Novel glass-ceramics of the nominal molar compositions 20Fe2O3·20B2O3·(60-x)V2O5· (xNa2O or xSrO) (where x?=?0 or 10) were prepared by traditional melt technique. Differential thermal analysis (DTA) was implemented to study the thermal behavior of the prepared glasses. Vanadium pentoxide (V2O5), iron vanadate (FeVO4), sodium vanadate (Na3VO4) and strontium vanadate (with different formulae) were crystallized and identified by X-ray diffraction (XRD) analysis under certain conditions of heat-treatment. Further characterization of glass and glass ceramics samples were performed using scanning electron microscope (SEM), density, electrical and dielectric measurements. In conclusion, our study elucidated that the substitution of vanadium by Na+ and Sr2+ ions enhanced the conductivity at 180?°C from 5.11?×?10?4 for unmodified glass to 2.93?×?10?3 and 1.03?×?10?2?S?cm?1 for Na- and Sr-modified glasses. 相似文献
A multifunctional fluorescent probe BHN-Fe3O4@SiO2 nanostructure for Fe3+ was designed and developed. It has a good selective response to Fe3+ with fluorescence quenching and can be recycled using an external magnetic field. With adding EDTA (2.5?×?10?5 M) to the consequent product Fe3+-BHN-Fe3O4@SiO2, Fe3+ can be removed from the complex, and its fluorescence probing ability recovers, which means that this constituted on-off type fluorescence probe could be reversed and reused. At the same time, the probe has been successfully applied for quantitatively detecting Fe3+ in a linear mode with a low limit of detection 1.25?×?10?8 M. Furthermore, the BHN-Fe3O4@SiO2 nanostructure probe is successfully used to detect Fe3+ in living HeLa cells, which shows its great potential in bioimaging detection. 相似文献
The aim of this research was to prepare magnesium ferrite (MgFe2O4) magnetic nanoparticles and to investigate their sorption characteristics towards Mn2+, Co2+, Ni2+, Cu2+ ions in aqueous solution. MgFe2O4 was synthesized by glycine-nitrate combustion method and was characterized by low crystallinity with crystallite size of 8.2?nm, particle aggregates of 13–25?nm, BET surface area of 14?m2/g and pore size of 8.0?nm. Sorption properties of MgFe2O4 towards Mn2+, Co2+, Ni2+, Cu2+ ions were studied using one-component model solutions and found to be dependent on metal ions concentration, contact time, pH and conditions of regeneration experiment. The highest sorption capacity of MgFe2O4 was detected towards Co2+ (2.30?mmol?g1) and Mn2+ (1.56?mmol?g?1) and the lowest towards Ni2+ (0.89?mmol?g?1) and Cu2+ (0.46?mmol?g?1). It was observed that sorption equilibrium occurs very quickly within 20–60?min. The pHzpc of sorbent was calculated to be 6.58. At studied pH interval (3.0–7.0) the sorption capacity of MgFe2O4 was not significantly affected. Regeneration study showed that the metal loaded sorbent could be regenerated by aqueous solution of 10?3 M MgCl2 at pH 6.0 within 120?min of contact time. Regeneration test suggested that MgFe2O4 magnetic sorbent can be efficiently used at least for four adsorption-desorption cycles. The high sorption properties and kinetics of toxic metal ion sorption indicates good prospects of developed sorbent in practice for wastewater treatment. 相似文献
In this study, the structural, electrical, and optical properties of CuCr1?xNixO2 epitaxial films (x?=?0, 0.01, 0.03, 0.05), which exhibited p-type properties, were investigated. The (001)-oriented epitaxial films were deposited on c-plane α-Al2O3 substrates using pulsed laser deposition at a growth temperature of 700?°C and oxygen pressure of 10 mTorr. The optical energy band gap of the CuCr0.95Ni0.05O2 film was determined to be 3.22?eV. The hole carrier concentration of the CuCrO2 film increased from 5.1?×?1014 to 2.2?×?1017 cm?3 upon doping with 5?at% Ni. Based on Hall measurement and X-ray photoelectron spectroscopy results, it was suggested that the substituted Ni2+ dopants at Cr3+ sites formed an acceptor level without any charge compensation with Cu2+ and/or Cr4+. 相似文献
