Materials Characterization Lecture Notes PDF

Materials Characterization Jayanta Das http://www.facweb.iitkgp.ernet.in/~jdas/ Topics to be discussed: - Optical Microscopy (OM) - Scanning Electron Microscopy (SEM) - Atomic Absorption Spectroscopy (AAS) - Nanoindentation (NI) - Thermal analysis (TA) - Scaning Probe Microscopy (...

Materials Characterization Jayanta Das http://www.facweb.iitkgp.ernet.in/~jdas/ Topics to be discussed: - Optical Microscopy (OM) - Scanning Electron Microscopy (SEM) - Atomic Absorption Spectroscopy (AAS) - Nanoindentation (NI) - Thermal analysis (TA) - Scaning Probe Microscopy (SPM) - Atomic Force Microscopy (AFM) - Scanning Tunnelling Microscopy (STM) - Surface Analysis by Spectroscopic Techniques - X-Ray Photoelectron Spectroscopy (XPS) - Auger Electron Spectroscopy (AES) Thermal analysis i. Differential Scanning Calorimetry ii. Differential Thermal Analysis iii. Thermogravimetric Analysis iv. Diletometry Differential Scanning Calorimetry Differential Thermal analysis Thermal analysis DSC/DTA Thermal analysis Differential Thermal analysis events Endothermic delta H + delta T - Exothermic delta H - delta T + R (Tr) R (Tr) Furnace (Tf) Furnace (Tf) sample (Ts) sample (Ts) here delta T has a nite value when fi  Thermal analysis Differential Thermal analysis DTA instrument delta T - Ts lags behind Tr during melting  Apparatus The key features of a diÆerential thermal analysis kit are as follows (Fig. 1): Thermal analysis Differential Thermal analysis 1. Sample holder comprising thermocouples, sample containers and a ceramic or m lic block. Characteristics of the reference 2. Furnace. material 3. Temperature programmer. (i) It should not undergo any phase transformation/ 4. Recording system. thermal event over the operating temperature range The last three items come in a variety of commercially available forms and are not be d (ii) It should not react with theTheholder in any detail. and thermocouple essential requirements of the furnace are that it should provide and su±ciently large hot–zone and must be able to respond rapidly to commands f (iii) thermal conductivity and temperature the programmer. heat capacity A temperature programmer isof the essential in order to obtain c heating rates. The recording system must have a low inertia to faithfully reproduce va reference should be in thesimilar to that of the sample experimental set–up. Example: Al2O3, SiC for inorganic silicone oil, octyl-phthalate for organic/polymers  Thermal analysis Differential Scanning Calorimetry Power compensated DSC The energy difference in the independent supplies to the sample and reference is recorded against the programme temperature Thermal analysis Principles of DTA/DSC  Thermal analysis Principles of DTA/DSC DTA heat ux DSC Power compensated DSC fl and reference are in good thermal contact. The temperature diÆerence is recorded and related to enthalpy change inin the the sample sample using causecalibration a diÆerenceexperiments. in its temperature relative to the reference; the resulting heat flow is small compared with that in diÆerential thermal analysis (DTA) because the sample and reference are in good thermal contact. The temperature diÆerence is recorded and related Thermal analysis to enthalpy change in the sample using calibration experiments. heat ux DSC Power compensated DSC - S & R enclosed in a single furnace - independent, separate and identical - small heat ow in the furnace (less than furnace DTA) Fig. 1: (a) Heat flux DSC; (b) power–compensation DSC- power input of the two furnace are varied - S & R are in good thermal contact to keep delta T =0 Heat–flux DSC Fig. 1: (a) Heat flux DSC; (b) power–compensation DSC This section is based largely on a description of the Dupont DSC system by Baxter and Greer. Effect The system is a subtle of following modification of DTA, parameters onfact diÆering only by the resolution of DSC that the sample and Heat–flux DSC (i) heating rate, (ii) Specimen size This section is based largely on a description of the Dupont DSC system by Baxter and Greer. fl fl Thermal analysis Differential Scanning Calorimetry Thermal analysis DSC: Application What we can do? - measurement of heat capacity (Cp) - measurement of thermal conductivity - determination of phase diagram Thermal analysis Differential Scanning Calorimetry Thermal analysis DSC: Application Thermo-gravimetry Thermal analysis Thermogravimetry Thermal analysis Thermogravimetry Thermal analysis Thermogravimetry: application Dilatometry thermo-dilatometry (TD) thermo-mechanical analysis (TMA)  Thermal analysis thermo-dilatometry (TD) - Linear variable displacement transformer (LVDT) - Laser - optoelectronic transducer (10-2 um for 1/10 time of LVDT)  Thermal analysis thermo-mechanical analysis (TMA) - sensitivity 4 nm - over all +- 5 mm - - penetration; extension; exure; torsion fl