Stability, detonation properties and pyrolysis mechanisms of polynitrotriprismanes C6H6-n（NO2）n （n=1-6）

To further test whether polynitriprismanes are capable of being potential high energy density materials (HEDMs), extensive theoretical calculations were carried out to investigate on a series of polynitrotriprismanes (PNNPs): C₆H_6−n (NO₂) _n (n=1−6). Heats of formation (HOFs), strain energies (SE), and disproportionation energy (DE) were obtained using B3LYP/6-311+G(2df, 2p)//B3LYP/6-31G* method by designing different isodesmic reactions, respectively. Detonation properties of PNNPs were obtained by the well-known KAMLET-JACOBS equations, using the predicted densities (ρ) obtained by Monte Carlo method and HOFs. It is found that they increase as the number of nitro groups n varies from 1 to 6, and PNNPs with n≥4 have excellent detonation properties. The relative stability and the pyrolysis mechanism of PNNPs were evaluated by the calculated bond dissociation energy (BDE). The comparison of BDE suggests that rupturing the C-C bond is the trigger for thermolysis of PNNPs. The computed BDE for cleavage of C-C bond (88.5 kJ/mol) further demonstrates that only the hexa-nitrotriprismane can be considered to be the target of HEDMs.     

方解石表面结构影响水分子吸附的微观机理

为研究方解石表面结构对水分子吸附的影响规律和机理,首先利用分子动力学模拟研究水分子在不同类型、不同尺寸的表面结构处的吸附特征,分析其对水分子吸附的影响规律. 而后利用分子动力学模拟研究水分子在发育表面缺陷的纳米狭缝中的吸附规律,解释纳米狭缝中的水锁现象. 最终,结合悬键特征和表面能理论定量解释水分子在不同表面结构处差异性吸附的机理. 研究结果表明:表面结构对于水分子吸附具有重要影响,水分子优先在表面结构处聚集吸附,吸附强度与密度远高于理想表面处; 表面结构的尺寸对水分子吸附有较大影响,尺寸越大对水分子吸附越强;纳米狭缝中水分子在表面凸起和空位处快速聚集,形成的吸附凸起结合为水膜阻断流动空间,水锁作用明显;空位表面、凸起表面和理想表面对应的悬键密度和表面能依次为7.275 nm^-2和0.734 J/m²、6.716 m^-2和0.721 J/m²、5.098 nm^-2和0.581 J/m². 空位表面和凸起表面具有更多的反应活性位点、更强的反应活性,因此,水分子优先吸附于空位表面和凸起表面.     

Development of high-energy-density materials

The performance of an energetic compound is mainly decided by parameters such as density, oxygen balance, heat of formation,and stability. Among these properties, density is the most important factor because it determines the detonation pressure and velocity. One of the trends in the development of high-energy-density materials(HEDMs) involves the study of energetic materials with high nitrogen levels. A compound with high nitrogen content can obtain substantial energy from the heat of formation rather than from the intramolecular oxidation of carbon skeleton to release energy in the form of a nitro group or nitrate ester. In addition to excellent performance, the newly developed energetic materials should also possess high working power and insensitivity toward external influences for ensuring the safety of charge and service, high energy release rate, long service life,good compatibility, excellent biological performance, low toxicity, safe battlefield environment, and low moisture absorption,which meet the requirements of military and civilian use. This review summarizes the research progress on global HEDMs.TNAZ, FOX-7, octanitrocubanane, TAM, TKX-50, and N5 were believed to show promise in achieving application goals. The prospective vision of HEDMs containing ions, total nitrogen, metal hydrogen, and nuclear energetic isomers, overcoming technical barriers, synthesis of all-nitrogen materials, theoretical studies on desorption/adsorption system, and challenging technical problems that need to be solved for the safety of synthetic nitrogen compounds were discussed to further elucidate the effect of this subject.     

高能炸药爆轰过程的广义插值物质点法模拟

针对运用标准物质点法(MPM)对高能炸药爆轰过程进行数值模拟时,由于跨网格误差的存在,求解精度较低,计算稳定性较差等不足,将一种新算法——广义插值物质点法(GIMP)扩展到此类问题的数值模拟中.爆轰气体采用无粘性流体模型来描述,并假设整个爆轰过程是绝热的,建立了欧拉形式的控制方程.高能炸药选用TNT,并采用JWL状态方程进行描述.采用GIMP方法分别对一维板条TNT爆轰和二维聚能装药爆轰进行了数值计算,给出了TNT板条起爆后几个典型时刻的密度、内能和压力分布曲线以及聚能装药爆轰过程中速度矢量图和压力分布云图,成功捕获了聚能装药爆轰过程中的主要物理特征.数值计算结果表明,GIMP比标准MPM在计算精度以及稳定性上都有很大的提高,能够很好地模拟高能炸药的爆轰过程.     

