Nano Project Report Vasu -

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PREPARATION AND CHARACTERIZATION OF NALIZNO3NANOPOWDERS

A PROJECT REPORT

Submitted by

G. VASUDEVA RAO

(Reg. No: Y9NT20007)

In partial fulfillment for the award of the degree of

Master of Science in N NO TECHNOLOGY

Under the supervision of

Dr.G.GiridharAssistant Professor

Department of Nanotechnology

Acharya Nagarjuna University

DEPARTMENT OF NANOTECHNOLOGY

ACHARYA NAGARJUNA UNIVERSITY

NAGARJUNA NAGAR, GUNTUR522 510

JULY, 2013


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DECLARATION

I hereby declare that the work reported in this thesis is entirely original and was

carriedout by me independently in the Department of Nano- technology, Acharya Nagarjuna

University, under the supervision of Dr.G.Giridhar. I further declare that this thesis has not

been submitted for the award of any degree, diploma of any University or Institution.

Date: (G. Vasudeva Rao)

Department of Nano-Technology,

Acharya Nagarjuna University

A.P, INDIA.


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CERTIFICATE

This is to certify that this project report entitled Preparation and

characterization of NaLiZnO3 Nanopowders by Mr. GURUGUBELLI

VASUDEVA RAO (Y9NT20007), submitted in partial fulfillment of the

requirements for the degree of Master of Science in NANO TECHNOLOGY, Acharya

Nagarjuna University, Guntur, during the academic year 2012-13, is a bonafide record

of work carried out under my guidance and supervision.

(G.GIRIDHAR)


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ACKNOWLEDGEMENTS

The author is indebted to Dr.G.Giridhar for kindly suggesting the problem, for his

inspiring guidance and encouragement throughout the progress of this work, without whose

help this work could not have taken this shape.

He is highly grateful to Asst. Prof M..Rami Reddy, Head, Dept. of Nano-Technology,

Acharya Nagarjuna University Campus College for providing department facilities for

conducting research work.

The author also conveys his sincere thanks to Mr. M. Syamsundhar for sparing his

valuable time for useful discussions during the progress of the work.

He expresses his gratitude to Mr. Ch. Basavaiah, Department of Nanotechnology his

support in research work.

The author is thankful to Prof. N. Veeraiah, Head, Dept of Physics, A.N.U. Campus,

for his encouragement in spectral recordings and analysis.

The author expresses his heart felt gratitude to Dr. R.V.S.S.N. Ravi kumar, Asst.

Professor in Physics and Asst. Coordinator to TePP Outreach Centre, DSIR, Acharya

Nagarjuna University Campus, for kindly helping in recording optical absorption spectra and

also for his help in analyzing various spectra.

He expresses his gratitude to Dr. R. Ramesh Raju Asst. Professor, Dept. of Chemistry,

Campus College, A.N.U., for his help in collecting literature.


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He expresses his thanks to Dr. A. Srinivasa Rao, Associate Professor, Department of

Applied Physics, Delhi Technological University, New Delhi for kindly allowing him to take

the X-Ray Diffraction, Scanning Electron Microscope measurements of the samples.

I wish to express my sincere thanks to my friends Ch. Mohana Kumar, V.Sai

Bhargava, J. Jashu, Y. Dileep, P. Venkatesh, G. Avinash, D .Siva Rama Krishna who gave

support throughout my project.

G.VASUDEVA RAO

(Y9NT20007)


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CONTENTS

1. INTRODUCTION

2. EXPERIMENTAL METHODS

3. RESULTS AND DISCUSSIONS

CONCLUSION


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ABSTRACT:

NaLiZnO3 nano powders were synthesized by combustion methods by taking all

chemicals in stochiometric ratios. All chemicals used in the experiment Na 2Co3, Li2Co3, and

ZnO are procured from LOBA, India., with 99% purity of AR grade as the starting materials.

