Venugopalan Demystifying Explosives

Concepts in High Energy Materials
1. Auflage 2015
ISBN: 978-0-12-801756-2
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 252 Seiten

Demystifying Explosives: Concepts in High Energy Materials explains the basic concepts of and the science behind the entire spectrum of high energy materials (HEMs) and gives a broad perspective about all types of HEMs and their interrelationships. Demystifying Explosives covers topics ranging from explosives, deflagration, detonation, and pyrotechnics to safety and security aspects of HEMS, looking at their aspects, particularly their inter-relatedness with respect to properties and performance. The book explains concepts related to the molecular structure of HEMs, their properties, performance parameters, detonation and shock waves including explosives and propellants. The theory-based title also deals with important (safety and security) and interesting (constructive applications) aspects connected with HEMs and is of fundamental use to students in their introduction to these materials and applications. - Explains the concept of high energy materials in simple language and down-to-earth examples - Worked examples and problems are given wherever required - Demystifies the concept of explosives - Limited use of big and complex equations - Questions and Suggested Reading are given at the end of each chapter

S. Venugopalan did his post-graduation in chemistry from St. Joseph's College, Tiruchirapalli, India in 1971. After working as a lecturer in chemistry in various colleges for 5 years, he served as a Quality Assurance officer attached to an ordnance factory manufacturing varieties of high explosives and propellants for small arms, guns and rockets for about 7 years. In 1983, he joined High Energy Materials Laboratory (HEMRL), Pune as a scientist and worked in the area of composite rocket propellants and synthesis of energetic oxidizers and polymeric binders. He was also heading the Safety Engineering Division of HEMRL for about 6 years. He has over 32 years of experience with exposure to different types of High Energy Materials (HEMs) in the diverse areas of production, quality assurance and Research and development.

Autoren/Hrsg.

Venugopalan, Sethuramasharma

Inhaltsverzeichnis

1;Front Cover;1
2;Demystifying Explosives: Concepts in High Energy Materials;2
3;A JOURNEY TOWARDS HIGHER EXPLOSIVE POWER;4
4;Copyright;5
5;Dedications;6
6;Contents;8
7;About the Author and Editor;14
8;Foreword 1;16
9;Foreword 2;18
10;Foreword 3;20
11;Preface;22
12;Acknowledgments;24
13;Abbreviations;26
14;Chapter 1 - In Pursuit of Energy and Energetic Materials;27
14.1;1.1 Introduction;27
14.2;1.2 Gunpowder to Nitrocubanes;27
14.3;1.3 Classification of Explosives;32
14.4;1.4 Explosives and Molecular Structure;34
14.5;1.5 Classification of Propellants;34
14.6;1.6 Pyrotechnics;37
14.7;Appendix A;41
14.8;Appendix B;42
14.9;Appendix C;42
14.10;Suggested Reading;43
14.11;Questions;43
15;Chapter 2 - Energetics of Energetic Materials;45
15.1;2.1 Are Explosives and Propellants High-Energy Materials?;45
15.2;2.2 Explosive: The Wonderful L46
15.3;2.3 Thermochemistry and Explosive Energy;48
15.4;Worked Example 2.1;58
15.5;Worked Example 2.2;65
15.6;Worked Example 2.3;68
15.7;Worked Example 2.4;70
15.8;Summary of Important Terms;72
15.9;Suggested Reading;74
15.10;Questions;75
16;Chapter 3 - Two Faces of Explosion: Deflagration and Detonation;77
