Fracture toughness determines materials' resistance to fracture, which is measured often using impact or bending tests. However, it is difficult to evaluate fracture toughness of coatings and small samples.In this ar...Fracture toughness determines materials' resistance to fracture, which is measured often using impact or bending tests. However, it is difficult to evaluate fracture toughness of coatings and small samples.In this article, using white irons as sample materials, we explore a possible approach of using electron work function(EWF) as an indicator in evaluating fracture toughness of hard metallic materials. This parameter is promising for being utilized to analyze toughness of protective coatings and small objects as well as bulk materials. Through comparison with results obtained from impact tests and elastic modulus measurement, effectiveness of this EWF approach is demonstrated.展开更多
The work functions before and after crystallization of two glassy alloys,Pd83.5Si16.5 and Cu70Ti30 have been measured by means of the con- tact potential difference method in the secondary electron field a...The work functions before and after crystallization of two glassy alloys,Pd83.5Si16.5 and Cu70Ti30 have been measured by means of the con- tact potential difference method in the secondary electron field at room temperature under 10-5 Pa vacuum.The results show that the work functions of both glassy alloys are higher than those of the corresponding crystalline alloys.展开更多
The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A...The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A major challenge to their performance is the corrosion occurring at phase boundaries under harsh operating conditions.This study investigates the effects of pulsed magnetic field treatment(PMT)on improving corrosion resistance at phase boundaries,specifically at the carbide/matrix Co interface,and seeks to clarify the underlying mechanisms.Advanced characterization techniques,including scanning electron microscopy(SEM),in situ transmission electron microscopy(TEM),in situ scanning kelvin probe force microscopy(SKPFM),and density functional theory(DFT)calculations,were employed.PMT samples exhibited no interface corrosion cracking or carbide spalling and showed a significant reduction in corrosion depth.TEM analysis revealed reduced lattice distortion at phase boundaries and a partial transformation of face-centered cubic(FCC)Co to hexagonal closepacked(HCP)Co.The enhanced corrosion resistance at phase boundaries is attributed to changes in the electronic work function(EWF),as determined by SKPFM measurements and DFT calculations.展开更多
