Effect of Y₂O₃ addition on the microstructure and density of AgSnO₂ contact material

Xianhui Wang,Juntao Zou,Shuhua Liang,Zhikang Fan,Peng Xiao 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6

AgSnO2-Y2O3 compound powders were prepared by a mechanical alloying (MA) method, AgSnO2-Y2O3 contact material was fabricated by pressing, sintering, repressing and resintering, the effect of Y2O3 addition, repressing and resintering on the microstructure and density of AgSnO2 contact material was investigated. The results show that there are drastic dedensifications or swelling, cracks and pores in AgSnO2 contact material fabricated by powder metallurgy, which thus has a lower density. The addition of Y2O3 is helpful in improving the microstructure and density significantly. The density increases significantly after repressing and resintering, and can reach 8.42 g/cm3. AgSnO2-Y2O3 compound powders were prepared by a mechanical alloying (MA) method, AgSnO2-Y2O3 contact material was fabricated by pressing, sintering, repressing and resintering, the effect of Y2O3 addition, repressing and resintering on the microstructure and density of AgSnO2 contact material was investigated. The results show that there are drastic dedensifications or swelling, cracks and pores in AgSnO2 contact material fabricated by powder metallurgy, which thus has a lower density. The addition of Y2O3 is helpful in improving the microstructure and density significantly. The density increases significantly after repressing and resintering, and can reach 8.42 g/cm3.

Solidification Structure and Segregation of High Magnetic Induction Grain-Oriented Silicon Steel

Xin Li,Min Wang,YanPing Bao,Jian Gong,Xianhui Wang,Pang Weiguang 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6

The solidification structure and centerline segregation of high magnetic induction grain-oriented silicon steel slabs werestudied to describe the characteristics of solidification and compare the degree of centerline segregation of continuouslycast slabs. Industrial experiments were conducted to investigate the solidification behavior of slabs by secondary coolingsegment electromagnetic stirring. Three typical slabs were produced by S-EMS with current intensities of 0, 200, and 350 A. Molten steel cast at a low stirring intensity (0 A) resulted in a coarse structure relative to those cast at higher stirring intensities(200 and 350 A). The centerline segregation of carbon and silicon markedly increased with increases in S-EMS currentintensity. Composition distribution by electron probe microanalysis identified segregation spots as the sources of centerlinesegregation. Experimental results indicate that to optimize the centerline segregation of grain-oriented silicon steel slabs,the columnar crystal zone should be enlarged and the equiaxed crystal zone be reduced.

Probabilistic design optimization of wind turbine gear transmission system based on dynamic reliability

Chen Huitao,Fan Junkai,Jing Shuangxi,Wang Xianhui 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2

In this paper, a probabilistic design optimization method for wind power gear drive system has been put forward based on the dynamic reliability. A pure torsional dynamic model of 1.5 MW wind turbine gear transmission system is developed which is based on lumped parameter method with incorporation of gear meshing stiffness and transmission error. By taking the wind load and the gear parameters as random variables, the variation in dynamic reliability of the system with time is obtained. The probabilistic optimization design model of the wind turbine gear transmission system with minimum displacement and volume is built. The parameters affecting the dynamic performance and reliability are taken as optimization design variables. The system reliability, the effects of random parameters on the reliability, the normal meshing condition and gear strength are taken as constraint conditions. We choose the gear transmission system of a 1.5 MW wind turbine for the system optimization and experimental verification. The results show that the system optimization based on dynamic reliability can reduce the volume of the system by 17.94 % and the system reliability is also guaranteed. Moreover, the vibration of each component of the system is reduced which is beneficial for smooth operation of the gear transmission system of wind turbine.

Comparison of Creep Fracture Behavior Between Selective Laser Melted and Forged Alloy 230 After Testing at 1200 °C

Yijiang Zeng,Yu Pan,Ning Wang,Jian Chen,Xianhui Cai 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.5

The creep fracture behavior between selective laser melted (SLMed) and forged alloy 230 after testing at 1200 °C under differentapplied stresses was compared. The results showed that both the creep behavior of SLMed and forged alloy 230 followedthe power law and obeyed the Monkman–Grant relation. The SLMed samples parallel to the building direction exhibitedsuperior creep resistance than those perpendicular to the building direction, and the forged samples were in between, whilethey all exhibited poor creep ductility compared with that of the forged samples. Furthermore, the relations of applied stressand maximum allowable creep lifetime could be built to evaluate the creep resistance of the alloys. The SLMed samplesparallel to the building direction showed discrete trans/intergranular cracks, while those perpendicular to the building directionand forged materials depicted continuous and discrete intergranular cracks, respectively. Furthermore, the creep fracturemodes at different loadings were revealed by correlating the creep damage tolerance factor with the fractured microstructure. In addition, the effects of the initial microstructure characteristics, such as grain morphology, grain boundaries, grain size,internal defects and precipitates, on the creep strength and life at high temperatures were presented and analyzed.

