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1.
The effect of Nb as a support modifier on the NiMo6/Al2O3–Nb2O5(x) (x?=?0, 1, 4, and 8?wt% Nb) catalysts was studied. The supports were prepared by one-pot coprecipitation from soluble precursors. The XRF analysis of the catalysts showed that the contents of Mo and Ni increased slightly with the presence of Nb. Micropore area and pore volume augmented importantly with Nb content, resulting in pore diameters between 5.3 and 9.3?nm. XPS analysis showed that the presence of Nb decreases the active metal–support interaction, improving the Mo and Ni sulfidation degree. The Raman spectra of sulfided catalysts suggested an increase in the number of layers of MoS2 in the presence of Nb. Generally, the thiophene HDS activity at normal pressure of sulfided NiMo6/Al2O3–Nb2O5(8) was greater than that of the sulfided catalysts with x?=?0, 1, and 4?wt% Nb, which can be attributed to the Nb promotion that would have an effect on the type of active site (Brønsted or Lewis acidic sites), since the number of sites by CO chemisorption for sulfided NiMo6/Al2O3–Nb2O5(x) did not show correlation with the catalytic activity. The high-pressure HDS activity of dibenzothiophene was also greater in the presence of Nb, and the hydrogenation route was preferred for the Nb-promoted solid, while the unpromoted one showed a larger yield of direct desulfurization products.  相似文献   

2.
The aim of this work was an investigation of structural and electrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) powders. The compounds obtained by sol-gel method are characterized by several techniques: X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), electrical and dielectrical measurements. The XRD, SEM and XPS analysis confirmed the formation of ZnFeTiO4 inverse spinel structure. The electrical and dielectrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) were measured by impedance spectroscopy, revealing a decrease in the electrical conductivity and the dielectric constant with Fe content.  相似文献   

3.
CaMn7O12 precursor sol was prepared by using Ca(NO3)2·4H2O and Mn(CH3COO)4·4H2O as the raw materials, acetylacetone (AcAcH) as the chelating agent, and methyl alcohol (MeOH) as the solvent. The CaMn7O12 crystalline film was obtained via dip-coating and annealing treatment on the LaAlO3 (001) single-crystal substrate. XRD θ-2θ scan indicated that the as-prepared CaMn7O12 film had strong preferred orientation along the c-axis. In addition, the results of the ω and ? scans demonstrated that the film exhibited outstanding out-of-plane and in-plane texture characteristics. The SEM characterization showed that the CaMn7O12 film was dense and free of cracks. The grain size was uniform with an average size of ~180?nm. Vibrating sample magnetometer (VSM) test results indicated the CaMn7O12 film was antiferromagnetic and had a saturation magnetization of 114.2?emu/cm3 at 50?K.  相似文献   

4.
Mg–Ti substituted strontium hexa-ferrites nanopowders (SrFe12?x(MgTi)x/2O19, x?=?0–3) were prepared by the sol–gel method. The morphology, structure and composition of the nanostructures were examined by field emission scanning electron microscopy (FESEM) and X-ray diffraction. The effect of Mg–Ti doping on the magnetic properties of the powders was investigated by vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) at ambient temperature. Experimental results showed that the materials exhibit hexagonal structures with tunable magnetic properties. The saturation magnetization and the coercive field (Hc) decreased through the Mg and Ti substitution. FMR proved that by incorporation of Mg and Ti in strontium ferrite lattice, crystalline anisotropy, and microwave absorption can be tuned. SrFe12?x(MgTi)x/2O19 ferrites are good candidate for applications at X-band microwave frequencies. A low field absorption signal was observed with the same phase as the FMR absorption in all doped ferrites.  相似文献   

5.
Prospective cathode materials Mg2-xMn x SiO4 (0.0?≤?x?≤?0.4) for magnesium-ion secondary battery were synthesized using sol gel method. Crystalline structure, morphology, particle size, electrical and electrochemical properties of the samples were investigated. X-ray diffraction patterns of the materials exhibited no extra peak for x?≤?0.6 indicated that Mg2-xMn x SiO4 materials were successfully synthesized. Mn doping in magnesium site did not affect the formation of single phase, and this probably due to the low concentration of Mn to induces structural changes. Mn doping contributed to the enhancement of the electrochemical performance of Mg2SiO4. For this work, Mg1.4Mn0.6SiO4 which possesses the largest unit cell volume, smallest charge transfer resistance, and highest conductivity value showed the most promising electrochemical performance compared to the other samples. These results indicated the suitability of the Mg2-xMn x SiO4 to be exploiting further for potential applications as solid electrolytes in electrochemical devices and strengthen the fact that doping could be an effective way to enhanched the structural, electrical and electrochemical performance of materials.  相似文献   

