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Shock-induced reactions in ball-milled Ti-Si powder mixtures

XI EPNM. Shock-induced reactions in ball-milled Ti-Si powder mixtures. J. J. Liu 1 , N. F. Cui 2 , P. W. Chen 2. 1 Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, China

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Shock-induced reactions in ball-milled Ti-Si powder mixtures

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  1. 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

  2. Outline Introduction Experimental Results and discussion Conclusions

  3. Introduction Composition: TiSi, TiSi2, Ti5Si3, Ti5Si4 Combustion synthesis Self-propagating reaction Mechanical alloying Shock induced reaction Ti-Si system Synthesis: Heat resistant material High hardness Microelectronics Photocatalyst Application:

  4. Ti-Si photocatalyst • 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. Ritterskamp P., et al, Angew.Chem. Int. Ed, 46:7770, 2007

  5. 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.

  6. 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

  7. Experimental • . • 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

  8. Experimental conditions

  9. 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.

  10. 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. Results and discussion Q7: The milled Ti-Si2 reacted to form little Ti5Si3 at 900rpm. 414:The next shock does not initiate further reaction.

  11. Figure 4 XRD patterns of shocked Ti5-Si3 mixtures(2.25km/s) at different rotary speeds (a)300rpm; (b)500rpm; (c)700rpm; (d)900rpm. Figure 3 XRD patterns of ball-milled Ti5-Si3 mixtures 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 .

  12. Results and discussion Why? 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.

  13. 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

  14. a b d c Results and discussion Partly react no reaction Partly react Obviously react Figure.7 SEM images of samples. (a) Q7, (b)Q8,(c)414, (d)415.

  15. Results and discussion Mill-activated(a>b) (Mill+Shock)-activated(b>a) Figure.8 DSC analysis of Ti-Si samples

  16. Photocatalytic test for producing hydrogen Figure.9 Curves of photocatalytic activity for Ti-Si samples Same activity sequence: shocked+milled(a)> shocked(c) >milled (b)

  17. 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.

  18. Thanks for your attention !

  19. Phase diagram of Ti-Si system Back

  20. 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

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