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Pengaruh pH, Suhu dan Waktu pada Sintesis LiFePO4/C dengan Metode Sol-Gel Sebagai Material Katoda untuk Baterai Sekunder Lithium Yuniarti, Endah; Triwibowo, Joko; Suharyadi, Edi
Berkala Ilmiah MIPA Vol 23, No 3 (2013)
Publisher : FMIPA UGM

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Abstract

Sintesis LiFePO4/C dengan metode sol-gel sebagai material katoda baterai sekunder litium telah dilakukan. Bahan pembentuk LiFePO4 adalah serbuk Li2CO3, FeC2O4.2H2O dan NH4H2PO4. Asam sitrat digunakan sebagai sumber karbon pada material katoda LiFePO4. Parameter sintesis yang telah diteliti adalah nilai keasaman (pH), suhu dan waktu sinter. Pengaruh parameter sintesis terhadap morfologi serbuk material katoda LiFePO4/C terkait dengan nilai konduktivitas dan performa elektrokimia telah dianalisis. Nilai keasaman (pH) prekursor divariasi dari 5; 5,4, dan 5,8. Suhu dan waktu pada proses sintesis divariasikan yaitu 600, 700 dan 800ºC serta 6, 8 dan 10 jam. Komposisi fasa dari material katoda hasil sintesis dianalisis dengan X-Ray Diffractometer (XRD). Hasil analisis menunjukkan bahwa fasa dominan yang terbentuk adalah LiFePO4. Morfologi material katoda dianalisis dengan Scanning Electron Microscopy (SEM). Kenaikan nilai pH akan memperkecil diameter butir. Selain itu, aglomerasi butir terjadi seiring meningkatnya suhu dan waktu sinter. Luas permukaan spesifik material katoda diperoleh dari uji Brunauer Emmett and Teller (BET) dengan nilai 7,743 m2/gr dihasilkan oleh sampel dengan pH 5,8 yang disinter pada suhu 700°C selama 10 jam. Hasil uji Electrochemichal Impedance Spectroscopy (EIS) menunjukkan bahwa konduktivitas listrik LiFePO4/C tertinggi diperoleh pada sampel ber-pH 5,8 dengan suhu sinter 700°C delama 6 jam yaitu 1,842x10-3 S/cm. Kurva Cyclic Voltammetry (CV) yang menunjukkan reaksi redoks paling stabil berdasarkan rentang pH 5, suhu sinter 600 sampai 800°C selama 6 sampai 10 jam diperoleh dari sampel dengan pH 5,8 yang disinter pada suhu 700°C selama 6 jam.
Initial Modelling of Bird Strike by Numerical Simulation in Varied L/D Ratio of Bird Geometry Yuniarti, Endah; H, Simon Shindu; Sitompul, Sahril Afandi
SENATIK STT Adisutjipto Vol 4 (2018): Transformasi Teknologi untuk Mendukung Ketahanan Nasional [ ISBN 978-602-52742-0-6 ]
Publisher : Sekolah Tinggi Teknologi Adisutjipto

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Abstract

This research studies influence of bird geometry on impact pressures during bird strike, namely Hugoniot and Stagnation pressure through initial modelling by numerical simulations. Bird geometry is capsule or cylinder with hemisphere end. The geometry is simulated with different L/D ratio, 1.4, 1.6, 1.8 and 2.0. Elastic-plastic hydrodynamic material model is used in simulation. Bird model simulation are using lagrangian method and initial velocities are 200 m/s. The results show variation of L/D ratio provide Hugoniot pressure 10-19 times higher than stagnation pressure in L/D = 1.4, 8-18 times in L/D = 1.6, 9-17 times in L/D = 1.8 and 4-16 times in L/D = 2. Hugoniot pressures show higher in ratio L/D = 1.8 and lower in ratio L/D = 1.6. Stagnation pressure show higher in ratio L/D = 2.0 and lower in ratio L/D 1.4.
EFFECT OF FLAT AND HEMISPHERICALLY ENDED CYLINDER BIRD MODEL WITH FINITE ELEMENT MODELLING OF BIRD STRIKE Yuniarti, Endah
Jurnal Teknologi Dirgantara Vol. 17 No. 1 Juni 2019
Publisher : Lembaga Penerbangan dan Antariksa Nasional

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Abstract

This research studies influence of bird model on impact pressures during bird strike, namely Hugoniot and Stagnation pressure through initial modelling by numerical simulations using finite element method. Finite element simulation of bird strike have primarily modelled the bird as either a flat or hemispherically ended cylinder. The geometry is simulated with different L/D ratio, 1.4, 1.6, 1.8 and 2.0. Elastic-plastic hydrodynamic material model is used in simulation. Bird model simulation are using lagrangian method and initial velocities are 100, 200 and 300 m/s. Simulation results of hemispherically ended cylinder bird models show variation of L/D ratio provide Hugoniot pressure 10-19 times higher than stagnation pressure in L/D = 1.4, 8-18 times in L/D = 1.6, 9-17 times in L/D = 1.8 and 4-16 times in L/D = 2. The Hugoniot pressure shows a lower value at an L/D ratio of 1.6 compared to other ratios and the Stagnation pressure is higher at L/D ratio 2. As for cylindrical bird model show variation of L/D ratio provide Hugoniot pressure 35-38 times higher than stagnation pressure in L/D = 1.4, 30-47 times in L/D = 1.6, 31-52 times in L/D = 1.8 and 28-48 times in L/D = 2. The Hugoniot pressure shows a lower value at an L/D ratio of 1.4 and 1.6 compared to other ratios and the Stagnation pressure is higher at L/D ratio 2.
ESTIMASI DISTRIBUSI BERAT SAYAP DAN DISTRIBUSI LIFT UNTUK OPTIMASI BENDING MOMENT DENGAN SISTEM FUEL TRANSFER PADA PESAWAT BOEING 737-500 Arifin, Mufti; Yuniarti, Endah; Sari, Rafika Arum; Said, Ahmad Akmal
JTK: JURNAL TEKNOLOGI KEDIRGANTARAAN Vol 4, No 2 (2019): JURNAL TEKNOLOGI KEDIRGANTARAAN
Publisher : JTK: JURNAL TEKNOLOGI KEDIRGANTARAAN

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Abstract

Aside from being a manufacturer of lift force, a wing is functioning hold the load that occurs in the structure of the aircraft, such as the shear load, twist and bending. Of all the load the load bending is the greatest burden are received by the wings. Setting the load bending is one of the major factors in reducing the burden experienced by the wing. However, the optimal value indicated opposite between on land and in the air, to take advantage of the situation to use fuel system transfers the load alleviation. Fuel transfer load alleviation is a system that automatically move the fuel more in the tank at the time in part on land and are on the outside of the tank at the time in the air so that the effect of the load bending bending loads can be reduced, which generated as the result of addition between the weight distribution and the distribution of lift that occurs on the wings so as to calculate the bending data needed weight distribution and the distribution of lift on the wing. This research aims to know the weight distribution occurs on the wings of the Boeing 737-500. The value of the weight distribution and distribution of lift yield optimization moment on two States namely, on land and in the air with three variations of the fuel transfer that is, constant with a value of 40134.53 N, linear with a value of 48059.53 N, and the maximum value of 172386.50 N.