156
Combustion
synthesis
Kashinath C Patil*, Singanahally
Many
innovative
(SHS)
self-propagating
techniques
centrifugal
thermite
solid-state
metathesis,
and densification
‘advanced
process
particle
process,
combustion,
field activated
synthesis
the
combustion,
flame synthesis
and simultaneous
have been developed
for the synthesis
materials’.
initiated
and mixtures
high-temperature
such as filtration
A novel
gas
producing
at low temperature
has been used
T Aruna and Sambandan
SHS
of
self-propagating
using redox compounds
for the
preparation
of fine
oxides.
Addresses
Department
of Inorganic and Physical
Science, Bangalore012, India
*e-mail: [email protected]
Current
2:156-l
Opinion
65
in Solid
Electronic
identifier:
0 Current
Chemistry
State
Chemistry,
& Materials
Indian institute
Science
of
1359-0266
Abbreviations
CH
CTPB
DFH
HC
MS
ODH
SHS
SSM
T
TEA
carbohydrazide
carboxy terminated
polybutadiene
diformyl hydrazine
hydrocarbon
mass spectroscopy
oxalyl dihydrazide
self-propagating
high-temperature
solid-state metathesis
adiabatic temperature
tetraformal trisazine
number
of technologically
useful oxide (refractory
oxides,
magnetic,
dielectric,
semiconducting,
insulators,
catalysts,
sensors, phosphors
etc.) and nonoxide
(carbides,
borides,
silicides,
nitrides
etc.) materials.
To date more than 500
materials
have been synthesized
by this process,
many
of which are commercially
manufactured
in Russia.
In
recent years, there has been tremendous
interest
in the
combustion
synthesis
of materials because it is simple, fast,
energetically
economic
and yields high purity products
compared
to the conventional
routes
used to prepare
these materials.
As it is a high-temperature
process, only
thermodynamically
stable phases can be prepared.
At the
same time, rapid heating
and cooling rates provide
the
potential
for the production
of metastable
materials
with
new and unique properties.
1997,
1359-0266-002-00156
Ltd ISSN
Ekambaram
synthesis
A number
of review
articles
[2”,3”,4-61
on the combustion
synthesis
of oxides
and nonoxides
have been
published
during
the last decade.
Merzhanov,
one of
the pioneers
of SHS has periodically
reviewed
[4,5] the
developments
in SHS and its applications.
His recent
article
[4] discusses
the theory
and practice
of SHS
world-wide
along with new directions
in the field. A quarterly journal,
‘International
Journal
of Self-Propagating
High-Temperature
Synthesis’
devoted
to SHS has been
published
by Allerton
Press Inc; New York, since 1992
with Alexander
G Merzhanov
as the ‘General
Editor’.
Three International
Symposia on SHS have been held, in
1991 (Alma-Ata,
Kazakhstan),
1993 (Honolulu,
USA) and
1995 (Wuhan, China) and the fourth one is being planned
in Spain during October
6-10, 1997.
Introduction
The
synthesis
of solids possessing
desired
structures,
composition
and properties
continues
to be a challenge
to chemists,
material scientists
and engineers.
Formation
of solids by the ceramic
method
is controlled
by the
diffusion
of atoms and ionic species through reactants and
products
and thus requires
repeated
grinding,
pelletizing
and calcination
of reactants
(oxides
or carbonates)
for
longer durations
(than soft chemical
routes) at high-temperatures.
Attempts
have recently been made to eliminate
the diffusion
control
problems
of solid synthesis
by
using various
innovative
synthetic
strategies
[l]. One
such approach
is ‘combustion
synthesis’
also known
as
‘self-propagating
high-temperature
synthesis’
(SHS) and
fire or furnaceless
synthesis.
The
process
makes
use
of highly exothermic
redox chemical
reactions
between
metals and nonmetals,
the metathetical
(exchange)
reaction between
reactive
compounds
or reactions
involves
redox compounds/mixtures.
The term ‘combustion’
covers
flaming (gas-phase),
smouldering
(heterogeneous)
as well
as explosive
reactions.
The
combustion
method
has
been
successfully
used in the preparation
of a large
A two part review
[2**,3**] on combustion
synthesis
of advanced
materials
by Moore
and Feng
gives an
account of the historical
perspectives
of SHS; parameters
that control
the SHS process;
and materials
that have
been
prepared
and their
applications.
Various
types
of SHS reaction
and proposed
models
of reaction
are
discussed,
the thermodynamics
and kinetics
of SHS
reactions
are also presented.
Important
parameters
that
control combustion
synthesis
such as the particle size and
shape of the reactants,
ignition techniques,
stoichiometric
ratio, processing
of reactant particles (green density, i.e. the
density
of the pellet before sintering)
and the adiabatic
temperature
(Tad) which is a measure of the exothermicity
of the reaction, have been discussed
in detail [2”,3”,4-61.
For this reason no attempt
is made here to elaborate
on these points. In this article, the recent trends in the
SHS, thermite,
solid-state
metathesis
(SSM) and flame
syntheses,
used in the preparation
of inorganic
materials
will be discussed.
The latter part of the article is devoted
to the combustion
synthesis
of oxide materials using redox
compounds
and mixtures.
