高纯硼粒子的包覆及其在高能富燃料推进剂中的应用

硼具有高热值和燃烧产物洁净等优点而广泛用于固体火箭冲压发动机的高能富燃料推进剂。硼在使用中存在点火和燃烧效率低、与黏合剂相容性差等缺点,最有效的解决方法是对硼粉进行包覆。详细介绍了用碳化硼、氟化锂、氟树脂、氟化石墨、高热值金属（如Ti、Mg和Al等）、TDI／TMP、GAP、PBT、HTPB、AP／KP、KNO,等包覆硼粒子的工艺及其在富燃料推进剂中的应用情况。不同包覆剂的作用机理不同,又各具特点。     

超细硼粉的氟化锂包覆

以LiOH、HF为主要原料,采用中和沉淀法对超细硼粉进行了表面包覆.研究了LiOH的浓度对包覆效果的影响.透射电镜、X-光电子能谱、酸度计、黏度计用于包覆效果分析.结果表明,硼粉颗粒表面包覆了均匀且致密的LiF薄膜,薄膜厚度25 nm.酸度及黏度测试结果表明,经LiF包覆后硼粉悬浊液体系的pH值明显增大,并有效地降低了HTPB体系的黏度.含包覆硼推进剂的点火延迟时间及燃烧残渣分析表明,含包覆硼粉的推进剂点火延迟时间明显缩短,由70.475 s减为23.585 s;包覆后推进剂中硼的燃烧效率明显提高,推进剂燃烧残渣中硼与B2O3的摩尔比由包覆前的37.5：1变为包覆后的3.1：1.     

硼粒子表面包覆对富燃料推进剂热分解特性的影响

借助于ＤＴＡ、ＴＧ、ＤＳＣ等热分析手段，研究了硼表面包覆对Ｂ／Ｍｇ／ＡＰ／ＨＴＰＢ富燃料推进剂热分解特性的影响。用于硼粒子表面包覆的材料有ＡＰ、ＫＰ及ＬｉＦ。为便于对比，对含未包覆硼的基础配方也作了相应分析。研究表明，硼包覆有助于提高硼粒子的反应活性，可促进燃料的热分解。从而对提高含硼富燃料推进剂的燃烧性能极为有利。     

含硼富燃料推进剂的技术现状与发展趋势

综述了国内外在硼粒子的点火、燃烧性能,硼粉的包覆、团聚造粒技术,硼粉处理对配方性能的影响,含硼富燃料推进剂配方及性能测试表征手段等方面的研究进展。总结了国内外含硼富燃料推进剂工程化应用的现状和存在的差距。     

CR244粘接型粉末氯丁橡胶的制备

用凝聚法制备出粉末粘接型氯丁橡胶(PCR244)。研究了包覆剂性质对PCR244粒径分布的影响，并用SEM对所得PCR244的形貌及断面进行了观察分析。研究表明，在CR244粉末化体系中，包覆剂必须具有一定的交联程度才能起粉末化作用。在研究范围内，包覆剂的θg对粒径小于0．9mm产物的成粉率几乎无影响，均达到98．6％以上。SEM分析表明，PCR244宏观粒子表面粗糙，粒子内外均分布着大量空隙，其形成过程可分为三个主要阶段，即在包覆剂作用下，首先由胶乳初级粒子聚结成次级粒子，再由次级粒子凝聚成团粒，最后团粒相互结合成宏观粒子PCR244。     

硼颗粒的包覆机理及工艺研究进展

阐述了不同包覆材料对硼颗粒的包覆机理,从5个方面总结了硼颗粒包覆材料的选取原则,包括:去除硼颗粒表面氧化膜、提高燃烧温度、降低硼的点火温度、提高表面相容性、催化硼颗粒的氧化反应。总结了沉淀法、表面反应包覆法、高分子吸附聚合法、气相包覆法和机械球磨法等多种硼颗粒包覆工艺的研究状况,分析并比较了不同工艺的作用机理和实际应用效果。介绍了现代硼颗粒表面包覆效果测试技术的特点和应用范围。评述了目前硼颗粒包覆技术的研究现状和不足,并对未来的研究方向进行了展望。     

超临界流体快速膨胀法粒子包覆技术喷嘴的设计

改进了RESS法粒子包覆技术中喷嘴的结构。改进后的喷嘴,其喷孔可调,克服了传统毛细喷嘴易堵管、喷出效率低及包覆不紧密的缺点;采用laval管作送粉喷管,使被包覆粒子以超音速喷出,极大的加强了被包覆粒子和包覆剂粒子的碰撞力度;通过添加内外反向旋流器,使被包覆粒子和包覆剂粒子在喷嘴出口处高速反向旋转碰撞,实现粒子的均匀包覆。     

