POLYMER
·
2024
·
IF 4.1
Zhongli Zhang,Zhensheng Wu,Fan Zou,Fuqiang Tian
Polyimide (PI) refers to a polymer containing an imide ring characteristic structure on the main chain. It has excellent thermal stability, insulation properties and other characteristics. The Tesla transformer is the core component of the primary pulse source of the high-current electron beam accelerator. It is also an essential component of the energy storage pulse power supply. Therefore, it has broad application prospects in the fields of national defense and civil industry. If the insulation performance of the turn-to-turn coils of the Tesla transformer does not meet the standards, it will break down during high-voltage corona discharge, causing transformer failure. Therefore, it is crucial to improve the insulation performance of Tesla transformer inter-turn wrapping materials. The incorporation of fluorine-containing groups has proven to be a transformative strategy that significantly enhances the physical, chemical, optical, and electrical properties of PI films. In addition, numerous studies have demonstrated that introducing inorganic fillers into the polyimide matrix can substantially enhance the insulating properties of polyimide films. This paper specifically concentrates on elevating the insulating and thermal attributes of polyimide. Initially, a range of polyimide films was synthesized for performance assessment by employing various fluorinated dianhydride and diamine components, utilizing them as substrates. Then, we used nano-silicon nitride (nano-Si 3 N 4 ) and nano-alumina (nano-Al 2 O 3 ) as doping phases to prepare PI composite films, which reduced the dielectric constant and increased the breakdown strength.
研究领域:
材料科学
·
电气工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
·
2024
·
IF 4.2
Xiao-Chun Deng,Guo-Hua Zhang
Ultra-high toughness and ultra-high hardness WC-10Co- x Al 2 O 3 cemented carbides were successfully prepared by vacuum liquid phase sintering (VS) and spark plasma sintering (SPS) using ultrafine WC and commercial Co powders as raw materials, respectively. The effects of nano-Al 2 O 3 content and sintering process on the relative density, average grain size, microstructure and mechanical properties of WC-10Co alloys were investigated. The results showed that the densification degree of the samples decreased with the increase of Al 2 O 3 content. In addition, the relative densities of the samples prepared by SPS were lower than those of the samples prepared by VS. For the samples prepared by VS, the average grain size increased first and then decreased as the Al 2 O 3 content increased from 3 wt% to 9 wt%, and the percentage of coarse grain showed the same trend. When the addition of Al 2 O 3 was 6 wt%, the average grain size reached the maximum value of 1.39 ± 1.03 μm. Meanwhile, the sample with 6 wt% Al 2 O 3 had a typical inhomogeneous dual-grain structure, and the percentages of fine grain (< 1 μm) and coarse grain (> 1 μm) were about 50%, which displayed the highest fracture toughness of 18.59 MPa·m 1/2 . The dual-grain structure not only improved the toughness, but also compensated the loss of hardness. However, for the samples prepared by SPS, with the increase of Al 2 O 3 content, the average grain size of WC decreased, while both hardness and toughness were continuously improved. When the Al 2 O 3 content increased to 9 wt%, the grain size reached the minimum value of 0.25 ± 0.08 μm, and meanwhile, the hardness and toughness reached the maximum value of 19.69 GPa and 12.29 MPa·m 1/2 , respectively. Moreover, as the Al 2 O 3 content increased, the transverse rupture strength (TRS) of the samples prepared by VS increased first and then decreased, and the TRS of sample with 3 wt% Al 2 O 3 reached the maximum value of 1410 MPa. However, the TRS of the sample prepared by SPS showed a decreasing trend.
研究领域:
材料科学
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机械工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Bionic Engineering
·
2024
·Vol. 21
·期 3
·1360-1374
·
IF 4.9
Liu Weilan,Li Kunlong,Shen Yizhou,Zhao Huanyu,Ni Yaru,Cai Zeyu,Zhao Lingfeng,Wang Zhen
Superhydrophobic coatings with high non-wetting properties are widely applied in anti-icing applications. However, the micro-nanostructures on the surfaces of superhydrophobic coatings are fragile under external forces, resulting in reduced durability. Therefore, mechanical strength and durability play a crucial role in the utilization of superhydrophobic materials. In this study, we employed a two-step spraying method to fabricate superhydrophobic FEVE-based coatings with exceptional mechanical durability, utilizing fluorinated TiO 2 nanoparticles and fluorinated Al 2 O 3 microwhiskers as the fillers. The composite coating exhibited commendable non-wetting properties, displaying a contact angle of 164.84° and a sliding angle of 4.3°. On this basis, the stability of coatings was significantly improved due to the interlocking effect of Al 2 O 3 whiskers. After 500 tape peeling cycles, 500 sandpaper abrasion tests, and 50 kg falling sand impact tests, the coatings retained superhydrophobicity, exhibiting excellent durability and application capability. Notably, the ice adhesion strength on the coatings was measured at only 65.4 kPa, while the icing delay time reached 271.8 s at -15 °C. In addition, throughout 500 freezing/melting cycles, statistical analysis revealed that the superhydrophobic coatings exhibited a freezing initiation temperature as low as -17.25 °C.
