激光熔覆铜锰合金选择性脱合金制备纳米多孔涂层的研究

本文通过激光加工结合电化学腐蚀脱合金法, 成功实现了纳米多孔涂层的制备. 采用激光熔覆首先在45钢表面制备了成形良好、稀释率低的铜锰合金熔覆层, 并通过快速重熔工艺实现了初始材料组织细化. 研究表明, 在不同的电解液下,铜锰合金的临界腐蚀电位出现了明显的偏移; 在不同的腐蚀电流下,铜锰合金腐蚀后的形貌迥异. 最终,通过选择性腐蚀成功实现了纳米多孔铜和纳米多孔锰涂层的制备, 并利用电位-pH图对脱合金的选择性腐蚀进行了详细的理论解释.     

Facile fabrication of forest‐like ZnO hierarchical structures on conductive fabric substrate

Forest‐like ZnO hierarchical structures were synthesized on the conductive fabric substrate via a simple one‐step electrochemical deposition process. By applying externally a high cathodic voltage to the samples, ZnO microrods were aligned on the seed coated layer and then ZnO branches were formed on the pillars of ZnO microrods, which was caused by the strong deposition potential between the pillars of ZnO microrods and the Zn²⁺ dissolved in growth solution. At the external cathodic voltage of –3 V, the optimized forest‐like ZnO hierarchical structures exhibited high density, high porosity, and good crystallinity. These fabricated forest‐like ZnO hierarchical structures are potentially useful for electronic and chemical sensing applications. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Enhancement in SERS intensity with hierarchical nanostructures by bimetallic deposition approach

We investigate the plasmonic enhancement arising from bimetallic (Au/Ag) hierarchical structure and address the fundamental issues relating to the design of multilayered nanostructures for surface‐enhanced Raman scattering (SERS) spectroscopy. SERS‐active nanosphere arrays with Ag underlayer and Au overlayer were systematically constructed, with the thickness of each layer altered from 40 to 320 nm. The SERS responses of the resultant bimetallic structures were measured with 2‐naphthalenethiol dye as the test sample. The results confirm the dependency of SERS enhancement on the thickness ratio (Au : Ag). Compared with Au‐arrays, our optimized bimetallic structures, which exhibit nanoprotrusions on the nanospheres, were found to be 2.5 times more SERS enhancing, approaching the enhancement factor of an Ag‐array. The elevated SERS is attributed to the formation of effective hot‐spots associated with increased roughness of the outer Au film, resulting from subsequent sputtering of Au granules on a roughened Ag surface. The morphology and reflectance studies suggest that the SERS hot‐spots are distributed at the junctions of interconnected nanospheres and over the nanosphere surface, depending on the thickness ratio between the Au and Ag layers. We show that, by varying the thickness ratio, it is possible to optimize the SERS enhancement factor without significantly altering the operating plasmon resonance wavelength, which is dictated solely by the size of the underlying nanospheres template. In addition, our bimetallic substrates show long‐term stability compared with previously reported Ag‐arrays, whose SERS efficiency drops by 60% within a week because of oxidation. These findings demonstrate the potential of using such a bimetallic configuration to morphologically optimize any SERS substrate for sensing applications that demand huge SERS enhancement and adequate chemical stability. Copyright © 2011 John Wiley & Sons, Ltd.     

Properties of passive nano films on zircaloy-4 affected by defects induced by hydrogen permeation

In this work, hydrogen absorption and the permeation behavior of the passive layer formed on zircaloy-4 are investigated. Potentiodynamic polarization, Mott–Schottky analysis, electrochemical impedance spectroscopy, and Raman scattering spectroscopy are employed to characterize the passive defects before and after hydrogen permeation. It is found that the nanoscale passive ZrO2 films play an important role in the resistance against corrosion; hydrogen impingement,however, reduces the passive impedance towards hydrothermal oxidation. The increase of defects(vacancies) in passive film is probably attributed to the degradation. We believe that this finding will provide valuable insight into the understanding of the corrosion mechanism of zircaloys used in light water reactors.     

