Ceramics

This page is intended to supplement the notes on ceramics technology for students in ITDPT 203, Material Processing, at Ball State University. It is designed to be viewed and projected at 640 x 480 pixels, allowing switching between text and graphics.

Disclaimer: The information on this page comes primarily from Modern Industrial Ceramics by Eugene Stafford and Engineering Materials Technology by James Jacobs and Thomas Kilduff. Send comments to Jim Flowers.

How many ceramic materials can you see on the BSU Fine Arts building?
 


Introduction

  • Ceramic Raw Materials
  • Crushed & Broken Stones
  • Dimension Stones
  • Gem Stones
  • Abrasives
  • Refractories
  • Gypsum & Plaster
  • Lime
  • Portland Cement & Concrete
  • Clay
  • Glaze
  • Porcelain Enamel
  • Glass
  • Some people use "ceramics" to refer to only clay. "Ceramics" is defined by Stafford (1980) and others as: "earthy, inorganic, non-metallic materials, usually subjected to heat in their formation process.”

    There are different ways to dissect the study of ceramics into major areas. The list at the left is based on Stafford's work, and each term is linked to a distinct area in this document.

    There are other ways to define the areas of ceramics. For example, consider distinguishing between artistic and technical ceramics.


    For an introduction, look through Greg Geiger's Introduction to Ceramics.


    If you are curious about current research in industrial ceramic technology, look at the table of contents and read an article from the current issue of the Journal of the American Ceramic Society.


    Ceramic Raw Materials

    Geologists tell us that rocks are constantly being formed, and they are also being destroyed. They use an illustration of "The Rock Cycle" to show the relationship among igneous, sedimentary and metamorphic rocks.

    Types of Rocks

    Igneous
    (formed from cooling lava and magma)
     e.g., basalt, granite, obsidian, pumice

     Sedimentary
    (formed from particles that bond)
     e.g., sandstone, limestone, shale

     Metamorphic
    (changed with time, pressure, heat, minerals)
     e.g., marble, slate

    In case you are interested in identifying rocks, there is an online guide to identifying rocks in thin section, a list of online illustrations of selected rocks and minerals, and various online guides to mineral identification. One aid is by examining the Moh's hardness of a rock.

    Illustration of the Rock Cycle by Michael J. Soreghan
    The rock cycle (from Michael J. Soreghan)
    http://faculty-staff.ou.edu/S/Michael.J.Soreghan-1/rock_cycle/rocksintro.html


    Procurement

    The ancient pyramids were the product of a massive dimension stone mining operation. Today, miners face many of the same challenges.

    Before a site can be mined, geologists and others use sophisticated prospecting technology to locate the deposit. A decision then has to be made whether to pursue mining the deposit. A number of factors should be considered, including cost, permits, environmental impact, social impact, and transportation.

    After prospecting, legal, and financial concerns, the site must be developed. Roads and drainage are usually of prime concern.

    "Winning" refers to actually removing the material from the ground. Most stone mines are open pits. Sometimes these are left untouched after mining; but other times, according to regulations and permit stipulations, miners are required to refill the mines, keeping the precious topsoil for the top layer.

    Sometimes there are other deposits above the deposit to be mined. These are referred to as overburden.

    Rockville Crushed Stone Quarry
    The Rockville Crushed Stone Quarry
    http://www.quirksworld.com/mm-marapr97.html

    Crushed Stone
    Crushed Stone
    http://www.sfmining.com/gray_crushed_stone.htm


    Crushed and Broken Stone

    After stone is broken from its deposit, it can be prepared for use as gravel, coarse aggregate for concrete, or other purposes. These process of "make the material better" has sometimes been called "beneficiation." It often includes comminution (reducing particle size), separation, and classification (determining grade or quality.)

    A variety of machines may be used to crush stone, either through compression, impact, or abrasion. These include jaw crushers, hammer mills, and ball mills.

    Typically, the stones are washed. Next, they are separated according to size by using a series of successively finer screens. Specialized equipment combines multiple functions, as illustrated to the right.

