CERAMICS - International University of Sarajevo

CERAMICS 1. 2. 3. 4. 5. 6. Structure and Properties of Ceramics Traditional Ceramics New Ceramics Glass Some Important Elements Related to Ceramics

Guide to Processing Ceramics 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Ceramic Defined An inorganic compound consisting of a metal (or semimetal) and one or more nonmetals Important examples: Silica - silicon dioxide (SiO2), the main ingredient in most glass products Alumina - aluminum oxide (Al2O3), used in various applications from abrasives to artificial bones More complex compounds such as hydrous

aluminum silicate (Al2Si2O5(OH)4), the main ingredient in most clay products 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Properties of Ceramic Materials High hardness, electrical and thermal insulating, chemical stability, and high melting temperatures Brittle, virtually no ductility - can cause problems in both processing and performance of ceramic products Some ceramics are translucent, window glass (based on silica) being the clearest example

2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Ceramic Products Clay construction products - bricks, clay pipe, and building tile Refractory ceramics capable of high temperature applications such as furnace walls, crucibles, and molds Cement used in concrete - used for construction and roads Whiteware products - pottery, stoneware, fine china, porcelain, and other tableware, based on mixtures of clay and other minerals

2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Ceramic Products (continued) Glass bottles, glasses, lenses, window pane, and light bulbs Glass fibers - thermal insulating wool, reinforced plastics (fiberglass), and fiber optics communications lines Abrasives - aluminum oxide and silicon carbide in grinding wheels Cutting tool materials - tungsten carbide, aluminum oxide, and cubic boron nitride 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version

Ceramic Products (continued) Ceramic insulators applications include electrical transmission components, spark plugs, and microelectronic chip substrates Magnetic ceramics computer memories Nuclear fuels based on uranium oxide (UO2) Bioceramics - artificial teeth and bones 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Three Basic Categories of Ceramics

1. Traditional ceramics clay products such as pottery, bricks, common abrasives, and cement 2. New ceramics more recently developed ceramics based on oxides, carbides, etc., with better mechanical or physical properties than traditional ceramics 3. Glasses based primarily on silica and distinguished by their noncrystalline structure 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Strength Properties of Ceramics Theoretically, the strength of ceramics should be higher

than metals because their covalent and ionic bonding types are stronger than metallic bonding But metallic bonding allows for slip, the mechanism by which metals deform plastically when stressed Bonding in ceramics is more rigid and does not permit slip under stress The inability to slip makes it much more difficult for ceramics to absorb stresses 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Imperfections in Crystal Structure of Ceramics Ceramics contain the same imperfections in their

crystal structure as metals vacancies, displaced atoms, interstitialcies, and microscopic cracks Internal flaws tend to concentrate stresses, especially tensile, bending, or impact Hence, ceramics fail by brittle fracture much more readily than metals Strength is much less predictable due to random imperfections and processing variations 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Compressive Strength of Ceramics The frailties that limit the tensile strength of ceramic

materials are not nearly so operative when compressive stresses are applied Ceramics are substantially stronger in compression than in tension For engineering and structural applications, designers have learned to use ceramic components so that they are loaded in compression rather than tension or bending 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Methods to Strengthen Ceramic Materials Make starting materials more uniform

Decrease grain size in polycrystalline ceramic products Minimize porosity Introduce compressive surface stresses Use fiber reinforcement Heat treat 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Physical Properties of Ceramics Density most ceramics are lighter than metals but heavier than polymers Melting temperatures - higher than for most metals

Some ceramics decompose rather than melt Electrical and thermal conductivities - lower than for metals; but the range of values is greater, so some ceramics are insulators while others are conductors Thermal expansion - somewhat less than for metals, but effects are more damaging because of brittleness 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Traditional Ceramics Based on mineral silicates, silica, and mineral oxides found in nature Primary products are fired clay (pottery, tableware, brick, and tile), cement, and natural abrasives such

as alumina Products and the processes to make them date back thousands of years Glass is also a silicate ceramic material and is sometimes included among traditional ceramics 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Raw Materials for Traditional Ceramics Mineral silicates, such as clays and silica, are among the most abundant substances in nature and are the principal raw materials for traditional ceramics Another important raw material for traditional

ceramics is alumina These solid crystalline compounds have been formed and mixed in the earths crust over billions of years by complex geological processes 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Clay as a Ceramic Raw Material Clays consist of fine particles of hydrous aluminum silicate Mostly based on kaolinite, (Al2Si2O5(OH)4) Mixed with water, clay becomes a plastic substance that is formable and moldable