Combustion synthesis Patil,
Materials prepared by SHS and related
processes
3Fe304
Synthesis of refractory materials: borides, carbides, nitrides, silicides, ceramics, intermetallics,
composites and
oxide materials continues to be the main thrust of SHS
processes. These materials can be prepared by igniting the
pellets of respective metals and nonmetals with a suitable
heat source. Once ignited, the combustion
reaction is
self-propagating with an adiabatic temperature (Tad) in the
range 1500-3000K.
The general chemical equation for the elemental
tion reaction can be represented
by:
mX + nY + X,Y,
combus-
(1)
where X=Ti, Zr, Hf, V, Ta, B, Be, Si act as fuels (metals)
and Y = B, C, N, S, Si, Se act as oxidizers (nonmetals).
The high ignition temperature (21500°C) required, can be
attained by laser radiation, a resistance heating coil, an
electric arc, a chemical oven and so on. Innovations in SHS
processes are aimed at lowering the ignition temperature
and using metal oxides/halides
instead of finely divided
metal powders.
+ 8Al+
AH&
Aruna and Ekambaram
4A1203 + 9Fe
159
(2)
= -3400 KJmol-’
A modified thermite reaction called a ‘centrifugal thermite
reaction’ has been used for coating the inner surface of
steel pipes. By coupling SHS with a centrifugal process
a surface layer of alumina and an inner layer of Fe is
formed in the pipe due to the difference
in density
between Fe and alumina. The composite pipe will have
the strength and toughness
of a metal and corrosion
and abrasion resistance of a ceramic. Orru et a/. [12]
have studied the influence of some of the processing
parameters, such as the mass ratio of thermite mixture to
substrate pipe and the presence of diluents on the final
product distribution, to gain an insight into the mechanism
of the centrifugal
thermite process. The experimental
and modelling studies of product separation during the
synthesis of Fe-A1203 materials in a field of centrifugal
forces has been investigated
[13].
The second type of thermite process involves the reduction of an oxide to the element which subsequently
reacts
with another element to form a refractory compound.
TiOz
+ Bz03
+ 5Mg+
TiBz
+ 5MgO
(3)
To lower the ignition temperature:
mechanical activation
and field activation
processes
are used. Mechanical
alloying has been successfully
used to synthesize Tic,
NbC and their solid solutions using Ti, Nb and graphite
powders [7]. The alloying was carried out by using steel
balls and vials in a SPEX-8000 mixer. Using ball milling
it was possible to ignite Ti, Zr, Hf metal powders with
C, B, Si or S. Some oxides of Cu, Ni, Fe and Zn
were also reduced with Ti, Zr and Hf by ball milling
[8*]. A TG-DTA-MS
study of self-ignition
in SHS of
mechanically activated Al-C powder mixtures showed that
the disordered C served as the ignition source for the SHS
reaction [9]. Field activated (ZOV) combustion
synthesis
has been used by Munir and co-workers to activate low
enthalpy of formation (AHf) (e.g. SIC, B&, WC, WSi2
etc.) reactions. Using this method intermetallics,
ceramics
and composites (e.g. MoSiz-xNb and MoSiz_yZrOz) have
been prepared [lo]. A recent study [ 1 l] on the relationship
between
the field direction
and wave propagation
in
activated combustion
synthesis
showed that the field
applied in a direction perpendicular
to wave propagation
resulted in an enhancement
of the wave velocity (which
helps in the completion
of the reaction and results in a
decrease in the particle size of the product).
Composites such as MgO-B&
[ 141 have been prepared by
coupling a highly exothermic Mg-Bz03 thermite reaction
with a weakly exothermic B&Z formation reaction. The
reaction mechanism
of the alumino-thermite
reaction
in the formation of MoSiz-A1203 has been investigated
using DTA and XRD [15]. The effect of reaction
parameters such as reactant particle size, use of diluent,
and use of reactant preheating during the aluminothermite
reduction of TiOz to Tic have been discussed [16]. The
structural transformations
that take place in all stages of
aluminochermic
SHS have been studied by performing
synthesis under gas pressure, in the field of centrifugal
forces, by quenching
and so on [ 171. One dimensional
mathematical
modelling has been used to describe the
SHS process for the preparation
of TiA13 and NiA13
intermetallics
[ 181. Titanium-aluminium-carbon
ternary
composites
with dispersed
fine TIC particles having
excellent elevated temperature
strength compared with
that of TiAl intermetallic
compounds have been reported
[19]. These
methods are of great importance
in the
synthesis of advanced ceramic and composite materials on
account of the economic advantages in using cheaper oxide
reactants compared with expensive elemental reactants.
Thermite reactions which involve metallo-thermic
reduction have been employed in the ceramic coating of pipes
as well as in the preparation of composites. There are two
types of thermite reactions. The first method involves the
reduction of an oxide to the element, for example:
Recently Merzhanov and his associates [20*] have reported
the synthesis
of electronic
engineering
materials such
as superconductors,
ferroelectric and magnetic materials
by an SHS reaction using metal oxide and peroxide
precursors.
160
Synthesis and reactivity of solids
3Cu
The
with
+ 2BaOz
+ 1/2YzO3 + YBa2Cu307_x(Y123)
(4)
properties
of SHS derived
products
are compared
those prepared
by the furnace method.
