SHEN Wangqiang^1，2，REN Nianzu¹ ，YE Junliang¹ ，ZHANG Shenming¹ ，GUO Minna¹ ，WEI Guangyao²

1. School of Materials Science and Engineering， Hefei University of Technology， Hefei 230009， China；

2. Triumph Quartz Materials （Huangshan） Co. ， Ltd. ， Huangshan 245400， China

Abstract

Significance Spherical silica micropowder has garnered significant attention as an inorganic filler due to its high thermal conductivity, excellent dielectric properties, good chemical stability, etc. These superior characteristics have led to its widespread application in various fields, including copper-clad laminates, epoxy resin encapsulants, coatings, cosmetics, drug delivery, catalysis. With continuous technological advancements and increasing demands from downstream industries, the quality requirements for silica micropowder are becoming more stringent. The excellent performance of spherical silica micropowder has driven its growing market demand, making it a key focus for the future development of silica micropowder techniques.

Progress Current research on spherical silica micropowder mainly focuses on its preparation methods and surface modification techniques. Preparation approaches can be broadly classified into two categories: physical and chemical methods. Physical methods, such as flame melting and plasma processing, have been employed to produce high-purity, uniformly sized particles. For instance, a study used angular silica micropowder as a raw material to produce spherical silica micropowder through flame fusion. Chemical methods, including sol-gel, microemulsion, chemical precipitation, spray drying, and vapor phase processes, have also been widely studied. For instance, a study used tetraethyl orthosilicate as the raw material and hydrochloric acid as the catalyst to synthesize spherical silica micropowder via the sol-gel method. Researchers have further innovated by exploring new silica sources and optimizing existing preparation processes, providing references for the preparation of spherical silica micropowder. For example, researchers used rice husks as the silica source and polyethylene glycol as the solvent to synthesize spherical silica micropowder via microwave-assisted sol-gel synthesis. In terms of surface modification, techniques such as organic modification, chemical etching, and polymer grafting are widely used. Silane coupling agents are the most commonly used modifiers. Initially, single-type silane coupling agents were generally applied, but combinations of multiple agents have been shown to enhance their properties. In a study, three different silane coupling agents, KH550, KH560, and phenyltrimethoxysilane, were combined to synthesize tri-functional modified spherical silica micropowder. The results indicated that these modifying agents introduced reactive groups to the spherical silica micropowder, enhancing its interfacial compatibility and adhesion with the epoxy resin matrix. Additionally, researchers have employed chemical etching on the surface of micropowder to create more active sites, thereby enhancing the modification effect. For example, researchers treated spherical silica micropowder with a hot NaOH solution. The results showed that the NaOH treatment improved the surface activity and hydroxylation of the spherical silica micropowder, increasing the number of anchoring points and enhancing the dispersion of nanoparticles within the matrix.