Structure and Properties of Konjac Glucomannan/Galactoglucomannan Nanofiber Membrane

Yi Yuan,Xin Hong,Ruojun Mu,Jingni Gong,Lin Wang,Rongxun Huang,Jiayu Wu,Yongsheng Ni,Xianhui Wu,Jie Pang 한국고분자학회 2017 Macromolecular Research Vol.25 No.10

Konjac glucomannan (KGM)/galactoglucomannan (GGM) nanofiber membranes were obtained through electrospinning technology. Rheological properties of KGM/GGM solutions were observed by using a rotary rheometer. The apparent morphological, characteristic group and thermal stability of nanofiber membranes were studied through scanning electron microscopy (SEM), Fourier transform infrared spectoscopy (FTIR) and differential scanning calorimeter (DSC) respectively. The physical and mechanical properties were also evaluated. Results revealed that the addition of GGM did not significantly affect the rheological properties of electrospinning solution. Increase in the amount of GGM in the nanofiber membrane resulted in gradual smoothening, uniformity and decrease in the number of nodes. KGM interacts with GGM through hydrogen-bond. Addition of GGM markedly enhanced the thermal stability, physical and mechanical properties of the nanofiber membrane. The study showed that the KGM/GGM nanofiber membrane have good potential for use in developing membrane based materials.

Propagating and evanescent waves in a functionally graded nanoplate based on nonlocal theory

Cancan Liu,Jiangong Yu,Bo Zhang,Xiaoming Zhang,Xianhui Wang Techno-Press 2023 Advances in nano research Vol.14 No.5

The purpose of this paper is to present the analysis of propagating and evanescent waves in functionally graded (FG) nanoplates with the consideration of nonlocal effect. The analytical integration nonlocal stress expansion Legendre polynomial method is proposed to obtain complete dispersion curves in the complex domain. Unlike the traditional Legendre polynomial method that expanded the displacement, the presented polynomial method avoids employing the relationship between local stress and nonlocal stress to construct boundary conditions. In addition, the analytical expressions of numerical integrations are presented to improve the computational efficiency. The nonlocal effect, inhomogeneity of medium and their interactions on wave propagation are studied. It is found that the nonlocal effect and inhomogeneity of medium reduce the frequency bandwidth of complex evanescent Lamb waves, and make complex evanescent Lamb waves have a higher phase velocity at low attenuation. The occurrence of intersections of propagating Lamb wave in the nonlocal homogeneous plate needs to satisfy a smaller Poisson's ratio condition than that in the classical elastic theory. In addition, the inhomogeneity of medium enhances the nonlocal effect. The conclusions obtained can be applied to the design and dynamic response evaluation of composite nanostructures.

TGF-β1/IL-11/MEK/ERK signaling mediates senescence-associated pulmonary fibrosis in a stress-induced premature senescence model of Bmi-1 deficiency

Haiyun Chen,Jialong Liang,Xin Gu,Jiawen Zhou,Chunfeng Xie,Xianhui Lv,Rong Wang,Qing Liu,Zhiyuan Mao,Haijian Sun,Guoping Zuo,Dengshun Miao,Jianliang Jin 생화학분자생물학회 2020 Experimental and molecular medicine Vol.52 No.-

To study whether TGF-β1/IL-11/MEK/ERK (TIME) signaling mediates senescence-associated pulmonary fibrosis (SAPF) in Bmi-1-deficient (Bmi-1−/−) mice and determines the major downstream mediator of Bmi-1 and crosstalk between p16INK4a and reactive oxygen species that regulates SAPF, phenotypes were compared among 7-week-old p16INK4a and Bmi-1 double-knockout, N-acetylcysteine (NAC)-treated Bmi-1−/−, Bmi-1−/−, and wild-type mice. Pulmonary fibroblasts and alveolar type II epithelial (AT2) cells were used for experiments. Human pulmonary tissues were tested for type Ι collagen, α-smooth muscle actin (α-SMA), p16INK4a, p53, p21, and TIME signaling by using enzyme-linked immunosorbent assay (ELISA). Our results demonstrated that Bmi-1 deficiency resulted in a shortened lifespan, ventilatory resistance, poor ventilatory compliance, and SAPF, including cell senescence, DNA damage, a senescence-associated secretory phenotype and collagen overdeposition that was mediated by the upregulation of TIME signaling. The signaling stimulated cell senescence, senescence-related secretion of TGF-β1 and IL-11 and production of collagen 1 by pulmonary fibroblasts and the epithelial-to-mesenchymal transition of AT2 cells. These processes were inhibited by anti-IL-11 or the MEK inhibitor PD98059. NAC treatment prolonged the lifespan and ameliorated pulmonary dysfunction and SAPF by downregulating TIME signaling more than p16INK4a deletion by inhibiting oxidative stress and DNA damage and promoting ubiquitinproteasome degradation of p16INK4a and p53. Cytoplasmic p16INK4a accumulation upregulated MEK/ERK signaling by inhibiting the translocation of pERK1/2 (Thr202/Tyr204) from the cytoplasm to the nucleus in senescent fibroblasts. The accumulation of collagen 1 and α-SMA in human lungs accompanied by cell senescence may be mediated by TIME signaling. Thus, this signaling in aging fibroblasts or AT2 cells could be a therapeutic target for preventing SAPF.