The advan-
tages of SHS process are time and energy
increas in the reactivity
of the products.
savings
and an
As all the SHS processes
yield porous materials,
newer
techniques
combining
SHS and densification
are being
developed
to produce dense materials free of pores. Using
simultaneous
densification
and field activated
combustion
synthesis,
hloSi2
with
99.2% theoretical
density
has
been obtained
[Zl]. Simultaneous
SHS and subsequent
densification
by an impact forging technique
of a TiBz-SiC
composite
resulted
in a density
in excess of 96% which
is the theoretical
value [Z]. Symmetric
compositionally
gradient
materials
of the Al20$TiC/Ni/TiC/Al203
and
Al203/Cr$Z
/Ni/Cr&/AlZOj
systems were fabricated
by
SHS/HIP
(hot isostatic pressing)
compaction.
These
materials exhibited
outstanding
properties
such as toughness,
hardness
and strength
compared
to conventional
alumina
ceramics
[23]. The density of composite
materials can be
further improved
by deliberately
generating
an excess of
liquid metal in situ with the combustion
reaction which
infiltrates the pores in the ceramic matrix (e.g. Tic-AIZ03)
[3”]. A two dimensional
mathematical
model of filtration
combustion
which takes into account
the dynamics
of
changes
in the gas temperature
and pressure
in a SHS
reactor, has been proposed
[24]. Other applications
of SHS
are in the field of functionally
gradient materials (FGhl’s)
(e.g. Ti-C-Ni)
which have better mechanical
properties
and corrosion
resistance
to oxidation
than metals
and
composites
[25].
Materials
(SSM)
prepared by solid-state
metathesis
Recently
Kaner and his associates
have reported
[26’,27’]
the synthesis
of a variety
of materials
by ‘solid-state
metathesis
(exchange)’
reactions.
Unlike
the SHS reactions (elemental
or thermite
reactions)
which employ
metals, nonmetals
and oxides, this method involves rapid,
low temperature
initiated
solid-state
exchange
reactions
between
reactive
metal halides
with alkali metal main
group compounds.
The
exothermicity
of the reaction
reaches
nearly
1050°C within
=300ms.
A generalized
reaction scheme is
hlX,
+ mAY,
ignite
+ hlY,
+ mAX
Where
hl= metal,
X= halide,
Y = nonmetal
or metalloid.
+ [(m.n) -211
A=alkali
metal
(5)
and
the precursors
changes
phase
or decomposes
enabling
increased
surface contact.
A number
of technologically
important
materials
for example,
superconductors
(NbN,
ZrN), semiconductors
(GaAs, InSb), insulators (BN, ZrOZ),
magnetic
materials
(GdP, SmAs), chalcogenides
(hloS2,
NiSz), intermetallics
(MoSi2, WSiz), pnictides(ZrP,
NbAs),
and oxides
(Cr203)
have been
prepared
by an SSM
reaction.
Formation
of high-temperature
cubic/tetragonal
202
and B-MoSiz
is reported
by this process.
Two
possible reaction pathways
proposed
are
(i) Elemental:
hlX3
+ AxY +
hlo
+ Y” + 3AX + hlY
(6)
(ii) Ionic:
hlX3
+ AjY +
M3+
+ y”-
+ 3AX +
h,lY + 3AX
(7)
A serious limitation
of this process is the requirement
of
anhydrous
halides which require handling
in dry box and
storage in presence
of inert atmosphere.
Materials
prepared by flame synthesis
Flame synthesis
differs from the typical SHS process in
that all reactions
take place in the gas-phase
and form
fine powders
(often nanoscale
as in carbon soot from HC
flames, fumed silica, titania etc.). The possible advantages
of this process over normal solid/solid,
solid/liquid,
SHS
processes
are its continuous
rather than batch process of
the latter and the higher purities
of the products.
hlany
high purity materials can be synthesized
by self-sustaining
gas-phase
reactions.
It is well known that metal halides
react spontaneously
when their vapours are brought
into
contact
with gaseous
or liquid reactive
metals
such as
sodium or magnesium
[28].
Sic&)
+ 4Na(g)
(Tad
NbC15(R)
+
Si(l) + 4NaCI(r,)
+ Nb(l)
(Tad
+ 512hIg:Clz(g,
(9)
= ZSOOK)
Similarly
oxidation
and hydrolysis
(flame
SiCIA, TiCI3 yield fine particle oxides.
SiCIJ
(8)
= 24OOK)
+ S/ZhIg(,)
+ 02 +
SiC1.l + 2HzO
The SShl reactions
can be initiated
either
by simply
mixing/grinding
or by a hot filament.
Once the SShl
reaction is initiated,
it becomes
rapidly self-sustaining
and
can reach high temperatures
(>lOOO”C) within
a short
period
(~2s). Initiation
generally
occurs when
one of
+ 3AX
+
SiOz(,)
SiOz(,)
+
hydrolysis)
ZC12(g)
+ 4HCI(,)
of
(10)
(11)
Such gas-phase
combustion
or flame synthesis
has been
used
to prepare
fine particle
metal
nitrides
(Si$KJ),
carbides
(Sic, BdC, TaC), borides (TiB2, ZrBz), silicides
(TiSiz),
photovoltaic
silicon,
advanced
fuels
(B) and
Combustion synthesis
refractory metals (Ti, Ta, Zr, Hf, and Nb). Nanosize
silica, titania, alumina and tialite (Al~Ti05) have been
prepared by flame synthesis using the corresponding metal
halides and Hz/air or HC/air flames (Rajan TSK, personal
communication).