All the mixture is taken into a mortar and finely grinded for 1h. The resultant mixture is

would be taken into a crucible and heated in furnace at 220oC for 45 min to remove the

internal gases from the mixture. Then the mixture is ball milled for 3hr to get the uniform

nanopowder. After fine gridning by ball miller, the powder is characterized by X-ray

diffraction, Scanning Electron Microscope. The results showed that the particles are well

mixed and are in sizes of nearly 65nm estimated by famous Scherrers formula. Scanning

Microscopc Images are also supporting the same. Such type of well dispersed mixtures are

very much useful in anodic materials for battery applications.


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CHAPTER 1

INTRODUCTION

1.1 Nanoparticle

In nanotechnology, a particle is defined as a small object that behaves as a whole unit with

respect to its transport and properties. Particles are further classified according to

diameter..Coarse particles cover a range between 10,000 and 2,500 nanometers. Fine

particles are sized between 2,500 and 100 nanometers. Ultrafine particles or nanoparticles are

sized between 1 and 100 nanometers. The reason for this double name of the same object is

that, during the 1970-80's, when the first thorough fundamental studies with "nanoparticles"

were underway in the USA (byGranqvist and Buhrman) and Japan, (within an ERATO

Project)they were called "ultrafine particles" (UFP). However, during the 1990s before

the National Nanotechnology Initiative was launched in the USA, the new name,

"nanoparticle" had become fashionable (see, for example the same senior author's paper 20

years later addressing the same issue, lognormal distribution of sizes.). Nanoparticles may or

may not exhibit size-related properties that differ significantly from those observed in fine

particles or bulk materials.. Although the size of mostmoleculeswould fit into the above

outline, individual molecules are usually not referred to as nanoparticles.

Nanoclusters have at least one dimension between 1 and 10 nanometers and a narrow

size distribution. Nanopowdersare agglomerates of ultrafine particles, nanoparticles, or

nanoclusters. Nanometer-sized single crystals, or single-domain ultrafine particles, are often

referred to as nanocrystals. Nanoparticle research is currently an area of intense scientific

interest due to a wide variety of potential applications in biomedical, optical and electronic

fields.
http://en.wikipedia.org/wiki/Nanoparticle#cite_note-1http://en.wikipedia.org/wiki/Nanoparticle#cite_note-1http://en.wikipedia.org/wiki/Nanoparticle#cite_note-1http://en.wikipedia.org/wiki/Nanoparticle#cite_note-Kish-4http://en.wikipedia.org/wiki/Nanoparticle#cite_note-Kish-4http://en.wikipedia.org/wiki/Nanoparticle#cite_note-Kish-4http://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Nanoparticle#cite_note-Kish-4http://en.wikipedia.org/wiki/Nanoparticle#cite_note-1


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1.1 SODIUM CARBONATE

Sodium carbonate (also known as washing soda or soda ash), Na2CO3is a sodium

salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which

readily effloresces to form a white powder, the monohydrate. Sodium carbonate is

domestically well known for its everyday use as a water softener. It can be extracted from the

ashes of many plants. It is synthetically produced in large quantities from salt (sodium

chloride) and limestone by a method known as the solvay process.

Uses

The manufacture of glass is one of the most important uses of sodium carbonate.

Sodium carbonate acts as a flux for silica, lowering the melting point of the mixture to

something achievable without special materials. This "soda glass" is mildly water soluble, so

some calcium carbonate is added to the pre-melt mixture to make the glass produced

insoluble. This type of glass is known as soda lime glass: "soda" for the sodium carbonate

and "lime" for the calcium carbonate. Soda lime glass has been the most common form of

glass for centuries.

Sodium carbonate is also used as a relatively strong base in various settings. For

example, sodium carbonate is used as a pH regulator to maintain stable alkaline conditions

necessary for the action of the majority of photographic film developing agents. It is a

common additive in municipal pools used to neutralize the corrosive effects of chlorine and

raise pH. In cooking, it is sometimes used in place of sodium hydroxide for lyeing,

especially with German pretzels and lye rolls. These dishes are treated with a solution of an

alkaline substance to change the pH of the surface of the food and improve browning.

In taxidermy, sodium carbonate added to boiling water will remove flesh from the skull or

bones of trophies to create the "European skull mount" or for educational display in

biological and historical studies.


