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Phase separation and rapid solidification of liquid Cu_(60)Fe_(30)Co_(10) ternary peritectic alloy

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Science China(physics,Mechanics & Astronomy) 2007年第4期50卷 509-518页

作者： DAI FuPing, CAO ChongDe & wei bingbo department of applied {4.,{4., xi’an 710072, China 1. department of applied physics Northwestern Polytechnical University Xi’an 710072 China

The metastable liquid phase separation and rapid solidification of Cu60Fe30Co10 ternary peritectic alloy were investigated by using the drop tube technique and the differential scanning calorimetry method. It was found that the critical temperature of metastable liquid phase separation in this alloy is 1623.5 K, and the two sepa- rated liquid phases solidify as Cu(Fe,Co) and Fe(Cu,Co) solid solutions, respec- tively. The undercooling and cooling rate of droplets processed in the drop tube increase with the decrease of their diameters. During the drop tube processing, the structural morphologies of undercooled droplets are strongly dependent on the cooling rate. With the increase of the cooling rate, Fe(Cu,Co) spheres are refined greatly and become uniformly dispersed in the Cu-rich matrix. The calculations of Marangoni migration velocity (VM) and Stokes motion velocity (VS) of Fe(Cu,Co) droplets indicated that Marangoni migration contributes more to the coarsening and congregation of the minor phase during free fall. At the same undercooling, the VM/VS ratio increases drastically as Fe(Cu,Co) droplet size decreases. On the other hand, a larger undercooling tends to increase the VM/VS value for Fe(Cu,Co) drop- lets with the same size.

关键词： ternary peritectic alloy metastable immiscibility rapid solidification reduced gravity liquid phase separation

Digital image processing of sectorial oscillations for acoustically levitated drops and surface tension measurement

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Science China(physics,Mechanics & Astronomy) 2010年第12期53卷 2260-2265页

作者： SHEN Changle, xiE WenJun & wei bingbo department of {4. physics,{4., xi’an 710072, China 1. department of applied physics Northwestern Polytechnical University Xi’an 710072 China

A type of non-axisymmetric oscillations of acoustically levitated drops is excited by modulating the ultrasound field at proper frequencies. These oscillations are recorded by a high speed camera and analyzed with a digital image processing method. They are demonstrated to be the third mode sectorial oscillations, and their frequencies are found to decrease with the increase of equatorial radius of the drops, which can be described by a modified Rayleigh equation. These oscillations decay exponentially after the cessation of ultrasound field modulation. The decaying rates agree reasonably with lamb’s prediction. The rotating rate of the drops accompanying the shape oscillations is found to be less than 1.5 rounds per second. The surface tension of aqueous ethanol has been measured according to the modified Rayleigh equation. The results agree well with previous reports, which demonstrates the possible application of this kind of sectorial oscillations in noncontact measurement of liquid surface tension.

关键词： acoustic levitation drop oscillation image processing surface tension

Delay induced transitions in an asymmetry bistable system and stochastic resonance

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Science China(physics,Mechanics & Astronomy) 2010年第4期53卷 745-750页

作者： ZHANG HuiQing , XU wei, XU Yong & ZHOU BingChang department of applied Mathematics, northwestern polytechnical university,{4., China 1. department of applied Mathematics Northwestern Polytechnical University Xi’an 710072 China

The delay Fokker-Planck equation is given for an asymmetry bistable system with correlated Gaussian white noises. The small delay approximation based on the probability density approach is used and the approximate stationary probability density function is obtained. The phenomenon of delay induced transitions is found. When a weak periodic signal is added, the phenomenon of stochastic resonance is investigated. Expression of the signal-to-noise ratio (SNR) is obtained by using the two-state theory. It is shown that the time delay can suppress or promote the stochastic resonance phenomenon.

关键词： stochastic resonance time-delayed asymmetry bistable system correlated noises

Rapid dendritic growth of Al-Ge hypoeutectic alloy in a drop tube

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Progress in Natural Science:Materials International 2003年第2期 79-82页

作者： lIU xiangrong, CAO Chongde and wei bingbo(department of {4. physics,{4., xi’an 710072, China) department of applied physics Northwestern Polytechnical University Xi'an 710072 China

Abstract Dendritic growth in Al-4.% Ge hypoeutectic alloy has been investigated during free fall in a 3 m drop tube. Calculationsindicate that the undercooling obtained for the falling Al-4.% Ge droplets ranges from 13 K to 201 K. The maximum undercooling attains0. 27 Tl. With the increase of undercooling, the primary (Al) phase undergoes a "columnar dendrite to equiaxed dendrite" structural tran-sition. According to the current rapid dendritic growth theory, the growth of primary (Al) phase is always controlled by solute diffusion.

关键词： dendritic growth undercooling containerless processing Al-Ge alloy.

Microstructure transition of Al-Cu eutectic alloy during containerless rapid solidification

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Progress in Natural Science:Materials International 2003年第2期 52-56页

作者： lU yongjun, WANG Nang and wei bingbo(laboratory of Materials Science in Space, department of {4. {4., northwestern polytechnical university, xi’an 710072, China) laboratory of Materials Science in Space Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China

Abstract Droplets of Al-32. 7% Cu eutectic alloy were rapidly solidified during containerless processing in a 3m drop tube. Themicrostructural evolution of Al-Cu eutectic alloy depends strongly on droplet size. The eutectic growth morphology changes from regularlamellar eutectic to a kind of anomalous eutectic with the decrease in droplet size. This microstructural transition was analyzed within thecurrent theories of eutectic growth. The results indicate that there exists a critical velocity for eutectic growth beyond which anomalous eu-tectic appears. The coupled zone of the Al-Cu eutectic alloy system has been calculated on the basis of the Trivedi-Magnin-Kurz(TMK)eutectic growth and the lipton- Kurz- Trivedi (lKT) / Boettinger- Coriell- Trivedi (BCT) dendrite growth models, which provides a furtherinterpretation for the morphological transition.