双酚A与双酚B的理论研究

利用量子化学密度泛函理论,采用B3LYP方法在6-311++G(d,p)水平上计算了双酚A的分子结构和电子结构。通过对双酚A的几何构型、键级、光谱、净电荷布局等进行分析,结合前线轨道理论探究了分子的稳定性和反应活性,同理推导了双酚B的相关性质。利用不同的计算方法探究2种分子的热力学性质,同时给出不同温度的热力学性质参数,为进一步的实验研究做有益的理论补充。     

应变速率对注浆体力学特性影响规律

为研究微震荷载作用下注浆加固体力学特性,以裂隙倾角30°、宽度4 mm的红砂岩裂隙注浆体为研究对象,借助岩石三轴伺服压力机进行变应变速率(10^-5 ~5×10^-3 s^-1)单轴压缩试验;然后从能量耗散、裂纹扩展及破坏形态等3个方面,分析变应变速率对注浆体力学特性的影响规律及机理. 研究表明:随着应变速率的增加,注浆体的峰值强度、弹性模量均随之而增大;且峰值强度与应变速率呈指数函数关系变化;注浆体受应变速率影响的响应分为敏感应变速率阶段和滞缓应变速率阶段,主要差异在于峰值强度变化率和弹性模量变化率;随着应变速率的增大,注浆体的总能量在增大;压密阶段是影响不同应变速率下注浆体力学特性的主要阶段;敏感应变速率阶段和滞缓应变率阶段中的压密阶段主要区别在于积散比大小,积散比进一步决定产生裂纹的多少和分布区域与规律;耗散能密度对注浆体破坏脱落面积以及粒径分布影响较大,耗散能密度越大,碎块越以大块为主(粒径大的比率逐渐增加),滞缓应变率阶段耗散能密度较敏感应变率阶段大,其破碎块体较敏感应变率阶段大. 研究在裂隙注浆加固体的变应变速率影响下力学特性,从能理原理、分形理论角度得到了其影响机理.     

表面活性剂对HMX重结晶形貌的影响

以丙酮、乙酸乙酯、二甲亚砜（DMSO）、丁内酯和乙腈为溶剂,水为反溶剂,采用溶剂-反溶剂法研究不同溶液体系中表面活性剂十六烷基三甲基氯化铵（1631）、山梨糖醇酐单油酸酯（斯潘80）及聚氧乙烯山梨醇酐单月桂酸酯（吐温20）对1,3,5,7-四硝基-1,3,5,7-四氮杂环辛烷（奥克托今,亦称HMX）结晶形貌的影响,并对影响机理进行讨论。实验结果表明,表面活性剂对HMX结晶形貌有显著影响,其中十六烷基三甲基氯化铵在大多数结晶体系中是一种更好的晶形控制剂。     

Oxygen adsorption on pyrite （100） surface by density functional theory

Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studiedby using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe^2 and S^2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.     

Effect of aluminum addition on microstructure and properties of SiO<Subscript>2</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO vitrified bond

Influence of aluminum addition on the structures and properties of SiO₂-B₂O₃-Al₂O₃-CaO vitrified bond at low sintering temperature and high strength was discussed. FTIR and XRD analyses were used to characterize the structures of the basic vitrified bond with different contents of aluminum. The bending strength and the thermal expansion coefficients were also tested. Meanwhile, the microstructures of composite specimens at sintering temperature of 660 °C were observed by scanning electron microscope (SEM). The experimental results showed that the properties of vitrified bond with 1wt% aluminum were improved significantly, where the bending strength, Rockwell hardness, and thermal expansion coefficient of the vitrified bond reached 132 MPa, 63 HRB, and 6.73×10^-6 °C^-1, respectively.     

