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Piezochromic materials refer to a class of matters that alter their photoluminescence (PL) colors in response to the external stimuli, which exhibit promising smart applications in anti‐counterfeiting, optoelectronic memory and pressure‐sensing. However, so far, most reported piezochromic materials have been confined to organic materials or hybrid materials containing organic moieties with limited piezochromic range of less than 100 nm in visible region. Here, we achieved an intriguing piezochromism in all‐inorganic zero‐dimensional (0D) Cs3Cu2Cl5 nanocrystals (NCs) with a considerable piezochromic range of 232 nm because of their unique inorganic rigid structure. The PL energy shifted from the lowest‐energy red fluorescence (1.85 eV) to the highest‐energy blue fluorescence (2.83 eV), covering almost the entire visible wavelength range. Pressure‐modulated self‐trapped exciton emission between different energy levels of self‐trapped states within Cs3Cu2Cl5 NCs was the main reason for this piezochromism property. Note that the quenched emission, which is over five times more intense than that in the initial state, is retained under ambient conditions upon decompression. This work provides a promising pressure indicating material, particularly used in pressure stability monitoring for equipment working at extreme environments. [ABSTRACT FROM AUTHOR]

Piezochromic materials refer to a class of matters that alter their photoluminescence (PL) colors in response to the external stimuli, which exhibit promising smart applications in anti‐counterfeiting, optoelectronic memory and pressure‐sensing. However, so far, most reported piezochromic materials have been confined to organic materials or hybrid materials containing organic moieties with limited piezochromic range of less than 100 nm in visible region. Here, we achieved an intriguing piezochromism in all‐inorganic zero‐dimensional (0D) Cs3Cu2Cl5 nanocrystals (NCs) with a considerable piezochromic range of 232 nm because of their unique inorganic rigid structure. The PL energy shifted from the lowest‐energy red fluorescence (1.85 eV) to the highest‐energy blue fluorescence (2.83 eV), covering almost the entire visible wavelength range. Pressure‐modulated self‐trapped exciton emission between different energy levels of self‐trapped states within Cs3Cu2Cl5 NCs was the main reason for this piezochromism property. Note that the quenched emission, which is over five times more intense than that in the initial state, is retained under ambient conditions upon decompression. This work provides a promising pressure indicating material, particularly used in pressure stability monitoring for equipment working at extreme environments. [ABSTRACT FROM AUTHOR]

The engineering activities of deep stratigraphic resources development and space utilization are often subjected to complex stress conditions. In terms of gas-bearing coal resource mining, the dynamic mechanical properties of coal at complex loaded stress and gas environment were researched in this paper. Through the split Hopkinson pressure bar (SHPB), the dynamics experiments were performed, in which the factors of axial static load, circumferential confining pressure, internal gas pressure, and outside impact load were considered. Based on the stress and strain results of gas-bearing coal, the dynamic compressive strength and peak failure strain characteristics with strain rates were obtained. Under different loaded conditions, both dynamic compressive strength and peak failure strain added linearly along with strain rates increasing. In fact, high strain rates were the results of comprehensive loading conditions, so the effects of them to coal mechanical properties were discussed. And the improved dynamic material model of gas-bearing coal at high strain rates was proposed, which considered pre-damage of static load, hardening effects of strain rate, and weakening role of gas. Through using this model in numerical simulation, the plastic deformation and stress distribution of coal specimens subjected to impact failure were researched, which verified the results of dynamics experiments. Dynamics achievements of gas-bearing coal at complex loaded environment will provide guides for disaster prevention and promote green mining. [ABSTRACT FROM AUTHOR]

