Effect of the TiO2 Nanoparticles on the Growth Behavior of Intermetallics in Sn/Cu Solder Joints

Shengyan Shang,Anil Kunwar,Jinye Yao,Yanfeng Wang,Haitao Ma,Yunpeng Wang 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2

In order to investigate the effect of TiO2 nanoparticles on growth behavior of interfacial Cu6Sn5 intermetallics compounds(IMCs) in Pb-free Sn/Cu system, the solder joints are fabricated by using flux doped with different content (0.0–2.0 wt% offlux) and particle diameter (5 nm and 50 nm) of TiO2 . In context of isothermal reflow soldering at 250 °C and subsequentair cooling, the increase in reflow duration from 10 to 120 s was characterized with an increment in IMC layer thicknessand grain size, due to the enhancement of Cu flux contribution for Ostwald ripening during constant temperature reflow andprecipitation kinetics during cooling. The increased proportion of TiO2 nanoparticles in flux was found to reduce the growthof IMC layer and grain size. The suppression effect on IMC was more pronounced for 5 nm particles as compared to the 50nm TiO2 . The TiO2 nanoparticles, adsorbed on IMC plane can retard the growth of the latter. Presence of sufficient amountof a given sized TiO2 nanoparticles among IMCs, by increasing the effective stress at the localized interfaces, and causingthe breaking of brittle Cu6Sn5 during growth stage; can help in the inhibition of IMC whisker formation. Particle diameterand mass proportion of TiO2 nanoparticles are important for soldering materials design.

The effects of proximities on the evolving structure of intercity innovation networks in the Guangdong–Hong Kong–Macao Greater Bay Area: comparison between scientific and technology knowledge

Ma Haitao,Xu Xuanfang 서울시립대학교 도시과학연구원 2023 도시과학국제저널 Vol.27 No.3

The various knowledge flows shape and change the regional innovation patterns, which are also influenced by regional conditions. What are the similarities, differences and connections between science and technology linkage, as two different types of knowledge network, deserve to be explored in depth. Drawing on scientific paper co-publications and patent transfer data, we constructed two different types of intercity innovation networks during 2006–2016 in the Guangdong–Hong Kong–Macao Greater Bay Area (GBA), a city region special for its ‘one country, two systems’ structure. After that, we explored the evolutionary characteristics of the networks and further examined the different impacts of multidimensional proximity on scientific collaboration and technology transfer. Our results show that technology transfer is more sensitive to spatial factors, institutional barriers caused by ‘one country, two systems’ is a bigger obstacle to technology transfer between cities, cultural proximity and cognitive proximity have a more significant impact on paper cooperation network. Moreover, geographical proximity can indirectly affect knowledge spillover by acting on the proximity of other dimensions. As for scientific collaboration, social, cognitive and institutional proximities can compensate for the lack of geographical proximity, and cultural proximity frequently goes along with geographical proximity; as for technology transfer, geographical proximity has neither substitutional or complementarity relations with cultural and cognitive proximities, the interrelatedness between geographical and institutional and social proximities are complementarity which is opposed to paper co-publications. This study explores the differences in spillover mechanisms of different knowledge types and contributes to enriching the empirical framework of multidimensional proximities and innovation network researches.

Ferrocene-based hydrazone energetic transition-metal complexes as multifunctional combustion catalysts for the thermal decomposition of ammonium perchlorate

Xiaoju Liu,Haitao Feng,Yang Li,Xiaoyan Ma,Fang Chen,Qilong Yan 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Three novel ferrocene-based hydrazone energetic transition-metal complexes denoted as M/E-FcDz-TMCs (M = Co (II), Fe (III), and Co(II)Fe(III)), were successfully prepared to improve the thermal decompositionof ammonium perchlorate (AP) and anti-migration performance of Fc-based catalysts. 1-hydrazinoethylene-ferrocene (E-FcDz) with unique electronic structure and energy bonds (C@N, NAN)as ligand reacted with transition metal Co, or Fe mono-metal nodes, and Co-Fe bimetal nodes, respectively. The chemical structure, crystalline texture, and morphology were confirmed, and the catalytic performancewas investigated. The thermal decomposition kinetics were estimated by applying Kissinger,FWO, and KAS methods. The results revealed that M/E-FcDz-TMCs had superior catalytic performancesfor AP decomposition compared to the traditional catalyst catocene due to their high electron transportcapacity. Especially, CoFe/E-FcDz-TMCs showed the best catalytic efficiency due to the hybridizationbetween Co (II) 3d and Fe (III) 3d orbitals in the structure led to electron redistribution, driving the optimalsynergistic catalytic effect of the bimetal Co-Fe nodes and E-FcDz, and further enhancing catalysis forAP. Moreover, AP/CoFe/E-FcDzTMCs showed the best combustion performance. In addition, the thermaldecomposition products of AP were explored by TG/FTIR, and the AP thermal decomposition processcould be explained by a possible mechanism following the principle of electron transfer theory.

