Rindang Fajarin

The effect of calcination temperature on the capacitive properties of WO3-based electrochemical capacitors synthesized via a sol-gel method

Electrochemical capacitor (EC) is a promising energy storage device which can be hybridized with other energy conversion or energy storage devices. One type of ECs is pseudocapacitor made of metal oxides. WO3 is an inexpensive semiconductor metal oxide which has many applications. However the application of WO3 as an EC material was rarely reported. Therefore in this research EC was prepared from WO3 nanomaterial synthesized by a sol-gel process. The WO3 gel was spin-coated on graphite substrates and calcined at various temperatures of 300°C, 400°C, 500°C and 600°C for 1 h. Cyclic voltammetry (CV) measurements were used to observe the capacitive property of the WO3 samples. SEM, XRD, FTIR and Brunauer-Emmett-Teller (BET) analyses were used to characterize the material structures. WO3 calcined at 400°C was proved to have the highest capacitance of 233.63 F·g−1 (1869 mF·cm−2) at a scan rate of 2 mV·s−1 in 1 mol/L H2SO4 between potentials −0.4 and 0.4 V vs. SCE. Moreover it also showed the most symmetric CV curves as the indication of a good EC. Hence WO3 calcined at 400°C is a potential candidate for EC material of pseudocapacitor type.

Pengaruh Variasi Komposisi BaM/PAni Matriks Cat Epoxy Pada Pelapisan Single Layer Dengan Metode Spray Coating Untuk Aplikasi Material Penyerap Radar

Penyerapan gelombang mikro dapat dilakukan melalui rekayasa material, menggunakan material RAM ( RadarAbsorbing Material ) yang terdiri dari material resistif dan material magnetik untuk menyerap gelombang radar. Material magnetik yang digunakan adalah BaM (Barium Heksafferit). Sintesis material BaM menggunakan metode solid state. Material BaM di dopping dengan Zn 2+ untuk meningkatkan nilai Magnetic Saturation (Ms) dari 58,97 emu/gr menjadi Ms 60,04 emu/gr dan menurunkan nilai koersivitas (Hc) dari 4743 Oe menjadi 833,17 Oe. PAni (Polianiline) merupakan material polimer konduktif yang digunakan pada penelitian ini. Material PAni didapatkan dengan proses polimerisasi oksidasi kimia. Penggunaan PAni dikarenakan memiliki stabilitas thermal dan konduktivitas listrik yang baik sebesar 1,579 x 10 -5 S/cm. Komposit BaM/PAni kemudian dicampurkan dengan cat epoxy dengan variasi persen berat 5,10,15 wt%. Kemudian dilapiskan pada material alumunium 2024 dengan metode spray coating dengan lapisan single layer. Untuk mengetahui nilai rugi refleksi dari material RAM yang telah dilapisi pada plat alumunium dilakukan pengujian VNA ( Vector Network Analyzer) pada rentang frekuensi 8-12 GHz. Didapatkan nilai R L maksimum sebesar -26,34 dB 9,33 GHz dengan ketebalan 59,1 micron pada komposisi BaM/PAni 15 wt%. Dari hasil penyerapan dan nilai ketebalan yang didapatkan, komposisi komposit BaM/PAni 15 wt% terhadap matriks cat epoxy sesuai untuk aplikasi RAM pada pesawat.

The Effects of the Addition of Silica Mol Fraction (x = 1.5; 2; 2.5) as a Solid Electrolyte on Ion Conductivity of NASICON (Na1-xZr2SixP3-xO12) Using Solid-State Method

Energy is a very important in modern life and need innovations to develop it. One innovation is the application of energyfor storage devices, such as batteries, capacitors, fuel cells, etc. For 30 years, the application of the NASICON (Na1+xZr2SixP3-xO12) into the NASICON gas sensor material was successfully prepared by using solid-state method. The raw materials such as SiO2, Na2CO3, ZrO2, and NaH2PO4 with a little methanol were mixed in Ballmill equipment. The silica powder was made by the extraction of bagasse ash by using sol-gel method. The x-ray diffraction patternshowedthat the result of silica extraction was amorphous and the NASICON structure wassynthesizedto bemonoclinic. The scanning electron microscopy results indicated that silica had non-uniform surface morphology and the NASICON had good surface morphology only on the form of Na3Zr2Si2PO12. The ionic conductivty of NASICON wasshown on LCR Nyquist plot of the three compositions. The highest NASICON conductivity was found inthe composition of x = 2.0, i.e. 1.142x10-8 S/m.

Milling time and temperature dependence on Fe2TiO5 nanoparticles synthesized by mechanical alloying method

Fe2TiO5 is one type of titanate oxides which has MxTiyOz crystal structure. It has various kinds of applications due to its electric and magnetic properties such as spintronics, electromagnetic devices, and gas sensor. In this study, Fe2TiO5 nanoparticles were synthesized by simple mechanical alloying using planetary ball milling machine with various milling times and sintering temperatures. TiO2 and Fe2O3 powders obtained from coprecipitation process were used as starting materials. The resulted Fe2TiO5 powders were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Vibration Sample Magnetometer (VSM) in order to observe crystal quality, particles morphology, and magnetic properties respectively. As the milling time increases and the sintering temperature decreases, the crystal size of Fe2TiO5 phase decreases. The smallest crystal size of the synthesized Fe2TiO5 nanoparticles was ∼ 51 nm obtained by the milling time of 25 hours and sintering at 1100°C. The distribution of t...