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1.
A composite electrode of Ni-ferrite/TiOx/Si(111) was synthesized by grafting Ni2+Fe2+Fe3+–LDH–TiCl3 (LDH: Layered Double Hydroxides) on n-Si(111) surface and calcined under 1100 °C. Photoelectric research results indicated that the electrode had good photovoltaic effects in an electrolyte solution containing 7.6 M HI and 0.05 M I2, while platinum plate was used as counter-electrode. The observed photo-voltages (Upv) and photocurrent densities (jpc) of the electrode were at ?0.75 V and 5.35 mA/cm2, respectively. Compared with electrodes of oxidized n-Si(111) crystal and n-Si(111) wafer covered by Ni-ferrites, jpc of the electrode Ni-ferrite/TiOx/Si(111) was increased greatly.  相似文献   

2.
《Solid State Sciences》2012,14(2):250-257
CO2 adsorption properties on Mg modified silica mesoporous materials were investigated. By using the methods of co-condensation, dispersion and ion-exchange, Mg2+ was introduced into SBA-15 and MCM-41, and transformed into MgO in the calcination process. The basic MgO can provide active sites to enhance the acidic CO2 adsorption capacity. To improve the amount and the dispersion state of the loading MgO, the optimized modification conditions were also investigated. The XRD and TEM characteristic results, as well as the CO2 adsorption performance showed that the CO2 adsorption capacity not only depended on the pore structures of MCM-41 and SBA-15, but also on the improvement of the dispersion state of MgO by modification. Among various Mg modified silica mesoporous materials, the CO2 adsorption capacity increased from 0.42 mmol g−1 of pure silica SBA-15 to 1.35 mmol g−1 of Mg–Al–SBA-15-I1 by the ion-exchange method enhanced with Al3+ synergism. Moreover, it also increased from 0.67 mmol g−1 of pure silica MCM-41 to 1.32 mmol g−1 of Mg–EDA–MCM-41-D10 by the dispersion method enhanced with the incorporation of ethane diamine. The stability test by 10 CO2 adsorption/desorption cycles showed Mg–urea–MCM-41-D10 possessed quite good recyclability.  相似文献   

3.
LiMn2O4 spinel nanorods prepared from nanowire MnO2 templates were capped with polyvinyl pyrrolidone (PVP) and coated with ZrC2O4 precursors in aqueous solution. Upon annealing at 600 °C in air, an amorphous ZrO2 nanoscale coating layer was obtained on the spinel nanoparticles with a particle size of <100 nm that formed from the splitting of the original spinel nanorods. The electrochemical cycling results clearly showed that nanoscale ZrO2 coating significantly improved the rate capability and cycle life at 65 °C in spite of very high surface area of the spinel nanoparticles.  相似文献   

4.
The crystal structure of the synthetic iron phosphate Na0.10(1)Fe6.99(1)(P1.00(1)O4)6 has been refined at 270 and 100 K from single-crystal X-ray diffraction data. The compound is triclinic, P−1, Z=1, lattice parameters: a=6.3944(9) Å, b=7.956(1) Å, c=9.364(1) Å, α=105.13(1)°, β=108.35(1)°, γ=101.64(1)° at 270 K and adopts the well-known howardevansite structure type. Iron, being both in the divalent and the trivalent valence state, is ordered on the four symmetry non-equivalent iron positions [Fe2+ on Fe(1) and Fe(3), Fe3+ on Fe(2) and Fe(4)]. Three of the four iron positions show octahedral oxygen atom coordination, the fourth one, which is occupied by Fe2+, is five-fold coordinated. The structure consists of crankshafts (buckled chains) of edge sharing Fe-oxygen polyhedra, passing through the unit cell in [101] direction. Structural investigation at 100 K shows no change of symmetry. The valence state and distribution of iron was determined by 57Fe Mössbauer spectroscopy. The compound shows 4 subspectra in agreement with the four different Fe sites. The assignment of the Fe2+ doublets to the Fe(1) and Fe(3) sites is trivial due to the 2:1 stoichiometry, also found in the Mössbauer spectra. For the Fe3+ sites, the temperature-dependent variation of structural distortion parameters and the quadrupole splitting led to a clear doublet assignment.  相似文献   

