1. 1 POSSIBILITY OF REACTION SYNTHESIS OF INTERMETALLICS USING CONICALLY SHAPED CHARGE * Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan **Shock Wave and Condensed Matter Research Center, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan ***Asahi-Kasei Chemicals Corp., Chikushino Plant, Chikushino 818-0003, Japan 1 Naoyuki WADA *, Kazuyuki HOKAMOTO **, Syoichiro KAI ***, Yasuhiro UJIMOTO ***

2. 2Contents  Introduction  Experimental  Results and Discussions  Summary 2

3. 3Introduction  About Ceramics and Nitrides  Properties of Nitrides  Synthetic methods and Shock Induced Chemical Reaction  Author’s Other Reseach ~Wire Explosion Technique~  Research ~Synthesis of Nitrides through the Reaction of a Metal Jet~ 3

4. 4 About Ceramics and Nitrides Ceramics  Oxides, Nitrides, Carbides, Borides, etc…. Nitrides, especially titanium nitride (TiN), aluminum nitride (AlN), and titanium aluminum nitride (TiAlN) are studied for their significant characteristics. Due to ceramic materials wide range of properties, they are used for a multitude of applications. In general, most ceramics are…. Advantages of Ceramics  Hard  Wear-resistant  Brittle  Refractory  Thermal insulators  Electrical insulators  Nonmagnetic  Oxidation resistant  Prone to thermal shock  Chemically stable 4

5. 5 Properties of Nitrides AlN TiN High melting point High strength Wear resistance High electric conductivity Coating material Cermet material High heat resistance Decorative purposes Application Properties High thermal conductivity Excellent electrical isolation High heat resistance High-corrosion resistance Properties Electronic substrate Power device Heatsink Application TiAlN Coating material Mold tool Optical apparatus Application High vickers hardness (TiAlN>TiN) High oxidation onset temperature High-corrosion resistance Powder colorPurple / Broun Vickers hardness2800 HV Oxidation temperature 788 ゜ C Frictional coefficient0.8 Properties 5

6. 6 To be obtained ultra-fine grained structure which is expected to improve the properties of the synthesized materials. The ultra-fine grained structure in the order of nanometer size can be obtained. Pressures up to the order of several tens of GPa can be applied. Synthetic methods and Shock Induced Chemical Reaction Problems  Low purity, prolonged heating  Difficult to use NH 3 gas  High cost of equipment  Carbothermal reduction-nitridation  Direct nitridation by using NH 3  CVD method Methods of Synthesizing Nitrides 6  Shock Induced Chemical Reaction New Research for Synthesizing has been investigated. This is the technique for synthesizing ceramics and intermetallics by using extremely high velocity and pressure and this technique has been investigated to synthesize various intermetallics by researchers by using Gas- gun or explosively accerelated assembly. Advantages of Shock Induced Chemical Reaction Vacuum pomp Target chamber Barrel Powder chamber

7. 77 Author’s Other Reseach ~Wire Explosion Technique~ When high current is loaded to wire, it is rapidly heated and changes to plasma. In this state, the reactivity of the excited metal is high, so it is possible to induce reaction with gas. About Wire Explosion Assembly used for wire wxplosion Synthesis of TiN powders through electrical wire explosion in liquid nitrogen *) Liquid nitrogen was used to react with the exploded Ti wire. Considering the excited condition of the exploded Ti material, it is easy to induce reaction between the dissimilar reactive atoms such as liquid nitrogen.  TiN powders were successfully recovered.  Ultrafine TiN particles in the order of 50 nm were observed. *) K. Hokamoto, N. Wada, S. Kai et all, J. Alloy. Compd. 485 (2009) 573-576.

8. 8 Conical shaped charges are well known for making holes on a thick metal plate. A metal jet formed by an extremely high-velocity material flow having an extremely high kinetic energy is generated ahead of the collision point of the metal cone.  Easy to induce high pressure by using metal jet.  Various intermetallics can be obtained.  Shortening in synthesis time.  The ultra-fine grained structure in the order of nanometer size can be obtained. Conical Shaped Charge and Metal Jet In this investigation, an aluminum metal jet was penetrated into liquid nitrogen mixed with titanium powders. The authors tried to synthesize TiN and AlN, TiAlN, and investigate the basic phenomenon from the recovered samples. New Research New Research ~Synthesis of Nitrides through the Reaction of a Metal Jet~ Properties of using Metal Jet for Synthesizing

9. 9Experimental  Experimental Devices  Experimental Method and Conditions  Penetration Experiments  Velocity of Metal Jet 9

10. 10 Experimental Devices Assembly used for recovery experiments 10 Details of Experimental devices Electric detonator Explosive (SEP) Al cone   Metal jet generation parts  Dimensions of Aluminum cone Thickness1.2 mm Angle  45° Diameter of charge  33.5 mm  Detonation : Electric detonator (Kayaku Japan Co.)  Explosive : SEP explosive (Kayaku Japan Co.) Detonation velocity 7.0 km/s Density 1300kg/s

