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Effects of B content on wear and corrosion resistance of laser-cladded Co-based alloy coatings

Xia Rong, Zhang Kun, Shu Fengyuan, Zhang Xin, Yan Liying, Li Cheng

Materials Science Poland

2023

Vol. 41, No. 4

13--23

To improve the surface properties of Ti alloy, (Co34Fe8Cr29Ni8Si7)100–x Bx alloy, coatings were prepared by laser cladding. The coatings—mainly composed of TiCr, Fe0.1Ti0.18V0.72, CoTi, Ti2Ni, and TiB—and amorphous phases were investigated in terms of microstructure, wear resistance, and corrosion resistance. The results showed that the microhardness of the Co-based coatings first increased and then decreased with the increase of B content. When the B content was 6%, the microhardness of the coating increased up to 1210 HV0.2 which was 3.4 times that of TC4 alloy substrate. The coatings exhibited diverse wear mechanisms that gradually transitioned from severe fatigue spalling and oxidative wear to slightly abrasive wear. The corrosion current density of Co-based coatings in 3.5 wt% NaCl solution first increased and then decreased as B contents increased. Coatings with 4% B content, however, exhibited the best corrosion resistance, which was most suitable for improving the corrosion resistance of Ti alloy.

Experimental Insight into the Catalytic Mechanism of MFe2O4 (M = Ni, Zn and Co) on the Thermal Decomposition of TKX-50

Hou Xiaoting, Zhang Ming, Zhao Fengqi, Yang Yanjing, An Ting, Li Hui, Pan Qing, Wang Xiaohong, Zhang Kun

Central European Journal of Energetic Materials

2021

Vol. 18, no. 2

223--244

Synthesized dihydroxylammonium 5,5’-bistetrazole-1,1’-diolate (TKX-50) owes its outstanding application prospects in the field of insensitive solid propellants not only to its high energetic performance but also to its low mechanical sensitivity. Based on the excellent catalytic activity of bimetallic iron oxides for the thermal decomposition of TKX-50, the catalytic mechanism of bimetallic iron oxides (NiFe2O4, ZnFe2O4 and CoFe2O4) for TKX-50 pyrolysis has been explored. For this study, the decomposition process of TKX-50, before and after mixing with the bimetallic iron oxides NiFe2O4, ZnFe2O4 and CoFe2O4 was monitored by in-situ FTIR and gas-phase MS-FTIR instruments. Of the different catalysts, ZnFe2O4 gave the best result for reducing the initial decomposition temperature of TKX-50. Additionally, the activation energy of functional group cleavage of TKX-50, before and after mixing with ZnFe2O4, was also calculated for mechanism analysis from the results of the in-situ FTIR measurements. The results showed that the condensate and the gas-phase decomposition products of TKX-50 remained unchanged after mixing with different catalysts, while the activation energy of tetrazole ring cleavage was significantly reduced. The results of this study will be helpful for the rational design of insensitive solid propellant formulations containing TKX-50, and for understanding the pyrolysis mechanisms of TKX-50 before and after mixing with the efficient catalyst ZnFe2O4.

Design and application of facial expression analysis system in empathy ability of children with autism spectrum disorder

Guo Chen, Zhang Kun, Chen Jingying, Xu Ruyi, Gao Lei

Annals of Computer Science and Information Systems

2021

Vol. 25

319--325

Empathy is an important social ability in early childhood development. One of the significant characteristics of children with autism spectrum disorder (ASD) is their lack of empathy, which makes it difficult for them to understand other's emotions and to judge other's behavioral intentions, leading to social disorders. This research designed and implemented a facial expression analysis system that could obtain and analyze the real-time expressions of children when viewing stimulus, and evaluate the empathy differences between ASD children and typical development children. The research results provided new ideas for evaluation of ASD children, and helped to develop empathy intervention plans.