Crystal Evolution of Calcium Silicate Minerals Synthesized by Calcium Silicon Slag and Silica Fume with Increase of Hydrothermal Synthesis Temperature

Abstract

In order to realize high-value utilization of calcium silicon slag (CSS) and silica fume (SF), the dynamic hydrothermal synthesis experiments of CSS and SF were carried out under different hydrothermal synthesis temperatures. In addition, phase category, microstructure, and micropore parameters of the synthesis product were analyzed through testing methods of XRD, SEM, EDS and micropore analysis. The results show that the main mechanism of synthesis reaction is that firstly β-Dicalcium silicate, the main mineral in CSS, hydrates to produce amorphous C–S–H and Ca(OH)2, and the environment of system is induced to strong alkaline. Therefore, the highly polymerized Si-O bond of SF is broken under the polarization of OH− to form (SiO4) of Q0. Next, amorphous C–S–H, Ca(OH)2 and (SiO4) of Q0 react each other to gradually produce various of calcium silicate minerals. With an increase of synthesis temperature, the crystal evolution order for calcium silicate minerals is cocoon-like C–S–H, mesh-like C–S–H, large flake-like gyrolite, small flake-like gyrolite, petal-like gyrolite, square flake-like calcium silicate hydroxide hydrate, and strip-like tobermorite. In addition, petal-like calcium silicate with high average pore volume (APV), specific surface area (SSA) and low average pore diameter (APD) can be prepared under the 230 °C synthesis condition.

Experimental Study on Subgrade Material of Calcium Silicate Slag

“…The overall compactness was high, and the crystal development was significantly improved. It can be observed in Figure 6 A that the hydration products of Ca(OH) 2 crystals in flakes and of different sizes, fine particles and less fibrous condensed particles were found in the hydration products at the age of 7 d when the CSS was mixed with 13%, and rod-shaped crystals were observed at point g. It can be inferred that the hydration products were mainly C-S-H colloids [ 26 ]. At 28 d of hydration age ( Figure 6 B), the fibrous crystal shape was observed at point h where no pores existed, the Ca(OH) 2 crystals were basically stacked together according to the plate-like structure, the overall denseness was higher, and the degree of crystal development was significantly enhanced.…”

Anti-thermal Quenching in Blue Phosphor Ba3YAl2O7.5: Tm3+

“…The emission intensity is enhanced as the increase of doped Tm 3+ content from 0 to 0.03, then decreases owing to the concentration quenching effect. With Tm 3+ concentrations increasing, the energy migration probability between Tm 3+ ions increases, resulting in the emission intensity of Tm 3+ decreasing [12,13]. The color coordinates are a vital factor to evaluate the luminescence property of the sample.…”

Behavior of Calcium Compounds under Hydrothermal Conditions during Alkaline Leaching of Aluminosilicates with the Synthesis of Fillers for Composites

“…For the CaO-SiO 2 -H 2 O system, more than 17 phases are known, and their composition depends on the initial CaO/SiO 2 ratio and on the temperature [6][7][8][9][10][11][12][13][14][15][16]. Unibasic (tobermoritic) and biaxial hydrosilicates are characteristic of alumina production and can be used as fillers during the preparation of composite materials [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. They are formed during the hydrochemical processing of the sinter due to the interactions of the 2CaO-SiO 2 sinter with dilute aluminate solutions as well as from alkali regeneration of sodium-calcium hydrosilicates during leaching with different variants of the Ponomarev-Sazhin method.…”