APPLICATIONS OF XRD,DSC,DTA

Presented by

Dr. A. Suneetha

Dept. of Pharm. Analysis

Hindu College of Pharmacy

Unknown at first,but now these

have a vital role in

materials analysis

X-RAY DIFFRACTION

• When a beam of X-radiation is incident

upon a substance, interactions of radiation

with electrons of substance results in

scattering.

• X-rays scattered from a crystalline structure

constructively interferes and produces a

diffracted beam.

APPLICATIONS OF X-RAY

DIFFRACTION

1) Identification of crystals

2) Characterization of polymers

3) For particle size & shape analysis

e.g.Accurate determination of oxide nano particle

size & shape based on X-ray powder diffraction

4) State of anneal in metals

5) Differentiation of various phases

6) Miscellaneous

IDENTIFICATION OF CRYSTALS

• The analytical applications of XRD are numerous.

• The patterns obtained are characteristic of the particular compound crystals

• Eg., NaCl crystals(a) and KCl crystals(b) gives different diffraction patterns.(c) mixed

• By comparing with standard we can identify unknown crystalline compounds

CHARACTERISATION OF POLYMER

• Powder method can be used to

determine the degree of crystallinity

of the polymer.

• The non crystalline portion simply

scatters the X-ray beam to give

continuous background while the

crystalline portion causes diffraction

lines .

• The ratio of the area of the diffraction

peaks to the scattered radiation is

proportional to the ratio of

crystallinity and non crystalline

material,gives purity of the polymer.

STATE OF ANNEAL IN METALS

• A property of metals that can be determined by x-ray diffraction is the state of anneal.

• Well-annealed metals are in well-ordered crystal form and give sharp diffraction lines.

• If the metal is subjected to drilling ,hammering its crystals become broken and the x-ray pattern more diffuse.

Diffraction angle(2 )

Inte

nsi

ty→

90 1800

Crystal

90 1800

Inte

nsi

ty→ Liquid / Amorphous solid

90 1800

Diffraction angle (2) →

Inte

nsi

ty→

Mono atomic gas

SCHEMATIC DIFFERENCE BETWEEN

THE DIFFRACTION PATTERNS OF VARIOUS PHASES

Diffraction angle(2 )

MISCELLANEOUS

1)SOIL CLASSIFICATION

• Different types of soils such as clay,sandy etc., exhibit

different types and degrees of crystallinity.

• This gives information concerning soil structure.It also

tells us the mechanism of soil erosion.

2)Weathering and degradation of natural minerals.Based on

the results stable polymers have been developed.

3)Corrosion of products can be identified. So Metals and

alloys that are resistant to corrosion have been developed.

4)Identification of crystalline compounds that may originate in the body (eg.,gall stones)

5)Tooth enamel and dentine have been examined by XRD.This gives possible approaches to cure the tooth decay.

6)XRD is a major tool in elucidating the structure of RNA and DNA

OTHER APPLICATIONS USING X-RAYS

• Electron Microprobe

• Absorptiometry

• Radiography

ELECTRON MICROPROBE

• Nondestructive

• Determines composition

of tiny amounts of solids.

• Virtually all elements can

be analyzed.

An Electron Microprobe

ABSORPTIOMETRY

• Chemical analysis is possible for gases, lipids or

solids to measure densities ,porosities as well as

coating, plating and insulation thickness.

• Most often applied to patients in measurements

of bone densities, iodine in the thyroid gland,

liver diseases and other medical uses.

• Two types Single and Dual X-ray

Absorptiometry.

SINGLE X-RAY ABSORPTIOMETRY

• Single X-ray absorptiometry is used to measure

the bone mineral content.

• Used for diagnosis of osteoporosis.

• Provides reasonable accuracy and precision and

low radiation exposure.

DUAL X-RAY ABSORPTIOMETRY

• Used when single X-

ray absorptiometry is

not feasible.

• Used in areas with

variable soft tissue and

composition such as

the spine, hip or the

whole body.A dual x-ray absorptiometry

RADIOGRAPHY

• Involves use of registration on film, of the

differential absorption of a beam passing

through a specimen.

• Medical uses.

• Industrial uses.

• Nondestructive method.

THERMAL ANALYSIS

DTADSC

DSC APPLICATIONS

• Liquid crystals

• Oxidative stability

• Estimate the degree of crystallinity

• General chemical analysis

• Food science

• Polymers

LIQUID CRYSTALS

DSC is used in the study of liquid crystals.