    One of the scales used to describe particle size (mostly for sedimentary rocks) is the Wentworth scale shown below. However, it is confusing because it uses the terms "sand" and "clay" to refer to size regardless of the mineral.

     

    Telsmith 36J/G-CC Portable Plant
    Telsmith 36J/G-CC Portable Plant
    http://www.telsmith.com/Equipment/


    PEP Screen Portable Tower Structure
    Lab Hammer Mill
    http://www.interquip.com.au/for_sale.htm

    Large Ball Mill
    Ball Mill
    http://www.usstoneware.com/ball.html


    Particle Size Classifications
    http://www.science.ubc.ca/~geol202/sed/sili/siligsize.html


    Dimension Stone

    Dimension stones are cut into regular shapes, often rectangular prisms. They are used for flooring, siding, countertops, grave monuments, and other structural and decorative purposes.

    Stones are sawn into standard geometric shapes (usually rectangular prisms), often with diamond saws. Water is used as a coolant and to carry away dust.

    Polishing is a critical phase of dimension stone processing. Using successively finer abrasive grits can produce smooth surfaces.

    hhhh


    Woodkirk Sandstone
    Woodkirk Sandstone
    http://www.londonuniversal.com/sandstone2.html


    Gem Stones

    Special Qualities
      Beauty
      Durability or hardness
      Rarity (or apparent rarity)


    Types
      Precious
       e.g., diamond, ruby, sapphire, emerald
      Semiprecious
       e.g., garnet, opal, quartz, turquoise
      “Organic”
       e.g., pearl, coral, amber
    Mining Aquamarine in Zambia
    Mining Aquamarine in Zambia
    http://www.africagems.com/safari/mining1.html


    Abrasives

     An abrasive is a material that can wear away another material if the two are moved against each other with the appropriate pressure, direction and speed.

    Special Properties:
     1. Hardness
     2. Toughness
     3. Friability (Ability to be crumbled)
     4. Fracture (Edges produced)

     Grit: "the size of the abrasive particle or the mesh number.  This is the number of holes per linear inch in a sieve" (Stafford, 1980).


    Types of Abrasives:
     1. Loose
       A. Transformation involves only beneficiation.

     2. Coated
       A. Backing Materials:
       1. Paper
       2. Cloth
       3. Fiber
       4. Other
      B. Adhesives
      C. Open Coat: Backing not completely covered with abrasive.
      D. Closed Coat: Backing completely covered with abrasive.
      E. Use (tearing trick)

     3. Bonded
       A. Vitreous Bonded (wheels and slip stones)
       B. Nonvitreous Bonded (wheels and discs)


    Grain: "the type of abrasive material."

    Natural Abrasive Grains
     Flint: SiO2
     Garnet: 3FeO·Al2O3·SiO2[approx.]
     Emery: Al2O3
     Corundum: Al2O3
     Diamond: C
     Pumice: (Lava)
     Rottenstone: CaCO3
     Tripoli: CaCO3
     Tin oxide: SnO2
     Cerium oxide: CeO2

    Synthetic Abrasive Grains
     Silicon carbide: SiC
     Aluminum oxide: Al2O3
     Crocus: FeO
     Rouge: FeO
     Diamond: C

     Silicon carbide (SiC) was developed by Dr. Edward G. Acheson in 1891.
     SiO2 + 3C ==> SiC + 2CO

    Silicon carbide
    Silicon Carbide
    http://www.pan-abrasives.com.sg/english/products/abrasives/carbide.html

    Coated Abrasives
    Coated Abrasives from Hermes
    http://www.hermesabrasives.com/

    Bonded Abrasives
    Bonded Abrasives from Hermes
    http://www.hermesabrasives.com/



    Coated Abrasives from Production Pruducts, Inc.
    http://www.productionproducts.com/prod_abrasives.htm


    Refractories

    In "An Introduction to Industrial Refractories," George Anderson (1998) defines refractories as "non-metallic materials capable of maintaining physical and chemical stability at high temperatures." 

    Refractoriness = “the ability of a material to withstand high temperatures: 1482°C (2700°F) or higher.” (Stafford, 1980, p.65.)

