Initial Sintering Mechanism of
     Mesocarbon Microbeads
       Christopher W. Norfolk
Alexander S. Mukasyan, Daniel E. E...
Motivation
Structure




            5 µm
Morphology




                     2 µm
             10 µm
Morphology

Sintering               Sintering
 Necks                   Necks




             10 µm   1 µm           2 µm
Final Density Characteristics
                                                                                          1....
Shrinkage Dynamics
                                0.12          Experimental Curve
                                      ...
Shrinkage Rate
                                3.00    I          II    III    IV         V           VI
    4
   Shrinkag...
Activation Energy Analysis
                              ∆L  x 
     n
                                          2
  x...
Activation Energy Analysis
                140
                          VI         V                      IV        3

  ...
Summary
!Is an activation energy approaching
 zero a reasonable result for a densifying
 sintering mechanism?
Evolution of ρpyc
                                     2.0
                                     2.0
     3                ...
Relative Density Results
   pyc                              1.00




                                    0.95
   Final re...
A Simple Example

                         ρoth=3Mo/4πro3
             ro                                      rf
        ...
Thermogravimetric Analysis
                               100
                                                            ...
Thermogravimetric Analysis
                                  6                                                            ...
Thermogravimetric Analysis
               3                                                               0.0



         ...
Titanium Carbide
                                      6

                                      4
   Shrinkage, Adjusted f...
Heating Schedule
                   1100                                               2

                                ...
Heating Schedule
                   1800                                       2
                                         ...
Conclusions
! The main role of the β-resin is to maintain
  particle cohesion
! Sample shrinkage due primarily to increasi...
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Initial Sintering Mechanism of Mesocarbon Microbeads

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Initial Sintering Mechanism of Mesocarbon Microbeads

  1. 1. Initial Sintering Mechanism of Mesocarbon Microbeads Christopher W. Norfolk Alexander S. Mukasyan, Daniel E. E. Hayes, Paul J. McGinn, and Arvind Varma Sintering ‘03 July 25th, 2003
  2. 2. Motivation
  3. 3. Structure 5 µm
  4. 4. Morphology 2 µm 10 µm
  5. 5. Morphology Sintering Sintering Necks Necks 10 µm 1 µm 2 µm
  6. 6. Final Density Characteristics 1.7 1.9 1.6 Curve 1 1.5 3 Final Density ρf, g/cm Density Ratio ρf/ρo 1.8 1.4 1.7 1.3 Curve 2 1.2 1.6 1.1 1.5 1.0 1.15 1.20 1.25 1.30 1.35 1.40 1.45 3 Initial Density ρo, g/cm
  7. 7. Shrinkage Dynamics 0.12 Experimental Curve Least Squares Polynomial Fit 0.10 Dimensionless Shrinkage, λ 0.08 0.06 0.04 0.02 0.00 -0.02 400 600 800 1000 1200 1400 1600 1800 Temperature, K
  8. 8. Shrinkage Rate 3.00 I II III IV V VI 4 Shrinkage Rate, dλ/dT, X10 2.00 1.00 0.00 -1.00 T1 T2 T3 T4 T5 400 600 800 1000 1200 1400 Temperature, K
  9. 9. Activation Energy Analysis ∆L  x  n 2  x Bt λ= =    = m r r r Lo  2r  −Q B = B oT e a RT x T = To + β t d (ln λ ) 2(a + 1) 2Q 1 = + ⋅ d (lnT ) n Rn T
  10. 10. Activation Energy Analysis 140 VI V IV 3 120 Curve 2 2 100 dλ/dT, X10 d lnλ/d lnT 80 1 60 4 0 40 Curve 1 20 -1 0 8 10 12 14 16 4 1/T, X10
  11. 11. Summary !Is an activation energy approaching zero a reasonable result for a densifying sintering mechanism?
  12. 12. Evolution of ρpyc 2.0 2.0 3 3 Pycnometric density ρ , g/cm 1.9 1.9 stage 2 stage 3 pyc pyc 1.8 1.8 1.7 1.7 1.6 1.6 stage 1 1.5 1.5 1.4 1.4 400 400 600 600 800 800 1000 1000 1200 1200 1400 1400 1600 1600 1800 1800 Temperature, K
  13. 13. Relative Density Results pyc 1.00 0.95 Final relative density, ρf /ρf 0.90 0.85 0.80 0.80 0.85 0.90 0.95 1.00 pyc Initial relative density, ρo/ρo
  14. 14. A Simple Example ρoth=3Mo/4πro3 ro rf Heat Lo Lf Treatment ro rf ρo=Mo/2πro3 ρoth=3Mo/4πro3 ρo=Mo/2πro3 ρfth=3Mf/4πrf3 ρf=Mf/2πrf3 ρf/ρo= ρfth/ρoth=(Mf/Mo)(ro/rf)3
  15. 15. Thermogravimetric Analysis 100 0.0 Mass Percent Remaining, W 98 -0.5 96 dW/dT, X 10 94 -1.0 92 -1.5 2 90 -2.0 88 86 -2.5 200 400 600 800 1000 1200 1400 1600 1800 Temperature, K
  16. 16. Thermogravimetric Analysis 6 0 -2 Mass #16 (Ion Current X 10 ) 11 5 -4 dW/dT X 10 4 -6 3 2 -8 2 -10 1 -12 200 400 600 800 1000 1200 1400 1600 1800 Temperature, K
  17. 17. Thermogravimetric Analysis 3 0.0 -0.5 2 dW/dT X 10 4 dλ/dT X 10 -1.0 1 -1.5 2 0 -2.0 -1 -2.5 200 400 600 800 1000 1200 1400 1600 1800 Temperature, K
  18. 18. Titanium Carbide 6 4 Shrinkage, Adjusted for Mass, λ Dimensionless Shrinkage, λ 2 50 wt % 0 -2 23 vol % -4 -6 Increasing TiC -8 -10 Content -12 -14 200 400 600 800 1000 1200 1400 1600 1600 1800 1800 Temperature, K
  19. 19. Heating Schedule 1100 2 0.01 1000 900 0 0.00 Dimensionless Shrinkage, λ Shrinkage Rate, dλ/dt 800 Temperature, K -0.01 700 -2 600 -0.02 500 -4 -0.03 400 300 -0.04 200 -6 0 200 400 600 800 1000 1200 Time, min
  20. 20. Heating Schedule 1800 2 0.01 1600 0 0.00 Dimensionless Shrinkage, λ 1400 -2 Shrinkage Rate, dλ/dt Temperature, K 1200 -0.01 -4 1000 -6 -0.02 800 -8 600 -0.03 400 -10 -0.04 200 -12 0 500 1000 1500 2000 Time, min
  21. 21. Conclusions ! The main role of the β-resin is to maintain particle cohesion ! Sample shrinkage due primarily to increasing theoretical density, caused by crystallographic transformation ! Sample porosity remains largely unaffected by the sintering process

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