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排序方式: 共有1546条查询结果,搜索用时 17 毫秒
1.
Bing Huang Meng Wang Guodong Xu Lin Hu Lin Chen Yijie Gu 《Ceramics International》2021,47(6):7700-7710
In this study, La was doped into the lithium layer of Li-rich cathode material and formed a layered-spinel hetero-structure. The morphology, crystal structure, element valence and kinetics of lithium ion migration were studied by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The La doped lithium-rich cathode material exhibited similar initial discharge capacity of 262.8 mAh g?1 at 0.1 C compared with the undoped material, but the discharge capacity retention rate can be obviously improved to 90% after 50 cycles at 1.0 C. Besides that, much better rate capability and Li+ diffusion coefficient were observed. The results revealed that La doping not only stabilized the material structure and reduced the Li/Ni mixing degree, but also induced the generation of spinel phase to provide three-dimensional diffusion channels for lithium ion migration. Moreover, the porous structure of the doped samples also contributed to the remarkable excellent electrochemical performance. All of these factors combined to significantly improve the electrochemical performance of the material. 相似文献
2.
使用分析纯物质模拟微晶玻璃熔体,分别采用柱体旋转法和拉曼光谱技术研究了La2O3含量对SiO2-CaO-Al2O3-MgO熔体黏度和结构的影响规律。结果表明:熔体黏度和黏流活化能随着La2O3含量的增加而降低;拉曼光谱表明La2O3能破坏硅酸盐结构(Qn),随着La2O3含量的增加,Q1、Q2的百分含量增加,Q3的百分含量减小,Q0的百分含量基本不变,表明熔体中非桥氧数量增加,熔体聚合度降低。La2O3在熔体中起网络修饰体的作用。 相似文献
3.
《International Journal of Hydrogen Energy》2020,45(7):3940-3947
Ternary Ni–P–La alloy was synthesized by the co-electrodeposition method on the copper substrate. The energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used for characterization of the synthesized alloy. The electrochemical performance of the novel alloy was investigated based on electrochemical data obtained from steady-state polarization, Tafel curves, linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) in alkaline solution and at ambient temperature. The results showed that the microstructural properties play a vital purpose in determining the electrocatalytic activity of the novel alloys. Also, the HER on investigated alloys was performed via the Volmer-Heyrovsky mechanism and Volmer step as RDS in this work. Ni–P–La catalyst was specified by ƞ250 = −139.0 mV, b = −93.0 mV dec−1, and jo = −181.0 μA cm−2. The results revealed that the Ni–P–La catalysts have a high potential for HER electrocatalysts in 1M NaOH solution. 相似文献
4.
《International Journal of Hydrogen Energy》2020,45(1):553-564
Ni/Al2O3 catalyst is the one of promising catalysts for enhancing H2 production from supercritical water gasification (SCWG) of biomass. However, due to carbon deposition, the deactivation of Ni/Al2O3 catalyst is still a serious issue. In this work, the effects of lanthanum (La) as promoter on the properties and catalytic performance of Ni/Al2O3 in SCWG of food waste were investigated. La promoted Ni/Al2O3 catalysts with different La loading content (3–15 wt%) were prepared via impregnation method. The catalysts were characterized using XRD, SEM, BET techniques. The SCWG experiments were carried out in a Hastelloy batch reactor in the operating temperature range of 420–480 °C, and evaluated based on H2 production. The stability of the catalysts was assessed by the amount of carbon deposition on catalyst surface and their catalytic activity after reuse cycles. The results showed that 9 wt% La promoter is the optimal loading as Ni/9La–Al2O3 catalyst performed best performance with the highest H2 yield of 8.03 mol/kg, and H2 mole fraction of 42.46% at 480 °C. La promoted Ni/Al2O3 catalysts have better anti-carbon deposition properties than bare Ni/Al2O3 catalyst, resulting in better gasification efficiency after reuse cycles. Ni/9La–Al2O3 catalyst showed high catalytic activity in SCWG of food waste and had good stability as it was still active for enhancing H2 production when used in SCWG for the third time, which indicated that La promoted Ni/Al2O3 catalysts are potential additive to improve the SCWG of food waste. 相似文献
5.
目的 为了探究玻璃沉积物CMAS(CaO-MgO-Al2O3-SiO2)对新型结构热障涂层在1250 ℃下的热冲击寿命的影响,揭示热障涂层的失效行为。方法 通过火焰喷涂技术将制备的CMAS粉体均匀地沉积到铈酸镧/氧化钇部分稳定二氧化锆双陶瓷层热障涂层(LC/YSZ DCL-TBCs)和梯度热障涂层(LC/YSZ FGM-TBCs)的表面,于1250 ℃热冲击实验中进行涂层样品的抗热冲击性能及失效机理研究。利用扫描电镜(SEM)和能谱仪(EDS)追踪CMAS的位置,观察CMAS与涂层反应层的厚度与形貌。采用X射线衍射仪(XRD)测试反应层产物,并总结其失效方式。结果 高温热冲击结果显示梯度涂层的热冲击寿命(435次)远高于双陶瓷层热障涂层的寿命(229次),约为铈酸镧/氧化锆双陶瓷层热障涂层寿命的1.9倍。铈酸镧层与梯度层都能在一定程度上阻碍CMAS渗入涂层内部,提高其CMAS腐蚀条件下的热冲击寿命。双陶瓷层热障涂层与梯度热障涂层的失效均是以层状剥落为主,剥落层主要是CMAS与LC的反应层以及反应层下的烧结层,反应层是由Ca2(LaxCe1-x)8(SiO4)6O6-4x、萤石相和MgAl2O4等难熔氧化物组成,这层致密氧化物类似于密封层,能阻止CMAS继续渗入。结论 功能梯度结构具有比双陶瓷层结构更优异的抗CMAS热冲击性能和更好的应力耐受性。 相似文献
6.
