In this study, the structure, viscosity characteristics, and crystallization behavior of CaO-SiO₂-B₂O₃ based melts were studied combining molecular dynamics (MD) simulation, Fourier transform infrared (FTIR) spectroscopy, rotating viscometer test, and FactSage thermodynamic calculation. The results showed that, in the ternary CaO-SiO₂-B₂O₃ glass system, stable structural units of [SiO₄]⁴⁻ tetrahedral, [BO₃]³⁻ trihedral and [BO₄]⁵⁻ tetrahedral were formed, and the Si-O and B-O structure depolymerize with the basicity increase from 1.15 to 1.25, then the B-O structure become complex with the basicity further increase to 1.35. In fluorine-free mold fluxes, with the basicity increases, the viscosity at 1300 °C increases, the liquidus temperature decreases and then increases, the network structure polymerizes, it indicates that the structural complexity rather than the melting property change plays a predominant role in increasing the viscosity at 1300 °C. Moreover, due to the changes in crystallization phase and solid solution ratio, the viscosity-temperature curve of fluorine-free slag shows the characteristics of alkaline slag and the break temperature increase with the basicity increase. The MD simulation, FTIR experiment, viscosity test, and FactSage calculation results are verified and complemented each other.

Real-time sensing of hydrogen sulfide (H₂S) at room temperature is important to ensure the safety of humans and the environment. Four kinds of different nanocomposites, such as MXene Ti₃C₂T_x, Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄, were synthesized using the hydrothermal method in this paper. Initially, the intrinsic properties of the synthesized nanocomposites were studied using different techniques. P-type butane and H₂S-sensing behaviors of nanocomposites were performed and analyzed deeply. Four sensor sheets were fabricated using a spin-coating method. The gas sensor was distinctly part of the chemiresistor class. The MXene Ti₃C₂T_x/NiCo₂O₄-based gas sensor detected the highest response (16) toward 10 ppm H₂S at room temperature. In comparison, the sensor detected the highest response (9.8) toward 4000 ppm butane at 90 °C compared with the other three fabricated sensors (Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄). The MXene Ti₃C₂T_x/NiCo₂O₄ sensor showed excellent responses, minimum limits of detection (0.1 ppm H₂S and 5 ppm butane), long-term stability, and good reproducibility compared with the other fabricated sensors. The highest sensing properties toward H₂S and butane were accredited to p–p heterojunctions, higher BET surface areas, increased oxygen species, etc. These simply synthesized nanocomposites and fabricated sensors present a novel method for tracing H₂S and butane at the lowest concentration to prevent different gas-exposure-related diseases.

By using FactSage calculations, Fourier transform infrared spectroscopy (FTIR), rotational viscometers, and X-ray diffraction (XRD), the combined effect of MgO and Al2O3 on fluorine-free mold flux was confirmed. The viscosity of the slag at 1300 oC decreased with 2-10 wt% MgO, and higher Al2O3 increased the overall viscosity. The trend of the experimental results was consistent with the models of Riboud and Iida, while the FactSage calculation values were relatively higher. The viscosity of the slag was more influenced by the Si-O network than by the Al(B)-O structure and the MgO has a dual effect on the slag structure. The viscosity-temperature curves changed from alkaline to acidic slag characteristics when Al2O3 increased from 8 wt% to 12 wt%, and the trend was not uniform with the addition of 2-10 wt% MgO. Both FactSage calculation and XRD patterns showed that increasing MgO content gradually promoted the growth of Ca3MgSi2O8 and Ca11Si4B2O22 crystals, while the addition of Al2O3 inhibited crystal precipitation.