1. Armor Ceramic Subgroup: Thursday, 31 January 2013
Hilton Hotel, Daytona Beach, Florida, Crystal Room 8:30am – 12:30pm
8:30-8: Welcome: Overview of the CCOMC, MCOE, DARPA and MEDE, Rich Haber, Rutgers
8:40-8: Comments on Programs, Jim McCauley, ARL
Overview of CCOMC
8:50-9: Overview of CCOMC, with highlights of specific programs, Rich Haber, Rutgers
Modeling in Ceramic Processing: John Matthewson
Low Cost Synthesis of Spinel Powders: Rik Riman
Characterization of Boron Carbide Powders: Vlad Domnich
USACA Transparent Armor Roadmap
9:45-10:30 Current Transparent Armor Roadmap, Doug Frietag, USACA
10:10-10:50 Break
10:50-12:00 Status of the New CRA – Materials for Extreme Dynamic Environments (MEDE)
 Overview of Program, KT Ramesh, JHU
Overview of the Modeling Programs within MEDE, Lori Brady, JHU
Overview of the Experimental Thrust within MEDE, KT Ramesh, JHU
Overview of the Ceramic Processing Thrust within MEDE, Rich Haber, Rutgers
Open Discussion of Linkage of University and Industry in MEDE
 12:00 Adjourn

2. Ceramic, Composite and Optical Materials Center, CCOMC
Annual Cooperative Research Budget > $1.5 Million
NSF’s Oldest Active IUCRC – 30 years old
Rutgers –Clemson University provide complementary expertise emphasizing synthesis, processing and materials design
The merger with Michigan State’s Center for Advanced Cutting Tool Technology is progressing
The merger with University of North Dakota’s SUNRISE Center is on hold
The MEDE was finally awarded. The CCOMC will be an integral part of this over the next 10 years!
DARPA Enhanced Materials Grant was awarded.
The next meeting will at Rutgers in the Spring – April 24-25, 2013
There will be a MEDE Annual Meeting in Baltimore, April 3-5, 2013
Ceramic and Composite Materials Center
An NSF Industry/University Cooperative Research Center

3. Rutgers CCOMC Armor Subgroup

4. ARL/MCOE Research Structure
Rutgers University and Johns Hopkins University: High Fidelity Design and Processing of Advanced Armor Ceramics – Extension of MCOE

5. Sometimes you do have an excuse to cancel a meeting – Sandy in NJ 11/2012

6. Projects Continuing in CCOMC
There are a total of 13 MS/PhD’s working on CCOMC sponsored research
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

7. A few examples of 2012 accomplishments
Modeling in Ceramic Processing: John Matthewson
Low Cost Synthesis of Spinel Powders: Rik Riman
Characterization of Boron Carbide Powders: Vlad Domnich
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

8. New Things Next meeting April 24-25, 2013 at Rutgers.
Wednesday, April 24 will be an Armor Subgroup
Thursday, April 25 will be the CCOMC review
From Wednesday through Friday, April the new characterization facilities will be available for tours.
On Wednesday morning will be a short course on the use of the sintering software developed by Prof. Matthewson.
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

9. Solution Crystallization of Magnesium Aluminate Spinel
CCOMC
Clemson
Rutgers
Ceramic, Composite and Optical Materials Center
Rutgers, The State University of New Jersey
Daniel Kopp and Richard Riman

10. Background
Magnesium aluminate spinel (MgAl2O4) is an attractive alternative material for the preparation of IR transparent windows with exceptional ballistic protection performance.
Traditional spinel synthesis requires high temperature (>1000oC) solid state reactions and energy intensive post-reaction milling.
Baikowski is the only manufacturer of high-quality spinel powder, and the cost is high ($60/kg).
There is no published route to crystallize spinel from water with the desired powder characteristics.
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