5.
The vibrational (infrared and Raman) spectroscopy is used in order to identify and characterize the following amphibole minerals with general formula W0–1X2Y5Z8O22(OH)2 (W = Na, K; X = Na, Ca; Y = Mg, Fe2+, Fe3+, Al; Z = Si, Al) originating from the localities in the Republic of Macedonia: glaucophane, Na2(Mg,Fe2+)3(Fe3+,Al)2Si8O22(OH)2; tremolite–actinolite, Ca2(Mg,Fe2+)5Si8O22(OH)2; hornblende (Na,K)0–1Ca2(Mg,Fe2+,Fe3+,Al)5(Si,Al)8 O22(OH)2 and arfvedsonite, NaNa2(Mg,Fe2+)4(Fe3+,Al)Si8O22(OH)2. The chemical composition of these minerals is not necessarily fixed. It is due to the possibility to form solid solution series with other minerals being their end-members (for example, tremolite–ferro-actinolite series, Ca2Mg5Si8O22(OH)2–Ca2Fe2+5Si8O22(OH)2). In this context, it is shown that the intensity and especially the number of the IR bands in the ν(OH) region could serve as a tool for exact mineral identification. Namely, it is based on the presence of different Y cations in various octahedral sites (M1 and M3), which is manifested by different spectral view. On the other hand, the expressed similarities in the 1300–370 cm−1 (IR) and 1200–100 cm−1 regions (Raman) of the spectra are observed due to their common structural characteristics (double chains of SiO4 tetrahedra). Thus, the bands in this region are tentatively prescribed mostly to the vibrations of the SiO4 tetrahedra. The results of our study are compared with the corresponding literature data for the analogous mineral species originating all over the world.  相似文献   

6.
The electrochemical reversibility of magnesium was observed in an electrolyte consisting of 0.5 M Mg[TFSI]2 in tetraglyme in the presence of a small amount of Mg[BH4]2. The cyclic efficiency of the cathodic/anodic process was found to increase initially with [BH4] then plateau at about 75% beyond 6 mM in these experiments. This concentration is in the region of that indicated by Karl Fischer analysis of the electrolyte as required of [BH4] as a dehydrating agent. Cyclic voltammetry showed the reduction onset potential at approximately − 0.35 V vs. Mg and subsequent oxidation around 0 V vs. Mg. Stable cyclic efficiency of approximately 75% over 500 cycles is demonstrated on a platinum substrate. Mg cycling on magnesium, copper and aluminium substrates all show stable cycling over 500 cycles with cyclic efficiency > 73%.  相似文献   

7.
Nano-magnetic magnesium ferrite particles were synthesized by a simple and cost-effective method using different ratios between Mg/Fe precursors and fuel. Significant effects of these ratios on the crystalline phases, crystallite size, particle size, lattice constant, morphological and magnetic properties of the as-synthesized nano-particles have been investigated. Phase evolution, morphological and magnetic characteristics were determined by XRD, SEM, EDX and VSM techniques. The results obtained revealed that the as-prepared Mg ferrite nano-particles have the nanometer size and partially inverse spinel structure. Nano-structured magnesium ferrite spinel has been synthesized with various cyrystallite sizes ranging from 8 to 66 nm. Room temperature magnetization results showed that the magnetic properties of Mg ferrite nano-particles depend upon their size and crystallinity. The saturation magnetization for the sample having the highest crystallite size was 32.85 emu/g.  相似文献   

8.
An in situ study of the effects of Na+, Mg2+ and Cr3+ on direct methanol fuel cell (DMFC) performance is reported. The result showed that dramatic decrease of the cell voltage was mainly ascribed to the increase of the cathode overpotential. Meanwhile, the different contamination effects by introducing Na+, Mg2+ and Cr3+ to the anode and the cathode were compared. When the same molar concentration of different cations was added to the anode feed, the contamination effect on the cell performance followed the order of Na+ > Mg2+ > Cr3+. Owing to the fast transfer speed and the low affinity to the sulfonic acid groups in the ionomer phase, the low-valent cations may cause much more proton losses than the high-valent cations in the cathode catalyst layer (CCL) within the same time. So the low-valent cations led to the higher cathode overpotential than the high-valent cations. When the same molar concentration of cations was directly added to the CCL, the contamination effects on the cell voltage showed an opposite trend which is Na+ < Mg2+ < Cr3+. This is presumably because a high-valent cation can exchange more protons than a low-valent cation in the CCL.  相似文献   

