Materials Science Forum Vol. 1102

Abstract: In this research, a comparison was made between the optical and chemical properties of ZnO-Ag composites with different ZnO and Ag ratios synthesized using extracts obtained from mimosa and Andrographis paniculata plants. The optical properties of the synthesized ZnO-Ag composites were analyzed, focusing on parameters such as absorption and bandgap energy. Moreover, the bandgap, which indicates the energy difference between the valence and conduction bands, was calculated to assess the compounds' electronic behavior. Furthermore, the chemical properties of the ZnO-Ag composites were investigated. This involved analyzing the chemical bond, crystal structure, and crystalline size using X-ray diffraction (XRD) and Fourier Transform Infrared Spectrometer (FT-IR). The experimental findings demonstrated that the crystal sizes of ZnO and Ag in ZnO-Ag composites synthesized using Mimosa pudica extract were considerably smaller compared to those synthesized using Andrographis paniculata extract. Consequently, the energy gap of the ZnO-Ag compounds synthesized with mimosa extract was higher in comparison to those synthesized with Andrographis paniculata extract. By comparing the optical and chemical properties of the ZnO-Ag composites synthesized from mimosa and Andrographis paniculata extracts, valuable insights can be gained regarding the influence of these plant extracts on the resulting composites.

Abstract: Aluminum-air batteries that use alkaline electrolytes have the advantage of a high operating voltage, but the aluminum alloy electrodes experience high corrosion rates. To address this issue, a promising solution is proposed, which involves mixing neutral electrolytes with the alkaline electrolyte. In this study, we analyzed the electrochemical characteristics of aluminum alloy electrodes in electrolyte solutions containing varying concentrations of NaCl added to a 1 M NaOH alkaline electrolyte solution to understand the effect of neutral electrolytes on the discharge performance of aluminum-air batteries. The results obtained from potentiodynamic polarization tests, electrochemical impedance spectroscopy, three-electrode discharge tests, and open-circuit potential tests confirmed that the corrosion reaction and discharge voltage of aluminum alloy electrodes are influenced by the concentration of NaCl in the alkaline electrolyte solution. The corrosion rates and discharge voltages decreased as the concentration of neutral electrolyte increased, indicating that the electrochemical properties of aluminum-air batteries are highly dependent on the electrolyte composition.

Abstract: At present, the preparation of conductive and corrosion-resistant carbon coatings by plasma-assisted chemical vapor deposition (PECVD) has received extensive research. In this paper, the acetylene plasma model was established by using the Particle in Cell/Monte Carlo method (PIC/MCC) to study the influence of different electrode voltages on the composition and particle energy of deposited particles, and explore the corresponding relationship between acetylene gas and deposited particles. The results show that increasing the electrode voltage can reduce the density of acetylene particles in the plasma, increase the ionization rate of acetylene, and reduce the particle density of C₂ and CH groups. The energies of C₂H₂ and CH particles increase with the increase of voltage, while the energies of C₂ and H particles are basically stable and not affected by the voltage. Keywords: PECVD, PIC/MCC, carbon film, electrode voltage, acetylene plasma, deposition particles.

Abstract: Titanium is promising candidates for bipolar plates in fuel cell, electrolysis, etc., due to the excellent corrosion resistance of titanium oxide (TiO₂). However, TiO₂ also possesses poor electrical conductivity and leads to high power losses, so that the conductivity of titanium needs to be further improved. In this work, the effect of thirty-nine metals on the conductivity of TiO₂ was studied based on the first-principles merged with the Boltzmann transport equation and Deformation potential theory. The results show that the conductivity meets the target of 100 S∙cm^-1 proposed by the U.S. Department of Energy when TiO₂ doped with Cr, Sb, Ga, etc. The Sb-doped not only enhances carrier concentration, reduces relaxation time, but also improve the chemical bond. The intermediate bands induced by Au, W, Rh, etc. is a special conductivity enhanced mechanism.