6.
In this study, the effective TiO2/Ag composite antibacterial aerogel powder is prepared by facile sol–gel method and ethanol supercritical technology. The surface morphology, structural properties, and chemical components are monitored by scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and energy disperse?spectroscopy (EDS). Meanwhile, absorbance spectra and specific surface area of TiO2/Ag composite aerogel are characterized by UV-Vis spectra and Brunauer–Emmett–Teller. The TiO2/Ag composite aerogel with Ti/Ag molar ratios of 10:1, 30:1, 50:1 are measured for its antibacterial property by using Escherichia coliform (E.coli) and Staphylococcus aureus (S. aureus). The results show that the size of TiO2 and Ag nanoparticles are 40?nm and 25?nm, respectively. Simultaneously, the obtained composite aerogel with a porous structure possessed a surface area of 148?m2/g, an average pore size 11.5?nm, and a pore volume 0.39?cm3/g. With the increase of Ag content, the antibacterial properties of composite aerogel are greatly improved compared with pure TiO2 aerogel. When Ag/Ti molar ratios was 1:10, the highest antibacterial rate can up to 99%, and the inhibition bands of E. coli and S. aureus are 23?mm and 19?mm, respectively.
Schematic representation of growth mechanism of TiO2/Ag composite aerogel (a) and antibacterial performance test (b, c)
  相似文献   

7.
BaM hexaferrites substituted with both Ca2+ and Mg2+ ions, namely, Ba1-2×CaxMgxFe12O19 (0.0?≤?x?≤?0.1), synthesized during a sol–gel auto-combustion route. The hexaferrite phase and morphology of all samples were investigated using X-ray powder diffraction, a field emission scanning electron microscope, a high-resolution transmission microscope, and Fourier transform infrared spectroscopy. In addition, an M-type hexagonal structure was confirmed using XRD for all samples. FE-SEM and TEM revealed the shape of the hexagonal plate. Measurements of the magnetization versus the field M(H) of Ba1-2×CaxMgxFe12O19 (0.0?≤?x?≤?0.1) nanohexaferrites were conducted at 300 and 10?K. A hard-ferrimagnetic behavior at both 300 and 10?K was noted for the different products produced. The squareness ratio indicates the uniaxial anisotropy for various products. The deduced values of saturation magnetization (Ms) in all substituted samples are higher than in the pristine sample (x?=?0). The Ba0.96Ca0.02Mg0.02Fe12O19 nanosized hexaferrite showed the highest values of Ms, remanence Mr, magneton number (nB), and magnetocrystalline anisotropy constant (Keff). In contrast, the values of the coercive field (Hc) and intrinsic coercivity (Hci) diminish with the increase in the amount of the substituted Ca and Mg elements.  相似文献   

8.
Flower-like ceria (CeO2) architectures consisting of well aligned nanosheets were first synthesized by a glycol solvothermal method. The size of CeO2 architectures is about 5?μm in width and 10?μm in length, with the nanosheets thickness below 100?nm. Subsequently, the adsorbed Ag ions on the surface of CeO2 were in situ reduced to form Ag nanoparticles (NPs), leading to the fabrication of Ag/CeO2 hybrid architectures (HAs). The formed Ag NPs with sizes of 20–40?nm were uniformly loaded on the surface of the CeO2 sheets. The antibacterial properties of Ag/CeO2 HAs against Gram-negative E. coli and Gram-positive S. aureus were evaluated by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and a filter paper inhibition zone method. The results demonstrated that Ag/CeO2 HAs displayed excellent antibacterial activity toward S. aureus and E. coli, which were attributed to the synergistic antibacterial effect between Ag NPs and CeO2 in HAs. Here, CeO2 nanoflowers as a new substrate could restrict Ag NPs aggregations and improve their antibacterial activities. Therefore, the resulted Ag/CeO2 HAs would be considered as a promising antibacterial agent.  相似文献   

9.
Bismuth ferrite (BiFeO3) nanopowder have been successfully synthesized for the first time via a microwave-assisted sol-gel combustion method by using citric acid as fuel. The resulting nanopowder was characterized using FT-IR, TG-DTA, XRD, EDX, VSM, SEM, and UV-Vis DRS. A ferromagnetic hysteresis loop with a saturation magnetization (MS) of 0.66?emu?g?1 has been observed at room temperature in the sample. The optical properties of the nanosized BiFeO3 showed its small band gap (=2.08?eV) indicates a possibility of utilizing much visible light for photocatalysis.  相似文献   

