3/5/2010 Ceramic Processing/S.Rattanachan 1

Ceramic ProcessingCeramic Processing

Engineering MaterialsEngineering Materials

3/5/2010 Ceramic Processing/S.Rattanachan 2

Ceramic ProcessingCeramic Processing

Ceramic powders/Raw materials Additives

Mixing

Forming

Drying

FiringDensificationSinteringVitrification

+

3/5/2010 Ceramic Processing/S.Rattanachan 3

Additives of ceramicsAdditives of ceramics

�Binder: ����������� �ก������

�Lubricant: ��������������� �� ��������� ������������ !����"#$%&'

�Plasticizer: ����(�ก� )��"$� ����������ก �*�������� ���(��

�Deflocculant: +��������(#��ก �,�����"$�

�Dopants: - $�- (����$"�����)../� ������ก�������

3/5/2010 Ceramic Processing/S.Rattanachan 4

ShapeShape--Forming ProcessesForming Processes

�Pressing�Uniaxial�Isostatic�Hot pressing�Hot isostatic

pressing

�Slip casting�Drain casting�Solid casting

� Tape casting�Doctor blade�Waterfall

� Plastic forming�Extrusion�Roll forming�Roller head �Injection molding

3/5/2010 Ceramic Processing/S.Rattanachan 5

UniaxialUniaxial PressingPressing

• Free-flowing Powder containing binder, moisture, lubricant• This cycle repeats typically 6 to 100 times per minute.• Presses have a capacity from 1 to 20 tons.

Process steps:• Preparation• Filling• Compression • Ejection • Recycle

3/5/2010 Ceramic Processing/S.Rattanachan 6

Dry pressingDry pressing

• Dry, Semidry or dust pressing •0 – 4 % moisture powder• Products: electrical parts (capacitor, substrate), Bricks

3/5/2010 Ceramic Processing/S.Rattanachan 7

IsostaticIsostatic pressing pressing Cold Cold isostaticisostatic pressing (CIP)pressing (CIP)

Products from CIP

• Pressure from multiple directions • high uniformity • the walls of die deform and transmit the pressure uniformly to the powder.

Process steps:• powder is sealed in a water-tight die• Sealed die is immersed in a liquid contained in a high pressure chamber• seal the chamber• Increase pressure of the liquid by hydraulic pumping• release pressure• remove die

3/5/2010 Ceramic Processing/S.Rattanachan 8

Hot Hot isostaticisostatic pressing (HIP)pressing (HIP)

• near-net shape and high density • Work pieces are heated and an inert gas, generally argon, applies uniform pressure. The temperature, pressure and process time are all controlled to achieve the optimum material properties.

3/5/2010 Ceramic Processing/S.Rattanachan 9

Slip castingSlip casting

• Slip (Ceramic particles suspended in water) is casted into porous plaster molds.• Complex shapes of thin uniform thickness

Process steps: • Slip preparation • Filling mold• Draining• Remove mold• trimming and drying

3/5/2010 Ceramic Processing/S.Rattanachan 10

Tape Tape casting:Doctorcasting:Doctor bladeblade

• Products: substrates and packages for electronics• Thin sheets in large quantity and low cost• Slip contains about 50 vol% organic binder

Process steps:• Slip preparation• de-airing• tape casting• drying • machining and finishing

3/5/2010 Ceramic Processing/S.Rattanachan 11

Plastic forming: ExtrusionPlastic forming: Extrusion

• Mixture of powder and additives are deformable under pressure.• 25 to 50 vol% organic additive.• Products: Dinnerware. Furnace tubes, pipe, bricks, tubular, catalyst support

Process steps:• Powder sizing• Batch formulation• Mixing • Extrusion• Drying • Densification

3/5/2010 Ceramic Processing/S.Rattanachan 12

Injection moldingInjection molding

• Mixture of the ceramic powders with a thermoplastic polymer plus a plasticizer, wetting agentand anti-foam agent.• Products: any complex shapes

Process steps: • mixture preparation• preheat in the barrel• Press the heated materials• injection• Release part from die• Extraction of organics• Densification

