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Diamond & Graphite

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This ppt is about diamond and graphite and their properties.

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Diamond & Graphite

  1. 1. Diamond & Graphite Mr. Rahul Dev M.Sc [Polymer Science] 1
  2. 2. Diamond • Introduction • In mineralogy Diamond is a metastable allotrope of carbon. • Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at standard conditions. • Most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers (87 to 118 mi) in the Earth's mantle. 2
  3. 3. Natural history • The formation of natural diamond requires very specific conditions exposure of carbon-bearing materials to high pressure, ranging approximately between 45 and 60 kilobars(4.5 and 6 GPa), but at a comparatively low temperature range between approximately 900 and 1,300 °C (1,650 and 2,370 °F). These conditions are met in two places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike. 3
  4. 4. Structure Of Diamond • In diamond, the carbon atoms are arranged tetrahedrally (sp3 hybridisation of C): each C atom is linked to its neighbours by four single covalent bonds. This leads to a three- dimensional network of covalent bonds. 4
  5. 5. Material Properties Formula Mass: 12.01 gmol-1 Density: 3.5-3.53 g/m3 Colours: Typically Yellow, Brown or Gray to colourless. Less often blue, green, black, translucent white, pink, violet, orange, purple and red. Crystal Structure: Octahedral 5
  6. 6. Properties • Mechanical Hardness ~98 Gpa • Compressive Strength > 110 Gpa • Highest Bulk Modulus- 1.2*1012 N/M2 • Lowest Compressibility- 8.3*10-13 M2/N • Highest Thermal Conductivity- 2*103 W/M/K • Optically Transparent From Deep UV To Far IR • Good Electrical Insulator- R~1016 Ω • Highest Melting Point- 3820K • Resistant To Corrosion By Acid Or Base • Negative Electron Affinity 6
  7. 7. Properties • Extreme Hardness • High Thermal Conductivity • Wide Bandgap And High Optical Dispersion • Resistant To Scratching • Excellent Electrical Insulators • Diamond Are Naturaly Liophilic And Hydrophobic • Diamonds Are Chemically Stable 7
  8. 8. Colour • Diamond has a wide bandgap of 5.5 eV corresponding to the deep ultraviolet wavelength of 225 nanometers. This means pure diamond should transmit visible light and appear as a clear colourless crystal. Colours in diamond originate from lattice defects and impurities. The diamond crystal lattice is exceptionally strong and only atoms of nitrogen, boron and hydrogen can be introduced into diamond during the growth at significant concentrations 8
  9. 9. Colour • Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the yellow and brown color in diamonds. Boron is responsible for the blue color. 9
  10. 10. Hope Diamond, 45.52 carats (9.104 g), dark grayish-blue Indian Kohinoor 105.602 carats (21.1204 g) Finest White 10
  11. 11. Synthetic Diamonds • Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth • The majority of commercially available synthetic diamonds are yellow and are produced by so-called High Pressure High Temperature (HPHT) processes • Another popular method of growing synthetic diamond is chemical vapour deposition (CVD). The growth occurs under low pressure (below atmospheric pressure). 11
  12. 12. Application • Optical Application • Glass Cutter • Jewelleries • Diamond guide • Speaker Domes • Windows • Antidote for Poison/Disease • Heat Sinks • Engraving • Diamond Microdermabrasion 12
  13. 13. Applications • Diamond Microdermabrasion offers intensive skin exfoliating. This treatment is non-invasive and uses a diamond encrusted tip to polish the skins surface without harsh chemicals or messy crystals. 13
  14. 14. • It is used in protective windows for space probes as it can keep out harmful radiations. • Because of its extra-ordinary sensitivity to heat rays, it is used in high precision thermometers. • Sharp-edged diamonds are used by eye surgeons remove cataract from eyes high precision. • It is used in dies for the manufacture of tungsten filaments for electric light bulbs. 14
  15. 15. Alternatives to Diamond • Boron Nitride o It’s hardness of 9.8 on the Mohs scale makes it very useful for cutting tools and abrasives o BN is isoelectronic with diamond, so it shares many of its properties • Tungsten Carbide o Can substitute for diamond in many places o Actually used in HPHT synthesis • But diamond is still the best 15
  16. 16. Graphite • Introduction • The mineral graphite is an allotrope of carbon. • It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek "to draw/write", for its use in pencils, where it is commonly called lead (not to be confused with the metallic element lead). • Graphite is the most stable form of carbon under standard conditions. Therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds. 16
