α/β-HMX混晶的机械感度和热分解性能

采用饱和溶液-冷却结晶法将β-HMX转化为α-HMX,并对α-HMX晶型进行了表征。研究了α-HMX对α-HMX和β-HMX组成混晶的机械感度和热分解性能的影响。结果表明,纯α-HMX的摩擦感度和撞击感度分别为100%和26.1cm,比纯β-HMX分别提高了14%和40.8%;纯α-HMX热分解反应的表观活化能为239.5kJ/mol,比纯β-HMX降低了4.1%。纯α-HMX的热分解反应放热量为1 063J/g,比纯β-HMX增加4.8%。随着混晶中α-HMX含量的增加,其摩擦感度和撞击感度升高,热分解反应的表观活化能降低,热分解放热量增大。     

几种多态含能材料构型转变的DFT研究

为了从分子层面上对含能材料不同分子构型间的转变情况有一个直观认识,借助Gaussian 09软件,运用密度泛函理论(DFT),采用TS算法搜寻β-RDX→α-RDX、γ-HMX→β-HMX、ε-CL-20→β-CL-20及β-FOX-7→α-FOX-7在分子构型转变过程中的过渡态结构,确定了它们的构型转变过程;并通过计算吉布斯自由能随构型转变路径的变化,比较多态含能材料分子构型转变的难易程度。结果表明,由亚稳晶型到稳定晶型的转变首先会越过过渡态,克服自由能能垒转变为亚稳态结构,实现β-RDX→α-RDX、γ-HMX→β-HMX、ε-CL-20→β-CL-20及β-FOX-7→α-FOX-7分子构型转变分别需要克服的自由能能垒分别为5.25、22.21、9.69和10.24kJ/mol。因此,常温常压下β-RDX→α-RDX、γ-HMX→β-HMX、ε-CL-20→β-CL-20及β-FOX-7→α-FOX-7构型转变的难度大小排序为:HMX>>FOX-7>CL-20>RDX。     

溶剂结晶法直接制备HMX粒度分级产品

在丙酮－乙酸乙酯溶剂中，加入醋酐法生产的粗品α-HMX，根据结晶，转晶原理，通过控制适当的工艺条件和恰当的操作方式，使α-HMX全部转化为β－HMX，同时直接制备出A、C、D、F四个不同粒度级别的产品。     

HMX晶体的习性变态研究

为改变醋酐法制备 HMX/RDX 的综合工艺中所制得 HMX 与 RDX 的混合物中的 HMX(α-HMX)的晶体习性,进行了 HMX 晶体的习性变态研究。经试验对比找到了 Sb_2O_3是 HMX 转晶的良好调节剂,为在硝解中直接得到β-HMX 晶体找到了新途径。     

HMX晶体的习性变态研究

为改变醋酐法制备 HMX/RDX 的综合工艺中所制得 HMX 与 RDX 的混合物中的 HMX(α-HMX)的晶体习性,进行了 HMX 晶体的习性变态研究。经试验对比找到了 Sb_2O_3是 HMX 转晶的良好调节剂,为在硝解中直接得到β-HMX 晶体找到了新途径。     

在硝酸-硝酸盐体系中DPT硝解反应的探索

本文主要在硝酸-硝酸锂,硝酸-硝酸锌,硝酸-硝酸钾,硝酸-硝酸铵-硝酸镁,硝酸-硝酸铵-硝酸钙等体系中,进行 DPT 硝解探索性试验。在硝酸-铵镁盐体系中,DPT 硝解成β-HMX 得率可达53%左右;硝酸-硝酸钾体系中,β-HMX得率可达46%左右;硝酸-硝酸钾-铵镁盐中,β-HMX 的得率可达50%左右,硝酸-硝酸铵及硝酸-硝酸钙铵复盐体系中,β-HMX 得率均达47%左右。     

在硝酸-硝酸盐体系中DPT硝解反应的探索

本文主要在硝酸-硝酸锂,硝酸-硝酸锌,硝酸-硝酸钾,硝酸-硝酸铵-硝酸镁,硝酸-硝酸铵-硝酸钙等体系中,进行 DPT 硝解探索性试验。在硝酸-铵镁盐体系中,DPT 硝解成β-HMX 得率可达53％左右;硝酸-硝酸钾体系中,β-HMX得率可达46％左右;硝酸-硝酸钾-铵镁盐中,β-HMX 的得率可达50％左右;硝酸-硝酸铵及硝酸-硝酸钙铵复盐体系中,β-HMX 得率均达47％左右。     

黑索今对变燃速发射药力学及燃烧性能的影响

变燃速发射药在其内层中添加高能硝铵炸药黑索今达到了内层快速燃烧的目的,同时黑索今的引入也影响了整体发射药的力学性能.通过抗拉强度、剪切强度的测试对比及密闭爆发器燃烧现象的比较,得出结论,随着黑索今含量的增加,变燃速发射药抗拉强度和剪切强度均减小,同时燃烧渐增性变优;随着黑索今粒度的变大,发射药抗拉强度减小,同时燃烧渐增性变差.     

