氢化锆在高温水蒸气中的氧化行为

通过恒温恒压氧化实验研究了氢化锆在300~700℃高温水蒸气中的氧化行为。结果表明,氢化锆的质量增重随着氧化温度的升高而增大。在氧化过程进行15h以后,OH-/O在氧化膜中的内扩散成为氧化反应的控速步骤。水蒸气中的H抑制了氢化锆在高温氧化条件下的氢损失。氧化膜主要由单斜相M-ZrO2组成,氧化膜的最外层由四方相T-ZrO2和立方相C-ZrO2组成。     

New chemistry of transition metal oxyhydrides

Abstract

In this review we describe recent advances in transition metal oxyhydride chemistry obtained by topochemical routes, such as low temperature reduction with metal hydrides, or high-pressure solid-state reactions. Besides the crystal chemistry, magnetic and transport properties of the bulk powder and epitaxial thin film samples, the remarkable lability of the hydride anion is particularly highlighted as a new strategy to discover unprecedented mixed anion materials.     

Nb90W5M5三元固溶体合金的结构和氢渗透性能

合金化是改善Nb金属氢脆问题的有效途径。本文制备了Nb90W5M5三元(M=Co,Ni,Mo,Ti)合金,利用XRD、SEM、PCT、电化学测试和三点弯曲试验研究其相结构、氢化物形成焓、氢扩散系数和机械力学性能。研究证实,Nb90W5M5(M=Co,Ni,Mo,Ti)均为Nb基固溶体结构(Nb-bcc),受原子半径的影响,Nb90W5M5三元合金均有不同程度的晶格畸变现象。Nb90W5Co5合金的晶胞体积畸变收缩明显、晶格点阵常数最小,在Nb基固溶体的晶界和晶内缺陷处有富Co的NbCo化合物固溶组织析出。Nb90W5Co5合金具有低的氢化物形成焓绝对值(-22.3 kJ/mol)、高的氢扩散系数(1.57×10-9 cm^2/s)、高临界载荷(78.4 N),表现出良好的抗弯力学性能和氢渗透性能,这与其多元掺杂导致的微观结构特征有关。     

Using MgO to improve the (de)hydriding properties of magnesium

Of all the materials presently being investigated to safely store high volumes of hydrogen for mobile applications; magnesium remains the most attractive. Magnesium is a light, low cost metal with high capacity for hydrogen storage but its (de)hydriding kinetics have to be improved for practical applications. Recently, hydrogen kinetics in magnesium have been significantly improved by mechanically milling magnesium hydride with catalyst transition metals or metal oxides. Here, we report that similar improvements can be achieved without using a catalyst. Our results demonstrate that magnesium hydride milled with magnesium oxide exhibits dehydriding and hydriding kinetics as fast as those obtained with catalyst transition metals or metal oxides.     

Sample preparation for quantitation of tritium by accelerator mass spectrometry

The capability to prepare samples accurately and reproducibly for analysis of tritium (3H) content by accelerator mass spectrometry (AMS) greatly facilitates isotopic tracer studies in which attomole levels of 3H can be measured in milligram-sized samples. A method has been developed to convert the hydrogen of organic samples to a solid, titanium hydride, which can be analyzed by AMS. Using a two-step process, the sample is first oxidized to carbon dioxide and water. In the second step, the water is transferred within a heated manifold into a quartz tube, reduced to hydrogen gas using zinc, and reacted with titanium powder. The 3H/1H ratio of the titanium hydride is measured by AMS and normalized to standards whose ratios were determined by decay counting to calculate the amount of 3H in the original sample. Water, organic compounds, and biological samples with 3H activities measured by liquid scintillation counting were utilized to develop and validate the method. The 3H/1H ratios were quantified in samples that spanned 5 orders of magnitude, from 10(-10) to 10(-15), with a detection limit of 3.0 x 10(-15), which is equivalent to 0.02 dpm tritium/mg of material. Samples smaller than 2 mg were analyzed following addition of 2 mg of a tritium-free-hydrogen carrier. Preparation of organic standards containing both 14C and 3H in 2-mg organic samples demonstrated that this sample preparation methodology can also be applied to quantify both of these isotopes from a single sample.     

