摘要：
In this study, we employed classic electrochemical techniques including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to perform electrochemical characterization on atomic-level single-crystal TiO2 electrodes and extract capacitive and resistive properties of single-crystal TiO2 electrode/solution interface in KCl and KCl/K3PO4 at various pH levels. The lattice structure and crystal appearance were characterized using X-ray diffractometry (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy to facilitate the in-depth exploration of heterogeneous reaction dynamics and theory. Furthermore, this study aimed to verify and improve the theory and application of capacitance at the single-crystal TiO2 electrode/solution interface. The electrochemical measurements indicate that, in the same pH, the presence of PO43- significantly increases the total capacitance (C-T), outer capacitance (C-O), electrical double-layer capacitance (C-dl), and diffusion layer capacitance (C-diff) at single-crystal TiO2 electrode/solution interface. This enhancement is attributed to the direct interaction between PO43- and the single-crystal TiO2 electrode surface, leading to the specific adsorption of PO43- on the electrode surface, revealing higher current and stronger electrochemical activity in the interaction between TiO2 and PO43-. Additionally, our XPS results indicate the adsorption of PO43- on the single-crystal TiO2 electrode surface. The interaction of PO43- with the TiO2 surface demonstrates increased hydrophilicity and enhanced adsorption capacity through mechanisms such as ligand exchange or cation bridging, thereby augmenting the C-dl at the single-crystal TiO2 electrode/solution interface.
摘要：
Thermal-mechanical damage is an important problem threatening the safety of deep rock engineering. In this paper, the effects of coupling damage on the deformation and failure characteristics of rock mass were studied via cyclic loading damage, thermal damage and uniaxial compression acoustic emission (AE) tests, and the microscopic fracture process of the damaged rock mass was numerically simulated. Results showed that during heat treatment, the colour of the sample changed significantly, the mass, the P-wave velocity and the number of mineral species decreased. The peak strength and elastic modulus reach their maximum values at 600 degrees C and 300 degrees C, respectively, exhibiting a trend of initial increase and subsequent decrease. The rapid growth period of AE activity increased noticeably with increasing temperature, and the effect of energy accumulation became more significant at higher peak strengths. The failure mode was influenced primarily by the cyclic loading amplitude. In addition, an increase in the stress or temperature after crack initiation leads to a sharp increase in the damage within the rock. Temperature had a more significant effect on the generation of damage than stress. Stress-induced microcracks were concentrated in the weakly bonded particles, whilst temperature-induced microcracks were concentrated in the strongly bonded particles. Temperature had a significant effect on the mineral composition of rock mass.The rapid growth period of AE activity was prolonged with the temperature increase.The failure mode of rock mass was mainly influenced by cyclic loading amplitude.Temperature-induced microcracks were concentrated in strongly bonded particles.
摘要：
The reduction of soluble U(VI) to insoluble and less toxic U(IV) by photocatalysis is an effective method to control uranium contamination. The graphitic carbon nitride nanosheet (CNN)/UiO-66 composites (CNNU) were prepared by thermal polymerization and solvothermal methods for the removal of U(VI). The morphology, crystal structure and optical properties of composites were analyzed by SEM, XRD, BET, UV-DRS, PL and EIS. The results showed the introduction of UiO-66 increased the specific surface of CNN from 9.07 m(2)/g to 46.24 m(2)/g, and effectively suppressed the recombination of photogenerated electrons and holes and improved the photocatalytic activity. The U(VI) removal capacity by adsorption and photocatalysis of CNNU was reached 779.47mg/g, which significantly higher than that of adsorption (478.38mg/g). The adsorption process was found to conform to the pseudo-second-order kinetic model and the Langmuir isothermal model. Meanwhile, U(VI) adsorbed on the CNNU was reduced to U(IV) via e(-) and ·O(2)(-) generated in the photocatalytic process. Therefore, this outstanding performance of CNNU in U(VI) removal is attributed to the synergistic effect of adsorption and photocatalytic reduction.
期刊：
Measurement Science And Technology,2023年34(6) ISSN：0957-0233
作者机构：
[Xie, Shuibo; Liao, Yanguo] Univ South China, Sch Resource Environm & Safety Engn, Hengyang 421001, Peoples R China.;[Liao, Yanguo] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.;[Xie, Shuibo] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.
