POSSIBILITY OF REACTION SYNTHESIS OF INTERMETALLICS USING CONICALLY SHAPED CHARGE Naoyuki WADA*, Kazuyuki HOKAMOTO**, Syoichiro KAI***, Yasuhiro UJIMOTO*** *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 2 Contents Introduction Experimental Results and Discussions Summary 3 Introduction 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~ 4 About Ceramics and Nitrides Ceramics Oxides, Nitrides, Carbides, Borides, etc…. Advantages of Ceramics Due to ceramic materials wide range of properties, they are used for a multitude of applications. In general, most ceramics are…. Hard Electrical insulators Wear-resistant Nonmagnetic Brittle Oxidation resistant Refractory Prone to thermal shock Thermal insulators Chemically stable Nitrides, especially titanium nitride (TiN), aluminum nitride (AlN), and titanium aluminum nitride (TiAlN) are studied for their significant characteristics. 5 Properties of Nitrides TiN Properties Application Coating material Cermet material High heat resistance Decorative purposes High melting point High strength Wear resistance High electric conductivity AlN Application Properties High thermal conductivity Excellent electrical isolation High heat resistance High-corrosion resistance Electronic substrate Power device Heatsink TiAlN Application Properties High vickers hardness (TiAlN>TiN) High oxidation onset temperature High-corrosion resistance Powder color Purple / Broun Vickers hardness 2800 HV Oxidation temperature 788 ゜C Frictional coefficient 0.8 Coating material Mold tool Optical apparatus Synthetic methods and Shock Induced Chemical Reaction Methods of Synthesizing Nitrides 6 Problems Carbothermal reduction-nitridation Low purity, prolonged heating Direct nitridation by using NH3 Difficult to use NH3 gas CVD method High cost of equipment New Research for Synthesizing has been investigated. Shock Induced Chemical Reaction Vacuum pomp Target chamber 試料室 真空ポンプ Barrel 発射管 Powder chamber 火薬室 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 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. Author’s Other Reseach ~Wire Explosion Technique~ 7 About Wire Explosion 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. 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. Intensity (a.u.) TiN 50nm 10˚ 20˚ 30˚ 40˚ 50˚ 60˚ 70˚ 80˚ 2q (Cu-Ka) Assembly used for wire wxplosion *)K. Hokamoto, N. Wada, S. Kai et all, J. Alloy. Compd. 485 (2009) 573-576. New Research 8 ~Synthesis of Nitrides through the Reaction of a Metal Jet~ Conical Shaped Charge and Metal Jet 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. Properties of using Metal Jet for Synthesizing 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. 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. 9 Experimental Experimental Devices Experimental Method and Conditions Penetration Experiments Velocity of Metal Jet 10 Experimental Devices Details of Experimental devices f Electric detonator Explosive (SEP) a Al cone Metal jet generation parts Detonation : Electric detonator (Kayaku Japan Co.) Explosive : SEP explosive (Kayaku Japan Co.) Detonation velocity 7.0 km/s Density 1300kg/s Dimensions of Aluminum cone Assembly used for recovery experiments Thickness 1.2 mm Angle a 45° Diameter of charge f 33.5 mm 11 Experimental Devices Details of Experimental devices Ti powders SUS304 pipe Liquid nitrogen Powder and Liquid container parts Spherical titanium powder : Average diameter 45mm Dimensions of SUS 304 pipe Assembly used for recovery experiments Outside diameter 30 mm Inside diameter 17mm Height 40 mm 12 Experimental Method and Conditions Experiment ・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. Experimental conditions No. 1 2 a (deg.) 45 f (mm) 33.5 distance d (mm) 20 10 Mass of Explosive (g) 24g Details of aluminum cone Assembly used for recovery experiments 13 Penetration Experiments Prior to the recovery experiments, the assembly was used for penetration experiment. Two kinds of penetration experiments were done to compare. Conditions of penetration experiments and its results No. a (deg.) 1 45 f (mm) Mass of Explosive (g) 24 33.5 2 60 20 Test plate Stainless steel plate Thickness of Plates (mm) Numbers of plates penetrated 20 10 (10layers of plates, each of 2mm thickness) 8 No.1, a=45° Electric detonator Explosive (SEP) Al cone a SUS plate Mild steel Schematic illustration of penetration examination No.2, a=60° 14 Velocity of Metal Jet The velocity of the jet is estimated based on a simple geometrical relationship as illustrated in Figures. The velocity of the metal plate Vp was estimated based on the Gurney equation expressed as follows, 1/ 2 Vp = Geometrical relationship for estimation of jet velocity. 