CENTRE FOR NANOSCIENCE AND TECHNOLOGY

COURSE INSTRUCTORDr A.SUBRAMANIA

PRESENTED BY R AVINASH KUMAR Reg no-11305014

METAL MATRIX NANOCOMPOSITES

OVERVIEW

• INTRODUCTION• CLASSIFICATION OF COMPOSITES• MANUFACTURING TECHNIQUES• PROPERTIES• APPLICATIONS • REFERENCES

INTRODUCTION

METAL MATRIX COMPOSITES• A metal matrix composite (MMC) is composite material

with at least two constituent parts, one being a metal. The other material may be a different metal or another material, such as a ceramic or organic compound.

COMPOSITIONS• REINFORCING MATERIAL + METAL MATRIX

MATRIX• The matrix is the monolithic material into which the

reinforcement is embedded• In structural applications, the matrix is usually a lighter

metal such as aluminum, magnesium, or titanium, and provides a complete support for the reinforcement

INTRODUCTION

REINFORCEMENT• The reinforcement material is embedded into the matrix• The reinforcement can be either continuous, or

discontinuous• Is also used to change physical properties such as wear

resistance, friction coefficient, or thermal conductivity.• Continuous reinforcement uses monofilament wires or

fibers such as carbon fiber or silicon carbide. Because the fibers are embedded into the matrix in a certain direction, the result is an anisotropic structure in which the alignment of the material affects its strength.

• Discontinuous reinforcement uses "whiskers", short fibers, or particles. The most common reinforcing materials in this category are alumina and silicon carbide

CLASSIFICATION OF COMPOSITES

NANOCOMPOSITES

• A nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm), or structures having nano-scale repeat distances between the different phases that make up the material.

• Carbon nanotube metal matrix composites (CNT-MMC) are an emerging class of new materials that are being developed to take advantage of the high tensile strength and electrical conductivity of carbon nanotube material

CARBON NANOTUBES REINFORCED METAL MATRIX COMPOSITE PRODUCTION METHODS

POWDER METALLURGY ROUTE

• The basic process steps consist of mixing CNTs with metal powder by grinding or mechanical alloying, followed by consolidation by compaction and sintering, cold isostatic pressing.

SPARK PLASMA SINTERING

Cu-CNT (5 vol.-%) composite processed through SPS of ball milled Cu-CNT powders

(SEM) of Cu-CNT (5 vol.-%) composite fabricated by SPS from molecular level mixed composite powders, showing homogeneous distribution of CNTs

In this process, a pulsed direct current is passed through a die and the powder, producing rapid heating and thus greatly enhancing the sintering rate, Efficient densification of powder can be achieved in this process through spark impact pressure, joule heating and electrical field diffusion.

MELTING AND SOLIDIFICATION ROUTE

• Melting and solidification, the most conventional processing techniques for MMCs, has also been utilised for synthesising CNT-reinforced composites

• due to the requirement of high temperature for melting. The process may cause damage to CNTs or formation of chemical reaction product at the CNT/metal interface.

• this route is mainly favoured for composites having low melting point matrix.

METAL INFILTRATION

The main idea of metal infiltration technique is to prepare a porous solid structure with dispersed CNTs and then infiltrating liquid metal into the pores and solidify to prepare a composite structure

Schematic of metal infiltration technique

THERMAL SPRAY

• Thermal spraying can be defined as the spraying of molten or semi-molten particles onto a substrate to form a coating deposit by way of impact and solidification

PLASMA SPRAYING AND HIGH VELOCITY OXY-FUEL (HVOF) SPRAYING In plasma spraying, the heat source is

a plasma created by the ionisation of an inert gas by an arc struck between a tungsten cathode and concentric copper anode (DC plasma spraying) or by high frequency radio waves (RF plasma spraying)

Free standing structures of Al–23 wt-%Si alloy containing10 wt-%CNT produced by plasma spray forming (PSF) and HVOF

In HVOF, the source of heat is high pressure combustion of a fuel-oxygen mixture.

