Post on 18-Feb-2020
Field Activated Sintering
Technique - Introduction
Joanna R. Groza and Dat V. Quach
Chemical Engineering & Materials
Science Department
University of California, Davis
Outline
Field-assisted sintering techniques
Evolution
Field / current-induced phenomena in
manufacturing and science
Processing – microstructures- properties
Future studies
What‟s in a name?
PECS – Pulsed Electrical Current Sintering
SPS - Spark Plasma Sintering
CAPAD – Current Activated Pressure
Assisted Densification
ECAS – Electric Current Assisted/Activated
Sintering
EPAC – Electric Pulse Assisted
Consolidation
PAS – Plasma Activated Sintering
P2C– Pressure Plasma Consolidation
Field-Assisted Sintering Technique
SPS variant
Voltage: up to 15 V,
currents ~ 5 kA, 12-2 pulsing (3.3 ms)
Modest pressures (< 100 MPa)
10-3 MPa vacuum
Graphite dies (reducing atmosphere)
Thermocouple/
pyrometer
Pulsed Current
GraphiteDie
GraphitePunch (electrical curent and axial pressure application)
Sample
High/low
pressure
Schematic of a SPS unit
Publications/Patents
Patents: 87 in 1900-
1989; 156 in 1990-
1999; 399 2000-2008
Publications: 50/mo in
2010 vs up to 50/year
in the 1990‟s.
China, Japan –
largest number of
publications 1
99
3
19
94
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US
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Fra
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Ita
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NSF Grants
About 12
Thermoelectrics (DOE/NSF, SBIRs)
Laminates (B4C and MgB2 (Al))
Ultrahigh temp ceramics (ZrB2, ZrB2-SiC)
Scale-up
Current Activated Tip-based Sintering
Theory
Historical Course Bloxam (1906) – resistance sintering
Taylor (1933) – resistance sintering in hot
pressing of cemented carbides
Cremer (1944) – field-assisted sintering (60Hz, ~
60 A/cm2, 100 MPa)
Lenel (1950‟) – resistance sintering under
pressure
Inoue, Lockheed – spark sintering (1960‟) – two
step current application (initial 500-1000 Hz AC
for 15-30 s, then resistance heating)
Temperature deviations
Other Electrical Current/Field
Processes Electrical Discharge Compaction (EDC) –
short time discharges of a capacitor bank,
<30 kV, ~ 10kA/cm2, subsequent pressure
application
Electroconsolidation – quasi-isostatic
pressure application (graphite powder)
resistance heating
Dynamic Magnetic Compaction (DMC)
Pulsed Current Application
SPS vs PAS, P2C
Spark Plasma Sintering (SPS)
Pulse Current, I ~ 1000 A
< 500 s
P ~ 100 MPa
Plasma Assisted Sintering (PAS)
Pulse Current DC current, I ~ 1000 A
P ~ 100 MPa
~ 30 s < 500 s
Pulse Effects in PAS – 750 A
Single pulse at 293K, 60 ms pulse duration,
60 s total
Multiple pulses at 293 K, 473 K, 773 K and
1273 K. 60s each pulse application.
α- and γ- Al2O3 (50 and 15 nm, respectively)
R. Mishra et al, JMR, 13, 86 (1998)
Al2O3 results – PAS
Manufacturing features Uses – all type of materials, any
preference?
Other processes (bonding, welding, free
forming, ?)
Current/temperature distribution
Net shape
High throughput (~ 30 min cycle)
Batch vs continuous process
Energy efficiency
Processing Features
No cold pressing, no binders
Pulsed direct current application
Direct heating by Joule effect or conduction,
depending on material and heating stages
High heating rate (up to ~ 1000oC/min)
Higher pressures and higher heating rates than
in hot pressing
Low vacuum
Flexible processing (rates, timing, levels)
Novel FAST Variants High pressure SPS, quasi-isostatic pressure
Current Activated Tip-based Sintering (CATS) –
electric current and pressure application by a
conducting tip for non-conductive ceramics and
polymers* and Spark Plasma Extrusion**
Temperature gradients
Custom machines – enhanced specific material
sintering
??? *Morsi K, Moon K S, Kassegne S, Ugle R, and Villar E (2009a), „Novel current-activated tip-based sintering (CATS):
Localization of spark plasma sintering‟, Scr. Mater., 60, 745-748.
**Morsi K, El-Desouky A, Johnson B, Mar A, and Lanka S (2009b), „Spark plasma extrusion (SPE): Prospects and
potential‟, Scr. Mater., 61, 395-398.
