Engineering Conferences InternationalECI Digital ArchivesUltra-High Temperature Ceramics: Materials ForExtreme Environmental Applications II Proceedings

Spring 5-17-2012

Advanced characterization of composite ultra hightemperature ceramic systemsW.E. LeeImperial College London

Emily EakinsImperial College London

Heather JacksonImperial College London

Doni JayaseelanImperial College London

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Recommended CitationW.E. Lee, Emily Eakins, Heather Jackson, and Doni Jayaseelan, "Advanced characterization of composite ultra high temperatureceramic systems" in "Ultra-High Temperature Ceramics: Materials For Extreme Environmental Applications II", W. Fahrenholtz,Missouri Univ. of Science & Technology; W. Lee, Imperial College London; E.J. Wuchina, Naval Service Warfare Center; Y. Zhou,Aerospace Research Institute Eds, ECI Symposium Series, (2013). http://dc.engconfintl.org/uhtc/20

Advanced Characterisation of UltraAdvanced Characterisation of Ultra--high high Temperature Ceramic SystemsTemperature Ceramic Systems

Bill Lee, Emily Eakins, Heather Jackson and Bill Lee, Emily Eakins, Heather Jackson and DoniDoni JayaseelanJayaseelanDoniDoni JayaseelanJayaseelan

Dept. of Materials and Centre for Advanced Dept. of Materials and Centre for Advanced Structural Ceramics, Imperial College London, Structural Ceramics, Imperial College London,

UKUK

UltraUltra--High Temperature Ceramics: Materials for Extreme Environmental High Temperature Ceramics: Materials for Extreme Environmental Applications II, Applications II, SchlossSchloss HernsteinHernstein, Austria May 17, Austria May 17thth, , 2012.2012.

Characterisation TechniquesCharacterisation Techniques

•• Microstructures: SEM, FIB, TEMMicrostructures: SEM, FIB, TEM

–– Laser melting Laser melting ZrCZrC and ZrBand ZrB22

–– Lessons from Lessons from RefractoriesRefractories

–– Oxidation of ZrBOxidation of ZrB22--SiC + LaSiC + La22

–– Dislocations in ZrBDislocations in ZrB22--SiCSiC

•• Surfaces: Surfaces: ToFToF--SIMS, FIBSIMS, FIB--SIMSSIMS

–– Oxidation of ZrBOxidation of ZrB22 + + SiCSiC

Materials and Processing.Materials and Processing.

•• ZrCZrC–– CarbothermalCarbothermal reduction ZrOreduction ZrO22, Spark Plasma , Spark Plasma

Sintered (SPS) at QMUL 1985Sintered (SPS) at QMUL 1985ooC, 50 C, 50 MPaMPa 66--8 8 min., >95% dense.min., >95% dense.

•• ZrBZrB22 ceramicsceramics22

–– ZrBZrB22, ZrB, ZrB22/20 vol.% /20 vol.% SiCSiC (ZS20) + 1(ZS20) + 1--10wt.% LaB10wt.% LaB66

or Laor La22OO33 (ZS20(ZS20--La).La).

–– SPS at QMUL over range T, t and P (1750SPS at QMUL over range T, t and P (1750--18501850ooC, 6C, 6--10min., 5010min., 50--70MPa) to typically >98% 70MPa) to typically >98% dense. dense.

40 mm

Inert

gas (

2 b

ar)

Laser Induced Melting at the Institute for Laser Induced Melting at the Institute for TransUraniumTransUranium Elements (ITU)Elements (ITU)

Laser Profiles

Peak Power 990 - 3800 W

Pulse Time 70 - 3600 ms

Beam Diameter 3 or 8 mm

Sapphire window (τ = 0.8539)

ZrC emissivity ~0.6

Pre

ssure

vessel

Sam

ple

Heating

High-power 1064.5 nm CW laser

Typical thermogram, commercial ZrC0.96

3 mm beam, 990 W, 70 msHeating 4.5 kW Nd-YAG

ArAr AtmosphereAtmosphere

800 µm

Inte

nsity (

arb

itra

ry u

nits)

10080604020

2θ (°)

Laser melted ZrC ZrC powder diffraction peaks

Molten pool consistent with ZrC by XRD

1 mm

Commercial ZrC0.96

3 mm beam

990 W, 70 ms

Melted Melted ZrCZrC Microstructure.Microstructure.

