Electrolyte Thermodynamics: A Crystallization Tool for Engineering Materials From the Nanoscale to the Microscale

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1 Electrolyte Thermodynamics: A Crystallization Tool for Engineering Materials From the Nanoscale to the Microscale Richard E. Riman and Eugene Zlotnikov Department of Materials Engineering Rutgers, The State University of New Jersey 607 Taylor Road Piscataway, NJ

2 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

3 Outline Hydrothermal-derived ceramic materials Rational approach to low temperature hydrothermal synthesis Thermochemistry-engineering the reaction medium for ceramic materials synthesis

4 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)

5 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<300 o C, P<250 atm) Anhydrous oxides form in a single process step P-T-H 2 O 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

6 Hydrothermal Reactor Heat Heat Outer Thickness Density Conductivity 5 Capacity 5 Mass Surface (m) (kg/m 3 ) Wt/(m deg) (kj /(kg deg) (kg) (m 2) Stainless steel Teflon Parr 4748 Autoclave, 125 ml, < 240 C

7 Batch Hydrothermal Crystallizers Parr Parr Instrument Company: Model Model Hastalloy C276 C276 alloy alloy Temperatures < 350 C 350 C Stirring Speed < rpm rpm

8 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

9 Equilibria of Ca(OH) 2 -H 3 PO 4 -NH 4 OH-HNO 3 -H 2 O System 1. H 2 O = H +1 + OH HP 2 O 7 = H P 2 O H 2 P 2 O 7 = H HP 2 O H 3 P 2 O 7 = H H 2 P 2 O 7 5. H 4 P 2 O 7 (aq) = H H 3 P 2 O HPO 4 = H PO H 2 PO 4 = H HPO H 2 PO 4 = (H 2 PO 4 ) 2 9. H 3 PO 4 (aq) = H H 2 PO HNO 3 (aq) = H NO NH 3 (aq) + H 2 O = NH 4 + OH NH 4 NO 3 (aq) = NH 4 + NO CaH 2 PO 4 = Ca H 2 PO CaNO 3 = Ca NO CaOH +1 = Ca +2 + OH CaPO 4 = Ca PO CaHPO 4 (aq) = Ca HPO Ca(OH) 2 (aq) = Ca OH Ca(NO 3 ) 2 (aq) = Ca NO Ca 5 (OH)(PO 4 ) 3 s = 5Ca +2 + OH PO CaHPO 4 (s) = Ca HPO CaHPO 4.2 H 2 O (s) = Ca HPO 4 + 2H 2 O 23. Ca 3 (PO 4 ) 2 (s) = 3Ca PO Ca(H 2 PO 4 ) 2 H 2 O (s) = Ca H 2 PO 4 + H 2 O 25. Ca(H 2 PO 4 ) 2 (s) = Ca H 2 PO Ca 4 O(PO 4 ) 2 (s) + H 2 O = 4Ca OH PO Ca 10 O(PO 4 ) 6 (s) + H 2 O = 10Ca OH PO Ca 4 H(PO 4 ) 3 (s) = 4Ca HPO 4 + 2PO Ca 8 H 2 (PO 4 ) 6.5 H 2 O (s) = 8Ca HPO 4 + 4PO 4 + 5H 2 O 30. Ca(NO 3 ) 2.3 H 2 O (s) = Ca NO 3 + 3H 2 O 31. Ca(NO 3 ) 2.4 H 2 O (s) = Ca NO 3 + 4H 2 O 32. Ca(NO 3 ) 2 (s) = Ca NO Ca(OH) 2 (s) = Ca OH (NH 4 ) 2 HPO 4.2H 2 O (s) = 2NH 4 + HPO 4 + 2H 2 O (NH 4 ) 2 HPO 4 (s) = 2NH 4 + HPO (NH 4 ) 3 PO 4.3 3H 2 O (s) = 3NH 4 + PO 4 + 3H 2 O (NH 4 )H 2 PO 4 (s) = NH 4 + H 2 PO (NH 4 )NO 3 (s) = NH 4 + NO H 2 O (v) = H 2 O 40. NH 3 (v) = NH 3 (aq) 41. HNO 3 (v) = HNO 3 (aq)

10 Calculated Solubility of Various Calcium Phosphates

13 Ca(OH) 2 has Limited Retrograde Solubility

14 Thermochemical Validation: Alkaline Earth Titanate Perovskites

15 Minimum Mineralizer Concentrations

17 Increasing Pb/Ti Reduces PT Processing Space

18 Use of EDTA to Eliminate Phase Heterogeneities No EDTA EDTA

19 Control of Phase Space Using EDTA No EDTA EDTA

20 Acmite Pourbaix Diagram NaOH + 2SiO 2 + Fe + H 2 O = NaFeSi 2 O 6 + (3/2)H 2 (g)

21 Na 2 SiO 3 Concentration Effects [m] - Concentration Soluble Species Fe(OH)4 X 2.0E E E E E E+00 0 mol/l 1 mol/l 2 mol/l Temperature [ C]

22 Reaction Rate Maximization 5 [X]*[Silicate] 10-5 *m T1, C1 0 T2, C Na 2 SiO 3 [m]

23 Na 2 SiO 3 Concentration Increases Acmite Thickness R R = ( I I 310) ( I ) Fe Acmite Na 2 SiO 3 [mole/kg] Temperature 210 C, Fe(NO 3 ) mole/kg, 11.5 h

24 Thermochemistry Breakthrough: Instant Hydrothermal 30 s BaTiO 3 Uses same precursors as conventional solid state reaction Reactions in open vessels Phase pure powder Controlled size distribution

25 Setting Nucleation Targets

28 Effect of Ethanol on ph ph vs. EtOH added to 28.8% w solution of NH4OH ph [EtOH] m

29 Non-ideality of Ethanol-Water-Ammonia Mixtures K 1 (1) NH 3 +H 2 O NH OH - K 2 (2) NH 3 + nc 2 H 5 OH [NH 3 (C 2 H 5 OH) n ] (3) [NH 3 ] 0 =[NH 3 ] + [NH 4 + ] + [NH 3 (C 2 H 5 OH) n ] (4) {[NH 3 ] 0 [OH - ] [OH - ] 2 /K 1 } / [OH - ] 2 /K 1 = K 2 (C 2 H 5 OH) n

30 Ethanol-Ammonia Interaction Parameters Ln-Ln Linearization for Water-Ethyl Alcohol -NH4OH 2.6 Ln(F([OH], [NH4OH]initial) R 2 = n=0.13 K 2 = Ln ([Ethyl Alcohol])

31 HA coated Titanium

32 In-Situ HA Coating/Synthesis Non-Isothermal Phosphate Kinetcs Conversion Temperature C Time [min] Conversion Temperature

33 HA & Ca-titanate: temperature scan

34 HA & Ca-Titanate: phosphate slow supply

35 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

36 Conclusion Thermochemical modeling is an effective design tool for engineering phase assemblage, precursor and reaction kinetics

37 Questions?

Consider a normal weak acid equilibrium: Which direction will the reaction shift if more A is added? What happens to the % ionization of HA?

Consider a normal weak acid equilibrium: Which direction will the reaction shift if more A is added? What happens to the % ionization of HA? ch16blank Page 1 Chapter 16: Aqueous ionic equilibrium Topics in this chapter: 1. Buffers 2. Titrations and ph curves 3. Solubility equilibria Buffersresist changes to the ph of a solution. Consider a