Materials Science Forum Vol. 1094

Abstract: This paper reports the results of synthesis and characterization PNI/zirconia composites. PANI/zirconia composites were synthesized by in-situ polymerization. Aniline was used as a monomer, hydrochloric acid as a dopant, ammonium peroxodisulphate as an oxidant and sodium dodecyl benzene sulfonate as a surfactant. The zirconia used is amorphous and crystalline (monoclinic). XRD test results show that the composite has been successfully formed, indicated by the absence of new peaks. FTIR spectrum analysis showed an interaction between PANI and zirconia. Composites with amorphous zirconia fillers have lower conductivity than PANI; on the other hand, composites with monoclinic zirconia fillers have better conductivity than PANI.

Abstract: CaCO₃ is one of abundant minerals in nature, which is a promising material in thermochemical energy storage (TCES). In this work, we have succeeded in synthesizing CaCO₃/ZrO₂ composites by physical mixing with a magnetic stirrer using CaCO₃ from natural limestone. The mixing was carried out by mechanical stirring with various molar percentages of CaCO₃:ZrO₂ of 100:0, 85:15, 70:30 and 50:50. The phase and structure of the CaCO₃/ZrO₂ composites were characterized by x-ray diffraction (XRD). Thermal properties were characterized by thermogravimetri analyzer. Morphology of the composites was observed by scanning Electron microscopy (SEM) with energy dispersive x-ray (EDX). Based on the XRD results, the peak intensity of CaCO₃ at the crystalline plane of (104) decreased with increasing percentage of ZrO₂. The lattice volume of CaCO₃ also relatively decreases with increasing percentage of ZrO₂. The increase in the percentage of ZrO₂ in the CaCO₃/ZrO₂ composites makes the decomposition temperature also decreases. This is probably due to heat and mass transfer of ZrO₂.

Abstract: Muon-spin relaxation (μSR) spectroscopy has let an understanding of the hydrogen interactions with graphene, providing insights for hydrogen storage technologies based on graphene-based compounds. We report an μSR study on the reduced graphene oxide (rGO, a product of ®Graphenea) at 300 K. Spontaneous muon-spin precession is not observed under the high statistic zero-field measurement. Instead, the spectra show a typical muon diffusion with a small fraction of muon experiencing dipolar interactions with neighboring protons. Measurements under longitudinal field conditions yield the obtained hyperfine field (B_hyp) a way much lower than the required field to recover free muonium, demonstrating a radical formation. Moreover, a noticable ratio of captured muoniums (~35%) in the sample illustrates strong interactions between hydrogen and rGO.

Abstract: The purpose of this research is to study the interrelation between Urbach energy (E_u), optical band gap energy (E_g), and complex dielectric constant (ε) in relation to the disorder induced properties of SiO₂/rGO thin films. The rGO-like carbon was created by annealing coconut shell carbon (csc) at different temperatures of 400°C, 600 ^oC, and 800 ^oC. From the analyses, it obtained E_g which was varied from 2.01 eV until 2.67 eV. While E_u from 0.13 eV until 0.26 eV. The results showed that the E_u varied inversely to the E_g. The Penn model and hydrogen-like atom model theories were used to investigate the interrelation between E_u and ε. Finally, it is shown that the Urbach energy is linearly and inversely related to the imaginary and real parts of dielectic constant, respectively.

Abstract: Research on the mechanical thermal stability of micro-porous carbon-based micro composites with marine paint matrices has been carried out. Microporous carbon has the property of absorbing radar waves so it is very interesting to research and develop into a microwave shielding material synthesized from coconut shell (cocoa nucifera) by carbonization process at 600°C for 45 minutes. The molecular structure and phases of micro porous carbon were characterized using Fourier Transform Infrared (FTIR) and X-Ray Diffraction (XRD) with the results confirmed of micro carbon with reduced graphene oxide (rGO) phase. Furthermore, micro-composites made from porous micro carbon with marine paint as a binder were made using the wet mixing-casting method. Mechanical thermal testing was carried out by means of a shear test at a temperature range of 30 – 70°C using a Dynamics Mechanical Analysis (DMA) tool. The test results showed that the value of the storage modulus of porous micro carbon composites was 1.653 MPa, 10.196 MPa, 13.068 MPa, 118.567 MPa, respectively. The value of the composite storage modulus increases with increasing concentration of porous micro carbon with an optimum value of mechanical thermal stability at a composition of 70:30 %wt. The results of mechanical thermal testing showed that porous micro carbon with rGO phase from coconut shells has the potential to be used as an anti-radar shielding material. 068 MPa, 118.567 MPa. The value of the composite storage modulus increases with increasing concentration of porous micro carbon with an optimum value of mechanical thermal stability at a composition of 70:30 %wt. The results of mechanical thermal testing showed that porous micro carbon with rGO phase from coconut shells has the potential to be used as an anti-radar shielding material. 068 MPa, 118.567 MPa. The value of the composite storage modulus increases with increasing concentration of porous micro carbon with an optimum value of mechanical thermal stability at a composition of 70:30 %wt. The results of mechanical thermal testing showed that porous micro carbon with rGO phase from coconut shells has the potential to be used as an anti-radar shielding material.

