Tailoring neutron-shielding boron-metakaolin geopolymers with BC filler; Surfactant-driven interfacial and microstructural control

Niu, X.*; Elakneswaran, Y.*; 菊池 亮佑*; Li, A.*; Seralathan, S.*; 平木 義久; 佐藤 淳也 ; 大杉 武史  ; 加美山 隆*; Walkley, B.*

Niu, X.*; Elakneswaran, Y.*; Kikuchi, Ryosuke*; Li, A.*; Seralathan, S.*; Hiraki, Yoshihisa; Sato, Junya; Osugi, Takeshi; Kamiyama, Takashi*; Walkley, B.*

The incorporation of boron (B) as a neutron absorber into metakaolin-based geopolymers for the remediation of radioactive debris following nuclear accidents has attracted considerable attention. In this study, boron carbide (BC) was employed as a functional filler, while cetyltrimethylammonium bromide (CTAB) acted as both a dispersant and a stabiliser to enhance the neutron shielding properties of metakaolin-based geopolymers. Although the addition of BC improved processability via a roller-ball effect and had no discernible impact on the geopolymerisation process, its weakly polar, negatively charged surface led to the formation of a loose, weak-shell interfacial transition zone (ITZ) between the filler and the matrix, thereby reducing mechanical strength and chemical stability. In contrast, CTAB self-assembled into an interdigitated monolayer on the BC surface, reversing its surface charge to positive and promoting its uniform dispersion within the matrix. This work offers a promising approach for engineering high-performance, multifunctional geopolymer composites for nuclear and environmental applications.