CHAPTER-1

INTRODUCTION

INTRODUCTION

1

Men’s desire to explore outer space and build a strong edifice had led to

development of many new explosives/energetic molecules for defence and civil

applications. The explosives are thought to have been discovered in the seventh

century by the Chinese and the first known explosive was black powder (also known

as gunpowder) which is a mixture of charcoal, sulphur and potassium nitrate. The

Chinese used it as an explosive, propellant and also for fireworks. Subsequently, with

the development of nitrocellulose (NC) and nitroglycerine (NG) in Europe, a new

class of explosive viz., low explosive came into existence. As this new class of

explosives burn slowly in a controlled manner giving out a large volume of hot gases

which can propel a projectile, these low explosives were termed as propellants. The

discovery of high explosives such as Picric Acid, trinitrotoluene (TNT),

Pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (research

department explosive RDX), Cyclotetramethylene tetranitramine (High melting

explosive HMX) etc. which are more powerful but relatively insensitive to various

stimuli (heat, impact, friction and spark), advocated there use as explosive filling for

bombs, shells and warheads etc. Similarly by following the principal of gunpowder

and in order to meet requirement of military for special effect (illumination, delay,

smoke, sound and incendiary etc) formulation based on fuel, oxidizer, and binders

along with additives were developed and classified as pyrotechniques. The broad

classification of explosives based on above explanation are given below1-

1.1 CLASSIFICATION OF EXPLOSIVES

These three branches of explosives viz., explosives, propellants and

pyrotechnics were developed independently until the early 1990s and during this time,

the number of reported explosive increased exponentially. In order to camouflage

research on explosives, propellants and pyrotechnics a new term ‘high energy

materials’ (HEMs) was coined by the explosives community for them. Thus all

explosives, propellants and pyrotechnics can be referred to as high energy materials

(HEMs) or energetic materials (EMs). In other words, the other name of HEMs/EMs

is explosives, propellants and pyrotechnics depending on their formulations and

intended use. Now-a-days the HEMs/EMs is generally used for any material that can

attain high energetic state mostly by chemical reactions.

1.1.1 Explosive: - An explosive is a chemical substance or mixture of chemical

substance when subjected to initiation undergoes a very rapid decomposition

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accompanied with release of large amount of heat and pressure in surroundings e.g.

RDX, HMX, TNT, baratol, cyclotol etc.

1.1.2 Pyrotechnics: - Pyrotechnics are mixture of materials capable of combustion

when suitably initiated to produce a special effect. In general pyrotechnic composition

consists of a fuel and oxidizer together with a binder to give structural integrity and

additive for special effect e.g. KNO3/Al/S, Mg/chlorates/PVC

1.1.3 Propellant: - Propellants are slow burning material containing themselves the

oxygen needed for their combustion and their main function is to impart motion to

projectile such as bullet, shell, rocket and missile. The propellants are classified,

1) On the basis of nature: Homogeneous and heterogeneous propellant.

2) On the basis of physical state: Liquid and solid propellant.

3) On the basis of application: Gun propellant and rocket propellant.

1.1.3.1 Homogeneous propellant

The main component of this class of propellant is nitrocellulose and

nitroglycerine. The propellants are also known as colloidal propellant or double base

propellant. These propellants are processed by extrusion technique or casting. To

achieve requisite properties some additives are used such as stabilizer, plasticizer, and

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3

burning rate modifiers. This class of propellant is very useful in short range missiles,

thrusters and anti-tank missiles.

A homogeneous propellant can be divided into three groups namely single,

double and triple base propellant.

Single Base propellant: Single base propellants mainly consist of nitrocellulose (NC)

with nitrogen content in the range of 12.5% to 13.25%. The formulation consists of

90% or more NC. The NC is gelled with plasticizer such as dibutyl phthalate and

stabilizer carbamite. This class of propellant find applications in bullet and artillery

shells.

Double Base propellant: Double base propellants mainly consist of nitroglycerine

and nitrocellulose. The ratio of NG and NC depends on the application and

performance requisite. This class of propellant is used in gun, rocket and missiles.

Triple Base propellant: To reduce flame temperature and muzzle flash, an energetic

material, i.e. nitroguanidine is incorporated in double base propellant. The percentage

of nitroguanidine varies from 50-55% as per performance required. This composition

is used in tank gun and large calibre guns.

The homogeneous propellant is having remarkably low specific impulse and

inferior low temperature properties compared to composite propellant.

1.1.3.2 Heterogeneous propellant

It includes the propellant having two distinguished phases solid particle (fuel

and oxidizer) and continuous matrix phase.

Composite modified double base: The composite modified double base propellants

are processed by incorporation of metallic fuel (aluminium) and inorganic oxidiser in

double base matrix. The composite modified double base propellant is highly

energetic propellant.

Composite propellants: Composite solid propellants are heterogeneous mixture in

which oxidiser and metallic fuel dispersed in polymeric binder matrix. Composite

propellants represent an important class of solid rocket propellants widely used in

defence and space applications due to its ease of processing and superior performance

in term of burning rate, characteristic velocity, specific impulse, density impulse and

low pressure exponent.1, 2, 3 Comparative performance of double base propellants and

composite propellants are presented in table 1.1.

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Table 1.1 Comparative performances of double base propellant and composite

propellant

Sr. No Parameter Double base propellant Composite propellant

1 Density(g/cc) 1.58-1.62 1.760-1.90

2 Flame temperature(K) 2800-3000 3000-3500

3 Specific impulse(s) 200-210 240-245

4 Characteristic velocity(m/s) 1350 1540

5 Pressure exponent 0.2-0.4 0.35-0.45

The composite propellant gives superior performance in comparison to double

base propellant. The composite propellant composed of two types of ingredients given

as follows,

Primary ingredients:

1. Polymeric binder

2. Inorganic oxidizer

3. Metallic fuel

4. Curative

Secondary ingredients:

1. Burning rate modifier

2. Process aid

3. Cross linking agent

4. Bonding agent

5. Curing catalyst

6. Anti-oxidant

The primary ingredients of composite propellant formulation provide the

mechanical and ballistic properties to propellant composition. The workhorse primary

ingredient, i.e., ammonium perchlorate4, 5 was studied and used in composite

propellant formulation from early 1930. Charles B. Henderson’s group6 at the Atlantic

research corporation, USA, have demonstrated the role of aluminium as a high-

performance ingredient in propellant formulations in 1955.

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1.2 ROLE OF POLYMERIC BINDER

The development of polymeric binder has major impact on composite

propellant. Polymeric binder is a resin or glue like substance used for surface coating

on particle for adhesion and to ensure uniform solidification which provides

mechanical strength and structural integrity. The suitable binder synthesized during

1930 to 1972 for composite propellant application are asphalt binder, polyisobutylene,

polyvinyl chloride and poly styrene and used as binder for the composite propellant in

early 1942. These binders showed problems of dimension stability, low performance

and working temperature limitation. In the meantime, the liquid polymeric resin

‘polysulfide’ was used as a binder in the heterogeneous composite propellants in

1942. However, aluminium powder could not be incorporated in polysulfide based

propellant formulation because of chemical reactions during storage which leads to

explosions.

The first cross linked binder based on butadiene polymers used in a propellant

formulation was liquid copolymer of butadiene and acrylic acid (PBAA) developed in

1954. The functional groups are distributed randomly over the chain, consequently

propellant formulation based on PBAA show poor reproducibility of mechanical

properties, tear resistance properties and post cure storage problem. Subsequently, in

quest of better mechanical properties, a new binder system based on polybutadiene

was developed, i.e., polybutadiene acrylonitrile acrylic acid (PBAN). The introduction

of acrylonitrile group improved the spacing of carboxyl group and Hydrogen Bridge

thereby improved mechanical properties, tear resistance properties and post cure

storage. However, the low temperature properties were poor due to nitrile group. The

quest to combine best properties of PBAA and PBAN led to development of carboxyl

terminated poly butadiene (CTPB). The CTPB based propellants show significantly

better mechanical properties particularly at lower temperatures compared to PBAA or

PBAN binder, without affecting the ballistic and physical properties. In quest of

excellence, Karl Klager demonstrated applicability of hydroxyl terminated poly

butadiene (HTPB) binder in 1961 for composite propellant and first HTPB based

composite propellant in a rocket motor was tested in 1972. It has high hydrocarbon

content, low viscosity and low density over other butadiene based binder. It exhibits

excellent mechanical property at low temperature and low glass transition temperature

compared to CTPB binder system. Thereafter, it is widely used in composite

propellant formulations due to its capability to take up to 90% solid loading. It has

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also been found that HTPB is the most suitable for the processing of propellant for

small and large size rocket motor.7, 8, 9 Comparative properties of different binders

used in composite propellant are presented in table.1.2

Table 1.2 Comparative properties of binders used in composite propellant

Sr.

No

Binder Average

Mol. wt.

Functionality Viscosity at

25 °C (poise)

Density

(g/cc)

Heat of

combustion

∆Hc (kcal/g)

1 PBAA 2500-4000 2.0 275-325 0.90-0.92 10.2-10.4

2 PBAN 3500 1.9 300-350 0.93 10.0

3 CTBP 3500-5000 2.0 180-350 0.92 10.2

4 HTPB 2500 2.4 40-60 0.90 10.0

1.3 ROLE OF OXIDIZER

The inorganic oxidizer is a major ingredient of composite propellant and

constitutes 65-70 % (by weight) of propellant composition to provide oxygen to the

system during combustion. An oxidizer should possess compatibility with other

ingredients, high oxygen content, low heat of formation, high density, high thermal

stability and low hygroscopicity. Number of oxidizers used in composite propellant

and their comparative properties are presented in table 1.3.

