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

Abstract

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 Na 2 SiO 3 as silica source. The average yield of Na 2 SiO 3 -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 Na 2 SiO 3 -based samples was round honeycomb-like structure. Hot Disk thermal constant analyzer results demonstrated that the thermal conductivity of the Na 2 SiO 3 -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 Na 2 SiO 3 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. KeywordsHollow silica nanospheres (HSN) • Sodium silicate (Na 2 SiO 3 ) • Tetraethyl orthosilicate (TEOS) • Thermal insulation

Silica-Coated Micrometer-Sized Latex Particles

“…Suitable silica precursors include tetraethyl orthosilicate (TEOS), 31 − 51 tetramethyl orthosilicate (TMOS), 31 , 52 − 56 and sodium silicate. 20 , 33 , 34 , 57 − 60 …”

“…One study compared silica deposition onto polystyrene latex particles using either sodium silicate or TEOS as precursors. 34 Sodium silicate formulations led to patchy, non-uniform overlayers and tended to produce aggregates. On the other hand, TEOS led to relatively uniform silica coatings with minimal particle aggregation.…”

“…More typically, a soluble silica precursor is utilized to form a smooth uniform overlayer via in situ hydrolysis-condensation reactions. Suitable silica precursors include tetraethyl orthosilicate (TEOS), − tetramethyl orthosilicate (TMOS), ,− and sodium silicate. ,,,− …”

“…Sodium silicate is a low-cost silica precursor that is often used for wholly aqueous formulations. ,,− For such syntheses, Si­(OH) 4 can be generated using either a cation exchange resin or by lowering the solution pH to pH 2. Alternatively, base-catalyzed condensation may be employed to produce a colloidal silica sol at pH 7–10. ,− Although sodium silicate is a greener and more cost-effective soluble silica precursor, , the growth of a silica shell is strongly pH-dependent and sometimes difficult to control. One study compared silica deposition onto polystyrene latex particles using either sodium silicate or TEOS as precursors .…”

Synthesis and Effective Thermal Conductivity Measurements of Hollow Mesoporous SiO2 Spheres for Heat‐Insulating Applications

“…[ 1,5 ] In previous works, low effective thermal conductivities were measured in a range from 20 up to 141 mW m −1 K −1 . [ 1,5a,e −g, 6 ] The reason for reduced thermal conductivity is assumed to be a significantly lower density associated with a reduced number of solid–solid interfaces and a reduced thermal conductivity via gas phase. [ 1 ] It has been shown that if a self‐assembled crystal made of hollow spheres deviates from the local order, the thermal conductivity is significantly reduced with decreasing pressure.…”