Modeling the Diffusion-Driven Growth of a Pre-Existing Gas Bubble

Anil Kunwar,Haitao Ma,Junhao Sun,Shuang Li,Jiahui Liu 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.5

Finite element method is utilized to solve the diffusion equation and model the diffusion driven growth of a pre-existing spherical gas bubble in molten tin at the solder/substrate interface for reflow time of 120 s and temperature of 250 °C. The gibbs free energy change required for determining the equilibrium concentration at liquid solder/gas bubble boundary was calculated using the thermodynamic polynomial coefficients. The rate of change of radius, as function of concentration flux, is calculated using the lagrangian mesh update methodology. With an initial diameter of 20 μm, the bubble growth is calculated as a function of contact angle. When the wetting angle is varied from a value of 30° to 135°, the numerical calculation has yielded the final sizes for the bubble to change from 62.87 μm to 82.8 μm respectively. The effect of wetting transition in the growth of bubble was studied by the in-situ observation of bubble dynamics through synchrotron radiation imaging technique. The scanning electron microscopy images of the morphologies of intermetallic compounds influenced by growing bubble in Sn/Cu solder joint and bubble pictures obtained through synchrotron radiation are utilized to get the experimental size of the bubble. The mean experimental bubble diameter has been obtained as 76.39 μm. The growing bubble inhibits the growth of intermetallic compound at its vicinity and thereby reduces the strength of solder joints.

In Situ-DRIFTS Study of Rh Promoted CuCo/Al₂O₃ for Ethanol Synthesis via CO Hydrogenation

Li, Fang,Ma, Hongfang,Zhang, Haitao,Ying, Weiyong,Fang, Dingye Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.9

The promoting effect of rhodium on the structure and activity of the supported Cu-Co based catalysts for CO hydrogenation was investigated in detail. The samples were characterized by DRIFTS, $N_2$-adsorption, XRD, $H_2$-TPR, $H_2$-TPD and XPS. The results indicated that the introduction of rhodium to Cu-Co catalysts resulted in modification of metal dispersion, reducibility and crystal structure. DRIFTS results of CO hydrogenation at reaction condition (P=2 MPa, $T=260^{\circ}C$) indicated the addition of 1 wt % rhodium improved hydrogenation ability of Cu-Co catalysts. The ethanol selectivity and CO conversion were both improved by 1 wt % Rh promoted Cu-Co based catalysts. The alcohol distribution over un-promoted and rhodium promoted Cu-Co based catalysts obeys A-S-F rule and higher chain growth probability was got on rhodium promoted catalyst.

Research on Nonlinear Friction Compensation of Harmonic Drive in Gimbal Servo-system of DGCMG

Bangcheng Han,Haitao Li,Jijun Ma 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.3

The purpose of this paper is to present our results in overcoming the influence of the nonlinear frictionafforded by harmonic drive to the gimbal servo-system of double-gimbal control momentum gyro (DGCMG). Theexistence of compliance and oscillation inherent in harmonic drive systems, and the lack of any technical informationon the internal dynamics of the transmission, make the development of friction compensation in harmonic drivesystem extremely challenging. In this paper, the modeling of nonlinear friction in harmonic drive gear transmissionin gimbal servo-system of the DGCMG is proposed. The relationship among the nonlinear friction, the angularvelocity and the angular position with an improved Coulomb-Viscous model is derived, and the experiments toidentify the various parameters of the improved model are given. At last a feed-forward compensation controllerbased on the improved model is designed to carry out the friction compensation study.

