Ceramics Advanced material and technologies MSc 2017 1

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Ceramics Advanced material and technologies, MSc 2017 1

Ceramics Advanced material and technologies, MSc 2017 1

1. Ceramics The role and perspectives of ceramics in engineering The chemical bonding of

1. Ceramics The role and perspectives of ceramics in engineering The chemical bonding of some elements of the earth's crust is such that it is considered as a ceramic compound. Ceramic systems: crystalline, inorganic, non-metallic material. Advanced technical ceramics used by engineering practice are highly transformed materials. 2

1. Ceramics: the origin of the word: keramos potter's earth (soil) Ancient occupation: potteries,

1. Ceramics: the origin of the word: keramos potter's earth (soil) Ancient occupation: potteries, stonewares later: porcelain glassware, building materials refractory materials so-called traditional ceramics Today in technical applications: • advanced technical ceramics • structural ceramics • high performance ceramics 3

1. Ceramics Comparison of main properties of ceramics and metals Property Advanced ceramics Metals

1. Ceramics Comparison of main properties of ceramics and metals Property Advanced ceramics Metals Ceramic/metal rate of property value Ductility Very low High (0, 001 -0, 01): 1 Density Low High 0, 5: 1 Fracture toughness Low High (0, 0 -0, 1): 1 Hardness High Low (3 -10): 1 Expansion Low High (0, 1 -0, 3): 1 Heat conductivity Low High (0, 05 -0, 2): 1 Electrical resistivity High Low (100 -1000): 1 4

Some examples of the benefits of using ceramic parts Application Benefit Ceramic materials Uncooled,

Some examples of the benefits of using ceramic parts Application Benefit Ceramic materials Uncooled, low-power diesel engine The specific fuel consumption is reduced by 10 -15% Zr. O 2, Si 3 N 4, Si. C, Al 2 O 3, Al 2 Ti. O 5 High performance adiabatic diesel engines The specific fuel consumption is reduced by 20% Zr. O 2, Si 3 N 4, Si. C, Al 2 O 3, Al 2 Ti. O 5 Low power gas turbines for cars The specific fuel consumption is reduced by 27% Si 3 N 4, Si. C, Li-Al-silicate Recuperative furnace for rod forging Specific energy consumption decreases by 41% Si. C Machining gray cast-iron Productivity increases by 220% Si 3 N 4, SIALON Copper wire drawing Productivity increases by 200% Zr. O 2 5

Base materials of non-oxide, high-performance ceramics Fields of application Material 1. Structural ceramics 1.

Base materials of non-oxide, high-performance ceramics Fields of application Material 1. Structural ceramics 1. 1 The cutting and shaping tools of metal processing, for example inserts, threading rings, rollers, cylinders Silicon nitride Titanium carbide, Titanium nitride, Titanium boride Boron nitride, Boron carbide Diamond 1. 2 Ceramics for engines: eg. diesel glow-plug, diesel pre-chambers, turbochargers, valves Silicon nitride Silicon carbide 1. 3 Elements of metallurgy and manufacturing technology: eg. crucibles, evaporators, ball mills, heat exchangers Silicon nitride Silicon carbide Aluminum nitride Boron nitride Titanium boride 1. 4 Wear parts: eg. pump seals, rotators, sandblasters, nozzles, bulletproof vests Silicon nitride Silicon carbide Boron carbide Titanium boride Titanium carbide 6

Fields of application Material 1. 5 Precision machine parts: Silicon nitride eg. ball bearings,

Fields of application Material 1. 5 Precision machine parts: Silicon nitride eg. ball bearings, turbine blades, machine spindles, Silicon carbide fittings 2. Ceramics for electrical applications 2. 1 Substrate for integrated circuits Aluminum nitride Aluminum carbide 2. 2 Magnetic heads Silicon nitride Titanium carbide 2. 3 Sensors, ignitors Zirconium boride Titanium nitride Aluminum nitride Silicon carbide 2. 4 Resistors Titanium nitride Chromium nitride Aluminum nitride Lanthanum hexaboride 3. Special refractory materials eg. bathtub lining, taps, spray lances Boron carbide Silicon carbide Boron nitride Silicon nitride Titanium nitride 7

