Materials Today Communications
·
2022
·
IF 3.662
Le Li,Xiaohan Dai,Yanda Li,Songsong Zhou,Hechen Liu,Yunfan Ma,Zhongyuan Zhang,Yunpeng Liu
In this study, epoxy resin containing hollow polymeric microspheres as an insulating material was synthesized and subjected to thermal and hydrothermal aging. Scanning electron microscopy (SEM) and three-dimensional computed tomography (3D CT) were used to examine the internal structures of the specimens as they aged. Thermogravimetric analysis (TGA) and Fourier transform infrared spectra (FT-IR) helped to elucidate the physical and chemical changes associated with aging. Tensile, flexural, dynamic mechanical analysis (DMA), and other mechanical tests were used to examine the mechanical properties of the syntactic foams (SFs) as they aged. Electrical tests such as the leakage current and breakdown strength were used to measure how effectively the SF materials maintained their insulating characteristics with aging. By comparing the aged and unaged specimens, the aging mechanism of the SF was elucidated. The findings demonstrated that the epoxy resin matrix composite foam packed with hollow polymeric microspheres had little effect on thermal aging and exhibited good hydrothermal aging resistance. The microstructures of the specimens subjected to thermal aging barely changed; however, hydrothermal aging resulted in dramatic changes. Notably, the comprehensive properties of the SF increased during thermal aging and hydrothermal aging, possibly due to an increase in secondary crosslinking density after a certain period of aging. The thermal and hydrothermal aging specimens had maximum tensile strengths of 14 and 13 MPa, respectively. The tensile strength dropped as aging time increased to 11.6 and 7 MPa, respectively. Furthermore, while the breakdown strengths of the hydrothermal samples continued to fall, the breakdown strengths of the thermal specimens initially increased and subsequently decreased, with a maximum value of 40.76 kV/mm. This was possibly related to the fact that the crosslinking reaction dominated the thermal aging process, whereas hydrothermal aging had numerous implications on the characteristics of the SF materials. This study showed that the SF filled with hollow polymeric microspheres had the potential for long-term durability in hot and humid environments, supporting its application as an insulation material in composite insulation cores.
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
Nanomaterials
·
2020
·Vol. 10
·期 11
·2170
·
IF 4.324
Jialing Chen,Gang Peng,Tingyu Liang,Wenbo Zhang,Wei Zheng,Haoran Zhao,Li Guo,Xiaoqin Wu
The NH3-SCR activities and hydrothermal stabilities of fivexCu/MCM-22 zeolites with different Cu loadings (x= 2–10 wt%) prepared by incipient wetness impregnation method were systematically investigated. The physicochemical properties ofxCu/MCM-22 zeolites were analyzed by XRD, nitrogen physisorption, ICP-AES, SEM, NH3-TPD, UV-vis, H2-TPR and XPS experiments. The Cu species existing inxCu/MCM-22 are mainly isolated Cu2+, CuOxand unreducible copper species. The concentrations of both isolated Cu2+and CuOxspecies inxCu/MCM-22 increase with Cu contents, but the increment of CuOxspecies is more distinct, especially in high Cu loadings (>4 wt%). NH3-SCR experimental results demonstrated that the activity ofxCu/MCM-22 is sensitive to Cu content at low Cu loadings (≤4 wt%). When the Cu loading exceeds 4 wt%, the NH3-SCR activity ofxCu/MCM-22 is irrelevant to Cu content due to the severe pore blockage effects caused by aggregated CuOxspecies. Among the fivexCu/MCM-22 zeolites, 4Cu/MCM-22 with moderate Cu content has the best NH3-SCR performance, which displays higher than 80% NOxconversions in a wide temperature window (160–430 °C). Furthermore, the hydrothermal aging experiments (xCu/MCM-22 was treated at 750 °C for 10 h under 10% water vapor atmosphere) illustrated that all thexCu/MCM-22 zeolites exhibit high hydrothermal stability in NH3-SCR reactions.Keywords:Cu/MCM-22;NH3-SCR;Cu loading;hydrothermal aging
