The Experts below are selected from a list of 402 Experts worldwide ranked by ideXlab platform
Ivona Fiamengo Houra - One of the best experts on this subject based on the ideXlab platform.
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kinetics and enthalpy of nitroglycerin evaporation from Double Base Propellants by isothermal thermogravimetry
Thermochimica Acta, 2010Co-Authors: Muhamed Suceska, Sanja Matecic Musanic, Ivona Fiamengo HouraAbstract:Abstract Double Base Propellants are composed of two basic components: nitrocellulose as a matrix and nitroglycerin as a plasticizer and blasting oil at the same time, and of additives such as stabilizers, burning catalysts, modifiers of ballistic properties, etc. In the course of time, a number of chemical and physical processes (e.g. stabilizer consumption, migration and evaporation of nitroglycerin, decomposition of nitroglycerin and nitrocellulose, etc.) take place in a propellant grain. The result is a change of Propellants’ physical, chemical, thermal, ballistic and mechanical properties. The final consequence is reduction of performances and decrease of safe service lifetime of Propellants. Reduction of mechanical properties of a propellant grain during ageing can be the factor that limits rockets safe service time. On the other hand, the change in amount of nitroglycerin significantly affects mechanical properties. This is the reason why the evaporation of nitroglycerin from Double Base Propellants is a subject of great importance. In this work we have studied a very early stage of evaporation of nitroglycerin from a Double Base rocket propellant applying isothermal thermogravimetry experiments. The experiments were done with a propellant containing 27% nitroglycerin, using thin plate samples having a thickness of 0.2–0.4 mm and weighing ∼4 mg. It was found that at a very early stage the evaporation can be described by the zero-order reaction model, while the entire process is characterized by power law decrees of the evaporation rate with time. The Langmuir vaporization equation, and equations proposed by Pieterse and Focke, and by Beverley et al. are used to relate nitroglycerin mass loss data and the vapor pressure. The activation energy of nitroglycerin evaporation was calculated to be 81.9 kJ mol−1 and the pre-exponential factor 5.6 × 107 s−1, while calculated enthalpy of nitroglycerin evaporation at 298.15 K lies between 80.0 and 90.5 kJ mol−1, depending on the calculation method applied.
Fengqi Zhao - One of the best experts on this subject based on the ideXlab platform.
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combustion mechanism of Double Base propellant containing nitrogen heterocyclic nitroamines i the effect of heat and mass transfer to the burning characteristics
Combustion and Flame, 2009Co-Authors: Xiaojiang Li, Ying Wang, Weihua Zhang, Fengqi ZhaoAbstract:Abstract In order to evaluate the actual pros and cons in the use of new nitroamines for solid rocket applications, the combustion properties of Double-Base Propellants containing nitrogen heterocyclic nitroamines such as RDX, TNAD, HMX and DNP are experimentally investigated by means of high-speed photography technique, thermogravimetry (TG) and differential scanning calorimetry (DSC). It was indicated that DNP and TNAD can yield a lower pressure exponent than that of RDX and HMX, especially, TNAD-CMDB can give plateau burning at higher pressure ( > 12 MPa ) with higher burning rates ( n 0.2 , r > 30 mm s − 1 ) than that of RDX and HMX. It was also concluded that the rate of change in space of the temperature gradient is negligible for these Propellants and the rate of mass diffusion is assumed to be small compared with the rate of mass convection. Furthermore, the reaction of CH2O + NO2 → CO + NO + H2O is probably the most important one in the foam layer of the Propellants containing nitrogen heterocyclic nitroamines and the thermodynamic phase transition consisting of both evaporation and condensation of NC, HMX, TNAD, RDX and DNP, are considered to provide a complete description of the mass transfer process.
Muhamed Suceska - One of the best experts on this subject based on the ideXlab platform.
