Thermal Decomposition of AMMO/AP Composite Propellants

Thermal decomposition of AMMO/AP composite propellants was studied by DTA, TGA and DSC in helium atmosphere. The effects of accelerated aging at 347 K for 370 days on decomposition kinetics were also measured. AMMO/AP propellant showed two different decomposition steps, which were mainly the AMMO binder decomposed region and the reaction of AP dominated region. These regions were separated at around 20 % weight loss point at the condition used in this study. AMMO binder decomposition and AP decomposition were strongly related each other. The heat generated by the AMMO binder decomposition initiated and accelerated the thermal decomposition of AP. Although both Fe₂O₃ and CFe activated the thermal decomposition of AMMO/AP propellants, CFe mainly accelerated the decomposition of AMMO binder and Fe₂O₃ catalyzed the AP reactions which consisted of the AP decomposition and the reaction between decomposed AP and decomposed AMMO binder. AMMO/AP composite propellants were thermally stable even after aging at 347 K for 370 days.     

BAMO/AMMO基ETPE的合成与性能

以3-溴甲基-3-甲基氧杂环丁烷(BrMMO)为单体,聚合形成溴代聚醚.叠氮溴代聚醚为叠氮聚醚PAMMO;以3,3-双叠氮甲基氧杂环丁烷(BAMO)为单体,直接开环聚合形成叠氮聚醚PBAMO.以四氢呋喃为溶剂,PBAMO为硬段预聚物,PAMMO为软段预聚物,甲苯二异氰酸酯(TDI)为二异氰酸酯单体,丁二醇氨酯型齐聚醇为扩链剂,按照一步法溶液聚合工艺,制成了数均分子量在25000左右的含能热塑性弹性体(ETPE).ETPE具有可熔可溶的特点,室温抗拉强度和延伸率约为5MPa和400%.     

Energetics of BAMO

3,3-Bis(azidomethyl)oxetane (BAMO) is a typical energetic azide polymer containing two N₃, bonds in the molecular structure. Since BAMO is a solidified polymer at room temperature, a liquid BAMO copolymer with tetrahydrofuran (THF) was synthesized in order to gain energetic binders for solid propellants. Various types of experiments were carried out to elucidate the decomposition and combustion processes of BAMO polymer, BAMO/THF copolymer, and crosslinked BAMO/THF copolymer. The heat produced by the decomposition is caused by the bond breakage of -N₃ to produce N₂, gas. The burning rate characteristics of crosslinked BAMO/THF copolymer depend largely on the mole fraction ratio of BAMO and THF.     

Mechanism of Catalytic Effects on AMMO/HMX Composite Propellants Combustion Rates

Thermal decomposition and the burning properties of AMMO/HMX propellants have been investigated. The heat generated by the AMMO decomposition initiated and accelerated the thermal decomposition of HMX, and the reaction between decomposed AMMO and HMX depended upon the heating rate. The rate determining step of the reaction path was different in higher and lower heating rate conditions. 2,2-bis(ethylferrocenyl)propane (CFe) and copper chromite (CuC) significantly altered the mechanisms of the thermal decomposition and the burning properties. CFe showed an increase in burning rate with a slight increase in burning rate exponent. However, CuC yielded high values for the burning rate exponent. The combined additive yielded the highest burning rate with the lowest burning rate exponent. The influence of CuC on the burning rate exponent disappeared by the combination with CFe. Though CFe and the combination additive improved the ignitability of the propellants, the propellant with CuC was difficult to ignite because of the relatively small quantity of heat feedback and/or heat released by the decomposition.     

BAMO/AMMO三嵌段共聚物的合成、表征及热分解动力学

以三氟化硼.乙醚/1,4丁二醇作引发体系,利用阳离子开环共聚合的方法合成出3,3′-双叠氮甲基环氧丁烷/3-叠氮甲基-3′-甲基环氧丁烷(BAMO/AMMO)三嵌段共聚物。用FTIR、1HNMR和GPC对共聚物的结构和相对分子质量进行了表征,用DSC测定了共聚物的玻璃化转变温度。结果表明,合成的BAMO/AMMO三嵌段共聚物的相对分子质量可控、且分布窄,并具有含能热塑性弹性体的性质。同时用Vyazovkin的非线性无模型函数方法研究其热分解动力学,得到叠氮基团的分解活化能约为150kJ/mol。三嵌段共聚物在叠氮基团分解之后形成了交联网络结构。     

