NANO2151 Week 3 Principles of Material Science Engineering PDF

NANO2151 Principles of Material Science Engineering DR.(MS.) P G D C K KARUNARATHNA Crystal Structure of carbon Allotropes of Carbon An element that can exist in more than one physical state is called allotropy. The allotropes of carbon can be categorized into two: Amorphous Carbon Al...

NANO2151 Principles of Material Science Engineering DR.(MS.) P G D C K KARUNARATHNA Crystal Structure of carbon Allotropes of Carbon An element that can exist in more than one physical state is called allotropy. The allotropes of carbon can be categorized into two: Amorphous Carbon Allotropes Crystalline Carbon Allotropes 2 Crystal Structure of carbon ctd. Types of Carbon Allotropes Diamond Graphite Amorphous carbon Fullerenes Carbon nanotubes 3 Crystal Structure of carbon ctd. Diamond It is the purest crystalline allotrope of carbon. Each carbon atom is tetra-headedly attached to four other carbon atoms forming a rigid three-dimensional structure. Thus it is the hardest element on earth 4 Crystal Structure of carbon ctd. Physical Properties of Diamond It is extremely hard It has a very high melting point It has a high relative density It is transparent to X-rays It has a high value of the refractive index It is a bad conductor of electricity It is a good conductor of heat It is insoluble in all solvents 5 Crystal Structure of carbon ctd. Graphite It is a pure form of carbon. Each C atom is linked to three C atoms via a C-C covalent bond. Each carbon here is sp2 hybridized. The remaining p orbital electron is delocalized to form a weak bond between the layer Therefore, graphite has a unique honeycomb layered structure. 6 Crystal Structure of carbon ctd. Properties of Graphite Since the layers are stacked over each other, this carbon allotrope can act as a lubricant. Graphite can be used as a dry lubricant for machines at high temperatures where we cannot use oil. It is a very good conductor of both heat and electricity. 7 Crystal Structure of carbon ctd. Amorphous carbon Carbon that does not have any crystalline structure is called amorphous carbon Some short-range order can be observed, but there is no long-range pattern of atomic positions Ex:- Coal and soot or carbon black 8 Crystal Structure of carbon ctd. Fullerenes Is one of a family of spherical carbon molecules sometimes called “buckyballs” Has the formula C60 The carbon atoms are arranged in hexagons and pentagons to give a geodesic spherical structure similar to a football 9 Crystal Structure of carbon ctd. Carbon nanotubes Carbon nanotubes are the member of the fullerene structural family. Also called buckytubes. Those are cylindrical carbon molecules with novel properties Ex:- Nanoelectronics, optics, material applications, etc. 10 Crystal Structure of Glass Glass is an amorphous, hard, brittle, transparent or translucent, super-cooled liquid, obtained by fusing a mixture of a number of metallic silicates, most commonly Na, K, Ca and Pb. It possesses no sharp melting point, crystalline structure and definite formula 11 Crystal Structure of Glass ctd. The basic raw materials for glass production are: Quartz sand (Silicon oxide (SiO2)) Soda ( Sodium carbonate (Na2CO3)) Limestone (Calcium carbonate (CaCO3)) Potash(Potassium carbonate (K2CO3)) Dolomite (Calcium magnesium carbonate (MgCa(CO3)2)) 12 Crystal Structure of Glass ctd. 13 Crystal Structure of inorganic compounds. Inorganic compounds can have various crystal structures depending on their chemical composition and bonding arrangements. 14 Crystal Structure of inorganic compounds. Some common crystal structures for inorganic compounds include: 1. Cubic Structures: Simple Cubic (sc): Is the simplest cubic lattice, with atoms or ions at the corners of a cube. It is not very common due to its low packing efficiency. Body-Centered Cubic (bcc): Atoms are present at the corners and in the center of the cube. Sodium and iron are examples of elements that can adopt a bcc structure. Face-Centered Cubic (fcc): Atoms are at the corners and on the faces of the cube. Copper, aluminum, and gold can have fcc structures. 15 Crystal Structure of inorganic compounds ctd. 2. Hexagonal Close-Packed (hcp) Structure: Atoms are arranged in a close-packed hexagonal lattice, with the layers slightly offset from each other. Magnesium and zinc can adopt this structure. 3. Tetragonal and Orthorhombic Structures: These structures have rectangular and parallelepiped unit cells, respectively. Ex:- Zirconium and barium sulfate 16 Crystal Structure of inorganic compounds ctd. 4. Monoclinic and Triclinic Structures: These structures have non-rectangular and non-cubic unit cells. They are less common and often have more complex arrangements. Ex:- calcium sulfate is an example of a mineral with monoclinic structure. Monoclinic Crystal System Axes relations: a≠b≠c, with angles α=γ=90∘\alpha = \gamma = 90^\circα=γ=90∘, but β≠90∘ Triclinic Crystal System Axes relations: a≠b≠ and α≠β≠γ≠90∘ 17 Crystal Structure of inorganic compounds ctd. 5. Trigonal (Rhombohedral) Structure: The rhombohedral lattice is also known as trigonal, and has no angles equal to 90°, but all sides are of equal length (a = b = c), thus requiring only by one lattice parameter, and all three angles are equal (α = β = γ) 18 Crystal Structure of inorganic compounds ctd. 6. Hexagonal Structure: A hexagonal crystal structure has two angles equal to 90°, with the other angle equal to 120°. For this to happen, the two sides surrounding the 120° angle must be equal (a = b), while the third side (c) is at 90° to the other sides and can be of any length. 19 Crystal Structure of inorganic compounds ctd. These are just a few examples of the many possible crystal structures that inorganic compounds can exhibit. The specific crystal structure of an inorganic compound depends on factors such as the types of atoms or ions involved, their sizes, and their bonding arrangements. 20 Q&A? 21