Some typical gas-phase reactions are as
follows:
Sic14 + CzH4 + 302 -+ SiOz(l) + ‘2C0~)
+ 4HCl
(12)
(Tad = 1543K)
Tic14 + QH4
+ 302 + TiOz(,)
+ ZCOZ(~) + 4HC1
(13)
(Tad = 1523K)
4AlX3 + 6Hz
+ 302 + ZAl2O3(,) + lZHX(,)
(14)
(Tad = 1393K)
High surface area SiO2 having nanosize particles are
prepared
by the addition
of ferrocene
to Sic14 [29].
Nanoparticle TiB2 (unagglomerated)
has been obtained by
the addition of NaCl [30]. Flame synthesis has also been
used to prepare nanosize Sic [31], TiB2 [30] and fullerenes
[32]. Diamond films which were produced using acetylene
earlier, have now been made using two inexpensive fuels:
MAPP (a mixture of methyl acetylene,
propadiene,and
propylene) [33].
Combustion synthesis of oxide materials
using redox compounds and mixtures
An entirely different approach to the synthesis of simple
and complex oxide materials is presented.
This approach involves the use of novel combustible
precursors
(redox compounds)
and redox mixtures.
It uses low
temperature
(<5OO’C) initiated gas-producing
exothermic
reactions which are self-propagating
and yield voluminous
fine particle oxides in few minutes.
Compounds
like
(NH&$2207
which contain both oxidizing (CrzO&
and
reducing (NH4+) groups when properly ignited (using
KClOx-sucrose-H2S04)
decompose
autocatalytically
to
yield voluminous green Cr203 (artificial volcano) [34].
(NH4)2Cr207(s)
2 Cr203(,)
+ N21p) + 4H20(,)
(15)
The exothermicity
of the combustion
reaction is due to
the oxidation of NH4+ to N2 and Hz0 by the dichromate
ion which itself is reduced to Cr3+. The combustion
is smbuldering
type (flameless) and is accompanied
by
the evolution
of gases resulting
in fine, voluminous
Cr203 powder. Mixed oxides such as spine1 chromites
[35], ferrites [36] and cobaltites [37] have been prepared
by the pyrolysis of (NH&M(Cr0&.6HzO
(M = Mg,Ni),
(NH&M(CrO&.ZNH3nX
(M = Cu,Zn),
MFe2(C20&
(NzH4)x (x=5 when M=Mg and x=6 when M=Mn,Ca,
Ni,Zn) and MCO~(C~O&(N~H~)X (x = 5 when M = Mg and
x = 6 when M = Ni) respectively. However exothermicity of
Patil, Aruna and Ekambaram
161
these precursors is not high enough to sustain combustion
and an external heat source is required for the completion
of the decomposition.
A new class of precursors containing a carboxylate anion,
hydrazide, hydrazine or hydrazinium
groups were accidentally found to ignite at low temperature
(120-350°C)
and decompose
autocatalytically
to yield fine particle,
large surface area oxides. The high exothermicity
(Tad
=lOOOK) of combustion was attributed to the oxidation of
strong reducing moieties such as COO-, NzHs- , NzH4
or N2Hs+ (present in the precursors) by atmospheric
oxygen to CO2, Hz0 and N2. The preparation,
crystal
structure and reactivity of various combustible
precursors
have recently
been reported
[38]. Table
1 gives a
list of these compounds
and the oxides formed. The
iron containing complexes, Fe(N2H$00)2
(N2H& and
N2HsFe(N2H$00)3.H20
and their solid solutions ignite
at -12o’C (they can be ignited with a match stick or candle
flame) and combust in the presence of atmospheric oxygen
like a Pharoah’s snake to yield nanosize Fe203 and ferrites.
The smouldering
type combustion
and the evolution of
large amounts of gaseous products (CO2, H20, NH3 etc.)
results in the formation of fine oxide products. The surface
area of these iron oxides range from 70 to 140mzg1. All
the ferrites when pelletized and sintered at 1000°C achieve
~98% theoretical density. Other nanosize oxides obtained
by the combustible
precursors are Ce02, TiOz and Y2O3.
Besides magnetic oxides a few ferroelectric titanates have
also been prepared by this route. Fine particle y-Fe203,
Fe304 and ferrites find use as recording materials and in
the preparation of liquid magnets. Titania, ferrites and
cobaltites are all good catalysts.
Although the preparation of fine particle oxide materials
by the combustion
of redox compounds
is simple and
attractive, it has certain limitations. Firstly, the preparation
of the precursors requires several days. Secondly the yield
is only =200/o of the precursor. Finally, not all metals
form complexes with the hydrazine carboxylate ligand and
therefore it is not possible to use this method to prepare
high-temperature
oxides like chromites, alumina and so
on.
An alternative
method to the combustible
redox compounds is the use of the redox mixtures
(oxidizerfuel) like gun powder (KNOs+C+S)
or solid propellant
(NH&l04+CTPB+Al)
which when ignited undergo selfpropagating combustion.
