•The concept of using polyurea coating to enhance ballistic performance of metallic corrugated core sandwich construction is proposed.•Deformation and failure mechanisms of sandwich panels ...with/without polyurea reinforcing are elucidated.•A finite element model based on the rate-dependent constitutive relation of polyurea works well to predict the ballistic impact response.•Key factors affecting the effectiveness of polyurea in mitigating high-velocity projectile impact are analyzed.
The ballistic impact resistance of metallic corrugated sandwich panels retrofitted with elastomeric coating (polyurea) is investigated through combined experimental and numerical efforts. Dynamic penetration process, failure mechanisms, ballistic limit velocity, and perforation energy threshold of polyurea-coated sandwich panels are firstly elucidated via experiments and then compared with those of non-coated sandwich panels. Subsequently, based upon a user-defined compressible model of polyurea, three-dimensional finite element (FE) simulations of both non-coated and coated sandwich panels are carried out to analyze the ballistic impact response, interrogate the energy absorption mechanisms, and assess the influence of coating position/thickness and projectile rigidity on ballistic performance. Excellent agreement between experimental measurements and numerical predictions is achieved. It is demonstrated that the presence of a sufficiently thick (e.g., ∼15 mm) impact-side elastomeric coating helps to curtail the kinetic energy of flat-ended projectiles, thus enhancing the penetration resistance considerably. The use of a thicker and impact-side coating is favored owing to its superior energy absorption capability. It is also ascertained that the effectiveness of polyurea coating in resisting rigid, flat-ended projectiles is much more remarkable relative to deformable, conical ones. Further, retrofitting an all-metallic sandwich panel with elastomeric coating broadens its multifunctionality significantly, enabling it to simultaneously carry structural loads, mitigate impact and blast loadings, and resist projectile penetration, at a minimal increase in fabrication cost and structural mass. The insights of this study provide a potential new avenue for enhancing the ballistic impact resistance as well as multifunctional attributes of all-metallic sandwich construction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ag catalysts supported on cobalt‐aluminum hydrotalcite derivative (CoAlO) nanosheet for CO oxidation are reported. A facile pre‐reduction treatment on reducible CoAlO support was employed to ...construct more oxygen vacancies for anchoring Ag sites to tune metal‐support interactions (MSI) and improve metal dispersion. The results show that directly loading Ag on CoAlO (Ag/CoAlO) can significantly promote the generation of active oxygen species by three times. Pre‐reduction of CoAlO enhances MSI of the Ag catalyst (Ag/CoAlO‐R), which further enlarges quantity of active oxygen species. Besides, the kinetic results demonstrate that compared with Ag/CoAlO, Ag/CoAlO‐R shows the additional advantages of the lower activation energy, the higher intrinsic activity of Ag sites, and especially the decreased reaction order of O2 from 0.20 to 0. The latter one indicates that enhancing MSI can readily activate gaseous oxygen at the interface of Ag and CoAlO, and the reaction mechanism obeys a typical Mars‐van Krevelen route.
Metal‐support interaction: Ag was successfully loaded on hexagonal CoAlO nanosheets derived from cobalt‐aluminium hydrotalcite by impregnation. A pre‐reducing support method was applied to construct more oxygen vacancies for anchoring Ag sites to tune metal‐support interactions and improve metal dispersion. The kinetic results show that pre‐reduction treatment not only reduces the activation energy of the reaction but also improves the intrinsic activity of Ag.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
In this study, a rapid and efficient method of recovering TiO2 from spent SCR (selective catalytic reduction) catalyst supplied by a coal-fired power plant in Shanghai was developed. The acid ...leaching and sodium roasting-water leaching residues (titanium slag) from spent SCR catalyst were employed as the raw material. First, titanium slag was dissolved into H2SO4 solution under different conditions. The optimal acidolysis conditions were 85 wt% H2SO4, 5.0 g/g acid-residues ratio, 90℃ acidolysis temperature and 2.0 h acidolysis time. Simultaneously, the highest acidolysis efficiency can reach 92.02%. The acidolysis solution was collected and concentrated to 200 g/L (measured by TiO2 concentration). Then, acidolysis solution was adjusted to pH 0.52-9.15, followed by adding 0-40 mL additional crystal seeds and reacting under certain conditions to obtain the hydrolysis product. The optimal hydrolysis conditions were 25 mL additional crystal seeds, pH 7.46, 120℃ hydrolysis temperature and 3.0 h hydrolysis time. Finally, the recovered product was obtained by roasting hydrolysis product at 700℃ for 2.0 h. The results of hydrolysis stability test indicated that this method can make the hydrolysis efficiency of acidolysis solution stabilize at approximately 90% under optimal conditions. The main component of recovered product was anatase TiO2 with the purity of 86.88%.