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CATALYSIS TODAY
·
2014
·
IF 3.309
Yuxi Gao,Xiaodong Wu,Shuang Liu,Duan Weng,Hongwei Zhang,Rui Ran
MnO x –CeO 2 mixed oxides were synthesized using a sol–gel method and the barium-loaded catalyst was prepared by a wet impregnation. Both catalysts were hydrothermally aged at 800 °C for 10 h. The fresh and aged catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), high-resolution transmission electron microscopy (HRTEM), H 2 temperature-programmed reduction (H 2 -TPR), NO temperature-programmed oxidation (NO-TPO) and soot temperature-programmed oxidation (soot-TPO). Compared with MnO x –CeO 2 , the Ba-modified mixed oxides show a much higher hydrothermal stability. Barium exists in the form of orthorhombic carbonate and cubic nitrate on the fresh sample. BaMnO 3 nanoparticles are identified to form at the interface of CeO 2 crystallites upon the hydrothermal ageing. The formation of the perovskites prohibits the sintering of ceria significantly, and consequently maintains the redox property of the aged mixed oxides to a great degree. Additionally, the nanoscaled perovskites themselves also contribute to the catalytic activity of the aged oxides catalyst.
研究领域:
催化材料
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
Energies
·
2025
·Vol. 18
·期 14
·3767
·
IF 3.2
Wenbo Zhu,Kaulya Pathiraja,Xu Guo,Baojun Hui,Mingli Fu,Linjie Zhao,Yuhuai Wang,Jin Li
A novel interfacial coating agent was developed by modifying silicone oil with polycyclic aromatic hydrocarbons (PAHs) to enhance the insulation performance of HVDC cable accessories. This study investigates the effects of corona and hot–cold cycle aging on the DC breakdown characteristics of the Cross-Linked Poly Ethylene and Ethylene Propylene Diene Monomer (XLPE/EPDM) interface. Interfacial breakdown tests, infrared spectroscopy, and a microstructural analysis were employed to investigate aging mechanisms. The results show that PAH-modified silicone oil significantly increases the breakdown voltage, with 2,4-dihydroxybenzophenone (C13H10O3) identified as the optimal additive via quantum chemical calculations (QCCs). Even after aging, the modified interface maintains its superior performance, confirming the long-term reliability of the coating.
研究领域:
高电压工程
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材料科学
·
电力系统绝缘技术
✓ 已验证
产品关联
DOI
高影响因子
Polymers
·
2024
·Vol. 17
·期 1
·50
·
IF 4.7
Jianyu Wu,Fangzhou Chen,Jiahao Liu,Rui Chen,Peijiang Liu,Hao Zhao,Zhenbo Zhao
During the thermal aging process of epoxy resin, microcracks, interfacial delamination, and warpage are the key factors leading to semiconductor device damage. Here, epoxy-resin specimens (EP-Ss) and epoxy-resin/silicon-wafer composites (EP-SWs) were prepared to analyze the distribution of residual stress (RS) in epoxy resin and its thermal aging process changes. The uniaxial tensile approach and Raman spectroscopy (RAS) showed that the peak shift of aliphatic C-O in EP-Ss was negatively correlated with the external stress, and that the stress correlation coefficient was −2.76 × 10−2cm−1/MPa. Then, RAS was used to evaluate the RS distribution of EP-SWs, obtaining a high-resolution stress-distribution image of 50 × 50 pixels and revealing a strong stress concentration at the interface between the epoxy resin and the silicon wafer. Additionally, Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), Field-emission scanning electron microscopy (FE-SEM), and RAS were used to analyze the chemical composition, molecular structure, interfacial microstructure, and RS of the epoxy resin during the thermal aging process. With the increase in the thermal aging time, the epoxy resin underwent secondary curing, the RS at the interface changed from tensile stress to compressive stress, and cracks were formed. The results illuminate the effect of the thermal aging process on the interface-failure mechanism of composite materials, aiding in the reliability evaluation and safety design of semiconductor devices.
