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CERAMICS

CERAMICS Duygu ALTINÖZ 20519517 Emine ÖZTAŞ 20519943 Melodi HASÇUHADAR 20772572 Merve ÇAY 20772639 11.11.2009 Hacettepe University KMU Outline What are ceramics? Classification of ceramics Thermal Properties of ceramics

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CERAMICS

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  1. CERAMICS • Duygu ALTINÖZ 20519517 • Emine ÖZTAŞ 20519943 • Melodi HASÇUHADAR 20772572 • Merve ÇAY 20772639 11.11.2009 Hacettepe University KMU

  2. Outline What are ceramics? Classification of ceramics Thermal Properties of ceramics Optical Properties Mechanical Properties Electrical Properties Ceramic Processing 7.3.2014

  3. Spectrum of Ceramics Uses http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf 7.3.2014

  4. What are ceramics? Periodic table with ceramics compounds indicated by a combination of one or more metallic elements (in light color) with one or more nonmetallic elements (in dark color). http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf

  5. What are ceramics? To be most frequently silicates, oxides, nitrides and carbides Typically insulative to the passage of electricity and heat More resistant to high temperatures and harsh environments than metals and polymers Hard but very brittle 7.3.2014

  6. Ceramic Crystal Structures • ceramics that are predominantly ionic in nature have crystal structures comprised of charged ions, where positively-charged (metal) ions are called cations, and negatively-charged (non-metal) ions are called anions – the crystal structure for a given ceramic depends upon two characteristics: 7.3.2014

  7. Ceramic Crystal Structures 1. the magnitude of electrical charge on eachcomponent ion, recognizing that the overallstructure must be electrically neutral 2. the relative size of the cation(s) and anion(s),which determines the type of interstitial site(s) for the cation(s) in an anion lattice 7.3.2014

  8. Example of Crystal Structure Rock salt structure(AX)(NaCl) Fluorite structure(AX2)(CaF2) Perovskite structure(ABX3)(BaTiO3) Spinel structure(AB2X4)(MgAl2O4) http://www.eng.uwo.ca/es021/ES021b_2007/Lecture%20Notes/Chap%2012-13%20SN%20-%20Ceramics.pdf

  9. Imperfections in Ceramics Include point defects and impurities Non-stoichiometry refers to a change in composition the effect of non-stoichiometry is a redistribution of the atomic charges to minimize the energy Charge neutral defects include the Frenkeldefects(a vacancy- interstitial pair of cations) and Schottky defects (a pair of nearby cation and anion vacancies) Defects will appear if the charge of the impurities is not balanced  7.3.2014

  10. Properties of Ceramics • Extreme hardness – High wear resistance – Extreme hardness can reduce wear caused by friction • Corrosion resistance • Heat resistance – Low electrical conductivity – Low thermal conductivity – Low thermal expansion – Poor thermal shock resistance 7.3.2014

  11. Properties of Ceramics • Low ductility – Very brittle – High elastic modulus • Low toughness – Low fracture toughness – Indicates the ability of a crack or flaw to produce a catastrophic failure • Low density – Porosity affects properties • High strength at elevated temperatures 7.3.2014

  12. General Comparison of Materials Property              Ceramic  Metal    Polymer Hardness Very High Low Very Low Elastic modulus Very High   High Low Thermal expansion High  Low Very Low Wear resistance  High  Low   Low Corrosion resistance  High Low  Low  7.3.2014

  13. General Comparison of Materials Property             Ceramic  Metal     Polymer Ductility Low High  High Density  Low  High  Very Low  Electrical conductivity  Depends   High   Low  on material Thermal conductivity  Depends   High  Low   on material Magnetic Depends High  Very Low  on material 7.3.2014

  14. Classification of ceramics 7.3.2014

  15. Classification of ceramics Traditional Ceramics the older and more generally known types (porcelain, brick, earthenware, etc.) Based primarily on natural raw materials of clay and silicates Applications; building materials (brick, clay pipe, glass) household goods (pottery, cooking ware) manufacturing ( abbrasives, electrical devices, fibers) Traditional Ceramics

