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All Journal International Journal of Acta Material
K. Nakagawa
Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan
Chemistry Materials Science & Nanotechnology Physics

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Microwave-Assisted Roasting-Leaching of Nickel from Indonesian Nickel Laterite Ore A. J. Muhammad; K. Nakagawa; I P. A. Karya; A. Ndita; L. O. M. Darusman; T. Iwamoto; Y. Terui; L. Agusu; I. N. Sudiana; F. Nishimura; T. Nishiumi; T. Asano; H. Kikuchi; S. Mitsudo
International Journal of Acta Material Vol. 1 No. 2 (2025): February 2025
Publisher : Faculty Mathematics and Natural Sciences, Halu Oleo University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.62749/ijactmat.v1i2.10

Abstract

This study investigated nickel extraction from nickel laterite ore from Indonesia using the microwave roasting leaching method. The study focused on investigating the effect of microwave power and roasting temperature on the extraction of nickel. Samples from each step were characterized using X-ray diffraction (XRD) and Atomic Absorption Spectroscopy (AAS). The method has the advantage of being carried out in atmospheric conditions with high nickel extraction at low temperatures, a rapid process, and without pre-roasting as in conventional roasting. It was obtained that 92.8% of nickel was extracted by application of microwave power at 540 W, at a roasting temperature of approximately 335°C for 30 minutes. The maximum result were obtained when the heating temperature is near to the boiling point of sulfuric acid (337oC). However, the amount of nickel extracted decreases when the heating temperature is above the boiling point of sulfuric acid. The results of XRD analysis of samples after roasting and solid leaching residue samples also revealed that the maximum nickel recovery occurred when the roasting process had transformed all iron sulfate-aqueous system (Fe(OH)(SO2)2.4H2O) into iron sulfate (Fe2(SO4)3) which also directly changed NiSO4.6H2O into NiSO4 which is highly soluble in water.
Rapid Anisotropic Crystallization from Amorphous Bi₂Te₃ Thin Films by Microwave Annealing K. Nakagawa; T. Iwamoto; I P. A. Karya; A. J. Muhammad; T. Asano; S. Mitsudo; T. Takizawa; M. Takashir
International Journal of Acta Material Vol. 2 No. 2 (2026): February 2026
Publisher : Faculty Mathematics and Natural Sciences, Halu Oleo University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.62749/ijactmat.v2i2.24

Abstract

We investigated the crystallization behavior of amorphous Bi₂Te₃ thin films subjected to microwave annealing using both slow and rapid heating protocols. Films were deposited by RF magnetron sputtering and annealed with 2.45 GHz microwave irradiation. Slow annealing, performed under controlled temperatures below the melting point of Te, yielded randomly oriented polycrystalline films, whereas rapid annealing with high-power short pulses resulted in strongly c-axis-oriented crystallites. X-ray diffraction (XRD) analyses confirmed enhanced crystallinity and increased Lotgering factors under rapid annealing conditions. SEM observations showed minimal grain growth, suggesting that microwave irradiation promotes preferential orientation without significant grain coarsening. These results indicate that microwave annealing provides a unique, rapid, and effective method for directional crystallization of Bi₂Te₃ thin films, which could significantly enhance their thermoelectric performance.
Co-Authors A. J. Muhammad A. J. Muhammad A. Ndita F. Nishimura H. Kikuchi I P. A. Karya I P. A. Karya I. N. Sudiana L. Agusu L. O. M. Darusman M. Takashir S. Mitsudo S. Mitsudo T. Asano T. Asano T. Iwamoto T. Nishiumi T. Takizawa Y. Terui