研究领域:
材料科学
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半导体工程
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
·
2025
·
IF 3.1
Zuhao Wang,Xiao Peng,Ioannis Chronis,Yingrui Wu,Constantinos S. Psomopoulos,Chao Tang
As the global power industry evolves, transformer insulation systems face increasing challenges. The aging of cellulose insulation paper (cellulose-IP) at elevated temperatures significantly impacts its insulation properties and overall lifespan. To enhance the thermal aging resistance and industrial usability of cellulose-IP, this study employs nano-boron nitride (h-BN) along with three silane coupling agents—3-ammonopropyltriethoxysilane (KH550), 3-glycidyloxypropyltrimethoxysilane (KH560), and 3-methacryloyloxypropyltrimethoxysilane (KH570)—to modified cellulose-IP. Upon evaluating the properties and simulation results of the modified cellulose-IP, KH550-hBN demonstrated superior properties and was selected for an accelerated thermal aging test lasting 60 days. The results indicated that KH550-hBN effectively mitigates the degradation of cellulose-IP. In the late aging stage, the mechanical properties of the modified cellulose-IP deteriorated more slowly than those of pure cellulose-IP. Additionally, thermal conductivity improved by 26.9%, while breakdown field strength increased by 12.1%. The introduction of KH550-hBN promotes the formation of a complete thermal conductivity network within the cellulose matrix, increases the number of intermolecular hydrogen bonds and introduces nano-barrier regions.These improvements enhance the interactions between the cellulose systems and effectively inhibit the generation and migration of polar derivatives during the aging process, resulting in a significant improvement in the longevity and stability of transformer internal insulation systems.
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
POLYMER COMPOSITES
·
2024
·
IF 4.8
Fei Yan,Junming Wang,Gang Li,Shengtao Dai,Yuhui Ao,Liu Liu
A carbon fiber-tannic acid-silicon dioxide (CF-TA-SiO 2 ) reinforcement with a “diatom frustule-like” structure was built via biomimetic mineralization to boost the performance of carbon fiber/epoxy resin (CF/EP) composites. As a bio-based polyphenolic compound, TA was used to modulate the mineralization of SiO 2 , and the easy agglomeration of SiO 2 was effectively avoided. The interfacial adhesion of the CF/EP composites was considerably heightened by improving the roughness and wettability of CF as well as by increasing the interfacial interactions between CF and the EP. Compared with the pristine composites, the flexural strength, interlaminar shear strength and interfacial shear strength of the CF-TA-SiO 2 /EP composites increased by 41.2%, 56.6%, and 50.4%, respectively. Moreover, the introduction of Si-O-Si and C-O-Si bonds at the interface led to a remarkable improvement in the hydrothermal aging resistance. This research provides a novel interfacial design for advanced composites with excellent interfacial properties, which broadens the application of these composites in hygrothermal environments. Highlights A “diatom frustules-like” structure was successfully constructed on the CF surface. This biomimetic mineralization was simple and environmentally friendly. This method solved the problem of easy agglomeration of SiO 2 . The interfacial properties of composites were obviously improved. The hydrothermal aging resistance of composites was enhanced.
