Inorganic materials can solve transportable and on-site hydrolytic hydrogen generation issues.CaH_(2)/(Al/Si)composites are preferable due to their notable chemical properties.However,these composites require pretreat...Inorganic materials can solve transportable and on-site hydrolytic hydrogen generation issues.CaH_(2)/(Al/Si)composites are preferable due to their notable chemical properties.However,these composites require pretreatments,an inert environment,and long hours of physical ball milling for high homogeneity and synergistic effects.CaH_(2)also inhibits the hydrolysis reaction by forming its products on the Al/Si surface,which hinders the direct utilization of composites.This work represents the first investigation of NaH-CaH_(2)(Al/Si)fuel composites,which greatly overcome these limitations and can be directly used for on-site hydrogen generation and proton exchange membrane(PEM)fuel cells.The NaH-CaH_(2)(Al/Si)fuel composites were prepared by using a straightforward mixing method with variable composition ratios,showing high H_(2)yield and fuel cell(FC)performance.NaH addition provides the bridge effect,which opens up a new way to enable efficient hydrolysis and greatly enhances the hydrolysis activity of CaH_(2)/(Al/Si)composites.The novel fuel composites(NaH-CaH_(2)/Al)have extraordinary FC performance and a 0.42 W/cm2 peak power density greater than commercial hydrogen generators.It provides high H_(2)yield 84.4%for NaH-CaH_(2)/Al and 82%for NaH-CaH_(2)/Si compared to NaOH-CaH_(2)(Al/Si),NaCl-CaH_(2)(Al/Si),and KCl-CaH_(2)(Al/Si)composites.The NaH bridge effect hinders the direct water contact and stops the formation of Ca(OH)2 around Al/Si,which provides adequate pathways for the CaH_(2)(Al/Si)hydrolysis.The impressive capabilities of novel fuel composites are anticipated to offer practical uses in fuel cells,automobile applications,and portable/on-board H_(2)generation.展开更多
为研究真空等离子喷涂Si/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)环境障涂层试样在涂层受压、涂层受拉时的室温弯曲强度及失效原因,采用超景深三维显微镜、SEM(Scanning Electron Microscope)等方法对喷涂后的试样进行了表征,并测量了涂层孔隙...为研究真空等离子喷涂Si/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)环境障涂层试样在涂层受压、涂层受拉时的室温弯曲强度及失效原因,采用超景深三维显微镜、SEM(Scanning Electron Microscope)等方法对喷涂后的试样进行了表征,并测量了涂层孔隙率;采用拉伸法测试了涂层的结合强度,并采用三点弯曲试验测试了裸材、涂层受压和涂层受拉时的室温弯曲强度。结果表明:Si/Yb_(2)Si_(2)O_(7)/Yb_(2)SiO_(5)涂层与SiC_(f)/SiC复合材料的结合强度为10.13 MPa,拉伸断裂主要在复材表层发生。计算涂层厚度时,涂层受压样的弯曲强度(503.21 MPa)与裸材(506.79 MPa)基本一致;不计算涂层厚度时,涂层受拉样的弯曲强度(499.77 MPa)与裸材一致;EBC涂层整体具有一定的压缩强度,其整体抗拉强度比复材自身抗拉强度小很多。压涂层时,在载荷增加至接近最大载荷时,复材层间发生破坏,并逐步失效,随后涂层发生飞崩,载荷迅速下降,试验停止;拉涂层时,在载荷很小时(约64 N)涂层就被拉开,随着载荷增加,直至接近最大载荷时,层间发生破坏并逐步失效。弯曲试验时复材的主要失效模式是SiC纤维断裂、复材的SiC基体开裂和复材层间撕裂,复材受拉面产生复材厚度方向的纵向裂纹;复材表层沉积的SiC膜层失效模式主要是开裂和剥落;EBC涂层在受压时的主要失效模式是整体飞崩和开裂,在受拉时,涂层在最大应力处断裂为2部分。本研究对含EBC涂层的SiC_(f)/SiC复材的最大弯曲载荷设计具有参考意义.展开更多
得益于高效率优势,混合SiC/Si有源钳位(active neutral point clamped,ANPC)三电平电路拓扑在光储发电系统中应用广泛。但传统混合SiC/Si功率模块中,Si器件的使用限制了效率提升,SiC器件引入后又可能导致热分布不均、电压过冲及振荡等...得益于高效率优势,混合SiC/Si有源钳位(active neutral point clamped,ANPC)三电平电路拓扑在光储发电系统中应用广泛。但传统混合SiC/Si功率模块中,Si器件的使用限制了效率提升,SiC器件引入后又可能导致热分布不均、电压过冲及振荡等问题。提出了一种综合设计方法,结合功率器件损耗均衡与功率模块布局寄生电感优化,以提高混合SiC/Si ANPC电路拓扑的功率模块性能。建立了功率模块损耗模型,并进行热性能优化,降低结温与芯片温差;构建了寄生电感模型,通过优化设计减小寄生电感;研制了基于ANPC拓扑的混合SiC/Si功率模块,并开展电热性能测试。实验结果验证了功率模块在损耗、寄生电感及热分布方面的显著优势。展开更多
The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with B...The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with Bi/Si ratio in low-melting glass was investigated.In addition,the relationships between laser power,low-melting glass solder with different Bi/Si ratios and laser sealing shear strength were revealed.The results show that a decrease in the Bi/Si ratio can cause a contraction of the glass network of the low-melting glass,leading to an increase of its characteristic temperature and a decrease of its coefficient of thermal expansion.During laser sealing,the copper ions in the low-melting glass play an endothermic role.A change in the Bi/Si ratio will affect the valence state transition of the copper ions in the low-melting glass.The absorbance of the low-melting glass does not follow the expected correlation with the Bi/Si ratio,but shows a linear correlation with the content of divalent copper ions.The greater the concentration of divalent copper ions,the greater the absorbance of the low-melting glass,and the lower the laser power required for laser sealing.The shear strength of the low melting glass solder after laser sealing was tested,and it was found that the maximum shear strength of Z1 glass sample was the highest up to 2.67 MPa.展开更多
