MATERIAL TECHNOLOGY

NEWLY DEVELOPED ENGINEERING MATERIAL

INTRODUCTION

Materials Technology is an interdisciplinary field involving the properties of

matter and its applications to various areas of technology and engineering. This

scientific field investigates the relationship between the structure of materials

at atomic or molecular scales and their macroscopic properties. It incorporates

elements of applied physics and chemistry. With significant media attention

focused on nanoscience and nanotechnology in recent years, materials science

has been propelled to the forefront at many universities. It is also an important

part of forensic engineering and failure analysis. Materials science also deals

with fundamental properties and characteristics of materials.

LIST OF NEWLY DEVELOPED ENGG. MATERIALS

1. Lead Zirconate Titanate (PZT)

2. Zirconium Dioxide (ZrO2)

3. Amorphus Silicon

4. Magneto Rheological Fluid

5. YAG (Yteum aluminium garnets) laser

6. Stellites

7. Vatillium

8. Titanium alloy

9. Silicon Bricks

1. Lead Zirconate Titanate (PZT)

Lead Zirconate Titanate (PZT) is a ceramic material made of lead (Pb),

oxygen (O) and titanium (Ti) or zirconium (Zr).

Chemical formula: Pb[ZrxTi1-x]O3; x = 0,52

The atoms are arranged in a cubical structure.

ATOMIC STRUCTURE OF PZT

At temperatures below the Curie temperature (depending on the material

between 150°C and 200°C) the titanium atom moves from its central

position and the electrically neutral lattice becomes a dipole.

This dipole lattice presents now piezoelectric characteristics and is

considered as one of the most economical piezoelectric material.

By doping the PZT material, its piezoelectric characteristics can be modified:

especially the hardness or softness of the material.

MAKING OF PZT

Lead zirconate titanate , also called PZT, is ceramic perovskite material

that shows a marked piezoelectric effect. PZT-based compounds are

composed of the chemical elements lead and zirconium and the chemical

compound titanate which are combined under extremely high temperatures.

A mechanical filter is then used to filter out the particulates.

APPLICATION OF PZT

Being piezoelectric, it develops a voltage (or potential difference) across

two of its faces when compressed (useful for sensor applications), or

physically changes shape when an external electric field is applied (useful

for actuator applications).

Being pyroelectric, this material develops a voltage difference across two of

its faces when it experiences a temperature change. As a result, it can be

used as a sensor for detecting heat.

In 1975 Sandia National Laboratories was working on anti-flash goggles to

protect aircrew from burns and blindness in case of a nuclear explosion.

The PZT lenses could turn opaque in less than 150 microseconds.

LIMITATION OF PZT

High mechanical stress can depolarize a PZT ceramic.

As the operating temperature increases, piezoelectric perfonamce of

material decreases .

the curie point is the maximum exposure temperature for PZT. And it has

it’s own curie point. When this ceramic element is heated above the curie

point, all piezoelectric properties are lost.

2. ZIRCONIUM DIOXIDE

Zirconium dioxide , sometimes known as zirconia , is a white

crystalline oxide of zirconium.

Chemical formula: ZrO2

The atoms are arranged in a cubical crystal structure.

Zirconium dioxide in powder form

ATOMIC STRUCTURE

Pure ZrO2 has a monoclinic crystal structure at room temperature and

transitions to tetragonal and cubic at increasing temperatures.

The volume expansion caused by the cubic to tetragonal to monoclinic

transformation induces very large stresses, and will cause pure ZrO2 to

crack upon cooling from high temperatures.

Several different oxides are added to zirconia to stabilize the tetragonal

and/or cubic phases: magnesium oxide (MgO), yttrium oxide, (Y2O3), calcium

oxide (CaO), and cerium(III) oxide (Ce2O3)

TetragonalMonoclinic

MAKING OF ZrO2

Monoclinic zirconium dioxide formed by a process comprising : Melting

zirconium silicate into a induction melting furnace with a sintering crust

crucible at a temperature in a range of 2500° to 3000° C.

Quenching the melt by drawing the melt off in a stream and cooling the

stream by subjecting the stream, while in a free fall, to a spray of fluid so

as to form thermally split zirconium silicate.

Leaching out amorphous silica from the thermally split zirconium silicate

with alkali lye at 100° to 200° and a molar ratio of SiO2 to alkali hydroxide

of 1 to at least 2 so as to obtain zirconium dioxide.

APPLICATION OF ZrO2

The cubic phase of zirconia has a very low thermal conductivity, which has

led to its use as a thermal barrier coating or TBC in jet and diesel

engines to allow operation at higher temperatures.

It is used as a refractory material, in insulation, abrasives and ceramic

glazes.

Zirconia is also an important high dielectric material that is being

investigated for potential applications as an insulator in transistor in

future nanoelectronic devices.

• Products made from Zirconium Oxide (ZrO2)

Bearing Technology in Automotive Engineering

Cutters

Dental Ceramics

Drawing Tools

Forming Applications

Sealing Technology (Seal Rings, Bearings)

Technical Cutters

Tubes and Pipes

LIMITATION

Use of zincronia is more expensive then metal .

It’s not easily available, number of process are required to get pure

zincronia.

Less resistant to stress or extra force, there is a risk of chipping or fracture.

3. AMORPHOUS SILICON

Amorphous silicon (a-Si or α-Si) is the non-crystalline allotropic form

of silicon.