Ionic bond 8

Ionic bond 8

Covalent bond - Formed by pair of electrons (XA, XB ~ ≥ 2, 1),

Covalent bond - Formed by pair of electrons (XA, XB ~ ≥ 2, 1), - High binding energy (e. g. : C, Si, Ge), - Directions in bonding (pl. CH 4). Energy of molecular hydrogen referred to separated, neutral atoms. Negative energy corresponds to chemical bond. Curve A refers to electrons with parallel spin states, curve S (stabile state) refers to electrons with antiparallel spin states. 9

Types of bonding in ceramics: • ionic bonding • covalent bonding Common crystal types

Types of bonding in ceramics: • ionic bonding • covalent bonding Common crystal types in ceramics: 10

Role of polymorfic transformations in properties of ceramic systems Structural character of polymorfic transformation:

Role of polymorfic transformations in properties of ceramic systems Structural character of polymorfic transformation: - Displacive: transformation connected with atomic displacement, - Reconstructive transformation: including dissociation and reconnection of atomic bonds 11

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Microstructure of ceramics: 14

Microstructure of ceramics: 14

Mechanical properties of ceramics: 15

Mechanical properties of ceramics: 15

Mechanical properties of ceramics: Fracture toughness (KC) E: Young’s modulus GC: strain energy release

Mechanical properties of ceramics: Fracture toughness (KC) E: Young’s modulus GC: strain energy release rate (k. J/m 2) For brittle materials, Gc can be equated to the surface energy of the (two) new crack surfaces Source: Courtney, Thomas (2005). Mechanical Behavior of Materials. 16

Expansion of ceramics: 17

Expansion of ceramics: 17

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Thermal stresses These are the most important limitations of wide-ranging applications. Results: cracks, rupture

Thermal stresses These are the most important limitations of wide-ranging applications. Results: cracks, rupture Origin of stresses: thermal or chemical, the former is more important Thermal expansion and stress: σ= -E∙α∙ (T 1 -T 0) (elastic, rod shape) E: Young modulus α: linear expansion coefficient T 0: initial temperature T 1: end temperature 19

Electrical resistivity of ceramics

Electrical resistivity of ceramics

Production of ceramics Traditional ceramics, glass production Glass Typical composition (wt%) Typical uses Soda-lime

Production of ceramics Traditional ceramics, glass production Glass Typical composition (wt%) Typical uses Soda-lime glass 70 Si. O 2, 10 Ca. O, 15 Na 2 O Windows, bottles, etc. ; easily formed and shaped Borosilicate glass 80 Si. O 2, 15 B 2 O 3, 5 Na 2 O Pyrex; cooking and chemical glassware; high-temperature strength, low coefficient of expansion, good thermal shock resistance Ca. O Decrease of viscosity Na 2 O mechanism: fragmentation of Si. O 2 -chains Base of forming proc. : Q: activation energy of viskous flow Flow rate: (η)-1

The difference between glass transition and crystallization Changes in thermodynamic functions during glass transition.

The difference between glass transition and crystallization Changes in thermodynamic functions during glass transition. G 1 and G 2 are different glassy states produced at different cooling rates.

pressing rolling require higher η–t float molding die casting require lower η–t igényel blowing

pressing rolling require higher η–t float molding die casting require lower η–t igényel blowing Heat treatment: stress relaxation

Advanced technical ceramics • oxide based (Al, Zr. O 2 based) • nitride based

Advanced technical ceramics • oxide based (Al, Zr. O 2 based) • nitride based (Si 3 N 4) • carbide based (B, Si-karbid) The common types and their most important properties: Cemented carbide Sintered aluminium oxide Al 2 O 3 -Ti. C composite Sialon (Si 3 N 4) 12, 3 -15, 1 15, 3 -15, 9 17, 0 -17, 4 12, 2 -15, 2 1400 2000 3140 (Ti. C) szétesik Heat exp. coeff. (10 -6 K-1) 4, 7 -5, 2 7, 5 7, 6 3, 2 Young modulus (GPa) 520 -660 440 420 300 10002400 700 -840 840 -940 830 2, 2 -2, 5 3, 1 -3, 5 3, 6 -5, 2 3, 8 -3, 9 4, 2 -4, 3 3, 35 Hardness (GPa) Melting point (°C) Flexural strength (MPa) Fract. toughness (MN/m 3/2) Density (kg/dm 3) 12, 0 -15, 1

