Browsing by Author "McDonald, SD"
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- ItemThe effects of temperature and solute diffusion on volume change in Sn-Bi solder alloys(Springer Nature, 2022-02-02) Hao, QC; Tan, XF; Gu, QF; Sweatman, K; McDonald, SD; Nogita, KThe different rates of thermal expansion of the many materials that make up an electronic assembly combined with temperature fluctuations are the driver of the thermal fatigue failure of solder joints. A characteristic of the Sn-Bi system, which provided the basis for many of the low process temperature solder alloys that the electronics industry is now adopting, is the very temperature-sensitive solubility of Bi and Sn in the other phase. In this study, in situ synchrotron powder x-ray diffraction was used to characterize the temperature dependence of the lattice parameters of the βSn and Bi phases in Sn-57wt%Bi and Sn-37wt%Bi. The effects of temperature and solute were separated by comparing with the data from pure βSn and pure Bi and verified using density functional theory calculations. Furthermore, the coefficients of thermal expansion of βSn and Bi during heating were also derived to reveal the thermal expansion behavior. © 2022 The Author(s) - Open access under a Creative Commons Attribution License
- ItemHydrogen sorption behaviour of Mg-5wt.%La alloys after the initial hydrogen absorption process(Elsevier B. V., 2022-04-29) Kim, MJ; Tan, XF; Gu, QF; McDonald, SD; Ali, Y; Matsumura, S; Nogita, KIn our earlier study, it has been shown that trace Na additions can improve the reaction kinetics of Mg–5%La (wt.%) alloys during the first absorption. However, the subsequent hydrogen desorption/absorption process of the Mg–5%La after the first absorption has not been investigated. In this study, we have investigated the hydrogen sorption behaviour of the Mg–5%La alloy after the first absorption in terms of phase evolution, and lattice expansion properties during desorption as function of temperature using in-situ synchrotron Powder X-ray Diffraction (PXRD) and in-situ High Voltage Transmission Electron Microscopy (HVTEM). Two distinct phase evolutions, a continuous phase transformation of LaH3 → LaH2 + ½ H2 (from 250 °C) and decomposition of MgH2 → Mg + H2 (between 440 and 460 °C) were identified during the desorption. It is determined that this alloy is cyclable in the absence of Mg12La intermetallic during the subsequent absorption/desorption cycling after the first hydrogen absorption. © 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd
- ItemIn-situ x-ray diffaction for hydrogen sorption study of Mg-La alloys(Australian Nuclear Science and Technology Organisation, 2021-11-24) Kim, MJ; Tan, XF; Gu, QF; McDonald, SD; Ali, Y; Matsumura, S; Nogita, KTrace Na additions can enhance the reaction kinetics of Mg-5%La (wt.%) alloys, resulting in a potential hydrogen storage material. In this study, we used in-situ synchrotron Powder X-ray Diffraction (PXRD) to examine the hydrogen sorption behaviour of the Na-modified Mg-5%La. A setup equipped with a hydrogen gas flow cell and a hot air blower at the Powder Diffraction beamline of the Australian Synchrotron facility is used to allow for PXRD data collection during hydrogen sorption reactions to study the phase evolutions and the cyclability of the alloy. To shed light on the underlying processes during the reactions, in-situ desorption and absorption were performed in a hydrogen atmosphere between 30-480 °C and atmospheric pressure to 2MPa H2. Rietveld refinement was conducted using the TOPAS-Academic V6 software to calculate the weight percentage and lattice expansion of each phase in the sample. In addition, in-situ High Voltage Transmission Electron Microscopy (HVTEM) was used as a complementary technique to study the volume expansion properties during desorption as a function of temperature. © The Authors
- ItemNa-modified cast hypo-eutectic Mg–Mg2Si alloys for solid-state hydrogen storage(Elsevier B. V., 2022-08-01) Tan, XF; Kim, MJ; Gu, QF; Pinzon Piraquive, J; Zeng, G; McDonald, SD; Nogita, KMg2Si is a promising catalyst for Mg-based H2 storage materials due to its low cost, light weight, and non-toxic properties. This study investigates the effects of Na in hypo-eutectic Mg-1wt.%Si alloys for H2 storage applications. The addition of trace amounts of Na is vital in improving the H2 sorption kinetics, achieving a H2 storage capacity of 6.72 wt.% H at 350 °C under 2 MPa H2, compared to 0.31 wt.% H in the non-Na added alloy. The hydrogen sorption mechanisms were analysed with Johnson-Mehl-Avrami-Kolmogorov models. It was identified that Na affects the surface of the Mg alloys, forming porous Na2O and NaOH in addition to MgO, facilitating the diffusion of H2. Finally, in-situ synchrotron powder X-ray diffraction showed the Mg2Si catalyst is stable during the H2 sorption reactions. This result demonstrates the potential use of Mg–Mg2Si casting alloys for large scale hydrogen storage and transportation applications. © 2022 Elsevier B.V
- ItemThe temperature-dependent phase transformation and microstructural characterisation in In-Sn solder alloys(Springer Nature, 2023-05-16) Zhou, J; Tan, XF; Gu, QF; McDonald, SD; Nogita, KIndium-based solder alloys are considered candidates for the next generation of low-temperature solder materials, especially for superconducting joints because of the properties of the β-In3Sn phase. The temperature-dependent phase transformation and thermal expansion behaviour of two different solder compositions including In-35Sn (in wt.%) and In-25.6Sn have been characterised using an in situ synchrotron powder X-ray diffraction method. The c-axis of the β-In3Sn unit cell in the In-35Sn alloy exhibited a complex relationship with increasing temperature compared to the positive increasing trend in In-25.6Sn due to the temperature-dependent solubility of Sn in β-In3Sn and change in the volume fraction of phases commencing at 80°C. In situ heating scanning electron microscopy recorded a real-time melting-solidification microstructure variation and phase transition during annealing at 90°C that was further analysed using energy dispersive X-ray spectroscopy. The observations are discussed with respect to the lattice parameters of the γ-InSn4 and β-In3Sn phases and the proportions and composition of both phases present within the alloys. © 2023 The Authors - Open Access - funded through CAUL.
- ItemThe use of variable temperature synchrotron XRD to characterise the behaviour of low temperature solder alloys(Australian Nuclear Science and Technology Organisation, 2021-11-26) Hao, QC; Tan, XF; Gu, QF; Sweatman, K; McDonald, SD; Nogita, KDuring the soldering process and the daily operation of the electronic devices, solder alloys experience temperature variation frequently. The mismatch in volume expansion of the solder alloys and the interconnected components can result in stresses which lead to failure. In a solder alloy system with high solubility of one element in another, the effects of thermal expansion and temperature dependent solubility limits are both important contributing factors to the thermally induced volume changes. In this study, Sn-57wt%Bi and Sn-37wt%Bi alloys which are promising materials for low-temperature solders were investigated by in-situ heating synchrotron powder X-ray diffraction (PXRD) to reveal the changes of the lattice parameters of Sn and Bi. The lattice parameters were derived by the Rietveld refinement of the PXRD patterns using TOPAS Academic V6 and following analyzed by the Coefficient of Thermal Expansion Analysis Suite (CTEAS) package using a tensor method to get the coefficient of the thermal expansion (CTE). Density functional theory (DFT) calculations were adopted to reveal the influence of the solid solution of Bi (or βSn) on the lattice parameters of βSn (or Bi), thereby decoupling the effects of thermal expansion and solid solution of Bi (or βSn) on the thermally induced volume change of βSn (or Bi). © 2021 The Authors