Mechanism of Fixation of Ozone and Its Medical Value

Because of both ozone gas and ozone solution are instable which limits the application of ozone, to solve the storage problem, it is necessary to find a kind ofideal ozone carrier which can combine ozone as an "ozonic compound" in which the bond strength between ozone and carrier should not be too high or too low, to appropriately release ozone from the ozonic compound. Combining Criegee's three-step reaction mechanism of ozone and olefins, the charge, covalent bond levels and energy levels of ozone, ethylene, butadiene and their ozonic compounds were calculated by the first-principles calculation method based on density functional theory methods. The stability of the ozonide, or the bond strength between ozone and ions of carrier were controlled felicitously to release ozone from the ozonide with proper velocity. Ozone antimicrobial was composed on the above principle. It can be used conveniently, especially for common families.     

Surface modification of magnesium hydroxide by γ-aminopropyltriethoxysilane

Magnesium hydroxide（MH）,which is commonly used as a halogen-free flame retardant filler in composite materials,was modified by silanization reaction with γ-aminopropyltriethoxysilane （γ-APS） in aqueous solution at different pH values （pH range from 8.0 to 12.0）. The surface properties of grafted γ-APS on MH surface as a function of solution pH value were studied using elemental analysis,Fourier transform infrared spectroscopy and zeta potential measurement. The results show that hydrolysis and condensation of γ-APS are activated in alkaline solution and lead to multilayer adsorption of γ-APS molecules on the surface of MH. The type of adsorption orientation of γ-APS on MH surface is a function of coverage density that is altered by changing solution pH value. At low coverage density （e.g. 55 nm^-2）,γ-APS molecules are preferentially adsorbed to the surface with the silicon moiety towards the surface,and increasing coverage density （e.g. 90 nm^-2） leads to parallel orientation. At an even higher coverage density （e.g. 115 nm^-2）,γ-APS molecules bond to the surface with the amino moiety towards the surface.     

超高性能轻质混凝土的力学性能及微观结构

超高性能轻质混凝土(ultra-high performance lightweight concrete,UHPLC)是一种由高强水泥浆体、漂珠和纤维组成的密度低于1 950 kg/m~3的新型水泥基结构材料。本文研究了不同养护制度及养护龄期对UHPLC抗压强度、轴拉力学性能和弯曲性能的影响,最后利用扫描电镜观察了UHPLC中漂珠的微观形貌。结果表明:随着龄期增长,UHPLC的抗压强度、轴拉性能和弯曲性能均提高,并出现明显的应变强化现象,说明养护龄期对UHPLC基体强度和纤维-UHPLC基体的界面黏结强度均有显著提高作用;高温蒸汽养护3 d可促进UHPLC基体早期强度发展,使UHPLC的抗压强度和弯曲性能迅速达到标准养护28 d时的水平,显著缩短养护龄期,但对纤维-基体界面黏结强度的贡献不大,黏结强度仍主要受龄期影响;UHPLC实测密度为1 815.2 kg/m~3,100 mm立方体抗压强度达103.1 MPa,极限抗拉强度达7.60 MPa,极限拉应变达0.431%,出现明显的应变强化现象,弯曲峰值强度达22.43 MPa,满足了RPC160的抗折强度要求,实现了水泥基结构材料轻质高强的目标。     

Extraction Difficulty of Lithium Ions from Various Crystal Planes of Lithium Titanate

To study the extraction difficulty of lithium ions from various crystal planes of Li₂TiO₃, according to the first principle, four representative crystal surfaces of Li₂TiO₃ (precursor), (-133), (-206), (002) and (-131), were selected to establish a model and to calculate the surface energy, bond length and population using Materials Studio 5.5 (MS 5.5). The results demonstrate that there is no direct relationship between the surface energy and the order of disappearance of the four diffraction peaks when lithium titanate is treated with hydrochloric acid, instead, the difficulty of Li⁺ extraction from various crystal faces corresponds to the Li-O bond strength. Lithium ion is easy to remove from (-133) and (-206) due to the relatively weak Li-O bond strength. In contrast, Li⁺ extraction requires a longer time for (002) and (-131).     

