MSE 102 MATERIALS SCIENCE AND ENGINEERING ORIENTATION

Transcription

1 MSE 102 MATERIALS SCIENCE AND ENGINEERING ORIENTATION Ceramics and Glasses Materials Science and Engineering Çankaya University

2 Previous Lecture Processing single crystal polycrystal: low porosity polycrystal: high porosity Structure Properties Performance Three disk specimens of aluminum oxide 2

3 Classification of Materials Based on Structure Crystalline Amorphous (non crystalline) Particles are in highly ordered arrangement. 3

4 Classification of Materials Metals and Alloys: Strong, ductile High thermal & electrical conductivity Opaque, reflective. Polymers/plastics: Covalent bonding à sharing of e s Soft, ductile, low strength, low density Thermal & electrical insulators Optically translucent or transparent. Ceramics and glases: ionic bonding (refractory) compounds of metallic & non-metallic elements (oxides, carbides, nitrides, sulfides) Brittle, glassy, elastic Non-conducting (insulators) 4

5 Classification of Materials Composite Materials Formed from two or more materials, producing properties not found in any single material. Consists of a filler material and a binding material Materials only bond, will not dissolve in each other. Mainly two types :- Fibrous: Fibers in a matrix Particulate: Particles in a matrix Matrix can be metals, ceramic or polymer Properties: Examples : Fiber Glass ( Reinforcing material in a polyester or epoxy matrix) Concrete ( Gravels or steel rods reinforced in cement and sand) Applications:- Aircraft wings and engine, construction.

6 Advanced Materials Materials that are unlized in high- technology (or high- tech) applicanons Semiconductors Smart Materials Biomaterials Nanomaterials Magnetic Materials Electronic materials Optical

7 Classification of Materials Metals and Alloys: Strong, ductile High thermal & electrical conductivity Opaque, reflective. Polymers/plastics: Covalent bonding à sharing of e s Soft, ductile, low strength, low density Thermal & electrical insulators Optically translucent or transparent. Ceramics and glases: ionic bonding (refractory) compounds of metallic & non-metallic elements (oxides, carbides, nitrides, sulfides) Brittle, glassy, elastic Non-conducting (insulators) 7

8 Classification of Materials Ceramics Inorganic crystalline materials Compounds between metallic and nonmetallic elements (combinations of metals with oxygen, nitrogen, carbon or boron) (oxides, nitrides, carbides, borides) CaO, Al 2 O 3, BN, SiC, TiB 2 Properties: Strong and hard but also very brittle, Highly susceptible to fracture. Have exceptional strength under compression Insulators of heat and electricity due to presence of porosity. Resistant to high temperature and harsh environments. Traditional ceramics Bricks, pouery, bathroom sinks, porcelain Advanced ceramics Structural: bioceramics, cuwng tools, engine components, armour. Electrical: Capacitors, insulators, magnets and superconductors SiC body armour Cutting tools

9 Structure of Ceramic Materials Bonding: -- Mostly ionic, some covalent. -- % ionic character increases with difference in electronegativity. Large vs small ionic bond character: Ceramic Bonding CaF 2 : large SiC: small Adapted from Fig. 2.7, Callister 7e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University. 9

10 Structure of Ceramic Materials Ceramic Bonding - Possess a covalent network structure, ionic bonding or some combination of two. - Atomic bonding is predominantly ionic, - Crystal structure can be thought as composed of electrically charged ions instead atoms - The metallic ions, or canons, are posinvely charged, the nonmetallic ions, or anions, are neganvely charged. - Two characterisncs of the component ions in crystalline ceramic materials influence the crystal structure: the magnitude of the electrical charge on each of the component ions, and the rela7ve sizes of the ca7ons and anions.

11 Structure of Ceramic Materials Ceramic Bonding - Stable ceramic crystal structures form when those anions surrounding a canon are all in contact with that canon Stable and unstable anion canon coordinanon configuranons. Red circles represent anions; blue circles denote canons.

12 Structure of Ceramic Materials Basic Categories of Ceramics 1. Crystalline Ceramics: Prepared in two ways: either produced in the desired shape by in situ reaction, or by "forming" powders into the desired shape, and then sintering to form a solid body. Particles are in highly ordered arrangement. 2. Non-crystalline ceramics (Glasses): Glass is an amorphous material, derived from a molten liquid. Lack of long-range order.