    Fire bricks and other refractories are used to line kilns and ovens, and as crucibles and other products requiring resistance to high temperatures.

    Most refractories are composed of clay with a higher concentration of alumina and silica.
     

    Furnace Refactory from Parkinson-Spencer
    Furnace Refractory from Parkinson-Spencer
    http://www.parkinson-spencer.co.uk/refractories/furnace.html
    Small, Cast Refractories
    Shaped Refractories
    http://www.refractaria.com/ingles/producto.htm


    Gypsum & Plaster

     Rock Gypsum: a soft, white sedimentary rock of hydrous calcium sulfate:

     CaSO4·2H20

    Calcining is the heating of gypsum (or another material), but not to the point of fusion, to drive off some or all of the chemically combined water.

    By calcining rock gypsum, plaster is produced (CaSO4). (Actually 3/4 of the water is typically driven off.)

    Powdered plaster can then be recombined with water to produce a solid material of a specified shape.  Heat is given off as plaster is rehydrated.


    US Deposits of Rock Gypsum
      1. TX, North to MI and East to NY.
      2. CA to NV, UT and MT.


    Gypsum Procurement:
     1. Prospecting
     2. Developing
     3. Winning


    Transformation:
      1. Beneficiation
       A. Comminution
       B. Classification
       C. Separation
     2. Calcining
     3. Rehydration (casting or molding)

    Read an overview of plaster mixing procedures.


    Utilization:
     1. Rock gypsum is used in peanut plants and mushroom beds.
     2. There are many powdered plasters, such as plaster of Paris and Keene cement.
     3. Plaster is used to manufacture aspirin, chalk, matches and toothpaste. United States Gypsum claims that the average person eats 28 pounds of gypsum in their life (but don't try this all at once.)
     4. The major use of plaster is in plasterboard. You can view an online animation of wallboard manufacture.
     5. Wet wall plaster was once more popular.


    Disposition:
     1. Reuse: if undamaged.
     2. Recycle: Some damaged products are repaired.  Recalcining is possible, but rare.
     3. Discarding (storage): usually as hard land fill.

    A Gypsum Mine
    A Gypsum Mine
    http://www.nra.gov.jo/nonmetalic/gypsum.htm

    Rock Gypsum
    Rock Gypsum
    http://www.yoshino-gypsum.com/gypsum-e.htm


    USG's Duramold Pottery Plaster
    Picture of Drywall
    http://outten.net/woodridge/20010813/pages/Hw_drywall.htm

    Plaster Casting
    Plaster Casting
    http://www.opcmia.org/union_profile.htm


    Lime

    Types
     1. Agricultural lime
      Calcium carbonate: CaCO3

     2. Quicklime (burnt lime; caustic lime)
      Calcium oxide: CaO
    (Check out an MSDS on CaO.)

     3. Slaked lime (builder's lime; hydrated lime)
      Calcium hydroxide: Ca(OH)2
    (Harry Francis contends that agricultural lime is ground limestone, and therefore not a type of lime. Visit his page of Definitions of Common Lime Terminology.)


    Procurement of Lime:
      Many raw materials (e.g., dolomite, limestone, calcite, marble).
     Primarily, calcium carbonate.

     1. Prospecting
     2. Developing
     3. Winning
      A. Superficial or open pit
      B. Subterranean
      C. Subaqueous


    Transformation of Lime
     1. Beneficiation
      A. Comminution
      B. Separation
      C. Classification
      (Agricultural lime produced)

     2. Calcining
      2500oF (1371oC)
      CaCO3 ==> CaO + CO2
      (Quicklime produced)

     3.  Slaking: allowing a material to hydrate or take on water at its own rate.
      CaO + H2O ==> Ca(OH)2 + heat
      (Slaked lime produced)


    Utilization of Lime
    1. Calcium carbonate's uses:
     A. Soil improvement, fertilizer
     B. Clay pigeons
     C. Flux in clay bodies
      D. Input in the manufacture. of calcium oxide.

