A novel Eu²⁺-Eu³⁺ co-activated ratiometric thermo-sensitive phosphor was developed and synthesized by solid-state reaction. The valence state of Eu, photoluminescence and thermo-sensitive performance of the phosphor prepared either in ambient air or carbothermally were investigated and discussed. The phosphor shows high sensitivity (S_a = 0.0173 K^–1, S_r = 0.461%/K) and superior signal discriminability (Δν = ∼10380 cm⁻¹). The thermo-sensitive performance is subject to the dual effects of different thermo-responses by Eu²⁺ versus Eu³⁺ combined with energy transfer from Eu²⁺ to Eu³⁺, so that the sensitivity of the phosphor in the temperature range presents a non-monotonic trend. The development of the BaAl₂B₂O₇:Eu²⁺,Eu³⁺ phosphor is not only expected to be relevant for application in the field of temperature sensing, but also of reference significance for improving the sensitivity by means of energy transfer between co-activator ions over a wider temperature range of Eu²⁺-Eu³⁺ co-activated ratiometric thermo-sensitive phosphors.

An in-depth exploration of the reaction kinetics and thermo-chemical behaviors of the raceway can offer practical insights for optimizing the operations of blast furnace (BF), thus achieving a more effective iron and steel production process. In this study, the dynamic characteristics and the flow, heat and mass transfer behaviors in the BF raceway were simulated by Discrete Element Method-Computational Fluid Dynamics (DEM-CFD) method at a particulate scale. The effects of coke size distribution and blast velocity on coke combustion characteristics, thermochemical behavior (particle volume fraction, raceway size, carbon loss, and coke temperature) and microscopic properties (coordination number (CN), contact normal force, pore structure and stress) were systematically investigated. The results show that as the blast velocity decreases or the size ratio λ (the largest coke particle size divided by the smallest coke particle size) increases, the raceway size becomes smaller, resulting in a smaller area of high oxygen (O₂) concentration and low carbon monoxide (CO) concentration in the raceway, and higher CO concentration in the packed bed. For the thermal-chemical behaviors, a lower blast velocity or a higher λ value decreases the number of particles experiencing mass loss, as well as increases individual particle mass loss, the average coke temperature and its variance. For microscopic properties, the CN distribution becomes wider as λ increases. The contact normal force in the coke bed with λ > 1 is significantly higher than that of λ = 1. As λ increases or blast velocity decreases, the pore distribution curve shifts to the left and the average pore volume decreases. The stress acting on the particles in the raceway increases with the blast velocity or λ. These new understandings of the complex reactive flow behaviors in the raceway will shed light on energy utilization and process optimization.

Understanding and controlling the composition segregation during powder spreading is of key importance in the additive manufacturing (AM) of composite materials. Under this circumstance, the segregation behavior of WC/316 L composite powders during spreading in laser powder bed fusion (LPBF) AM was numerically investigated by the discrete element method. The effects of process conditions (i.e., spreader velocity and geometry) and powder properties (i.e., size and shape of the WC powder) on the powder bed composition segregation and related characteristics were systematically analyzed. Corresponding mechanisms were identified from microscopic scale in terms of particle velocity, motion trajectory, mechanical behavior, and energy information. Finally, proper solutions in designing and constructing WC/316 L composite materials with desired gradient structures were proposed. The results show that the small blade velocity (V) will enhance the negative segregation, increase the average packing density ρ¯, and decrease uniformity ρ_vc in the WC/316 L composite powder bed. Compared with the blade, the roller can increase the negative segregation (Se_roller = −0.027 < Se_blade = −0.019) and the average packing density (ρ¯_roller = 0.31>ρ¯_blade = 0.20). When the WC/316 L size ratio increases from 25 μm/45 μm to 45 μm/45 μm, the negative segregation becomes weaker, and its value increases from −0.084 to −0.007. When the size ratio increases to 65 μm/45 μm, the powder behaves positive segregation with Se_max = 0.017; in this case, the packing density is the lowest (0.14), and the uniformity is the worst (0.17). In comparison with spherical shape, polyhedral WC powder can reduce the negative segregation of the powder bed (Se_sphere = −0.019 < Se_polyhedron = −0.008), while the WC shape has less effect on the packing density and uniformity. The density difference of the WC and 316 L powders leads to the difference in energy and force, resulting in different motion and segregation behaviors in the composite powder bed. For WC/316 L composite powder with a fixed composition, the condition of V = 0.025 m/s, WC/316 L size ratio = 25 μm/45 μm, roller spreader, and spherical WC can realize the proper composition gradient along the spreading direction in the composite powder bed.

In this paper, the transition from random to ordered packings of mono-sized cylindrical particles under 3D mechanical vibration was simulated by discrete element method (DEM). The effects of particle aspect ratio, size of the particulate system and container wall on the granular crystallization were investigated. And the mechanisms were analyzed through the characterization of the order transition process in terms of packing density, coordination number (CN), orientational ordering parameter (O), nucleation and growth of cluster and granular temperature (θ). The results show that nearly perfect crystallization of mono-sized cylindrical particles can be achieved with specific aspect ratio and proper vibration conditions in a cylindrical container. The orientational ordering parameter demonstrates that the crystallization firstly starts from the container wall and then propagates inward gradually. The lower granular temperature in a cuboid container indicates less vibration energy transferred to the granular assembly compared with that in a cylindrical container, illustrating the critical role of container shape in crystallization. The vibrated crystallization of mono-sized cylindrical particles is analogous to entropy-driven process, which can be gradually achieved by the self-assembly of particles with parallel alignments along the already formed ordered clusters (nuclei)or the container wall. These results can help design complex and ordered granular structures.