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All Journal Journal of Engineering and Technological Sciences Teknologi Indonesia Journal of Engineering and Technological Sciences
Yuyun Irmawati
Pusat Penelitian Fisika (P2F) - LIPI Jl. Sangkuriang/Cisitu No.21/154D, Bandung
Aerospace Engineering Automotive Engineering Chemical Engineering, Chemistry & Bioengineering Civil Engineering, Building, Construction & Architecture Computer Science & IT Electrical & Electronics Engineering Engineering

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Comparative Study of Bacterial Cellulose Film Dried Using Microwave and Air Convection Heating Indriyati, I.; Irmawati, Yuyun; Puspitasari, Tita
Journal of Engineering and Technological Sciences Vol 51, No 1 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (241.249 KB) | DOI: 10.5614/j.eng.technol.sci.2019.51.1.8

Abstract

An investigation was conducted to analyze and compare the properties of bacterial cellulose (BC) films dried using microwave and air convection heating. Prior to the drying process, 90% of the water content inside the BC pellicles was removed through vacuum filtration. After that, the required drying time was only 3-5 min using microwave heating, 95% shorter than that observed for air convection heating. The properties of the BC sheets were characterized by Fourier transform infrared (FTIR), X-ray diffractometer (XRD), color difference meter, and tensile tester machine. The results showed that the structure of the BC films was the same for the BC films dried by microwave and air convection heating, i.e. cellulose I, as observed from FTIR spectra and XRD diagrams. Moreover, their color (L*, a*, and b* values) and mechanical properties were also almost identical. However, a slightly lower crystallinity and a higher swelling degree were observed for the BC film dried using microwave heating. These results suggest that microwave heating could be an alternative method of drying BC pellicles in order to shorten the processing time and reduce energy consumption when compared to air convection heating.
INVESTIGATION OF THE PERFORMANCE OF SINGLE AND MULTI-CELL STACKS OF PEMFC -, Indriyati; Irmawati, Yuyun; Subhan, Achmad
Teknologi Indonesia Vol 38, No 3 (2015)
Publisher : LIPI Press

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (16.054 KB) | DOI: 10.14203/jti.v38i3.132

Abstract

The performance of single, 3-cell, and 5-cell stacks of PEMFC have been experimentally investigated. Emphasiswas placed on the effect of different operating condition including hydrogen/oxygen flow rate and pressure on thePEMFC performance through analysis of polarization curves. The results showed that flow rate slightly affected theperformance of single-cell PEMFC at higher current densities whereas no significant differences were observed atlower current densities. Similar curve patterns were obtained when testing the single and 3-cell PEMFC stacks withvariation of backpressure. Increasing backpressure gives positive effect on the stack performance due to improvingthe reaction at the electrodes. However, this behavior did not occur on 5-cell PEMFC stack the performance of which decreased as the backpressure increased from 5 to 10 psi due to increasing water production in the cathode. In this study, the highest operational (at voltage of 0.6 V) current density of 85.6 mA/cm2 was obtained from 3-cell stack with flow rate of H2/O2 and backpressure 800/1,000 ml/min and 10 psi, respectively. This good performanceis more evident when the 3-cell stack was evaluated over a quite long operation time. After decreasing gradually at the first 50 min operation, the performance of 3-cell stack of PEMFC remained stable up to 200 min, while it fluctuated in 5-cell stack due to poor water management. This study confirms that the performance of PEMFC stack is highly influenced by the number of cell and operating condition, and the performance of PEMFC stack is not linear as function of number of cell.
Solvent-free Synthesis of Transition Metals Nanoparticles Decorated Foamy Flakes-like Nitrogen-doped Carbon as Bifunctional-catalyst for High-performance Rechargeable Zn-air Batteries Persada, Pilar Bela; Tan, Davin Adinata; Akmalia, Rachendra; Irmawati, Yuyun; Sumboja, Afriyanti
Journal of Engineering and Technological Sciences Vol. 56 No. 5 (2024)
Publisher : Directorate for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2024.56.5.10

Abstract

Transition metal-nitrogen-carbon (M/NC) demonstrates a promising effective electrocatalyst for enhancing oxygen evolution/reduction reactions (OER/ORR). However, synthesizing these catalysts is often complex, time-consuming, and involves hazardous solvents while producing a low yield. This work introduces a versatile, eco-friendly, and straightforward solvent-free method to produce M/NC (M = Co, Ni, and Fe) catalysts in ~3 h using a glucose, urea, and metal nitrate hydrate mixture. The high-yield M/NC catalysts exhibit a porous architecture and uniform distribution of metal nanoparticles within a foaming flakes-like nitrogen-doped carbon matrix. The metal nanoparticles are wrapped with protective nitrogen-doped carbon layers, producing stable active sites. Possessing these unique properties, the obtained M/NC catalysts show high-performance and stable bifunctional OER/ORR. As the best result, Co/NC presents an OER/ORR potential difference (ΔE) of 0.78 V and retains 96% and 89% of its OER and ORR performance after a 10 h stability test. In practical application, the Co/NC-based Zn-air battery depicts a high power density of 184 mW cm−2 and good rechargeability of up to 120 h, outperforming the battery with noble metal-based catalysts. This work sheds light on the versatile, eco-friendly, and scalable synthesis of M/NC catalysts while presenting a strategy to accelerate the generation of inexpensive and highly effective bifunctional OER/ORR catalysts.
Co-Authors -, Indriyati Achmad Subhan Akmalia, Rachendra Indriyati, I. Persada, Pilar Bela Sumboja, Afriyanti Tan, Davin Adinata Tita Puspitasari