2 3 R 2E 2 R 5R 4 E : Gurney energy In the case of SEP, E=2.16×106 J/kg 2) R : the mass ratio of explosive c and metal plate m R=c / m Then, the velocity of the metal jet Vj is estimated based on the Brikhoff’s equation 3) as follows Cross section diagram of metal jet generation device Explosive (SEP) Density(kg/m3) 1310 Velocity(m/s) 7000 cos β / 2 cos( β / 2) β Vj = Vp sin tan γ 2 sin γ Al Density(kg/m3) Solid state properties 2700 Using the equation, the velocity of the aluminum jet was estimated as… Vj = 6000 m/s 15 Results and Discussions Experiment #1 (d = 20mm) Appearance and SEM images X-ray Diffraction Pattern Experiment #2 (d = 10mm) Appearance and Optical Microscope Images X-ray Diffraction Pattern SEM Images EPMA Results Process of Reaction 16 Experiment #1 (d = 20mm) Appearance and SEM Images X-ray Diffraction Pattern 17 Results ~Experiment #1~ Appearance and SEM images Experiment #1 (d = 20mm) 10mm (a) (b) Appearance of recovered powders (a) and its SEM image (b). Broun colored powders were recovered. From SEM images, it seems that an aluminum droplet was trapped on a spherical titanium powder. Results ~Experiment #1~ X-ray diffraction pattern 18 Experiment #1 (d = 20mm) X-ray diffraction pattern (Cu-Ka) 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 Experiment #2 (d = 10mm) Appearance and Optical Microscope Images X-ray Diffraction Pattern SEM Images EPMA Results Process of Reaction Results ~Experiment #2~ Appearance and Optical Microscope Images Experiment #2 (d = 10mm) (a) (b) Appearance of small blocks recovered (a) and its Microstructure of cross-section (b). 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. 20 Results ~Experiment #2~ X-ray diffraction pattern Experiment #2 (d = 10mm) X-ray diffraction pattern (Cu-Ka) for recovered block. The peaks of TiN and TiAlN are confirmed. TiAlN is identified as Ti2AlN and Ti3AlN. It is interesting to note that aluminum is not the major component of the reaction products even though an aluminum jet was used. 21 Results ~Experiment #2~ SEM Images Experiment #2 (d = 10mm) (b) (a) (c) SEM image of recovered block (a) and its backscattered electron image (b), enlarged backscattered image (c) 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). 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. 22 Results ~Experiment #2~ EPMA Results Experiment #2 (d = 10mm) Al SEM 2 1 50mm Ti N Central area is composed of TiN and the other area is composed of TiAlN whose composition is closer to Ti3AlN. The area composed of Ti2AlN is not clearly confirmed because of the slight difference in the chemical composition in the area containing Ti, Al and N2. Since TiAlN was confirmed especially in the edge of the block, the location should be closer to the central axis of the powder container. Mapping of elements for recovered block taken by EPMA Chemical components measured by EPMA for recovered block. Position No. 1 2 Ti content (at %) 40.30 60.86 Al content (at %) 4.07 18.22 N content (at %) 55.63 20.92 23 Results ~Experiment #2~ Reaction process 24 Experiment #2 (d = 10mm) Al jet 1) Ti powders Propagation of reaction between Ti and LN2 2) LN2 Ti-Al-N reacted area 3) Reaction 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 Hightemperature synthesis) process. Cooling 4) Cooling During the cooling from liquid, the area was separated into small fragments (blocks) and central and other cavities are formed by rapidly cooling process. TiN Ti-Al-N Crack Pore Results ~Experiment #2~ Micro Vickers Hardness Experiment #2 (d = 10mm) Area Average Hardness Range Bright (TiN) 767 HV 648 HVmax – 839 HVmin Dark (TiAlN) 1067 HV 867 Hvmax – 1219 HVmax 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. 25 26 Summary 27 Summary 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. 28 Thank you for your kind attention!