  16. Classifications of ceramics Advanced Ceramics have been developed over the past half century Include artificial raw materials, exhibit specialized properties, require more sophisticated processing Applied as thermal barrier coatings to protect metal structures, wearing surfaces, Engine applications (silicon nitride (Si3N4), silicon carbide (SiC), Zirconia (ZrO2), Alumina (Al2O3)) bioceramic implants

  17. Classification of ceramics Oxides: Alumina, zirconia Non-oxides: Carbides, borides, nitrides, silicides Composites: Particulate reinforced, combinations of oxides and non-oxides CERAMICS Oxides Nonoxides Composite

  18. Classification of ceramics Oxide Ceramics: Oxidation resistant chemically inert electrically insulating generally low thermal conductivity slightly complex manufacturing low cost for alumina more complex manufacturing higher cost forzirconia. zirconia

  19. Classification of ceramics Non-Oxide Ceramics: Low oxidation resistance extreme hardness chemically inert high thermal conductivity electrically conducting difficult energy dependent manufacturing and high cost. Silicon carbide cermic foam filter (CFS) http://images.google.com.tr/imgres?imgurl=http://www.made-in-china.com/image/2f0j00avNtpdFnLThyM/Silicon-Carbide-Ceramic-Foam-Filter-CFS-.jpg&imgrefurl

  20. Classification of ceramics Ceramic-Based Composites: Toughness low and high oxidation resistance (type related) variable thermal and electrical conductivity complex manufacturing processes high cost. Ceramic Matrix Composite (CMC) rotor http://images.google.com.tr/imgres?imgurl=http://www.oppracing.com/images/cmsuploads/Large_Images/braketech%2520cmc%2520rotor%2520oppracing%2520cbr1000rr.jpg&imgrefurl

  21. Classification of ceramics 7.3.2014

  22. Classifications of ceramics Amorphous the atoms exhibit only short-range order no distinct melting temperature (Tm) for these materials as there is with the crystalline materials Na20, Ca0, K2O, etc CERAMICS amorphous crystalline Amorphous silicon and thin film PV cells http://images.google.com.tr/imgres?imgurl=http://simeonintl.com/sitebuilder/images/A-Si_Solar-510x221.jpg&imgrefurl=http://simeonintl.com/Solar.html&usg=__ktCHUAO742PE0hh3U1fGw8goPrM=&h=221&w=510&sz=17&hl=tr&start=68&sig2=9OC7pTtJz2SuK_AKdrqTAA&um=1&tbnid=xQRh5yfCftf89M:&tbnh=57&tbnw=131&prev=/images%3Fq%3Damorphous%2Bceramic%26ndsp%3D18%26hl%3Dtr%26rlz%3D1G1GGLQ_TRTR320%26sa%3DN%26start%3D54%26um%3D1&ei=9Kv1SrTfAoej_gbrz6WtAw

  23. Classifications of ceramics Crystalline atoms (or ions) are arranged in a regularly repeating pattern in three dimensions (i.e., they have long-range order) Crystalline ceramics are the “Engineering” ceramics – High melting points – Strong – Hard –Brittle – Good corrosion resistance • a ceramic (crystalline) and a glass (non-crystalline)

  24. Thermal properties most important thermal properties of ceramic materials: Heat capacity : amount of heat required to raise material temperature by one unit (ceramics > metals) Thermal expansion coefficient: the ratio that a material expands in accordance with changes in temperature Thermal conductivity : the property of a material that indicates its ability to conduct heat Thermal shock resistance: the name given to cracking as a result of rapid temperature change 7.3.2014