In this study, the gradient grain induced by punching deformation and recovery treatment on a cupronickel alloy surface sample were investigated, and their effects on corrosion resistance were measured by atom force m...In this study, the gradient grain induced by punching deformation and recovery treatment on a cupronickel alloy surface sample were investigated, and their effects on corrosion resistance were measured by atom force microscopy(AFM), X-ray diffraction(XRD),electrochemical measurement, electron work function(EWF), and contact electrical resistance(CER). The cupronickel alloy surface experienced punching deformation for 60 min and recovery at 300 ℃ for 1 h to produce gradient surface. The grain size measured by XRD is bigger than that measured by AFM, due to X-ray intensity of95 % produced at the depth of 12-20 μm for the crystal planes of(111),(200), and(220). The gradient grain surface, compared to the original surface, shows a 13.7-fold decrease in passivation current density(i), and corrosion potential(Ec) increases by approximately 9.8 %. These results are attributable to the increase in EWF and formation of passivation film with better adhesion and compactness after treatment.展开更多
通过原位腐蚀观察和基于密度泛函理论的第一性原理计算方法,从微观角度研究了稀土元素铈(Ce)对J5不锈钢中夹杂物的改性和夹杂物诱导腐蚀的机理.采用扫描电子显微镜与能谱分析了稀土元素Ce改性夹杂物的过程中夹杂物成分和类型的变化,观...通过原位腐蚀观察和基于密度泛函理论的第一性原理计算方法,从微观角度研究了稀土元素铈(Ce)对J5不锈钢中夹杂物的改性和夹杂物诱导腐蚀的机理.采用扫描电子显微镜与能谱分析了稀土元素Ce改性夹杂物的过程中夹杂物成分和类型的变化,观察到的代表夹杂物为Ce Al O3-Ce2O2S、Ce2O3-Ce2O2S、Mn S等.根据形成能计算,经稀土元素Ce处理后,生成了稳定的Ce2O3、Ce2O2S、Ce Al O3夹杂物.通过表面能判断了晶面的稳定性,Fe(100)-2面的表面能经收敛测得为2.4374 J·m-2,该晶面的功函数为4.7352 e V.通过对比夹杂物与钢基体的功函数与计算电势差,分析了不同含Ce夹杂物诱导点蚀的趋势,探讨了不同原子位置、原子数量和不同slab模型对功函数的影响.研究表明,与Fe(100)-2面的电子功函数相比,Mn S以及改性后3种夹杂物Ce S、Ce2O3和Ce2O2S电势差大多小于0,Ce Al O3的电势差在0 e V左右.夹杂物不同晶面对功函数影响很大,O、S等非金属原子数量多的晶面功函数平均值较高,添加稀土元素Ce可以有效降低晶面功函数.5种夹杂物和钢基体的平均功函数大小顺序为Ce Al O3>Fe>Mn S>Ce S>Ce2O2S>Ce2O3.结合不锈钢中复合夹杂物的实验结果可知,Ce2O3诱导点蚀发生的概率最高,Ce Al O3可以有效提高钢的耐腐蚀能.展开更多
钼具有高熔点、低的热膨胀系数和极佳的稳定性,在等离子体推进和电真空器件领域具有广阔的应用前景,其二次电子发射特性也逐渐引起了研究者们的关注。本研究首先对钼的二次电子发射系数(secondary electron yield, SEY)和二次电子能谱(s...钼具有高熔点、低的热膨胀系数和极佳的稳定性,在等离子体推进和电真空器件领域具有广阔的应用前景,其二次电子发射特性也逐渐引起了研究者们的关注。本研究首先对钼的二次电子发射系数(secondary electron yield, SEY)和二次电子能谱(secondaryelectronspectrum, SES)展开实验研究,其次利用相关唯象模型对测试数据进行分析;最后建立钼SEY的蒙特卡罗模型,用于分析功函数对SEY的影响规律。结果表明:钼SEY的最大值为1.77,相比镀银铝合金明显降低。当入射电子能量改变时,SES中真二次电子峰的最可几能量基本不变,而弹性背散射电子峰的位置和强度均随之改变。在各类二次电子中,真二次电子受功函数的影响最大。展开更多
利用原子力显微镜、电化学测试、电子功函数和钝化膜接触电阻显微划擦方法研究了机械剧烈压入形变和稳定化处理对Cu30Ni合金表面梯度组织和耐腐蚀行为的影响。结果发现,对机械剧烈压入和稳定化处理的试样,表层晶粒尺寸呈梯度变化。从基...利用原子力显微镜、电化学测试、电子功函数和钝化膜接触电阻显微划擦方法研究了机械剧烈压入形变和稳定化处理对Cu30Ni合金表面梯度组织和耐腐蚀行为的影响。结果发现,对机械剧烈压入和稳定化处理的试样,表层晶粒尺寸呈梯度变化。从基体到表层,随着晶粒尺寸从40μm逐渐细化到50 nm,电子功函数从4.55 e V提高至4.85 e V,表面电子稳定性提高,钝化膜粘附性能和致密性较好,耐腐蚀性能提高,ip从1.750×10-5A/cm2逐渐降低到0.119×10-5A/cm2,而腐蚀电位EV从-212 m V提高到-193 m V,这是由于机械剧烈压入形变和稳定化处理诱发晶粒呈梯度细化和组织结构中大量结构缺陷存在。展开更多
提出了基于第一性原理的密度泛函理论框架下的广义梯度近似投影缀加波赝势法,在结构优化的基础上采用平板模型计算了GaAs(110)表面单一吸附0.5 ML Cs元素、单一吸附0.5 ML O元素及0.5 ML Cs、0.5 ML O共吸附系统的特定吸附位、吸附系统...提出了基于第一性原理的密度泛函理论框架下的广义梯度近似投影缀加波赝势法,在结构优化的基础上采用平板模型计算了GaAs(110)表面单一吸附0.5 ML Cs元素、单一吸附0.5 ML O元素及0.5 ML Cs、0.5 ML O共吸附系统的特定吸附位、吸附系统总能及吸附系统的电子结构。吸附系统总能的计算结果对比及电子结构图表明:当Cs、O元素吸附量在GaAs(110)表面达到Θ=1 ML时,它们并非各自在表面形成局域畴形态的竞争性共化学吸附,而是将在表面形成混合均匀相的协同共化学吸附。采用偶极子校正进一步计算三种吸附系统的功函数分别是4.423 e V、5.749 e V、4.377 e V,从而得出GaAs光电阴极制备过程中提高并保持光电阴极发射性能的方法及机理。展开更多
基金financial support from the Natural Science and Engineering Research Council of CanadaCamber Technology Corporation+3 种基金Suncor Energy Inc.Shell Canada Ltd.Magna International Inc.Volant Products Inc.