Radar-absorbing Performances of Camouflage Fabrics with 3D Warp-knitted Structures

Ziyu Zhao,Pibo Ma,Haitao Lin,Fenglin Xia 한국섬유공학회 2020 Fibers and polymers Vol.21 No.3

In this paper, 3D warp-knitted camouflage fabrics were fabricated with two kinds of bottom structure. Polyesterand coating treated PE flat wire were used as raw materials. The samples were manufactured by the RD6N warp-knittingmachine. The properties of camouflage fabrics were tested and analyzed. Results show that the lowest reflection loss of 2 cmheight of 3D warp-knitted camouflage fabrics with mesh was -38.49 dB at 15.45 GHz. And the 3D warp-knitted camouflagefabric has excellent absorption performance, tensile breaking strength and flame retardant property. The findings havetheoretical and practical significance for the applications of 3D warp-knitted camouflage fabrics.

In Situ-DRIFTS Study of Rh Promoted CuCo/Al2O3 for Ethanol Synthesis via CO Hydrogenation

Fang Li,Hongfang Ma,Haitao Zhang,Weiyong Ying,Dingye Fang 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.9

The promoting effect of rhodium on the structure and activity of the supported Cu-Co based catalysts for CO hydrogenation was investigated in detail. The samples were characterized by DRIFTS, N2-adsorption, XRD, H2-TPR, H2-TPD and XPS. The results indicated that the introduction of rhodium to Cu-Co catalysts resulted in modification of metal dispersion, reducibility and crystal structure. DRIFTS results of CO hydrogenation at reaction condition (P=2 MPa, T=260 oC) indicated the addition of 1 wt % rhodium improved hydrogenation ability of Cu-Co catalysts. The ethanol selectivity and CO conversion were both improved by 1 wt % Rh promoted Cu-Co based catalysts. The alcohol distribution over un-promoted and rhodium promoted Cu-Co based catalysts obeys A-S-F rule and higher chain growth probability was got on rhodium promoted catalyst.

Response spectrum analysis considering non-classical damping in the base-isolated benchmark building

Huating Chen,Ping Tan,Haitao Ma,Fulin Zhou 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.4

An isolated building, composed of superstructure and isolation system which have very different damping properties, is typically non-classical damping system. This results in inapplicability of traditional response spectrum method for isolated buildings. A multidimensional response spectrum method based on complex mode superposition is herein introduced, which properly takes into account the non-classical damping feature in the structure and a new method is developed to estimate velocity spectra from the commonly used displacement or pseudo-acceleration spectra based on random vibration theory. The error of forced decoupling method, an approximated approach, is discussed in the viewpoint of energy transfer. From the baseisolated benchmark model, as a numerical example, application of the procedure is illustrated companying with comparison study of time-history method, forced decoupling method and the proposed method. The results show that the proposed method is valid, while forced decoupling approach can’t reflect the characteristics of isolated buildings and may lead to insecurity of structures.

Neural Network‐Based Analysis of Thiol Proteomics Data in Identifying Potential Selenium Targets

Lee, Jong‐,Sik,Ma, Yong‐,Beom,Choi, Kyoung‐,Soo,Park, Soo‐,Yeon,Baek, Sun‐,Hee,Park, Young‐,Mee,Zu, Ke,Zhang, Haitao,Ip, Clement,Hong Kim, Yeul,Park, Eun‐,Mi MARCEL DEKKER, INC 2006 PREPARATIVE BIOCHEMISTRY AND BIOTECHNOLOGY Vol.36 No.1

<P>Generation of a monomethylated selenium metabolite is critical for the anticancer activity of selenium. Because of its strong nucleophilicity, the metabolite can react directly with protein thiols to cause redox modification. Here, we report a neural network-based analysis to identify potential selenium targets. A reactive thiol specific reagent, BIAM, was used to monitor thiol proteome changes on 2D gel. We constructed a dynamic model and evaluated the relative importance of proteins mediating the cellular responses to selenium. Information from this study will provide new clues to unravel mechanisms of anticancer action of selenium. High impact selenium targets could also serve as biomarkers to gauge the efficacy of selenium chemoprevention.</P>