研究领域:
材料科学
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表面工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2020
·
IF 4.939
Liying Zeng,Yizhou Wang,Jun Mou,Fei Liu,Chunliang Yang,Tianxiang Zhao,Xiaodan Wang,Jianxin Cao
γ-Al 2 O 3 was composited with ZSM-5 molecular sieve to improve its catalytic performance and hydrothermal stability during the conversion of crude methanol into dimethyl ether (DME). When prepared by a liquid-phase coating chemical compounding, the ZSM-5/γ-Al 2 O 3 composite catalyst reached an excellent methanol conversion of 91.9% and DME selectivity of 100%. The DME yield was increased by about 13% compared to only using γ-Al 2 O 3 . Partial desiliconization and dealumination of the ZSM-5 molecular sieve effectively reduced the surface acid center strength and increased the mesoporous ratio. The special composite phase interface effectively decreased surface charge density of γ-Al 2 O 3 and formed the B (Brønsted) - L (Lewis) synergistic active centers. All these factors contribute to improving the catalytic performance, hydrothermal stability and resistance to deactivation of ZSM-5/γ-Al 2 O 3 during the conversion of crude methanol to DME.
研究领域:
化学工程
·
催化材料科学
✓ 已验证
产品关联
DOI
高影响因子
Heliyon
·
2023
·
IF 4
Honglin Zhang,Ke Zhang,Zhiguo Zhiguo,Jian Hao
In this work, the metalloporphyrin film of PtOEP/Poly (St-co-TFEMA) modified by nano Al 2 O 3 powder was prepared, and the enhancement performance of oxygen sensing was studied in detail. It was verified that the modified film extended the residence time of oxygen through the characterization of SEM. The phosphorescence intensity changes with the content of Al 2 O 3 and PtOEP were studied. The Stern-Volmer equations before and after modification of Al 2 O 3 powder was compared. It was found that the linearity of the calibration curve was still high, but the oxygen sensitivity value of K SV was significantly improved due to the increase of quenching probability between indicator and oxygen. Finally, the stability test shows that the Al 2 O 3 @PtOEP/Poly (St-co-TFEMA) oxygen sensing film presents a strong anti-photo-bleaching ability, and the response time is shortened.
研究领域:
材料科学
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化学传感器
·
光学检测
✓ 已验证
DOI
高影响因子
Surface Topography-Metrology and Properties
·
2024
·Vol. 12
·期 1
·015005
·
IF 2
Jiaqi He,Huijian Li,Huajie Tang,Zihan Guo
Artificial intelligence algorithms including two artificial neural network and two machine learning algorithms were employed to predict the four-ball tribology behavior of MoS2-Al2O3 hybrid nanofluid. MoS2-Al2O3 composite nanoparticles were synthesized using solvothermal method and then dispersed in water-based fluids. 27 groups of tribology tests were conducted according to Box-Behnken experimental design were set as the training groups. The input variables (velocity of friction pairs, test force, test temperature, nanoparticle concentration) and output parameters (friction coefficient, wear scar diameter, wear surface roughness) were selected as the main variables. It was found that the random forest (RF) had better predict accuracy and stability for the four-ball tribology behavior of MoS2-Al2O3 nanofluid than multilayer perceptron (MLP), back propagation (BP) and k-nearest neighbors (KNN) algorithms. Besides, Pearson correlation analysis was carried out to reveal the relationship between input and output as well as different output variables. Through in-depth characterization of worn surface, a tribofilm in the thickness of 15 ∼ 20 nm composed of amorphous phases, ultra-fine nanoparticles and iron compounds was found. Finally, the lubrication mechanism of MoS2-Al2O3 nanofluid were discussed based on analyzing the tribology behavior data and tribofilm structure. Through the above findings, we hope to promote the application and development of artificial intelligence techniques in lubricants design and performance evaluation in the future.
