TEOS and Na2SiO3 as silica sources: study of synthesis and characterization of hollow silica nanospheres as nano thermal insulation materials

Hollow structured material (HSM) consisting of monodisperse hollow silica nanospheres (HSN) shows a promising potential for construction insulation due to its affordable cost and simple process. Yet the studies of high-yield and low-energy for the synthetic of HSN are still insufficient. This research reported the comparison of morphology and performance of synthesize HSN utilizing TEOS and Na2SiO3 as silica source. The average yield of Na2SiO3-based samples can reach 93.75%, which is about 10 times higher that of TEOS-based samples. Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) results revealed that the shell morphology of TEOS-based samples was raspberry-like or smooth structure, while the shell of the Na2SiO3-based samples was round honeycomb-like structure. Hot Disk thermal constant analyzer results demonstrated that the thermal conductivity of the Na2SiO3-based samples was lower than that of the TEOS-based samples with similar inner-diameter and shell thickness. Thereafter, the influence mechanism of the morphology on thermal insulation performance was also investigated. The prepared HSN as filler significantly enhanced the thermal insulation of acrylic coating. This research confirms that the synthesis route with Na2SiO3 was a greener method which can solve the low yield and high energy consumption caused using TEOS as a silica source. Excellent thermal insulation properties indicate HSN will have a broad application prospect in heat-insulating and energy-saving construction.