Surface Energetics and Adhesion

The relationships between surface energetics and adhesion are critically reviewed. New data that confirm such relationships, for peel tests as well as lap shear tests, are presented. The effect of hydrothermal aging of aluminum surfaces on surface energetics can be used to predict degradation in bond strength. The mechanism of failure for elastic adhesives (such as Scotch ® tape) in peel tests may be essentially the same as for more brittle adhesives (such as epoxies) in lap shear tests. This mechanism may involve brittle fracture that forms a critical flaw at the adherend-adhesive interface (on a microscopic level), followed by crack propagation which then may include considerable elastic and plastic deformation. The locus of propagation (fractography) is generally not (but may be) relevant to the problem of how to remedy mechanical weakness in an adhesive joint, since the local region of critical flaw formation rather than the general surface area determines the joint strength.     

Energetics of point defects in TiC

Density functional theory was used to evaluate the energetics of point defects in TiC_x (x < 1): C vacancies and Al substitution at a C site. Our ambition is to contribute towards understanding the underlying atomic mechanisms enabling the Al intercalation into TiC_x and the subsequent formation of Ti₃AlC₂. The difference between the energy of formation for an Al substitution at a C site and a bulk C vacancy is 0.224 eV. Furthermore, only 49 meV/vacancy is required to order the existing bulk C vacancies. Surface effects were also considered: the energy of formation for Al on TiC(1 0 0) at a vacant surface C site is smaller by 2.779 eV than in the case of the C surface vacancy, indicating that Al is likely to be incorporated. Based on these energy differences, it is reasonable to assume that Ti₃AlC₂ is formed by Al surface ingress into TiC_x and that vacancy ordering takes place.     

Energetics of Nitro/Azide Propellants

A new type of double-base propellant which contains GAP was studied in order to elucidate the burning rate characteristics and combustion wave structure. This class of propellants is termed “nitro/azide propellants”. Experimental results revealed that the burning rate and temperature sensitivity are increased when 12.5% DEP is replaced with 12.5% GAP. The reaction rate in the dark zone is increased by the replacement of DEPo with GAP. However, the gas phase structure of NG/NC/GAP propellant is fundamentally the same as that of NG/NC/DEP propellant and the basic chemical reaction mechanism in the gas phase zone remains unchanged for both propellants.     

Energetics and structures of carbon nanorings

Molecular dynamics (MD) simulation is adopted to study the stability of carbon nanorings, where the force-field function describes the interactions of the carbon atoms. A nanoring is formed by bending a straight nanotube (n, m) and connecting its two ends together. Both armchair and zigzag nanorings are investigated, and the critical diameters for stable nanorings are obtained. It is found that zigzag nanorings have a larger critical diameter than armchair nanorings.     

Energetics of gas sorption in glassy polymers

The molar enthalpy for gas sorption in glassy polymers at a fixed concentration, often called the isosteric enthalpy of sorption, exhibits a clearly discernable minimum when plotted as a function of penetrant concentration. This unexpected behaviour has been observed in several glassy polymer systems including poly(ethylene terephthalate), polyacrylonitrile and polycarbonate. The behaviour can be modelled by analysing the temperature dependence of the various equilibrium parameters comprising the so-called dual mode sorption model for gas sorption in glassy polymers. The fundamental significance of the various enthalpies describing the temperature dependence of the Henry's law solubility constant, the Langmuir affinity constant and the Langmuir capacity constant are included in the discussion. Provision is made for non-ideal vapours and gases by introduction of the compressibility factor in the expression for the isosteric enthalpy. Application of relationships for calculating both the isosteric and the isothermal enthalpies of sorption is made to the case of CO₂ in poly(ethylene terephthalate) in the temperature range 35° to 115°C. These results and analyses complement the wealth of equilibrium and transport data which are consistent with the dual mode sorption model for penetrant sorption in glassy polymers.     

Energetics of methyl branches in hydrocarbon crystals

Semi-empirical energy calculations are reported for methyl branched hydrocarbon molecules in orthorhombic and monoclinic crystalline arrays of linear molecules. The 19 molecules in the array are flexible and twenty methylene units long. Two modes of packing the defect molecule in the crystals are found and for each the mechanical relaxation criterion of there being two or more sites available to the molecule is met. However, there is no significant relaxation strength because the differences in site energies are too large. This result holds for all cases because the unfavourable orientation of the molecular stem in one of the sites makes the energy much greater than in the other for which the stem has a favourable orientation. For the case with the lowest defect energy, the unit cell dimensions are comparable to those found experimentally for the same methyl group concentration. Drawings showing the molecular distortion are presented.     

