# Energy and Deformation during Explosive Compaction ofZrB2-SiC Ultrahigh Temperature  Ceramics

Authors: Jin-Ping Li; Song-He Meng; Jie-Cai Han; Bao-Lin Wang
Journal: Scholarly Research Exchange
 (2008)

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## Abstract

To introduce a new technique and to choose the process parameters,ZrB2-SiC ultrahigh temperature ceramics (UHTCs) were prepared by mixing and explosive compaction. The explosive kinds or explosive mass was variable so as to change the explosive impact energy. We have studied the relationships of the explosive impact energy, the tube deformation energy, the powder compaction energy and the ratio of the explosive mass to the tube mass  (R), the relationships of the tube deformation energy, the tube equivalent strain and the mass ratio R, and the relationships of the densities of the ZrB2 composites and the powder compact energy. The results show that the densities of the  ZrB2  composites reach 93.37% of theory density. For any kind of explosive, the reduction of the outer diameter and  the equivalent strain of the steel tubes raises gradually with the rise of the mass ratio R. Generally speaking, the higher the explosion speed of the explosive is, the larger the deformation degree and the equivalent strain of the steel tubes are. The explosive impact energy can be divided into two parts: the tube deformation energy and the powder compact energy; with the rise of the mass ratio R, the tube deformation energy hardly changes, while the explosive impact energy and powder compact energy increase synchronously, and the densities of the ZrB2 composites also increase gradually. The density of the ZrB2 composites produced by different explosives orders from big to small as RDX, Ammonium Nitrate, TNT, and Urea Nitrate.


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## Body

## 1. Introduction

Ultrahigh
temperature ceramics  (UHTCs)
[1–3] are fragile composites which are
composed of ZrB2 or
HfB2, ZrC or HfC, and SiC.
Essentially, these structural ceramics possess an excellent and unique set of
bulk properties including unusually high melting points,
high thermal conductivity,   high elastic modulus, retained strength at high
temperatures, relatively good thermal shock resistance, and modest thermal
expansion [4].Strategic
interest in UHTCs has provided the aerospace industry with concrete
opportunities to design a new generation of space vehicles with sharp leading
edges (1 mm in radius) and
smooth surfaces, resulting in much smaller, lighter and more efficient space
vehicles than ever before. Moreover, such a new class of materials may overturn
an age-old belief of aerodynamics that only a blunt-nosed as the vehicle
repeatedly tears through the terrestrial atmosphere during hypersonic flights
[5].In 1930s,
the American Air Force developed UHTCs initially. With many years’ efforts of
scientists and researchers, it has been shown that the UHTCs have good oxidation
resistance by1600°C and have been used in trial manufacture. There are two
key techniques in preparing UHTCs: one is to control the process exactly, and the other
is to introduce the advanced preparation process. Explosive compaction is a
kind of process which produces high pressure and high temperature at the moment
to compact the powder when the explosive is detonated
[6]. The merits
[7, 8]
of this process are as follows: since explosion and sintering are
completed in ultra short time (about several microseconds), not only the
crystal grain does not grow up, but also the compound interface hardly diffuses
or the diffusion degree is quite little (less than 100 nm). Thus, explosive
compaction may be an optimal way to prepare new materials such as the bulk amorphous
materials, the quasicrystal materials, and the nanocrystal materials.Based on the
research of theZrB2-SiC UHTCs prepared by mixing
and hot pressing
[9, 10], we adopted mixing and explosive compaction
to prepare the ZrB2-SiC UHTCs, and we have studied the relationships of the explosive impact
energy, the tube deformation energy, the powder compaction energy, and the
ratio of the explosive mass to the tube mass (R),
the relationships of the tube deformation energy, the tube equivalent strain
and the mass ratio R, and the relationships of the densities
of the ZrB2 composites and the powder compact energy, in order to
optimize the technological parameters during explosive compaction of the ZrB2-SiC
UHTCs.


