Combustion of Propellants with Ammonium Dinitramide

This paper reports a series of experiments involving ammonium dinitramide (ADN), a new energetic oxidizer of potential use in composite solid propellants. The experiments include (a) self‐deflagration of pressed pellets of ADN; (b) combustion of sandwiches with ADN laminae on both sides of a binder lamina that is either “pure” or filled with particulate oxidizer and other additives; and, (c) combustion of propellants with a bimodal oxidizer size distribution, wherein, combustion of coarse ADN and fine AP (ammonium perchlorate) and vice versa were used, in addition to mixtures of coarse ADN and AP, fine ADN and AP, and all‐ADN or all‐AP formulations.     

An Overview on the Synthetic Routes and Properties of Ammonium Dinitramide (ADN) and other Dinitramide Salts

In recent years, there has been a considerable interest in the development of novel type of high performance propellants for use in solid rocket motors. Ammonium salt of dinitramidic acid NH₄N(NO₂)₂ (ADN) has attracted wide interest as a potentially useful energetic oxidizer for rocket propellants because of its clean and environment‐friendly exhaust products during burning. ADN contains one N (NO₂)₂ group and its synthesis requires new type of N‐nitration. The present paper reviews the general synthetic methods used for the synthesis of inorganic, organic and metal dinitramide salts and their properties, with a special emphasis on ammonium dinitramide. The salient features with reference to the extent of conversion and ease of separation of the products of the various synthetic methodologies are also addressed.     

Thermal Decomposition and Combustion of Ammonium Dinitramide (Review)

A comprehensive review of thermal decomposition and combustion of ammonium dinitramide (ADN) has been conducted. The basic thermal properties, chemical pathways, and reaction products in both the condensed and gas phases are analyzed over a broad range of ambient conditions. Detailed combustion-wave structures and burning-rate characteristics are discussed. Prominent features of ADN combustion are identified and compared with other types of energetic materials. In particular, the influence of various condensed- and gas-phase processes in dictating the pressure and temperature sensitivities of the burning rate is examined. In the condensed phase, decomposition proceeds through the mechanisms ADN → NH₄NO₃ + N₂O and ADN → NH₃ + HNO₃ + N₂O, the former mechanism being the basic one. In the gas phase, the mechanisms ADN → NH₃ + HDN and ADN → NH₃ + HNO₃ + N₂O are prevalent. The gas-phase combustion-wave structure in the range of 5–20 atm consists of a near-surface primary flame followed by a dark-zone temperature plateau at 600–1000°C and a secondary flame followed by another dark-zone temperature plateau at 1000–1400°C. At higher pressures (60 atm and above), a final flame is observed at about 1800°C without the existence of any dark-zone temperature plateau. ADN combustion is stable in the range of 5–20 atm and the pressure sensitivity of the burning rate has the form r _b = 20.72p ^0.604 [mm/sec] (p = 0.5–2.0 MPa). The burning characteristics are controlled by exothermic decomposition in the condensed phase. Above 100 atm, the burning rate is well correlated with pressure as r _b = 8.50p ^0.608 [mm/sec] (p = 10–36 MPa). Combustion is stable, and intensive heat feedback from the gas phase dictates the burning rate. The pressure dependence of the burning rate, however, becomes irregular in the range of 20–100 atm. This phenomenon may be attributed to the competing influence of the condensed-phase and gas-phase exothermic reactions in determining the propellant surface conditions and the associated burning rate. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 54–79, November–December, 2005.     

Characterization and thrust measurements from electrolytic decomposition of ammonium dinitramide (ADN) based liquid monopropellant FLP-103 in MEMS thrusters

Although ammonium dinitramide (ADN) has been targeted as a potential green monopropellant in future space vehicles, its application potential in Micro-electrical-Mechanical System (MEMS) thrusters or microthrusters has been seldom reported in open literature. In this paper, electrolytic decomposition of Ammonium Dinitramide (ADN)-based liquid monopropellant FLP-103 was carried out in an open chamber and MEMS thrusters were fabricated from poly-dimethylsiloxane (PDMS) to characterize the power consumption. Two thrust measurement methods were employed to investigate the electrolytic decomposition of FLP-103 in MEMS microthrusters. The results show that the monopropellant can be successfully ignited at room temperature through 80 V, 0.1 A (8 W) using copper wire as electrodes. In the current thruster design, low thrust was obtained at FLP-103 flowrate of 40 μl·min^-1 but it generated the highest specific impulse, Isp, among all the flowrates tested. The experiments successfully demonstrated the potential application of electrolytic decomposition of FLP-103 in MEMS thrusters.     

