Dispersion of carbon fiber in cement matrix is one of main challenges for fabricating carbon fiber reinforced cement based materials. In this study, the dispersion of carbon fiber was improved by pre-dispersion of carbon fiber in basic aqueous solution using different concentrations of CMC. The relationships of CMC concentration and pH solution toward carbon fiber dispersion in aqueous solution was evaluated by UVvis spectroscopy. In order to understand how carbon fiber is dispersed in cement matrix, morphology fiber carbon reinforced composite was examined. Experimental results show that aqueous solution of CMC is effective to disperse carbon fiber. In addition, dispersion of carbon fiber increases with increasing of pH of CMC solution.
Carbon Fiber Cementitious Composites (CFCC) is one of the most important materials in smart concrete applications. CFCC should be able to have the piezoresistivity properties where its resistivity changes when there is applied a stress/strain. It must also have the compressive strength qualification. One of the important additives in carbon fiber cementitious composites is dispersant. Dispersion of carbon fiber is one of the key problems in fabricating piezoresistive carbon fiber cementitious composites. In this research, the uses of dispersants are methylcellulose, mixture of defoamer and methylcellulose and superplasticizer based polycarboxylate. The preparation of composite samples is similar as in the mortar technique according to the ASTM C 109/109M standard. The additives material are PAN type carbon fibers, methylcellulose, defoamer and superplasticizer (as water reducer and dispersant). The experimental testing conducts the compressive strength and resistivity at various curing time, i.e. 3, 7 and 28 days. The results obtained that the highest compressive strength value in is for the mortar using superplasticizer based polycarboxylate dispersant. This also shown that the distribution of carbon fiber with superplasticizer is more effective, since not reacting with the cementitious material which was different from the methylcellulose that creates the cement hydration reaction. The research also found that the CFCC require the proper water cement ratio otherwise the compressive strength becomes lower.
Nickel pulse electrodeposition is one of the coating methods that used to increase the corrosion resistance and improve the mechanical properties. In this study, nickel was used as the anode and martensitic stainless steel 410 was used as the cathode. The solution used in the method of nickel pulse electrodeposition include nickel sulfate, nickel chloride, and boric acid. Pulse electrodeposition parameters are variation of duty cycle of 70, 80, 90% and frequency variations valued at 0.1, 1, 10, and 20 kHz. Temperatures used in research nickel pulse electrodeposition at 50 ºC, with a current density of 15 A / dm² and 18 minutes. The Scanning Electron Microscopy analysis determine the microstructure and grain size changes after a nickel pulse electrodeposition. The polarization test determine optimum rate of corrosion when 90 % duty cycle and 20 kHz frequency.
IntisariProses pelapisan nikel dengan metode pulse electrodepostion pada AISI 410 dilakukan untuk menurunkan laju korosi AISI 410 pada aplikasi industri, yaitu turbin blade yang sering mengalami masalah korosi. Proses pelapisan menggunakan larutan nickel sulphate 250 g/l, boric acid 50 g/l dan nickel chloride 45 g/l pada temperatur 50 -60 °C dengan variasi rapat arus 10, 15, 20 dan 25 A/dm² dan lamanya proses pelapisan 10, 15 dan 20 menit. Duty cylce yang digunakan adalah 80% dan frekuensi pulse 100 Hz. Pengujian strukturmikro dilakukan menggunakan SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy) untuk melihat ukuran butir dan ketebalan lapisan nikel yang terbentuk. Pengujian laju korosi dilakukan menggunakan alat CMS (corrosion measurement system). Hasil penelitian menunjukkan bahwa semakin besar rapat arus dan semakin lama proses pelapisan maka ukuran butir dalam strukturmikro lapisan semakin kecil dan laju korosi yang terukur semakin kecil. Laju korosi paling kecil adalah 0,00027 mmpy pada rapat arus 25 A/dm² dan waktu pelapisan 20 menit.
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