Publications by authors named "Christina W Kartikowati"

The increasing demand for sustainable materials necessitates advancements in bio-composites with enhanced properties. This study addresses the limitations of Durio zibethinus Murr (DZM) seed starch bio-composites, particularly their poor mechanical strength and thermal stability. Using solution casting, zinc oxide (ZnO) nanofillers and nanocrystalline cellulose (NCC) were incorporated into the starch matrix.

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This research aims to study the effects of the sintering mechanism on the crystallization kinetics when the geopolymer is sintered at different temperatures: 200 °C, 400 °C, 600 °C, 800 °C, 1000 °C, and 1200 °C for a 3 h soaking time with a heating rate of 5 °C/min. The geopolymer is made up of kaolin and sodium silicate as the precursor and an alkali activator, respectively. Characterization of the nepheline produced was carried out using XRF to observe the chemical composition of the geopolymer ceramics.

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Globally, there is an increasing need for ceramic materials that have a variety of applications in the environment, for precision tools, and for the biomedical, electronics, and environmental industries. However, in order to obtain remarkable mechanical qualities, ceramics have to be manufactured at a high temperature of up to 1600 °C over a long heating period. Furthermore, the conventional approach presents issues with agglomeration, irregular grain growth, and furnace pollution.

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Magnetic wires in highly dense arrays, possessing unique magnetic properties, are eagerly anticipated for inexpensive and scalable fabrication technologies. This study reports a facile method to fabricate arrays of magnetic wires directly assembled from well-dispersed α-FeN/AlO and FeO nanoparticles with average diameters of 45 nm and 65 nm, respectively. The magnetic arrays with a height scale of the order of 10 mm were formed on substrate surfaces, which were perpendicular to an applied magnetic field of 15 T.

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Highly crystalline single-domain magnetite FeO nanoparticles (NPs) are important, not only for fundamental understanding of magnetic behaviour, but also for their considerable potential applications in biomedicine and industry. FeO NPs with sizes of 10-300 nm were systematically investigated to reveal the fundamental relationship between the crystal domain structure and the magnetic properties. The examined FeO NPs were prepared under well-controlled crystal growth conditions using a large-scale liquid precipitation method.

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Aligning the magnetic orientation is one strategy to improve the magnetic performance of magnetic materials. In this study, well-dispersed single-domain core-shell α''-Fe16N2/Al2O3 nanoparticles (NPs) were aligned by vertically applying magnetic fields with various strengths to a Si wafer substrate followed by fixation with resin. X-ray diffraction indicated that the alignment of the easy c-axis of the α''-Fe16N2 crystal and the magnetic orientation of the NPs depended upon the applied magnetic field.

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Two kinds of ferromagnetic nanocomposite fiber comprising α″-Fe16N2 and α-Fe nanoparticles (NPs), which have the highest magnetic moments as hard and soft magnetic materials, respectively, embedded in polyvinylpyrrolidone (PVP) have been synthesized via the magneto-electrospinning method. Both α″-Fe16N2 and α-Fe were single-domain core-shell NPs with an average outer diameter of 50 nm and Al2O3 as the shell. Ferrofluid precursors used for the electrospinning were prepared by dispersing these NPs in a PVP-toluene-methanol solution.

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Magnetic materials such as α″-Fe16N2 and α-Fe, which have the largest magnetic moment as hard and soft magnetic materials, are difficult to produce as single domain magnetic nanoparticles (MNPs) because of quasistable state and high reactivity, respectively. The present work reports dispersion of agglomerated plasma-synthesized core-shell α″-Fe16N2/Al2O3 and α-Fe/Al2O3 in toluene by a new bead-mill with very fine beads to prepare single domain MNPs. As a result, optimization of the experimental conditions (bead size, rotation speed, and dispersion time) enables the break-up of agglomerated particles into primary particles without destroying the particle structure.

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