Impact of Firing Duration on the Density, Porosity, and Macrostructure of Crucible Specimens Made from Evaporation Boat Waste and Sodium Silicate

¹ Department of Mechanical Engineering, Faculty of Engineering, Diponegoro University, Semarang, Jawa Tengah, 50275, Indonesia.
² Department of Mechanical Engineering, Faculty of Engineering, Universitas Negeri Semarang, Kampus Sekaran, Gunungpati, Semarang, 50229, Indonesia

^* Corresponding author: me_rusiyanto@mail.unnes.ac.id

Abstract

The growing demand for durable and high-performance materials in the metal casting industry has highlighted the need for efficient and sustainable refractory materials, such as crucibles. Traditional materials like graphite face limitations in durability and thermal resistance. This study explores the potential of evaporation boat waste, consisting of Boron Nitride (BN) and Titanium Diboride (TiB₂), as a sustainable alternative for crucible production when combined with sodium silicate as a binder. The research aims to assess the impact of retention time during the firing process on the density, porosity, and macrostructure of the resulting crucible specimens. A quantitative experimental approach was employed, with crucibles fired at varying retention times (60, 90, 120, 150, and 180 minutes) at a temperature of 1150°C. The findings indicate that increased retention time improves density and reduces porosity, with the highest density of 2.138 g/cm³ and lowest porosity of 1.14% observed at 180 minutes. SEM analysis revealed significant improvements in particle bonding and macrostructure uniformity with longer holding times. This study demonstrates that retention time plays a critical role in optimizing crucible properties, offering a 5.1% increase in density and a 2.7% decrease in porosity at optimal conditions, providing a sustainable, cost-effective alternative to traditional materials.