research progress - okabe.iis.u-tokyo.ac.jp filemetallurgical process: ti, mg rare earth : la, ce,...
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Research Progress
Hongmin ZHU
University of Science & Technology BeijingBeijing, China
Zhu / USTB MIT workshop March 1, 2007
Our targets
New processNew materials
Zhu / USTB MIT workshop March 1, 2007
research topic
Nano-sized powder production: Ta, Nb, Si3N4, TiN
Metallurgical process: Ti, Mg
Rare earth : La, Ce, Nd
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
Nano - productsTiN
10nm
Zhu / USTB MIT workshop March 1, 2007
products
Zhu / USTB MIT workshop March 1, 2007
TiN ceramic
Products
TiN nano-powder
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
Fig1.5 TEM images of powders after a)1350℃、b) 1450℃ and c) 1500℃heat-treatments for 2h
Zhu / USTB MIT workshop March 1, 2007
Fig3.2 TEM images of Si3N4 powder a) and
15vol%TiN- Si3N4 b)
Zhu / USTB MIT workshop March 1, 2007
Fig4.1 SEM images of fractured surface of 10vol%TiN-Si3N4 bulk produced by in-situ coating
Properties of Si3N4-TiN bulks microstructures
Zhu / USTB MIT workshop March 1, 2007
20vol%TiN-Si3N4 Si3N4
Fig TEM images of fractured surface 20vol%TiN-Si3N4 a) and Si3N4 bulks b)
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
EletrochemicalCo-deposition of Magnesium Alloy
in Alkali Chloride Melt
Zhu / USTB MIT workshop March 1, 2007
MagnesiumMagnesium--based alloybased alloyss
Low density
Good mechanical and chemical properties
Good recycling capability
Excellent Excellent performancesperformances
Wide applicationsWide applications
Background
Zhu / USTB MIT workshop March 1, 2007
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)
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
How can we control the component of the alloy??
time
AlCl3wt%
feeding
Al wt%
time
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
Experimental SetExperimental Set--upup
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
-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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
-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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
-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
Zhu / USTB MIT workshop March 1, 2007
image of Mg-Al (12.85wt%) alloy after 10-hour electrolysis; (b) metallic phase image of the alloy amplified to 200 times.
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
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
Zhu / USTB MIT workshop March 1, 2007
Thanks!
Thank you for your
attention!
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