er Metastable Pathway to cBN

Metastable Pathway to cBN(hBN conversion to cBN)

Metin Ornek1, Chawon Hwang1, K. Madhav Reddy2, Kelvin Y. Xie2,

Vladislav Domnich1, Steve L. Miller3, William E. Mayo3, Silvio DaSilva4,

João Calado4, Kevin Hemker2, and Richard A. Haber1

Ceramic, Composite and Optical Materials Center

Fall 2018 Industrial Advisory Board Meeting

October 23-24, 2018, Clemson University

1Dept. of Materials Science and Engineering, Rutgers University, NJ

2Dept. of Mechanical Engineering, Johns Hopkins University, MD

3H&M Analytical Services, Inc., NJ

4Innovnano, Materiais Avancados SA., Portugal

CCOMC

Clemson

Ceramic, Composite and

Optical Materials Center

Rutgers

CCOMC

Clemson



Rutgers

Boron Nitride (BN)?

• BN polymorphs – Structures*

* M.I. Petrescu and M.G. Balint, U.P.B. Sci. Bull., Series B, 69 35 (2007)

Hexagonal BN (hBN)sp2

Rhombohedral BN (rBN)sp2

Cubic BN (cBN)sp3

a=2.504 Å

c=6.661 Å

a=2.504 Å

c=10.01 Å

a=3.615 Å

Boron

Nitrogen

Low-density phase

(2.10-2.29 g/cm3)

High-density phase

(3.45-3.50 g/cm3)

Thermodynamically

stable phase

Wurtzite BN (wBN)sp3

a=2.55 Å

c=4.20 Å

1.45 Å

1.45 Å

1.57 Å

1.58 Å

2

[Properties & characteristics]*1,2

• High thermal stability in air (up to 1000°C)

• Low friction coefficient in dry air (0.24 in dry air)

• Chemical inertness

• Non-wettability to water and high-temperature melts

• Low density (2.28 g/cm3), High thermal conductivity (a/b axis, 0.627 W/cm-1K-1), Wide band gap (5.96 eV), Easy workability…

[Application fields]*1,2

• Refractory crucible & mold

• High-temperature lubricant or insulator

• Thermal conductor, Additive to cosmetic products, Cement in dentistry & medicine, Ultraviolet emitter, etc.

[Representative manufacturers]

Kennametal, Saint-Gobain, ZYP Coating, H.C. Starck, Momentive, etc.

*1. R. Haubner, Springer-Berlin, pp 1-45., (2002); 2. B. Ertug, Sintering Applications, (2013); 3. Image courtesy of Denka; 4. Image courtesy of ALB Materials

Fig. Images of hexagonal boron nitride powders*3 and crucibles*4

Why BN? Hexagonal BN (hBN)3

Why BN? Cubic BN (cBN)4

[Properties & characteristics]

• Super-hardness (45-70 GPa)*1

• High temperature oxidation resistance (up to 1000°C)*2,3

• Chemical stability to ferrous metals (up to 1200°C)*4

• High thermal conductivity (13 W/cm-1K-1)*2, Wide band gap (6.36 eV)*5, Can be doped as n-/p-type semiconductors*6

[Application fields]

• Abrasive: grinding powders & cutting tools (especially for machining steels and cast iron)

• High-temperature semiconductor, Electrical insulator, Heat sink, Protective coating for optical devices*7,8

[Representative manufacturers]

Sumitomo, Showa Denko, UK Abrasives, De Beers, Sandvik, etc.

*1. O. O. Kurakevych, J. Superhard Mater., 31 139 (2009); 2. B. I. Konyashin et al., Chem. Vap. Deposition, 3 239 (1997); 3. K. Teii et al., Appl. Mater.

Interfaces, 5 2535 (2013); 4. L. Vel et al., Mater. Sci. Eng., B10 149 (1991); 5. D. A. Evans et al., J. Phys.: Condens. Matter, 20 075233 (2008);

6. C. B. Samantaray et al., I. Mat. Rev., 50 313 (2005); 7. X. W. Zhang et al., J. Mater. Sci. 36 1957 (2001); 8. R. H. Wentorf et al., Science, 208 872 (1980);

9. Image courtesy of NGK Spark Plugs; 10. C. Sorensen et al. Friction Stir Weld. 2017.

Fig. Images of cubic boron nitride powders, cutting tools*9, and friction stir welding pin*10

10 μm

• Cubic BN has been synthesized by high pressure processing*1

• Limited size availability (mostly up to 0.5 mm*2; max ca. 3.0 mm by a seed growth process*3,4)

Have limited a more widespread application of cBN

Critical Issues with cBN

Fig. Boron nitride phase equilibrium diagram*5 and the lines of direct transformations between the BN polymorphs*6.

