化学沉积法制备氧化锰/多孔炭复合材料及其电化学性能

通过化学沉积法制备了氧化锰/多孔炭（Porous carbon,简称PC）复合材料,考察了氧化锰负载量及热处理温度对其理化性能的影响,探讨了氧化锰/多孔炭复合电极的充放电机理。SEM照片及孔结构测试结果表明,常温下化学沉积法负载氧化锰不但负载均匀,而且还对多孔炭的孔结构起到修饰作用;但经400℃以上高温处理后,其均匀性受到破坏。XRD测试结果表明,经110℃干燥处理及400℃高温处理的复合电极材料负载的氧化锰为无定型结构,800℃时则转变为γ-Mn2O3。经电化学测试表明化学沉积法负载氧化锰可以有效地提高多孔炭电极材料的电能存储容量,当多孔炭负载质量分数1.7%氧化锰,在空气中110℃干燥,制得复合材料的单电极比电容达到340F/g,比单纯的多孔炭电极提高34%。     

镁掺杂对二氧化钛晶化行为的影响

采用溶胶-凝胶法在较低的热处理温度下制备了镁掺杂的TiO2。通过差热分析（DTA）并经过计算，发现在TiO2溶胶中加入Mg（NO3）2，可以让TiO2从无定型到锐钛矿相和锐钛矿相到金红石相的晶型转变活化能分别从137．7和163．7kJ／mol降低到70．5和108．4kJ／mol；采用X射线衍射分析（XRD），确定了在600℃热处理，获得了具有锐钛矿相和金红石相混晶的镁掺杂TiO2；通过紫外光催化降解甲基橙水溶液实验，证明了镁掺杂的TiO2薄膜的光催化活性高于未掺杂TiO2薄膜。     

Preparation of Pt-Ru-Ni ternary nanoparticles by microemulsion and electrocatalytic activity for methanol oxidation

Ternary platinum-ruthenium-nickel nanoparticles are prepared by water-in-oil reverse microemulsions of water/Triton X-100/propanol-2/cyclohexane. Nanoparticles formed in the microemulsions are characterized by transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffractometry (XRD), energy dispersive X-ray analysis (EDX). These resulting materials showed a homogenous alloy structure, the mono-dispersion and an average diameter of 2.6 ± 0.3 nm with a narrow particle size distribution. The composition and particle size of ternary Pt-Ru-Ni nanoparticles can be controlled by adjusting the initial metal salt solution and preparation conditions. Pt-Ru-Ni ternary metallic nanoparticles showed an enhanced catalytic activity towards methanol oxidation compared to Pt-Ru bimetallic nanoparticles.     

Order-disorder phase transitions and high-temperature oxide ion conductivity of Er2+xTi2−xO7−δ (x = 0, 0.096)

The Er_2+xTi_2−xO_7−δ (x = 0.096; 35.5 mol% Er₂O₃) solid solution and the stoichiometric pyrochlore-structured compound Er₂Ti₂O₇ (x = 0; 33.3 mol% Er₂O₃) are characterized by X-ray diffraction (phase analysis and Rietveld method), thermal analysis and optical spectroscopy. Both oxides were synthesized by thermal sintering of co-precipitated powders. The synthesis study was performed in the temperature range 650-1690 °C. The amorphous phase exists below 700 °C. The crystallization of the ordered pyrochlore phase (P) in the range 800-1000 °C is accompanied by oxygen release. The ordered pyrochlore phase (P) exists in the range 1000−1200 °C. Heat-treatment at T ≥ 1600 °C leads to the formation of an oxide ion-conducting phase with a distorted pyrochlore structure (P2) and an ionic conductivity of about 10⁻³ S/cm at 740 °C. Complex impedance spectra are used to separately assess the bulk and grain-boundary conductivity of the samples. At 700 °C and oxygen pressures above 10⁻¹⁰ Pa, the Er_2+xTi_2−xO_7−δ (x = 0, 0.096) samples are purely ionic conductors.     

Apparent Activation Energy of Concrete in Early Age Determined by Adiabatic Test

The apparent activation energy of concrete in early age was determined by adiabatic temperature rise test with different initial temperatures. The influence of mineral admixtures such as fly ash, slag and silica fume on the apparent activation energy of concrete was investigated. The equivalent age that expresses the maturity of concrete was calculated to evaluate the cracking risk of concrete in structures. The results reveal that a substitution of 20% fly ash for Portland cement obviously decreases the apparent activation energy of concrete, however, a substitution of 10% silica fume for Portland cement increases the apparent activation. Finite element method analysis of a simulating concrete wall shows that the concrete containing 20% fly ash has the lowest cracking risk.     

