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Steel containment vessels for nuclear power plants can experience gas leakage due to minute defects such as cracks, corrosion, and aging, leading to gas leakage. A gas leakage model for microchannels is established to elucidate the mechanism underlying gas leakage within microchannels caused by these defects, specifically addressing the issue of unidirectional gas flow. Computational Fluid Dynamics (CFD) and the UK R6 method are employed to calculate the gas leakage rate within microchannels. Furthermore, the characteristics of gas flow within microchannels are explored, including the factors affecting the gas leakage rate. Validation of the calculation results is verified experimentally. The results indicate that the gas mass flow rate exhibits a linear decrease with decreasing internal pressure and a non-linear decline as temperature increases. Additionally, the gas mass flow rate demonstrates a negative correlation with the microchannel length but a positive association to its hydraulic diameter. The primary influencing factors on gas leakage rates are hierarchically ranked as follows: pressure difference, microchannel cross-sectional area, temperature, microchannel length, and microchannel hydraulic diameter.

Summary: Piezoelectric atomization is becoming mainstream in the field of inhalation therapy due to its significant advantages. With the rapid development of high-viscosity gene therapy drugs, the demand for piezoelectric atomization devices is increasing. However, conventional piezoelectric atomizers with a single-dimensional energy supply are unable to provide the energy required to atomize high-viscosity liquids. To address this problem, our team has designed a flow tube internal cavitation atomizer (FTICA). This study focuses on dissecting the atomization mechanism of FTICA. In contrast to the widely supported capillary wave hypothesis, our study provides evidence in favor of the cavitation hypothesis, proving that cavitation is the key to atomizing high-viscosity liquids with FTICA. In order to prove that the cavitation is the key to atomizing in the structure of FTICA, the performance of atomization is experimented after changing the cavitation conditions by heating and stirring of the liquids.

Impact toughness is essential for evaluating the mechanical properties of ship hull steels. This study focused on understanding the embrittlement mechanism of NiAl precipitation-strengthened HSLA steels by integrating advanced characterization and atomic-scale calculations. The factors causing the deterioration of the impact toughness of NiAl precipitation-strengthened steels, which have been contentious, were identified. The embrittlement mechanism and crack propagation mode were revealed using first-principles calculations and 3D impact fracture morphology, respectively. The results suggested that the numerous homogeneous NiAl nanoparticles within the bcc-Fe matrix reduced the impact toughness of the HSLA steels. As the precipitate interparticle spacing (L) decreased, the impact toughness decreased until it attained a critical value (∼27 nm). This is interpreted effectively by the calculations indicating that the shear modulus (75 GPa) and fracture energy (4.5 J/m2) of the NiAl phase, particularly the NiAlMn phase (46 GPa, 4 J/m2), are significantly lower than those of bcc-Fe (83 GPa, 5 J/m2). This induces the fracture of nanoparticles under rapid impact loading, which functions as numerous crack initiations before plastic deformation of the matrix. The small L achieved after peak-hardening aging can result in the interconnection of these crack sources and cause instantaneous cleavage fractures, similar to brittle materials.

It is attractive to fabricate molds and dies using additive manufacturing (AM) technology because the increased freedom of design makes higher cooling efficiency possible. However, little is known so far about the thermal properties of the tool steels fabricated by AM, as well as how to balance between the thermal and mechanical properties. In this work, an H13 tool steel was processed by selective laser melting (SLM) followed by heat treatments and the thermal and mechanical properties in relation to microstructure were investigated. The as-built H13 showed lower thermal conductivities compared with conventional counterparts and exhibited anisotropy with a lower thermal conductivity along the building direction. Heat treatments generally increased the values of thermal conductivities and largely reduced anisotropy, but the final thermal conductivity differed when using different heat-treating schedules. It was found that porosity, retained austenite, the melt-pool structure and the ultra-fine cellular-columnar microstructure, which were functions of SLM and heat-treating parameters, were factors determining the thermal conductivity of H13. Based on the present study of SLMed H13, it is proposed that a trade-off is necessary between thermal and mechanical properties when designing the processing route.