P (

GP

a)

T (K)

15

10

5

01000 2000 3000 40000

cBN

hBNLiq.

wBN

rBN

wBN cBN

cBN

hBN, rBN

rBN hBN

wBN hBN

*1. F. P. Bundy and R. H. Wentorf, J. Chem. Phys., 38 1144 (1963); *2. R. H. Wentorf, New Diamond Sci. Technol. (MRS Int. Conf. Proc.), 1029 (1991);

*3. S. Yazu et al, US Patent 4699687 (2007); *4. R. J. Caveney, Mater. Sci. Eng. B11 197 (1992); *5. F. R. Corrigan and F. P. Bundy, J. Chem. Phys.,

63 3812 (1975); *6: M. I. Petrescu et al., U.P.B. Sci. Bull., 69 35 (2007)

S 5

5

6Typical Methods for cBN Synthesis

S 6

Fig. Typical methods for cBN synthesis and their condition-regions.

* Phase equilibrium diagram: V. L. Solozhenko et al., "Refined Phase Diagram of Boron Nitride," J. Phys. Chem. B, 103 2903 (1999)

Direct transformation

(static compression)

Precursor optimization

: hBN with small particle size, low

crystallinity, defective structure; aBN;

tBN; rBN; milled BN

Catalyst-solvent process

Super-critical fluid system

Vapor phase deposition or

Solvothermal/ Hydrothermal

[ cBN powder/film, Low pressure ]

: liquid/vapor-state diffusion

[cBN Bulk High pressure]

: diffusionless/solid-state diffusion

P (

GP

a)

T (K)

10

8

4

0800 2400 3200 40000

cBN

6

2

1600400 1200 2000 2800 3600

9

5

7

3

1

hBN Liq.

7Threshold Pressures of Typical Approaches

Pre

ssu

re

*1. F. P. Bundy and R. H. Wentorf, J. Chem. Phys., 38 1144 (1963); *2. V. P. Alexeevsky et al., US Patent 3876751 (1975); *3. M. Wakatsuki et al., Mat.

Res. Bull., 7 999 (1972); *4. T. Semenic et al., J. Am. Ceram. Soc., 101 4791 (2018)

Small particle size hBN*36.0 GPa

Direct transformation + hBN*111.5 GPa

Defective hBN*28.0 GPa

How can we further reduce the threshold

pressure for cBN synthesis?

How?

High energy milled hBN*45.5 GPa

“Activate

the energy state of

BN precursor”

Our Approach

Current Pathway to High Pressure Phase

Amorphous

Phase

Low Density

Phase

Intermediate Density

Phase

High Density

Phase

8

Metastable Pathway to High Pressure Phase

Alter the transformation sequence to stable high

pressure phase through the used of metastable phase.

Metastable

Phase

High Density

Phase

aBN

En

erg

y

Phase

hBN

cBN

Metastable BN

defective hBN

8 GPa

small size hBN

6 GPa

milled hBN

5.5 GPa

Direct transformation

11.5 GPa

Activation

energy

barrier

(Ea)

“Metastable Pathway”

Metastable BN Phases? How to Prepare?9

• Metastable Amorphous Phase

: Amorphous BN/BCNO (before crystallization happens)

* BCNO compound is one of the most common precursors for the synthesis of BN.

However, limited information on the BCNO compounds and their synthesis.

Investigate the synthesis of BCNO compounds.

• Metastable Crystalline Phase

: tBN, rBN, eBN, oBN, wBN

Utilize processes that create non-equilibrium environment such as ‘Plasma spray’ and

‘Emulsion detonation synthesis’, which provides high temperature or

high temperature high pressure conditions followed by fast cooling process.

Objective & Scope10

Synthesize Metastable

Amorphous BCNO Compounds

• With varying chemistries and structural ordering

M. Ornek, C. Hwang and R. Haber et al., Ceramics

International, 44(13) 14980 (2018)*

Metastable Amorphous Phase

Investigate BN Formation

from aBCNO Compounds

under Heat or Heat & Pressure

* Related paper published or accepted.


Crystalline BN Phase

• Plasma Spray

K. M. Reddy, C. Hwang and R. Haber et al., Acta Mater.,

116 155 (2016)*

• Emulsion Detonation Synthesis

- M. Ornek C. Hwang and R. Haber et al. Scripta Mater.

