Toto Sudiro

Cr-Al Coatings on Low Carbon Steel Prepared by a Mechanical Alloying Technique

Four different compositions of Cr and Al coatings as Cr10o, Cr87.5Al12.5, Cr5oAl5o, and Al100 have been prepared on the surface of low carbon steel by a mechanical alloying technique. The composition of each powder was milled for 2 hour in a stainless steel crucible with a ball to powder ratio of 10:1. Hereafter, the Cr-Al powder and substrate were mechanical alloyed in air for 1 hour. Heat treatment of coated sample were carried out at 800°C in a vacuum furnace. In order to characterize the phase composition and microstructure of the coating before and after heat treatment, XRD and SEM-EDX were used. The results show that Cr, Cr-Al or Al coatings were formed on the surface of low carbon steel. After heat treatment, new phases and interdiffusion zone were formed in the coating and at the coating/steel interface, depending on the coating composition.

Synthesis of CuMn2O4 spinel and its magnetic properties characterization

Cooper manganite (CuMn2O4) has been widely known as a material that has unique magnetic properties because it depend on the synthesize method. In this paper, a promising method has been developed to synthesize the CuMn2O4 spinel using high purity Cu and Mn powders. The mixing of Cu and Mn powders was carried out through wet milling technique with Cu and Mn atomic ratio (%) of 1:2. The powder was then calcinated in order to form the CuMn2O4 spinel. The formation of oxide spinel was studied at temperature of 700, 800, 900 and 1000°C for 18u2005h, separately. The phase formation and magnetic properties of the samples were characterized by x-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. According to the XRD patterns, the single crystal phase of spinel can be obtained for calcination at 800°C and 900°C. However, at 1000°C, the spinel decomposed into MnO and CuO compounds. Meanwhile, the magnetic properties of samples are depend on the calcination temperature. The results of magnetic characterization are discussed in this paper.Cooper manganite (CuMn2O4) has been widely known as a material that has unique magnetic properties because it depend on the synthesize method. In this paper, a promising method has been developed to synthesize the CuMn2O4 spinel using high purity Cu and Mn powders. The mixing of Cu and Mn powders was carried out through wet milling technique with Cu and Mn atomic ratio (%) of 1:2. The powder was then calcinated in order to form the CuMn2O4 spinel. The formation of oxide spinel was studied at temperature of 700, 800, 900 and 1000°C for 18u2005h, separately. The phase formation and magnetic properties of the samples were characterized by x-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. According to the XRD patterns, the single crystal phase of spinel can be obtained for calcination at 800°C and 900°C. However, at 1000°C, the spinel decomposed into MnO and CuO compounds. Meanwhile, the magnetic properties of samples are depend on the calcination temperature. The results of magnetic ...

Effects of Sintering Holding Time on the Structural, Electrical and Magnetic Properties of Zn0.95Ni0.05O

Zn0.95Ni0.05O has been synthesized by mixing 5% mol of NiO into ZnO using solid state reaction and high-speed shaker mill method. The samples were sintered at 900 °C with holding time for 2, 4 and 8 hours. Crystal structure, electrical and magnetic properties of Zn0.95Ni0.05O were characterized by using XRD, I-V, C-V and VSM. XRD results showed that variation of holding time does not change the structure of ZnO and no other secondary phase observed. The value of lattice parameters (a and c) tends to decrease proportionally to the holding time. The Intensity value changes and the peak shifted to a higher 2θ angle due to holding time variation. In general, the conductance of Zn0.95Ni0.05O decreases and the magnetic properties decrease also as the holding time is increased.

Preparation and characterization of zinc oxide doped with ferrite and chromium

In this paper, the effect of doping concentrations of Fe and Cr on ZnO powder was studied by using X-ray diffraction (XRD). The ZnO was doped using solid state reaction method with High Speedshaker Mill (HSM) and continued with sintering at 900°C for 4 hours. Samples doped with Fe and Cr have polycrystalline hexagonal wurtzite structure. XRD pattern of ZnO doped with Fe is not far different from that with Cr. The intensity decrease and the peak shifted to a higher 2θ angle indicate the change in the crystal parameters such as lattice parameters, crystalline sizes, and d-spacing.In this paper, the effect of doping concentrations of Fe and Cr on ZnO powder was studied by using X-ray diffraction (XRD). The ZnO was doped using solid state reaction method with High Speedshaker Mill (HSM) and continued with sintering at 900°C for 4 hours. Samples doped with Fe and Cr have polycrystalline hexagonal wurtzite structure. XRD pattern of ZnO doped with Fe is not far different from that with Cr. The intensity decrease and the peak shifted to a higher 2θ angle indicate the change in the crystal parameters such as lattice parameters, crystalline sizes, and d-spacing.

PREPARASI MAGNET SINTER Pr-Fe-B DENGAN MENGGUNAKAN SPARK PLASMA SINTERING

Penelitian ini bertujuan untuk mempreparasi sinter Pr-Fe-B dengan teknik spark plasma sintering (SPS). Proses fabrikasi dilakukan di dalam ruang vakum bertekanan kurang dari 60 Pa di mana powder dikompaksi pada tekanan 40 MPa pada temperatur yang berbeda: 800 o C, 900 o C, dan 1050 o C. Komposisi fase dari kompak material tersebut dianalisis dengan X-ray diffractometer (XRD Shimadzu-7000 TM ;). Sampel kemudian dimagnetisasi dengan impulse magnetizer K-series, Magnet-Physik Dr. Steingroever GmbH TM . Hasil penelitian menunjukkan bahwa dengan meningkatnya temperatur SPS, kuat medan magnet permukaannya menurun. Hal ini diduga disebabkan oleh pembentukan Fe phase yang memiliki sifat buruk terhadap properti magnet Pr-Fe-B.

Fe-Si-Al Alloys Prepared by a Spark Plasma Sintering Technique

Fe-Si alloys with various concentration of Al (0, 1, 3 and 5 % by mass) were synthesized by a spark plasma sintering technique. The specimens were prepared in an evacuated chamber of less than 4 Pa and under compressive stress of 40 MPa. During spark discharge, the heating rate was fixed at 10°C/min. After the SPS process was completed, the specimen surfaces were ground with silicon carbide papers. The metallographic characterization was performed by mean of X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX) spectroscopy. According to sintering curves, all samples seem to have a similar sintering behavior. The densification of specimens was completed in the temperature range of about 1020-1050°C. Microstructure and phase characterization revealed that the alloys were mainly composed of FeSi2 and FeSi phases containing oxide inclusions. The SEM images indicated that the fraction of FeSi phase and oxide inclusions appears to decrease with increase in Al concentration in the Fe-Si alloy.