Molecular dynamics simulations of hydrogen adsorption/desorption by palladium decorated single-walled carbon nanotube bundle

Utilising molecular dynamics simulations, the hydrogen molecules adsorption isotherms of the (8,?0) palladium decorated single-walled carbon nanotube (SWNT) were obtained. The hydrogen adsorption was studied on the external, interstial and internal surfaces of the SWNT bundle at several temperatures ranging from 77 to 400?K. The results were compared with the bare single-walled carbon nanotube bundle under the same conditions. The decorated carbon nanotube bundle hydrogen adsorption was significantly higher than that of the bare one. The hydrogen desorption and readsorption were studied using temperature as the readsorption/desorption variable. The rate constants were calculated for the hydrogen desorption at different temperatures. The calculated decorated SWNT bundle hydrogen desorption activation energy was higher than that for the bare SWNT bundle. The calculated activation energies for the hydrogen desorption in both nanotube bundles specified the temperature dependency of hydrogen desorption.     

DFT study of hydrogen storage in Pd-decorated C60 fullerene

Hydrogen storage reactions on Pd-doped C₆₀ fullerene are investigated by using the state-of-the-art density functional theory calculations. The Pd atom prefers to bind at the bridge site between two hexagonal rings, and can bind up to four hydrogen molecules with average adsorption energies of 0.61, 0.45, 0.32, and 0.21 eV per hydrogen molecule. With no metal clustering, the system gravimetric capacities are expected to be as large as 5.8 wt%. While the desorption activation barriers of the complexes nH₂ + Pd–C₆₀ with n = 1 are outside the department of energy (DOE) domain (?0.2 to ?0.6 eV), the desorption activation barriers of the complexes nH₂ + Pd–C₆₀ with n = 2–4 are inside this domain. While the interaction of 1H₂ with Pd + C₆₀ is irreversible at 459 K, the interaction of 2H₂ with Pd + C₆₀ is reversible at 529 K. The hydrogen storage of the irreversible 1H₂ + Pd–C₆₀ and reversible 2H₂ + Pd–C₆₀ interactions are characterised in terms of densities of states, infrared, Raman, and proton magnetic resonance spectra, electrophilicity, and statistical thermodynamic stability.     

氢在Nd晶体中行为的分子动力学模拟

由三维Mobius反演变换所得的金属Nd原子和H原子间的相互作用势和组合规则的方法得到的Nd H原子间的相互作用势 ,利用正则系统分子动力学算法研究了在一定加载应力强度因子K =0 .6MPam下 ,氢在Nd晶体中的行为。模拟结果表明 ,氢在Nd晶体裂尖富集成许多氢原子团或氢气团。这可用来部分地解释NdFeB稀土永磁体吸氢后的氢爆行为。     

水中脉冲放电产生过氧化氢及其影响因素

采用介质涂覆的球-筒电极结构,用以脉冲电压条件下在水中产生放电,通过比色法检测放电产生的过氧化氢,研究了不同电压脉冲幅值、脉冲宽度（储能电容的大小）、水的电导率以及脉冲频率对过氧化氢产生速率的影响,实验结果表明过氧化氢的产率随电压脉冲幅值的增大而增大。当电压脉冲幅值足够高时,水中放电由流注放电形式转换为电弧放电形式,此时过氧化氢产率也大幅提高,而在相同电压条件下,随水的电导率的增大,过氧化氢的产率减小。在相同电压下,脉冲频率的增大,导致放电平均功率增大,水中放电产生过氧化氢的浓度提高。在3.3 W功率时,120 min后水中过氧化氢浓度达到0.2 mmol/L,从而证明了所用电极结构的优越性。     

水中脉冲放电产生过氧化氢及其影响因素

采用介质涂覆的球-筒电极结构,用以脉冲电压条件下在水中产生放电,通过比色法检测放电产生的过氧化氢,研究了不同电压脉冲幅值、脉冲宽度(储能电容的大小)、水的电导率以及脉冲频率对过氧化氢产生速率的影响,实验结果表明过氧化氢的产率随电压脉冲幅值的增大而增大。当电压脉冲幅值足够高时,水中放电由流注放电形式转换为电弧放电形式,此时过氧化氢产率也大幅提高,而在相同电压条件下,随水的电导率的增大,过氧化氢的产率减小。在相同电压下,脉冲频率的增大,导致放电平均功率增大,水中放电产生过氧化氢的浓度提高。在3.3 W功率时,120 min后水中过氧化氢浓度达到0.2 mmol/L,从而证明了所用电极结构的优越性。     

Glauber amplitudes for transitions from low lying states in hydrogen atom by charged particle impact

The Glauber amplitudes for the general transitionnlm→n’l’m’ in charged particle hydrogen atom collisions have been obtained in the form of a one-dimensional integral. The final expression involves only a few hypergeometric functions ifn is not too large and is particularly suited to study excitation to highly excited states from a low lying state.     

