Engineering Materials Chemistry Reviewer PDF

Summary

This document is a reviewer of Engineering Materials, which covers topics such as the properties of materials, including physical, chemical, and electrical properties, and their different types such as metals, ceramics, polymers, and composites. It also details the effect of alloys and different fabrication methods. The document is geared toward Engineering students who are studying engineering materials.

Full Transcript

ENGINEERING MATERIALS ❖ Understanding the properties (physical and chemical) of materials ❖ Designing (engineering) the structure of a material for a particular application or use ❖ Structure → Atomic structure, arrangement of atoms throughout the material ❖ Property → Chemical properti...

ENGINEERING MATERIALS ❖ Understanding the properties (physical and chemical) of materials ❖ Designing (engineering) the structure of a material for a particular application or use ❖ Structure → Atomic structure, arrangement of atoms throughout the material ❖ Property → Chemical properties (e.g. resistance to corrosion) → Physical properties (e.g. strength, flexibility) → Electrical and magnetic properties (e.g. conductivity) ❖ Processing → Manufacturing History ❖ Performance ❖ Metal ❖ Refractories ❖ Ceramic → ceramics that are designed to withstand very high temperature ❖ Polymers ❖ Alloys ❖ Composites → mixture of metals ❖ Composites → materials that are composed of two or more materials which combine to give a material superior than those of the individual component ENGINEERING MATERIALS ❖ Have definite volume ❖ An amorphous solid does not possess a ❖ Have definite shape well-defined arrangement and long-range ❖ Molecules are held in specific locations molecular order. → By electrical forces ❖ Vibrate about equilibrium positions ❖ Can be modeled as springs connecting molecules ❖ Crystalline → Regular, repeating geometric arrangement ❖ Amorphous → Random arrangements ❖ Melting point Crystalline solids → Sharp melting point, they change into liquids at definite temperature Amorphous solids → On heating, they do not turn abruptly into liquids, but instead, soften and start flowing in a semi-solid ❖ Crystalline solids’ molecules are arranged neatly forms in lattices of cells ❖ A unit cell is the basic repeating structural unit of ❖ Cooling Characteristics a crystalline solid. Crystalline Solids → Slow Cooled Amorphous solids → Fast Cooled Crystalline Solids → Diamond, Sodium chloride Amorphous solids ❖ At lattice points: → Glass → Atoms → Molecules → Ions ENGINEERING MATERIAL ❖ Ionic Crystals ❖ Tensile strength → Lattice points occupied by cations and anions ❖ Elasticity → Held together by electrostatic attraction ❖ Ductility → Hard, brittle, high melting point ❖ Malleability → Poor conductor of heat and electricity ❖ Brittleness ❖ Density ❖ Covalent Crystals ❖ Coefficient of Thermal Expansion → Lattice points occupied by atoms ❖ Specific heat/latent heat → Held together by covalent bonds ❖ Thermal/Electrical Conductivity → Hard, high melting point ❖ Hardness → Poor conductor of heat and electricity ❖ Magnetic Susceptibility ❖ Molecular Crystals → Lattice points occupied by molecules → Held together by intermolecular forces ❖ Chemical composition → Soft, low melting point ❖ Corrosion resistance → Poor conductor of heat and electricity ❖ Acidity or alkalinity ❖ Molecular/Crystal structure ❖ Metallic Crystals → Lattice points occupied by metal atoms → Held together by metallic bonds → Soft to hard, low to high melting point → Good conductors of heat and electricity ALLOYS ❖ A partial or complete solution of one or more ❖ Manganese elements in a metallic matrix When added up to 1-1.5%, it Complete solid solution alloys increases toughness, → give single solid phase strength and brittleness Partial solution When added 11 – 14%, it → give 2 or more phases that may be homogeneous in imparts high degree of distribution depending on thermal properties strength ❖ Nickel ❖ Usually have different properties from those of the Improves corrosion and heat original components resistance, elasticity, toughness, ductility and tensile strength. ❖ Molybdenum Improves corrosion and abrasion resistance and strength at elevated temp; brittleness can be eliminated. ❖ Tungsten Improves toughness, abrasion and shock ❖ Chromium resistance and hardness at → improves hardness and toughness simultaneously higher temperature When added up to 12% : imparts high corrosion resistance When added up to 15%: enhances tensile strength ❖ Vanadium Improves tensile strength, ductility and shock-resistance POLYMERS ❖ Large molecules consisting of a long or chains of atoms covalently bonded ❖ Polymers are referred to as macromolecules → molecules of high molecular mass. ❖ Made up of monomers → small molecules used to synthesize the large polymeric chain ❖ Monomers add to the growing polymer chain in such a way that the product contains all the atoms of the starting material. ❖ No other product is formed ❖ LDPE- low density polyethylene ❖ HDPE – high density polyethylene ❖ PVC (or V)– polyvinyl chloride ❖ PS - polystyrene ❖ PP - polypropylene ❖ PET (or PETE) – polyethylene terephthalate ❖ ABS – acrylonitrile butadiene styrene ❖ PPO – polyphenylene oxide ❖ SAN – styrene acrylonitrile ❖ PBT – polybutylene terephthalate ❖ PEEK – polyether ether ketone ❖ PPS – polyphenylene sulfide ❖ PTFE – polytetrafluoroethylene ❖ LCP – liquid crystal polymer