Determination of thermodynamic data on the formation of Bi2O3 was established by emf measurements as a function of temperature in the range 660–820°C on the system Metal, Bi(1)|Bi2O3|Pt, O2. From the results using a tungsten electrode the following relation was found: ΔG0 = ?(134.7 ± 1.2) + (64.0 ± 1.2) × 10?3 T kcal mole?1 (validity range: 940–1080 K). Standard thermodynamic data at 298 K were calculated as ΔG0 = ?119.2 ± 2.1 kcal mole?, ΔH0 = ?139.0 ± 1.2 kcal mole?1, and ΔS0 = ?66.3 ± 1.2 eu. 相似文献
In this work, transparent amorphous‐MgNb2O6 thin films were fabricated on ITO/glass substrates using the sol–gel method. The change in the chemical states, as well as the optical and dielectric properties of MgNb2O6 films at various annealing temperatures is investigated. In this study, MgNb2O6 films exhibited the amorphous phase when the annealing temperature was below 600°C. From X‐ray photoelectron spectroscopy, the major parts of the films' chemical states can be indexed as Mg2+, Nb5+, Nb4+, and O2?. Furthermore, the Nb4+ element can be reduced at higher annealing temperatures. The average transmission percentage in the visible range (λ = 400–800 nm) is over 80% for all MgNb2O6/ITO/glass samples, whereas the optical band gap (Eg) for all samples is estimated at ~4 eV. In addition, the dielectric constant was calculated to be higher than 20 under a 1 MHz AC electric field, with a leakage current density below 2 × 10?7 A/cm2 at 1 V. In this study, the fabrication procedure and experiment results of MgNb2O6 films are introduced for transparent microelectronics. 相似文献
A new compound, CdPb2O2Cl2, is synthesized by the method of solid-phase reactions. The compound has monoclinic symmetry, space group C2/m, a = 12.392(8) Å, b = 3.8040(14) Å, c = 7.658(5) Å, β = 122.64(5)°, and V = 304.0(3) Å3. The structure contains one symmetrically independent position of the Pb2+ cation coordinated by three O2? anions (Pb2+-O2? = 2.29–2.34 Å) and five Cl? anions (Pb2+-Cl? = 3.35–3.57 Å). The Cd2+ cation has a symmetric coordination with the formation of two bonds Cd-O = 2.15 Å and four bonds Cd-Cl = 2.73 Å. The oxygen atom is tetrahedrally coordinated by three Pb2+ cations and one Cd2+ cation, which leads to the formation of oxo-centered heterometallic OPb3Cd tetrahedra. The tetrahedra are linked together into chains through common Pb atoms and into layered complexes due to sharing of the equatorial Cd atoms. The chlorine atoms are located above the cavities of the oxo-centered layer. 相似文献
The thermo electric power, ΔE/ΔT, of the cell $$\begin{gathered} O_2 + N_{2, } Pt/Bi_2 O_3 (\delta phase)/Pt, O_2 + N_2 \hfill \\ (T + \Delta T) (T) \hfill \\ \end{gathered}$$ has been measured as a function of oxygen pressure (10?4 atm ? p(O2) ? 1 atm) in the temperature range 650–800° C. The experimental result can be described by: $$[ \in ({\rm O}_2 /{\rm O}^{2 - } ) - \in (e, Pt)] = [45.6 \pm 5.6 log p(O_2 ) - 261](\mu VK^{ - 1} )$$ within experimental error, where ε(O2/O2), the Seebeck coefficient ofδ-Bi2O3, stands for \(\mathop {\lim }\limits_{\Delta T \to 0} \Delta E/\Delta T\) The change of ΔE/ΔT with oxygen pressure corresponds to the change of the partial molar entropy of O2. The heat of transport of O2? ions is calculated to be 0.13 eV ± 0.01 whereas the activation enthalpy for ionic conduction is 0.30 eV. From this discrepancy it is concluded that the free ion model of Rice and Roth cannot be applied, while the extended lattice gas model of Girvin might explain the results when strong polaron coupling is assumed. 相似文献