## 2. Experimental Method

### 2.1. Process of Explosive
Compaction

The set [11] as shown in
Figure 1 is usually used in
the direct method of the explosive compaction. The powder is packed into the close
metal tube surrounded by a layer of homogeneous explosive. When the explosive is
detonated, the powder is compressed by the steel tube which is compressed down
by the convergent columnar impact wave from one side of the system. In this paper,
the powders were put into a 20#-seamless steel
tube, and the bottom of the tube was blocked by a steel plug. When being packed
into the powder, the tube vibrated making the powder homogeneous and dense. Then,
it was blocked by the other plug and set in the position of axis of the
columnar paper tube. The wooden cone was set on the top of the steel tube to
make the explosive produce the front edge of the compression. Homogeneous and dense
explosive was put into the clearance between the steel tube and the paper tube.
The explosive exploded vertically after the detonator was detonated.Figure 1
The set of explosive compaction.The sizes
of the steel tubes are as follows: the outer diameter is 18 mm, the wall thickness is 2 mm, the length is 100 mm, and the mass of each tube is about 18.9 g. The material of the upper plug and
the lower plug is the 20# seamless steel bar, the sizes are both Φ14⁢mm×10⁢mm, and the masses are both about 12.1 g. The size of the wooden cone is Φ18⁢mm×15⁢mm; the size of the wooden base is Φ60⁢mm×20⁢mm. The powder in the steel tube is ZrB2-20SiC
mixing powder, and the sum mass of the steel tube and the powder is about 28.6 g. Namely, the relative density of
the loading powders is about 42% of the theory density of ZrB2-20SiC.During explosion, the radial pressure and
impact wave appear after the front edge of the explosion wave went through. The
part of the steel tube between the upper plug and the lower plug in
Figure1
is deformed. The radial velocity (νp) of the steel tube increases with the ratio
of explosive mass to tube mass (R), and it usually affects the final compact density
of the ZrB2-20SiC UHTCs.We only measured the size change of the length
and the outer diameter of the steel tubes. There were some evident scratch
marks on the surface of the steel tubes after the explosive compaction; the
part of the steel tube between the upper plug and lower plug was deformed radically
and homogeneously. Thus, the deformation of steel tube occurred in plane and
the deformation degree was decided only by the reduction of the outer diameter
of the steel tubes.


### 2.2. Experiment Analysis

In the course of explosive compaction, one part of the total impact
energy of the explosive is consumed on the steel tubes, and other part is
consumed on the powder. Besides, there is a part of energy consumed on the air
and voice. Since it is so little, it is often neglected. The common method only
offers approximately, but it cannot judge the distribution of two parts of the
explosive impact energy. The method in this paper can offer the effective
impact energy and judge the distribution of two parts of the explosive impact
energy, thus our work is essential and important.The basic
parameters in the formula include the radial velocity (νp) of the steel tubes, the explosion velocity (νD) of the explosive and the ratio of explosive
mass to tube mass (R). The research on the explosive compaction is
expressed by these parameters, because these parameters are easy to understand,
moreover, these parameters are usually adopted in the specific explosive
compaction experiment. The detail deduction of the formula can be seen in
[12–14].


### 2.3. The Explosive Characteristics

We chose four kinds  of
explosive and all characteristics were shown in
Table1. The actual explosion velocity of the explosive is relevant to the
packing density of the explosive. With the rise of the packing density, the
actual explosion velocity increases, and the relationship between them is parabolic
[11, 15]. Since the packing density of each explosive was lower than
the theory density and the relative density was different in this experiment,
the actual explosion velocity of each explosive also decreased differently. However, the range of the packing
density was so small in this research that explosion velocity of each
explosive could be regarded as a constant [6, 13, 14].Table 1
The
characteristic of the four kinds of explosive.
NameFormulaAppearanceTheory
velocity
(m/s)Theory
density
(g/cm3)Actual
density
(g/cm3)Relative
density
(%)Actual  velocity
(m/s)Ammonium NitrateNH4NO3Hoariness
grain35001.100.78671.52800Urea
NitrateCH5N3O4White
crystals41901.690.78646.53100TNTC7H5N3O6Light
yellow powder67001.600.78649.15000RDX(CH2NNO2)3White
powder84001.790.78643.96000


