应力对Ni_3Al合金表面氧化膜成分的影响

研究了Ni-23Al-0.5Zr—0.1B和Ni-17Al-8Cr—0.5Zr-0.1B(at-%)在应力作用下表面氧化成分的变化结果表明,在拉应力作用下氧化膜中的Ni含量明显增加分析和计算发现由于Ni和Al具有不同的氧化体积膨胀,在拉应力作用下Ni在氧化表层的富集可以减小氧化表面的弹性形变能。

Boosting chiral carboxylic acid hydrogenation by tuning metal-MO_(x)-support interaction in Pt-ReO_(x)/TiO_(2) catalysts

Engineering the surface microenvironment by tuning the binary interactions between a supported metal with a secondary metal oxide(MO_(x))or support has been a common method for improving the catalytic performance of supported metal catalysts.However,few studies have investigated the ternary interactions among the metal,MO_(x),and support.Here,we report for the first time the formation of metal-MO_(x)-support interaction(MMSI)in reducible TiO_(2)-supported PtReO_(x) catalysts,affording 87% yield and 100% ee in the tandem hydrogenation of an aqueous chiral cyclohexane-1,2-dicarboxylic acid into the corresponding diol;the catalytic activity is eight times higher than that obtained with non-reducible support counterparts in the same reaction via traditional batch synthesis with multiple steps and unfriendly reagents.Detailed experimental and computational studies suggest that the TiO_(2) crystalline phase-dependent density of the oxygen vacancies induces different Pt-ReO_(x)-TiO_(2) interactions,which dominate the electron transfer therein and tune the adsorption strength of the carbonyl moiety of the substrate/intermediate,thus promoting the hydrogenation activity and selectivity.In addition,the strong MMSI endows the optimal rutile TiO_(2) supported PtReO_(x) catalyst with an outstanding lifetime of 400 h in a fixed-bed reactor under acidic aqueous conditions and ensures efficient applications in the selective hydrogenation of aliphatic dicarboxylic acids and functional carboxylic acids.This work provides a promising strategy for the development of efficient and stable supported catalysts for the selective hydrogenation of diverse C-O and C=O bonds.

Copper and silver interactions at various exposure levels in a marine copepod, Acartia erythraea

Marine copepods, Acartia erythraea, were exposed separately to aqueous Cu and Ag media and to a Cu＋Ag mixture in a series of experiments during which the metal body burden and partitioning in the exoskeleton and polar and nonpolar parts of the animal cells were measured and the uptake and effiux rate constants for Cu and Ag were calculated. The metal uptake and effiux rate constants were 1.04×10^3±1.00×10^2 L·g^-1·d^-1 and 9.28× 102＋ 1.43×10-2 d^-1 for Cu and 1.60× 104＋1.78×10^3L·g^-1·d^-1and 9.23×10^2 -4- 9.1 1×10^3d^-1 for Ag, respectively. For both Cu and Ag, the uptake rate constants when the copepods were exposed to solutions of a single metal were generally higher than that when the copepods were exposed to metal mixtures. The results suggest an antagonistic interaction between waterborne Cu and Ag exists in marine copepods. The different distributions of Cu and Ag among the exoskeleton and polar and nonpolar parts of the copepods revealed that the metal bioavailability in copepods exposed to metal mixtures enhanced in some degree compared to copepods exposed to single metal solutions.

Promoting NO_(x)reduction via in situ activation of perovskite supported Pd catalysts under alternating lean-burn/fuel-rich operating atmospheres

Herein,we report the excellent De-NO_(x)performance of La0.7Sr0.3MnO3(LSM)perovskite-supported Pd catalysts(Pd-LSM)in alternating lean-burn/fuel-rich atmospheres using C3H6 as reductant and describe the in situ activation of the Pd catalysts via metal-support interaction(MSI)tuning.The NO_(x)reduction conversion of the Pd-LSM catalyst increased significantly from 56.1%to 90.1%and the production of N2O was suppressed.Our results demonstrated that this behavior was mainly attributed to the in situ transformation of Pd2+into Pd0 during the reaction.The generated Pd0 species could readily activate the C3H6 reductant and achieve an eight-fold higher turnover frequency than Pd2+for the reduction of NO_(x).Moreover,excessive MSIs inhibited the in situ generation of Pd0,and thereby,lowered the De-NO_(x)activity of the catalyst even at high Pd dispersion.In addition,the Pd-LSM catalysts exhibited much higher S tolerance than conventional Al_(2)O_(3)-supported catalysts.Our study provides a new approach for analyzing and designing highly active metal catalysts operated under dynamic alternating oxidizing/reducing atmospheric conditions.

