Investigation on the Reaction of Powdered Tin as a Metallic Fuel with Some Pyrotechnic Oxidizers

Thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) have been used to examine the thermal behavior of Sn+KClO₃, Sn+KNO₃, and Sn+KClO₄ pyrotechnic systems and the results were compared with thermal characteristics of individual constituents. TG curves for tin powder, heated alone in air, showed a relatively slow oxidation above 570 °C. From thermal results the decomposition temperatures of KClO₃, KClO₄, and KNO₃, in nitrogen atmosphere, were measured at 472, 592 and 700 °C, respectively. For the Sn+KNO₃ pyrotechnic system, the tin oxidation was completed within the range of 480 to 500 °C. Replacing KNO₃ with KClO₄ led to an increase of thermal stability of the pyrotechnic mixture. Among above‐mentioned pyrotechnic mixtures, Sn+KClO₃ has the lowest ignition temperature at about 390 °C. The apparent activation energy (E), ΔG^#, ΔH^# and ΔS^# of the combustion processes were obtained from the DSC experiments. Based on these kinetic data and ignition temperatures, the relative reactivity of these mixtures was found to obey in the following order: Sn+KClO₃>Sn+KNO₃>Sn+KClO₄.     

Studies of Free Field and Confined Explosions of Aluminium Enriched RDX Compositions

Research on the effect of aluminium contents and its particle size on free field and confined explosions characteristics of RDX‐based compositions containing 15–60% aluminium was carried out. Parameters of blast waves produced by charges of the investigated explosives detonating in an open space were measured by the use of piezoelectric gauges. Simultaneously, photodiode set‐ups were used to measure light output of the detonating charges. Quasi‐static pressure measurements were conducted in steel chambers of 0.15 and 7 m³ volume filled with air. Moreover, the heat of detonation was measured with a calorimetric set in a 5.6 dm³ bomb filled with argon. The results of QSP and detonation heat measurements were compared with those obtained from thermochemical calculations.     

Ion Chromatographic Analysis of Ammonium Dinitramide–Oxidizer for Propellant and Pyrotechnic Applications

Analysis of ammonium dinitramide (ADN), the advance rocket propellant oxidizer, in pure form as well as in mixtures was carried out by ion chromatography (IC). The purity of ammonium dinitramide was directly determined by estimating the dinitramide ions and indirectly by estimating the impurities. Both methods gave results comparable with those determined by Differential Scanning Calorimetry and UV spectroscopy. The chemical composition of ADN in mixtures containing nitrate, chromate, chlorate, perchlorate, and thiocyanate ions was quantitatively estimated in the same solution without any interferences or prior separation of analyte ions. The newly developed ion chromatographic methods for the analysis of ADN are simple and fast with good accuracy and precision when compared to other analytical techniques. The IC methods are found to be highly suitable for quality control analysis of ADN containing compositions and for the online process monitoring of the formation of ADN in the reaction mixture.     

The Development of a Confined Impact Test for Evaluating the Safety of Polymer‐Bonded Explosives During Warhead Penetration

During warhead penetration, which lasts several milliseconds, warheads undertake moderate pressures reaching hundreds of MPa. Previous methods have been unable to mimic such stimuli to evaluate the safety of ammunitions. Hence, new safety evaluation methods with moderate pressures and long durations to assess the stability of the explosive charges during actual penetrations are needed. Based on existing explosives safety estimation technologies and preliminary understanding of overload environments during penetration, a confined impact model was developed. The peak stimuli pressure is more than 0.3 GPa and the duration of the pressure is between 1 to 3 milliseconds. Various scales of a polymer‐bonded explosive (PBX‐9) were subjected to this confined impact test to study the response characteristics. The ignition mechanism of PBX‐9 was obtained by synthesizing results from X‐ray photoelectron spectroscopy (XPS), computed tomography (CT) scanning, differential scanning calorimetry (DSC) and thermalgravimetric analysis (TG). It was found that cracks formed on the surface during impact and the initial ignition of PBX‐9 is mainly due to the decomposition of Ammonium perchlorate (AP) and hydroxyl‐terminated polybutadiene (HTPB) on the interface at low temperature. Our study indicates that the designers of the PBX formulation should try to control the early decomposition of AP and HTPB in order to let the PBX survive the penetration.     

