The purpose of this study was to evaluate regulation of mechanical impact (i.e. impactor sizes and shapes) on triangle, cylinder, and cube as well as disk rotation speed (from 600 to 1500 rpm) in disk mill for controlling size-reduction process. As a model of size-reduced material, rice husk was selected. The study was done by evaluating the final milling product size, which was completed by the measurement of energy impact during the milling process. Experimental results showed that the product size was controllable in the range of between 50 and 1000 μm. The impactor sizes and shapes influenced the contact diameter and area of impactor for making more materials being collided, whereas disk rotation speed led to giving more collision number (between rice husk and impactor) and increasing impact from the collision (due to less time contact during collision). This study provides an important information, which can be further generalized in the use of milling process as a tool for materials size-reduction and mechanochemical process.
This study aims to evaluate zinc oxide (ZnO) nanoparticles as a learning media to enhance students' understanding of View of Nature of Science and Technology (VNOST). The method used in this study: (i) understanding how to synthesize ZnO nanoparticles using a liquid-phase synthesis; (ii) implementation of ZnO nanoparticles to students and analysis their comprehension using Transcript Based Lesson Analysis (TBLA) on the Learning Video Recording and Adaptation Learning Transcript VNOST questionnaire, which is linked to the implementation and pattern of knowledge construction; and (iii) descriptive qualitative analysis to analyze the understanding of VNOST for each Category (Naïve, Has Merit and Realist). To support this study, several analyses were done, such as a scanning electron microscope and X-ray diffraction to characterize ZnO nanoparticles’ morphology and crystal structure, respectively, prior to giving this material for further learning to students. Experimental results showed that the use of ZnO nanoparticles is effective to improve the student comprehension. The understanding in the principle of nucleation and growth can be explained well since the reaction of ZnO is relatively fast. Students became more serious in listening during the learning process and more curious to study science and technology. Based on a comparative analysis of the initial and final ability of VNOST, it is proved that there was a change in students' views related to science and technology.
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