9.
This study examined the effect of the interlayer spacing of a Mg–Al layered double hydroxide (Mg–Al LDH) on the ability of the Mg–Al LDH to take up a nonionic organic material. Mg–Al LDHs, intercalated with 1-propanesulfonate (PS?), 1-hexanesulfonate (HS?), and 1-dodecanesulfonate (DS?), were prepared by coprecipitation, yielding PS·Mg–Al LDH, HS·Mg–Al LDH, and DS·Mg–Al LDH, respectively. The increase in the alkyl chain lengths of the Mg–Al LDHs (PS? < HS? < DS?) resulted in the perpendicular orientation of the organic acid anions in the interlayer of Mg–Al LDH, which in turn resulted in more organic acid anions being accommodated in the interlayer space. An organic acid anion with a large molecular length was more easily intercalated in the interlayer of Mg–Al LDH than one with a small molecular length. This was attributed to the hydrophobic interaction between the alkyl chains, affecting the intercalation of the organic acid anions. The uptake of N,N-dimethylaniline (DMA) by Mg–Al LDHs increased in the order PS·Mg–Al LDH < HS·Mg–Al LDH < DS·Mg–Al LDH. The uptake was attributed to the hydrophobic interactions between DMA and the intercalated PS?, HS?, and DS?. Thus, Mg–Al LDH, which has a lot of large interlayer spacings when intercalated with organic acid anions, can take up a large number of DMA molecules from an aqueous solution.  相似文献   

10.
Crystal structure of a new natural strontium, iron and aluminium hydroxyphosphate (lulzacite): Sr2Fe(Fe0.63Mg0.37)2Al4(PO4)4(OH)10. The crystal structure of a new natural strontium, iron and aluminium hydroxyphosphate (lulzacite) has been solved through an X-ray study of a single crystal:– symmetry: triclinic (P1̄);– unit cell parameters: a=5.457(1) Å, b=9.131(2) Å, c=9.769(2) Å, α=108.47(3)°, β=91.72(3)° and γ=97.44(3);– structural formula: (Sr0.96Ba0.04)2Fe(Fe0.63Mg0.37)2Al4[(P0.98V0.02)O4]4(OH)10 (Z=1).The structure presents along the b axis the alternation, on one hand of infinite chains of edge sharing octahedra (one Fe2+O6 and an AlO6 pair), and, on the other hand, of trimers with a central AlO6 octahedron framed by two mixed (Fe2+,Mg)O6 octahedra. Trimers and chains are linked by the corners of one AlO6 octahedron and two PO4 tetrahedra. Strontium ions are located in the channels of the structure. This structure is isotypic with that of jamesite, a lead arsenate. Similar octahedral building blocks are present in other mineral species: trimers in ludlamite (iron phosphate), chains in various hydroxysalts. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASlulzacite / hydroxyphosphate / phosphate / strontium / iron / aluminium  相似文献   

11.
The Fex(Cr2O3)1?x system, with 0.10  X  0.80, was mechanically processed for 24 h in a high-energy ball-mill. In order to examine the possible formation of iron–chromium oxides and alloys, the milled samples were, later, thermally annealed in inert (argon) and reducing (hydrogen) atmospheres. The as-milled and annealed products were characterized by X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy and magnetization. The as-milled samples showed the formation of an Fe1+YCr2?YO4?δ nanostructured and disordered spinel phase, the α1-Fe(Cr) and α2-Cr(Fe) solid solutions and the presence of non-exhausted precursors. For the samples annealed in inert atmosphere, the chromite (FeCr2O4) formation and the recrystallization of the precursors were verified. The hydrogen treated samples revealed the reduction of the spinel phase, with the phase separation of the chromia phase and retention of the Fe–Cr solid solutions. All the samples, either as-milled or annealed, presented the magnetization versus applied field curves typical for superparamagnetic systems.  相似文献   

12.
Aluminum–magnesium alloys, fabricated by bi-directional rotation ball milling, were used as a kind of promising solid fuel in “reactive material” that can be ignited by impact to release a large quantity of heats. Different percentages of Mg were added to Al to yield Al90%–Mg10% and Al70%–Mg30% alloys in order to probe the effect of Mg content on the microstructure and thermal reactivity of Al–Mg alloys. Structural characterization revealed that a nanometer-scale structure was formed and oxidation of as-fabricated alloy powders was faint. Moreover, as the Mg percentage increased, the particle size of alloy decreased with increasing brittleness of Al–Mg. TGA/DSC curves of the [Al70%–Mg30%]–O2 system exhibited an intense exothermic peak before melting with reaction heat of 2478 J g?1 and its weight increase reached 90.16% of its theoretical value, which contrasted clearly with 181.2 J g?1 and 75.35% of [Al90%–Mg10%]–O2 system, respectively. In addition, other than [Al90%–Mg10%]–Fe2O3 system, the [Al70%–Mg30%]–Fe2O3 system exhibited a considerable solid–solid reaction and a low activation energy. Finally, target penetration experiments were conducted and the results confirmed that a projectile composed of [Al70%–Mg30%]–Fe2O3 displayed a more complete ignition of target than that of Al–Fe2O3 formulation.  相似文献   

