Micropowders of oxide-dispersion-strengthened (ODS) steel have been synthesized using the ultrasonic irradiation method with variations in amplitude. The ultrasonic irradiation process is performed for 50 h at a frequency of 20 kHz with 40%, 50%, and 60% amplitudes in toluene solution. The formation of Fe-Cr microalloys in the preparation of Fe-15Cr-0.5Y 2 O 3 powder was analyzed using SEM-EDS, X-ray diffraction (XRD), and TEM-EDS. The percentage of Fe-Cr phase mass fraction of ODS steel micropowder formed during ultrasonic irradiation with 40%:50%:60% amplitude was 12.2%:34.1%:22.1%, with 25.67:77.02:38.51 nm crystallite size. The crystallite size at 50% amplitude was the largest, and the diffusion process of Fe-Cr-Y 2 O 3 microparticles was most dominant at 50% amplitude. The Fe and Cr phases are still present when the ODS particles successfully dispersed in the main particle. AbstrakSintesis Baru Paduan Mikro Baja ODS dengan Irradiasi Ultrasonik Amplitudo Tinggi. Serbuk mikro dari baja yang diperkuat dengan dispersi oksida (ODS) telah disintesis menggunakan metode iradiasi ultrasonik dengan variasi amplitudo. Proses iradiasi ultrasonik dilakukan selama 50 jam pada frekuensi 20 kHz dengan amplitudo 40%, 50%, dan 60% dalam larutan toluena. Pembentukan paduan mikro Fe-Cr dalam preparasi serbuk Fe-15Cr-0.5Y2O3 dianalisis menggunakan SEM-EDS (scanning electron microscopy-energy-dispersive spectroscopy), difraksi sinar-X (XRD), dan TEM-EDS (transmission electron microscopy-energy-dispersive spectroscopy).

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Multiband electromagnetic wave absorption have been studied on nanocrystalline (1-x) NiFe2O4 (NFO)/(x)BaTiO3 (BTO) composites. The samples were synthesized by solid state reaction using high energy milling (HEM) instrument. The composite samples were characterized using X-ray Diffractometer (XRD) and vibrating sample magnetometer (VSM) instrument. The X-ray diffraction (XRD) patterns of all the samples show single phase and free from impurities. The NFO sample can be indexed to a single cubic crystal structure with a space group of Fd-3m, No. 227. While, the BTO sample can be indexed to a single tetragonal crystal structure with a space group of P4mm, No. 99. The composite samples consist of two phases, namely NFO and BTO showing soft magnetic performance. The mass magnetization is in the range of 20.0–49.0 emu/g. The electromagnetic parameters of the composites were measured by a vector network analyser in the frequency range of 2 GHz to 18 GHz. The results indicated that (1-x) NiFe2O4 / (x) BaTiO3 composites display three-band electromagnetic wave absorption. The 0.5NiFe2O4 / 0.5BaTiO3 composite displays three-band reflection loss which is larger than the other one and the three-band reflection loss are almost the same, i.e., below the -15 dB. From these experiments it can be concluded that the 0.5NiFe2O4 / 0.5BaTiO3 composite is good candidate for electro-magnetic wave absorption.

High Chromium ODS ferritic steel dispersed by zirconia was synthesized by the Mechanical Alloying process for application as high-temperature nuclear reactor structure material. The zirconia was chosen as dispersoid to increase the oxidation resistance of the steel. The powders of Fe and Cr with composition of Fe-25 wt.% Cr and 0.5 wt.% Zr2O3 were processed by milling and isostatic compaction then continued with the sintering process for consolidation. The process of sintering was performed by the plasma-based heating using the new apparatus of APS (Arc Plasma Sintering). The sintering was processed with 40 A current and 22 minutes sintering time to result in the optimal Fe-Cr alloy formation. A microscopy technique with scanning electron microscopy (SEM), and X-ray diffraction (XRD) were applied to analyze the mechanism of the alloying process. The Vickers hardness measurement and the oxidation test were carried out to evaluate the mechanical and high-temperature oxidation behavior. The alloying process was considered by the Fe-Cr interdiffusion with Cr the faster one. The distribution of zirconia observed by SEM-mapping showed the homogeneity distribution in the matrix of the alloy. The Vicker hardness of 142.8 VHN was believed caused by the oxide strengthen and fining the grain. The parabolic oxidation curve obtains from the MSB oxidation test showed good oxidation resistance caused by the formation of the protective layer of Fe2O3 and some metastable of ZrO.

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