1

Production of Scandium and Al-Sc Alloy

Masanori Harataa, Takao Nakamurab

Hiromasa Yakushijic, Toru H. Okabea

aThe University of TokyobChiba Institute of TechnologycPacific Metals Co., Ltd.

2

1. Introduction

2.Metallothermic reduction

3.Molten salt electrolysis

4.Summary

Production of Scandium and Al-Sc Alloy

3

Scandium?

Halide lamp

・One of the rare earth elements・Low density (2.99 g / cm3)・High chemical reactivity・High price (10,000~ yen / g)

Bicycle frame

Sc metal

Al-Sc alloy Al-Sc alloy

MIG29

4

Crustal abundance of scandium

01 08 O 46.60 24 30 Zn 07.0×10-3・・・ ・・・ ・・・ ・・・

02 14 Si 27.72 25 58 Ce 06.0×10-3 46 68 Er 02.8×10-4

03 13 Al 08.13 26 29 Cu 05.5×10-3 49 50 Sn 02.0×10-4

04 26 Fe 05.00 27 39 Y 03.3×10-3 50 73 Ta 02.0×10-4

05 20 Ca 03.63 28 57 La 03.0×10-3 51 92 U 01.8×10-4

06 11 Na 02.83 29 60 Nd 02.8×10-3・・・ ・・・ ・・・ ・・・

07 19 K 02.59 30 27 Co 02.5×10-3 55 74 W 01.5×10-4

08 12 Mg 02.09 31 21 Sc 02.2×10-3 56 63 Eu 01.2×10-4

09 22 Ti 00.44 ・・・ ・・・ ・・・ ・・・・ 57 67 Ho 01.2×10-4

10 01 H 00.14 33 07 N 02.0×10-3 58 65 Tb 08×10-5

11 15 P 00.105 34 41 Nb 02.0×10-3 59 53 I 05×10-5

12 25 Mn 00.095 35 31 Ga 01.5×10-3 60 69 Tm 05×10-5

13 09 F 00.0625 36 82 Pb 01.3×10-3 61 71 Lu 05×10-5

・・・ ・・・ ・・・ ・・・ 37 05 B 01.0×10-3・・・ ・・・ ・・・ ・・・

16 16 S 00.026 38 59 Pr 08.2×10-4 67 80 Hg 08×10-6

17 06 C 00.020 ・・・ ・・・ ・・・ ・・・ 68 47 Ag 07×10-6

・・・ ・・・ ・・・ ・・・ 40 62 Sm 06.0×10-4・・・ ・・・ ・・・ ・・・

20 17 Cl 00.013 41 64 Gd 05.4×10-4 73 78 Pt 01×10-6

・・・ ・・・ ・・・ ・・・ 42 66 Dy 04.8×10-4 74 45 Rh 05×10-7

23 28 Ni 07.5×10-3 43 70 Yb 03.0×10-4 75 79 Au 04×10-7

Rank. Atomicnumber,Z

Element Content ofearth crust(%)

Rank Atomicnumber,Z

Element Content ofearth crust(%)

Rank. Atomicnumber,Z

Element Content ofearth crust(%)

Scandium is the 31st most abundant element in the earth crust.

31st abundant

5

Thortveitite 25.0~48.3Zircon 0.005~0.3Beryl 0.0005~1.2Garnet 0.02~0.4Olivine 0.0003~0.02Pyroxene ~0.04Xenotime 0.0015~1.5Monazite 0.002~0.5Apatite 0.0003~0.08Davidite 0.02Columbite 0.01~0.8Uraninite 0.15~0.2Wolframite 0.005~1.3Magnetite 0.001~0.04Hematite ~0.15Titanomagnetit 0.0002~0.02Ilmenite 0.0015~0.15Rutile 0.005~0.16Laterite 0.003~0.03

Silicates

Form Mineral nameContent ofSc2O3 (mass%)

Phosphates

Oxides

Scandium-containing minerals

Sc is distributed very widely among 800 different earthly species of minerals.

Currently, Sc is recovered from rare earth ores or as a by-product from uranium mill tailings.

