碳化硅(SiC)电子器件的性能和成本受衬底质量影响,因此生长大直径高品质SiC单晶意义重大。物理气相传输(PVT)法是一种常用的生长方法,但其主要面临热场设计与气流控制问题。本工作对电阻加热PVT法生长150 mm SiC单晶完整过程开展数值仿...碳化硅(SiC)电子器件的性能和成本受衬底质量影响,因此生长大直径高品质SiC单晶意义重大。物理气相传输(PVT)法是一种常用的生长方法,但其主要面临热场设计与气流控制问题。本工作对电阻加热PVT法生长150 mm SiC单晶完整过程开展数值仿真研究,建立描述SiC原料热解和再结晶及其多孔结构演变、热-质输运、晶体形貌变化的数理模型,用数值模拟手段研究晶体生长、原料演变与热场变化等过程间的耦合关系。结果显示:原料区侧面高温导致气流不均匀,晶面呈“W”形,原料区底部高温得到均匀气流和微凸晶面;长晶界面通过径向温度变化调节气相组分平衡压力,使晶面生长成等温线形状;晶体生长速率与原料温度、剩余原料量呈正相关。模拟结果与已报道实验结果吻合,对优化生长SiC单晶有指导意义。展开更多
A conductive carbon nanofiber(CNF)paper is described for the actuation of shape recovery of a shape-memory polymer(SMP)by electrically resistive Joule heating.The CNF paper was manufactured using a traditional physica...A conductive carbon nanofiber(CNF)paper is described for the actuation of shape recovery of a shape-memory polymer(SMP)by electrically resistive Joule heating.The CNF paper was manufactured using a traditional physical vapor deposition process and the microscale morphology and structure of the CNF paper were observed using a scanning electron microscope.The CNF paper was found to be porous,with the pore size determined by the weight concentration of CNF.The excellent electrical properties of pure CNF papers and their SMP composites were characterized by the four-point probe method.Shape recovery actuation of this type of SMP composite induced by electrically resistive heating was achieved with a 12 V voltage.Additionally,the thermomechanical properties of the SMP composite were studied with respect to the volume fraction of CNF paper.展开更多
文摘碳化硅(SiC)电子器件的性能和成本受衬底质量影响,因此生长大直径高品质SiC单晶意义重大。物理气相传输(PVT)法是一种常用的生长方法,但其主要面临热场设计与气流控制问题。本工作对电阻加热PVT法生长150 mm SiC单晶完整过程开展数值仿真研究,建立描述SiC原料热解和再结晶及其多孔结构演变、热-质输运、晶体形貌变化的数理模型,用数值模拟手段研究晶体生长、原料演变与热场变化等过程间的耦合关系。结果显示:原料区侧面高温导致气流不均匀,晶面呈“W”形,原料区底部高温得到均匀气流和微凸晶面;长晶界面通过径向温度变化调节气相组分平衡压力,使晶面生长成等温线形状;晶体生长速率与原料温度、剩余原料量呈正相关。模拟结果与已报道实验结果吻合,对优化生长SiC单晶有指导意义。
文摘A conductive carbon nanofiber(CNF)paper is described for the actuation of shape recovery of a shape-memory polymer(SMP)by electrically resistive Joule heating.The CNF paper was manufactured using a traditional physical vapor deposition process and the microscale morphology and structure of the CNF paper were observed using a scanning electron microscope.The CNF paper was found to be porous,with the pore size determined by the weight concentration of CNF.The excellent electrical properties of pure CNF papers and their SMP composites were characterized by the four-point probe method.Shape recovery actuation of this type of SMP composite induced by electrically resistive heating was achieved with a 12 V voltage.Additionally,the thermomechanical properties of the SMP composite were studied with respect to the volume fraction of CNF paper.