INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2020
·
IF 4.939
Meng Zhang,Xuezhang Xiao,Zhouming Hang,Man Chen,Xuancheng Wang,Nan Zhang,Lixin Chen
Magnesium hydride, as a potential solid state hydrogen carrier has attracted great attention around the world especially in the energy storage domain due to the high hydrogen storage capacity and the good cycling stability. But kinetic and thermodynamic barriers also impede the practical application and development of MgH 2 . Nanoscale catalysts are deemed to be the most effective measure to overcome the kinetic barrier and lower the temperature required for hydrogen release in MgH 2 . NbN nanoparticles (~20 nm) with intrinsic Nb 3+ -N and Nb 5+ -N were prepared using the molten salt method and used as catalysts in the MgH 2 system. It is found that the NbN nanoparticles exhibit a superior catalytic effect on de/rehydrogenation kinetics for the MgH 2 /Mg system. About 6.0 wt% hydrogen can be liberated for the MgH 2 +5NbN sample within 5 min at 300 °C, and it takes 12 min to desorb the same amount of hydrogen at 275 °C. Meanwhile, the MgH 2 +5NbN sample can absorb 6.0 wt% hydrogen within 16 min at 150 °C, and absorb 5.0 wt% hydrogen within 24 min even at 100 °C. Particularly, the catalyzed samples exhibit excellent hydrogen absorption/desorption kinetic stability. After multiple cycles, there is no kinetic attenuation and the hydrogen capacity remains at about 6.0 wt%. It is demonstrated that the NbN nanoparticles with intrinsic multiple valence can be the critical effect in improving the hydrogen storage kinetics of MgH 2 . The stability of Nb 4 N 3 phase and Nb 3+ -N and Nb 5+ -N valence states can ensure a stable catalytic effect in the system.
研究领域:
材料科学
·
能源存储
✓ 已验证
DOI
高影响因子
JOURNAL OF LUMINESCENCE
·
2019
·
IF 2.961
Su Zhang,Lingling Lv,Hongjie Wang,Chongyang Zhu,Ran Pang,Jing Feng,Da Li,Guanyu Liu,Lihong Jiang,Chengyu Li
The 0.8CaWO 4 -0.2EuMO 4 (M = Nb, Ta) solid solution and Eu 3+ , Ta 5+ and Nb 5+ single doped CaWO 4 were prepared by a high-temperature solid state reaction technique. Experiments show that the addition of Nb 5+ and Ta 5+ can increase the red luminescence of Eu 3+ in CaWO 4 . In this paper, the composition and structure of solid solution were analyzed by X ray diffraction (XRD), Fourier transform infrared spectrum and Raman spectrum analysis. The luminescence properties of the solid solution were studied by means of stable photoluminescent spectra, diffuse reflectance spectra (DRS), fluorescent decay curves and variable temperature spectra. By combining structural analysis, J-O theoretical calculation and experimental results, we believe that the significant improvement of the emission efficiency comes from the decrease of non-radiation relaxation rate.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2020
·
IF 3.83
Dan Xu,Wenjie Zhao,Wenping Cao,Weili Li,Weidong Fei
The lead-free BiFe 1- x (Li 0·5 Nb 0.5 ) x O 3 ceramics with x = 0.00, 0.01, 0.02, 0.04, 0.06, and 0.08 were modified by Li/Nb co-doping. X-ray diffraction measurements indicated that all the ceramics had a rhombohedral distorted perovskite structure and secondary phases appeared when x = 0.00, 0.04, and 0.06. The BiFeO 3 ceramics with a small amount of Li/Nb co-doping exhibited improvements in the remnant polarization (2 P r ) and ferroelectric P - E loop shape compared with the results of pure BiFeO 3 (BFO). The decreased dielectric loss and leakage current indicated that proper Li/Nb co-doping for the Fe-site in BFO was a promising route to improve the leakage behavior and enhance the resistivity. These improved electrical properties were related to the reduction of oxygen vacancies and suppression of the formation of Fe 2+ . The leakage mechanism was also discussed and analyzed.
