Thermal Decomposition Behavior and Non-isothermal Decom-position Reaction of Copper(II) Salt of 4-Hydroxy-3,5-dinitro- pyridine Oxide and Its Application in Solid Rocket Propellant

Introduction Copper(II) salt of 4-hydroxy-3,5-dinitropyridine ox-ide (4HDNPOCu) is an energetic material containing energetic groups of NO2, which can be used as an ener-getic auxiliary catalyst substituting the inertia copper salt to improve the catalysis of the main catalyst (lead salt) in Composite Modified Double Base propellant containing RDX (RDX-CMDB propellant).1 Thermal behavior is one of the most important aspects affecting its catalytic efficiency for propellant. However, …     

Magnetic properties of molecular compounds based on a new polydentate ligand

We have obtained a new Cu-based ligand using diaminobenzidine which has four coordination sites, opening new possibilities to synthesize extended structures with magnetic interactions. Two metal complexes, Cu₂Mn₂(bopba) and Cu₂Co₂(bopba), where Cu₂(bopba) is a new polydentate ligand, were successfully obtained and characterized by elemental analysis, IR-spectroscopy, X-ray diffraction and magnetic measurements. The results indicate a ferrimagnetic character of the Mn₂Cu₂ compound, with a high saturation moment at temperatures above liquid helium and a weak ferromagnetic behavior of the Co₂Cu₂ compound.     

从另一个角度处理“原子结构”内容的尝试

从教材内容和课程设计的科学性论证了基础无机化学课程中“原子结构”应分为“原子和原子结构”和“元素与周期律”两章.“原子和原子结构”包括原子结构、核外电子的运动状态和原子核结构,“元素与周期律”包括元素的起源、周期律的建立和元素基本性质的规律性.通过教学实践,说明这样的处理有利于探索教材结构处理对教学效果的影响,符合认识论规律.教法的改革有利于从基础课教学方面提高学生的科学研究意识.     

Enhanced photocatalytic degradation of rhodamine B under visible light irradiation on mesoporous anatase TiO2 microspheres by codoping with W and N

Mesoporous anatase TiO₂ microspheres were prepared via solvothermal method. Ammonium tungstate was used as the W source, and ammonia gas flowing in an ammonothermal reactor as the N source for codoping. TiO₂:(W,N) mesoporous microspheres, which were prepared from solvothermal treatment at 160 °C for 16 h and thermal ammonolysis at 500 °C for 2 h after calcination, have high specific surface area of 106 m² g⁻¹. XPS results indicate the presence of N_O, N_i and W⁶⁺ in the codoped mesoporous TiO₂ microspheres. Monodoping with N shifts the absorption band edge of anatase TiO₂ from ultraviolet region to visible region. Although codoping with W makes the visible light absorbance decrease a little, the photocatalytic degradation of a cationic dye rhodamine B (RhB) on mesoporous TiO₂:(W,N) microspheres is increased to 1.7 times of that on mesoporous TiO₂:N microspheres. This may due to decreasing recombination centers by W-doping charge compensation.     

Solvent-dependent turn-on probe for dual monitoring of Ag and Zn in living biological samples

A novel, solvent-dependent “off–on” probe with benzoylthiourea moiety as the functional receptor and fluorescein as the fluorophore was designed for monitoring of Ag⁺ in EtOH–H₂O (2:8, v/v) solution and Zn²⁺ in CH₃CN–H₂O (2:8, v/v) solution at physiological range with sufficient selectivity and sensitivity. The Ag⁺ promoted desulfurization of thiosemicarbazide functionality in formation of the 1,3,4-oxadiazole and the coordination of Zn²⁺ to the O atom and N atom of the spoirolactam moiety and the S atom of the benzoylthiourea moiety were investigated to be the power that promoted the fluorescent enhancement. This probe was tested highly suitable for mapping Ag⁺ and Zn²⁺ in living human osteosarcoma MG-63 cells and microbial cell–EPS–mineral aggregates, thus, providing a wonderful candidate for tracking Ag⁺ and Zn²⁺ in biological organisms and processes.     