3/5/2010 Ceramic Processing/S.Rattanachan 13

� Evaporation from a free water surface: depend on the air temperature, air velocity, water content of air and water temperature

� Drying rates of ceramic body:

Rate of water loss in drying moist clay

Dark to light

DryingDrying

3/5/2010 Ceramic Processing/S.Rattanachan 14

Densification /SinteringDensification /Sintering

� A removal of pores between the starting particles -> shrinkage -> strong bonding

3/5/2010 Ceramic Processing/S.Rattanachan 15

Stages of sinteringStages of sintering

� 1st stage (initial)� Rearrangement� Neck formation

� 2nd stage (intermediate)� Neck growth� Grain growth� High shrinkage� Pore phase continuous

� 3rd stage (final)� Grain growth� Discontinuous pore phase� Grain boundary pores

eliminated

3/5/2010 Ceramic Processing/S.Rattanachan 16

Microstructure after sinteringMicrostructure after sintering

Silicate ceramic: porcelain

Advanced Ceramics

Grain boundary

grain

Closed pores

Intergranular pores

3/5/2010 Ceramic Processing/S.Rattanachan 17

Phase diagramPhase diagram

• Mullite3Al2O3.2SiO2

• Mullite melts inconguently at 1890ºC.

• Refractory ceramic materials

3/5/2010 Ceramic Processing/S.Rattanachan 18

Glass Glass

3/5/2010 Ceramic Processing/S.Rattanachan 19

Glass and crystallineGlass and crystalline

Changes in volume and temperature of a liquid cooling to the glassy or crystalline state.

� Reprinted with permission from Arun K. Varshneya, Fundamentals of Inorganic Glasses. Copyright © 1994 Academic Press, Inc.

Glass: • ไมตกผลึก • ขนาดเปลี่ยนแปลงอยางชาๆขณะเย็นตัว • มี Tg (glass transition temperature)

Crystal:• มีการเปลี่ยนแปลงขนาดอยางรวดเร็วที่ Tm (melting temperature)

3/5/2010 Ceramic Processing/S.Rattanachan 20

Viscosity of silica glasses at varying Viscosity of silica glasses at varying temperaturetemperature

� Viscosity decreases with T� Impurity lower Tdeform� T deform : แกวออนตัวและสามารถขึ้นรูปได

Melting point(จุดหลอม): แกวเปนของเหลว

� Working point (จุดขึ้นรูป): viscosity is 104 P, แกวมีการไหลตัวเพียงพอตอการขึ้นรูป

� Softening point (จุดออนตัว) : viscosity is 4 x 107 P, แกวเกิดการเปลี่ยนรูปโดยน้ําหนักของตัวมันเองได

� Annealing point(จุดอบออน): เปนจุดที่ความเคนภายในลดลง

� Strain point(จุดความเครียด) : Tg will be above the strain point or below the strain point , fracture will occur before the onset of plastic deformation. จุดที่ความเครียดภายในลดลงถึงคาต่ําสุดภายหลัง 4 ชั่วโมง และที่อุณหภูมิต่ํากวานี้ แกวจะเกิดการแข็งตัว

3/5/2010 Ceramic Processing/S.Rattanachan 21

Glass Glass forming forming ก��������ก�ก��������ก�Pressing and blowing

เริ่มจากการผลิตแกวเปนกอนที่เรียกวา gob ซึ่งแกวอยูในชวงออนตัวไดเนื่องจากความรอน จากนั้นกอนน้ําแกวจะลงสูแบบพิมพ โดยแบบพิมพตัวลางจะมีชองหัวปลายแหลมที่เปนชองเขาของอากาศ จากนั้นอัดอากาศ น้ําแกวจะขยายตัวเต็มแบบพิมพ ซึ่งไดขวดแกวทีภ่ายในกลวง

3/5/2010 Ceramic Processing/S.Rattanachan 22

Drawing and fiber forming Drawing and fiber forming ก�� ��ก�����������ก�� ��ก�����������

