Armor Ceramic Subgroup: Thursday, 31 January 2013 Hilton Hotel, Daytona Beach, Florida, Crystal Room 8:30am – 12:30pm   8:30-8:40 Welcome: Overview of the CCOMC, MCOE, DARPA and MEDE, Rich Haber, Rutgers 8:40-8:50 Comments on Programs, Jim McCauley, ARL Overview of CCOMC 8:50-9:45 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

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

Rutgers CCOMC Armor Subgroup

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

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

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

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

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 24-26 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

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

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

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

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

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

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): 1815-820. Print. Ceramic, Composite and Optical Materials Center An NSF Industry/University Cooperative Research Center

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

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

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

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 1mjohnm@fracture.rutgers.edu, 2rich.haber@rutgers.edu, 3jpantina@eden.rutgers.edu

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

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

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

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

Evolution of Pressure with Time 23 23

Evolution of Pressure in a Porous Body 24 24

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

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

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

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