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1.
The electrochemical formation of Mg-Li alloys was investigated in a molten LiCl-KCl(58-42 mol%)eutectic melt at 723 K. The cyclic voltammogram for a Mo electrode showed that the electroreduction of Li~ proceeds in a single step and the deposition potential of Li metal was -2.40 V(vs.Ag/AgCl).For Mg electrode,the electroreduction of Li~ takes place at less cathodic potential than that at the Mo electrode which was caused by the formation of Mg-Li alloys.Phase of the deposited Mg-Li alloys could be controlled by the electrolysis potential,and the samples were characterized by X-ray diffraction and scanning electron microscopy. The results showed thatα-Mg andβ-Li phases were obtained at -2.35 and -2.55 V,respectively.  相似文献   

2.
The effects of 1 wt.% Ca or 1 wt.% Ca + 1 wt.% Ag addition and heat treatment on the corrosion behavior of Mg-7Sn (wt.%) alloy in 3.5 wt.% NaCl solution were investigated by electrochemical measurements and immersion tests. The alloys were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that all alloys were corroded by pitting corrosion and grain boundary corrosion and further corroded with time going. Loose layers of compounds, including Mg (OH)2, MgO, SnO2, and other compounds containing Ca and Ag elements, were calibrated on the surface of corroded Mg-7Sn-1Ca-1Ag alloy. The Ca addition improved the corrosion resistance of Mg-7Sn alloy due to the formation of relatively stable compounds containing calcium element and grains refinement. Furthermore, the solid solutioned alloys obtained a superior corrosion resistance due to the dissolve of eutectic Mg2Sn phase and homogenization treatment. However, the aging treatment is slightly detrimental to the corrosion resistance of Mg-7Sn alloys with the formation of Mg2Sn precipitates. In conclusion, the aged Mg-7Sn-1Ca-1Ag alloy exhibited a better corrosion resistance and a noticeable micro-hardness property compared with those of as-cast Mg-7Sn alloy. And this study provides an important idea for the research on the comprehensive properties of Mg-Sn alloys.  相似文献   

3.
Poly(3??,4??-Ethylenedioxy-2,2??:5??,2??-terthiophene) was synthesized by chemical oxidative polymerization of 3??,4??-Ethylenedioxy-2,2??:5??,2??-terthiophene using FeCl3 as an oxidant. The resulting polymer was characterized by FTIR and 1H NMR. p-doping behaviors of substituted polyterthiophene with different organic sulfonic acids (methanesulfonic acid, p-toluene sulfonic acid, and ??-naphthalene sulfonic acid) in different solvents (CH3CN, CHCl3, THF and DMF) were studied by UV-VIS spectroscopy. The results from structural characterizations showed that the ??,????-bonding predominates in polyterthiophene. The spectroscopic changes in UV-VIS showed that ??-naphthalene sulfonic acid was an efficient doping acid for polymer while varying the solvents. Meanwhile, CH3CN showed a high efficiency for p-doping of polyterthiophene while varying the doping acids.  相似文献   

4.
A semirigid bipyrazolyl ligand, 4,4??-bis[(3??,5??-diethyl-1H-pyrazol-4??-yl)methylene)]-1,1??-biphenyl (H2L), and four of its Ag(I) and Cu(II) complexes have been prepared and structurally characterized. X-ray analysis demonstrates that the Ag(I) complexes are dinuclear molecular rectangle, while the Cu(II) complexes display a twisted rectangular structure. Two different conformations, namely cis and trans, have been observed for this bipyrazolyl ligand.  相似文献   

5.
A comparative chemical bonding analysis for the germanides La2MGe6 (M=Li, Mg, Al, Zn, Cu, Ag, Pd) and Y2PdGe6 is presented, together with the crystal structure determination for M=Li, Mg, Cu, Ag. The studied compounds adopt the two closely related structure types oS72-Ce2(Ga0.1Ge0.9)7 and mS36-La2AlGe6, containing zigzag chains and corrugated layers of Ge atoms bridged by M species, with La/Y atoms located in the biggest cavities. Chemical bonding was studied by means of the quantum chemical position-space techniques QTAIM (quantum theory of atoms in molecules), ELI-D (electron localizability indicator), and their basin intersections. The new penultimate shell correction (PSC0) method was introduced to adapt the ELI-D valence electron count to that expected from the periodic table of the elements. It plays a decisive role to balance the Ge−La polar-covalent interactions against the Ge−M ones. In spite of covalently bonded Ge partial structures formally obeying the Zintl electron count for M=Mg2+, Zn2+, all the compounds reveal noticeable deviations from the conceptual 8−N picture due to significant polar-covalent interactions of Ge with La and M ≠ Li, Mg atoms. For M=Li, Mg a formulation as a germanolanthanate M[La2Ge6] is appropriate. Moreover, the relative Laplacian of ELI-D was discovered to reveal a chemically useful fine structure of the ELI-D distribution being related to polyatomic bonding features. With the aid of this new tool, a consistent picture of La/Y−M interactions for the title compounds was extracted.  相似文献   

6.

