This study aims to investigate the effect of rice husks’ particle size on resin-based brake pad performance (i.e. compressive strength, puncture strength, mass loss, wear rate, friction coefficient, and heat resistance). Bisphenol A-epichlorohydrin and cycloaliphatic amine were mixed to form resin and used as the brake pad's base material. In the experiment, rice husk with a specific particle size (i.e., 250, 500, dan 1000 μm) was added to the resin. Rice husk has received considerable interest due to its lignin, cellulose, and silica content, making it suitable as friction material due to its ceramic-like behavior. The experimental results showed small rice husk particles improved compressive strength, puncture strength, and bulk density. This can be obtained from the analysis of the maximum compressive strength for brake pad supported by particles with sizes of 250, 500, and 1000 μm having values of 0.238; 0.173; and 0.144 MPa, respectively. In contrast, large particles formed coarse surfaces and pores, decreased mass loss rate, and improve friction properties (i.e. wear rate, friction coefficient). The friction coefficient values of brake pad supported by particles with sizes of 250, 500, and 1000 µm were, respectively, 0.2075; 0.2070; and 0.3379. Particle size affected interpacking, interfacial bonding, pores number and size, thermal softening, mechanical properties, and friction properties of the brake pad. Comparison between the prepared resin-based and commercial brake pad was also done, confirming the utilization of agro-waste as a potential alternative for friction material in the brake pad.
This study aims to evaluate the adsorption isotherm of carbon microparticles prepared from pumpkin (Cucurbita maxima) seeds for adsorbing curcumin (as a model of dye). The results were derived and compared using the kinetics approach based on several standard adsorption isotherm models, namely the Langmuir, Temkin, Freundlich, and Dubinin-Radushkevich models. The second aim is to evaluate the effects of carbon particle size (from 100 to 1000 mm) on the adsorption characteristics. The experimental results showed that the adsorption on the surface of carbon microparticles occurred in monolayer with a physical phenomenon. This is because the active areas are located only on the outer surface of carbon and no surface structure in the carbon is available. This is confirmed by the fact that the produced carbon has less porosity and the pores themselves are mostly produced from the release of inorganic contents during carbon synthesis, while the amount of inorganic content is very less. The confirmation of the adsorption profile was also achieved by testing various sizes of carbon microparticles. Smaller particles have direct impacts on the improvement of adsorption capacity, which is due to the existence of a larger surface area, a larger number of adsorption sites, and additional cooperative adsorption, i.e. adsorbate-adsorbate interaction. Understanding the adsorption phenomena occurring on carbon particles is useful for further developments and applications, such as those of catalysts and adsorbents, especially concerning the production of carbon materials from organic waste.
The purpose of this study was to identify misconceptions using the certainty of response in undergraduate students through a case study of mathematical chemistry subject by experimental demonstration of adsorption. The concept of mathematical chemistry was conveyed to students by using an explanation video. The video also directs students to do practical experiments on adsorption. The data obtained can be used to determine the isotherm adsorption model that fits with their experimental phenomena. Students analyze the data obtained by using their understanding of the mathematical chemistry concepts that have been taught. Misconceptions on students were analyzed using pretest-posttest by giving 20 questions followed by the guess level (CRI). Based on the answers given, students' understanding of the concepts being taught can be identified as understanding the concept, lucky guess, do not understand the concept, and misconceptions. This research can be used as a reference to identify misconceptions in students and can be applied in various subjects.
The purpose of this study was to evaluate the economic feasibility of producing copper oxide (CuO) nanoparticles using the green synthesis method on an industrial scale for 10 years by evaluating from an engineering and economic perspective. Various economic parameters are used to analyze economic viability, including Gross Profit Margin (GPM), Cumulative Net Present Value (CNPV), Payback Period (PBP), as well as economic variations in sales, taxes, raw materials, labor wages, and utilities to ensure project feasibility. Technical analysis to produce 100 kg of CuO nanoparticles per day requires a total production cost of 220,322.850.00 IDR and the gross profit margin is 16,721,250.000,00 IDR per year. PBP analysis shows that the investment will be profitable after more than three years. This project can compete with PBP capital market standards because of the short investment return. The profit is relatively economical, so this project can be run for 10 years under ideal conditions. This research is expected to be a reference for technical and economic analysis of industrial-scale production of CuO nanoparticles
The purpose of this study was to demonstrate distance learning innovation in teaching chemistry in vocational school using the concept of isotherm adsorption of carbon microparticles. The subjects were 60 vocational school students in Bandung, Indonesia, who took a 15-question pre-test and post-test with a learning video for supporting distance learning process. The subjects were focused to understand the successful teaching process, which were divided into the control class and the experimental class. The control class was done by giving a video containing conventional teaching process (without experimental demonstration), while the experimental class was done by giving a video containing experimental demonstration. To support the teaching process, the experimental video was chosen as the suitable teaching medium, including the production of carbon microparticles, adsorption measurement, data analysis, and an explanation of the adsorption mechanism. The results showed increases in the post-test scores compared to the pre-test. The t critical two-tailed value was 2.04, which was higher than the t statistic value (-2.52), ensuring the successful teaching for improving the students’ understanding on carbon adsorption phenomena. The learning video was provided visual and audio experiences. Video learning media gave positive impacts to students’ understanding, which was prospective for distance learning process. However, additional experimental demonstration inside the video learning media enhanced student’s interest in particular subjects and motivated them to learn more about the teaching subject, in which this become new innovation in the distance learning process. This study demonstrated the importance of combination between experimental demonstration and video as a teaching media for improving students’ comprehension, which can be implemented during special condition, for example COVID-19 pandemic.
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