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UNIT IV

MATERIAL CHARACTERIZATION

TESTING

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MATERIAL CHARACTERIZATION TESTING

Principles, Types, Advantages and Limitations, Applications of

  • Macroscopic and Microscopic observations
  • Optical and Electron microscopy (SEM and TEM)
  • Diffraction techniques
  • Spectroscopic Techniques
  • Electrical and Magnetic Techniques

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Macroscopic and Microscopic observations�

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Explain the principle of operation

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Electrical Characterization Techniques

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Hall Effect

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Spectroscopy Technique

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Spectroscopy

  • Exactly how light is absorbed and reflected, transmitted, or refracted changes the info and is determined by different techniques

sample

Reflected

spectroscopy

Transmittance

spectroscopy

Raman

Spectroscopy

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Optical Spectroscopy

  • Techniques concerned with how light reflects, absorbs, or transmits through minerals from near UV to mid-infrared (250 – 3000 nm wavelengths)
  • Dealing with energy which excited electrons from a standard to an excited state
  • It uses light source for analysis

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USES

  • Gives information about electronic structure of a system.
  • Key technique in semiconductor research.
  • To study the interaction of matter and light.
  • Widely used in industry and quality assurance

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Reflectance Spectroscopy

  • Can be optical or vibrational
  • Non-destructive form of analysis, used to ‘see’ some of the chemistry, bonding
  • Spectroscopy is particularly good at detecting water and OH groups in minerals (especially in IR)
  • Good at differentiating between different clays because it detects OH groups well

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Raman Spectroscopy

  • Another kind of spectroscopy which looks at a scattering effect and what that tells us about the chemistry, oxidation state, and relative proportions of different ions.

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  • It is a light scattering technique,whereby a molecule scatters incident light from a high intensity laser light source.

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Mossbauer Spectroscopy

  • Special effect, restricted to specific isotopes of certain elements which causes a very characteristic emission (after getting hit with a beam of gamma radiation) which is sensitive to the bonding environment of that isotope (only 57Co, 57Fe, 129I, 119Sn, 121Sb)
  • Generally used to study Fe – tells us about how Fe is bonded and it’s oxidation state.

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APPLICATIONS:

  • It is used to study the structure of atoms and molecules.
  • It is also helpful in finding the information of space objects in space.
  • It is used in environmental analysis for detecting dissolved oxygen content in water bodies.

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Magnetic technique

  • Magnetic method are potential methods for evaluation of surface manifestations such as microstructural degradation residual stresses

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Common Methods :

  • Magnetic Adhesive Force Methods:

It uses the distance dependency of the magnetic

attractive force between a ferromagnetic substrate

and a permanent magnet touching the surface of

Coating, which must be made from a non magnetic

material. Used to find holding power of magnet

  • Magnetically inductive method:

Another popular method is the magnetically inductive method which is based on measuring the magnetic flux that the passes through a non ferromagnetic coating into a ferromagnetic substrate.

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  • Magnetic Barkhausen emission method:
  • Magnetic flux perturbation and acoustic emissions are generated when an induced magnetic field is swept in a hysteresis loop in ferromagnetic materials.
  • This referred to as Magnetic Barkhausen Emission (MBE)
  • Surface characteristics such as hardness, residual stress and fatigue damage have been shown to influence barkhausen activity and MBE technique is routinely used for evaluation of these characteristics both on production line and in operating components.

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