Ignition Characteristics of Ti/Teflon Pyrolants: Safety Igniter with Partition

By using partitions in smoke generators, luminous flame agents or other pyrotechnic agents, the vapor and sublimated materials are confined in a chamber. Titanium (Ti), polytetrafluoroethylene (Teflon), and Viton pyrolants (TTV), which generate high temperature products, can be used in a partition type igniter. The ignition delay time, τ_ig, decreased with the increase of the concentration of Ti, ξ(Ti), and also the physical ignition delay time, τ_p, decreased with the increase of ξ(Ti). On the other hand the chemical ignition delay time, τ_c, remained unchanged in the range of ξ(Ti) from 0.4 to 0.7. As τ_p of TTV pyrolants is larger than τ_c, the ignition delay time is dominated by physical processes.     

Development of MTV Compositions as Igniter for HTPB/AP Based Composite Propellants

MTV compositions were prepared by keeping the magnesium/Teflon ratio constant and increasing the Viton content of the mixture up to 14% by an increment of 2% to investigate the effect of binder content on the heat of explosion, which is found to increase with the increasing Viton percentage as the magnesium content concomitantly goes down toward the stoichiometric value. In the second part of the study, fuel-rich MTV compositions were prepared by changing the magnesium content and keeping the Viton fraction constant at a specific value to investigate the effect of magnesium content on the heat of explosion and combustion characteristics. The observed general trend is that the heat of explosion of MTV compositions decreases as the magnesium content increases. All the MTV compositions were tested in a closed vessel to measure the maximum pressure achieved and the rate of reaching this pressure. The ignition performance of three selected MTV compositions was examined in 2.75 inch rocket motor by using the same charge of igniter and the same HTPB/AP composite propellant of the equal amount in each test. Two of them have excellent ignition performance and, therefore, can be used as igniter for the HTPB/AP based composite rocket propellants.     

Development and Performance of the W/Sb2O3/KIO4/Lubricant Pyrotechnic Delay in the US Army Hand‐Held Signal

Gassy pyrotechnic delays composed of tungsten, antimony(III) oxide, potassium periodate, and various lubricants have been developed for use in the US Army hand‐held signal. The new compositions were developed to replace the current formulation, which contains potassium perchlorate and barium chromate, chemicals that are facing increasing scrutiny due to environmental regulation. The hand‐held signal delay housing was used to demonstrate the burning rate tunability of the new compositions. The addition of 1–5 % of waxy lubricants (stearic acid or calcium stearate) was found to have a profound effect on burning rate. The effect of tungsten content and the Sb₂O₃/KIO₄ ratio on burning rate was also probed. A wide range of inverse burning rates (2 to 15 s cm⁻¹) were demonstrated, which encompasses the 7 to 8.5 s cm⁻¹ range required by the hand‐held signal. The W/KIO₄ reaction produces I₂, which was observed by visible spectroscopy in the vapor above a sample of combustion residue.     

受限于碳纳米管中水分子微观结构的分子动力学模拟研究

利用分子动力学模拟研究受限于不同管径中水分子的微观结构,改变温度,做出受限水分子的径向分布函数图,并对比说明。通过做水分子在碳纳米管内的均方位移与时间关系图,利用Einstein法算出不同管径中水分子的扩散系数,与利用Knudsen扩散公式计算出的水分子的扩散系数进行比较。     

金属离子配位作用下PA6的受限结晶

采用熔融共混法,制备了聚酰胺6/氯化钙(PA6/CaCl2)复合材料。通过差示扫描量热法(DSC)、X射线衍射法(XRD)研究了PA6基体在受限条件下的非等温结晶及晶型转变行为。结果表明:金属离子Ca2+与酰胺基团的络合配位作用使PA6/CaCl2复合材料中PA6的结晶行为和结晶度受到了限制。随着CaCl2含量的增加,PA6的结晶度、结晶峰温度、熔融峰温度逐渐降低,结晶速率减小,结晶半峰宽增大,当CaCl2的含量大于8%时,PA6变为无定形态;此外,CaCl2的引入有利于PA6中α晶的生成。     

Experimental and Numerical Simulation Study of Heat Transfer Due to Confined Impinging Circular Jet

