© 2013 SRI International
Fluidized bed processes for production of metal alloys and composites
Jordi Perez, Esperanza Alvarez, Fran Tanzella and Angel Sanjurjo
SRI International
Titanium USA 2015, Orlando FL, Oct 5th 2015
© 2013 SRI International
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Chemical Vapor Deposition in Fluidized Bed Reactors
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Combination of 2 technologies extensively used in industry
CVD– Tools– Semiconductor industry– Solar cells– Decoration– …
FBR– Petrochemical– Polymer – Nuclear– Surface treatments– …
+
FBR-CVD allows gas-solid chemical processes to form new materials taking advantage of the excellent heat and mass transfer of fluidized beds: homogeneous deposition, lower temperatures and higher deposition rates than conventional CVD.
© 2013 SRI International
Applications of FBR-CVD for coatings, thin films…
4
0
5
10
15
20
25
30
0 200 400 600 800 1000
displacement / nm
H /
GPa
TiSiN (9 Si at%)
SiNx
TiN
TiN/W
TiN/TaN
• Diffusion coatings– Corrosion protection of steel– Cr, Si,…
• Ceramic thin films– TiN, Si3N4, SiO2,…
• Composite films– Metal-ceramic multilayers– Ceramic-ceramic nanocomposites
• Coating porous structures– Filters for coal gasifier
• Thin films for solar cells– C-Si films
Si on steel
EDX depth profile
Uncoated steel TiN/steel GD-OES depth profile
nanoindentation
TiN/SiNx
TiAlN/Nb
Filter cross-section
TiAlN/Nb film
Film cross-section
Top view, textured filmP doping
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…for particle modification and production of metals
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Full encapsulation• Corrosion protection• Appearance• Electrical properties
Deposition of islands• Catalysts
Molybdenum• MoCl5 + H2• 70% single pass yield in
preliminary runs• 39 ton·m-2·year-1
Vanadium production• VCl4 + H2
• W interlayers
© 2013 SRI International
Thermochemical data
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Gibbs free energy of formation of several metal chlorides per mol of Cl2 (analogous to Ellingham diagram for oxide stability)• Reduction reaction MClx + (x/2) H2 = M + x HCl is favored at high T because of entropy
contribution to ΔH − TΔS• Chlorides above dashed H2 line can be reduced directly by H2
• For chlorides below dashed H2 line, direct reduction is not possible
© 2013 SRI International
Thermochemical data - Ti
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• Measurements: high T equilibria in the Ti-H-Cl system [1]: – new standard enthalpies of formation of TiCl, TiCl2, and TiCl3– Above 1200 K, P[TiCl3] is about an order of magnitude higher than P[TiCl4]
• Model prediction: – with H2 present, Ti deposited at T>1100 K– higher H2 concentrations result in higher conversion to Ti
Temperature (K)700 900 1100 1300 1500
Partial
Press
ure (at
m)
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
TiCl
TiCl2
TiCl4
TiCl3Ar/TiCl4/Ti = 1/0.1/10Total Pressure = 1 atm
Temperature (K)
900 1100 1300 1500 1700 1900 2100
Mole
10-4
10-3
10-2
TiCl2(c)
Ti(c)
H/TiCl3 = 10/0.01
H/TiCl3 = 1.5/0.01
Ti(c)
Ti(c)
H/TiCl4 = 4/0.01
TITANIUM FORMATION AT VARIOUS H/TiClX RATIOSNOVEL THERMOCHEMISTRY DETERMINED BY SRI
[1] D.L. Hildenbrand et al., High Temp. Mater. Sci., 35 (1996) 151
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Ti production in fluidized bed
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• Thermal reduction of TiCl4 by H2
• Ti deposition shown in multiple runs at lab scale• Direct production of alloys demonstrated by simultaneous reduction of TiCl4 and VCl4• Limitation during scale-up related to particle aggregation at high temperature
TiCl4/VCl4 molar ratio Film Composition (wt%)
0.8 19 (Ti) / 81 (V)
13.1 75 (Ti) / 24 (V)
36.7 90 (Ti) / 10 (V)
87.3 97 (Ti) / 3 (V)
© 2013 SRI International
Direct production of advanced alloys is possible
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• A shell composed of titanium silicides was formed on Si seed particles by treating them with TiCl4 in a fluidized bed (red arrow on phase diagram).
• The process could be continued to fully convert Si particles.• If a C source was also present, the desired Ti3SiC2 phase could be formed
(blue arrow in phase diagram)
An example: MAX phases• High temperature wear, corrosion resistance, and toughness• Electrically and thermally conductive • Stiff but they can be machined as easily as metals
© 2013 SRI International
A step forward: adding electrical arcs to FBR-CVD
Destruction of organic molecules using MAFBR
Multi-arc fluidized bed reactor (MAFBR)• Atmospheric pressure
– Low cost• Plasma-like environment
– High reactivity
Applications include:• Destruction of contaminants• Deposition of coatings• Synthesis of materials
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• Production of granules that are ready to use in powder metallurgy (particle sizes from 10s of microns to mm)
• Use of atomic hydrogen as reducing agent
• Direct production of alloys• Applicable to other metals, ceramics…
MAFBR in operation with Ti alloy particles
ARPA-E METALS: direct production of Ti alloys in MAFBR
© 2013 SRI International
MAFBR- Experimental setup
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Quartz reactors with porous disk as gas distributor, lateral ports for thermocouple, electrodes and TiCl4 injector.
