Effects of Aluminum on Thermal Decomposition of Hexogen/Ammonium Perchlorate

Thermogravimetry-differential scanning calorimetry-mass spectrometry-Fourier transform infrared spectrometry（TG-DSC-MS-FTIR） simultaneous analysis was used to study the effects of 10.7 μm and 40 nm Al on the thermal decomposition of the Hexogen/ammonium perchlorate（RDX/AP,1/2,mass ratio） mixture.TG-DSC results show that there are two mass loss processes for the thermal decomposition of RDX/AP/Al.The first one is mainly ascribed to the thermal decomposition of RDX.The reaction rate of RDX/AP/10.7 μm Al is so fast that the apparent activation energy,calculated by model-free Friedman method,is negative,which is the same as that of RDX/AP.30％（mass fraction） 40 nm Al added in RDX/AP change the activation energy from negative to positive value.The second mass loss process of the RDX/AP/A1 mixture is ascribed to the thermal decomposition of AP.This process can be divided into three stages for RDX/AP with and without Al.The kinetics model is not changed in the presence of micro-sized Al,while it is changed from CnB/D1/D1 to CnB/D1/D4 after the addition of 40 nm Al to RDX/AP.The reaction rate constant of the first stage and the end temperature of the second stage decrease,while the end temperatures of the third stage increase in the presence of 40 nm Al.The MS-FTIR results show there is a competition between the formation reactions of HNCO,N2O and NO2 during the second mass loss process.     

氢催化的二硝酰胺铵热分解的从头算分子动力学研究

Thermal decomposition of a famous high oxidizer ammonium dinitramide (ADN) under high temperatures (2000 and 3000 K) was studied by using the ab initio molecular dynamics method.Two different temperature-dependent initial decomposition mechanisms were observed in the unimolecular decomposition of ADN,which were the intramolecular hydrogen transfer and N-NO₂ cleavage in N (NO₂)^-.They were competitive at 2000 K,whereas the former one was predominant at 3000 K.As for the multimolecular decomposition of ADN,four different initial decomposition reactions that were also temperature-dependent were observed.Apart from the aforementioned mechanisms,another two new reactions were the intermolecular hydrogen transfer and direct N-H cleavage in NH₄⁺.At the temperature of 2000 K,the N-NO₂ cleavage competed with the rest three hydrogen-related decomposition reactions,while the direct N-H cleavage in NH₄⁺ was predominant at 3000 K.After the initial decomposition,it was found that the temperature increase could facilitate the decomposition of ADN,and would not change the key decomposition events.ADN decomposed into small molecules by hydrogen-promoted simple,fast and direct chemical bonds cleavage without forming any large intermediates that may impede the decomposition.The main decomposition products at 2000 and 3000 K were the same,which were NH₃,NO₂,NO,N₂O,N₂,H₂O,and HNO₂.     

Photocatalytic Activity of N-doped TiO2 Photocatalysts Prepared from the Molecular Precursor (NH4)2TiO(C2O4)2

We developed a novel approach for the preparation of N-doped TiO₂ photocatalysts by calcining ammonium titanium oxalate at different temperatures. The structures of N-TiO₂ were characterized by powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, N₂ adsorption-desorption isotherms, X-ray photoelectron spectroscopy, diffuse reflectance UV-Vis spectroscopy, and scanning electron microscope. The N-doped TiO₂ photocatalysts calcined below 700 oC are the pure anatase phase but that calcined at 700 oC is a mixture of anatase and rutile phases. The doped N locates at the interstitial site of TiO₂ which leads to the narrowing of bad gap of pure anatase N-TiO₂. Among all photocatalysts, N-TiO₂ photocatalysts calcined at 600 and 400 oC exhibit the best performance in the photodegradation of methyl orange under the UV light and all-wavelength light illuminations, respectively; however, because of the perfect crystallinity and the existence of anatase-rutile phase junctions, N-TiO₂ photocatalyst calcined at 700 oC exhibits the highest specific photodegradation rate, i.e., the highest quantum yield, under both the UV light and all-wavelength light illuminations.     

甲酸铵催化转移氢化还原肽链中的芳香硝基——对氨基苯丙氨酸的间接引入

研究了用甲酸铵催化转移氢化法(AF-CTH)对不同类型肽中的芳香硝基的还原行为, 这些肽类化合物包括促黑激素(MSH: 四肽)、促黄体素释放激素(LHRH: 十肽)和强腓肽(十七肽)的类似物. 用HPLC对还原过程进行了跟踪监测, 结果显示, 除含对氯苯丙氨酸残基的LHRH类似物因发生脱氯副反应不适合用AF-CTH还原外, 其余序列还原过程中均无明显副反应发生, 硝基几乎定量地转化成为相应的氨基, 实现了对氨基苯丙氨酸向肽链的间接引入. 另外发现, 硝基还原所需的时间与肽链长度有关, 肽链越长, 还原所需时间越长, 但与其在序列中的位置关系不明显.     