pH-sensitive solid-state electrode based on electrodeposited nanoporous platinum

The nanoporous platinum oxide (H1-ePtO) as a hydrogen ion-selective sensing material is reported. Bare nanoporous platinum oxides exhibit near-Nernstian behavior (e.g., -55 mV/pH in PBS), ignorable hysteresis, a short response time, and high precision, which are remarkably better than those of flat platinum oxides. The electrode potential of a nanoporous platinum oxide responds exclusively to hydrogen ion, which implies its usefulness as a solid-state pH sensor. In the present study, the performance of nanoporous platinum oxide was investigated and compared with that of IrOx in terms of selectivity and the influences of ionic strength, temperature, complexing ligands, and surfactants. H1-ePtO functions well as a pH-sensing solid-state material, and it is viewed as a promising alternative to IrOx. Interference by redox couples was successfully suppressed by covering the H1-ePtO surface with a protective layer, e.g., an electropolymerized polyphenol thin film. Since the nanoporous platinum oxide with such a protective layer is particularly suitable for miniaturization and micropatterning, our findings suggest its usefulness in applications such as solid-state pH sensors embedded in chip-based microanalysis systems.     

面向21世纪的稀土工业

中国拥有世界上最丰富的稀土资源。1998年中国稀土氧化物(REO)的生产能力已达到20000t,几乎为世界需求的2倍,严重依赖出口,出口量占生产量的2／3。文章论述了稀土在冶金、永磁、储氢合金、催化剂、固体氧化物燃料电池和激光材料等方面的应用进展;指出我国未来稀土工业的方向是开发高技术含量和高附加值的产品,拓宽国内和国际市场。     

Amorphous Oxysulfide Reconstructed from Spinel NiCo2S4 for Efficient Water Oxidation

The progress of effective and durable electrocatalysts for oxygen evolution reaction (OER) is urgent, which is essential to promote the overall efficiency of green hydrogen production. To improve the performance of spinel cobalt-based oxides, which serve as promising water oxidation electrocatalysts in alkaline electrolytes, most researches have been concentrated on cations modification. Here, an anionic regulation mechanism is employed to adopt sulfur(S) anion substitution to supplant NiCo₂O₄ by NiCo₂S₄, which contributed to an impressive OER performance in alkali. It is revealed that the substitution of S constructs a sub-stable spinel structure that facilitates its reconstruction into active amorphous oxysulfide under OER conditions. More importantly, as the active phase in the actual reaction process, the hetero-anionic amorphous oxysulfide has an appropriately tuned electronic structure and efficient OER electrocatalytic activity. This work demonstrates a promising approach for achieving anion conditioning-based tunable structure reconstruction for robust and easy preparation spinel oxide OER electrocatalysts.     

Synthesis and electrochemical performances of LiNiCuZn oxides as anode and cathode catalyst for low temperature solid oxide fuel cell

Low temperature solid oxide fuel cell (LTSOFC, 300-600 degrees C) is developed with advantages compared to conventional SOFC (800-1000 degrees C). The electrodes with good catalytic activity, high electronic and ionic conductivity are required to achieve high power output. In this work, a LiNiCuZn oxides as anode and cathode catalyst is prepared by slurry method. The structure and morphology of the prepared LiNiCuZn oxides are characterized by X-ray diffraction and field emission scanning electron microscopy. The LiNiCuZn oxides prepared by slurry method are nano Li0.28Ni0.72O, ZnO and CuO compound. The nano-crystallites are congregated to form ball-shape particles with diameter of 800-1000 nm. The LiNiCuZn oxides electrodes exhibits high ion conductivity and low polarization resistance to hydrogen oxidation reaction and oxygen reduction reaction at low temperature. The LTSOFC using the LiNiCuZn oxides electrodes demonstrates good cell performance of 1000 mW cm(-2) when it operates at 470 degrees C. It is considered that nano-composite would be an effective way to develop catalyst for LTSOFC.     

Ca掺杂Sr2Fe1.5Mo0.5O6-δ材料的合成与作为对称固体氧化物燃料电池电极催化剂的性能研究

对称固体氧化物燃料电池由于生产过程简单、成本低, 受到了研究者的广泛关注。然而较低的电极催化性能制约了其进一步的发展。本研究利用溶胶-凝胶法合成了一系列钙取代Sr₂Fe_1.5Mo_0.5O₆的钙钛矿材料(Sr_2-xCa_xFe_1.5Mo_0.5O_6-δ, x=0, 0.2, 0.4, 0.6), 并研究了其作为对称固体氧化物燃料电池电极催化剂的性能。X射线衍射(XRD)测试表明所有样品在空气与氢气气氛中均能保持立方钙钛矿结构。而在程序升温还原(TPR)过程中, Ca ²⁺的掺入能有效降低还原温度, 提升其对析氧反应的催化活性。对称阳极电池在氢气气氛中的测试表明, 当Ca ²⁺的掺入量为0.6时电池极化阻抗最小。利用流延骨架与湿化学浸渍法制备了单电池SC_0.6FMO|La_0.9Sr_0.1Ga_0.8Mg_0.2O₃(LSGM)| SC_0.6FMO。以氢气作为燃料时, 单电池在800与650 ℃的最大功率密度分别为1.05与0.41 W?cm ^-2。以上结果表明Sr_2-xCa_xFe_1.5Mo_0.5O_6-δ可以作为高效对称燃料电池的电极催化剂。     

