Key Engineering Materials Vol. 860

Abstract: Ultraviolet (UV) irradiation in biomaterial synthesis is commonly used to do sterilization and increase physical characteristics. This study had a goal to evaluate the characteristics of polyvinyl alcohol-Aloe vera (PVA-AV) nanofibers from the electrospinning process that was exposed by UV with the power of 8, 10, 15, and 20 W for 6 h. The physical properties of the fiber were characterized by using Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC) test, and water absorption test. The SEM images showed that the nanofibers were formed with s homogeneous structure and no beads. The diameter and the thickness of the nanofibers increased with the increase of the power of UV exposure to the sample. The biggest diameter was 319.60 ± 56.17 nm at UV exposure power of 20 W. The FTIR test result indicated that there was no new chemical bond after the PVA-AV was exposed by UV. DSC test result showed that the increase of power could increase the melting temperature (Tm) with the highest value of 189.51°C at UV exposure power of 20 W. The water absorption test showed that the highest water absorption was 739.6 % at UV exposure power of 20 W.

Abstract: The electrical and optical properties of nanomaterials depend on their structural form. As an effort to develop an advanced nanomaterial, zinc oxide (ZnO) is interesting to synthesis for many applications such as active material for solar cells and biosensors. This paper provides the role of palladium and plasmonic materials in growing ZnO nanostructure, with a focus on its structural analysis. Nanomaterial ZnO was grown by seed-mediated hydrothermal method with layering by plasmonic materials, i.e. gold (Au) and platinum (Ag). X-ray diffraction analysis shows the presence of three dominant peak angles, i.e 34.43^o, 36.32^o, and 47.49^o corresponding to crystal orientation of (002), (101) and (102), respectively. Palladium (Pd) treatment plus layering by plasmonic materials give a higher size of the nanostructure, but their electric band gaps are decreasing slightly. These findings also supported by high absorbance in UV-vis spectra. Gold layering on the nanomaterial gives a more significant role than platinum which indicated by higher size in diameter and higher absorption of UV-Vis spectra. The average size of pristine ZnO, ZnO:Pd, ZnO:Pd:Ag, and ZnO:Pd:Ag are 44.13, 45.99, 45.28, and 44.81 nm, respectively.

Abstract: Since the discovery of hexagonal ferrite or known as hexaferrites, research into the development of these materials related to commercial fields and technology has been very rapid. The use of hexaferite as a magnetic material that can be mass produced has a wide application field. Therefore, the magnetic properties of hexaferrites should be adjusted to meet these applications requirements. In this respect, cation substitution is one of the most effective ways to obtain a suitable material. Double layer coating design with variations in thickness of 1 mm, 2 mm, 3 mm, and 4 mm on Radar Absorbent Material (RAM), with Barium M-Hexaferrite (BaM) BaFe_12-xZn _xO₁₉ as magnetic material with variations in doping concentration of Zn²⁺ ions x = 0, 0.3 and 0.9 have been successfully synthesized by the solid state reaction method. Likewise with Polyaniline (PANi) with Dodecylbenzene Sulfonic Acid (DBSA) dopant as a conductive material, it have been successfully synthesized by the polymerization method. Radar absorbing materials (RAM) are characterized using X-Ray Diffraction (XRD), Four Point Probes (FPP), Fourier Transform Infrared (FTIR), Vector Network Analyzer (VNA), and Scanning Electron Microscope (SEM). The results of XRD characterization showed that the largest primary phase was obtained at BaM x= 0.9 which was 96.56%. The increassing of concentration dopping of Zn²⁺ ions to influence of decreasing the magnetic dipole of magnetic materials and the magnetic properties be come softmagnet materials. The variations in thickness coating radar absorbing materials the influence of absorption of electromagnetic waves occurs optimally, and the increase of thickness coating have coused the value of loss of reflection and widening of the absorption band of the X-Band range (8-12 GHz) increasing. The highest reflection loss and widening of the absorption band value is obtained from coating BaM x = 0.9 with a thickness of 4 mm, which are respectively - 16.29 dB, and 3.78 GHz. So that it can be concluded that the addition of the doping concentration of Zn²⁺ ions and the dimensions of the layer thickness can increase the absorption ability of RAM material.

Abstract: Utilization of abundant natural resources has been an important issue in recent years. CaCO₃ was successfully prepared from natural sand by purification bubbling methods with flowing CO₂ gas into an aqueous Ca(OH)₂ medium with NaOH as catalyst. In the experimental set-up, natural sand was dissolved with different NaOH concentrations of 5, 6, and 7 M, respectively. In the carbonation process, room temperature is used as reaction temperature, while CO₂ gas flow rate was carried out at 5 SCFH (Square Cubic Feet per Hour) and the speed of stirring was kept constant. The reaction was occurred around 5 minutes to produce precipitation of CaCO₃. The influences of reaction parameters such as the various concentrations of NaOH were studied by using X-ray fluorescence spectrometer (XRF), X-ray powder diffraction (XRD), Particle size analyzer (PSA), and Scanning Electron Microscopy (SEM) to investigate the element composition, crystal structure, size of particles, and morphology of particles, respectively. The results showed that NaOH concentration effected not only on the phases of CaCO₃ but also on the microstructure and morphology of CaCO₃. Calcite and vaterite phases are observed which have a rhombic and spherical morphology in micro-scale, respectively.

