Rike Yudianti
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EFFECT OF DIELECTRIC CONSTANT AND DISPERSION OF PARTICLE ON HYDROPHOBICITY OF CARBON NANOTUBE BASED ELECTROCATALYST FILM Yudianti, Rike; Onggo, Holia; Syampurwadi, Anung
Jurnal Sains Materi Indonesia Vol 14, No 1 (2012): Oktober 2012
Publisher : BATAN

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Abstract

Preparation Carbon Nanotube (CNT) based of electrocatalyst film using filtration methode is recently performed. Hydropobicity of electrocatalyst is prerequisite to eliminating PolyTetraFluoroEthylene (PTFE) treament as hydrophobic agent that commonly performed on the comercial electrocatalyst. The preparation was carried out using hydrophilic membrane to obtaining good electrocatalyst film. Technique of preparation and formulation of dispersed solution were optimized to improve hydrophobicity of electrocatalyst film without decreasing its performance. The results indicate that the hidrophobic electrocatalyst film (>90°) is obtained by contribution of solvents which have dielectric constant (ε) >10. The solvents are able to form solution state and totally dissolve of nafion ionomer inducing coverage of carbon fiber surface. Hydropobicity of electrocatalyst film tend to be lower (<90°) in colloidal state by contribution of tetrahydrofuran and chloroform as solvent. Evaluation of hydrophobicity of electrocatalyst film was conducted by contact angle meter using half angle technique. Change of morphological surface of electrocatalyst film on the effect of nafion treatment and dispersion of CNT was analyzed by Scanning Electron Microscope. Relationship between nafion treatment and hydrophobicity of electrocatalyst film was discussed in this paper.Keywords: Hydrophobicity, CNT, Electrocatalyst, Solution state, Colloidal state.
STUDYING ON INFLUENCE OF VARIATION FOR VOLTAGES AND HYDROGEN RATES TO POWER DENSITY PRODUCTION OF POLYMER ELECTROLYTE MEMBRANE FUELCELL Irmawati, Yuyun; ., Indriyati; Onggo, Holia; Yudianti, Rike
Jurnal Sains Materi Indonesia Vol 13, No 3 (2012): Juni 2012
Publisher : BATAN

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Abstract

The studying on influence of variation fan voltages and hydrogen flow rates to power density production of polymer electrolyte membrane fuel cell (PEMFC) had been done. There was also a polarisation curve fitting method to investigate dependence of over potential losses with variation hydrogen flow rates (20-100 mL/minute). Double cells of open cathode PEMFCs stack with active area of 30 cm2 was applied with different fan voltages (3-12Volt) which were got fromexternal electric circuit. As a result, there was an increase of power density in the voltage variation by 47-67% (compared with power density without fan) which rose from 45.16 mW/cm2 to about 70 mW/cm2. The highest power was achieved from 3 volt of fan voltage (73.26 mW/cm2). From the variation of hydrogen flow rates, dead point, which was caused by unbalance stoikiometri between hydrogen and oxygen, was introduced at low flow rate (20-40 mL/minute) and the optimum power (79 mW/cm2) was the result of 50 mL/minute of hydrogen flow rate. Based on polarisation curve fitting, increasing hydrogen flow rate caused increased in activation over potential activation but decreased in diffusion over potential which were results of hydrogen crossover and membrane dehydration. Meanwhile, the ohmic over potential remained constant for all hydrogen flow rate.Keywords: PEMFC, Open cathode, Polarisation curve fitting.
MORPHOLOGICAL AND THERMAL PROPERTIES OF ALKALI TREATED BACTERIAL CELLULOSE FROM COCONUT WATER Indrarti, Lucia; Yudianti, Rike
Jurnal Sains Materi Indonesia Vol 13, No 3 (2012): Juni 2012
Publisher : BATAN

