A New Powder Production Route for Transparent Spinel Windows ...

Applications of TDA’s SurfaceFunctionalized NanoparticlesCeramic WindowsNanocolorantsNegative Control(No biocides)Nanoparticle Biocides250020001500Blank5% TDA-15% TDA-25% TDA-3All Silica5% SilicaPositive Control(0.25% biocides,no nanoparticles)Hysteresis Plots SB Rubber SamplesTethered Biocide(0.225% biocide)Growth on sampleSurface is less thanon surrounding agarImbeddedBiocide(0.225% IPBC)Zero fungalgrowthCO 2 Concentration / %0.300.250.200.150.10BackgroundWith catalyst @ 50 ppmTotal gas flow = 20 slpmRT = 35 msO 2 = 20%Fuel = 0.24 volume %0.05150°C0.00400 450 500 550 600 650 700Fluid Temperature / °CAlodine 1200/40%Chromate120°CSoluble NanocatalystsAlodine 1200/0.5% NanoCIStress (psi)1000500Film edgeTransparentNanocomposites00 20 40 60 80 100 120 140Strain (%)Hysteresis Improvementin TiresNano Corrosion InhibitorsTDAR e s e a r c h

Spinel Powder Production: Needs! Impurity Control! With ceramic windows you see your mistakes!Both anions and cations degrade optical properties! Particle Size Control! Sinterability! Scalability! CostTDAR e s e a r c h

Methods for Productionof Spinel Powders! Traditional Methods! Ceramics!Heat Beat and Hope: mixed metal oxide particles mix,heat, grind, repeat.! Sol-Gel!Hydrolyze sol gel: mixed sol-gels or aluminum sol-gelplus Mg complex.! Formation of Soluble Complexes!Various methods including citric acid method! Room Temperature Metal Exchange! Boehmite basedTDAR e s e a r c h

Boehmite Nanoparticle Based SpinelPowder Production! Why Boehmite! Available in high purity fromhydrolysis of aluminum alkoxides! Hydrolysis conditions have beenextensively investigated!Particle shape and size arecontrollable! Surface modified boehmiteundergoes a topotactic metalexchange reaction! Thermal transformation gives γ-alumina with the spinel structureTDAR e s e a r c h

Powder Processing Flow ChartAl(OR) 3 + H 2 O → Al(O)OH + ROHAl(O)OH + xRCOOH → Al(O)(OH) 1-x (O 2 CR) xAl(O)(OH) 1-x (O 2 CR) x + yMg(acac) 2 → Al 1-y Mg y (O)(OH) 1-x (O 2 CR) xSpinelTDAR e s e a r c h

Controllable Spinel Powder Size! Synthesis process dependson many co-interactingprocess variables! Polynomial neural networkused to model synthesisparameters! Three variables (hydrolysistime, hydrolysis temperatureand “ripening time”) controlsurface area.Predicted Surface Area (m 2 /g)454035302520151050-5y = 0.9948x + 0.0673R 2 = 0.99480 10 20 30 40 50Measured SA (m 2 /g)TDAR e s e a r c h

Topotactic Metal Exchange ProcessIntensity800700600500400300Catapal ABoehmite20010005 15 25 35 45 55 65 75Two ThetaIntensity300250200150100500Propionato-alumoxaneMg-exchanged PA-Boehmite5 15 25 35 45 55 65 75Two ThetaBoehmite crystal structure is unaltered by metal exchangeTDAR e s e a r c h

Spinel Formed Directly FromMetal Exchanged BoehmiteIntensity (counts)130012001100100090080070060050040030020010005 25 45 65Two Theta (degrees)Intensity (counts)360032002800240020001600120080040005 25 45 65Two Theta (degrees)1000°C 1200°CSingle phase magnesium aluminate (spinel) produced frommetal exchanged precursorTDAR e s e a r c h

Hot Pressed Spinel DiscsSpinel with ZnAl 2 O 4 impurities (3,4)Pure spinel (5)TDAR e s e a r c h

Optical Properties: Initial Materials0.9TDA 548-350.80.7TDA 548-21-1BTrasmittance0.60.50.4TDA 548-21-1A0.30.2UV-Vis Near-IR IR0.10 1 2 3 4 5 6 7Wavelength (in microns)TDAR e s e a r c h

Optical Characterization: BestPowders1.00.9TDASpinel Ultraviolet-Visible Transmittance0.8CoorsHot pressed spinels fromTDA powder meet orexceed legacy powders.Tests carried out by DanHarris (NAWC, China Lake)Transmittance0.70.60.50.40.3ARLRCS0.20.1TDA spinel 548-21-1-HPR15-2.24 mm thickGilde ARL Spinel 4/00 - 2.74 mm thickRCS Spinel 169-163 10/95 2.65 mm thickCoors #3 1.81 mm thick0.00.2 0.3 0.4 0.5 0.6 0.7 0.8Wavelength (µm)TDAR e s e a r c h

Summary and Acknowledgements! Boehmite based spinel powder production offerscontrol over purity, doping particle size! Topotactic metal exchange of boehmite powdersoffers direct conversion to pure spinel! High quality spinel windows can be producedfrom metal exchanged boehmite powders! Work funded by an Army Phase I SBIR (ContractNumber DAAH01-03-C-R142) and Army Phase IISBIR (W31P4Q-05-C-R137) contracts (Jim KirschU.S. Army Aviation & Missile Command.)TDAR e s e a r c h