Application of Liquid Paraffin in Castable CL-20-Based PBX

Hydroxy-terminated polybutadiene (HTPB)/CL-20 castable explosives plasticized with liquid paraffin were processed successfully by a cast-curing method. The compatibility of liquid paraffin with CL-20, influence of liquid paraffin on CL-20 phase transition, and viscosity of the cast mixture were tested and analyzed. The thermal decomposition characteristics, thermal stability, mechanical sensitivity, and velocity of detonation (VOD) of the HTPB/CL-20 plastic-bonded explosives (PBXs) were also measured. The experimental results showed that liquid paraffin was well compatible with CL-20, and it did not have a distinct effect on the ?- to γ-phase transition of CL-20. In addition, the casting mixture was free-flowing with sufficiently low viscosity. When the content of CL-20 is 90% by weight, the measured VOD reached 8,775 m/s (density of 1.78 g/cm³), and the PBXs exhibited moderate mechanical sensitivity and good thermal stability.     

Preparation and Characterization of Nano-CL-20 Explosive

Nano-CL-20 was prepared via precipitative crystallization by spraying a solution of CL-20 in a solvent (ethyl acetate) into a nonsolvent (isooctane). Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) were used to characterize the appearance and the size of the particles. The results revealed that nano-CL-20 particles have the shape of spheres or ellipsoids with an average size of 95 nm. Due to their small diameter and high surface energy, the particles tended to agglomerate. Impact sensitivity of nanosize CL-20 was decreased in comparison to micrometer-size CL-20.     

Investigation on the Thermal Expansion of Four Polymorphs of Crystalline CL-20

The thermal expansion behaviors of α-CL-20 · 1/2H₂O, anhydrous α-, β-, ε-, and γ-CL-20 crystals have been investigated by means of variable-temperature X-ray powder diffraction (XRD) together with Rietveld refinement. The results show that hexanitrohexaazaisowurtane (CL-20) with four polymorphs exhibits linear thermal expansion. The ε phase performs approximately isotropic expansion in the temperature range of 30 to 130°C, but α, β, and γ phases exhibit anisotropic expansion in the temperature ranges of 30 to 130°C, 30 to 120°C, and 30 to 180°C, respectively. The different expansion behaviors are due to the different structures of the four polymorphs. The different thermal expansion behaviors of α-CL-20 · 1/2H₂O and anhydrous α are revealed in this work. The a-axis expansion of α-CL-20 · 1/2H₂O exhibits a switch from positive thermal expansion (PTE) to negative thermal expansion (NTE) at 90°C, whereas the a-axis of anhydrous α is resilient to PTE. The cause is the loss of the structural water. Moreover, it is easily found that the b-axis of the γ phase shows a constriction that may be attributed to the distortion of the six-membered ring.     

GAP/CL-20-Based Compound Explosive: A New Booster Formulation Used in a Small-Sized Initiation Network

With ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and glycidyl azide polymer (GAP) as the solid filler and binder, respectively, GAP/CL-20-based compound explosives were designed and prepared. Using micro injection charge technology, the compound explosives were packed into small grooves to explore their application in a small-sized initiation network. The detonation reliability, detonation velocity, mechanical sensitivity, shock sensitivity, and brisance of the explosive were measured and analyzed. The results show that when the solid content of CL-20 is 82 wt%, the explosive charged in the groove has a smooth surface from a macroscopic view. From a microscopic view, a coarse surface is bonded with many CL-20 particles by GAP binder. The GAP/CL-20-based explosive charge successfully generates detonation waves in a groove larger than 0.6 mm × 0.6 mm. When the charge density in the groove is 1.68 g·cm^?3 (90% theoretical maximum density), the detonation velocity reaches 7,290 m·s^?1. Moreover, this kind of explosive is characterized by low impact and shock sensitivity.     

Heteropolyacids: An Efficient Catalyst for Synthesis of CL-20

CL-20, a high-energy material with a cage-like structure, is considered the most powerful explosive today. It is usually prepared via nitration with concentrated nitric and sulfuric acid, but this technique pollutes the environment. In this article, CL-20 was synthesized by nitration of 2,6,8,12-tetraacetyl 2,4,6,8,10,12-hexaazatetracyclo[5,5,0,0^3,11,0^5,9]dodecane (TAIW) using a clean nitrating agent, heteropolyacids. Using the new nitrating agent caused the elimination of concentrated sulfuric acid during the reaction. This is an environmentally friendly technique.     

