ADVANCED ENGINEERING MATERIALS
·
2025
·
IF 3.3
Xinwei Geng,Yongfeng Xia,Ming Zhu,Jun Zhao,Dongxu Yao,Yu-Ping Zeng
Ti 4 O 7 is one of the most promising electrically functional materials among the Magnéli phase. To further broaden its applications in areas such as battery electrodes and pollutant treatment, extensive research has been conducted to optimize its mechanical and electrical properties. In this study, Ti 4 O 7 ceramics, as well as Al 2 O 3 and Ta 2 O 5 -doped Ti 4 O 7 ceramics, are fabricated via hot-press sintering using a solid-state method. While the introduction of secondary phases did not result in a significant improvement in the mechanical properties of Ti 4 O 7 ceramics, the effectiveness of Al–Ta co-doping in enhancing electrical conductivity is validated through three commonly used measurement techniques: the Van der Pauw method, the two-probe method, and the four-probe method, yielding conductivity increases of 46.20, 1.98, and 17.98%, respectively. Detailed electrical characterization further elucidated the electrical features of polycrystalline Ti 4 O 7 ceramics and effect of doping. Furthermore, the reaction between Ti 4 O 7 and Ta 2 O 5 , leading to the formation of the ternary oxide TiTaO 4 , is observed.
研究领域:
材料科学
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陶瓷材料
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电气工程
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固态物理
·
机械工程
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DOI
高影响因子
China Foundry
·
2025
·
IF 2.3
Zhai Xiao-fei,Chen Jing-yi,Zhang Xue-qin,Qian Yuan-hong,Chen Rong,Zhang Wei,He Ru-jie
The complex ceramic core used for hollow turbine blades requires a high porosity and a high flexural strength. For a better balance between porosity and flexural strength, ceramic materials with porous structures are preferred. In order to achieve the transition from disordered pore formation to ordered pore formation, Al 2 O 3 ceramic cores with triply periodic minimal surface (TPMS) micro lattice structures with different structural configurations (gyroid, diamond, and neovius) and different volume fractions of lattice structures (30, 40, and 50, vol.%) were designed and prepared by vat photopolymerization 3D printing. The effects of structural configuration and volume fraction of the lattice structure on the following structural shrinkage, microstructure, and flexural strength were investigated. The shrinkage relationship of the three lattice configurations is: neovius>diamond>gyroid. Besides, it is found that with an increase in the volume fraction of the 3D printed Al 2 O 3 ceramic micro lattice structures, their flexural strength correspondingly increases ranging from 54.95 MPa to 139.1 MPa. The maximum average flexural strength of the 3D printed Al 2 O 3 ceramic micro lattice structures is obtained when the structural configuration is diamond and with a volume fraction of 50vol.%, which is 139.1 MPa. Even when the volume fraction of the lattice structure is 30vol.%, that is to say the porosity is 70%, the flexural strength is as high as 50–70 MPa, which can still be maintained at a high level. In addition, when the volume fraction of the lattice structure is a certain value, the sample with diamond configuration has a higher strength. The internal pore morphology, pore size, and porosity of the cores are precisely controlled, achieving both a high porosity and a high strength. Therefore, this study maintains high porosity and high strength simultaneously, providing a new lattice structure design idea for 3D printed ceramic cores.
研究领域:
材料科学
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机械工程
·
陶瓷工艺
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DOI
高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Tianqi Zheng,Wei Wang,Jinxing Sun,Jing Liu,Jiaming Bai
Digital Light Processing (DLP) is a promising approach to fabricate delicate ceramic components with high-fidelity structural features. In this work, the alumina and zirconia/alumina ceramic suspensions with low viscosity and high solid loading (40 vol%) were prepared specifically for DLP 3D printing . After debinding and sintering, the final parts were obtained without any defects. The surface morphologies and mechanical properties of alumina (Al 2 O 3 ) and zirconia toughened alumina (ZTA) composites were investigated and the results showed that the final parts exhibited high relative densities and good interlayer combination at the sintering temperature of 1600 °C. Comparing with the Al 2 O 3 , the ZTA composites exhibited significantly enhanced density (99.4%), bending strength (516.7 MPa) and indentation fracture toughness (7.76 MPa m 1/2 ).