研究领域:
材料科学
·
仿生学
✓ 已验证
产品关联
DOI
高影响因子
POLYMER COMPOSITES
·
2024
·
IF 4.8
Wei Wang,Guangchao Ye,Ying Zhang,Xiujie Bian,Peng Lin,Yuanyuan Dong,Pengfei Hao,Xiang Wang
The enhanced durability of biobased polylactide (PLA) is a critical prerequisite for it to be considered a viable alternative to petroleum-based polymers for long-term applications. Leveraging the performance improvements achieved through interface construction, PLA-biomass composites have garnered considerable interest and have been widely utilized as a completely degradable material. The hydrolytic behavior of PLA biocomposites in photo-hydrothermal environments was examined in this study in relation to the impact of biomass components and the specifically designed interface. We observed that biomass could act as an effective stabilizer in the composites, leading to a 25.6% reduction in the hydrolysis reaction rate constant. This stabilization occurs as biomass impedes the diffusion of water molecules and the extension of PLA molecular chains across various hydrothermal environments, thereby enhancing the hydrolytic resistance of PLA. The intriguing aspect is that this stabilizing effect of biomass could be moderated by an interface created through surface treatment, which facilitates enhanced transfer of active small molecules during the photolysis-hydrolysis process. Consequently, this approach presents a novel method for producing PLA biocomposites that offers excellent hydrolytic resistance, an adjustable degradation cycle, and expected potential applications in advanced packaging and agricultural domains. Highlights Biomass significantly enhances the hydrolysis resistance of polylactide (PLA) biocomposites. This stability boosts due to the obstructive and shielding effects of biomass. Effective interface could regulate the usable life of PLA biocomposites. The role that biomass/ interfaces play also applies to PLA photodegradation. Photo-hydrolysis mechanism is not affected by biomass or designed interface.
研究领域:
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2019
·
IF 14.229
Tong Zhang,Hui Li,Zhi Yang,Fengren Cao,Liang Li,Haijun Chen,Hui Liu,Ka Xiong,Jie Wu,Zhanglian Hong,Weichao Wang
Nanofiber catalysts are potentially promising to be equipped in the lean-burned vehicle exhaust emission system considering its facile synthesis, low-cost, long durability in contrast to the traditionally complicated powder based catalyst. Here, via electrospinning method, we synthesized YMn 2 O 5 nanofibers (average diameter: ˜93 nm) including nanowire stacked with particles, and hollow tubes with or without inside nanowires. The morphologies remained even after hydrothermal aging at 800 ℃ for 10 h with 10% H 2 O stream. X-ray photoelectron spectrum revealed Mn 4+ /Mn 3+ ratio 0.589 on the surface of YMn 2 O 5 catalyst (YMO), indicating the existence of oxygen vacancies. The highest conversion of electrospun mullite fibers at 310 ℃ is ˜18% higher than powder-based YMO at 352 ℃ in the presence of 5% H 2 O at WHSV = 240,000 ml g −1 h −1 . The extracted activation energy from NO-to-NO 2 conversion curves of YMO nanofiber (61.68 kJ/mol) is slightly lower than that of powder-based mullite (91.45 kJ/mol), consistent with calculated 68.16 kJ/mol on the fiber YMO surface (121) with a rate-limiting step of the NO 2 desorption. The catalytic activity can be attributed to the unit occupy of the e g ( d z 2 and d x 2 -y 2 ) orbitals of Mn-dimer atoms around fermi level based on the combination of the theoretical calculations and DRIFTS spectra analysis. Importantly, after the hash hydrothermal-aging, the highest NO oxidation conversion of powder-based mullite is less than 50%, while the fiber maintains a conversion of 62%. Moreover, the fresh YMO fiber maintained superior oxidation stability for 12 h at its maximum conversion of 66%. This work provides the possibility for mullite oxide fibers to replace powder-based precious metal catalyst coating on monolith converter.