非硫黄调节型粉末CR的制备与性能

采用凝聚包覆法制备非硫黄调节型粉末CR，研究包覆剂的玻璃化温度(L)和用量对粉末CR性能的影响，并对粉末CR的粒子形貌进行了分析。结果表明，采用L为55．3或84．2℃的包覆剂制备的粉末CR的平均粒径较小，且粒径分布较窄；随包覆剂用量的增大，粉末CR的平均粒径减小，硫化胶的物理性能提高SEM分析表明，粉末CR的宏观粒子由多颗细小的初级粒子聚集而成，宏观粒子中存在大小不一的空洞，这些空洞有利于粉末CR的快速干燥。     

超细硼粉的HTPB包覆

采用表面直接反应包覆及物理包覆法研究了硼粉的端羟基聚丁二烯(HTPB)的包覆技术,经过研究发现:经表面直接反应包覆法的包覆效果较好。研究了包覆方法和反应时间对包覆效果的影响。经过红外光谱、X-光电子能谱、透射电镜等对包覆效果进行了表征。结果表明,以苯为溶剂,于80℃经14 h的酯化反应后,以TDI为固化剂,于70～80℃固化处理后,可以成功地实现HTPB对硼粉的包覆。经透射电镜观察,包覆的硼粒子表面变得规整。     

酸化絮凝包覆法制备硫调节型粉末氯丁橡胶

采用酸化絮凝包覆法制备硫调节型粉末氯丁橡胶(PCR),采用均匀试验设计的方法研究了胶乳酸化后pH值、NaCl用量、羧酸钠用量和包覆剂用量对PCR粒子的析出时间、粒径分布及其硫化胶物理机械性能的影响,建立了酸化絮凝包覆法制备PCRS工艺的粉末化模型,发现DH为8．4时,可以获得最为均匀的粒径介于1～3mm之间的产物粒子,并通过逐步回归建立了制备工艺与产物最终性能之间的关系模型。SEM分析表明,PCR粒子具有多孔结构,这种结构为PCR粒子的快速干燥提供了良好的条件。能谱分析表明,酸化絮凝法制备的PCR表面的Ca含量较粒子内部要高,说明粒子的表面钙化是形成包覆和隔离的主要原因。     

Preparation and Properties of Boron‐Based Nano‐B/NiO Thermite

Boron particles have several major burning problems, such as incomplete combustion, poor ignitability, and a complex burning process in solid propellants. It is documented that the low ignitability and combustion efficiency of boron are caused by the oxidation of its surface. In order to improve the combustion efficiency of boron particles, a precipitation method was employed to prepare nanometer‐sized NiO and coat it on boron particles. The morphology and coating results of the B/NiO nanocomposite thermite were characterized using different approaches such as SEM, X‐ray Diffraction (XRD), and EDS. The results indicated that the boron particles were well distributed and coated completely by nanocomposite NiO. The B/NiO nanocomposite thermite reaction process was tested by TG‐DTA. The results showed that the reaction temperature of B/NiO particles is about 30 °C lower than that of boron particles. The B/NiO thermite and boron powder were added to Mg/PTFE propellant to be measured for their respective combustion performance. The results showed that the burning rate of the B/NiO‐Mg/PTFE propellant increased by 22.8–25.2 %, mass burning rate by 26.7–30.8 %, and combustion temperature increased by 8–56 °C compared to the B‐Mg/PTFE propellant. The above results indicate that NiO coating of boron particles has a significant effect on the combustion behavior and increases the combustion performance of the propellant compared with uncoated particles.     

三氢化铝稳定化方法研究进展

系统介绍了三氢化铝(α-AlH3)作为固体推进剂高能燃料的重要应用价值,和当前阻碍其广泛使用的两大因素。从提高α-AlH3的热稳定性出发,综述了导致α-AlH3不稳定的本征原因(热力学性质)和非本征原因(晶体品质和纯度),以及各种稳定化处理方法,包括表面包覆法、表面钝化法和掺杂法等;在此基础上,总结了α-AlH3各种稳定化方法的内在机理和热稳定性表征方法。对α-AlH3稳定化处理的发展方向和趋势进行了梳理,指出今后研究的重点方向为:探索有效的包覆层材料,在维持α-AlH3燃烧热值的基础上,提高其热稳定性及组分相容性;精确控制α-AlH3颗粒包覆层结构,提高稳定性和降低感度;进一步研究α-AlH3在固体推进剂中的稳定化机理。     

Role of Oxalic Acid in Promoting Ignition and Combustion of Boron: an Experimental and Theoretical Study