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In chemistry, it is often used as an electrolyte. This is because electrolytes are usually salt-

based, and sodium carbonate acts as a very good conductor in the process of electrolysis. In

addition, unlike chloride ions, which form chlorine gas, carbonate ions are not corrosive to

the anodes. It is also used as a primary standard for acid-base titrations because it is solid and

air-stable, making it easy to weigh accurately.

1.2 Li thium carbonate

Lithium carbonate is an inorganic compound, the lithium salt of carbonate with

the formula Li2CO3. This white salt is widely used in the processing of metal oxides and has

received attention for the treatment for manic and bipolar disorder. It exists as the rare

mineral zzabuyelite.

Properties

Like related lithium salts, Li2CO3is an ionic compound. Its solubility in water is low

relative to other lithium salts. The isolation of lithium from aqueous extracts of

lithium ores capitalizes on this poor solubility. Its apparent solubility increases tenfold under

a mild pressure of carbon dioxide; this effect is due to the formation of the metastable

bicarbonate:

Li2CO3+ CO2+ H2O 2 LiHCO3

The extraction of lithium carbonate at high pressures of CO2 and its precipitation

upon depressuring is the basis of the Quebec process. Approximately 30,000 tons were

produced in 1989. Lithium carbonates, and other carbonates of Group 1, do not decompose

readily, unlike other carbonates. Li2CO3decomposes at temperatures >1300 C.

Uses

Lithium carbonate is an important industrial chemical. It forms low-

melting fluxes with silica and other materials. Glasses derived from lithium carbonate are

useful in ovenware. Lithium carbonate is a common ingredient in both low-fire and high-fire


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ceramic glaze. Its alkaline properties are conducive to changing the state of metal oxide

colorants in glaze particularly red iron oxide (Fe2O3). Cement sets more rapidly when

prepared with lithium carbonate, and is useful for tile adhesives. When added to aluminum

trifluoride, it forms LiF which gives a superiorelectrolyte for the processing ofaluminum.

Lithium carbonate is an active material of carbon dioxide sensors. It is also used in the

manufacture of mostlithium-ion battery cathodes, which are made oflithium cobalt oxide.

1.3 Zinc oxide

Zinc oxide is aninorganic compound with theformulaZnO.ZnO is a white powder

that is insoluble in water, which is widely used as an additive in numerous materials and

products including plastics, ceramics, glass, cement, lubricants, paints, ointments, adhesives,

sealants, pigments, foods (source of Znnutrient), batteries, ferrites, fire retardants, and first

aid tapes. It occurs naturally as the mineralzincitebut most zinc oxide is produced

synthetically.

Inmaterials science, ZnO is a wide-bandgap semiconductor of theII-VI

semiconductor group (sinceoxygen was classed as an element of VIA group (the 6th main

group, now referred to as 16th) of theperiodic table andzinc,a transition metal, as a member

of the IIB (2nd B), now 12th, group). The nativedoping of the semiconductor (causes are as

yet unknown) is n-type. This semiconductor has several favorable properties, including good

transparency, highelectron mobility, widebandgap, and strong room-

temperatureluminescence. Those properties are used in emerging applications for

transparentelectrodes inliquid crystal displays,in energy-saving or heat-protecting windows,

and in electronics as thin-filmtransistors andlight-emitting diodes.