16.1;3.1 Explosion;77
16.2;3.2 Deflagration and Detonation;78
16.3;3.3 Linear Burning and Mass Burning;80
16.4;3.4 Shock Wave and Detonation Wave;81
16.5;3.5 Detonation Theory;86
16.6;3.6 Theoretical Estimation: VOD and Pd;88
16.7;3.7 Deflagration-to-Detonation Transition;93
16.8;Suggested Reading;94
16.9;Questions;95
17;Chapter 4 - HEMs: The Facet of Explosive Performance;97
17.1;4.1 Why Do Explosives Explode?;97
17.2;4.2 Two Aspects of Explosive Performance;103
17.3;4.3 A Travel by Explosive Train;107
17.4;4.4 Performance Parameters of Military Explosives;113
17.5;4.5 Industrial Explosives;120
17.6;4.6 Processing of the Compositions;126
17.7;Suggested Reading;128
17.8;Questions;129
18;Chapter 5 - The Propulsive Facet of HEMs: I (Gun Propellants);131
18.1;5.1 Introduction;131
18.2;5.2 Gun: the Heat Engine;131
18.3;Worked Example 5.1;133
18.4;5.3 Unfolding Drama inside the Barrel;134
18.5;5.4 Energetics of Gun Propellant;136
18.6;Worked Example 5.2;138
18.7;5.5 Configuration of Propellant Grains;138
18.8;5.6 Salient Aspects of Internal Ballistics of Guns;142
18.9;Worked Example 5.3;143
18.10;5.7 The Chemistry of Gun Propellant Formulations;146
18.11;Worked Example 5.4;151
18.12;Suggested Reading;157
18.13;Questions;157
19;Chapter 6 - The Propulsive Facet of High Energy Materials—II (Rocket Propellants);159
19.1;6.1. Introduction to Rocketry;159
19.2;6.2 Basic Principles of Rocket Propulsion;159
19.3;6.3 Specific Impulse;164
19.4;Worked Example 6.1;165
19.5;6.4 Thermochemistry of Rocket Propulsion;166
19.6;6.5 Some Vital Parameters in the Internal Ballistics of Rockets;168
19.7;6.6. Design of a Rocket Propellant Grain;171
19.8;Worked Example 6.2;172
19.9;6.7. Chemistry of Solid Rocket Propellants;173
19.10;6.8 Future of Rocket Propellants;179
19.11;Suggested Reading;180
19.12;Questions;180
20;Chapter 7 - High Energy Materials in Pyrotechnics;183
20.1;7.1 Introduction;183
20.2;7.2 Applications;183
20.3;7.3 Basic Principles of Pyrotechnics;185
20.4;7.4 Conclusion;189
20.5;Suggested Reading;189
20.6;Questions;189
21;Chapter 8 - HEMs: Concerns of Safety;191
21.1;8.1 Introduction;191
21.2;8.2 Nature of Hazards;191
21.3;8.3 Hazard Classification of HEMs;192
21.4;8.4 The Damages;193
21.5;8.5 General Safety Directives;194
21.6;Suggested Reading;198
21.7;Questions;198
22;Chapter 9 - HEMs: Concerns of Security;199
22.1;9.1 HEMs: Concerns of Security;199
22.2;9.2 Detection of Explosives;200
22.3;Suggested Reading;205
22.4;Questions;205
23;Chapter 10 - HEMs: Characterization and Evaluation;207
23.1;10.1 Introduction;207
23.2;10.2 Chromatographic Techniques;208
23.3;10.3 Spectroscopic Techniques;210
23.4;10.4 Thermal Evaluation of Energetic Materials;212
23.5;10.5 Sensitivity Tests of HEMS;217
23.6;Suggested Reading;219
23.7;Questions;219
24;Chapter 11 - HEMs: Trends and Challenges;221
24.1;11.1 Introduction;221
24.2;11.2 Primary Explosives;221
24.3;11.3 High Explosives;222
24.4;11.4 Propellants;228
24.5;11.5 Polynitrogen Cages: Promising a Revolution in Future HEMs?;233
24.6;Suggested Reading;235
24.7;Questions;235
25;Chapter 12 - HEMs: Constructive Applications;237
25.1;12.1 HEMs Have Shaped Our World;237
25.2;12.2 Controlled Demolition;238
25.3;12.3 Air Bags;240
25.4;12.4 Explosive Welding;242
25.5;12.5 Avalanche Control;243
25.6;12.6 Life Saving Applications;244
25.7;Suggested Reading;244
25.8;Questions;245
26;Index;247
27.1;Abbreviations;26