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kinetics and enthalpy of nitroglycerin evaporation from Double Base Propellants by isothermal thermogravimetry
Thermochimica Acta, 2010Co-Authors: Muhamed Suceska, Sanja Matecic Musanic, Ivona Fiamengo HouraAbstract:Abstract Double Base Propellants are composed of two basic components: nitrocellulose as a matrix and nitroglycerin as a plasticizer and blasting oil at the same time, and of additives such as stabilizers, burning catalysts, modifiers of ballistic properties, etc. In the course of time, a number of chemical and physical processes (e.g. stabilizer consumption, migration and evaporation of nitroglycerin, decomposition of nitroglycerin and nitrocellulose, etc.) take place in a propellant grain. The result is a change of Propellants’ physical, chemical, thermal, ballistic and mechanical properties. The final consequence is reduction of performances and decrease of safe service lifetime of Propellants. Reduction of mechanical properties of a propellant grain during ageing can be the factor that limits rockets safe service time. On the other hand, the change in amount of nitroglycerin significantly affects mechanical properties. This is the reason why the evaporation of nitroglycerin from Double Base Propellants is a subject of great importance. In this work we have studied a very early stage of evaporation of nitroglycerin from a Double Base rocket propellant applying isothermal thermogravimetry experiments. The experiments were done with a propellant containing 27% nitroglycerin, using thin plate samples having a thickness of 0.2–0.4 mm and weighing ∼4 mg. It was found that at a very early stage the evaporation can be described by the zero-order reaction model, while the entire process is characterized by power law decrees of the evaporation rate with time. The Langmuir vaporization equation, and equations proposed by Pieterse and Focke, and by Beverley et al. are used to relate nitroglycerin mass loss data and the vapor pressure. The activation energy of nitroglycerin evaporation was calculated to be 81.9 kJ mol−1 and the pre-exponential factor 5.6 × 107 s−1, while calculated enthalpy of nitroglycerin evaporation at 298.15 K lies between 80.0 and 90.5 kJ mol−1, depending on the calculation method applied.
Zhao Fengqi - One of the best experts on this subject based on the ideXlab platform.
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sensitivity characteristics of Double Base Propellants containing super thermites
Journal of Propulsion Technology, 2013Co-Authors: An Ting, Zhao Fengqi, Gao Hongxu, Hao Haixia, M A HaixiaAbstract:Super thermites Al/PbO,Al/CuO and Al/Bi2O3 were prepared by ultrasonic dispersion method using nano-Al,micro-Al,nano-PbO,nano-CuO and nano-Bi2O3 as the raw materials.On the Bases of results of compatibility evaluation between super thermites and some Double-Base(DB) propellant components,these super thermites were applied in DB propellant.According to the national military standard methods,the mechanical sensitivity of different MIC-DB Propellants was reviewed.Electrostatic spark sensitivity tester was employed to evaluate the risk of different MIC-DB Propellants v.s.electrostatic response.The thermal sensitivity of several MIC-DB Propellants was studied by 5s explosion temperature method.The results show that the effect of impact sensitivity of thermites on DB Propellants is smaller,the friction sensitivities of several MIC-DB Propellants are slightly larger,and the type of thermites has little effect on the friction sensitivity of MIC-DB Propellants.The electrostatic spark sensitivity of all MIC-DB Propellants is relatively low.The thermal sensitivity of several MIC-DB Propellants is affected by the size of nano-Al and the category of super thermites.In comparison with the MIC-DB Propellants with micro thermites,the heat-resistance of nano-MIC-DB Propellants is larger.
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a study of kinetic behaviours of the effective centralite stabilizer consumption reaction of Propellants using a multi temperature artificial accelerated ageing test
Journal of Hazardous Materials, 2007Co-Authors: Zhao Fengqi, Gao Hongxu, Heng Shuyun, Hu Rongzu, Han FangAbstract:Abstract Using a multi-temperature artificial ageing testing apparatus and a standard method of determining the effective centralite/stabilizer content, the effective centralite/stabilizer content for varying time period in Propellants heated at 95 °C, 90 °C, 85 °C, 75 °C and 65 °C was measured. Bethelot's equation and Semenov's equation in the temperature range of 65–95 °C for 81 Propellants were established. The safe storage life at 30 °C, kinetic parameters [the apparent activation energy (E) and the pre-exponential constant (A)] and isolife temperatures obtained from the established equations and the activation energy (Eα=0.5) obtained by integral isoconversional non-linear method for 81 Propellants: single-Base gun Propellants (DF-01–DF-16), Double-Base gun Propellants (SF-01–SF-13), tri-Base gun Propellants (SG-01–SG-02), nitramine gun Propellants (GSF-01–GSF-18), Double-Base Propellants (ST-01–ST-13), and composite modified Double-Base Propellants (GST-01–GST-19), were given. Information was obtained on the effective centralite/stabilizer consumption reaction and the kinetic compensation effect.
W P C De Klerk - One of the best experts on this subject based on the ideXlab platform.
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mechanical analysis on rocket Propellants
Journal of Thermal Analysis and Calorimetry, 2003Co-Authors: G Herder, F P Weterings, W P C De KlerkAbstract: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.