Author: Hubert BiteauPublisher:
ISBN:
Category :
Languages : en
Pages : 392
Book Description
Characterisation of the Thermal and Chemical Behaviour of an Energetic Material and the Heat Release Rate Issue
Author: Hubert BiteauThermal and Chemical Behaviour of an Energetic Material and a Heat Release Rate Issue
Author: Hubert BiteauPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Energetic materials encompass a wide range of chemical compounds all associated with a significant risk of fire and explosion. They include explosives, fireworks, pyrotechnics, powders, propellants and other unsteady chemicals. These materials store a high level of chemical energy and are able to release it rapidly without external contribution of oxygen or any other oxidizer. The behaviour of these materials in case of explosive detonations is relatively wellknown from empirical and practical points of view. However, fundamental scientific questions remain unanswered related to the mechanisms of heat release. The current understanding of these mechanisms lacks appropriate thermochemical characterisation. The aim of the study is the analysis of thermal and chemical characteristics of energetic materials under conditions that exclude detonations. Detonation is excluded in order to better isolate the thermal and chemical mechanisms involved in the burning process. The experimental work has been conducted using the FM Global Fire Propagation Apparatus (FPA) [ASTM E2058-03]. One of the benefits of using this experimental apparatus rather than the Cone Calorimeter is that it allows controlling the feed of heat and oxidizer to the reaction zone. The material chosen to conduct experiments on is a ternary smoke powder based on a mixture of starch and lactose as fuel components and potassium nitrate as oxidizer. This product is currently used by fire brigades to assess smoke venting systems efficiency of buildings. The kinetics associated with the combustion of the material was assessed slow enough to allow measuring instruments to capture the thermal and chemical evolution during combustion reaction. Thermal analysis has first been carried out by means of DSC, TGA, DTA, MS and FTIR data in order to understand the decomposition of the material and its energetic evolution when undergoing heating. However, if the latter methods help defining the decomposing path of the material, they do not provide an integral view of its combustion behaviour, in particular, the emissions of toxics which are kinetic path dependent. Subsequently, combustion tests have been carried out using the FPA. Its ability to capture the evolution of gases emissions formed during the reaction has been proved. The influence of two configuration parameters on the combustion behaviour and on the gaseous emissions of the material has been investigated. The proportion fuel/oxidizer has been varied as well as the composition of the reacting atmosphere. Results shows that the quantity of oxidizer in the material affects the kinetics of the reactions taking place in the condense phase. Increasing the concentration of potassium nitrate in the mixture enhanced the reaction rate of the smouldering combustion. Higher quantity of volatiles is released which favoured the initiation of a diffusion flame regime in the gaseous phase, above the sample. While the kinetics of the condense phase is governed by the oxidizer concentration, experiments show that the flaming regime is influenced by the concentration of oxygen (O2) in the reacting atmosphere. A transition from diffusion to premixed flame is found when the concentration of O2 surrounding the sample is reduced below 18%. An analytical model has been used to explain the existence of a transition for a critical O2 concentration. Finally, thermal and combustion analyses have allowed to characterise the behaviour of the material under critical conditions, in terms of decomposition taking place in the condense phase but also potential toxic emissions that can be released. Toxicity, kinetics, temperature evolution do not provide a complete view of the combustion phenomenon. Beside these elements that characterise the behaviour of a material for given conditions as well as also the degree of fire hazard encountered, the energetic issue holds as an essential feature that cannot be neglected. The heat release rate (HRR) is a critical parameter that defines a fire. It does not constitute an intrinsic material property but it describes the energetic response of the couple formed by the material and its environment. Oxygen Consumption calorimetry (OC) and Carbon Dioxide Generation calorimetry (CDG) are widespread methods to calculate the HRR resulting from a combustion reaction. Apparatuses such as the FPA or the cone calorimeter have already proved their potential to qualify the burning behaviour of common fuels in addition to polymers when their data are combined with an adapted calorimetric procedure. The same approach has been applied to energetic materials. However, prior to using these techniques, it is fundamental to have identified their restrictions. These techniques provide approximate estimations of the HRR. Results are affected by the propagation of uncertainties. Several sources of uncertainties can be found. One can cite: 1. Uncertainties associated with the sample material; 2. Uncertainties associated with the test conditions; 3. Uncertainties associated with the measurements; 4. Uncertainties associated with calculation assumptions. If uncertainties cannot always be estimated, the three first sources cited have received attention in the past from the scientific community, alike the last one. The restrictions associated with the assumptions developed for using the OC and CDG principles have to be clarified. The limits of validity of the hypotheses have to be clearly defined. In particular, the present dissertation questions the relevance of the energy constants that have been specified for OC and CDG as well as their related uncertainties. One of the purposes of the research deals with the ability to estimate accurate error bars for the calculation of the HRR. Once uncertainties related to the calorimetric methods are assessed, a method adapted from the basic OC and CDG principles is introduced that allows estimating the HRR of energetic materials. The approach is based on considering the chemical decomposition of the burning compound and defining a fictitious molecule for which energy coefficients can be calculated. Nevertheless, it requires the material to be known. Finally, the question of the advantage brought by these techniques over others, in terms of accuracy, is discussed within the framework of unconventional products, such as energetic materials or compounds whose composition is ignored. The results from this work will contribute to the development of fireanalysis methodologies and validate their use with energetic materials.
