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Electrolyte Thermodynamics:A Crystallization Tool for Engineering Materials
From the Nanoscale to the Microscale
Richard E. Riman and Eugene ZlotnikovDepartment of Materials Engineering
Rutgers, The State University of New Jersey607 Taylor Road
Piscataway, NJ 08854-8065
Sponsors
• Office of Naval Research• Defense Advanced Projects Research
Agency• National Science Foundation• New Jersey Commission on Science and
Technology• PPG Industries, Inc.• Ceramare Corporation
Outline
• Hydrothermal-derived ceramic materials• Rational approach to low temperature
hydrothermal synthesis• Thermochemistry-engineering the reaction
medium for ceramic materials synthesis
Current Research Areas
• Processing Science– Hydrothermal/Solvothermal Crystallization – Mixing– Assembly
• Functional Areas– Biomedical(tissue engineering)– Electronic (piezoelectric, dielectric) – Optical (amplifiers, lasers, taggants,
chameleon optics)– Structural (corrosion, ferroelastics)
Hydrothermal Synthesis• Chemical precursors are heterogeneous slurries, gel and or
homogeneous solutions, acid or base mineralizer required
• Aqueous, mixed solvent or solvothermal solution medium
• Focus is on mild reaction conditions (T<300oC, P<250 atm)
• Anhydrous oxides form in a single process step
• P-T-H2O interaction => unique phase equilibria
• Solution-mediated reaction => labile reaction kinetics relative to solid state reaction
• Controlled nucleation, growth and aging => controlled size and morphology
• Inexpensive processes
Hydrothermal Reactor
Thickness
(m)
Density
(kg/m3)
Heat
Conductivity5
Wt/(m deg)
Heat
Capacity5
(kJ /(kg deg)
Mass
(kg)
Outer
Surface
(m2)
Stainless steel 304 0.008 7900 0.502 3.27 0.04
Teflon 0.011 2120
16.0
0.26 0.350 0.44 0.02
Parr 4748 Autoclave, 125 ml, < 240°C
Batch Hydrothermal Crystallizers
Parr Instrument Company: Model 4530Hastalloy C276 alloy
Temperatures < 350˚CStirring Speed < 1700 rpm
Parr Instrument Company: Model 4530Hastalloy C276 alloy
Temperatures < 350˚CStirring Speed < 1700 rpm
Rational Approach to Low Temperature Hydrothermal Synthesis
• Compute thermodynamic equilibria as a function of the processing variables for phase of interest
• Generate equilibrium diagrams to map processing variable space for phase of interest
• Design hydrothermal experiments to test and validate computed diagrams
• Utilize processing variable space maps to explore opportunities for control of reaction and crystallization kinetics
Equilibria of Ca(OH)2-H3PO4-NH4OH-HNO3-H2O System1. H2O = H+1 + OH-1
2. HP2O7-3 = H+1 + P2O7
-4
3. H2P2O7-2 = H+1 + HP2O7
-3
4. H3P2O7-1 = H+1 + H2P2O7
-2
5. H4P2O7 (aq) = H+1 + H3P2O7-1
6. HPO4-2 = H+1 + PO4
-3
7. H2PO4-1 = H+1 + HPO4
-2
8. 2 H2PO4-1 = (H2PO4)2
-2
9. H3PO4 (aq) = H+1 + H2PO4-1
10. HNO3 (aq) = H+1 + NO3-1
11. NH3 (aq) + H2O = NH4+1 + OH-1
12. NH4NO3 (aq) = NH4+1 + NO3
-1
13. CaH2PO4+1 = Ca+2 + H2PO4
-1
14. CaNO3+1 = Ca+2 + NO3
-1
15. CaOH+1 = Ca+2 + OH-1
16. CaPO4-1 = Ca+2 + PO4
-3
17. CaHPO4 (aq) = Ca+2 + HPO4-2
18. Ca(OH)2 (aq) = Ca+2 + 2OH-1
19. Ca(NO3)2 (aq) = Ca+2 + 2NO3-1
20. Ca5(OH)(PO4)3 s = 5Ca+2 + OH-1+ 3PO4-3
21. CaHPO4 (s) = Ca+2 + HPO4-2
22. CaHPO4.2•H2O (s) = Ca+2 + HPO4-2+ 2H2O
23. Ca3(PO4)2 (s) = 3Ca+2 + 2PO4-3