硫铵蒸发结晶的影响因素研究与优化

就硫铵蒸发结晶过程中的几个重要影响因素进行了实验研究,包括溶液pH值、溶液蒸发温度及搅拌速度,得出较优结晶工艺操作条件:溶液pH值为3.0、蒸发温度为70℃、搅拌速度为100 r/min。将该操作条件下得到的硫铵晶体与上海石化股份有限公司化工部丙烯腈装置硫铵回收单元的产品相比较,发现在粒径和粒径分布方面,实验所得晶体优于工业产品。结果表明,该优化条件具有可行性,可应用于硫铵工业生产。     

低聚醚季铵盐表面活性剂的动态表面张力研究

通过环氧氯丙烷、三乙胺和三氟化硼乙醚合成一种低聚合度的阳离子表面活性剂,测定了不同质量浓度水溶液的动态表面张力(DST)。结果表明:溶液浓度越高,动态表面活性越高,DST达到平衡越快,DST曲线越低;在研究的浓度范围内,吸附初期属扩散控制吸附,后期属混合动力吸附。测定了基本的表面活性,其CMC值为6.99g.L-1,γCMC为41.04mN.m-1。     

联合法制碱生产中氯化铵结晶添加剂的研究

本文通过间歇与连续结晶实验,筛选出联碱生产过程中氯化铵冷冻结晶的最佳添加剂,由一系列关于联碱生产中加入该添加剂的可行性试验,表明该添加剂改变了氯化铵结晶的质地,增大了粒度,对于氯化铵产量及纯碱的产、质量均无明显影响。由于添加剂在制碱母液中循环,不影响生产成本,由此说明这种添加剂用于联碱生产是可行的。     

Melt Crystallization of Ammonium Dinitramide (ADN) Investigated by Means of X-ray Diffraction

Ammonium dinitramide (ADN) is a promising oxidizing agent for solid rocket propellants. In situ XRD investigations of ADN and ADN suspensions have been performed in order to understand and refine the emulsion crystallization process for manufacturing spherical ADN particles (prills). The investigation revealed that the melt crystallization behavior depends on ADN quality, humidity, maximum temperature of temperature cycles, and suspension agents. Further investigations will focus on additives for controlling the mechanisms investigated, e.g., by seeding.     

Characterization of ADN and ADN‐Based Propellants

Ammonium dinitramide (ADN), NH₄N(NO₂)₂ is being considered as one of the potential new energetic oxidizers for composite propellants. In this study, ADN crystals, prills and two ADN‐based propellants having different relative amounts of ingredients were characterized. The concentration of the crystals and the prills samples was determined using ion chromatography. The thermal behavior of the crystals, prills and propellants was studied using DSC, simultaneous TG‐DTA‐FTIR‐MS, ARC (accelerating rate calorimeter), HFC (heat flux calorimeter) and INC (isothermal nanocalorimeter). Decomposition of ADN was observed from all of the samples at temperatures above the melting point of ADN (~ 92 °C). Formation of N₂O, NO₂, H₂O, CO₂, CO, N₂ and NO was detected during the ADN decomposition. The thermal stability of the ADN samples at temperatures below the melting point of ADN was studied. Early solid decomposition of ADN, which generates N₂O and H₂O, was observed at 60 °C. Electrostatic discharge (ESD) and impact sensitivity of the ADN samples were determined. The crystals and prills are sensitive to impact, while the two propellants are relatively less ESD and impact sensitive.     

Preparation and Characterization of Fe2O3/Ammonium Perchlorate (AP) Nanocomposites through Ceramic Membrane Anti‐Solvent Crystallization

A novel ceramic membrane anti‐solvent crystallization (CMASC) method was proposed to prepare Fe₂O₃/AP nanocomposites with core‐shell structure. For the preparation of Fe₂O₃/AP nanocomposites, several key advantages of the CMASC method are as follows. Firstly, both well‐dispersed Fe₂O₃ nanoparticles and the superfine AP preparation can be achieved at one step. Secondly, no non‐component of solid propellant was involved in this composite process. Thirdly, the size and morphology of Fe₂O₃/AP nanocomposites can be effectively controlled by using the ceramic membrane with regular pore structure as feeding template. The morphology and structure of Fe₂O₃/AP nanocomposites were characterized by inductively coupled plasma spectrophotometry (ICP), IR spectroscopy, SEM, and HRTEM. The results verified that the size and morphology of Fe₂O₃/AP nanocomposites are controllable, and the dispersion of Fe₂O₃ nanoparticles is greatly improved in Fe₂O₃/AP nanocomposites. Moreover, the thermal decomposition of the as‐prepared Fe₂O₃/AP nanocomposites was measured with TG‐DSC. The results showed that the Fe₂O₃ nanoparticles in Fe₂O₃/AP nanocomposites exhibit better catalytic activity on the thermal decomposition of AP. In addition, the mechanism was also discussed.     

