METALLIC GLASSES

PRESENTED BY:AKSHAYA SAI.VDEPARTMENT:CSE-ADATE:01-03-15

CONTENTS

*Definition *Types *Preparation *Glass Transition Temperature *Properties *Application

DEFINITION OF METALLIC GLASS:Metals are crystalline, malleable and ductile and glasses are amorphous, transparent,and brittleThe combination of both properties of metal and glass is known as metallic glassesIn year 1970, scientists discovered metallic glasses with non crystalline structure

METALLIC GLASSES=AMORPHOUS METAL

TYPES OF METALLIC GLASSES:

There are two types of metallic glasses namely

1)Metal-metal metallic glasses 2)Metal metalloid metallic glasses

METAL-METAL METALLIC GLASS: Combination of metals

METAL-METALLOIDMETALLIC GLASS:Combination of metal and metalloids

METAL METAL

Nickel(Ni) Niobium(Nb)

Magnesium(Mg) Zinc(Zn)

Copper(Cu) Zirconium(Zr)

METAL METALLOIDS

Fe,Co,Ni B,Si,C,P

PREPARATION OF METALLIC GLASS:Principle: “Extreme rapid cooling of molten metal alloy called ‘quenching’ “. Cooling so rapidly that there is no formation of crystalline structure forming solid frozen in liquid structure. There are three types of preparation *Melt Spinning system *Twin Roller system *Melt Extraction system

MELT SPINNING SYSTEM:

->A melt spinner consist of copper roller,refractory tube and induction heater.->The metal is passed through the refractory tube, this metal is melted by the induction heater in inert atmosphere which is coiled over the refractory tube .->Thus the molten metal is passed over the spinner and the metal is cooled suddenly in this process.->Thus a ribbon of metallic glass is obtained.

WORKING:

TWIN ROLLER SYSTEM: In a twin roller there are two spinners that rotate in opposite direction

MELT EXTRACTION SYSTEM:In this method a roller sweeps of the molten metal

GLASS TRANSITION TEMPERATURE:THE TEMPERATURE AT WHICH TRANSITION FROM LIQUID TO SOLID OCCURS IS KNOWN AS GLASS TRANSITION TEMPERATURE

Crystalline solid

Metallic glasses

Molten liquidSpecific volume (V)

Temperature(T)Tg Tm

A

C B

E D

2

1

Case(1): The curve ABDE shows the change from molten liquid to crystalline solid by normal cooling at a temperature called MELTING POINT TEMPERTURE

Case(2): The curve ABC shows the change from molten liquid to metallic glass by rapid cooling at GLASS TRANSITION TEMPERATURE The glass transition temperature of metallic glasses is 20◦-30◦ C

PROPERTIES:STRUCTURAL PROPERTY:1.No crystal defect such as grain boundary, dislocation etc.2.Possess tetrahedral close packingMECHANICAL PROPERTY:1.High strength due to absence of point defect2.High elasticity3.Higly ductile4.It is work harden material.

ELECTRICAL PROPERTY:1.High electrical resistivity2.Eddy current loss is small3.temperature coefficient is zero or negativeMAGNETIC PROPERTY:1.They possess both soft and hard magnetic property2.Magnetisation and de-magnetisation are easy due to high permeability.3.High saturation magnetisation. 4.Less core loss5.Narrow hysteresis loop

CHEMICAL PROPERTY:1.Resistant to corrosion due to random ordering .2.Higly reactive and stable.3.Act as catalyst

FERROMAGNETIC MATERIAL METALLIC GLASS

APPLICATIONS:STRUCTURAL APPLICATION:

(1)Used in reinforcing cement in concrete,plastic,rubber.(2)Simple filament winding is used to reinforce pressure vessel and to construct large fly wheels(3)Razor blades and springs

ELECTRICAL AND ELECTRONICS:

(1)Tape recorder heads ,cores of high power transformers and magnetic shield.(2)Used in motors to reduce core loss(3)Superconducting metallic glasses are used in levitation effect.(4)Used to make accurate standard resistance,computer memories and magneto resistance sensors.

(5)Transformer core due to small eddy current loss.NUCLEAR REACTOR ENGINEERING:

(1)Used in nuclear waste disposal(2)Magnets for fusion reaction.(3)Chromium and phosphorous metallic glasses are used in inner surface of the reactor

BIO-MEDICAL INDUSTRIES:

(1)used in making surgical instruments.(2)Used in prosthetic materials for implantation in human body