Uses

The applications of zinc oxide powder are numerous, and the principal ones are

summarized below. Most applications exploit the reactivity of the oxide as a precursor to
http://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Carbon_dioxide_sensorhttp://en.wikipedia.org/wiki/Lithium-ion_batteryhttp://en.wikipedia.org/wiki/Lithium_cobalt_oxidehttp://en.wikipedia.org/wiki/Inorganic_compoundhttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Nutrienthttp://en.wikipedia.org/wiki/Zincitehttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/List_of_semiconductor_materials#Group_II-VIhttp://en.wikipedia.org/wiki/List_of_semiconductor_materials#Group_II-VIhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Periodic_tablehttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/Electron_mobilityhttp://en.wikipedia.org/wiki/Bandgaphttp://en.wikipedia.org/wiki/Luminescencehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Liquid_crystal_displayhttp://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Liquid_crystal_displayhttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Luminescencehttp://en.wikipedia.org/wiki/Bandgaphttp://en.wikipedia.org/wiki/Electron_mobilityhttp://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Periodic_tablehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/List_of_semiconductor_materials#Group_II-VIhttp://en.wikipedia.org/wiki/List_of_semiconductor_materials#Group_II-VIhttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Zincitehttp://en.wikipedia.org/wiki/Nutrienthttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Zinchttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Inorganic_compoundhttp://en.wikipedia.org/wiki/Lithium_cobalt_oxidehttp://en.wikipedia.org/wiki/Lithium-ion_batteryhttp://en.wikipedia.org/wiki/Carbon_dioxide_sensorhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Electrolyte


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other zinc compounds. For material science applications, zinc oxide has highrefractive index,

high thermal conductivity, binding, antibacterial and UV-protection properties. Consequently,

it is added into materials and products including plastics, ceramics, glass, cement, rubber,

lubricants, paints, ointments, adhesive, sealants, pigments, foods, batteries, ferrites, fire

retardants, etc.

1.4 Nano-powders:-

Innanotechnology,a particle is defined as a small object that behaves as a whole unit

in terms of its transport and properties. It is further classified according to size: In terms of

diameter, fine particles cover a range between 100 and 2500 nanometers, while ultrafine

particles, on the other hand, are sized between 1 and 100 nanometers. Similarly to ultrafine

particles, nanoparticles are sized between 1 and 100 nanometers, though the size limitation

can be restricted to two dimensions. Nanoparticles may or may not exhibit size-related

intensive properties that differ significantly from those observed in fine particles or bulk

materials.

Nano clusters have at least one dimension between 1 and 10 nanometers and a narrow

size distribution. Nano powders are agglomerates of ultrafine particles, nanoparticles, or

Nano clusters. Nanometer sized single crystals, or single-domain ultrafine particles, are often

referred to as Nano crystals.

The contribution Nano powders bring to the products is mainly that it ensures more

resistance to heat, a higher capacity. Moreover, it upgrades the mechanical properties of the

products in which it is incorporated
http://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Nanotechnologyhttp://en.wikipedia.org/wiki/Nanotechnologyhttp://en.wikipedia.org/wiki/Refractive_index


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CHAPTER 2

EXPERIMENTAL TECHNIQUES

2.1 SYNTHESIS OF THE MATERIAL

As a part of the experiment, Na2Co3, Li2Co3, and ZnO are used as starting materials.

All these are taken in equal percentages of stochiometric ratios. Then a mortar is cleaned and

wiped dry and all these chemicals are taken into the mortar and finely grinded for 10min.

then this compound is collected into a crucible and kept in furnace at 220oC for 1h to dry the

sample. A white powder is obtained which is allowed to cool for a while. Then this powder is

sent for ball milling and done upto 4hr with 10mm ZrO2balls. Then the as prepared sample is

sent to different characterization techniques and conformed the sizes of the particles in the as

prepared samples are nearly 150-200nm in size.

2.2 BALL MILLING

Technological and scientific challenges coupled with environmental considerations

have attracted a search for robust, green and energy-efficient synthesis and processing routes

for advanced functional nanomaterials.

It is a ball milling process where a powder mixture placed in the ball mill is subjected

to high-energy collision from the balls. This process was developed by Benjamin and his

coworkers at the International Nickel Company in the late of 1960. It was found that this

method, termed mechanical alloying, could successfully produce fine, uniform dispersions of

oxide particles (Al2O3, Y2O3, ThO2) in nickel-base superalloys that could not be made by

more conventional powder metallurgy methods. Their innovation has changed the traditional

method in which production of materials is carried out by high temperature synthesis. Besides

materials synthesis, high-energy ball milling is a way of modifying the conditions in which


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chemical reactions usually take place either by changing the reactivity of as-milled solids

(mechanical activation increasing reaction rates, lowering reaction temperature of the

ground powders)or by inducing chemical reactions during milling (mechanochemistry). It

is, furthermore, a way of inducing phase transformations in starting powders whose particles

have all the same chemical composition: amorphization or polymorphic transformations of

compounds, disordering of ordered alloys, etc.