The ultralight hypoeutectic α-phase Mg–4.5Li–1.5Al alloy and hypereutectic β-phase Mg–12Li–1.5Al alloy in as-cast state were fabricated and subjected to modification by 0.2 mass% TiB and 0.2 mass% Sr grain modifiers. The crystallisation sequence of Mg–Li–Al alloys has been investigated in detail by using thermal-derivative analysis and microstructural observations. The presented work includes the effects of grain refiners on grain size and microstructure and thermal events registered during crystallisation of ultralight Mg–Li–Al alloys by recording and analysis of the temperature vs time, i.e. as TN, Tα, Tβ, Tη(LiAl) and TSOL. Microstructure and phase observation has been done by light microscope, X-ray diffraction and energy dispersive X-ray spectroscopy. The changes of characteristic temperature points for phase transformation are studied in detail. Due to the addition of 0.2 mass% TiB and 0.2 mass% Sr, the grain structure of the alloy was refined, and mechanical properties were improved. When a TiB and Sr added simultaneously, the average grain size of the analysed alloys strongly decreases. When the TiB or Sr content was severally added, a low effect of improvements of mechanical properties was observed. With the TiB and Sr content, the liquidus and solidus decrease gradually.

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7.
In the work, Gibbs energy showed that MgCl2 can chloridize Dy2O3 and release Dy(III) ions in the LiCl–KCl–MgCl2–Dy2O3 melts. Dy(III) ions were observed by cyclic voltammetry, square wave voltammetry in melts. X-ray diffraction (XRD) pattern of melts indicated that Dy2O3 was chlorinated by MgCl2 and formed DyCl3. XRD pattern of non-dissolved residue, which was left after the melts were washed with water to remove the soluble salt, showed that the new compounds (i.e., DyOCl, MgO, and Dy(OH)3) were produced. The concentration of Dy(III) reached a maximum when the concentration of Mg(II) ions exceeded 8?×?10?4 mol cm?3 in melts by inductive coupled plasma atomic emission spectrometer analyses of melts. Galvanostatic electrolysis was conducted to extract Dy element from LiCl–KCl–MgCl2–Dy2O3 melts by forming Mg–Li–Dy alloys. The components of Dy and Li in alloys were controlled within a small range by the concentration of MgCl2 in melts, current density, and additions of Dy2O3. XRD patterns of alloys indicated that Mg3Dy phase was formed. Scanning electron microscope images with energy-dispersive X-ray spectroscopy showed that Dy elements were mainly distributed in the grain boundary. Grain size was refined, due to a more content of Dy elements in alloys by optical microscopy images.  相似文献   

8.
A mixture of Li and Mg vapors at 900°C was optically pumped at 488 nm by an Ar+ ion laser. The resulting Li2 fluorescence and LiMg* excimer chemiluminescence intensities were analyzed to determine rate constants for the reactions Li2(B1π) + Mg → LiMg* + Li and LiMg* + Li → Li2(a3π) + Mg and the radiative decay rates of Li2(B1π) and LiMg*.  相似文献   

9.
用化学镀法制备 Pd/Ag 膜时膜厚和组成的控制   总被引:1,自引:0,他引:1  
曾高峰  史蕾  徐恒泳 《催化学报》2009,30(12):1227-1232
 研究了不同 Pd2+含量的镀液在多孔陶瓷载体上的化学沉积规律, 发现当 Pd 沉积层厚度达到约 5 μm 后, 即使镀液中反应物的消耗比例很小, 膜厚增长也明显变缓, 沉积反应主要受膜层表面的催化活性位控制; 当镀液中 Pd2+含量只能沉积形成小于 4 μm 的 Pd 膜时, 在 323 K 化学镀 180 min 后, 镀液中 Pd2+的转化率高于 90%. 与之相似, 当 Ag 镀液中的 Ag+含量等于 0.5~2 μm 的 Ag 膜层所需量时, 在 333 K 化学镀 120 min 后, Ag+的转化率可达 95%. Ag+的高转化率与 Ag 颗粒的择向生长特性有关. 根据 Pd 和 Ag 的化学镀沉积规律, 通过调节镀液中金属离子的含量能够预先设计和精确控制超薄 Pd/Ag 膜的膜厚和组成.  相似文献   

