The structure and electrochemical characteristics of La0.67Mg0.33 (Ni0.8Co0.1Mn0.1) x (x=2.5–5.0) multiphase alloys for nickel-metal hydride batteries

This paper presents results concerning structure and electrochemical characteristics of the La_0.67Mg_0.33 (Ni_0.8Co_0.1Mn_0.1) _x (x=2.5–5.0) alloy. It can be found from the result of the Rietveld analyses that the structures of the alloys change obviously with increasing x from 2.5 to 5.0. The main phase of the alloys with x=2.5–3.5 is LaMg₂Ni₉ phase with a PuNi₃-type rhombohedral structure, but the main phase of the alloys with x=4.0–5.0 is LaNi₅phase with a CaCu₅-type hexagonal structure. Furthermore, the phase ratio, lattice parameter and cell volume of the LaMg₂Ni₉phase and the LaNi₅ phase change with increasing x. The electrochemical studies show that the maximum discharge capacity increases from 214.7 mAh/g (x=2.5) to 391.1 mAh/g (x=3.5) and then decreases to 238.5 mAh/g (x=5.0). As the discharge current density is 1,200 mA/g, the high rate dischargeability (HRD) increases from 51.1% (x=2.5) to 83.7% (x=3.5) and then decreases to 71.6% (x=5.0). Moreover, the exchange current density (I ₀) of the alloy electrodes first increases and then decrease with increasing x from 2.5 to 5.0, which is consistent with the variation of the HRD. The cell volume reduces with increasing x in the alloys, which is detrimental to hydrogen diffusion and accordingly decreases the low-temperature dischargeability of the alloy electrodes.     

加压下中国典型煤二氧化碳气化反应的热重研究

用TG-151加压热天平，测定了三种典型中国煤在二氧化碳气氛下的气化反应活性。结果表明，反应速率与温度的关系符合Arrhenius定律，同时反应速率随着压力的增加而增加，但是随着压力的增加，压力对反应速率的影响越来越小。用下式dx/dt=k0 Pco2/1 αPco2 exp(-Eα/(RT)(1-X)^n模拟实验曲线的结果表明，n值随着温度的升高而降低，随压力的增加而增大。     

Synthesis and properties of conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains

A versatile synthetic route to conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains was developed, and new ruthenium complexes with various ligands were synthesized and characterized. These bimetallic complexes showed a remarkable absorption in the visible region (λ_max: 452-483 nm), and undergo trans-to-cis isomerization under UV light irradiation for short time. Electrochemical study showed that the metal centers in bimetallic complexes containing the CHCHC₆H₄NNC₆H₄CHCH bridge interact with each other.     

Optical properties of nanocrystalline Y2O3:Eu depending on its odd structure

The structure of nanocrystalline Y2O3:Eu prepared by a combustion reaction was analyzed by XRD and high-resolution electron microscopy. Compared with a large-scale particles, 5-nm Y2O3:Eu particles presented as distorted crystallite and rough surfaces. Luminescent and absorption properties of nano-Y2O3:Eu showed remarkably particle size effects. At Y2O3:Eu particle sizes smaller than 10 nm some new results were observed: (a) a red shift of the charge-transfer-state absorption; (b) new emission bands of Eu3+ in the 5D0 --> 7F2 region; (c) luminescent decay of energy level 5D0 of Eu3+ turning to a two-step exponential; and (d) a pronounced increase in quenching concentration and much lower phonon density compared with those of the bulk material. All these phenomena can be attributed to the effect of the softened lattice and surface state of the nanomaterial. The latter was confirmed by stronger excitation by the host absorption after the surface modification.     

High extraction ability of 1,3-dialkynyl calixarene towards mercury（Ⅱ） ion

The reaction of 1,3-dipropyn-2-yloxycalix[4]arene with mercury(II)acetate could give mercury-containing alkynyl calixarenepolymer.The extraction behavior of 1,3-dipropyn-2-yl-oxycalix[4]arene towards mercury(II)ion was examined.When the moleratio of Hg~(2 )/calixarene was 1:1,the extractive percent can reach to 99.1%,and the extraction capacity was up to 431 mg/g.It couldalso decrease the Hg~(2 )concentration from 5 to 0.85 mg/L,which was only 17%of the national standard of effluent and satisfied thenational standard of drinking water.The extraction process included chemical reaction.     

