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Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
Ceramic Processing 2
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Ceramic Processing 2

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  • 1. 620211 Introduction to Ceramic Engineering Nutthita Chuankrerkkul 21 January 2011
  • 2. Polymers Hydraulic ceramics Advanced oxide ceramicsMetals Ceramics SiO2 Glasses Ceramics Advanced non- Classic silicate oxide ceramics ceramics MgO, CaO Al2O3, Fe2O3 2
  • 3. 3
  • 4. 4
  • 5. TAXONOMY OF CERAMICSGlasses Clay Refractories Abrasives Cements Advanced products ceramics -optical -whiteware -bricks for -sandpaper -composites engine -composite -bricks high T -cutting -structural -rotors reinforce (furnaces) -polishing -valves -containers/ Adapted from Fig. 13.1 and discussion -bearings -household in Section 13.2-6, Callister 6e. -sensors• Properties: --Tmelt for glass is moderate, but large for other ceramics. --Small toughness, ductility; large moduli & creep resist.• Applications: --High T, wear resistant, novel uses from charge neutrality.• Fabrication --some glasses can be easily formed --other ceramics can not be formed or cast. www.uwstout.edu/faculty/schultzf/chem-341/docs/Chapter_13.ppt 5
  • 6. TopicsProcessing & Machinery: comminution, mixingRheology: binder, viscosityForming techniques: hand throwing, uniaxial die pressing, isostatic pressing (CIP, HIP), injection moulding, extrusion, slip casting, tape casting, gel castingPorous ceramics, Ceramic matrix composites (CMC)Literature review on research & development in ceramics 6
  • 7. กระบวนการผลิตเซรามิก 7
  • 8. Plastic formingPowder injection moulding- Ceramic injection moulding (CIM)- Metal injection moulding (MIM)Extrusion 8
  • 9. กระบวนการฉีดขึ้นรูปวัสดุผง Powder Injection Moulding เหมาะสาหรับการผลิต - ชิ้นส่วนขนาดเล็กที่มีรูปร่างซับซ้อน - วัสดุที่มีจุดหลอมเหลวสูง ได้แก่ เซรามิก หรือ โลหะบางชนิด - ชิ้นงานมีรูปร่างใกล้เคียงรูปร่างสุดท้าย (near net shape) มีข้อดีคือ - ประหยัด และลดการสูญเสียวัตถุดิบ - ลดขั้นตอน และลดค่าใช้จ่ายในการตัดแต่ง ชิ้นงาน 9
  • 10. VDO Powder injection mouldingMIMhttp://www.youtube.com/watch?v=zCfUd7ZEOjgMIM & CIMhttp://www.youtube.com/watch?v=Ecn3Gl3AaZ8
  • 11. Mixing/MillingClay + waterCeramic powder + binderPowder A + Powder BPowder + binder + additives 11
  • 12. Particle size distribution of WC powders, planetary milledfor various times 100 15 min 30 min 80 45 min 60 min Volume (%) 60 40 20 0 0.1 1 10 100 1000 Particle Diameter (mm) 12
  • 13. Powder Morphology 30 mm WC Powder A (as-received) 30 mmWC Powder B (after milling) http://www.purdue.edu/REM/rs/sem.htm 13
  • 14. Density of the mixturePowder density = 3.9 g/cm3Binder density = 1.1 g/cm3Powder 95 wt% + Binder 5 wt%Density of the mixture =?3.76 g/cm3 3.46 g/cm3 14
  • 15. The prediction of theoretical density for a mixture of two powders or a powder and a binder is a common problem that is often solved wrongly. Mass of powder A WA WT  WA  WB Mass of binder B WB WA WB Volume V VA  VB  A B Density  WT WA  WB T   VT WA  WB A B 15
  • 16. Density of the mixtureDensity Powder A = 15.6 g/cm3Density Powder B = 8.9 g/cm3Density of the mixture =?94 wt% Powder A + 6 wt% Powder B15.20 g/cm3 14.93 g/cm3 16
  • 17. Powder Injection Moulding Source: http://www.designinsite.dk/Source: http://www.azom.com 17
  • 18. กระบวนการฉีดขึ้นรูปวัสดุผง ตัวประสานสาหรับกระบวนการฉีดขึ้นรูปวัสดุผง เป็นองค์ประกอบที่มีความสาคัญ - ทาหน้าที่นาพาผงวัสดุเข้าไปในแม่พิมพ์ - ยึดจับอนุภาคทาให้ชิ้นงานคงรูปอยู่ได้ ก่อนที่จะทาการเผาซินเทอร์ - มีบทบาทสาคัญต่อกระบวนการผลิต - ส่วนใหญ่ใช้ตัวประสานที่เป็นพอลิเมอร์อย่างไรก็ตามไม่มีตัวประสานชนิดใดที่ดีที่สุด จึงมีการพัฒนาตัวประสานผสม(multi-component binder) เพื่อให้เหมาะกับการผลิตแต่ละประเภท 18
