Yuxing Xu

Hollow MO x -RuO2 (M = Co, Cu, Fe, Ni, CuNi) nanostructures as highly efficient electrodes for supercapacitors

Engineering the internal structure and chemical composition of nanomaterials in a cost-effective way has been challenging, especially for enhancing their performance for a given application. Herein, we report a general strategy to fabricate hollow nanostructures of ruthenium-based binary or ternary oxides via a galvanic replacement process together with a subsequent thermal treatment. In particular, the as-prepared NiO-RuO2 hollow nanostructures loaded on carbon nanotubes (hNiO-RuO2/CNT) with RuO2 mass ratio at 19.6% for a supercapacitor adopting the KOH electrolyte exhibit high specific capacitances of 740 F g−1 at a constant current density of 1 A g−1 with good cycle stability. The specific capacitance for hNiO-RuO2/CNT electrodes maintains 638.4 F g−1 at a current density of 5 A g−1. This simple approach may shed some light on the way for making a wide range of metal oxides with tunable nanostructures and compositions for a variety of applications.摘要以低成本的方式调控纳米材料的内部结构和化学成分对增强其在特定应用中的性能非常重要, 但挑战巨大. 本文将电置换反应与一种热处理过程相结合, 报道了一种具有普适性的途径制备钌基二元和三元氧化物纳米中空结构, 并测定了其作为超级电容器电极材料的性能. 结果表明, 采用KOH为电解质, 在RuO2的质量分数仅为19.6%时, 所获得的负载于碳纳米管表面的中空NiO-RuO2纳米结构在恒电流密度为1A g-1时具有740 F g-1的比容量, 并且具有良好的循环稳定性. 在恒电流密度为5 A g-1时, 比容量仍可以保持在638.4 F g-1.本文以RuO2提高过渡金属的导电性, 以过渡金属降低RuO2材料成本并结合中空结构增加材料表面积的思路, 可以借鉴用来制备其它金属氧化物体系以满足特定应用的需求.

Preparation and Properties of Ce0.9Sm0.1O1.95 as the Electrolytes of IT-SOFC

Sm0.1Ce0.9O1.95 (SDC) films, as promising electrolyte materials, have been successfully prepared on Al2O3 ceramic substrates by RF magnetron sputtering growth. The relationship between sputtering parameters and film microstructure was discussed. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to characterize the morphology and crystal structure of the SDC films. The SEM images show that the crystallinity becomes better and better with the increase of sputtering power from 100W to 300W. X-ray diffraction patterns indicate that the thin SDC electrolyte film on the Al2O3 ceramic substrate grows preferentially along the (111) compact plane with a pure fluorite structure when the RF power reaches 300W. After annealing treatment at 600°C and 800°C, respectively, it can be seen that SDC film becomes denser with few pinholes at the annealing temperature of 800°C. High oxygen ion conductivity (1.46×10-2 Scm-1) of the SDC film was obtained when the RF sputtering power and annealing temperature were 300W and 800°C, respectively.

Mixtures of TiO2·0.2H2O and LiFePO4 as Li-ion Battery Cathode Materials

Mixtures of TiO2•0.2H2O (HTO) and LiFePO4 were prepared via three main composite methods: 2-2 series model, 2-2 parallel model and 3-3 model. HTO had been reported to exhibit high specific capacity (~200 mAh/g at 1 C) as well as excellent cycle property, whereas its voltage plateau was too low (about 1.7 V vs. Li) as a cathode material. LiFePO4 was a promising cathode material for its high voltage plateau (about 3.4 V vs. Li), low cost and high specific capacity (~150 mAh/g at 1 C). However, because of its low conductivity, the rate property as well as cycle property was limited. The mixtures of HTO and LiFePO4 were considered to combine the advantages of both materials. By comparison, the 2-2 parallel model excelled in both rate property and cycle property. Its specific capacity can reach as high as 220 mAh/g with a high specific energy of 450 Wh/Kg at 0.1 C. Even after cycled 200 times at 2 C, the capacity can still be higher than 100 mAh/g. CV measurements and a combined constant current and constant voltage tests supported a two plateaus process for 2-2 parallel model. The charge-discharge voltage gap increased for the 2-2 parallel composites, which was supposed to be related to the interface. In general, the specific energy was much higher than HTO while the specific capacity as well as cycle property was much better than LiFePO4 as a cathode material. .

XPS Research on SrTiO3-Based Voltage-Sensitive Material

SrTiO3-based voltage-sensitive material was prepared successfully. The structure and properties were investigated using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. It was observed that the average grain size was greater than 3μm and a cubic perovskite structure was obtained. XPS analysis of oxygen indicated that there existed multiform chemical state oxygen at the surface of the grain. Further researches shown that there were a few [AO12] polyhedrons and many cation vacancies in the material discussed, which demonstrated that a lot of oxygen volatilized and a well-known semiconductivity level was achieved.

Effect of Treatment Process on the Structure and Properties of Sr0.48Ba0.24Ca0.28TiO3-Based Varistor Ceramics

Sr0.48Ba0.24Ca0.28TiO3-based varistor ceramics with an excellent capacitor-varistor multifunctional characteristics (V1mA = 11 ~ 49 ν.mm-1, α = 6.1 ~ 11.3, ε r max=3.5×105, tanδmin = 5%) were prepared using conventional solid method. The effect of oxidation temperature and time on structure and electrical properties were investigated. The results show that with increasing the oxidation temperature from 800°C to 900°C, the varistor voltage V1mA and non-linearity coefficient α defining varistor characteristics increase linearly, while the dielectric constant ε r and dielectric loss tanδ decrease linearly. There exists an optimum α value when the specimens were oxidized at 850°C for 3h. This behavior was explained through various defect reactions of dopants.

Effect of Li+ and Mn2+ Doping on the Electrical Properties of SrTiO3-Based Varistor Ceramics

Effect of Li+ and Mn2+ doping on the electrical properties of SrTiO3-based varistor ceramics was investigated. The results showed that the varistor ceramics cannot possess ideal electrical properties when only Li+ or Mn2+ was doped. However, when Li+ and Mn2+ were properly doped together, the samples acquired excellent electrical properties: V1mA = (5.7 ~ 11.7)V/mm; α = 6.8 ~ 11.0; er = (2.4 ~ 4.4) × 105; tan d = (7.1 ~ 10.4)%. When the contents of Li2CO3 and MnCO3 were 1.00 mol% and 0.05 mol% respectively, the nonlinear coefficient α reached the largest value of 11.0. Compared with only Mn2+ doping, the addition of Li+ increases the α value significantly.