Predicting the pathways of string-like motions in metallic glasses via path-featurizing graph neural networks.

String-like motions (SLMs)-cooperative, "snake"-like movements of particles-are crucial for dynamics in diverse glass formers. Despite their ubiquity, questions persist: Do SLMs prefer specific paths? If so, can we predict these paths? Here, in Al-Sm glasses, our isoconfigurational ensemble simulations reveal that SLMs do follow certain paths. By designing a graph neural network (GNN) to featurize the environment around directional paths, we achieve a high-fidelity prediction of likely SLM pathways, solely based on the static structure. GNN gauges a structural measure to assess each path's propensity to engage in SLMs, akin to a "softness" metric, but for paths rather than for atoms. Our GNN interpretation reveals the critical role of the bottleneck zone along a path in steering SLMs. By monitoring "path softness," we elucidate that SLM-favored paths transit from fragmented to interconnected upon glass transition. Our findings reveal that, beyond atoms or clusters, glasses have another dimension of structural heterogeneity: "paths."

New Insights into the Penetration Depth of Sulfuric Acid and Leaching Effect in the Sulfuric Acid Curing-Leaching Process of Vanadium-Bearing Stone Coal.

In the process of sulfuric acid curing-leaching vanadium-bearing stone coal, the curing effect is very important. The main purpose of this study is to capture the difference in the curing effect between coarse and fine stone coal, with a V2O5 content of 0.88%. In this work, the effects of various factors such as sulfuric acid concentration, curing time, curing temperature, and different agents for curing on the leaching efficiency of vanadium were investigated by the comparison of the two size fractions. The results showed that the leaching efficiency of vanadium was 87.65% under the optimum curing conditions of 25 wt % sulfuric acid, curing time of 8 h, and curing temperature of 130 °C. It was clearly found that, under the same curing condition, the curing effect of fine stone coal was better than that of coarse stone coal. The penetration part of stone coal particles by sulfuric acid was loose, while the non-penetration part was dense after acid curing. Moreover, the penetration depth of sulfuric acid into the particles was mainly 0.5-0.7 mm on average. There was more sericite/illite in coarse leaching residues, which were mostly dense and hard carbonaceous siliceous slate. Thus, sulfuric acid was difficult to penetrate into and reach the interior of the particle, which resulted in that the leaching efficiency of coarse vanadium-bearing stone coal ore was lower than that of fine vanadium-bearing stone coal ore.

Structural origin for vibration-induced accelerated aging and rejuvenation in metallic glasses.

Glassy materials are nonequilibrium and their energy states have crucial influences on properties. Recent studies have shown that oscillating deformations (vibrations) can cause either accelerated aging (lowering energy) or rejuvenation (elevating energy); however, the underlying atomic mechanisms remain elusive. Using metallic glasses (MGs) as model systems, we show that the vibration-induced accelerated aging is correlated with the strain field of the stringlike atomic motions stemming from the Johari-Goldstein (ß) relaxation, whereas the rejuvenation is associated with nonlinear response and the formation of nanoscale shear bands attributing to the activation of α relaxation. Both processes are affected by thermal fluctuations, which result in an optimal temperature for accelerated aging. These results suggest intrinsic correlations among relaxation dynamics, mechanical properties, and the vibration induced structural rearrangements in MGs.