No abstract

In this work, taking FeWO 4 nanosheets as an example, the activation of oxalic acid (OA) based on facet engineering for the enhanced generation of active radical species was reported, revealing unprecedented surface Fenton activity for pollutant degradation. Density functional theory calculations confirmed the more efficient generation of reactive oxygen species over FeWO 4 nanosheets with the {001} facet exposed (FWO-001) under visible light irradiation compared to the efficiency of FeWO 4 nanosheets with the {010} facet exposed (FWO-010), which could be attributed to a higher density of iron and the efficient activation of OA on the {001} facet. The H 2 O 2 -derived • OH tended to diffuse away from the active sites of FWO-001 into solution to favor the continuous activation of OA into the active radicals for pollutant redox reactions, but preferred to remain on FWO-010 to hinder the further activation of OA on the {010} facet. Additionally, the generation of • CO 2 − endowed FeWO 4 with a strong reduction ability. Compared with FWO-010, FWO-001 exhibited enhanced redox activity for the catalytic degradation of organic pollutants and Cr(VI) in the optimized conditions. These findings can help in understanding the facet dependent surface Fenton chemistry of catalytic redox reactions and in designing efficient catalysts for environmental decontamination.

No abstract

The development of a facile method for large scale production of insensitive HMX particles is of great importance for energetic materials, especially for insensitive munitions. Inspired by mussels, HMX particles with a thin, robust, wettable and uniform coating based on the self‐polymerization of dopamine were prepared by one‐step solution stirring processes in the study. The as‐prepared HMX@PDA particles showed stable shape, size, and polymorphy compared with original HMX particles. With PDA (polydopamine) coating, the HMX@PDA particles exhibited better wettability, which could improve the adhesive properties between particles and other liquid components in a PBX (plastic bonded explosive). Furthermore, the mechanical sensitivities were decreased for the HMX@PDA particles because of the uniform and smooth PDA coating decreasing the hot spots on the surface of the HMX particles. HMX@PDA particles produced by a facile scalable process might provide a promising substitute for sensitive HMX particles to enhance the safety and adhesive properties when used in PBX.

Three-dimensional (3D) printing will create a revolution in the field of microfluidics due to fabricating truly three-dimensional channels in a single step. During the 3D-printing process, sacrificial materials are usually needed to fulfill channels inside and support the printed chip outside. Removing sacrificial materials after printing is obviously crucial for applying these 3D printed chips to microfluidics. However, there are few standard methods to address this issue. In this paper, engineering techniques of removing outer and inner sacrificial materials were studied. Meanwhile, quantification methods of removal efficiency for outer and inner sacrificial materials were proposed, respectively. For outer sacrificial materials, a hot bath in vegetable oil can remove 89.9% ± 0.1% of sacrificial materials, which is better than mechanics removal, hot oven heating, and an ethanol bath. For inner sacrificial materials, injecting 70 °C vegetable oil for 720 min is an optimized approach because of the uniformly high transmittance (93.8% ± 6.8%) and no obvious deformation. For the industrialization of microfluidics, the cost-effective removing time is around 10 min, which considers the balance between time cost and chip transmittance. The optimized approach and quantification methods presented in this paper show general engineering sacrificial materials removal techniques, which promote removing sacrificial materials from 3D-printed microfluidics chips and take 3D printing a step further in microfluidic applications.

No abstract

In this study, a model for assessing urban water security is developed using an evaluation method of catastrophe theory. To overcome the defects of the traditional catastrophe evaluation method, two aspects of improvement are assessed. One is expanding the scope of application of the traditional catastrophe approach, i.e., new normalization formulae for five lower level indicators contained in the index at the higher level is proposed in theory. The other is solving the problem that the synthetic values are generally high and the differences are not obvious based on the theories of Cramer's Rule and Vander monde determinant. The assessment results in Wuhan city are in good agreement with the actual situation. The comparison between the results of the improved method and a fuzzy comprehensive evaluation method verifies the science and reliability of the developed method. Consequently, it is concluded that the improved method can be an effective tool for assessment of urban water security and provide a valuable reference for improving inadequacies in urban water security.

Degradation mechanism of the K–Fe/oxalic acid/H2O2/visible light system.