11. 11 Experimental Devices Assembly used for recovery experiments 11 Details of Experimental devices Powder and Liquid container parts  Dimensions of SUS 304 pipe Outside diameter30 mm Inside diameter17mm Height40 mm  Spherical titanium powder : Average diameter 45  m SUS304 pipe Ti powders Liquid nitrogen

12. 12 Experimental Method and Conditions Experimental Method and Conditions Assembly used for recovery experiments 12 ・ The explosive SEP was detonated by electric detonator placed on the upper side of the cone. ・ After the detonation, an aluminum metal jet was penetrated into liquid nitrogen mixed with titanium powders. ・ In this state, ceramics like TiN or AlN, TiAlN will be generated. Experiment Experiment Details of aluminum cone No.  (deg.)  (mm) distance d (mm) Mass of Explosive (g) 1 4533.5 20 24g 210 Experimental conditions

13. 13 Schematic illustration of penetration examination   45 ° Penetration Experiments Penetration Experiments Prior to the recovery experiments, the assembly was used for penetration experiment. Two kinds of penetration experiments were done to compare. No.  (deg.)  (mm) Mass of Explosive (g) Test plate Thickness of Plates (mm) Numbers of plates penetrated 145 33.5 24 Stainless steel plate 20 (10layers of plates, each of 2mm thickness) 10 260208   60 ° Conditions of penetration experiments and its results

14. 14  The velocity of the metal plate V p was estimated based on the Gurney equation expressed as follows, E : Gurney energy In the case of SEP, E=2.16×10 6 J/kg 2) R : the mass ratio of explosive c and metal plate m R=c / m  Then, the velocity of the metal jet V j is estimated based on the Brikhoff’s equation 3) as follows Explosive (SEP) Density(kg/m 3 )1310 Velocity(m/s)7000 Al Density(kg/m 3 )2700  Using the equation, the velocity of the aluminum jet was estimated as… Vj = 6000 m/s Cross section diagram of metal jet generation device The velocity of the jet is estimated based on a simple geometrical relationship as illustrated in Figures. Solid state properties Velocity of Metal Jet Velocity of Metal Jet Geometrical relationship for estimation of jet velocity.

15. 15 Results and Discussions Results and Discussions  Experiment #1 (d = 20mm)  Experiment #2 (d = 10mm) 15 Appearance and SEM images X-ray Diffraction Pattern Appearance and Optical Microscope Images X-ray Diffraction Pattern SEM Images EPMA Results Process of Reaction

16. 16  Experiment #1 (d = 20mm) Appearance and SEM Images X-ray Diffraction Pattern

17. 17  Broun colored powders were recovered.  From SEM images, it seems that an aluminum droplet was trapped on a spherical titanium powder. Results ~Experiment #1~ Appearance and SEM images 17 10  m Appearance of recovered powders (a) and its SEM image (b). (a) (b)  Experiment #1 (d = 20mm)

18. 18 Results ~Experiment #1~ X-ray diffraction pattern  Experiment #1 (d = 20mm) X-ray diffraction pattern (Cu-K  ) for recovered powders.  The XRD pattern shows the peak of Ti and Al, and no reacted product was confirmed by this experiment.  It is considered that the reaction was not induced due to the decrease in the velocity of the metal jet during relatively long travelling distance in air.

19. 19  Experiment #2 (d = 10mm) Appearance and Optical Microscope Images X-ray Diffraction Pattern SEM Images EPMA Results Process of Reaction

20. 20  Small blocks were recovered, and the blocks were small fragments in the order of several mm in length.  It is confirmed that the cross-section contains many pores. These pores are formed during the cooling from the molten phase. Results ~Experiment #2~ Appearance and Optical Microscope Images 20 Appearance of small blocks recovered (a) and its Microstructure of cross-section (b). (a) (b)  Experiment #2 (d = 10mm)

21. 21 X-ray diffraction pattern (Cu-K  ) for recovered block. Results ~Experiment #2~ X-ray diffraction pattern  The peaks of TiN and TiAlN are confirmed. TiAlN is identified as Ti 2 AlN and Ti 3 AlN.  It is interesting to note that aluminum is not the major component of the reaction products even though an aluminum jet was used.  Experiment #2 (d = 10mm)

22. 22  About backscattered image It illustrates the distribution of the elements where bright area is composed of heavy element(s) and dark area includes light element(s). SEM image of recovered block (a) and its backscattered electron image (b), enlarged backscattered image (c) (b) (a)(c)  Since the bright region is composed of heavy element(s), such region close to the central cavity seems to be TiN. The other area close to the edge of a block is considered as TiAlN.  Experiment #2 (d = 10mm) Results ~Experiment #2~ SEM Images

23. 23 Position No. Ti content (at %) Al content (at %) N content (at %) 140.304.0755.63 260.8618.2220.92  Central area is composed of TiN and the other area is composed of TiAlN whose composition is closer to Ti 3 AlN.  The area composed of Ti 2 AlN is not clearly confirmed because of the slight difference in the chemical composition in the area containing Ti, Al and N 2.  Since TiAlN was confirmed especially in the edge of the block, the location should be closer to the central axis of the powder container. SEM 1 2 Ti 50  m Al N Results ~Experiment #2~ EPMA Results  Experiment #2 (d = 10mm) Chemical components measured by EPMA for recovered block. Mapping of elements for recovered block taken by EPMA