Effect of Nb on plasticity and oxidation behavior of TiAlNb intermetallic compound by density functional theory

Based on the pseudo potential plane-wave method of density functional theory (DFT), Ti_1−x Nb _x Al ( _x =0, 0.062 5, 0.083 3, 0.125, 0.250) crystals’ geometry structure, elastic constants, electronic structure and Mulliken populations were calculated, and the effects of doping on the geometric structure, electronic structure and bond strength were systematically analyzed. The results show that the influence of Nb on the geometric structure is little in terms of the plasticity, and with the increase of Nb content, the covalent bond strength remarkably reduces, and Ti-Al, Nb-M (M=Ti, Al) and other hybrid bonds enhance; meanwhile, the peak district increases and the pseudo-energy gap first decreases and then increases, the overall band structure narrows, the covalent bond and direction of bonds reduce. The population analysis also shows that the results are consistent with the electronic structure analysis. The density of states of TiAlNb shows that Nb doping can enhance the activity of Al and benefit the form of Al₂O₃ film. All the calculations reveal that the room temperature plasticity and the antioxidation properties of the compounds can be improved with the Nb content of 8.33%–12.5% (mole fraction).     

Ti-Al金属间化合物的力热性能及其能带计算

为了比较Ti-Al合金中主要合金相的力热性能和电子结构的差异,对Ti-Al合金中的TiAl、TiAl_2、TiAl_3与Ti3Al金属间化合物的生成热、结合能、弹性系数、电子能带和电子态密度进行了计算,且计算中采用了基于密度泛函理论的第一性原理以及Materials Studio软件中的CASTEP软件包.结果表明,4种金属间化合物中Ti3Al相的合金化形成能力最强,结构也最稳定,Ti3Al相呈韧性,且抗变形能力和刚性最强.4种金属间化合物均无能量禁带,均属于金属性材料,其中Ti3Al相金属性最强,Ti A13相金属性最弱.     

低温等离子体点火乙炔／空气爆震特性试验

为研究交流驱动低温等离子体点火触发爆震特性,在长1.5 m、内径60 mm的爆震管上,以乙炔为燃料,空气为氧化剂,按分压法配气,通过循环,使爆震管内混气混合均匀,进行气相单次爆震实验.采用交流驱动低温等离子体点火,单次放电时间0.5 ms,放电能量约为0.2 J.在点火的同时,用压力传感器和离子探针同时采集爆震管内的压力波和火焰传播特性.实验表明:交流驱动低温等离子体实现了乙炔/空气点火起爆过程,余气系数0.6及1.0混气产生很强的爆震波,余气系数下降,混气压力下降,爆震波传播速度和峰值压力下降,DDT距离和时间增加;余气系数1.4混气不能产生爆震波.     

1,1,3,3-四硝基环丁烷生成热和爆轰参数的计算

在密度泛函理论（DFT）B3LYP/6-31G水平下,选择环丁烷作为母体,结合等键反应,精确计算了1,1,3,3-四硝基环丁烷（TNCB）生成热与燃烧焓,并根据Kamlet假设对TNCB的爆轰参数进行了计算,计算结果表明TNCB的爆速、爆热、爆压均比较高,表明TNCB可能是一种优良的新型含能材料。     

脉冲爆震火箭发动机模型实验研究

阐述了脉冲爆震火箭发动机的工作原理及其特点。设计并建立了整套脉冲爆震火箭发动机实验模型。以液体燃料航空煤油为燃料、氧气为氧化剂、压缩氮气为隔离气体，在内径为25mm，长度为0．8m的爆震管内产生了充分发展的爆震波。测量了不同工作频率下的爆震波压力，并对其进行了分析。实验结果表明，在设计的实验模型中，采用低的点火能量（50mJ）能够在较短的距离内产生充分发展的爆震波。     

Detonation Propagation Characteristics of Superposition Explosive Materials

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Energy consumption in rock fragmentation at intermediate strain rate

In order to determine the relationship among energy consumption of rock and its fragmentation, dynamic strength and strain rate, granite, sandstone and limestone specimens were chosen and tested on large-diameter split Hopkinson pressure bar (SHPB) equipment with half-sine waveform loading at the strain rates ranging from 40 to 150 s⁻¹. With recorded signals, the energy consumption, strain rate and dynamic strength were analyzed. And the fragmentation behaviors of specimens were investigated. The experimental results show that the energy consumption density of rock increases linearly with the total incident energy. The energy consumption density is of an exponent relationship with the average size of rock fragments. The higher the energy consumption density, the more serious the fragmentation, and the better the gradation of fragments. The energy consumption density takes a good logarithm relationship with the dynamic strength of rock. The dynamic strength of rock increases with the increase of strain rate, indicating higher strain rate sensitivity. Foundation item: Projects(50674107, 10472134, 50490274) supported by the National Natural Science Foundation of China