Search

In this paper, the acceleration process of BaTiO3 ceramic particles under different vacuum cold spraying parameters was simulated, and the effect of process parameters on particle velocity was discussed. The results were verified using particle image velocimeter. BaTiO3 ceramic coatings were prepared using vacuum cold spraying method and their properties were tested. The simulation results showed that the particle velocity increased with the increase of gas pressure and preheating temperature. It was observed that under the same gas pressure and preheating temperature, the smaller the diameter of the particle, the more it was affected by the bow shock wave. The acceleration pattern of multiple particles was found to be similar to that of a single particle. According to the results obtained from particle image velocimetry, under the condition of and 300 K and 373 K at 0.2 MPa, the velocity of BaTiO3 particles differed from the simulation results by about 10.2% and 8.1%, respectively. Under the process parameters, as indicated by the simulation results, the continuous and dense BaTiO3 coatings with a thickness around 2 to 3 μm were fabricated by vacuum cold spraying, and the binding force was found to be 8 N. The research results indicated that the process parameters and their influence laws, obtained through numerical simulation combined with particle image velocimetry, were reliable and could be used to guide the preparation of flexible ceramic films.

In recent years, as an emerging dynamic bonding, silyl ether linkages have been concerned and applied. However, the reprocessability of vitrimers based on it is far from satisfactory because of the inactive dynamic exchange reaction. At the same time, the mechanical properties of polysiloxane elastomers are poor because of the high flexibility of polysiloxane molecular chains and weak intermolecular forces. Herein, we have successfully synthesized a PDMS elastomer incorporating Zn(II)‐amine coordination bonds as sacrificial units, which are crosslinked through dynamic silyl ether linkages. Importantly, the presence of Zn ions promotes the exchange between the silyl ether linkages and hydroxyl groups. The elastomers exhibited excellent mechanical properties (35 times improvement in toughness) and outstanding reprocessability. The mechanical property recovery of the PDMS elastomers reached approximately 90% after four reprocessing cycles. Meanwhile, small‐molecule simulation experiments were conducted to verify the significant catalytic effect of Zn (II) ions as Lewis acid catalysts on the exchange reaction of silyl ether linkages and hydroxyl groups. In a word, this work provides a facile strategy to simultaneously enhance the mechanical properties and reprocessing performance of silyl ether‐linked polysiloxane elastomers. [ABSTRACT FROM AUTHOR]

In this study, the low-cost and high-wear-resistant iron-based surfacing alloy powder is used to prepare composite coatings on the 2 mm thick Al7075 substrate with different volume ratios of Al6061 powder (3:4, 5:4 and 2:1) by the low pressure cold spray equipment. The thickness of composite coatings increases with the increasing in preheating temperature and is approximately 60-80 μm thick in single pass. The percentage of iron-based surfacing alloy powder increased with the decrease in the proportion of Al6061 powder. The microhardness and bonding strength of the coatings increase with the increase in the percentage of surfacing alloy powder due to the tamping and work-hardening effect. The wear mechanism of cold sprayed composite coatings involves both abrasive and adhesive wear on the worn surface under different loads. The wear mechanism of the micro-arc oxidation sample transforms via abrasive wear to abrasive and adhesive wear as the load changes from 5 to 10 N. Investigation about wear properties reveals that the micro-arc sample has better wear resistance at the load of 5 N, but the cold sprayed composite coatings have better wear resistance at 10 N. The Al2O3 layer is worn out and the substrate is exposed during sliding for micro-arc oxidation samples at the higher load. The results indicate that the low pressure cold spraying may replace the micro-arc oxidation technique under the higher load condition in industrial applications. [ABSTRACT FROM AUTHOR]

Convection and diffusion are key pathways for the migration of total petroleum hydrocarbons (TPH) and heavy metals (HMs) from soil to groundwater. However, the extent of their influence on pollutant migration, as well as the nonlinear relationships between these processes and pollutants, remains unclear. This study investigates the spatial distribution of TPH and HMs at a petrochemical site with complex hydrogeological conditions in southwestern China. In addition, machine learning (ML) was used to assess the effects of convection and diffusion on pollutant migration at the soil-groundwater interface. The analysis identifies and reveals TPH, Co, and Ni as the primary pollutants, with soil concentrations reaching 47.427, 7.024, and 4.766 times their respective screening values. Among various ML models, Random Forest (RF) was identified as the most effective, based on R 2 , and RMSE performance metrics. The RF model demonstrates that the concentrations of TPH and As are closely related to soil depth. Furthermore, importance indices calculated by RF indicate that the significance of convection and diffusion varies across different soil-groundwater systems. Specifically, at the soil-perched water interface, convection plays a more significant role than diffusion in influencing the migration of TPH and As. However, at the soil-pore water interface, diffusion more significantly influences the migration of all pollutants compared to convection. Additionally, a threshold or saturation effect was observed for the impact of the convection factor on pollutant concentrations in groundwater. These findings highlight the distinct roles of convection and diffusion across various water interfaces, providing new insights into the mechanisms governing contaminant migration and fate., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)