摘要Fracture toughness determines materials' resistance to fracture, which is measured often using impact or bending tests. However, it is difficult to evaluate fracture toughness of coatings and small samples.In this article, using white irons as sample materials, we explore a possible approach of using electron work function(EWF) as an indicator in evaluating fracture toughness of hard metallic materials. This parameter is promising for being utilized to analyze toughness of protective coatings and small objects as well as bulk materials. Through comparison with results obtained from impact tests and elastic modulus measurement, effectiveness of this EWF approach is demonstrated.
摘要The work functions before and after crystallization of two glassy alloys,Pd83.5Si16.5 and Cu70Ti30 have been measured by means of the con- tact potential difference method in the secondary electron field at room temperature under 10-5 Pa vacuum.The results show that the work functions of both glassy alloys are higher than those of the corresponding crystalline alloys.
基金financially supported by the National Key Research and Development Program of China(No.2020YFA0714900)the Joint Fund of the Ministry of Education(No.8091B012201)
摘要The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A major challenge to their performance is the corrosion occurring at phase boundaries under harsh operating conditions.This study investigates the effects of pulsed magnetic field treatment(PMT)on improving corrosion resistance at phase boundaries,specifically at the carbide/matrix Co interface,and seeks to clarify the underlying mechanisms.Advanced characterization techniques,including scanning electron microscopy(SEM),in situ transmission electron microscopy(TEM),in situ scanning kelvin probe force microscopy(SKPFM),and density functional theory(DFT)calculations,were employed.PMT samples exhibited no interface corrosion cracking or carbide spalling and showed a significant reduction in corrosion depth.TEM analysis revealed reduced lattice distortion at phase boundaries and a partial transformation of face-centered cubic(FCC)Co to hexagonal closepacked(HCP)Co.The enhanced corrosion resistance at phase boundaries is attributed to changes in the electronic work function(EWF),as determined by SKPFM measurements and DFT calculations.
基金financially supported by the National Natural Science Foundation of China (No.51301086)the Natural Science Foundation of Jiangsu Province (No. BK20130738)Jiangsu Province Key Laboratory of High-End Structural Materials Foundation(No.hsm1405)
摘要In this study, the gradient grain induced by punching deformation and recovery treatment on a cupronickel alloy surface sample were investigated, and their effects on corrosion resistance were measured by atom force microscopy(AFM), X-ray diffraction(XRD),electrochemical measurement, electron work function(EWF), and contact electrical resistance(CER). The cupronickel alloy surface experienced punching deformation for 60 min and recovery at 300 ℃ for 1 h to produce gradient surface. The grain size measured by XRD is bigger than that measured by AFM, due to X-ray intensity of95 % produced at the depth of 12-20 μm for the crystal planes of(111),(200), and(220). The gradient grain surface, compared to the original surface, shows a 13.7-fold decrease in passivation current density(i), and corrosion potential(Ec) increases by approximately 9.8 %. These results are attributable to the increase in EWF and formation of passivation film with better adhesion and compactness after treatment.