145 126 (2018)*

- M. Ornek C. Hwang and R. Haber et al., J. Amer. Ceram.

Soc. 101 (8) 3249 (2018)*

Metastable Crystalline Phase

Investigate Phase Transformation

Behavior of Metastable BN Phase


How chemistry & structural ordering of aBCNO impact

the formation of BN under,

• Heat: 1400-1800°C

M. Ornek, C. Hwang and R. Haber et al., Journal of Solid

State Chemistry, Accepted.*

• Heat & pressure: 1200°C & 1 GPa

C. Hwang and R. Haber et al., Diam. Relat. Mater., 87 156

(2018)*

Synthesis of BCNO Compounds11

• Starting material

: Boric acid (H3BO3)/ B source and Melamine (C3H6N6) or Urea (CO(NH2)2)/ N source

• Preparation method

: Solid-state reaction method; 2-step heating process

Cooling & Pulverizing

NoteExperimental Procedure

Mixing H3BO3 and C3H6N6 or CO(NH2)2

2nd Heating: 400-1000 °C; 3 h; N2 gas (2 L/min)

BNCO compounds

with varying chemistries & crystallinities

1st Heating: 200 °C; 2 h; air

Cooling & Crushing & Mixing

H3BO3:C3H6N6 = 1:1 – 6:1 (mole)

* Control factor 1: Staring composition

DTA/TG analyses

* Control factor 2: Heating temperature

XRD, SEM, EDS*, FTIR, Raman, TEM, EELS*

* EDS: Energy-dispersive X-ray spectroscopy , EELS: Electron energy loss spectroscopy.

(b)(a)

BCNOs with Varying Chemistries & Structural Ordering12

Fig. 1. Chemical composition (a) and XRD patterns of representative BCNOs.

Fig. 2. TEM micrographs of BCNOs, of which synthesis temperature=400, 500, and 600°C and the starting H3BO3:C3H6N6 =6:1.

* M. Ornek, C. Hwang and R. Haber et al., Ceramics International, 44(13) 14980 (2018)*

• Based on XRD characterizations, selected aBCNO compounds and subjected them to post treatment.

Formation of BN from aBCNO Compounds13

• Investigate how chemistry & structural ordering of aBCNO impact the formation of BN under

heat or heat and pressure.

* Control factor: i) Staring composition for aBCNO (H3BO3:C3B6N6 ratio); ii) Synthesis temperature for aBCNO

Metastable aBCNOs with

varying chemistry & structural ordering

Post Heat Treatment

High temperature graphite resistance furnace

(Model 1000A, Thermal Technology LLC)

• Temperature range considered: 1400-1800°C • Pressure & temperature conditions: 1 GPa & 1200°C

High pressure high temperature equipment

(QuickPress, Depths of the Earth Inc.)

Post Heat & Pressure Treatment

Formation of BN from aBCNO under Heat14

• After post heat-treatment at 1800°C, tBN/hBN formed from aBCNOs.

• H3BO3:C3H6N6 (BA:M) ratio for BCNO ↑ Formation and structural ordering of BN ↑.

aBCNO tBN/hBN1800°C x 1h

10 20 30 40 50 60 70 80 90

BA:M=6:1

BA:M=3:1

Inte

nsity (

a.u

.)

2 theta (°)

BA:M=1:1

Fig. Normalized XRD patterns of BCNOs post heated at 1800°C for 1h.Fig. Normalized XRD patterns of BCNOs, of which synthesis

temperature is 400°C.

* M. Ornek, C. Hwang and R. Haber et al., Journal of Solid State Chemistry, Accepted.

BA:M


• H3BO3:C3H6N6 (BA:M) ratio for BCNO ↑ Formation and structural ordering of BN ↑.

aBCNO tBN/hBN1400~ 1800°C x 1h


BA:M

Fig. FE-SEM micrographs of synthesized BN powders. Scale bars in micrographs correspond to 1μm.


• Amorphous BCNO (BA:M=6:1) treated at 1800°C for 1h showed a well-developed crystal structure of BN.


aBCNO

(BA:M=6:1)Well-developed hBN1800°C x 1h

Fig. TEM study of BN powders synthesized using BA:M = 6:1 molar ratio at 1800°C.

Formation of BN from aBCNO under Heat & Pressure17

• After post treatment at 1200°C and 1 GPa, tBN/hBN formed from aBCNOs.