电动汽车和相关电源材料的现状与前景

论述了电动汽车（EV）、电动汽车用镍氢电池、锂离子电池、质子交换膜燃料电池（PEMFC）、固体氧化物燃料电池（SOFC）及相关材料的研发现状、产业化前景，指出以电动汽车代替燃油内燃机汽车，以氢能代替碳基燃料，是当前运输业的主要发展方向。     

New high concentration–high temperature hydrogenation method for slow strain rate tensile tests

The aim of the present paper is to propose an innovative hydrogenation method based on metal hydride dissociation.By heating metal hydride, high pressure of molecular hydrogen is generated, which can be used to promote diffusion through the steel, resulting in very high atomic hydrogen concentration.This new hydrogenation method was tested on a F82H steel, a Reduced Activation Ferritic/Martensitic (RAFM) steel developed for nuclear fusion application, where high temperature Hydrogen Embrittlement (HE) is a matter of serious concern.The main goal of this study is to propose a methodology to perform tensile tests on steel at high temperature and high hydrogen contents.The technique is easy and cheap. Furthermore, by using different metal hydrides and tuning temperatures, different hydrogen concentrations can be tested.     

Effect of high heating rate on thermal decomposition behaviour of titanium hydride (TiH2) powder in air

DTA and TGA curves of titanium hydride powder were determined in air at different heating rates. Also the thermal decomposition behaviour of the aforementioned powder at high heating rates was taken into consideration. A great breakthrough of the practical interest in the research was the depiction of the P _H2-time curves of TiH ₂ powder at various temperatures in air. In accordance with the results, an increase in heating rate to higher degrees does not change the process of releasing hydrogen from titanium hydride powder, while switching it from internal diffusion to chemical reaction. At temperatures lower than 600 °C, following the diffusion of hydrogen and oxygen atoms in titanium lattice, thin layers TiH _x phase and oxides form on the powder surface, controlling the process. On the contrary, from 700 °C later on, the process is controlled by oxidation of titanium hydride powder. In fact, the powder oxidation starts around 650 °C and may escalate following an increase in the heating rate too.     

Softening of α-Ti by electrochemically introduced hydrogen

The substantial and permanent modification of the elastic and inelastic properties of α-Ti have been achieved by hydrogen charging with cathodic polarization in an alkaline solution at RT, with the effects being dependent on the hydrogen state of the metal. The decrease in the elastic modulus to values close to those characteristic for bones have been caused by the distortion of the Ti lattice due to the supersaturation of the solid solution with hydrogen and (or) due to the formation of hydride precursors and precipitates. The low, but still detectable decrease in the elastic modulus has been observed by the formation of a compact hydride layer. On the basis of a thorough examination of the effect of cathodic polarization on the formation and morphology of the hydride phase and on the state of the α-Ti lattice, the electrochemical parameters provided: (1) the presence of hydrogen in supersaturated solid solution, (2) the formation of hydride precipitates of various stoichiometry and (3) the formation of the compact hydride surface layer have been determined.Taking into account the hydrogen induced metal softening, the easiness of electrochemical alloying the metal with hydrogen and no health hazard produced by this element when dissolved in body liquids, the electrochemical hydrogen treatment of Ti implants can be considered as very promising.     

Interstitial oxide ion conductivity in the layered tetrahedral network melilite structure

High-conductivity oxide ion electrolytes are needed to reduce the operating temperature of solid-oxide fuel cells. Oxide mobility in solids is associated with defects. Although anion vacancies are the charge carriers in most cases, excess (interstitial) oxide anions give high conductivities in isolated polyhedral anion structures such as the apatites. The development of new families of interstitial oxide conductors with less restrictive structural constraints requires an understanding of the mechanisms enabling both incorporation and mobility of the excess oxide. Here, we show how the two-dimensionally connected tetrahedral gallium oxide network in the melilite structure La(1.54)Sr(0.46)Ga(3)O(7.27) stabilizes oxygen interstitials by local relaxation around them, affording an oxide ion conductivity of 0.02-0.1 S cm(-1) over the 600-900 degrees C temperature range. Polyhedral frameworks with central elements exhibiting variable coordination number can have the flexibility needed to accommodate mobile interstitial oxide ions if non-bridging oxides are present to favour cooperative network distortions.     

