Thermal decomposition and combustion characteristics of Al/AP/HTPB propellant

Journal of Thermal Analysis and Calorimetry - Aluminum(Al)/ammonium perchlorate(AP)/hydroxyl-terminated polybutadiene (HTPB) propellant is the most widely used propulsion system currently. Its...     

Solid propellants: AP/HTPB composite propellants

In this article we mainly discuss about AP/HTPB composite solid propellants. Classification, components, properties, burning rate and ignition behavior of propellants are mentioned here. Combustion of AP monopropellant, HTPB and AP/HTPB is discussed in detail.     

Influence of tailored CuO and Al/CuO nanothermites on the thermocatalytic degradation of nitrocellulose and combustion performance of AP/HTPB composite propellant

Cellulose - Al/CuO nanothermites have displayed unique catalytic activities in accelerating the thermolysis of nitrocellulose (NC) and combustion characteristics of AP/HTPB propellant depending on...     

Experimental study on ballistic behaviour of an aluminised AP/HTPB propellant during accelerated aging

The chemical stability of a propellant and its influence on the ballistic properties during aging is a subject of interest. The effect of aging on ballistic properties, viz., ignition delay, burning rate, and heat of combustion for an aluminised ammonium perchlorate–hydroxyl-terminated polybutadiene (AP/HTPB) composite propellant during accelerated aging were investigated. Samples of composite propellants were aged at 60 and 70 °C at relative humidity of 50% in a climatic chamber. The propellant samples were tested with pressurized nitrogen gas environment for ignition delay measurement. Test results indicate that aging does not have any appreciable effect on ignition delay. The change in ignition delay time is less than 3% within the scatter of the data. Experiment results indicate that burn rate do affect with pressure but aging does not have much effect on burn rate. It was also observed that the burning rate at low pressures did not undergo significant changes during the aging period. The most significant of all the ballistic properties of this propellant is the burning rate exponent which increased by about 10% during the aging period.     

Effect of tetramethylammonium perchlorate on ammonium perchlorate and propellant decomposition

The thermal decomposition of ammonium perchlorate (AP) is considerably modified when it is cocrystallized or mixed with small amounts of tetramethyl- ammonium perchlorate. The decomposition is sensitized when tetramethylphosphonium perchlorate is added to AP. The effect on the isothermal decomposition of AP when it is mixed with tetramethylammonium perchlorate, appears to be similar to that of AP-based composite propellant having the same mixed AP composition.     

The influence of porosity of ammonium perchlorate (AP) on the thermomechanical and thermal properties of the AP/polyvinylchloride (PVC) composite propellants

The influence of porous ammonium perchlorate (P_OAP) on the thermomechanical and combustion behavior of solid rocket propellants based on polyvinylchloride binder has been investigated. Differential scanning calorimetry, differential thermogravimetry, dynamic mechanical thermal analysis, and scanning electronic microscopy measurements were used for thermomechanical and thermal decomposition properties assessment. The results obtained indicate that lower glass transitions of the propellants and catalytic effect of combustion are obtained with P_OAP.     

Thermal decomposition properties of double-base propellant and ammonium perchlorate

The thermal decomposition properties and the heat of combustion (ΔH) of samples with different ammonium perchlorate (AP)/double base propellant (DB) mass ratios under argon atmosphere were studied by the thermogravimetry–differential scanning calorimetry–mass spectrometry–Fourier transform infrared spectroscopy (TG–DSC–MS–FTIR) and automatic calorimeter method. The results show that decomposition process of AP/DB samples in negative and zero oxygen balance (OB) is different from that in positive OB. With the increasing of AP in the AP/DB samples, the decomposition of the samples becomes more and more severe. When the OB of the samples is positive, the phenomenon of deflagration or explosion could be observed in the decomposition process. The sample with OB = 0 has the greatest heat of combustion.     