Benzylamine-Free,Heavy-Metal-Free Synthesis of CL-20 via Hexa(1-propenyl)hexaazaisowurtzitane

Base-catalyzed isomerization of recently reported hexaallylhexaazaisowurtzitane produced a new derivative, hexa(1-propenyl)hexaazaisowurtzitane (HPIW). Photooxygenation of this intermediate by singlet oxygen oxidized most of the 1-propenyl substituents to formyl substituents. The course of this reaction of singlet oxygen with HPIW involves peroxide intermediates, which may include relatively stable macrocyclic (tetroxocane) derivatives. The resulting nitrolyzable polyformylhexaazaisowurtzitane was found to be a promisingly efficient new precursor to CL-20 (in a single preliminary experiment without any process development). The new intermediate HPIW also underwent direct nitrolysis to form CL-20, though not as efficiently as its photooxygenation product did.     

Preparation and Safety of Well-Dispersed RDX Particles Coated with Cured HTPB

HTPB/IPDI (hydroxyl terminated polybutadiene & Isophorone diisocyanate) and TNT (2,4,6-trinitrotoluene) were successively coated on RDX (hexogen) particles by solvent evaporation and aqueous slurry melting, respectively. When HTPB coated on RDX particles cured completely, TNT was removed by solvent dissolution and the well-dispersed RDX particles coated with cured HTPB were obtained successfully. SEM (scanning electron microscopy), TEM (transmission electron microscopy), XPS (X-ray photoelectron spectrometry), and laser granularity measurement were employed to characterize the coated samples, and the mechanical sensitivity and thermal stability were measured and analyzed. Results show that TNT on the outer layer effectively hinders the adhesion among the particles resulting from the curing of inner layer (i.e., HTPB and IPDI). The final coating particles disperse well and their mechanical sensitivity decreases significantly. When the covering amount of HTPB is 2 wt.%, drop height (H₅₀) of RDX increases from 37.2 to 66.5 cm and explosion probability (P) decreases from 92 to 16%. Compared with that of uncoated samples, the activation energy and self-ignition temperature of coated samples do not vary.     

Ab initio calculations of the NO2 fission for CL-20 conformers

NO₂ fission is regarded to be the most important initial decomposition process of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20). In this study, four CL-20 conformers based on the ε-CL-20 were obtained after the optimization at m062x/cc-pvtz level, and the bond length, bond order and bond dissociation energy of the N-N bonds were examined to investigate the stability of these bonds. In addition, the rate constants and activation energy of the NO₂ fission were evaluated using the microcanonical variational transition state theory (μVT). The calculation results have shown that N-N bonds in the case of pseudo-equatorial and axial of nitro groups are the most stable and the least stable, respectively, by evaluating the bond length, bond order and minimum energy path (MEP). The NO₂ fission rate constants are affected by not only the stability of N-N bonds but also the repulsion forces from the other nitro groups, and the fission process for pseudo-equatorial positioning of nitro groups is easier to be accelerated due to the increase of the repulsion forces. The decomposition of CL-20 conformer may mainly originate from the fission of the pseudo-equatorial positioning of nitro groups, especially for CL-20 III conformer because of the significant low activation energy.     

Recrystallization of CL-20 and HNFX from Solution for Rigorous Control of the Polymorph Type: Part II,Experimental Studies

The recrystallization of CL-20 and HNFX to form different polymorphs was investigated by employing various experimental analyses, including micro-crystallization under myriad conditions, novel means of crystallization, analysis of polymorphs using powder diffraction, and Rietveld analysis. In the investigation all three groups of solvents: polar protic, non-polar aprotic, and dipolar aprotic solvents were employed. These results are reported in two parts with the experimental results reported here and the mathematical modeling results reported in Part I of this paper. The conventional crystallization techniques included combinations of solvent and anti-solvent system (including high molecular weight polymer melts), combination of solvents, the use of habit modifiers, and seeding. Other recrystallization techniques, which were also investigated included recrystallization under UV, under microwaves, upon freeze drying, upon annealing, in the presence of high molecular weight polymers, and under different hydrodynamic and hence different micro-mixing conditions.

As will be seen in Part I of this paper (this issue) our computations suggest (in agreement with earlier studies) that multiple polymorphs with various densities for both CL-20 and HNFX are possible. However, the recrystallization studies reported here revealed only one type of polymorph for HNFX, i.e., the Ci R-3 polymorph. On the other hand, CL-20 gave rise to indeed multiple polymorphs which changed with the crystallization conditions, especially with the solvent/anti-solvent systems utilized. An X-ray based method was used to determine the types of polymorphs and also the percentages of the polymorphs generated upon crystallization. The presence of multiple polymorphs or polymorph impurities in CL-20 may have significant ramifications in the sensitivity and other ultimate properties of energetic grains containing CL-20. On the other hand the existence of only one low-density polymorph for HNFX significantly limits the application areas for HNFX.     

