分子动力学模拟研究温度对ε-CL-20结晶晶体形貌的影响

为了研究温度对六硝基六氮杂异伍兹烷(CL-20)在乙酸乙酯/三氯甲烷体系中结晶时晶体形貌的影响,采用分子动力学模拟方法,使用修正后附着能模型计算了CL-20晶体能量和晶习,对比了不同温度(293、303、313、323、333K)下CL-20晶体形貌模拟结果与实验结果。结果表明,温度可以显著改变CL-20晶体形貌;随着温度升高,CL-20晶体形貌趋于非球形化,293K下可以获得球形化程度更好的CL-20晶体;温度对不同晶面影响程度不同,(2 0 0)、(0 1 1)、(2 0-1)晶面生长易被温度影响,附着能绝对值较大,晶面生长速率快,在CL-20晶体表面面积占比减小,最终在CL-20晶体中无法保留;当温度为333K时,对(2 0-1)晶面的附着能影响较大,最终使该晶面在CL-20形貌中显露。     

水性聚丙烯酸酯顿感包覆CL-20

以CL-20(六硝基六氮杂异伍兹烷)为主体炸药、水性聚丙烯酸酯为胶粘剂,采用泥浆法制备了CL-20基PBX(聚合物粘接炸药)。通过FE-SEM(冷场发射扫描电镜)、XRD(X射线衍射)法对PBX的性能进行了表征。研究结果表明:泥浆法可使水性聚丙烯酸酯成功包覆在CL-20颗粒表面,包覆前后CL-20的晶型没有变化,包覆后CL-20的撞击感度明显降低,其热安定性更好。     

CL-20晶型ε→γ等温相变动力学

为研究多晶型炸药CL-20的晶相转变规律,采用原位漫反射红外光谱法研究了CL-20的晶型ε→γ等温相变动力学,通过ε-CL-20红外特征峰强度的降低表征相转变程度;采用Avrami-Erofeev方程描述了温度为160、165、170和175℃下CL-20晶型的ε→γ相转变程度-时间曲线,获得等温相变的动力学参数。结果表明,以相转变程度18%为转折点,相变过程可分为两个阶段并分别符合不同的动力学机理函数;当相转变程度为1%~18%时,其相变机理符合随机成核与生长(n=0.60~0.76)的Avrami-Erofeev方程,表观活化能(Ea)和指前因子ln(A/s~(-1))分别为150.6kJ/mol和38.1;当相转变程度为18%~94%时,其相变机理符合随机成核与生长(n=1.18~1.25)的Avrami-Erofeev方程,表观活化能(Ea)和指前因子ln(A/s~(-1))分别为289.4kJ/mol和74.7。     

超临界GAS的工艺条件对CL-20粒度和晶型的影响

采用超临界气体抗溶剂(GAS)技术的半连续-静态工艺制备出平均粒径721.9nm的亚微米级ε型六硝基六氮杂异戊兹烷(CL-20),探讨了工艺条件对CL-20粒径和晶型的影响,测试了CL-20细化前后的冲击波感度和撞击感度。得到制备亚微米级ε型CL-20的最佳工艺条件为:压力平均升高速率4.0MPa/min,溶液初始浓度8g/100mL,系统压力10.5MPa,系统温度50℃。亚微米级ε型CL-20冲击波感度的隔板值降低58.6%,撞击感度的特性落高值提高84.1%。     

奥克托今的转晶技术

研究了 HMX在废酸转晶中的主要影响因素 ,消除了在工艺中生成的类似 γ- HMX晶型的片状结晶 ,并探讨了其形成机制。     

六硝基六氮杂异伍兹烷在硝酸中的转晶

采用硝酸含水体系将α、γ-HNIW晶体转晶成-εHNIW晶体;用在线粒度仪实时监测HNIW晶体成核、生长的动力学过程;研究了降温、不溶溶剂水的加入、晶种的加入对ε-HNIW晶体析出的影响;用FTIR、SEM、激光粒度仪对转晶得到的样品进行了晶型、形貌及粒度分布的表征。结果表明:在温度低于64℃、有ε-HNIW晶种存在的条件下,通过降温和加入不溶溶剂水,可以转晶得到ε-HNIW晶体,得率98%。     