13.
In this paper, we discuss the synthesis and electrochemical properties of a new material based on iron oxide nanoparticles stabilized with poly(diallyldimethylammonium chloride) (PDAC); this material can be used as a biomimetic cathode material for the reduction of H2O2 in biofuel cells. A metastable phase of iron oxide and iron hydroxide nanoparticles (PDAC–FeOOH/Fe2O3-NPs) was synthesized through a single procedure. On the basis of the Stokes–Einstein equation, colloidal particles (diameter: 20 nm) diffused at a considerably slow rate (D = 0.9 × 10? 11 m s? 1) as compared to conventional molecular redox systems. The quasi-reversible electrochemical process was attributed to the oxidation and reduction of Fe3+/Fe2+ from PDAC–FeOOH/Fe2O3-NPs; in a manner similar to redox enzymes, it acted as a pseudo-prosthetic group. Further, PDAC–FeOOH/Fe2O3-NPs was observed to have high electrocatalytic activity for H2O2 reduction along with a significant overpotential shift, ΔE = 0.68 V from ? 0.29 to 0.39 V, in the presence and absence of PDAC–FeOOH/Fe2O3-NPs. The abovementioned iron oxide nanoparticles are very promising as candidates for further research on biomimetic biofuel cells, suggesting two applications: the preparation of modified electrodes for direct use as cathodes and use as a supporting electrolyte together with H2O2.  相似文献   

14.
A series of brucite-like materials, undoped and doped zinc layered hydroxide nitrate with 2% (molar) Fe3+, Co2+ and Ni2+ were synthesized. Organic–inorganic nanohybrid material with gallate anion as a guest, and zinc hydroxide nitrate, as an inorganic layered host was prepared by the ion-exchange method. The nanohybrid materials were heat-treated at various temperatures, 400–700 °C. X-ray diffraction, thermal analysis and also Fourier transform infrared results showed that incorporation of the doping agents within the zinc layered hydroxide salt layers has enhanced the heat-resistivity of the nanohybrid materials in the thermal decomposition pathway. Porous carbon materials can be obtained from the heat-treating the nanohybrids at 600 and 700 °C. Calcination of the nanohybrids at 700 °C under nitrogen atmosphere produces mesoporous and high pore volume carbon materials.  相似文献   

15.
Ultrasonic pulse echo-overlap technique at 300 K (9 MHz) has been employed to study the elastic properties of Al3+-substituted CuFe2O4 spinel ferrite system. The longitudinal and transverse wave velocities are used to compute elastic moduli and these are corrected to the zero porosity by employing different models. Contrary to expectation, the magnitude of elastic moduli is found to decrease by 75% with only 30% of Al3+-substitution for Fe3+ in the system. The lowering of elastic stiffness is mainly due to residual stress-induced spontaneous cracking and presence of oxygen vacant sites in the material. The lower value of lattice energy for polycrystalline specimens as compared to their single crystalline counterparts have been explained in the light of an increase degree of disorientation at the grain boundary with Al3+-substitution.  相似文献   

16.
Transition-metal doped double-perovskite structure oxides GdBaCo2/3Fe2/3Ni2/3O5+δ (FN-GBCO), GdBaCo2/3Fe2/3Cu2/3O5+δ (FC-GBCO), GdBaCoCuO5+δ (C-GBCO) and pristine GdBaCo2O5+δ (GBCO) were synthesized via a citrate combustion method. The thermal-expansion coefficient (TEC) and electrochemical performance of the oxides were investigated as potential cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The TEC exhibited by the FC-GBCO cathode up to 900 °C is 14.6 × 10?6 °C?1, which is lower than the value of GBCO (19.9 × 10?6 °C?1). Area specific resistances (ASR) of 0.165 Ω cm2 at 700 °C and 0.048 Ω cm2 at 750 °C were achieved for the FC-GBCO cathode on a Ce0.9Gd0.1O1.95 (CGO) electrolyte. An electrolyte supported (300 μm thick) single-cell configuration of FC-GBCO/CGO/Ni-CGO attained a maximum power density of 435 mW cm?2 at 700 °C. The unique composition of GBCO co-doped with Fe and Cu ions in the Co sites exhibited reduced TEC and enhancement of electrochemical performance and good chemical compatibility with CGO, and this composition is proving to be a potential cathode for IT-SOFCs.  相似文献   