Recently, possibility of recoveringSc from Ni laterite ore is focused.

Thortveitite ore [(Sc, Y)2Si2O7]

~48.3 mass%Sc2O3

6

Possibility of recovering scandium from nickel ore

Pyrometallurgical process

Ni ore containing Sc

Sc2O3 in a slag can not be recovered.

Hydrometallurgical process

Matte/Metal

Leachant

Ni

Slag Ni and Co recovery

Ni and Co Leachant

Sc2O3

Sc2O3 in leachant can be recovered at a low cost.

Containing Sc2O3

Pyrometallurgy

Ni ore containing Sc

Hydrometallurgy

7

Fluorination: Sc2O3 (s) + 6 HF (g) → 2 ScF3 (s) + 3 H2O (g)

Reduction: 2 ScF3 (l) + 3 Ca (g) → 2 Sc (l) + 3 CaF2 (l)

973 K

~1873 K

⋅The production cost is high because an expensive reaction apparatus is required for handling fluorides.

⋅Contamination from the crucible can not be prevented due to the high temperature reaction.

Disadvantage

Development of a new process which can produce Sc metal or Al-Sc alloy directly from Sc2O3 at low temperatures (~1273 K).

Purpose of this study

Purpose of this study

Conventional process

Sta

ndar

d G

ibbs

ene

rgy

of fo

rmat

ion,

ΔGﾟ f

/kJ

mol

-1

Ellingham diagram

Temperature, T / K

-1200

-1000

300 500 700 900 1100 1300

-800

4/3 Sc + O2= 2/3 Sc2O3

4/3 Al + O 2= 2/3 Al 2O 3

Ti + O2= TiO2

4/3 La + O2= 2/3 La2O32/3 Sc + F2 = 2/3 ScF3

Ca + F2= CaF2

-900

-1100

-1300

2 Ca + O 2= 2 CaO

8

1. Introduction

2.Metallothermic reduction

3.Molten salt electrolysis

4.Summary

Production of Scandium and Al-Sc Alloy

9

The concept of metallothermic reduction

Stainless steel reactionchamber

Ta crucible

Ca shots

Ti sponge

Sc2O3 (+ Al + CaCl2)

Ca vapor

Reduction:

4 Sc2O3 (s) + 3 Ca (g) → 2 Sc (s) + 3 CaSc2O4 (s)

Reduction and alloying:

Sc2O3 (s) + Al (l) + 3 Ca (g) → Al-Sc alloy (l) + 3 CaO (s)

Metallothermic reduction

Temperature, Tred = 1273 K

Time: t’red = 6 h

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Reduction experiment in the absence of a collector metalExp. A: Sc2O3 (0.005 mol) + Ca (0.030 mol, vapor)

Angle, 2θ / degreeIn

tens

ity, I

(a.u

.)10 20 30 40 50 60 70 80 90 100

Result (1)

×

×

××

×

×

×

×

×

×

×

××

×

×

××

×

××

×

××

×

×

×

××××

◆

◆

○

JCPDS # 17-0714JCPDS # 05-0629JCPDS # 20-0234

◆ Sc× CaSc2O4○ Sc2O3

A complex oxide (CaSc2O4) was formed and reduction was incomplete.

Obtained sample

Sc2O3 (+ Al) + Ca

●

●

●● ●

● ●●

▼

▼

▼▼

▼×

×

× ×

× ×

●Al3Sc▼Al×Al4Ca

JCPDS # 17-0412JCPDS # 04-0787JCPDS # 14-0428

10 20 30 40 50 60 70 80 90 100Angle, 2θ(degree)

Inte

nsity

, I(a

. u.)

Reduction experiment using a collector metalExp. B: Sc2O3 (0.0011 mol), Ca (0.0065 mol), Al (0.036 mol)

Sc2O3 was successfully reduced to metallic Sc and alloyed in situ to form liquid Al-Sc alloy without forming CaSc2O4.