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Abstract

Alkali treatment is one ofwide chemical treatment for removing non cellulosic materials and other impurities of bacterial cellulose (BC). Presently, BC produced by synthetic medium such as Schramm Hestrin or coconut water fermentation using pure culture of Acetobacter xylinum. In this research BC produced from coconut water fermentation using inoculums as suspension of mixture culture of bacteria A. xylinum in coconut water which commercialised in West Java (Cianjur). Purpose of this research is to know the native and the effect of alkali treatment on the BC (heterofermentive) with evaluation ofmorphological, elemental analysis and thermal properties by Scanning ElectronMicroscope (SEM)-Energy Dispersive X-ray Spectroscopy (EDX) and Thermo-Gravimetry Analysis (TGA), respectively. Observation on morphological surface of native BC showes that there were noncellulosic materials entangled on the network of cellulose fibrils whichwere identified by EDX analysis as sodium(Na),magnesium(Mg), aluminium (Al), silica (Si) and potassium (K) in addition to carbon (C) and oxygen(O). On thermal analysis, stepwise of decomposition are observed on the native BC indicating the presence of non-cellulosic components which decomposed at different temperatures.While the alkali- treated BC sheet shows a single decomposition stage. The amount of residue formed after alkali treatment was relatively lower than native BC. Thermal degradation properties of the BC produced from coconut water was higher than that of BC belonging to synthetic medium. Based on this data, it is concluded that alkali treated cellulose can be used as a reasonable substitute for various non biodegradable synthetic polymers for large scale industrial in specific applicationKeywords: Bacterial cellulose, Acetobacter xylinum, Alkali treatment.
ANALYSIS OF CRUSHED MULTI WALLED CARBON NANOTUBES Yudianti, Rike; Oemry, Ferensa; Indrarti, Lucia; Onggo, Holia
Jurnal Sains Materi Indonesia Vol 11, No 2 (2010): Februari 2010
Publisher : BATAN

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Abstract

Crushing Multi-Walled Carbon Nanotubes (MWCNTs) by cryogenic crusher is one of mechanical methods to create good dispersion Carbon Nanotube (CNT) as structural modification of MWCNT for potential hybrids materials. Crushing in 15 and 30 minutes effectively cut tubes to be shorter and densely-packed structure formed after crushing 30 minutes. Based on Raman spectroscopy and thermal behavior of crushed MWCNTs, functionalization of MWCNT unidentified after crushing. Burn temperature of crushed MWCNTs (601.6 oC and 603.6 oC) appeared to be sooner than that’s of pristine MWCNT (642.2 oC). The low oxidation resistance of crushed MWCNT pointed out presence of defective carbon corresponding to too short-CNT due to cutting.Keywords: MWCNT, Crushing, Carbon Nonotube, Short-CNT.
ANALYSIS OFCRUSHED MULTI-WALLED CARBON NANOTUBES Yudianti, Rike; Oemry, Ferensa; Indrarti, Lucia; Onggo, Holia
Jurnal Sains Materi Indonesia Vol 11, No 2 (2010): Februari 2010
Publisher : BATAN

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (41.834 KB)

Abstract

Crushing Multi-Walled Carbon Nanotubes (MWCNTs) by cryogenic crusher is one of mechanical methods to create good dispersion Carbon Nanotube (CNT) as structural modification of MWCNT for potential hybrids materials. Crushing in 15 and 30 minutes effectively cut tubes to be shorter and densely-packed structure formed after crushing 30 minutes. Based on Raman spectroscopy and thermal behavior of crushed MWCNTs, functionalization of MWCNT unidentified after crushing. Burn temperature of crushed MWCNTs (601.6 °C and 603.6 °C) appeared to be sooner than that’s of pristine MWCNT (642.2 °C). The low oxidation resistance of crushed MWCNT pointed out presence of defective carbon corresponding to too short-CNT due to cutting.Keywords: MWCNT, Crushing, Carbon Nonotube, Short-CNT.
MORPHOLOGICAL AND THERMAL PROPERTIES OF ALKALI TERATED BACTERIAL CELLULOSE FROM COCONUT WATER Indrarti, Lucia; Yudianti, Rike
Jurnal Sains Materi Indonesia Vol 13, No 3: Juni 2012
Publisher : BATAN

