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.
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 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.
Copper nanoparticles are the most frequently used materials in the field of nanoscience because of their electrical, optical, biomedical, antifungal, and antibacterial properties. The synthesis of copper nanoparticles with biological methods is known to be environmentally friendly, inexpensive, simple, and capable of producing better nanoparticles than other methods. This study aims to determine the feasibility of an industrial project to manufacture Cu nanoparticles through a biosynthetic method using Citrus medica Linn. extract and evaluate it from an engineering and economic point of view. Some of the parameters used for economic evaluation are Payback Period (PBP), Break Even Point (BEP), and Cumulative Net Present Value (CNPV). The analysis is supported using data taken from online shopping websites. The results showed that the number of Cu nanoparticles that could be produced in one year was 24,000 kg. The total initial capital cost is 272,640.00 USD and the profit is 698,655.90 USD/year. PBP occurred in the 3rd year with the CNPV/TIC value reaching 3.746% in the 9th year. Based on the economic evaluation, the project is concluded to be feasible to run with the anticipated tax and percentage of sales. The results of this study are expected to provide an overview of the economic evaluation of industrial-scale Cu nanoparticles production by biosynthetic method using Citrus medica Linn. extract.
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