水合五氧化二锑吸附锶的热力学研究

研究了水合五氧化二锑在稀硝酸溶液中对锶的吸附热力学特性,在293～323 K温度范围内水合五氧化二锑对锶的平衡吸附数据符合Freundlich吸附等温方程。对等量吸附焓、自由能和吸附熵的计算表明,吸附是一吸热过程且吸附能自发进行,交换吸附过程是物理与化学吸附共同作用的结果。     

Thermodynamic Properties of Nonstoichiometric Yttria-Stabilized Zirconia at Low Oxygen Pressures

Thermodynamic properties of 8-mol%-yttria-stabilized zirconia have been determined in the 810° to 1040°C temperature range at low Po₂. A high-temperature solid-state coulometric titration method was used. The mass action constant, K_ma, can be represented at low Po₂ as K_ma=0.677 exp [(–3.98 ±0.03 eV)/kT].     

Acidic Characterization of Copper Oxide and Niobium Pentoxide Supported on Silica–Alumina

Copper oxide and niobium pentoxide were supported on silica–alumina with 2, 5, 10, 15 and 25 mass% loadings and 1:1 mass ratio of CuO:Nb₂O₅. XRD and BET measurements confirmed that monolayer coverage is reached with loadings between 5–10 mass% (～308 m² g^?1). The DRIFTS spectra of pyridine adsorbed catalysts showed bands associated with Brönsted, Lewis and a combination of both acidic sites. Thermal analysis and liquid phase microcalorimetry provided the parameters for the best catalyst (10 mass%), which has the highest number of acidic sites (0.38 mmol g^?1) and enthalpies of interaction with pyridine for Brönsted and Lewis sites (ΔH₁ = ?107.5 and ΔH₂ = ?64.4 kJ mol^?1, respectively).     

非整比化合物的化学教学探索

通过对非整比化合物概念在无机化学教学中深入分析,强调非整比化合物在教学中的重要性,阐述了非整比化合物的理论基础和广泛应用.采用理论与实践相结合的方法进行教学活动,使学生掌握了从事化学学科所必须的现代化学的基本理论、基本知识和基本技能,锻炼了自我获取知识、更新知识和拓宽知识的能力.增强了教学效果,完成了教学目的.     

Thermodynamic Model of the Cubic → Tetragonal Transition in Nonstoichiometric Zirconia

Nonstoichiometric zirconia is described with a model recently developed for ZrO₂—Y₂O₃ alloys. It is thus possible to rationalize the experimental information on the cubic/tetragonal phase boundaries in zirconia.     

包钢含铌尾矿铌富集的热力学分析和实验研究

在对采用含碳团块技术进行铌铁矿还原过程热力学分析的基础上,以包钢选矿厂稀土尾矿(含铌)为原料,以CO为还原剂,进行了铌的还原富集实验研究。并且,对含铌尾矿和渣样进行了化学成分分析,对金属样进行了扫描电镜测试。结果表明:当温度高于1300K,采用含碳团块技术可以实现铌尾矿中铁、磷和铌的有效分离。     

An Upconversion Niobium Pentoxide Bulk Glass Codoped with Er3+/Yb3+ Fabricated by Aerodynamic Levitation Method

(82?x)NbO_2.5–17.4LaO_1.5–xZrO₂(NLZ) (x = 7.5, 10, 12.5, 15, 17.5, and 20) bulk glasses codoped with Er³⁺/Yb³⁺ were successfully fabricated by aerodynamic levitation method for the first time. The structure, thermal stability, and luminescent properties of the samples were investigated systemically by XRD, differential scanning calorimetry, and upconversion spectra. Under 980 nm laser excitation, all samples exhibited green and red upconversion emissions centered at 531, 546, and 674 nm. Results showed that the sample with 15 mol% ZrO₂ obtained the most efficient upconversion luminescence and good thermal stability with the glass‐transition temperature as high as 743 °C. The effect of the addition of ZrO₂ on the structure behavior and the phonon density in the glass was investigated by Raman spectra, which are the key factors for the upconversion luminescence intensity.     