When heated to a sufficiently elevated temperature (firing), clay fuses into a dense, strong material Thus, clay can be shaped while wet and soft, and then fired to obtain the final hard product 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Silica as a Ceramic Raw Material Available naturally in various forms, most important is quartz Main source of quartz is sandstone Low cost Hard and chemically stable Principal component in glass, and an important

ingredient in other ceramic products including whiteware, refractories, and abrasives 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Alumina as a Ceramic Raw Material Bauxite - most alumina is processed from this mineral, which is an impure mixture of hydrous aluminum oxide and aluminum hydroxide plus similar compounds of iron or manganese Bauxite is also the principal source of aluminum Corundum - a more pure but less common form of

Al2O3, which contains alumina in massive amounts Alumina ceramic is used as an abrasive in grinding wheels and as a refractory brick in furnaces 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Traditional Ceramic Products Pottery and Tableware Brick and tile

Refractories Abrasives 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version New Ceramics Ceramic materials developed synthetically over the last several decades Also refers to improvements in processing techniques that provide greater control over structures and properties of ceramic materials New ceramics are based on compounds other than variations of aluminum silicate

New ceramics are usually simpler chemically than traditional ceramics; for example, oxides, carbides, nitrides, and borides 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Oxide Ceramics Most important oxide ceramic is alumina Al2O3 Although included among traditional ceramics, alumina is also produced synthetically from bauxite Through control of particle size and impurities, refinements in processing methods, and blending with small amounts of other ceramic ingredients, strength and toughness of alumina are improved substantially

compared to its natural counterpart Alumina also has good hot hardness, low thermal conductivity, and good corrosion resistance 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Products of Oxide Ceramics

Abrasives (grinding wheel grit) Bioceramics (artificial bones and teeth) Electrical insulators and electronic components Refractory brick Cutting tool inserts Spark plug barrels Engineering components 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Alumina ceramic components (photo courtesy of Insaco Inc.)

2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Carbide Ceramics Includes silicon carbide (SiC), tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC), and chromium carbide (Cr3C2) Production of SiC dates from a century ago, and it is generally included among traditional ceramics WC, TiC, and TaC are hard and wear resistant and are used in applications such as cutting tools WC, TiC, and TaC must be combined with a metallic binder such as cobalt or nickel in order to fabricate a useful solid product

2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Nitrides Important nitride ceramics are silicon nitride (Si3N4), boron nitride (BN), and titanium nitride (TiN) Properties: hard, brittle, high melting temperatures, usually electrically insulating, TiN being an exception Applications: Silicon nitride: components for gas turbines, rocket engines, and melting crucibles Boron nitride and titanium nitride: cutting tool materials and coatings 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version

Glass A state of matter as well as a type of ceramic As a state of matter, the term refers to an amorphous (noncrystalline) structure of a solid material The glassy state occurs when insufficient time is allowed during cooling from the molten state to form a crystalline structure As a type of ceramic, glass is an inorganic, nonmetallic compound (or mixture of compounds) that cools to a rigid condition without crystallizing 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version

Why So Much SiO2 in Glass? Because SiO2 is the best glass former Silica is the main component in glass products, usually comprising 50% to 75% of total chemistry It naturally transforms into a glassy state upon cooling from the liquid, whereas most ceramics crystallize upon solidification 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Other Ingredients in Glass

Sodium oxide (Na2O) Calcium oxide (CaO) Aluminum oxide (Al2O3) Magnesium oxide (MgO) Potassium oxide (K2O) Lead oxide (PbO)

Boron oxide (B2O3) 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Functions of Other Ingredients in Glass Act as flux (promoting fusion) during heating Increase fluidity in molten glass for processing Improve chemical resistance against attack by acids, basic substances, or water Add color Alter index of refraction for optics

2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Glass Products Window glass Containers cups, jars, bottles Light bulbs

Laboratory glassware flasks, beakers, glass tubing Glass fibers insulation, fiber optics Optical glasses - lenses 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version GlassCeramics A ceramic material produced by conversion of glass into a polycrystalline structure through heat treatment Proportion of crystalline phase range = 90% to 98%, remainder vitreous material Grain size significantly smaller than the conventional ceramics, which makes glassceramics much

stronger than the glasses from which they are made Due to crystal structure, glassceramics are opaque (usually grey or white), not clear 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Processing of Glass Ceramics Heating and forming techniques used in glassworking create product shape Product is cooled and then reheated to cause a dense network of crystal nuclei to form throughout Nucleation results from small amounts of nucleating agents, such as TiO2, P2O5, and ZrO2 Once nucleation is started, heat treatment is

continued at a higher temperature to cause growth of crystalline phases 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Advantages of GlassCeramics Efficiency of processing in the glassy state Close dimensional control over final shape Good mechanical and physical properties High strength (stronger than glass) Absence of porosity; low thermal expansion High resistance to thermal shock 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version

Applications of Glass-Ceramics Cooking ware (e.g., Corning ware) Heat exchangers Missile radomes 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Elements Related to Ceramics Carbon Two alternative forms of engineering and commercial importance: graphite and diamond Silicon and Boron