Table.1.3 Comparative properties of oxidizers used in composite propellant

Sr.

No.

Oxidizer Molecular

formula

Density

(g/cc)

Oxygen balance

(%)

Heat of formation

∆Hf (kcal/mole)

1 AN NH4NO3 1.72 +20.00 -87.37

2 AP NH4ClO4 1.95 +34.04 -70.74

3 KP KClO4 2.52 +46.19 -102.4

4 RDX (CH2N2O2)3 1.82 -21.60 +14.70

5 HMX (CH2N2O2)4 1.91 -21.60 +17.90

6 ADN NH4N(NO2)2 1.81 +26.00 -35.8

7 HNF N2H5C(NO2)3 1.86 +13.00 -17.20

The ammonium perchlorate satisfies most of the requirements such as high

oxygen content, compatibility with different binders, low heat of formation, high

density, high thermal stability, low hygroscopicity, safe to handle, long shelf life, and

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easily available compared to other oxidizers. Hence, it is most widely used in the

composite propellant all over the world.

1.4 ROLE OF METAL FUELS

Metal powders are incorporated in propellants primarily to achieve high

volumetric energy release due to their high heat of reaction with oxygen,

improvement of propellant density, reduction in pressure exponent and suppression of

combustion instability1. The metal powders generally used in propellant composition

are presented in table 1.4.

Table 1.4 Comparative properties of metal fuels used in composite propellant

Sr.

No.

Metal Fuel Formula Density

(g/cc)

Heat of Combustion

∆Hc (kcal/g) 1 Beryllium Be 1.85 15.89

2 Boron B 2.35 14.0

3 Magnesium Mg 1.74 5.90

4 Aluminium Al 2.70 7.40

5 Zirconium Zr 6.51 2.90

Today most of the rockets and missiles are propelled by composite propellant

contains basically an inorganic oxidizer mainly ammonium perchlorate, fuel cum

binder hydroxyl terminated polybutadiene and a metallic fuel aluminium powder

along with certain process aids as well as ballistic modifiers. In a solid rocket motor,

the combustion reaction generates a large amount of thermal/potential energy which is

converted into kinetic energy by expansion through nozzle, whereby required lift of

thrust is created.

1.5 THE IMPORTANT CHARACTERISTICS FOR PROPELLANT

PERFORMANCE

Composite propellant must have specified mechanical, thermal and ballistic

properties for their flawless performance in rocket motors are described in brief.

1.5.1 Mechanical properties

It is necessary to retain the structural integrity of solid rocket motor under a

wide variety of mechanical load, which impose on it during storage and operational

phase to perform successfully in its mission. The structural integrity of the motor is

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governed by the mechanical properties of propellant and design consideration. When

composite propellant is used in case bonded form, the propellant must exhibit the

greatest possible % elongation at maximum load during the thermal cycle and at the

time of firing. On the other hand to withstand g-load due to gravity and acceleration,

high tensile strength is preferred. For the smooth functioning of the composite

propellant in rocket motor along with other properties, a set of mechanical properties

are required.

The mechanical properties of solid propellants depends on

A) Intrinsic or constitutional variable

B) Extrinsic or environmental variables.

One of the important intrinsic variables is quality and quantity of filler. The

fillers incorporated in composite propellant are ammonium perchlorate, aluminium

powder and ballistic modifiers or burning rate catalysts. The increase in filler quantity

or fine particles increases tensile strength and decreases elongation10. The minimum

mechanical properties required for the base propellant composition to retain its

structural integrity are -

a) Tensile Strength>5.0 Kgf/cm2,

b) Elastic modulus 30-50 Kgf/cm2 and

c) % Elongation 30-50 %.

1.5.2 Thermal properties

The effect of burning rate catalyst on HTPB/AP/Al composite propellant

decomposition and the combustion pattern has been focal point for investigation in the

last few decades. The thermal properties of propellant composition give idea about its

thermal stability, ingredient compatibility, behaviours of propellant at elevated

temperatures and effect of catalyst on thermal decomposition. The thermal properties

of composite propellant formulation are generally studied by Differential Scanning

Calorimeter (DSC) and Thermo Gravimetric Analyzer (TGA).11

1.5.3 Ballistic properties

There are many ballistic parameters used to evaluate the composite

formulation such as characteristic velocity, specific impulse, density, calorimetric

value, pressure exponent and burning rates. However, in the present study density,

calorimetric value, pressure exponent and burning rate were evaluated in detail.

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1.5.3.1 Density

The density of the propellant should be as high as possible to store as more

energy per unit volume as possible. In order to accommodate a large weight of

propellant in a given combustor volume, a dense propellant is preferred. This permits

smaller vehicle size and weight, which also results in lower aerodynamic drag. The

average propellant density has an important effect on the maximum flight velocity and

range of any rocket-powered propulsion systems. The average propellant density can

be increased by addition of metal powders like aluminium into the propellant

formulation.12

1.5.3.2 Calorimetric value

The important feature of solid propellants is their energy characteristics, i.e.,

their calorimetric value and specific impulse (specific thrust). The calorimetric value

of a propellant is determined by the quantity of heat which is released during

combustion of 1g of substance in inert atmospheric condition that all combustion

products are reduced to standard conditions (to a temperature of 25°C and pressure of

760 mm Hg).

The calorimetric value of rocket propellants, which is a measure of their

potential chemical energy, does not yet completely characterize rocket propellants as

sources of energy of rocket motion. The fact is that during the discharge of propellant

combustion products from the nozzle of a jet engine, they are not cooled to room

temperature at which the calorific value is determined13.

1.5.3.3 Burning rate

The burning rate is governed by Saint Robert and Ville’s burning rate law, i.e.

r = a·Pn

Where,

r is the burning rate;

a is the variable which depends on initial grain temperature, chemical composition

and gas velocity of combustion gas along the surface of the grain;

P is the pressure in combustion chamber;

n is the pressure exponent.

The burning rate can be defined as rate of regression of burning surface in the

direction essentially perpendicular to the burning surface of a propellant grain. The

burning rate is usually expressed in cm/s, mm/s or in/s. The burning rate is one of the

important ballistic properties of composite propellant. Further, the rocket motor

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operation and design depend on the combustion characteristics, its burning rate,

burning surface and grain geometry. Burning rate of composite propellant depends on

several factors such as combustion chamber pressure, initial temperature of propellant

surface, percentage of high energy material in the formulation, burning rate modifier

and percentage of oxidizer.14

1.5.3.4 Pressure exponent (n)

The pressure exponent ‘n’ of propellant is a measure of the increase in burning

rate of a propellant which occurs as the chamber pressure is increased. The pressure

exponent is the tangent to the curve which can be drawn when the log of burning rate

is plotted against log of chamber pressure. The pressure exponent of a propellant is

zero when burning rate is totally independent of pressure. However, when it is

substantial positive, the rocket will over pressure and may explode. A pressure

exponent of less than 0.5 is necessary for a propellant to be acceptable for use in

rocket propulsion sub-systems. The exception is pressure sensitive propellants which

are intended for use in controllable motor.15

The well-known method for effecting some reduction of pressure exponent is

to reduce ammonium perchlorate content or resort to the use of ammonium

perchlorate of larger weight mean diameter. However, these approaches are

unacceptable because they adversely affect the burning rate. Burning rate promoters

have been found to have little effect on pressure dependence of burning rate.

Literature survey also reveals that copper salts and their chelates reduces the pressure

exponent of composite propellant.15

1.6 DIFFERENT APPROACHES TO ENHANCE BURNING RATE

Generally to achieve the desired burning rate of a composite propellant

formulation, the amount of oxidizer, particle size of oxidizer and burning rate

modifiers are used as variable. Ammonium perchlorate is used as an oxidizer in

composite propellant formulation, which is a major ingredient in composite propellant

studied widely. Different size fraction of AP used in propellant formulation to achieve

required burning rate. As the fine and superfine particle fraction of AP increases,

burning rate increases, concurrently viscosity of propellant slurry increases and it is

very difficult to cast such slurry. Further, the superfine particle is very sensitive and

prone to agglomeration16.

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Another way to achieve the required burning rate is addition of burning rate

modifier. These are secondary ingredient of composite propellant formulation. The

burning rate modifiers are transition metal complexes17or transition metal oxides

(TMOs) 18. The first approach to enhance burning rate of composite propellant

formulation is incorporation of complexes of transition metal/binder grafted

complexes of transition metal, which on decomposition produces fine metal oxide

powder in-situ. Thus, in-situ formed transition metal oxides (TMOs) affects thermal

decomposition of AP and binder which enhances burning rate of propellant. The

metallocene family (e.g. ferrocene and catocene) shows a promising avenue for

increasing propellant burning rate. However, such chemicals greatly increase

propellant sensitivity and exhibiting significant hazards for processing and handling

as well as migration of catalyst.

The second approach to enhance burning rate of composite propellant

formulation is incorporation of transition metal oxides (TMOs). These modifiers

added in small quantities which increases the burning rate by lowering the

decomposition temperature of AP and binder. The transition metals are placed in d-

block of periodic table. The d–block comprises of three series of elements formed by

filling of electrons to 3d, 4d and 5d shells sequentially. These elements are generally

called as transition metals. The d-block elements are having incompletely filled d

shell. These three element series are presented in table 1.5.