双核茂铁四氮唑的合成及对高氯酸铵热分解的催化作用

首先以二茂铁为原料合成丙基桥联的双聚二茂铁(DFP), 经甲酰化得到丙基桥联的双聚二茂铁甲醛(DFP-CHO, 1), 再与NH₂OH·5HCl进行缩合反应得到双核二茂铁肟(2), 然后脱水得到丙基桥联双聚二茂铁甲腈(3), 最后在(n-C₄H₉)₃SnCl 的催化作用下与NaN₃进行[2+3]环加成反应, 生成目标产物丙基桥联双聚二茂铁四唑(4); 通过¹H NMR, FTIR和ESI-MS对目标产物的结构进行了表征. 利用差示扫描量热分析(DSC)和热重(TG)分析研究了这2个双聚二茂铁氮杂衍生物的燃速催化性能, 结果表明, 通过添加质量分数为5%的丙基桥联双聚二茂铁氮杂化合物3和4均使高氯酸铵(AP)的热分解温度降至100℃左右.     

A micellar electrokinetic chromatography approach using diastereomeric derivatization and a volatile surfactant for the enantioselective separation of selenomethionine

A MEKC methodology with UV detection was developed for the enantioselective separation of selenomethionine (SeMet). The use of (+)‐1‐(9‐fluorenyl)ethyl chloroformate (FLEC) as chiral derivatization reagent to form SeMet diastereomers enabled their subsequent separation using ammonium perfluorooctanoate (APFO) as a volatile pseudostationary phase. The effect of APFO concentration and pH, temperature, injection volume, and derivatization conditions (time and FLEC/SeMet ratio) were evaluated in order to select the best separation conditions. A chiral resolution of 4.4 for DL‐SeMet was achieved in less than 6 min using 100 mM APFO at pH 8.5 as electrophoretic buffer. Satisfactory results were obtained in terms of linearity, precision (RSD from 3.4 to 5.1% for migration times and from 1.8 to 4.6% for corrected peak areas), accuracy, and LODs (3.1 × 10^?6 M and 3.7 × 10^?6 M for d and l enantiomers, respectively). The method was successfully applied to the determination of l ‐SeMet in food supplements.     

卡拉胶包覆APP微球阻燃水性环氧树脂

以氯化钡提纯k-卡拉胶, 经过氧化氢降解, 通过反相乳液聚合的方式制备了一系列卡拉胶包覆聚磷酸铵(APP)阻燃微球(k-CM/APP); 将其加入到水性环氧树脂(EP)中, 制备了3种钢结构防火涂层EP2, EP3和EP4. 利用红外光谱(IR)、 扫描电子显微镜(SEM)及元素分析(EDS)对k-CM/APP的结构及形貌进行了表征. 利用极限氧指数(LOI)、 垂直燃烧(UL-94)、 背温测试法、 热重分析(TG)、 锥形量热(CONE)、 附着力测试、 IR和SEM等方法分析了涂层的阻燃、 隔热及力学性能. 结果表明, k-CM/APP(3/1)球形结构完整, 800 ℃时的残炭量高达59.5%. 与其它阻燃涂层体系相比, 添加了k-CM/APP(3/1)的EP3防火涂层的极限氧指数达到28.5%, UL-94达到了V-0级, 60 min防火涂层耐火温度为253 ℃. 相比于纯EP涂层, EP3涂层的热释放速率峰值降低了58.26%, 总热释放量降低了20.84%, 附着力达到8.74 MPa.     

Metal-water interactions and hydrogen bonding in dittmarite-type compounds M'M''PO4.H2O (M'=K+, NH4+; M''=Mn2+, Co2+, Ni2+). Correlations of IR spectroscopic and structural data

The vibrational behavior of the uncoupled nu(OD) modes and of the water librations in dittmarite-type compounds M'M'PO4.H2O (M'=K+, NH4+; M'=Mn2+, Co2+, Ni2+) is analyzed in terms of the influence of two types of metal-water interactions (M+-H2O and M2+-H2O), the hydrogen bonding and the repulsion potential of the lattices. The M+-H2O interaction is found to be the main factor, which influences nuOD. The strong K+-H2O interaction weakens in a higher degree the intramolecular O-H bonds than the corresponding M2+-H2O interactions (M2+=Mn, Co, Ni). As a result nuOD is shifted to lower wavenumbers in the potassium series than in ammonium one, irrespective of the synergetic effect of M2+, the hydrogen bond lengths and the repulsion potential of the lattices. The analysis of the spectroscopic data evidences for the dominating influence of the M2+-H2O interaction on the wagging mode. The blue shift of nuwag strictly follows the increasing synergetic effect of M2+, i.e. nuM'/Mn相似文献   

Bandwidths studied as a function of temperature in ammonium halides near Tlambda

This study gives our analysis of the Raman bandwidths using the soft mode-hard mode coupling model applied to ammonium halides. The temperature dependence of our observed bandwidths for the nu5(174 cm-1) Raman mode of NH4Cl and nu5(177 cm-1) Raman mode of NH4Br, is analyzed close to phase transitions. From our analysis, we obtain beta=0.13 as the values of the critical exponent for the order parameter in the first order phase region for the ammonium halides.     

Ammonium Chlorochromate Adsorbed on Montmorillonite K-10: Oxidative Deprotection of Tetrahydropyranyl Ethers Using Microwaves in a Solventless System

Summary.  Tetrahydropyranyl ethers were rapidly and selectively oxidized to the corresponding carbonyl compounds by clay supported ammonium chlorochromate under solvent free conditions using microwaves. Received July 25, 2000. Accepted September 7, 2000