载氢与掺锗石英光纤的光致折射率改变

对载氢掺锗石英光纤的紫外光敏特性以及载氢条件对光纤紫外光敏性的影响进行了系统地实验研究. 实验结果表明: ①载氢光纤的光致折射率改变随紫外曝光时间的变化规律( Δn=3.3×10^-4t^0.31689)是先呈指数增长到达一定的时间基本达到饱和, 如果继续照射, 光致折射率改变继续增大, 并对紫外光敏机理进行了讨论; ②随着载氢压力的增大, 光纤的紫外光敏性呈正比例增大, 两者之间的关系为Δn=1.34times10^-5+4.66×10^-5P; ③掺锗石英光纤的紫外光敏性的大小随着载氢时间的延长, 呈指数增长, 最后达到饱和.     

A Comparative Analysis of Catalysts for the Preparation of Germanium through Hydrogen Reduction of Germanium Tetrachloride

We have synthesized catalysts for the hydrogen reduction of germanium tetrachloride: a catalyst based on multiwalled carbon nanotubes and a hybrid catalyst based on multiwalled carbon nanotubes whose surface was decorated with copper-containing nanoparticles. The hybrid catalyst has been characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results demonstrate that it consists of multiwalled carbon nanotubes whose surface is decorated with copper nanoparticles in a cuprous oxide shell (Cu₂O/Cu/MWCNTs). The catalytic activity of the hybrid catalyst exceeds that of the as-prepared MWCNTs. The use of the Cu₂O/Cu/MWCNT hybrid catalyst as a catalyst for the hydrogen reduction of germanium tetrachloride allows the reaction temperature to be lowered and ensures 95.7% germanium tetrachloride conversion at 873 K.     

Mass Transport of Molecular Hydrogen in Porous Vycor Glass

The dynamics of adsorbed hydrogen molecules on the pore surface of Vycor glass has been investigated with a torsional oscillator technique at temperatures between 7.5 K and 22 K. Whereas most experiments carried out previously on this system were performed under thermodynamic equilibrium, we concentrated on the dynamics of the mass transport. Since the free energy of hydrogen inside the Vycor is a function of both temperature and film thickness, a temperature change causes a gradient in the chemical potential between inside and outside of the Vycor which leads to mass transport of the hydrogen molecules as consequence of a wetting or a solidification transition. We find a thermally activated motion with an activation energy of 25 K corresponding to the value for surface self-diffusion of quench-condensed hydrogen films.     

掺锗石英光纤光致折射率变化的实验研究

对掺锗石英光纤的紫外光敏特性进行了实验研究. 实验结果表明: 未载氢光纤经过紫外光照射后折射率变化在10^-4数量级; 而载过氢光纤的折射率变化在10^-3数量级, 比未载氢的 光纤折射率变化提高了一个数量级. 载氢前后光纤的折射率变化随曝光时间的变化规律是不同的, 这表明载氢前后光纤的光敏性微观机理是不同的. 对载氢前后光纤的光敏性机理进 行了分析与讨论, 分别解释了未载氢光纤和载氢光纤的折射率随紫外光曝光时间的变化过程.     

Manipulating the Rectifying Contact between Ultrafine Ru Nanoclusters and N-Doped Carbon Nanofibers for High-Efficiency pH-Universal Electrocatalytic Hydrogen Evolution

The rational design of ingenious strategies to boost the intrinsic activity and stability of ruthenium (Ru) is of great importance for the substantial progression of water electrolysis technology. Based on Mott–Schottky effect, electronic regulation within a metal/semiconductor hybrid electrocatalyst represents a versatile strategy to boost the electrochemical performance. Herein, a typical Mott–Schottky hydrogen evolution reaction (HER) electrocatalyst composed of uniform ultrafine Ru nanoclusters in situ anchored on N-doped carbon nanofibers (abbreviated as Ru@N-CNFs hereafter) through a feasible and scalable “phenolic resin-bridged” strategy is reported. Both spectroscopy analyses and density functional theory calculations manifest that such rectifying contact can induce the spontaneous electron transfer from Ru to N-doped carbon nanofibers to generate a built-in electric field, thus enormously promoting the charge transfer efficiency and HER intrinsic activity. Moreover, the seamless immobilization of Ru nanoclusters on the substrate can prevent the active sites from unfavorable migration, coarsening, and detachment, rendering the excellent structural stability. Consequently, the well-designed Ru@N-CNFs afford prominent pH-universal HER performances with small overpotentials of 16 and 17 mV at 10 mA cm⁻² and low Tafel slopes of 31.8 and 28.5 mV dec⁻¹ in acidic and alkaline electrolytes, respectively, which are superior to the state-of-the-art commercial Pt/C and Ru/C benchmarks.     