H2–containing gas pre-heated using resistive furnaces
Electrical arcs: ΔV between top and bottom electrodes.
TiCl4 was supplied into the system using a standard bubbler.
© 2013 SRI International
MAFBR- Proof-of-concept tests with alumina seeds
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First tests with alumina seeds:• Visual assessment• Easy chemical analysis (XRF)
Untreated alumina (left) and alumina after Ti deposition in the MAFBR
But…Limitations of low temperature:• TiCl2 solid can be hard to reduce
© 2013 SRI International
Starting material
Run 16327-122(V deposition)
Run 16327-123(V-Ti co-deposition)
wt% Al 1.2 0.5 0.5wt% Ti 97.0 83.7 85.2wt% V 1.8 15.8 14.3
MAFBR- Ti:V co-deposition
• Bed temperature ~ 700 °C
• Seeds: Ti6Al4V 400-500 microns
• Reactant mixture: H2, TiCl4, VCl4• Particles had metallic appearance
• No Cl detected by XRF
• Mass gain, but low yield
• Higher mass gain in V-only run
• Alloy production took place, but competing
etching mechanism (back-reaction with HCl)
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Surface of particles after V run
Surface of particles after Ti:V run
Surface of original seeds
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Multiple-zone reactor
SEM of original seeds SEM of particles after run SEM of particles after run
• Particles circulate between zones at different temperatures
• Low-T zones for partial reduction of TiCl4• High-T zones to increase partial pressure of
subchlorides• Subchlorides recovered in low-T zones• Mass gain found in short preliminary runs• Single pass yield >60% (non-optimized)• Energy consumption ~ 60 kWh/kg Ti
© 2013 SRI International
MAFBR- Low temperature partial reduction
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• Partial reduction of TiCl4 takes place at very low temperature (500 °C) due to activation of reactants
• Combination of arcs, H2 and Ti in the bed are needed
• Resulting solids are dark and hygroscopic• Mass balance included water wash and Cl- ion
measurements:• 35% of incoming TiCl4 was reduced to Ti• 54% of incoming TiCl4 was reduced to TiClx
• Reduction to Ti can be finished electrochemically
SEM of particles after run
Run Ti bed Arcs H2Ti subchlorides
16242-114 NO YES YES NO
16242-115 YES NO YES NO
16242-116 YES YES NO Very small
16242-107 YES YES YES YES
Before After
© 2013 SRI International
MAFBR- Low T partial reduction + electrowinning
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Proof-of-concept test:• Product from low-T MAFBR partial reduction
transferred into electrochemical cell• Electrodes: graphite• Electrolyte: LiCl+KCl• T = 650 °C• Recovery of products by washing with water (O
content in recovered powders is artificially high)• Using 1” MAFBR reactor, 2.5 g of Ti were produced
in 1 hour• Based on preliminary data we estimate that Ti can
be produced by MAFBR+ electrowinning with energy consumption <55 kWh/kg_Ti (including energy to produce reactants)
• Development of a system to transfer TiClx from MAFBR to electrowinning steps is needed
Electrode configuration
Voltage and current during test
© 2013 SRI International
New applications for synthesis of materials in FBs
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NANOSTRUCTURED POWDERSNanometer-size layers easily formed by FBR-CVD (example: W nano-layer in a V particle)
• Powders with multiple metal layers can be produced.
• Ceramic inclusions in metal alloys are possible.
METAL-CERAMIC NANOCOMPOSITES
Infiltration of porous ceramic powders (i.e. alumina) with metals.
• Controlled composition• Controlled micro /
nanostructure
INFILTRATION OF TITANIUM SPONGE
Deposition of metals such as V, Al, B, W, Nb… on Ti sponge:
• Oxygen content in sponge can be lowered
• Products are ready for PM, 3D-printing…
• Successful first tests
wt% Ti wt% V wt% W
Run A 96.8 2.0 1.2
Run B 90.2 8.4 1.3
IMPACT• Scalable production of feedstock for 3D-printing, laser sintering, powder metallurgy,…• Materials with better mechanical properties at high temperatures• Lightweight alloys and composites with high strength
© 2013 SRI International
Aknowledgements
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• SRI team: Esperanza Alvarez, Fran Tanzella, Angel Sanjurjo, Chia-Pin Pan, JianEr Bao, Anoop Nagar, Kai-Hung Lau, Marc Hornbostel, Gopala Krishnan
• Collaborators:– Eugene Thiers– James Withers
• Funding: – ARPA-E (DE-AR0000460)*– DARPA
Contact: Jordi Perez, [email protected]
* The information, data or work presented herein was funded in part by the Advanced Research Projects Agency-energy (ARPA-E), U.S. Department of Energy under Award Number DE-AR0000460
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