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MFGT 104 Materials and Quality Ceramics and Glasses. Professor Joe Greene CSU, CHICO Add Refractory Information!!! Add tensile properties of non ferrous. MFGT 104. Chap 7: Ceramics. Objectives

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Mfgt 104 materials and quality ceramics and glasses l.jpg
MFGT 104Materials and Quality Ceramics and Glasses

Professor Joe Greene

CSU, CHICO

Add Refractory Information!!!

Add tensile properties of non ferrous

MFGT 104


Chap 7 ceramics l.jpg
Chap 7: Ceramics

  • Objectives

    • Understand the compositions and applications of various ceramic materials and products, including glass, stone, clay, cement, brick, and refractory materials.

    • Describe the development of these materials as well as the various products made from them.

    • Explain the major types and uses of modern, synthetic abrasives


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Introduction

  • Ceramics are

    • complex compounds and solutions that contain both metallic and nonmetallic elements,

    • heated at least to incandescence during processing applications,

    • typically hard and brittle,

    • exhibit high strength and high melting points,

    • exhibit low thermal and electrical conductivity.

  • Applications

    • Pottery, brick, tile, glass, ovenware, magnets, refractories, cutting tools.

    • Furnace linings and tiles for space shuttle due to high resistance to heat.

    • Superconductivity applications


Ceramics l.jpg
Ceramics

  • Traditional ceramics are made from clay, silica, and feldspar

  • Structural clays for bricks, sewer pipes, drain tiles, and floor tiles are made from natural clays made from three basic components

  • Traditional ceramic products are china, dental porcelain, and sanitary-ware

  • Technical ceramics are mainly pure compounds or nearly pure compounds of primarily oxides, carbides, or nitrides.

  • Normally hot pressed in dry powder form onto useful products.


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Ceramics

  • Ceramics comes from Greek word keramos, which means potter’s clay.

  • Ceramics are diverse group of nonmetallic, inorganic solid compounds with a wide variety of compositions and properties.

  • Ceramics are crystalline compounds made up of metallic and nonmetallic compounds with properties that differ from the constituents.

  • Ceramics in the form of pottery are among the oldest products manufactured by humans.

    • Clay is inexpensive material and is found throughout the world.

    • Early clay products were sun dried not fired.

    • Firing as used in pottery dates back to around 2000 to 3000 B.C.


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Ceramics Properties

  • Ceramics are crystalline like steel but have few free electrons at room temperature and thus are low conductivity.

  • Ceramics strengths have higher compressive than tensile.

  • Ceramics are totally elastic, exhibiting no plasticity when load is applied with little or no deformation prior to fracture.

  • In general ceramics have the highest melting points of any materials. Range from 3500F to as high as 7000F.

  • Manufacturing of ceramics involves

    • blending fine starting materials with water to form mass that is shaped

    • formation includes extrusion, pressing, and casting,

    • use of potter’s wheel for cups, bowls, saucers, etc.

    • extruded to make bar shapes or poured into mold as slip slurry

    • after forming product is dried to remove water and fired for strength

    • forming provides fusion(sintering) and chemical reaction for bonding

    • glazing with ceramic coating for smooth surface



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Ceramics Materials

  • Properties

    • Vary depending on composition, microstructure, and processing.

    • Excellent resistance to

      • compressive loads, abrasion, heat, and staining

      • chemical attacks, weather attacks, bending (excellent rigidity)

    • Poor resistance to tensile loads, spalling (thermal cracking ceramics)

    • Most ceramics will crack if thermal cycled, except Pyrex glass which contains boric oxide to provide expansion properties.

  • Applications

    • dielectric materials for capacitors with disk capacitors (mainly barium titanate) being the most common.

    • Semiconductor applications with sintered oxides, e.g., thermistors, which are thermally sensitive resistors used for temperature control

    • Piezoelectric ceramics (Barium titanate) is used in accelerometers and speakers. The transducers convert input sound energy into electrical response or convert electrical inputs into sound energy.

    • Nanocomposites for plastics and composites


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Glass

  • Glasses are described as super-cooled liquids.

    • Glasses do not behave like metals but more like polymers when cooled from molten condition

      • Metals exhibit a definite quantity of heat given off when cooled and form a crystaline (or regular) structure when cooled.

        • Heat is called heat of solidification

      • Polymers exhibit changes in volume when cooled which may form a crystalline or amorphous structure depending upon the nature of the polymer and versus temperature that has an inflection point, know as glass transition temperature.

