Lydia Rohmawati
Jurusan Fisika FMIPA, Universitas Negeri Surabaya

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Sifat Mekanik Beton Polimer Epoksi dengan Pengisi Partikel Nanokalsit-silika Nugrahani Primary Putri; Diah Hari Kusumawati; Lydia Rohmawati
Sains dan Matematika Vol. 2 No. 2 (2014): April, Sains & Matematika
Publisher : Universitas Negeri Surabaya

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Polymer concrete environmentally friendly by utilizing the waste has been developed, one with waste mussel shells and sidoarjomud. Utilization of the waste is not optimal, for it to be used as filler in polymer concrete waste will be expected to have a highereconomic value. This research aimed to utilize the waste of cockle's shells and sidoarjo mud as filler of polymer concrete. Both waste firstsynthesized into nano particles by taking calcite and silica alone (mussel shells into nanocalsite and sidoarjo mud into nanosilica), beforebeing used as a filler. Once formed nanocalsite and nanosilica, composites with epoxy resin matrix and filler nanocalsite and nanosilicacreated by varying the percentage weight of each filler 5-10% by weight. Then the characterization was conducted in the form of tensiletest, hardness, bending and impact test. The test results showed that the resulting polymer concrete has physical properties, mechanical,thermal and microscopic good and has an optimum value at 10% filler calcite + 10% silica, which is 218.39 MPa compressive strength,tensile strength of 3.32 MPa, a strong fracture of 8.04 MPa and hardness values ranged from 16.08 to 18.3 HVN. Overall the resultshave met the standards for the characterization of polymer concrete.
Stabilitas Termal dan Kristalinitas Komposit Polyvinylidene Fluoride) PVDF/SiO2 Pasir Vulkanik Kelud Ria Inus Sholikah; Woro Setyarsih; Istiqomah Istiqomah; Ajeng Hefdea; Entang Wulancahayani; Lydia Rohmawati
Sains dan Matematika Vol. 5 No. 2 (2017): April, Sains & Matematika
Publisher : Universitas Negeri Surabaya

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Polyvinylidene fluoride (PVDF) merupakan material plastik yang memiliki konstanta piroelektrik dan piezoelektrik yang relatif tinggi sehingga dapat dijadikan sebagai bahan dielektrik pada superkapasitor. PVDF dikompositkan dengan SiO2 untuk mendapatkan stabilitas termal dan kristalinitas yang mendukung sifat bahan dielektrik. Penelitian ini bertujuan untuk mengetahui karakteristik stabilitas termal dan kristalinitas dari PVDF/SiO2. Komposit PVDF/SiO2 disintesis menggunakan metode inversi fasa dengan variasi komposisi SiO2 (1 wt%, 2 wt%, 3 wt%, 4 wt% dan 5 wt%) dan bahan dikarakterisasi menggunakan XRD dan analisis termal DSC/TGA. Hasil uji XRD menunjukkan bahwa puncak intensitas PVDF semakin menurun seiring dengan meningkatnya komposisi SiO2 dalam komposit PVDF/SiO2, ini disebabkan oleh kristalinitas PVDF yang mengalami penurunan akibat penyebaran partikel SiO2 pada komposit. Hasil uji TGA menunjukkan komposit PVDF/SiO2 dengan 2 wt% SiO2 memiliki stabilitas termal paling baik. PVDF murni memiliki persen kristalinitas terbesar dibandingkan dengan komposit PVDF/SiO2 yaitu 36.3%. Polyvinylidene fluoride (PVDF) is a plastic material that has relatively high pyroelectric and piezoelectric constants so that it can be used as a dielectric material in supercapacitors. PVDF is composed with SiO2 to obtain thermal stability and crystallinity that support the properties of dielectric material. This study aimed to determine the characteristics of thermal stability and crystallinity of PVDF/SiO2. Composite PVDF/SiO2 synthesized using phase inversion methods with composition variations of SiO2 (1 wt%, 2 wt%, 3 wt%, 4 wt% and 5 wt%) and material characterized using XRD and DSC/TGA thermal analysis. X-Ray Diffraction measurement showed that the peak intensity of PVDF decreases as the number of SiO2 composition in the composite PVDF/SiO2, this happens because the crystallinity of PVDF decline caused by the spread of SiO2 particles in composite disrupt crystal growth of PVDF. TGA measurement showed that composite PVDF/SiO2 - 2 wt% SiO2 had the best thermal stability of the others composite. Pure PVDF had the largest percent crystallinity compared to composites PVDF/SiO2 was 36.3%.
Karakteristik Reduced Graphene Oxide (rGO) Berbahan Dasar Limbah Batang Padi Puji Rahayu; Nugrahani Primary Putri; Lydia Rohmawati
Sains dan Matematika Vol. 6 No. 1 (2017): Oktober, Sains & Matematika
Publisher : Universitas Negeri Surabaya

