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Ceramic - Coggle Diagram

- - - - Raw materials preparation
        
        Glasses is silica, primary source is natural quartz in sand.
        
        Other components (soda ash, limestone, aluminium oxide and potash) are added in proportions to achieve the desired composition.
        
        Recycled glass is added to preserve the environment and facilitates melting.
        
        Glass melting
        
        Starting materials to be melted （charge) is charging where melting temperature for glass are around 1500 °C to 1600 °C with 24-48 hours melting cycle.
        
        The temperature at which the glass is tapped depends on the viscosity required for the shaping process.
    - - Discrete processes
        
        Pressing- production of flat products, glass formed by apply of pressure and mold is steel with graphite lining.
        
        Process (a) glass hob is fed into mold from furnace, (b) pressing into shape by plunger, and (c) plunger is retracted and finished produced is removed.
        .
        
        Press and blowing- production of width mouth containers.
        
        Process (a) molten gob is fed into mold cavity, (b) pressing to form a parison, (c) the partially formed parison, held in a neck ring is transferred to the blow mold, and (d) blown into final shape.
        .
        
        Blow and blowing- production for smaller mouth containers.
        
        Process (a) gob is fed into inverted mold cavity, (b） mold is covered, (c) first blowing step, (d) partially formed piece is reoriented and transferred to second blow mold and (e) blown to final shape.-
        .
        
        Casting-for relatively massive objects.
        
        Process (a) sufficiently fluid molten glass poured into a mold.(b) After cooling and solidifying, the piece must be finished by lapping and polishing.
      - Continuous processes
        
        -: Drawing for flat glass
        
        Rolling of flat plate-Starting glass from melting furnace is squeezed through opposing rolls whose gap determines sheet thickness, followed by grinding and polishing for parallelism and smoothness.
        
        Float process- Molten glass flows onto the surface of a molten tin bath, where it spreads evenly across the surface, achieving a uniform thickness and smoothness - no grinding or polishing is needed.
        .
        
        -: Drawing for tubular glass
        
        Danner process- Molten glass flows around a rotating hollow mandrel through which air is blown while the glass is drawn.
      - Fiber-making process
        
        Fibrous glass for thermal insulation, acoustical insulation, and air filtration, produced by centrifugal spraying. The molten glass flows into a rotating bowl with many small orifices around its peripheryl. Centrifugal force causes the glass to flow through the holes to become a fibrous glass.
        .
        
        Long continuous filaments suitable for fiber reinforced plastics, fabrics and fiber optic, produced by drawing. Continuous glass fibers of small diameter are produced by drawing strands of molten glass by gravity through small orifices in a heated plate made of a platinum alloy. As it drops, it cools and forms a thread.
    - - Principle of annealing
        
        Heating to elevated temperature and holding for a time to eliminate stresses and temperature gradients; then slow cooling to suppress stress formation, followed by more rapid cooling to room temperature.
        
        Function
        
        Removes internal stress caused by uneven cooling rate between the surface and interior regions.
      - Principle of tempering
        
        Reheating to a temperature somewhat above annealing temperature into the plastic range, followed by quenching of surfaces, usually by air jets, to create a desired stress profile within the material.
        When the surfaces cool, they contract and harden while interior is still plastic. As the internal glass cools, it contracts, putting the hard surfaces in compression.
  - - - 1. Preparation of raw material
        
        Characteristics of powders include: particle size, shape, size distribution, degree of segregation and agglomeration.
        
        Preparation of the starting powders include crushing and grinding (mechanical method) to the desired size range and chemically treating (chemical method) to separate phases and compounds and to achieve specified purity.
        
        Small and uniform in size, homogeneous particles.
      - 2. Shaping process
        
        Powder injection molding- ceramic particles are mixed with a thermoplastic polymer, then heated and injected into a mold cavity.
        .
        
        Powder pressing- used for both clay and non-clay composition. Powder compacted by pressure in a mold.
        .
        (i) Uniaxial compression- compacted in single direction. The die cavity is filled with powder, then pressure applied and the compacted piece ejected.
        (ii) Isostatic compression- pressure applied by fluid-powder in rubber envelope. Uses hydrostatic pressure to compact the ceramic powders from all directions.
        (iii) Hot pressing- pressure + heat. Carried out at elevated
        temperatures so sintering of the product is accomplished simultaneously with pressing.
        .
        
        Slip casting
        (a) Preparation of a powdered ceramic material and a liquid, slip (b) Pour the slip into mold and allowing the slip to be absorbed by the mold, solid layer is formed against the mold surface. (c) drain casting, (d) trimming and renewing mold.
        .
        
        Tape casting- Thin sheets ( form casted slip that contain ceramic, organic solvent, binders and plasticizers) of green ceramic are casted as a flexible tape. Used for integrated circuits and capacitors. Slip undergoes tape casting become dried green sheet then sintered it.
      - 3. Sintering - to produce a strong final product and reduction in surface energy
        
        Useful for both clay and non-clay compositions.
        
        During firing the formed piece shrinks, and experiences a reduction of porosity and an improvement in mechanical integrity.
        
        Stages of sintering process: (a) powder touches to form neck, (b) neck gradually thickens and (c) the grain boundary develop.
        
        Factors: composition of powders, green density, pore content and extent mixing.
      - 4. Finishing- to increase dimensional accuracy, improve surface finish and make minor changes in part geometry.
- - - - Glass - Non-crystalline, but Ceramic - Crystalline, semi- crystalline or non- crystalline.
        
        Glass - Exhibit glass transition behavior, but Ceramic - No glass transition behavior.
        
        Glass - transparent, but Ceramic - mostly opaque.
        
        Glass - can melted and remoulded, but Ceramic - cannot melted and remoulded.
        
        Glass - cheap, but Ceramic - mostly expensive.
      - Differences