An experimental and numerical simulation study of heat transfer due to a confined impinging circular jet is presented. In this research, a stainless steel foil heated disk was used as the heat transfer surface of a simulated chip, and the thermocouples were mounted symmetrically along the diameter of the foil to measure the temperature distribution on the surface. Driven by a small pump, a circular air jet (1.5 mm and 1 mm in diameter) impinged on the heat‐transfer surface with middle and low Reynolds numbers. The parameters, such as Reynolds number and ratio of height‐to‐diameter, were changed to investigate the radial distribution of the Nusselt number and the characteristics of heat transfer in the stagnation region. Numerical computations were performed by using several different turbulence models. In wall bounded turbulent flows, near‐wall modeling is crucial. Therefore, the turbulence models enhanced wall treatment, such as the RNG κ‐? model, may be superior for modeling impingement flows. The numerical results showed reasonable agreement with the experimental data for local heat transfer coefficient distributions. The impinging jet may be an effective method to solve the cooling problem of high power density electronic packaging.     

An Investigation of the Performance of a Boron/Potassium‐Nitrate Based Pyrotechnic Igniter

The performance of a boron/potassium‐nitrate based pyrotechnic igniter, used as an initiator in airbag gas generators, was investigated at different initial temperatures. Igniter firings were conducted in a small vented combustion chamber in order to measure the instantaneous chamber pressures. A theoretical model, which considers multi‐phase products and lumped chamber parameters, was adopted to determine the discharging gas phase and condensed phase mass flow rates from the igniter. The data reduction model used experimentally obtained pressure‐time traces and the total burned mass as input data. The calculated instantaneous mass flow rates of the igniter at various initial temperatures showed that the initial temperature has a major influence on the igniter's performance. For the temperature range tested (−20 °C to 60 °C), the pressurization rate and the total mass flow rate of the igniter increased with temperature and ranged from 322 GPa/s to 721 GPa/s and 4.3 kg/s to 6.1 kg/s, respectively. It was found that the condensed‐phase products comprised the majority of the igniter discharge products. The mass fraction of the condensed‐phase products indicated a weak dependency on initial igniter temperature. Under similar test conditions, the recorded pressure‐time traces during igniter firings were found to be quite reproducible.     

减小高装填密度发射装药膛内压力波的实验研究

研究了两种能降低某大口径火炮高装填密度发射装药的膛内压力波的点传方案。第一种点传火方案是在制式点传火结构基础上增加横向传火具,增加点火药包;第二种点传火方案是改变制式传火结构为低爆速传火结构,同时增加横向传火具。高装填密度发射装药射击试验表明,这两种点传火方案均能满足点传火要求。第一种点传火方案较制式可燃中心传火管能实现迅速全面的点火,但出现了压力波增大的现象。而第二种点传火方案较第一种点传火方案的传火速度快,能迅速建立点火压力,发射药床的着火延迟时间小,最重要的是能抑制膛内有害压力波。压力波的频谱分析表明在高装填密度装药中,采用第二种点传火方案能削弱和抑制压力波的高频振荡成分,改善其振动特性。     

共晶体木糖醇/山梨醇的合成研究

研究了一种新型食品添加剂——共晶体木糖醇／山梨醇的合成及应用,考察了加入晶种的温度、晶种的量以及降温速度、搅拌速度对共晶体形成的影响,并验证了所得共晶体木糖醇／山梨醇产品的性能。结果表明：当山梨醇／木糖醇熔融物温度降至80℃时,加入熔融物质量分数为5％的晶种,控制搅拌速度在20r／min,使物料温度在1．5h后降至45℃,此时所得共晶体木糖醇／山梨醇(以n(山梨醇)：n(木糖醇)=65：35为例),吸潮性低,可压缩性好,压片后表面光滑,易于保存,容易满足客户要求。     

环氧树脂/再生非金属粉末复合材料性能研究

将废旧印制线路板回收非金属粉与环氧树脂混合制备得到了不同非金属粉含量的环氧树脂复合材料。研究表明:随着非金属粉的加入,环氧树脂复合材料的弯曲强度得到了显著提高,降低了复合材料的热膨胀系数,同时环氧复合材料的绝缘性没有恶化。采用非金属回收粉填充环氧树脂复合材料是一种可行的废旧线路板回收利用方式。     