析晶污垢生长影响因素概述

结垢问题存在于各个行业,尤其在油田表现更甚。但材料表面特性对油田采出水中析晶污垢的影响并没有得到太多关注。主要对影响析晶污垢生长的三种主要表面特性因素进行简要综述。     

FA共聚物/SiO_2杂化薄膜的制备及表面性能的研究

以含氟丙烯酸酯(FA)共聚物乳胶粒为模板,四甲氧基硅烷(TMOS)为硅源,环境条件下仿生矿化制备得到核壳型FA共聚物/SiO2杂化纳米粒子,其中壳层由数十个纳米级的小SiO2粒子组成。进一步采用溶剂直接挥发法制备得到FA共聚物/SiO2杂化薄膜,结果证实无机SiO2粒子杂化可有效提高薄膜表层粗糙度,降低表面自由能,导致水滴静态接触角明显增加,并且一定范围内TMOS用量的增加和矿化反应时间的延长均有利于提高杂化薄膜的疏水、疏油性能。     

Surface free energy changes of stainless steel after one atmospheric pressure plasma treatment

Stainless steel plates (AISI 304L) were treated by an atmospheric pressure plasma treatment at room temperature in order to modify the surface properties. After plasma treatment, the surface wettability and the surface free energy were both improved. The wettability and the surface free energy of stainless steel plates before and after plasma treatment were measured from the results of contact angle test. Through the results of contact angle and surface free energy, optimum plasma treatment conditions were obtained, such as the treatment time of 60 sec and the treatment power of 120 W. In addition to this, the optimum aging time was 3 to 5 min in air.     

Energetic Abilities of Solid Composite Propellants Based on 3,4,5-Trinitropyrazole and Ammonium Dinitramide

The investigation aims at the expansion of the basis of formulations of solid composite propellants by introducing new compositions with lower sensitivity to mechanic impact and improved thermal stability.The formulations based on trinitropyrazole(TNP)contains a binder(a hydrocarbon or active one),aluminum and inorganic oxidizer ADN.The results show that a binary formulation TNP+active binder(18%-19%)(volume fraction)with no metal is well designed which would achieve high specific impulse(at Pc∶Pa=40∶1)of 248s,high density of 1.80g/cm3 and combustion temperature Tcabout 3 450K.In terms of energy,metal-free compositions with TNP lose a bit to those with HMX,only if HMX fraction in formulation is higher than 45%-50%.     

表面修饰剂对制备超细聚磷酸铵的影响

以十六烷基三甲基溴化铵（CTAB）为修饰剂,采用球磨和超声波振荡对工业阻燃剂聚磷酸铵（APP）进行超细化处理,用X射线衍射仪、扫描电镜及红外光谱对处理后的产品进行了表征。结果表明,利用球磨法可制备颗粒直径为200nm APP的超细粉体,该粉体的分散性良好;经球磨处理的超细化APP并未改变化学性质。     

钙硅比对钙铁硅铁磁体微晶玻璃核化与晶化的影响

为了研制用作温热治疗癌症的铁磁体微晶玻璃热种子材料,制备了一组化学组成为40Fe2O3xCaO(60-x)SiO23B2O33P2O5玻璃(x=20、25、30、35质量分数),用XRD、DTA、VSM对其核化与晶化过程进行了研究.研究发现,钙铁硅微晶玻璃在还原气氛下热处理后,除了磁铁矿和硅灰石及少量赤铁矿晶相外,还会出现钙铁辉石、方石英晶相.钙硅比较小的玻璃,热处理温度-时间相图中钙铁辉石相区范围较大;钙硅比较大的,钙铁辉石相区范围较小.另外,钙硅比不同,玻璃的成核机理、开始析出磁铁矿的温度也不同.     

Kinetics of crystal nucleation of poly(L-lactic acid)

The kinetics of crystal nucleation of poly(L-lactic acid) (PLLA) has been analyzed by fast scanning chip calorimetry in a wide temperature range between 313 and 383 K, that is, between temperatures about 30 K below and 40 K above the glass transition temperature. The relaxed melt was rapidly cooled to the analysis temperature and subsequently aged between 10⁻¹ and 10⁴ s, to permit formation of nuclei. The number of formed crystal nuclei has been probed by analysis of the crystallization rate at 393 K. The nucleation rate is maximal at 370–375 K and decreases monotonously with decreasing temperature in the analyzed temperature range. The observation of a monomodal dependence of the nucleation rate on temperature points to predominance of a single nucleation mechanism in the analyzed temperature range, regardless nucleation occurs in the glassy or devitrified amorphous phase. The collected data suggest that nuclei formation at ambient temperature requires a waiting time longer than about 10⁸ s. The performed study is considered as a quantitative completion of nucleation-rate data available for PLLA only at temperatures higher than 360 K, suggesting that the nucleation mechanism is independent on temperature in the analyzed temperature range between 313 and 383 K.     