Obtained Al-Sc alloy

11

Reduction experiment using a collector metal and flux

◆

◆

◆ ◆

◆■

◆

■

■ ■

■□□

■□ □ □ □ □ □

10 20 30 40 50 60 70 80 90 100In

tens

ity, I

(a.u

.) Angle, 2θ / degree

◆ Al■ Al3Sc□ Al4Ca

JCPDS # 04-0787JCPDS # 17-0412JCPDS # 14-0428

Al3Sc

Al4Ca

(a) Aluminum (b) Scandium (c) Calcium

Exp. C: Sc2O3 (0.0011 mol), Ca (0.0065 mol), Al (0.036 mol), CaCl2 (0.0095 mol)

EPMA analysis

Result (2)

Metallic phase was easily separated from slag phase.

Obtained Al-Sc alloy

Sc2O3 + Al + Ca +CaCl2

12

1. Introduction

2.Metallothermic reduction

3.Molten salt electrolysis

4.Summary

Production of Scandium and Al-Sc Alloy

13

e-

↓ Sc2O3

CaCl2 + Sc2O3 molten salt

Carbon electrode (anode)

Al liquid electrode (cathode)

Cathodic reaction : Sc3+ (in salt) + 3 e- → Sc (l, in Al)Anodic reaction : C (s) + x O2- (in salt) → COx (g) + 2x e-

Overall reaction : Sc2O3 (in salt) + C (s) → 2 Sc (in Al)+ COx (g)

O

e-

Al liquid electrode

Solid Sc2O3particle

e-

O2-

Molten salt

The concept of molten salt electrolysis

Electrolysis

T = 1173 K

14

5 mm

(c) Calcium(a) Aluminum (b) Scandium

Sectioned sample

Al3Sc

Molten salt electrolysis (XRD, EPMA)

10 20 30 40 50 60 70 80 90 100

●

●

●

●

●

●▼ ▼ ▼ ▼

Angle 2θ/ degree In

tens

ity, I

(a.u

.) ●Al▼Al3Sc

JCPDS # 17-0412 JCPDS # 04-0787

10 20 30 40 50 60 70 80 90 100

●

●

●

●

●

●▼ ▼ ▼ ▼

Angle 2θ/ degree In

tens

ity, I

(a.u

.) ●Al▼Al3Sc

JCPDS # 17-0412 JCPDS # 04-0787

XRD analysis

EPMA analysis

Sc segregated at the surface of the sample.

Analysis area

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Exp. # Molten salt system Current, i /A Time, t /s Al Sc Ca Fed-11 CaCl2-1.37mol%Sc2O3 1.00 1800 88.3 11.5 0.14 <0.01

d-12 CaCl2-1.37mol%Sc2O3 1.00 1800 96.9 3.1 <0.01 <0.01 d-21 CaCl2-2mol%Sc2O3 0.25 7200 97.4 2.2 0.21 0.26d-31 CaCl2-2mol%Sc2O3 1.00 1800 83.3 16.3 0.28 0.19d-41 CaCl2-2mol%Sc2O3 1.00 3600 95.6 3.9 0.46 <0.01 d-51 CaCl2-4mol%Sc2O3 0.25 3600 98.9 0.8 0.08 0.21d-61 CaCl2-4mol%Sc2O3 0.50 3600 92.4 6.7 0.45 0.47d-71 CaCl2-4mol%Sc2O3 1.00 1800 93.2 6.2 0.35 0.25d-81 CaCl2-4mol%Sc2O3 1.00 3600 85.7 13.8 0.39 0.09d-91 CaCl2-8mol%Sc2O3 0.25 3600 67.0 32.3 0.65 <0.01 d-92 CaCl2-8mol%Sc2O3 0.25 3600 83.1 16.5 0.10 0.27d-101 CaCl2-8mol%Sc2O3 0.25 7200 89.4 9.6 0.39 0.60

XRF results of the samples obtained after the electrolysis.

1 Surface of the sample was analyzed.2 Section of the sample was analyzed.

Molten salt electrolysis (XRF)

Al-Sc alloy with low Ca contamination (<0.65 mass%) was successfully produced by electrolysis of CaCl2-Sc2O3 molten salt.