10.
The completeness of ??-phase decomposition reaction in the Cu?C11wt%Al?Cxwt%Ag alloys (x?=?0, 1, 2, and 3) was studied using differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and optical microscopy (OM). The results indicated that ??-phase transformations are highly dependent on cooling rate and on the presence of Ag. On slow cooling, the silver presence prevents the ??- and ??1-phase decomposition; thus, inducing the martensitic phase formation. After rapid cooling, a new thermal event is observed and the reverse martensitic transformation is shifted to lower temperatures.  相似文献   

11.
Achieving the full potential of magnesium-ion batteries (MIBs) is still a challenge due to the lack of adequate electrodes or electrolytes. Grignard-based electrolytes show excellent Mg plating/stripping, but their incompatibility with oxide cathodes restricts their use. Conventional electrolytes like bis(trifluoromethanesulfonyl)imide ((Mg(TFSI)2) solutions are incompatible with Mg metal, which hinders their application in high-energy Mg batteries. In this regard, alloys can be game changers. The insertion/extraction of Mg2+ in alloys is possible in conventional electrolytes, suggesting the absence of a passivation layer or the formation of a conductive surface layer. Yet, the role and influence of this layer on the alloys performance have been studied only scarcely. To evaluate the reactivity of alloys, we studied InSb as a model material. Ex situ X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy were used to investigate the surface behavior of InSb in both Grignard and conventional Mg(TFSI)2/DME electrolytes. For the Grignard electrolyte, we discovered an intrinsic instability of both solvent and salt against InSb. XPS showed the formation of a thick surface layer consisting of hydrocarbon species and degradation products from the solvent (THF) and salt (C2H5MgCl−(C2H5)2AlCl). On the contrary, this study highlighted the stability of InSb in Mg(TFSI)2 electrolyte.  相似文献   

12.
Uneven lithium (Li) electrodeposition hinders the wide application of high-energy-density Li metal batteries (LMBs). Current efforts mainly focus on the side-reaction suppression between Li and electrolyte, neglecting the determinant factor of mass transport in affecting Li deposition. Herein, guided Li+ mass transport under the action of a local electric field near magnetic nanoparticles or structures at the Li metal interface, known as the magnetohydrodynamic (MHD) effect, are proposed to promote uniform Li deposition. The modified Li+ trajectories are revealed by COMSOL Multiphysics simulations, and verified by the compact and disc-like Li depositions on a model Fe3O4 substrate. Furthermore, a patterned mesh with the magnetic Fe−Cr2O3 core-shell skeleton is used as a facile and efficient protective structure for Li metal anodes, enabling Li metal batteries to achieve a Coulombic efficiency of 99.5 % over 300 cycles at a high cathode loading of 5.0 mAh cm−2. The Li protection strategy based on the MHD interface design might open a new opportunity to develop high-energy-density LMBs.  相似文献   

13.
We present a systemic investigation of a galvanic replacement technique in which active‐metal nanoparticles are used as sacrificial seeds. We found that different nanostructures can be controllably synthesized by varying the type of more noble‐metal ions and liquid medium. Specifically, nano‐heterostructures of noble metal (Ag, Au) or Cu nanocrystals on active‐metal (Mg, Zn) cores were obtained by the reaction of active‐metal nanoparticles with more noble‐metal ions in ethanol; Ag nanocrystal arrays were produced by the reaction of active‐metal nanoparticles with Ag+ ions in water; spongy Au nanospheres were generated by the reaction of active‐metal nanoparticles with AuCl4? ions in water; and SnO2 nanoparticles were prepared when Sn2+ were used as the oxidant ions. The key factors determining the product morphology are shown to be the reactivity of the liquid medium and the nature of the oxidant–reductant couple, whereas Mg and Zn nanoparticles played similar roles in achieving various nanostructures. When microsized Mg and Zn particles were used as seeds in similar reactions, the products were mainly noble‐metal dendrites. The new approach proposed in this study expands the capability of the conventional nanoscale galvanic replacement method and provides new avenues to various structures, which are expected to have many potential applications in catalysis, optoelectronics, and biomedicine.  相似文献   

