铒镱共掺铋磷酸盐玻璃光谱性能的研究

基于光通信技术发展对光放大器材料的带宽要求,研究了掺铒铋磷酸盐玻璃的结构、熔制性能,以及其光谱性能,并且用Judd-Ofelt理论进行了光谱计算分析。得到了一种以铋磷酸盐为基质的光放大器玻璃材料,其折射率为1.778,荧光半峰全宽为54nm,发射截面为0.61×10-20cm2,其荧光寿命达到了8ms。结果表明,铒镱共掺铋磷酸盐玻璃是一种良好的宽带放大器材料。     

Effect of sulfur and nickel doping on morphology and electrochemical performance of LiNi0.5Mn1.5O4−xSx spinel material in 3-V region

The effect of nickel and sulfur substitution for manganese and oxygen on the structure and electrochemical properties of the LiNi_0.5Mn_1.5O_4−xS_x is examined. The LiNi_0.5Mn_1.5O_4−xS_x (x = 0 and 0.05) compounds are successfully synthesized at 500 and 800 °C by co-precipitation using the metal carbonate (Ni_0.5Mn_1.5)CO₃ as a precursor. The resulting powder with sulfur doping exhibits different morphology from a Ni-only doped spinel in terms of particle size and surface texture. The LiNi_0.5Mn_1.5O_4−xS_x (x = 0 and 0.05) powders are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and galvanostatic charge–discharge cycling. The nickel- and sulfur-doped spinel displays excellent capacity retention and rate capability in the 3-V region, compared with Ni-only doped spinel material.     

Electrochemical performances of lithium-ion polymer battery using LiNi1/3Co1/3Mn1/3O2 as cathode materials

In this work, a gel polymer electrolyte (GPE) was prepared using polyoxyalkylene glycol acrylate (POAGA) as a macromonomer. LiNi_1/3Mn_1/3Co_1/3O₂/GPE/graphite cells were prepared and their electrochemical properties were evaluated at various current densities and temperatures. The ionic conductivity of the GPE was more than 6.2 × 10⁻³ S cm⁻¹ at room temperature. The GPE had good electrochemical stability up to 5.0 V versus Li/Li⁺. POAGA-based cells were showed good electrochemical performances such as rate capability, low-temperature performance, and cycleability. No leakage of the electrolyte or an explosion was observed at the overcharge test.     

Nano-structured spherical porous SnO2 anodes for lithium-ion batteries

Spherical porous tin oxide was fabricated via a spray pyrolysis technique. TEM revealed that the primary SnO₂ crystals had an average size of about 5 nm. The electrochemical measurements showed that the spherical porous SnO₂ samples have excellent cyclability, which can deliver a reversible capacity of 410 mAh g⁻¹ up to 50 cycles as a negative electrode for lithium batteries. The second step of the study was to thermal treat the initial tin oxide for 3 h at 600, 800, 1000 and 1200 °C, respectively, in order to identify the particle size effect on the electrochemical performance toward lithium. It was found that the morphologies of these spherical clusters could be maintained even after thermal treatment at 1200 °C. It was also proved that finer the size of the tin oxide particles the better the electrochemical performance.     

Electrochemical properties of nano-sized Fe2O3-loaded carbon as a lithium battery anode

Nano-sized Fe₂O₃-loaded carbon material was prepared by loading Fe₂O₃ on carbon using a chemical method. Fe(NO₃)₃ was impregnated on carbon in an aqueous solution, and the mixture was dried and then calcined for 1 h at 400 °C in flowing Ar. Transmission electron microscopy (TEM) coupled with X-ray diffraction measurements revealed that small Fe₂O₃ particles (a few tenths of nanometers) were distributed on the carbon surface. The obtained nano-sized Fe₂O₃-loaded carbon material acted as an anode in a Li cell. High charge capacities of over 1000 mAh g⁻¹ (reduction of Fe₂O₃) in the first charge process suggested that Fe³⁺ in Fe₂O₃ was electrochemically reduced to Fe⁰. Investigation of the charge material by X-ray photoelectron spectroscopy (XPS) confirmed that Fe³⁺ is reduced to Fe⁰. Nano-sized Fe₂O₃-loaded acetylene black (AB), which, due to the larger surface area of AB, gave a greater distribution of nano-sized Fe₂O₃ particles than graphite, provided a larger capacity than nano-sized Fe₂O₃-loaded graphite.     