In this paper, 4?mol% ZnO-doped Zr0.92Y0.08O2-α (8YSZ) and its 8YSZ+4ZnO/NaCl-KCl composite electrolyte were synthesized by a solid-state reaction. The X–ray diffraction (XRD) analysis indicates that 8YSZ+4ZnO and inorganic chlorides phases can coexist. The inorganic chlorides decrease the synthesis temperature of 8YSZ+4ZnO. The highest conductivities of 8YSZ+4ZnO and 8YSZ+4ZnO-NK are 7.0?×?10?3 S?cm?1 and 7.7?×?10?2 S?cm?1 at 700?°C, respectively. The oxygen concentration discharge cell shows that 8YSZ+4ZnO and 8YSZ+4ZnO-NK are good oxide ionic conductors under an oxygen-containing atmosphere. Finally, an H2/O2 fuel cell based on the 8YSZ+4ZnO-NK electrolyte reached the maximum power density (Pmax) of 315.5?mW?cm?2 at 700?°C. 相似文献
Electrochemical oxidation and reduction of H2O2 on Ag were studied in alkaline solution of 10?3?0.3 M H2O2 and 2 × 10?3 ?1.0 M KOH under N2 bubbling. Steady i-φ curves obtained by a cyclic potential sweep method in a potential range where no electrode oxidation takes place, lead to the following results: (1) icd (A cm?2) (cathodic limiting current density) = 1.0 × [H2O2]1.0T (M), (2) i1d (A cm?2 (anodic limiting one) = icd ([KOH] ? [H2O2]T) or 1.0 × [KOH] < [H2O2]T), (3) φm (V) (mixed potential) = 0.126-0.060 log [KOH]1.0 and (4) (?φ/?i)φ=φm (Ωcm2) (reaction resistance at φ = φm) = 0.057 × [H2O2]?1.0T (M?1), where [H2O2]T designates a total H2O2 concentration and the others have their usual meanings.The above results are explained by the following mechanism; HO?2 formed by the reversible chemical reaction, H2O2 + OH ? HO?2 + H2O, is oxidised in anodic reaction by two steps: HO?2 HO2 (a) + e? and HO2(a) + OH? → O2 + H2O + e?, whereas in cathodic reaction, H2O2 is reduced by H2O2 + e? OH(a) + OH?, OH(a) + e? → OH?. Here, designates a rate determining step,Catalytic decomposition of H2O2 on the electrode is also discussed. 相似文献
Solid solutions of 12CaO·7Al2O3 (C12A7) and 12SrO·7Al2O3 (S12A7) crystals were synthesized under high pressure. X‐ray diffraction patterns revealed that the lattice constants of the synthesized samples depend linearly on the compositional ratio of C12A7 and S12A7. Electron‐probe X‐ray microanalyses show that the chemical compositions of the crystals are represented by xC12A7·(1?x)S12A7 (0<x<1). These results indicate that the variation in the lattice constants is originated from a difference in the ionic radii of Ca2+ and Sr2+ ions. From impedance measurements, it was found that S12A7 has the highest conductivity (~1 × 10?3 Scm?1 at 550°C) among the solid solutions in the C12A7–S12A7 system. 相似文献
To investigate the effects of Yb3+ doping on phase structure, thermal conductivity and fracture toughness of bulk Nd2Zr2O7, a series of (Nd1-xYbx)2Zr2O7 (x?=?0, 0.2, 0.4, 0.6, 0.8, 1.0) ceramics were synthesized using a solid-state reaction sintering method at 1600?°C for 10?h. The phase structures were sensitive to the Yb3+ content. With increasing doping concentration, a pyrochlore-fluorite transformation of (Nd1-xYbx)2Zr2O7 ceramics occurred. Meanwhile, the ordering degree of crystal structure decreased. The substitution mechanism of Yb3+ doping was confirmed by analyzing the lattice parameter variation and chemical bond of bulk ceramics. The thermal conductivities of (Nd1-xYbx)2Zr2O7 ceramics decreased first and then increased with the increase of Yb3+ content. The lowest thermal conductivity of approximately 1.2?W?m?1 K?1 at 800?°C was attained at x?=?0.4, around 20% lower than that of pure Nd2Zr2O7. Besides, the fracture toughness reached a maximum value of ~1.59?MPa?m1/2 at x?=?0.8 but decreased with further increasing Yb3+ doping concentration. The mechanism for the change of fracture toughness was discussed to result from the lattice distortion and structure disorder caused by Yb3+ doping. 相似文献