14.
The binary alloy phase ϵ‐Ag7+xMg26–x with x ≈ 1 and small amounts of the β′‐AgMg phase crystallize by annealing of Ag–Mg alloys with starting compositions between 24–28 At‐% Ag at 390 to 420 °C. A model structure for the ϵ‐phase consisting of a fcc packing of Mackay clusters was derived from the known structure of the ϵ′‐Ag17Mg54 phase. Crystals of the ϵ‐phase were obtained by direct melting of the elements and annealing. The examination of a single crystal yielded a face‐centered cubic unit cell, space group Fm3 with a = 1761.2(5) pm. The refinement was started with the parameters of the model: wR2(all) = 0.0925 for 1093 symmetrically independent reflections. A refinement of the occupancy parameters indicated a partial replacement of silver for magnesium at two metal atom sites, resulting in the final composition ϵ‐Ag7+xMg26–x with x = 0.96(2). There are 264 atoms in the unit cell and the calculated density is 3.568 gcm–3. The topology of the model was confirmed. Mackay icosahedra are located at the lattice points of a face‐centered cubic lattice. Differences between model and refined structure and their effects on the powder patterns are discussed. The new binary structure type of ϵ‐Ag7+xMg26–x can be described in terms of the I3‐cluster concept.  相似文献   

15.
Magnesium alloys are the basis for the creation of light and ultra‐light alloys. They have attracted attention as potential materials for the accumulation and storage of hydrogen, as well as electrode materials in metal‐hydride and magnesium‐ion batteries. The search for new metal hydrides has involved magnesium alloys with rare‐earth transition metals and doped by p‐ or s‐elements. The synthesis and characterization of a new quaternary carbide, namely dimagnesium lithium aluminium carbide, Mg1.52Li0.24Al0.24C0.86, belonging to the family of hexagonal close‐packed (hcp) structures, are reported. The title compound crystallizes with hexagonal symmetry (space group Pm2), where two sites with m2 symmetry and one site with 3m. symmetry are occupied by an Mg/Li statistical mixture (in Wyckoff position 1a), an Mg/Al statistical mixture (in position 1d) and C atoms (2i). The cuboctahedral coordination is typical for Mg/Li and Mg/Al, and the C atom is enclosed in an octahedron. Electronic structure calculations were used for elucidation of the ability of lithium or aluminium to substitute magnesium, and evaluation of the nature of the bonding between atoms. The presence of carbon in the carbide phase improves the corrosion resistance of the Mg1.52Li0.24Al0.24C0.86 alloy compared to the ternary Mg1.52Li0.24Al0.24 alloy and Mg.  相似文献   

16.
Condensation of 2-naphthylamine with formaldehyde and methyl 2,2-dimethyl-4,6-dioxocyclohexanecarboxylate afforded depending on the reaction conditions methyl 9,9-dimethyl-11-oxo-8,9,10,12-tetrahydro-7H-benzo[a]acridine-10-carboxylate or 4-alkoxymethyl-1,4-dihydro-2??,6??-dioxo-4??,4??-dimethyl-2??H,3H,6??Hspirobenzo[f]quinoline-2,1??-cyclohexyl-3??-carboxylate. The condensation of N-benzyl-2-naphthylamines with formaldehyde and methyl 2,2-dimethyl-4,6-dioxocyclohexanecarboxylate provided with the quantitative yield the corresponding methyl 4-benzyl-1,4-dihydro-2??,6??-dioxo-4??,4??-dimethyl-2??H,3H,6??H-spirobenzo[f]quinoline-2,1??-cyclohexyl-3??-carboxylates.  相似文献   