  25. Thermal properties Thermal expansion The coefficients of thermal expansion depend on the bond strength between the atoms that make up the materials. Strong bonding (diamond, silicon carbide, silicon nitrite) → low thermal expansion coefficient Weak bonding ( stainless steel) → higher thermal expansion coefficient in comparison with fine ceramics Comparison of thermal expansion coefficient between metals and fine ceramics

  26. Thermal properties Thermal conductivity generally less than that of metals such as steel or copper ceramic materials, in contrast, are used for thermal insulation due to their low thermal conductivity (except silicon carbide, aluminium nitride) • http://global.kyocera.com/fcworld/charact/heat/images/thermalcond_zu.gif

  27. Thermal properties Thermal shock resistance A large number of ceramic materials are sensitive to thermal shock Some ceramic materials → very high resistance to thermal shock is despite of low ductility (e.g. fused silica, Aluminium titanate ) Result of rapid cooling → tensile stress (thermal stress)→cracks and consequent failure The thermal stresses responsible for the response to temperature stress depend on: -geometrical boundary conditions -thermal boundary conditions -physical parameters (modulus of elasticity, strength…) 7.3.2014

  28. OPTICAL PROPERTIES OF CERAMICS REFRACTION Light that is transmitted from one medium into another, undergoes refraction. Refractive index, (n) of a material is the ratio of the speed of light in a vacuum (c = 3 x 108 m/s) to the speed of light in that material. n = c/v http://matse1.mse.uiuc.edu/ceramics/prin.html 7.3.2014

  29. OPTICAL PROPERTIES OF CERAMICS http://matse1.mse.uiuc.edu/ceramics/prin.html 7.3.2014

  30. OPTICAL PROPERTIES OF CERAMICS Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 7.3.2014

  31. OPTICAL PROPERTIES OF CERAMICS • ABSORPTION • Color in ceramics • Most dielectric ceramics and glasses are colorless. • By adding transition metals (TM) • Ti, V, Cr, Mn, Fe, Co, Ni Carter, C., B., Norton, M., G., Ceramic Materials Science And Engineering, 7.3.2014

  32. MECHANICAL PROPERTIES OF CERAMICS STRESS-STRAIN BEHAVIUR of selected materials Al2O3 thermoplastic http://www.keramvaerband.de/brevier_engl/5/5_2.htm 7.3.2014

  33. MECHANICAL PROPERTIES OF CERAMICS Flexural Strength The stress at fracture using this flexure test is known as the flexural strength. Flexure test :which a rod specimen having either a circular or rectangular cross section is bent until fracture using a three- or four-point loading technique Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 7.3.2014

  34. MECHANICAL PROPERTIES OF CERAMICS • Stress is computed from, • specimen thickness • the bending moment • the moment of inertia of the cross section For a rectangular cross section, the flexural strength σfs is equal to, L is the distance between support points When the cross section is circular, R is the specimen radius Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 7.3.2014

  35. MECHANICAL PROPERTIES OF CERAMICS Callister, W., D., (2007), Materials Science And Engineering, 7th Edition, 7.3.2014

  36. MECHANICAL PROPERTIES OF CERAMICS Hardness Hardness implies a high resistance to deformation and is associated with a large modulus of elasticity. In metals, ceramics and most polymers, the deformation considered is plastic deformation of the surface.For elastomers and some polymers, hardness is defined at the resistance to elastic deformation of the surface. Technical ceramic components are therefore characterised by their stiffness and dimensional stability. Hardness is affected from porosity in the surface, the grain size of the microstructure and the effects of grain boundary phases. http://www.dynacer.com/hardness.htm http://www.keramvaerband.de/brevier_eng/5/3/%_3_5.htm http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Hardness.htm 7.3.2014

  37. MECHANICAL PROPERTIES OF CERAMICS Test procedures for determining the hardness according to Vickers, Knoop and Rockwell. Some typical hardness values for ceramic materials are provided below: The high hardness of technical ceramics results in favourable wear resistance. Ceramics are thus good for tribological applications. http://www.dynacer.com/hardness.htm 7.3.2014