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (365.66 KB) | DOI: 10.17146/jsmi.2012.13.3.4676

Abstract

MORPHOLOGICAL AND THERMAL PROPERTIES OF ALKALI TERATED BACTERIAL CELLULOSE FROM COCONUT WATER. Alkali treatment is one ofwide chemical treatment for removing non cellulosic materials and other impurities of bacterial cellulose (BC). Presently, BC produced by synthetic medium such as Schramm Hestrin or coconut water fermentation using pure culture of Acetobacter xylinum . In this research BC produced from coconut water fermentation using inoculums as suspension of mixture culture of bacteria A. xylinum in coconut water which commercialised inWest Java (Cianjur). Purpose of this research is to know the native and the effect of alkali treatment on the BC (heterofermentive) with evaluation of morphological, elemental analysis and thermal properties by Scanning ElectronMicroscope (SEM)-Energy Dispersive X-ray Spectroscopy (EDX) and Thermo-Gravimetry Analysis (TGA), respectively. Observation on morphological surface of native BC showes that there were noncellulosic materials entangled on the network of cellulose fibrils whichwere identified by EDX analysis as sodium(Na),magnesium(Mg), aluminium (Al), silica (Si) and potassium (K) in addition to carbon (C) and oxygen(O). On thermal analysis, stepwise of decomposition are observed on the native BC indicating the presence of non-cellulosic components which decomposed at different temperatures.While the alkali- treated BC sheet shows a single decomposition stage. The amount of residue formed after alkali treatment was relatively lower than native BC. Thermal degradation properties of the BC produced from coconut water was higher than that of BC belonging to synthetic medium. Based on this data, it is concluded that alkali treated cellulose can be used as a reasonable substitute for various non biodegradable synthetic polymers for large scale industrial in specific application
INFLUENCE OF FUNCTIONALIZED MULTI-WALLED CARBON NANOTUBES ON FILTERABILITY AND MECHANICAL PROPERTIES OF RAYON NANOCOMPOSITE FILAMENTS Onggo, Holia; Yudianti, Rike; Ruchiat, Endang
JURNAL SELULOSA Vol 3, No 01 (2013): JURNAL SELULOSA
Publisher : Center for Pulp and Paper

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (879.116 KB) | DOI: 10.25269/jsel.v3i01.41

