Browsing by Author "Niu, X"

Now showing 1 - 2 of 2

item: Conference-Abstract
Interaction of organic liquid with metakaolin-based geopolymer
(Department of Earth Resources Engineering, 2023-08-28) Fang, C; Elakneswaran, Y; Niu, X; Hiroyosi, N
In recent years, there has been growing interest in geopolymer cement as a more sustainable alternative to traditional concrete. Metakaolin-based geopolymers have a high capacity to immobilise radioactive cations such as Cs+ and Sr2+ via an ion exchange mechanism. In the meantime, the geopolymer has a high potential to solidify organic liquid waste and has been considered for developing porosity-controlled materials. However, the interaction mechanism between organic liquid and metakaolin-based geopolymer has not been fully understood. In this study, the appropriate control of organic liquid in the geopolymer has been studied. Firstly, alkali-activated solution (K2O:SiO2:H2O molar ratio of 1:1:13) was mixed with the lubricant (FBK Turbine 32) and cationic surfactant (CTAB) to form an emulsion. Then metakaolin-based (Sobueclay) geopolymers were synthesised in the emulsion (Al: Si molar ratio of 1:1). The interaction mechanism between the oil with emulsion and geopolymer (with or without surfactant) was evaluated using the zeta potential, paste slump flow, SEM, and compressive strength. The metakaolin-based geopolymer could not solidify the oil. However, the geopolymer can successfully solidify oil content with the help of a surfactant that changes the surface of the oil from negative to positive, allowing it to interact with the opposing surface of the geopolymer. However, the compressive strength of the resulting composite decreased as the oil content increased due to an increase in porosity, and as the hydration products filled the pores over time, the strength increased. These findings suggest that geopolymer could be a promising solution for solidifying oil. However, careful consideration must be given to the porosity induced by the presence of oil to ensure that the resulting composite has sufficient strength for its intended application.
item: Article-Full-text
Topological relations and piezoelectric responses of crystal-axis-oriented BaTiO3/CaTiO3 nanocomposites
(Royal Society of Chemistry, 2017) Hu, D; Niu, X; Ma, H; Zhang, W; Sewvandi, GA; Yang, D; Wang, X; Wang, H; Kong, X; Feng, Q
2D crystal-axis-oriented mesocrystalline BaTiO3/CaTiO3 (BT/CT) nanocomposites with high-density heteroepitaxial interfaces were synthesized by a two-step solvothermal soft chemical process. The nanostructures, formation mechanism, topological relations between the BT and CT, and piezoelectric responses of the nanocomposites were investigated. The mesocrystalline nanocomposites are polycrystals constructed from crystal-axis-oriented BT and CT nanocrystals with the same crystal-axis orientation, respectively. The directions of the [001] and [1−10] of crystalline BT correspond to the directions of the [0−10] and [100] of crystalline CT, respectively. The mesocrystalline nanocomposites were formed via an in situ topochemical mesocrystal conversion mechanism. The density of the artificial BT/CT heteroepitaxial interface in these mesocrystalline nanocomposites can be adjusted by regulating the fraction of BT and CT in the nanocomposites. The mesocrystalline BT/CT nanocomposite with the composition close to BT/CT = 1/1 presents a large piezoelectric response owing to the lattice strain derived from its heteroepitaxial interfaces with the high density in the nanocomposite.