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