查找使用阿拉丁产品的科研文献

ZrO2 and MxOy (M= La, Ce, and Nb) synergistically reinforced porous cordierite ceramics synthesized via a facile solid-state reaction

Lulu Wang,Beiyue Ma,Xinming Ren,Chao Yu,Chengji Deng,Chunming Liu,Chuanbo Hu

In an attempt to enhance the sintering and mechanical performance of porous cordierite ceramics (Mg 2 Al 4 Si 5 O 18 ) as support materials for vehicle exhaust catalysts, ZrO 2 and M x O y (M = La, Ce, and Nb) were simultaneously introduced into cordierite sintered at 1350 °C for 4 h. Then, the reinforced function of ZrO 2 and M x O y on the properties of porous cordierite ceramics was systematically evaluated, especially for the sample co-doped with ZrO 2 and La 2 O 3 . The results displayed a distinct enhancement in mechanical and thermal performance, and the cold compressive strength increased from 72.74 to 158.59 MPa as well as thermal conductivity ranged from 1.66 to 2.01 W m −1  K −1 , respectively. It is found that ZrO 2 facilitated activation sintering introduced via lattice distortion in cordierite and La 2 O 3 accelerated the formation of cordierite and ZrSiO 4 microcrystalline through the low-temperature liquid phase. The synergic effect between ZrO 2 and La 2 O 3 , therefore, had a significant role in the reinforced mechanical and thermal performance of porous cordierite ceramics. This work not only offers a feasible strengthening strategy, but also expands the possibilities for building high-performance structural and functional ceramics .

Structure and magnetic properties of M-type barium ferrite co-doped with Sm and Nb prepared by solid-phase sintering

Shuo Shan,Jie Li,Xuan Zhao,Siwen Pi

M-type barium ferrite with the formula Ba 1− x Sm x Fe 12− y Nb y O 19 ( x  = 0.00–0.10, y  = 0.00–0.20), which was co-doped with Sm 3+ and Nb 5+ ions, was synthesized experimentally by a modified solid-phase reaction method. The crystal structure of samples was determined by X-ray diffraction, which confirmed that they were of high purity. The X-ray diffraction data were fitted with a full-spectrum correction using GSAS software. By Fourier transform infrared spectroscopy, the samples were observed to exhibit bands due to tetrahedral and octahedral sites at 598 cm −1 and 445 cm −1 , respectively. The samples were examined by field emission scanning electron microscopy, which showed that they partly comprised hexagonal structures but mostly consisted of irregular structures with rounded edges. Characterization of the elemental contents of the samples by energy-dispersive spectroscopy revealed an increase in the contents of Sm and Nb and a decrease in the contents of Ba and Fe. The magnetic properties of the samples were examined using a vibrating sample magnetometer. The results showed that the saturation magnetization and residual magnetization of the samples decreased slightly with an increase in the contents of the dopants. The coercivity reached its maximum value, namely, 3367.53 Oe, when x  = 0.04 and y  = 0.08.

Defect engineering enabling p-type Mo(S,Se)2:TM (TM = V, Nb, Ta) towards high-efficiency kesterite solar cells

Junjie Fu,Afei Zhang,Dongxing Kou,Zewen Xiao,Wenhui Zhou,Zhengji Zhou,Shengjie Yuan,Yafang Qi,Zhi Zheng,Sixin Wu

One important issue limiting the development of Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells is the severe recombination loss at CZTSSe/Mo(S,Se) 2 /Mo back contact, primarily arising from the non-matched potential barrier and inferior electric contact between absorber and weak n -type Mo(S,Se) 2 interfacial layer. It is expected that a p-type Mo(S,Se) 2 can effectively improve the hole extraction and enhance the device performance. In this work, we propose a plausible direction to build up an electrically benign back surface field by in-situ doping Mo(S,Se) 2 with group VB elements (TM = V, Nb and Ta). It is turned out that the generated V Mo , Nb Mo , or Ta Mo shallow acceptors could convert Mo(S,Se) 2 from weak n -type to p-type conductivity and increase its work function ( W F ) and hole concentration. With the contact of p-type absorber ( W F,absorber  <  W F,Mo(S,Se)₂ ), a benign ohmic contact with favorable downward band bending is formed, thereby accelerating the holes extraction and minimizing interface recombination loss. With significant gains in open-circuit voltage ( V oc ) and fill factor (FF), the Mo(S,Se) 2 :Ta device finally increases the efficiency from 10.82 % to 12.72 %. This convenient in-situ Mo(S,Se) 2 doping strategy is different from previous complicated or unstable cases and should serve as a basis for high-quality back contact engineering in kesterite photovoltaics.