Crystal s tructures, characteristics, and preparations of 12CaO·7Al2O3 family and CaO–Al2O3 (C–A) system have been reviewed in detail with relevant thermodynamic parameters being assessed or recalculated. 12CaO·7Al2O3 (shortened as C12A7) can form several derivatives of type C12A7:Mn? or C12A7–Mn? through replacing so‐called “free oxygen ion” by many anions including OH?, H?, O?, , F?, Cl?, and e? in their cages, or being adopted by rare earth metals or alkaline earth metal oxides at cation sites (Ca2+ or Al3+). These doped C12A7 derivatives show unique material properties of transparent conduction, catalysis, and antibacterial with potential applications in fast ion conductors, optoelectronics, oxidants, and catalysts etc. 相似文献
Based on phase equilibria, thermodynamic, and crystal structure data, the thermodynamic modeling of HfO2–La2O3–Al2O3 system is presented. Liquid phase is described by the modified quasichemical model considering the short‐range ordering in liquid solution. Solid solutions are described by the ionic sublattice model considering respective crystal structure. The model (La3+, Hf4+)2(Hf4+, La3+)2(O2?, Va)6(O2?)1(Va, O2?)1 successfully describes the structure defect, homogeneity range, and thermodynamic property of pyrochlore solid solution. A set of optimized model parameters is obtained which reproduces most experimental data well. Isothermal sections, liquidus and solidus projections, and Scheil reaction scheme are constructed. 相似文献
A galvanic cell with a Ag/AgCl reference electrode and a pO2? indicating electrode—made of a solid-state membrane in zirconia stabilized by calcia and filled by a mixture of Ni + NiO—has been constituted for working in the molten mixture NaCl-KCl (1:1), from 700 to near 1000°C. The response of the zirconia electrode in the fused salt has been tested by known variations of pO2?, due to coulometric titrations of free oxide ions, then of hydroxide ions, by means of metallic ions (Ni2+, Cu+) forming scarcely soluble metallic oxides. The results of measurements were in a good accordance with the variation laws theoretically established, giving the proof that measurements of pO2?, between about 2 and 12, are possible in the electrolytic and temperature range considered, by means of this system. An alteration of the electrode can arise in media with too low a pO2? value.Equilibrium constants have been determined: solubility products (Ks) of the oxides NiO and Cu2O, constant values of the equilibria 2OH? ? H2O (g) + O2? (K1) and H2O (g) + 2Cl? ? O2? + 2HCl (g) (K2); as functions of the absolute temperature T/°K and in the molar fraction scale (partial pressure of the gazeous substances in atm): The solubility product values (at 727°C) for a few metallic oxides have been calculated from the free enthalpy values of formation and experimental values of the activity coefficients of the metallic ions and O2? dissolved in NaCl-KCl.Limitations to the ability of the membrane electrode for measuring pO2? have been established by an analysis based on the chemical and electrochemical behaviour of zirconia. A potential-pO2? diagram shows the area inside which one has to work. 相似文献
In this study, we have successfully coated the CeO2 nanoparticles (CeONPs) layer onto the surface of the Ni-rich layered LiNi0.7Co0.2Mn0.1O2 cathode materials by a wet chemical method, which can effectively improve the structural stability of electrode. The X-ray powder diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) are used to determine the structure, morphology, elemental composition and electronic state of pristine and surface modified LiNi0.7Co0.2Mn0.1O2. The electrochemical testing indicates that the 0.3?mol% CeO2-coated LiNi0.7Co0.2Mn0.1O2 demonstrates excellent cycling capability and rate performance, the discharge specific capacity is 161.7?mA?h?g?1 with the capacity retention of 86.42% after 100 cycles at a current rate of 0.5?C, compared to 135.7?mA?h?g?1 and 70.64% for bare LiNi0.7Co0.2Mn0.1O2, respectively. Even at 5?C, the discharge specific capacity is still up to 137.1?mA?h?g?1 with the capacity retention of 69.0%, while the NCM only delivers 95.5?mA?h?g?1 with the capacity retention of 46.6%. The outstanding electrochemical performance is assigned to the excellent oxidation capacity of CeO2 which can oxidize Ni2+ to Ni3+ and Mn3+ to Mn4+ with the result that suppress the occurrence of Li+/Ni2+ mixing and phase transmission. Furthermore, CeO2 coating layer can protect the structure to avoid the occurrence of side reaction. The CeO2-coated composite with enhanced structural stability, cycling capability and rate performance is a promising cathode material candidate for lithium-ion battery. 相似文献
