Chee Wah Loy; Khamirul Amin Matori; M.M. Haslinawati; Mohd Hafiz Mohd Zaid; Norhazlin Zainnudin
Abstract
A low thermal diffusivity SiO2-based ceramic was fabricated by sintering Malaysia agricultural waste rice husk at 800 °C. This paper presents the effect of sintering temperatures on the phase transformation, microstructure and thermal diffusivity of rice husk ash (RHA) as a thermal insulating ...
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A low thermal diffusivity SiO2-based ceramic was fabricated by sintering Malaysia agricultural waste rice husk at 800 °C. This paper presents the effect of sintering temperatures on the phase transformation, microstructure and thermal diffusivity of rice husk ash (RHA) as a thermal insulating material. A series of SiO2-based ceramics were fabricated from rice husk via two sintering stages. Rice husk was pre-sintered at 700 °C and then ground into powder. The RHA powder was compacted into pellets and then re-sintered at a single temperature between 700 and 1400 °C. Sintering of the RHA induces phase transformation from amorphous silica to crystalline α-cristobalite, α-tridymite and β-tridymite. The thermal diffusivities of RHA were evaluated using the laser flash analysis technique. The results indicate RHA-800 °C has the lowest thermal diffusivity, which is 0.17 ± 0.1 mm 2 s −1 at 25 °C. The RHA particle morphologies were observed using a field-emission scanning electron microscopy. Low-frequency vibrational modes of silica such as lattice vibration were investigated using Fourier-transform infrared spectroscopy technique. X-ray fluorescence result indicated that RHA-800 °C contains ~90 wt % of SiO2.
K. Kaviyarasu; M. Jayachandran; M. Maaza; E. Manikandan; J. Kennedy
Abstract
The electronics industry is heavily reliant on the use of silicon in devices ranging from solar panels to circuitry. This is of growing concern due to the environmental impact of sourcing and refining the material. Thus, a green source of silicon is of vital importance to meet the growing demand for ...
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The electronics industry is heavily reliant on the use of silicon in devices ranging from solar panels to circuitry. This is of growing concern due to the environmental impact of sourcing and refining the material. Thus, a green source of silicon is of vital importance to meet the growing demand for silicon in the industry. Rice husk represents an abundant source of nano silica. Currently the husk is considered a waste product that is separated from the grain during the milling process. Several methods have been trailed to extract the nano silica from rice husk. This paper reviews these current methods and presents suggestions of innovative research directions for processing techniques. This work reveals that the structural nature of superfine silica from rice husk ash is independent of the purification method, but dependent on the incineration temperature used. The paper concludes by advocating the physic-chemical process for producing high purity reactive nanosilica from rice husk. This method has the advantage of having high volume production versatility and being environmentally friendly. However, control of the morphology, shape, size, crystalline structure and chemical composition of rice husk nanostructures remains a challenge in the development of 3D nanopores arrays controllable by synthesis methods. We hope this article can provide the reader with snapshots of the recent development and future challenges.