The alloying process can be carried out using different apparatus, namely, attritor,

planetary mill or a horizontal ball mill. However, the principles of these operations are same

for all the techniques.

Planetary ball mill is a most frequently used system for mechanical alloying since

only a very small amount of powder is required. Therefore, the system is particularly suitable

for research purpose in the laboratory. The ball mill system consists of one turn disc (turn

table) and two or four bowls. The turn disc rotates in one direction while the bowls rotate in

the opposite direction. The centrifugal forces, created by the rotation of the bowl around its

own axis together with the rotation of the turn disc, are applied to the powder mixture and

milling balls in the bowl. The powder mixture is fractured and cold welded under high energy

impact.

The figure below shows the motions of the balls and the powder. Since the rotation

directions of the bowl and turn disc are opposite, the centrifugal forces are alternately

synchronized. Thus friction resulted from the hardened milling balls and the powder mixture

being ground alternately rolling on the inner wall of the bowl and striking the opposite wall.

The impact energy of the milling balls in the normal direction attains a value of up to 40

times higher than that due to gravitational acceleration. Hence, the planetary ball mill can be

used for high-speed milling.


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Schematic view of motion of the ball and powder mixture.

During the high-energy ball milling process, the powder particles are subjected to

high energetic impact. Microstructurally, the mechanical alloying process can be divided into

four stages: (a) initial stage, (b) intermediate stage, (c) final stage, and (d) completion stage.

(a) At the initial stage of ball milling, the powder particles are flattened by the compressive

forces due to the collision of the balls. Micro-forging leads to changes in the shapes of

individual particles, or cluster of particles being impacted repeatedly by the milling balls with

high kinetic energy. However, such deformation of the powders shows no net change in

mass.

(b) At the intermediate stage of the mechanical alloying process, significant changes occur in

comparison with those in the initial stage. Cold welding is now significant. The intimate

mixture of the powder constituents decreases the diffusion distance to the micrometer range.

Fracturing and cold welding are the dominant milling processes at this stage. Although some


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dissolution may take place, the chemical composition of the alloyed powder is still not

homogeneous.

(c) At the final stage of the mechanical alloying process, considerable refinement and

reduction in particle size is evident. The microstructure of the particle also appears to be more

homogenous in microscopic scale than those at the initial and intermediate stages. True alloys

may have already been formed.

(d) At the completion stage of the mechanical alloying process, the powder particles possess

an extremely deformed meta-stable structure. At this stage, the lamellae are no longer

resolvable by optical microscopy. Further mechanical alloying beyond this stage cannot

physically improve the dispersed distribution. Real alloy with composition similar to the

starting constituents is thus formed.

Planetary ball mills are smaller than common ball mills and mainly used in

laboratories for grinding sample material down to very small sizes. A planetary ball mill

consists of at least one grinding jar which is arranged eccentrically on a so-called sun wheel.

The direction of movement of the sun wheel is opposite to that of the grinding jars (ratio: 1:-2

or 1:-1 or else). The grinding balls in the grinding jars are subjected to superimposed

rotational movements, the so-called Coriolis forces. The difference in speeds between the

balls and grinding jars produces an interaction between frictional and impact forces, which

releases high dynamic energies. The interplay between these forces produces the high and

very effective degree of size reduction of the planetary ball mill.

Briefly, Major Steps involved in ball milling method are:

1. As the name suggests, the ball milling method consists of balls and a mill chamber.

Therefore over all a ball mill contains a stainless steel container and many small iron,


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hardened steel, silicon carbide, or tungsten carbide balls are made to rotate inside a mill

(drum).

2. The powder of a material is taken inside the steel container. This powder will be made into

nanosize using the ball milling technique. A magnet is placed outside the container to provide

the pulling force to the material and this magnetic force increases the milling energy when

milling container or chamber rotates the metal balls. The ball to material mass ratio is

normally maintained at 2 ratio1.

