High-resolution X-ray diffraction has been employed to investigate the diffuse scattering in a （0001） oriented GaN epitaxial film grown on sapphire substrate. The analysis reveals that defect clusters are present in...High-resolution X-ray diffraction has been employed to investigate the diffuse scattering in a （0001） oriented GaN epitaxial film grown on sapphire substrate. The analysis reveals that defect clusters are present in GaN films and their concentration increases as the density of threading dislocations increases. Meanwhile, the mean radius of these defect clus- ters shows a reverse tendency. This result is explained by the effect of clusters preferentially forming around dislocations, which act as effective sinks for the segregation of point defects. The electric mobility is found to decrease as the cluster concentration increases.展开更多
Electrochemical nitrogen reduction reaction (eNRR) is an alternative promising manner for sustainable N2 fixation with low-emission. The major challenge for developing an efficient electrocatalyst is the cleaving of t...Electrochemical nitrogen reduction reaction (eNRR) is an alternative promising manner for sustainable N2 fixation with low-emission. The major challenge for developing an efficient electrocatalyst is the cleaving of the stable Ntriple bondN triple bonds. Herein, we design a new MoS_(2) with in-plane defect cluster through a bottom-up approach for the first time, where the defect cluster is composed of three adjacent S vacancies. The well-defined in-plane defect clusters could contribute to the strong chemical adsorption and activation towards inert nitrogen, achieving an excellent eNRR performance with an ammonia yield rate of 43.4 ± 3 μg h^(−1) mgcat.^(−1) and a Faradaic efficiency of 16.8 ± 2% at −0.3 V (vs. RHE). The performance is much higher than that of MoS_(2) with the edge defect. Isotopic labeling confirms that N atoms of produced NH4+ originate from N2. Furthermore, the in-plane defect clusters realized the alternate hydrogenation of nitrogen in a side-on way to synthesize ammonia. This work provides a prospecting strategy for fine-tuning in-plane defects in a catalyst, and also promotes the progress of eNRR.展开更多
We investigate the microstructures of the pure aluminium foil and filter used on the space solar telescope, irradiated by photons with different doses. The vacancy defect clusters induced by proton irradiation in both...We investigate the microstructures of the pure aluminium foil and filter used on the space solar telescope, irradiated by photons with different doses. The vacancy defect clusters induced by proton irradiation in both samples are characterized by transmission electron microscopy, and the density and the size distribution of vacancy defect clusters are determined. Their transmittances are measured before and after irradiating the samples by protons with energy E = 100 keV and dose φ = 6 × 10^11/mm^2. Our experimental results show that the density and the size of vacancy defect clusters increase with the increase of irradiation doses in the irradiated pure aluminium foils. As irradiation dose increases, vacancies incline to form larger defect clusters. In the irradiated filter, a large number of banded void defects are observed at the agglomerate boundary, which results in the degradation of the optical and mechanical performances of the filter after proton irradiation.展开更多
The interaction of Ag atoms with a defective MgO（001） surface is systematically studied based on density functional theory. The Ag clusters are deposited on neutral and charged oxygen vacancies of the MgO（001） sur...The interaction of Ag atoms with a defective MgO（001） surface is systematically studied based on density functional theory. The Ag clusters are deposited on neutral and charged oxygen vacancies of the MgO（001） surface. The structures of Ag clusters take the shape of simple models of two- or three-dimensional （2D and 3D） metal particles deposited on the MgO surface. When the nucleation of the metal clusters occurs in the Fs （missing neutral O） centre, the interaction with the substrate is considerably stronger than that in the Fs^＋ （missing O-） centre. The results show that the adsorption of Ag atoms on the MgO surface with oxygcn vacancy is stronger than on a clear MgO surface, thereby attracting more Ag atoms to cluster together, and forming atomic islands.展开更多
While considerable progress has been achieved in radiation influence on the solid states, the quantitative assessment of defect production is very scarce. In this paper radiation defects studies in silicon crystals ar...While considerable progress has been achieved in radiation influence on the solid states, the quantitative assessment of defect production is very scarce. In this paper radiation defects studies in silicon crystals are briefly reviewed and comprehensively analyzed depending on irradiation energy and dose, paying special attention to electron irradiation in wide energy spectrum when crystal lattice disordered regions (clusters) occur. Electron irradiation, which is a simple way to introduce intrinsic defects, was used as one of the most powerful techniques to study point and cluster defects which affect properties of semiconductors depending on irradiation energy. Fundamental aspects of radiation induced defects are discussed and it is shown that they bring information on the threshold energy for atomic displacement, on the recombination of vacancy—interstitial pair and mainly, on radiation defects cluster formation which essentially influences on the irradiating material properties. The determination of the irradiation critical dose and energy for the formation of homogeneous disordered regions (clusters) are detailed.展开更多
