNT >97% 2.1 30 - 40 nm


SEM images of CVD synthesized CNTs(source: (a) Shenzhen Nanotech )

(b) MMD SEM Analysis Malik Tayyab

Material Engineer

SEM images of Aluminium powder at different magnifications.


µm

Histogram showing the particle size distribution of Aluminium powder. Malik Tayyab

Material Engineer

• Laser Particle Size Analysis depends upon analysis of the"halo" of diffracted light produced when a laser beam passesthrough a dispersion of particles in air or in a liquid.

• The angle of diffraction increases as particle size decreases,so that this method is particularly good for measuring sizesbetween 0.1 and 3,000 μm.

Analysis indicated that Aluminium powder has a wideparticle size distribution ranging from 10 μm– 200 μm,with average particle size around 30 μm. Malik Tayyab

Material Engineer

The following challenges must be met:

1. Overcome the huge surface energy, enormous surface area or largesurface to volume ratio.

2. Ensure all Nano materials with desired size, and provide uniformdistribution.

3. Interfacial bond strength between CNT and metal matrix.

4. Chemical and structural stability of CNTs.


Illustration of dislocation interaction in a particulate composite (or age hardened alloy) and carbon nanotube reinforced metal matrix composite.


This is my own interpretation; I haven’t found this in any resource.

Processing routes for CNT-MM Nano composites.


• Powder Metallurgy is the most popular & widely applied technique.

• Electro deposition & Electro less deposition are the second most important technique for deposition of thin coatings.


Basic process steps consist of mixing CNTs with metal powder by grinding or mechanical alloying, Followed by consolidation by compaction and sintering.


Disentangled CNTs

CNTs

Ultra sonication of CNTs in ethanol for 1 hour.

AluminiumCNT-Al Powder

Ball Milling Powder Compaction Sintering

CNT-Al Nano compositeProcess flow diagram for CNT-Al Nano composite.


Plastic Coupling Agent (PCA, an organic solvent: e.g. ethanol) isadded to vial to avoid excessive welding and straining of theparticles. Malik Tayyab

Material Engineer

Ball Mill Vial with Steel Balls

(a) Schematic representation of ball mill vialshowing the impact of milling media on powderparticles (b) Ball-powder-ball impact. Malik Tayyab

Material Engineer

During milling Al-CNT powder, following set of events occur :-• Particle Deformation or Flattening,• Sandwiching• Particle Welding,• Fracturing causing grain size reduction.

Malik Tayyab Malik TayyabMaterial Engineer

1 % CNT, 200 RPM, 3 hours2% CNT, 200 RPM, 3 hours5% CNT, 200 RPM, 3 hours

Sample # % Composition Weight of CNT/g Weight of Al/g

1 Pure Al - 5

2 1%CNT-Al 0.05 4.95

3 2%CNT-Al 0.10 4.90

4 5%CNT-Al 0.25 4.75


Powder handling was performed in Vacuum Glove Box, Argongas was supplied for inert atmosphere.

In order to avoid environmental effects like oxidation ofAluminium powder, moisture adsorption.Aluminium powder is highly reactive, Resources indicate that athin passivation layer of alumina (4 nm thickness) forms in about100 picoseconds on any exposed aluminium surface(AluminiumNano clusters).

Vacuum Glove Box.Malik Tayyab

Material Engineer

Milled powder samples were compacted by a 100 Ton

Hydraulic press.Compaction pressures were calculated and determined by trail and error method.

In Accordance to ASTM Green density vs. CompactionPressure plot for 601AB Aluminium, 40 M Pa appearedto be the optimum pressure.


• Process based on Atomic Diffusion.

• Driving force for densification is the change in free energyfrom the decrease in surface area.

Solid state sinteringLiquid phase sintering

540 °C

0.5 hour

Time (hours)

Tem

pera

ture

(°C

)


Characterisation Technique• Scanning Electron Microscopy• X Ray Diffraction

The dispersion of CNTs in Aluminium matrix was investigated.

CNTs were observed at the weld interfaces between Aluminiumparticles.


2% CNT-Al Nano composite showing weld splats of fine Al particles on coarse ones.

Uniform distribution of CNTs found in the Al matrix.


Figure showing 2% CNT-Al Nano composite showing CNT reinforcement in Al matrix.


A perfect view of CNT at the weld interface in 2% CNT-Al Nano composite.

Agglomerates of CNTs in 5% CNT-Al Nano composite.


Individual X-Ray diffratograms of CNTs (100% intensity at 26°) and Aluminium overlapped.

CNTs Aluminium


X-Ray diffraction pattern of 2% CNT-Al Nano composite, no carbon peak observed.Malik Tayyab

Material Engineer

• Improper powder handling.• Oxygen pick up by Aluminium

powder during processing.• Improper calculation of the plastic

coupling agent (PCA). One of the failed sintered compacts.

Fractured surface of failed Nano composite compact.

CNTs observed at the fractured surface.

Elements Weight % Atomic %

C K 13.12 25.33

Al K 86.88 74.67

Totals 100.0

Energy Dispersive Spectroscopy confirming the presence of CNTs in the 2% CNT-Al Nano composite (Elemental Detection). Malik Tayyab

Material Engineer

Elements Weight % Atomic %

O K 5.67 9.21

Al K 94.33 90.79

Totals 100.00

EDS pattern showing no carbon peaks, Oxides were observed in the matrix.


X-Ray Mapping Images showing the distribution ofCNTs in aluminium matrix of 2% CNT-Al Nanocomposite along with oxide dispersions.

SEM X Ray Mapping ImageSEM Secondary Electron Image


Time provided was not sufficient due to some constraints else the nanofiber like image had appeared in the C x-ray map.

• Ball milling has been proven to be a very promising technique for thedispersion of CNTs in Al matrix. It has also been noticed that this techniqueexcessively strain hardens the matrix as the milling time increases.

• CNTs were found to be embedded in the matrix as an interphase at theAluminium powder particle weld interfaces.

• The fractured green compact also revealed CNTs in between the Aluminiumcrystallites.

Future Work and Recommendations• CNT-Al can also be prepared via Electrodeposition; this process gives added

benefit for coating surfaces requiring wear resistance.

• Pure Al and Aluminium alloys are known to generate hydrogen from alkalinewater for Polymer Electrolyte Membrane Fuel Cells. CNT-Al nanocomposites canbe used for hydrogen generation as a green renewable energy source.

• Hybrid Nano composite comprising of two different Nano reinforcements mightbe another interesting approach to enhance the mechanical and otherphysical characteristics of the nanocomposites (CNT/ Dispersed Oxides/ AlComposite or using two different types of CNTs). Malik Tayyab

Material Engineer

http://berkeley.edu/news/media/releases/2003/07/23_motor.shtml

Synthesis & Characterisation of CNT reinforced Al Nanocomposite

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