Since the serendipitous
preparation of a-Al203 foam (Fig. 1) by rapidly heating a
solution of aluminium nitrate-urea mixture [39], a number
of advanced materials [40] (aluminates,
aluminosilicates,
chromites, ferrites, ferroelectrics and zirconia) have been
prepared by the solution combustion
process. In addition
to urea CH, ODH, DFH, and glycine have been used
as fuels in the solution combustion
process. Glycine has
been used in the preparation of high T, superconductors,
manganites and chromites [ 1,41,42].
162
Synthesis and reactivity of solids
Table 1
Metal carboxylate
precursors to fine particle oxides.*
Precursors
WNd-l~C00)&V-Ld2
Zn(N2HsC00)2.(N2H&
Ce(N2HsC00),.3HsO
Y(N2HsC00)s.3H20
N,HsFe(N2HsC00)s.H20
N2HsM,,aFe2,a(N2HsCOO)s.H20
M=Mg
M=Mn
M=Co
M=Zn
M=Cd
_
Oxides
rkP3
ZnO
Ce02
y203
-t-Fe203
MPG4
MnFeoO4
CoFe204
ZnFe204
CdFe204
(N~Hs)aNixZnl_xFe~(N~HsC00)a.3H~0
x = 0.2
x = 0.4
x = 0.5
x = 0.6
x = 0.0
Surface area (m2/g)
68
67
90
55
75
Particle size (nm)
17-23
114
140
116
108
93
1O-25
91
86
90
85
91
1 O-20
N~H~M~/~CO~/~(N~H~COO)~H~O
M=Mg
M=Mn
M=Co
M=Zn
MnCo204
FeCoz04
ZnCo204
47
24
116
65
MgMg20,
ZnMn204
CoMn204
NiMn204
TiO2
ZrTi04
PbTiOs
PbZr03
PZT
PLZT
28
61
76
20
114
11
23
13
44
30
4@@4
20
35
20
*Reproduced with permission from [38].
Fiaure 1
Solution combustion synthesized c(-A1203 foam. Reproduced with
permission from [39].
A recipe [43-l given for the synthesis
of oxide materials
with
the
desired
composition
and structure
(spine],
perovskite,
KzNiF4, garnets etc.) using metal nitrate-oxalyl
dihydrazide
(C~H~NJO~)
illustrates
the simplicity
and
novelty
of this technique.
During
the period
of this
review, a variety of useful oxide materials such as catalysts
[44,45], phosphors
[46&S], pigments
[49,50], refractories
[51,52] and SYNROC
(synthetic
rock) for nuclear waste
immobilization
[53] have been prepared.
The materials
prepared,
fuel used and their properties
are listed
in
Table 2. The solution combustion
method not only yields
nanosize
Ti02 [40], ZrOz [54,55] and hexdferrites
[56]
but it also yields metastable
phases
like y-Fez03
1571,
t-202
[54,55] and anatase TiOz [44]. The process has also
been useful in preparing
Vq+ doped zircon (blue pigment)
without
the use of any mineralizer
[SO]. The advantages
of the solution combustion
process over other combustion
methods
are: firstly, being a solution process, it has control
over the homogeneity
and stoichiometry
of the products;
secondly, it is possible to incorporate
desired impurity ions
Combustion
mechanism
controlling
in the oxide hosts and prepare industrially useful materials
such as pigments, phosphors as well as high T, cuprates
and SOFC (solid oxide fuel cell) materials; thirdly, the
process is simple and fast and does not need any special
equipment
as in other SHS methods.
synthesis
Patil, Aruna and Ekambaram
163
of the process and the role of the fuel in
the combustion process.
Conclusions
Almost all known advanced materials (both oxide and
nonoxide) in various forms (nanosize, films, whiskers) have
been made by a combustion process. The materials arise
from the combustion
residues (ash) like a ‘Phoenix’, the
mythological
bird that burnt itself on pyre and arose
from the ashes with renewed youth to live again. The
combustion
process being simple, fast and energetically
economic is attracting the attention of material scientists
The advent of the solution combustion
method offers a
versatile means to synthesize
technologically
important
oxide materials. The future direction of the process will
be towards the synthesis of nonoxide materials such as
sulfides, nitrides, carbides and so on. There is scope,
however, for further investigations
to understand
the
Table 2
Oxide materials
prepared
by the solution combustion
process during 19951996.
Properties
Oxides
Catalysts
TiO0
Li*M04(M=Co,
Ni,Cu)
Phosphors
Y203:Eu3+
CeMgAl”O’a:Tba+
BaMgAlloO’
7:Eu2+
CHt ODHt
TFTA#
Oxidation of
methylene blue,
ammonia
ODH*
U’
U*lDFHl
Emission band
k=611 nm
h=543nm
h=450nm
U’
U’
CHt
CHt
CHt
CHt
Colours
pink
blue
rose
blue
yellow
red
Pigments
Al2O3CP+
Al0Os:C02+
Mg2B205:Co2+
ZrSiO4:V4+
ZrSiO4:PI”+
ZrSi04:Fes+
Synroc phases
perovskiie, CaTiOs
zirconolite, CaZrTi007
hollandite, BaAI,TieO’e
Synroc-B
CHt
Nanomaterials
Ti02
Applications
Oxidation of
water and air
pollutants
fluorescent
lamps, colour
Thermal expansion coefficients
a=l0.80x10-6K-’
a=9.04
x 1 O-SK-’
a=8.30
x 1 O-SK-’
a=8.72xlOaK-’
Particle size
20 nm
ODH*
Zr02,PSZ
BaFe’2O’a
1441
1451
WI
picture tubes
1471
1481
tiles
sanitarywares
etc.
