Modulation of Electron Structure and Dehydrogenation Kinetics of Nickel Phosphide for Hydrazine-Assisted Self-Powered Hydrogen Production in Seawater

The electrocatalytic production of hydrogen from seawater provides a low-cost way to realize energy conversion, but is restricted by high potential for seawater electrolysis and the chlorine oxidation reaction (ClOR) at the anode. Here, the self-growth of Mo-doped Ni₂P nanosheet arrays with rich P vacancies on molybdenum-nickel foam (MNF) (Mo-Ni₂P_v@MNF) is reported as bifunctional catalyst for Cl-free hydrogen production by coupling hydrogen evolution reaction (HER) with hydrazine oxidation reaction (HzOR) in seawater. Impressively, the Mo-Ni₂P_v@MNF electrode as bifunctional catalyst has an excellent activity for overall hydrazine splitting (OHzS) with an ultralow voltage of only 571 mV at 1000 mA cm⁻² and can maintain stability for an ultra-long time of 1000 h at 100 mA cm⁻². Moreover, integration of OHzS into self-assembled hydrazine fuel cells (DHzFC) or solar cells can enable the self-powered H₂ production. The industrial hydrazine sewage as feed for the above eletrolysis system can be degraded to ≈5 ppb rapidly. Density functional thoery calculations demonstrate that the electronic structure modulation induced by P vacancies and Mo doping can not only achieve thermoneutral ΔG_H* for hydrogen evolution reaction but also enhance dehydrogenation kinetics from *N₂H₄ to *NHNH₂ for HzOR, achieving enhanced dehydrogenation kinetics.     

CH4气体光纤传感器的研究

在对ＣＨ４分子近红外吸收光谱分析比较的基础上,并考虑与８光纤的低耗窗口相一致和价格等因素,采用价廉的１．３ｕｍ波段的ＬＥＤ作为光源,实现了对甲烷气体的,检测灵敏度为１３００ｐｐｍ／ｍ。研究表明,灵敏度可通过提高入射光功率、气室长度等而进上步提高。     

K17镍基铸造高温合金环境损伤的研究

本文研究了镍基铸造高温合金K17在真空、空气和热腐蚀环境中热暴露前后持久性能和高温拉伸性能的变化.结果表明,真空中热暴露对K17合金的持久寿命没有影响,但降低高温瞬时拉伸强度,提高持久塑性和高温瞬时拉伸塑性;空气和热腐蚀环境中热暴露明显降低持久性能和高温瞬时拉伸性能,其中尤以热腐蚀环境最严重,空气环境暴露造成晶界氧化并贫Cr,热腐蚀环境暴露引起晶界严重硫化,晶界两侧贫Cr富S,因而弱化晶界,降低性能.     

Effect of 0.1 at.% zirconium on the cyclic oxidation resistance ofβ-NiAl

The effect of 0.1 at.% Zr (0.2 wt.% Zr) on the cyclic oxidation of hipped -NiAl was studied. Oxidation testing was performed in static air at 1100–1200 °C, using 1-hr exposure cycles for test times up to 3000 hr. The weight change versus time data were modeled with the COSP computer program to analyze and predict cyclic-oxidation behavior. Zr additions significantly change the nature of the scale-spalling process during cooling so that the oxide spalls near the oxide-air interface at a relatively low depth within the scale. Without Zr, the predominantly -Al₂O₃ scale tends to spall randomly to bare metal at relatively high effective-scale-loss rates, particularly at 1150°C and 1200°C. This leads to higher rates of Al consumption for the Zr-free aluminide and much earlier depletion of Al, leading to eventual breakaway (i.e., failure).     