Synthesis,Characterization, and Thermal and Explosive Properties of Alkali Metal Salts of 5,7-Diamino-4,6-Dinitrobenzofuroxan (CL-14)

Potassium, rubidium, and cesium salts of 5,7-diamino-4,6-dinitrobenzofuroxan (CL-14) have been prepared by reacting sodium salt of 5,7-diamino-4,6-dinitrobenzofuroxan with alkali metal nitrate in an aqueous medium. The structure of the compounds was unequivocally confirmed by spectra data, elemental analyses, and estimation of metal content. Further, the compounds have been evaluated for explosive and thermal properties and found more suitable as compared to alkali metal salts of 4,6-dinitrobenzofuroxan (DNBF).     

超稳含硅介孔Al2O3及其催化裂化应用

利用水解正硅酸四乙酯对薄水铝石进行后修饰,通过焙烧可以得到含硅Al₂O₃。采用X射线衍射、红外、物理吸附、固体核磁共振、NH₃程序升温脱附等手段表征含硅Al₂O₃的孔道结构和酸性质。考察了含硅Al₂O₃的热稳定性和水热稳定性及其对烃类的催化裂化活性。结果表明,SiO₂主要以单层形式嫁接在γ-Al₂O₃表面Al-OH上,形成了Si-O-Al键,并大幅提高其对烃类的裂化活性。当1 nm2的γ-Al₂O₃表面含32个Si原子时,其对异丙基苯的催化裂化转化率为原料γ-Al₂O₃的27倍。在1100℃高温空气下焙烧,或在800℃高温水蒸气气氛下焙烧,含硅Al₂O₃的晶体结构和催化活性都能较好地保留。     

Synthesis and Characterization of a New Co-Crystal Explosive with High Energy and Good Sensitivity

A new energetic co-crystal consisting of one of the most powerful explosive molecules 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and the military explosive cyclotrimethylenetrinitramine (RDX) was prepared with a simple solvent evaporation method. Scanning electron microscopy (SEM) revealed the morphology of the bar-shaped product, which differed greatly from the morphology of the individual components. Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction spectrum (XRD), and differential scanning calorimetry (DSC) proved the formation of the co-crystal at the molecular level. The result of mechanical sensitivity test indicated the sensitivity was effectively reduced compared to raw CL-20. Finally, a possible crystallization mechanism was discussed.     

Preparation and Characterization of the Solid Spherical HMX/F2602 by the Suspension Spray-Drying Method

Solid spherical octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine/fluororubber2602 (HMX/F₂₆₀₂) was prepared by the suspension spray-drying method as follows: firstly, thinning octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was obtained by a solvent–anti-solvent method. Secondly, thinning HMX suspended in ethyl acetate solvent in a solution of a binder—F₂₆₀₂—was made into a suspension. Finally, the samples were prepared by spray drying. The samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), and Fourier transform infrared (FTIR), and its thermal stability as well as mechanical and spark sensitivities were measured. The results of SEM showed that the grain of HMX/F₂₆₀₂ was solid spherical and the particle distribution was homogeneous. The results of XPS indicated that F₂₆₀₂ can be successfully coated on the surface of HMX crystals. Compared to raw HMX, th characteristic drop height was increased from 19.60 to 40.37 cm, an increase of 79.10%. The friction sensitivities of HMX reduced from 100 to 28% and the spark sensitivity of HMX/F₂₆₀₂ increased. The critical explosion temperatures of raw HMX and HMX/F₂₆₀₂ were 275.43 and 274.30°C, respectively. The amount of gas evolution of raw HMX and HMX/F₂₆₀₂ was 0.15 and 0.12 ml·(5 g)^?1, respectively. The results of DSC and vacuum stability tests (VSTs) indicate that the thermal stability of HMX/F₂₆₀₂ was equal to that of raw HMX and HMX and F₂₆₀₂ had good compatibility.     

