1. College of Engineering and Applied Sciences, Nanjing University, Nanjing 210023, China2. School of Information Management, Nanjing University, Nanjing 210023,China3. Novoray Corporation, Lianyungang 222346,Chinaet al.
Rutile-phase TiO2 is frequently employed as an inorganic ceramic filler in polymer-based copper-clad laminates to enhance the dielectric and mechanical properties of the polymer matrix, owing to its superior characteristics such as high mechanical strength, high breakdown voltage, and low dielectric loss. However, the scalable production of spherical TiO2 powder that also possesses high flowability remains a significant challenge. This review systematically examines chemical and physical methods for synthesizing spherical TiO2 particles with high industrial potential. For chemical approaches (primarily hydrothermal and solvothermal methods), the analysis focuses on the influence of factors like soluble titanium source type, temperature field, reaction pressure, and reaction medium on the hydrolysis kinetics of the titanium precursor and the kinetics governing the assembly of primary Ti(OH)4 colloids into spherical structures. Regarding physical methods (mainly spray granulation and high-temperature melting spheroidization), the review investigates the impact of process parameters such as particle assembly/spheroidization techniques and heat treatments for particle densifying on the production of high-quality spherical particles. Additionally, it summarizes the effects of heat treatment atmosphere, type and concentration of impurity elements, particle size, and heat treatment parameters on the kinetics of the anatase-to-rutile phase transformation. Our analysis indicates that chemical synthesis routes still face significant scientific and technical challenges, including the difficulty in precisely controlling titanium precursor hydrolysis kinetics, inadequate particle size uniformity, and limited tunability of the particle size range. In contrast, physical methods readily yield products with high sphericity and allow particle size adjustment over a wide range, but they also encounter the technical bottleneck of insufficient particle size uniformity.