为解决电池模组极柱焊接缺陷检测精度低、效率低的问题,提出了一种基于机器视觉的焊接缺陷检测算法。首先,对采集图像进行预处理操作;其次,通过组件筛选结合改进的Canny算法获取目标区域的无干扰边缘轮廓,为了改善拟合干扰现象,利用基...为解决电池模组极柱焊接缺陷检测精度低、效率低的问题,提出了一种基于机器视觉的焊接缺陷检测算法。首先,对采集图像进行预处理操作;其次,通过组件筛选结合改进的Canny算法获取目标区域的无干扰边缘轮廓,为了改善拟合干扰现象,利用基于密度的聚类(density-based spatial clustering of applications with noise,DBSCAN)算法对焊接区域的内外圆边缘点集进行分离;然后,采用改进的最小二乘法对内外圆点集分别进行拟合得到精准的焊接区域;最后,以焊接区域内外圆的面积差和同心度来检测焊接面积缺陷和焊偏,通过双向扫面检测法进行焊接区域灰度值遍历,根据对应的灰度值范围和区域大小来检测焊穿和炸点缺陷。实验表明,该算法能够精确拟合焊接区域并准确识别出焊接缺陷,具有较高的检测精度和效率,能够满足工业生产需求。展开更多
Donor-acceptor co-doped rutile TiO_(2) ceramics with colossal permittivity(CP)have been extensively investigated in recent years due to their potential applications in modern microelectronics.In addition to CP and low...Donor-acceptor co-doped rutile TiO_(2) ceramics with colossal permittivity(CP)have been extensively investigated in recent years due to their potential applications in modern microelectronics.In addition to CP and low dielectric loss,voltage stability is an essential property for CP materials utilized in high-power and high-energy density storage devices.Unfortunately,the voltage stability of CP materials based on codoped TiO_(2) does not catch enough attention.Here,we propose a strategy to enhance the voltage stability of co-doped TiO_(2),where different ionic defect clusters are formed by two acceptor ions with different radii to localize free carriers and result in high performance CP materials.The(Ta+Al+La)co-doped TiO_(2) ceramic with suitable La/Al ratio exhibits colossal permittivity with excellent temperature stability as well as outstanding dc bias stability.The density functional theory analysis suggests that La^(3+)Al^(3+)V_(0)Ti^(3+)defect clusters and Ta^(5+)-Al^(3+)pairs are responsible for the excellent dielectric properties in(Ta+Al+La)co-doped TiO_(2).The results and mechanisms presented in this work open up a feasible route to design high performance CP materials via defect engineering.展开更多
文摘High-resolution X-ray diffraction has been employed to investigate the diffuse scattering in a （0001） oriented GaN epitaxial film grown on sapphire substrate. The analysis reveals that defect clusters are present in GaN films and their concentration increases as the density of threading dislocations increases. Meanwhile, the mean radius of these defect clus- ters shows a reverse tendency. This result is explained by the effect of clusters preferentially forming around dislocations, which act as effective sinks for the segregation of point defects. The electric mobility is found to decrease as the cluster concentration increases.
基金This work was supported by the National Natural Science Foundation of China(22078063,21825801).
文摘Electrochemical nitrogen reduction reaction (eNRR) is an alternative promising manner for sustainable N2 fixation with low-emission. The major challenge for developing an efficient electrocatalyst is the cleaving of the stable Ntriple bondN triple bonds. Herein, we design a new MoS_(2) with in-plane defect cluster through a bottom-up approach for the first time, where the defect cluster is composed of three adjacent S vacancies. The well-defined in-plane defect clusters could contribute to the strong chemical adsorption and activation towards inert nitrogen, achieving an excellent eNRR performance with an ammonia yield rate of 43.4 ± 3 μg h^(−1) mgcat.^(−1) and a Faradaic efficiency of 16.8 ± 2% at −0.3 V (vs. RHE). The performance is much higher than that of MoS_(2) with the edge defect. Isotopic labeling confirms that N atoms of produced NH4+ originate from N2. Furthermore, the in-plane defect clusters realized the alternate hydrogenation of nitrogen in a side-on way to synthesize ammonia. This work provides a prospecting strategy for fine-tuning in-plane defects in a catalyst, and also promotes the progress of eNRR.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50671042)the Program for Innovative Research Team of Jangsu University and the Program for Exellent Talents of Jangsu University (Grant No. 07JDG032)
文摘We investigate the microstructures of the pure aluminium foil and filter used on the space solar telescope, irradiated by photons with different doses. The vacancy defect clusters induced by proton irradiation in both samples are characterized by transmission electron microscopy, and the density and the size distribution of vacancy defect clusters are determined. Their transmittances are measured before and after irradiating the samples by protons with energy E = 100 keV and dose φ = 6 × 10^11/mm^2. Our experimental results show that the density and the size of vacancy defect clusters increase with the increase of irradiation doses in the irradiated pure aluminium foils. As irradiation dose increases, vacancies incline to form larger defect clusters. In the irradiated filter, a large number of banded void defects are observed at the agglomerate boundary, which results in the degradation of the optical and mechanical performances of the filter after proton irradiation.
