ABSTRACT
Iron oxide/carbon-based nanocomposites are known as an ideal combination of magnetic-conductive materials that were recently developed in radar absorption application; one example is the Fe3O4/multiwalled carbon nanotubes (MWCNTs). In this study, we try to boost their radar absorption ability by Mn-ion doping. Mn is an appropriate Fe substitute that is predicted to alter the magnetic properties and enhance the conductivity, which are crucial to developing their radar absorption properties. Diethylamine (DEA) is also used as a capping agent to improve the size and shape of the nanocomposite. In this study, a MnxFe3-xO4-DEA/MWCNT nanocomposite is successfully prepared by the coprecipitation method using a variation of x = 0, 0.25, 0.5, 0.75, and 1. We found that the sample's magnetic saturation (Ms) decreases, while the reflection loss (RL) increases with increasing the molar fraction of Mn. The enhancement of the radar wave absorption in the sample is dominated by dielectric losses due to the increase of electrical conductivity and interfacial polarization with the addition of Mn in the nanocomposites. We believe that our finding could shed light on the role of doping elements to develop the radar absorption properties, and further pave the way for the real implementation of iron oxides/graphene-based nanocomposite as radar-absorbing materials (RAMs).
ABSTRACT
Computational thinking (CT) is an essential skill in the twenty-first century. The computational physics course (CPC) is one subject that is designed to support students in the practice of CT. Many studies show that the worksheets could be a solution in a CPC as a scaffold to achieve the CT objectives both online and offline. The study aims to develop the worksheet and integrate it with CT in a computational physics course. This study applied the research and development (R & D) method with the ADDIE model approach. In the results, the evaluation test from the experts reached a very good interpretation score based on the learning media expert (96%), the teaching material expert (95%), and the pedagogy experts (92%). So that this media is declared feasible to be used in the CPC. Furthermore, after the experimental study of students who took the computational physics course (n = 31), the study showed that the modified course could significantly improve student skills regarding overall CT (p value <0.05). However, this research also found that cooperative learning as part of CT had no improvement (p value >0.05). The experiment was conducted amid the COVID 19 pandemic wherein the students could only study at home for the whole semester. These findings indicate that the pandemic has impacted the collaborative skills of students on the course.
