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91.
Detao Pan Yanyang Wu Kui Chen Bin Wu Lijun Ji 《Phosphorus, sulfur, and silicon and the related elements》2016,191(10):1306-1312
The crystal transformation of ammonium polyphosphate crystalline form V (APPv) was studied. The effects of heating time and water content in the reactor were explored. The results showed that APPv underwent complete conversion to crystalline form II (APPii) when heated at 200°C. The pure and water-insoluble APPii was obtained under the alternate wet ammonia and dry ammonia atmosphere. Then, the thermal behavior of APPv and APPii was investigated. The TG analysis showed APPv had high thermal stability over the range of 300°C to 580°C, which was possibly due to its highly cross-linked structures. 相似文献
92.
Eldad Herceg 《Surface science》2006,600(19):4563-4571
The formation of a well-ordered p(2 × 2) overlayer of atomic nitrogen on the Pt(1 1 1) surface and its reaction with hydrogen were characterized with reflection absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The p(2 × 2)-N overlayer is formed by exposure of ammonia to a surface at 85 K that is covered with 0.44 monolayer (ML) of molecular oxygen and then heating to 400 K. The reaction between ammonia and oxygen produces water, which desorbs below 400 K. The only desorption product observed above 400 K is molecular nitrogen, which has a peak desorption temperature of 453 K. The absence of oxygen after the 400 K anneal is confirmed with AES. Although atomic nitrogen can also be produced on the surface through the reaction of ammonia with an atomic, rather than molecular, oxygen overlayer at a saturation coverage of 0.25 ML, the yield of surface nitrogen is significantly less, as indicated by the N2 TPD peak area. Atomic nitrogen readily reacts with hydrogen to produce the NH species, which is characterized with RAIRS by an intense and narrow (FWHM ∼ 4 cm−1) peak at 3322 cm−1. The areas of the H2 TPD peak associated with NH dissociation and the XPS N 1s peak associated with the NH species indicate that not all of the surface N atoms can be converted to NH by the methods used here. 相似文献
93.
The temperature dependence of pressure broadening of 134 rovibrational transitions of several branches in the ν4 and 2ν2 bands of ammonia perturbed by H2 and N2 has been measured using a high-resolution Fourier transform spectrometer. The temperature range covered during the experiments was between 235 and 296 K. The pressure-broadening linewidths were obtained using the method of multipressure fitting to the measured shapes of the lines. These broadenings were also calculated using a semiclassical model leading to a reasonable agreement with the observations and reproduces well the strong systematic experimental J and K quantum number dependencies. The retrieved values of the linewidths, along with those previously determined from the spectra at room temperature, were used to derive the temperature dependence of both H2 and N2 broadening of NH3 lines. The broadening coefficients were shown to fit closely the well-known exponential law. For both experimental and theoretical results, the temperature exponent n has been obtained. Careful inspection of the experimental values shows that, contrary to the linewidths, the coefficient n is nearly K independent within each J multiplet. Also for a given J it does not seem to exhibit any noticeable variation with the type of rotational transition. On the other hand, the calculated n values exhibit a strong J and K systematic dependencies. n increases with K for a given J, decreases with J for a given K and are independent of the type of rotational transition. 相似文献
94.
氨及其氟取代物与氟化氢形成氢键络合物的系列理论研究 总被引:1,自引:0,他引:1
采用ab initio方法,在6-31G水平上,对NH3…NF、NH2F…HF、NF3…HF4种氢键络合物的5组构型进行了一系列能量梯度法的构型优化和能量计算,取得到关于这些分子络合物的结构特征,氢键键能与键级,单体电荷迁移量等信息,分析,比较得出了在每种构型下各体系的重要物理量随氟基数的递变规律,并探讨了氟基的诱导效应对上述体系氢键作用的影响。 相似文献
95.
96.
唐德中 《宁波大学学报(理工版)》1989,(2)
本文根据近年来在能源研究中广为重视的有效能概念和有效能分析法,对化工生产和制冷工程上广泛应用的氨饱和液、饱和蒸汽与过热蒸汽在工程范围内的有效能值进行了计算,给出了在环境温度分别为0℃与25℃下的有效能表。本表不仅使用简便,而且有相当的精度,在节能管理中有实用价值。 相似文献
97.
Anna.Og. Dikovska P.A. Atanasov B.S. Zafirova T.R. Stoyanchov 《Applied Surface Science》2007,254(4):1087-1090
In this work, thin ZnO films have been produced by pulsed laser deposition on side-polished fiber for optical gas sensor applications. The influence was investigated of the processing parameters, such as substrate temperature and oxygen pressure applied during deposition, on the sensitivity to ammonia of the sensing element. A shift of the spectral position of the resonance minimum to the longer wavelengths was observed at room temperature for the sample prepared at 150 °C substrate temperature and 20 Pa oxygen pressure. Spectral changes in the range 0.16-1.13 nm for NH3 concentrations between 500 and 5000 ppm were also observed. 相似文献
98.
In this work, a Hamiltonian formalism and a 6D vibrational calculation procedure is described and implemented, designed for the exploration of vibrational motion in ammonia (and any XH3 molecule). The 6D potential energy surface of ammonia was modelled in simple analytical form (including the inversion potential) at the planar, totally symmetric (D3h) reference configuration. Using the described method (which is an adaptation of the formalism, previously developed and applied to benzene), 6D calculations were carried out on the vibrational level system of ammonia 14NH3, at the lower levels of vibrational excitation. On the basis of the satisfactory agreement between the calculated and the experimentally measured vibrational frequencies, the values of some important harmonic and anharmonic force constants, characterizing the ammonia PES were determined. 相似文献
99.
100.
G.I Gurina 《Journal of solid state chemistry》2004,177(3):909-915
Interaction between lead(II) iodide and ammonia was studied with the help of an X-ray in situ analysis, DTA-TG analysis, DSC measurements and IR spectroscopy. A two-stage mechanism of the reaction was defined. At the first stage of the reaction two phases with trigonal symmetry and a phase with monoclinic symmetry are developed. At the second stage of the reaction the structure changes lead to formation of a compound with orthorhombic symmetry. The results were discussed along with the data of thermal analysis and IR spectroscopy. The value of enthalpy of formation for the compound PbI2(NH3)4 was determined. 相似文献