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Sebagai negara agraris, Indonesia memiliki lahan persawahan yang sangat luas. Padi yang kemudian diolah menjadi beras merupakan bahan pangan utama masyarakat Indonesia. Batang padi selama ini dibuang sebagai limbah dan tidak termanfaatkan dengan baik, padahal dengan kandungan karbon didalamnya, batang padi dapat dimanfaatkan sebagai bahan dasar reduced graphene oxide (rGO). Penelitian ini bertujuan untuk menganalisis pengaruh variasi suhu pemanasan terhadap nilai kapasitansi dan morfologi rGO berbahan dasar limbah batang padi. Pembuatan rGO meliputi beberapa tahap, yaitu dehidrasi, karbonasi dan kalsinasi. Tahap dehidrasi dilakukan pada suhu 110ËšC selama 12 jam yang dilanjutkan dengan karbonasi pada suhu 400ËšC selama 1,5 jam. Sampel karbon hasil karbonasi diuji proximate untuk menentukan kandungan fixed carbon pada sampel, dan diuji Thermal Gravimetric Analysis (TGA) untuk mengetahui posisi perubahan massa bila dikenai perubahan suhu. Dari hasil uji proximate dan TGA diketahui bahwa kandungan fixed carbon adalah 18,23% dan perubahan massa terjadi pada suhu 200ËšC hingga 350ËšC. Langkah selanjutnya dilakukan tahap karbonasi dengan variasi suhu, dan dilakukan uji X-ray Diffractometer (XRD) dan Voltametri siklik. Hasil karakerterisasi XRD diidentifikasi keberadaan puncak rGO dan GO. Nilai kapasitansi rGO dari batang padi cukup kecil bila dibandingkan dengan rGO komersial. As an agrarian country, Indonesia has a very large rice field. Rice which is then processed into rice is the main foodstuff of the Indonesian people. Rice stalks have been thrown away as waste and are not utilized properly, whereas with the carbon content in them, rice stems can be used as a basis for reduced graphene oxide (rGO). This study aims to analyze the effect of heating temperature variations on the capacitance and morphological values of rGO based on rice stem waste. Making RGO includes several stages, namely dehydration, carbonation and calcination. The dehydration stage is carried out at 110ËšC for 12 hours followed by carbonation at 400ËšC for 1.5 hours. Carbon samples from carbonation results were tested proximate to determine the fixed carbon content of the samples, and tested by Thermal Gravimetric Analysis (TGA) to determine the position of changes in mass when subjected to changes in temperature. From the proximate and TGA test results it is known that the fixed carbon content is 18.23% and mass changes occur at temperatures of 200 ° C to 350 ° C. The next step is the carbonation stage with temperature variations, and the X-ray Diffractometer (XRD) and cyclic voltammetry tests are performed. From the results of XRD characterization identified the existence of the peak rGO and GO. The capacitance value of rGO from rice stalks is quite small when compared to commercial ones.