Herein, we report the high De-NOx performance of the A-site defective perovskite-based Pd/La0.5Sr0.3MnO3 catalyst. The formation of the defective perovskite structure can be proved by both the ...increased Mn4+/Mn3+ ratio and serious lattice contraction due to cationic nonstoichiometry. It promotes the Sr doping into perovskite lattice and reduces the formation of the SrCO3 phase. Our results demonstrate that below 300 °C the A-site defective perovskite can be more efficiently regenerated than the SrCO3 phase as NOx storage sites due to the latter's stronger basicity, and also exhibits the higher NO oxidation ability than the A-site stoichiometric and excessive catalysts. Both factors promote the low-temperature De-NOx activity of the Pd/La0.5Sr0.3MnO3 catalyst through improving its NOx trapping efficiency. Nevertheless, above 300 °C, the NOx reduction becomes the determinant of the De-NOx activity of the perovskite-based catalysts. A-site defects can weaken the interactions between perovskite and Pd, inducing activation of Pd sites by in-situ transformation from PdO to metallic Pd in the alternative lean-burn/fuel-rich atmospheric alternations, which boosts the De-NOx activity of the Pd/La0.5Sr0.3MnO3 catalyst. The Pd/La0.5Sr0.3MnO3 catalyst exhibits the high sulfur tolerance as well. These findings provide insight into optimizing the structural properties and catalytic activities of the perovskite-based catalysts via tuning formulation, and have potential to be applied for various related catalyst systems.
We designed and prepared A-site defective Pd/La0.5Sr0.3MnO3 perovskite catalyst with high De-NOx activity. The defective structure promotes the Sr doping in A-site and inhibits the formation of the segregated SrCO3 phase. Compared with SrCO3, the A-site defective perovskite sites can be more easily regenerated due to the relatively weak basicity. The A-site defective structure also promotes the in-situ generation of the active Pd0 species in the reaction atmosphere. Display omitted
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IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Charge transfer in perovskite oxide heterostructures could break the delicate balance among charge, spin, orbital and lattice order at the interface, producing exotic phenomena that cannot ...be observed in bulk materials. Here, opposite interfacial charge transfer directions are observed in SrIrO
3
/NdNiO
3
and SrIrO
3
/LaNiO
3
3
d
/5
d
perovskite heterostructures. This is accompanied with an inverse change of Ni
e
g
orbital polarization and Ni-O
pd
hybridization across the interface, by stretching/compressing the out-of-plane Ni-O bond in the opposite internal electrical field due to the opposite electron transfer direction. These interfacial reconstructions finally bring about a manipulation on the transport and magnetic characteristics. This work reveals that A site cation in perovskite heterostructures could be a knob to control the interfacial charge transfer direction, and the 3
d
/5
d
perovskite interfaces are excellent platform to study the complex interplay between various order parameters and stimulate novel interfacial effects.
All-metallic truncated conical sandwich shells with corrugated cores (TCSS) were investigated for crashworthiness under quasi-static oblique compression using a combined experimental and numerical ...approach. Subsequently, multi-objective optimization design of the TCSS was also performed by adopting the algorithm of NSGA-II to achieve maximum specific energy absorption (SEA) and minimum peak force (
). Compared with a monolithic shell, the TCSS exhibits much higher SEA and lower
under oblique loading, especially with its semi-apical angle set around 10° to 15°. The results provide valuable guidance for the application of truncated conical sandwich tubes in protective engineering, such as vehicle crashworthiness.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
To meet the increasing demand for efficient and durable catalysts for exhaust aftertreatment system, a mesoporous SiO2‐encapsulated nano‐Co3O4 catalyst was synthesized, which possesses a unique ...pitaya‐like structure with high CO oxidation activity and thermal stability. Though the silica matrix is inert, the encapsulated Co3O4 exhibits increased oxygen storage capacity, enhanced CO2 desorption behavior and high lattice oxygen reactivity. Additionally, the SiO2‐encapsulated Co3O4 catalyst can be effectively regenerated rather than the supported Co3O4/SiO2 and pure Co3O4. The kinetic results demonstrate that the L−H mechanism is followed over the pure Co3O4 nanoparticles catalyst, while the CO oxidation over the silica‐supported Co3O4 catalysts obey to both L−H and MVK mechanism. The encapsulation structure of the as‐prepared catalyst can effectively restrain the aggregation of Co3O4 during high temperature operations and improves the utilization efficiency of cobalt resources, as well, which would be suitable for practical applications.
Improved stability: Nano‐Co3O4 catalysts are incapsulated in mesoporous SiO2 matrix, which presents a unique pitaya‐like structure. Compared with the unsupported Co3O4 catalyst, the encapsulation structure can effectively restrain aggregation of Co3O4 nanoparticles under high temperature operating conditions and improves utilization efficiency of cobalt resources by exposing more active sites. The Co3O4@SiO2 catalyst exhibits high activity, and superior thermal stability and regeneration ability for CO oxidation, which could be potentially applied in practical catalytic systems.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
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