Didik Aryanto

Preparation and structural characterization of ZnO thin films by sol-gel method

ZnO thin films were prepared on glass substrate by sol-gel spin-coating method using zinc-acetate dihydrate as precursor. Effect of precursor concentration on the morphological and structural of the films was investigated. The diffraction patterns of X-ray diffraction (XRD) characterization indicated that all of ZnO thin films were polycrystalline with a hexagonal wurtzite crystal structure. The peaks were indexed to (100), (002) and (101) planes. Intensity of all diffraction peaks increased and became broader in full width at half maximum (FWHM) values with increasing precursor concentration. The calculation of texture coefficient (TC) indicated that ZnO thin films exhibited the preferential orientation growth along the c-axis. Increasing precursor concentration resulted in decreasing crystalline size and crystallization of the film. The lattice constants (a and c) and d-spacing also changed as function of precursor concentration. It was demonstrated by the bond length, volume per unit cell, lattice strain and dislocation density. The scanning electron microscopy (SEM) images of surface morphology of the films confirmed the results of XRD characterization. The grain size of ZnO thin films decreased as result of increasing precursor concentration. Cross-section of SEM images showed that the thickness of ZnO thin film increases from 149.4 nm to 447.7 nm with increasing precursor concentration. This works shown that morphological and structural of ZnO thin films prepared using sol-gel spin coating methods were strongly influenced by precursor concentration.

Structure and high temperature oxidation of mechanical alloyed Fe-Al coating

The structure and high temperature oxidation resistance of Fe-Al coating on low carbon steel were investigated. The Fe-Al coating was deposited on the surface of low carbon steel using a mechanical alloying method. The coating was then annealed at 600°C for 2 hour in a vacuum of 5u2005Pa. The cyclic-oxidation tests of low carbon steel, Fe-Al coatings with and without annealing were performed at 600°C for up to 60h in air. The structure of oxidized samples was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy X-ray spectroscopy (EDS). The results show that the Fe-Al coatings exhibit high oxidation resistance compared to the uncoated steel. After 60u2005h exposure, the uncoated steel formed mainly Fe3O4 and Fe2O3 layers with the total thickness of around 75.93u2005µm. Fe-Al coating without annealing formed a thin oxide layer, probably (Fe,Al)2O3. Meanwhile, for annealed sample, EDX analysis observed the formation of two Fe-Al layers with difference in elements concentration. The obtained results suggest that the deposition of Fe-Al coating on low carbon steel can improve the oxidation resistance of low carbon steel.The structure and high temperature oxidation resistance of Fe-Al coating on low carbon steel were investigated. The Fe-Al coating was deposited on the surface of low carbon steel using a mechanical alloying method. The coating was then annealed at 600°C for 2 hour in a vacuum of 5u2005Pa. The cyclic-oxidation tests of low carbon steel, Fe-Al coatings with and without annealing were performed at 600°C for up to 60h in air. The structure of oxidized samples was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy X-ray spectroscopy (EDS). The results show that the Fe-Al coatings exhibit high oxidation resistance compared to the uncoated steel. After 60u2005h exposure, the uncoated steel formed mainly Fe3O4 and Fe2O3 layers with the total thickness of around 75.93u2005µm. Fe-Al coating without annealing formed a thin oxide layer, probably (Fe,Al)2O3. Meanwhile, for annealed sample, EDX analysis observed the formation of two Fe-Al layers with difference in elements concentration. The...

REMANENSI DAN FLUX DENSITY DARI BERBAGAI BENTUK GEOMETRI MAGNET PERMANEN

dari berbagai bentuk geometri magnet permanen berbasis ferrite (BaFe 12 O 19 ) dan logam tanah jarang (NdFeB). Nilai remanensi magnet (B r ) diperoleh dari kurva histerisis (B-H curve) yang diukur dengan alat permagraph dan flux density B z diukur secara langsung dengan menggunakan gaussmeter. Bentuk geometri dan jenis sampel uji adalah cube, ring, dan disk dari magnet permanen berbasis NdFeB dan BaFe 12 O 19 . Dari hasil penelitian diketahui bahwa magnet permanen berbasis NdFeB memiliki nilai remanensi yang lebih besar dibanding dengan magnet permanen berbasis BaFe12O19. Dari pengukuran magnet permanen berbasis BaFe 12 O 19 didapatkan nilai Br = 1:17 kG untuk bentuk geometri ring dan untuk disk didapat sebesar Br = 1:78 kG, sedangkan dari magnet permanen berbasis NdFeB yang berbentuk cube (tipe 1), cube tipe 2, dan disk didapatkan nilai Br = 7:5 kG, Br = 10:8 kG, dan Br = 5:2 kG. Untuk pengukuran flux density Bz sebagai fungsi jarak z didapatkan kesesuaian antara eksperimen dan teori. Berdasarkan hasil penelitian didapatkan bahwa nilai B r dan B z sangat dipengaruhi oleh bentuk geometri dan jenis magnet permanen.

The Orientation Study of Ba-Sr Hexaferrite Particles by Parallel Magnetic Field Press

It is well known that an orientation treatment on magnetic particles may increase magnetic flux density than that of those without treatment. In this work, the study on orientation of Barium Stronsium Hexaferrite (Ba-Sr Hexaferrite) particles using parallel system of magnetic field press was conducted to investigate the effect of powder orientation on its characteristic. Samples were compacted while the varied magnetic field induction were given, molded and then sintered at 1200°C for 1 hour. The measurement of magnetic properties showed that orientation process increased the value of magnetic remanence up to 173% (1264 Gauss). The magnetic field induction of 0.4 T was found to be the optimum value, where further increase of magnetic field did not give significant change. The crystal structure analysis showed the increase of peak of <001> plane which is correlated with the c-axis of Ba-Sr Hexaferrite crystal. In addition, the peak which is correlated with the opposite direction of c-axis disappeared, while the peaks between those directions decreased significantly. The micrograph of Ba-Sr Hexaferrite particles showed the alignment of c-axis parallel to the given magnetic field induction. These results showed the phenomenon of mechanical particle revolving and particle arrangement during the orientation process by which determined the obtained magnetic remanence.

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.

Fabrication and Characterization of Stacked Self-Assembled In0.5Ga0.5As/GaAs Quantum Dots Grown by MOCVD

Stacked self-assembled In0.5Ga0.5As/GaAs quantum dots (QDs) were grown using metal organic chemical vapor deposition (MOCVD). Atomic force microscopy (AFM), transmission electron microscopy (TEM) and high resolution X-ray diffraction (HR-XDR) show the effects of stacking on morphology and structure of QDs. Strains due to the buried QDs affect the shape and alignment of the successive layers. Capping of these QDs also determine the quality of the top most QDs structure.