13 Structure of Glass Basic Unit: 4- Si0 4 tetrahedron Si 4+ O 2 - Glass is amorphous Amorphous structure occurs by adding impurities (Na +,Mg 2+,Ca 2+, Al 3+ ) Impurities: interfere with formation of crystalline structure. Quartz is crystalline SiO2: Na + Si 4+ O 2 - Lack of long-range order. (soda glass) Adapted from Fig , Callister, 7e.

14 Structure of Glass Specific volume (1/ρ) vs Temperature (T): Specific volume Supercooled Liquid Liquid (disordered) Crystalline materials: -- crystallize at melting temp, Tm -- have abrupt change in spec. vol. at Tm Glass (amorphous solid) Crystalline (i.e., ordered) T g T m solid T Glasses: -- do not crystallize -- change in slope in spec. vol. curve at glass transition temperature, Tg -- transparent - no crystals to scatter light Adapted from Fig. 13.6, Callister, 7e.

15 Ceramic Materials Taxonomy of Ceramics Glasses Clay products Refractories Abrasives Cements Advanced ceramics -optical - composite reinforce - containers/ household -whiteware - bricks -bricks for high T (furnaces) -sandpaper - cutting - polishing -composites - structural engine - rotors - valves - bearings -sensors Adapted from Fig and discussion in Section , Callister 7e.

16 Ceramic Materials Basic Categories of Ceramics Traditional Ceramics - Raw materials include clay minerals such as kaolinite, alumina - Based on mineral silicates, silica and mineral oxides - Products include bricks, tableware, toilets, bathroom sinks, refractories (heat resistant material), and abrasives.

17 Glasses Ceramic Materials Basic Categories of Ceramics - A familiar group of ceramics; containers, lenses, and fiberglass rep- resent typical applicanons. - Noncrystalline silicates containing other oxides, notably CaO, Na2O, K2O, and Al2O3, which influence the glass propernes. - OpNcal transparency and the relanve ease with which they may be fabricated.

18 Ceramic Materials Silica (SiO 2 ) The most widely used ceramic material. Essential ingredient in glasses and many glassceramics. Low in cost. Used in thermal insulation, refractories, as fiberreinforced composites and laboratory glassware.

19 Ceramic Materials Glasses Compositions and Characteristics of Some of the Common Commercial Glasses

20 Ceramic Materials Glass Ceramics - Transformation from a noncrystalline state to a crystalline one by the proper high-temperature heat treatment. This process is called crystallization. - The product is a fine-grained polycrystalline material which is often called a glass ceramic. - Formation by a a phase transformation, which involves nucleation and growth stages. A glass- ceramic cooktop - Are manufactured commercially under the trade names of PyroceramTM, CorningwareTM, CercorTM, and VisionTM.

21 Ceramic Materials Glass Ceramics - RelaNvely high mechanical strengths - Low coefficients of thermal expansion (to avoid thermal shock) - RelaNvely high temperature capabilines; - Good dielectric propernes (for electronic packaging applicanons); - Good biological companbility. - Some glass ceramics may be made opncally transparent; others are opaque. - Most common uses for these materials are as ovenware, tableware, oven windows, and rangetops primarily because of their strength and excellent resistance to thermal shock. - They also serve as electrical insulators and as substrates for printed circuit boards, and are used for architectural cladding, and for heat exchangers and regenerators.

22 Ceramic Materials Clay Products - One of the most widely used ceramic raw materials - Low in cost - Naturally occurred in great abundance - Structural clay products: Building bricks, tiles, and sewer pipes - Whiteware ceramics become white after the high-temperature firing. Products are porcelain, pottery, tableware, china, and plumbing fixtures (sanitary ware).

23 Ceramic Materials Refractories - Withstand high temperatures without melting or decomposing, - Withstand severe environments. - Thermal insulator - Bricks are the most common refractory materials - Typical applications include furnace linings for metal refining, glass manufacturing, metallurgical heat treatment, and power generation.

24 Ceramic Materials Refractories - Porosity is one microstructural variable that must be controlled to produce a suitable refractory brick. - Strength, load-bearing capacity, and resistance to attack by corrosive materials all increase with porosity reduction.

25 Diamonds are utilized as abrasives; but they are relatively expensive. Silicon car- bide, tungsten carbide (WC), aluminum oxide and silica sand are typically used as abrasives. Ceramic Materials Abrasives - Abrasive ceramics are used to wear, grind, or cut away other material, which necessarily is softer. - Therefore, hardness or wear resistance; a high degree of toughness is significant for them for abrasive particles do not easily fracture.