纳米SiO_2改性酚醛泡沫的制备及表征

分别以亲水型A200和疏水型R805两种纳米SiO2为增强剂,采用超声分散/高速剪切法,制备出纳米SiO2改性酚醛泡沫,对比了它们的泡体结构、压缩性能和热稳定性的差异。实验结果表明,两种纳米SiO2颗粒的化学结构基本相同,但R805纳米SiO2颗粒的表面接有含烷基的疏水层。当A200纳米SiO2质量分数分别为1.5%和1.0%时,改性酚醛泡沫的压缩强度和压缩模量达到最大值;R805纳米SiO2改性酚醛泡沫的压缩强度和压缩模量均下降。两者的初始热分解温度和残碳量均有一定程度的提高,但前者的初始分解温度较高,而后者的最终残碳量较多。改性酚醛泡沫的泡体结构、纳米SiO2与酚醛的界面结合优劣,对其压缩性能和热稳定性的增强起到了重要作用。     

二苄基甲苯的合成表征及热稳定性能的研究

通过GC,IR,NMR和TG等分析手段对实验室合成的二苄基甲苯进行了结构表征,并进行了理化性能测试和1000h的热稳定性实验。结果表明,合成的二苄基甲苯各项理化性能指标可以满足GB23971—2009的指标要求,通过了340℃的热稳定性实验,达到了L—QD340产品的质量指标要求。     

SO_4~(2-)改性的镧-锆双组分交联累托土固体酸催化剂的制备和表征

用镧-锆双组分交联剂交换Na基累托土中的水合钠离子,再引入SO42-作促进剂进行改性,制备了SO42-改性的镧-锆双组分交联累托土固体酸催化剂(SO42-/La-Zr-CLR)。采用XRD、TGA、DTA和IR等分析手段对催化剂进行了表征,考察了催化剂的制备条件对其催化活性的影响。实验结果表明,将La引入到Zr交联剂中,交联后得到的交联粘土热稳定性明显提高。以乙酸和正丁醇酯化反应作探针,催化剂的最佳制备条件为:交联剂中n(La)/n(Zr)=0.15,n(Zr)/m(Na-R)=3.5 mmol/g,焙烧温度600℃。在此条件下制得催化剂的乙酸转化率达到96.74％,反复再生4次后,乙酸转化率仅下降4.68％。     

改性炭黑制备工艺与性能研究

采用机械研磨的方法探讨了研磨时间、研磨介质、研磨介质类型对炭黑物理性能的研究,利用红外光谱仪、ASAP表面吸附仪对改性炭黑的显微组织形貌、表面结构、基团种类、孔道大小、孔容等进行了分析测试。结果表明:在相同工艺条件下,研磨时间是影响炭黑粒子结构改变的重要因素,研磨时间越长,炭黑粒子结构被改变的越多。研磨使炭黑粒聚结体结构被破坏,使表面基团的种类和数量发生改变,表面活性和极性增加,降低炭黑再附聚趋势,改善了炭黑的性能白炭黑复合改性炭黑性能实验结果表明:白炭黑添加量为10%的复相炭黑较白炭黑添加量为5%的复相炭黑性能优异     

机械球磨对沥青质分子结构及其调和油样临氢热转化生焦的影响

以塔河常压渣油(THAR)为原料,正己烷为溶剂分离出C6 沥青质(As)和脱沥青油(DAO)。将As进行球磨预处理后,回调至DAO中配制成含不同球磨时间沥青质的调和渣油,以此为原料进行临氢热转化实验。采用元素分析、1H NMR、13C NMR、XRD、SEM、FT IR、Raman和TG分析手段系统分析了球磨前后沥青质的分子结构、晶体结构、表面形貌、官能团、热解特性。结果表明,机械力作用可使沥青质颗粒明显细化,表面变得光滑平整,致密的堆积结构逐渐消失;同时,使其芳香核在横向和纵向上均发生了部分芳环的解聚,致使单元结构缔合度、片层结构有序度及残炭量降低,抑制了其在热作用下的缩合生焦倾向。另外,调和渣油临氢热转化反应产物中汽、柴油收率均呈先增加后不变的趋势,焦炭收率显著降低,由2366%降至1724%。     

Preparation and Properties of Surface-Coated HMX with Viton and Graphene Oxide

To improve the safety performance of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) particles, the new carbon material graphene oxide (GO) and Viton were used to coat HMX via a solvent–slurry process. For comparison, the HMX/Viton/graphite (HMX/Viton/G) and HMX/Viton composites were also prepared by the same process. Atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetry (DSC) were employed to characterize the morphology, composition, and thermal decomposition of samples. The impact sensitivity and shock wave sensitivity of HMX-based composites were also measured and analyzed. The results of SEM, XRD, and XPS indicate that the cladding layer of HMX-based composites is successfully constructed. HMX/Viton/GO composites exhibit better thermal stability compared to HMX and HMX/Viton. The results show that both impact and shock wave sensitivities of HMX/Viton/GO composites are much lower than that of HMX/Viton. In addition, GO sheets exhibit a better desensitizing effect than G sheets. These combined properties suggest that nano-GO has good compatibility with explosives and can be utilized as a desensitizer in HMX particles.