11. Overall Goals
Develop an inexpensive synthesis method to hydrothermally crystallize phase-pure spinel directly from solution without post-synthesis treatment steps.
Develop in-situ x-ray diffraction to monitor the phase transformation and reaction propagation.
Develop a thermodynamic and kinetic model to predict the behavior of the particle formation during hydrothermal synthesis of spinel.
Periodically supply 20-50g of spinel powder to Center groups for sintering and microstructure property studies.
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

12. Current Research
We have discovered an inexpensive solution crystallization route for the formation of magnesium aluminate spinel (MgAl2O4)
Hydrothermal route allows for the control of the chemical and physical characteristics.
Precursor and spinel phase characterization
Particle size and morphology analysis (DLS, SEM)
Phase composition (X-ray diffraction)
Impurities
Metal (EDS, XRD)
OH, H2O (IR spectroscopy)
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

13. Results Direct crystallization at the LOWEST documented temperature.
XRD pattern of solution crystallized spinel powder.
**Actual synthesis temperature is proprietary and should not be reported.
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

14. Morphology Literature Review
SLEEM image of spinel crystals grown on the surface of α-Al2O3 by Matsuda et al (2006)*.
**Optional slide**
*Matsuda, K., T. Matsuki, I. Müllerov, L. Frank, and S. Ikeno. "Morphology of Spinels and Al2O3 Particles in an Al2O3/Al-Mg-Si Composite Material Revealed by Scanning Low Energy Electron Microscopy." Materials Transactions 47.7 (2006): Print.
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

15. Morphology
Location of spinel crystals
100 nm
SEM image of solution crystallized spinel at the lowest temperature ever recorded.
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

16. Cost Function for Spinel Precursors
Precursor price will approach $11/kg with processing ~$8-10/kg at volume
Prices were collected for various quantities of powder and points were empirically fit, China-based suppliers advertise MgO powder of similar quality at prices as low as $200 per ton, when bought in quantities greater than 25 tonnes; less than $0.5 per kg. Source of cost data is Inframat Advanced Materials web site.
99.9% pure, average particle size, surface area >20 m2/g
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

17. Conclusion New process for MgAl2O4 spinel powder synthesis.
Capital equipment, energy and raw materials costs are kept low (< $20/kg) because milling and high temperature processing steps are eliminated
Opportunity for commercialization
First low temperature spinel synthesis method that also offers control of particle size and morphology without milling
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

18. Modeling the Densification of Non-Oxide Ceramics
Principal Investigators: M.J. Matthewson1 and R.A. Haber2
Graduate Student: Joseph Pantina3
January 31st, 2013
Ceramic, Composite and Optical Materials Center
An NSF Industry/University Cooperative Research Center

19. Modeling Early Stages of Sintering - Gas Transport can be Important
Outline
Modeling Early Stages of Sintering - Gas Transport can be Important
Motivation
Removal of undesirable oxides from non-oxide ceramics
SiO2 from SiC, B2O3 from B4C
Binder removal, drying, other phenomena…
Other systems, e.g. Si from SiO2 + C
Background
Removal of SiO2 from SiC using C
primary product CO gas
model multispecies gas diffusion
Similarly B2O3 from B4C using C
Current Research
Effect of temperature and ramping rate (heating profiles) on time for complete oxide removal, final composition, and the rate of CO effusion
Conclusions 19

20. Oxide Contaminants of Non-Oxides
Why the oxide is present:
Unreacted oxide during production of raw powder
SiO2 from SiC, B2O3 from B4C
Oxide passivation layer
Air exposure
Aqueous processing
Reasons to remove oxide:
Hinders densification
Leads to high equilibrium partial pressures at sintering temperatures
>> 1 atm CO(gas) at 2000 K (C/SiC/SiO2 material system)
Secondary oxide phase diminishes mechanical properties of sintered product
Methods to eliminate oxide:
Better raw powder production (may be infeasible)
Storage and processing still an issue
Acid washing of raw powder
Useful to eliminate significant oxide concentration, but not complete
Reaction with excess Carbon during sintering cycle
Produces CO(gas) that must be evacuated prior to densification 20

