Key Engineering Materials Vol. 1014

Abstract: The purification of mixed hydroxide precipitate leaching solution from impurities was conducted via solvent extraction using the commercial extractant di(2-ethylhexyl) phosphoric acid (P₂₀₄ or D2EHPA). The impurities that were removed are Mn²⁺, Cu²⁺, Ca²⁺, Mg²⁺, and Zn²⁺, while the desired metals remained in aqueous phase which are Co²⁺ and Ni²⁺. Solvent extractions were studied on a batch scale to improve the effect of organic-to-aqueous phase ratio, extractant concentration, saponification rate, and feed solution pH to the removal of impurities. High selectivity of impurities was obtained at a phase ratio organic to aqueous of 1.6:1, extractant concentration of 30 vol%, with saponification rate of 40%, and feed solution pH of 5. The extraction rate achieved for Mn²⁺, Cu²⁺, Ca²⁺, Mg²⁺, and Zn²⁺ are 88.46%, 82.24%, 95.21%, 38.10%, and 99.99% respectively while the co-extracted of Co²⁺ and Ni²⁺ are 17.76%, and 12.52%.

Abstract: The magnetic structure of the one-dimensional (1D) compounds A₃MXO₆ (where A is Ca or Sr, M and X are transition metal cations) can be tuned from collinear to spiral by merely changing the identity of the M and X atoms constituting the 1D chains. This suggests the prospect of realizing ferroelectricity that is induced by different types of magnetic order. To date, magnetism-driven ferroelectricity in these 1D compounds has only been discovered in Ca₃CoMnO₆ with a collinear magnetic structure, whereas other magnetic structures such as spin spirals have been much less discussed. Here, the magnetoelectric effect in 1D Ca₃NiMnO₆ with a spiral magnetic structure is investigated. The presence of magnetoelectric coupling in the sample is evidenced by changes in capacitance of up to 1.5 % in an applied magnetic field of 8 T at a temperature of 5 K. These results highlight the relation between magnetic and electric order in 1D compounds with a spiral magnetic structure and provide more insight into magnetoelectric coupling mechanisms in 1D compounds in general.

Abstract: Graphene, with its hexagonal arrangement of carbon atoms, exhibits high electrical conductivity and charge carrier mobility due to its zero bandgap. However, its semi-metallic nature limits its application in semiconductor devices. This study explores the modification of graphene’s electronic and magnetic properties by introducing defects and nitrogen substitutions in its crystal structure using spin-polarized density functional theory (DFT). Structural relaxation showed variations in supercell expansion with increasing nitrogen doping. The DFT results revealed that nitrogen substitution in a 4 × 4 × 1 graphene supercell opened an energy gap, and converting graphene into a p-type semiconductor. Additionally, nitrogen doping induced a magnetic transition, with pyridinic and combined pyrolic-pyridinic configurations showing notable spin polarization. These findings highlight the potential of nitrogen-doped graphene for magnetic and electronic applications.

Abstract: LiFe(P,Si)O₄ is a material that belong to parent compound of LiFePO₄ widely known as cathode material for lithium-ion battery (LIB). Previous study reports that electrochemical performance of LiFePO₄ can be improved by silicon (Si) substitution to the phosphorus (P) site. The sample was obtained via a solid-state synthesis route with the amount of Si doping to the P site is ∼3%. The electrochemical performance of silicon substituted LiFePO₄ has been widely studied in other report whilst the magnetic properties is still less explored. Here we investigate the magnetic properties of LiFe(P,Si)O₄ using superconducting quantum interference device (SQUID) and muon spin relaxation (µSR). The two measurements display a good agreement result showing two anomalies at the temperature of ∼27 K and ∼52 K that represent the Neel Temperature (Τ_N) of Li₂FeSiO₄ and LiFePO₄, respectively. The presence of Li₂FeSiO₄ that is also a candidate of cathode of LIB has been confirmed by X-ray Diffraction (XRD). Based on the current study, there is no alteration of Τ_N on LiFePO₄ phase due to Si doping.

Abstract: Fe₃O₄ and Fe₂O₃ nanocrystals have been successfully synthesized from iron sand by the coprecipitation method using a semi-automatic coprecipitator. The composition of iron sand used was 12, 18, and 24 gram, to investigate the performance of the coprecipitator. The synthesized Fe₃O₄ and Fe₂O₃ nanocrystals were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive X-Ray (SEM-EDX), and Vibrating Sample Magnetometer (VSM). The best phase composition of Fe₃O₄ nanocrystals is 100 wt% which has a magnetite crystal size range of 5 to 13 nm, and the mass obtained is in the range of 7.01 to 12.71 gram. The best phase composition of Fe₂O₃ nanocrystals is 99.89 wt% hematite (α – Fe₂O₃) which has a crystal size range of 23 to 26 nm, the mass obtained is in the range of 3.51 to 7.49 gram. The highest gain of Fe₃O₄ and Fe₂O₃ nanocrystals was 67.62% and 41.58%, respectively, obtained from 18 gram iron sand composition. The morphology of Fe₃O₄ and Fe₂O₃ nanocrystals is almost spherical. The highest magnetization was obtained from Fe₃O₄ nanocrystals with a saturation magnetization of 8.87 emu/gram. The magnetic properties of Fe₃O₄ and Fe₂O₃ nanocrystals are ferrimagnetic and weak ferrimagnetic, respectively.