POLYMER DEGRADATION AND STABILITY
·
2021
·
IF 5.03
Yiwei Long,Jian Gao,Zhuolin Cheng,Daoyuan Chen,Kangning Wu,Jianying Li,Fusheng Zhou
The skin-core structure of thermally aged epoxy resin consisting of the aged surface-layer and the unaged inner-layer, was studied in this paper. A new tan δ peak appeared in the results of dynamic mechanical analysis (DMA) after the specimens were thermally aged. It steadily diminished when the surface of the specimens was gradually removed, which indicates that the newly detected peak arose from formation of surface-layer during ageing. Thickness of the surface-layer could reach up to 0.09 mm after thermal ageing for 480 h. According to Fourier transform infrared spectroscopy (FTIR) results, formation of the surface-layer was found to closely correlated with thermal oxidation and re-crosslinking processes. The former induced oxidized molecular chains while the later might be related to the production of carboxylic acid dimers and etherification reactions to result in strengthened networks. This was further ascertained by the results of dielectric spectroscopy and isothermal surface potential decay (ISPD) tests. The relaxation process of aged epoxy resin displayed higher relaxation time, strength, and activation energy than unaged specimens, and evident growths of both deep and shallow level traps densities were also observed after thermal ageing. This casts new light on the thermal ageing mechanism of epoxy resin and could provide a feasible method for its insulation degradation assessment.
研究领域:
材料科学
·
电绝缘研究
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DOI
高影响因子
Journal of Physical Chemistry C
·
2021
·
IF 4.126
Tamara Russ,Zhixiang Hu,Benjamin Junker,Huan Liu,Udo Weimar,Nicolae Barsan
Lead sulfide (PbS) is a p-type semiconductor that is often applied in photodetectors and solar cells. One major problem that researchers are regularly confronted with is the loss of performance when operated in air. The sensitivity to the ambient, however, makes it an interesting material for the application in gas sensors. Although a lot of research has been focused on the aging of PbS, the influencing factors and the associated material changes are still a matter of debate. Resistance measurements of differently prepared PbS samples operated as sensors for the detection of NO2 (a strongly oxidative gas) in combination with surface-sensitive methods (diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy) enabled the investigation of the changes associated with aging and their influence on the sensing mechanism. The aging mechanism was found to be predominantly influenced by the presence of residuals of the stabilizing agent oleic acid that was adsorbed at the surface of the colloidal quantum dots. Additionally, it was found that a byproduct of the consumption of oleic acid enhanced the detected sensor signal.
研究领域:
材料科学
·
表面化学
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DOI
高影响因子
ACS Applied Materials & Interfaces
·
2022
·
IF 10.383
Yalan Zhang,Tinghuan Yang,Raja sekhar Bobba,Abiral Baniya,Tianqi Niu,Sally Mabrouk,Shengzhong Liu,Quinn Qiao,Kui Zhao
The combination of organic ligands and inorganic Pb–I frameworks in layered perovskites has bestowed upon them high structural tunability and stability, while their microscopic degradation mechanism remains unclear. Here, we found the key role of ligands in intrinsic structural stability and the consequent morphological evolution in layered perovskites during long-term ambient aging based on (GA)(MA)nPbnI3n+1 (GA = guanidinium, = 4) and (BDA)(MA)n−1PbnI3n+1 (BDA = 1,4-butanediammonium, < n > = 4) perovskites. The BDA-based perovskites have a low intrinsic stability due to high crystal formation energy (ΔH), which are prone to hydration during ambient aging. We overserved changed crystal orientation from perpendicular to parallel, a delayed charge populating time from <1 ps to >50 ps, an inhibited carrier transfer kinetics between quantum wells, an increase of 0.9 μs of charge carrier transport time and a decrease of 1.2 μs of charge carrier lifetime in the BDA-based film during ambient aging, which accounts for a large power-conversion efficiency (PCE) loss (14.2% vs 11.2%). By contrast, the GA ligand increases the intrinsic structural stability of perovskites, which not only yields an initial PCE as high as 20.0% but also helps retain excellent optoelectronic properties during aging. Therefore, only a slight PCE loss (20.0% vs 19.1%) was observed. Our work reveals the key role of organic–inorganic interaction affecting the intrinsic structural stability and optoelectronic properties, and provides a theoretical basis for the future design of stable and efficient optoelectronic devices.
研究领域:
材料科学
·
物理化学
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产品关联
DOI
PubMed
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
·
2020
·
IF 9.038
Ruofan Mao,Mengfan Lang,Xiaoqin Yu,Renren Wu,Xiaomei Yang,Xuetao Guo
Microplastics are formed by the degradation of plastic wastes under the action of physicochemical mechanisms in environment, and they are becoming a new type of pollutant that is attractings global attention. However, research on the aging characteristics and mechanism of microplastics is limited. The aging mechanism of Polystyrene (PS) with UV irradiation under different conditions (air, pure water and seawater) and the effect of aging on heavy metal adsorption were studied. The results show that PS have different characteristics with UV irradiation under different conditions, and the aging of PS is the most obvious in air. Based on the 2D-COS analysis, different aging mechanisms were identified under different aging conditions, aging sequence of aged PS functional groups in air and water were clearly definited. An isothermal adsorption model shows that aging can significantly increase the adsorption of heavy metals by PS. The adsorption of heavy metals is also affected by different aging methods. Over all, a 2D-COS analysis was an effective method for understanding the aging process of PS. These results further clarify the aging mechanism of PS, and provides a theoretical basis for the assessment of environmental behavior and ecological risk when microplastics and heavy metals coexist.
研究领域:
环境科学
·
化学
·
生态学
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DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2025
·Vol. 36
·期 25
·1-13
·
IF 2.8
Lu Jiajun,Kong Wenwen,Xie Juntao,Zhao Yan,Zhao Qing,Chang Aimin
High-temperature thermistors face significant challenges in maintaining stability under extreme temperature conditions, meaning that stringent requirements for material selection and structural design are needed. To address this issue, negative temperature coefficient (NTC) thermistor ceramics of Ba 2 ReNbO 6 (Re = La, Nd, and Sm) were successfully prepared using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that Ba 2 ReNbO 6 (Re = La, Nd, and Sm) had an ordered double perovskite structure. Scanning electron microscopy (SEM) revealed that as the difference in cationic radii between B′/B″ decreased, the porosity of the materials gradually increased. After Ba 2 ReNbO 6 (Re = La, Nd, and Sm) underwent aging tests at 1173 K for 720 h, the resistance drift rates were 1.33, 3.80, and 5.88%, respectively, and the aging mechanism was explained using cation diffusion theory. These ceramics exhibited typical NTC characteristics over a wide temperature range from 773 to 1473 K, with the degree of linearity exceeding 0.999 for all the samples.
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产品关联
DOI
高影响因子
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