气-质联用法检测韭菜中香味成分的研究

运用GC／MS条件,研究了韭叶石油醚提取物及氯仿提取物的化学成分,共发现10种含硫化合物,其中4种化合物首次从该植物中找到。其中主要香味成分为甲基硫代亚磺酸甲酯,通过仿生合成和探讨其波谱性质验证了其结构。     

中高温太阳光谱选择性吸收涂层的研究进展

近年来,中高温太阳光谱选择性吸收涂层(以下简称为中高温吸收涂层)的研制及其在工业上的应用成为人们日益关注的焦点。本文在分类总结中高温吸收涂层的基本类型、作用机理和制备方法的同时,介绍了国内外不少科研工作者的研究工作和最新成果,并对中高温吸收涂层的制备方法优缺点及其发展方向进行了探讨。     

大中型鼠笼式异步电动机起动方式的合理选择

鼠笼式异步电动机被广泛用于一般机械的动力驱动,但其起动冲击电流大,且会产生机械冲击。根据系统容量、鼠笼式异步电动机和生产机械的动热稳定性等条件,对电动机的实际起动参数进行计算,并根据计算结果合理选择电动机的起动方式。     

Preparation of TaB2-SiC oxidation protective coating for carbon materials by liquid phase sintering

To control the microstructure and amounts of TaB₂ phase in the TaB₂-SiC coating, a novel liquid phase sintering method was developed on the basis of in-situ reaction method to prepare the TaB₂-SiC coating, which includes synthesis of TaB₂ powders and further preparation of TaB₂-SiC coating. With Ta₂O₅, B₂O₃ and C employed as raw materials, hexagonal TaB₂ powders were prepared by carbothermal reduction method at 1500?°C, whose mean particle size is 491?nm. The TaB₂, SiC, C powders, and the low melting point phases Si and silica sol were used to prepare the TaB₂-SiC coating by liquid phase sintering at 2373?K. The thickness of the coating is about 350?µm. Compared with the SiC coating, the weight loss of the samples modified by TaB₂ decreased from 17.7% to 11.8%, and the average weight loss rate of the fastest weightloss zone reduced from ?6?×?10^?3 mg?cm^?2 s^?1 to ?5?×?10^?3 mg?cm^?2 s^?1. During oxidation, the Ta-oxides would gradually dissolve in the silicate glass to form Ta-Si-O glass ceramics with dendritic structure, which significantly improved the toughness and stability of the glass layer. The Ta-Si-O glass ceramics possesses the ability of sealing and arresting the microcracks, which can enhance the oxidation protective ability of the coating.     

CPVC/ABS/CPE三元共混体系的组成与性能关系研究

研究了氯化聚氯乙烯(CPVC)、丙烯腈-丁二烯-苯乙烯共聚物(ABS)和氯化聚乙烯(CPE)三元共混体系的组成与性能之间的关系。结果表明,ABS树脂可以有效降低CPVC/ABS/CPE三元共混体系的平衡扭矩,缩短三元共混体系的塑化时间,改善其流动性;当CPE含量固定、共混体系中CPVC与ABS的质量比为7:3时,共混体系的拉伸强度和缺口冲击强度达到最佳,共混体系具有较好的综合力学性能;随着CPE含量的增加,三元共混体系的缺口冲击强度显著提高,CPE对三元共混体系具有优良的增韧作用,用量以15份为宜。     

Development of a 68Ge/68Ga Generator to Avail 68Ga in Organic Medium for Industrial Radiotracer Applications

A chromatographic ⁶⁸Ge/⁶⁸Ga generator using nano zirconia as the sorbent matrix was developed to avail ⁶⁸Ga in an organic medium for industrial radiotracer applications. Acetylacetone was used as the eluent for the extractive desorption of ⁶⁸Ga ions from the sorbent phase. The effect of varying the amount of acetylacetone on ⁶⁸Ga yield and achieving ideal experimental conditions were studied. The major advantage of this generator is its ability to deliver ready to use “industrial ⁶⁸Ga tracer” with > 90% yield and high radionuclidic and radiochemical purity. The performance of the generator remained consistent on repeated elutions over a period of 1 year.