Size-Defined Ru Nanoclusters Supported by TiO2 Nanotubes Enable Low-Concentration Nitrate Electroreduction to Ammonia with Suppressed Hydrogen Evolution

Anthropogenic nitrate pollution has an adverse impact on the environment and human health. As part of a sustainable nitrate management strategy, electrochemical denitrification is studied as an innovative strategy for nutrients recycling and recovering. It is, however, challenging to selectively electro-reduce nitrate with low-concentration for ammonia. Herein, the photo-deposition of size-defined Ru nanoclusters (NCs, average size: ≈1.66 nm) on TiO₂ nanotubes (NTs) is demonstrated, which show improved performance for nitrate-to-ammonia electroreduction with a maximum yield rate of ≈600 µg h⁻¹ cm⁻² and a faradic efficiency (FE) of > 90.0% across a broad range of potentials in comparison with electrodeposited Ru nanoparticles (NPs, average size: ≈23.78 nm) on TiO₂ NTs. Experimental and theoretical evidence further suggests the small-size Ru NCs with the intrinsically enhanced selectivity and activity because of the strong metal/substrate interaction and unsaturated coordination state. The findings highlight the size effect on Ru-based catalyst supported on metal oxides, a versatile catalytic model, which allows the regulation of hydrogen adsorption to favor ammonia production over the competing hydrogen evolution reaction.     

Superconductivity in β-Tin Germanium

The superconducting properties of the β-tin germanium under pressure have been investigated by the first-principles calculations based on density functional perturbation theory. The electron–phonon coupling strength as a function of pressure was calculated, and it deceases with the application of pressure. Using the calculated electron–phonon coupling strength, the superconducting transition temperature T _c has been estimated. Assuming a nominal Coulomb repulsion parameter of 0.1, the calculated T _c is in excellent agreement with experimental data. The T _c correlates with electron–phonon coupling strength, indicating phonon-mediated superconductivity in β-tin Ge phase. Our findings have great implications to other Group IVa elements.     

氢燃料电池电解质P2O5-SiO2快质子导电玻璃的Sol-Gel法合成

采用Sol-Gel法制备了P2O5-SiO2快质子导电玻璃,用四探针薄层电阻测试仪、XRD、IR等手段对玻璃的电性能、物相结构和组成进行了表征,并探讨了质子导电机理.结果表明P2O5-SiO2快质子导电玻璃中的强氢键、分子水、结构的不完整性是导致高质子导电率的主要原因.     

Low-Iridium-Content IrNiTa Metallic Glass Films as Intrinsically Active Catalysts for Hydrogen Evolution Reaction

Although various catalytic materials have emerged for hydrogen evolution reaction (HER), it remains crucial to develop intrinsically effective catalysts with minimum uses of expensive and scarce precious metals. Metallic glasses (MGs) or amorphous alloys show up as attractive HER catalysts, but have so far limited to material forms and compositions that result in high precious-metal loadings. Here, an Ir₂₅Ni₃₃Ta₄₂ MG nanofilm exhibiting high intrinsic activity and superior stability at an ultralow Ir loading of 8.14 µg cm⁻² for HER in 0.5 m H₂SO₄ is reported. With an overpotential of 99 mV for a current density of 10 mA cm⁻², a small Tafel slope of 35 mV dec⁻¹, and high turnover frequencies of 1.76 and 19.3 H₂ s⁻¹ at 50 and 100 mV overpotentials, the glassy film is among the most intrinsically active HER catalysts, outcompetes any reported MG, representative sulfides, and phosphides, and compares favorably with other precious-metal-containing catalysts. The outstanding HER performance of the Ir₂₅Ni₃₃Ta₄₂ MG film is attributed to the synergistic effect of the novel alloy system and amorphous structure, which may inspire the development of multicomponent alloys for heterogeneous catalysis.     