ELECTROCHEMICAL ROUTE• electrochemical deposition is the second most popular

route after powder metallurgy techniques.

ELECTRODEPOSITION• Electro deposition requires the traditional

electrochemical cells in which composite film is deposited by current flow between anode and cathode.

ELECTROLESS DEPOSITION• Electroless plating does not require any external

energy source. This is basically a chemical process, in which thermochemical decomposition of metallic salts takes place in the bath to release metallic ions that forms composite with CNTs.

THIS METHOD IS CAPABLE OF PRODUCING COMPOSITE PARTICLES OR 1D NANOSTRUCTURE OF CNT COATED WITH METAL. THE PROCESS REQUIRES CNTS TO BE ACID TREATED AND FUNCTIONALISED BEFORE INTRODUCING THEM INTO THE METAL-SALT BATH, THUS AIDING THE CNT SUSPENSION AND SURFACE METAL DEPOSITION ON THEIR SURFACE. SUBSEQUENTLY, THE BATH IS SONICATED TO PREPARE A CNT-METAL ION PRECURSOR WHICH GOES THROUGH DRYING, CALCINATIONS, AND A REDUCTION PROCESS, IN SERIES, TO PRODUCE METAL-CNT COMPOSITE POWDER

Improvement in mechanical properties of different MM-CNT composites as a function of CNT content, classified

according to processing routes employed

a) image (TEM) of CuO/CNT powder prepared by molecular level mixing method,47

b) b image (SEM) of the fracture surface of Al/CNT powder prepared by ball milling for 48 h,35 and image (SEM) of spray dried Al–Si agglomerates containing

c) 5 wt-%CNT and d) 10 wt-%CNT (reproduced with permission from Wiley Interscience

and Elsevier)

Other properties affected by CNTreinforcement in metals

• Electrical and Electronic Properties Al-12/5 vol.-%CNT composite prepared by powder metallurgy displayed

increased electrical resistivity by 66%

• Thermal properties1. Carbon nanotubes are known to have very high thermal

conductivity and very low coefficient of thermal expansion. Hence, MM-CNT composites have a great potential to be used for thermal management

2. The improvement in thermal properties of MM-CNT composites largely depend on the distribution of CNTs and their bonding with the matrix

• Wear and friction properties studies have reported a decrease in the coefficient of friction (COF)

and increase in the wear resistance with addition of CNTs to the metal matrix.

• Corrosion properties• Hydrogen storage properties Mg-CNT composites have a better hydrogen-storage

capacity and absorption-desorption rate than other hydrogen storage materials.

• Applications as sensors and catalysts

Other properties affected by CNTreinforcement in metals

POTENTIAL APPLICATIONS

• NANONETWORK• NANOROBOTICS• FUTURE SOLDIER• NANO ARMOUR• SPACE ELEVATOR• ADVANCED

MODULAR ARMOR PROTECTION

Industry Application Property desired

Automobile industry Break shoes, cylinder liners, piston rings,gears

High strength, wear resistance, good thermalconductivity, low density

Aerospace industry Aircraft brakes, landing gears Good wear resistance, good thermal conductivity,low density, high strength

Space applications High gain antenna boom, structural radiators

Low density, high strength, low coefficient ofthermal expansion, good electrical conductivity

Sports industry Light weight bicycles, tennis and badminton

High strength, high elastic modulus

Electronic packaging Heat sinks for thermal management, solders

High thermal conductivity, low coefficient of thermalexpansion, increased strength

MEMS and sensors Micro-beams, micro-gears High elastic modulus, high surface area

Battery and energystorage

Anodes and anode coatings, hydrogen storagematerials

Large surface area, high current density, reducedresponse times

REFERENCES

• CARBON NANOTUBE REINFORCED METAL MATRIX NANOCOMPOSITES – A RIVIEW by S. R. Bakshi, D. Lahiri and A. Agarwal

• WIKIPEDIA