  • 19. กระบวนการฉีดขึ้นรูปวัสดุผงExample of powder-binder mixtures for PIM powder binder solids density, moulding green wt % loading, g/cm3 temp. strength, vol % ºC MPa 0.4 µm 92 polyethylene Al2O3 8 paraffin wax 60 2.74 110 5 0.5 µm 65 polyethylene glycol Si3N4 8 paraffin wax 58 2.28 155 12 10 µm 55 paraffin wax steel 45 polypropylene 67 5.60 130 15 5 stearic acid Feedstock คือ ส่วนผสมสาหรับการฉีดขึ้นรูป ประกอบด้วยผงวัสดุ ตัวประสาน รวมทั้งตัวเติมชนิดต่างๆ 19
  • 20. กระบวนการฉีดขึ้นรูปวัสดุผงFeedstock นิยมรายงานส่วนผสมเป็นร้อยละโดยปริมาตร (volume%) ปริมาณตัวประสานอยู่ในช่วง 40-50 vol% Low density (Al2O3 3.9) 84.2 wt% High density (WC-Co 14.93) 95.3 wt% Binder (1.1 g/cm3) 60 vol% solids loading => What is the weight % ? 20
  • 21. กระบวนการฉีดขึ้นรูปวัสดุผง Injection moulding Feedstockเพิ่มอุณหภูมิให้กับ feedstock (อุณหภูมิที่ตวประสานกลายเป็น ั ของเหลว) เพื่อให้ feedstock ถูกฉีดเข้าไปในแม่พมพ์ได้ ิ http://www.technologystudent.com/equip1/inject1.htm 21
  • 22. Moulded System The delivery system provides passage for feedstock from the machine nozzle to the part cavity, generally includes: a sprue cold slug wells a main runner branch runners gatesThe moulded system includes a delivery systemand moulded parts. 22
  • 23. Injection moulding : Lab-scale injection moulding machine : Industrial-scale injection moulding machine 23
  • 24. Injection mouldingAfter moulding, the delivery system is trimmed off and recycled. Therefore, the delivery system is normally designed to consume minimum material, while maintaining the function of delivering feedstock to the cavity in a desirable shape. 24
  • 25. Factors that influence injection pressure requirements Higher injection Lower injection pressure required pressure requiredPart thinknessPart surface areaGate sizeFlow length http://www.scudc.scu.edu/cmdoc/dg_doc/develop/process/physics/b3200009.htm 25
  • 26. Factors that influence injection pressure requirements Higher injection Lower injection pressure required pressure requiredMelt temperatureMould-wall (coolant)temperatureRam speedMelt flow index http://www.scudc.scu.edu/cmdoc/dg_doc/develop/process/physics/b3200009.htm 26
  • 27. กระบวนการฉีดขึ้นรูปวัสดุผงDebinding การกาจัดตัวประสาน 1. Thermal debinding สะดวก แต่ นาน 2. Wicking debinding เร็วกว่า แต่ ทาต่อเนื่องไม่ได้ 3. Solvent debinding เร็ว แต่ มีข้อจากัดกับผงบางชนิด ตัวทาละลายบางชนิดเป็นพิษ ติดไฟ 4. Catalytic debinding เร็ว แต่ ต้องซื้อ Feedstock สาเร็จรูป 27
  • 28. กระบวนการฉีดขึ้นรูปวัสดุผง Thermal debinding The binder is degraded to form volatile products. It diffused through the mouldings to their surfaces. The formation of gases must be sufficiently slow to prevent bubbles developing and pressure build-up. This can take up to several days toA model pore geometry during complete, depending on the thickness ofthermal debinding (German and Bose 1997) the components. 28
  • 29. กระบวนการฉีดขึ้นรูปวัสดุผง Wicking debinding The components are embedded in a wicking material, such as powders of alumina, silica, clay, graphite or zirconia. This powder bed helps prevent distortion and provides moreWicking debinding with an embedded uniform heating.part in a low density powder with a The porous wicking powder allowssmall pore size (German and Bose 1997) the liquid binder to be drawn out of the component by capillary action. 29
