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.
Intensity Intensity Intensity SCHEMATIC DIFFERENCE BETWEEN THE DIFFRACTION PATTERNS OF VARIOUS PHASES Crystal Mono atomic gas 0 90 180 Diffraction angle(2 ) Liquid / Amorphous solid 0 90 180 Diffraction angle (2 ) 0 90 180 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 A 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.
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 DSC DTA
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 themogram the 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 points Miscellaneous
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. SOLID M.P LIQUID B.P 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
STUDYING THE THERMAL BEHAVIOUR OF A SIMPLE INORGANIC SPECIES DTA thermogram is obtained by heating calicium oxalate mof onohydrate 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 www.xraydiffrac.com/xrd.htm