Table 1.5 d –block elements of periodic table

Group

3 4 5 6 7 8 9 10 11 12

Sc

21

Ti

22

V

23

Cr

24

Mn

25

Fe

26

Co

27

Ni

28

Cu

29

Zn

30

Y

39

Zr

40

Nb

41

Mo

42

Tc

43

Ru

44

Rh

45

Pd

46

Ag

47

Cd

48

La

57

Hf

72

Ta

73

W

74

Re

75

Os

76

Ir

77

Pt

78

Au

79

Hg

80

The properties of transition metal and their compounds are dependent on the

electronic configuration. The distinctive properties of transition metal and their

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compound are due to partially filled d-shell. The transition metals and their

compounds show following properties

1. Variable oxidation state

2. Formation of co-ordination compounds or complexes.

3. Acts as catalyst for chemical reactions

“A catalyst is a body or a material which can induce the phenomenon of

catalysis. It enhances the rate of reaction and while being intimately involved in the

reaction sequence, it is regenerated at the end of it.” 19

The transition metals and their compounds act as good catalysts due to

multiple oxidation states and their ability to form number of complexes. The reason

for transition elements to have strong tendency to form complexes as they posses

highly charged smaller ion and vacant low energy orbital to accept the lone pair of

electron from ligand and groups. The atomic and ionic radii of the elements show

progressive decrease with increasing atomic number in a row of the transition

elements. The first series of elements have small atomic and ionic radii compared to

second and third20.

The nano and micron sized transition metal oxides have been selected for the

present study on the bases of position of metal in periodic table21 due to their inherent

properties, such as variable valences or oxidation state, ability to form intermediate

complexes and electron donor /acceptor property which modify oxidation

/decomposition path and product. To understand the effect of TMOs on burning rate

of composite propellant, it is essential to know the decomposition mechanism of

ammonium perchlorate, binder and composite propellant formulation. Ammonium

perchlorate is the major ingredient of composite propellant formulation, hence it is

very essential to understand the decomposition mechanism of AP and the effect of

TMOs.

1.7 THERMAL DECOMPOSITION BEHAVIOUR OF AMMONIUM

PERCHLORATE

Ammonium perchlorate is a white crystalline powder. The thermal

decomposition of ammonium perchlorate has been extensively studied because of its

inherent chemical properties and its application as an oxidizer in solid rocket

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propellants. The thermal decomposition of ammonium perchlorate depends on several

factors such as temperature, pressure, particle size, lattice defect and impurity.

Thermal decomposition process of ammonium perchlorate comprises three

distinguished stages, it undergoes phase transition from orthorhombic to cubic

structure at 240°C followed by two stage decomposition first only 30% incomplete

decomposition at 300°C and second 70% decomposition at 440°C. These two

decomposition temperatures are termed as low temperature decomposition (LTD) and

high temperature decomposition (HTD), respectively. The different reviewers have

proposed the decomposition products of AP which are mainly temperature dependent

as 22

T<300 °C 4NH4ClO4 2Cl2 + 2N2O + 3O2 + 8H2O

T>300 °C 2NH4ClO4 Cl2 + 2NO + O2 + 4H2O

1.7.1 Thermal decomposition mechanism of ammonium perchlorate

Ammonium perchlorate is one of the most studied molecules for its all aspects

and it has been reviewed by several researchers.22, 23 Actual mechanism of

decomposition of ammonium perchlorate is still issue of debate. Two mechanisms are

proposed for decomposition of ammonium perchlorate, viz.,

1. Electron transfer mechanism

2. Proton transfer mechanism

1. Electron transfer mechanism

The kinetic analysis of decomposition products of ammonium perchlorate in

the temperature range of 200-300°C leads to electron transfer between an anion and

interstitial cation which results in generation of NH4 radical. Further, this radical

undergoes dissociation and produces ammonia and hydrogen.

NH4 NH3 + H

ClO4- + NH4

+ ClO4 + NH4

The ClO4 radical formed in the body of crystal gets stabilized by crystalline

force field and pick up electron from adjacent ClO4- ion or from hydrogen atom

generated in above reaction and migrated to surface by electron transfer process.

ClO4 + H HClO4

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The hydrogen atom can react with HClO4 molecule as-

H + HClO4 H2O + ClO3

The ClO3 radical which acts as electron trap increases the ammonium

perchlorate decomposition.

2. Proton transfer mechanism

In proton transfer mechanism, the proton from ammonium ion transfers to

perchlorate ion resulting in ammonia (NH3) and perchloric acid (HClO4) in the form

of gas and get adsorbed on ammonium perchlorate surface. The adsorbed NH3 and

HClO4 get evaporated in the gas phase depending upon experimental conditions.

NH4+ + ClO4

- NH3 (a) + HClO4(a)

NH3 (g) + HClO4(g)

The perchloric acid decomposed in reactive intermediates

2 HClO4 ClO3+ + ClO4

- + H2O

The reactive intermediates then oxidize the ammonia which gives products

and additional reactant.24

1.7.2 Catalysed decomposition of ammonium perchlorate

The catalysed thermal decomposition of ammonium perchlorate in the

presence of TMOs is a topic of great interest for the researcher. A lot of work has

been carried out to explore the mechanism of catalysed thermal decomposition of AP,

but exact mechanism of catalysed thermal decomposition of AP is not clear as on

today. The effect of several catalysts, viz., CuO, Cu2O, Cr2O3, Fe2O3, MnO2 and

CuCrO4 has been studied widely on catalysed thermal decomposition of AP. The

effect of catalyst on catalysed thermal decomposition of AP has been illustrated on

the basis of mechanism of decomposition of AP.

The first mechanism for catalysed thermal decomposition of AP reveals that,

catalysed AP decomposed into NH3 and HClO4 through proton transfer mechanism.

Subsequently, oxidation of ammonia occurs by HClO4, which adsorbed on the surface

of catalyst. The migration of ClO4- by diffusion on the catalyst surface considered to

be important feature. The cleavage of Cl-O bond of ClO4- is considered as rate

controlling step.

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The second mechanism for catalysed thermal decomposition of AP reveals

that AP decomposition occurs through electron transfer mechanism. It is assumed in

electron transfer mechanism that, TMOs acts as a bridge for electron transfer process.

Further, thermal decomposition of AP at low temperature favours electron transfer

process is considered to be rate controlling step. Kishore et al25a proposed electron

transfer mechanism for catalysed decomposition of AP in the presence of MnO2.

Kuratani25b proposed that p-type of semiconductor of the TMOs are effective

in catalysed decomposition of AP and responsible for electron transfer reaction. The

n-type of semiconductors are ineffective in electron transfer reaction, although O2 is

anomalous.25c

1.8 ROLE OF BINDER IN COMBUSTION

The polymeric binder is second most important ingredient of composite solid

propellant having continuous phase in nature. Initially, it is in the liquid state called

prepolymer. The prepolymer is having reactive groups along with chain extender and

cross linking agent. It reacts with curing agent during curing to form solid. The binder

holds firmly solid ingredient and functions as fuel, which further provides mechanical

strength and structural integrity to the propellant. The binder also plays important role

in composite solid propellant combustion.

The reactions involved in process of polymeric combustion can be divided

into three phases.

1. Sub surface condensed phase

2. Surface phase

3. Gas phase

Fristrom26 has summarised the preliminary combustion process by considering

the gas phase reactions similar to the diffusion flame of hydrocarbon and substituted

hydrocarbon mixture. The least understood reaction occurs at combustion surface

which may be liquid or solid char. The solid phase or condensed phase reactions

occur due to degradation of polymer.

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Condensed phase reaction

The polymeric back bone does not contain any free radical or oxidizing

species, therefore, thermal initiation is required for breaking of C-C or C-Z bond (like

C-N, C-O) The char formation takes place by following mechanism which involves

cross linking and formation of double bonds followed by cyclization and then

dehydrogenation.

1.8.1 Decomposition of Binder

Uncatalyzed decomposition of binder

The combustion process is mainly controlled by ammonium perchlorate in

composite propellant which contributes large percentage of composition. The

importance of binder in combustion process is realized with development of

combustion modelling and tailoring. The thermo-oxidative decompositions for variety

of binders are studied by various workers. 28 The major findings are summarised as

follows

1. There is no significant weight loss up to 300°C; therefore the endothermic

pyrolysis reaction may occur below 300°C.

2. The surface regression of polymer starts around 300°C.

3. Polymer –oxygen endothermic reaction seemingly occur before ignition.

4. When a regression of polymer begins, ignition seems to start in oxygen.

5. The fast pyrolysis reaction results seem to be reasonable extrapolation of the

results from conventional test.

Kishore and Verneker27 have studied correlation between heat of

depolymerisation and activation energy of degradation of polymer. They found that

the heat of depolymerisation of the polymer were almost equal to the activation

energy for their degradation and proposed the degradation in the following way. 28

Primary reaction Secondary Polymer (solid) Monomer (gas) other products E Reaction

1.8.2 Decomposition of cured HTPB

The first step is the cleavage of urethane linkage in the decomposition of

diisocyanate cured HTPB binder. Further, it cross links exothermally, cyclizes and

depolymerizes to butadiene fragments, formaldehyde and oligomers. According to

Brazier et al29 exothermic degradation /decomposition may be due to the precursor

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reaction which leads to depolymerisation, cyclization and cross linking. Initially, there

is proton abstraction which leads to cross linking at 200°C along with disintegration

of main chain to the low molecular entities. Consequently, depolymerisation at 350°C

leads to the gaseous products. The solid residue decomposed at high temperature,

450°C, and above which is formed due to cross linking and cyclization to form main

volatile gaseous products such as 1, 5-hexadiene, 1, 3-cyclopentene, cyclopentane and

vinyl cyclohexane, etc.30, 31

1.8.3 Catalysed decomposition of binder

The transition metal oxides (TMOs) are well known for their catalytic effect

on binder decomposition. They catalyse hydrocarbon oxidation reaction by inducing

free radical decomposition of hydroperoxide formed by reaction of oxidizer and

hydrocarbon.32 The mechanism of formation of hydroperoxide followed by

decomposition pattern can be postulated as-

The metal salts like cupric stearate acts as accelerator for oxidation of

hydrocarbon by lowering the activation energy of hydroperoxide decomposition. The

catalytic activity can be correlated with redox potential of the metal ion. The catalytic

effect of fatty acid metallic salts is given below. The order of catalytic activity is

based on oxygen adsorption curve and activation energy33.