    2. Calcium oxide's uses:
     A. Flux for iron and steel
     B. Waste and sewage treatment
     C. Manufacture. of calcium carbide (for acetylene)
     D. Manufacture of calcium hydroxide.

    3. Calcium hydroxide's uses:
     A. Water treatment
     B. Mortar
     C. Bleaching and cleansing agents.


    Disposition of Lime Products:
     Usually discarding
     Rarely a problem.


    Mining Limestone
    http://www.linwood-mining.com/mine.html



    Screening Limestone
    http://www.linwood-mining.com/mine.html


    Bag of lime
    Mason/Plaster Type S Lime from US Mix
    http://www.usmix.com/distributed.html


    Lime aids in subgrade stabilization.
    Laying block with mortar containing builder's lime
    http://www.wacohs.com/waco-web/Masonry.htm


    Portland Cement and Concrete

    1. Who invented Portland Cement?
    2. When was it invented?
    3. What are the basic components of PC?
    4. What is a clinker?
    5. Why is gypsum added?
    6. What are the differences among different types of PC?
    7. What are the components of concrete?
    Cement Ingredients in a Rotary Kiln
    Cement Ingredients in a Rotary Kiln
    http://www.lonestarind.com/prodsale11.html


    Clay

    Formation: weathering of feldspar.

    Potash feldspar + water + carbon dioxide ==>
     kaolinite + quartz + potassium carbonate

    K2O·Al2O3·6SiO2 + 2H2O + CO2 ==>
     Al2O3·2SiO2·2H2O + 4SiO2 + K2CO3

    Kaolinite
      "the major clay mineral used for clay products."
      hydrous silicate of alumina
      Al2O3·2SiO2·2H2O (formula used for all clays)

    Other clay minerals exist (Nacrite, Vermiculite, etc.)

    Types of Clay
      Primary: clay found at its origin; residual clay; it tends to be white when fired.

      Colluvial: clay that "has been transported a short distance from its origin;" it tends to be white when fired.

      Secondary: clay that "has been transported a great distance from its origin;" sedimentary or transported clay; many impurities; most abundant.

    Read about how clay forms, and how clay is processed into a usable material according to the China Clay Producers 


    Properties of Clay
      Solid particles
      Plasticity
      Porosity
      (Plastic clay that lacks enough water to be formed is termed "short" and will develop cracks when deformed.)
      Shrinkage upon drying

    Drying stages
      Plastic
      Leatherhard
      Bone dry

    Firing Clay
     Shrinkage
      Vitrification: formation of a glassy bond.
      Bisque firing (no glaze)
      Glaze firing
      Look at the cone chart for firing temperatures.

     Properties of fired clay
      "Water absorption is a measure of vitrification." (varies proportionally)
      Hardness increases with vitrification.  "The higher the firing temperature, the harder the clay."
      Color is now permanent.

    Read about historic brickmaking, and bricks.
     

    Overburden Above Clay Deposit
    Illustration from the China Clay Producers Association
    http://www.kaolin.com/geology/index.htm

    Large Rotary Vacuum Filter
    Large Rotary Vacuum Filter
    http://www.kaolin.com/ccpmin.htm

    Slaking Clay
    Slaking Clay
    http://www.glendale.cc.ca.us/~rkibler/clay.html

    Extrusion of bricks.
    Read about Throwing Pots
    http://potteryguide.com/throw1.htm

    Vitrified Clay Pipes
    Clay Pipes
    http://www3.jaring.my/gbhgroup/vcp/vcp1.htm

    Bricks
    Bricks
    http://www.spec-net.com.au/bowralbricks/short.htm


    Glaze

    "a glassy coating fired onto clay products."

    Why glaze?
     Hard surface.
     Non-absorbent.
     Easily cleaned.
     Decorative.
     Other.