10.
Phase relationships in the subsolidus region of the system Na2MoO4-MnMoO4-Cr2(MoO4)3 were studied by means of X-ray diffraction and differential-thermal analyses. The possibility of obtaining a variablecomposition phase Na1?x Mn1?x Cr1+x (MoO4)3 (0 ≤ x ≤ 0.5) and ternary molybdate NaMn3Cr(MoO4)5 was examined. The temperature dependence of the conductivity of the phase Na1?x Mn1?x Cr1+x (MoO4)3 was analyzed.  相似文献   

11.
The subsolidus region of the Ag2MoO4-MgMoO4-Al2(MoO4)3 ternary salt system has been studied by X-ray phase analysis. The formation of new compounds Ag1 ? x Mg1 ? x Al1 + x (MoO4)3 (0 ≤ x ≤ 0.4) and AgMg3Al(MoO4)5 has been determined. The Ag1 ? x Mg1 ? x Al1 + x (MoO4)3 variable-composition phase is related to the NASICON type structure (space group R \(\bar 3\) c). AgMg3Al(MoO4)5 is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P \(\bar 1\), Z = 2) with the following unit cell parameters: a = 9.295(7) Å, b = 17.619(2) Å, c = 6.8570(7) Å, α = 87.420(9)°, β = 101.109(9)°, γ = 91.847(9)°. The compounds Ag1 ? x Mg1 ? x Al1 + x (MoO4)3 and AgMg3Al(MoO4)5 are thermally stable up to 790 and 820°C, respectively.  相似文献   

12.
The subsolidus phase composition of the M2O-CdO-V2O5 systems with M = Li or Na is studied. Double orthovanadates MCdVO4 and MCd4(VO4)3 form solid solutions of composition Li1 ? 2x/3Cd x/3CdVO4 (0 ≤ x ≤ 1, orthorhombic space group Cmcm, modulation at x = 0.6) and Na3 ? 2x Cd3 + x (VO4)3 (0 ≤ x ≤ 0.10 and 0.30 ≤ x ≤ 1, orthorhombic space group Cmcm and Pn21 a or Pnma, respectively). In the range 0.10 < x < 0.30, the end-members of the solid solutions coexist. Isothermal sections of the systems are mapped.  相似文献   

13.
Perovskite-related oxide Tm x Cu3V4O12 (space group Im \(\bar 3\), Z = 2, a = 7.262?7.273 Å) with vacancies in the cationic sublattice has been prepared for the first time under barothermal conditions (p = 7.0?9.0 GPa, T = 900?1100°C). Electric resistivity (10–300 K) and magnetic susceptibility (0–300 K) were studied as a function of temperature. Tm x Cu3V4O12 is shown to have a metallic conductivity and paramagnetism.  相似文献   

14.
A continuous solid solution LaMn1?y Cr y O3 with an orthorhombic structure is found to exist in the range of 0.0 ≤ y ≤ 1.0. An orthorhombic solid solution La1?x Sr x CrO3 exists in the range of 0.0 ≤ x ≤ 0.1. The stability boundaries are determined for the perovskite phase La1?x Sr x Mn1?y Cr y O3. An isobaric-isothermal section LaMnO3-SrMnO3-SrCrO4-LaCrO3 of the system La2O3-SrO-Mn3O4-Cr2O3 in air at 1100°C is designed.  相似文献   

15.
Brick-shaped zinc tungstate nanoparticles have been synthesized by ecofriendly solvent-free process using molten salts. Zinc tungstate nanobricks (ZnWO4 Nbs) were characterized by powder x-ray diffraction (PXRD), FTIR, Raman, energy dispersive and electron microscopic studies. ZnWO4 Nbs are used as the multifunctional electrode materials to oxygen generation reactions (OGR), oxygen reduction reactions (ORR) and supercapacitors (SCs) as well as photo-catalysts in the waste-water treatment by the degradation of organic dyes. Low overpotential (?10?=?0.475?V), low tafel slope (140?mV/dec), high current density (~70?mA/cm2) and good stability of the electrodes are the key results of the present studies for water electrolysis (OGR/ORR). ZnWO4 Nbs have also shown great interest in supercapacitors with efficient charge–discharge activities in 1?M KOH. The specific capacitance and energy density of ZnWO4 Nbs were found to be 250?F/g and 80?Wh/kg, respectively, at 5?mV/s, these values are relatively higher than that of previously reported specific capacitance and energy density value of metal tungstate nanoparticles. ZnWO4 Nbs as the photo-catalysts work very significantly for photocatalytic degradation of aqueous MB dye solution (~85 % in 3?h) in neutral medium.
ZnWO4 Nanobricks show significant multifunctional electro-chemical activities in alkaline medium and photocatalytic degradation of organic dye in neutral medium.
  相似文献   

