Polycarbosilane (PCS) solution was used to form PCS fibers by electrospinning and curing them by thermal process. The cured PCS fibers were then pyrolized under inert atmosphere to obtain silicon oxycarbide (SiOC) fibers. The PCS solution contained 1.2 g/mL PCS with 30% N, N-dimethylformamide (DMF)/70% toluene. The needle inner diameters used for spinning were 0.5 and 0.3 mm and variation for the applied voltage were 10, 12 and 14 kV. The electrospun PCS fibers were cured at 200°C in oxygen atmosphere for 1 hour and then pyrolyzed at 1000°C in inert atmosphere for 1 hour. Nonwoven SiOC fibers diameter ranging between 3 to 8 µm were analyzed by SEM and EDS. The oxygen embodied on the surface of cured PCS fibers arising during the curing process resulted in the SiOC fibers with larger diameters. Rapid solvent evaporation during the pyrolysis caused the SiOC fibers to have ribbon-shapes.
Polycarbosilane (PCS) fibers have been made using a solvent which is a mixture of N,N-dimethylformamide (DMF) in toluene. Polycarbosilanes (PCS) obtained from NaBond with concentration 1.2 g/ml dissolved in solution toluene and N,N-dimethylformamide (DMF) was stirred gently for 24 h at ambient temperature. DMF was mixed with toluene at ratios 22%, 24%, 26%, 28% and 30%. Electrospinning apparatus (nanoE-Spinning) from NaBond was used. In a vertical electrospinning set up, the solution in a glass syringe delivered to the tip of a 6-gauge (0.5 mm inner diameter) stainless steel needle. The tip to collector distance was adjusted to 100 mm with applied high voltage at 10kV. A stainless steel plate with dimension 100 mm x 100 mm wrapped by aluminum foil was used as collector. The electrospinning non-woven fiber was cured at temperature 200°C (2°C/min), for 1h, 1.5h, and 2h, and fibers with DMF concentration 30% was also pyrolysis at 1000 °C for 3 h in inert atmosphere. The samples were tested and observed with FTIR spectroscopy, and SEM-EDS apparatus. The results showed that PCS fibers can be made from dissolving PCS with toluene with the addition of DMF to increase the polarity of the solvent and the formation of fibers is done by using electrospinning which is supported by the presence of voltage from the outside. Fiber curing is done at 200 °C to evaporate the toluene, the DMF, and resulting stronger fibers than before. The addition concentration of DMF in toluene and curing time will affect the composition of the resulting PCS fiber. Curing time on PCS fibers will affect the composition of solvents such as DMF and Si-H bond on which to assert their PCS fiber cross linking conditions. PCS fiber morphology is known of changes in fiber diameter and fiber uniformity. Smallest PCS fiber average diameter 4.81 μm resulted from 28% DMF with curing time 2 hours and the largest achieved from 22% DMF with curing time 1 hour around 14.22 μm. Composition of pyrolyzed fiber was SiO0.587C0.413, with average density 3.1033 g/cc and average diameter the fiber was 3.06 μm.
PELAPISAN PERMUKAAN BAJA TAHAN KARAT AISI 304 DENGAN KHROM OKSIDA MENGGUNAKAN METODE SPUTTERING. Baja tahan karat digunakan sebagai bahan struktur reaktor daya tipe LWR, AGR dan LMFBR. Permasalahan bahan struktur yang timbul adalah ketahanan korosi rendah dan swelling dalam lingkungan iradiasi tinggi. Salah satu cara yang digunakan adalah melapisi permukaan kelongsong baja tahan karat dengan khrom oksida. Tujuan penelitian adalah mendapatkan karakter mikrostruktur, kekerasan mikro, dan senyawa yang terbentuk pada lapisan permukaan baja tahan karat AISI 304. Metode yang digunakan adalah pelapisan permukaan SS 304 dengan metode DC-sputtering. Proses pelapisan menggunakan bahan pelapis berupa target khrom, argon sebagai gas sputter, yang didoping gas oksigen dengan konsentrasi bervariasi dari 0 – 50 %volume, arus 10 – 20 mA, dan waktu 1 - 3 jam. Karakterisasi lapisan meliputi pengamatan mikrostruktur menggunakan mikroskop optik, kekerasan dengan microhardness Vickers tester, dan senyawa dalam lapisan dengan X-ray difractometer. Hasil penelitian menunjukkan bahwa mikrostruktur base metal tersusun dari fasa austenit dan endapan karbida, antarmuka logam-lapisan terlihat jelas, serta lapisan kompak dan homogen dengan ketebalan cenderung naik dalam rentang 0 – 30 %volume, menurun pada 30 – 40 %volume, dan bertambah tebal pada 40 – 50 %volume gas O2 Kekerasan lapisan bertambah tinggi hingga doping gas oksigen 30 %volume, kemudian menurun hingga 50 %volume gas O2. Pada konsentrasi dopan tetap dengan arus 10 – 20 mA dan waktu proses 1 – 3 jam diketahui kekerasan lapisan permukaan SS 304 bertambah tinggi seiring dengan bertambah besarnya arus dan waktu sputtering. Pada konsentrasi dopan 30 %volume O2, arus 10 mA dan waktu 2 jam, lapisan yang terbentuk mengandung CrO2 Kata kunci: Karakterisasi, lapisan permukaan, bahan struktur, SS 304, mikrostruktur, kekerasan, senyawa lapisan.
Digital literacy is critical in the current era of digitalization. Therefore, students are required to be digitally literate. This study aims to improve students’ digital literacy using an android-based e-module in chemical bonding. This study used a quasi-experimental method with a pre-experimental design that included a pretest and posttest for one group. For this study, 70 preservice teachers (10 males and 60 females) from the Department of Chemistry Education at a private university in Indonesia were recruited. The Digital Literacy Questionnaire (DLQ) was used to measure students’ digital literacy. To analyze the data, we used paired t-tests and N-gain. The results indicated a significant increase in digital literacy scores before and after treatment. Thus, it can be concluded that using an android-based e-module significantly enhances students’ digital literacy on chemical bonds. Due to its effectiveness, we recommend teachers use this e-module to elevate students’ academic performance, in general, in chemistry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.