149,501
nuclear waste
immobilization
catalyst,
refractory
recording tapes
1Onm
70 nm
References
[531
[44,54-561
1561
Magnetic
materials
recording tapes
ODH*
Tt=fA#
BaFe’2O’a
M,**=29.8-59.0
emu/g
Heft-1 925-5375
Oe
Ferroelectrics
tan 6@=0.02,
Pb(Zn’,sNb2,s)Os:BaTiOaTFTA
Pb(Zn’,aNb&0s:PbTi03
Low thermal expansion coefficient
Al’ sB4Oss
NaZrpPsO’2
KZr2P30’2
Ca0.5Zr2P3O’
Dm
actuators
[-I
refractories
batteries
electrochemical
151,591
DI#L=102
materials
2
SOFWmaterials
ZrO2:CaO
(10 moW0)
ZrO2: Y2O3
lU,
tan 6@=0.006,
CGt
U*
CHt
a=l.O5x
a=1.5Ox
CH’
CHt
a=1 .OO x 1 O-SK-’
a=l.2Ox
1 O-SK-’
ODHt
Resistance
CH4N20;
tCH, CHsN4O; *ODH, C0HsN4O2; *DFH, C2H4H202;
TFfA,
solid oxide fuel cell; ggtan 6, dissipation factor; “D, dielectric displacement.
1 O-SK-’
1 O-eK-’
sensors
= 112 Kohms
C4H,eHeO2;
Solid electrolyte
** M,, saturation magnetization; ttH,,
1601
coercivity; WOFC,
164
Synthesis
and reactivity
and engineers
to prepare
special applications
under
high pressure
conditions.
of
solids
new and exotic materials
corrosive high-temperature
for
and
Acknowledgements
l‘hr authors thank CNR Rao for his interest and encouragement. Aruna is
grateful to the Council of Scientific and Industrial
Research (CSIR), New
Delhi, lndla fur the award of a Junior Research Fellowship. Ekambaram is
grateful co the hlinistry of Nonconventional Energy Sources (hlNES), New
Delhi for funding.
References
and recommended
reading
15.
Deevi SC, Deevi S: In-situ synthesis of MoSi,-Al,O,
composite
by a thermite reaction. Scr Metal/ Mater 1995, 33:415-420.
16.
Bowen CR, Derby B: The formation of TiC/AI,O,
microstructures
by a self-propagating
high-temperature
synthesis reaction. J
Mater Sci 1996, 31:3791-3803.
1 7.
Yukhvid VI, Vishnyakova GA, Silyakov SL, Sanin VN, Kachin AR:
Structural macrokinetics of aluminothermic self-orooaoatinahigh- temp-synthesis (SHS) processes. ht J Se/;-Propig
Hi&Temp Synth 1996, 5:93-l 05.
18.
Sohn HY, Wang X: Mathematical and experimental investigation
of the self-propagating
high-temperature
synthesis (SHS) of
TiAIs and Ni,AI intermetallic compounds. J Mater Sci 1996,
31:3281-3288.
19.
Tomoshige R, Matsushita T: Production of titanium-aluminumcarbon ternary composites with dispersed fine TiC particles by
combustion synthesis and their microstructure observations. J
Ceram Sot Jpn 1996, 104:94-l 00.
Papers of particular interest, published within the annual period of review,
have been highlighted as:
.
l
1.
*
of special interest
of outstanding interest
Rao CNR:Combustion synthesis. In Chemical Approaches to
the Synthesis of inorganic Materials. New Delhi: Wiley Eastern
Limited; 1994:28-30.
Moore JJ, Feng HJ: Combustion synthesis of advanced
materials: part I. Reaction parameters. frog Mater Sci 1995,
39:243-273.
An excellent review covering all aspects of combustion synthesis. Historical
perspectives of combustion and various parameters that control combustion
are discussed. A list of SHS products and their applications are given.
20.
Avakyan PB, Nersesyan MD, Merzhanov AG: New materials for
.
electronic engineering. Am Ceram Sot Bull 1996, 75:50-55.
The synthesis of ferrites, ferroelectrlcs and high T, oxide superconductors
by SHS and furnace methods demonstrating the superiority of SHS are
described. The use of ferroelectric materials as sensors is also discussed.
21.
Shon IJ, Munir ZA, Yamazaki K, Shoda K: Simultaneous
synthesis and densification of MoSi2 by field-activated
combustion. I Am Ceram Sot 1996, 79:1875-l
880.
22.
Hoke DA, Kim DK, LaSalvia JC, Meyers MA: Combustion
synthesis/dynamic
densification of a TiB2-SiC composite.
Am Ceram Sot 1996, 79:177-l 82.
2.
..
3.
..
Moore JJ, Feng HJ: Combustion synthesis of advanced
materials: part II. Classification, applications and modelling.
frog Mater Sci 1995, 39:275-316.