研究领域:
材料科学
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陶瓷工程
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DOI
高影响因子
Molecular Catalysis
·
2020
·
IF 3.687
Juan Liu,Wen-Ying Li,Jie Feng,Xiang Gao
The hydrodenitrogenation of nitrogen-containing heterocycles over noble metals has fundamental importance for energy and environmental science. To develop more efficient catalyst, mechanistic investigation has been conducted with a method combining in situ Fourier transformation infrared experiments and density functional theory calculations in this work. The in situ experiments indicate flatly adsorbed pyridine molecules convert to pyridinium and α -pyridyl species at higher temperature on metallic Pt of Pt/γ-Al 2 O 3 catalysts. Pyridine hydrogenation distinctly takes place at 150 °C with the appearance of methylene stretching vibrations, and a stepwise mechanism is identified as the temperature further increases. The adsorption, hydrogenation and hydrogenolysis of pyridine on Pt are studied in detail by theoretical calculations. In line with these findings, the geometry optimization confirms pyridine preferentially adsorbs on Pt(111) and Pt(211) both in a parallel configuration. Based on the Langmuir–Hinshelwood mechanism, the results show successive hydrogenation markedly lowers the energy barrier for subsequent hydrogenolysis. The C N bond cleavage occurs via nucleophilic attack of pentahydropyridine, rather than piperidine, which determines the reaction products, including piperidine, n -pentylamine and n -pentane. The comparative study reveals both hydrogenation and hydrogenolysis are kinetically and thermodynamically more competitive on Pt(211) than Pt(111). Especially for hydrogenolysis, the coordinatively unsaturated Pt step atoms play an essential role in C N bond cleavage. Thus, hydrogenolysis is more geometric‒dependent than hydrogenation. This provides instructive information for the design of catalysts with adjustable product selectivity.
研究领域:
催化化学
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环境科学
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计算化学
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能源科学
·
表面化学
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DOI
高影响因子
METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE
·
2016
·Vol. 47
·期 5
·2830-2836
·
IF 1.474
Long Hongming,Wu Xuejian,Chun Tiejun,Di Zhanxia,Yu Bin
In this study, the assimilation behaviors between calcium ferrite (CF), calcium diferrite (CF 2 ) and sintered Al 2 O 3 , and MgO were explored by an improved sessile drop technique, and the interfacial microstructure was discussed. The results indicated that the apparent contact angles of CF slag on Al 2 O 3 and MgO substrate were 15.7 and 5.5 deg, and the apparent contact angles of CF 2 slag on Al 2 O 3 and MgO substrate were 17.9 and 7.2 deg, respectively. Namely, CF and CF 2 slag were wetting well with Al 2 O 3 and MgO substrate. The dissolution of Al 2 O 3 substrate into the CF and CF 2 slag was found to be the driving force of the wetting process. For the CF-MgO and CF 2 -MgO substrate systems, CaO contrarily distributed with MgO after wetting. For the CF-MgO system, after wetting, the slag was composed of CF and C 2 F, and most of the Fe 2 O 3 permeated into substrate and formed two permeating layers.
研究领域:
材料科学
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冶金学
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陶瓷学
·
高温化学
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DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Binbin Zhao,Jieqi Zou,Chen Chen,Qian He,Qiong Tang,Lei Liu,Jinxiang Dong
Pt-WO x -based catalyst has been considered as a promising candidate for the conversion of glycerol to 1,3-propanediol, but the catalytic performance was quite susceptible to the structure and chemical state of WO x species. Herein, we develop a facile approach to construct the single-atom tungsten-doped Al 2 O 3 with a low chemical state through in-situ migration of WO 3 nanoparticles under the H 2 atmosphere. The characterization results demonstrated that the tetrahedral W 5+ could disperse and stabilize the platinum species more effectively, and exhibited stronger interaction with platinum than the octahedral W 6+ species. The enhanced catalytic performance is attributed to the rich oxygen defects on in-situ generated tetrahedral WO x on the catalyst, which facilitated the construction of Pt-WO x interface and strengthened the synergetic effects between them. The analysis of structure-performance correlation revealed that the mono-dispersed tetrahedral W 5+ species [(-O-) 3 W(=O)] played a pivotal role in tuning catalyst acidity and improving the catalytic performance, which assists the adsorption of glycerol and captures H for in-situ formation of Brønsted acid site, and ultimately affected the selectivity toward 1,3-PDO and catalytic activity.