Leseproben

Chapter 2 Energetics of Energetic Materials
Abstract
This chapter mainly discusses the thermochemistry of high-energy materials (HEMs). It first discusses the basic difference between fuels and HEMs, showing that the term “high-energy material” is actually a misnomer. It gives a lucid illustration of the importance of heat of formation and oxygen balance of HEMs and the difference between calorific and calorimetric values and adiabatic and isochoric flame temperatures. The role played by these thermochemical parameters in the ultimate performance of HEMs, such as propellants and explosives, is summed up in the HEM network chart given at the end of the chapter. Keywords
Flame temperature; Heat content (enthalpy); Heat of combustion (calorific value); Heat of explosion (calorimetric value); Heat of formation; Hess's law; High-energy materials; Impetus (force constant); Oxygen balance 2.1. Are Explosives and Propellants High-Energy Materials?
Explosives are storehouses of energy. The potential energy lying dormant in the molecules of these materials is released when they are properly triggered or initiated and the release of this energy originates at the breaking of the energetic chemical bonds in the molecule of the explosive compound. The explosives (and propellants, which are categorized as low explosives) are sometimes referred to as “high-energy materials” (HEMs) or “energetic materials.” Is one justified in using these terms for explosives? Let us compare the most powerful high explosive in use today—HMX (an abbreviation for High Melting Explosive; chemical name being cyclic tetramethylene tetranitramine)—with a well-known fuel—coal—in terms of their energetics. From Table 2.1, it is seen that for every gram, coal produces more than 5 times the heat produced by HMX. The heat evolved by 1 g of coal and HMX is illustrated as a chart in Figure 2.1. A similar comparison will show us that all fuels of day-to-day use release far more heat than any known explosive. Therefore, in a thermochemical sense, explosives and propellants are not really HEMs. However, we also observe that HMX detonates in much less time than a piece of coal takes to burn. The former undergoes the process of detonation accompanied by shock waves whereas the latter takes its own time for combustion with the help of oxygen available in air. If we take the rate at which the heat is released, then the power of HMX is approximately 5.6 × 109 W in comparison to 488 W of coal in the above example. This power generation by HMX is far more than the capacity of all of the power generators in the country put together. The better term for explosives may not be HEMs but “power-packed materials.” In the above example, an arbitrary figure of 60 s has been given for the burning of coal. Under static wind conditions, the time taken for 1 g of coal to burn depends on its surface area exposed to air. As we go on breaking it into pieces, the burning time of coal comes down drastically. At its extreme, when the same 1 g of coal is finely powdered and dispersed as coal dust in air, facilitating the exposure of the maximum surface area to air, each such dust particle is in intimate contact with the oxygen molecules of air. When initiated, the combustion reaction takes place so fast that it is virtually converted into a violent detonation. Disastrous coal-dust explosions in coal mines are a result of this phenomenon. Such dust explosions are not uncommon in many other industries. Table 2.1 Heat generated by coal and HMX. 1. Heat evolved 7000 cal (heat of combustion) 1355 cal (heat of explosion) 2. Time (burning/detonation) 60 s 10-6 s 3. Power 488 W 5.6 × 109 W
Figure 2.1 Comparison of Heat Evolved by 1 g of Coal and HMX. 2.2. Explosive: The Wonderful Lamp
An explosive is similar to the genie that we come across in the ever-fascinating tale of Aladdin and the Wonderful Lamp. It has great potential, but then it has to be kept under check or “bottled-up.” Only when its services are needed do we open the bottle, and, in the case of explosives, we give the necessary trigger energy. An explosive is a substance in a metastable equilibrium, in a “ready-to-go-off” stage with huge potential energy. The relation between the energy needed to make an explosive and the energy released by it on explosion can be qualitatively understood by comparing it with a huge boulder brought to the apex of a cliff. Figure 2.2(a) and (b), respectively give an analogy between a boulder kept on the brink of a cliff and an explosive synthesized and “kept” in a metastable state. One has to make great efforts (or spend much energy) to place the boulder on the cliff (A) in Figure 2.2(a). The boulder continues to remain there until someone decides to push it (giving an energy equal to B) so that it falls off from a great height, converting the potential energy into kinetic energy, which is dissipated as heat and sound when it strikes the ground. Release of energy is equal to C. Likewise, the synthesis of an explosive molecule is done by packing in it a great amount of potential energy such as high bond energy, structural strain, etc., and it is kept in the metastable state as shown in Figure 2.2(b). (D–E) is the effective energy spent in such a synthesis. If the reactants are assumed as elements such as carbon, hydrogen, and oxygen, (D–E) is referred to as the heat of formation of the explosive. The explosive now needs only a trigger energy (generally called activation energy) equal to F, so that a net energy equal to G is liberated during the explosive process and the formation of stable products.
Figure 2.2 A Boulder on a Cliff and an Explosive Molecule. The chemist who wants to synthesize an explosive ensures that (1) as far as possible the product has a high positive heat of formation (i.e., the energy level of the explosive molecule is higher than that of the elements from which it is made), (2) it has its own supply of oxygen in the molecule to be independent of external or atmospheric oxygen to affect the process of explosion, and (3) the explosive reaction results in a large amount of gases. Factors 1 and 2 will ensure that the explosion process releases a large amount of heat (heat of explosion), thereby enormously increasing the temperature of the products, normally more than 2000 °C. Factor 3 will ensure that, with so many gases at a high temperature, there will be development of very high pressures. The gases expand rapidly from very high pressures to the atmospheric pressure, thereby performing a large amount of work in a short time; that is, the produced gases will work as a powerful working fluid to perform certain assigned tasks such as the blast effect produced by high explosives in microseconds, the work of throwing a projectile through a gun barrel in a few milliseconds, or the self-propulsion by a rocket in a time period varying from a few seconds to even a few minutes. Is an oxidation reaction always necessary in a chemical explosion? Although most of the chemical explosions involve fast oxidation of fuel elements, it need not be so in some cases. For example, lead azide (Pb(N3)2), a well-known primary explosive, does not contain any oxygen atoms in its molecule. However, it has a positive heat of formation. The azide (–N–NN) groups attached to the lead atom have weak linkages and are themselves at a higher energy level. Only a small trigger energy is necessary to rupture these linkages to produce more stable products with the evolution of energy. (-N(-)-N(+)=N)2?Pb+3N2+110.8kcal 2.3. Thermochemistry and Explosive Energy
Chemical reactions are accompanied by energy changes, mainly in the form of heat. The branch of science that deals with the heat changes during chemical reactions is called “thermochemistry.” It is essential to remember certain basic concepts in thermochemistry to obtain better insight into the heat transactions during the formation and explosion of explosives. The concepts about the three important parameters—internal energy (E), heat content or enthalpy (H), and work (W)—should also be clear. The internal energy of a substance is the total quantity of energy it possesses by virtue of its kinetic portion of energy (due to translational, vibrational, and rotational motions associated with the molecules) and the potential portion of energy (due to various interatomic, intermolecular, and submolecular forces of attraction and repulsion). In a chemical reaction in which certain bonds of the reactant molecules are broken and certain bonds of the product molecules are formed, it is mostly the kinetic portion of the internal energy that undergoes a change and may be positive or...