近红外光谱法测定HMX中α-HMX杂质晶型的含量

为了快速检测HMX中杂质晶型α-HMX的含量,在制备建模样品的基础上,利用近红外光谱技术,采用偏最小二乘法建立了HMX光谱与其α-HMX杂质晶型含量的计算模型。讨论了建模样品的代表性、模型光谱范围的选择及模型的优化过程。结果表明,模型具有广泛代表性,最佳光谱范围为6 476~6 446cm-1和4 602~4 424cm-1,交互验证决定系数(R2)为0.996,参考值交互验证残差均方根(RMSECV)为0.20%;外部验证的残差均方根(RMSEP)为0.27%;该法误差均小于0.13%,标准偏差为0.1%;近红外光谱法操作简单、快速、无损、绿色环保,可用于HMX中α-HMX杂质晶型含量的检测。     

硝基胍发射药膛压温度系数α_p(t)初速温度系数α_(Vo)(t)偏高原因的剖析

前言硝基胍发射药爆温低、比容大,有高能低烧蚀的特性。我国自六十年代中期对硝基胍发射药进行了工艺、配方的研究,已在几种弹药上完成设计定型和生产定型。其膛压温度系数α_(p(t))一般均在15～20%,初速温度系数α_(Vo)(t))在3. 5～4. 5%,而国外 M30、 M30m 硝基胍发射药的α_(a(t))仅为6～10%,α_((Vo(t))为2. 0～2. 5%。此项明显差异虽不属发射药内弹道指标要求,但却影响了火炮战术技术性能的提高。本文着重从发射药所用原材料、成型工艺等方面所进行的试验加以分析,以三胍-11发射药为例,通过试验,查明了自制硝基胍发射药α_(p(t))、α_(Vo(t))偏高的原因,从而为提高自制硝基胍发射药的性能提供了重要依据。     

硝酸-水重结晶HMX工艺研究

硝酸-水（溶剂非溶剂法）重结晶β-HMX,通过优化工艺条件,制备出高能低感的球形化HMX晶体颗粒。实验结果表明,撞击感度与重结晶工艺密切相关。温度为5℃、搅拌速度为100r／min、稀释速率为0.375mL／min、静置时间为0min的条件下,重结晶出的HMX颗粒孔隙率较小,球形化程度较高,撞击感度较低。     

铜酞菁的晶相调整及后处理研究(I)——铜酞菁的晶相性质及调整方法

本文运用各种仪器和测试方法,对α-和β-铜酞菁颜料的晶体性质、晶相调整和颜料化方法进行了研究.发现不同晶相铜酞菁色光的差别本质在于晶体中的分子堆积形式不同.本文考察了酸溶法制α-铜酞菁颜料中稀释温度与颜料质量的关系.并找到了一些不使α-铜酞菁转相的有机溶剂,用这类溶剂回流处理α-铜酞菁颜料能提高颜料的质量.本文还探索了国外新的β-铜酞菁颜料化方法——晶种法.     

Structure formation in stretched sheets of poly(butylene terephthalate)

Crystalline and amorphous sheets of poly(butylene terephthalate) (PBT) were drawn in the temperature range of 20–150°C. The molecular orientation and the relative amount of α- and β-form crystals in the stretched sheets were studied by wide-angle X-ray diffraction (WAXD) and density measurements. When crystalline PBT sheets are drawn at lower temperatures, α-form crystals are partially transformed into β-form crystals. Both α- and β-form crystals are formed by drawing amorphous PBT sheets. The relative amount of α- and β-form crystals is much more sensitive to drawing temperature than to draw ratio. The α-form crystallinity is higher at higher drawing temperature and increases slightly with increasing draw ratio. The second moments of orientation functions of α- and β-form crystals increase with increasing draw ratio, and the increase of the orientation function is suppressed at higher draw ratio. The orientation function of α-form crystals is higher than that of β-form crystals in a same sample.     

The influence of stem conformation on the crystallization of isotactic polypropylene

The influence of stem conformation on the crystallization of i-PP is studied by growing α-form lamellae in melts of β-form lamellae at different temperatures. The melting of β-form lamellae and the crystallization of α-form lamellae is observed in situ at the interface of α- and β-form spherulites by AFM. The growth rate of α-form lamellae in the melt of β-form lamellae is much lower than that in the isotropic melt due to the stem conformation barrier, which originates from the difference in the α and β unit cell packing models.     

Wear properties of α- and α/β-SiAlON ceramics obtained by gas pressure sintering and spark plasma sintering

In this study, α- and α/β-SiAlON materials, doped with Y₂O₃ and Nd₂O₃, were sintered using two different sintering processes: spark plasma sintering (SPS) and gas pressure sintering (GPS). The wear and mechanical properties of the samples were compared related to the composition, additives and sintering processes. The results show that the hardness was not affected by the processing type whereas the toughness values were lower for spark plasma sintered materials than gas pressure sintered materials. This can be explained by the changed microstructure of the two different types of material. Additionally, α/β-SiAlON materials, sintered using gas pressure sintering, showed a lower wear than the spark plasma sintered materials. The results of the wear test were compared with β-Si₃N₄ materials and it was observed that α/β-SiAlON, sintered by GPS, has better wear properties than the tested β-Si₃N₄ materials.     