60 µm60 µm

2θ (°)

Dendritic structure characteristic of melting and recrystallisation

HF Jackson et al., “Laser Melting of Zirconium Carbide: Determination of Phase Transitions in Refractory Ceramic Systems,” J. Am. Ceram. Soc. 94 [10] 3561-69 (2011)

Homogeneous, single phase ZrC at melted surface

Melted Melted ZrCZrC Microstructure.Microstructure.

Fast quenching produces Fast quenching produces metastablemetastable eutectic, but repeated eutectic, but repeated melting homogenises the surface melting homogenises the surface zonezone

10 µm ZrCx at melted surface

ZrC

ZrCy-C eutectic10 µm

Metastable ZrCy+C eutectic forms sub-surface layer

Unmelted bulk

0.5 mm

Commercial ZrCCommercial ZrC0.960.96

8 mm beam8 mm beam4 laser pulses of 25004 laser pulses of 2500--3800 W3800 W

400 ms each400 ms each

ZrC

5 µm

FIBFIB--milled milled sectionssections

Graphite

TEM of Melted TEM of Melted ZrCZrC EutecticEutectic

a = 4.6-4.8 Å

0.5 µm

Linear streaks

000020

220

0002

(graphite)

Elliptical streaks

000020

220

Graphite

Graphite diffraction Graphite diffraction rings, spot pattern rings, spot pattern from nearby from nearby ZrCZrCyy

Distinct Distinct ZrZr--rich and rich and CC--rich regionsrich regions

A – Pyrometer

B – Laser collimating optics (4.0 kW Nd:YAG)

C – Ceramic disc on Ta sheet on refractory brick

Laser testing was carried out in air

Laser Profiles

Peak Power 600 - 1800 W

Laser Melting at TWILaser Melting at TWI

Heating Time 30 – 300 s

Beam Diameter 10 mm

sample (10 mm x 3 mm)

Ta support

zirconia brick

∆T

~5

00

oC

2343oC – recorded max temperature within 0.2s of laser off

Temperature uncertainty

Air AtmosphereAir Atmosphere

2.5MW/m2.5MW/m22, , 300s300s

Surface of Laser Heated ZrBSurface of Laser Heated ZrB22..

•• All is ZrOAll is ZrO22..•• Low Low magnification shows uneven magnification shows uneven

surface surface includingincluding radial flow of radial flow of liquid. liquid.

Burst bubbles, craters and porous Burst bubbles, craters and porous structure fromstructure fromoo rapid volatilisation of rapid volatilisation of boriaboriaoo volume shrinkage from ZrOvolume shrinkage from ZrO2 2

transitions transitions

DD Jayaseelan, HF Jackson, E Eakins, P Brown and WE Lee, “Laser Modified Microstructures in ZrB2, ZrB2/SiC & ZrC,” J. Euro. Ceram. Soc. 30 [11] 2279-88 (2010).

2.5MW/m2.5MW/m22, , 300s300s

Surface of Laser Heated ZrBSurface of Laser Heated ZrB22..

Multifaceted surface ZrOMultifaceted surface ZrO22 grains grains between fine web ZrObetween fine web ZrO22 matrixmatrix

Faceted smooth grains in fine web Faceted smooth grains in fine web matrixmatrix

Heterogeneous; surface features vary from region to region possibly Heterogeneous; surface features vary from region to region possibly due to differing due to differing local local cooling conditions. cooling conditions.

�� DendriticDendritic microstructure in microstructure in ZrCZrC suggests direct melting of suggests direct melting of the carbide. the carbide.

�� XRD, SEM and TEM confirm presence of XRD, SEM and TEM confirm presence of ZrCZrCxx and and metastablemetastable eutectic eutectic ZrCZrCyy--C where x and y have not been C where x and y have not been characterised.characterised.