The manufacturing process of ceramics: 1. the production of ceramic powder raw material and

The manufacturing process of ceramics: 1. the production of ceramic powder raw material and other materials 2. the shaping of the desired workpiece 3. establish a bond between powder particles 4. finishing Synthesis of powder Make the powder ready Shaping Remove adhesive Sintering Finishing

Shaping technologies Dry pressing Uniaxial Isostatic Extrusion Casting Injection moulding

Shaping technologies Dry pressing Uniaxial Isostatic Extrusion Casting Injection moulding

Sintering

Sintering

Tsintering 2/3 Tmelting The driving force behind the sintering process is to reduce surface

Tsintering 2/3 Tmelting The driving force behind the sintering process is to reduce surface energy: For example: in the case of Al 2 O 3 powder with particle size of 1μ, the surface of 10 cm 3 material ≈ 1000 m 2, and the interfacial energy is approx. 1 k. J. The change of density as a function of time and temperature: a: particle size C: constant Q: activation energy 32

Connecting ceramics to each other and joining them to other materials: - with adhesive,

Connecting ceramics to each other and joining them to other materials: - with adhesive, - glaze bonding, - diffusion bonding, - metallisation and brazing.

The aspects of designing structural elements made of ceramics and the principles of their

The aspects of designing structural elements made of ceramics and the principles of their use Careful selection of the manufacturing technology and the raw material (taking into account the properties appropriate to the purpose, + costs). Manufacturing technology and scaling are desirable to minimize postmachining. However, post-machining (grinding, polishing, laser machining etc. can not be excluded from the technology, eg. engine or gas turbine components). Avoid point loads at applications. The stresses at the load transfer sites must be minimized by surface-like shaping. It is advisable to avoid sharp corners and large size changes. Minimize thermal stresses. Use the smallest cross section as far as possible, and divide the parts as far as possible into simpler elements. Machining sizes are necessarily larger. Shrinkage occurs during sintering.

The size of the parts must be minimized (due to the crack distribution of

The size of the parts must be minimized (due to the crack distribution of ceramics, the strength is a function of size, therefore smaller parts are more reliable). Avoid impacts (where this is not possible, design small angle impact). Machining of the parts must be careful (cracks reducing the strength of the parts arise often on the surface or near the surface during machining). Failure probability of ceramic components is proportional to the overlap of the distribution curves which represent the strength and the applied load on the part.

Due to the high melting point and the embrittlement of ceramics the socalled secondary

Due to the high melting point and the embrittlement of ceramics the socalled secondary machining is not applicable in the extent and sense as in the case of metals or metal alloys (cold or hot rolling, forging). Due to the costly mechanical machining, the workpiece needs to be manufactured in approximately the final size, therefore suitable technological processes are required. In the production of ceramics the so -called powder metallurgy plays a major role.

Ceramics in automotive industry 1. Window glass, windshield 2. Insulation element for spark plugs

Ceramics in automotive industry 1. Window glass, windshield 2. Insulation element for spark plugs 3. Carrier material in catalytic converter (development since 1970) requirements: - large surface, - temperature stability and thermal shock tolerance - resistance against weathering base material: cordierite or iolite (Mg 2 Al 4 Si 5 O 18) 4. Ceramic sensors: the most important sensors used in cars: - gas composition, - pressure, - temperature, - speed, - voltage, - ignition position.

Eg. pressure sensor: ceramic is a capacitive element, aluminum oxide base. Why it is

Eg. pressure sensor: ceramic is a capacitive element, aluminum oxide base. Why it is ceramics? → high thermal stability Piezoelectric materials: Pb-Zr titanate (dynamic pressure measurement in combustion chamber) Oxygen sensor: check O 2 --fuel ratio, material: Ti. O 2, operating principle: resistometry.