改性海泡石除磷热力学研究

通过对改性海泡石的热力学性能研究,确定了改性海泡石对磷进行吸附的吸附容量、去除率和改性海泡石用量的关系。根据实验数据求解出吸附等温方程并绘制出等温吸附曲线。对等温吸附曲线进行拟合并比较相关系数的大小,得到改性海泡石的等温吸附方程。它符合修正后的Freundlich等温吸附方程:qe=10.4 4 Ci1.148 29.90。此方程较精确地描述了改性海泡石对P O34--的吸附量随浓度的变化,为改性海泡石的工业化除磷应用提供了理论依据。     

Energetics of electron-transfer reactions in soft condensed media

The coupling of electronic transitions within molecules to condensed-phase media involves a complex hierarchy of spatial and dynamical scales. Thermodynamics of activation is related to the length scale of microscopic interactions reflected in the non-Arrhenius reaction kinetics. Solvent dynamics make a particularly strong impact on the activation barrier when the time scale of the reaction is comparable to the relaxation time of the solvent, and the reaction barrier becomes nonergodic. Finally, molecular polarizability is responsible for complex nonparabolic free energy surfaces for electron transfer. We discuss the application of these ideas to soft condensed solvents such as supercooled liquids, liquid crystals, and photosynthetic reaction centers.     

Energetics of stress relaxation of glassy polymers at high pressure

Kinetic changes of relaxation of the shift stress of glassy poly(methyl methacrylate) were studied when temperatures and pressures were changed in isobaric, isothermal, and isochoric conditions. In isochoric conditions the relaxation rate depends slightly on temperature. The volume of the polymer is the main parameter for the rate of stress relaxation. Isobaric and isochoric activation energies and activation vohime of stress relaxation were determined. The results are shown to satisfy the thermodynamic relation of the activation parameters of the relaxation process. The dimensions of elementary kinetic unit of the stress relaxation process were estimated.     

Energetics analysis of polyethylene crystallization: single crystal growth surfaces

Semiempirical energy calculations have been used to investigate the structure and energetics of molecular attachment and mobility on the {110} and {200} growth faces of polyethylene single crystals. The results indicate that, while the crystallographic position of the first nucleating segment on the {110} face is a low energy position, other dispositions of the molecule have somewhat lower energy. Growth layers nucleated by molecules in the lowest energy position are substantially different from the crystallographic structure. After inclusion of a few molecules however, this growth layer must undergo a rearrangement requiring the cooperative motions of several molecules in order to assume the now lower energy crystalline structure. Comparisons of the energies and mobility of molecular segments on the {110} and {200} growth faces indicate that there is a greater attraction of the segments to the {200} face, but that chain mobility is substantially greater on the {110} face. Correlation of these factors with the observed dependence of degree of truncation of polyethylene single crystals on crystallization temperature and the concentration of polymer in solution suggests that the nucleation energetics take precedence over factors of chain mobility, but the total truncation behaviour observed is probably the result of an interplay between these two factors. Energetics calculations also provide an explanation for the observed lower melting temperature of the {200} sectors.     

Lix@C60: Calculations of the Encapsulation Energetics and Thermodynamics

Li@C₆₀ and Li@C₇₀ can be prepared and thus, their calculations at higher levels of theory are also of interest. In the report, the computations are carried out on Li@C₆₀, Li₂@C₆₀ and Li₃@C₆₀ with the B3LYP density-functional theory treatment in the standard 3-21G and 6-31G* basis sets. The computed energetics suggests that Li_x @C₆₀ species may be produced for a few small x values if the Li pressure is enhanced sufficiently. In order to check the suggestion, a deeper computational evaluation of the encapsulation thermodynamics is carried out.     

The Concept of Chamber Design for Explosive Thermonuclear Fusion Energetics

The possibility of realizing the solution of mankind's energy problem by the explosive thermonuclear fusion method that was proposed by Academician A. D. Sakharov is assessed. The essence of the method consists of the use of the energy of low–power thermonuclear explosions performed cyclically in stationary explosion–proof chambers equipped with a means for selection and utilization of the thermal energy of the explosion. Here the basic problem is to design airtight chambers capable of withstanding multiple thermonuclear explosions whose power is equal to 10—25 ktons of TNT. The available data on this problem are examined. The concept of designingreliable explosion–proof chambers for the solution of the indicated problem is formulated.