Abstract

Carbon nanotube-rayon composite filaments was fabricated by spinning and coagulation of the mixture of 100mL functionalized carbon nanotube dispersion (containing 0.72 g FCNT) and cellulose xanthate in NaOH solution using viscose process. In the process, CNT was functionalized using mixture of acidic solution ( H2SO4/HNO3, 3:1 v/v). Influence of functionalized (FCNT) and non-functionalized carbon nanotubes (nFCNT) on the fabrication of rayon nanocomposite filament was studied. Physical and morphological properties of the nanocomposite filaments were characterized by single filament tenacity tester, photo micrograph, scanning electron microscope (SEM) and transmission electron microscope (TEM). Filterability and mechanical properties of FCNT-rayon nanocomposite filament greatly improved by reducing clogging constant from 1689 to 153 and increasing tenacity from 2.72 to 3.01 g/denier and decreasing elongation from 57.1 to 36.5% respectively compared with those of nFCNT-rayon nanocomposite filament.Keywords: functionalized multi-walled carbon nanotubes, nanocomposite filament, mechanical properties, filterability, dispersion  ABSTRAKRayon nanocomposite filaments telah dibuat melalui proses pemilinan (spinning) dan koagulasi (coagulation) dari campuran 100 mL larutan functionalized carbon nanotube dispersion (FCNT=0,72 g), selulosa santat dalam larutan NaOH melalui proses viskosa. CNT di functionalisasi (FCNT) menggunakan campuran larutan asam (H2SO4/HNO3, 3:1 v/v). Pengaruh fungsionalisasi CNT pada pembuatan rayon nanocomposite filaments dipelajari dengan cara membandingkannya dengan CNT tanpa fungsionalisasi (nFCNT). Sifat fisik dan morfologi dari rayon-nanocomposite filaments dikarakterisasi menggunakan tenacity tester, photo micrograph, scanning electron microscope (SEM) dan transmission electron microscope (TEM). Viskosa FCNT memiliki daya saring (Kw) cukup baik yaitu 155, sedangkan viskosa nFCNT  memiliki daya saring 1689 (tidak baik). Kekuatan mekanik dari FCNT-rayon nanocomposite filaments berturut turut adalah 3,01 g/denier (tenacity), dan 36,5% (elongation), lebih baik dibandingkan dengan nFCNT-rayon nanocomposite filament: 2,72 g/denier (tenacity) dan 57,1% (elongation).Kata kunci: fungsionalisasi multi-walled carbon nanotubes, rayon-nanocomposite filament, sifat mekanik, daya saring, dispersi
PENGARUH KONSTANTA DIELEKTRIK DAN DISPERSITAS PARTIKEL TERHADAP HYDROPHOBICITY ELEKTROKATALIS BERBASIS CARBON NANOTUBE Yudianti, Rike; Onggo, Holia; Syampurwadi, Anung
Jurnal Sains Materi Indonesia Vol 14, No 1: Oktober 2012
Publisher : BATAN

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/jsmi.2012.14.1.4636

Abstract

PENGARUH KONSTANTA DIELEKTRIK DAN DISPERSITAS PARTIKEL TERHADAP HYDROPHOBICITY ELEKTROKATALIS BERBASIS CARBON NANOTUBE. Pada penelitian ini dilakukan pembuatan lapisan elektrokatalis berbasis Carbon Nanotube (CNT) dengan teknik filtrasi untuk meningkatkan sifat hydrophobicity. Sifat hydrophobicity elektrokatalis diperlukan untuk mengurangi penggunaan hydrophobic agent, yaitu PolyTetra Fluoro Ethylene (PTFE) yang ditambahkan pada elektrokatalis komersial Pt/C untuk mengatasi air yang dihasilkan di elektroda. Pembuatan lapisan elektrokatalis dilakukan dengan metode filtrasi dari elektrokatalis terdispersi menggunakan membran hidrofilik. Beberapa teknik pembuatan dan formulasi larutan dilakukan untuk meningkatkan hydrophobicity tanpa mengurangi performanya. Pada kondisi larutan padat antara pelarut yangmempunyai konstanta dielektrik (ε) >10 dengan ionomer nafion akan menghasilkan hydrophobicity yang tinggi (>90°). Sedangkan pada kondisi colloidal state antara pelarut dengan konstanta dielektrik (ε) <10 dan ionomer nafion cenderung tidak mengubah sifat hydrophobicity (<90°). Sifat hydrophobicity elektrokatalis diukur dengan teknik Half Angle menggunakan Contac Angle Meter. Perubahan morfologi permukaan lapisan elektrokatalis akibat penambahan nafion dan dispersi partikel CNT diamati dengan Scanning Electron Microscope. Hubungan antara penambahan larutan nafion dan hydrophobicity film dibahas pada makalah ini.
KAJIAN KINERJA POLYMER ELECTROLYTE MEMBRANE FUEL CELL OPEN CATHODE TERHADAP VARIASI TEGANGAN KIPAS KATODA DAN VARIASI LAJUALIR HIDROGEN Irmawati, Yuyun; Indriyati, Indriyati; Onggo, Holia; Yudianti, Rike
Jurnal Sains Materi Indonesia Vol 13, No 3: Juni 2012
Publisher : BATAN