16.
The presented study deals with relation between chemical composition of precursor sols and surface free energy of inorganic-organic films. Inorganic-organic films were prepared from precursor sols in “tetraethoxysilane (TEOS) - triethoxy(octyl)silane (OTES) - distilled water - nitric acid - isopropyl alcohol” system. The fifteen sols were prepared, where the ratio of K?=?x(OTES)/(x(TEOS)?+?x(OTES)) varied from 0 to 0.5 and ratio of R?=?x(H2O)/(x(TEOS)?+?x(OTES)) varied from 2 to 6. The relationship between chemical composition and surface free energy of inorganic-organic films was quantified by model selection approach. Model, which describes the studied relationship in the best way, was selected on the basis of Akaike information criterion. Based on the analysis of selected (the best describing) model, it was found out that the surface free energy as well as its dispersion and polar component are dependent only on K ratio in observed range of K and R values. Form the physico-chemical aspect, the observed dependences of surface free energy, its dispersive and polar component on chemical composition of precursor sols are explained by the influence of octyl groups on the sequences of hydrolysis and condensation reactions leading to formation of particles in precursor sol. In addition, the arrangement of octyl groups is used for explanation of particles arrangement on film surface.  相似文献   

17.
The phase composition has been studied and an equilibrium phase diagram has been designed for the Al2O3-Li2O-R2O5 (R = Ta or Nb) systems in the subsolidus region up to 1000°C and 85 mol % Li2O. New phases with the composition Li1+x Al1?x O2?x , where x = 0–0.67, have been found.  相似文献   

18.
A robust synthesis approach to Ni2+-substituted Mg0.25-xNi x Cu0.25Zn0.5Fe2O4 (0?≤?x?≤?0.25?mol.) ferrimagnetic oxides using citrate assisted sol–gel process is reported. The route utilizes simple metal nitrate precursors in aqueous solution, thus eliminating the need for organometallic precursors. Citric acid acts as a fuel for the combustion reaction and forms stable complexes with metal ions preventing the precipitation of hydroxilated compounds to yield the composite ferrite structure by auto-combustion process. The XRD signatures, especially (3 1 1) plane, confirmed the formation of spinel structure. The linear growth of lattice constant from 8.385 to 8.409?Å was observed by Ni2+ substitution from 0 to 0.25. The dense microstructure is observed with the average grain size of 0.42–2.18?µm. The transport properties revealed the semiconducting behavior of as-prepared ferrite material, with an increase in the DC-electrical resistivity by the incorporation of nickel. The magnetic properties viz. initial permeability (µi) and magnetic moment (nB) are explained, based on the deviation in saturation magnetization (Ms), anisotropy constant (K1), density values, and exchange interactions. Furthermore, the effect of adding Ni2+ on the Curie temperature, frequency-dependent dielectric properties of the ferrite material are also discussed.  相似文献   

19.
Barium zirconium titanate (Ba(Zr x Ti1?x)O3, BZT) super smooth thin films are synthesized through modified sol-gel dip coating route on fluorine-doped tin oxide substrates with a suitably low calcination temperature. The Fourier tranformed infrared spectroscopy proves that impurities and starting materials are completely removed in the calcination process. Crystallographic phases of the samples are identified by the X-ray diffractometry and confirms that all samples are crystallized into a single perovskite phase. Introducing zirconium into the structure causes a reduction in dielectric constant of barium titanate. The optical properties of the films are also investigated. The results indicate that all samples are highly transparent and zirconium reduces the absorption coefficient. Moreover, the band gap energy of barium titanate increases when doped with zirconium and the highest band gap energy of about 3.71?eV along with the lowest dielectric constant of 850 at frequency of 100?kHz are obtained in 15 at.% zirconium-doped sample.  相似文献   

20.
Mixed metal oxides of tin with strontium (xSnO2.SrO) in different molar ratio {where x?=?1 (1), 2 (2), 4(3); SnO2 doped with Sr+2(4), SnO2 doped with Sr+2 and co-doped with F?(5)} have been prepared by sol–gel technology in basic medium using SnCl2.2H2O as precursor in isopropanol as solvent. Structural analysis by XRD patterns have shown formation of particles at nanoscale and phase separation of SnO2 in tetragonal rutile framework in these mixed metal oxides. This fact was further supported by TEM. SEM images of all these samples have shown formation of various geometrical patterns ranging from spherical particles to nanorods. In the IR spectra of all these oxides, Sr–O absorption bands were present only in sample (1). UV–Vis spectroscopy has shown reduction in optical band gap in mixed metal oxides and the lowest value of band gap was observed for sample (3). Photoluminescence spectra of all these derivatives are found to be almost similar again indicated retention of tetragonal rutile SnO2 framework. IV curves of all these oxides are non-linear and lowest resistance was observed for sample (3). This fact was further supported by impedance measurements.  相似文献   

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