Materials prepared by combustion are discussed under different headings
and the reactions are classified according to the element/compound or state
(solid, liquid or gas) of the reactants. Thermodynamics, kinetics and models
of SHS reactions are also discussed.
4.
Merzhanov AG: Theory and practice of SHS: worldwide state
of the art and the newest results. Int J Self-Propag High-Temp
Synth 1993, 2:113-l 58.
5.
Merzhanov AG: New manifestations of an ancient process.
In Chemistry of Advanced Materials: A Chemistry for the
27s’ Century. Edited by Rao CNR. London: Blackwell;
1993:19-39.
6.
Subrahmanyam J, Vijayakumar M: Self-propagating
hightemperature synthesis. J Mater Sci 1992, 27:6249-6273.
7.
Liu ZG, Ye LL, Guo JT, Li GS, Hu ZQ: Self-propagating
temperature synthesis of TIC and NbC by mechanical
J Mater Res 1995, lo:31 29-3135.
highalloying.
8.
.
Takacs L: Ball milling-induced combustion in powder mixtures
containing titanium, zirconium, or hafnium. J Solid State Chem
1996, 125:75-84.
This is an interesting paper on ball-milling induced reactions involving Ti, Zr
and Hf metal powders with S, C and metal oxides.
9.
Tsuchida T, Hasegawa T: TG-DTA-MS study of self-ignition in
self-propagating high-temperature
synthesis of mechanically
activated AI-C powder Mixtures. Thermochim Acta 1996,
276:123-l
29.
J
23.
Miyamoto Y, Tanihata K, Kimiaki L, Zenshi, Kang YS, Murakawa
H: Development of symmetric gradient structures for
hyperfunctional materials by SHSIHIP compaction. Adv Sci
Techno/ 1995, 10:87-98.
24.
Grachev W, lvleva TP, Borovinskaya IP: Filtration combustion in a
self-propagating
high-temperature
synthesis (SHS) reactor. Int
J Self-Propag High-temp Synth 1995, 4:245-252.
25.
Shcherbakov VA, Shteinberg AS: Macrokinetics of SHS
infiltration. Combust Sci Techno/ 1995, 107:21-29.
26.
.
Treece RE, Gillan EG, Kaner RB: Materials synthesis via solidstate metathesis reactions. Comment Inorganic Chem 1995,
16:313-337.
This article reviews the synthesis of thermodynamically stable inorganic
solids (oxides, sulphides, nitrides. intermetallics) by the use of a highly
exothermic solid-state metathesis reaction between metal halide and alkali
metal main group compounds.
27.
.
Gillan EG, Kaner RB: Synthesis of refractory ceramics via rapid
metathesis reactions between solid-state precursors. Chem
Mater 1996, 8:333-343.
This is a detailed article on SSM reactions, its predictive ability and applications in the rapid synthesis of refractory materials such as nitrides is
documented.
28.
Glassman I, Davis KA, Brezinsky K: A gas-phase combustion
synthesis process for non-oxide ceramics. Twenty-Fourth
Symposium (International) on Combustion/The Combustion
Institute 1992:1877-l
882.
29.
Fotou GP, Scott SJ, Pratsinis SE: The role of ferrocene
synthesis of silica. Combust Flame 1995, 101:529-538.
in flame
10.
Shon IJ, Munir ZA: Synthesis of MoS&xNb and MoSi2-yZrOz by
the field-activated combustion. Mater Sci Eng 1995, 202:256261.
30.
Dufaux DP, Axelbaum RL: Nanoscale unagglomerated
nonoxide
particles from a sodium coflow flame. Combust Name 1995,
100:350-358.
11.
Feng A, Munir ZA: Relationship between field direction and
wave propagation in activated combustion synthesis. J Am
Ceram Sot 1996, 79:2049-2058.
31.
Keil DG, Calcote HF, Gill RJ: Flame synthesis of high purity,
nanosized crystalline silicon carbide powder. Mater Res Sot
Symp Proc 1996, 410:167-l
72
12.
Orru R, Simoncini B, Virdis PF, Cao G: Further studies on a
centrifugal SHS process for coating preparation and structure
formation in the thermite process. Int J Self-Propag High-Temp
Synth 1995, 4:137-l 47.
32.
Feldman Y, Wasserman E, Srolovitz DJ, Tenne R: High-rate,
gas-phase growth of MO!& nested inorganic fullerenes and
nanotubes. Science 1995, 267:222-225.
13.
33.
Puszynski JA, Kattamuri DS, Stefansson B, Jagarlamudi S:
Simultaneous combustion synthesis and densification with
product separation. Adv Powder Metal/ Part Mater 1995,
2:187-l 98.
Shin HS, Goodwin DG, Harris SJ: Alternative fuels for
combustion synthesis of diamond. Proc . Nectrochem
1995, 95:231-236.
14.
Wang LL, Munir ZA, Birch J: Formation of MgO-B& composite
via a thermite-based
combustion reaction. I Am Ceram Sot
1995, 78:756-764.
Sot
34.
Patil KC, Soundararajan R: Pyrotechniques
Ind J Chem Edn 1979, 6:29-30/
35.
Wold A, Dwight K: Synthesis of oxides containing transition
elements. J Solid State Chem 1990, 88:229-238.
for entertainment.