Evaluation of A Statistical Thermodynamic Method for Calculating the Composition Dependence of Chemical Potentials in Nonstoichiometric Zirconium Carbide

Mathematical expressions for carbon and zirconium activities in zirconium carbide are derived from a statistical thermodynamic model, on the assumption that nonstoichiometry is due to vacancies in the carbon sublattice while the zirconium sublattice remains filled. The energy term in the partition function is obtained by using a first- and second-neighbor quasi-chemical model. Values for the parameters used in the model are determined from available data as a function of composition. For C/Zr atom ratios between 0.59 and 0.85 the energy parameters are approximately composition-independent, whereas in the composition range 0.85 to 0.99 they are strongly composition-dependent. The vibrational partition functions of C and Zr in zirconium carbide are estimated and are shown to influence the value obtained for the model parameters.     

Thermodynamic Model for Nonstoichiometric Ionic Phases — Application to CeO2–x

A two-sublattice model for reciprocal solid solutions is applied to an ionic phase with vacancies on the anion sublattice, assuming that there are some cations with a lower valency than normal. The model is applied to CeO_2–x, where x can take values up to 0.3. Experimental data on P o₂, as a function of temperature and composition can be well represented by this model, if interactions are described by two parameters, corresponding to a regular and a subregular solution parameter.     

Nonstoichiometric Hexagonal Close-Packed Uranium Sesquinitride

When uranium metal is nitrified in 1 atm N₂, the well-known uranium sesquinitride with the bcc structure is obtained as a single phase at 1150° to 1175°C and below. A single phase of another sesquinitride with the hep structure is formed at 1330° to 1350°C. Between these temperatures, a kinetically stable mixture of sesquinitrides is obtained. Both sesquinitrides are nonstoichiometric; the bcc sesquinitride is UN_1.66–1.56 and the hep one UN_1.44–1.45 Above 1350°C, the sesquinitride decomposes into the mononitride. The transformation between the bcc and hep phases is not allotropic; a change in stoichiometry accompanies the transformation. For the sesquinitrides and the mononitride, the interplanar spacings and relative intensities of the X-ray reflection lines are reported and the lattice constants are presented. For the bcc sesquinitride, an approximate linear relation between stoichiometry and lattice constant is illustrated.     

Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy Study of Nonstoichiometric Silicon-Carbon-Oxygen Glasses

Crystallization behavior of Si-C-O glasses in the temperature range of 1000°–1400°C was investigated using transmission electron microscopy (TEM) in conjunction with electron energy-loss spectroscopy (EELS). Si-C-O glasses were prepared by pyrolysis of polysiloxane networks obtained from homogeneous mixtures of triethoxysilane, T^H, and methyldiethoxysilane, D^H. Si-C-O glass composition depended on the molar ratio of the precursors utilized. At a ratio of T^H/D^H= 1, the formation of a carbon-rich glass was observed, whereas a ratio of T^H/D^H= 9 yielded a Si-C-O glass with excess free silicon. Both materials were amorphous at 1000°C, but showed a distinct difference in crystallization behavior on annealing at high temperature. Although T^H/D^H= 1 revealed a small volume fraction of SiC precipitates in addition to a very small amount of residual free carbon at 1400°C, T^H/D^H= 9 showed, in addition to SiC crystallites, numerous larger silicon precipitates (20–50 nm), even at 1200°C. Both materials underwent a phase separation process, SiC _x O_2(1-x)→ x SiC + (1 - x )SiO₂, when annealed at temperatures exceeding 1200°C.     

Cation-Induced Coiling of Vanadium Pentoxide Nanobelts

Single-crystalline V₂O₅·xH₂O nanorings and microloops were chemically assembled via an ion-induced chemical spinning route in the designed hydrothermal system. The morphology and structure of products were investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray powder diffraction (XRD) measurement, energy-dispersive X-ray spectroscopy (EDS) microanalysis and thermal gravimetric analysis (TGA) revealed that the composition of nanorings and microloops is V₂O₅·1·1H₂O. For these oxide nanorings and microloops, the cation-induced coiling growth mechanism of vanadium pentoxide nanobelts has been proposed on the basis of crystallographic structure of vanadium pentoxide. Our proposed chemical spinning process and the rational solution-phase synthesis route can also be extended to prepare novel 1D materials with layered or more complex structures.     

五氧化二磷醇解宏观动力学

在研究五氧化二磷和辛醇生成烷基磷酸单酯的机理和分析总体反应控制步骤的基础上,建立了五氧化二磷醇解的宏观反应动力学模型,采用微分法和参数回归分析得出宏观反应速率常数和活化能.结果表明, 五氧化二磷醇解反应为二级动力学反应,反应活化能为42.8 kJ/mol.模型的计算值和实验值吻合较好,证明了动力学模型的合理性.