  • 30. กระบวนการฉีดขึ้นรูปวัสดุผงCatalytic debinding The binder is depolymerised into its monomer using gaseous nitric acid or oxalic acid as a catalyst. Gaseous formaldehyde is formed and subsequently burntLoading of the debindingchamber using oxalic acid out.solution(Ebenhoch and Hesse 1994) 30
  • 31. กระบวนการฉีดขึ้นรูปวัสดุผงSolvent debinding (a) as-moulded state (b) initial state (c) intermediate state (d) final state Diagrams of binder distributions (Yang et al. 2003) 31
  • 32. SEM micrograph shows fracture surface of as-moulded specimen (green sample) 32
  • 33. SEM micrograph of a 316L stainless steel specimenafter water leaching for 120 minutes (Anwar et al. 1995) 33
  • 34. กระบวนการฉีดขึ้นรูปวัสดุผง Water leaching - Various times and temperatures Leaching test on B8 specimens 100 90 80 % PEG removed 70 60 40 °C 50 60 °C 40 30 20 10 0 0 1 2 3 4 5 6 7 Time (hr)*B8 is composed of 60vol% powder loading and 85-15 binder composition 34
  • 35. DebindingThermal debindingAdvantages - The application of the process is easy as one furnace can be used for both debinding and sintering. - The process is safe.Disadvantages - The debinding time is long and depends on the thickness of the mouldings. - Volatile products, generating from the process, result in defects. 35
  • 36. DebindingWickingAdvantages - Debinding time is short compared to thermal debinding. - Shape stability is good. - The process is simple.Disadvantages - It is difficult for fine powders, i.e. ceramic components. - It is not suitable for continuous processing. 36
  • 37. DebindingSolvent debindingAdvantages - Debinding time is comparatively short. - Control of distortion is better, compared to thermal debinding as the process starts from the surface and gradually continues into the bulk.Disadvantages - Powder corrosion is possible. - Swelling tendency and cracks can be caused by solvent attack. - Toxicity and flammability, when organic solvents are used. 37
  • 38. DebindingCatalytic debindingAdvantages- Debinding time is short.- Highly accurate temperature control is not mandatory.- Green strength is good.Disadvantages - The process is corrosive to some metal powders. - Toxic gases are created. - Hydrogen reduction is occasionally required. - Only premixed feedstocks are available. 38
  • 39. Powder injection moulding Powder Binder Feedstock Injection moulding Debinding Sintering 39
  • 40. Sintering 40
  • 41. Sintering processing effects, adapted from German (1996) Changes to aid sintering Effects Advantage Drawback Decrease in particle size Faster sintering  Greater expense  Higher impurity level  Increased hazards  Increase in time Greater expense  Grain growth and  coarsening Increase in temperature Greater shrinkage  Grain growth  Greater expense  Less precision  Higher properties  Furnace limitations  Pore coarsening  41
  • 42. Changes to aid sintering Effects Advantage DrawbackIncrease in green Less shrinkage density Smaller pores  Higher final density  Uniform dimensions  Density gradients  reducedIncrease in alloying/ Higher strength additives Homogeneity problems  Higher sintering  temperaturesUse of sintering aids Faster sintering  Lower sintering  temperature Embrittlement  Distortion  Grain growth control  42
  • 43. RheologyGreek: rheos = stream currentRheology is the science of flow and deformation 43
  • 44. www.vscht.cz/sil/sil_cz/seminar/2003/13_Sarraf_Hamid.ppt 44
  • 45. Common flow behaviours Newtonian Pseudoplastic Dilatant (shear thinning) (shear thickening) Shear stressShear stress Shear rate Shear rate Shear rate ViscosityViscosity Shear rate Shear rate Viscosity Shear rate 45

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