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
ACS Sustainable Chemistry & Engineering
·
2018
·
IF 6.14
Bifu Luo,Yuanzhi Hong,Di Li,Zhenyuan Fang,Yaping Jian,Weidong Shi
Two-dimensional (2D) nanosheet photocatalysts with appropriate band structure have aroused a great deal of research interest owing to their unique structural and electronic properties. In this work, carbon nitride quantum dots (CNQDs) with up-conversion property were constructed on SnNb2O6 ultrathin nanosheets by a facial hydrothermal process. The as-prepared CNQDs/SnNb2O6 0D/2D nanocomposites exhibited an enhanced photocatalytic performance of H2 production under visible light irradiation (λ > 420 nm). The up-conversion behavior of CNQDs endow the CNQDs/SnNb2O6 nanocomposites with the ability of photocatalytic H2 production at wavelengths greater than 600 nm. Moreover, the introduced CNQDs could serve as effective electron collectors and promote the transfer of photogenerated charge carriers, which is elucidated by the transient photocurrent response and electrochemical impendence spectra. Finally, a plausible photocatalytic mechanism was proposed for CNQDs/SnNb2O6 nanocomposite toward the H2 production from water splitting.
研究领域:
材料科学
·
能源化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2013
·
IF 3.172
Wei Li,Rui Gao,Min Chen,Shuxue Zhou,Limin Wu
In this paper, monodisperse poly(styrene-co-acrylmide) (PSAM)/Nb 2 O 5 hybrid hollow spheres were synthesized using a hollowing mechanism similar to the Kirkendall effect. When these hybrid hollow spheres were calcinated at different temperatures, totally different structures, pseudohexagonal TT phase hollow Nb 2 O 5 spheres, and orthorhombic T phase short rods were obtained. Both of them exhibited stronger photocatalytic activity than the commercial Nb 2 O 5 , especially the as-obtained Nb 2 O 5 hollow spheres displayed significantly enhanced photocatalytic property and auto-accelerated photocatalytic kinetics compared to the commercial TiO 2 (P25). Moreover, the Nb 2 O 5 hollow sphere-based nanofilm fabricated using oil–water interfacial self-assembly presented excellent UV photodetective performance.
研究领域:
材料科学
·
光催化
·
光电检测
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Seokyoung Choi,Wuliang Feng,Zhongzhu Liu,Yongyao Xia
Spinel LiMn 1.5 Ni 0.5 O 4 (LMNO) is one of the promising cathode materials for the next generation Li-ion batteries due to its voltage platform. However, the dissolution of the transition metal at high voltage is the biggest obstacle that LMNO suffers from. In this study, we successfully suppressed transition metal dissolution in LMNO by the morphology control from regular octahedron to spherical. Niobium was integrated as a dopant, which restricted the growth of (1 1 1) crystal face, and increased the indices of crystal faces by homogenizing the surface energy. By changing to a smaller surface area with spherical morphology, the contact area with the electrolyte was reduced, thus suppressing the dissolution of the Mn ion. Consequently, the niobium-doped LMNO exhibited superior rate performance, capacity retention with 74.1% at 1C after 500 cycles in half-cell, and thermal stability compared to pristine LMNO.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
ADVANCED MATERIALS
·
2022
·Vol. 34
·期 16
·2200756
·
IF 32.086
Xi Lin,Shuhui Xia,Liang Zhang,Yuanyuan Zhang,Songmei Sun,Yuehui Chen,Shuo Chen,Bin Ding,Jianyong Yu,Jianhua Yan
Achieving high selectivity and conversion efficiency simultaneously is a challenge for visible-light-driven photocatalytic CO 2 reduction into CH 4 . Here, a facile nanofiber synthesis method and a new defect control strategy at room-temperature are reported for the fabrication of flexible mesoporous black Nb 2 O 5 nanofiber catalysts that contain abundant oxygen-vacancies and unsaturated Nb dual-sites, which are efficient towards photocatalytic production of CH 4 . The oxygen-vacancy decreases the bandgap width of Nb 2 O 5 from 3.01–2.25 eV, which broadens the light-absorption range from ultraviolet to visible-light, and the dual sites in the mesopores can easily adsorb CO 2 , so that the intermediate product of CO* can be spontaneously changed into *CHO. The formation of a highly stable Nb CHO* intermediate at the dual sites is proposed to be the key feature determining selectivity. The preliminary results show that without using sacrificial agents and photosensitizers, the nanofiber catalyst achieves 64.8% selectivity for CH 4 production with a high evolution rate of 19.5 µmol g −1 h −1 under visible-light. Furthermore, the flexible catalyst film can be directly used in devices, showing appealing and broadly commercial applications.