3. These silicon carbide balls provide very large amount of energy to the material powder and

the powder then get crushed. This process of ball milling is done approximately 100 to 150

hrs to get uniform fine powder.

4. Ball milling is a mechanical process and thus all the structural and chemical changes are

produced by mechanical energy.

Advantages of ball milling process:

1. Nanopowders of 2 to 20 nm in size can be produced. The size of nanopowder also depends

upon the speed of the rotation of the balls.

2. It is an inexpensive and easy process.

Disadvantages;

1. As the process is not so sophisticated, therefore the shape of the nanomaterial is irregular.

2. There may be contaminants inserted from ball and milling additives.

3. This method produces crystal defects.


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RETSCH - Planetary Ball Mill PM 400 Model is used for the present synthesis.

10mm zirconium balls are used in 50ml steel jar and milled the sample for 4h continuously.

2.3 X-RAY DIFFRACTION:

W.L.Bragg showed that the X-Rays reflected from lattice plane and the effect

associated with it could be derived by the equation n=2dsin (Braggs Law) in which n is

an integer, the wavelength of X-Rays, d the inter-planar spacing, the angle of incidence

of X-Ray beam on the lattice plane.

In a crystalline sample, the tiny crystals are oriented at random, if an X-Ray beam

strikes such a sample, many planes will be oriented that the Braggs law is simultaneously

satisfied and an X-Ray diffraction pattern is obtained. To be certain that all possible planes

are exposed to the X-ray beam. The specimen is usually rotated by an angle on its own

axis during exposure. Most of the X-ray beam will pass directly through the samples and the

diffracted beams are collected by a detector (scintillation counter) which is rotated by 2,

the output of which is processed and then fed into an automatic recorder. The result is a chart,

which gives a record of counts per second (proportional to diffracted beam intensity) versus

diffraction angle 2.

Glassy or amorphous materials do not have a long range atomic order, i.e., atoms are

arranged randomly. Therefore, a diffraction pattern containing sharp peaks is not expected as

observed in crystalline materials. All glasses investigated were subjected to the X-Ray

diffraction measurements to ascertain whether the samples were really amorphous or not.

The amorphous state of the prepared glasses was checked by X-Ray diffraction

spectra recorded on PHILIPS XPERT PRO X-RAY diffraction system at Hyderabad. The

Cu K radiation (=1.5418A) was used/ the X-Ray machine was operated with 60


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2.4 SCANNING ELECTRON MICROSCOPE (SEM):

The scanning electron microscope (SEM) uses o focused beam of high-energy

electrons to generate a variety of signals at the surface of solid specimens. The signals that

derive from electron sample interactions reveal information about the sample including

external morphology (texture), chemical composition and crystalline structure and orientation

of materials making up the sample. In most applications, data are collected over a selected

area of surface of the sample, and a 2-dimensional image is generated that displays spatial

variations in these properties. Areas ranging from approximately 1cm to 5 micron in width

can be imaged in a scanning mode using conventional SEM techniques (magnification

ranging from 20X to approximately 30,000X, spatial resolution of 50 to 100 nm). The SEM is

also capable of performing analyses of selected point locations on the sample; this approach

is especially useful in qualitative or semi-qualitative determining chemical compositions

(using EDS), crystalline structure, and crystal orientations (using EBDS), the design and

function of the SEM is very similar to the EPMA, and considerable overlap in capabilities

exists between the two instruments.