Energetic Materials
Author: Ulrich TeipelPublisher: John Wiley & Sons
ISBN: 3527604936
Category : Science
Languages : en
Pages : 643
Book Description
Incorporation of particular components with specialized properties allows one to tailor the end product's properties. For instance, the sensitivity, burning behavior, thermal or mechanical properties or stability of energetic materials can be affected and even controllably varied through incorporation of such ingredients. This book examines particle technologies as applied to energetic materials such as propellants and explosives, thus filling a void in the literature on this subject. Following an introduction covering general features of energetic materials, the first section of this book describes methods of manufacturing particulate energetic materials, including size reduction, crystallization, atomization, particle formation using supercritical fluids and microencapsulation, agglomeration phenomena, special considerations in mixing explosive particles and the production of nanoparticles. The second section discusses the characterization of particulate materials. Techniques and methods such as particle size analysis, morphology elucidation and the determination of chemical and thermal properties are presented. The wettability of powders and rheological behavior of suspensions and solids are also considered. Furthermore, methods of determining the performance of particular energetic materials are described. Each chapter deals with fundamentals and application possibilities of the various methods presented, with particular emphasis on issues applicable to particulate energetic materials. The book is thus equally relevant for chemists, physicists, material scientists, chemical and mechanical engineers and anyone interested or engaged in particle processing and characterization technologies.
Nano and Micro-Scale Energetic Materials
Author: Weiqiang PangPublisher: John Wiley & Sons
ISBN: 3527835334
Category : Science
Languages : en
Pages : 1005
Book Description
Provides an up-to-date account of innovative energetic materials and their potential applications in space propulsion and high explosives Most explosives and propellants currently use a small number of ingredients, such as TNT and nitrocellulose. In comparison to conventional materials, nano- and micro-scale energetic materials exhibit superior burning characteristics and much higher energy densities and explosive yields. Nano and Micro-scale Energetic Materials: Propellants and Explosives provides a timely overview of innovative nano-scale energetic materials (nEMs) and microscale energetic materials (μEMs) technology. Covering nEMs and μEMs ingredients as well as formulations, this comprehensive volume examines the preparation, characterization, ignition, combustion, and performance of energetic materials in various applications of propellants and explosives. Twenty-two chapters explore metal-based pyrotechnic nanocomposites, solid and hybrid rocket propulsion, solid fuels for in-space and power, the sensitivity and mechanical properties of explosives, new energetic materials, and more. Explores novel energetic materials and their potential for use in propellants and explosives Summarizes the most recent advances of leading research groups currently active in twelve countries Discusses how new environmentally friendly, high-combustion energetic materials can best be used in different applications Explains the fundamentals of energetic materials, including similarities and differences between composite propellants and explosives Nano and Micro-scale Energetic Materials: Propellants and Explosives is an important resource for materials scientists, explosives specialists, pyrotechnicians, environmental chemists, polymer chemists, physical chemists, aerospace physicians, and aerospace engineers working in both academia and industry.
Nanoenergetic Materials
Author: Djalal TrachePublisher: MDPI
ISBN: 3036500103
Category : Technology & Engineering
Languages : en
Pages : 234
Book Description
This highly informative and carefully presented book discusses the preparation, processing, characterization and applications of different types of nanoenergetic materials, as well as the tailoring of their properties. It gives an overview of recent advances of outstanding classes of energetic materials applied in the fields of physics, chemistry, aerospace, defense, and materials science, among others. The content of this book is relevant to researchers in academia and industry professionals working on the development of advanced nanoenergetic materials and their applications.
Scientific and Technical Aerospace Reports
Author: Characterization of Energetic Material Response to Thermal Environments
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 5
Book Description
Results of experiments designed to characterize the pressure-time response of heated, confined energetic materials are presented. These experiments were aimed at characterizing the state of energetic material near ignition, but were not intended to be cookoff tests. We examined several materials, including HMX, TATB, PBX 9501, PBX 9502 and AI/AP/HTPB propellant. We observed complex coupling between the mechanical and chemical response of these decomposing materials and could observe phase transitions, endo- and exothermic reactions and gas pressurization. Samples were recovered for postmortem examination of chemical and physical changes.
Fire Technology Abstracts
Author: Characterization of Thermally Degraded Energetic Materials
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
We report the results of recent experiments on thermally degraded HMX and HMX/binder materials. Small-scale samples were heated confined in either constant-volume or load- controlled configurations. A main emphasis of the work reported here is developing an understanding of the complex coupling of the mechanical and chemical responses during thermal degradation.
High-energy Combustion Agents of Organic Borohydrides
Author: XiaoHong ZhangPublisher: Royal Society of Chemistry
ISBN: 1839167130
Category : Science
Languages : en
Pages : 259
Book Description