Thermodynamic properties of 4-amino-3-furazanecarboxamidoxime

4-Amino-3-furazanecarboxamidoxime (AAOF) is an important precursor for synthesizing new furazano (furoxano) energetic compounds. Its thermal behaviour was studied under a non-isothermal condition by DSC methods. The results of this study show that there are one melting process and two exothermic decomposition processes. Its kinetic parameters of the intense exothermic decomposition process are obtained from analysis of the DSC curves. The apparent activation energy (E_a), pre-exponential factor (A) and the mechanism function (f(α)) were (146 ± 18) kJ · mol⁻¹, (10^10.9±1.8) s⁻¹ and (1 − α)², respectively. The specific molar heat capacity (C_p,m) of AAOF was determined by a continuous C_p mode of micro-calorimeter. The self-accelerating decomposition temperature (T_SADT), thermal ignition temperature (T_TIT) and critical temperatures of thermal explosion (T_b) were obtained to evaluate its thermal safety.     

Soluble and degradable polyimides with phenyl-2-pyridyl ether structure: Synthesis and characterization

A diamine monomer o-phenylenedioxybis(5-amino-2-pyridine) was synthesized via reduction of a dinitro compound o-phenylenedioxybis(5-nitro-2-pyridine), producing a series of new polyimides from this diamine and various commercially available aromatic dianhydrides via conventional two-stage processes. The resulting polyimides are able to form tough and transparent films, with decomposition temperatures in the range of 529–551 °C, and can be dissolved in organic polar solvents. Meanwhile, these polyimides can be degraded in a hydrazine hydrate medium, a degradation mechanism proposed by analyzing the degradation products suggests that the degradable properties could be attributed to the phenyl-2-pyridyl ether structure in the polymer. In addition, the transformation of the compound structure from dinitro compound to damine monomer in the synthetic process is discussed in respect to X-ray structure.     

从氨的合成认识氮分子化学键的稳定性和活化

先从氮分子的化学键讨论其稳定性,再从最早工业化的合成氨出发,讨论氮分子化学键活化的相关研究,意欲探索一种元素化学新的教学方法。目的在于引导学生灵活学习并运用知识去认识自然世界,提高分析问题和解决问题的能力。     

Band gap modulation of transition-metal dichalcogenide MX2 nanosheets by in-plane strain

The electronic properties of quasi-two-dimensional honeycomb structures of MX₂ nanosheets (M=Mo, W and X=S, Se) subjected to in-plane biaxial strain have been investigated using first-principles calculations. We demonstrate that the band gap of MX₂ nanosheets can be widely tuned by applying tensile or compressive strain, and these ultrathin materials undergo a universal reversible semiconductor-metal transition at a critical strain. Compared to WX₂, MoX₂ need a smaller critical tensile strain for the band gap close, and MSe₂ need a smaller critical compressive strain than MS₂. Taking bilayer MoS₂ as an example, the variation of the band structures was studied and the semiconductor-metal transition involves a slightly different physical mechanism between tensile and compressive strain. The ability to tune the band gap of MX₂ nanosheets in a controlled fashion over a wide range of energy opens up the possibility for its usage in a range of application.     

An improved fusion algorithm for infrared and visible images based on multi-scale transform

In this paper, an improved fusion algorithm for infrared and visible images based on multi-scale transform is proposed. First of all, Morphology-Hat transform is used for an infrared image and a visible image separately. Then two images were decomposed into high-frequency and low-frequency images by contourlet transform (CT). The fusion strategy of high-frequency images is based on mean gradient and the fusion strategy of low-frequency images is based on Principal Component Analysis (PCA). Finally, the final fused image is obtained by using the inverse contourlet transform (ICT). The experiments and results demonstrate that the proposed method can significantly improve image fusion performance, accomplish notable target information and high contrast and preserve rich details information at the same time.