Radiation Heat Transfer

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View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge.  Photoshoped pics  are developed.  Some pics and GIF from Google.   Videos from YouTube ( Engineering Sights ).
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Ceramics

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Ceramics

It is defined as, "when two metal react with each other to form a compound not solid solution".
  • Inorganic material (between metallic & non-metallic materials)
  • Firing or Burnt Stuff  ⇉  Desired properties of ceramics are achieved at very high temperature heat treatment process.
  • Ceramic structure  ⇉  more complex structure than metals and has at least 2 elements.
Characteristics of Ceramic Structure
  1. Exhibit combinations of ionic and covalent bond.
  2. Degree of ionic character depend on electronegativity.

Influence on Ceramic Structure

  1. Magnitude of charge on each component (crystal should be neutral).
  2. Relative sizes of cation and anions (cation radii < anion radii  i.e. rC/rA < 1).

Coordination Configuration 

It is defined as, "Maximum number of neighboring touching center atoms". 
  • Stable Ceramic structure  ⇉  form when anions surrounding a cation are in contact.
  • For a specific coordination number  ⇉  critical or min. rC/rA has a constant value.
Computation of Cation-Anion Ratio
  1. Consider Hard-Sphere model.
  2. Size of an ion depend upon coordination number.
  3. Charge on ion will influence its radius.

Types of Ceramic Structure

1. AX Type Crystal Structure

It is defined as, "materials in which there are equal number of cations and anions". Eg: NaCl (FCC), CsCl (BCC).

2. AmXp Type Ceramic Structure

It is defined as, "materials having different number of cations and anions (different charges on atoms)". Eg: CaF2 (FCC).

Defects in Ceramic Structure

  1. Frankel Defect   ⇉  Defect involve cation-vacancy or cation-interstitial pair.
  2. Schottky Defect  ⇉  Defect involve cation-anion pair vacancy.

Plastic Deformation in Ceramics

  1. Crystalline Ceramics  ⇉  Slip is difficult because of strong covalent bond. It is brittle in nature.
  2. Non-Crystalline Ceramics  ⇉  No regular structure. Material deform by viscous flow (breaking or reforming of atomic bonds).

Mechanical Properties of Ceramics

  1. A good structural material under compression.
  2. Brittle.
  3. Fracture strength  ⇉  enhanced by introducing compressive stresses at surface.
  4. Compressive strength  ⇉  10 times tensile strength.

Note: 

References:

  • Material from Class Lectures + Book named Materials Science and Engineering: An Introduction by Callister and Rethwick + my knowledge. 
  • Pics and GIF from Google Images.  
  • Videos from YouTube (Engineering Sights).

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