抗CO中毒的Pt-HxWO3电沉积制备及其对甲醇氧化的催化作用

用循环伏安法在玻碳电极上制备出铂-氢钨青铜(Pt-HxWO3)催化剂, 用扫描电子显微镜(SEM)、Raman光谱和循环伏安法研究了催化剂的组成、结构及其对甲醇氧化的催化作用. 结果表明, Pt-HxWO3的活性与制备溶液中铂与钨原子比及酸度有关, 与相同条件下制备的纯铂(Pt)催化剂相比, Pt-HxWO3对甲醇的氧化有更强的催化活性. 当制备溶液中铂和钨的原子比为1:8时, 得到的催化剂Pt-HxWO3中铂与钨原子比为4:1, 其催化活性最佳, 甲醇氧化电流是Pt作为催化剂时的1.7倍. Pt-HxWO3的强催化活性归因于其抗CO中毒能力, CO在Pt-HxWO3上氧化起始电位提前了50 mV.     

Mutual indirect probing of platinized platinum/tungstate nanostructural features

The comparative study of isopolytungstates immobilized on smooth Pt and platinized Pt (Pt/Pt) provides a possibility to separate several specific effects on H- and O-upd at an external platinum surface and inside the pores of Pt/Pt. In the former case, a solid rechargeable product is formed (nonstoichiometric tungsten bronze), which an inherent porous structure allows solution penetration and does not prevent charging of the Pt/solution interface. Electrochemical responses of smooth Pt give more precise information on the film behaviour, when adsorption phenomena are clarified on the basis of data for Pt/Pt. Electrocatalytic tests (nitrate reduction) confirm unambiguously that the major part of the internal Pt/Pt surface area is modified by adsorbed polytungstate. This result gives, in its turn, new understanding of the size of Pt/Pt pores on the nanometre scale.

Effect of heat treatment on the microstructure and microhardness of cold-sprayed tin bronze coating

Tin bronze (TB) powder was deposited on a stainless steel substrate by cold spraying. Post-deposition heat treatment was conducted in an electrical resistance furnace under nitrogen atmosphere at a temperature of 850 °C for 3 h. The effect of heat treatment on the microstructure and microhardness of cold-sprayed TB coating was investigated. It was found that the as-sprayed TB coating presented a dense microstructure. Heat treatment significantly influenced the microstructure and microhardness of cold-sprayed TB coating. A distinguishable diffusion layer of about 150 μm was formed in the coating near the coating/substrate interface. A compound was precipitated in the diffusion layer. The microhardness in the coating was changed gradually along the coating from the interface to the coating surface after heat treatment. The microhardness in the diffusion layer was high owing to the precipitation of hard phase, while it was much low in other area due to the obvious grain growth during annealing.     

Indofluorides in the AMF3-InF3 systems (A=K, Rb, Cs and M=Mg, Zn) and optical properties of Cr:K0.38Mg0.38In0.62F3

Among the fluorides disclosed in the AMF₃-InF₃ systems (A=K, Rb, Cs/M=Mg, Zn), the most favorable material for optical applications in relation with the optical quality of its crystals is K_0.38Mg_0.38In_0.62F₃ (KMI), a distorted monoclinic Magnéli-bronze, which crystals are grown from the melt. Cr³⁺ introduced in this host is optically characterized by optical spectroscopy. The chromium ions in the single crystals occupy simultaneously centrosymmetric and non-centrosymmetric sites. The broad emission band (⁴T_2 g→⁴A_2 g transition) obtained in the near infrared range is characteristic of a small crystal field effect (Dq=1476 cm⁻¹). Crystal field analysis leads to a very good agreement between calculated and experimentally observed energy levels. Furthermore, dips observed in the absorption at about 15370 cm⁻¹ are related to the calculated mixing between the wave functions, connected with the ⁴T_2 g (⁴F) and ²E_g (²G) and ²T_1 g (²G) electronic levels.     

Date identification of the Zhouji materials during the period of King Xin--The chronology Solving method of oracle boneS and bronzes in the Shang and Zhou dynasties

By identifying the dates of the Zhouji materials (one kind of oracle bone) during the period of King Xin (also called Zhou the last monarch in Shang Dynasty), this paper establishes a new "Direct Solving Method" (DSM) to solve the chronology problems in the Shang and Zhou dynasties. The mathematical models are more suitable for those materials with the Ganzhi (the Heavenly Stems and Earthly Branches, the Chinese ancient date recorded method being of the 60-day cycle, that the repetitive cycle is independent of any astronomical parameter, each day within this cycle has its own name and can also be expressed by the numbers from l to 60) record of the date, lunar month, and their year intervals and all of them are in history documents, oracle bones and bronze vessels. For example, taking the 12 Zhouji materials in the period of King Xin,we derive the two best results of the first year when Xin assumed the reins of government in probably 1063 BC or 1052 BC.     