Thermotropic Liquid Crystals Based on Extended 2,5‐Disubstituted‐1,3,4‐Oxadiazoles: Structure–Property Relationships,Variable‐Temperature Powder X‐ray Diffraction,and Small‐Angle X‐ray Scattering Studies

A class of extended 2,5‐disubstituted‐1,3,4‐oxadiazoles R¹‐C₆H₄‐{OC₂N₂}‐C₆H₄‐R² (R¹=R²=C₁₀H₂₁O 1 a , p‐C₁₀H₂₁O‐C₆H₄‐C?C 3 a , p‐CH₃O‐C₆H₄‐C?C 3 b ; R¹=C₁₀H₂₁O, R²=CH₃O 1 b , (CH₃)₂N 1 c ; F 1 d ; R¹=C₁₀H₂₁O‐C₆H₄‐C?C, R²=C₁₀H₂₁O 2 a , CH₃O 2 b , (CH₃)₂N 2 c , F 2 d ) were prepared, and their liquid‐crystalline properties were examined. In CH₂Cl₂ solution, these compounds displayed a room‐temperature emission with λ_max at 340–471 nm and quantum yields of 0.73–0.97. Compounds 1 d , 2 a – 2 d , and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized‐light optical microscopy and differential scanning calorimetry. Structure determination by a direct‐space approach using simulated annealing or parallel tempering of the powder X‐ray diffraction data revealed distinctive crystal‐packing arrangements for mesogenic molecules 2 b and 3 a , leading to different nematic mesophase behavior, with 2 b being monotropic and 3 a enantiotropic in the narrow temperature range of 200–210 °C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable‐temperature X‐ray diffractometry. Nondestructive phase transitions (crystal‐to‐crystal, crystal‐to‐mesophase, mesophase‐to‐liquid) were observed in the diffractograms of 1 b, 1 d , 2 b, 2 d , and 3 a measured at 25–200 °C. Powder X‐ray diffraction and small‐angle X‐ray scattering data revealed that the structure of the annealed solid residue 2 b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure–property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions.     

Anion and Additive Effects on the Structure of Mercury(II) Halides Complexes with Tripodal Ligand

The metal complexes [Hg₂(tbim)₂Br₄]·2DMF ( 1 ) and [Hg₂(tbim)I₄]·1.5DMF ( 2 ) were prepared by reactions of 1,3,5‐tris(benzimidazol‐1‐ylmethyl)‐2,4,6‐trimethylbenzene (tbim) with HgBr₂, HgI₂, respectively, and [Hg₂(tbim)I₄]·0.5(FeCp₂)·H₂O ( 3 ) was obtained by the same method with addition of ferrocene (FeCp₂) as additive. Their structures were determined by X‐ray crystallographic analyses. Complex 1 has a macrocyclic binuclear structure with one benzimidazole arm of the ligand free of coordination and the binuclear units are further connected by C‐H···N hydrogen bonds to give an infinite zigzag chain. Complexes 2 and 3 have a 2D network structure in which tbim serves as a tridentate ligand. The results showed that the halides of bromide and iodide have remarkable impact on the structure of the complexes. The FeCp₂ molecules are trapped in the voids of framework 3 .     

Facial selectivity of the Ireland-Claisen rearrangement of allylic esters of 2-methyl and 2-methoxycyclopentanecarboxylic acids

Ketene silylacetals derived from prenyl and (Z)- and (E)-crotyl 2-methylcyclopentanecarboxylates (9) were subjected to the Ireland-Claisen rearrangement. All three substrates rearranged with complete facial selectivity, but the (Z)- and (E)-crotyl systems gave a mixture comprised of the same diastereomers of 1-(1-methyl-2-propenyl)-2-methylcyclopentanecarboxylic acid (14) in ratios of 2:1 and 1:2, respectively. In contrast, the ketene silylacetals prepared from allyl and prenyl 2-methoxycyclopentanecarboxylates (22) underwent rearrangements with both facial stereochemistries.     

CoCl_2·6H_2O or LaCl_3·7H_2O Catalyzed Biginelli Reaction. One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1 H)-ones

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The preparation and fluorescence properties of europium nanoparticles

A new structured metallic nanomaterial of europium nanoparticle was prepared using tannic acid as the reductive agent,and nanoeuropium protein conjugates were synthesized by the method of lipoic acid modification on the surface of nanoparticle,which opens a new field of application of lanthanides in nanotechniques.Their properties were also characterized by UV-vis absorption spectroscopy,transmission electron microscopy (TEM),and fluorescence spectroscopy.The europium nanoparticle and its protein conjugates solution were stable and water-soluble.The fluorescence intensity of the composite europium nanoparticles was significantly increased in the presence of trace protein,and was linear proportional to the concentration of proteins under optimum conditions.According to this,a fluorimetric method for the determination of protein was developed in this paper.