Carbon, silicon, and boron are not ceramic materials, but they sometimes Compete for applications with ceramics Have important applications of their own 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Graphite Form of carbon with a high content of crystalline carbon in the form of layers Bonding between atoms in layers is covalent and strong, but parallel layers are bonded to each other by weak van der Waals forces Structure makes graphite properties anisotropic

As a powder it is a lubricant, but in traditional solid form it is a refractory As a fiber, it is a high strength structural material (e.g., fiber reinforced plastics) 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Diamond Carbon with a cubic crystalline structure with covalent bonding between atoms for high hardness Applications: cutting tools and grinding wheels for machining hard, brittle materials or materials that are very abrasive; also used in dressing tools to sharpen grinding wheels that consist of other abrasives

Synthetic diamonds date back to 1950s Fabricated by heating graphite to around 3000C (5400F) under very high pressures 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Synthetically produced diamond powders (photo courtesy of GE Superabrasives, General Electric Company). 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Silicon Semi-metallic element in the same periodic table group as carbon One of the most abundant elements in Earth's crust,

comprising 26% by weight Occurs naturally only as chemical compound in rocks, sand, clay, and soil either as silicon dioxide or as more complex silicate compounds Properties: hard, brittle, lightweight, chemically inactive at room temperature, and classified as a semiconductor 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Applications and Importance of Silicon Greatest use in manufacturing are as ceramics (SiO2 in glass and silicates in clays) and alloying elements

in steel, cast iron, aluminum, and copper Pure silicon is of significant technological importance as the base material in semiconductor manufacturing in electronics The vast majority of integrated circuits produced today are made from silicon 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Boron Semi-metallic element in same periodic group as aluminum Comprises only about 0.001% of Earth's crust by

weight, commonly occurring as minerals borax (Na2B4O710H2O) and kernite (Na2B4O74H2O) Properties: lightweight, semiconducting properties, and very stiff (high modulus of elasticity) in fiber form Applications: B2O3 in certain glasses, as a nitride (cBN) for cutting tools, and in nearly pure form as a fiber in polymer matrix composites 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version Guide to Processing Ceramics Processing of ceramics can be divided into two basic

categories: 1. Molten ceramics - major category of molten ceramics is glassworking (solidification processes) 2. Particulate ceramics - traditional and new ceramics (particulate processing) 2010 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 4/e SI Version

Recently Viewed Presentations

  • 1, 2 Thessalonians Living Between The Times Bethany

    1, 2 Thessalonians Living Between The Times Bethany

    Each chapter of 1 Thessalonians ends with a reference to the second coming of Christ. ... It is spare in the extreme, especially compared to John in the book of Revelation. John uses grand, colorful, vivid descriptions of animals with...
  • Allusion and Parody - Weebly

    Allusion and Parody - Weebly

    Allusion and Parody Bringing in some "outside help" to form figurative connections Allusion When a text makes a reference to or mentions another work within its body Example: In The Outsiders, S.E. Hinton alludes to the southern gentlemen in Gone...
  • 2006 UAF Radiation Safety Training

    2006 UAF Radiation Safety Training

    The QF for neutron radiation is 10. The QF for alpha radiation is 20. Thus, alpha radiation is considered 20x more harmful than beta or gamma radiation with regard to biological damage. ... Needle should go into "BAT TEST" area.
  • DfE Template (Arial) v1.0 April 2012

    DfE Template (Arial) v1.0 April 2012

    Dominic Herrington . Regional Schools Commissioner for South East and South London. Main responsibilities: Take action when an academy is underperforming. Decide on the development of new academies. Address underperformance in maintained schools through sponsored academies .
  • Data Summary for: '2006 New Student Satisfaction Survey ...

    Data Summary for: '2006 New Student Satisfaction Survey ...

    Data Summary for: "2006 New Student Satisfaction Survey" First-time Freshman and Transfer Students Margie Bennett, Ph.D. Executive Assistant to the President
  • Fahrenheit and Celsius Conversion Formulas

    Fahrenheit and Celsius Conversion Formulas

    Fahrenheit and Celsius Conversion Formulas Fahrenheit to Celsius: Celsius to Fahrenheit: Conversion between Celsius and Kelvin (K) Later when you solve problems dealing with gases it will be important to convert Celsius temperatures into Kelvin temperatures by using the following...
  • Preliminary Inputs for Wisconsin RPS Analysis

    Preliminary Inputs for Wisconsin RPS Analysis

    The climate projections for 2100 that apply to Minnesota are as follows: Temperatures will increase overall, with winter warming by 6-10 °F, and summers by as much as 7-16 ° F. This will produce more heat waves and the growing...
  • Georgia State Government Click on the subject you

    Georgia State Government Click on the subject you

    Judicial Branch. The job of the judicial branch of government is to interpret the law. This means this branch makes decisions about the law and decides if laws go against the Georgia Constitution. The Georgia Constitution is a document that...