Characterization of Zn- and Fe-substituted LiMnO2 as cathode materials in Li-ion cells

Layered LiMn_1−xM_xO₂ (M = Zn or Fe) (0 ≤ x ≤ 0.3) samples are synthesized from the corresponding sodium analogues by an ion-exchange method using LiBr in n-hexanol at 160 °C. The samples are subjected to physicochemical and electrochemical characterization. X-ray diffraction data indicate the formation of layered structures for the LiMn_1−xZn_xO₂ samples up to x = 0.3 and for LiMn_1−xFe_xO₂ samples up to x = 0.2. Among these, LiMn_0.95Zn_0.05O₂ and LiMn_0.95Fe_0.05O₂ provide the highest capacity values of 180 and 193 mAh g⁻¹, respectively. Both Zn- and Fe-substituted samples display good capacity retention up to 30 charge–discharge cycles. Electrochemical impedance spectroscopy and galvanostatic intermittent titration data corroborate the results obtained from cyclic volatmmetry and charge–discharge cycling.     

Electrochemical impedance spectroscopy study of methanol oxidation on nanoparticulate PtRu direct methanol fuel cell anodes: Kinetics and performance evaluation

Electrochemical impedance spectroscopy (EIS) along with cyclic voltammetry (CV) has been applied as a tool for the mechanistic investigation of methanol oxidation on nanoparticulate PtRu fuel cell anodes of a commercially available state of the art membrane electrode assembly (MEA). The spectra could be fitted to a circuit derived analytically for multi-step single adsorbed intermediate reactions. The analysis has indicated that methanol adsorption and surface blocking occur below the onset and the surface is ‘poisoned’ to the highest degree just before the onset, implying that the removal of residues before the onset, if any, is slower compared to the formation. The onset potential is marked by a sudden change in the mechanism as the impedance becomes pseudoinductive. It has also been demonstrated that EIS can be applied for analyzing and singling out different contributions behind electrode performance for methanol oxidation reaction under fuel cell operating condition.     

Investigation of the porous structure of battery separators using various porometric methods

The aim of the investigation is to determine and compare the basic characteristics of the pores in battery separators using mercury porosimetry, which measures the volume of mercury penetrating into the pores, capillary flow porometry, which measures the flow rate passing through the pores, and scanning electron microscopy. Two groups of separators are investigated: PVC and glass mat.Two types of each group are analysed: PVC-R and PVC-E supplied by different manufacturers; and AGM and MAGM (modified AGM—new product developed by LABD at IEES).It has been established that: the PVC-R and PVC-E separators have similar porous structures; the AGM separator and MAGM separator have different pore size distribution, as clearly evidenced by the flow porometry data; though the glass mat separators have greater total pore volume (respective porosity), the PVC separators are characterized by greater permeability, because the pores in their narrowest part have greater diameters than those for the glass mat separators. The two methods used, mercury porosimetry and capillary flow porometry, give information about different characteristics of the porous structure. A combination of both methods will provide a more detailed information about the porous structure of the separators and a clearer idea about the dynamics of the processes that take place in the lead-acid batteries, than the data supplied by each of the techniques used alone.     

Influence of nickel content on the chemical bonding character of LiMn2−xNixO4 spinel oxides

A relationship between the chemical bonding nature of LiMn_2−xNi_xO₄ and the Ni content has been systematically investigated. According to X-ray diffraction analysis, nickel-substituted lithium manganates crystallize with a cubic spinel structure without the formation of any impurity phase such as NiO in the present substitution range of 0 ≤ x ≤ 0.4. Micro-Raman analysis showed that Ni substitution gave rise to an increase in the intensities and energies of the two main phonon lines at ∼580 and ∼620 cm⁻¹, indicating enhancement of the average Mn oxidation states and reinforcement of the MnO bonds. This was confirmed by Mn K-edge X-ray absorption spectroscopic (XAS) analysis. Also, a new phonon line appeared at ∼495 cm⁻¹ after the Ni substitution, which can be assigned as an Ni–O vibration mode rather than as a T_2g(2) mode of LiMn₂O₄. Ni K-edge XAS and micro-Raman analyses clearly demonstrate that divalent nickel ions existed in the octahedral sites of the cubic spinel lattice without a significant change in the chemical environment with the Ni content. In this regard, the poor electrochemical performance of heavily Ni-substituted compounds for the 3 V region is not attributable to the variation in the local environment of Ni ions with the Ni content, but to the low structural stability of the substituted NiO₆ octahedra.     

Polymer electrolyte membrane resistance model

A model and an analytical solution for the model are presented for the resistance of the polymer electrolyte membrane of a H₂/O₂ fuel cell. The solution includes the effect of the humidity of the inlet gases and the gas pressure at the anode and the cathode on the membrane resistance. The accuracy of the solution is verified by comparison with experimental data. The experiments were carried out with a Nafion 112 membrane in a homemade fuel cell test station. The membrane resistances predicted by the model agree well with those obtained during the experiments.