Significant performance enhancement of all-inorganic CsPbBr3 perovskite solar cells enabled by Nb-doped SnO2 as effective electron transport layer

Ruxin Guo,Yan Zhao,Yongshang Zhang,Quanrong Deng,Yonglong Shen,Wei Zhang,Guosheng Shao

All-inorganic CsPbBr 3 -based perovskite solar cells (PSCs) have attracted great attention because of their high chemical and thermal stabilities in ambient air. However, the short-circuit current density ( J sc ) of CsPbBr 3 -based PSCs is inadequate under solar illumination because of the wide bandgap, inefficient charge extraction and recombination loss, leading to lower power-conversion efficiencies (PCEs). It is envisaged that in addition to narrowing the bandgap by alloying, J sc of the PSCs could be enhanced by effective improvement of electron transportation, suppression of charge recombination at the interface between the perovskite and electron transporting layer (ETL), and tuning of the space charge field in the device. In this work, Nb-doped SnO 2 films as ETLs in the CsPbBr 3 -based PSCs have been deposited at room temperature by high target utilization sputtering (HiTUS). Through optimizing the Nb doping level alone, the J sc was increased by nearly 19%, from 7.51 to 8.92 mA·cm −2 and the PCE was enhanced by 27% from 6.73% to 8.54%. The overall benefit by replacing the spin-coated SnO 2 with sputtered SnO 2 with Nb doping was up to 39% increase in J sc and 62% increase in PCE. Moreover, the PCE of the optimized device showed negligible degradation over exposure to ambient environment (T ˜ 25 °C, RH˜45%), with 95.4% of the original PCE being maintained after storing the device for 1200 h.

Submicron-Sized Nb-Doped Lithium Garnet for High Ionic Conductivity Solid Electrolyte and Performance of Quasi-Solid-State Lithium Battery

Yan Ji,Cankai Zhou,Feng Lin,Bingjing Li,Feifan Yang,Huali Zhu,Junfei Duan,Zhaoyong Chen

The garnet Li7La3Zr2O12(LLZO) has been widely investigated because of its high conductivity, wide electrochemical window, and chemical stability with regards to lithium metal. However, the usual preparation process of LLZO requires high-temperature sintering for a long time and a lot of mother powder to compensate for lithium evaporation. In this study submicron Li6.6La3Zr1.6Nb0.4O12(LLZNO) powder―which has a stable cubic phase and high sintering activity―was prepared using the conventional solid-state reaction and the attrition milling process, and Li stoichiometric LLZNO ceramics were obtained by sintering this powder―which is difficult to control under high sintering temperatures and when sintered for a long time―at a relatively low temperature or for a short amount of time. The particle-size distribution, phase structure, microstructure, distribution of elements, total ionic conductivity, relative density, and activation energy of the submicron LLZNO powder and the LLZNO ceramics were tested and analyzed using laser diffraction particle-size analyzer (LD), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electrochemical Impedance Spectroscopy (EIS), and the Archimedean method. The total ionic conductivity of samples sintered at 1200 °C for 30 min was 5.09 × 10−4S·cm−1, the activation energy was 0.311 eV, and the relative density was 87.3%. When the samples were sintered at 1150 °C for 60 min the total ionic conductivity was 3.49 × 10−4S·cm−1, the activation energy was 0.316 eV, and the relative density was 90.4%. At the same time, quasi-solid-state batteries were assembled with LiMn2O4as the positive electrode and submicron LLZNO powder as the solid-state electrolyte. After 50 cycles, the discharge specific capacity was 105.5 mAh/g and the columbic efficiency was above 95%.Keywords:solid-state electrolyte;submicron powder;garnet;lithium-ion conductivity;solid-state batteries

High performance and colossal permittivity of (Nb+La) co-doped rutile TiO2 ceramics induced by composition regulation

Yang Yu,Wei-Li Li,Wei-Dong Fei

Enhanced Ionic Transport and Structural Stability of Nb-Doped O3-NaFe0.55Mn0.45–xNbxO2 Cathode Material for Long-Lasting Sodium-Ion Batteries

