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In this work, to modify the magnetic and microwave absorbing properties of barium monoferrite, Mn4+/Ni2+ co-substitution barium monoferrite with the nominal composition of Ba0.9Sr0.1Fe(2−2x)(Mn,Ni)xO4 (0.0 ≤ x ≤ 0.5) have been synthesized via solid-state reaction method. Rietveld refinement process was carried out to reveal the structural parameters, bond lengths, and bond angles. The lattice constants showed variation associated to the lattice distortion as evidenced from the fluctuations of the bond angles and bond lengths, the results also in accordance with phonon modes of Raman spectra. The microstructure of the samples obtained from scanning electron microscope (SEM) showed spherical particle size with strong tendency for particles to agglomerate. Magnetic property parameters were obtained from vibrating sample magnetometer (VSM) measurement. It was found that the sample changed its magnetic behavior from hard to soft ferromagnetic due to the Mn4+/Ni2+ substitution; the field coercivity value was found to decrease by 80.3% with a slight substitution of x = 0.1. Moreover, it has been explained on the basis of the Stoner-Wohlfarth equation regarding the relation between field coercivity, saturation magnetization, and magneto-crystalline constant (K). In the frequency range of 9–12 GHz, the Mn4+/Ni2+ substitution made the reflection loss (RL) curve to have a broad feature with multiple attenuation peaks. The RL bandwidth at higher microwave attenuation level (RL < − 16.5 dB, ≈ 97% attenuation) varied at 1.44 GHz to 1.65 GHz, while the original sample was 0.67 GHz. These features were attributed to the magnetic resonance loss and hysteresis loss which originated from to the natural ferromagnetic resonance. Moreover, The RL minimum was shifted to a lower frequency due to the decreasing K value in the substituted samples. [ABSTRACT FROM AUTHOR]

A new synthesized 56Fe25Ni16.6Cr0.9Si0.5Mn austenitic stainless steel (ASS) was produced through casting and then annealing and normalizing at 1100 °C, followed by cooling at different rates. Microstructures of the samples were studied by using X-ray and neutron diffractometers, scanning, and transmission electron microscopes. The stainless steel had a face center cubic structure (X-ray diffraction profile). The microstructure of ASS consists of γ-austenite matrix and high Cr carbide particles in the interior grains and grain boundaries. It seemed that the annealing process affected information of γ-austenite grain size in the ASS, growing larger compared to grain size formed in the normalizing process, similarly by cooling into the air, water, and oil media. The M23C7 islands in the grain boundary formed into a larger size after annealing or normalizing processes, and in addition, the island shape was more elongated. No significant changes were found concerning the particle size and shape of M7C6 at the grain boundary of the ASS after annealing or normalizing. Neutron diffraction patterns confirmed the Fm3m space group symmetry of ASS as obtained by the XRD method, therefore establishing ASS as an austenite phase. Results of the uniform deformation method (UDM) analysis applied upon the high-resolution powder neutron diffractometer (HRPD) intensity showed that the deformation strain was 2.3705 × 10-4. TEM results for ASS showed that the sizes of rectangular precipitates ranged from 63 × 32 nm to 84 × 42 nm with larger-sized irregulars reaching about 190 nm across. All these results showed that an ASS has been successfully synthesized and that it has a promising future to be used as a high-temperature structural material. [ABSTRACT FROM AUTHOR]

Magnetism of graphene-based compounds has drawn growing interest owing to its tunability by various defects presented in the compounds. Reduced graphene oxides (rGOs), particularly, provide an ideal playground as they have significant defects and functional groups on their layers. Herein, we propose a green synthesize method, a simple way in preparing rGO from coconut shells. The rGO has been synthesized from coconut shells by thermal reduction process at 400 °C, 600 °C, and 1000 °C followed by an exfoliation process. We found that the rGO sample prepared at 1000 °C (rGO-1000) exhibits stronger room temperature magnetization, where the saturation magnetization increases approximately 35 times as large as those prepared at 400 °C (rGO-400) and 600 °C (rGO-600). The concentration of defects increases and the oxygen-containing functional groups reduce with an increase in the heating temperatures, contributing to the increment in magnetization. The observed results in this paper indicate that defect-induced magnetism of the obtained rGO can be enhanced by controlling the temperature in the reduction process. [ABSTRACT FROM AUTHOR]

The present study reports on the ultrasonic enhancement of the liquid carbon dioxide (CO 2 ) extraction of luteolin and apigenin from the leaves of Perilla frutescens (L.) Britt., to which ethanol is added as a cosolvent. The purpose of this research is also to investigate the effects of the particle size, temperature, pressure, irradiation power, irradiation time, and ethanol content in the liquid CO 2 solution on the extraction yield using single-factor experiments. We qualitatively and quantitatively analyzed the yields in the extract using HPLC (high-performance liquid chromatography). The liquid CO 2 mixed with ethanol was used at temperatures of 5, 20 and 25 °C with extraction pressures from 8 to 14 MPa. The yields of luteolin and apigenin in the extraction were clearly enhanced by the ultrasound irradiation, but the selectivity of the extract was not changed. The yields of luteolin and apigenin in the extract were also significantly improved by adjusting the operating temperature, the irradiation time, and the ethanol content in the liquid CO 2 solution, but no change in the selectivity of the extract was observed. [ABSTRACT FROM AUTHOR]