• Still, increase in H3BO3:C3H6N6 (BA:M) ratio for BCNO promotes formation and structural ordering of BN.

aBCNO tBN/hBN1200°C x 1 GPa

Fig. XRD patterns of BNCO compounds post treated at 1200°C and

1 GPa.

* C. Hwang and R. Haber et al., Diam. Relat. Mater., 87 156 (2018).

10 20 30 40 50 60 70 80

Inte

nsity (

a.u

.)

2 theta (°)

(10)

(10)

(110)(004)(102)

(101)

(100)

h-BN

BA:M=6:1

BA:M=3:1

BA:M=1:1

(002)

(101)

(100)

10 20 30 40 50 60 70 80 90

BA:M=6:1

BA:M=3:1

Inte

nsity (

a.u

.)

2 theta (°)

BA:M=1:1

Fig. Normalized XRD patterns of BCNOs, of which synthesis

temperature is 400°C.

BA:M=2:1

BA:M=6:1

Why Increase in BA:M Promotes BN Formation?18

• Temperature dependence of Gibbs free energies

: More negative with increase in BA:M ratio, leading to lower theoretical formation temperature of BN.

An increase in BA:M ratio promotes BN formation.

Fig. Gibbs free energy for the formation of BN from H3BO3-C3H6N6 mixtures.

* M. Ornek, C. Hwang and R. Haber et al., Ceramics International, 44(13) 14980 (2018).

Objective & Scope19





International, 44(13) 14980 (2018)*








• Plasma Spray


116 155 (2016)*



145 126 (2018)*


Soc. 101 (8) 3249 (2018)*







• Heat: 1400-1800°C





(2018)*

√

√

Synthesize Metastable Crystalline BN Phase: High Energy Plasma Spray20

• Through a high energy plasma spray method, rapid quenching of particles from the fully molten state

can be achieved.

Plasma

spray gun

Feeding of starting

materials (20-50 um)

Plasma sprayed

and quenched

metastable

particles

3000 ~ 5000 °C

Water-cooled

copper chill plate

Water-cooled

copper roller

Water quenching type (Cooling rate: -104 K/sec)

Splat quenching type (104-106 K/sec)

Twin-roller quenching type (105-108 K/sec)

Water

• DC Axial Plasma Spray Technology*

Fig. Schematic diagram of plasma spray method.*

* Z. H. Kalman and W. E. Mayo et al. US Patent publication 0020916 A1 (2009)

High Energy Plasma Spray21

Plasma spray nozzle with shroud Plasma spraying aBCNO on a chill plate Deposition on the

chill plate after plasma

spraying aBCNO

10 20 30 40 50 60 70 80

0

20

40

60

80

100

Inte

nsity

(%

)

2 Theta (degree)

hBN

H3BO3

cBN

Aluminum

(from chill plate)

Fig. 1. The XRD pattern of aBCNO- H3BO3 mixture after plasma spraying. Fig. 2. TEM images of cBN in aBN after plasma spraying.

Nanosize cBN (4-5 nm size)

embedded in aBN phase

cBN

(111)

Fig. 4. Simulated image of cBN.Fig. 3. High magnification TEM micrograph of experimental cBN.

* K. M. Reddy, C. Hwang and R. Haber et al., Acta Mater., 116 155 (2016).

Nanosized cBN Formation through Plasma Spray Process22

• Observed the formation of nanosized cBN in aBN matrix after plasma spraying.

* K. M. Reddy, C. Hwang and R. Haber et al., Acta Mater., 116 155 (2016).

Improvement of cBN Formation during Plasma Spray23

• Improved cBN formation by adding boron to the precursor.

β-B

β-B

tBN (0002)

cBN (111)

cBN (200)

cBN (220)

•Precursor: aBCNO + H3BO3 (25 wt%) •Precursor: aBCNO + H3BO3 (20 wt%) + B (20 wt%)

311220

111

200

tBN (0002)

cBN combined in tBN

“cBN content: about 10 %”

(quantitative TEM approximation)

Fine grain size (<20 nm) cBN

Fig. Electron diffraction patterns and low-resolution TEM images of plasma sprayed precursors

Increase of

cBN peak

intensity

New Method for the Preparation of Metastable Phase

- Emulsion Detonation Synthesis (EDS) - 24

Water-in-oil Emulsion Detonation

Reactions in the plasma under HPHT

Quenching of particles formed

(1012 bar/s; 109 K/s)

“High Temp. + High P + Fast quenching”“Homogeneous dispersion of precursors”

Oil

Droplet of

precursor-H2O-

NH4NO3

[SEM image of emulsion matrix*1]

[Merits of EDS process]

• Reactions proceeds under high pressure (1-10 GPa or more) and high temperature (500-3500 °C or more).