CaCu3-xCrxTi4O12 (x?=?0.00–0.20) ceramics were prepared via a polymer pyrolysis solution route. Their dielectric properties were improved by Cr3+ doping resulting in an optimal dielectric constant value of 7156 and a low tanδ?value of 0.092 in a sample with x?=?0.08. This might have resulted from a decrease in oxygen vacancies at grain boundaries. XANES spectra confirmed the presence of Cu+ ions in all ceramic samples with a decreasing Cu+/Cu2+ ratio due to an increased content of Cr3+ ions. All CaCu3-xCrxTi4O12 ceramics showed nonlinear characteristic with improvement in both the breakdown field (Eb) and its nonlinear coefficient (α). Interestingly, the highest values of α, ~ 114.4, and that of Eb, ~8455.0?±?123.6?V?cm?1, were obtained in a CaCu3-xCrxTi4O12 sample with x?=?0.08. The improvement of dielectric and nonlinear properties suggests that they originate from a reduction of oxygen vacancies at grain boundaries. 相似文献
Evolution of the microstructure, optical, and magnetic properties have been investigated systematically in multiferroic CuFe1-xSnxO2 (x?=?0–0.05) ceramics. Substitution of Sn4+ for Fe3+ results in expansion of CuFeO2 lattice, and reduces the density of the material, but the metal oxidation states are unchanged. Observation of the optical properties shows that the value of the direct optical band gap (Eg) decreases with increasing Sn doping level, and that the CuFe1-xSnxO2 (x?=?0–0.04) series with values >?3.1?eV. Magnetic susceptibility measurements show that Sn4+ doping decreases the Curie-Weiss temperature, i.e. weakens the strength of the antiferromagnetic interaction between high-spin Fe3+ ions, but does not affect the stability of the antiferromagnetic phase, and all samples undergo successive magnetic transitions at about TN1 =?15?K and TN2 =?11?K. However, magnetization curves show that changes occur in the magnetic interactions and both ferromagnetism and antiferromagnetism co-exist in the Sn4+-doped samples. The maximum value of the saturation magnetization of 1.8?emu·g?1 was observed for the x?=?0.03 sample in a 2.5?kOe field. The changes in the magnetic behavior are closely related to the lattice distortion and charge compensation, which are discussed in detail in this work. 相似文献
Lanthanum molybdate, La2Mo2O9, has been attracted considerable attention owing to its high concentration of intrinsic oxygen vacancies, which could be reflected by enhanced phonon scattering and low thermal conductivity. A new series of La2Mo2O9‐based oxides of the general formula La2?xSmxMo2?xWxO9, where x ≤ 0.2, were synthesized by citric acid sol–gel process. The variation in thermal conductivity with Sm3+and W6+ fractions was analyzed based on structure information provided by X‐ray diffraction and Raman spectroscopy. The fully dense La2?xSmxMo2?xWxO9 ceramics showed a minimum thermal conductivity value [κ = 0.84 W·(m·K)?1,T = 1073 K] at the composition of La1.8Sm0.2Mo1.8W0.2O9, which stems from the multiple enhanced phonon scatterings due to mass and strain fluctuations at the La3+ and Mo6+ sites as well as the high concentration of intrinsic oxygen vacancies embedded in the crystal lattice. The thermal conductivities present an abrupt decrease at the structural transition, which is due to the phase transformation from a low‐temperature ordered form (monoclinic α‐La2Mo2O9) to a high‐temperature disordered form (cubic β‐La2Mo2O9). 相似文献