International Journal of Microstructure and Materials Properties (10 papers in press)

Regular Issues

• AC ageing performance of Ag+ doped high voltage gradient ZnO varistors  
  by Lei Wang, Jian Zhang, Zhongyuan Li, Lu Li, Wenbo Yu, Jingke Guo 
  Abstract: Zinc oxide (ZnO) varistor, exhibiting excellent nonlinear volt-ampere characteristics, has now been widely applied to overvoltage protection in electrical equipment. However, the greater severity of AC aging is a realistic issue facing the high-voltage gradient varistors used in ultra-high-voltage surge arresters. To some degree, silver (Ag) doping is effective in improving the performance of varistors. In spite of this, it remains necessary to explore its influence on the aging process of varistors. In this study, an investigation is conducted into the microstructure, macroscopic electrical properties, and barrier potential of varistors with different Ag doping concentrations, so as to determine the optimal level of doping concentration required for improving the long-term stability of varistors. Furthermore, the mechanism of Ag+ improving aging resistance is accounted for in theory. The research results indicate the best anti-aging performance is achieved at the doping concentration of 50 ppm.
  Keywords: varistors; doped; ac aging; C-V characteristic.
  
  

Special Issue on: The Development of Nanomaterials in Smart Construction Materials

• The influence of water cement ratio and sand ratio on the compressive strength of ceramic aggregate concrete at room temperature  
  by Yingjun Liang, Ju Yi 
  Abstract: This research explores the influence of water-cement and sand-aggregate ratios on ceramic aggregate concrete’s compressive strength at ambient temp. By fabricating nine specimens with distinct mix proportions, the study explored the influence of cement content varying from 16.6% to 17.5%. The specimens were subjected to compressive strength tests at 3, 7, and 28 days, and the interrelationships between the water-to-cement ratio, sand-to-aggregate ratio, and the 28-day compressive strength were scrutinised using grey relational analysis. The results indicate that the sand-to-aggregate ratio profoundly affects the 28-day compressive strength of ceramic aggregate concrete across various mix ratios, with a grey correlation degree of 0.7645, underscoring its significance as a pivotal parameter. The water-to-cement ratio also played a role in the experiment, albeit with a lower grey correlation degree of 0.5811, suggesting that it should not be overlooked.
  Keywords: water-cement ratio; sand ratio; ceramisite concrete; compressive strength at room temperature.
  
  
• Compressive strength testing of epoxy coated reinforced concrete based on ultrasonic SH wave  
  by Yu Zhang, Huanan Liang, Lei Jian 
  Abstract: In order to overcome the problems of low signal strength and significant difference between the measured and actual compressive strength values in traditional epoxy coated reinforced concrete testing methods, a new compressive strength testing of epoxy coated reinforced concrete based on ultrasonic SH wave is proposed. Firstly, prepare epoxy coated reinforced concrete specimens. Secondly, ultrasonic signals are emitted to the epoxy coated reinforced concrete specimens, and the concrete data signals are captured using ultrasonic SH wave. Finally, the least squares method is used to fit the concrete data, and the compressive strength value of epoxy coated reinforced concrete is calculated based on the data fitting results to obtain relevant testing results. The experimental results show that the maximum signal strength under the application of the proposed method is 58.7W/m2, and the compressive strength testing value of epoxy coated reinforced concrete is basically consistent with the actual value.
  Keywords: ultrasonic SH wave; epoxy coated; reinforced concrete; compressive strength testing; least squares method.
  
  
• Reinforcement treatment and freeze-thaw resistance performance analysis of concrete materials  
  by Long Ke 
  Abstract: In order to improve the stability and freeze-thaw resistance of concrete structures, this study designed a reinforcement treatment method using carbon fibre composite materials. After preparing concrete specimens, carbon fibre composite materials are prepared using adhesive fibres and epoxy resin as the main materials, and they are pasted on the surface of the specimens. After compression and curing, reinforcement treatment is completed. After applying this method, the maximum axial compressive strength of concrete specimens can reach 115.6 MPa, and the maximum uniaxial tensile strength can reach 96.1 MPa, indicating that the mechanical properties of the specimens reinforced with this method are better. After freeze-thaw cycles, it was found that the mass loss rate of the specimens did not exceed 0.5%, the relative dynamic modulus of elasticity remained above 6,800 MPa, the flexural strength remained above 34 MPa. Moreover, the use of full wrapping can improve the freeze-thaw resistance of the specimens.
  Keywords: concrete specimens; carbon fibre composite materials; epoxy resin; viscose fibre; reinforcement treatment; freeze-thaw resistance.
  
  
• Research on seismic performance of fiber reinforced high-strength concrete steel beam assembly joints  
  by Xiang Gao 
  Abstract: In order to calculate the bearing capacity of steel beam assembly joints and improve the stiffness of assembly joints, this paper studies the seismic performance of fibre-reinforced high-strength concrete steel beam assembly joints. Firstly, design fibre reinforced high-strength concrete steel beam assembly node specimens; then, construct a constitutive model of concrete steel beams and determine the equilibrium conditions of the upper half of the nodes; finally, the bending moments on both sides of the node area are obtained through beam end sensors, and the shear bearing capacity of the assembly node is calculated to achieve seismic performance research of the node. The results show that under the method proposed in this paper, the degradation of node strength is relatively small, stable between 0.97 and 1.10, and the bearing capacity can reach 905.22 kN, indicating that the method proposed in this paper can effectively improve the seismic performance of nodes.
  Keywords: assembly nodes; seismic performance; beam end sensor; applied bending moment; node bearing capacity.
  