《International Journal of Hydrogen Energy》2020,45(52):28163-28174
Element replacement and mechanical milling are considered as the most effective ways to improve Mg-based alloys in their hydrogen storage performance. The as-milled La7RE3Mg80Ni10 (RE = Sm, Ce) alloys were prepared in this experiment by introducing both element replacement (replacing La by Ce or Sm partially) and mechanical milling technologies. The influence made by different replacing elements on the structure and hydrogen storage property of La7RE3Mg80Ni10 (RE = Sm, Ce) alloys was investigated in detail. X-ray diffraction, transmission electron microscope, automatic Sievert apparatus, thermogravimetry and differential scanning calorimetry were used to investigate the experimental alloys. The experiment reveals that a nanocrystalline and amorphous structure appears after mechanical milling. Moreover, comparing with the RE = Sm alloy, the RE = Ce alloy has a superior hydrogen desorption property, including larger hydrogen absorption capacity, faster hydriding/dehydriding rate, lower onset hydrogen desorption temperature, and lower dehydrogenation activation energy. 相似文献
7.
Santosh K. Gupta Maya Abdou Partha S. Ghosh Jose P. Zuniga Ezhilarasan Manoharan HyeongJun Kim Yuanbing Mao 《Journal of the American Ceramic Society》2020,103(1):235-248
Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A2B2O7, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La2Zr2O7 (LZO) and La2Hf2O7 (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu3+ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O2−→Zr4+/Hf4+ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu3+-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu3+ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays. 相似文献
8.
Yang-huan ZHANG Ya-qin LI Hong-wei SHANG Zhong-hui HOU Yan QI Dong-liang ZHAO 《中国有色金属学会会刊》2018,28(4):711-721
The La-Mg-Ni-Co-Al-based AB2-type La0.8–xCe0.2YxMgNi3.4Co0.4Al0.1 (x=0, 0.05, 0.1, 0.15, 0.2) alloys were prepared via melt spinning. The analyses of the X-ray diffraction (XRD) and scanning electron microscopy (SEM) proved that the experimental alloys contain the main phase LaMgNi4 and the second phase LaNi5. Increasing Y content and spinning rate lead to grain refinement and obvious change of the phase abundance without changing phase composition. Y substitution for La and melt spinning make the life-span of the alloys improved remarkably, which is attributed to the improvement of anti-oxidation, anti-pulverization and anti-corrosion abilities. In addition, the discharge capacity visibly decreases with increasing the Y content, while it firstly increases and then decreases with increasing spinning rate. The electrochemical kinetics increases to the optimum performance and then reduces with increasing spinning rate. Moreover, all the alloys achieve to the highest discharge capacities just at the initial cycle without activation. 相似文献
9.
在390℃温度下对AZ31镁合金进行固态扩渗Zn+La2O3(扩渗剂中的质量分数为0.4%)处理,扩渗时间分别为0、2、4、6h。研究了不同扩渗时间下镁合金表面渗层组织的变化,并测试了镁合金表面扩渗层的硬度和耐腐蚀性能。结果表明:当扩渗时间为2h时,未出现渗层;当扩渗时间为4h时,扩渗层中出现了Mg0.97Zn0.03固溶体和Mg-Zn化合物(MgZn+Mg2Zn3+MgZn2+ Mg2Zn11)。随着扩渗时间的延长,使得Zn原子的扩渗能力增强,Mg和Zn反应扩散形成了多种化合物,在AZ31镁合金表面得到了渗层。当扩渗时间为6h时,Mg7Zn3作为一种新相出现在了渗层中,同时,渗层组织粗化。扩渗试样的硬度随扩渗时间的增加而增加,而耐腐蚀性能在扩渗时间为4 h时为最佳。 相似文献
10.
SHEN Wan YANG Zhi-min XING Guang-jian MAO Chang-hui DU Jun 《材料研究与应用》2005,(3):439-443
Thin film microbattery is a promising micropower source for its high energy density and good cell performances, and the application of fast lithium ion conducting solids as electrolytes is thus very important. (Li0.5 La0.5 )TiO3 (LLTO) thin film electrolytes for thin film microbattery were prepared onto Pt/Si substrates using magnetron sputtering. As-deposited LLTO thin films showed amorphous-like phases and when deposition temperature increases the ionic conductivity raises accordingly. The ionic conductivity of LLTO thin film reaches 8. 7 × 10-6 S/cm when the deposition temperature is 400℃, which shows that the LLTO thin films deposited by magnetron sputtering are suitable for application as an electrolyte for thin film microbattery. 相似文献