Optical fiber

3/5/2010 Ceramic Processing/S.Rattanachan 23

Float Float glass glass ก����������ก���กก����������ก���ก

�ก�����������������������ก������� ������������ !ก"�"�������ก�#$��%$������&���$����� �ก�'�(�����������ก������)�*!�� 1050ºC �����ก��*����ก'�( 600ºC (ก����ก����0�����ก1�ก���ก����*'$2�-����!�-2���ก�)

3/5/2010 Ceramic Processing/S.Rattanachan 24

Heat treating Heat treating glassesglassesก���5�(�"����6�������ก1��ก�ก���5�(�"����6�������ก1��ก�

� Annealing: Thermal stress (the difference in cooling rate and thermal contraction between the surface and interior regions.

� Annealing heat treatment -> heat at annealing point and slowly cooled to room temperature.

Hot Thermal stresscool

ก�����"������ก1�����ก���ก�� ���)�*!�������� 620-640ºC ���'9������6��1��������6 ��&�����ก��:����6�'�(����)���������ก���ก$��:���ก�# ����������6���6ก��*���� '9�����ก�ก����1����ก�"���"�� �'�(����)�����"���"���1'�(�ก�ก������ก���ก '9����ก���ก����'�����ก���'ก���

3/5/2010 Ceramic Processing/S.Rattanachan 25

Glass temperingGlass tempering

� Tempered glass is manufactured through heat-strengthening process. Strength of Tempered Glass is roughly four times of the regular float glass.

� Manufacturing Process� Float glass is heated to 1150ºC

with tempering oven and then rapidly cooled with high-pressured air at high airflow rate.

� Heat-treated glass hasincreased resistance to impact,mechanical loads and thermalstress breakage as comparedto regular float glass and heat-strengthened glass

3/5/2010 Ceramic Processing/S.Rattanachan 26

Toughened Toughened glass glass ก���ก�'�����;ก���ก�'�����;

� Sheets of glass are heated to about 700º C in a furnace, then chilled rapidly by cold air blown onto both surfaces. Toughened glass is four to five times stronger than float glass and, if broken, disintegrates into small fragments with dull edges which are unlikely to cause serious injury. Glass is now a primary construction material and can form

3/5/2010 Ceramic Processing/S.Rattanachan 27

Laminated Laminated glass glass ก���ก���������5�����ก5����������'�1�ก���ก���������5�����ก5����������'�1� ��&�ก���ก���������&�ก���ก�������

� PVB laminated :Two or more sheets of glass arebonded together with one or more layers ofpolyvinyl butyral (PVB), a plastic interlayer in sheetform. Its principle benefit being its performanceunder impact. The glass may fracture but anybroken fragments will remain firmly bonded to theinterlayer.

� Resin laminated glass is manufactured by pouring liquid resin into the cavity between two sheets of glass which are held together until the resin cures. This method is ideal for laminating glass having a heavily textured or patterned surface. Not all resin laminates have safety performance. They are principally used for decorative and accoustic purposes, where safety is normally of secondary importance.

3/5/2010 Ceramic Processing/S.Rattanachan 28

�ก�:������<�ก�:������<

� Fuse silica: �ก��� ��������ก����ก����ก�������� ������ � !"���#�$�ก %&�'�(���)���ก��*$�ก�+ �*�,���-.�.� ���'��/�ก�0����*�)���1

� Soda-lime glass: �ก��� �-.���-� � SiO2 7-73%, Na2O 12-14%, CaO 10-12% ��� �ก���)� Al2O3 � �� �� �!2���� %&�'��,��ก���ก 3�&�� ����/�ก�0���)����*���� �

� Borosilcate glass: %&� B2O3 �� Na2O��� K2O ��4��ก���!$�$)����$ �#���กก��.����ก� Pyrex '��/�ก�0�ก��.���������ก�

� Lead glass: �)�ก����ก-�.� �ก� ��/.(�� )�)�'� %&���4� solder sealing glass (��.3� (��.5�#����*���)� Optical glass �ก��(�ก�(!���*�*#