Fundamental Principles of Scanning Electron Microscopy (SEM)

Accelerated electrons in a SEM carry significant amount of kinetic energy, and the

energy is dissipated as a variety of signals produced by electron-sample interactions when the

incident electrons are decelerated in the solid sample. These signals include secondary

electrons (that produce SEM images), backscattered electrons (BSE), diffracted backscattered

electrons (EBSD, that are used to determine crystal structures and orientations of minerals),

photons (characteristic X-Rays that are used for elemental analysis and continuum X-Rays),

visible light (cathodoluminescence-CL), and heat. Secondary electrons and backscattered

electrons are commonly used for imaging sample: secondary electrons are most valuable for

showing morphology and topography on samples and backscattered electrons are most


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valuable or illustrating contrasts in composition in multiphase samples (i.e. for rapid phase

discrimination). X-ray generation is produced by inelastic collisions of the incident electrons

with electrons in discrete orbitals (shells) of atoms in the sample. As the excited electrons

return to lower energy states, they yield X-rays that are of fixed wavelength (that is related to

the difference in energy levels of electrons in different shells for a given element). Thus,

characteristic X-rays are produced for each element in mineral that is excited by the

electron beam. SEM analysis is considered to be non-destructive; that is, X-rays generated

by electron interactions do not lead to volume loss of the sample, so it is possible to analyze

the same material repeatedly.

2.5 RAMAN SPECTROSCOPY

Basic Features of Raman spectroscopy are:

A vibrational spectroscopy

- IR and Raman are the most common vibrational spectroscopies for assessing

molecular motion and fingerprinting species

- Based on inelastic scattering of a monochromatic excitation source

- Routine energy range: 200 - 4000 cm1

Complementary selection rules to IR spectroscopy

- Selection rules dictate which molecular vibrations are probed

- Some vibrational modes are both IR and Raman active

Great for many real-world samples

- Minimal sample preparation (gas, liquid, solid)

- Compatible with wet samples and normal ambient

- Achilles Heal is sample fluorescence

Basically, Vibrational spectroscopy includes several different techniques, the most

important of which are mid-infrared (IR), near-IR, and Raman spectroscopy. Both mid-IR


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and Raman spectroscopy provide characteristic fundamental vibrations that are employed for

the elucidation of molecular structure and are the topic of this chapter. Near-IR spectroscopy

measures the broad overtone and combination bands of some of the fundamental vibrations

(only the higher frequency modes) and is an excellent technique for rapid, accurate

quantization. All three techniques have various advantages and disadvantages with respect to

instrumentation, sample handling, and applications. Vibrational spectroscopy is used to study

a very wide range of sample types and can be carried out from a simple identification test to

an in-depth, full spectrum, qualitative and quantitative analysis. Samples may be examined

either in bulk or in microscopic amounts over a wide range of temperatures and physical

states (e.g., gases, liquids, latexes, powders, films, fibers, or as a surface or embedded layer).

Vibrational spectroscopy has a very broad range of applications and provides solutions to a

host of important and challenging analytical problems. Raman and mid-IR spectroscopy are

complementary techniques and usually both are required to completely measure the

vibrational modes of a molecule. Although some vibrations may be active in both Raman and

IR, these two forms of spectroscopy arise from different processes and different selection

rules. In general, Raman spectroscopy is best at symmetric vibrations of non-polar groups

while IR spectroscopy is best at the asymmetric vibrations of polar groups. Table 1.1 briefly

summarizes some of the differences between the techniques.

Infrared and Raman spectroscopy involve the study of the interaction of radiation with

molecular vibrations but differs in the manner in which photon energy is transferred to the

molecule by changing its vibrational state. IR spectroscopy measures transitions between

molecular vibrational energy levels as a result of the absorption of mid-IR radiation. This

interaction between light and matter is a resonance condition involving the electric

dipolemediated transition between vibrational energy levels. Raman spectroscopy is a two-

photon inelastic light-scattering event. Here, the incident photon is of much greater energy


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than the vibrational quantum energy, and loses part of its energy to the molecular vibration

with the remaining energy scattered as a photon with reduced frequency. In the case of

Raman spectroscopy, the interaction between light and matter is an off-resonance condition

involving the Raman polarizability of the molecule.

The IR and Raman vibrational bands are characterized by their frequency (energy),

intensity (polar character or polarizability), and band shape (environment of bonds). Since the

vibrational energy levels are unique to each molecule, the IR and Raman spectrum provide a

fingerprint of a particular molecule. The frequencies of these molecular vibrations depend

on the masses of the atoms, their geometric arrangement, and the strength of their chemical

bonds. The spectra provide information on molecular structure, dynamics, and environment.

