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The calcination process and the ratio of to calcium to silicon in raw materials are the key factors affecting the mineral composition and properties of natural water hard lime(NHL). This study prepared NHL was by different calcination processes using argillaceous limestone tailings with different chemical compositions as raw materials. This paper studied the mineral composition and compressive strength of the prepared NHL by a combination of orthogonal and single-factor tests, and analyzed the effect of calcination process and calcium-silica ratio on its performance. Results showed that: ① With the increase of calcination temperature, the content of CaO in NHL decreased, and the content of dicalcium silicate(Ca2SiO4, C2S)increased in NHL. ② Calcination temperature had the most significant effect on the mineral composition and compressive strength of NHL, followed by holding time and heating rate. ③ In the calcination temperature range of 1 000~1 100 ℃, the natural hydrostatic lime prepared by the given argillaceous limestone tailings meets the requirements of NHL2 and NHL3.5 strength grades. ④ When the calcium-silicon ratio is in the range of 3.55~6.76, the compressive strength of NHL decreases and then increases with the increase of calcium-silicon ratio, while the CaO content shows continuous increases.

An Al-based energetic micro-unit Al@PFPE@AP fuel powder with the oxidant AP coated on the surface of fluoride-modified Al powder was designed and prepared by the component composite technique to address the two major problems of incomplete combustion and component polarization of Al powder in solid propellants. The morphology, particle size, combustion properties and combustion products of the micro-unit powder were analyzed by scanning electron microscopy, laser particle size measurement, oxygen bomb calorimetry, inductively coupled plasma emission spectrometry and X-ray diffraction. The results show that the energetic microunits Al@PFPE@AP present a more obvious core-shell structure with uniform particle size, and when the addition amount of PFPE is 5%, the combustion heat value of Al@5%PFPE@AP is increased by 63.86%, the particle size of combustion products is decreased by 61.83%, and the active aluminum content of combustion products is decreased by more than 57% compared with the mechanically mixed AP+Al samples. Combustion mechanism analysis shows that PFPE can occur with Al powder pre-ignition reaction, increase the reaction activity of Al powder, and the surface of Al powder has a catalytic effect on the decomposition of AP, which reduces AP high temperature decomposition temperature and low temperature decomposition temperature were reduced by 12 ℃ and 10 ℃ respectively. The micro-unit structure has a significant contribution to the improvement of the combustion performance of the system and can substantially increase the energy performance of the important propellant components during combustion.

Livestock dung, discarded crop straws, and residual plastic film are the primary agricultural non-point sources of pollution. For livestock dung and discarded crop straw, the general treatment focuses on compost, animal fodder, industrial raw material, and new energy. The development of degradable mulch film is the main way to solve pollution from residual plastic film. However, an effective way to solve the above three types of pollution simultaneously and use them for ecological circular agriculture has been less studied. In this study, using cow dung and flax straw wastes as raw materials, we prepared natural, fibre-based paper mulch using the rapid-Kothen method and analysed the film-forming mechanism. Based on the Van Soest method, the cow dung and flax straw waste contain abundant cellulose fibres: 36.75% and 54.69%, respectively. The tensile strength and tear strength of fibre paper mulch are 1.87 kN/m and 19.91 N/mm, respectively. To enhance the adaptability of the fibre paper mulch in humid environments, the surface of the mulch was treated with alkyl ketene dimer (AKD). The AKD-coated fibre paper mulch displays hydrophobic properties, indicated by a contact angle of 128° ± 2°. It has a wet tensile strength of 0.64 kN/m and a wet tear strength of 8.23 N/mm. Additionally, it exhibits a dry tensile strength and a tear strength of 2.13 kN/m and 16.43 N/mm, respectively. Notably, the dry tensile strength is increased by 16.31%. In this way, the livestock dung and discarded crop straw can be reused, reducing dung pollution and straw burning in livestock farms, and the final products can alleviate the residual film pollution simultaneously. [ABSTRACT FROM AUTHOR]