High-Pressure SPS equipment
Bonding
Superalloy (MA 956 – 75 Fe-4.5Al-0.5Ti-
0.5Y2O3)- Fe3Al (28Al-2Cr-0.5Y2O3)at
1273-1373 K, 20-40 MPa, 30-60 min
Good bonding, minimal porosity, grain
growth contained (vs hot press- sample
fractured during EDM)
cBN on Cu 1273/3min/57 MPa (retention of
cubic structure)
Near Net Shape Capability
Optical micrographs of the FG semicup; from top to bottom: 100% Al2O3, 75% Al2O3 : 25% Ti, 50% Al2O3 : 50% Ti, 25% Al2O3 : 75% Ti, and 100% Ti (cold spraying and quasi-isostatic pressing in FAST at 1250oC for 5 min).
The layers are relatively dense with porosity from 2-4%.
Net shape modeling
Jener = Joule heating
t=370s
Why is FAST different?
Short processing times
Lower temperatures (?)
High heating rates
Thermal
Non-thermal (athermal)
Unique properties
Field / Current-Induced Phenomena
Pulsed current: specific to FAST
Electrical discharges and possible plasma
Electrical contact phenomena (e. g., “melting”
voltage or heat generation/dissipation)
Electrical conduction and direct ohmic
heating
Joule heating – current and sintering
temperature are dependent parameters
Enhanced mass transport (electromigration)
Defect generation and kinetics (vacancies)
FAST Results Material FAST Processing Feature Comparison to Other
Techniques
Reference
Earlier
densification
onset
Al2O3 (0.4 µm)
Y2O3 20 nm (undoped)
Densification starts at 1223K
Densification starts at 873 K
NA
CS: starts at ~ 1473 K
Shen et al, 2002 a
Yoshida et al,
2008
Enhanced
densification rate
ZnO, ZrO2, Al2O3 Maximum shrinkage rates at 973
K for ZnO, 1373 K for ZrO2 and
1423 k for Al2O3
1-2 orders of magnitude
faster shrinkage rate
than in CS
Nygren and Shen,
2003
Higher densities ZrW2O8
SnO2
98.6 % at 873 K/10 min/50 MPa
92.4% at 1163K/
10 min/40 Mpa
HP: 63.1 % at 873 K/1h
CS: 61.3% at 1273 K/3h
Kanamori et al,
2008
Scarlat et al, 2003
Lower sintering
temperatures
Ultrafine Ni
Undoped Y2O3 20 nm
773K/1min/150 MPa
1123 K at 10 K/min/ 83 MPa
HIP : 973 K
/150 min/140 MPa
CS: 1873 K at 5C/min,
air/180 min
Gubicza et al,
2009
Yoshida et al 2008
Additive free
composites
ZrB2 – 15 vol% MoSi2 2023 K/7 min/ 30 MPa HP: > 2373K Guo, 2009
Enhanced
reaction rate
FeCr2S4 from
and Cr2S3
1273 K/10 min/45 MPa Conventional
reaction:>5 days
Zestrea et al, 2008
Transparent
ceramics
Al2O3 1423K/8 min/K /20 min/80 MPa CS: Slow heating rate Kim et al.,
2007
Densification of
metastable
phases
Co65Ti20W15 Final amorphous structure 99.6% dense,
~300K/min
El-Eskandarany et
al., 2005
Controlled
porosity
Al – high strength
foam
773K/5min/20 MPa CS: 923 K/3h Oh et al, 2000
Good bonding Cubic BN on Cu 1273/3min/57 MPa NA Yoo et al,
1996
Superplasticity Al2O3 (50%)-Al2MgO4
(50%)
1253 K, 75% dense. Strain rate
of 10-2 s-1 at 1273 K
NA Zhan et al., 2005
Unique Properties
•Ionic conductivity and permitivity (2x CS) in BaZrYO (Ricote et al, 2008) and BaTiO3 (Tomonari et al 1999) •Maximal photoluminescence in ZnO (Wang and Gao, 2005) •Different magnetic properties (highest magnetic entropy, higher magnetization and magnetic energy, Yue et al, 2009, Lupu et al, 2009) Or grain size/material dependent response?
Demonstrated/ Active Research (S&E)
Applicable to wide variety of materials
Enhanced kinetics/heating rate
Pressure effects
Electromigration/enhanced solid state reactivity
Pulse/plasma phenomena (“bark” effect)
Field or current
Energetics (phase, defect eq, γ) or kinetics
Grain boundary (equilibrium, velocity)
Heating rate effects
Lower temperatures (unified energy term)
Energy efficiency
Barking dog
Big solar storms vs smaller space storms?
