XI EPNM
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, China
2State Key Laboratory of Explosion Science and
Technology, Beijing Institute of Technology, Beijing,
100081, China
2012.5.4 Strausbourg France
Outline
Introduction
Experimental
Results and discussion
Conclusions
Introduction
Composition: TiSi, TiSi2, Ti5Si3, Ti5Si4
Ti-Si
system
Synthesis:
Combustion synthesis
Self-propagating reaction
Mechanical alloying
Shock induced reaction
Application:
Heat resistant material
High hardness
Microelectronics
Photocatalyst
Ti-Si photocatalyst
Ritterskamp P., et al, Angew.Chem. Int. Ed, 46:7770, 2007
• As new functional materials, the light-absorption characteristics in UV-visible
region (ca.360800nm) of TiSi2 are ideal for solar applications and have a
good photocatalytic activity of splitting water into hydrogen.
TiSi2  6 H 2O  TiSi2oxides  6 H 2
1
H 2O  O2  2 H   2e
2
2 H   2e  H 2
Ti-Si photocatalyst
Liu 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 300900rpm for 3h
Experimental
.
Scheme of shock-loading apparatus
(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
Experimental conditions
Photocatalytic test
Set-up scheme of photocatalytic evaluation
1. Hg lamp, 2.rubber plug, 3. quartz reactor, 4.water and photocatalyst,
5.magnetic stirrer, 6.dark box.
Results and discussion
Q7: The milled Ti-Si2 reacted to form little Ti5Si3 at 900rpm.
414:The next shock does not initiate further reaction.

Intensity/(a.u.)

Si
Ti
Ti5Si3



Millled
Ti-Si2






d
c
b
a
10
20


30
40


50

60

70
Q7
Q5
Q3
Q1
80
90
O
2/( )
Figure 1 XRD patterns of ball-milled
Ti-Si2 mixtures at different rotary
speeds
(a)300rpm;
(b)500rpm;
(c)700rpm; (d)900rpm.
Intensity/(a.u.)

Si
Ti
Ti5Si3
(Milled+Shocked)
Ti-Si2



414
10







d
412
c
410
b
408
a
20
30
40
50
60
70
80

90
O
2/( )
Figure 2 XRD patterns of shocked
Ti-Si2 mixtures(2.25km/s) at different
rotary speeds (a)300rpm; (b)500rpm;
(c)700rpm; (d)900rpm.
Results and discussion
Q8: The milled Ti5-Si3 has not any reaction at 900rpm.
415:The next shock initiated reaction to form little Ti5Si3 .


Si
Ti

Si
 Ti
 Ti Si
5 3

Millled
Ti5-Si3
10


d
c
b
a
20
 



30
40
50
60
70

Q8
Q6
Q4 
Q2
80
90
O
Intensity/(a.u.)
Intensity/(a.u.)



(Milled+Shocked)
Ti5-Si3





415
d


413
 


c

411
b
409
10
20
a

30
40
50
60
70

80
90
O
2/( )
2/( )
Figure 3 XRD patterns of ball-milled
Ti5-Si3 mixtures at different rotary
speeds
(a)300rpm;
(b)500rpm;
(c)700rpm; (d)900rpm.
Figure 4 XRD patterns of shocked
Ti5-Si3
mixtures(2.25km/s)
at
different rotary speeds (a)300rpm;
(b)500rpm; (c)700rpm; (d)900rpm.
Results and discussion
Intensity/(a.u.)


414
Si

Ti5Si3

 


20
30




40
Ti

TiSi2
Why?

Q7



 
288
10




50
(c) 


(b)




(a) 

60
70
80
90
O
2/( )
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.
Results and discussion

Intensity/(a.u.)
415
10




Si
Ti


Ti5Si3





  


(c)


Q8








(b)

(a) 

271
20

 
30
40

50
60
70
80
90
O
2/( )
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
Results and discussion
a
b
Partly
react
no reaction
c
d
Partly
Obviously
react
Figure.7 SEM images of samples. (a) Q7, (b)Q8,(c)414, (d)415.
react
Results and discussion
Mill-activated(a>b)
(Mill+Shock)-activated(b>a)
1.5
1.0
2.0
Q7(a)
Q8(b)
414(a)
415(b)
1.5
1.0
0.5
0.5
628 C
0.0
b
-0.5
DSC/(W/g)
DSC/(W/g)
O
-1.0
-1.5
0.0
a
a
-0.5
-1.0
-1.5
exo
O
530 C
O
640 C
b
exo
-2.0
-2.5
-2.0
-3.0
0 100 200 300 400 500 600 700 800 9001000
O
T/( C)
Figure.8 DSC analysis of Ti-Si samples
0 100 200 300 400 500 600 700 800 9001000
O
T/( C)
Photocatalytic test for
producing hydrogen
20
8
414(a)
Q7 (b)
288(c)
16
14
12
Ti-Si2
a
c
10
8
b
6
4
6
5
Ti5-Si3
a
c
b
4
3
2
1
2
0
415(a)
Q8 (b)
271(c)
7
H2 amount/(mol)
H2 amount/(mol)
18
0
10
20
30
40
50
60
70
Reaction time/(min)
80
90
100
0
0
10
20
30
40
50
60
70
80
90
100
Reaction time/(min)
Figure.9 Curves of photocatalytic activity for Ti-Si samples
Same activity sequence: shocked+milled(a)> shocked(c)
>milled (b)
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.
back
Ref: Guan Q.L., et al, J.Mater.Sci., 44:1902, 2009