17.
Herein, the Sr2Fe1.5Mo0.5O6 (SFM) precursor solution is infiltrated into a tri-layered “porous La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM)/dense LSGM/porous LSGM” skeleton to form both SFM/LSGM symmetrical fuel cells and functional fuel cells by adopting an ultra-fast and time-saving procedure. The heating/cooling rate when fabricating is fixed at 200 °C/min. Thanks to the unique cell structure with high thermal shock resistance and matched thermal expansion coefficients (TEC) between SFM and LSGM, no SFM/LSGM interfacial detachment is detected. The polarization resistances (Rp) of SFM/LSGM composite cathode and anode at 650 °C are 0.27 Ω·cm2 and 0.235 Ω·cm2, respectively. These values are even smaller than those of the cells fabricated with traditional method. From scanning electron microscope (SEM), a more homogenous distribution of SFM is identified in the ultra-fast fabricated SFM/LSGM composite, therefore leading to the enhanced performance. This study also strengthens the evidence that SFM can be used as high performance symmetrical electrode material both running in H2 and CH4. When using H2 as fuel, the maximum power density of “SFM-LSGM/LSGM/LSGM-SFM” functional fuel cell at 700 °C is 880 mW cm 2. By using CH4 as fuel, the maximum power densities at 850 and 900 °C are 146 and 306 mW cm 2, respectively.  相似文献   

18.
The newly prepared homo-bimetallic complexes [M2(imda)2(H2O)4], [M2(imda)2(Bipy)2] (M = Co, Ni or Cu) and [Fe2(imda)2(H2O)3Cl] (H2imda = iminodiacetic acid and Bipy = 2,2′-bipyridine) have been studied employing IR, FAB-mass, 1H and 13C NMR, EPR and ligand field spectra, which indicated a high-spin state of metal ion with hexa-coordinate environment. 57Fe Mössbauer data of the homo-bimetallic complex [Fe2(imda)2(H2O)3Cl] confirm a high-spin configuration with Fe (±3/2  1/2) nuclear transitions and the presence of Kramer's double degeneracy. At RT, the spin–spin interactions of the neighbouring nuclei (Fe3+–Fe3+ = S5/2–S5/2) are anti-ferromagnetically coupled. However, at LNT, the complex acquires a mixed-valent [FeIII–FeII] composition corroborated from the X-band EPR data. CV studies indicated the presence of quasi-reversible redox CuII/I, CuII/III, FeIII/II, FeIII/I and FeII/I couples.  相似文献   

19.
A versatile route has been explored for the synthesis of nanorods of transition metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates using reverse micelles. Transmission electron microscopy shows that the as-prepared nanorods of nickel and copper oxalates have diameter of 250 nm and 130 nm while the length is of the order of 2.5 μm and 480 nm, respectively. The aspect ratio of the nanorods of copper oxalate could be modified by changing the solvent. The average dimensions of manganese, zinc and cobalt oxalate nanorods were 100 μm, 120 μm and 300 nm, respectively, in diameter and 2.5 μm, 600 nm and 6.5 μm, respectively, in length. The aspect ratio of the cobalt oxalate nanorods could be modified by controlling the temperature.The nanorods of metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates were found to be suitable precursors to obtain a variety of transition metal oxide nanoparticles. Our studies show that the grain size of CuO nanoparticles is highly dependent on the nature of non-polar solvent used to initially synthesize the oxalate rods. All the commonly known manganese oxides could be obtained as pure phases from the single manganese oxalate precursor by decomposing in different atmospheres (air, vacuum or nitrogen). The ZnO nanoparticles obtained from zinc oxalate rods are ~55 nm in diameter. Oxides with different morphology, Fe3O4 nanoparticles faceted (cuboidal) and Fe2O3 nanoparticles (spherical) could be obtained.  相似文献   

20.
Spectral and molecular model computations on homo-dinuclear complexes [M2L2(H2O)2Cl2] [L = 1-(salicylaldeneamino)-3-hydroxypropane, M = Cr3+, Mn3+, Fe3+, Co3+, Ni3+ or Cu3+] are consistent with a distorted hexa-coordinate geometry. X-band EPR spectral data indicated a rhombic distortion around Cu(II) ion. Magnetic moment and 57Fe Mössbauer data confirmed a high-spin state electronic configuration (t2g3eg2, S = 5/2) and asymmetric ligand environment around Fe(III) with nuclear transitions Fe(±3/2  1/2) exhibiting Kramer's double degeneracy. The neighboring Fe(III) nuclei in the homo-dinuclear species are antiferromagnetically coupled.  相似文献   

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