Wahyu Bambang Widayatno

Analysis of aluminum base-reaction effect in density, porosity, and thermal insulation of porous fire bricks

This paper reports the effect of aluminium corrosion reaction on the density, porosity, and thermal insulation capability of porous fire bricks. The reaction between aluminium and alkaline solution produces hydrogen and other sediment products. The test specimens of fire bricks were made from the mixture of castable cement, aluminium powder of 325 mesh in size (0, 0.1, 1, and 2 wt% with respect to castable cement), and 0.185 M KOH solution. The structural examination of the specimens shows the increase of porosity to 22.7 - 30.6% and the decrease of density in the range of 1.135-1.503 g/mL. In addition, the samples possess average pore size of 0.001-0.003 cm3 with the thermal insulation in the range of 47-78%.This paper reports the effect of aluminium corrosion reaction on the density, porosity, and thermal insulation capability of porous fire bricks. The reaction between aluminium and alkaline solution produces hydrogen and other sediment products. The test specimens of fire bricks were made from the mixture of castable cement, aluminium powder of 325 mesh in size (0, 0.1, 1, and 2 wt% with respect to castable cement), and 0.185 M KOH solution. The structural examination of the specimens shows the increase of porosity to 22.7 - 30.6% and the decrease of density in the range of 1.135-1.503 g/mL. In addition, the samples possess average pore size of 0.001-0.003 cm3 with the thermal insulation in the range of 47-78%.

Characterization of Sumbawa manganese ore and recovery of manganese sulfate as leaching products

The aims of this research were to study the leaching process of manganese ore which originated from Sumbawa, Indonesia and its characterization. A high grade Indonesian manganese ore from Sumbawa, West of Nusa Tenggara was characterized by X-Ray Fluorescence (XRF). The result showed composition of 78.8 % Mn, 17.77% Fe and the rest were trace elements such as Si, Co, Ti, Zn, V and Zr contents. X-Ray Diffraction analysis showed that the manganese ore was consisted of pyrolusite (MnO2), rhodonite (MnSiO3), rhodochrosite (MnCO3) and hematite (Fe2O3). Manganese ore was also analyzed by thermal analysis to observe their thermal decomposition character. In this study, sulphuric acid (H2SO4, 6 M) was deployed as leaching agent. The leaching process was performed at 90 °C for two hours with the addition of NH4OH to control pH. Recovery percentage of leaching process yielded of 87 % Mn extracted. The crystallization process result at heating temperature of 200 °C was confirmed by XRD as manganese sulfate.The aims of this research were to study the leaching process of manganese ore which originated from Sumbawa, Indonesia and its characterization. A high grade Indonesian manganese ore from Sumbawa, West of Nusa Tenggara was characterized by X-Ray Fluorescence (XRF). The result showed composition of 78.8 % Mn, 17.77% Fe and the rest were trace elements such as Si, Co, Ti, Zn, V and Zr contents. X-Ray Diffraction analysis showed that the manganese ore was consisted of pyrolusite (MnO2), rhodonite (MnSiO3), rhodochrosite (MnCO3) and hematite (Fe2O3). Manganese ore was also analyzed by thermal analysis to observe their thermal decomposition character. In this study, sulphuric acid (H2SO4, 6 M) was deployed as leaching agent. The leaching process was performed at 90 °C for two hours with the addition of NH4OH to control pH. Recovery percentage of leaching process yielded of 87 % Mn extracted. The crystallization process result at heating temperature of 200 °C was confirmed by XRD as manganese sulfate.

CRYSTAL STRUCTURE TRANSFORMATION OF Ba-Sr HEXAFERRITE AND ITS EFFECT ON PARTICLE ORIENTATION IN RECYCLE PROCESS

CRYSTAL STRUCTURE TRANSFORMATION OF Ba-Sr HEXAFERRITE AND ITS EFFECT ON PARTICLE ORIENTATION IN RECYCLE PROCESS . In general, during its fabrication, 2-5%of total products of Ba-Sr hexaferrite permanent magnet will be rejected.Accordingly, an increase in rejected product of permanent magnet needs to be considered. It is expected that the re-utilization of rejected product can increase the production efficiency in order to achieve zero waste-production. In the present work, the recycling process of Ba-Sr hexaferrite permanent magnet was studied by applying 1 T magnetic field (anisotropic) to align the powder. The rejected products were milled using shaker mill PPF-UG for 10-40 min and then sintered at 1200 oC for 60 min. The results show that the remanence of original powder was increased by 50% after the particle orientation. However, the recycled sample doesn’t show a significant different. SEM and XRD analysis show the crystalline structure transformation from symmetrical hexagonal to asymmetrical hexagonal structure with crystalline growth in a-b axis direction. This transformation leads to lost in its magneto crystalline anisotropy. Therefore, it was difficult to align the particle.

Characterization of dross and its recovery by sulphuric acid leaching

This paper reports the characterization of dross from galvanizing process and its recovery using acidic leaching method. The diffraction profile of dross showed identical peaks with that of ZnO. The X-ray Fluorescence (XRF) analysis identified the content of following metals: Zn, Fe, Mn, Ga, Co, and W. The thermal behaviour examination revealed the existence of some volatiles within the initial sample. The acidic leaching at various concentrations of sulphuric acid was conducted to determine the optimum concentration for zinc recovery and the highest yield of zinc sulphate. It is concluded that the optimum concentration of H2SO4 for this kind of dross is 4 M with 71.9% yield of ZnSO4. The result of leaching process was confirmed by infrared spectrum, where various absorptions corresponding to SO4 2- and Zn-O bands were observed.

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.

In Situ Al/Al2O3 Composite Coating on Steel Substrate Prepared by Mechanical Alloying at High Temperature

In this study a new technique for producing an Al/Al2O3 composite coating on a steel substrate by an in situ process was examined. The pre-treating of the steel substrate with Al was carried out by MA at room temperature, followed by MA using a low-energy ball mill at 200-500°C. An Al/Al2O3 coating layer with a homogenous distribution of Al2O3 particles were achieved. The coating layer has not only high hardness but also high fracture toughness.