### 2.4. The Numbering Rule of the Test Samples

The test samples were divided into four groups, and each group was made
of a different explosive. The letters A, N, T, and S referred to Ammonium Nitrate,
Urea Nitrate, TNT and
RDX, respectively. The
numbers 1, 2, 3, 4, and 5 were used to show the increase of the
explosive mass in turn, respectively. In other words, the explosive mass was 225,
250, 275, 300, and 325 g,
respectively. For example, the A3 test sample was prepared by explosive
compaction using 275 g ammonium
nitrate explosive.


## 2.1. Process of Explosive
Compaction

The set [11] as shown in
Figure 1 is usually used in
the direct method of the explosive compaction. The powder is packed into the close
metal tube surrounded by a layer of homogeneous explosive. When the explosive is
detonated, the powder is compressed by the steel tube which is compressed down
by the convergent columnar impact wave from one side of the system. In this paper,
the powders were put into a 20#-seamless steel
tube, and the bottom of the tube was blocked by a steel plug. When being packed
into the powder, the tube vibrated making the powder homogeneous and dense. Then,
it was blocked by the other plug and set in the position of axis of the
columnar paper tube. The wooden cone was set on the top of the steel tube to
make the explosive produce the front edge of the compression. Homogeneous and dense
explosive was put into the clearance between the steel tube and the paper tube.
The explosive exploded vertically after the detonator was detonated.Figure 1
The set of explosive compaction.The sizes
of the steel tubes are as follows: the outer diameter is 18 mm, the wall thickness is 2 mm, the length is 100 mm, and the mass of each tube is about 18.9 g. The material of the upper plug and
the lower plug is the 20# seamless steel bar, the sizes are both Φ14⁢mm×10⁢mm, and the masses are both about 12.1 g. The size of the wooden cone is Φ18⁢mm×15⁢mm; the size of the wooden base is Φ60⁢mm×20⁢mm. The powder in the steel tube is ZrB2-20SiC
mixing powder, and the sum mass of the steel tube and the powder is about 28.6 g. Namely, the relative density of
the loading powders is about 42% of the theory density of ZrB2-20SiC.During explosion, the radial pressure and
impact wave appear after the front edge of the explosion wave went through. The
part of the steel tube between the upper plug and the lower plug in
Figure1
is deformed. The radial velocity (νp) of the steel tube increases with the ratio
of explosive mass to tube mass (R), and it usually affects the final compact density
of the ZrB2-20SiC UHTCs.We only measured the size change of the length
and the outer diameter of the steel tubes. There were some evident scratch
marks on the surface of the steel tubes after the explosive compaction; the
part of the steel tube between the upper plug and lower plug was deformed radically
and homogeneously. Thus, the deformation of steel tube occurred in plane and
the deformation degree was decided only by the reduction of the outer diameter
of the steel tubes.


## 2.2. Experiment Analysis

In the course of explosive compaction, one part of the total impact
energy of the explosive is consumed on the steel tubes, and other part is
consumed on the powder. Besides, there is a part of energy consumed on the air
and voice. Since it is so little, it is often neglected. The common method only
offers approximately, but it cannot judge the distribution of two parts of the
explosive impact energy. The method in this paper can offer the effective
impact energy and judge the distribution of two parts of the explosive impact
energy, thus our work is essential and important.The basic
parameters in the formula include the radial velocity (νp) of the steel tubes, the explosion velocity (νD) of the explosive and the ratio of explosive
mass to tube mass (R). The research on the explosive compaction is
expressed by these parameters, because these parameters are easy to understand,
moreover, these parameters are usually adopted in the specific explosive
compaction experiment. The detail deduction of the formula can be seen in
[12–14].