关键词：
transversely isotropic materials;cylindrical indentation;elastic parameters;dimensional analysis;finite element (FE);three-dimensional (3D)
摘要：
Based on the cylindrical indention experiments, a novel model has been established to characterize the elastic mechanical property of transversely isotropic materials. In the first place, the influences of different loading orientations for indentation, and elastic parameters of materials on the indentation modulus of transversely isotropic materials are analyzed by means of theoretical and dimensional analysis. In the second place, three dimensional (3D) indentation experiments that encompass the wide range of transversely isotropic material parameters are simulated by finite element (FE) approach. Each quantity (transversely isotropic Young's modulus, EP, longitudinal Young's modulus, EL, longitudinal shear modulus, GL, and loading orientation angle, ) how affects the normalized indentation modulus is investigated. Then, the dimensionless analytical relationship between indentation modulus and elastic parameters is put up at three different indentation orientation angles . To prove the correctness of the proposed model, several groups of transversely isotropic materials are selected as input parameters to carry out indentation numerical experiments and the error analysis is made in detail. Simultaneously, the technique is specialized to the particular case of a Zinc single crystal material to verify the accuracy of these formulas derived. These good agreements show that the proposed method is reliable and it could be used to quantify the elastic parameters of the transversely isotropic materials.
摘要：
The thermal effect of electrokinetic remediation (EKR) is a kind of energy dissipation, which is an important part of the useless work in the process of EKR. Therefore, this study aims to reveal the phenomenon and mechanism of thermal effect and the energy distribution mechanism in the process of EKR. To explore the distribution mechanism of soil temperature during the EKR process, nine groups of orthogonal EKR experiments lasting 120 h were carried out. The experimental results show that the phenomenon of thermal effect is common in the process of electric remediation of uranium pollution, and it is positively correlated with the current of the system. At the same time, soil pH, moisture, and conductivity are all related to soil temperature. According to the range analysis, the voltage gradient has the greatest impact on the current utilization rate. Under the conditions of 0.5 V/cm and 0.5 mol/L citric acid (CA), the maximum removal efficiency of U(VI) in the soil is 36.58%, and the maximum current utilization rate eta is 3.85%. In general, the study of the general law of thermal effect in the process of EKR will provide theoretical support for weakening the effect of thermal effect, avoiding wasting more energy, improving the utilization efficiency of energy, and transforming the EKR process. Therefore, this study has a positive significance for the law of thermal effect in the process of EK and the engineering application of EKR technology. Highlights center dot Current utilization efficiency and energy distribution mechanisms were discovered during the EKR process. center dot The distribution mechanism of temperature in soil cell was revealed in the EKR process. center dot Optimizing experimental combination, providing a theoretical basis for engineering practical application.
作者机构：
[Fan, Junwei; Sun, Bing; Yang, Haowei] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Liu, Xiling] Cent South Univ, Sch Resources & Safety Engn, Changsha 410083, Peoples R China.;[Zeng, Sheng] Univ South China, Sch Resources Environm & Safety Engn, Hengyang 421001, Peoples R China.
通讯机构：
[Sheng Zeng] S;School of Resources Environment and Safety Engineering, University of South China, Hengyang 421001, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
rock mechanics;cyclic loading and unloading;acoustic emission;energy evolution;damage characteristic;ultimate damage energy
摘要：
In order to study the deformation and failure characteristics of rocks under different cyclic loading and unloading paths, three stress path tests were conducted, and acoustic emission (AE) monitoring was conducted simultaneously. The mechanical characteristics and AE characteristics under different stress paths were analyzed, and the influences of the different stress paths on the energy dissipation and deformation damage were investigated. The law of energy evolution considering viscoelasticity under different stress paths was obtained. The concept of ultimate damage energy and its calculation method was proposed. The results show that the “hardening effect” of sandstone and granite under the constant lower limit (CLLCL) is the most significant in maximizing the mechanical property. The CLLCL imparts a stronger elastic property to rocks than the variable lower limit (VLLCL) does, while the VLLCL causes more damage to rocks than the CLLCL. A significant linear relationship between the proportion of damage energy and the proportion of elastic energy was discovered. Based on this linear relationship, the ultimate damage energy can be calculated for sandstone and granite. The evolution of the damage variable based on damage energy was compatible with the real damage condition, which validates the ultimate damage energy calculation method. The research results lay a theoretical foundation for the design and construction of geotechnical engineering.