Due to the disordered nature of the material atoms have a dangling bond.

These dangling bonds are defects in the continuous random network and

cause anomalous electrical behavior.

ATOMIC STRUCTURE OF AMORPHOUS SILICON

Silicon is a fourfold coordinated atom that is normally tetrahedrally bonded

to four neighboring silicon atoms.

In crystalline silicon this tetrahedral structure is continued over a large

range, forming a well-ordered crystal lattice.

If desired, the material can be passivated by hydrogen, which bonds to the

dangling bonds and can reduce the dangling bond density by several orders

of magnitude.

Hydrogenated amorphous silicon (a-Si:H) has a sufficiently low amount of

defects to be used within devices.

MAKING OF AMORPHOUS SILICON

In the manufacture of amorphous silicon, thin monocrystalline silicon wafers

are made by cutting a crystal of monocrystalline silicon. For further

processing these wafers are fixed on a polishing block. The exposed surface

of each wafer is then polished in order to remove the surface irregularities

which are caused by the cutting of the crystal of monocrystalline silicon.

Generally, the silicon wafers are processed in successive steps with grinding

or polishing agents of different particle size. These process steps comprise

the lapping and/or the so-called Blanchard grinding by which rough

irregularities are removed from the surface, and finally one or several

mechanical or chemical precision polishing processes which produce an

extremely smooth and defect-free surface which subsequently is subjected

to the known processing methods for making semiconductor devices.

APPLICATION OF AMORPHOUS SILICON

Amorphous silicon has become the material of choice for the active

layer in thin-film transistors (TFTs), which are most widely used in large-

area electronics applications, mainly for liquid-crystal displays (LCDs).

Amorphous silicon has been used as a photovoltaic solar cell material.

LIMITATION

In this material the converge takes place below the temperature of 250K,

so the valance place has been occurred between the molecular of the

material.

This limitation is known as hole mobility of the material.

4. MAGNETO RHEOLOGICAL FLUID

A magneto rheological fluid (MR fluid) is a type of smart fluid in a carrier

fluid, usually a type of oil. When subjected to a magnetic field, the fluid

greatly increases its apparent viscosity, to the point of becoming

a viscoelastic solid. Importantly, the yield stress of the fluid when in its

active ("on") state can be controlled very accurately by varying the

magnetic field intensity. The upshot of which is that the fluid's ability to

transmit force can be controlled with an electromagnet, which gives rise to

its many possible control-based applications.

WORKING OF MR FLUID

The magnetic particles, which are typically micrometer or nanometer scale

spheres or ellipsoids, are suspended within the carrier oil are distributed

randomly and in suspension under normal circumstances, as below.

When a magnetic field is applied, however, the microscopic particles

(usually in the 0.1–10 µm range) align themselves along the lines

of magnetic flux. When the fluid is contained between two poles (typically

of separation 0.5–2 mm in the majority of devices), the resulting chains of

particles restrict the movement of the fluid, perpendicular to the direction of

flux, effectively increasing its viscosity. Importantly, mechanical properties

of the fluid in its “on” state are anisotropic. Thus in designing a magneto

rheological (or MR) device, it is crucial to ensure that the lines of flux are

perpendicular to the direction of the motion to be restricted.

Shear strength

Low shear strength has been the primary reason for limited range of

applications. In the absence of external pressure the maximum shear

strength is about 100 kPa. If the fluid is compressed in the magnetic field

direction and the compressive stress is 2 MPa, the shear strength is raised

to 1100 kPa. If the standard magnetic particles are replaced with elongated

magnetic particles, the shear strength is also improved.

APPLICATIONS OF MAGNETO RHEOLOGICAL FLUID

Mechanical Engineering

Magnetorheological dampers of various applications have been and

continue to be developed. These dampers are mainly used in heavy

industry with applications such as heavy motor damping, operator seat/cab

damping in construction vehicles, and more.

Military and Defense

The U.S. Army Research Office is currently funding research into using MR

fluid to enhance body armor. In 2003, researchers stated they were five to

ten years away from making the fluid bullet resistant. In addition, Humvees,

certain helicopters, and various other all-terrain vehicles employ dynamic

MR shock absorbers and/or dampers.

Optics

Magnetorheological Finishing, a magneto rheological fluid-based optical

polishing method, has proven to be highly precise. It was used in the

construction of the Hubble Space Telescope's corrective lens.

Automotive and Aerospace

If the shock absorbers of a vehicle's suspension are filled with MR fluid

instead of plain oil, and the whole device surrounded with an electromagnet,

the viscosity of the fluid (and hence the amount of damping provided by the

shock absorber) can be varied depending on driver preference or the weight

being carried by the vehicle - or it may be dynamically varied in order to

provide stability control.

Human Prosthesis

Magnetorheological dampers are utilized in semi-active human prosthetic

legs. Much like those used in military and commercial helicopters, a damper

in the prosthetic leg decreases the shock delivered to the patients leg when

jumping, for example. This results in an increased mobility and agility for the

patient.

LIMITATION

High density, due to presence of iron, makes them heavy. However,

operating volumes are small, so while this is a problem, it is not

insurmountable.

High-quality fluids are expensive.

Fluids are subject to thickening after prolonged use and need replacing.

Settling of ferro-particles can be a problem for some application.