Sodium sulfate (SS) is a neutral activator. SS-activated alkali-activated slag cement (AASC) has lower shrinkage. However, it sets slowly, and the mechanical property develops slowly. Slaked lime (SL) is an alkaline substance widely used in industry that can be used as an activator in AASC. In this paper, SL was used alone, and SL and SS were mixed together to prepare AASC. The effects of SL content on the setting time, shrinkage properties and mechanical strength of AASC were investigated. Furthermore, the mechanism was explored with the analysis of microscopic tests. The results showed that SS could not be used as an activator alone, while SL could be used as an activator alone, and SS could be combined with SL to prepare AASC. The setting time of the SL system or the SS-SL mix system decreased with the increase in SL. The mechanical properties of the SL system were poor. The SS-SL system showed the highest mechanical properties when SL was 3%. With the increase in SL, the autogenous and drying shrinkage of the SL system increased, while the former of the SS-SL system increased and the latter decreased. At the same time, due to the different changes in pore structure and mesoporous volume in the two systems, the drying shrinkage showed different changes. Compared with the SL system, ettringite (AFt) with a slight expansion property and more crystal phases were formed in the SS-SL system, which reduced the drying shrinkage. [ABSTRACT FROM AUTHOR]

Enhancing the photocatalytic stability of Cu2O in the degradation of tetracycline is a great challenge in combating environmental water pollution because it is prone to deactivation by photocorrosion in aqueous environment. In this study, Cu2O/cellulose microfiber aerogel is synthesized through freeze‐drying, utilizing the self‐curling effect of cellulose and then calcined to produce Cu2O/C composite aerogel. The derived Cu2O/C composite aerogel features hollow carbon microfibers anchored with Cu2O nanocubes. Due to the curling structure and conductivity of the carbon microfibers, the photodegradation efficiency of the obtained Cu2O/C composite aerogel for tetracycline is drastically improved to 97.3% under 120 min of visible‐light irradiation, and remains a cycling photodegradation rate of 84.3% after 10 cycles. The Cu2O/C composite aerogel shows remarkable strategies for designing and constructing Cu2O‐based photocatalyst in the practical photodegradation of tetracycline under visible‐light exposure. [ABSTRACT FROM AUTHOR]

To improve the utilization rate of flax straw and the clean treatment of livestock manure, an experimental study was conducted on the process and performance of making fibre paper films by mixing cow dung and flax straw fibre. Cow dung and flax straw were used as the main raw materials, and functional additives were not added. The whole technological process of the pretreatment, the beating process, the determination of the beating degree, the basis weight of the paper, papermaking, drying, sample cutting, and the determination and analysis of the related mechanical properties of the film-making materials were studied. In this study, the Box–Behnken experimental design principle in the response surface methodology was adopted, and the effect of each factor on the tensile strength and tear strength of fibre paper film made of mixed fibres was determined using the combined experimental design comprising four factors and three levels centres. The results showed that the optimum technological parameters were as follows: the beating degree of the cow dung fibre was 37 °SR, the beating degree of the flax straw fibre was 85 °SR, the paper basis weight was 80 g/m2, and the addition of flax straw fibre was 65%. At a drying temperature of 80 °C and a drying time of 8 min, under the conditions of the hybrid fibre paper film placed in the laboratory environment (humidity of 30%~40%, temperature of 18 °C) for 24 h, the measured tensile strength was about 8.26 MPa, and the tear strength was about 19.91 N/mm. This study provides a reference that can be used for the further study of fibre paper film. [ABSTRACT FROM AUTHOR]

Building resilient cities has become a hot topic in urban planning and risk management. Adopting the perspective of the social‐ecological system (SES), this paper incorporated economy–ecology–society–infrastructure into an integrated research framework and established a system for assessing the urban resilience development level. The entropy weight method was combined with a cloud model to systematically calculate and classify the resilience of 31 provinces (cities) in China. The evaluation results show that (1) the overall level of urban resilience in China was relatively low; the regional analysis showed that (2) the urban resilience of the eastern region was higher than the national average and that of the central and western regions, and from the perspective of the four subsystems, (3) the comprehensive development of each subsystem was the key to improving urban resilience. Finally, five improvement strategies were proposed to provide ideas for enhancing urban SES ability. [ABSTRACT FROM AUTHOR]