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
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Contents
Introduction
Experimental
Results and Discussions
Summary
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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~
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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.
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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
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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~
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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
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~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.
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Experimental
Experimental Devices
Experimental Method and Conditions
Penetration Experiments
Velocity of Metal Jet
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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
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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
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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
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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)
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No.1, a=45°
Electric detonator
Explosive (SEP)
Al cone
a
SUS plate
Mild steel
Schematic illustration of penetration examination
No.2, a=60°
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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
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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
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Experiment #1 (d = 20mm)
Appearance and SEM Images
X-ray Diffraction Pattern
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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
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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.
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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.
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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.
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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.
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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
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Results ~Experiment #2~
Reaction process
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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.
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Summary
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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.
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