## 2.3. The Explosive Characteristics

We chose four kinds  of
explosive and all characteristics were shown in
Table1. The actual explosion velocity of the explosive is relevant to the
packing density of the explosive. With the rise of the packing density, the
actual explosion velocity increases, and the relationship between them is parabolic
[11, 15]. Since the packing density of each explosive was lower than
the theory density and the relative density was different in this experiment,
the actual explosion velocity of each explosive also decreased differently. However, the range of the packing
density was so small in this research that explosion velocity of each
explosive could be regarded as a constant [6, 13, 14].Table 1
The
characteristic of the four kinds of explosive.
NameFormulaAppearanceTheory
velocity
(m/s)Theory
density
(g/cm3)Actual
density
(g/cm3)Relative
density
(%)Actual  velocity
(m/s)Ammonium NitrateNH4NO3Hoariness
grain35001.100.78671.52800Urea
NitrateCH5N3O4White
crystals41901.690.78646.53100TNTC7H5N3O6Light
yellow powder67001.600.78649.15000RDX(CH2NNO2)3White
powder84001.790.78643.96000


## 2.4. The Numbering Rule of the Test Samples

The test samples were divided into four groups, and each group was made
of a different explosive. The letters A, N, T, and S referred to Ammonium Nitrate,
Urea Nitrate, TNT and
RDX, respectively. The
numbers 1, 2, 3, 4, and 5 were used to show the increase of the
explosive mass in turn, respectively. In other words, the explosive mass was 225,
250, 275, 300, and 325 g,
respectively. For example, the A3 test sample was prepared by explosive
compaction using 275 g ammonium
nitrate explosive.