  
• Prediction of compressive strength of nano concrete used in construction under freeze-thaw cycles  
  by Xiaoyuan Xiong, Xuyang Li 
  Abstract: In order to clarify the compressive strength performance of nano concrete under harsh conditions of freeze-thaw cycles, a study was conducted on the prediction of compressive strength of nano concrete for construction under freeze-thaw cycles. Firstly, analyze the preparation raw materials and properties of nano concrete, and prepare nano concrete specimens according to the preparation process of nano concrete. Secondly, set the conditions for freeze-thaw cycles and select the pressure machine for the experiment. Finally, taking the dosage of nano SiO2 as input and the predicted compressive strength as output, a BP neural network was used to construct a nano concrete compressive strength prediction model, and the predicted compressive strength results were obtained. The research results indicate that the relative error in predicting the compressive strength of nano concrete proposed in this article is relatively small, with a maximum relative error not exceeding 8%.
  Keywords: freeze-thaw cycle; building nano concrete; prediction of compressive strength; BP neural network.
  
  
• Preparation of modified silica superhydrophobic coating for exterior wall decoration and its stain resistance  
  by Lili Chen 
  Abstract: In order to optimise the application of modified silica superhydrophobic coating for building exterior wall decoration, the research on the preparation of modified silica superhydrophobic coating and its pollution resistance was carried out. First select material to prepare modified nano SiO2 particles, and then use the modified nano SiO2 particles, PVDF and DMF components with excellent superhydrophobic properties of modified silica coating preparation, finally explore the influence of different SiO2 particles on the performance of coating and coating on different substrate film drying time and stain resistance. The test results show that when the SiO2 particle addition amount is 80 wt% and the matrix is horse mouth iron, the superhydrophobic performance, wear resistance and stain resistance of the coating reach the best.
  Keywords: building exterior wall decoration; modified silica; super hydrophobic coating; stain resistance.
  
  
• Influence of nano silicon powder content on the corrosion resistance of reinforced concrete  
  by Tingting Wu, Xiaochao Su 
  Abstract: This study aims to investigate the effect of different dosages of nano silica powder on the corrosion resistance of reinforced concrete. Through electrochemical corrosion treatment experiments, the corrosion rate of steel bars, Tafel polarisation curve, electrochemical impedance and other parameters were measured, and the microstructure was analysed. The experimental results show that the dosage of nano silicon powder has a significant impact on the corrosion resistance of reinforced concrete. When the dosage is 2%, the corrosion resistance of reinforced concrete is significantly improved, the corrosion rate is significantly reduced, the Tafel polarisation curve shows good stability, and the electrochemical impedance is significantly increased. However, when the dosage increases to 4%, the corrosion resistance shows a downward trend, and the corrosion rate and negative displacement value both increase. Microscopic analysis shows that the appropriate addition of nano silicon powder can reduce the formation of corrosion products and cracks.
  Keywords: nano silicon powder; reinforced concrete; corrosion resistance performance; corrosion rate.
  
  
• Research on the application of nano modified epoxy resin adhesive in the repair of cracks in building concrete  
  by Yungen Zhang, Long Ke 
  Abstract: In order to optimise the performance of repair materials and improve the mechanical properties of cracked concrete structures, this paper studies the application effect of nano modified epoxy resin adhesive materials in the repair of cracks in building concrete after preparing them. Three sets of samples were prepared by modifying epoxy resin adhesives with nano Al2O3 , nano CaCO3 , and nano SiO2 materials. It was found that the adhesive modified with 2% nano Al2O3 material performed better. Finally, after testing and repairing cracked concrete specimens, it was found that the maximum compressive strength of cracked concrete specimens can still reach 193.47 N/mm2 after being repaired with nano modified epoxy resin adhesive. After multiple freeze-thaw cycles, the flexural strength of the specimens is still close to 80 MPa, indicating that nano modified epoxy resin adhesive has a good crack repair effect.
  Keywords: nano materials; modified epoxy resin adhesive; building concrete specimens; concrete cracks; crack repair.
  
  
• Study on mechanical property decrease of locally corroded reinforcement in concrete  
  by XiaoDong Li 
  Abstract: In order to explore the influence of reinforcement corrosion on the performance of concrete structure, this study was carried out on the decrease of mechanical properties of locally corroded reinforcement in concrete. This time, firstly, the theoretical analysis of the stress-strain performance and strength of steel bars caused by corrosion is carried out, and then the finite element model of locally corroded reinforced concrete specimens is built based on ANSYS software. Finally, based on the model of components, the finite element analysis of reinforced concrete specimens under different degrees of corrosion is carried out. The results show that the greater the corrosion rate of steel bar, the greater the relative slip between concrete and steel bar interface, the smaller the cross-sectional area of steel bar, the reduced the yield strength and ultimate strength of steel bar in the specimen, and the weaker the bearing capacity.
  Keywords: concrete; corroded reinforcement; mechanical properties; decrease characteristics.