HTPB固体推进剂增塑剂选取分子模拟研究

固体推进剂中增塑剂要求同粘合剂体系相容性良好,并提高体系的低温性能.本文采用分子动力学(MD)方法,首先计算了端羟基聚丁二烯(HTPB)粘合剂及增塑剂癸二酸二辛酯(DOS)、己二酸二辛酯(DOA)、壬酸异癸酯(TOA)、邻苯二甲酸二丁酯(DBP)和邻苯二甲酸二辛酯(DOP)的溶度参数,以此从相容性角度选取推进剂增塑剂;计算数值基本吻合实验值,表明常用的增塑剂从相容性都能满足要求.其次模拟获取了HTPB及HTPB/增塑剂混合体系的比体积-温度关系得到了体系的玻璃化转变温度(Tg),揭示增塑剂对HTPB体系低温性能的影响.结果显示:(1)HTPB的Tg模拟值为202K,基本吻合实验值196K.(2)HTPB/DOS混合体系中,当增塑剂DOS的质量含量从12%、22%、29%到36%(摩尔含量分别为50%、66%、75%和90%)增加时,体系的Tg线性降低;TOA和DOP增塑的粘合剂体系(摩尔含量为75%)Tg也降低,而增塑剂DOA和DBP对体系的Tg影响不大.因此,基于相容性及提高粘合剂低温性能考虑,DOS、DOA和DOP作为HTPB的增塑剂优于TOA和DBP.     

A quadridentate Schiff base as an extractant for thorium/IV/, uranium/VI/ and zirconium/IV/

Liquid-liquid extractions of zirconium/IV/, thorium/IV/ and uranium/VI/ with a tetradentate Schiff base, bis/salicylidene/ ethylenediamine /H₂Salen/ in benzene as the diluent have been studied. Comparison of such results with those in case of a bidentate Schiff base, N-salicylidene-p-toluidine /HSalTol/ shows that the extraction of UO ₂ ²⁺ is significantly improved if H₂Salen is used instead of HSalTol². A single extraction at pH 6.5 with H₂Salen removes uranium/VI/. Extraction of all the three metals becomes quantitative at pH 6.5. The extracted species, which have been derived from slope-analyses of extraction results, seem to be of the type [Zr₄/OH/₁₂ /HSalen/₂]Cl₂, [UO₂/OH/ /HSalen/] and [Th/OH/₃ /HSalen/].     

Nafion/PTFE and zirconium phosphate modified Nafion/PTFE composite membranes for direct methanol fuel cells

We prepared Nafion/PTFE (NF) and zirconium phosphate (ZrP) hybridized Nafion/PTFE composite membranes (NF–ZrP). NF–ZrP composite membranes were prepared via two processes. One is impregnating sub-μm porous PTFE membrane directly in a Nafion/ZrOCl₂ solution (NF–Zr–d). The other is impregnating sub-μm porous PTFE membrane in a Nafion solution to prepare NF composite membrane, and then the NF membrane was impregnated in a ZrOCl₂ aqueous solution via in situ precipitation method (NF–Zr–I). The ZrOCl₂ inserted in NF composite membranes was then reacted with phosphoric acid to form ZrP and thus NF–ZrP–d and NF–ZrP–I composite membranes were obtained. The direct methanol fuel cell (DMFC) performances of membrane electrode assemblies prepared from Nafion-117, NF, NF–ZrP–d, and NF–ZrP–I composite membranes were investigated. The effects of introducing sub-μm porous PTFE film and ZrP particles into Nafion membranes on the DMFC performance were investigated. The influence of ZrP hybridizing process into NF membranes (the process of preparing NF–ZrP–I is inserting ZrOCl₂ into NF membranes after Nafion is annealed and the process of preparing NF–ZrP–d is mixing ZrOCl₂ into a Nafion solution before Nafion is annealed) on the morphology of NF–ZrP composite membranes and thus on the DMFC performance was also discussed.     