Improvement of the determination of hydrogen content in a multicomponent sample by D-T generator

If a D-T generator is used as a neutron source to simultaneously measure the content of carbon, hydrogen and oxygen in a multicomponent sample by NIPGA (Neutron Induced Prompt Gamma-ray Analysis), the 14 MeV neutron flux can be regarded as a constant value. The relationship between the production of the hydrogen characteristic gamma-rays and its content is nonlinear. In this paper, we use MCNP (Monte Carlo N-Particle Transport code) to simulate the relationship and analyze it. In practical measurement of the characteristic gamma-ray, it's impossible to get the net count. Therefore, we use the experiment to obtain the relationship between the hydrogen content and the total count of its characteristic gamma-rays. If we use the relationship combined with the simulation result to calculate the hydrogen content, the metrical precision can be much increased. The deviation of hydrogen content between NIPGA and chemical analysis is less than 0.25%, which meets the requirement of coal industry.     

New observations on hydrogen bonding in ice by density functional theory simulations

In this paper, we report on a series of computational simulations on hydrogen bonding in two ice phases （Ih and Ic） using CASTEP with PW91 and RPBE exchange-correlation based on ab initio density functional theory. The strength of the H-bond is correlated with intramolecular O-H stretching, and the energy splitting exists for both the H-bond and covalent O-H stretching. By analyzing the dispersion relationship of to（q）, we observe the separation of the longitudinal optic （LO） mode from transverse optic （TO） mode at the gamma point, seemingly interpreting the controversial two H-bond peaks in the vibrational spectrum of ice recorded by inelastic incoherent neutron scattering experiments. The test of ambient environment on phonon density of sates （PDOS） shows that the relaxed tetrahedral structure is the most stable structural configuration for water clusters.     

Bias temperature instability analysis on memory properties improved by hydrogen annealing treatment in Ti/HfOx /Pt capacitors

The influence of the hydrogen annealing treatment on the reliability of Ti/HfO_x /Pt capacitors is investigated by analyzing bias temperature instability (BTI). As compared to the N₂‐annealed sample, in the case of hydrogen‐annealed samples, both the set/reset voltages and currents are reduced from 6.5 V/–1.6 V to 3.8 V/–1.2 V and from 4 mA/170 nA to 800 µA/30 nA at 0.1 V, respectively. Of particular interest is the dramatic reduction in the set voltage variation from 3.3 V to 1.8 V. In addition, in BTI experiments, the current shift at the high resistance state (HRS) is reduced from 1.5 µA to 40 nA under a bias stress of –1 V/1000 s and from 40 µA to 0.5 µA under a temperature stress of 120 °C/1000 s. These results show that the hydrogen annealing treatment is very effective in improving the reliability of RRAM cells because it reduces the leakage current under bias temperature stress. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

炸药爆轰制备纳米石墨粉储放氢性能实验研究

介绍了一种新的制备纳米石墨粉的方法——炸药爆轰法.通过对爆轰合成的黑色粉末进行x射线衍射分析，确认其为六方结构的纳米石墨，平均晶粒度为1.86—2.61nm.用BET气体吸附仪测试纳米石墨粉的比表面积约为500—650m2/g，由比表面积计算得到的纳米石墨粒度为4.41—6.85nm.在室温（≈290K）和12MPa压力条件下对纳米石墨粉进行储放氢气性能测试，结果表明纳米石墨粉样品的储放氢量为0.33wt%—0.37wt％.在相同实验条件下，纳米石墨粉原始样品的储放氢能力较原始纳米炭纤维（0.15wt%—0.35wt％）和多壁碳纳米管（0.15wt%—0.20wt％）的储放氢能力略强,但低于超级活性炭（0.92wt%—0.98wt％）.纳米碳材料的比表面积在其储放氢实验中起关键作用. 关键词： 爆轰 纳米石墨粉 比表面积 储放氢量     

Primary kinetic hydrogen isotope effects in deprotonations of a nitroalkane by intramolecular phenolate groups