�� Laser modifies grain surface by heating, melting, molten Laser modifies grain surface by heating, melting, molten zone solidification on cooling to give variety of grain zone solidification on cooling to give variety of grain

Summary of Laser Melting Studies.Summary of Laser Melting Studies.

zone solidification on cooling to give variety of grain zone solidification on cooling to give variety of grain morphologies, sizes and porosities. morphologies, sizes and porosities.

�� Resulting microstructures are heterogeneous with range of Resulting microstructures are heterogeneous with range of morphologies.morphologies.

�� Mechanisms of microstructure formation are a complex Mechanisms of microstructure formation are a complex function function locallocal t, T and atmosphere and extent to which t, T and atmosphere and extent to which solid, liquid or vapour involved. solid, liquid or vapour involved.

Applying Applying RefractoriesRefractories Concepts to Concepts to UHTCsUHTCs

•• Control of Control of locallocal equilibrium/environment.equilibrium/environment.

•• Use of Use of in situ in situ reactions to provide protection, reactions to provide protection, dodo--itit--yourself coatings. yourself coatings.

WE Lee and RE Moore, “The Evolution of in situ Refractories in the 20th Century,” J. Am. Ceram. Soc. 81 [6] 1385-1410 (1998).

•• Natural Natural graphite graphite flakes.flakes.

•• Oxide Oxide ceramic ceramic aggregate.aggregate.

•• Deoxidising Deoxidising

OxideOxide--C Steelmaking Bricks: True C Steelmaking Bricks: True Composite SystemsComposite Systems

•• Deoxidising Deoxidising metal metal additions.additions.

•• NanoscaleNanoscalecarbon bond carbon bond derived from derived from phenolicphenolicpolymerpolymer resin.resin.

Dense Dense MgOMgO Layer Formation in Layer Formation in MgOMgO--C C Bricks.Bricks.

•• RefractoriesRefractories may react with furnace atmosphere may react with furnace atmosphere but but local local atmosphere in brick may be different.atmosphere in brick may be different.but but local local atmosphere in brick may be different.atmosphere in brick may be different.

•• Create Create reducing atmosphere internally within brick reducing atmosphere internally within brick in an otherwise oxidising in an otherwise oxidising Basic Oxygen Basic Oxygen Steelmaking Steelmaking environment. environment.

•• MgOMgO/C reaction forms Mg vapour which travels to /C reaction forms Mg vapour which travels to brick surface and reacts with available oxygen to brick surface and reacts with available oxygen to form dense form dense MgOMgO layer which protects the brick layer which protects the brick from further slag penetration. from further slag penetration.

Local Local Liquid.Liquid.

•• Composition of Composition of most penetrating most penetrating liquid may be very liquid may be very different from bulk different from bulk slag due to more slag due to more rapid diffusion of rapid diffusion of rapid diffusion of rapid diffusion of certain certain cationscations in in silicate slag (e.g. silicate slag (e.g. Fe, Cr, Fe, Cr, MnMn, Ni) or , Ni) or reaction with reaction with refractory matrix. refractory matrix.

Local Local EquilibriumEquilibrium

•• By controlling this By controlling this equilibrium e.g. using equilibrium e.g. using solids with open crystal solids with open crystal structures able to structures able to accommodate these accommodate these

SpinelSpinel

accommodate these accommodate these cationscations (e.g. (e.g. MgOMgO, , MgAlMgAl22OO44) can slow ) can slow penetration by forming penetration by forming more viscous local liquid more viscous local liquid or less soluble reaction or less soluble reaction interlayersinterlayers..

SpinelSpinel

PericlasePericlase

Single Phase Single Phase MgOMgO Grain CorrosionGrain Corrosion..SILICATE SILICATE SLAGSLAG

MgOMgO GRAINGRAIN

•• Fe,MnFe,Mn from slag diffused into from slag diffused into MgOMgO to form (to form (Mg,Fe,MnMg,Fe,Mn)O )O layer.layer.

•• Indirect attack.Indirect attack.

•• Local slag thus silicaLocal slag thus silica--rich and viscous. rich and viscous.