  38. MECHANICAL PROPERTIES OF CERAMICS Elastic modulus The elastic modulus E [GPa] of almost all oxide and non-oxide ceramics is consistently higher than that of steel. This results in an elastic deformation of only about 50 to 70 % of what is found in steel components. The high stiffness implies, however, that forcesexperienced by bonded ceramic/metal constructions must primarily be taken up by the ceramic material. http://www.keramverband.de/brevier_engl/5/3/4/5_3_4.htm 7.3.2014

  39. MECHANICAL PROPERTIES OF CERAMICS Density The density, ρ (g/cm³) of technical ceramics lies between 20 and 70% of the density of steel. The relative density, d [%], has a significant effect on the properties of the ceramic. http://www.keramverband.de/brevier_engl/5/3/4/5_3.htm 7.3.2014

  40. MECHANICAL PROPERTIES OF CERAMICS A comparison of typical mechanical characteristics of some ceramics with grey cast-iron and construction steel http://www.keramverband.de/brevier_engl/5/5_2.htm 7.3.2014

  41. MECHANICAL PROPERTIES OF CERAMICS Change in elastic modulus with the amount of porosity in SiOC ceramic foams obtained from a preceramic polymer Porosity Technical ceramic materials have no open porosity. Porosity can be generated through the appropriate selection of raw materials, the manufacturing process, and in some cases through the use of additives. This allows closed and open pores to be created with sizes from a few nm up to a few µm. http://www.ucl.ac.uk/cmr/webpages/spotlight/articles/colombo.htm http://www.keramverband.de/brevier_engl/5/3/5_3_2.htm 7.3.2014

  42. MECHANICAL PROPERTIES OF CERAMICS • Strength • The figure for the strength of ceramic materials, [MPa] is statistically distributed depending on • the material composition • the grain size of the initial material and the additives • the production conditions • the manufacturing process Strength distribution within batches http://www.keramverband.de/brevier_engl/5/3/3/5_3_3.htm 7.3.2014

  43. MECHANICAL PROPERTIES OFCERAMICS • Toughness • Ability of material to resist fracture • affected from, • temperature • strain rate • relationship between the strenght and ductility of the material and presence of stress concentration (notch) on the specimen surface http://www.subtech.com/dokuwiki/doku.php?id=fracture_toughness 7.3.2014

  44. MECHANICAL PROPERTIES OF CERAMICS Some typical values of fracture toughness for various materials http://en.wikipedia.org/wiki/Fracture_toughness 7.3.2014

  45. Electrical properties of ceramic • Electrical conductivity of ceramics varies with • The Frequency of field applied effect • charge transport mechanisms are frequency dependent. • The temperature effect • The activation energy needed for charge migration is achieved through thermal energy and immobile charge career becomes mobile. 7.3.2014

  46. Electrical properties of ceramic Most of ceramic materials are dielectric. (materials, having very low electric conductivity, but supporting electrostatic field). Dielectric ceramics are used for manufacturing capacitors, insulators and resistors. 7.3.2014

  47. Superconducting properties Despite of very low electrical conductivity of most of the ceramic materials, there are ceramics, possessing superconductivity properties (near-to-zero electric resistivity). Lanthanum (yttrium)-barium-copper oxide ceramic may be superconducting at temperature as high as 138 K. This critical temperature is much higher, than superconductivity critical temperature of other superconductors (up to 30 K). The critical temperature is also higher than boiling point of liquid Nitrogen (77.4 K), which is very important for practical application of superconducting ceramics, since liquid nitrogen is relatively low cost material. 7.3.2014

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  49. Preparation of Raw Materials Crushing & Grinding(to get ready ceramic powder for shaping) 7.3.2014

  50. Powder processing • Ceramic powder is converted into a useful shape at this step. • Processing techniques • Tape casting • Slip casting • Injection molding http://janereynoldsceramics.co.uk/images/ceramic1.jpg 7.3.2014

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