      • Glass is a transparent silica product which may form an amorphous or crystalline structure depending upon heat treatment during production.

      • Glass do not exhibit any indication of transition or a clear point of inflection when cooling from molten state.

      • Glass is considered a viscous liquid when cooled from molten state.

      • Glass has the appearance and feel of a solid material but will flow like a liquid given time, e.g., thicker glass at bottom of window pane.

    • Crystallinity of glasses is measured with X rays and X-ray diffraction.

      • More crystalline the glass the more rays are diffracted


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Glass Flow

  • Glass flows over time (Figure 7-1)


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Glass History

  • Glass is one of the oldest manufactured materials without a known discovery date. Nature makes natural glass.

  • Natural glass

    • Obsidian is a common natural glass product formed by intense volcanic heat and is usually black, but can be red, brown, or green.

    • Obsidian was used by early peoples to make jewelry, weapons, tools.

    • 5000 B.C.: glass was found around campfires on sandy beaches.

    • 5000 B.C.: First attempts to make glass in region of Syria.

    • 4000 B.C.: Glass beads and bottles found near Mesopotamia

    • Egyptians used glass products as adornments for the rich and powerful because glass production was very expensive.

    • 200 B.C.: Babylonians invented the process of glass blowing that changed the production rate from a couple of hours to several minutes.

    • Romans were first to produce a relatively clear glass and flat glass.

    • Glassmaking spread throughout the Roman Empire to Syria, Egypt, Greece, Italy, Gaul, and Brittany.


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Early Glass Manufacturing

  • Glass blowing process

    • Glass blowpipe is a hollow iron tube from 4 to 5 ft long with a knob at one end and a mouthpiece at the other end.

    • Dip knob end into melted glass, where glass sticks to the end of pipe.

    • Air is blown gently while rotating pipe which produces a hollow bulb of glass, where the thickness of the bulb depends on size of bulb.

    • The bulb cools and solidifies into a number of symmetrical shapes.

    • Molds are used to rapidly cool glass and allow more many shapes, including, bottles, dishes, lamps, and jars.

  • Glass slabs

    • Early attempts included rolling hot, clear glass over stone slabs covered with sand leaving rough pockmarks that distorted the light passing through it, making it unsuitable for window glass.

    • 600 C.E., Syrians discovered efficient way to manufacturer sheet glass which involved blowing a bubble of glass that was spun and produced a crown in the center, named crown glass.


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Middle Ages to Modern Glass Manufacturing

  • Glass production moves to Venice after Crusades.

    • Stain glass became common in churches.

    • 4 centuries of Venetian influence elevated glassmakers to noble status.

    • Production methods and craftsmen were highly guarded and were prohibited from emigration upon penalty of death.

  • Modern Glass Manufacturing

    • 16th Century, Venetians perfected first colorless and transparent glass.

    • Product called cristallo glass and was used to make lenses for microscopes, telescopes, and early cameras.

    • 16th and 17th Centuries marked the beginning of the modern period of glass since glass became a tool of science.

    • In 1675 flint glass (produced with lead oxide) developed to give distictive brilliance and comparative softness for easy forming.

    • In1688 the French perfected making quality flat glass by pouring molten glass over flat iron tables and rolling out with rolling pins and then polished by hand. Similar process is automated today.


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Glass Manufacturing in America

  • Glass making started in Jamestown Virginia in 1608.

  • Caspar Wistar imported Belgian glass-workers to New Jersey in 1739 and set up glass business for high quality glass ware.

  • Henry Stiegel founded glassworks in Penn. in 1765 and made finest blown glass and the first flint glass. Closed 1774.

  • Winstar plant closed in 1781

  • Boston and Sandwich Company founded in 1825 and was the first large scale production plant.

    • Credited with inventing the method of pressing glass into iron molds to make less expensive glass for the general public.

    • Closed in 1887

  • Since 1887 many U.S. glass companies have formed and failed

  • Today glass manufactures are conglomerates, e.g., Owens-Corning Fiberglass, Vetrotex Certaineed, Fiberglass Industries


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Glass Composition

  • Glass is made primarily of sand (silicon dioxide)

  • Silica or quartz glass is pure silicon dioxide (very stable)

  • Window glass is made of sand (SiO2), limestone (CaCO3), and soda ash (Na2Co3)

  • Figures 7-4 and 7-5


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Glass Composition and Properties

  • Figures 7-6, 7-7, and 7-8


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Glass Composition and Properties

  • Figure 7-9 and Table 7-2


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