17.
Interactions of group 12 metal(II) species (Hg2+, Cd2+, Zn2+, Hg(H2O) n 2+ , Cd(H2O) n 2+ , and Zn(H2O) n 2+ (n?=?1, 2) with neutral (RSH), deprotonated (RS?), and doubly deprotonated cysteine species (abbreviated as ??H2cys??, ??Hcys???, and ??cys2???, respectively) are examined with the Becke three-parameter Lee?CYang?CParr (B3LYP) hybrid functional after preliminary screening in a conformation analysis with the Parameterized Model number 3 (PM3) semiempirical method. Effects of water on aqueous solution are evaluated by microsolvation and polarized continuum model (PCM) approaches. In the most stable conformations of M(H2cys)2+ and M(Hcys)+ complexes (M?=?Hg2+, Cd2+, and Zn2+), the SH group of the cysteine moiety is already deprotonated and undergoes strong binding with the metal ion. Among Hg(H2cys)2+ complexes, cysteine complexes of Hg2+ without deprotonation of the SH group and mercury(II) carboxylato-type structures are at least 83 and 117?kJ/mol less stable in energy than the most stable complex (B3LYP/6-311++G(d,p)-SDD+d+f//B3LYP/6-31G(d)-SDD+d). Although Zn2+ binds more strongly than Hg2+ to a H2cys molecule at the high-level CCSD(T)/6-311++G(d,p)-SDD+d+f//B3LYP/6-311++G(d,p)-SDD+d+f level, [Hg(H2O)2]2+ is stronger than [Zn(H2O)2]2+ because the deformation of [Zn(H2O)2]2+ required to bind to cys is much more than in [Hg(H2O)2]2+. Complexes with a deprotonated cysteine, M(Hcys)+ and M(cys), prefer a multidentate structure.  相似文献   

18.
运用共沉淀和元素化学沉积相结合的方法,制备出了具有Ag/C 包覆层的层状富锂固溶体材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2. 通过X 射线衍射(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、恒流充放电、循环伏安(CV),电化学阻抗谱(EIS)和X 射线能量散射谱(EDS)方法,研究了Ag/C 包覆层对Li[Li0.2Mn0.54Ni0.13Co0.13]O2电化学性能的影响. 结果表明,Ag/C 包覆层的厚度约为25 nm,Ag/C 包覆在保持了固溶体材料α-NaFeO2 六方层状晶体结构的前提下,显著地改善了Li[Li0.2Mn0.54Ni0.13Co0.13]O2 的电化学性能. 在2.0-4.8 V(vs Li/Li+)的电压范围内,首次放电(0.05C)容量由242.6 mAh·g-1提高到272.4 mAh·g-1,库仑效率由67.6%升高到77.4%;在0.2C倍率下,30 次循环后,Ag/C 包覆的电极材料容量为222.6 mAh·g-1,比未包覆电极材料的容量高出14.45%;包覆后的电极材料在1C下的容量仍为0.05C下的81.3%. 循环伏安及电化学交流阻抗谱研究表明,Ag/C包覆层抑制了材料在充放电过程中氧的损失,有效降低了Li[Li0.2Mn0.54Ni0.13Co0.13]O2颗粒的界面膜电阻与电化学反应电阻.  相似文献   

19.

La1?x Ca x MnO3 (x ranges from 0.28 to 0.34) ceramics with Ag addition were synthesized by sol–gel method using methanol as solvent. The EDS elemental mapping shows that Ag element was detected dominantly on the sample surface. The sample of x?=?0.28 has almost no pore and bigger grain size, which indicated that it has better crystallization and high density. Temperature dependence of resistivity shows that the samples for all Ca content exhibit sharp metal–insulator transition, and the corresponding metal–insulator temperature shift toward higher temperature with increasing Ca content. The temperature coefficient of resistance value for x?=?0.28 reaches its the highest value, 71.8%·K?1. This temperature coefficient of resistance value is even higher than the previously reported for LCMO films and single crystals, and it shows a very promising application for the infrared and bolometric detectors. The high magnetoresitance for x?=?0.28 reaches up to 69.3% in magnetic field of 1?T near room temperature. It was concluded that it improved the properties of LCMO:Ag composites are attributed to its improved crystallization by Ag addition, homogeneity and Mn4+/Mn3+ ratio. Different theoretical models are employed to analyze the resistance behaviors in different temperature regions, which give good agreements with experimental results.

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20.
To reduce the biocorrosion rate and enhance the biocompatibility by surface modification, MgF2 coatings were prepared on Mg–1Ca alloy using vacuum evaporation deposition method. The average thickness of the coating was about 0.95 µm. The results of immersion test and electrochemical test indicated that the corrosion rate of Mg–1Ca alloy was effectively decreased after coating with MgF2. The MgF2 coating induced calcium phosphate deposition on Mg–1Ca alloy. After 72 h culture, MG63 cells and MC3T3‐E1 cells were well spread on the surface of the MgF2‐coated Mg–1Ca alloy, while few cells were observed on uncoated Mg–1Ca alloy samples. In summary, MgF2 coating showed beneficial effects on the corrosion resistance and thus improved cell response of the Mg–1Ca alloy effectively and should be a good surface modification method for other biomedical magnesium alloys. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

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