Carbon Nanostructures Derived through Hypergolic Reaction of Conductive Polymers with Fuming Nitric Acid at Ambient Conditions

Hypergolic systems rely on organic fuel and a powerful oxidizer that spontaneously ignites upon contact without any external ignition source. Although their main utilization pertains to rocket fuels and propellants, it is only recently that hypergolics has been established from our group as a new general method for the synthesis of different morphologies of carbon nanostructures depending on the hypergolic pair (organic fuel-oxidizer). In search of new pairs, the hypergolic mixture described here contains polyaniline as the organic source of carbon and fuming nitric acid as strong oxidizer. Specifically, the two reagents react rapidly and spontaneously upon contact at ambient conditions to afford carbon nanosheets. Further liquid-phase exfoliation of the nanosheets in dimethylformamide results in dispersed single layers exhibiting strong Tyndall effect. The method can be extended to other conductive polymers, such as polythiophene and polypyrrole, leading to the formation of different type carbon nanostructures (e.g., photolumincent carbon dots). Apart from being a new synthesis pathway towards carbon nanomaterials and a new type of reaction for conductive polymers, the present hypergolic pairs also provide a novel set of rocket bipropellants based on conductive polymers.     

Metal–organic frameworks as hypergolic additives for hybrid rockets

Hybrid rocket propulsion can contribute to reduce launch costs by simplifying engine design and operation. Hypergolic propellants, i.e. igniting spontaneously and immediately upon contact between fuel and oxidizer, further simplify system integration by removing the need for an ignition system. Such hybrid engines could also replace currently popular hypergolic propulsion approaches based on extremely toxic and carcinogenic hydrazines. Here we present the first demonstration for the use of hypergolic metal–organic frameworks (HMOFs) as additives to trigger hypergolic ignition in conventional paraffin-based hybrid engine fuels. HMOFS are a recently introduced class of stable and safe hypergolic materials, used here as a platform to bring readily tunable ignition and combustion properties to hydrocarbon fuels. We present an experimental investigation of the ignition delay (ID, the time from first contact with an oxidizer to ignition) of blends of HMOFs with paraffin, using White Fuming Nitric Acid (WFNA) as the oxidizer. The majority of measured IDs are under 10 ms, significantly below the upper limit of 50 ms required for functional hypergolic propellant, and within the ultrafast ignition range. A theoretical analysis of the performance of HMOFs-containing fuels in a hybrid launcher engine scenario also reveals the effect of the HMOF mass fraction on the specific impulse (I_sp) and density impulse (ρI_sp). The use of HMOFs to produce paraffin-based hypergolic fuels results in a slight decrease of the I_sp and ρI_sp compared to that of pure paraffin, similar to the effect observed with Ammonia Borane (AB), a popular hypergolic additive. HMOFs however have a much higher thermal stability, allowing for convenient mixing with hot liquid paraffin, making the manufacturing processes simpler and safer compared to other hypergolic additives such as AB.

Hypergolic hybrid rocket propulsion, achieved through the addition of metal–organic frameworks, can contribute to reduce launch costs by simplifying engine design and operation.     

Towards N‐Alkylimidazole Borane‐based Hypergolic Fuels

Over the past few decades, toxic and highly volatile hydrazine derivatives have been the main fuel choices for liquid bipropellants, especially in traditional hypergolic rocket engines. The search for new hypergolic fuels as replacements for hydrazine derivatives is of great interest to researchers. In this study, a series of N‐alkylimidazole borane compounds has been synthesized and characterized. Interestingly, these compounds display promising applications as potential hypergolic fuels owing to their excellent physiochemical properties including low melting points, high thermal stability, low viscosities, and unique hypergolic reactivity. Compared with popular hypergolic ionic liquids, the cost‐effective and scaling‐up advantages of these materials highlight their promising potential as high‐performance fuels in liquid bipropellant formulations.     