Rate constants and kinetic isotope effects have been determined for the formation of nitronate anions from the ethers 1‐(2‐methoxyphenyl)‐2‐nitropropane, 7 (X = H, L = H and D) and 1‐(2‐methoxy‐5‐nitrophenyl)‐2‐nitropropane, 7 (X = NO₂, L = H and D), and from the corresponding phenols, 1‐(2‐hydroxyphenyl)‐2‐nitropropane, 3 (X = H, L = H and D), and 1‐(2‐hydroxy‐5‐nitrophenyl)‐2‐nitropropane, 3 (X = NO₂, L = H and D), in aqueous basic medium. For the ethers 7 , rates of deprotonation by hydroxide are comparable with those found for deprotonations of 2‐nitropropane, with k^H/k^D (25 °C) = 7.7 and 7.8, respectively. In both the cases, the isotope effects are conventionally temperature dependent. For the corresponding phenols 3 , conditions have been established under which the deprotonations of the nitroalkane are dominated by intramolecular deprotonation by the kinetically first‐formed phenolate anion, with an estimated effective molarity EM ～ 250. For 3 (X = H, L = H or D), k^H/k^D (25 °C) = 7.8, with E ? E = 6.9 kJ mol^?1 and A^H/A^D = 0.5. For 3 (X = NO₂, L = H or D), rates of intramolecular deprotonation are reduced 30‐fold, and an elevated kinetic isotope effect is found (k^H/k^D (25 °C) = 10.7). Activation parameters (E ? E = 17.8 kJ mol^?1 and A^H/A^D = 0.008) are compatible with an enhanced tunnelling contribution to reactivity in the H‐isotopomer. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigation of the interaction of sodium nitrite with hydrogen peroxide in aqueous solutions by the chemiluminescence method

An investigation is made of the chemiluminescence (luminol-dependent and spontaneous) of aqueous solutions of NaNO₂ and H₂O₂ in the pH range of 4.0–9.0. In the presence of luminol at pH>7 the initiator of luminescence is H₂O₂. At pH<7 the luminescence revealed seems to be initiated by peroxynitric acid (HOONO) produced by the interaction of NaNO₂ with H₂O₂ in weakly acid and acid solutions. Cysteine added to the solution prior to introducing H₂O₂ completely suppresses luminescence development in the pH range investigated. Moreover, cysteine quenches the luminescence already developed. Mannite and ethanol do not exert a substantial influence on the development of the luminescence. The solution of NaNO₂ and H₂O₂ is also characterized by spontaneous chemiluminescence, the intensity of which is one-two orders of magnitude lower than that of the luminol-dependent chemiluminescence. The intensity of the spontaneous chemiluminescence of the solutions of NaNO₂ and H₂O attains its maximum in the pH region of 6.5 to 7.0. It is assumed that the revealed spontaneous luminescence of the solutions of NaNO₂ and H₂O₂ is also attributable to formation of peroxynitrit acid in an activated state (HOONO^*). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 436–440, May–June, 1999.     

Helium/hydrogen synergistic effect in reduced activation ferritic/martensitic steel investigated by slow positron beam

Here, we investigated the irradiation defect in reduced activation ferritic/martensitic steels by slow positron beam. Three ion-irradiation experiments were carried out: (i) He²⁺ irradiation, (ii) H⁺ irradiation and (iii) He²⁺ irradiation followed by H⁺ irradiation, at temperature 450?°C. The presences of vacancy defects, represented by ?S_He+H parameter, induced by sequential irradiations was larger than the sum of defects, ?S_He parameter + ?S_H parameter, caused by single He ions and single H ions. The synergistic effect of He and H was confirmed clearly from the perspective of positron annihilation spectroscopy.     

Bubble-loop complexes induced by helium irradiation and effect of pre-irradiation and post-irradiation of hydrogen in reduced-activation ferritic/martensitic steel

In the present work, the synergistic effect of high concentration hydrogen and helium on the dislocation loops and bubbles as well as their correlations in reduced-activation ferritic/martensitic (RAFM) steels is investigated. Such an effect was transmuted from 14?MeV neutron irradiation and has been one of the most challenging issues for RAFM steels for future fusion reactors. After low dose (0.18?dpa) high concentration (5000 appm) single-ion helium irradiation at 723?K, very large dislocation loops were observed, and the majority of bubbles were inside dislocation loops, forming bubble-loop complexes. These bubble-loop complexes defects were also present in hydrogen/helium and helium/hydrogen sequential-ion irradiated steels. Pre-irradiated hydrogen ion effectively inhibited the later growth of loops induced by helium post-irradiation, and the higher the ratio of hydrogen to helium fluence, the greater the effect of inhibition. At high fluence of hydrogen pre-irradiation, the structure of bubble-loop complexes disappeared. On the other hand, hydrogen post-irradiation promoted the growth of loops induced by helium pre-irradiation, and the higher the ratio of hydrogen to helium fluence, the greater the effect of promotion. The mechanisms for hydrogen/helium synergistic effects are discussed.