A series of 3d-4f heterometallic frameworks comprising 2D lanthanide-organic layers and diverse Cu-complex pillars

Six novel 3D layer-pillared lanthanide-transition metal coordination polymers,LnCuX(IN)2(Ac)(H2O)(Ln = Tb,X = Br(1);Ln = Er,X = Cl(2)),[LnCuCl(IN)2(Ac)].H2O(Ln = Gd(3);Ln = Eu(4)),and [LnCu2Br2(IN)2(Ac)(H2O)].nH2O(Ln = Dy,n =0(5);Ln = Gd,n = 0.5(6))(IN = isonicotinate,Ac = acetate),have been obtained by linking Ln-organic layers and diverse Cu-complex pillars under hydrothermal conditions.1 and 2 are isostructural and formed by 2D Ln-IN-Ac layers and CuX(IN)2 pillars(X = Br(1),X= Cl(2));3 and 4 are isomorphic and comprised of 2D Ln-IN-Ac layers and dimeric Cu2Cl(IN)4 pillars;while 5 and 6 are isostructural and built from 2D Ln-IN-Ac layers and tetrameric Cu4Br4(IN)4 pillars.The magnetic susceptibility investigation of 3 and 6 shows the presence of weak antiferromagnetic exchange interactions between the Ln3+ ions.Compounds 1-6 represent good examples of using 2D Ln-organic layers and diverse Cu-complex pillars as building units to construct intriguing 3D Ln-TM-organic frameworks.

Influence of Organo-Metal Interactions on Regeneration of Exhausted Clay Mineral Sorbents in Soil Columns Loaded with Heavy Metals

Natural clay minerals can play an important role in crude remediation of wastewater polluted with the heavy metals （HMs） Cu, Zn and Ni. The presence and timing of ddition of natural dissolved organic matter （DOM） have a significant effect on the HM removal by clay mineral sorbents. However, the influence of the presence of DOM on the remediation of the used clay mineral sorbents once saturated with HMs is largely unknown. To resolve this, clay mineral-rich soil column of varying composition, loaded （i） with Cu, Zn and Ni only, （ii） first with DOM followed by Cu, Zn and Ni, or （iii） with DOM, Cu, Zn and Ni simultaneously, was used in a set of desorption experiments. The soil columns were leached with 0.001 mol L-1 CaCI2 dissolved in water as control eluent and 0.001 tool L-1 CaC12 dissolved in DOM as treatment eluent. During the preceding loading phase of the sorbent, the timing of DOM addition （sequential or concurrent with HMs） was found to have a significant influence on the subsequent removal of the HMs. In particular when the column was loaded with DOM and HMs simultaneously, largely irreversible co-precipitation took place. Our results indicate that the regeneration potential of clay mineral sorbents in wastewater treatment will be significantly reduced when the treated water is rich in DOM. In contrast, in manured agricultural fields （where HMs enter together with DOM）, HM mobility will be lower than expected from interaction dynamics of HMs and clay minerals.

Ferromagnetic interactions in EO-azido-bridged binuclear transition metal(Ⅱ) systems: Syntheses, crystal structures and magnetostructural correlations

Three new isostructural binuclear transition metal complexes with azido ion and 1,2-bis（3-（pyridin-2-yl）-lH-pyrazol-1- yl）ethane （bppe）, formulated as [M2（N3）2（bppe）2]（C104）2 （M = Co, 1; Ni, 2; Cu, 3）, were successfully synthesized. They were structurally and magnetically characterized. In 1-3, the double azido ions link two adjacent octahedral metal centers together in the end-to-on mode （EO）, with the M-NEo-M angles of 99.41°, 100.24° and 99.80°, respectively. The co-ligand bppe acts as terminal ligand to saturate the remaining coordination sites. The magnetic properties of 1-3 have been investigated in the tem- perature range of 2-300 K. Fitting of the magnetic susceptibility data revealed the occurrence of the strong ferromagnetic in- teractions [J = 26.32 cm-1 （1）, J = 38.23 cm-1 （2） and J = 139.83 cm-1 （3）]. Density functional theory calculations have been performed on 1-3 to provide a magneto-structural correlation of the ferromagnetic behavior.