Shock-induced reactions in ball-milled Ti-Si powder mixtures J. J. Liu 1, N. F. Cui 2, P. W. Chen 2...
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Transcript of Shock-induced reactions in ball-milled Ti-Si powder mixtures J. J. Liu 1, N. F. Cui 2, P. W. Chen 2...
Shock-induced reactions in ball-milled Ti-Si powder mixtures
J. J. Liu1, N. F. Cui2, P. W. Chen2
1Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, China2State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing, 100081, China
2012.5.4 Strausbourg France
XI EPNM
Outline
Introduction
Experimental
Results and discussion
Conclusions
Introduction
Ti-Si system
Composition: TiSi, TiSi2, Ti5Si3, Ti5Si4
Synthesis:
Application:
Combustion synthesisSelf-propagating reactionMechanical alloyingShock induced reaction
Heat resistant materialHigh hardnessMicroelectronicsPhotocatalyst
Ti-Si photocatalyst
• As new functional materials, the light-absorption characteristics in UV-visible region (ca.360800nm) of TiSi2 are ideal for solar applications and have a good photocatalytic activity of splitting water into hydrogen.
2 2 2 2
2 2
2
6 6
12 2
2
2 2
TiSi H O TiSi oxides H
H O O H e
H e H
Ritterskamp P., et al, Angew.Chem. Int. Ed, 46:7770, 2007
Ti-Si photocatalystLiu J J., et al, AIP Conf.Proc., 1426: 1403, 2012
The coupled photocatalyst of Ti5Si3 and Ti8O15 were shock-sythesized by adding oxidant and exhibits superior photocatalytic activity.
Experimental
• A planetary ball mill (Fritsch, P-7) was used for grinding the Ti-Si samples.
300 steel balls of 3mm diameter (32g)and 8g of mixed powder in 80 ml bowl
At 300900rpm for 3h
Experimental
.
(1) detonator; (2) upper cover; (3) booster charge; (4) nitromethane; (5) bottom cover; (6) flyer;(7) steel protection tube; (8) copper sample container; (9) sample; (10) copper screw lid;(11) PVC plastic tube;(12) steel momentum block Scheme of shock-loading apparatus
Experimental conditions
Photocatalytic test
Set-up scheme of photocatalytic evaluation1. Hg lamp, 2.rubber plug, 3. quartz reactor, 4.water and photocatalyst,
5.magnetic stirrer, 6.dark box.
Results and discussion
10 20 30 40 50 60 70 80 90
dcba
Ti5Si3
TiSi
MillledTi-Si2
Q7
Q5Q3Q1
Inte
nsity
/(a.
u.)
2/(O)
10 20 30 40 50 60 70 80 90
(Milled+Shocked)Ti-Si2
d
c
b
a
412
414
410
408
Ti5Si3
Ti
Si
Inte
nsity
/(a.
u.)
2/(O)
Figure 1 XRD patterns of ball-milled Ti-Si2 mixtures at different rotary speeds (a)300rpm; (b)500rpm; (c)700rpm; (d)900rpm.
Figure 2 XRD patterns of shocked Ti-Si2 mixtures(2.25km/s) at different rotary speeds (a)300rpm; (b)500rpm; (c)700rpm; (d)900rpm.
Q7: The milled Ti-Si2 reacted to form little Ti5Si3 at 900rpm.
414:The next shock does not initiate further reaction.
Results and discussion
10 20 30 40 50 60 70 80 90
dcba
TiSi
MillledTi5-Si3
Q8
Q6Q4Q2
Inte
nsity
/(a.
u.)
2/(O)
Figure 3 XRD patterns of ball-milled Ti5-Si3 mixtures at different rotary speeds (a)300rpm; (b)500rpm; (c)700rpm; (d)900rpm.
10 20 30 40 50 60 70 80 90
(Milled+Shocked)Ti5-Si3Ti5Si3
d
c
b
a409
TiSi
415
413
411
Inte
nsity
/(a.
u.)
2/(O)
Figure 4 XRD patterns of shocked Ti5-Si3 mixtures(2.25km/s) at different rotary speeds (a)300rpm; (b)500rpm; (c)700rpm; (d)900rpm.
Q8: The milled Ti5-Si3 has not any reaction at 900rpm.
415:The next shock initiated reaction to form little Ti5Si3 .
Results and discussion
Figure 5. XRD patterns of samples derived from Ti-Si2 at different conditions: a direct shock loading at 3.37km/s without ball-mlling; b ball-milling after 3h at 900rpm; and c shock loading of sample b at 2.25km/s.
10 20 30 40 50 60 70 80 90
(c)
TiSi2
288
(b)
(a)
Ti5Si3
TiSi
Q7
414
Inte
nsity
/(a.
u.)
2/(O)
Why?
Results and discussion
Figure 6 XRD patterns of samples derived from Ti5-Si3 at different conditions: a direct shock loading at 2.25km/s without ball-mlling; b ball-milling after 3h at 900rpm; and c shock loading of sample b at 2.25km/s
10 20 30 40 50 60 70 80 90
(c)
271
Ti5Si3
(b)
(a)
TiSi
415
Q8
Inte
nsity
/(a.
u.)
2/(O)
Results and discussion
Figure.7 SEM images of samples. (a) Q7, (b)Q8,(c)414, (d)415.
b
c d
a
Partly react
Obviously react
no reaction
Partly
react
Results and discussion
0 100 200 300 400 500 600 700 800 9001000
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
exo
628OC
b
a
Q7(a) Q8(b)
DS
C/(
W/g
)
T/(OC)
0 100 200 300 400 500 600 700 800 9001000
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
b
a
exo
640OC530OC
414(a) 415(b)
DS
C/(
W/g
)
T/(OC)
Mill-activated(a>b) (Mill+Shock)-activated(b>a)
Figure.8 DSC analysis of Ti-Si samples
Photocatalytic test for producing hydrogen
0 10 20 30 40 50 60 70 80 90 1000
2
4
6
8
10
12
14
16
18
20
Ti-Si2
c
b
a
414(a) Q7 (b) 288(c)
H2
amou
nt/(m
ol)
Reaction time/(min)
Same activity sequence: shocked+milled(a)> shocked(c) >milled (b)
0 10 20 30 40 50 60 70 80 90 1000
1
2
3
4
5
6
7
8
Ti5-Si3
cb
a
415(a) Q8 (b) 271(c)
H2
amou
nt/(m
ol)
Reaction time/(min)
Figure.9 Curves of photocatalytic activity for Ti-Si samples
Conclusions
• Milling treatment to some extent could decrease the threshold of shock reaction of Ti-Si and the reaction product is different from the designed one.
• The direct shock synthesis may give a designed Ti-Si product under heavier loading conditions.
• Both of milling and shock loading can activate and initiate reaction of the Ti-Si samples which exhibit better photocatalytic activity than that of only milling or shock loading.
Phase diagram of Ti-Si system
Back
Results and discussion
• Thermodynamic stability of TixSiy compounds:
• TiSi2<TiSi<Ti5Ti4<Ti5Si3• Ti5Si3 is easier to form than TiSi2 or if TiSi2 is
formed, has a tendency to transform to Ti5Si3.
• However, the direct shock loading could get the metastable TiSi2 because of high quenching and strain rate.
Ref: Guan Q.L., et al, J.Mater.Sci., 44:1902, 2009back