Co > Mn > Cu > Fe > V > Ni > Ti > Al > Mg > Ba

1.9 COMBUSTION OF COMPOSITE PROPELLANT

Combustion of composite propellant is a complex phenomenon which

involves chemical, physical changes, mass transfer and heat transfer. The combustion

process of composite propellant results in generation of reactive gaseous products.

The generated gaseous products react in gaseous phase and produces large amount of

heat. A part of heat produced is fed back to condensed phase required for exothermic

decomposition reaction. The condensed phase of exothermic heterogeneous reactions

at propellant surface and subsurface again provides heat to gaseous phase. The

conceptual combustion models can be divided into two broad classes:

1) Condensed phase model: it assumes that rate determining step occur at propellant

surface or subsurface and to be part of vaporization process

INTRODUCTION

18

2) Gaseous phase model: it assumes rate determining step occur in gas phase

reaction and flame which consume the vapour derives from the propellant surface.

Several models have been proposed to understand the combustion of

composite propellant such as sandwich columnar diffusion model, granular diffusion

flame model, condensed phase model thermal layer theory and multiple flame models.

The most acceptable model for combustion behaviour of composite propellant is

Beckstead Derr Price (BDP) model or multiple flame models. Further, its extension is

used for explanation of composite propellant formulation containing burning rate

catalysts34.

1.9.1 BDP (Beckstead Derr Price) model or Multiple Flame Model

It assumes rate controlling processes occur in gas phase reaction and flame

which consumes the vapour derives from the propellant surface. This model was

proposed for an ideal propellant. The ideal propellant composition consists of

monomodal AP particle distribution, without metal fuel and catalyst. The

assumptions, approximation and combustion mechanism adopted in this model has

major role in development of combustion model for composite propellant. The view

of multiple flames modal or BDP is presented in Fig 1.2.

Fig 1.2 BDP view of multiple flames modal

1.9.2 Combustion behaviour of composite propellant

Composite propellant is a heterogeneous mixture composed of dispersed AP

particle in continuous fuel binder matrix. When composite propellant ignites the large

size (300-400 µm) AP particle are exposed to burning surface surrounded by binder.

AP plays dual role as monopropellant and oxidizer whereas binder act as fuel. At

interface of AP and binder, direct reaction takes place which produce primary flame

enriched with fuel. These gases are generated from interface of AP and binder due to

INTRODUCTION

19

pyrolysis and gaseous oxidizer rich decomposition products formed from AP surface.

The rate of diffusion and reaction of mixed reactants (oxidizer and fuel gases)

determine the height of the primary flame from the burning propellant surface. The

AP particles exposed to burning surface, considerably large size and burning is at high

pressure. All the gases coming from the oxidizer particle not reacting with pyrolyzed

fuel vapours, however, the oxidizer gases react itself and produce monopropellant

flame above the oxidizer particle. The gaseous products formed in monopropellant

flame are oxidizer rich. It further reacts with fuel gases to form the final flame. The

final flame is controlled by diffusion process as oxidizing gases coming from the

monopropellant flame is at high temperature. The reaction between the hot gases with

fuel gases are very fast comparing with the diffusion and mixing of these gases. The

reaction paths assigned for different flame formed during combustion process are

given below:

The BDP model further extended to explain the propellant composition with

multi model oxidizer, aluminium, nitramine and burning rate catalyst35.

1.9.3 Combustion of catalysed composite propellants

The most accepted model proposed by Krishann and Jeenu36 on the basis of

BDP model for combustion of catalysed composite propellant is surface reaction

model. The model is formulated by studying the allocation of masses and energy. The

BDP model was successfully extended to predict the effect of catalyst and oxidizer

INTRODUCTION

20

particle size at low pressure as well as operating pressure of rocket by incorporation

of variable heat release from surface and subsurface.

1.9.4 Surface reaction of catalysed composite propellant

As per the BDP model, the heat necessary for the decomposition of AP and

binder is provided from the gas phase flames and from the exothermic decomposition

of AP at the surface. The heat available from the exothermic decomposition of AP is

assumed to be constant in BDP model. The surface decomposition of AP can be

possible through two routes:

1. Condensed phase exothermic decomposition (CPED)

4NH4ClO4 2Cl2 + 2N2O + 3O2 + 8H2O

2. Sublimation –endothermic

The heat provided to surface and subsurface on decomposition of AP

determines fractions decomposed through CPED and sublimation. Considering these

two parallel decomposition processes of AP and the probability of interfacial reaction

of AP–binder particularly when high temperature, penetrates deep into the surface.

The following phenomenon is possible in the surface decomposition of composite

propellant containing burning rate catalyst.

1. The CPED exist as parallel process to the endothermic dissociation of AP

2. The CPED gives reactive products which reacts with nearby fuel element through

AP- binder heterogeneous reaction

3. It is possible that propellant composition containing catalyst, burning rate

controlling reactions located in condensed phase.

4. It is proposed that catalyst may increase CPED in the peripheral area to AP

particle.

5. As a result catalyst increases the AP-binder interfacial heterogeneous reaction.

1.10 GENERAL ASPECTS OF NANO MATERIALS

Nano materials deal with small structures or small sized materials. The term

nano material is employed to describe the creation and exploitation of structure with

feature in between atom and bulk materials with at least one dimension in nano meter

range (1 nm = 10-9 m). The properties of material of nanometeric dimensions are

significantly different from those of atom as well as those of bulk materials. The

INTRODUCTION

21

suitable control of the properties of nano meteric scale structures lead to new science

as well as new devices and technology. The importance of nano technology was

pointed out by Feynman as early as 1959, in his often cited lectures entitled there is

plenty room at the bottom37.

There has been remarkable growth of nano science and nano technology in last

few years, because of availability of new strategies for synthesis of nano materials and

new tools for characterisation and manipulation. Several methods of synthesizing

nano materials and their assemblies have been discovered. Nanomaterials

synthesizing methods can be classified according to whether their assembly followed

either by

a) Bottom-up approach- Where smaller components of atomic or molecular

dimensions self-assemble together, according to a natural physical principle or an

externally applied driving force, to give rise to larger and more organized systems or

b) Top-down approach- a process that starts from a large piece and

subsequently uses finer and finer tools for creating correspondingly smaller structures.

Attrition or milling is typical top down method in making nano particles whereas the

colloidal dispersion is good example of bottom up approach in synthesis of nano

particles38.

The methods most widely used in characterization of nano materials are X-ray

diffraction, scanning electron microscopy (SEM) and transmission electron

microscopy (TEM). X-ray diffraction is used for determination of crystallinity and

crystal structure, whereas SEM and TEM together have been commonly used in

characterisation of nano materials for determination of particle size, shape and surface

morphology.

Nano materials have drawn increasing interest due to their novel properties

which are caused by size and surface effect and are different from those of bulk

materials, especially nano materials are used in various fields such as catalysis, non-

linear optics, electronics, and magnetics as advanced materials for special

applications39.

INTRODUCTION

22

1.11 RECENT DEVELOPMENT IN BALLISTIC MODIFIERS BASE D ON

TRANSITION METALS

The transition metals are used in the form of nano oxide, nano alloy, nano

metal powder and complexes as ballistic modifiers in composite propellant. The

exhaustive literature survey has been carried out on ballistic modifiers used in HTPB

binder systems are summarized in brief.

1.11.1 Transition metal complexes as ballistic modifier in composite propellant

The effect of transition metal oxides (TMO’s) on composite propellant

formulations have been studied by several researchers keeping in mind to enhance the

burning rate and their behaviour on decomposition phenomenon. The most prominent

research groups working in this field are mentioned adequately. Gurdip Singh et al

have reported that a large number of transition metal complexes are used as burning

rate modifiers such as metal hexammine perchlorates,40 bis(ethylenediamine) metal

perchlorate (BEMP)41 and bis(ethylenediamine) metal (II) nitrate (BEMN), i.e.

[M(EDA)2](NO3)2,42 and [M(en)2](NO3)2

43 complexes on AP and AP-HTPB based

propellant composition. They concluded that these complexes accelerate thermal

decomposition of AP and enhances burning rate of propellant.

Further, they have also studied transition metal-NTO salt as burning rate

modifier in AN-HTPB44 and AP-HTPB45composite propellant composition and

reported that these salts are very effective in accelerating burning rate of the

composition. In addition to this, Cu (NTO) 2 and Fe (NTO)3, salts were also studied in

detail in AP-HTPB based composite propellant46. The effect of copper oxalate

nanocrystals (CONs) on thermal decomposition of AP composite propellant were also

studied and it is found effective catalyst for AP decomposition and enhances burning

rate of composite propellant47.

Gore et al have evaluated effect of partial replacement of HTPB binder in AP-

HTPB composite propellant formulation with butacene48.They found that 25%

replacement of HTPB with butacene gave excellent performance with respect to

burning rate and pressure exponent. Further, ferrocene polyglycol oligomer (FPGO) 49

in AP-HTPB composite propellants were also studied by the same team and found

effective enhancement in burning rate. The transition metal salts of 3-nitro-1, 2, 4-

triazol-5-one (NTO) and 2, 4, 6-trinitroanilino benzoic acid (TABA) in AP-HTPB

based composite propellant formulation have also been studied by Asthana et al. They

INTRODUCTION

23

observed that Fe-NTO salt gives remarkable performance with respect to burning rate

and pressure exponent50.