24. 24 Results ~Experiment #2~ Reaction process It is considered that the aluminum jet plays a role to ignite a sustainable reaction between the components placed at the position based on the SHS (Self-propagating High- temperature synthesis) process.  During the cooling from liquid, the area was separated into small fragments (blocks) and central and other cavities are formed by rapidly cooling process.  Experiment #2 (d = 10mm) Al jet Ti powders LN 2 Ti-Al-N reacted area Propagation of reaction between Ti and LN 2 TiN Ti-Al-N 1)2) 3)4) Cooling Pore Crack Reaction Cooling

25. 25  Experiment #2 (d = 10mm) Results ~Experiment #2~ Micro Vickers Hardness AreaAverage HardnessRange Bright (TiN)767 HV648 HV max – 839 HV min Dark (TiAlN)1067 HV867 Hv max – 1219 HV max  The average micro-Vickers under load 0.098N (10g) was in the order of 650 – 1200 HV.  These values are slightly lower than the reported data which may be caused by the presence of the cavities in the bulk region recovered after cooling from molten phase.

26. 26Summary

27. 27Summary  A new method to synthesize nitride ceramics using conical shaped charges is proposed and the possibility to induce chemical reaction of the elements is demonstrated.  An aluminum cone was highly accelerated as metal jet in the order of 6 km/s and collided with liquid nitrogen mixed with titanium powders.  Under a moderate condition, some small blocks having high hardness were recovered and the blocks were composed of titanium nitride and titanium-aluminum nitrides formed by chemical reaction.  The reaction process was discussed based on the chemical component analysis at different positions in the cross-sectional area. 27

28. 28 Thank you for your kind attention!

29. 29  The velocity of the metal plate V p was estimated based on the Gurney equation 1) expressed as follows, E : Gurney energy In the case of SEP, E=2.16×10 6 J/kg 2) R : the mass ratio of explosive c and metal plate m R=c / m  Then, the velocity of the metal jet V j is estimated based on the Brikhoff’s equation 3) as follows SEP Density(kg/m 3 )1310 Velocity(m/s)7000 Al Density(kg/m 3 )2700  Using the equation, the velocity of the aluminum jet was estimated as… Vj = 5999 m/s Cross section diagram of metal jet generation device 1) M. A. Meyers, Dynamic Behavior of Materials, John Wiley & Sons Inc. (1994) 2) S. Itoh, Handbook of Shock Waves (Eds., G.Ben-Dor, O.Igra, Tov Elperin), Academic Press, 3 (2001) 263-313. 3) G. Brikhoff, D. P. Macdougall, E. M. Pugh, G. Taylor, J. Appl. Phys. 19-7 (1948) 563- 582. The velocity of the jet is estimated based on a simple geometrical relationship as illustrated in Figures. Solid state properties Velocity of Metal Jet Velocity of Metal Jet Geometrical relationship for estimation of jet velocity.

30. 30 SEM image of recovered block (a) and its backscattered electron image (b), enlarged backscattered image (c) (b) (a)(c)  Figure 8 (a) shows the cross-section of one block and the central large cavity suggests that the block is formed by cooling from a molten part.  The backscattered image (Fig. 8 (b) and (c)) illustrates the distribution of the elements where bright area is composed of heavy element(s) and dark area includes light element(s). In Fig.8 (c), there are two compositionally different areas.  Since the bright region is composed of heavy element(s), such region close to the central cavity seems to be titanium nitride. The other area close to the edge of a block is considered as titanium- aluminum nitride(s).  Experiment #2 (d = 10mm) Results ~Experiment #2~ SEM Images

31. 31 Position No. Ti content (at %) Al conten (at %) N content (at %) 140.304.0755.63 260.8618.2220.92  Mapping analysis suggest that the central area is composed of TiN and the other area is composed of titanium-aluminum nitride whose composition is closer to Ti 3 AlN.  The area composed of Ti 2 AlN is not clearly confirmed by the SEM and EPMA images because of the slight difference in the chemical composition in the area containing titanium, aluminum and nitrogen.  Since titanium-aluminum nitride was confirmed especially in the edge of the block, the location should be closer to the central axis of the powder container. SEM 1 2 Ti 50  m Al N Results ~Experiment #2~ EPMA Results  Experiment #2 (d = 10mm) Chemical components measured by EPMA for recovered block. Mapping of elements for recovered block taken by EPMA

32. 32 Results ~Experiment #2~ Reaction process It is considered that the aluminum jet plays a role to ignite a sustainable reaction between the components placed at the position based on the SHS (Self-propagating High- temperature synthesis) process.  During the cooling from liquid, the area was separated into small fragments (blocks) and central and other cavities as illustrated in the figure are formed.  Experiment #2 (d = 10mm) Al jet Ti powders LN 2 Ti-Al-N reacted area Propagation of reaction between Ti and LN 2 TiN Ti-Al-N 1)2) 3)4) Cooling Pore Crack Reaction Cooling