CL-20/FOX-7/蜡复合粒子的制备及性能研究

为了提高六硝基六氮杂异伍兹烷(CL-20)的安全性,采用水溶液-悬浮法将FOX-7、微晶蜡包覆在CL-20表面,制备了4种包覆样品;采用扫描电子显微镜法(SEM)、X-射线衍射法(XRD)、傅里叶变换红外光谱法(FTIR)、X射线光电子能谱法(XPS)、差示扫描量热法(DSC)、感度测试法对其微观形貌、晶型、结合方式、包覆效果、耐热性、摩擦感度进行了系统测试分析。结果表明,4种包覆样品均为物理复合,CL-20晶型未发生改变,其中水悬浮法制得的CL-20/FOX-7混合物与机械混合物相比,CL-20表面存在更多的FOX-7粒子,其包覆率为49.83%,热分解峰温为242.79℃,摩擦感度的临界载荷为168N;在混合物中加入微晶蜡后,复合粒子呈类球形,CL-20晶体几乎无外露,但微晶蜡加入的方式对复合粒子性能有较大影响,蜡外包样品的包覆率为64.73%,热分解峰温244.98℃,摩擦感度的临界载荷为360N,较蜡内包样品包覆率提升了5.03%,热分解峰温提升了2.31℃,摩擦感度的临界载荷提升了144N。表明采用FOX-7、微晶蜡可共同对CL-20进行包覆改性,且蜡外包的样品综合性能最好。     

基于纳米HNS及共晶技术高效降低CL-20感度的研究

以硬脂酸修饰的纳米六硝基茋(HNS)为表面活性剂，采用Pickering乳液法制备出CL-20-TNT共晶/HNS复合物(CL-20-TNT/HNS),并对其形貌、晶型、热分解性能和安全性能进行了表征。结果表明，Pickering乳液法制备的CL-20-TNT/HNS球形复合物粒径约为5μm, HNS均匀包覆在其表面；CL-20和TNT通过分子间相互作用形成了共晶；CL-20-TNT/HNS热分解峰温为251.5℃,较原料CL-20升高了8.1℃,其撞击感度H₅₀为68cm,远高于原料CL-20和CL-20/TNT/HNS三者的机械混合物，较大幅度地提高了CL-20的安全性能。采用的Pickering乳液法中基本不含非含能组分，与以非含能材料(如吐温、司班等)为表面活性剂制备的复合物相比，未降低CL-20-TNT共晶/HNS复合物的能量。     

β晶型聚丙烯的研究进展

对近年来在β晶型聚丙烯(PP)形态结构，影响β晶型含量的因素，β晶型成核剂，β晶型转变及β晶型PP性能等方面的研究工作进行了综述。添加成核剂可得到高含量的β晶型。与α晶型相比，β晶型PP的球晶尺寸大幅度减小，晶粒细化，具有良好的抗冲击性能和较高的热变形温度。     

CL-20结晶形貌的预测

为研究六硝基六氮杂异伍兹烷(CL-20)在真空和溶剂中的晶体形貌和生成机理,基于CL-20的晶胞参数和主要生长面,分别构建了CL-20晶体模型以及晶面和水、甲醇分子的六种吸附模型,用分子动力学模拟计算出溶剂分子与各晶面的吸附能,并据此修正各晶面的附着能,用附着能法对CL-20在真空、水和甲醇中的结晶形貌进行了预测,并与实验结果进行了对比。结果表明,真空中生长基元在晶面的极化程度越高,该面生长越快,且外形为长四棱柱;水和甲醇均会抑制各面的生长,且但程度不同,致使CL-20在水中结晶成扁平的六面体,在甲醇中为四棱柱。     