Advanced energetic materials: novel strategies and versatile applications

Novel efficient synthetic strategies, including green methodologies, to basic and perspective high-energy density compounds, bearing active oxygen sources (C-, N- and O-nitro groups and N-oxide fragments) and high-enthalpy polynitrogen heterocycles, are briefly overviewed. Recently developed synthetic approaches to nitro group-free hypergolic ionic liquids (HILs) and strained 1,5-diaza- bicyclo[3.1.0]hexane derivatives capable of ultrafast ignition upon mixing with an oxidizer, and to high-energy liquid hydrocarbons with strained cyclopropane fragments are also considered. Physicochemical properties, energetic performances and potential applications of energetic compounds and composites as key components of explosives, powders and solid or liquid rocket propellants are critically discussed with a focus on original reports published in the period 2016–2021.     

Towards Safer Rocket Fuels: Hypergolic Imidazolylidene‐Borane Compounds as Replacements for Hydrazine Derivatives

Currently, toxic and volatile hydrazine derivatives are still the main fuel choices for liquid bipropellants, especially in some traditional rocket propulsion systems. Therefore, the search for safer hypergolic fuels as replacements for hydrazine derivatives has been one of the most challenging tasks. In this study, six imidazolylidene‐borane compounds with zwitterionic structure have been synthesized and characterized, and their hypergolic reactivity has been studied. As expected, these compounds exhibited fast spontaneous combustion upon contact with white fuming nitric acid (WFNA). Among them, compound 5 showed excellent integrated properties including wide liquid operating range (?70–160 °C), superior loading density (0.99 g cm^?3), ultrafast ignition delay times with WFNA (15 ms), and high specific impulse (303.5 s), suggesting promising application potential as safer hypergolic fuels in liquid bipropellant formulations.     

Artificial ageing of double base rocket propellant

The ageing of double base rocket propellants (DB rocket propellants), which is a consequence of chemical reactions and physical processes that take place over time, has significant effect on their relevant properties (e.g. chemical composition, mechanical properties, ballistic properties, etc.). The changes of relevant properties limit the safe and reliable service life of DB rocket propellants. This is the reason why numerous research efforts are devoted to finding out reliable methods to measure the changes caused by ageing, to assess the quality at a given moment of time, and to predict remaining life-time of DB rocket propellants. In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at elevated temperatures, in order to detect and quantify changes in dynamic mechanical properties caused by the ageing. Dynamic mechanical properties were studied using dynamic mechanical analyser (DMA). The results obtained have shown that the ageing causes significant changes of DMA curve’s shape and positions. These changes are quantified by following some characteristic points on DMA curves (e.g. glass transition temperatures; storage modulus, loss modulus and tanδ at characteristic temperatures, etc.). It has been found out that the most sensitive parameters to the ageing process are: storage modulus at viscoelastic and softening region, peak width and height on loss modulus curve, glass transition and softening temperature, and tanδ at viscoelastic region.     

Mechanical analysis on rocket propellants

The mechanical properties of solid rocket propellants are very important for good functioning of rocket motors. During use and storage the mechanical properties of rocket propellants are changing, due to chemical and mechanical influences such as thermal reactions, oxidation reactions or vibrations. These influences can result in malfunctioning, leading to an unwanted explosion of the rocket motor. Most of modern rocket propellants consist of a polymer matrix (i.e. HTPB) filled with a crystalline material (i.e. AP, AN). However, the more conventional double base propellants consist of a solid gel matrix with additives, such as stabilizers. Both materials show a mechanical behaviour, quite similar to that of general polymers. To describe the material behaviour of both propellants a linear visco-elastic theory is often used to describe the mechanical behaviour for small deformations. Because the time-temperature dependency is also valid for these materials a mastercurve can be constituted. With this mastercurve the response properties (stiffness) under extreme conditions can be determined. At TNO-PML a mastercurve of a double base propellant was constituted using dynamical mechanical analysis (DMA) and compared with a mastercurve reduced from conventional (static) stress relaxation tests. The mechanical properties of this double base propellant determined by DMA were compared with conventional (quasi-static) tensile test results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Applications of nano-catalyst in new era

In the era of nanoscience where all the devices and technologies are going to smaller and smaller in size with improved properties; catalysis is an important field of application. In this review article we are trying to summarize data reported in literature for application of nano sized catalyst in our daily life which are useful for human beings. Improvement in catalytic properties due size of catalyst reduced to nano scale is discussed here. Introductive points regarding nanoscience; their functional approaches; current research are also here.Main applications of nanocatalysts in water purification; fuel cell; energy storage; in composite solid rocket propellants; bio diesel production; in medicine; in dye; application of carbon nano tubes and several other point of application are discussed here in detail.     