基金Project supported by the Scientific Research Fund of Hunan Provincial Education Department, China (Grant No. 09B021)
文摘The interaction of Ag atoms with a defective MgO（001） surface is systematically studied based on density functional theory. The Ag clusters are deposited on neutral and charged oxygen vacancies of the MgO（001） surface. The structures of Ag clusters take the shape of simple models of two- or three-dimensional （2D and 3D） metal particles deposited on the MgO surface. When the nucleation of the metal clusters occurs in the Fs （missing neutral O） centre, the interaction with the substrate is considerably stronger than that in the Fs^＋ （missing O-） centre. The results show that the adsorption of Ag atoms on the MgO surface with oxygcn vacancy is stronger than on a clear MgO surface, thereby attracting more Ag atoms to cluster together, and forming atomic islands.
文摘While considerable progress has been achieved in radiation influence on the solid states, the quantitative assessment of defect production is very scarce. In this paper radiation defects studies in silicon crystals are briefly reviewed and comprehensively analyzed depending on irradiation energy and dose, paying special attention to electron irradiation in wide energy spectrum when crystal lattice disordered regions (clusters) occur. Electron irradiation, which is a simple way to introduce intrinsic defects, was used as one of the most powerful techniques to study point and cluster defects which affect properties of semiconductors depending on irradiation energy. Fundamental aspects of radiation induced defects are discussed and it is shown that they bring information on the threshold energy for atomic displacement, on the recombination of vacancy—interstitial pair and mainly, on radiation defects cluster formation which essentially influences on the irradiating material properties. The determination of the irradiation critical dose and energy for the formation of homogeneous disordered regions (clusters) are detailed.
文摘为解决电池模组极柱焊接缺陷检测精度低、效率低的问题,提出了一种基于机器视觉的焊接缺陷检测算法。首先,对采集图像进行预处理操作;其次,通过组件筛选结合改进的Canny算法获取目标区域的无干扰边缘轮廓,为了改善拟合干扰现象,利用基于密度的聚类(density-based spatial clustering of applications with noise,DBSCAN)算法对焊接区域的内外圆边缘点集进行分离;然后,采用改进的最小二乘法对内外圆点集分别进行拟合得到精准的焊接区域;最后,以焊接区域内外圆的面积差和同心度来检测焊接面积缺陷和焊偏,通过双向扫面检测法进行焊接区域灰度值遍历,根据对应的灰度值范围和区域大小来检测焊穿和炸点缺陷。实验表明,该算法能够精确拟合焊接区域并准确识别出焊接缺陷,具有较高的检测精度和效率,能够满足工业生产需求。
基金financially supported by the Fundamental Research Foundation for University of Heilongjiang Province(No.2018-KYYWF-1628)the National Natural Science Foundation of China(Nos.51471057 and 51677033)。
文摘Donor-acceptor co-doped rutile TiO_(2) ceramics with colossal permittivity(CP)have been extensively investigated in recent years due to their potential applications in modern microelectronics.In addition to CP and low dielectric loss,voltage stability is an essential property for CP materials utilized in high-power and high-energy density storage devices.Unfortunately,the voltage stability of CP materials based on codoped TiO_(2) does not catch enough attention.Here,we propose a strategy to enhance the voltage stability of co-doped TiO_(2),where different ionic defect clusters are formed by two acceptor ions with different radii to localize free carriers and result in high performance CP materials.The(Ta+Al+La)co-doped TiO_(2) ceramic with suitable La/Al ratio exhibits colossal permittivity with excellent temperature stability as well as outstanding dc bias stability.The density functional theory analysis suggests that La^(3+)Al^(3+)V_(0)Ti^(3+)defect clusters and Ta^(5+)-Al^(3+)pairs are responsible for the excellent dielectric properties in(Ta+Al+La)co-doped TiO_(2).The results and mechanisms presented in this work open up a feasible route to design high performance CP materials via defect engineering.
