Research Progress - okabe.iis.u-tokyo.ac.jp fileMetallurgical process: Ti, Mg Rare earth : La, Ce,...

Research Progress

Hongmin ZHU

University of Science & Technology BeijingBeijing, China

Zhu / USTB MIT workshop March 1, 2007

Our targets

New processNew materials


research topic

Nano-sized powder production: Ta, Nb, Si3N4, TiN

Metallurgical process: Ti, Mg

Rare earth : La, Ce, Nd


research in our group

Nano-powder of Transition Metals Produced through Homogeneous Reduction

11

Tantalum nano-powder after heat treatment at various temperatures

1170℃ 1250℃

1300℃1400℃

SEM image of nano-powder and anode pellet

1170℃

powder

1250℃/5V

pellet

1250℃/5V

press

Sintering

TEM image of anode pellet 1250℃/5V

TEM image of oxide film

1400℃/25V

CV value vs surface area

CV =CV =εεεε00 AA //ββ

0100200300400500600700800

0 5 10 15

CV

/ kµF

V g

-1

surface area / m2 g-1

100%80%

60%

40%

20%

Ta2O5

Ta

Other opportunities!!

•Si3N4

• TiN

• GaN


Nano - productsTiN

10nm


products


TiN ceramic

Products

TiN nano-powder


Synthesis of Si3N4 nanopowders

Fig1.1 X-ray diffraction patterns of product powders a), after 1350℃ heat treatment

for 2h b) and by-product c)

10 20 30 40 50 60 70 80 90

NaCl

0

10000

20000

30000

40000

2Theta/deg

0

1 00 0

2 00 0

3 00 0

4 00 0

5 00 0

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0

1 3 5 0 ?

a -S i3 N 4

2 T h e ta /d e g

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0

u nh ea t-t rea tm en t

0

1 00 0

2 00 0

3 00 0

4 00 0

5 00 0

2T h eta /d eg


Fig1.5 TEM images of powders after a）1350℃、b） 1450℃ and c) 1500℃heat-treatments for 2h


Fig3.2 TEM images of Si3N4 powder a） and

15vol%TiN- Si3N4 b)


Fig4.1 SEM images of fractured surface of 10vol%TiN-Si3N4 bulk produced by in-situ coating

Properties of Si3N4-TiN bulks microstructures


20vol%TiN-Si3N4 Si3N4

Fig TEM images of fractured surface 20vol%TiN-Si3N4 a) and Si3N4 bulks b)


90.8

91.5

97.6

98.1

Relative D/

/ %

5.7±0.617.0±1.5Si3N4-15vol%TiN

5.6±1.015.5±0.3Si3N4-30vol%TiN

4.4±0.515.6±0.6Si3N4-20vol%TiN

4.6514.4Si3N4-10vol%TiN

KIC

/MPa·m1/2

HV

/GPaSamples

Produced by in-situ coating


Conductivity of Si3N4-TiN

3.60×10-320

9.44×10-430

3.26×10-215

10910

10130

Electrical resistivity

/Ω·cm

TiN content / vol%

Ref.1 Shuichi Kawano, Junichi Takahashi, Shiro Shimada. Key.Eng. Mater. 2002,206-213

Produced by in-situ coating

-5

0

5

10

15

0 20 40 60 80 100

TiNvol%

Ref1Ref2


EletrochemicalCo-deposition of Magnesium Alloy

in Alkali Chloride Melt


MagnesiumMagnesium--based alloybased alloyss

Low density

Good mechanical and chemical properties

Good recycling capability

Excellent Excellent performancesperformances

Wide applicationsWide applications

Background


Current Producing MethodCurrent Producing Method

Simple approach, easy control

Long process

High metal waste rate

Environmental problems

electrolysis

reduction initial Mg refine pure Mg

electrolysis initial Al refine pure Al meltmix

electrolysis

reduction initial Znrefine

pure ZnAlloy

Gaseous protective agent(containing SF6)


Shama‘s approach: adding alloying agent metal previous ly in the bottom of cell (cathode)