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NEW JOURNAL OF CHEMISTRY
·
2023
·Vol. 47
·期 39
·18450-18460
·
IF 3.3
Yao Shen,Fang Lin,Kang Wang,Xitao Wang
CaO-doped γ-Al2O3 beads were prepared by an alginate assisted sol–gel method, followed by grafting with alkyl groups and impregnation of NbCl5 to construct multi-functionalized γ-Al2O3 beads for efficient catalytic conversion of glucose to 5-hydroxymethylfurfural (5-HMF). Doping with CaO improved the binding capacity of the catalyst with glucose and increased the Lewis acid amount. However, a high CaO content would cover the Lewis acid sites of γ-Al2O3, resulting in a lower isomeric conversion of glucose to fructose. When the C8–Ca(10%)–γ-Al2O3 catalyst was loaded with Nb2O5, intermediate fructose was consumed rapidly resulting in complete conversion of glucose, which indicated that conversion of glucose to 5-HMF involved the isomeric conversion of glucose to fructose followed by dehydration of fructose to 5-HMF. This was necessary to balance hydrophilic isomerization reactions with restraining the rehydration of 5-HMF by hydrophobic modification. This is similar to the reaction in which a medium with a certain amount of water was beneficial for glucose isomerization. Under the synergistic effect of Lewis acid provided by γ-Al2O3 and Brønsted acid offered by Nb2O5, C8–Ca(10%)–γ-Al2O3–Nb(3%), a glucose conversation rate of 100% and the highest yield of 5-HMF (68.4%) were achieved in the reaction medium with a dimethylsulfoxide/H2O (V/V) ratio of 4 : 1, a catalyst amount of 33 mg, a reaction temperature of 140 °C and a reaction time of 4 h.
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Molecular Catalysis
·
2023
·
IF 4.6
Bowen Wu,Yixi Chen,Mingtai Liu,Yi Tang,Gengfeng Zheng,Linping Qian
The surface properties of CoMg/Al 2 O 3 were evaluated in the aerobic oxidation of p -cresol. The surface interaction is enhanced greatly after Co and Mg impregnation with the mole ratio of Co/Mg from 2 : 1 and 2 : 3. The strongest interaction for the nonpolarity and benzene ring was found on CoMg/Al 2 O 3 with Co/Mg of 2 : 3. But for the interaction with p -π group bonding with negative anion, the highest value appears on the catalyst with the Co/Mg of 2 : 2. In aerobic oxidation of p -cresol, the conversion is significantly increased with Co addition and reaches around 60 % after 24 h' reaction at 338 K. The highest selectivity of p -hydroxybenzaldehyde of 99 % is achieved on Al 2 O 3 with the co-impregnation mole ratio of Co/Mg of 2 : 2. It is suggested that medium adsorption of the reactants and strong stabilization of the intermediates facilitate the aerobic oxidation of p -cresol to p -hydroxybenzaldehyde.
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Crystals
·
2023
·Vol. 13
·期 8
·1261
·
IF 2.7
Zhen Pei,Haixiao Huang,Xingzhong Guo,Jinming Zhang,Mingxing Chen
MgO–Al2O3–SiO2(MAS) glass–ceramics with controllable crystalline phases were successfully prepared using the melting method followed by heat treatment. The effects of the main components of glass on the crystallisation kinetics, nucleation, crystallisation and properties of glass–ceramics were investigated in detail. As the Al2O3and MgO contents increase and SiO2content decreases, the crystallisation peak temperature and activation energy of MAS glass decrease, while the crystal growth tends to follow a homogeneous nucleation crystallisation. The MAS glass nucleation temperature and time increase with higher concentrations of Al2O3and MgO and with a lower SiO2concentration. Mg2(Al4Si5O18) indialite and MgAl2O4spinel precipitate simultaneously in the MAS glass after crystallisation; the relative proportion of crystalline phases is related to the composition and crystallisation temperature. A higher SiO2content allows the formation of a dominant indialite phase, while higher MgO and Al2O3contents promote the formation of a dominant spinel phase. The MAS glass ceramic with a greater indialite phase has good dielectric properties with a dielectric constant of 6.499 and dielectric loss of 0.0064, while that of a higher spinel phase possesses improved mechanical properties, with a Vickers hardness of 715 Hv and a bending strength of 244.9 MPa.