Lei Zhang,Tao Yuan,Luke Soule,Hao Sun,Yuepeng Pang,Junhe Yang,Shiyou Zheng

Sodium-ion batteries (SIBs) are promising candidates for inexpensive and sustainable energy storage devices for the widespread utilization of intermittent renewable energy because of the natural abundance of sodium raw materials. However, since the ionic radius of Na+ is inherently larger than that of Li+, Na-based intercalation materials often suffer from poor stability and slow reaction kinetics. Regarding SIB cathodes, layered transition metals oxides (NaxTMO2) show promising theoretical capacities but low stability. In this work, a series of O3-NaFe0.55Mn0.45–xNbxO2 (x = 0, 0.01, 0.02, and 0.03) compounds are synthesized and show superior stability and rate-capability compared with the pure oxide. For instance, the best-performing sample, NaFe0.55Mn0.44Nb0.01O2, has a specific capacity of 127 mAh g–1 and 80% capacity retention over 100 cycles at 0.1 C. Ex situ X-ray diffraction (XRD) result shows that the Nb incorporation could suppress TMO2 slip and reduce the energy barrier of the O3–P3 phases’ transition. When coupled with a hard carbon (HC) anode in a full cell, the battery exhibits significant weight and volume energy and power densities. It is believed that Nb-doping enlarges lattice spacing of the oxide and partially reduces Mn4+ to Mn3+, increasing the ionic conductivity of the cathodic materials.

Effect of different transition metal fluorides TMFx (TM=Nb, Co, Ti) on hydrogen storage properties of the 3NaBH4-GdF3 system

Tianping Huang,Jianxin Zou,Huabing Liu,Wenjiang Ding

Three kinds of transition metal fluorides TMF x (TM = Nb, Co, Ti) were introduced into the 3NaBH 4 -GdF 3 hydrogen storage system via mechanical milling. Their effects on the hydrogen storage behaviors of 3NaBH 4 -GdF 3 were systematically investigated by means of DSC and volumetric methods. All TMF x exhibited promoting effect on hydrogen desorption properties of 3NaBH 4 -GdF 3 to different degrees, especially when NbF 5 or TiF 3 was added. For example, the hydrogen desorption peak temperature was decreased by 17 °C with doping 3 mol% of NbF 5 . Besides, TiF 3 improved also the hydrogen absorption capacity and reversibility of 3NaBH 4 -GdF 3 . Based on XRD analyses, the role of TMF x on the dehydrogenation and the promoting effect of TiF 3 on the reversibility of 3NaBH 4 -GdF 3 were clarified. This work helped to understand the combination effect of rare earth metal fluoride (GdF 3 ) and transition metal fluorides on the reversible hydrogen storage properties of NaBH 4 .

Regulation of the electronic structure of Co4N with novel Nb to form hierarchical porous nanosheets for electrocatalytic overall water splitting

Xiao Hui Chen,Qing Zhang,Li Li Wu,Li Shen,Hong Chuan Fu,Juan Luo,Xiao Lin Li,Jing Lei Lei,Hong Qun Luo,Nian Bing Li

Heretofore, the metal elements constituting the electrolyzed water catalysts are almost all Fe, Co, and Ni, and the accelerator elements are V, W, Ce, etc., but there is a lack of exploration for other elements. Niobium (Nb) is a promising promoter due to its complex chemical properties and the ability to react with many elements to form abundant compounds. Taking Co 4 N as the research case, this work incorporates Nb atoms to tune the d orbital of metallic Co 4 N nanowires . Experimental results and density functional theory calculations show that due to the adjustment of Nb atoms, the d-band center of Co 4 N moves down, which helps facilitate the desorption of H 2 . At the same time, abundant Co 3+ active sites are generated on the surface of Nb–Co 4 N, which is crucial for the formation of oxygen evolution reaction (OER) intermediates (∗OOH). Nb-regulated Co 4 N nanosheets on the three-dimensional Ni foam (Nb–Co 4 N/NF) drives the current density of 20 mA cm −2 at a low overpotential of 90 mV for hydrogen evolution reaction and 273 mV for OER, respectively. This work inspires a novel idea for the rational design and synthesis of highly efficient electrocatalysts composed of novel less used elements for overall water splitting.