Two different approaches are used for the interpretation of vibrational spectroscopy and

elucidation of molecular structure.

1) Use of group theory with mathematical calculations of the forms and frequencies of

the molecular vibrations.

2) Use of empirical characteristic frequencies for chemical functional groups.

Many empirical group frequencies have been explained and refined using the

mathematical theoretical approach (which also increases reliability).

In general, many identification problems are solved using the empirical approach.

Certain functional groups show characteristic vibrations in which only the atoms in that

particular group are displaced. Since these vibrations are mechanically independent from the

rest of the molecule, these group vibrations will have a characteristic frequency, which

remains relatively unchanged regardless of what molecule the group is in. Typically, group

frequency analysis is used to reveal the presence and absence of various functional groups in

the molecule, thereby helping to elucidate the molecular structure.


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The basic function of a Raman system is

Deliver the laser to the sampling point

With low power loss through the system

Illuminating an area consistent with sampling dimensions

Provide a selection/choice of laser wavelengths

Collect the Raman scatter

High aperture

High efficiency optics

High level of rejection of the scattered laser light

Disperse the scattered light

Short wavelength excitation requires high dispersion spectrometers

Detect the scattered light

Graphically / mathematically present the spectral data


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Laser wavelength selection concerns for classical Raman

As the laser wavelength gets shorter

- Raman scattering efficiency increases

-The risk of fluorescence increases (except deep UV)

-The risk of sample damage / heating increases

-The cost of the spectrometer increases

Basic Lasers for excitation for different applications

1) UV lasers 244 nm- biological, catalysts (Resonance Raman) 325 nm-

wide bandgap semiconductors

2) visible lasers 488 nm & 514 nm- semiconductor, catalysts,

biological, polymers, minerals & general purpose

633 nm- corrosion & general purpose

3) NIR lasers 785 nm - polymers, biological & general purpose

830 nm- biological


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Dispersive instrument basics


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CHAPTER 3

RESULTS AND DI SCUSSIONS

3.1 X-ray diffraction analysis

The crystal structures of the samples were examined using an XRD system at room

temperature with CuK1 radiation operating at 40 kV and 100 mA. Figure shows XRD

patterns of undoped Na2Co3Li2Co3 ZnO nanopowders . The (h k l) values corresponding to

most prominent peaks and d-values were evaluated and shown in XRD patterns. The particle

size d was estimated by using the Scherrer equation:

d = 0.9/ cos (1)

Where is the wavelength of the CuK1 radiation, is the full-width at half-maximum

(FWHM) and is the diffraction angle. The average particle size of the Na2Co3Li2Co3

ZnO was estimated to be 65 nm.


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From the above figure (hkl) values are denoted in a, b, c, and their values are shown

below in brief

a = 210, b = 211, c = 012, d = 022, e = 302, f = 330, g = 032, h = 132, I = 510, j = 412,

k = 023, l = 332, m = 142 , n = 403, o = 541

3.2 Scanning Electron Microscopy

Below figure shows the SEM image of the NaLiZnO3 nanopowder. Particle size

obtained by SEM measurement was ~ 150 nm. This was in good agreement with that

estimated by Scherrer formula and identified that the compound is going to agglomerate

rapidly .


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3.3 Raman Spectroscopy

Raman spectra of the as prepared sample is shown in figure. Only one vibrational

mode is observed corresponding to Na.

200 400 600 800 1000 1200 1400 1600 1800 2000

0

1000

2000

In

tens

ity

Raman Shift (cm-1)

Na


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Conclusions

LiNaZnO3 nano powder is successfully prepared by using the Ball Miller with

Zirconium Balls of size 10mm by grinding the powder for four hours and the collected

powder is characterized by XRD, Scanning Electron Microscope and Raman spectroscopy.

By the Scherrer formula confirmed the nano sizes. (hkl) values are calculated and assigned by

using trial and error method.

The powder is conformed that is in the ranges of nano. The present sample is useful

for battery applications

Nano Project Report Vasu -

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