Abstract: Graphene-based materials have been widely developed in various applications, both in electronics and optoelectronics. It is because of their attractive characteristics, such as flexible structure, large surface area, and excellent thermal, mechanical, and optoelectronic properties. In this research, the optical absorbance of coconut shell-based carbon materials was studied in the exfoliation process and the type of solvent. To determine the effect of optical absorption and particle size of graphene carbon from coconut shells on solvents, we used two types of solvents, namely Deionized (DI) water and a mixture of DMSO and DI (DMSO/DI) with a fraction of 1:10. The exfoliation process is carried out by dissolving graphene powder from coconut shell powder that has been synthesized and heated at 400°C into DI water and DMSO/DI mixture with a concentration of 0.01 g/ml. Ultrasonication is carried out with time variations of 60, 180, 300, and 420 minutes. After ultrasonication for 420 minutes, the absorbance peak was at 241 nm with an average particle size of 134 nm in the solvent DMSO/DI mixture. For the DI solvent, the absorbance peak was at 243 nm with an average particle size of 198 nm. This study showed that the DMSO/DI mixed solvent with a fraction of 1:10 could produce a smaller average particle size than the DI solvent, but the absorbance spectrum is less clear at a wavelength of less than 240 nm compared to the DI water. Furthermore, these two solvents can be used to prepare graphenic carbon films from coconut shells because they are easy to obtain, cheap, and can reduce particle size by ultrasonication.

Abstract: The presence of N-dopant in Reduced Graphene Oxide has contributed to the change of their optical band gap. In this research, this mechanism has been implemented to synthesize nitrogen-doped graphenic carbon (NGC) proposed as an n-type semiconducting layer. The graphenic-based carbon (GC) was derived from coconut shells by a green synthesis method. The two sources of nitrogen dopants were prepared from ammonia water (NH₄OH) and urea (CH₄N₂O). Synthesis of NGC was conducted from GC and a particular dopant with a ratio of 1:20 and 1:40 by wet mixing. Then the NGC solution was deposited onto a 1x1 cm² glass substrate using a nanospray method to form a layer. X-ray diffraction (XRD) of NGC film has indicated an amorphous characteristic of the film. According to Energy Dispersive X-ray (EDX) spectroscopy, the presence of nitrogen as a doping material in the GC was successfully demonstrated. The SEM cross-section image has performed the NGC layer on the substrate. Absorbance analysis from UV-Vis spectroscopy also explains the occurrence of electronic transitions, both in the form of a solution and a layer of NGC material. The further analysis explained that the optical band gap of the NGC material ranged from 1.66 – 1.86 eV, which exhibits the semiconductor characteristic of the NGC material.

Abstract: Graphenic carbon (GC) provides a potential ability as photovoltaic material due to its tunable properties. Here, we investigate the optical energy gap and the thickness of B-GC material as a p-type in solar cell application. The GC was prepared from old charcoal powders of coconut shells by heating process at 400°C and B-GC powders were prepared by wet mixing method using boric acid as B atom source. B-GC films were then prepared by employing nebulizer as a nanospraying method. All samples were examined through various characterization techniques such as X-Ray Diffarction (XRD), SEM cross section, and UV-Vis spectroscopy. The amorphous characteristic of B-GC is confirmed by broad peaks in XRD patterns, similar to that of reduced graphene oxide (rGO). The present of B along with O and dominant C elements is determined by SEM-EDX result. The B dopants affect the optical bandgap energy (E_g) of GC as an intrinsic material. The thickness of B-GC films was found to be thinner than in a previous study that used a similar method but different equipment. The average thickness of B-GC films is in the range of 127 to 420 nm, followed by an increase in the deposition time for 5 to 20 s. Estimation of the E_g value indicated that B-GC has an energy gap around 2 eV, which is most suitable as a window layer in solar cell applications.

Abstract: Graphenic carbon (GC) has been successfully synthesized from biomass (coconut shell charcoal) using the liquid phase exfoliation method. The dopants, in the form of light atoms such as boron (B-GC), were introduced with the aim of improving their magnetic properties. X-ray diffraction was used to identify the GC and B-GC, and the results show broad peaks around 24° and 43°, indicating the presence of graphene-like carbon structure. The bonding structure was also analyzed using X-ray photoelectron (XPS). It reveals the main bonds in GC consist of sp², sp³, and C=O. While the B-GC sample shows an additional bond, namely the B-C bond, as an indicator of the successful doping process of B into the GC structure. Both GC and B-GC show weak room temperature ferromagnetism. Furthermore, these findings show that introducing boron atoms into the graphenic structure can improve magnetization.

Abstract: The purpose of this research is to develop a vibration isolator using auxetic viscoelastic sheet technology. The procedure for the design and elaboration of the insulator using polymers and by means of fatigue analysis using impacts is exposed, the absorption of energy by cycles is compared and the damage that is produced in the viscoelastic is observed with an optical microscope. This is to compare the variation in the force that the fatigue equipment exerts to deform the sheet in the same magnitude and to be able to establish, through the ratio of absorbed energy and returned energy, criteria on the useful life of the element for future designs.