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

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NSF Grants

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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.