关键词： Al-Cu alloy crystal growth microstructure phase transition.

Rapid growth of primary dendrite in highly undercooled copper-antimany alloy

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Progress in Natural Science:Materials International 2002年第12期12卷 57-61页

作者： YAO Wenjing , CAO Chongde and wei bingbo(laboratory of Materials Science in Space, department of applied {4.,{4., xi’an 710072, China) northwestern Polytech Univ Dept Appl Phys Lab Mat Sci Space Xian 710072 Peoples R China

The droplets of Cu-11wt. %Sb hypoeutectic alloy have been rapidly solidified during containerless processing in a 3 m drop tube. The undercooling and cooling rates are estimated, and both play a dominant role in the dendritic growth of primary Cu phase. Undercoolings up to 200 K (0. I&Tl, where Tl is the liquidus temperature) have been obtained in the experiment. With the increase of undercooling, the microstructural evolution of primary Cu phase proceeds from remelted dendrites to the equiaxed grains. A coarse dendritic grain microstructure can form in the undercooling range of 61 - 102K and at cooling rates of 1.35X 102-2.66X 103K/s. The seg-regationless solidification of Cu-llwt. %Sb hypoeutectic alloy occurs when undercooling is more than 176 K. The growth of primary Cu phase is mainly controlled by solute diffusion.

关键词： rapid growth undercooling copper dendrlte drop tube.

Dendrite growth characteristics within liquid Fe-Sb alloy

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Science China(physics,Mechanics & Astronomy) 2009年第5期52卷 720-728页

作者： WANG weili lüyongjun QIN HaiYan wei bingbo department of applied physics Northwestern Polytechnical UniversityXi’an 710072China

Bulk samples and small droplets of liquid Fe-10%Sb alloys are undercooled up to 4.9 K (0.24.l) and 568 K (0.32Tl), respectively, with glass fluxing and free fall techniques. The high undercooling does not change the phase constitution, and only the αFe solid solution is found in the rapidly solidified alloy. The experimental results show that when the undercooling is below 296 K, the growth velocity of αFe dendrite rises exponentially with the increase of undercooling and reaches a maximum value 1.38 m/s. Subsequently, the growth velocity begins to decrease if undercooling further increases. The αFe phase grows into coarse dendrites under small undercooling conditions, whereas it becomes vermicular dendrites in highly undercooled melts. The solute trapping is closely related to the dendrite growth velocity and cooling rate rather than undercooling. Although the solute trapping can be remarkably suppressed by the rapid dendrite growth, the segregationless solidification is not observed in the present experiments due to the large solidification temperature range.

关键词： liquid physics dendrite growth solute distribution segregationless solidification

The liquid phase separation of Bi-Ga hypermonotectic alloy under acoustic levitation condition

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Chinese Science Bulletin 2007年第11期52卷 1446-1450页

作者： HONG ZhenYu lV yongjun xiE WenJun wei bingbo department of applied physics Northwestem Polytechnical University Xi'an 710072 China

Containerless treatment of Bi-58.5at%Ga hypermonotectic alloy is successfully performed with acous-tic levitation technique. Under acoustic levitation condition,the second phase (Ga) distributes almost homogeneously in solidification sample,opposite to macrosegregation in solidification sample under conventional condition. Stokes motion of the second liquid droplet (Ga) is significantly restrained un-der acoustic levitation condition. The analyses indicate that the melt vibration in the gravity direction forced by acoustic field can induce steady flow around the second liquid droplet,which influences droplet shape during its moving upward and consequently restrains Stokes motion velocity of the second liquid droplet.

关键词：声悬浮高导磁率合金液相分离斯托克司运动光谱运动

The new challenges for the development of NH_(3)-SCR catalysts under new situation of energy transition in power generation industry

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Chinese Chemical letters 2024年第6期35卷 95-103页

作者： Feibin wei Yongfang Rao Yu Huang wei Wang Hui Mei Science and Technology on Thermostructural Composite Materials laboratory School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Key laboratory of Aerosol Chemistry and physics State Key Laboratory of Loess and Quaternary Geology(SKLLQG)Institute of Earth EnvironmentChinese Academy of SciencesXi’an 710061China Center of Excellence in Quaternary Science and Global Change Chinese Academy of SciencesXi’an 710061China university of Chinese Academy of Sciences Beijing 100049China department of Environmental Science and Engineering Xi’an Jiaotong UniversityXi’an 710049China

NH_(3)-SCR was one of the most promising de NO_x technologies and it has been widely applied in industrial NO_x ***,with the further development of energy transformation in power generation sector,the development of NH_(3)-SCR catalysts is facing some new *** is becoming an urgent problem to solve low catalytic activity and stability of NH_(3)-SCR catalysts at the working condition of ultra-low temperature(≤200℃)and high concentrations of H_(2)O+SO_(2) due to the gradual deployment of new energy power ***,the traditional coal-fired power plants would need flexible operation with the increasing share of renewable energy *** NH_(3)-SCR catalysts which were applied in coal-fired power industry would be requested to work in a wide temperature window from 200℃ to 500℃ in the near ***,in this review,we summarized the progress of NH_(3)-SCR catalysts in solving these different industrial problems in recent *** the research directions which were deserved to be focused on the development of NH_(3)-SCR catalysts for the energy transition of power generation sector are proposed.

关键词： NH_(3)-SCR NOx reduction Power generation Ultra-low temperature Wide temperature windows