Abstract: Water is one of the basic needs that must be fulfilled by living things, especially humans, starting from daily activities such as cooking, washing, and so on. It is possible that the water source has been contaminated with other contaminants. Various methods are used to obtain proper water, one of which is the solar distillation method. Solar distillation is a method of purifying water that has not been widely used due to its low productivity. Copper Oxide Nanoparticles (CuO) were chosen as the material to be added to the black paint on the bottom of the distillation basin, this was done to increase its productivity. Experiments were carried out with concentrations of copper oxide (CuO) nanoparticles by weight of 10%, 15%, and 20%. It was found that adding nanoparticles to the paint increased the heat transfer rate and water temperature. The results obtained showed that CuO nanoparticles increased efficiency by 6.66%, 16.91% and 27.93% compared to conventional distillation apparatus at concentrations of heavy fractions of 10%, 15% and 20%, respectively. From this modification of the tool, the highest condensate mass was obtained at the concentration of the heavy fraction of 20% CuO nanoparticles with an average of 806 ml/day, while the other variations obtained an average condensate mass of 512 ml/day and 655 ml/day at the concentration of the heavy fraction respectively. 10% and 15% respectively.

Abstract: The use of technology in Indonesia has resulted in an increasing demand for electronic and electrical goods, including printed circuit board (PCB) waste. Currently, PCB waste amounts to 20-50 million tons and continues to grow annually. Given that the composition of PCB waste consists of approximately 40% metals such as Ag, Cu, Fe, Au, Sn, and Mn, recycling PCB FR-2 waste can significantly increase its added value. One effective method is employing a concentration technique to recover these metals. This study aims to investigate the impact of particle size and centrifugal force variations on the content and recovery of Cu and Ag metals in PCB FR-2 waste using a Knelson concentrator. The concentration process involved three size variations: -63+100, -100+150, and-150#, along with three centrifugal force values: 60, 90, and 120 G Force. The results indicate that the size variation-100+150# and a centrifugal force value of 90 G Force exhibited effectiveness in recovering Cu and Ag metals, with a minimal mass loss of 3.9%. The Cu and Ag levels reached 67.49% and 0.18%, respectively, with recovery rates of 53.22% and 39.96%.

Abstract: A detailed a-Si Electronic Portal Imaging Device (EPID) was implemented in GATE (Geant4 application for tomographic emission) toolkit for Monte Carlo simulations, employing the standard electromagnetic processes and optical photon processes. The composition of the scintillating material is varied using the conventional terbium-doped gadolinium oxysulfide phosphor (Gd₂O₂S:Tb) and cerium-doped lutetium oxyorthosilicate (Lu₂SiO₅:Ce) which is widely used in Positron Emission Tomography (PET) detectors due to its supremacy in aiding the detection of low-energy photons. It was found that the number of optical photons produced is higher when using the Lu₂SiO₅:Ce scintillator resulting in a slightly better signal-to-noise ratio (SNR). The scattering within the EPID components was also investigated where the majority of the detected secondary particles were created in the scintillator. The results also show that the copper plate layer of the EPID contributes to additional Compton electrons and bremsstrahlung and annihilation photons to the measurements in the scintillator and photodiode layer. The glass substrate, graphite plates, electronic components, and aluminum bottom cover are also found to contribute a huge fraction of backscattered particles to the measurements at the photodiode layer.

Abstract: External beam radiotherapy is a crucial method in treating cancer as it requires a high level of accuracy in patient positioning. Hence, commercial thermoplastic masks have a significant role during radiotherapy treatment as it is an efficient way of accurately positioning the patient without risking their safety and comfort. However, these commercial masks are expensive due to the use of costly compounds and additives, and several studies have concluded that commercial masks can significantly increase the surface dose. This study examined the effects of various thermoplastic reinforced composites for an alternative economic mask in terms of depth-dose distribution through Monte Carlo simulations in GEANT4 Application for Tomographic Emission (GATE). The simulations were varied by incident beams and their energies, material composition of the phantom, and varying thermoplastic reinforced composites. In general, the results indicated that PCL/PLA (polycaprolactone/polylactic acid), PLA/PU (polylactic acid/polyurethane), PCL/RH (polycaprolactone/rice husk), LDPE/PALF (low-density polyethylene/pineapple leaf fiber), and PP/PALF (polypropylene/pineapple leaf fiber) composites showed relatively accurate dose delivery in the target volume, which the slight difference will accumulate the 5% marginal error in treatment planning systems.

