Hot-dip aluminizing（HDA） is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been repor...Hot-dip aluminizing（HDA） is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions： an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al_7Cr and Al_3Fe dispersed in an Al matrix. Twinning was observed in both the Al_7Cr and the Al_3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe_2Al_5, Al_7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed.展开更多
An optical phased array(OPA)featuring all-solid-state beam steering is a promising component for light detection and ranging(LiDAR).There exists an increasing demand for panoramic perception and rapid target recogniti...An optical phased array(OPA)featuring all-solid-state beam steering is a promising component for light detection and ranging(LiDAR).There exists an increasing demand for panoramic perception and rapid target recognition in intricate LiDAR applications,such as security systems and self-driving vehicles.However,the majority of existing OPA approaches suffer from limitations in field of view(FOV)and do not explore parallel scanning,thus restricting their potential utility.Here,we combine a two-dimensional(2D)grating with an FOV-synthetization concept to design a silicon-based top-facing OPA for realizing a wide cone-shaped 360°FOV.By utilizing four OPA units sharing the 2D grating as a single emitter,four laser beams are simultaneously emitted upwards and manipulated to scan distinct regions,demonstrating seamless beam steering within the lateral 360°range.Furthermore,a frequency-modulated dissipative Kerr-soliton(DKS)microcomb is applied to the proposed multi-beam OPA,exhibiting its capability in large-scale parallel multi-target coherent detection.The comb lines are spatially dispersed with a 2D grating and separately measure distances and velocities in parallel,significantly enhancing the parallelism.The results showcase a ranging precision of 1 cm and velocimetry errors of less than 0.5 cm/s.This approach provides an alternative solution for LiDAR with an ultra-wide FOV and massively parallel multi-target detection capability.展开更多
文摘Hot-dip aluminizing（HDA） is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions： an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al_7Cr and Al_3Fe dispersed in an Al matrix. Twinning was observed in both the Al_7Cr and the Al_3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe_2Al_5, Al_7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed.
基金National Key Research and Development Program of China(2022YFA1404001)National Natural Science Foundation of China(62135004)Key Research and Development Program of Hubei Province(2021BAA005)。
文摘An optical phased array(OPA)featuring all-solid-state beam steering is a promising component for light detection and ranging(LiDAR).There exists an increasing demand for panoramic perception and rapid target recognition in intricate LiDAR applications,such as security systems and self-driving vehicles.However,the majority of existing OPA approaches suffer from limitations in field of view(FOV)and do not explore parallel scanning,thus restricting their potential utility.Here,we combine a two-dimensional(2D)grating with an FOV-synthetization concept to design a silicon-based top-facing OPA for realizing a wide cone-shaped 360°FOV.By utilizing four OPA units sharing the 2D grating as a single emitter,four laser beams are simultaneously emitted upwards and manipulated to scan distinct regions,demonstrating seamless beam steering within the lateral 360°range.Furthermore,a frequency-modulated dissipative Kerr-soliton(DKS)microcomb is applied to the proposed multi-beam OPA,exhibiting its capability in large-scale parallel multi-target coherent detection.The comb lines are spatially dispersed with a 2D grating and separately measure distances and velocities in parallel,significantly enhancing the parallelism.The results showcase a ranging precision of 1 cm and velocimetry errors of less than 0.5 cm/s.This approach provides an alternative solution for LiDAR with an ultra-wide FOV and massively parallel multi-target detection capability.