The effect of Mg/Si mass ratio on the microstructure and mechanical properties of Al-Mg-Si cast aluminum alloys under sub-rapid solidification conditions was investigated.This study utilized four different Mg/Si ratio...The effect of Mg/Si mass ratio on the microstructure and mechanical properties of Al-Mg-Si cast aluminum alloys under sub-rapid solidification conditions was investigated.This study utilized four different Mg/Si ratios:2.83,1.91,1.73,and 1.53.To analyze the evolution of the microstructure,particularly the second phase,various techniques were employed:optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and electron backscatter diffraction(EBSD).Additionally,thermodynamic calculations were performed using the Thermal-calc software to further understand the microstructural changes.Results show that as the Mg/Si ratio decreases from 2.83 to 1.53,α-Al grains become more uniformly distributed.Meanwhile,the morphology of the Mg_(2)Si phases changes from skeletal to short stick shapes with a decreasing aspect ratio.An as-cast Al-Mg-Si alloy with a Mg/Si ratio of 1.53 exhibits high strength,achieving an ultimate tensile strength(UTS)of 320.6 MPa and a yield strength(YS)of 249.9 MPa.The cast alloy with a Mg/Si ratio of 2.83exhibits the highest elongation,reaching 5.31%.This superior elongation is attributed to the uniform distribution of Mg_(2)Si phases,which possess a long skeletal shape.Conversely,the alloy with a Mg/Si ratio of 1.53 demonstrates the lowest elongation,primarily due to the central concentration of Mg_(2)Si phases,which are characterized by their short stick shapes.展开更多
基金financial support granted by the National Natural Science Foundation of China (No. 22402225)the Gusu Innovation and Entrepreneurship Leading Talent Plan(No. ZXL2023193)+2 种基金the Sinano Talents Plan (No. 2022000175)the Guangdong Basic and Applied Basic Research Foundation (No.2023A1515111133)the ANSO Scholarship for Young Talents
文摘Inorganic materials can solve transportable and on-site hydrolytic hydrogen generation issues.CaH_(2)/(Al/Si)composites are preferable due to their notable chemical properties.However,these composites require pretreatments,an inert environment,and long hours of physical ball milling for high homogeneity and synergistic effects.CaH_(2)also inhibits the hydrolysis reaction by forming its products on the Al/Si surface,which hinders the direct utilization of composites.This work represents the first investigation of NaH-CaH_(2)(Al/Si)fuel composites,which greatly overcome these limitations and can be directly used for on-site hydrogen generation and proton exchange membrane(PEM)fuel cells.The NaH-CaH_(2)(Al/Si)fuel composites were prepared by using a straightforward mixing method with variable composition ratios,showing high H_(2)yield and fuel cell(FC)performance.NaH addition provides the bridge effect,which opens up a new way to enable efficient hydrolysis and greatly enhances the hydrolysis activity of CaH_(2)/(Al/Si)composites.The novel fuel composites(NaH-CaH_(2)/Al)have extraordinary FC performance and a 0.42 W/cm2 peak power density greater than commercial hydrogen generators.It provides high H_(2)yield 84.4%for NaH-CaH_(2)/Al and 82%for NaH-CaH_(2)/Si compared to NaOH-CaH_(2)(Al/Si),NaCl-CaH_(2)(Al/Si),and KCl-CaH_(2)(Al/Si)composites.The NaH bridge effect hinders the direct water contact and stops the formation of Ca(OH)2 around Al/Si,which provides adequate pathways for the CaH_(2)(Al/Si)hydrolysis.The impressive capabilities of novel fuel composites are anticipated to offer practical uses in fuel cells,automobile applications,and portable/on-board H_(2)generation.