Ga取代Mn对固体氧化物燃料电池阳极材料La_4Sr_8Ti_(11)Mn_(1-x)Ga_xO_(38-δ)微结构、性能的影响

采用球磨-高温固相法合成固体氧化物燃料电池阳极材料La4Sr8Ti11Mn1-xGaxO38-δ(x=0、0.25、0.50、0.75),并研究Ga取代量对该系列材料(LSTMG)的晶体结构、热膨胀系数(TEC)、电子电导率的影响规律。研究结果表明,随着Ga取代量的增加,LSTMG的晶格常数逐渐减小,电子电导率先增加后降低,热膨胀系数呈现先降低后增加的趋势。当x=0.50时,该系列材料具有较好的综合性能。     

Hydriding and dehydriding rates and hydrogen-storage capacity of Mg–14Ni–3Fe2O3–3Ti prepared by reactive mechanical grinding

The magnesium prepared by mechanical grinding under H₂ (reactive mechanical grinding) with transition elements or oxides showed relatively high hydriding and dehydriding rates when the content of additives was about 20 wt%. Ni (expected to increase hydriding and dehydriding rates) was chosen as transition element to be added. Fe₂O₃ (expected to increase hydriding rate) was selected as an oxide to be added. Ti was also selected since, it was considered to increase the hydriding and dehydriding rates by forming Ti hydride. A sample, Mg–14Ni–3Fe₂O₃–3Ti, was prepared by reactive mechanical grinding and its hydrogen storage properties were investigated. This sample absorbed 4·02 wt% H for 5 min, 4·15 wt% H for 10 min and 4·42 wt% H for 60 min at n?=?2. It desorbed 2·46 wt% H for 10 min, 3·98 wt% H for 30 min and 4·20 wt% H for 60 min at n?=?2.     

Effect of hydrogen on the low-temperature mechanical properties of V-5 at % Ti alloys

The effects of grain size and hydrogen in solid solution or as hydrides on the strength and ductility of V-5 at % Ti was studied over the temperature range 15–448 K. Comparison of the strength and ductility characteristics of hydrogenated alloys where hydrides were not observed down to 78 K (1.8 and 1.9 at % H alloys) or where hydrides were observed to form near 230 K (3.8 and 3.9 at % H alloys) indicated that the presence of hydride precipitates had no apparent influence on the strength or ductility characteristics. It appears that the main consequence of hydride precipitation is that hydrogen is removed from solid solution making strengthening less effective than expected based on the total hydrogen content. Decreasing grain size from 31 m to 8 m had no apparent effect on ductility in the nonhydrogenated alloys (< 0.05 at % H) but it did increase the strength over most of the temperature range and especially at 15 K. In the hydrogenated alloys this decrease in grain size lowered the transition temperature about 10 K and it appreciably increased the degree of ductility return at 78 K and below. The ductility return below 78 K peaked near 50 K before decreasing below 30 K with the improvement in ductility being greatest in the alloys with the lower hydrogen contents.     

3-Methyltrimethylammonium poly(2,6-dimethyl-1,4-phenylene oxide) based anion exchange membrane for alkaline polymer electrolyte fuel cells

Hydroxyl ion (OH^?) conducting anion exchange membranes based on modified poly (phenylene oxide) are fabricated for their application in alkaline polymer electrolyte fuel cells (APEFCs). In the present study, chloromethylation of poly(phenylene oxide) (PPO) is performed by aryl substitution rather than benzyl substitution and homogeneously quaternized to form an anion exchange membrane (AEM). ¹H NMR and FT-IR studies reveal successful incorporation of the above groups in the polymer backbone. The membrane is characterized for its ion exchange capacity and water uptake. The membrane formed by these processes show good ionic conductivity and when used in fuel cell exhibited an enhanced performance in comparison with the state-of-the-art commercial AHA membrane. A peak power density of 111 mW/cm² at a load current density of 250 mA/cm² is obtained for PPO based membrane in APEFCs at 30 °C.     

Phase Transformations of a CeCo3-Based Intermetallic Hydride at Temperatures from 200 to 950°C

Inorganic Materials - Samples obtained by heating a CeCo3-based intermetallic hydride with a low hydrogen content (1.0 H/FU) to a high temperature in an inert atmosphere have been characterized by...