In situIn situ RefractoriesRefractories..

•• The product(s) of reaction within a The product(s) of reaction within a refractory system or between the refractory system or between the refractory and furnace contents leading refractory and furnace contents leading to beneficial refractory behaviour.to beneficial refractory behaviour.

•• Types ITypes I--IV.IV.•• Types ITypes I--IV.IV.

WE Lee, S Zhang and H Sarpoolaky, “Different Types of in situ Refractories,” pp.245-252 in Ceramic Transactions 125 (2001).

Type I Type I In SituIn Situ RefractoriesRefractories..

•• Arise from reactions between Arise from reactions between refractoriesrefractories components due to high components due to high temperature producing useful temperature producing useful phases.phases.

•• E.g. self forming E.g. self forming spinelsspinels in in castablescastablesfrom fine from fine MgOMgO and Aland Al22OO33 powder.powder.

•• SpinelSpinel formation formation in matrix of dry in matrix of dry vibratablevibratable from from reaction of fine reaction of fine MgOMgO and Aland Al22OO33..

Type II Type II In SituIn Situ RefractoriesRefractories..

•• Reactions occur within the refractory but Reactions occur within the refractory but assisted by reaction with the (liquid or assisted by reaction with the (liquid or vapour) furnace contents.vapour) furnace contents.

Type II Type II in Situin SituCeramics from Ceramics from Reaction of Reaction of Al Al Metal Metal Additives Additives with Furnace with Furnace Atmosphere.Atmosphere.

AlN Whiskers

Type III Type III In SituIn Situ RefractoriesRefractories..

Single Phase AlSingle Phase Al22OO3 3 Grain Corrosion.Grain Corrosion.

SILICATE SILICATE SLAGSLAG

ALUMINA ALUMINA GRAINGRAIN

•• White White Fused Fused Alumina (WFA) formed Alumina (WFA) formed CACA66 and complex and complex spinelspinel layers.layers.

•• CACA66 layer adjacent layer adjacent WFA WFA is is integral so integral so direct dissolution direct dissolution WFA impossibleWFA impossible..

Type IV Type IV In SituIn Situ RefractoriesRefractories..

Example: Slag splashing in BOS vessel extended

lining lives from ~200 to >1000.

SiO2

ZrO

2

ZrB2 ZrB2/20% SiC (ZS20)

ZrOLa2Zr2O7/ZrO2

ZS20-10% LaB6

Comparing oxidised ZrBComparing oxidised ZrB22, ZrB, ZrB22--SiC (ZS20) SiC (ZS20) and ZrBand ZrB22--SiCSiC--LaBLaB66 after oxidation at after oxidation at

16001600ooC/1hC/1h

50 µµµµm

ZrB

2

10 µµµµm

ZrO2

ZrB2/SiC

2 2 7 2

ZrB2/SiC

Porous ZrOPorous ZrO22 top top layerlayerUn protectiveUn protective

SiOSiO22 top layertop layerProtective ( < 1800Protective ( < 1800ooC)C)

LaLa22ZrZr22OO77 top layertop layerProtective (~ 2000Protective (~ 2000ooCC))

La2Zr2O7/ZrO2

ZS20-10% LaB6

WhenWhen addingadding RERE toto ZSZS2020,, thethefollowingfollowing reactionsreactions occuroccur duringduringoxidationoxidation..

Formation of Refractory Coatings in ZrBFormation of Refractory Coatings in ZrB22 + 20 + 20 volvol% % SiCSiC +10% LaB+10% LaB66 after 1h at 1600after 1h at 1600ooCC

10 µµµµm ZrB2/SiCLightLight LaLa22ZrZr22OO77 isis continuouscontinuous andanddarkdark silicatesilicate liquidliquid presentpresent asasisolatedisolated dropsdrops..

DD Jayaseelan, E Zapata-Solvas, P Brown and WE Lee, “In-situ Formation of Oxidation Resistant Refractory Coatings on SiC-reinforced ZrB2 Ultra High Temperature Ceramics,” J. Am. Ceram. Soc. 95 [4] 1247-54 (2012).