Preparation of reduced Ni-Nb-O composite hydrogenation catalysts for highly selective conversion of free fatty acids to n-alkanes

Lei Chen,Guangci Li,Mingjie Zhang,Da Wang,Shuangju Li,Chuanhui Zhang,Xuebing Li,Keng H. Chung

Catalytic deoxygenation of fatty acids to alkanes is an ideal route to produce biodiesel with high heating value . However, traditional transition-metal sulfide and noble metal catalysts are sulfide-contaminated, high cost, or easily poisoned. To overcome the above issues, this work developed a non-noble and sulfide-free reduced transition-metal composite Ni x Nb y O z , which was effective to selectively hydrogenate stearic acid , a typical fatty acid model compound, to diesel-range alkanes. By using a simple slurry method, reduced Ni x Nb y O z catalysts have been successfully prepared with an outstanding catalytic performance. The results showed that catalyst Ni 0.5 Nb 0.5 O z effectively converted stearic acid to n -alkanes with nearly 100% conversion and >99% n -alkanes selectivity at mild conditions (513 K and 3.5 MPa of H 2 pressure). Appropriate Nb species improved the dispersion of Ni species, which may supply more hydrogenation active sites. Two possible reaction routes of stearic acid were proposed, and the hydrogenolysis of stearyl stearate was confirmed as the rate-determining step based on the kinetics experiments. Because of moderate acidity of Nb species, the ratio of C 17 /C 18 alkane was not markedly affected by reaction conditions when the conversion of stearic acid was higher than 99%. Moreover, catalyst Ni 0.5 Nb 0.5 O z showed a high recycle ability and compatibility for other long-chain fatty acids, demonstrating that catalyst Ni 0.5 Nb 0.5 O z is a promising green catalyst for producing biodiesel from fatty acids.

Ultrahigh electrical conductivities and low lattice thermal conductivities of La, Dy, and Nb Co-doped SrTiO3 thermoelectric materials with complex structures

Daquan Liu,Yanxia Wang,Xue Jiang,Huijun Kang,Xiong Yang,Xiaoying Zhang,Tongmin Wang

Microstructural modifications and appropriate element doping are necessary to simultaneously enhance the electrical conductivities and reduce the lattice thermal conductivities of thermoelectric materials . Herein, we propose a strategy of multielement doping combined with a burial sintering process to promote thermoelectric properties. Three-element doped Sr 0.9 La 0.05 Dy 0.05 Ti 1− x Nb x O 3 ( x = 0, 0.05, 0.10, 0.15, and 0.20) powders were synthesized by high-energy ball milling, and corresponding bulk samples were prepared by carbon burial sintering. In the bulk samples, we obtained the desired microstructures composed of shell-vesicular architectures with dense dislocations and second phase particles. These materials had ultrahigh electrical conductivities (∼5300 S cm −1 at 300 K), low lattice thermal conductivities (∼1.6 W m −1 K −1 from 700 to 1100 K when x = 0.2) and low total thermal conductivities (minimum value of 2.95 W m −1 K −1 when x = 0.05 at 1100 K). The maximum zT values were 0.28 when x = 0.05 and 0.27 when x = 0.2 at 1100 K. This strategy provides a possible direction for improving the thermoelectric properties of SrTiO 3 based materials.

Synthesis of Single-Crystalline Ni-Rich Cathodes for Lithium-Ion Batteries With Superior High-Voltage Stability by Mo/Nb Dual Doping

Guomeng Xie,Ziqin Xu,Delai Qian,Ruiwu Li,Qingsong Hua,Shun Lu,Haitao Fang

Single-crystalline Ni-rich cathodes are promising candidates for high-energy density lithium-ion batteries due to their grain-boundary-free structures, which effectively reduce structural degradation associated with intergranular microcracks often seen in polycrystalline materials. However, these single-crystalline cathodes face challenges such as slow Li + diffusion kinetics, significant parasitic interface reactions, and irreversible phase transitions at elevated cut-off voltages, which can lead to the formation of intragranular cracks and impede their practical usage. In this study, the single-crystalline LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) was synthesized by stripping grain boundaries from polycrystalline NCA through Mo/Nb dual doping. The Mo doping near the grain surface significantly reduces parasitic interface reactions, while Nb doping within the bulk of grains helps to improve harmful irreversible phase transitions. The synergistic effect of Mo/Nb dual doping in single-crystalline NCA effectively suppresses intragranular crack formation during prolonged cycling at high cut-off voltages. Therefore, the Mo/Nb co-doped cathode demonstrates enhanced structural stability and electrochemical activity, achieving an impressive capacity retention of 82.4% after 500 cycles at 1 C between 2.8 and 4.7 V, surpassing both polycrystalline and single-crystalline NCA doped only with Mo or Nb. This work provides a new strategy to synthesize single-crystalline NCA combined with effective dual doping, advancing the development of high-energy density lithium-ion batteries.