研究领域:
材料科学
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人工智能
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机械工程
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2017
·
IF 4.601
Wei-Tu Li,Xian-Yong Wei,Xue-Ke Li,Xiang-Xue Liu,Zhan-Ku Li,Zhi-Min Zong
Catalysts Ni/γ-Al 2 O 3 , Mg 2 Si/γ-Al 2 O 3 , and Ni-Mg 2 Si/γ-Al 2 O 3 were prepared. Their activities for catalytic hydroconversions (CHCs) of some lignite-related model compounds were examined. For the CHCs of oxydibenzene (ODB), benzyloxybenzene, and oxybis(methylene)dibenzene, the suitable loadings of Ni and Mg 2 Si are 33 and 20% in Ni-Mg 2 Si/γ-Al 2 O 3 , respectively, and the optimal reaction conditions are 4 MPa of initial hydrogen pressure, 240 °C, and 2 h, under which ODB was almost completely converted to cyclohexane. The formation of possible intermediates during the CHC of ODB was discussed. Ni-Mg 2 Si/γ-Al 2 O 3 was proposed to have 3 functions, i.e., activating H 2 to biatomic active hydrogen (H⋯H), releasing H − , and heterolytically splitting H⋯H to release H − as well, resulting in the hydrogenation of aromatic rings and the hydrocracking of C O bonds, respectively.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Omega
·
2025
·
IF 4.3
Xueni Sun,Qiang Fu,Lidong Li,Chunxiang Huang,Jun Wang,Hui Shao
Experiments and molecular simulations were combined to investigate the adsorption mechanism of dimethyl carbonate (DMC) and methanol (MeOH) azeotrope onto α-Al2O3 while the differences and similarities between pure and azeotropic components were discussed. Static experimental results have shown that α-Al2O3 exhibited capacities in an unexpected order as azeotropic MeOH > pure DMC > pure MeOH > azeotropic DMC. MeOH-DMC and pure MeOH both fitted the PFO model with proximal kinetic constants, while the pure DMC exhibited a different behavior with a diffusion-controlled stage followed by chemisorption. The interfacial configuration as well as the mechanism at the molecular level was studied by molecular dynamics and density functional theory. Molecular simulation results indicate that a multilayer adsorption conformation is formed on the α-Al2O3 (0 0 1) surface for MeOH-DMC with most Al sites being occupied by MeOH followed by DMC constructing a bilayerlike structure with the preadsorbed MeOH molecules. Moreover, the adsorption of DMC can further reduce the dissociation of preadsorbed MeOH. This factor seems to promote the adsorption of more MeOH molecules on the α-Al2O3 (0 0 1) surface, leading to DMC aggregation outside the MeOH layer.
研究领域:
化学工程
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材料科学
·
计算化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Environmental Sciences
·
2021
·
IF 5.565
Chang Cui,Yan Zhang,Wenpo Shan,Yunbo Yu,Hong He
Alumina supported Pd catalyst (Pd/Al 2 O 3 ) is active for complete oxidation of methane, while often suffers transient deactivation during the cold down process. Herein, heating and cooling cycle tests between 200 and 900°C and isothermal experiments at 650°C were conducted to investigate the influence of NO x on transient deactivation of Pd/θ-Al 2 O 3 catalyst during the methane oxidation. It was found that the co-fed of NO alleviated transient deactivation in the cooling ramp from 800 to 500°C, which was resulted from the in situ formation of NO 2 during the process of methane oxidation. Over the Pd/θ-Al 2 O 3 , thermogravimetric analysis and O 2 temperature programmed oxidation measurements confirmed that transient deactivation was due to the decomposition of PdO particles and the hysteresis of Pd reoxidation, while the metal Pd entities were less active for methane oxidation than the PdO ones. CO pulse chemisorption and scanning transmission electron microscopy characterizations rule out the NO 2 effect on Pd size change. Powder X-ray diffraction and X-ray photoelectron spectroscopy characterizations were used to obtain palladium status of Pd/θ-Al 2 O 3 before and after reactions, indicating that in lean conditions at 650°C, the presence of NO 2 increases the content of active PdO on the catalyst surface, thus benefits methane oxidation. Homogeneous reaction between CH 4 , O 2 , and NO x may be partially responsible for the alleviation above 650°C. The interesting research of alleviation in transient deactivation by NO x , the components co-existing in exhausts, are of great significance for the application.