Nitrato Functionalized Polymers for High Energy Propellants and Explosives: Recent Advances

Future propellants and explosive research focus on developing compositions with less vulnerability without compromising performance. This has provided impetus for research in the area of high energy materials and compounds free from pollution, for safe handling, high performance, reliability and reproducibility. The energetic oxidizers and energetic binders are being developed in this scenario for use in composite propellants and explosives. In a propellant, the binder holds together the matrix containing solid oxidizer particles and finely divided metal particles. It provides structural integrity and aid the combustion of the propellant. Any new development in this area wherein the binder can contribute to the energetic is of immense importance. This can be achieved by incorporation of energetic groups such as nitrato (?ONO₂), azide (?N₃) or flurodinitro CF(NO₂)₂ as side chain or on to the existing polymer backbone. Among these, nitrato functionalized energetic binders can find application in myriad areas like boosters, plastic bonded explosives, gas generators and pyrogen igniters. The present article is a concise review on various types of nitrato binders; their synthesis, properties and their propellant studies. Copyright © 2017 John Wiley & Sons, Ltd.     

Reactive Nanocomposites as Versatile Additives for Composite Propellants

A new approach to improve the performance of composite propellants was developed in which reactive nanocomposites (RNCs) are used as replacements for aluminum powders in composite solid rocket propellants. The new materials are mechanically activated nanothermites comprising of nano‐powders of aluminum as the fuel as well as oxides of copper, iron, molybdenum, or nickel as the oxidizer. The obtained RNCs were characterized using X‐ray diffraction, scanning electron microscopy, and laser diffraction particle size analyzer. The obtained RNCs were used for preparation of modified composite solid rocket propellants (CSRPs). Burning rate, thermal decomposition behavior, heat of combustion, sensitivity, and mechanical properties of CSRPs were determined. The results showed increases in the combustion energy and the burning rate of the modified propellants were achieved, and that RNCs can be considered to be promising multi‐function additives for composite solid rocket propellants. In addition, the mechanical properties and sensitivities of the modified propellants are within the desired range.     

Application of dinitramide salts (Review)

Published data on application areas of ammonium and other salts of dinitramide, new components of condensed energetic systems, are discussed. Originally suggested as nearly exclusively oxidants for rocket propellants and explosives, these compounds have significantly expanded their application areas, and this occurred not only in defense, but also in nondefense fields.     

Thermal behavior and decomposition kinetics of composite solid propellants in the presence of amide burning rate suppressants

The employment of burning rate suppressants in the solid rocket propellant formulation is long known. Different research activities have been conducted to well understand the mechanism of suppression, but literature about the action of oxamide (OXA) and azodicarbonamide (ADA) on the thermal decomposition of composite propellant is still scarce. The focus of this study is on investigating the effect of burning rate suppressants on the thermal behavior and decomposition kinetics of composite solid propellants. Thermogravimetric analysis (TG) and differential thermal analysis have been used to identify the changes in the thermal and kinetic behaviors of coolant-based propellants. Two main decomposition stages were observed. It was found that OXA played an inhibition effect on both stages, whereas the ADA acts as a catalyst in the first stage and as coolant in the second one. The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) based on the TG data obtained at different heating rates. The mechanism of action of coolants on the decomposition of solid propellants was confirmed by the kinetic investigation as well.     

Regularities in the Dependence of the Enthalpies of Formation of Certain Conjugated Polynitrogen Heterocyclic Compounds on Their Structure

Russian Journal of Applied Chemistry - In recent decades, the chemistry of rocket propellants has been actively developing in the direction of searching for new high enthalpy polynitrogen...     