    Glaze Components:
      1. Glass former, cullet and frits
      2. Flux
      3. Stiffener
      4. Opacifier
      5. Matting agent (reduces glossiness)
      6. Colorant
      7. Binder (help keeps glaze in suspension)
      8. Other

    Glaze Application Methods:
      1. Dipping
      2. Pouring
      3. Brushing (rec.: 3 coats)
      4. Spraying (rec.: 6 coats)
      5. Other

    Typical Steps in Glazing:
      1. Prepare glaze.
      2. Dampen piece to remove dust.
      3. Apply glaze.
      4. Allow glaze to dry.
      5. Carefully stack in kiln with stilts.
      6. Glaze fire.
      7. Remove stilt marks.

    There is an instructional web site on glaze technology.


    Glazing Hints:
      1. "Use less glaze on the bottom third of the pieces."

      2. "You can lightly rub a dry glaze to remove the lumps, pinholes, or other blemishes.  Allow the glaze dust to remain on the piece."

      3. "Melted paraffin was or wax resist can be applied to the foot of a piece.  This prevents glaze from adhering.  The was will burn off in firing, leafing a piece with a dry foot."  Do not glaze the foot!

      4. "The color of a liquid glaze seldom resembles its fired color."

    Glazing looks like fun.
    Glazing looks like fun.
    http://www.potterville.com/glazeapot.htm

    Glazing Tile
    Applying Glaze to Tile
    http://www.terraglaze.com/html/factory_factory.html

    Oxblood Glaze
    Oxblood Glaze
    http://members.tripod.com/~andavall/CopperRed.html


    Porcelain Enamel

    a glassy coating fired onto glass and metal products.

    Typical Firing Temperatures:
     On Aluminum and Glass: 1000oF (538oC)
     On Copper and Silver: 1550oF (843oC)

    Typical Copper Enameling Procedure:
      1. Shape metal.
      2. Clean metal.
      3. Apply protective coating to back.
      4. Dry.
      5. Apply frit to face.
      6. Fire.
      7. Cool.
      8. Clean back.
      9. Apply frit to back.
      10. Fire
      11. Cool.

    Enameling Powders or Frits
    Enameling Powders or Frits
    http://www.enamelingsupplies.com/

    Small Electric Enameling Kiln
    Electric Enameling Kiln
    http://www.7ceramic.com/NYCBDOFED.htm

    Enameled Cast Iron Cookware
    Enameled Cookware
    http://www.theagashop.com/html/cast_iron_cookware.htm


    Glass 

    "an inorganic product of fusion which has cooled to a rigid condition without crystallizing." (ASTM)

     Non-crystalline (amorphous) if cooled quickly

    Super-cooled liquid ==> always flowing

    Rigid, vitreous bond

     Nearly perfectly elastic (i.e., no plastic range)
      ==> do not use Rockwell hardness tests

    Fracture characteristics

    Amorphous usually means without a shape or form, but material scientists use it to mean non-crystalline.

    “Amorphous materials do not have clearly defined freezing or melting points.”

    Devitrification
     Some crystals
     Slow cooling
     “Glass ceramics”

    Read an introduction to glass, A Brief History of Glass, Fashioning Glass, Part I, and a very informative web site on Making Glass.


    Raw Materials:

      1. Glass Former: the primary material.  (e.g., silicon dioxide {SiO2; silica},  melts at about 3110oF {1710oC})

      2. Flux: lowers melting temp. (e.g., sodium carbonate, calcium carbonate)

      3. Decolorizer: complements or neutralizes the green tint from iron oxide impurities. (e.g., manganese dioxide)

      4. Colorant: imparts color. (e.g., metal oxides or carbonates).
      Cobalt carbonate ==> blue
      Iron oxide ==> green
      Manganese dioxide ==> purple.

      5. Firing agent: helps gather and expel gas bubbles from molten glass. (e.g., potassium nitrate and arsenic compounds)

      6. Strengthener/Stiffener: increase strength or stiffness. (e.g., aluminum oxide).

      7. Brightener: increase transparency. (e.g., barium carbonate and lead compounds).

      8. Opacifier: reduces transparency. (e.g., zirconium, tin oxide, phosphorus and antimony compounds).

      9. Other.

    Synthetic Materials
      1. Cullet: "waste glass, rejects and recycled glass products."  Cullet speeds melting.