CERAMICS ❖ A wide-ranging group of materials whose ❖ Advanced Ceramics ingredients are clays, sand and feldspar. These materials have seen significant development over the past fifty years, with applications including: ❖ Clays → Rich in silicates, potassium,magnesium, and Structural components: Wear parts, engine calcium compounds. components, and armor. ❖ Sand Electrical applications: Capacitors and insulators. → Primarily consists of silica and feldspar or Coatings: Protecting tools and industrial parts. aluminum potassium silicate. ❖ Ceramic Armor Ceramic armor is utilized in military applications due to its lightweight yet strong properties. Typical ❖ Whitewares materials include alumina and silicon carbide. The → Includes crockery, tiles, sanitary ware, electrical design often features a hard outer layer that porcelain, and decorative ceramics. shatters projectiles, while an inner ductile layer absorbs residual energy. ❖ Refractories → Designed to withstand high temperatures (up to 2050°C), these materials are essential in industries like steel making and glass production. ❖ Glasses → Amorphous ceramics primarily made from silica; they can be tempered for increased toughness. ❖ Abrasives → Used for cutting and polishing, these can be natural (like diamond) or synthetic (like silicon carbide). ❖ Cements → Fundamental for construction, used in concrete for roads and buildings. ❖ Refractories are crucial for thermal protection in high-temperature applications. They typically have a porosity greater than 10% and contain oxides such as alumina and silica. Common uses include Fire Bricks for furnaces Thermal insulation in various industrial processes ❖ The main ingredient in Glass is silica (SiO2). Depending on the cooling process, glass can either be crystalline or amorphous. Types of glass include: Soda-lime glass Commonly used for windows and containers. Lead glass Enhances refractive index due to lead oxide. Borosilicate glass Known for its thermal resistance (e.g., Pyrex). NANOTECHNOLOGY ❖ Nanotechnology is the study of matter at an incredibly small scale, generally between 1 and 100 nanometers. ❖ 1 nm is 10^-9 of a meter. ❖ Nanotechnology encompasses a broad range of materials, manufacturing processes and technologies that are used to create and enhance many products that people use daily. NANOTECHNOLOGY NANOMATERIALS ❖ Materials having at least 1 dimension 100 nm or less. ❖ Temperature ❖ It can be nanoscale in 1 dimension (e.g. ❖ pH surface films); 2 dimensions (e.g. strands or ❖ Concentration fibers) or 3 dimensions (e.g. particles) ❖ Chemical Composition ❖ They can exist in single, fused or ❖ Surface modification agglomerated forms with spherical, tubular ❖ Process Control and irregular shapes. ❖ Top – down ❖ Class of allotrope of carbon which Refers to the mechanical crushing of source conceptually are graphene sheets rolled into materials using a milling process. tubes or spheres. These include the carbon nanotubes or silicon nanotubes which possess Nanomaterial is derived from a bulk substrate mechanical strength and electrical and obtained by progressive removal of conductivity material, until desired nanomaterial is ❖ FULLERENE obtained. Buckminsterfullerene, C60 (or buckyballs), resembles the balls used ❖ Bottom – up (chemo-physical production in association football process) In this method, nanomaterials are obtained starting from the atomic or molecular ❖ Allotropes of carbon with cylindrical precursors and gradually assembling it until nanostructure. the desired structure is formed. ❖ Exceptionally strong, and stiff ❖ Have extraordinary thermal conductivity, Structures are built up by chemical processes; mechanical and electrical properties. They based on physico-chemical principles of are added to various structural materials. molecular or atomic self-organization. This approach produces selected, more complex structures from atoms or molecules; ❖ Fabrication of nanomaterials includes better controlling sizes, shapes and size nanostructure surfaces, nanoparticles, range. nanoporous materials. Includes aerosol processes, precipitation reactions, and sol gel processes ❖ Particle Size ❖ Chemical Composition and desired feature of the nanomaterial ❖ Crystallinity ❖ A mechanical production approach to crush microparticles ❖ Applied in producing metallic and ceramic nanomaterials ❖ Involves thermal stress and is energy intensive ❖ Longer process (might contaminate the particles) ❖ A chemical or chemo-physical reaction accompanies the milling process NANOMATERIALS ❖ Most common industrial scale technologies for producing nanomaterials in powder or film form. ❖ Production of initial nanomaterials (liquid or solid) takes place via homogeneous nucleation ❖ Depending on the process, further particle growth ❖ Supramolecular structures are large molecules formed by grouping or bonding smaller molecules together ❖ Milling – breaking solid materials into smaller pieces by grinding, crushing, or cutting in a mill; a process of using rotary cutters ❖ Nucleation – initial process that occurs in the formation of a crystal from solution, a liquid or a vapor, in which smaller number of ions, atoms or molecules become arranged in a pattern characteristic of a crystalline solid, forming a site upon which additional particles are deposited as crystals grow. Wishing you all the best on your exam! -NARDO 🥳

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