DFT Studies on a Series of Nitramines Containing Pyridine Ring

In this article, a series of nitramines containing pyridine ring were studied by density functional theory (DFT). The gas-phase heats of formation were predicted based on the isodesmic reactions and the condensed-phase heats of formation and heats of sublimation were estimated with the Politzer's approach. The detonation velocity and pressure were calculated using the empirical Kamlet-Jacobs equation. Many title compounds have better performance than RDX (hexahydro-1,3,5-trinitro-1,3,5-trizine) and HMX (1,3,5,7-tetranitro-1,3,5,7- tetraazacyclooctane). The impact sensitivity was evaluated with the characteristic height (h₅₀). It is found that most of the studied compounds have lower sensitivities than CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12- hexaazaisowurtzitane). The crystal structures were predicted with the molecular mechanics method and optimized by the CA-PZ local density approximation of DFT. Analysis of the crystal energy gap indicates I-13, II-1, III-1, and IV-1 are nearly conductors and other compounds are semiconductors. For I-1～I-8 and I-11, the largest contribution to the valence bands is mainly from the p states of the C and N atoms in the pyridine and fused ring and for the other compounds, from the p states of the C and N atoms in the amino group and pyridine.     

CL-20/DNT共晶炸药的制备及其性能研究

以丙酮为溶剂,通过蒸发结晶法制得六硝基六氮杂异伍兹烷(CL-20)/二硝基甲苯(DNT)共晶炸药。利用扫描电镜(SEM)、X射线衍射(XRD)和热重/差示量热法(TGA/DSC)研究了共晶炸药的形貌、结构和热分解特性,测试了CL-20/DNT共晶炸药的机械感度和5s爆发点温度,并计算了其爆轰性能。结果表明,共晶炸药的微观形貌不同于原料CL-20,呈条状晶体;衍射峰明显不同于CL-20/DNT物理混合物的衍射峰,表明有新物相生成。在DSC曲线上,CL-20/DNT共晶几乎没有DNT的熔化吸热峰,而CL-20/DNT物理混合物中有明显的熔化峰,且二者的放热峰峰形和峰位不同;与原料CL-20相比,共晶炸药的分解峰温提前了21℃,放热量(ΔH)和最大热流量(Qmax)分别增加了39%和104%。与CL-20/DNT物理混合物相比,共晶炸药的5s爆发点温度和表观活化能分别增加3.9℃和65.7kJ/mol,撞击感度降低88.9%,摩擦感度降低40%,说明共晶炸药热稳定性增强。CL-20/DNT共晶炸药的理论爆速达到8 340m/s。     

Aluminized nitramine-based nanocomposites: Manufacturing technique and structure study

A technique for producing ultrafine nitramine powders and aluminized nanocomposites based on them is described. Powders of RDX, HMX, and 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIWor CL-20) with an average crystal size of about 1 μm were produced by spray drying of solutions. Results of x-ray phase analysis showed that resulting nitramine was formed in an unstable crystalline phase state and the time of relaxation to an stable phase state is several tens of days. Experimental batches of explosive aluminized nanocomposites were produced by spray drying of a suspension of nanoaluminum (nAl) in a solution of nitramines with a mass content of nAl of 5, 15, and 25%. The effect of the composition of the barrier coating on nAl surfaces (an oxide coating, an organic coating based on unsaturated carboxylic acid, an organosilicon coating based on organosilazanes) and the nAl particle size on the structure of the nanocomposite product was studied. The effect of the suspension spraying conditions on the structure of nanocomposites is discussed.     

Optimization of the Synthesis of 2,4,6,8,10,12‐Hexaallyl‐ 2,4,6,8,10,12‐Hexaazaisowurtzitane

2,4,6,8,10,12‐Hexaallyl‐2,4,6,8,10,12‐hexaazaisowurtzitane (HALLIW) was obtained in a condensation reaction of glyoxal with allylamine in the presence of a protonic acid as a catalyst. Optimization of the synthesis was accomplished by means of a mathematical experiment planning theory with the steepest descent method. The effect of the following parameters was examined: process temperature, amount of the catalyst, amount of the solvent, glyoxal addition time, reaction time, and the ratio of the substrates. As a result of the study an improved yield was achieved from 20 to 66.5%. The highest yield for the reaction was found for the conditions (mole ratios relative to glyoxal): catalyst (formic acid) 0.1 : 1; solvents: acetonitrile 9.35 : 1, water 0.18 : 1; allylamine 2.2 : 1; temperature 15 °C; glyoxal addition time 15 min, reaction time 60 min. The studies were conducted on a small laboratory scale where the yield and purity of the product obtained were examined. A method was developed for purification of HALLIW. NMR, IR spectroscopy, DSC, and TG analyses were employed in the study and their results are reported.     