Abstract: Zinc oxide (ZnO) has attracted considerable attention because of its potential applications in optoelectronic devices. Many scientists have reported on the preparation of ZnO based photodetectors in metal-semiconductor-metal (MSM) structures where expensive noble metals are used as electrodes. Here, we propose the preparation of full metal-oxide photoconductors by using indium tin oxide (ITO) as the electrodes and ZnO thin films as sensing materials. ZnO thin films were prepared by employing a simple ultrasonic spray pyrolysis (USP) technique with a commercial ultrasonic nebulizer (1.7 MHz). In this work, we developed a high performance ZnO based photodetector on interdigitated ITO with a simple and low-cost USP method. The I-V characteristic shows that ZnO thin film works in a photoconductive mode and has better performance as a UV (325 nm) detector than other wavelengths (505, 625 and 810 nm). As a UV detector, the devices exhibit high sensitivity (1255.51%), high responsivity (22.6 x 10³ A/W), high detectivity (1.49 x 10¹⁴ Jones), good stability, a fast response time of 0.87 s and a relatively slow recovery time of 34.8 s. This high performance may be related to the large crystallite size that facilitates higher electron mobility.

Abstract: The Density Functional Theory method was employed to investigate the electronic structure and muonium hyperfine interaction of muonium trapped near carbon atom labelled as '5' in cytosine nucleobase. Eighteen different basis sets in combination with B3LYP functional were examined in geometry optimization calculations on the muoniated radical. There are significant quantitative differences in the calculated total energy. The employment of basis set that does not include polarization function produces an optimized structure with high total energy. The 6-311++G(d,p) basis set yielded the lowest total energy as compared to other basis sets. The bond order of muonium trapped at C5 atom is in the range of 0.841 to 0.862. The 6-31G basis set produced the muonium Fermi contact coupling constant that is the closest to the experimental value.

Abstract: We investigated the magnetic properties of pyrochlore ruthenates, R₂Ru₂O₇, by using the muon spin relaxation (μSR) method. The appearance of a magnetically ordered state was confirmed below 145 K by observing the decrease in the initial asymmetry of the muon-spin polarization. This was due to a long-range ordering of Ru⁴⁺ spins. An additional anomaly in the μSR time spectrum was observed around 30 K. A part of the lost initial asymmetry was recovered and gradually decreases again with decreasing temperature below 30 K. This anomaly was supposed to be due to a magnetic ordering of Nd³⁺ spins which was coupled with ordered Ir moment via the 3d-4f exchange interaction.

Abstract: The extraction process is a crucial part of the synthesis of Molecularly Imprinted Polymers (MIP). The process will have a significant impact on the number of its cavities that affects the polymers’ ability to recognize targets with the same physical and chemical properties as the analytes. Caffeine polymers have been prepared by the cooling-heating method using methacrylic acid (MAA) as a monomer, ethylene glycol dimethacrylate (EDMA) as a crosslinker, benzoyl peroxide (BPO) as an initiator, and chloroform as a solvent. The resulting caffeine polymer powder was extracted using chloroform, methanol / acetic acid (1:20), and methanol, respectively. Finally, the polymer powder is washed using the aquabidest, which is heated at 60°C. The results of FTIR, XRD, and SEM characterization showed that caffeine concentration was significantly reduced. The number of cavities obtained from caffeine MIP is 604 more than before extracted, which is 132 pieces.

Abstract: This work reports the acoustic evaluation of a tungsten-epoxy composite which is functioned as a backing material of an ultrasonic transducer. The composite is prepared by mixing tungsten powder in epoxy at a weight ratio of 4:1 using a shaker milling and curing the mixture under a vacuum condition. The sound velocity and acoustic attenuation in the prepared composite is measured by propagating a 200-kHz ultrasonic wave with a through transmission mode. The prepared composite is subsequently assembled with a 1-MHz piezoelectric disk (PZT-8) and an epoxy layer as the active element and the matching layer, respectively, into a fabricated ultrasonic transducer. A square-wave burst pulse is used as an excitation signal for the evaluation of the fabricated transducer. The generated ultrasonic wave shows a higher damping in the presence the backing layer. In addition, the measured sound velocity and acoustic attenuation of prepared composite showed that the ratio of 4:1 is sufficient composition in order to apply as a backing material. In conclusion, control the transducer characteristics is determined by the acoustic properties of tungsten-epoxy composite.

Abstract: The separation technique in industrial processes with membrane technology is very important. Ultrafiltration membrane is one type of membrane using the principle of pressure-push force. One of the most commonly used ultrafiltration membrane materials is cellulose acetate (CA) membrane. The advantage of CA as a membrane material is that easily produced and its raw material which is a renewable source. The aim of this work is to present a simple experimental and simulation studies to illustrate the phase separation in the membrane synthesis process by the phase inversion technique. Simulation is used to determine the surface characteristics of the synthesized membrane. Two systems commonly used for the preparation of membrane synthesis are waste cigarette butts (WCB)/acetone/water. The effect of adding WCB concentrations (1 and 2 pieces) to the initial polymer casting solution was studied through simulation and compared with available experimental data. The experimental results are in accordance with the simulation was carried out. It shows that the surface profile of the membrane with the composition of the polymer film during precipitation can provide important information about the structure and substructure of the membrane formed. This also shows that the influence of CA concentration is closely related to changes in pore size on the membranes that are formed. The asymmetrical membrane structure prepared by the phase inversion process is influenced by the type and concentration of the polymer (WCB), solvent, membrane thickness and temperature and processing time.