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The hydration kinetics of Portland cement with and without nano-SiO₂ (NS) were evaluated via isothermal calorimetry and investigated based on the mathematic method of the Krstulovic-Dabic model in this paper. NS was used to substitute Portland cement at 0, 1 and 3 wt.% by mass. The test results obtained in this study indicated that the hydration process of Portland cement was dramatically promoted in terms of increasing the heat released and the heat release rate when NS was added. From the Krstulovic-Dabic model, the dynamics process of Portland cement was controlled by nucleation and crystal growth (NG), phase boundary interactions (I) and the diffusion (D) process, it does not matter whether there was NS or not, but the transformation of the controlling process occurred at a lower hydration degree for the NS-added pastes. Moreover, the increase in NS content increased the values of the kinetics parameters KNG and KI, but decreased KD and the reaction exponent to a different degree.

The present research investigated the influence of steel slag (SS) with variable particle size on the workability and mechanical properties of concrete. Different SS size ranges (0-15 μm, 15-30 μm, 30-45 μm and 45-80 μm) were obtained by sieving and then were characterised by a laser particle size analyser and a scanning electron microscope (SEM). The slump, compressive strength, pore structures and thermal analysis were used to evaluate the effect of the SS particle size on cement and concrete properties. The experimental results showed that finer SS (0-15 μm and 15-30 μm) resulted in negative effects on the workability, while 30-45 μm and 45-80 μm SS particles presented completely opposite results. Both of these effects were more apparent as the steel slag replacement ratio was increased up to 30 wt.%. Concrete samples with 0-15 μm and 45-80 μm SS particles presented comparable 7- and 28-day compressive strength to the control concrete when their replacement ratios were less than 10 wt.%. Moreover, the concrete samples with 45-80 μm SS particles at 5% dosage developed the highest compressive strengths at 7 and 28 days, which were 2% and 5% higher than the control sample, respectively. The pore structure results indicated that a composition of 5% 45-80 μm SS particles was advantageous for refining the pore structures of cement paste, further contributing to the 28-day compressive strength development of concrete.

Homologous recombination, a central concept in biology, is defined as the exchange of DNA strands between two similar or identical nucleotide sequences. Unfortunately, undergraduate students majoring in biotechnology often experience difficulties in understanding the molecular basis of homologous recombination. In this study, we developed and implemented a 12-week laboratory course for biotechnology undergraduates in which gene targeting in "Streptococcus suis" was used to facilitate their understanding of the basic concept and process of homologous recombination. Students worked in teams of two to select a gene of interest to create a knockout mutant using methods that relied on homologous recombination. By integrating abstract knowledge and practice in the process of scientific research, students gained hands-on experience in molecular biology techniques while learning about the principle and process of homologous recombination. The learning outcomes and survey-based assessment demonstrated that students substantially enhanced their understanding of how homologous recombination could be used to study gene function. Overall, the course was very effective for helping biotechnology undergraduates learn the theory and application of homologous recombination, while also yielding positive effects in developing confidence and scientific skills for future work in research.

Calcium sulfoaluminate (CSA) cement has some attractive qualities, such as rapid setting, high early strength, and micro-expansion. It was commonly used to improve properties of Portland cement (PC). In this paper, the investigated results show that the setting times are notably reduced as the CSA cement content is increased. The compressive strength is slightly lower for the PC-CSA blends containing less than 10% CSA cement, but notably lower for the PC-CSA blend containing 20% CSA cement when compared to PC. High amounts of CSA cement significantly delay the hydration of alite, thereby increasing the porosity. Furthermore, the addition of CSA cement changes the ettringite morphology.

The polyacrylic acid/tungsten oxide (PAA/WO3) composite films with good electrochromic properties have been prepared by a layer-by-layer method. The porous PAA layers were used as a template for the deposition of WO3, and finally, the composite film showed a network structure with high porosity. The electrochromic performance of the PAA/WO3 composite film was investigated by means of cyclic voltammogram (CV), chronoamperometry (CA), and transmittance measurements. The PAA/WO3 film also exhibited a remarkable electrochromism ability with the reversible color change from transparent colorless to dark blue and the transmittance change from 83% to 24% at 620 nm. This research provided a cost-effective approach for the preparation of PAA/WO3 composite films with controllable microstructure and good electrochromic property.

Hard carbon (HC) has attracted considerable research interest as the most promising anode for potassium‐ion batteries (PIBs) due to its tunable interlayer spacing and abundant voids to accommodate K+. However, the practical application of hard carbon is severely hampered by low initial Coulombic efficiency (ICE) and high plateau potential. Herein, a manganese ion‐catalyzed pyrolysis strategy is explored to regulate the graphitic microcrystalline structure and localized electron distribution in hard carbon that greatly improve K+ plateau storage and ICE. Systematic experimental measurements, in situ/ex situ observations, dynamic analysis, and density functional theory calculations elucidate that the introduction of Mn2+ ions could catalyze the formation of short‐ordered graphitic nanodomains in hard carbon to provide abundant insertions of K+, and meanwhile induce localized electron distribution through the Mn─N3─C coordination structure to enable dynamic K+ diffusion and electron transfer kinetics. Consequently, the modulated hard carbon exhibits a high low‐potential–plateau capacity, excellent rate capability, and high initial Coulombic efficiency in potassium half‐cell configurations. More importantly, the charge storage mechanism of "adsorption–intercalation" is proposed based on the correlation between carbon structures and discharge/charge plateau. This work provides an in‐depth insight into the fundamentals of microstructure regulation of hard carbon anode for high‐performance PIBs. [ABSTRACT FROM AUTHOR]

Nanoporous composites have been extensively applied in aerospace applications for their outstanding thermal insulation and ablation resistance. A ceramizable polysilazane (PSZ)‐modified phenolic resin (PSZ‐PR)/carbon fiber fabric (PSZ‐PR/CF) aerogel composite was synthesized through ambient pressure drying (APD). The homogeneous nanopore structure and improved thermal stability of the PSZ‐PR aerogel matrix provided the composites with good performance (thermal conductivity as low as 0.126 W/(m·K)). The PSZ‐PR/CF composites achieved high compressive strength (up to 43.75 MPa), tensile strength (59.22–124.75 MPa), and bending strength (23.35–97.94 MPa). Furthermore, the generation of ceramization products during the oxyacetylene flame ablation process, specifically SiC and Si3N4, enhanced the ablation resistance of PSZ‐PR/CF composites: the linear ablation rates are as low as 0.112 and 0.018 mm/s at 4.18 MW/m2 (20 s) and 1.20 MW/m2 (120 s) of oxyacetylene heat flow, respectively. The corresponding maximum back temperatures are only 51.0°C and 60.3°C. Notably, the carbon/ceramic network is still present in the ablation layer to protect the carbon fibers from oxidation. This ceramizable PSZ‐PR/CF composite has good potential for application in the field of thermal protection. Highlights: PSZ improves thermal stability and ablation properties of PSZ‐PR/CF.The PSZ‐PR/CF composites exhibit excellent mechanical and ablation properties.The ceramic products improve the scouring resistance of aerogel matrixes.The ceramizable PSZ‐PR/CF was prepared by low‐cost ambient pressure drying. [ABSTRACT FROM AUTHOR]