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RSC Advances
·
2023
·Vol. 13
·期 36
·24944-24954
·
IF 3.9
Lin Li,Tao Zeng,Hongyu Huang,Jun Li,Noriyuki Kobayshi,Xiaohu Yang
In this study, the influences of nano γ-Al2O3 on the thermal storage performance of LiCl were experimentally investigated. The XRD results show that a complex of lithium aluminium oxychloride (LiAlOCl2) was formed through the LiCl·H2O and γ-Al2O3 composites preparation process. The in situ diffuse reflectance infrared Fourier transform spectroscopy measurement reveals that the addition of γ-Al2O3 accelerated the hydration rate of LiCl composites, concentrated the spectrum utilization range, and promoted the desorption rate of physical adsorbed H2O and low-frequency structural –OH in the materials. The highest specific surface area of the composite is 34.5 times higher than that of pure LiCl. The addition of γ-Al2O3 can increase the conversion rate of LiCl·H2O to approximately 100% at the hydration time of 1 h and the addition content of γ-Al2O3 at 15 wt%. A maximum heat storage density (HSD) for the LiCl·H2O-γ-Al2O3 composite can reach 714.7 kJ kgLiCl·H2O−1 in 1 h when the addition content of γ-Al2O3 was 15%wt and its water uptake can reach 0.26 g g−1 in 1 h. It also can be found that the addition of Al2O3 in LiCl resulted in a decrease of the activation energy from 90.89 kJ mol−1 to 79.76 kJ mol−1. However, the thermal conductivity of the LiCl·H2O-γ-Al2O3 composite slightly decreased with the increase of nano γ-Al2O3 content.
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产品关联
DOI
PubMed
高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2023
·
IF 9.9
Yang Li,Yuchang Qing,Haoyang Yao,Hailong Xu,Hongjing Wu
High-performance microwave absorption coatings are critically required in the stealth defense system of military platforms. Regrettably, just optimizing the property but neglecting the application feasibility seriously inhibits its practical application in the field of microwave absorption. To face this challenge, the Ti 4 O 7 /carbon nanotubes (CNTs)/Al 2 O 3 coatings were successfully fabricated by a plasma-sprayed method. For the different oxygen vacancy-induced Ti 4 O 7 coatings, the enhanced ε' and ε'' values in the frequency of X-band is due to the synergistic manipulation of conductive path, defects and interfacial polarization. The optimal reflection loss of Ti 4 O 7 /CNTs/Al 2 O 3 sample (0 wt% CNTs) is −55.7 dB (8.9 GHz of 2.41 mm), while the electromagnetic interference shielding effectiveness of Ti 4 O 7 /CNTs/Al 2 O 3 sample (5 wt% CNTs) increases to 20.5 dB as the enhanced electrical conductivity. In special, the flexural strength of Ti 4 O 7 /CNTs/Al 2 O 3 coatings first increases from 48.59 MPa (0 wt% CNTs) to 67.13 MPa (2.5 wt% CNTs) and then decreases to 38.31 MPa (5 wt% CNTs), demonstrating that an appropriate amount of CNTs evenly dispersed in the Ti 4 O 7 /Al 2 O 3 ceramic matrix can effectively play the role of CNTs as the strengthening phase of the coatings. This research will provide a strategy by tailoring synergistic effect of dielectric loss and conduction loss for oxygen vacancy-mediated Ti 4 O 7 material to broaden the application of absorbing or shielding ceramic coatings.
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DOI
PubMed
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2023
·Vol. 47
·期 21
·10397-10408
·
IF 3.3
Ning Gao,Xuanyu Gu,Jining Liu,Mengjie Fan,Yingwen Chen
At present, it is challenging to improve the activity and humidity resistance of ozone catalysts. Herein, an integrated MnOx–Al2O3 aerogel was prepared by a sol–gel method in this study, and its application in catalytic ozonation of toluene was explored preliminarily. Compared with the MnOx–SiO2 aerogel and impregnation catalysts (MnOx–silicalite-1 and MnOx–γ-Al2O3), the MnOx–Al2O3 aerogel exhibited superior performance in toluene removal and enhanced ozone utilization efficiency under optimal conditions (room temperature, O3 : C7H8 = 14 : 1, GHSV = 45 000 h−1 and 120 ppm C7H8). After reacting for 360 min, the 5 wt% MnOx–Al2O3 aerogel still showed stable catalytic ability, with the efficiency of toluene removal and ozone degradation maintained at 64.1% and 62.7%, respectively. Based on SEM characterization, the MnOx–Al2O3 aerogel demonstrated low MnOx agglomeration. From XPS and NH3-TPD analyses, it was found that the catalyst had a high content of Mn3+/Mn, Oβ/O, oxygen vacancies and acid sites, which was positively related to ozone degradation. Among them, an increase in the number of weak acid and moderately strong acid sites could prolong the life of active oxygen, which was the key to promoting the deep oxidation of toluene effectively. In addition, the MnOx–Al2O3 aerogel exhibited remarkable load-adjustability and humidity resistance. Therefore, the development of aerogel catalysts for catalytic ozonation of toluene is an effective strategy to alleviate the current ozone catalyst problem.
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