Microstructure Evolution and Mechanical Properties of Lean Duplex Stainless Steel Bars Prepared by a Short Process

Xinghai Zhang,Qingdi Gong,Jiaqi Li,Chunting Liu,Jingyuan Li 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9

The effect of cold deformation and annealing temperature on the microstructure evolution and mechanical properties isshown in this research together with a unique short strategy for manufacturing lean duplex stainless steel bars. Furthermore,the effects of post-weld heat treatment (PWHT) and cooling treatments on the microstructure and mechanical properties ofLDX 2101 bars are being investigated. The results demonstrate that the austenite produces a large number of deformationtwins and strain-induced martensite (SIM) as cold deformation increases, and the SIM and austenite follow the traditionalK–S and N–W orientation relationships. The best mechanical properties overall are achieved in LDX 2101 bars that havebeen annealed at 1020 °C. Moreover, short-time PWHT improves the austenite proportion in the heat-affected zone andweld metal, and PWHT can greatly enhance the overall mechanical properties of the welded joints. Additionally, the optimalheat treatment temperature of the welded joints is 1050–1080 ℃. Furthermore, compared to those treated with air cooling,the mechanical properties of the welded joints treated with water quenching following flash butt welding are superior. As aresult, it is recommended that following flash butt welding, the welded joints are given a water-quenching treatment.

Fabrication of belt-like VO2(M)@C core-shell structured composite to improve the electrochemical properties of VO2(M)

Yifu Zhang,Chongxue Chen,Juecheng Zhang,Ling Hu,Weibing Wu,Yalan Zhong,Yuliang Cao,Xinghai Liu,Chi Huang 한국물리학회 2013 Current Applied Physics Vol.13 No.1

VO2(M) nanobelts encapsulated into carbon coreeshell structured composite (VO2(M)@C) was successfully synthesized by the thermal treatment with the precursor V3O7$H2O@C composite under the inert atmosphere. The as-obtained sample was characterized by XRD, EDS, EA, FT-IR, Raman, SEM and TEM measurements. The core exhibited monoclinic phase VO2(M) and the carbon coated on the surface of VO2(M) was amorphous. The average thickness of carbon was about 18.5 nm. The possible formation mechanism of VO2(M)@C was proposed as that the reaction underwent the solid state reaction by the interface reaction between V3O7 core and carbon shell. Furthermore, VO2(M) and VO2(M)@C composite were explored as the cathode materials to apply in lithium-ion batteries, indicating that the VO2(M)@C composite electrode exhibited the better electrochemical properties than that of pure VO2(M), achieving the aim of improving the electrochemical properties of VO2(M).

Improvement of the electrochemical properties of V_3O_7ㆍH_2O nanobelts for Li battery application through synthesis of V_3O_7@C core-shell nanostructured composites

Yifu Zhang,Min Zhou,Meijuan Fan,Chi Huang,Chongxue Chen,Yuliang Cao,Houbin Li,Xinghai Liu 한국물리학회 2011 Current Applied Physics Vol.11 No.5

V_3O_7ㆍH_2O@C core-shell structured composites have been successfully synthesized using V_3O_7ㆍH_2O nanobelts as the cores and glucose as the source of carbon in the presence of sodium lauryl sulfate (SDS). The as-obtained V_3O_7ㆍH_2O@C core-shell materials were characterized by X-ray powder diffraction (XRD),transmission electron microscopy (TEM), elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR) and Raman spectrum. The thickness of the carbon shell can be controlled by the hydrothermal reaction time and the quantity of glucose. The surfactants have great influence on fabricating V_3O_7ㆍH_2O@C core-shell composites, which have been discussed in detail. V_3O_7@C composites were subsequently obtained through thermal treatment with V_3O_7ㆍH_2O@C. The electrochemical properties of V_3O_7@C core-shell composites were studied, indicating that the discharge capacity is still 151.2 mAh/g after 45 cycles, which is better than that of pure V_3O_7ㆍH_2O nanobelts.