• The reaction product is quenched at high rates retention of metastable phase or nanocrystalline state.

Ideal for synthesizing metastable phases.

*1. Z.W. Han et al. Combustion, Explosion, and Shock Waves, 50(4) 477 (2014); *2 Da Silva, SMP. US Patent 8,557,215 (2013); *3 Da Silva, JMC, US Patent

2013/0251623; *4 N. Neves et al. J. Eur. Ceram. Soc. 34 (10) 2014.

[So far by EDS process]• Nanostructured cubic zirconia (ZrO2), alumina (Al2O3), titanium dioxide (TiO2), spinel (MgAl2O4), aluminum nitride (AlN),

magnetite (Fe3O4) and aluminum doped zinc oxide (AZO) ceramics*2,3,4

Formation of Metastable eBN through EDS25

• Observed the formation of nanosized eBN in hBN matrix after EDS process.

hBN wt%

in Emulsion

Oil wt%

in Emulsion

Emulsion

Density (g/cm-3)

Calculated Detonation

Velocity (m/s)*1

Calculated Pressure

P(C,J)*1

10 15 1.1 4300 5 GPa

• Experimental Conditions

*1. THOR Program ; 2. FFT: Fast Fourier transform

Fig. (a) SAED pattern, (b) the extracted profile intensity vs. d spacing values of the SAED, (c) HR TEM image taken along <111>

orientation, (d) a zoom-in HRTEM image taken along〈211〉orientation and the corresponding FFT*2 inset image.

• eBN

- ‘e’ is standing for explosion, since it was first synthesized by explosive shock compression.

- Promising from the view point of metastable pathway, since eBN is a metastable phase with cubic structure (face-centered cubic)

- eBN is called “Metastable cBN”.

*M. Ornek C. Hwang and R. Haber et al. Scripta Mater., 145 126 (2018).

Improve the Pressure Being Generated26

• Change in cylinder configuration.

[Previous]

Single-cylinder

[Present]

Double-cylinder

Outer cylinder

: Emulsion wo hBN

Inner cylinder

: Emulsion w hBN

5 GPa 7 GPa

Outer cylinder

Outer cylinder

Inner cylinder

[Design Concept]*

• Shock velocity in inner cylinder < that in outer cylinder.

The impedance mismatch generates a converging shock

and a subsequent Mach reflection at the center of the inner

cylinder.

Resulting Mach configuration propagates through the rest

of the cylinder.

Formation of Metastable wBN through EDS27

• Increased pressure from 5 GPa to 7 GPa Observed the formation of wBN in hBN matrix.

* M. Ornek C. Hwang and R. Haber et al., J. Amer. Ceram. Soc. 101 (8) 3249 (2018).

• w-BN formation from nano (50 nm) to ~micron size.

• w-BN formation in h-BN matrix (particle-like).

• w-BN formation as separate grain(sheet-like).

Fig. STEM/EELS mapping of EDS product and w-BN phase*

Fig. TEM and EELS*1 analysis of the EDS’ed particles.

(a) Bright field image of the particle, (b) SAED* taken from the entire grain, and

EELS spectra taken from Area 1 (c) and Area 2 (d) on (a).

Fig. TEM and STEM/EELS map analysis of the

particle with sheet morphology.

(a) Bright field and (b) high annular dark-field

(HAADF) micrographs. Chemical mapping using

the energy range from B-K edge (189-220 eV) in

(c) total boron count. (d) Low intensity signal was

observed in p count only. A similar observation was

made in the N-K edge maps as shown in (e) total

nitrogen counts and (f) only p count.

*1. EELS: Electron energy loss spectroscopy.;

2. SAED: Selected area electron diffraction

Area 1

: h-BN

Area 1Area 2

Area 2

: w-BN

Summary28





International, 44(13) 14980 (2018)*








• Plasma Spray


116 155 (2016)*



145 126 (2018)*


Soc. 101 (8) 3249 (2018)*







• Heat: 1400-1800°C





(2018)*

Team & Acknowledgements29

CCOMC

Clemson



Rutgers

CCOMC

Clemson



Rutgers

Questions & Answers

CCOMC

Clemson



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Clemson



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er Metastable Pathway to cBN