R. Sharma. Electrolytic production process for magnesium and its alloy．EP0747509，1996.12.11

Increase the density of the alloy so that molten salt will cover the metalLarge changes in contents,Mg: 0- 95%, hard to get uniformMg deposit, not alloyNeed alloy metal previously


Our propose: electrochemical co-deposit of all elements:

get alloy directly, favored for the sinking of deposited metalless variation in content less process for alloyingdirect feeding in saltscontinuous production

Mg Mg 2+ + 2e + 2e →→ MgMgZn Zn 2+ + 2e + 2e →→ ZnZnAl Al 3+ + 3e + 3e →→ AlAl


Purpose of the Current Work

conform the possibility of direct co-deposition

understand the electrochemical behavior of the system

perform the lab-scale electrolysis of co-deposition


Possibility of Electrochemical Co-deposition

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3 5

pote

ntia

l, -E

/ V

Cl2/Cl-

Zn2+/ Zn

Al3+/ Al

Ce2+/ CeMg3+/ Mg

2.826CeCl3 = Ce + 3/2Cl3 (g)

1.444ZnCl2 = Zn + Cl2 (g)

1.766AlCl3 = Al + 3/2Cl3 (g)

2.538MgCl2 = Mg + Cl2 (g)

E0 / Vat 700℃reaction


Possibility of Electrochemical Co-deposition

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3 5

pote

ntia

l, -E

/ V

Cl2/Cl-

Zn2+/ Zn

Al3+/ Al

Ce2+/ CeMg3+/ Mg

depositon seriese of metal: Zn Al Mg Cethermodynamicly they will not deposited at the same potential


Possibility of Electrochemical Co-

deposition with kinetics

With low enough concentration of Al3+

and Zn2+ , Mg might be able to be co-deposited

Mg2++2e→Mg

Al3++3e→Al

E vs Cl2

idAl

i

-1.73 V -2.54 V

iMg

Eco

Schematic polarization curve of Mg, and Al deposition


How can we control the component of the alloy??

Mg2++2e→Mg

Al3++3e→Al

E vs Cl2

idAl

i

-1.73v -2.51v

iMg

Eco E'coshift

i =idAl+iMg feeding

E''co

Keeping the content of feed material same as in alloy expected

Set constant current consistentwith the amount of feed material in the fixed periodSchematic polarization curve

of Mg, and Al deposition


How can we control the component of the alloy??

time

AlCl3wt%

feeding

Al wt%

time


Experimental

electro-analysicaltechnique cyclic voltammetry, chronopotentiometryThree-electrode system, working: W, Mo, reference: Ag/AgCl, counter: graphite

I

1.Feeding tube（MgCl2-AlCl3-ZnCl2）

2.Graphite crucible

4.Constant current5.Electrolyte6.Mo cathode electrode7.MgO crucible

8.Mg-based alloy

3.Ag/AgCl RE


Experimental SetExperimental Set--upup


Electrochemical analysis, LiCl-NaCl-AlCl3 ,W electrode, AlCl3 :0.07M

-0.08

-0.07

-0.06

-0.05

-0.04

-0.03

-0.02

-0.01

0.00

-1.80 -1.70 -1.60 -1.50 -1.40 -1.30 -1.20

i p / A

cm

-2

E / V Cl 2 / Cl -vs

5Hz10Hz12.5Hz

(a)

-0.05

0.00

0.05

0.10

-1.8 -1.6 -1.4 -1.2 -1.0

i / A

cm

-2

E / V Cl2 / Cl-vs

0.1V s-10.2V s-10.3V s-10.4V s-1

(a)

square wave voltammogramCyclic voltammogram

a a reversablereversable process with 3 electron, process with 3 electron, AlAl3+3++3e+3e→→AlAl，，at potential of at potential of --1.58 V 1.58 V vsvs ClCl22, , diffusion coefficient: 2.73diffusion coefficient: 2.73××1010--55cmcm--22 ss--11


