Prepared by the IAPD Education Committee (Module 1) Presented courtesy of Modern Plastics, Inc.

The International Association of Plastics DistributorsThe International Association of Plastics Distributors

The IAPD Plastics Primer, Module 1The IAPD Plastics Primer, Module 1

Prepared by the IAPD Education Committee (Module 1)

Presented courtesy of Modern Plastics, Inc.

PROCESSING OF CERAMICS AND CERMETS

• Processing of Traditional Ceramics• Processing of New Ceramics• Processing of Cermets• Product Design Considerations





Overview of Ceramics Particulate Processing

• Traditional ceramics are made from minerals occurring in nature Products include pottery, porcelain, bricks, and

cement • New ceramics are made from synthetically produced

raw materials Products include cutting tools, artificial bones,

nuclear fuels, and substrates for electronic circuits • The starting material for all of these items is powder





Overview of Ceramics Particulate Processing - continued

• For traditional ceramics, the powders are usually mixed with water to temporarily bind the particles together and achieve the proper consistency for shaping

• For new ceramics, substances other than water are used as binders during shaping

• After shaping, the green parts are fired (sintered), whose function is the same as in powder metallurgy: To effect a solid state reaction which bonds the

material into a hard solid mass





Preparation of the Raw Material for Traditional Ceramics

• Shaping processes for traditional ceramics require the starting material to be a plastic paste This paste is comprised of fine ceramic powders

mixed with water • The raw ceramic material usually occurs in nature as

rocky lumps, and reduction to powder is the purpose of the preparation step in ceramics processing





Ingredients of Ceramic Paste for Shaping

1. Clay (hydrous aluminum silicates) - usually the main ingredient because of ideal forming characteristics when mixed with water

2. Water – creates clay-water mixture with suitable plasticity for shaping

3. Non‑plastic raw materials, such as alumina and silica - reduce shrinkage in drying and firing but also reduce plasticity of the mixture during forming

4. Other ingredients, such as fluxes that melt (vitrify) during firing and promote sintering, and wetting agents to improve mixing of ingredients





Shaping Processes

• Slip casting The clay-water mixture is a slurry

• Plastic forming methods The clay is plastic

• Semi‑dry pressing The clay is moist but has low plasticity

• Dry pressing The clay is basically dry (less than 5% water) and

has no plasticity





Four categories of shaping processes used for traditional ceramics, compared to water content and pressure required to form the

clay





Slip Casting

Sequence of steps in drain casting, a form of slip casting: (1) slip is poured into mold cavity, (2) water is absorbed into plaster mold to form a firm layer, (3) excess slip is poured out, and (4) part is removed from mold and trimmed





Plastic Forming Methods

• Hand modeling (manual method)• Jiggering (mechanized method)• Plastic pressing (mechanized method)• Extrusion (mechanized method)





Jiggering Similar to potter's wheel methods, but hand throwing is

replaced by mechanized techniques

Sequence in jiggering: (1) wet clay slug is placed on a convex mold; (2) batting; and (3) a jigger tool imparts the final product

shape





Semi-dry Pressing Uses high pressure to overcome the clay’s low plasticity

and force it into a die cavity

Semi‑dry pressing: (1) depositing moist powder into die cavity, (2) pressing, and (3) opening the die sections and ejection





Drying

The drying process occurs in two stages: • Stage 1 - drying rate is rapid and constant as water

evaporates from the surface into the surrounding air and water from the interior migrates by capillary action to the surface to replace it This is when shrinkage occurs, with the risk of

warping and cracking• Stage 2 - the moisture content has been reduced to

where the ceramic grains are in contact Little or no further shrinkage occurs





Firing of Traditional CeramicsHeat treatment process that sinters the ceramic material• Performed in a furnace called a kiln • Bonds are developed between the ceramic grains,

and this is accompanied by densification and reduction of porosity

• Therefore, additional shrinkage occurs in the polycrystalline material in addition to that which has already occurred in drying

• In the firing of traditional ceramics, a glassy phase forms among the crystals which acts as a binder





Glazing

Application of a ceramic surface coating to make the piece more impervious to water and enhance its appearance

• The usual processing sequence with glazed ware is: 1. Fire the piece once before glazing to harden the

body of the piece2. Apply the glaze3. Fire the piece a second time to harden the glaze





Advanced CeramicsAdvanced Ceramics

Structural:Structural: Wear parts, bioceramics, cutting Wear parts, bioceramics, cutting tools, engine components, armour.tools, engine components, armour.