As some forms of matter go from solid to liquid they

go through a third state, which displays properties of

both phases.

This anisotropic liquid is known as a liquid crystalline

or mesomorphous state.

Using DSC, it is possible to observe the small energy

changes that occur ,as matter transitions from a solid

to a liquid crystal and from a liquid crystal to an

isotropic liquid.

OXIDATIVE STABILITY

Using differential scanning calorimetry , stability to

oxidation can be studied.

First, the sample is brought to the desired test temperature

under an inert atmosphere, usually nitrogen.

Then, oxygen is added to the system. Any oxidation that

occurs is observed as a deviation in the baseline.

Such analysis can be used to determine the stability and optimum storage conditions for a material or compound

ESTIMATE THE DEGREE OF CRYSTALLIZATION

DSC is used to monitor the isothermal crystallization of polyethylene.

From the given themogramthe area under the exothermic peak can be used to estimate the degree of crystallinity that has occur at this temperature.

At 124˚c,20 min are required for maximum crystallinity.

GENERAL CHEMICAL ANALYSIS

• Freezing-point depression can be used as a purity analysis

tool when analyzed by DSC

This is possible because the temperature range over which a

mixture of compounds melts is dependent on their relative

amounts

• Consequently, less pure compounds will exhibit a broadened

melting peak that begins at lower temperature than a pure compound.

POLYMERS

• DSC is used widely for examining polymers to check their

composition, Melting points and glass transition temperatures

• This method can show up possible polymer degradation by

the lowering of the expected melting point.

APPLICATIONS OF DTA

Characterization of polymers Identification of polymers Study of phase transitions Studying the thermal behavior of simple inorganic

species Determination of melting and boiling pointsMiscellaneous

CHARACTERISATION OF POLYMERS

DTA is a powerful and

widely used tool for

studying and

characterizing polymers.

The given thermogram

illustrates the type of

physical and chemical

changes in polymeric

materials

In the given differential

thermogram of a physical

mixture of seven commercial

polymers. Each peak

corresponds to the melting

point of one of the

components.

As melting point is

characteristic to each

polymer .

Clearly DTA has the potential

use of identifying polymers.

An important use of DTA is for the generation of phase diagrams and the study of phase transitions.

An example is shown in figure which is a differential thermogram of sulphur in which the peak at 113°C corresponds to the solid-phase change from rhombic to monoclinic form where as the peak at 124°C corresponds to M.P of the element.

Liquid sulphur is known to exist in atleast in three forms and the peak at 179°C apparently involves these transitions while the peak at 446°C corresponds to the B.P of sulphur.

DIFFERENTIAL THERMOGRAM OF SULPHUR

B.P

LIQUID

SOLID

M.P

STUDYING THE THERMAL BEHAVIOUR OF A SIMPLE INORGANIC SPECIES

DTA thermogram is obtained by heating calicium oxalate mofonohydrate in a flowing stream of air.

The two minima indicate that the sample became cooler than the reference material as a consequence of the two endothermic reactions that are shown by the equations below the minima.

The single maxima indicates that oxidation of calcium oxalate to give calcium carbonate and carbon dioxide is exothermic.

DTA provides a simple and accurate way of determining the melting, boiling and decomposition points of organic compounds.

The given thermogram for benzoic acid at atmospheric pressure(A) and at 200psi(B).

The first peak corresponds to the melting point and the second peak corresponds to the boiling point of the benzoic acid.

MISCELLANEOUS

DTA is of great importance in the fields of ceramics,minerology

and metallurgy.

Composition of mixed clays can be quickly identified.

Characterization of limestone used in Portland cement .

Thermograms of typical explosives and propellants provide

useful information regarding the manufacture, storage and

applications of these high energy materials.

REFERENCES

PRINCIPLES OF INSTRUMENTAL ANALYSIS ---

SKOOG. HOLLER. NEIMAN

INSTRUMENTAL METHODS OF CHEMICAL ANALYSIS ---

B.K. SHARMA

INSTRUMENTAL METHODS OF CHEMICAL ANALYSIS ---

GURDEEP R. CHATWAL, SHAM K. ANAND

INSTRUMENTAL METHODS OF ANALYSIS ---

WILLARD, MERRITT, DEAN, SETTLE

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