Furthermore, Iron and Copper salts of 4,6-dinitrobenzofuroxan were also

studied in HTPB based composite propellant formulation as burning rate modifier and

found that iron salt gives better performance as compared to iron oxide51. The

ferrocene-grafted hydroxyl-terminated polybutadiene (Fc-HTPB), 52 containing

varying weight % of iron evaluated as binder in composite propellant. The

composition based on Fc-HTPB gives remarkably higher burning rate compared to

AP-HTPB. Jiang, Xiao-hong et al53 have reported that nano-particles of copper

oxalate is a better catalyst compared to the nano-particles of CuO. Zou Min et al54

have studied the effect of micrometer-sized cobalt oxalates with different

morphologies as a catalysts on the thermal decomposition of ammonium perchlorate

(AP).

1.11.2 Nano Transition metal particles as ballistic modifier in composite

propellant

Different transition metal nano-particles (TMNs) of 3d series (Cu, Co, Ni, and

Fe) were studied for their effect on thermal decomposition of AP and found that

TMNs are better than their corresponding nano-oxides55. The composite materials of

nano iron and cobalt particles on carbon matrix were also studied for thermal

decomposition of AP56.

Co nanoparticles with different morphology57, 58and Co nanoparticles

supported on carbon nanotubes (CNTs) 59, 60 were studied by various researchers to

evaluate their effect on thermal decomposition of AP. They found that Co

nanoparticles and Co nanoparticle/CNTs have significant effect on thermal

decomposition of AP. In the same way, Cu nanoparticles with different morphology,

61, 62 composite particles of CNTs/Cu, 63porous Cu film with micro-holes and nano-

dendrites, 64 and composite of foamed porous copper (FPCu) and AP65were evaluated

for their effect on thermal decomposition of AP and observed that these catalysts

decrease the thermal decomposition temperature of AP immensely.

Along with metal nanoparticles, binary metal nanoparticles and alloy were

attractive catalyst for the thermal decomposition of AP66 such as Ni, Cu, Al and NiCu

powders. Chaturvedi et al67 have studied transition metal nanoalloys Co-Cu, Co-Fe,

and Co-Zn for thermal decomposition of AP and found very effective.

INTRODUCTION

24

Further, Gurdip Singh et al investigated the effect of bimetallic nanocrystals

such as Cu-Co,68 Cu-Fe,68 Cu-Zn,68 Ni-Cu,69 Ni-Co,69 and Ni-Zn69on thermal

decomposition of AP. The effect of ternary alloy nanoparticles70 on thermal

decomposition of AP were also studied and found all nano alloy particles are effective

on thermal decomposition of AP. They also evaluated bimetallic nanocomposites of

Mn with Co, Ni and Zn71 in AP- HTPB composite solid propellants and observed

enhancement in burning rate.

1.11.3 Nano metals oxides and mixed transition metal oxides as ballistic modifier

in composite propellant

Different nano particle72, 73 of TMOs, shell-core nanocomposites of metal

oxide/AP 74 and TMOs/AP composite nanoparticles75 have been studied for thermal

decomposition of AP. These metal oxide nanoparticles and composite nanoparticles

affect the second decomposition of AP significantly and shift to lower temperature. In

addition to this, (TMO)/CNTs76 such as Fe2O3/CNTs, NiO/CNTs and Co3O4/CNTs

were investigated for thermal decomposition of AP and AP/HTPB composite

propellant and found that TMO/CNTs composite particles decreases high

decomposition temperature peak. Dixon et al77 have reported same findings on high

energy-density propellants containing nano-particles as burning rate catalyst.

Nanometer-sized CuO, Fe2O3 and CuO/Fe2O378 studied for thermal decomposition of

AP and concluded that CuO/Fe2O3 is better catalyst for decomposition of AP and

enhances burning rate of AP based composite propellant compared to basic

composition.

Individual metal oxide nano particles and their mixed oxide systems were

studied for thermal decomposition of AP such as nano-sized CuO, Co3O4 , CuCo2O4,79

Nd2O3, Cr2O3, NdCrO380

and it is found that mixed system demonstrated better

catalytic effect on decomposition of AP. In the same spirit, CdFe2O4, Cd nano

crystals81 and CdCo2O4 nanoparticles (CCNs) 82 were also studied for thermal

decomposition on AP, HTPB and composite solid propellant and found that

significant enhancement in burning rate of composite propellant.

Further, the perovskite-type oxides like LaMO3 (M = Fe, Co, Ni) 83 and

Orthorhombic structural perovskite NdCrO3 nanocrystals84 were investigated for

thermal decomposition of AP and found that effective catalytic behaviour on thermal

INTRODUCTION

25

decomposition of AP. Furthermore, LaCoO3 also enhances burning rate of composite

propellant compared to basic propellant.

The mixed oxide system such as FeTiO3 nanosheets, 85 zinc cobaltite

(ZnCo2O4) nanorods86were also studied for thermal decomposition of AP and findings

reveal the effective decomposition of AP. Also, the mixed transition metal oxides

(MTMO) nanoparticles of 3d series (NiCo2O4, CuCo2O4, and ZnCo2O4) are reported

to have effective influence on burning rate of AP-HTPB based composite propellant87.

One of the most studied and practically applicable mixed oxide system is

copper chromite in composite propellant formulations. Li, Wei and Cheng, Hua88

studied Cu-Cr-O nanocomposites in AP-HTPB based composite propellant and

observed that catalysts enhance burning rate as well as lowers the pressure exponent

significantly. They also found that Cu-Cr-O nanocomposites with a Cu/Cr molar ratio

of 0.7 exhibits the most stable combustion at all pressures. Patil et al89have studied

nano-CuO and CuCr2O4 on thermal decomposition AP and revealed that nano-copper

chromite (CuCr2O4) is most effective catalyst compared to nano-CuO. The nano-

crystals of CoxZn1-xCr2O4 (x = 0.7, 0.8, 0.9, 0.95, and 1)90 mixed oxide systems were

also studied on thermal decomposition of AP and found very effective.

Ferrite type mixed oxide systems such as nano CuFe2O491 nano cobalt ferrite

(CoFe2O4)92 and nano-MnFe2O4

93particles were studied on thermal decomposition of

AP. It was observed that, these ferrite type mixed oxides affect the thermal

decomposition of AP significantly.

Further to this, Gurdip Singh et al94 have also studied ferrite nanoparticles of

Mn, Co and Ni in detail on thermal decomposition of AP and composite solid

propellant. They found that these catalysts shift the decomposition of AP towards low

temperature and enhances burning rate. They also studied binary transition metal

ferrite (BTMF) nanocrystals of formula MFe2O4 (M = Cu, Co, Ni) 95 on thermal

decomposition of AP and revealed that these binary transition metal ferrite affect the

thermal decomposition temperature of AP. The nanocrystallites of mixed ternary

transition metal ferrite (MTTMF) 96a has been studied by same group on thermal

decomposition of AP and found that these compounds affect the thermal

decomposition significantly. Furthermore, thermal decomposition study of AP, HTPB

and composite solid propellants (CSPs) with quaternary ferrite nanoparticles (QFN)

reveal that burning rate of CSPs has been considerably enhanced.96b

INTRODUCTION

26

Liu et al97 have studied the effect of Ni/Co/Cu/Fe nano-composite oxides

(Ni/Co/Cu/Fe-NCOs) system on thermal decomposition of AP. They observed that

incorporation of these compounds in AP accelerates the thermal decomposition of AP.

1.11.4 Nano mixed transition metal hydroxide as ballistic modifier in composite

propellant

Zhang et al98 have studied the catalytic effect of Al (OH) 3.Cr(OH)3

nanoparticle on thermal decomposition of AP. They found that incorporation of this

catalyst shifts the high temperature decomposition of AP to lower temperature.

Similarly, Liu et al99 studied the catalytic effect of Cu-Co layered double hydroxide

(LDH) nano rods on thermal decomposition of AP, and results indicate that the

catalyst show higher catalytic activity compared to mechanical mixture of CuO and

Co2O3.

1.11.5 Application of nano iron oxide as ballistic modifiers

Iron Oxide having different shape and size such as nano ferric oxide,100

ultrafine α-Fe2O3 nanoparticles,101 α-Fe2O3 nanotube,102 smooth α-Fe2O3

nanotubes,103 nano α-Fe2O3104and CNT (carbon nano tube) supported Fe2O3

105were

prepared and evaluated for catalytic activity on thermal decomposition of ammonium

perchlorate. It is found that all shapes and size of iron oxide found to be active to

accelerate the thermal decomposition of AP. Further, nano rods and micro-

octahedrons of α-Fe2O3106 were also studied for thermal decomposition of AP. They

found that nano rods are more active to enhance the thermal decomposition of

ammonium perchlorate, in comparison to micro-octahedrons.

The effect of nano iron oxide on AP as well as AP-HTPB based composite

propellant has been carried out with respect to thermal analysis.107, 108 the results show

that nano iron oxide accelerates the thermal decomposition of AP-HTPB based

composite propellant. Fujimura et al109 have studied the effect of iron oxide particle

size and surface area on burning rate of AP-HTPB based composite propellant and

worked out a correlation between burning rate and particle size of iron oxide.

Furthermore, Fe2O3/AP nano composites having core-shell structures110were

studied for thermal decomposition of AP. The Fe2O3 nanoparticles in Fe2O3/AP nano

composites showed good catalytic effect on the thermal decomposition of AP. Along

with nanocomposites, energetic crystals with inclusion of nanoparticle such as nano

INTRODUCTION

27

sized iron (III) oxide-ammonium perchlorate system111 was prepared and studied and

findings reveal effective thermal decomposition of AP. Chen et al112 studied

monodispersed hematite α-Fe2O3 and magnetite Fe3O4 nanocrystals on thermal

decomposition of AP, where α-Fe2O3 was more effective on thermal decomposition of

AP compared to Fe3O4.