摘要通过原位腐蚀观察和基于密度泛函理论的第一性原理计算方法,从微观角度研究了稀土元素铈(Ce)对J5不锈钢中夹杂物的改性和夹杂物诱导腐蚀的机理.采用扫描电子显微镜与能谱分析了稀土元素Ce改性夹杂物的过程中夹杂物成分和类型的变化,观察到的代表夹杂物为Ce Al O3-Ce2O2S、Ce2O3-Ce2O2S、Mn S等.根据形成能计算,经稀土元素Ce处理后,生成了稳定的Ce2O3、Ce2O2S、Ce Al O3夹杂物.通过表面能判断了晶面的稳定性,Fe(100)-2面的表面能经收敛测得为2.4374 J·m-2,该晶面的功函数为4.7352 e V.通过对比夹杂物与钢基体的功函数与计算电势差,分析了不同含Ce夹杂物诱导点蚀的趋势,探讨了不同原子位置、原子数量和不同slab模型对功函数的影响.研究表明,与Fe(100)-2面的电子功函数相比,Mn S以及改性后3种夹杂物Ce S、Ce2O3和Ce2O2S电势差大多小于0,Ce Al O3的电势差在0 e V左右.夹杂物不同晶面对功函数影响很大,O、S等非金属原子数量多的晶面功函数平均值较高,添加稀土元素Ce可以有效降低晶面功函数.5种夹杂物和钢基体的平均功函数大小顺序为Ce Al O3>Fe>Mn S>Ce S>Ce2O2S>Ce2O3.结合不锈钢中复合夹杂物的实验结果可知,Ce2O3诱导点蚀发生的概率最高,Ce Al O3可以有效提高钢的耐腐蚀能.
摘要钼具有高熔点、低的热膨胀系数和极佳的稳定性,在等离子体推进和电真空器件领域具有广阔的应用前景,其二次电子发射特性也逐渐引起了研究者们的关注。本研究首先对钼的二次电子发射系数(secondary electron yield, SEY)和二次电子能谱(secondaryelectronspectrum, SES)展开实验研究,其次利用相关唯象模型对测试数据进行分析;最后建立钼SEY的蒙特卡罗模型,用于分析功函数对SEY的影响规律。结果表明:钼SEY的最大值为1.77,相比镀银铝合金明显降低。当入射电子能量改变时,SES中真二次电子峰的最可几能量基本不变,而弹性背散射电子峰的位置和强度均随之改变。在各类二次电子中,真二次电子受功函数的影响最大。
摘要利用原子力显微镜、电化学测试、电子功函数和钝化膜接触电阻显微划擦方法研究了机械剧烈压入形变和稳定化处理对Cu30Ni合金表面梯度组织和耐腐蚀行为的影响。结果发现,对机械剧烈压入和稳定化处理的试样,表层晶粒尺寸呈梯度变化。从基体到表层,随着晶粒尺寸从40μm逐渐细化到50 nm,电子功函数从4.55 e V提高至4.85 e V,表面电子稳定性提高,钝化膜粘附性能和致密性较好,耐腐蚀性能提高,ip从1.750×10-5A/cm2逐渐降低到0.119×10-5A/cm2,而腐蚀电位EV从-212 m V提高到-193 m V,这是由于机械剧烈压入形变和稳定化处理诱发晶粒呈梯度细化和组织结构中大量结构缺陷存在。
摘要提出了基于第一性原理的密度泛函理论框架下的广义梯度近似投影缀加波赝势法,在结构优化的基础上采用平板模型计算了GaAs(110)表面单一吸附0.5 ML Cs元素、单一吸附0.5 ML O元素及0.5 ML Cs、0.5 ML O共吸附系统的特定吸附位、吸附系统总能及吸附系统的电子结构。吸附系统总能的计算结果对比及电子结构图表明:当Cs、O元素吸附量在GaAs(110)表面达到Θ=1 ML时,它们并非各自在表面形成局域畴形态的竞争性共化学吸附,而是将在表面形成混合均匀相的协同共化学吸附。采用偶极子校正进一步计算三种吸附系统的功函数分别是4.423 e V、5.749 e V、4.377 e V,从而得出GaAs光电阴极制备过程中提高并保持光电阴极发射性能的方法及机理。