Belt-like VO2(M) with a rectangular cross section: A new route to prepare, the phase transition and the optical switching properties

Yifu Zhang,Meijuan Fan,Fei Niu,Weibing Wu,Chi Huang,Xinghai Liu,Houbin Li,Xin Liu 한국물리학회 2012 Current Applied Physics Vol.12 No.3

Belt-like VO2(M) with a rectangular cross section was first synthesized by the irreversible transformation of VO2(A) at the elevated temperatures under the inert atmosphere to the best of our knowledge. The asobtained samples were characterized by a combination of techniques including XRD, SEM and TEM. The processes of converting VO2(A) to VO2(M) were briefly discussed. The as-obtained VO2(M) has belt-like morphology with a rectangular cross section with typical lengths up to several tens of micrometers,widths ranging from tens of nanometers to several micrometers, and thicknesses about 60e150 nm. The morphology and size of the VO2(M) were dependent on that of the precursor VO2(A). The phase transition properties of VO2(M) were investigated by DSC, indicating that it exhibited a strong phase transition at 67.9 ℃ in the heating cycle and 61.1 ℃ in the cooling cycle. Furthermore, the optical switching property of VO2(M) was studied by the variable-temperature infrared spectra, and it was found that the as-obtained VO2(M) could be used as the optical switch.

Microfluidic continuous flow synthesis of 1,5-ditosyl-1,5-diazocane- 3,7-dione using response surface methodology

Yang Zou,Tao Zhang,Guannan Wang,Mengwen Zhou,Yabo Xiong,Shaoyun Huang,Houbin Li,Xinghai Liu 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.82 No.-

3,3,7,7-tetrakis(difluoroamino) octahydro-1,5-dinitro-1,5-diazocine (HNFX) is a high-density energeticoxidizer with four difluoroamino groups (-NF2). In this study, 1,5-ditosyl-1,5-diazocane-3,7-dione, as animportant intermediate for synthesis of HNFX, was successfully synthesized using Swern oxidation in atraditional batch reactor and a continuousflow microreactor, respectively. 1,5-dotosyl-1,5-diazocane-3,7-dione was characterized by HPLC, FTIR, 1H NMR, 13C NMR, Mass spectrometry, and X-ray crystaldiffraction. Compared with the traditional batch reactor, the microreactor showed several advantages,including less reaction time, milder reaction temperature, higher yield and selectivity for 1,5-ditosyl-1,5-diazocane-3,7-dione. Moreover, the microreactor could ensure the safer and large-scale industrialproduction of 1,5-ditosyl-1,5-diazocane-3,7-dione. However, some solids produced in Swern oxidationwhich might block the channels (diameter of 0.3 mm) in the microreactor. To overcome the challenges,the experimental device was modified to suit for Swern oxidation, contributing to wider application ofthe microreactor. Besides, response surface methodology (RSM) was introduced and an appropriatemathematical model was built to optimize experimental conditions. The optimum experimentalparameters were recommended as 7.8 C for the reaction temperature, 7.7 mL/min for theflow rate, and6% for the concentration of oxalyl chloride. The actual yield of 1,5-ditosyl-1,5-diazocane-3,7-dione was89.7%, which was in great agreement with the highest predicted yield (90.1%).

Backstepping Based Trajectory Tracking Control of a TBM Steel Arch Splicing Manipulator

Yuxi Chen,Guofang Gong,Xinghai Zhou,Yakun Zhang,Weiqiang Wu 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.2

At present, the splicing of steel arches for open-type TBM suffers from the problems of labor-intensive, time-consuming, low efficiency and greater potencial risk to workers. Rock-fall and collapse caused by untimely support is still one of the main construction accidents. In this paper, a novel steel arch splicing manipulator is developed for unmanned and automated steel arch splicing, and a backstepping method based cascade control strategy is proposed to improve the trajectory tracking control performance. Firstly, the inner-loop controller is designed to compensate the flow coupling between each joint-driven hydraulic cylinder based on dynamic analysis and feedback linearization. Secondly, the adaptive robust controller is adopted for outer-loop controller design to deal with parametric uncertainties and external disturbances. Finally, the system stability is proved by Lyapunov function, then comparative experiments are conducted to verify the effectiveness and superiority of the proposed control scheme. It can be concluded that the proposed controller has a better trajectory tracking control performance, while the control input is much smoother than that of traditional PID controller.