1.11.6 Application of nano copper oxide as ballistic modifiers

The different shapes of CuO such as nano rods, 113 Claw-like nanocrystals,114

shuttle-like - flower-like nanocrystals115 and nano/microspheres116 were studied for

their catalytic effect on thermal decomposition of AP. These additives are found to be

effective for the thermal decomposition of AP. Also, hierarchical Cu2O

nanostructures117 has been investigated for their effect on thermal decomposition of

AP. The study reveals that hierarchical Cu2O nanostructures has strong influence on

thermal decomposition of AP. Fu et al118 observed that incorporated nano composite

of CuO on mesoporous silica SBA-15 composite material in AP-HTPB based

composite propellant increases burning rate at the same time pressure exponent

decreases.

1.11.7 Application of nano cobalt oxide as ballistic modifiers

Different forms of Co3O4 like nano crystals, 119 octahedral, 120 nanoflakes121,

has been studied for their effect on thermal decomposition of AP and found very

effective catalyst. Some researchers122, 123 have evaluated graphite oxide (GO)-

supported Co3O4 nanoparticles and Co3O4/graphene oxide composites for catalytic

effect on thermal decomposition of AP. The graphite oxide (GO)-supported Co3O4

nanoparticles and Co3O4/graphene oxide composites were also found excellent in

lowering the decomposition temperature of AP.

1.11.8 Application of nano manganese oxide as ballistic modifiers

MnOOH (Manganese Oxohydroxide) nanocrystals 124 dispersed on graphene

and nano Mn3O4-graphene (Mn3O4-GR) hybrids125 were studied for thermal

decomposition of AP. These catalysts are found to be very effective in thermal

decomposition of AP. Chandru et al126 evaluated the mesoporous β-MnO2 on thermal

decomposition of AP and as ballistic modifier in AP-based composition. The findings

INTRODUCTION

28

reveal that the mesoporous β-MnO2 is excellent catalyst for decomposition of AP and

very good ballistic modifier for AP-based composite propellant.

1.11.9 Application of nano transition metal oxides (TMOs) as ballistic modifiers

in HTPB/AP/Al based composition

Fuente et al127 has demonstrated the enhancement in performances of

composite propellant by incorporating CuO nano-powder as burning rate catalyst

compared to micron sized CuO. They observed that composite propellant with nano-

structured CuO yields high stable burning rates over a broad pressure range compared

to composite propellants as CuO micro particles are less stable due to over sensitivity

to pressure variations. Further, they also noted that incorporation of CuO

nanoparticles in formulations of these energetic materials also improves their

combustion and thermal properties. The results indicate the advantages using these

nanoparticles as additive for solid rocket propulsion applications.

Lu et al128 have studied mainly the burning characteristics of AP/Al/HTPB

composite solid propellant containing nano-sized ferric oxide (Fe2O3). They used the

dispersed technique to prepare propellant samples with ferric oxide (micron-sized /

nano-sized) powder. The SEM technique was used to observe the dispersion effect of

ferric oxide powder in the propellant samples. They also conducted pull-testing

machine to evaluate the mechanical properties and concluded that nano-sized ferric

oxide powder reduces thermal decomposition temperature of AP and enhances the

burning rate of AP/Al/HTPB composite solid propellant.

Manship et al129 have developed high burning rate composition by

incorporating varying levels of nano-aluminium, nano-iron oxide, iron complex of the

energetic ligand bistetrazolamine in HTPB based propellants and dicyclopentadiene-

based propellants. They observed that nano-additives have a significant effect on

propellant burning rate. The high-burning rate of 4.62 cm/s at 6.9 MPa was obtained

for dicyclopentadiene-based propellant that contains nano and micron aluminium

blend, micron-sized iron oxide, and ammonium perchlorate in a 3:1 (20:200 µm) fine-

to-coarse ratio while in case of HTPB based propellant low burning rate is observed.

INTRODUCTION

29

1.12 LIMITATION OF THE EARLIER STUDIES AND OBJECTIV ES OF

THESIS

The burning rate of propellant formulations is greatly affected by the use of

smaller particle size of the catalyst. Smaller particle creates larger interfacial area and

increase number of atoms or molecules at the particle interface which in turns

enhances catalytic activity. Application of nano sized catalyst for accelerated

decomposition of the AP has been reported previously, which is the main ingredient

of composite propellant. Accelerated decomposition of ammonium perchlorate

enhances burning rate of composite propellant formulation. The detailed literature

survey reveals that most of the studies reported using nano sized burning rate

modifiers/ nano sized TMOs are based on the thermal decomposition of ammonium

perchlorate and few studies on HTPB/AP composite propellant without aluminium

powder. However, few studies have also been reported using nano sized TMOs on

HTPB/AP/Al composition concentrating on thermal and ballistic properties.

Literature also reveal that there is no systematic study has been reported covering

with effect of nano sized TMOs on AP and Binder as well as mechanical, thermal and

ballistic properties of HTPB/AP/Al based propellant composition. Therefore, in order

to understand the effect of nano TMOs in aluminized composite propellant

formulations, different nano sized TMOs and micron sized TMOs were incorporated

and evaluated for their effect on mechanical, thermal and ballistic properties in detail.

In view of above, the present work entitled “Studies on mechanical, thermal

and ballistic properties of composite propellant formulations using nanoparticles

of different transition metal oxides” was undertaken for systematic study on effect

of nanoparticles of different transition metal oxides on HTPB/AP/Al based composite

propellant formulations for their mechanical, thermal and ballistic properties.

1.13 THE SCOPE OF PRESENT RESEARCH WORK INCLUDES

• Preparation of nano-Fe3O4 by chemical reduction method and its characterization

for particle size, purity and surface area.

• Study of nano-Fe3O4 in composite propellant formulation in comparison to nano-

Fe2O3.

• Study of nano-CuO and micron sized CuO in composite propellant formulation.

• Study of nano-Cr2O3 and micron sized Cr2O3 in composite propellant formulation.

INTRODUCTION

30

• Study of nano-Co3O4 and micron sized Co3O4 in composite propellant formulation.

• Study of nano-MnO2 and micron sized MnO2 in composite propellant formulation

• Evaluation of following properties-

1. Mechanical properties – It provides structural integrity to the system.

The parameters evaluated are-

a) Tensile strength.

b) Elastic Modulus.

c) Elongation, %.

2. Thermal properties – It provides thermal stability of system at

different environmental conditions.

3. Ballistic properties – It provides performance of the system. It

basically covers density, cal-val, burning rate and pressure exponent (n).

INTRODUCTION

31

1.14 REFERENCES:

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perchlorate and various inorganic additive, Journal Propulsion, 4, 27-40,1988.

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ammonium Perchlorate, Chemistry, Review, 69 (4) 551–590,1969

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41. Singh, G.; Pandey, D. K., Studies on energetic compounds. Part 43: Effect of

some BEMP complexes on the combustion and condensed phase thermolysis of

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some BEMN complexes on the condensed phase thermolysis of HTPB-AP

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365, 2003

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transition metal salts of NTO as burning rate modifiers for HTPB-AN composite

solid propellants Combustion and Flame, 135(1-2), 145-150,2003

45. Singh, G.; Siril, P. F., Studies of energetic compounds, part 29: effect of NTO

and its salts on the combustion and condensed phase thermolysis of composite

solid propellants, HTPB-AP Combustion and Flame 132(3), 422-432, 2003

46. Singh, G; Kapoor, I. P. S.; Tiwari, S. K.; Siril, P. F.; Ninan, K. N.; Varghese, T.

L., Studies on energetic compounds. Part 15: transition metal salts of NTO as

potential energetic ballistic modifiers for composite solid propellants. From

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47. Singh, G.; Kapoor, I. P. S.; Dubey, R.; Srivastava, P., Preparation,

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48. Gore, G. M.; Nazare, A. N; Divekar, C. N.; Hait, S. K.; Asthana S. N., Studies

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49. Gore, G. M.; Bhatewara, R. G.; Tipare, K. R.; Nazare, A. N.; Asthana, S. N.,

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50. Kulkarni, P. B.; Reddy, T. S.; Nair, J. K.; Nazare, A. N.; Talawar, M. B.;

Mukundan T.; Asthana, S. N., Studies on salts of 3-nitro-1,2,4-triazol-5-one

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(NTO) and 2,4,6-trinitroanilino benzoic acid (TABA): potential energetic

ballistic modifiers Journal of Hazardous Materials, 123(1-3), 54-60, 2005

51. Shinde, P. D.; Mehilal; Salunke, R. B.; Agrawal, J. P, Some transition metal

salts of 4,6-dinitrobenzofuroxan: Synthesis, characterization and evaluation of

their properties Propellants, Explosives, Pyrotechnics, 28(2), 77-82, 2003

52. Saravanakumar, D.; Sengottuvelan, N.; Narayanan, V.; Kandaswamy, M.;

Varghese, T. L., Burning-rate enhancement of a high-energy rocket composite

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binder, Journal of Applied Polymer Science 119(5), 2517-2524, 2011

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decomposition of ammonium perchlorate catalyzed by cobalt oxalate, Journal of

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55. Singh G.; Sengupta, S. K.; Kapoor, I. P. S; Dubey, S; Dubey, R.; Singh, S.,

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of Ammonium Perchlorate, Part 62, Journal of Energetic Materials, 31(3), 165-