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0.6

0

0.2

0.4

0 1000 2000 3000 4000Electrical charge Q / C

Cal

cula

ted

mas

s of

Sc

in th

e sa

mpl

e, w

Sc/ g

(a) CaCl2-2mol%Sc2O3 molten salt

▲0.25 A■ 1 A

Theoretical maximum

ε = 100%

▲ 0.25 ATheoretical maximum

0.6

0

0.2

0.4

0 1000 2000 3000 4000Electrical charge Q / C

Cal

cula

ted

mas

s of

Sc

in th

e sa

mpl

e, w

Sc/ g

(c) CaCl2-8mol%Sc2O3 molten salt

ε = 100%

▲ 0.25 A○ 0.5 A■ 1 A

Theoretical maximum

0.6

0

0.2

0.4

0 1000 2000 3000 4000

Cal

cula

ted

mas

s of

Sc

in th

e sa

mpl

e, w

Sc/ g

Electrical charge Q / C

(b) CaCl2-4mol%Sc2O3 molten salt

ε = 100%

0.6

0

0.2

0.4

0 1000 2000 3000 4000Electrical charge Q / C

Cal

cula

ted

mas

s of

Sc

in th

e sa

mpl

e, w

Sc/ g

(a) CaCl2-2mol%Sc2O3 molten salt

▲0.25 A■ 1 A

Theoretical maximum

ε = 100%

▲ 0.25 ATheoretical maximum

0.6

0

0.2

0.4

0 1000 2000 3000 4000Electrical charge Q / C

Cal

cula

ted

mas

s of

Sc

in th

e sa

mpl

e, w

Sc/ g

(c) CaCl2-8mol%Sc2O3 molten salt

ε = 100%

▲ 0.25 A○ 0.5 A■ 1 A

Theoretical maximum

0.6

0

0.2

0.4

0 1000 2000 3000 4000

Cal

cula

ted

mas

s of

Sc

in th

e sa

mpl

e, w

Sc/ g

Electrical charge Q / C

(b) CaCl2-4mol%Sc2O3 molten salt

ε = 100%

・Current efficiency of each sample varied widely.・In some experiment, current efficiencywas more than 100%.

wSc = wAl-Sc × CScwSc : Mass of Sc in the sample.wAl-Sc: Mass of the sample obtained

after electrolysis.CSc : Concentration of Sc in the

sample determined by XRF.

Evaluation of current efficiency

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・When Al was used as a collector metal for the reduction of Sc2O3,metallic Sc was successfully obtained directly from Sc2O3 and alloyedin situ to form liquid Al-Sc alloy.

Metallothermic reduction

Molten salt electrolysis

・When aluminum was used as a collector metal, excess calcium remained in the alloy sample in the form of Al4Ca.

Summary

・ Al-Sc alloy（0.81~32.31 mass%) with low calcium impurity(~0.69 mass%)was successfully produced by the electrolysis of CaCl2-Sc2O3 molten salt.

・ It was difficult to evaluate the current efficiency of electrolysis becauseSc segregated around the surface of the Al-Sc alloy sample.

For producing Sc and Al-Sc alloy directly from Sc2O3 at low temperatures,metallothermic reduction and molten salt electrolysis were conducted.

18

Future Process of high performance Al alloy production

Al-Sc liquid alloy

e-

↓

Sc2O3

CaCl2 + Sc2O3 molten salt

Carbon electrode (anode)

Al-Sc liquid alloy

VA

COx (g)Al

Al-Sc liquid alloy

e-

↓

Sc2O3

CaCl2 + Sc2O3 molten salt

Carbon electrode (anode)

Al-Sc liquid alloy

VA

COx (g)Al

Al-Sc liquid alloy with low Ca

Cathodic reaction:Sc3+ (in salt) + 3 e- → Sc (l, in Al)Anodic reaction:C (s) + x O2- (in salt) → COx (g) + 2x e-

Overall reaction:Sc2O3 (in salt) + C (s)

→ 2 Sc (in Al)+ COx (g)