24. Ca(H2PO4)2 • H2O (s) = Ca+2 + 2H2PO4-1 + H2O
25. Ca(H2PO4)2 (s) = Ca+2 + 2H2PO4-1
26. Ca4O(PO4)2 (s) + H2O = 4Ca+2 + 2OH-1 + 2PO4-3
27. Ca10O(PO4)6 (s) + H2O = 10Ca+2 + 2OH-1 + 6PO4-3
28. Ca4H(PO4)3 (s) = 4Ca+2 + HPO4-2 + 2PO4
-3
29. Ca8H2(PO4)6.5 • H2O (s) = 8Ca+2 + 2HPO4-2 + 4PO4
-3 + 5H2O
30. Ca(NO3)2.3 H2O (s) = Ca+2 + 2NO3-1 + 3H2O
31. Ca(NO3)2.4 H2O (s) = Ca+2 + 2NO3-1 + 4H2O
32. Ca(NO3)2 (s) = Ca+2 + 2NO3-1
33. Ca(OH)2 (s) = Ca+2 + 2OH-1
34. (NH4)2HPO4.2H2O (s) = 2NH4+1 + HPO4
-2+ 2H2O
35. (NH4)2HPO4 (s) = 2NH4+1 + HPO4
-2
36. (NH4)3PO4.3 • 3H2O (s) = 3NH4+1 + PO4
-3+ 3H2O
37. (NH4)H2PO4 (s) = NH4+1 + H2PO4
-1
38. (NH4)NO3 (s) = NH4+1 + NO3
-1
39. H2O (v) = H2O
40. NH3 (v) = NH3 (aq)
41. HNO3 (v) = HNO3 (aq)
Calculated Solubility of Various Calcium Phosphates
Stability Field Diagrams for HA
Ca(OH)2 has Limited Retrograde Solubility
Thermochemical Validation: Alkaline Earth Titanate Perovskites
Minimum Mineralizer Concentrations
Increasing Pb/Ti Reduces PT Processing Space
Use of EDTA to Eliminate Phase Heterogeneities
No EDTA EDTA
Control of Phase Space Using EDTA
No EDTA
EDTA
Acmite Pourbaix DiagramNaOH + 2SiO2 + Fe + H2O = NaFeSi2O6 + (3/2)H2 (g)
Na2SiO3 Concentration Effects
0.0E+00
4.0E-06
8.0E-06
1.2E-05
1.6E-05
2.0E-05
20 40 60 80 100 120
Temperature [°C]
Con
cent
ratio
n Fe
(OH
) 4- [m]
0 mol/l
1 mol/l
2 mol/l
Solu
ble
Spec
ies
X
Reaction Rate Maximization
0
1
2
3
4
5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0Na2SiO 3 [m]
T2, C2
T1, C1
[X]*
[Sili
cate
] 10-5
*m2
Na2SiO3 Concentration Increases Acmite Thickness
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 0.2 0.4 0.6
Na2SiO3 [mole/kg]
R
Fe
Acmite
IIIR
)()(
110
310221 +=
Temperature 210°C, Fe(NO3)30.124 mole/kg, 11.5 h
Thermochemistry Breakthrough:Instant Hydrothermal
• Uses same precursors as conventional solid state reaction
• Reactions in open vessels
• Phase pure powder• Controlled size
distribution
30 s BaTiO3
Setting Nucleation Targets
Effect of Ethanol on pH
pH vs. EtOH added to 28.8% w solution of NH4OH
11.1
11.4
11.7
12
12.3
0 4 8 12 16
[EtOH] m
pH
Non-ideality of Ethanol-Water-Ammonia Mixtures
K1
(1) NH3 +H2O ↔ NH4+ + OH-
K2
(2) NH3 + nC2H5OH ↔ [NH3•(C2H5OH)n]
(3) [NH3]0 =[NH3] + [NH4+] + [NH3•(C2H5OH)n]
(4) {[NH3]0 – [OH-] – [OH-]2/K1} / [OH-]2/K1 = K2 (C2H5OH)n
Ethanol-Ammonia Interaction Parameters
Ln-Ln Linearization for Water-Ethyl Alcohol -NH4OH
R2 = 0.97142
2.2
2.4
2.6
0 2 4Ln ([Ethyl Alcohol])
Ln(F
([OH
], [N
H4O
H]in
itial
)
n=0.13
K2=2.14
HA coated Titanium
In-Situ HA Coating/Synthesis
Non-Isothermal Phosphate Kinetcs
0
0.2
0.4
0.6
0.8
1
0 50 100 150
Time [min]
Con
vers
ion
40
80
120
160
200
Tem
pera
ture
°C
ConversionTemperature
HA & Ca-titanate: temperature scan
HA & Ca-Titanate: phosphate slow supply
Summary• Design of materials
– Phase pure materials– Optimization of formulations
• Design of processes– Optimization of processes– Process insight– Assessment of parametric sensitivity– Process monitoring
• Design of experiments– Feasible ranges of processing variables– Phase diagrams validation– “Go-Not Go” study
Conclusion
• Thermochemical modeling is an effective design tool for engineering phase assemblage, precursor and reaction kinetics
Questions?
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