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RISS 인기검색어
- 검색키워드
- 저자 : Anil Kunwar (검색결과 5 건)
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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.
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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.
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Roma Gurung,Anil Kunwar,Il Min Jo,Seok Geun Park,Jae Kyoo Lim 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.2
This study highlights the impact toughness improvement of brittle Polylactic acid(PLA) matrix of glass fiber reinforced composite by addition of Maleic Anhydride grafted Linear Low Density Polyethylene(LLDPE-g-MA) copolymer. Hydrothermal process(green chemistry approach) has been utilized for producing the coplymer; hence ensuring its compatibility with PLA. The experimental results for Charpy impact test have indicated the increase of the impact strength with the increased LLDPE-g-MA content. The impact energy values were also calculated analytically by the progressive impact fracture model and thus compared with experimental ones. The parameters for the correction factor that approximates the analytically obtained energy values to those given by experiments have been proposed in this paper.
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pyMPEALab Toolkit for Accelerating Phase Design in Multi-principal Element Alloys
Upadesh Subedi,Anil Kunwar,Yuri Amorim Coutinho,Khem Gyanwali 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.1
Multi-principal element alloys (MPEAs) occur at or nearby the centre of the multicomponent phase space, and they have theunique potential to be tailored with a blend of several desirable properties for the development of materials of future. The lackof universal phase diagrams for MPEAs has been a major challenge in the accelerated design of products with these materials. This study aims to solve this issue by employing data-driven approaches in phase prediction. A MPEA is frst representedby numerical fngerprints (composition, atomic size diference , electronegativity , enthalpy of mixing , entropy of mixing, dimensionless Ω parameter, valence electron concentration and phase types ), and an artifcial neural network (ANN) isdeveloped upon the datasets of these numerical descriptors. A pyMPEALab GUI interface is developed on the top of thisANN model with a computational capability to associate composition features with remaining other input features. With theGUI interface, an user can predict the phase(s) of a MPEA by entering solely the information of composition. It is furtherexplored on how the knowledge of phase(s) prediction in composition-varied AlxCrCoFeMnNi and CoCrNiNbx can help inunderstanding the mechanical behavior of these MPEAs.
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Shengyan Shang,Anil Kunwar,Yanfeng Wang,Jinye Yao,Yingchao Wu,Haitao Ma,Yunpeng Wang 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.2
Solder ball of initial diameter 1.4 mm, was refl ow soldered with Cu substrate at 523.15 K using fl ux doped with Cu@Agcore–shell nanoparticles (NPs) in the proportion 0–2 wt%. The solders were then air cooled to room temperature. The use ofNPs, by reducing the base height (H) of the solder and enhanced the diameter (W) of the solder, caused an overall increase inthe spread ratio of the solder. The altered magnitudes of heat and mass transfer in these geometrically diff erent but constantvolume specimens were analyzed using fi nite element method. The occurrence of diff erential concentration gradient, radialthermal gradient and velocity magnitudes, in solders with diff ering geometry were numerically elaborated. The Cu6Sn5 intermetalliccompound (IMC) formed at the Cu/Sn interface, was obtained to be the thickest for the specimen using undopedfl ux, whereas it was found to be smallest for the sample processed with fl ux containing 0.5% NPs. From the growth kineticsstudy, it has been inferred that IMC thickness is linearly proportional to the geometrical parameter H and Wb , with b < 1.
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