  17. 17. History • Graphite was used by the 4th millennium B.C. Marita culture to create a ceramic paint to decorate pottery during the Neolithic Age in southeastern Europe. • Historically, graphite was called black lead or plumbago 17
  18. 18. Identification • Chemical Formula : C • Colour: Silver Grey To Black • Streak: Black • Crystal Structure: Hexagonal 3D Crystal Atlas • Crystal Forms and Aggregates : Crystals consist of thin hexagonal plates or distorted clusters of flaky plates on a matrix. Large thick hexagonal crystals are rare. Most often occurs as veins and in massive form, and can be very large in size. Small, rounded ball-like aggregates and radiating spheres also occur. 18
  19. 19. Identification • Transparency: Opaque • Luster : Metallic • Tenacity : Brittle; thin flakes are flexible • Other ID Marks : 1) Has a greasy feel. 2) Smudges the hands when touched. 3) Is a good conductor of electricity (although it is a poor conductor of heat). • In Group : Native Elements; Non-Metallic Elements • Striking Features : Low weight, greasy feel, smudge, and low hardness. • Environment : Most often in metamorphic rock caused from the metamorphism of carbonates. 19
  20. 20. Occurence • Graphite occurs in metamorphic rocks as a result of the reduction of sedimentary carbon compounds during metamorphism. • It also occurs in igneous rocks and in meteorites. • Minerals associated with graphite include quartz, calcite,micas and tourmaline. In meteorites it occurs with troilite and silicate minerals. • Small graphitic crystals in meteoritic iron are called clifonite. 20
  21. 21. Structure Properties • Structure- Graphite has a layered, planar structure. In each layer, the carbon atoms are arranged in a honeycomb lattice with separation of 0.142 nm, and the distance between planes is 0.335 nm. • The two known forms of graphite, alpha (hexagonal) and beta (rhombohedral) have very similar physical properties, except that the graphene layers stack slightly differently. The hexagonal graphite may be either flat or buckled Graphite's unit cell 21
  22. 22. 22
  23. 23. 1. Ball and stick model of graphite (two graphene layers) 2. Side view of layer stacking 3. Plane view of layer stacking 23
  24. 24. Properties • High Thermal Conductivity. • High Thermal Shock Resistance. • High Melting Temperature. • Low Density (28% Of Steel). • Low Hardness. • Low Friction And Self Lubrication. • Electrical Conductivity Highest Of Non-metallic Materials. • Low Coefficient Of Thermal Expansion. • High Strength (Particularly Compressive Strength), Which Increases With The Temperature Rise. • High Stiffness (Modulus Of Elasticity). 24
  25. 25. • High Thermal Resistance. Graphite Is Capable To Work In The Temperature Range From Absolute Zero To 6330°F (3500°C) In Inert Atmosphere. • High Chemical And Corrosion Resistance; • Good Oxidation Resistance. Graphite Starts To Be Oxidized In Oxidizing Atmosphere At 932°F (500°C). • Low Absorption Coefficient For X-rays. • High Resistance To Neutron Radiation. Graphite Slows Down Fast Neutrons And Scatters Thermal Neutrons. • High Radiation Emissivity; • Ability To Absorb Radio Waves; • Low Wettability By Liquid Metals; • Good Machinability; • Ability To Absorb Gases. 25
  26. 26. Application • Graphite is mostly used in pencils, steelmaking, expanded graphite, brake linings,batteries,foundry facings and lubricants. 26
  27. 27. Application • As a lubricant at higher temperatures. • As a refractory material of making crucibles and electrodes for high temperature work. • In electrotyping and in the manufacture of gramophone records: Graphite is used for making the non-conducting (generally wax) surface, so that electroplating can be done. • For manufacturing lead pencils and stove paints. • It is a component of printers’ ink. 27
  28. 28. Differences Diamond Graphite Diamond Is Transparent Graphite Is Black And Opaque Diamond Is A Poor Conductor Of Electricity, But Is A Good Conductor Of Heat. Graphite On The Other Hand Is A Good Conductor Of Heat And Electricity. Diamond Is Hardest Substance Known In Nature Graphite Is Soft And Slippery To Touch Density Of Diamond Is More Density Of Graphite Is Comparatively Less It Is Insoluble In All Solvents It Is Insoluble In All Ordinary Solvents Diamond Is The Ultimate Abrasive Graphite Is A Very Good Lubricant Diamond Crystallizes In The Isometric System Graphite Crystallizes In The Hexagonal System It Occurs As Octahedral Crystals It Occurs As Hexagonal Crystals 28
  29. 29. Reference • Properties and Growth Of Diamond By G. Davies (1994). • Applications of Diamond Films and Related Materials. Elsevier. A . Feldman and L.H. Robins (1991). • Optical Properties of Diamond: A Data Handbook. Springer. A.M. Zaitsev (2001). 29
  30. 30. ThanK YoU 30