Electrical:Electrical: Capacitors, insulators, integrated Capacitors, insulators, integrated circuit packages, piezoelectrics, magnets circuit packages, piezoelectrics, magnets and superconductorsand superconductors

Coatings:Coatings: Engine components, cutting tools, Engine components, cutting tools, and industrial wear partsand industrial wear parts

Chemical and environmental:Chemical and environmental: Filters, Filters, membranes, catalysts, and catalyst membranes, catalysts, and catalyst supportssupports





Processing of New Ceramics

• The manufacturing sequence for the new ceramics can be summarized in the following steps: 1. Preparation of starting materials2. Shaping3. Sintering4. Finishing

• While the sequence is nearly the same as for the traditional ceramics, the details are often quite different





Powder Injection Molding (PIM)

Ceramic particles are mixed with a thermoplastic polymer, then heated and injected into a mold cavity

• The polymer acts as a carrier and provides flow characteristics for molding

• Upon cooling which hardens the polymer, the mold is opened and the part is removed

• Because temperatures needed to plasticize the carrier are much lower than those required for sintering the ceramic, the piece is green after molding

• The plastic binder is removed and the remaining ceramic part is sintered





Hot Pressing

Similar to dry pressing except it is carried out at elevated temperatures so sintering of the product is accomplished simultaneously with pressing

• This eliminates the need for a separate firing step • Higher densities and finer grain size are obtained, but

die life is reduced by the hot abrasive particles against the die surfaces





Sintering of New Ceramics

• Since the plasticity needed to shape the new ceramics is not normally based on water, the drying step required for traditional green ceramics can be omitted for most new ceramic products

• The sintering step is still very much required • Functions of sintering are the same as before:

1. Bond individual grains into a solid mass2. Increase density3. Reduce or eliminate porosity





Powder PressingSintering - powder touches - forms neck &

gradually neck thickens– add processing aids to help form neck– little or no plastic deformation

Adapted from Fig. 13.16, Callister 7e.

Uniaxial compression - compacted in single direction

Isostatic (hydrostatic) compression - pressure applied by fluid - powder in rubber envelope

Hot pressing - pressure + heat





Sintering: useful for both clay and non-clay compositions.• Procedure: -- produce ceramic and/or glass particles by grinding -- place particles in mold -- press at elevated T to reduce pore size.• Aluminum oxide powder: -- sintered at 1700°C for 6 minutes.

15 m





Sheet Glass Forming

• Sheet forming – continuous draw– originally sheet glass was made by “floating”

glass on a pool of mercury – or tin

Adapted from Fig. 13.9, Callister 7e.





• Annealing: --removes internal stress caused by uneven cooling.• Tempering: --puts surface of glass part into compression --suppresses growth of cracks from surface scratches. --sequence:

Heat Treating Glass

further cooled

tensioncompression

compression

before cooling

hot

surface cooling

hotcooler

cooler

--Result: surface crack growth is suppressed.





• Pressing:

GLASSFORMING

Ceramic Fabrication Methods

Gob

Parison mold

Pressing operation

• Blowing:

suspended Parison

Finishing mold

Compressed air

plates, dishes, cheap glasses

--mold is steel with graphite lining

• Fiber drawing:

wind up

PARTICULATEFORMING

CEMENTATION





Anatomy of a tree Pith Heartwood Sapwood Cambium Phloem Bark

2 growth spurts Earlywood Latewood





Hardwoods vs. Softwoods Softwoods

Coniferous Grow rapidly Wide bands of earlywood Earlywood – large less dense

cell structure Hardwoods

Deciduous Grow slowly Narrow bands of earlywood Earlywood dense cell structure





Common Hardwoods Red Oak

White Oak

Hard Maple

Cherry

Walnut





Typical lumber cuts Plain-sawn

Maximizes lumber Prone to distortion

Through-and-through Simplest method Lumber is unstable

Quartersawn Produces less lumber Close, tight, straight grain More expensive





Lumber Drying Methods ‘Green’ Lumber Air Drying Kiln Drying





Common Lumber Distortions 4 types of distortion

Bow Crook Cup Twist





Common Lumber Defects Pitch Pockets

Spalling

Loose Knots

Checks

Splits

Shakes

Honeycomb

Wormholes

Wane





Sheet Goods Cover large area w/no

seams Dimensionally stable Minimise waste Relatively inexpensive

Plywood Particleboard Medium-density Fiberboard

(MDF) Melamine board









Veneering

Veneer is a very thin slice of wood. It is cut like a pencil sharpener cutting a pencil. Each slice of wood is about the thickness of an annual ring. A slice of veneer is called a leaf. As the leaves are cut they are stacked in order. This means you will get the best possible match of grain and colour. Veneer can be applied to a manufactured board to produce a cheap stable large board or it can be used to produce decorative effects. If an interesting grain pattern is found the veneers can create a pattern. This is called BOOK MATCHING. Examples are shown below.





layer it …

slot it together it …..

Bend it …..

turn it …..





Bent wood technology





The suitable material for bending

Material with good grain condition (with a little shake)High ductility in characteristic.

Use materials that are free of defects such as knots and checks





Laminated Wood Bending

Laminating wood to bend it is a fairly simple process. need a form or mold but you won’t need to build a steam

box or risk burns with steam. Thin pieces of wood bend easier than thicker ones, but

aren’t as strong. So by laminating thin strips of wood together in a mold or form adds strength and when the glue dries it will hold the

shape also.





Kerf-cut Bending

Kerf-cut bending is done by using your saw to cut slots

across the stock. This will allow the stock to be bent because the kerfs can

compress together. The kerfs are usually only

used on the inside of the bend. then you would use a veneer you cover the entire piece.





Kerf-cut Bending





Steaming





Equipment used for bending process

1.Steamer2.Bending strap

3.Former4.Shim





Microwave heatingBending small pieces of wood becomes a very simple process with

the use of a microwave; Microwave bending is also steam bending but in a much quicker,

more manageable way. To generate steam when microwaving, wrap the wood in a piece of wet paper towel, place it in a microwave oven and microwave it on

high.





Eight basic wood joints 1. Edge2. Butt3. Rabbet4. Dado5. Miter6. Lap7. Mortise and Tenon8. Dovetail





Wood Joints

The following are common methods of strengthening joints.– Biscuits– Using thin wood wafers called biscuits can

strengthen wood joints by providing more glue bonding area. Biscuit will expand 2X.

– You can use a biscuit joiner (also called a plate joiner) to cut precision mating slots in boards for the biscuits.





Wood Joints The following are common methods of

strengthening joints.Glue Block-small triangular or square blocksCorner Blocks-larger than a glue block





Glues White glue (polyvinyl acetate, or PVA): PVA

glue is a white liquid, usually sold in plastic bottles.– It is recommended for use on porous materials -- wood,

paper, cloth, porous pottery, and nonstructural wood-to-wood bonds.

– It is not water resistant. Clamping is required for 30 minutes to 1 hour to set the glue; curing time is 18 to 24 hours





Glues Plastic resin glue (urea formaldehyde): Plastic resin glue is recommended for laminating layers of

wood and for gluing structural joints. It is water resistant but not waterproof and is not

recommended for use on outdoor furniture. This glue is resistant to paint and lacquer thinners. Clamping is required for up to 8 hours; curing time is 18 to

24 hours.





Glues Polyurethane glue is one of the best waterproof

glues…

This reaction causes an expansion of the glue, filling all voids and giving an exceptionally solid glue joint.If the material is dry, spraying a light mist onto it before gluing accelerates the curing process.

In many ways, polyurethane may be the best wood glue. It both accepts wood stains and sands well in thin coatings, neither of which are true for PVA wood glues.

Most other adhesives act as a sealer on the wood surface. And removing these other adhesives can be difficult because they dry to a "gummy" texture that resists removal from the wood by sanding... the second strong reason to consider trying polyurethane glue for your next project.





Basic Clamping Systems

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Prepared by the IAPD Education Committee (Module 1) Presented courtesy of Modern Plastics, Inc.

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