The performance enhancement of 3D‐printed electrode comprised of polylactic acid (PLA) and graphite (Gr) doped with graphene oxide (GO) was studied to detect five heavy metal ions in trace level. The pretreatment of PLA/Gr/GO electrode with potential cycling in H2SO4 solution achieved the most sensitive response. The characteristics of the composite electrodes were verified using XPS, FE‐SEM, EDXS, Raman, and impedance spectroscopy. The experimental variables affecting the response current were optimized with respect to pH, deposition time, ratio of PLA/Gr/GO, and supporting electrolytes. The pretreated 3D‐PLA/Gr/GO electrode showed a wide dynamic range from 0.5 ppb to 1.0 ppm with low detection limits of 0.039–0.13 ppb. The reliability of the PLA/Gr/GO electrode was evaluated by analyzing the reference samples of European Reference Materials.
-The dephosphorization (de-P) efficiency of SiMn alloy melt using CaO-CaF2 flux was measured at 1823 K under a strongly reducing atmosphere. De-P efficiency increased by increasing the CaO content up to CaO saturation point in the CaO-CaF2 flux at 1823 K, indicating that the phosphorus was removed from the SiMn melt by the reducing refining mechanism. When the Vee ratio (= CaO/SiO2) of the reducing de-P slags is greater than about 1.35, the lime and dicalcium silicate phases precipitated during solidification, resulting in an increase in the emission rate of PH3 gas due to an increase in the reaction area. However, when the Vee ratio of the slags is lower than about 1.35, the fluorite, cristobalite, and wollastonite phases appeared from the phase diagram, resulting in less amount of PH3 emission during cooling because the reaction between Ca3P2 and H2O was restricted to the surface of bulk slag.
Because sulfur and phosphorus are very harmful in steel products, there are increasing requirements for refining these elements from ferroalloys industries. Hence, in the present study, simultaneous desulfurization (de-S) and reducing dephosphorization (Rde-P) from silicomanganese (SiMn) alloy were investigated using metal-slag equilibration method under highly reducing condition at 1773 K. Experiments were carried out by equilibration between SiMn alloy and MnO-based slag in graphite crucible under p(O 2 ) = 10 −18 atm. Slag composition was designed by changing basicity (CaO/SiO 2 ) and MnO content at fixed Al 2 O 3 (=20%) and MgO (=5%) contents. De-S ratio increased with increasing basicity until C/S = 1.5 whereas Rde-P ratio was not significantly affected by slag basicity. This was because thermodynamic driving force of de-S reaction was greater than that of Rde-P reaction under present experimental conditions. The de-S and Rde-P ratios commonly increased with decreasing oxygen partial pressure.
We investigated the effect of solution temperature (Tsol. = 440–530 °C) on the mechanical properties of the Al–3.4Cu–0.34Mg–0.3Mn–0.17Ag alloy, finding that the investigated Al alloy showed the highest mechanical strength of σUTS = ~329 MPa at a Tsol. value of 470 °C. The microstructural investigation demonstrates that the mechanical properties for different Tsol. values stem from grain growth, precipitation hardening, and the formation of large particles at the grain boundaries. On the basis of Tsol. = 470 °C, the effect of each microstructural evolution is significantly different on the mechanical properties. In this study, the relationships between the microstructural evolution and the mechanical properties were investigated with respect to different values of Tsol.
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