研究领域:
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
Materials
·
2021
·Vol. 14
·期 2
·257
·
IF 3.623
Xiaodong Zhang,Fei Chen,Zhimin Su,Taiping Xie
The effects of electron beam irradiation on ethylene-tetrafluoroethylene copolymer (ETFE) were studied. Samples were irradiated in air at room temperature by a universal electron beam accelerator for various doses. The effect of irradiation on samples and the cross-linked ETFE after aging were investigated with respect to thermal characteristics, crystallinity, mechanical properties, and volume resistivity using thermo-gravimetric analysis (TGA), differential scanning calorimeter (DSC), universal mechanical tester, and high resistance meter. TGA showed that thermal stability of irradiated ETFE is considerably lower than that of unirradiated ETFE. DSC indicates that crystallinity is altered greatly by cross-link. The analysis of mechanical properties, fracture surface morphology, visco-elastic properties and volume resistivity certify radiation-induced cross-linking is vital to aging properties.Keywords:ETFE;irradiation;aging;mechanical properties;crystallization kinetics
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2019
·
IF 8.355
Han Jiang,Bin Guan,Xuesong Peng,Reggie Zhan,He Lin,Zhen Huang
This study focuses on investigating the influence of ion-exchange method (ION-F and ION-A) and one-pot method (ONE-F and ONE-A) on catalytic properties and hydrothermal stability of Cu/SSZ-13. It was found that ONE-F catalyst showed better SCR activity, especially at low temperature range below 400 °C. After hydrothermal aging, ION-A exhibited higher low temperature efficiency than ONE-A. The effect of synthesis method on the physicochemical structure, acidity intensity, and Cu species migration or transformation of the fresh and aged Cu/SSZ-13 catalysts were comprehensively characterized by NH 3 -TPO, H 2 -TPR, NH 3 -TPD, ICP, XRF, BET, XRD, SEM, and TEM. ONE-F has more isolated Cu 2+ sites, higher ratio of active sites Cu 2+ -2Z/[Cu(OH)] + -Z, more Lewis acid sites, and smaller particle size than ION-F. However, hydrothermal aging had severe effect on Cu/SSZ-13 prepared by one-pot method, leading to particle aggregation and decrease of active copper sites. According to NH 3 -SCR kinetic studies, smaller particle size and more uniformly distributed active sites over ONE-F resulted in less effect of pore diffusion limitation. Furthermore, in situ DRIFTS results indicated that more monodentate nitrates adsorbed sites and Lewis acid sites existed in ONE-F. On the other hand, monodentate nitrates were identified to be the most active nitrate species, and Lewis acid sites were ascertained to be more active than Brønsted acid sites. Therefore, ONE-F showed more excellent SCR performance than ION-F. However, hydrothermal aging resulted in loss of majority of nitrate adsorbed sites and acid sites over catalyst prepared by one-pot method, leading to lower SCR performance. In conclusion, Cu/SSZ-13 prepared by ion-exchange method has higher hydrothermal stability, however, fresh Cu/SSZ-13 prepared by one-pot method has excellent catalytic properties.
研究领域:
催化材料
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2019
·
IF 2.846
Lei Chen,Ding Wang,Jiadao Wang,Duan Weng,Li Cao
The CeO 2 -TiO 2 (CeTi) and CeO 2 /WO 3 -TiO 2 (CeWTi) catalysts were prepared by sol-gel method. The as-prepared catalysts were hydrothermally treated at 760 °C for 48 h in air containing 10 vol% H 2 O to obtain the hydrothermal aged catalysts. The sulfur aged catalysts were treated at 400 °C with 100 ppm SO 2 , 10% water vapor, air balance for 48 h and catalysts. The powder X-ray diffraction (XRD) and Raman results indicate that the crystallization of hydrothermal aged catalysts is more serious than sulfur aged catalysts. In addition, tungsten species can stabilize the CeTi catalyst from grain growth. According to the results of in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), temperature-programmed desorption of ammonia (NH 3 -TPD), H 2 temperature-programmed reduction (H 2 -TPR) and ammonia oxidation , the aging process leads to loss of surface area, redox properties, surface acidities and surface ceria concentration, especially for the hydrothermal aging. The NH 3 -NO/NO 2 SCR performances of sulfur aged catalysts are better than that of hydrothermal aged catalysts. Compared with CeTi catalyst, the addition of tungsten inhibits the crystallization of catalyst. So that more acid sites and active sites are retained. This is also the reason why tungsten addition improves the NH 3 -NO/NO 2 SCR performance of CeTi catalyst.
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）