Some hydration studies of α-dicalcium silicate

Infrared spectroscopic and DTA examination of 1:1 mixes of stabilised α-dicalcium silicate and water over a three year period revealed that α-dicalcium silicate does possess hydraulic properties. Calcium silicate hydrate of a similar type to that formed from α'- and β-dicalcium silicate is produced, although the rate of formation is lower.     

The Effect of Monoglyceride Polymorphism on Cold-Flow Properties of Biodiesel Model Fuel

The cloud point (CP) of biodiesel refers to the temperature at which crystallization begins on cooling. However, solid precipitates are often formed at a temperature higher than the CP during storage. Such precipitates are known to consist largely of monoglycerides (MGs) as intermediate compounds. MGs have high melting points, which are detrimental to the cold‐flow properties of biodiesel. MGs have several polymorphic forms, including α, β′ and β, with different melting points (α < β′ < β), and this fact makes the behavior of biodiesel at low temperature complicated. In this study, the precipitation behavior of MGs in biodiesel is discussed focusing on polymorphism using 1‐monopalmitin and methyl oleate mixtures as a model biodiesel fuel. The CPs measured were close to the calculated solid‐liquid equilibrium curve for α‐type 1‐monopalmitin. However, precipitates formed at temperatures higher than the CP when the mixtures were held at temperatures lower than the equilibrium curve of the β′ form. This indicates that the β′ form causes a risk of precipitation at temperatures above the CP and that the CP is not a suitable indicator of the cold‐flow properties of biodiesel.     

Structure and electric properties of poly(vinylidene fluoride-tetrafluoroethylene) copolymer studied with density functional theory

The internal rotation, geometry, energy, vibrational spectra, dipole moments and molecular mean polarizabilities of poly(vinylidene fluoride-tetrafluoroethylene) (P(VDF-TeFE)) of α- and β-chain models were studied with density functional theory at B3PW91/6-31G(d) level and compared with those of poly(vinylidene fluoride) homopolymer and P(VDF-TrFE) copolymer. The electric properties, chain conformation and stability of the copolymer influenced by the chain length and TeFE content were examined. Based on the internal rotation curves of P(VDF-TeFE) dimer models (H[CH₂CF₂-CF₂CF₂]H and H[CF₂CH₂-CF₂CF₂]H), the conformational angles, relative stabilities of α- and β-conformation, and the transition energy barriers of β → α and α → β were discussed. The results show that the β-conformation is more stable than the α-conformation thermodynamically and the β → α transition in P(VDF-TeFE) is more difficult than that in PVDF. Thus the copolymer should be in favor of preventing the piezoelectric phase from depolarization. The ideal β-chains are curved with a radius of about 30 Å, which is very close to those in both PVDF and P(VDF-TrFE). Similar to P(VDF-TrFE), the α-chain P(VDF-TeFE) containing 0.50 mole fraction of TeFE is also a helical structure. However, the α-chain with 0.33-0.20 mole fraction of TeFE are almost linear in structure, which might be responsible for enhancing crystallinity of the copolymer. The contribution of average dipole moment per monomer unit in the β-chain is affected by the chain curvature and TeFE content, and there is a weakly parabolic dependence on the VDF content. The chain length and TeFE content will not significantly affect the mean polarizability per monomer unit. The calculations show that there are some characteristic vibrational modes that may be used in the identification of the α- and β-phase P(VDF-TeFE) with different TeFE contents.     

Efficient α/β-Bi2O3 composite for the sequential photodegradation of two-dyes mixture

A mixture of α/β-Bi₂O₃ and α-Bi₂O₃ powders were obtained by a simple solid state reaction–annealing route at 550 °C. The structure, optical properties and surface area of the commercial α and β-Bi₂O₃ and the synthesized α-phase and α/β-composite were well characterized by X-ray diffraction, diffuse reflectance spectra and N₂ physisorption. The annealed sample at 550 °C showed 20% of β-phase, forming a heterojunction of α/β-Bi₂O₃ whereas annealing at elevated temperature (650 °C) lead to the α-phase. Optical properties showed that the presence of the β-phase is mainly responsible for narrowing the energy band gap. The photocatalytic activity of the commercial α and β-Bi₂O₃ and the synthesized α-phase and α/β-composite were investigated in degradation of single dyes, Indigo Carmine (IC) and Rhodamine-B (RhB) under both UV and visible light-induced photocatalysis. For the best photocatalyst, the photodegradation in a two-dye mixture solution was systematically studied considering the type of dye, the adsorption capacity of the samples and the behavior of dye photodegradation. The photocatalytic performance of α/β-Bi₂O₃ was comparatively much higher than the commercial α and β-Bi₂O₃, indicating that better performance of efficient charge separation and transfer across α/β-Bi₂O₃ composite was obtained. Possible mechanism of the single dye and two-dye mixture degradation was given by using α/β-Bi₂O₃ composite.