Conferences, Symposia, Workshops
“Field Assisted Sintering Technology” at The
Pennsylvania State University, August 24 and 25th
Sintering 2011- Novel Sintering Processes, Jeju Island,
Korea, Aug 28-Sept 11, 2011
2nd International Workshop on Spark Plasma Sintering,
Capbreton France, October 20-21, 2011
Novel Sintering Processes and News in Traditional
Sintering and Grain Growth – MS&T conference
(deadline extended to March 29th)
MPIF Special Interest Program June 10-13, 2012
Fundamental Studies (e. g., grain growth)
Field effects on grain boundary structure, ledge formation/migration?
How does the field influence grain boundary energy and mobility?
What are external field/current effects on constraint equilibrium structure of grain boundaries?
What are field/current effects on interface structures (e. g., clean grain boundaries, ledge formation/migration,…), segregation or cleaning? Evaporation?
What are the temporal and spacial effects of field/current on grain bondaries? What is their material dependence (what key material structure/feature is critical to maximize field/current)?
Modeling to quantify thermal vs electrical effects in field assisted grain boundary migration (mobility/diffusion)
???
Actions
FAST-based ERC?
MWNs?
Workshops?
Gordon Conference?
???
References El-Eskandarany M S, Omori M, Inoue A (2005), Solid-state synthesis of new glassy Co65Ti20W15 alloy powders and
subsequent densification into a fully dense bulk glass‟, J Mater Res, 20, 2845-2853.
Groza J R (1998), „Field-Activated Sintering‟, ASM Handbook, 7, 583-580, ASM International, Metals Park, OH
Groza J R, and Zavaliangos A (2000), „Sintering activation by external electric field‟, Mat Sci Eng A, 287, 171-177.
Gubicza J, Bui H.-Q, Fellah F and Dirras G F (2009), „Microstructure and mechanical behavior of ultrafine-grained
Ni processed by different powder metallurgy methods‟, J Mater Res, 24, 217-226.
Guo S-Q (2009) „Densification of ZrB2-based composites and their mechanical and physical properties: A review‟,
J. Eur. Ceram. Soc., 29, 995-1011.
Hulbert D M, Anders A, Dudina D V, Andersson J, Jiang D, Unuvar C, Anselmi-Tamburini U, Lavernia E J, and
Mukherjee A K (2008), „The absence of plasma in “spark plasma sintering”‟, J. Appl. Phys., 104, 033305/1-7.
Kanamori K, Kineri T, Fukuda R, Nishio K, Hashimoto M and Mae H (2008), ‟Spark plasma sintering of sol-gel
derived amorphous ZrW2O8 nanopowder‟, J Am Ceram Soc, Volume Date 2009, 92(1), 32-35.
Kim B-N, Hiraga K, Morita K and Yoshida H (2007), „SPS of Transparent Alumina‟, Scr Mater., 57, 607-610.
Lupu N, Grigoras M, Lostun M, Chiriac H (2009), „Nd2Fe14B/soft magnetic wires nanocomposite magnets with
enhanced properties‟, J. Appl. Phys., 105, 07A738/1-3.
Munir, Z. A., D. V. Quach, M. Ohyanagi, “Electric current Activation of Sintering : Review of PECS” JACS (2011),
94, 1-19.
Nygren M and Shen Z (2003), „On the preparation of bio-, nano- and structural ceramics and composites by spark
plasma sintering‟, Solid State Sci., 5, 125-131.
Oh, S-T, Tajima, K-I and Ando M (2000), Strengthening of porous alumina by pulse electric current sintering
and nanocomposite processing , J. Am Ceram Soc 83(5), 1314-1316
Scarlat O, Mihaiu S, Aldica Gh, Zaharescu M and Groza J R (2003), „Enhanced properties of Ti(IV) oxide based
materials by field-activated sintering‟, J Am Ceram Soc 86, 893-897.
Timsit, R. S., The “Melting” Voltage in Electrical Contacts, Trans IEEE (Comp, Hybr, Manu Tech) (1991), 14, 285
Yoo S, Groza J R, Sudarshan T S, and Yamazaki K (1996), „Diffusion Bonding of Boron Nitride on Metal
Substrates by Plasma Activated Sintering (PAS) Process‟, Scr Met. 43, 1383-86.
Yoshida H, Morita K; Kim B-N, Hiraga K, Kodo M, Soga K, and Yamamoto T (2008), „Densification of
nanocrystalline yttria by low temperature spark plasma sintering‟, J. Am. Ceram. Soc., 91, 1707-1710.