The true triaxial stress are typical stress state in the deep underground. 3D surface flaws, one of the most common type of flaws, extensively existed in the rocks. Therefore, the study on evolution of the 3D surface flaw under true triaxial stress is crucial to determine the fracture behaviors of the rock in some deep underground spaces. Gypsum, as a rock-like material, has been extensively used in studies of crack initiation and propagation. In this study, we prefabricate a pair of 3D surface flaws at 45° in the cubic gypsum specimen and investigates the effect of the intermediate principal stress on initiation and peak stresses (characteristic stress thresholds) of flaws and crack propagation patterns of 3D surface flaws parallel to the intermediate principal stress. The true triaxial apparatus and acoustic emission (AE) technique were used to test and monitor the mechanical behaviors of the samples. The internal crack propagation pattern was observed by X-ray CT scan. The results demonstrate that the intermediate principal stress strongly affects crack patterns but has a limited influence on characteristic stress thresholds. Both the intermediate and minimum principal stresses affect the difference in the crack peak and initiation stress, which elucidates how the true triaxial stress affects the fracture behavior of the specimen. Additionally, the intermediate principal stress effect on characteristic stresses is closely related to the magnitude of minimum principal stress. When the magnitude of minimum principal stress is small, with the rising intermediate principal stress, the characteristic stresses increase slowly. When the magnitude of minimum principal stress is large, the intermediate principal stress almost has no effect on characteristic stresses. The surface wing cracks and anti-wing cracks initiate from the flaw when the magnitude of intermediate principal stress is relatively small. With the intermediate principal stress increasing, the surface crack propagation pattern is shift from tensile crack to shear crack. Through the CT image reconstruction technique, the propagation patterns of the inner tips of single 3D surface flaw were illustrated in this paper. It is observed that the large intermediate principal stress can restrict the crack wrapping and even make the internal flaw propagation patterns same with that on the specimen surface, providing insights into the validity of simplifying 3D flaws as 2D flaws for analyzing and computing crack propagation.

Aromatic micropollutants found in wastewater pose threats to human health, and it is necessary to remove them from wastewater. Cyclodextrin hydrogel is one of the most promising environmentally friendly materials for removing aromatic micropollutants from wastewater by means of adsorption. In this study, we have synthesized a cyclodextrin hydrogel designed to simultaneously adsorb a cationic dye (methylene blue, MB) and an endocrine-disrupting compound, EDC (bisphenol A, BPA) and provide insights into the design of adsorbents for multicomponent wastewater purification. Polymeric dextran-poly(acrylic acid)-β-cyclodextrin (Dex-PAA-CD) was prepared by the copolymerization of glycidyl methacrylate (GMA), methacrylate-substituted dextran (Dex-MA), acrylic acid, and vinyl-derivatized β-cyclodextrin (β-CD-MA). The adsorption of MB and BPA by the Dex-PAA-CD hydrogel presented short equilibrium time. The adsorption of MB and BPA was independent of each other, and their adsorption mechanisms were proved to be electronic interaction and cyclodextrin host-guest interaction, respectively. The maximum adsorption capacities of MB and BPA onto Dex-PAA-CD are determined to be 5.60 and 0.144 mmol/g by the Sips isotherm. The Dex-PAA-CD hydrogel retains a high adsorption capacity even after five adsorption/desorption cycles and demonstrates the feasibility of designing reusable adsorbents to remove multiple pollutants from wastewater.

A biocompatible Dex-MA/PAA hydrogel was prepared through copolymerization of glycidyl methacrylate substituted dextran (Dex-MA) with acrylic acid (AA), which was applied as the adsorbent to remove cationic dyes from aqueous solutions. Dex-MA/PAA hydrogel presented a fast adsorption rate and the removal efficiency of Methylene Blue (MB) and Crystal Violet (CV) reached 93.9% and 86.4%, respectively within one minute at an initial concentration of 50 mg L^-1. The adsorption equilibrium data fitted the Sips isotherm model well with high adsorption capacities of 1994 mg g^-1 for MB and 2390 mg g^-1 for CV. Besides, dye adsorption occurred efficiently over the pH range 3-10 and the temperature range 20-60 °C. Moreover, the removal efficiencies for MB and CV were still >95% even after five adsorption/desorption cycles which indicates the robust nature of the Dex-MA/PAA hydrogel and its potential as an eco-friendly adsorbent for water treatment.

Tungsten coatings were deposited on diamond particles by vacuum magnetron sputtering. The coated diamond particles were firstly heat treated at different temperatures, and diamond/copper (Cu) composites were fabricated by using a pressureless infiltration method afterwards. The influences of heat treatment on the microstructure and composition of tungsten based coating surface and diamond/copper composites were analysed. Notable differences were found in the microstructure with heating temperatures. Moreover, the tungsten based coating surface contained large quantities of oxidised tungsten, and the phase composition of the coatings varied within the range of tungsten–W ₂ C–WC as the heat treatment temperature increased. The fracture surface morphologies in the copper matrix composites reinforced with diamond particles with coatings were identically characterised with the presence of ductile fracture of matrix accompanied by dissociation of diamond particles from the matrix. The thermal conductivity (TC) and gas tightness behaviours of the diamond/copper composites were also explored. A maximum TC of 768 W m ⁻¹ K ⁻¹ and a fine gas tightness of 2.5 × 10-10 Pa m ³ /s were obtained with reinforcement of tungsten-coated diamond particles treated at 800 °C. The value of the interface thermal resistance between copper and diamond particles was also estimated and specifically discussed.

Chitosan has been used to cross-link poly(acrylic acid) to give three pH-sensitive hydrogels designed to control the release of the drugs amoxicillin and meloxicam. The extent of cross-linking and solution pH was found to dominate the swelling behavior of these hydrogels as shown by scanning electron microscopy and swelling time dependencies. The rates of release of amoxicillin and meloxicam from the loaded hydrogels increased with increase in pH consistent with the extent of hydrogen bonding between hydrogel components and between the hydrogel and the drugs being important determinants of release rate. Both the Korsemeyer-Peppas and Weibull models fitted release data consistent with drug release occurred through a combination of drug diffusion and hydrogel relaxation processes. These hydrogels appear to provide an ideal basis for controlled drug delivery systems.