21. Prior Experimental Observations
Ness and Rafaniello suggest higher sintered densities at the surface of samples are due to faster removal of CO(gas)
primary reaction
SiO2 + 3C  SiC + 2CO(gas) (1)
Vgas ~ 1000·Vpore
need long enough hold for complete outgassing
But, excessively long intermediate hold times
coarsens SiC grains
impedes densification
Thickness vs. Density
Effect of thickness on sintered bulk density, ramped at 10o/min to 2120oC2
Cube Density Through Compact Center
Cube sectioning for the center of the SiC compact
‘Selected’ cubes are in red
E. A. Ness and W. Rafaniello,J. Am. Ceram. Soc., 77 [11] 2879–84 (1994).2
Densities of individual cubes following 2-hour vacuum holds at the indicated temperatures.2 21

22. Previous Approach to Oxide Removal
Needs to address a complex parameter space (increases factorially)
Green body parameters
Thickness, porosity, tortuosity, pore size, composition
Heating parameters
Heating rates, hold times
Ad Hoc Methods
Produce numerous samples to experimentally explore the parameter space
Measure gas effusion, density, shrinkage, etc. to characterize the effectiveness of one particular experimental system
Any change in a single processing parameter may invalidate all previous experimental insight
Modeling Approach:
Circumvents huge experimental parameter space by identifying trends
Cost effect method to optimize processing conditions
Need only a few experiments to validate modeling predictions 22 22

23. Evolution of Pressure with Time23 23

24. Evolution of Pressure in a Porous Body24 24

25. Temperature Ramping Constant rate of heating: two competing processes
pCO increases rapidly with increasing temperature
driving force for effusion increases
surface layers depleted of SiO2 thicken
pressure gradient decreases
driving force for effusion decreases
pCO more sensitive to temperature gas transport
effusion rate increases with increasing temperature
effusion rate decreases if temperature held constant 25 25

26. Description of the Problem
CO effusion rate too high
Influenced by specimen thickness, heating profile, etc.
May exceed vacuum pump capacity…
CO effusion rate too high
Influenced by specimen thickness, heating profile, etc.
May exceed vacuum pump capacity…
Oxide not completely removed from thicker specimens
Looks like a success...
CO effusion rate too high
Remove oxide layer from a SiC green body prior to densification
All oxide removed (pCO→ 0 atm)
Internal pCO approaching critical levels (thicker samples)
CO effusion rate too high
Influenced by specimen thickness, heating profile, etc.
Linear heating profile (4.5 °C /min)
CO effusion rate increases rapidly
Surface oxide layer depleted
Hold for 2 hrs (1350 °C)
CO effusion rate decreases
Resume heating (4.5 °C /min)
Oxide depleted from 2 cm sample
CO effusion rate too high
Hold until oxide removed (1600 °C)
CO effusion rate decreases rapidly
Try holding the temperature constant
2 hours (Starting at 1675 K)
Try continuing to ramp
4.5 K/min (Starting at 1675 K)
Try a controlled heating profile
4.5 K/min (Starting at 1275 K)
Try holding the temperature constant
Until oxide is removed (Starting at 1875 K) 26 26

27. Description of the Problem
Heating profile is far from optimal
Highly non-uniform rate of oxide removal
increases production time and energy costs
Incomplete oxide removal prior to reaching densification
internal pressure may exceed critical value
Furnace pressure too high
Influenced by specimen quantity, thickness, composition, furnace volume, etc.
flux profiles difficult to predict for scaling production
may exceed vacuum pump capacity… 27 27

28. Simulation can guide process optimization
Conclusions
JCO controls the time for complete oxide removal
Specimen thickness, quantity, composition, etc. control the total CO effused
Number of specimens, batch size
Furnace and vacuum pump capacity may be design factors
Linear heating rates are inefficient
Competing effects do not scale linearly
Linear heating with holding
Decreasing flux to steady state doesn’t signify near oxide removal
Simulation can guide process optimization
Demonstrated ability to simulate oxide removal for a prescribed heating profile
Material and processing parameters can be incorporated for specific problems 28