用复合添加剂调变活性炭孔隙制备中孔活性炭

以宁夏某商品无烟煤活性炭为原料，以硝酸钾和助剂作为复合添加剂，选择不同的浸渍量及配比，进行再活化、酸洗、水洗，制备中孔发达的活性炭．通过测定活性炭的碘值、亚甲蓝吸附量及氮吸附、脱附等温线，研究了添加剂浸渍量及配比和活化工艺的改变对活性炭碘值、亚甲蓝值及孔结构的影响规律．结果表明：复合添加剂有助于提高碘值和亚甲兰值，但过高的烧失率却会使碘值下降；提高复合添加剂的量，有利于活性炭中孔和大孔的发展，使微孔率降至35％左右，而中孔率33％～35％；复合添加剂以1：1配比时，不仅使中孔率更大，而且在较低的烧失率下就可以获得较大的孔容（0．64～0．66mL／g）；选择2％，49／6和69／6的添加剂量，可以灵活调整活性炭微孔、中孔和大孔的比例，实现活性炭孔隙的定向调变．     

基于ALR的Hopfield神经网络在高程拟合中的应用

运用具有正规化项的增广拉格朗日函数作为神经网络的能量函数，辅助二次曲面拟合，进一步探索Hopfield神经网络在高程拟合中的应用。实际算例表明，该方法可以大大提高神经网络的计算效率和可靠性。     

Cover Picture: A Hierarchically Structured Ni(OH)2 Monolayer Hollow‐Sphere Array and Its Tunable Optical Properties over a Large Region (Adv. Funct. Mater. 4/2007)

The fabrication of hierarchically structured Ni(OH)₂ monolayer hollow‐sphere arrays with the shell composed of building blocks of nanoflakelets is reported on p. 644 by Weiping Cai and co‐workers. The morphology can be easily controlled by the synthesis parameters, and the arrays show a tunable optical transmission stop band. Tuning can be achieved by changing the size or morphology of the hollow spheres. Such arrays may have potential applications in optical devices, photonic crystals, and as sensors for gas detection. The fabrication of a hierarchically structured Ni(OH)₂ monolayer hollow‐sphere array with the shell composed of building blocks of nanoflakelets is demonstrated based on a colloidal monolayer and electrochemical deposition. The morphology can be easily controlled by the colloidal monolayer and deposition parameters. Importantly, such monolayer hollow‐sphere array shows a morphology‐ and size‐dependent tunable optical transmission stop band. This stop band can be easily tuned from 455–1855 nm by changing the size of the hollow spheres between 1000 and 4500 nm, and also fine‐adjusted by changing the deposition time. The array exhibits a nearly incident‐angle‐independent position of the stop band that 3D photonic crystals do not possess. This structure may have potential applications in optical devices, photonic crystals, and sensors for gas detection.     

Effect of Aluminum Doping on the Performance and Microstructure of Methyl-Modified SiO2 Sol

Abstract

With methyltriethoxysilane as hydrophobic precursors and aluminum isopropoxide as the aluminum source, the Al₂O₃/SiO₂ sols and their gel materials were prepared. The effects of aluminum content (n_Al) on the viscosity (η), density (ρ), reaction rate constant (k), Gibbs energies of activation for viscous flow (ΔG*), particle size of Al₂O₃/SiO₂ sols were studied. And the high temperature calcined materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The results show that, with the increase of n_Al, the η, n and ΔG* values of the Al₂O₃/SiO₂ sols decrease while the k and ρ values and average particle sizes increase. There is strong intermolecular interaction between the Al₂O₃ and SiO₂ sol molecules. The Al-O-Si bond exists in the Al₂O₃/SiO₂ materials before and after calcination at 350?°C. Calcination at 350?°C in N₂ atmosphere can change the phase structure of Al₂O₃/SiO₂ sample greatly, which can make the γ-AlOOH in the Al₂O₃/SiO₂ gel material convert to γ-Al₂O₃ through dehydration.     

Probing hydroxyl radical generation from H<Subscript>2</Subscript>O<Subscript>2</Subscript> upon plasmon excitation of gold nanorods using electron spin resonance: Molecular oxygen-mediated activation

Gold nanostructures are among the noble metal nanomaterials being intensely studied due to their good biocompatibility, tunable localized surface plasmon resonance (SPR), and ease of modification. These properties give gold nanostructures many potential chemical and biomedical applications. Herein, we demonstrate the critical role of oxygen activation during the decomposition of hydrogen peroxide (H₂O₂) in the presence of photoexcited gold nanorods (AuNRs) by using electron spin resonance (ESR) techniques. Upon SPR excitation, O₂ is activated first, and the resulting reactive intermediates further activate H₂O₂ to produce ?OH. The reactive intermediates exhibit singlet oxygen-like (¹O₂-like) reactivity, indicated by ¹O₂-specific oxidation reaction, quenching behaviors, and the lack of the typical ¹O₂ ESR signal. In addition, by using the antioxidant sodium ascorbate (NaA) as an example, we show that hydroxyl radicals from H₂O₂ activation can induce much stronger NaA oxidation than that in the absence of H₂O₂. These results may have significant biomedical implications. For example, as oxidative stress levels are known to influence tumorigenesis and cancer progression, the ability to control redox status inside tumor microenvironments using noble metal nanostructures may provide new strategies for regulating the metabolism of reactive oxygen species and new approaches for cancer treatment.

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