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (565.059 KB) | DOI: 10.17146/jsmi.2012.13.3.4675

Abstract

KAJIAN KINERJA POLYMER ELECTROLYTE MEMBRANE FUEL CELL OPEN CATHODE TERHADAP VARIASI TEGANGAN KIPAS KATODA DAN VARIASI LAJUALIR HIDROGEN. Kajian untuk pengaruh variasi tegangan kipas dan laju alir gas hidrogen terhadap hasil rapat daya serta fitting kurva potensial untukmendapatkan parameter over potensial pada Polymer Electrolyte Membrane Fuel Cell (PEMFC) dengan sistem open cathode telah dilakukan. Pada stack PEMFC yang terdiri atas dua sel dengan aktif area 30 cm2, dipasang tegangan kipas dengan variasi 3Volt hingga 12Volt yang berasal dari tegangan listrik eksternal. Dari rapat daya yang diperoleh, variasi tegangan kipas, yang berfungsi sebagai pendingin stack dan mampu meningkatkan produksi rapat daya sebesar 47%hingga 67% dibandingkan bila tidak menggunakan kipas. Nilai rapat daya maksimal (73,26 mW/cm2) diperoleh pada tegangan kipas 3 Volt. Untuk variasi laju alir hidrogen yang rendah sebesar 20mL/menit hingga 40mL/menit, diperoleh adanya dead point disebabkan ketidak-seimbangan stoikiometri hidrogen dengan oksigen sehingga potensial sel turun tajam menuju nol. Pada laju alir hidrogen 50 mL/menit menghasilkan nilai rapat daya optimum sebesar 79 mW/cm. Berdasarkan hasil fitting kurva polarisasi dengan persamaan empiris, penambahan laju alir hidrogenmenyebabkan meningkatnya overpotensial aktivasi dan menurunnya over potensial difusi yang disebabkan oleh faktor hidrogen crossover dan dehidrasi membran, sedangkan untuk over potensial ohmik terlihat relatif konstan.
PEMBUATAN GAS DIFFUSION ELECTRODE DENGAN TEKNIK SCREEN PRINTING : PENGARUH MICROPOROUS LAYER TERHADAP STRUKTURMIKRO DAN KINERJA ELEKTROKATALIS Onggo, Holia; Syampurwadi, Anung; Yudianti, Rike
Jurnal Sains Materi Indonesia Vol 14, No 4: JULI 2013
Publisher : BATAN

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (825.546 KB) | DOI: 10.17146/jsmi.2013.14.4.4382

Abstract

PEMBUATAN GAS DIFFUSION ELECTRODE DENGAN TEKNIK SCREEN PRINTING : PENGARUH MICROPOROUS LAYER TERHADAP STRUKTURMIKRO DAN KINERJA ELEKTROKATALIS. Pembuatan Gas Diffusion Electrode (GDE) dengan teknik screen printing dilakukan untuk mengetahui efektivitas teknik ini terhadap kinerja dan strukturmikro elektrokatalis. Lapisan katalis dibuat dari Pt/C dan nafion ionomer dengan variasi rasio berat nafion ionomer/katalis (Pt/C) adalah 35/65; 25/75; dan 15/85. Perubahan morfologi permukaan lapisan katalis akibat perubahan rasio nafion/Pt/C diamati dengan Scanning Electron Microscope (SEM). Analisis komposisi elemen permukaan dan electrochemical surface area dari partikel Pt dilakukan berturut-turut dengan Energy Dispersive X-Ray Spectroscopy (EDS) dan voltametrik siklik.Hasil penelitian menunjukkan bahwa teknik screen printing cukup efektif untuk mendapatkan lapisan elektrokatalis dengan Pt loading rendah. Penelitian ini juga menjelaskan bahwa microporous layer yang dibentuk antara lapisan katalis dan carbon paper meningkatkan kinerja elektrokatalis.