177, 2013

56. Zhao, J.; Zhou, W.; Xu, F., Preparation of carbon-coated nano-Fe, Co particles

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57. Li, S.K.; Huang, F.Z;, Guo, X. ; Yu, X.R.; Lv, C. ; Shen, Y. H.; Xie, A.J.,

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superstructures and their thermal catalytic property Materials Research Bulletin,

47(11), 3499-3507, 2012

58. Liu, Z.T.; Li, X., Liu, Z.W.; Lu, J., Synthesis and catalytic behaviours of cobalt

nanocrystals with special morphologies Powder Technology, 189(3), 514-519,

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59. Zhang, X.; Jiang, W.; Song, D.; Liu, Y.; Geng, J.; Li, F., Preparation and

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60. Sui, J.; Zhang, C.; Li, . Yu, Z.; Cai, W., Microwave absorption and catalytic

activity of carbon nanotubes decorated with cobalt nanoparticles, Materials

Letters, 75, 158-160, 2012

61. Dubey, R.; Srivastava, P.; Kapoor, I. P. S.; Singh, G., Synthesis,

characterization and catalytic behaviour of Cu nanoparticles on the thermal

decomposition of AP, HMX, NTO and composite solid propellants, Part 83,

Thermochimica Acta, 549, 102-109, 2012

62. Shi, X.Q.; Jiang, X. H.; Lu, L.; Yang, X.J.; Wang, X., Synthesis and

characteristic of self-assembled diamond/copper nanocomposites, Materials

Research Bulletin, 43(11), 2872-2879, 2008

63. Ping, C.; Li, F.; Jian, Z.; Wei, J., Preparation of Cu/CNT composite particles and

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64. Ye, Y.; Shen, R.; Wang, C.; Hu, Y.; Zhu, P., Effect of porous copper on thermal

decomposition of ammonium perchlorate Proceedings of the International

Pyrotechnics Seminar, 38, 680-687, 2012

65. Wang, C.; Zhang, H.; Ye, Y.; Shen, R.; Hu, Y., Effect of nanostructured foamed

porous copper on the thermal decomposition of ammonium perchlorate,

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66. Liu, L.; Li, F.; Tan, L.; Ming, Li; Yi, Y., Effects of nanometer Ni, Cu, Al and

NiCu powders on the thermal decomposition of ammonium perchlorate,

Propellants, Explosives, Pyrotechnics, 29(1), 34-38, 2004

67. Chaturvedi, S.; Dave, P. N.; Patel, N.N., Nano-Alloys: Potential Catalyst for

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68. Srivastava, P.; Dubey, R.; Kapoor, I. P. S.; Singh, G., Synthesis, characterization

and catalytic effect of bimetallic nanocrystals on the thermal decomposition of

ammonium perchlorate, Indian Journal of Chemistry, Section A: Inorganic, Bio-

inorganic, Physical, Theoretical & Analytical Chemistry, 49A(10), 1339-1344,

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69. Singh, G.; Kapoor, I. P. S.; Dubey, S., Bimetallic nanoalloys: Preparation,

characterization and their catalytic activity, Journal of Alloys and Compounds,

480(2), 270-274, 2009

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70. Singh, S.; Srivastava, P.; Singh, G., Synthesis, characterization of Co-Ni-Cu

trimetallic alloy nanocrystals and their catalytic properties, Part – 91, Journal of

Alloys and Compounds, 562, 150-155, 2013

71. Dubey, R.; Chawla, M.; Siril, P. F.; Singh, G., Bi-metallic nanocomposites of

Mn with very high catalytic activity for burning rate enhancement of composite

solid propellants, Thermochimica Acta, 572, 30-38, 2013

72. Singh, G.; Kapoor, I. P. S.; Dubey, S.; Siril, P. F., Preparation, characterization

and catalytic activity of transition metal oxide nanocrystals, Journal of Scientific

Conference Proceedings, 1(1), 11-17, 2009

73. Kapoor, I. P. S.; Srivastava, P.; Singh, G., Nanocrystalline Transition Metal

Oxides as Catalysts in the Thermal Decomposition of Ammonium Perchlorate

Propellants, Explosives, Pyrotechnics, 34(4), 351-356, 2009

74. Zhou, Z.; Tian, S.; Zeng, D.; Tang, G.; Xie, C., MOX (M = Zn, Co, Fe)/AP

shell-core nanocomposites for self-catalytic decomposition of ammonium

perchlorate Journal of Alloys and Compounds, 513, 213-219, 2012

75. Ma, Z.; Li, F.; Chen, A., Preparation and thermal decomposition behaviour of

TMOs/AP composite nanoparticles, Nanoscience, 11(2), 142-145, 2006

76. Liu, J.; Wang, Z.; Jiang, W.; Liu, Y.; Li, F., Effects of nano TMO/CNTs

composite particles on the thermal decomposition of AP and AP/HTPB Theory

and Practice of Energetic Materials, Proceedings of the International Autumn

Seminar on Propellants, Explosives and Pyrotechnics, 7th, Xi'an, China, Oct. 23-

26, 595-600, 2007

77. Dixon, S. J.; Tunick, B. R.; Brown, E. D., High-energy-density solid propellants

based on vinyl resin binder and metal oxide burn rate modifiers U.S. Pat. Appl.

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78. Wang, Y.; Xia, X.; Zhu, J.; Li, Y.; Wang, X.; Hu, X., Catalytic Activity of

Nanometer-Sized CuO/Fe2O3 on Thermal Decomposition of AP and

Combustion of AP-Based Propellant, Combustion Science and Technology,

183(2), 154-162, 2011

79. Alizadeh-Gheshlaghi, E.; Shaabani, B.; Khodayari, A.; Azizian-Kalandaragh, Y.;

Rahimi, R., Investigation of the catalytic activity of nano-sized CuO, Co3O4

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Powder Technology, 217, 330-339, 2012

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80. Jiang, X.; Zou, M.; Wu, X.; Lu, L.; Chuyko, S. V.; Wang, Xin, Study on the

catalytic properties of bicomponent nanooxides in the thermal decomposition of

ammonium perchlorate, Integrated Ferroelectrics, 128(1), 37-43, 2011

81. Singh, G.; Kapoor, I. P. S.; Dubey, R.; Srivastava, P., Preparation,

characterization and catalytic behavior of CdFe2O4 and Cd nanocrystals on AP,

HTPB and composite solid propellants, Part: 79, Thermochimica Acta, 511(1-

2), 112-118, 2010

82. Singh, S.; Srivastava, P.; Kapoor, I.P. S.; Singh, G., Synthesis, characterisation

and catalytic activity of cadmium cobaltite nanoparticles: part 87, Journal of

Experimental Nanoscience 2013.

83. Wang, Y.; Yang, X.; Lu, L.; Wang, X., Experimental study on preparation of

LaMO3 (M = Fe, Co, Ni) nanocrystals and their catalytic activity,

Thermochimica Acta, 443(2), 225-230, 2006

84. Yu, Z.; Sun, Y.; Wei, W.; Lu, L.; Wang, X., Preparation of NdCrO3

nanoparticles and their catalytic activity in the thermal decomposition of

ammonium perchlorate by DSC/TG-MS, Journal of Thermal Analysis and

Calorimetry, 97(3), 903-909, 2009

85. Guan, X. F.; Zheng, J.; Zhao, M, L.; Li, L.P.; Li, G. S., Synthesis of FeTiO3

nano sheets with {0001} facets exposed: enhanced electrochemical performance

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86. Jia, Z.; Ren, D.; Wang, Q.; Zhu, R., A new precursor strategy to prepare

ZnCo2O4 nanorods and their excellent catalytic activity for thermal

decomposition of ammonium perchlorate ,Applied Surface Science,270, 312-

318, 2013

87. Singh, G.; Kapoor, I. P. S.; Dubey, S., Nanocobaltite: preparation,

characterization, and their catalytic activity, Propellants, Explosives,

Pyrotechnics, 36(4), 367-372, 2011

88. Li, W.; Cheng, H., Cu-Cr-O nanocomposites: Synthesis and characterization as

catalysts for solid state propellants, Solid State Sciences, 9(8), 750-755, 2007

89. Patil, P. R.; Krishnamurthy, V. N.; Joshi, S.S., Effect of nano-copper oxide and

copper chromite on the thermal decomposition of ammonium perchlorate

Propellants, Explosives, Pyrotechnics, 33(4), 266-270, 2008

90. Han, A.; Zhang, L.; Ye, M.; Hu, D.; Chen, H., Synthesis of CoxZn1-xCr2O4

solid solutions and its catalytic performance for thermal decomposition of

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ammonium perchlorate Advanced Materials Research (Durnten-Zurich,

Switzerland), 347-353, 2012

91. Liu, T.; Wang, L.; Yang, P.; Hu, B., Preparation of nanometer CuFe2O4 by auto-

combustion and its catalytic activity on the thermal decomposition of ammonium

perchlorate, Materials Letters, 62(24), 4056-4058, 2008.