研究领域:
材料科学
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Nanomaterials
·
2024
·Vol. 14
·期 7
·608
·
IF 4.4
Wei Liu,Yang Zou,Yuang Chen,Zijian Lei,Lili Zhao,Lixin Song
This work involves the introduction of niobium oxide into lanthanum aluminate (LaAlO3) via a conventional solid-state reaction technique to yield LaAlO3:Nb (LaNbxAl1−xO3+δ) samples with Nb5+doping levels ranging from 0.00 to 0.25 mol%. This study presents a comprehensive investigation of the effects of niobium doping on the phase evolution, defect control, and reflectance of LaNbxAl1−xO3+δpowder. Powder X-ray diffraction (XRD) analysis confirms the perovskite structure in all powders, and XRD and transmission electron microscopy (TEM) reveal successful doping of Nb5+into LaNbxAl1−xO3+δ. The surface morphology was analyzed by scanning electron microscopy (SEM), and the results show that increasing the doping concentration of niobium leads to fewer microstructural defects. Oxygen vacancy defects in different compositions are analyzed at 300 K, and as the doping level increases, a clear trend of defect reduction is observed. Notably, LaNbxAl1−xO3+δwith 0.15 mol% Nb5+exhibits excellent reflectance properties, with a maximum infrared reflectance of 99.7%. This study shows that LaNbxAl1−xO3+δpowder materials have wide application potential in the field of high reflectivity coating materials due to their extremely low microstructural defects and oxygen vacancy defects.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Molecular Catalysis
·
2024
·
IF 3.9
Jianwei Yuan,Kwame Nana Opoku,Pin Zhou,Jiaqing Cao,Yaorao Gao,Haoyang Peng,Baoliang Liu,Xiaohui Chen,Zhenwei Zhang,Fu Yang
The highly efficient green catalytic synthesis of jet fuel from low-chain biomass molecules is very attractive to afford sustainable development. Herein, ultrafine Ni nanoparticles assembled on Nb 2 O 5 nanofibers were constructed and effectively utilized in the reductive coupling of n-octanoic acid, offering a novel approach distinct from traditional hydrogenation methods for fatty acids. During the process, a synergistic effect was observed between the metallic Ni phase and the fibrous Nb 2 O 5 , facilitating immediate ketonization following reduction. This enabled the conversion of n-octanoic acid into pentadecane, a crucial component of aviation kerosene. The key factor driving this conversion was the attainment of a production rate of 8-pentadecanone higher than that of n-octane, particularly under optimal conditions, resulting in a significant yield of pentadecane. The catalytic assessment results show that adjusting Ni loading altered the performance of the catalyst in which 1.0 % Ni/Nb 2 O 5 afforded the best catalytic activity. By precisely controlling the reaction temperature at 300 °C and maintaining a hydrogen pressure of 1 MPa, an impressive pentadecane yield of 70.5 % was achieved. This innovative approach, which combines reduction with ketonization, offers a promising strategy for producing long-carbon chain alkanes from short-carbon chain fatty acids within a single reactor. This not only reduces economic costs but also streamlines overall processes, presenting a significant advancement in sustainable fuel production.