Abstract: The implementation of advanced radiotherapy techniques such as Intensity-Modulated RadiationTherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) allows much more accuratecontrol of the irradiation area and more conformal dose delivery. Since these treatments are characterizedby high dose gradients and hence small error margins, they also require advanced and highlyeffective treatment verification techniques. Fortunately, an imaging modality, originally intended forset-up verifications, called the Electronic Portal Imaging Device (EPID) was reported to have hugepotential for dosimetry and treatment verification applications. However, methods and algorithmspreviously developed for EPID dosimetry are not yet widely adopted in cancer centers due to complexitiesin the implementation. These motivate more investigation and development of new methodsto encourage cancer centers to practice EPID dosimetry and improve patient safety.This research generally aims to develop an in-vivo dosimetry method that can be used in the future toapproximate the actual dose delivered inside the target by utilizing the transmitted fluence detectedby the EPID. In this study, Monte Carlo simulations are carried out using the Geant4 Application forTomographic Emission (GATE) to implement a virtual set-up composed of a water target irradiatedwith a monoenergetic 2 MeV photon beam and an EPID model to detect the total transmitted fluence.A mathematical model has been proposed to calculate the target absorbed dose by utilizing the transmittedprimary fluence. This involves back-projection of the transmitted fluence to determine fluencevalues at certain depths inside the irradiated homogeneous medium. This is followed by the calculationof the collision kerma using the back-projected fluence and the values of the linear attenuation coefficientand mass energy absorption coefficient in the National Institute of Standards and Technology(NIST) database. The results show accurate prediction of the fluence values inside the target, calculationof the corresponding values of the collision kerma, and determination of the proportionalityconstant β that relates the collision kerma to the target absorbed dose.

Abstract: Advancements in imaging systems including Electronic Portal Imaging Devices (EPIDs) play a great role in radiotherapy treatment. It was developed as a verification tool for patient setup during radiotherapy sessions and also become a promising tool for the determination of the accurate placement of radiation beams. However, as part of quality assurance, individual patient treatments are often verified by patient-specific quality control measurements such as before treatment (pretreatment) or during treatment (in vivo). It has been shown that in vivo dosimetry using an electronic portal imaging device (EPID) is an effective QC tool to detect errors and this method has been clinically applied to various treatments. The introduction of advanced EPID technology has led to an interest in its application for dose conformation and dose deposition. Moreover, dose deposition is subject to uncertainties due to several factors, including the presence of secondary particles. Thus, knowing the physical processes that produced the secondary particles as well as their average kinetic energy will help to provide valuable information about the effective filtering of these particles or the possible use of these particles for other applications. In this study, Monte Carlo simulations are performed to determine the average kinetic energy of detected secondary particles, specifically photons, electrons, and positrons produced by each particular physical interaction as a function of detector position using GATE v9.0. The virtual radiotherapy set-up is composed of the box water phantom, which is the target in the simulations with a dimension of 20 cm × 20 cm × 20 cm, an EPID system (detector), and a beam source in which it uses three (3) beams situated at varying positions with an energy of 6 MeV. The monoenergetic pencil beam source is placed 90 cm away from the center of the target and is directed toward the target (+x-axis) while the EPID (detector) is set as 120 cm SDD (source-to-detector distance). Moreover, the photon beam with 10 million primaries is set with varying field sizes of 1 cm × 1 cm, 3 cm × 3 cm, 6 cm × 6 cm, and 9 cm × 9 cm. Overall, the results show that the highest average kinetic energy among secondary particles produced by each physical interaction are electrons coming from Compton scattering (∼ 3 MeV), followed by positrons and electrons from pair production (∼ 2.4 MeV), photons from annihilation and bremsstrahlung (∼ 0.5 MeV), and electrons from ionization (∼ 0.13 MeV).