92. Zhao, S.; Ma, D., Preparation of CoFe2O4 nanocrystallites by solvothermal

process and its catalytic activity on the thermal decomposition of ammonium

perchlorate, Journal of Nanomaterials, Journal of Nanoparticles, 1-5, 2010

93. Han, A.; Liao, J.; Ye, M.; Li, Y.; Peng, X., Preparation of nano-MnFe2O4 and its

catalytic performance of thermal decomposition of ammonium perchlorate,

Chinese Journal of Chemical Engineering 19(6), 1047-1051, 2011

94. Singh, S.; Srivastava, P.; Singh, G., Nanorods, nanospheres, nanocubes:

Synthesis, characterization and catalytic activity of nanoferrites of Mn, Co, Ni,

Part-89 ,Materials Research Bulletin, 48(2), 739-746, 2013

95. Singh, G.; Kapoor, I. P. S.; Dubey, S.; Siril, P. F., Kinetics of thermal

decomposition of ammonium perchlorate with nanocrystals of binary transition

metal ferrites, Propellants, Explosives, Pyrotechnics, 34(1), 72-77, 2009

96. a) Singh, G.; Kapoor, I. P. S.; Dubey, S.; Siril, P. F.; Yi, J.H.; Zhao, F.Q.; Hu,

R.Z., Effect of mixed ternary transition metal ferrite nanocrystallites on thermal

decomposition of ammonium perchlorate, Thermochimica Acta, 477(1-2), 42-47,

2008 b) Srivastava, P.; Kapoor, I. P. S.; Singh, G., Nanoferrites: Preparation,

characterization and catalytic activity ,Journal of Alloys and Compounds 485(1-

2), 88-92,2009

97. Liu, H. B.; Huang, Z. Y.; Guo, B. Z.; Jiao, Q.Z., Preparation of hydrotalcites

derived Ni/Co/Cu/Fe nano-composite oxides and their catalytic activities for

thermal decomposition of ammonium perchlorate, Advanced Materials Research

(Durnten-Zurich, Switzerland), 683, 534-539, 2013

98. Zhang, W. J.; Li, P.; Xu, H. B.; Sun, R.; Qing, P.; Zhang, Y., Thermal

decomposition of ammonium perchlorate in the presence of Al(OH)3·Cr(OH)3

nanoparticles, Journal of Hazardous Materials, 268, 273-280, 2014

99. Liu, H.; Jiao, Q.; Zhao, Y.; Li, H.; Sun, C.; Li, X., Mixed oxides derived from

Cu-Co layered double hydroxide nanorods: Preparation, characterization and

their catalytic activities, Journal of Alloys and Compounds, 496(1-2), 317-323,

2010

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100. Rajeev, R.; Suraj, S.; Catherine, K. B.; Ninan, K. N., Synthesis of nano grade α-

ferric oxide and evaluation of its catalytic properties, International Journal of

Nanotechnology, 8(10/11/12), 916-92, 2011

101. Zhang, Y.; Fan, M.; Zhong, Y.; Nie, J.; Huang, C.; Liu, X.,Ultrafine α-Fe2O3

nanoparticles: facile synthesis, characterization and their catalytic activity on

ammonium perchlorate, Advanced Materials Research (Durnten-Zurich,

Switzerland), 295-297, 2011

102. Song, L.; Zhang, S.; Chen, B.; Ge, J.; Jia, X., A hydrothermal method for

preparation of α-Fe2O3 nanotubes and their catalytic performance for thermal

decomposition of ammonium perchlorate, Colloids and Surfaces, A:

Physicochemical and Engineering Aspects, 360(1-3), 1-5, 2010

103. Shao, H.; Zhang, X.; Chen, F.; Liu, S.; Ji, Y.; Zhu, Y.; Feng, Y., Preparation of

α-Fe2O3 nanotubes via electrospinning and research on their catalytic properties,

Applied Physics A: Materials Science & Processing, 108(4), 961-965, 2012

104. Yang, Y.; Li, F.S.; Liu, H.Y.; Jiang, W.; Cui, P., Catalysis of nanometer α-Fe2O3

on the thermal decomposition of AP, Journal of China Ordnance, 1(2), 169-172,

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105. Liu, P.; Kong, J.; Xu, X.; Sun, F.; Liu, Q., Preparation and catalytic activity of

Fe2O3/CNT to thermal decomposition of ammonium perchlorate, Advanced

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106. Xu, H.; Wang, X.; Zhang, L., Selective preparation of nano rods and micro-

octahedrons of Fe2O3 and their catalytic performances for thermal

decomposition of ammonium perchlorate, Powder Technology, 185(2), 176-180,

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107. Patil, P. R.; Krishnamurthy, V. N.; Joshi, S. S., Differential scanning calorimetric

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Propellants, Explosives, Pyrotechnics, 31(6), 442-446, 2006

108. Fujimura, K.; Miyake, A., Effect of the particle size of ferric oxide on the

thermal decomposition of AP-HTPB composite propellant ,Science and

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109. Fujimura, K.; Miyake, A., Effect of the particle size and specific surface area of

ferric oxide catalyst on the burning rate of AP/HTPB solid propellant, Science

and Technology of Energetic Materials, 71(3-4), 65-69, 2010

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110. Ma, Z.; Wu, R.; Song, J.; Li, C.; Chen, R.; Zhang, L., Preparation and

Characterization of Fe2O3/ammonium perchlorate (AP) Nanocomposites through

ceramic membrane anti-solvent crystallization, Propellants, Explosives,

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111. Reese, D.A.; Son, S. F.; Groven, L. J., Preparation and Characterization of

Energetic Crystals with Nanoparticle Inclusions, Propellants, Explosives,

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112. Chen, L. Q.; Liu, W. P.; Chen, J. L.; Yang, X. F.; Liu, J.; Fu, X. H.; Wu, M. M.,

Facile shape and size-controlled growth of uniform magnetite and hematite

nanocrystals with tunable properties, Science China: Chemistry, 54(6), 923-929,

2011

113. Chen, L.; Li, L.; Li, G., Synthesis of CuO nanorods and their catalytic activity in

the thermal decomposition of ammonium perchlorate, Journal of Alloys and

Compounds, 464(1-2), 532-536, 2008

114. Wang, J.; He, S.; Li, Z.; Jing, X.; Zhang, M., Synthesis of claw-like CuO and its

catalytic activity in the thermal decomposition of ammonium perchlorate,

Materials Science-Poland, 27(2), 501-507, 2009

115. Wang, J.; He, S.; Li, Z.; Jing, X.; Zhang, M.; Jiang, Z., Self-assembled CuO nano

architectures and their catalytic activity in the thermal decomposition of

ammonium perchlorate ,Colloid and Polymer Science, 287(7), 853-858, 2009

116. Zhang, Z.K.; Guo, D.Z.; Zhang, G.M., Preparation, characterization and catalytic

property of CuO nano/microspheres via thermal decomposition of cathode-

plasma generating Cu2(OH)3NO3 nano/microspheres ,Journal of Colloid and

Interface Science, 357(1), 95-100, 2011

117. Gong, X.Y.; Gao, Y.P.; Wang, L.B.; Guo, P.F., Microwave-assisted synthesis

and catalytic performance of hierarchical Cu2O nanostructures, NANO, 8(5),

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118. Fu, T.; Chen, W.; Gu, Z.; Liu, L.; Li, F., Preparation of CuO modified SBA-15

and applications as catalyst in AP/HTPB solid state propellants ,Combustion

Science and Technology 181(6), 892-901, 2009

119. Jin, L.N.; Liu, Q.; Sun, W. Y., Shape-controlled synthesis of Co3O4

nanostructures derived from coordination polymer precursors and their

application to the thermal decomposition of ammonium perchlorate, Crystal

Engineering Communication, 14(22), 7721-7726, 2012

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120. Zhou, H.; Lv, B.; Wu, D.; Xu, Y., Synthesis and properties of octahedral Co3O4

single-crystalline nanoparticles enclosed by (111) facets, Crystal Engineering

Communication, 15(41), 8337-8344, 2013

121. Zhang, D.E.; Li, F.; Chen, A.M.; Xie, Q.; Wang, M.Y.; Zhang, X.B; Li, S,Z.;

Gong, J.Y.; Han, G.Q.; Ying, A.L.; A facile synthesis of Co3O4 nanoflakes:

Magnetic and catalytic properties, Solid State Sciences, 13(6), 1221-1225, 2011

122. Xu, Chao; Wang, Xin; Zhu, Junwu; Yang, Xuejie; Lu, Lude, Deposition of

Co3O4 nanoparticles onto exfoliated graphite oxide sheets, Journal of Materials

Chemistry, 18(46), 5625-5629, 2008

123. Zhao, J.; Liu, Z.; Qin, Y.; Hu, W., Fabrication of Co3O4/graphene oxide

composites using supercritical fluid and their catalytic application for the

decomposition of ammonium perchlorate, Crystal Engineering Communication,

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124. Chen, S.; Zhu, J.; Huang, H.; Zeng, G.; Nie, F.; Wang, X., Facile solvothermal

synthesis of graphene-MnOOH nanocomposites, Journal of Solid State

Chemistry, 183(11), 2552-2557, 2010

125. Li, N.; Geng, Z.; Cao, M.; Ren, L.; Zhao, X.; Liu, B.; Tian, Y.; Hu, C., Well-

dispersed ultrafine Mn3O4 nanoparticles on graphene as a promising catalyst for

the thermal decomposition of ammonium perchlorate, Carbon, 54, 124-132, 2013

126. Chandru, R. Arun; Patra, S.; Oommen, C.; Munichandraiah, N.; Raghunandan, B.

N., Exceptional activity of mesoporous β-MnO2 in the catalytic thermal

sensitization of ammonium perchlorate, Journal of Materials Chemistry, 22(14),

2012

127. Fuente D.L., Luis J.; Gonzalo M.; Rodrigo P., High performance HTPB-based

energetic nanomaterial with CuO nanoparticles Journal of Nanoscience and

Nanotechnology, 9(12), 6851-6857, 2009

128. Lu, K.T.; Yang, T.M.; Li, J.S.; Yeh, T.F., Study on the burning characteristics of

AP/Al/HTPB composite solid propellant containing nano-sized ferric oxide

powder Combustion Science and Technology, 184(12), 2100-2116, 2012

129. Manship, T. D.; Heister, S. D.; O'Neil, P. T., Experimental investigation of high-

burning-rate composite solid propellants, Journal of Propulsion and Power, 28(6),

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