研究领域:
催化化学
·
环境科学
✓ 已验证
DOI
高影响因子
Crystals
·
2023
·Vol. 13
·期 1
·107
·
IF 2.7
Shaocong He,Yehua Li,Xiao Zong,Shanghua Wu
In this work, Al2O3-AlN composite ceramics with high bending strength and thermal conductivity were fabricated by Digital Light Processing (DLP). The influence of AlN content on the rheological and cure behavior of Al2O3-AlN suspensions, as well as the microstructure, thermal conductivity, and bending strength of Al2O3-AlN ceramics, were systematically investigated. The result shows that the viscosity and cure ability of the suspensions were decreased with the increase of AlN content, which are beneficial to the spreading and printing accuracy of the suspensions. Besides, the bending strength of ceramics can be improved due to the residual stress by the introduction of AlN. Approaches were employed to minimize the formation of AlON in Al2O3-AlN ceramics by optimizing the amount of AlN and the sintering temperature. The thermal conductivity and bending strength of Al2O3-AlN ceramics were 31.72 ± 0.45 W/(m·K) and 572.73 ± 59.40 MPa, respectively, which are much higher than those of Al2O3ceramics fabricated under the same condition. Finally, complex-shaped Al2O3-AlN ceramics components have been successfully fabricated by DLP, which may provide an opportunity to broaden the application of Al2O3-AlN composite ceramics in heat dissipation components.Keywords:Al2O3-AlN composite ceramics;Digital Light Processing;mechanical properties;thermal conductivity
研究领域:
材料科学
·
制造工程
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2024
·
IF 20.2
Haitao Yan,Didi Li,Zhaocong Jiang,Haoyuan Gu,Mengyuan Zhu,Yi-Fan Han,Minghui Zhu
Cu-based catalysts have been extensively used in the methanol steam reforming (MSR) reaction owing to low cost and high efficiency. In this work, we investigated the promotional effect of Fe on the Cu/ZnO/Al 2 O 3 catalysts prepared by an incipient-wetness impregnation method using a series of (quasi) in situ characterization techniques. The form of the Fe species was found to strongly depend on the Fe content. Fe species are present as highly dispersed FeO x in small amount of Fe with improved the dispersion of Cu. As Fe content increases, Fe species gradually transition to CuFe alloy and eventually to Fe 3 O 4 particles, leading to a decrease in Cu dispersion. With the gradual increase in Fe content, the apparent activity shows a volcanic trend, with CuAl-0.1Fe showing highest activity, whereas the intrinsic activity gradually decreases. Compared with CuAl- x Fe, adding moderate Fe to Cu/ZnO/Al 2 O 3 promotes the dispersion of Cu and Zn, forming abundant Cu-ZnO x interfacial sites, which improves both apparent and intrinsic activities. The best catalytic performance was obtained with the CuZnAl-0.1Fe catalyst, achieving the highest H 2 production rate of 134.7 mmol g cat −1 h −1 at 200 °C. This study reveals the role of Fe in Cu-based catalysts for MSR and inspires the design of improved Cu-based catalysts.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Frontiers in Chemistry
·
2022
·
IF 5.545
Huang Meng,Huang Wenbin,Li Anqi,Yang Han,Jia Yijing,Yu Zhiqing,Xu Zhusong,Wang Xiaohan,Zhou Yasong,Wei Qiang
Experiments were carried out to research the different contents of Ga2O3 modification effects on the hydrodesulfurization (HDS) performance of 4,6-dimethyldibenzothiophene (4,6-DMDBT) catalyzed by the stepwise impregnation method. Characterization techniques such as XRD, BET, HRTEM, NH3-TPD, and Py-FTIR were performed to determine the effects of each modification of the catalyst by Ga on the properties of the prepared supports and catalysts. The catalytic effect of gallium is reflected in the fact that the empty d-orbitals of Ga elements participate in the formation of molecular orbitals in the active center and change their orbital properties, thus generating a direct desulfurization active phase suitable for complex sulfides for endpoint adsorption. The characterization results indicated that the introduction of Ga2O3 with appropriate content (2 wt.%) promoted Ni and Mo species to disperse uniformly and doping of more Ni atoms into the MoS2 crystals, which also increased the average stacking number and the length of MoS2. As a result, more NiMoS active phases were favored to form in the system. The specific surface area and the amounts of acid sites were increased, facilitating the adsorption of reactant molecules and the HDS reactions. The HDS results also suggested the effects of Ga modification play a very important role in the catalytic performance of the corresponding catalysts. The catalyst Ga–Ni–Mo/Al2O3 exhibited the highest conversion rate towards 4,6-DMDBT HDS when the amount of Ga2O3 loading was 2 wt.% with an LHSV of 2.5 h−1 at 290°C and Ga modification also can effectively improve the direct desulfurization (DDS) route selectivity in varying degrees.
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）