Boron is an attractive fuel for propellants and explosives because of its high energy density. However, its combustion is inhibited by the oxide layer that covers the particles. The use of oxalic acid as an additive was shown to promote boron oxidation. In this study, the thermodynamic model FactSage 6.2 and a laser ignition facility were used to investigate the effect of oxalic acid on the burning characteristics of boron particles. The results of the thermodynamic analyses show that oxalic acid can reduce B₂O₃(l) production during boron combustion. This enables removal of the the oxide film and promotes the burning of boron. However, only at high temperatures (>1500 K) H₂O(g) (produced from H₂C₂O₄) can react with B₂O₃ and remove the oxide film. The evolution of boron combustion flame takes place in three stages: ignition, stable combustion, and extinction; the bright yellow color in the flame indicates boron ignition, the bright white color indicates boron combustion, and the bright green color is interpreted as BO₂ emission. Addition of oxalic acid into boron powders can significantly promote boron ignition and combustion. The ignition delay time of the resulting mixture is reduced by 42.4 %, the combustion intensity is raised by 16.7 %, and the combustion efficiency of boron is increased by 21.5 percentage points. The mechanism of action of oxalic acid on enhancing the combustion of boron was studied by scanning electron microscopy.     

含AP包覆硼的富燃推进剂燃烧机理研究

通过微热电偶测温和火焰单幅照相技术测试了含硼富燃料推进剂燃烧波温度分布及燃烧火焰结构;用扫描电镜对熄火表面形貌进行了观察,并通过能谱仪进行局部元素分析;对DSC曲线进行积分,得到推进剂的凝相放热量;测量推进剂燃烧的爆热和低压燃速,获得了其低压燃烧特性和一次燃烧放热情况。结果表明,含AP包覆硼的推进剂燃烧更剧烈,推进剂的绝热火焰温度更高,AP包覆硼提高了含硼富燃料推进剂的凝相放热、爆热和低压燃速。初步确定了该类推进剂的燃烧过程,为建立含硼富燃料推进剂燃烧物理模型提供了依据。     

铝/有机氟化物复合物对含铝HTPB推进剂燃烧性能的影响

为研究有机氟化物(OF)对含铝HTPB固体推进剂燃烧性能的影响,采用球磨法制备了纳米和微米铝/有机氟化物复合物(nmAl/OF和μmAl/OF),将其作为复合添加剂替代微米铝粉加入HTPB推进剂中,并考察其对推进剂燃烧性能的影响。采用SEM、TEM、粒度分析等对nmAl/OF和μmAl/OF复合物及推进剂凝聚相燃烧产物进行了表征。结果表明,nmAl/OF和μmAl/OF复合物有不同的结合状态;添加OF、nmAl/OF和μmAl/OF后,推进剂的爆热值下降约2%;添加nmAl/OF的推进剂配方燃速最低,在3MPa时仅为6.28mm/s,添加OF和μmAl/OF体系的推进剂燃速压强指数相比于原配方降低约20%;添加nmAl/OF的推进剂配方凝聚相燃烧产物粒度(D_(50))比原配方降低约47%。     

阻燃剂包覆药与常规火药混合物的密闭爆发器燃烧试验及数值计算

采用高分子阻燃材料对多孔火药表面进行包覆处理,将包覆药与常规火药混合装填在密闭爆发器内进行点火燃烧实验,通过测量爆发器内火药燃气的压力变化规律来研究包覆药的延迟燃烧特性.建立了一个包含火药燃气与包覆层之间传热传质过程的火药延迟燃烧数学模型,并对包覆药的延迟燃烧过程进行了数值计算.结果表明,包覆药的延迟燃烧时间随着燃气压...     

Burning Rate – Pressure Relationship of NG‐PE‐PCP‐based High Energy Propellants

Nitramines are known to produce lower burning rates and higher pressure exponent (η) values. Studies on the burning rate and combustion behavior of advanced high‐energy NG/PE‐PCP/HMX/AP/Al based solid propellant processed by slurry cast route were carried out using varying percentages of HMX and AP. It was observed that propellant compositions containing only AP and Al loaded (total solids 75 %) in NG plasticized PE‐PCP binder produce comparatively lower pressure exponent (η) values similar to AP‐Al filled HTPB based composite propellants. However, energetic propellants containing high level of nitramine (40–60 %) produce high pressure exponent (0.8–0.9) values in the same pressure range. Incorporation of fine particle size AP (ca. 6 μm) and change in its concentration in the propellant composition reduces η value marginally and influences the burning rate. However, such compositions have higher friction sensitivity.     

Application of Cerimetric Methods for Determining the Metallic Aluminum Content in Ultrafine Aluminum Powders

Ultrafine (nano‐sized) aluminum is a promising component for solid propellants, gel propellants, explosives, etc. The work is focused upon a problem of determining active (metallic) aluminum content in nanoAl powders as one of the characteristics of their reactivity. It is shown that the high reactivity, the presence of either the gases adsorbed or coating matter on the particle surface restricts the traditionally used permanganatometric and volumetric analytic methods. A new technique determining the active aluminum content is presented. This is the adaptation of known cerimetric method based on the analytical reaction Ce⁴⁺+e⁻=Ce³⁺. The method can be applied for analysis of metallic aluminum in the probes of nanoAl (including ones with organic coating), as well as micron sized aluminum, and their condensed combustion products.