-0.6

-0.4

-0.2

0.0

0.2

0.4

-3 -2.5 -2 -1.5 -1

i / A

cm

-2

E / V Cl2 / Cl-vs

0.1V s-1

0.2V s-1

0.3V s-1

-0.32

-0.28

-0.24

-0.20

-0.16

-0.12

-0.08

-2.8 -2.7 -2.6 -2.5 -2.4 -2.3

i / A

cm

-2

E / V Cl 2 / Cl-

10Hz12.5Hz16.7Hz

vs

Cyclic voltammogram square wave voltammogram

a a reversablereversable process with 2 electron,process with 2 electron, ：：MgMg2+2++2e+2e→→MgMg，， at potential of at potential of --2.52 V 2.52 V vsvs ClCl22, diffusion , diffusion coefficient: 1.84coefficient: 1.84××1010--55cmcm--22 ss--11

• Electrochemical analysis, LiCl-NaCl-MgCl2 ,W electrode, MgCl2 :0.43M


LiCl-NaCl-MgCl2-AlCl3 systemMgCl2：0.43M，AlCl3：0.11M

-0.6

-0.4

-0.2

0.0

0.2

0.4

-3.0 -2.5 -2.0 -1.5 -1.0

i / A

cm

-2

E / V Cl2 / Cl-

B

A

vs

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

-2.80 -2.40 -2.00 -1.60 -1.20

i / A

cm

-2

E / V Cl2 / Cl-

A

B

vs

Cyclic voltammogram，sweep rate : 0.1V s-1

square wave voltammogram，frequency：10Hz


LiCl-NaCl-MgCl2-AlCl3-ZnCl2 systemMgCl2：0.2M，AlCl3：0.3M, ZnCl2: ：0.2M

Cyclic voltammogram，sweep rate : 0.1V s-1

-0.5

0.0

0.5

1.0

-3.0 -2.6 -2.2 -1.8 -1.4 -1.0 -0.6

i / A

cm

-2

E / V Cl2/Cl-

B AC

A'

B'C'

vs

A: Zn A: Zn 2+2+ + 2e + 2e →→ ZnZnB: Al B: Al 3+ 3+ + 3e + 3e →→ AlAlC: Mg C: Mg 2+2+ + 2e + 2e →→ MgMg


-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8

E /

V

C

l 2 /

Cl -

t / s

A

B

C

vs

0.134A cm -2

0.179A cm -2

0.224A cm -2

Chronopotentiometry with various current

• LiCl-NaCl-MgCl2-AlCl3 system, MgCl2：0.43M，AlCl3：0.11M

A: Zn A: Zn 2+2+ + 2e + 2e →→ ZnZnB: Al B: Al 3+3+ + 3e + 3e →→ AlAlC: Mg C: Mg 2+2+ + 2e + 2e →→ MgMg


Al-Mg co-deposition

-2.6

-2.4

-2.2

-2.0

-1.8

-1.6

-1.4

0 40 80 120 160

E /

V

Cl 2

/ Cl-

t / s

B

vs

Pt electrode，I：0.018A cm-2，MgCl2：0.200M，AlCl3：0.106M


-5

-4

-3

-2

-1

0

0 2 4 6 8 10Time / hr

Feeding time: ２０min

Long term contant current electrolysis, 3A

ic=1A/cm2


image of Mg-Al (12.85wt%) alloy after 10-hour electrolysis; (b) metallic phase image of the alloy amplified to 200 times.


In propertional, mor than 75%

Current efficient reached: 90%

Relationship between the contents in alloy and feed material

0

5

10

15

20

0 5 10 15 20

ZnAl a

lloyi

ng a

gent

in a

lloy

/

%

alloying agent in feed material / %

theoretical line

wt

wt


1. An electrochemical co-deposition method for magnesium base alloy was proposed;

2. The results of electroanalysicalmeasurements provide the possibility of continuous electrolysis of co-deposition;

3. Lab-scale test was performed to obtain the alloy, and the current efficient reached 90%.

in summary


Thanks!

Thank you for your

attention!

Research Progress - okabe.iis.u-tokyo.ac.jp fileMetallurgical process: Ti, Mg Rare earth : La, Ce,...

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