      2. Other.


    Types of Glass
     1. Natural Glasses (e.g., obsidian, fulgurites, teletites).

    2. Synthetic Glasses
      A. Soda Lime
       1. Made from silica, soda ash and limestone.
      2. Least expensive.
      3. Most common (>90% of all glass).
      4. 4000 years old.
       5. Soft and easy to form.
       6. Susceptible to thermal shock and splintering.
       7. Used for bottles and windows.

      B. Lead Alkali
       1. Made from silica, soda ash, litharge, pearl ash, soda niter and feldspar.
       2. Clear, brilliant and electrically resistant.
       3. Soft.
       4. Susceptible to thermal shock.
       5. Used for crystal glassware and eye glasses.

      C. Borosilicate
       1. Made from silica, boric acid, borax and alumina.
       2. Hard and relatively resistant to temperature change, acid and electricity.
       3. Used for oven ware and laboratory glassware.

      D. 96% Silica
       1. Made from silica and borax.
       2. Hard and highly resistant to temperature change, acid and electricity.
       3. High UV transmission.
       4. Used for chemical ware and sun lamps.

      E. Fused Silica
       1. Made from pure silica.
       2. Most costly.
       3. Most heat resistant.
       4. Hard and very corrosion resistant.
       5. Used for aircraft cameras and astronomical telescopes.

      F. Aluminosilicate
       1. Made from silica, alumina, borax, boric acid, limestone and magnesium oxide.
       2. Extremely hard.
       3. Extremely heat resistant.
       4. Used for top-of-stove ware and high temperature thermometers.

    There are many specialty glasses.


    Glass Fibers

    Cellular Glass

     Glass Ceramics: "materials which have been converted from their original glassy state to crystalline ceramics by a process of controlled nucleation."

     "Most glass-ceramics are opaque and stronger than glass."

     "Pyroceram" by Corning.

    Processing Glass
     Melting the Glass Batch
     Hand Forming
     Machine Forming
      Pressing
      Blowing (gob)
      Drawing
      Rolling
      Floating
      Other
     Glass "Finishing"
      Thermal (Lehr)
      Chemical
      Mechanical

     Annealing: the slow cooling of glass to provide "homogeneous structure by reducing internal stresses to give isotropic (equal in all directions) properties."

     Tempering: "rapid cooling of the outer surface of glass while still in the plastic state."
      => surface in compression
      => different fracture characteristics

    Devitrification

    Obsidian, a natural glass
    Obsidian, a Natural Glass
    http://www.oakland.edu/~aszanoni/docs/gallery/geo/geo2.htm

    Continuous Glass Fiber Forming Machine
    Continuous Glass Fiber Forming Machine
    http://www.inglen.com/tech/fiber.htm

    Guardian Fiberglass (loose)
    Fiberglass Insulation
    http://guardianfiberglass.com/

    Micrograph of Glass Fracture Surface
    Micrograph of a Glass Fracture Surface
    http://www.cs.alfred.edu/~maurojc/papers/microscopy/labreport2/index.html
    Cutting Glass
    Cutting Glass
    http://members.tripod.com/GILRAPHAL/Mechanik/Bohle/silberschnitt_2000.htm
    A Glass Blower
    A Glass Blower
    http://www.planetlighting.com.au/noframes_site/glassworks.htm
    $4500 Lampworked borosilicate glass, blown, sculpted, sandblasted, oil-painted
    Borosilicate Glass: Organism Series
    Sirius Blue, 1998

    http://www.mickelsenstudios.com/catalog/sirius_blue.htm
    Precisely Machined Glass
    Precisely Machined Glass
    http://www.louwers.nl/welcome2.htm

    CERAN Glass Ceramic Cooking Surface
    CERAN® Glass Ceramic Cooking Surface
    http://www.schott.de/english/ceran/vielfalt.htm?e=J&keinframe=Y
    The glass is transparent.The glass is opaque.
    “Privalite turns opaque by electrical control"
    http://members.tripod.com/GILRAPHAL/sri_eng.htm