The pore structure of coal plays a key role in controlling the storage and migration of CH4/N2. The pore structure of coal is an important indicator to measure the gas extraction capability and the gas displacement effect of N2 injection. The deformation characteristic of coal during adsorption–desorption of CH4/N2 is an important factor affecting CH4 pumpability and N2 injectability. The pore structure characteristics of low-permeability coal were obtained by fluid intrusion method and photoelectric radiation technology. The multistage and connectivity of coal pores were analyzed. Subsequently, a simultaneous test experiment of CH4/N2 adsorption–desorption and coal deformation was carried out. The deformation characteristics of coal were clarified and a coal strain model was constructed. Finally, the applicability of low-permeability coal to N2 injection for CH4 displacement technology was investigated. The results show that the micropores and transition pores of coal samples are relatively developed. The pore morphology of coal is dominated by semi-open pores. The pore structure of coal is highly complex and heterogeneous. Transition pores, mesopores and macropores of coal have good connectivity, while micropores have poor connectivity. Under constant triaxial stress, the adsorption capacity of the coal for CH4 is greater than that for N2, and the deformation capacity of the coal for CH4 adsorption is greater than that for N2 adsorption. The axial strain, circumferential strain, and volumetric strain during the entire process of CH4 and N2 adsorption/desorption in the coal can be divided into three stages. Coal adsorption–desorption deformation has the characteristics of anisotropy and gas-difference. A strain model for the adsorption–desorption of CH4/N2 from coal was established by considering the expansion stress of adsorbed gas on the coal matrix, the compression stress of free gas on the coal matrix, and the expansion stress of free gas on micropore fractures. N2 has good injectability in low-permeability coal seams and has the dual functions of improving coal seam permeability and enhancing gas flow, which can significantly improve the effectiveness of low-permeability coal seam gas control and promote the efficient utilization of gas resources. Highlights: The pore structure characteristics of low-permeability coal were obtained by fluid intrusion method and photoelectric radiation technology. The multistage and connectivity of coal pores were analyzed. A simultaneous test experiment of CH4/N2 adsorption–desorption and coal deformation was carried out. The deformation characteristics of coal were clarified and a coal strain model was constructed. The applicability of low-permeability coal to N2 injection for CH4 displacement technology was investigated. [ABSTRACT FROM AUTHOR]

Overburden strata fracture evolution is critical to dynamic disaster prevention and gas-relief drainage, so it is important to accurately determine the evolution relationships with mining disturbance. In this paper, experiments and numerical simulation were adopted jointly to characterize the time-varying fracture area of overlying strata. The experimental results showed that the roof strata gradually broke and collapsed with coal mining, which indicated the fractures of overburden strata developed in an upward direction. The fracture development causes were explained by numerical simulation, which showed that stress increase exceeded the strength of coal and rock strata, and fractures were formed and expanded. Both experiments and numerical simulation results showed the two sides and the top of fracture areas provided channels and spaces for gas migration and reservoir, respectively. In addition, the breaking angle of overburden strata and the height of fracture areas were analyzed quantitatively. Through microseismic monitoring at the mining site, the fracture scales and ranges of overburden strata were verified by the energy and frequency of microseismic events, which were consistent with the support of maximum resistance. The position of drainage boreholes was considered based on the results of overburden strata fracture evolution. Our study is aimed at promoting coal mining in safety and improving gas drainage with a sustainable approach. [ABSTRACT FROM AUTHOR]

A research article published in Angewandte Chemie International Edition by Guanjun Xiao et al. discusses the discovery of an all-inorganic zero-dimensional metal-halide perovskite with a significant piezochromic range of 232 nm. The article describes the use of a diamond anvil cell to observe pressure-induced piezochromic behavior in Cs3Cu2Cl5 nanocrystals. The nanocrystals exhibited a shift in emission energy from red fluorescence to blue fluorescence, covering the entire visible wavelength range. This discovery has potential applications in visual pressure monitoring and sensing. [Extracted from the article]

A recent research article published in Angewandte Chemie by Guanjun Xiao et al. discusses the discovery of an all-inorganic zero-dimensional metal-halide perovskite with a significant piezochromic range. The researchers used a diamond anvil cell to observe the pressure-induced piezochromic behavior in Cs3Cu2Cl5 nanocrystals. The nanocrystals exhibited a shift in emission energy from red fluorescence to blue fluorescence, covering the entire visible wavelength range. This discovery has potential applications in visual pressure monitoring and sensing. [Extracted from the article]

Warm WLED with high color rendering index (CRI) are greatly required for the widespread use of solid-state lighting especially indoors. Here, a remarkable improvement of CRI in alloyed CdS0.7Se0.3 QDs was achieved by pressure engineering. Notably, white light with enhanced CRI of 93, higher than pristine CRI of 47, was retained upon the complete release of pressure, accompanied by a color change from 'natural' (4298 K) to 'warm' white light (2170 K). Synchrotron ADXRD shows that CdS0.7Se0.3 QDs experienced an irreversible phase transition from the zinc blende phase to rocksalt structure. Warm white light with enhanced color rendering index of 93 is achieved by pressure processing, accompanied by a color change from 'natural' (4298 K) to 'warm' white light (2170 K). [ABSTRACT FROM AUTHOR]