Solids

This work investigates the effect of Co incorporation on the physicochemical properties and dry reforming of methane (DRM) performance of Ni catalysts supported on surface-modified γ-Al₂O₃ containing 9 wt% MgO and 1 wt% ZrO₂ (MS). Bimetallic catalysts containing 5 and 10 wt% Co with a fixed Ni loading of 10 wt% were prepared by co-impregnation. H₂-TPR and H₂-TPD analyses revealed the Co incorporation reducibility and hydrogen adsorption–desorption characteristics of the catalysts. These changes were accompanied by enhanced DRM activity and increased H₂/CO ratios, which may reflect changes in the contributions of competing reactions, including the reverse water–gas shift reaction. Although 10Ni10Co/MS exhibited the highest CH₄ and CO₂ consumption rates and H₂/CO ratio, its enhanced activity was accompanied by more-pronounced graphitic carbon features and greater catalytic deactivation. In contrast, 10Ni5Co/MS maintained more stable catalytic performance while retaining improved reactant utilization and H₂/CO ratio. These findings suggest that controlled Co incorporation provides a favorable balance between DRM activity and resistance to carbon-associated deactivation, with 5 wt% Co providing the best activity–stability balance among the investigated catalysts.

The premature failure (service life ≈ 4 months) of AISI 321 steel plungers due to galling in critical dosing pumps at a thermoelectric power plant significantly compromises system reliability. This study identifies the root cause of this recurring failure and develops a robust engineering solution. Finite element analysis (FEA) was employed to diagnose the original component and numerically validate a redesign using 17-4 PH H900 steel. Additionally, economic viability was assessed through a Life-Cycle Cost (LCC) analysis. The FEA revealed a severe stress concentration where the original design operated at 97.3% of its yield strength, with a critical safety factor of 1.03. This finding suggested that the structural deficiency may have indirectly contributed to the observed galling damage by compromising the contact conditions in the guiding elements. This coupling is proposed as a mechanistic hypothesis, not as an experimentally validated tribological mechanism. The redesigned plunger achieved a safety factor of 5.74, representing a 457% increase in the structural safety margin. Furthermore, the LCC analysis demonstrated the economic superiority of locally manufacturing the improved component rather than importing the original spare part. Ultimately, the proposed solution eliminates the failure’s root cause, proving to be structurally robust and economically viable. The methodology presented offers a transferable framework for diagnosing and redesigning critical industrial components.

This work introduces a methodology for numerical predictions of the compressive strength of unidirectional composites with realistic fiber orientation distributions, which were obtained via structure tensor analysis of 3D X-ray computed tomography scans of specific carbon fiber-reinforced polymer samples. Experimental characterization was performed on the material properties of the constituents, as well as the actual composite. The extracted fiber orientation distribution and the material parameters of the constituents were implemented in a two-dimensional finite element model. The model performs mesh-objective material homogenization for the fibers and matrix constituents, in which the fiber diameter defines the characteristic material length scale. The numerical prediction of the compressive strength was compared with experimental measurements. A kink band-driven failure mechanism was predicted by using the finite element model. The results show that the model can predict the compressive strength potential of the pultruded material, while accounting for the actual distribution of fiber orientation.