Supercapacitor is an electronic device with characteristic of having higher power density than battery and higher energy density than conventional capacitor. In order to achieve exceptional power and ...energy density, it is necessary to use materials with high specific surface area as its electrodes. In this study, we prepared a rolled supercapacitor device model using carbon sheet as the electrodes and 1 M KCl electrolyte. A carbon sheet was soaked in 1 M KCl and assembled as a rolled supercapacitor device model. Performance of the rolled supercapacitor device model was measured using a cyclic voltammetry (CV) in a voltage range of-0.8 V to +0.1 V with scan rate variations of 1 mV/s, 5 mV/s, 10 mV/s, 15 mV/s and 20 mV/s. Cyclic voltammetry measurement provide results as follows, Esp = 0.289 to 0.103 Wh/kg and Psp = 5.024 to 35.738 W/kg. By using Ragone plot we found that the prepared rolled supercapacitor using carbon-sheet as electrodes had met criteria of supercapacitor. The result show that the carbon sheet has a good prospect to be used as electrodes for rolled supercapacitor.
Polydimethylsiloxane (PDMS) is one of the most superior materials and has been used as a substitute for vitreous humor in the human eye. In previous research, we have succeeded in producing PDMS with ...low and medium viscosity using octamethylcyclotetrasiloxane (D4) monomer with a low grade of 96%. Both have good physical properties and are comparable to commercial product PDMS and PDMS synthesized using D4 monomer with a high grade of 98%. An improvement of the synthesis process is needed to ensure that PDMS synthesized from a low-grade D4 monomer under specific synthesis conditions can repeatedly produce high-quality PDMS. Apart from good physical properties, the PDMS as a substitute for vitreous humor must also be safe and not cause other disturbances to the eyes. Here, we reported the process of synthesizing and characterizing the physical properties of low- and medium-viscosity PDMS using a low-grade D4 monomer. We also reported for the first time the in vitro toxicity test using the Hen's Egg Test Chorioallantoic Membrane (HET-CAM) test method. We have succeeded in obtaining PDMS with viscosities of 1.15 Pa.s, 1.17 Pa.s, and 1.81 Pa.s. All samples have good physical properties such as refractive index, surface tension, and functional groups that are similar to commercial PDMS. The HET-CAM test results showed that all samples did not show signs of irritation indicating that samples were non-toxic. From the results of this study, it can be concluded that PDMS synthesized from a low-grade D4 monomer under specific synthesis conditions by the ROP method is very safe and has the potential to be developed as a substitute for vitreous humor in human eyes.
The trivalent erbium (Er3+) doped sodium lithium borate glass with composition (65-x)B2O3-15Na2O-10PbO-5ZnO-5Li2O-xEr2O3 have been successfully fabricated by melt-quench technique. The structural ...properties were investigated by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR). The absorption and luminescence spectra of glass samples were measured to determine the spectroscopic properties. The Judd–Ofelt parameters were calculated based on absorption spectra with values of Ω2, = 4.39, Ω4 = 3.22, and Ω6 = 0.91 (×10−22 cm2) for 2.0 mol% Er3+ ion doped sodium lithium borate glass. Furthermore, radiative properties including effective bandwidth (Δλeff), radiative transition probability (AR), radiative lifetime (τR), and branching ratio (βR) were also calculated and analyzed. A strong emission band at 1532 nm was observed corresponding to 4I15/2 → 4I13/2 transition under the excitation wavelength of 528 and 976 nm. The stimulated emission cross-section (σe) and figure of merit (FWHM xσe) were calculated and compared with other glasses in order to evaluate the properties of the present samples for optical amplifier. Based on the characterization results, we found that the glass with 2.0 mol% Er3+ ion doped sodium lithium borate glass had the highest stimulated emission cross section compared to other samples and were comparable with the previous reports.
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•Er3+ doped sodium lithium borate glass was fabricated by melt-quench.•All samples are amorphous without any crystalline phase.•A strong emission band at 1532 nm was observed corresponding to 4I15/2 → 4I13/2 transition.•2.0 mol% Er3+ ion doped sodium lithium borate had the highest emission cross section.
Polydimethylsiloxane (PDMS) is a substitute for vitreous humour in vitreoretinal surgery and is usually produced from octamethylcyclotetrasiloxane (D4). In Indonesia, both commercial PDMS and D4 are ...limited and expensive. Dichlorodimethylsilane (DCMS) can be an alternative to produce PDMS. DCMS is cheaper and easier to obtain than D4. However, more extra effort is needed in order to produce PDMS from DCMS. Therefore, this study aimed to produce PDMS from DCMS by varying the ratio of DCMS precursor to dichloromethane (DCM) solvent at ratios of 1:1 and 1:4 through the hydrolysis–condensation method under neutral conditions. The PDMS produced had medium- (2.06 Pa·s) and high viscosity (3.59 Pa·s), with densities ranging from 0.96 to 0.99 g/mL. The refractive index was 1.4034–1.4036 and surface tension was 21 × 10−3 N/m, while they were able to transmit ~100% visible light, which were similar values to the commercial PDMS characteristics. PDMS samples were characterized using IR and NMR spectroscopy, which confirmed they were of PDMS type. The most optimum DCMS:DCM ratio was 1:1 due to the medium-viscosity PDMS type that could be produced. The in vitro HET–CAM toxicity test showed that samples were non-irritant, similar to PDMS produced from D4. PDMS from DCMS was non-toxic and ready to be used as a vitreous humuor substitution.