Combustion synthesis Patil, Aruna and Ekambaram
165
36.
Gajapathy D, Patil KC: Mixed metal oxalate hydrazinites as
compound precursors of spine1 ferrites. Mater Chem Phys
1993, 9:423-439.
40.
Kottaisamy M, Jeyakumar D, Jagannathan R, Mohan Rao M:
Yttrium oxide: Eu3+ red phosphor by self-propagating high
temperature synthesis. Mater Res Buff 1996, 31 :I 013-l 020.
37.
Patil KC, Gajapathy D, Pai &maker VR: Low temperature
cobaltite formation using mixed metal oxalate hydrazinite
precursor. J Mater Sci Lett 1963, 2~272-274.
49.
Patil KC, Ghosh S, Aruna ST, Ekambaram S: Ceramic pigments:
a solution combustion approach. The lndian Potter 1996,
3411-g.
36.
Patil KC, Sekar MMA: Synthesis, structure and reactivity of
mete1 hydrazine carboxylates: combustible precursors to fine
particle oxide materials. Int J Se/f-Propag High-Temp Synth
1994, 3:181-196.
50.
Muthuraman M, Dhas NA, Patil KC: Preparation of zirconia
based colour pigments by combustion route. J Mater Synth
Processing 1996, 4:115-l 20.
51.
39.
Kingsley JJ, Patil KC: A novel combustion process for the
synthesis of fine particle a-alumina and related oxide
materials. Mater Letf 1988, 6:427-432.
Ekambaram S, Dhas NA, Patil KC: Synthesis and properties
of aluminum borate (a light weight ceramic). lnt J Self-Propag
High-Temp Synth 1995, 4105-93.
52.
Chandran RG, Chandrashekar BK, Ganguly C, Patil KC: Sintering
and microstructural investigations on combustion processed
mullite. J Eur Ceram Sot 1996, 16:941-949.
53.
Muthuraman M, Patil KC, Senbagaraman S, Umarji AM:
Sintering. microstructural and dilatometric studies of
combustion synthesized synroc phases. Mater Res Bull 1996,
31:1375-l
361.
54.
Venkatachari KR, Huang D, Ostrander SP, Schulze WA, Stangle
GC: A combustion synthesis process for synthesizing
nanocrystelline zirconia powders. J Mater Res 1995,
10:746-755.
55.
Venkatachari KR, Huang D, Ostrander SP, Schulze WA, Stangle
GC: Preparation of nanocrystelline yttria-stabilized zirconia. J
Mater Res 1995. 10:756-761.
56.
Castro S, Gayoso M, Rivas J, Greneche JM, Mira J, Rodriguez
C: Structural and magnetic properties of barium hexeferrite
nanaostructured particles prepared by the combustion method.
J Magn Magn Mater 1996,162:61-69.
57.
Suresh K, Patil KC: A combustion process for the instant
synthesis of y-iron oxide. J Mater Sci Lett 1993, 12:572-574.
56.
Sekar MMA, Patil KC: Low-temperature
synthesis and
propertiesof microwave resonator materials. Mater Sci Eng B
1996, 39:273-279.
59.
Dhas NA Patil KC: Combustion synthesis and properties
NASICON materials. J Mater Chem 1995, 5:1463-l 466.
60.
Shukla AM, Sharma V, Dhas NA, Patil KC: Oxide-ion conductivity
of celcia- and yttria-stabilized rirconias prepared by a rapid
combustion route. Mater Sci Eng B 1996, 40:153-l 57.
40.
Patil KC: Advanced ceramics: combustion synthesis and
properties. Bull Mater Sci 1993, 16:533-541.
41.
Honeyboume CL, Rasheed RK: Nitrogen dioxide and volatile
sulfide sensing properties of copper, zinc and nickel chromite.
J Mater Chem 1996, 6:277-263.
42.
Bates JL, Chick LA, Weber WJ: Synthesis, air sintering
and properties of lanthanum and yttrium chromites and
manganites. Solid State lonics 1992, 52:235-242.
Suresh K, Patil KC: A recipe for an instant synthesis of
fine particle oxide materials. In Perspectives in So/id State
Chemistry. Edited by Rao KJ. New Delhi: Narosa Publishing
House; 1995:376-369.
Gives a ready to use recipe for the combustion synthesis of spin& (aluminates, chromites and ferrites), perovskites (LnM03, M=Al, Fe, Cr), KzNiFd
type (La2M04, M=Mn, Co, Ni and Cu) and garnets (Ln3Fe5012 and YIAG
[yttrium iron aluminium garnet]).
43.
.
44.
Aruna ST, Patil KC: Synthesis and properties of nanosize
titenia. J Mater Synth Processing 1996, 4:175-l 79.
45.
Ramesh S, Manoharan SS. Hegde MS, Patil KC: Catalytic
oxidation of ammonia over high surface area La2M04 (M-Co,
Ni & Cu). J Catal 1995, 157:749-751.
46.
Ekambaram S, Patil KC: Synthesis and properties of rare earth
doped lamp phosphors. Bull Mater Sci 1995, l&921 -930.
47.
Ekambaram S, Patil KC: Synthesis and properties of I%*+
activated blue phosphors. J Alloys Compounds 1997, in press.
of