EPDM对CL-20的包覆及表征

以CL-20为主体炸药、EPDM为黏结剂,采用水悬浮法制备了CL-20基PBX炸药,用SEM、XRD和FT-IR对产物进行了表征,并测试了其撞击感度和热安定性。结果表明,该包覆工艺可使EPDM成功地包覆在CL-20表面,在包覆过程中CL-20晶型没有发生变化。与原料CL-20相比,包覆样品的撞击感度明显降低,特性落高由15.9cm提高到40.7cm,热安定性更好。     

拉伸聚丙烯的相转变

用广角X射线衍射考察了不同晶型的IPP单轴拉伸时的相转变情况。发现提高拉伸速率和减小拉伸比不利于α晶相向近晶相的转化,β晶型IPP拉伸后仍含有β晶相,而近晶型IPP拉伸后仅能得到近晶相。由此表明,拉伸样品对起始形态有"记忆"效应,该结果符合拉伸中结晶结构的转化是含片层的倾斜及沿分子链方向的剪切形变模型而不符合熔融重结晶形变机理。     

高压下CL-20拉曼光谱和红外光谱相变研究

为了更好地认识和了解CL-20晶体结构演变规律和相变行为,利用金刚石对顶砧超高压实验技术,在0~50GPa下,研究了高压下ε-CL-20的原位拉曼光谱和红外光谱。结果表明,CL-20晶体在整个加压过程中存在两个相变,第一个相变发生在4.2~7.5GPa,认为是ε相到对称性更低的γ相转变,相变产生的原因是在压强的作用下,笼环外的硝基方向发生改变,电子云密度重置导致的分子构型转变;第二个相变发生在14.2~18.9GPa,属于γ相到ζ相的晶体结构转变;卸压后,拉曼和红外光谱恢复常压状态,表明CL-20晶体在研究压强范围内的相变过程是可逆的。     

退火热处理对iPP片材固相拉伸强化效果的影响

对等规聚丙烯（iPP）片材在退火固相拉伸过程中的晶体转变过程进行了研究。X射线衍射（XRD）表征了结晶衍射峰，定量计算出β晶的相对含量；二维小角X射线散射（2D-SAXS）揭示了α?β 晶型转变过程；差示扫描量热仪（DSC）揭示了iPP的熔融性能。结果表明，iPP片材在固相拉伸过程中发生了晶型转移，XRD衍射曲线中出现了β晶典型衍射峰β（300），2D-SAXS图中出现了取向串晶结构；在110 ℃拉伸作用下能够产生相对高β晶含量的iPP，最高含量为6.75 %；拉伸强度的增加幅度不大但其缺口冲击韧性显著提高；对固相拉伸作用后的iPP片材进行了退火处理，表明退火温度在110 ℃前串晶结构不会受到破坏，超过110 ℃退火后串晶结构被破坏再次形成球晶结构。     

Phase transformation and dielectric properties of polyvinylidene fluoride/organic-montmorillonite nanocomposites fabricated under elongational flow field

Compounding montmorillonite (MMT) with polymorphic polyvinylidene fluoride (PVDF) by melt intercalation method can induce the crystal phase transformation of PVDF, which is of great significance to obtain the electroactive PVDF. In this research, PVDF/Organic-Montmorillonite (OMMT) nanocomposites were prepared by a novel vane mixer, which was dominated by the elongational flow field in the whole plasticizing. The dispersion of OMMT, the crystal phase transformation of PVDF, and the resulting properties of nanocomposites were experimentally studied. The results of TEM and WAXD evidenced that homogeneous dispersion and desirable intercalation structure of OMMT were formed in the PVDF matrix under the effect of the elongational flow field. WAXD, FTIR, and DSC tests demonstrated that large amounts of β-phase of PVDF was formed due to the introduction of OMMT. The intercalation structure of OMMT and the crystal transformation of PVDF increased the dielectric constant and piezoelectric properties of nanocomposites, while the dielectric loss still maintained at a very low level. Finally, the effect of unique ''double-layer peeling'' mechanism of OMMT on the properties of nanocomposites was discussed.