26 Ceramic Materials Cements - Produced in extremely large quannnes. - When mixed with water, they form a paste that subsequently sets and hardens

27 Ceramic Materials Basic Categories of Ceramics Advanced Ceramics - Materials made by refining naturally occurring ceramics and by other special processes. - Used in substrates that house computer chips, sensors an actuators, capacitors, wireless communications, spark plugs, inductors, electrical insulation. - Tiles for space shuttle, barrier coatings in turbine engines, oxygen sensors used in cars. - Medicine, electrical and electronics industries. SiC body armour Cutting tools

28 ApplicaNons: Advanced Ceramics Heat Engines Advantages: Run at higher temperature Excellent wear & corrosion resistance Low fricnonal losses Ability to operate without a cooling system Low density Disadvantages: Brittle Too easy to have voidsweaken the engine Difficult to machine Possible parts engine block, piston coatings, jet engines Ex: Si 3 N 4, SiC, & ZrO 2 28

29 ApplicaNons: Advanced Ceramics Ceramic Armor Al 2 O 3, B 4 C, SiC & TiB 2 Extremely hard materials shauer the incoming projecnle energy absorbent material underneath 29

30 ApplicaNons: Advanced Ceramics Electronic Packaging Chosen to securely hold microelectronics & provide heat transfer Must match the thermal expansion coefficient of the microelectronic chip & the electronic packaging material. AddiNonal requirements include: good heat transfer coefficient poor electrical conducnvity Materials currently used include: Boron nitride (BN) Silicon Carbide (SiC) Aluminum nitride (AlN) thermal conducnvity 10x that for Alumina good expansion match with Si 30

31 Ceramic Materials Basic Categories of Ceramics Alumina (Al 2 O 3 _Aluminum oxide) - is used to contain molten metal or in applications where a materials must operate at high temperatures with high strength. Insulators in spark plugs, in dental and medical use, for making lasers, as catalyst supports.

32 Related to Ceramic Materials Carbon Exists in various polymorphic forms, as well as in the amorphous state. This group of materials does not really fall within any one of the tradinonal metal, ceramic, polymer classificanon schemes. Graphite, one of the polymorphic forms, is somenmes classified as a ceramic, and, in addinon, the crystal structure of diamond, another poly- morph, is similar to that of zinc blende

33 Elements of Ceramic Materials Carbon Forms: Diamond Carbon black amorphous surface area ca m 2 /g Diamond tetrahedral carbon hard no good slip planes briule can cut it large diamonds jewelry small diamonds oken man made - used for cuwng tools and polishing diamond films hard surface coat tools, medical devices, etc. Adapted from Fig , Callister 7e.

34 Elements of Ceramic Materials Carbon Forms - Graphite layer structure aromanc layers Adapted from Fig , Callister 7e. weak van der Waal s forces between layers planes slide easily, good lubricant

35 Elements of Ceramic Materials Carbon Forms Fullerenes and Nanotubes Fullerenes or carbon nanotubes wrap the graphite sheet by curving into ball or tube Buckminister fullerenes Like a soccer ball C 60 - also C 70 + others Adapted from Figs & 12.19, Callister 7e.

36 Properties of Ceramics Due to their crystalline structure and chemical composinon. Mechanical propernes Electrical propernes - Semiconductors - SuperconducNvity - Ferroelectricity and supersets - PosiNve thermal coefficient OpNcal propernes

37 Mechanical Properties of Ceramic Materials - Important in structural and building materials as well as textile fabrics Strong and hard but also very brittle (problems in processing and performance) Highly susceptible to fracture. Have exceptional strength under compression CuWng disks made of SiC The Porsche Carrera GT's carbon- ceramic (silicon carbide) disc brake

38 Electrical Properties of Ceramic Materials Some ceramics are semicondctors. Most of them are transinon metal oxides such as zinc oxide. Under some condinons, such as extremely low temperature, some ceramics exhibit high temperature superconducnvity. The Meissner effect demonstrated by levita5ng a magnet above a cuprate superconductor, which is cooled by liquid nitrogen

39 Properties of Ceramic Materials Insulators of heat and electricity due to presence of porosity. Resistant to high temperature and harsh environments. - Can withstand very high temperatures (from 1000 C to 1600 C) - Can withstanding erosion from the acid and bases applied to it. Some ceramics are translucent, window glass (silica+).

40 Sources 1. Textbook: CHEMISTRY: The Central Science, 9 th edinon, Some of the images were taken from textbook, Wikipedia and Google. 3. Materials Science and Engineering, W. FD. Callister, D. G. Rethwisch, 8 th edinon,