Direct Interfacial Excitation from TiO2 to Cu(II) Nanoclusters Enables Cathodic Photoresponse for Hydrogen Evolution under Visible-Light Irradiation

The titanium dioxide (TiO₂) photocatalyst is only active under UV irradiation due to its wide-gap nature. A novel excitation pathway denoted as interfacial charge transfer (IFCT) has been reported to activate copper(II) oxide nanoclusters-loaded TiO₂ powder (Cu(II)/TiO₂) under visible-light irradiation for only organic decomposition (downhill reaction) so far. Here, the photoelectrochemical study shows that the Cu(II)/TiO₂ electrode exhibits a cathodic photoresponse under visible-light and UV irradiation. It originates from H₂ evolution on the Cu(II)/TiO₂ electrode, while O₂ evolution takes place on the anodic side. Based on the concept of IFCT, a direct excitation of electrons from the valence band of TiO₂ to Cu(II) clusters initiates the reaction. This is the first demonstration of a direct interfacial excitation-induced cathodic photoresponse for water splitting without any addition of a sacrificial agent. This study is expected to contribute to the development of abundant visible-light-active photocathode materials for fuel production (uphill reaction).     

原子吸收光谱法测定有机锗(Ge-132)中的锗及其杂质

用火焰原子吸收法测定了有机锗(Ge-132)中的锗,线性浓度范围为0～1.25毫克/毫升,相对标准偏差<2%,平均回收率为99.5%。用塞曼石墨炉原子吸收法测定杂质 Pb 和 As,测Pb 时用(NH_4)_2HPO_4+Mg 作改进剂,测 As 时用 Pd 作改进剂,特征质量分别为8.2pg 和8pg,相对标准偏差分别为2.1%和2.2%,还讨论了有关机理问题。     

Intrinsic–Field Cooperative Freezing into Orientational Glass–Phase in Solid Hydrogen. Theory and Experiment

We report on the mechanism of orientational freezing in ortho–para–hydrogen mixtures. We argue that instead of the Zeeman–type uncorrelated intrinsic field, which dominats at high temperatures, the molecular ordering field, strongly correlated by the reaction Onsager–type field, drives the cooperative short–range ordering into the glass–like states. This mechanism is in accord with the observed unsaturated orientational order caused by moderation of the ordering field     

钛合金片层组织中纳米团簇析出分析

以Ti-5Al-2Zr-1Sn-1Mo-1V合金为研究对象,发现其片层组织经950℃热处理后,局部区域出现α相的球化转变,而且经不同温度热处理后都有团簇物析出。应用聚焦离子束(FIB)微区精准取样,采用透射电镜对团簇析出物进行形貌观察和晶体结构衍射分析。结果表明,片层组织中的团簇析出物由多个尺寸不超过100 nm的Sn单晶颗粒聚集而成。     

Field Effect and Photoconduction in Au25 Nanoclusters Films

Quantum‐confined Au nanoclusters exhibit molecule‐like properties, including atomic precision and discrete energy levels. The electrical conductivity of Au nanocluster films can vary by several orders of magnitude and is determined by the strength of the electronic coupling between the individual nanoclusters in the film. Similar to quantum‐confined, semiconducting quantum dots, the electrical coupling in films is dependent on the size and structure of the Au core and the length and conjugation of the organic ligands surrounding it. Unlike quantum dots, however, semiconducting transport has not been reported in Au nanocluster films. Here, it is demonstrated that through a simple yet careful choice of cluster size and organic ligands, stable Au nanocluster films can electronically couple and become semiconducting, exhibiting electric field effect and photoconductivity. The molecule‐like nature of the Au nanoclusters is evidenced by a hopping transport mechanism reminiscent of doped, disordered organic semiconductor films. These results demonstrate the potential of metal nanoclusters as a solution‐processed material for semiconducting devices.     

Preparation of Germanium Oxynitride Films in Ammonia

The surface reaction of single-crystal germanium with ammonia was studied by microgravimetry. The results indicate that the forming germanium nitride vaporizes and then deposits in the form of germanium oxynitride on a substrate located in the cold zone of the reactor. The formation of the oxynitride film is due to the presence of small amounts of water vapor in ammonia.     

四氯化锗提纯工艺研究进展

四氯化锗用于制备高纯二氧化锗及石英光导纤维的搀杂剂等.介绍了四氯化锗的质量标准和提纯基本原理,综述了国内外四氯化锗的提纯工艺,着重介绍了除去粗四氯化锗中金属杂质以及含氢杂质的工艺.