新型高能氧化剂的合成方法及性能研究

新型高能氧化剂在固体推进剂中占据较大比重,是提高固体推进剂能量水平的关键材料之一。本文以ADN、HNF、TNAZ及HNFX为例,着重对其合成路线、物理化学、爆轰性能及改性等方面的最新研究进展进行综述,并展望了其在固体推进剂中的发展方向与应用前景。     

Thermal decomposition studies of catalysed double base propellants

To understand the rote of lead salts of organic acids in the combustion of double base rocket propellants, thermal decomposition behaviour of propellants was studied bydta andtg methods. Catalysed propellants decomposed at lower temperatures than the control. Percent thermal decomposition of propellants containing lead salts was also higher. Rate constants were higher and energy of activation was lower for catalysed propellants. Results obtained suggest that condensed phase reactions may be the site for the action of lead salts in the combustion of double base propellants     

Hypergolic Triggers as Co‐crystal Formers: Co‐crystallization for Creating New Hypergolic Materials with Tunable Energy Content

We demonstrate a co‐crystal‐based strategy to create new solid hypergols, that is, materials exhibiting spontaneous ignition when in contact with an oxidant, from typically non‐hypergolic fuel molecules. In these materials, the energy content and density can be changed without affecting the ignition delay. The use of an imidazole‐substituted decaborane as a hypergolic “trigger” component in combination with energy‐rich but non‐hypergolic nitrobenzene or pyrazine yielded hypergolic co‐crystals that combine improved combustion properties with ultrashort ignition delays as low as 1 ms.     

Thermogravimetric analysis of cobalt sulfate

Morpholine is a base of moderate strength, comparable with that of ammonia, and capable of forming -onium-type salts. Extensive studies [1,2] have been made on the thermal stability of ammonium perchlorate because of its technological use as an oxidant in solid state rocket propellants. The preparation, characterization and thermal behaviour of morpholinium perchlorate are reported in this note. The study was followed by XRD, IR, TG, DTA and mass spectral techniques.     

Thermal decomposition of high-energy density materials at high pressure and temperature

High-energy density materials (HEDMs) are being investigated for use as propellants in rocket, air-breathing, and combined-cycle applications. These types of materials may be attractive alternatives to conventional propellants because of their high heat of combustion, density, and high strain energy. Because advanced propulsion systems may operate at very high pressure and temperature (>25 atm and temperatures exceeding 500 °C), the thermal decomposition of individual HEDMs is of interest to future fuel system designers. A laboratory-scale flow reactor was used to subject small amounts (approximately 1 ml) of deoxygenated HEDM to controlled conditions of temperature and residence-time-at-temperature at constant pressure (34 atm) in the liquid or supercritical phase. The reactor was 316 stainless steel HPLC tubing. Using an in-line analytical system, as well as off-line chromatographic analysis of products, the thermal stability of the parent material, as well as the thermal fragmentation products of each HEDM was measured. Some of the candidate materials tested (dimethyl-2-azidoethylamine (DAMEZ), quadricyclane, and bicyclopropylidene (BCP)) showed only marginal thermal stability with major decomposition occurring before 400 °C (3 s residence time). Other candidate materials (JP-10, RP-1, RG-1, RJ-6, and RJ-7) showed excellent thermal stability: little decomposition even at 600 °C. Results show the pyrolytic stability of candidate materials relative to each other, and provided insights to the mechanisms of thermal decomposition for specific fuel candidates.     

Synthesis,anti‐migration and burning rate catalytic mechanism of ferrocene‐based compounds

One of the most important components of solid rocket propellant is the burning rate catalysts (BRC) which enhance burning rate of solid composite propellant. Low‐pressure exponents and stable burning rate are the key features of an excellent solid propellant. Addition of BRC to the propellant results in the increase of burning rate of the propellant and decrease in pressure exponents. Among all BRC, ferrocene‐based BRC have attracted much attention because of their better microscopic homogeneities in distribution, ignitability of the propellants and good compatibility with organic binder. However, the main barrier for the development and practical applications of ferrocene‐based BRC is their migration property. This article reviews the field and highlights recent progress. Copyright © 2014 John Wiley & Sons, Ltd.     

高氮化合物及其含能材料

高氮含能化合物及其含能材料是新型含能材料领域的研究热点之一。相比于传统的含能材料,高氮含能材料具有很多优异或独特的理化性能和爆轰性能。本文综述了新型高氮化合物及其含能材料的研究进展,介绍了国内外近十年来众多研究小组的相关工作,重点阐述了四嗪、四唑和呋咱3大类高氮含能化合物的合成、性能及应用研究进展。结合作者的研究工作,进一步探讨了高氮含能化合物在钝感高能炸药、推进剂和新型气体发生剂等含能材料领域中的应用前景。