We studied the characteristic of reduced graphene oxide (RGO) as a counter electrode (CE) in Pt-free dye-sensitized solar cell (DSSC) using single diode model equation based on current ...density-voltage (J-V) measurement. The electrical characteristics of DSSC was investigated by electrochemical impedance spectroscopy (EIS) in order to knowing the catalytic properties of RGO as counter electrode. The RGO thin film as CE was deposited on fluorine-doped tin oxide (FTO) substrate and stacked with FTO/TiO2/ruthenium dye/mosalyte/RGO/FTO DSSC structure. The RGO film was obtained from GO (graphene oxide) film that was thermally reduced at 200°C for one hour under argon flow. The performance of DSSC with RGO as CE was characterized by current-voltage measurement and the interface between each layer was observed by Electrochemical Impedance Spectroscopy (EIS). The device efficiency (η) of DSSC that used GO and RGO film as CE are 0.09% and 3.43%, respectively. DSSC parameters such as series resistance (RS) shunt resistance (RSH), and ideality factor (n) were obtained from J-V curve which analyzed using single diode model equation. All samples have a Rs value of 2 indicates that all devices have a good ohmic contact. The RSH of device using RGO-1mg/ml is increase (from 2850 to 3670 Ω.cm2) compared with GO indicate that thermal reduction is successes. The RGO film shows a comparable performance to Pt-conventional CE thus it is a good candidate as alternative of DSSC counter electrode.
Polydimethylsiloxane (PDMS) is a tamponade substance that is used as vitreous humour substitutes in vitreoretinal surgery. PDMS can be obtained from monomers of Octamethylcyclotetrasiloxane (D4) that ...was reacted with Hexamethyldisiloxane through polymerization reactions in a base condition. The monomers are very difficult to obtain in Indonesia, therefore another alternative monomer is needed to produce PDMS with specific properties for vitreoretinal surgery. Here, we reported the synthesis of monomer for replacing D4 through hydrolysis process of Dichlorodimethylsilane (DCMS). Furthermore, the synthesized monomer was used to produce PDMS. The process of DCMS hydrolysis assisted by KOH 0.5 M along 18 hours in reflux system. The synthesized monomer has viscosity of 171 mPas, refractive index of 1.4005 and surface tension of 17 mN/m. PDMS was produced using synthesized monomer by ring-opening polymerization. It is found that the properties of PDMS are very similar with that of commercial PDMS of 5500 cSt.
Abstract
Eggshell (ES) membrane is a semipermeable membrane that is insoluble in water and has a high surface area. We modified ES membranes with graphene oxide (GO) using self-assembled technique ...and used it to remove dye pollutants such as methylene blue (MB) in water. The ES membranes were obtained from fresh eggs that have been removed from albumen and yolk, then immersed in 15% acetic acid for 30 minutes. The ES membranes were immersed in 0.5 mg/mL dispersed GO and ultrasonicated for 3 hours. The modified ES-GO membrane was then used to filter 5 mg/L MB solutions. Filtration of MB solution was performed by pouring the solution over the ES-GO membrane with a help of constant pressure of 45 psi. We found that the modified ES-GO membrane could filter MB up to 33.53% and reduce MB concentration from 4.91 mg/L to 3.53 mg/L. The result of membrane permeability is 2.488 x10
−3
darcy and the flow rate of the filtration is relatively constant about 4 mL/s.
The conduction properties of polymer composite PTMSPMA-PEO as electrolyte in lithium-ion batteries has been investigated. The gel polymer of PTMSPMA was synthesized by sol-gel method using ...3-(Trimethoxysilyl)-propyl-methacrylate as monomer. The Composite of PTMSPMA-PEO with various composition (50:50, 60:40, 80:20; wt%) was made by solution method. The polymer electrolyte was composed of LiClO4 salt dissolved in propylene carbonate and mixed with PTMSPMA-PEO. The ionic conduction of polymer electrolyte was characterized by electrochemical impedance spectroscopy. The battery performance of polymer electrolyte was estimated with coin cell, where LiFePO4 was used as cathode and graphite was use as anode. The high ionic conductivity of 6.67 x10-3 S/cm has been observed for the composition of PTMSPMA : PEO 60:40 (wt%) in room temperature. The performance of cell battery was investigated by charge-discharge using constant current 0,1 mA/cm2. The operational voltage of cell battery is around 1 V until 2.2 Volt with Columbic efficiency around 60%.
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