钠紫青铜NaMo_6O_(17)的热电势研究

报道了在 １０～３００ Ｋ 温度范围内,对准二维电荷密度波导体 Ｎａ Ｍｏ６ Ｏ１７紫青铜热电势的测量结果． 在８０ Ｋ 附近, Ｎａ Ｍｏ６ Ｏ１７ 的热电势发生突变是该物质存在 Ｐｅｉｅｒｌｓ 相变的又一个实验例证． 温度高于８０ Ｋ 时,热电势可以用一个经验公式： Ｓ＝ Ａ Ｔ＋ Ｂ／ Ｔ 来描述;而在温度低于 ３０ Ｋ 时,热电势可以拟合为： Ｓ＝ Ａ Ｔ＋ Ｂ Ｔ３ , 说明总的热电势均存在着来自载流子自身的热扩散和声子对载流子的散射两方面的贡献,但高温区和低温区声子对载流子的散射机制是不一样的． 总的热电势值揭示,无论 Ｐｅｉｅｒｌｓ 相变前后,主要载流子均是电子． 上述这些实验结果与 Ｋ Ｍｏ６ Ｏ１７的实验结果比较,有助于进一步加深对紫青铜结构、 Ｐｅｉｅｒｌｓ 相变等物理性质的理解     

Effects of Pressure and Temperature on the Formation of Tungsten-Bronze-Related Phases, RExWO3+y, with RE=La and Nd

The influence of pressure (P) and temperature (T) on the formation of tungsten-bronze-related phases containing lanthanum and neodymium was investigated. A large number of samples with bulk compositions RE_xWO₃, prepared by solid-state reaction in the pressure and temperature regions P= 10-80 kbar and T= 1170-1620 K were examined by X-ray powder diffraction and electron microscopy, and a (P-T) diagram showing the phase relations was drawn. Three tungsten-bronze-related phases with perovskite (PTB)-, hexagonal (HTB)- and intergrowth (ITB)-type structures were identified. The PTB bronze RE_xWO₃ with x≈ 0.10 was formed at p≤50 kbar. The HTB-related phase with x≈ 0.10 was observed in samples prepared at P≥20 kbar, whereas phases of (n)-ITB-type were observed only in the 25-50 kbar region. In the latter pressure region, the PTB and ITB phases were only seen in samples prepared at T > 1520 K, while the HTB-related phase was found in almost all samples. The HTB- and ITB-related compounds are metastable, probably fully oxidized, high-pressure phases of composition RE_xWO_3+3x/2 with x≤0.13. They transform to a cubic PTB bronze during annealing in inert atmosphere under ambient pressure conditions. According to microanalysis studies of individual crystals, less than 40% of the hexagonal tunnel sites in the HTB and ITB structures are occupied by RE³⁺ ions. A superstructure of HTB-type with ≈60% occupancy of the hexagonal tunnel sites (x≈0.20) was observed in a few crystals from the samples prepared at P= 80 kbar. Ordered, defect and intergrowth structures are presented.     

Synthesis, Crystal Structures and Characterization of Ba5LiTiNb9O30

A new niobate compound with the chemical composition of Ba5LiTiNb9O30 was synthesized by doping Li^ into the system BaO-TiO2-Nb2O5 in conventional solid state reaction method. The crystalline structure was determined by X-ray diffraction analysis (XRD). The results showed that crystal structure of Ba5LiTiNb9O30 belongs to tetragonal tungsten bronze structure with space group P4bm and its unit cell parameters: a=b=1.2512(2) nm, c=0.4008(5)nm. The microstructure of reaction products was observed by scanning electron microscopy (SEM).     

Investigation of patinas formed on Chinese bronzes using modern multianalytical techniques

This paper presents an integrated study on nine natural Chinese bronze patinas without causing any damage to the bronze substrates, employing five modern analytical techniques including X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) and Raman spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP‐AES), and inductively coupled plasma mass spectrometry (ICP‐MS). Two artificial Chinese bronze patinas were also investigated by the same techniques for comparative purposes. As a result, XRD determined the chemical compositions of all selected samples and showed that the primary compound was malachite in natural soil environment under the general situation. Meanwhile, some interesting corrosion products such as gerhardtite and free copper were also observed. Three groups were classified according to the XRD results in order to provide a deeper insight into their spectroscopic characterization. Spectroscopic data of these patinas from FT‐IR and Raman spectroscopy are shown and interpreted in detail. ICP‐AES and ICP‐MS analyses provided valuable quantitative information, and made the study of the patinas more profound. Furthermore, all analytical results indicated that bronze patinas are extremely complex by virtue of the storage environment and their substrate alloys. The natural samples were rather heterogeneous and the artificial samples, especially the sample formed in the laboratory, were rather homogeneous of which the chemical constituents could be well defined. Copyright © 2007 John Wiley & Sons, Ltd.     

Chemical Processing of Potassium Substituted (Pb0.6Ba0.4)Nb2O6 Powders and Thin Films Through Metallo-Organics

Highly oriented tungsten bronze K_0.4(Pb_0.6Ba_0.4)_0.8Nb₂O₆ ferroelectric thin films have been prepared from metal alkoxides and metal acetate by chemical process. The formation of solid solution with potassium was found to be very effective to form the tungsten bronze phase at lower temperatures compared with (Pb_0.6Ba_0.4)Nb₂O₆. The amount of potassium in the composition of K_x(Pb_0.6Ba_0.4)_{1 – x/2}Nb₂O₆ [0 x 0.4] is also important to crystallize in the tungsten bronze phase. K_0.4(Pb_0.6Ba_0.4)_0.8Nb₂O₆ films with c-axis preferred orientation were successfully synthesized on MgO(1 0 0) and Pt(1 0 0)/MgO(1 0 0) substrates above 700°C. KPBN60 thin film on Pt(1 0 0)/MgO(1 0 0) showed a remnant polarization of 20 C/cm² and a coercive field of 140 kV/cm at –150°C.