Investigation of the thermal degradation of the aged pyrotechnic titanium hydride/potassium perchlorate

In previous works, the effects on the devitrification mechanism of a certain composition calcium phosphate with additives of TiO₂, SiO₂, Al₂O₃, CeO₂ have been studied. It was found that some metal oxide additives played a key role as the nucleation agent in calcium phosphate glass-ceramics, and the devitrification mechanism of calcium phosphate glass system was changed drastically by addition such as metal oxide. Hydroxyapatite (HAp), tricalcium phosphate (TCP) and β-calcium phosphate (β-CaP₂O₆) whisker are the three most biologically compatible materials to human bone in bio-ceramics field. In this work, the effect on devitrification mechanism and the physical properties of certain composition calcium phosphate glass with three above additives were investigated, and the result shown that although no fine crystalline was induced in the certain composition of calcium phosphate glass when a large amount of additive was added, but such additives play a catalyst role by lowering the activation energies of devitrification. It would supplement the mechanical properties and the biocompatibility for the calcium phosphate glasses.     

Synthesis and crystal structure of (2.2.2-cryptand)potassium perchlorate

A new complex (2.2.2-cryptand)potassium perchlorate [K(Crypt-222)]ClO₄ is synthesized, and its structure is studied by X-ray diffraction analysis (space group R32, a = 8.441 Å, c = 30.475 Å, Z = 3). The structure is solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.032 for 1222 independent (with allowance for anomalous dispersion) reflections (CAD4 automated diffractometer, λMoK _α radiation). The centers of the ClO ₄ ^? anion and [K(Crypt-222)]⁺ complex cation are in the positions (0,0,0) and (0,0,1/2), respectively, with the point symmetry 32. The ClO ₄ ^? anion is randomly disordered. The complex cation (with the high symmetry D ₃) is of the host-guest type and is somewhat disordered and exists as two different conformations with probabilities of 87 and 13%. The coordination polyhedron of the K⁺ cation (coordination number 8) is a two-base-centered trigonal prism distorted toward antiprism.     

Vibrational spectroscopy at high pressure of the permanganate anion trapped in potassium bromide and potassium perchlorate matrices

The effect of high pressure on the resonance Raman spectra of the permanganate ion isolated in potassium bromide and potassium perchlorate matrices has been investigated at room temperature for pressures up to 50 kbar. The pressure dependences of the anharmonicity constants and harmonic frequencies have been determined from the overtones of the totally symmetric nu1(A1) mode of the permanganate ion. For both matrices, as the pressure increases, the anharmonicity constants decrease slightly, while the harmonic frequencies increase steadily. The effect of the potassium bromide phase transition from a face-centered to a body-centered structure was observed on the permanganate ion Raman spectrum at approximately 24 kbar. The perchlorate matrix does not exhibit any phase transition under the experimental conditions used in this study.     

Removal of cesium and strontium from acid solution using a composite of zirconium molybdate and zirconium tungstate

A composite mixture of zirconium molybdate and zirconium tungstate was prepared and studied for the sorption of cesium and strontium as a function of nitric acid, metal ion concentration, time and temperature. The distribution coefficient (K_d) of 7000 ml/g (~90% sorption) and 70 ml/g (~20% sorption) was obtained for the sorption of cesium and strontium in 0.1M nitric acid, respectively. Experimental sorption capacity, b for cesium was found to be 50 mg/g from 0.1M HNO₃ and 30 mg/g for strontium from 0.001M nitric acid. The sorption of strontium on the sorbent was accompanied by the absorption of heat but the sorption of Cs⁺ results in the liberation of heat. Column studies were conducted by following a breakthrough (BT) curve of cesium and strontium up to C/C₀=1 and the results are reported.     

A novel one-pot reductive amination of aldehydes and ketones with lithium perchlorate and zirconium borohydride-piperazine complexes

A novel, one-pot reductive mono-alkylation method of amines (primary and secondary), 1,2-phenylenediamine, O-trimethylsilylhydroxylamine, and N,N-dimethylhydrazine was developed using LiClO₄ (5 mol %) as a source for in situ generation of imine, iminium ion, oxime, and hydrazone, and zirconium borohydride-piperazine complex as reducing agent. This condition is especially useful for situations in which it is not practical to use the amine in excess (as is typically the case under acid-catalyzed conditions) or for acid-sensitive compounds.