The oxidation of Fe-19.6Cr-15.1Mn stainless steel

The oxidation behavior in air of Fe-19.6Cr-15.1Mn was studied from 700 to 1000°C. Pseudoparabolic kinetics were followed, giving an activation energy of 80 kcal/mole. The scale structure varied with temperature, although spinel formation occurred at all temperatures. At both 700 and 800°C, a thin outer layer of -Mn₂O₃ formed. The inner layer at 700°C was (Fe,Cr,Mn)₃O₄, but at 800°C there was an intermediate layer of Fe₂O₃ and an inner layer of Cr₂O₃ + (Fe, Cr,Mn)₃O₄. Oxidation at 900°C produced an outer layer of Fe₃O₄ and an inner layer of Cr₂O₃+(Fe,Cr,Mn)₃O₄. Oxidation at 1000°C caused some internal oxidation of chromium. In addition, a thin layer of Cr₂O₃ formed in some regions with an intermediate layer of Fe₃O₄ and an outer layer of (Fe,Mn)₃O₄. A comparison of rates for Fe₃O₄ formation during oxidation of FeO as well as for the oxidation of various stainless steels, which form spinels, gave good agreement and strongly suggests that spinel growth was rate controlling. The oxidation rate of this alloy (high-Cr) was compared with that of an alloy previously studied, Fe-9.5Cr-17.8Mn (low-Cr) and was less by about a factor of 12 at 1000°C and by about a factor of 100 at 800°C. The marked differences can be ascribed to the destabilization of wustite by the higher chromium alloy. No wustite formation occurred in the high-Cr alloy, whereas, extensive wustite formed in the low-Cr alloy. Scale structures are explained by the use of calculated stability diagrams. The mechanism of oxidation is discussed and compared with that of the low-Cr alloy.     

Oxidation pretreatment to reduce corrosion of 20%Cr-25%Ni-Nb stainless steel. II. Surface morphology and oxide characterization

Improved corrosion behavior of 20%Cr-25%Ni-Nb steel resulting from a low pressure oxidation pretreatment in CO2 has been related to changes in elemental composition and distribution in the oxide scale. Auger electron spectroscopy, secondary ion mass spectroscopy, electron microprobe, and X-ray diffraction techniques have been used to investigate the properties of the oxide scale formed on both untreated and pretreated specimens when oxidized at 823 K and 923 K in a CO₂-1%CO atmosphere. A sputter ion plating technique has been used to separate the oxide from the metal and the incorporation of chromium and silicon at the metal-oxide interface has been investigated at grain centers and grain boundaries by depth profiling. The improvement in oxide adhesion and oxidation rates, using data from Parts I and II of this study, is assessed in terms of oxide formation by solid-state displacement reactions.     

In Situ observation of the effect of temperature on Cu2O scale morphology

The effect of temperature on copper oxide scale morphology was studied during in situ oxidation of OFHC copper in a hot-stage environmental scanning electron microscope (HSESEM). Cuprous oxide scales grown at low temperature [0.2T_m(Cu₂O)] and intermediate temperatures 0.6–0.7T_m(Cu₂O)] were found to be crystallographically oriented. At intermediate temperatures, scales exhibited nonplanar features such as ridges and growth pyramids. At high temperatures [T> 0.8T_m(Cu₂O)], scales had planar morphologies and a few dislocation growth pits. Downquenching and upquenching of the Cu₂O scales from steady-state oxidation temperatures induced morphological changes such as cavity formation and surface reconstruction.     

High-temperature oxidation of Pt-45Pd-10Rh

The surfaces of Pt-45Pd-10Rh foils oxidized over the range 875–1075 K in a 20% O₂-Ar mixture at atmospheric pressure were examined by Auger electron, X-ray photoelectron, and Raman spectroscopy. The composition of the oxide formed on the surface was found to vary with temperature from predominantly PdO at 875 K to PdRhO₂ at 1075 K. Only a few atomic percent Pt was observed, present in both the metallic and (apparently) +1 oxidation states at 875 K and in the metallic state at 1075 K. The formation of PdRhO₂ (and no Rh₂O₃) at 1075 K was found to persist upon reoxidation following a low-temperature reduction cycle in which the increased Rh concentration on the surface was retained. An oxidation-induced Rh enrichment of the surface of the alloy foil beyond 50 at. % does not appear likely within the temperature/pressure regime investigated.     

The location of hydrogen in the kinetics of oxidation of ferrous alloys by superheated steam

The rate of emission of hydrogen from the metal surface and from the oxide surface has been determined during the oxidation of ferrous alloys at 501°C. The kinetics were in accordance with the assumption of a parabolic rate law, and the rate constants were in agreement with those calculated from the thickness of the oxide layer at the end of the reaction. The proportion of hydrogen emitted from the metal to that from the oxide surface showed a dependence on the partial pressure of steam for the 9%Cr-1%Mo alloy at 501°C. The ratio was dependent on the alloy composition, and also on temperature, as shown by results for the 9%Cr-1%Mo alloy at 450 and 552°C. For this alloy, the activation energy and rate constants are consistent with a rate-determining step dependent on cation diffusion. The oxide film is almost impermeable to hydrogen gas. A possible oxidation mechanism is suggested.