文摘得益于高效率优势,混合SiC/Si有源钳位(active neutral point clamped,ANPC)三电平电路拓扑在光储发电系统中应用广泛。但传统混合SiC/Si功率模块中,Si器件的使用限制了效率提升,SiC器件引入后又可能导致热分布不均、电压过冲及振荡等问题。提出了一种综合设计方法,结合功率器件损耗均衡与功率模块布局寄生电感优化,以提高混合SiC/Si ANPC电路拓扑的功率模块性能。建立了功率模块损耗模型,并进行热性能优化,降低结温与芯片温差;构建了寄生电感模型,通过优化设计减小寄生电感;研制了基于ANPC拓扑的混合SiC/Si功率模块,并开展电热性能测试。实验结果验证了功率模块在损耗、寄生电感及热分布方面的显著优势。
基金Funded by the National Natural Science Foundation of China(No.52472012)Opening Project of State Silica-Based Materials Laboratory of Anhui Province(No.2022KF11)the Research and Development of Glass Powder for Laser Sealing and Its Sealing Technology(No.K24556)。
文摘The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with Bi/Si ratio in low-melting glass was investigated.In addition,the relationships between laser power,low-melting glass solder with different Bi/Si ratios and laser sealing shear strength were revealed.The results show that a decrease in the Bi/Si ratio can cause a contraction of the glass network of the low-melting glass,leading to an increase of its characteristic temperature and a decrease of its coefficient of thermal expansion.During laser sealing,the copper ions in the low-melting glass play an endothermic role.A change in the Bi/Si ratio will affect the valence state transition of the copper ions in the low-melting glass.The absorbance of the low-melting glass does not follow the expected correlation with the Bi/Si ratio,but shows a linear correlation with the content of divalent copper ions.The greater the concentration of divalent copper ions,the greater the absorbance of the low-melting glass,and the lower the laser power required for laser sealing.The shear strength of the low melting glass solder after laser sealing was tested,and it was found that the maximum shear strength of Z1 glass sample was the highest up to 2.67 MPa.
基金supported by the WQ&UCS (Binzhou)Industrialization Research Institute。
文摘The effect of Mg/Si mass ratio on the microstructure and mechanical properties of Al-Mg-Si cast aluminum alloys under sub-rapid solidification conditions was investigated.This study utilized four different Mg/Si ratios:2.83,1.91,1.73,and 1.53.To analyze the evolution of the microstructure,particularly the second phase,various techniques were employed:optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and electron backscatter diffraction(EBSD).Additionally,thermodynamic calculations were performed using the Thermal-calc software to further understand the microstructural changes.Results show that as the Mg/Si ratio decreases from 2.83 to 1.53,α-Al grains become more uniformly distributed.Meanwhile,the morphology of the Mg_(2)Si phases changes from skeletal to short stick shapes with a decreasing aspect ratio.An as-cast Al-Mg-Si alloy with a Mg/Si ratio of 1.53 exhibits high strength,achieving an ultimate tensile strength(UTS)of 320.6 MPa and a yield strength(YS)of 249.9 MPa.The cast alloy with a Mg/Si ratio of 2.83exhibits the highest elongation,reaching 5.31%.This superior elongation is attributed to the uniform distribution of Mg_(2)Si phases,which possess a long skeletal shape.Conversely,the alloy with a Mg/Si ratio of 1.53 demonstrates the lowest elongation,primarily due to the central concentration of Mg_(2)Si phases,which are characterized by their short stick shapes.
