Key Engineering Materials Vols. 594-595

Abstract: This paper presents a study on the relationship between porosity and compressive strength for geopolymer paste. In this research, geopolymer paste was made from fly ash class F based geopolymer mixed with alkaline activator; sodium hydroxide solution and sodium silicate solution. Twelve mixes were cast in 50mm x 50mm x 50mm moulds and the samples were cured for 24 hrs at 60 °C in the oven. The samples were examined after 7, 14, 28 and 90 days in terms of porosity test, pulse velocity test and compressive strength test. It was concluded that the sample at day 90 had the highest compressive strength of 56.50 N/mm² had porosity 3.77%. Thus, the sample with lowest porosity had highest pulse velocity 3303 m/s during ultrasonic testing with lowest transmission time 15.17 μs. Keywords: porosity, compression strength, geopolymer, pulse velocity

Abstract: In this work the influence of electrolytic-plasma nitriding on the abrasive wear-resistance of R6M5 high-speed steel were under research. We registered that after electrolytic-plasma nitriding on R6M5 steel surface modified layer is formed with 20-40 μm thickness and with increased microhardness of 9000-12200 MPa. Testing mode for the nitrided samples high-speed steel on abrasive wear developed. It is established, that electrolyte-plasma nitriding allows to increase wear-resistance of R6M5 steel surface layer comparing to original. It was determined that abrasive wear-resistance of R6M5 steel surface layer is increased to 25% as a result of electrolytic plasma nitriding. Thus, studies have demonstrated the feasibility and applicability of electrolytic-plasma nitriding in order to improve cutting tools work resource, working under friction and wear conditions.

Abstract: This paper presents theoretical and experimental research works on the effect of aluminium heat sink and heat dissipation in a portable thermoelectric (TE) cooling system. In this study, three units of TE modules were utilized with an inputs of 3 A and 8 V. The aluminium heat sink was used to spread the heat generated by TE modules through its fins and surface area. The cold temperature was spread through by an aluminium cold sink with direct blow to the cooling space. The air flow rate was accelerated by the use of centrifugal blower on both sides of the heat dissipation system. The temperature of the cooling space caused was examined. The performance of TE module with the utilization of hot and cold sinks has shown that a greater heat dissipation rate was achieved.

Abstract: Two different shapes of knives (L and Y-shaped) for the rotary slasher with 300 knife cutting angle at three cutting speeds (1830, 2066 and 2044 rpm) were used to indicate their effects on the power consumption for pulverizing sweet potato vine which passed through the sieve (< 28 mm²). The results indicated that all the treatments were significant at p 0.01 significance level for the power consumption on sweet potato vine pulverizing. The best result was recorded from L-shaped knife with a power consumption of 52.12 Watts for sweet potato vine pulverization. Meanwhile, the best result was for the mower speed at 1830 rpm with the lowest power consumption of 61.23 Watts. The best performance for interaction between knife shapes and the cutting speeds was achieved by the L-shaped knife at 1830 rpm with lowest power consumption of 50.23 Watts at p 0.01.

Abstract: Zinc Oxide (ZnO) has been successfully electrodeposited on a fluorine doped tin oxide (FTO) coated glass substrates using a simple aqueous solution containing zinc nitrate hydrate by low temperature galvanostatic electrolysis. The solution temperature of zinc nitrate hydrate was varied from 60°C to 75°C in order to investigate the effect of solution temperature on electrodeposit-ZnO thin film. The properties of ZnO film were investigated by X-ray diffraction (XRD), Field-Emission Scanning electron microscope (FE-SEM) and Atomic force microscopy (AFM). The solution temperature shows a significant effect on structural and morphological of deposit-ZnO. The XRD patterns exhibited the increment of (002)-ZnO peak when the solution temperature increased and the highest peak was observed at 75°C. The morphology of ZnO was changed from planar to nanopillar with the solution temperature. In conclusion, ZnO nanopillar with an excellent structural properties was obtained at solution temperature of 75°C.

Abstract: This paper described the performance of transformer affected by different limb assembling. The experiment that used to investigate core is no-load, short circuit and load test to find the core loss, copper loss, flux leakage at corner joint and limb and total harmonic distortion of the flux at flux density range from 0.2 T to 1.6 T, 50 Hz. From the result of this investigation shows the core loss of transformer assembled with 2 limbs is 18.45% and 32.21% better than the transformer assembled with 3 and 5 limbs respectively at a flux density of 1.6T, 50 Hz. To increase the numbers of core limb assemble will reduce the efficiency of transformer.