## 3. The Results and the Discussion

The technological parameters and the experiment results are shown in
Table2, and Figures
2, 3, and
4 are drawn according to the relevant data.
Figure 2 shows the relationships between the reduction of the outer diameter
and the ratio of explosive mass to tube mass (R). From Figure 2, we can see that, with the
rise of the mass ratio R,
the reduction of the outer diameter changes similarly and increases gradually. Namely,
the deformation of the steel tube monotonically increases with the rise of the
explosive mass. It is the same when the steel tube is empty
[13], but
it is on the contrary to the instance of explosive compaction of the CuCr alloy
powder [14]. When CuCr alloys were prepared by the explosive
compaction, the steel tube hardly changed with the rise of the explosive mass.Table 2
The technological parameter and experimental results.
No.Reduction of outer diameter (mm)Tube deformation energy (Nm/cm3)Power packing density (g/cm3)Mass ratio
(R)Velocity of steel tube (m/s)Explosive impact energy  (Nm/cm3)Powder compaction energy (Nm/cm3)Ceramic blanks density   (%)A114.6553.720.5902.473908.7221.67167.9583.94A214.5355.650.6552.747951.1269.59213.9486.42A314.4656.780.7213.022989.0320.88264.1088.07A414.4157.580.7863.2971023.0374.27316.6989.15A514.3957.900.8513.5711053.5429.74371.8489.66N115.5139.930.5902.4731006.1271.74231.8168.57N215.2244.580.6552.7471053.0337.34292.7673.21N315.0247.800.7213.0221095.0393.35345.5576.68N414.9449.430.7863.2971132.6458.76409.3378.23N514.9149.550.8513.5711166.4526.79477.2478.82T114.9349.230.5902.4731622.7706.87572.3678.44T214.7751.800.6552.7471698.4859.67807.8781.38T314.6953.080.7213.0221766.11023.24970.1683.15T414.6354.050.7863.2971826.81193.481139.4384.38T514.5954.700.8513.5711881.31370.431315.7385.25S114.4656.780.5902.4731947.21017.85961.0788.05S214.3458.700.6552.7472038.11237.951179.2590.78S314.2859.650.7213.0222119.31473.441413.7992.23S414.2560.150.7863.2972192.11718.521658.3792.78S514.2360.480.8513.5712257.51973.321912.8493.37Figure 2
The relationships between the reduction of the outer diameter
and the ratio of explosive mass to tube mass (R).Figure 3
The relationships between the equivalent strain and the mass ratio (R).Figure 4
The relationships between the per volume energy and the mass ratio (R)
in the
condition of ammonium nitrate.The reason may be that during the explosive compaction of the ceramic
powder, the blanks density is comparably low. With the rise of mass of the
explosive, the deformation of the steel tube gradually increases, and the blanks
density also increases monotonically. It perhaps does not reach the maximum.
However, during explosive compaction of the CuCr alloys, the deformation of the
steel tube and the compacts density both increased first, and then decreased, each
of them had a maximum. However, the variation range of the density of the CuCr
alloys was very small and the steel tube changed very little, too.When compared
with four kinds of the explosive, the reduction of the outer diameter of the steel
tube orders from big to small as RDX, Ammonium Nitrate, TNT, and Urea Nitrate.
Generally speaking, the higher the explosion velocity is, the bigger the
deformation of the steel tube is. Only ammonium nitrate is an exception, and its
explosion velocity is the lowest, but the deformation of the steel tube is not
the smallest. On the contrary, it even exceeds the deformation made by TNT and Urea Nitrate,
and
next to that by the RDX explosive.Figure3 shows the relationships between the equivalent strains and the
mass ratio R.
The change tendency in  Figure 3 is similar to that in
Figure 2. From  Figure
3, we can see that, with the rise of the mass ratio R,
the equivalent strain increases monotonically. Namely, with the rise of the
explosive mass, the deformation of the steel tubes increases monotonically, and
the equivalent strain of the steel tubes also increases in synchronism.Figure4 shows the relationships among the explosive
impact energy, the
tube deformation energy, the powder compaction energy, and the mass ratio
R in the condition of the ammonium nitrate. With
the rise of ratio of explosive mass to tube mass (R), the deformation energy of the steel tube
hardly changes, but the explosive impact energy and the powder compaction
energy increase in synchronism. The situations of the other explosive are the same
as those of the Ammonium Nitrate. With the rise of the explosive mass, the
explosive impact energy increases, but the deformation energy of the steel tube
does not change, thus the increased energy is totally used to compact the
ceramic powder. From Table 2 we can also get that, with the rise of the
explosive mass, the deformation energy of the steel tube increases, and the
density of the ceramic blanks increases monotonically. Generally speaking, the
higher the powder compaction energy is, the higher the density of the ceramic
blank is. However, ammonium nitrate is an exception. Its explosion velocity is
the lowest, and the powder compaction energy is the lowest too, but the density
of the ceramic blanks is superior to that prepared by Urea Nitrate and TNT,
and just inferior to that prepared by RDX.


## 4. Conclusion

(1)
The
density ofZrB2-SiC composites prepared by mixing and explosive
compaction reaches to 93.37% of theory density.(2)
During explosive compaction, whatever kind of explosive is
selected, both the reduction of the outer diameter and the equivalent strain of
the steel tubes increase monotonically with rise of the mass ratioR.
To the different kinds of explosive, the higher the explosion velocity is, the
bigger the deformation and the equivalent strain are.
Only ammonium nitrate is  excepted.(3)
The explosive impact energy is divided into the tube deformation
energy and the powder compaction energy. With the rise of the explosive mass, the
tube deformation energy hardly changes, while the explosive impact energy and
powder compaction energy increase in synchronism.(4)
With
the rise of the mass ratioR,
namely, with the rise of the explosive mass, the powder compaction energy
increases, and the density of the ceramic blanks also increases gradually. The density
of the ceramic blanks produced by different explosives orders from big to small
as RDX, Ammonium Nitrate, TNT, Urea
Nitrate.



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*Source: 754838-2008-08-11.xml*