研究领域:
催化化学
·
绿色能源
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Liujia Tian,Fan Peng,Xuemei Song,Wei Zheng,Ziwei Liu,Yiling Huang,Yi Zeng
High-entropy rare-earth niobates have garnered significant attention in the field of thermal barrier coatings (TBCs) due to their ultra-low thermal conductivity. However, the exceptional thermal properties of fluorite-phase high-entropy rare-earth niobates and the outstanding mechanical properties of monoclinic-phase high-entropy rare-earth niobates cannot be simultaneously harnessed. To address this limitation, this paper investigates and synthesizes five single-phase high-entropy rare-earth niobates: (RE 1/5 Ho 1/5 Er 1/5 Y 1/5 Yb 1/5 ) 3 NbO 7 (RE = Ce, Sm, Eu, Dy, Lu), and five composite-phase high-entropy rare-earth niobates with a molar ratio of (RE 1/5 Ho 1/5 Er 1/5 Y 1/5 Yb 1/5 )NbO 7 : (RE 1/5 Ho 1/5 Er 1/5 Y 1/5 Yb 1/5 )NbO 4 = 1:2 (RE = Ce, Sm, Eu, Dy, Lu). The objective is to fabricate niobate coatings that exhibit both outstanding thermal and mechanical properties. The test results reveal that the intrinsic thermal conductivity of the composite-phase samples stands at a mere 1.46 W m −1 ·K −1 at 1000 °C. Comparatively, the experimental thermal conductivity of the single-phase samples slightly surpasses that of the composite-phase at 1000 °C, registering a minimum of 1.57 W m −1 ·K −1 . Importantly, both values adhere to the TBC standard. The mechanisms behind the low thermal conductivity of the composite-phase and single-phase samples are elucidated by the phonon scattering mechanism and the Cahill model, respectively. Furthermore, the thermal expansion coefficient of the composite-phase samples exceeds that of the single-phase samples overall, and they demonstrate exceptional mechanical properties, offering nearly twice the fracture toughness of the single-phase samples while maintaining high hardness. Experimental evidence shows that composite-phase niobates exhibit enhanced thermodynamic properties compared to single-phase niobates. This work serves as a valuable reference for the utilization of high-entropy rare-earth niobates in the realm of thermal barrier coatings.
研究领域:
材料科学
·
热力学工程
✓ 已验证
产品关联
DOI
高影响因子
Advanced Science Letters
·
2012
·Vol. 10
·期 1
·274-278
·
IF 0
Liu Chenglu,Wang Fang,Zhou Zhiqiang,Jia Peiyun
YNbO4:Eu nano-phosphors were successfully prepared in NaNO3 molten salt. X-ray diffraction was used to characterize the structure of the samples. The results indicate that a suitable amount of NaOH in NaNO3 molten salt can effectively improve the crystallinity
of the samples annealed at same temperature; meanwhile, the elevation of annealing temperature increases the crystallinity, and transfers the crystalline phase from scheelite to fergusonite. The micrographs of transmission electron microscopy reveal that the grain size increases with the elevation
of annealing temperature. Upon excitation into the niobate groups at 260 nm, YNbO4:Eu nano-phosphors exhibit weak emission at 405 nm, originated from Nb–O charge transfer transition and the characteristic emission of Eu3+, which indicates there is an energy transfer
from niobate group to Eu3+. Monitored by emission of 615 nm, the excitation spectrum shows that the f-f transition of 7F0–5L6 at 396 nm is more intense than the Nb–O charge transfer band at 260 nm. This intense absorption at
396 nm make YNbO4:Eu nano-phosphors an excellent candidate of white light emitting diode.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
CERAMICS INTERNATIONAL
·
2017
·
IF 2.986
Yue Li,Feng-Qiang Xiong,Ruiling Ou,Lipeng Wan,Congling Yin,Ruxin Che,Minghui Yang
Highly crystalline (110) layered perovskite Sr 2 Nb 2 O 7 , (111) layered perovskite Sr 5 Nb 4 O 15 and complex perovskite Sr 4 Nb 2 O 9 were prepared by NaCl-KCl flux growth method from SrCO 3 and Nb 2 O 5 . This flux synthesis achieves single strontium niobate phase in contrast to mixed niobates from the solid state reaction with the same heating parameters. A little excess of Sr source was found to be required for the synthesis of Sr 5 Nb 4 O 15 and Sr 4 Nb 2 O 9 at elevated temperature due to slight evaporation. The three strontium niobates were converted to perovskite SrNbO 2 N via thermal ammonolysis under NH 3 flow at 900 °C. Post-wash treatment was performed to remove the byproduct SrO. This makes additional nanopores in SrNbO 2 N in the cases of Sr 5 Nb 4 O 15 and Sr 4 Nb 2 O 9 , and results in increasing surface areas of SrNbO 2 N with Sr:Nb ratios in the precursors (from 9.9 to 19.8 and 35.5 m 2 /g). On the other hand, the UV–Vis diffusion reflectance spectra reveal decreasing light absorption by defects in SrNbO 2 N in this order. This suggests fewer low-valent Nb defects in SrNbO 2 N prepared from precursor with higher Sr:Nb ratio. SrNbO 2 N prepared from Sr 4 Nb 2 O 9 would be advantageous for applications that require high surface area and low defect density of the material.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
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