Solid Oxidation Products.Solid Oxidation Products.

•• Continuous solidContinuous solidrefractory layer formation, refractory layer formation, isolated liquidisolated liquid silica. silica.

•• Form solid using rare earth Form solid using rare earth additives and control of additives and control of reaction between the reaction between the UHTC+RE system and the UHTC+RE system and the UHTC+RE system and the UHTC+RE system and the atmosphere.atmosphere.

•• Improved oxidation Improved oxidation resistance in UHTCs may resistance in UHTCs may be derived from be derived from in situ in situ generation of solid generation of solid protective layers.protective layers.

E Eakins, DD Jayaseelan and WE Lee, “Toward Oxidation-resistant ZrB2-SiC Ultra High Temperature Ceramics,” Met. and Mats. Trans. 42A 878-887 (2011).

WG Fahrenholtz and GE Hilmas, “Oxidation of Ultra-high Temperature Transition Metal Diboride Ceramics,” Int. Mater. Reviews 57 1 61-72 (2012).

TEM of Dislocations in TEM of Dislocations in ZrBZrB22-- SiC.SiC.

Samples Samples Hot Pressed Hot Pressed at ISTEC at ISTEC 50MPa, 50MPa, 19001900ooC 20C 20--120mins120mins

ZrBZrB22 + 5vol%SiC + 5vol%SiC

120mins120mins

ZrBZrB22 +10vol% +10vol% SiCSiC

ZrBZrB22 + 15vol% + 15vol% SiCSiC

Average ZrBAverage ZrB22 Dislocation Density versus Dislocation Density versus SiCSiC Content for SPS and HP Samples.Content for SPS and HP Samples.

More More dislocations dislocations with more with more SiCSiCdue to due to ααmismatch.mismatch.

More More dislocations dislocations with SPS than with SPS than HP? HP?

Impact of Impact of internal stress internal stress on properties?on properties?Emily Eakins, Nanoscale characterisation of effect of SiC on microstructure

and oxidation behaviour of ZrB2-based ceramics, PhD Thesis 2011, Dept. of Materials, Imperial College London.

Microstructure SummaryMicrostructure Summary

•• Range of techniques needed for full Range of techniques needed for full characterisation of UHTCs including SEM, characterisation of UHTCs including SEM, FIB and TEM.FIB and TEM.

•• We can learn lessons from over a century We can learn lessons from over a century of of refractoriesrefractories research and use.research and use.of of refractoriesrefractories research and use.research and use.

•• Gaps in our knowledge of linear and planar Gaps in our knowledge of linear and planar defects in these systems which need defects in these systems which need linking to processing and properties.linking to processing and properties.

SurfacesSurfaces

•• Surface analysis using Secondary Ion Mass Surface analysis using Secondary Ion Mass Spectroscopy (SIMS).Spectroscopy (SIMS).

ION TOF ION TOF TOFTOF--SIMS/LEIS FEI FIB 200 SIMSSIMS/LEIS FEI FIB 200 SIMS

SIMS SIMS ProcessProcess

• Typically Typically GaGa primary beam.primary beam.•• Mass analyse sputtered species via magnetic deflection/time of flight.Mass analyse sputtered species via magnetic deflection/time of flight.

•• All elements and all isotopes can be analysedAll elements and all isotopes can be analysed

•• Sensitivity: parts per millionSensitivity: parts per million

•• Lateral resolution: beam width 5nmLateral resolution: beam width 5nm--50µm50µm

•• Depth resolution: beam energy (~ R ~ several nm)Depth resolution: beam energy (~ R ~ several nm)

•• Information depth (a few atomic layers)Information depth (a few atomic layers)

Mass spectrometry

All elements and isotopes

Depth profiling

Distribution of elements with Analysis Parameters:

PI:

Sample: Venetian Glass

Bi 3+

Origin: Imperial Co

File:

Energy: 25 keVCurrent: 0.40 pA

Comment:

110

210

Com

positio

n /

weig

ht%

Symbol Substance

CsNa

CsMg

CsK

CsCa

CsSiO

Cs2H

Adjacent Average: 10

RX02129B.TFDPolarity: positive

---

SIMS Modes of operationSIMS Modes of operation

Distribution of elements with depth resolved to 0.3nm

Imaging

Lateral distribution of elements (100nm easy and 5nm with FIB)

tascon GmbH · Münster, Germany

PI DD: 4.34E+013 Ions/cm²Area: 99.6x99.6 µm²

Sputter Parameters:

SpI: Cs+

Area:Sp DD:

300.0x300.0 µm²1.65E+018 Ions/cm²

Energy: 1 keV

Current: 0.40 pA

Current: 138.00 nA

Depth/nm200 400 600

010

Com

positio

n /

weig

ht%

O 2 flooding: -

Polymer (PP)

Melt Stabiliser

Antioxidant Polymer, Stabiliser, Antioxidant

Field of View: 284 x 284 µm2

Polymer (PP)

Melt Stabiliser

Antioxidant

Polymer (PP)

Melt Stabiliser

Antioxidant Polymer, Stabiliser, Antioxidant

Field of View: 284 x 284 µm2

FIBFIB--SIMS Analysis of Hot Pressed ZrBSIMS Analysis of Hot Pressed ZrB22

+ 20vol% + 20vol% SiCSiC 1h at 15001h at 1500ooC.C.

•• Layers:Layers:

–– Outer glassOuter glass

–– Mixed layer.Mixed layer.–– Mixed layer.Mixed layer.

–– UnoxidisedUnoxidised bulk.bulk.

Emily Eakins, Nanoscale characterisation of effect of SiC on microstructure and oxidation behaviour of ZrB2-based ceramics, PhD Thesis 2011, Dept. of Materials, Imperial College London.

FIBFIB--SIMS Analysis of Outer Glassy SIMS Analysis of Outer Glassy Layer.Layer.

•• All regions contain Si, O, B.All regions contain Si, O, B.

•• C, N, O containing species C, N, O containing species vary.vary.

•• No other impurities.No other impurities.

FIBFIB--SIMS Analysis of Mixed Layer.SIMS Analysis of Mixed Layer.

•• 4 phases detected:4 phases detected:

–– ZrBZrB22

–– ZrOZrO22

–– Glass Glass

–– Phase 4.Phase 4.

FIBFIB--SIMS Analysis of Phase 4.SIMS Analysis of Phase 4.

•• Phase 4 is a Phase 4 is a ZrZr--rich oxide + traces B, rich oxide + traces B, Si and C + impurities such as Na, Ca Si and C + impurities such as Na, Ca and K introduced during powder and K introduced during powder production or on oxidation. production or on oxidation.

•• Also contains hydroxide, HAlso contains hydroxide, H22OO++ and and

HH22OO-- presumably arising on removal presumably arising on removal

of sample from furnace due to highly of sample from furnace due to highly reactive new oxide. reactive new oxide.

•• Phase 4 is an impurity sink + Phase 4 is an impurity sink + pores/trapped glass.pores/trapped glass.

•• Surface glass has lost alkali Surface glass has lost alkali impurities. impurities.

SIMS SummarySIMS Summary

• Light element analysis (e.g. B, O, C) crucial in examination of UHTCs (also to check stoichiometry in carbides).

• Amount of light element may vary with location (again local environment)

• Need to characterise O/OH levels from e.g. • Need to characterise O/OH levels from e.g. RT oxidation/hydration of powders.

• Cannot ignore water, pick-up may have implications for re-use.

• Minor impurities e.g. alkalis important.

Important UHTC IssuesImportant UHTC Issues..

•• LocalLocal environment/environment/equilibriaequilibria..

•• Beneficial use of Beneficial use of in situ in situ environment.environment.

•• Need to understand impact of processing Need to understand impact of processing on internal stress and impact of internal on internal stress and impact of internal on internal stress and impact of internal on internal stress and impact of internal stress on properties.stress on properties.

•• Need to use a range of characterisation Need to use a range of characterisation techniques including for analysis of light techniques including for analysis of light elements.elements.

•• Cannot ignore water.Cannot ignore water.