Crystallization behavior and mechanical properties of polypropylene/halloysite composites

In this work, halloysite nanotubes (HNTs), a new type of inexpensive filler, were used for the modification of polypropylene (PP). HNTs were first surface treated by methyl, tallow, bis-2-hydroxyethyl, quaternary ammonium, then melt mixed with PP. Scanning electron microscope (SEM) was used to examine the dispersion of HNTs in PP matrix. Differential scanning calorimetry (DSC), polarized light microscope (PLM), dynamic melt rheometry and wide angle X-ray diffraction (WAXD) were employed to investigate the crystallization behavior of the prepared PP/HNT composites. The mechanical properties were evaluated by Instron and impact tests. SEM results revealed that HNTs could be well-dispersed in PP matrix and had a good interfacial interaction with PP, even up to a high content of 10 wt%. DSC data indicated that HNTs could serve as a nucleation agent, resulting in an enhancement of the overall crystallization rate and the non-isothermal crystallization temperature of PP. PLM showed a constant spherulite growth rate and a decreased spherulite size at given isothermal crystallization temperature, suggesting that nucleation and growth of a spherulite are two independent processes. The result obtained by dynamic melt rheometry indicated that HNTs mainly promoted nucleation and had not much influence on the growth of PP crystallization. Nevertheless, by fast cooling the samples, almost constant spherulite size can be obtained for both pure PP and PP/HNT composites due to the limited nucleation effect of HNTs on PP crystallization. WAXD showed that HNTs mainly facilitated α-crystal form of PP. Though a good dispersion of HNTs in PP matrix was observed, out of our expectation, not much enhancement on mechanical properties of PP/HNT composites had been achieved, and this could be mainly ascribed to the constant crystallinity and spherulite size of PP as well as the small length/diameter ratio of HNTs.     

Synthesis and Surface Properties of Novel Quaternary Ammonium Gemini Surfactants with Polar Head Groups Containing 2-Hydroxypropyl Moieties

The purpose of this paper is to comprehend in-depth the effect of the surfactant structure on its and physicochemical properties such as surface/interfacial properties, foam stability, wettability, and biodegradability. To this end, quaternary ammonium Gemini surfactants, alkanediyl-α,ω-bis[(2-hydroxypropyl)dodecylammonium] dibromide (abbreviated as C_m-n-C_m[iso-Pr(OH)]₂ with m = 12, 14 and n = 2, 3, 4) were synthesized via substitution and quaternization reactions, and their chemical structures were characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (¹HNMR) spectroscopies. The results showed that with the decrease of the spacer length, the surface tension was reduced more strongly, and with the increase of the alkyl tail length, micelles were more easily formed. Besides, the highest surface activity of C₁₄-2-C₁₄[iso-Pr(OH)]₂ was observed by increasing NaCl concentration to 200 g L⁻¹. The temperature had a great influence on thermodynamic parameters of the adsorption and micellization. The interfacial tension between 0.26 g L⁻¹ C₁₄-2-C₁₄[iso-Pr(OH)]₂ solution and oil could reach 0.022 mN m⁻¹. An elongation of the spacer chain in C₁₄-n-C₁₄[iso-Pr(OH)]₂ was unfavorable to foam stability. Besides, the oil-wetted core, which was aged in 0.6 g L⁻¹ C₁₄-2-C₁₄[iso-Pr(OH)]₂ solution, exhibited more hydrophilicity. C_m-n-C_m[iso-Pr(OH)]₂ surfactants produced higher biodegradable rates in river water (≥ 90% after 28 days) than the biodegradable surfactant of international recommendation (71% after 28 days) at 30 °C.     

Crystallization kinetics and morphology of poly(trimethylene terephthalate)

In this work, the isothermal crystallization kinetics of polytrimethylene terephthalate (PTT) was first investigated from two temperature limits of melt and glass states. For the isothermal melt crystallization, the values of Avrami exponent varied between 2 and 3 with changing crystallization temperature, indicating the mixed growth and nucleation mechanisms. Meanwhile, the cold crystallization with an Avrami exponent of 5 indicated a character of three-dimensional solid sheaf growth with athermal nucleation. Through the analysis of secondary nucleation theory, the classical regime I→II and regime II→III transitions occurred at the temperatures of 488 and 468 K, respectively. The average work of chain folding for nucleation was ca. 6.5 kcal mol⁻¹, and the maximum crystallization rate was found to be located at ca. 415 K. The crystallite morphologies of PTT from melt and cold crystallization exhibited typical negative spherulite and sheaf-like crystallite, respectively. Moreover, the regime I→II→III transition was accompanied by a morphological transition from axialite-like or elliptical-shaped structure to banded spherulite and then non-banded spherulite, indicating that the formation of banded spherulite is very sensitive to regime behavior of nucleation.