查看更多>>摘要：Bi2Se3-based flexible thin film with high ther-moelectric performance is promising for the waste heat recovery technology.In this work,a novel post-seleniza-tion method is employed to prepare n-type Bi2Se3 flexible thin films with highly textured structure.The strengthened texture and Se vacancy optimization can be simultaneously achieved by optimizing the selenization temperature.The highly oriented texture leads to the increased carrier mobility and results in a high electric conductivity of～290.47 S·cm-1 at 623 K.Correspondingly,a high Seebeck coefficient(＞110 μW·K-1)is obtained due to the reduced carrier concentration,induced by optimizing vacancy engineering.Consequently,a high power factor of 3.49 μW·cm-1·K-2 at 623 K has been achieved in as-prepared highly-bendable Bi2Se3 flexible thin films sel-enized at 783 K.This study introduces an effective post-selenization method to tune the texture structure and vacancies of Bi2Se3 flexible thin films,and correspondingly achieves high thermoelectric performance.
查看更多>>摘要：In this article,in-situ scanning electron micro-scope characterization of the tensile properties of TiB/Ti-2Al-6Sn titanium matrix composite(TMC)was conducted before and after electroshocking treatment(EST).After EST,the tensile strength increased by 113.2 MPa.The effect of EST on the tensile strength and fracture behavior of TiB was investigated using in-situ characterization of the fracture morphology and crack propagation path of the matrix and TiB.Before EST,TiB fracture introduced cracks that extended into the matrix,resulting in material failure.After EST,the refined TiB improved the bearing capacity of the matrix,thereby improving TMC strength.Moreover,after EST,the cracks were introduced into the matrix,and resulting the fracture of matrix first.With an increase in the external load,cracks in the matrix were observed to propagate to TiB,and the refined TiB was fractured,detached,and pulled out,resulting in the for-mation of pores.Analyzing the propagation path of the main crack after EST showed that the deflection angle of the main crack increased.The microstructure of the frac-ture surface indicated that the fracture of the matrix was plastic,whereas that of TiB was brittle.After EST,the size and area of the dimples increased,confirming the increase in plasticity.The results revealed that the comprehensive mechanical properties of TiB/Ti-2Al-6Sn improved after EST.Hence,EST is an efficient method for tailoring the microstructures and mechanical properties of TMCs.
查看更多>>摘要：This study investigates the influence of high-current pulsed electron beam(HCPEB)modification on the microstructure and shear strength of Cu/CuW joints.Reliable solid-state diffusion bonding of modified-Cu(M-Cu)and modified-CuW(M-CuW)was achieved by HCPEB modification pretreatment at a temperature of 800-900 ℃ and a pressure of 5 MPa for 10-50 min.Experiments demonstrate that HCPEB modification facili-tates the dissolution of W and Cu,resulting in the forma-tion of a Cu0.4W0.6 solid solution and thus enhancing the uniform distribution of microstructures.Additionally,HCPEB-induced defects play a beneficial role in promoting the diffusion process by providing fast diffusion paths for elements.The optimal joints with the maximum shear strength of 213.7 MPa were obtained through bonding M-Cu and M-CuW at 900 ℃ and 5 MPa for 30 min,which attributes to the combined effects of fine-grained strengthening and solid solution strengthening.Overall,the application of HCPEB modification showcases its effec-tiveness in promoting element diffusion and enhancing the mechanical performance of the joints.
查看更多>>摘要：A novel γ-γ'(Ni solid solution—Ni3Al)NiPtAl coating was produced on advanced single-crystal(SC)superalloy N5 by electroplating of a thin Pt coating with～3 μm in thickness followed by heat treatment at 1000 ℃ in vacuum.For comparison,a traditional γ-γ'NiPtAl coating was also produced by electroplating of a thick Pt coating with～6 μm in thickness followed by heat treatment at 1100 ℃ in vacuum.The novel coating has a mass gain of～0.5 mg·cm-2 after 100 h 1-h cyclic oxidation at 1150 ℃,showing better oxidation resistance than the traditional coating.An oxide scale mostly con-sisting of α-Al2O3 grew on the novel coating because the element Cr from the SC alloy substrate contributes to the formation of α-Al2O3.Pt content in the novel coating has significant effect on the oxidation resistance.The opti-mized Pt content in the coating is about 16 at％,which is helpful to reduce the diffusion of harmful elements from the substrate into the coating but also to reduce the cost of the coating.
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