ABSTRACT
This paper investigates the effects of the reinforcement ratio, volume fraction of steel fibers, and prestressing on the uniaxial tensile behavior of carbon textile reinforced mortar (CTRM) through uniaxial tensile tests. The results show that the tensile strength of CTRM specimens increases with the reinforcement ratio, however the textileâ»matrix bond strength becomes weaker and debonding can occur. Short steel fibers are able to improve the mechanical properties of the entire CTRM composite and provide additional "shear resistant ability" to enhance the textileâ» matrix bond strength, resulting in finer cracks with smaller spacing and width. Investigations into the fracture surfaces using an optical microscope clarify these inferences. Increases in first-crack stress and tensile strength are also observed in prestressed TRM specimens. In this study, the combination of 1% steel fibers and prestressing at 15% of the ultimate tensile strength of two-layer textiles is found to be the optimum configuration, producing the highest first-crack stress and tensile strength and the most reasonable multi-cracking pattern.
ABSTRACT
Four-point bending tests were adopted to investigate the influences of the number of textile layers, volume content of steel fibres, and prestress on the flexural behaviour of carbon textile-reinforced concrete (TRC). The failure mode of the specimen changed from debonding failure to shear failure, accompanied by the matrix-textile interfacial debonding with an increasing number of textile layers. The interfacial bonding performance between the textile and matrix improved with the addition of steel fibres in the TRC specimens. The presence of prestress or steel fibres improved first-crack and ultimate stresses of the TRC specimen. In comparison with the first-crack stress, a more pronounced enhancement in the ultimate stress was achieved by the addition of steel fibres. However, the effect of prestress on the first-crack stress was found to be more significant than on the ultimate stress. The prestress combined with steel fibres further improved the flexural behaviour of the TRC specimens. The prestressed TRC specimens with 1% volume content of steel fibres effectively avoided debonding. Thus, the utilization of the textiles could be improved.
ABSTRACT
Nowadays, novel synthesis routes of nanoparticles are attracting a considerable attention of relative scientists. In this work, monodispersed spherical ZnS quantum dots (QDs) were synthesized by an oil-water interface method. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Typical TEM images showed that the average size of ZnS QDs was 3.3 nm. The ZnS QDs with the largest yield and UV absorbance were obtained with the mole ratio of [S2-]/[Zn2+] = 1.2/1.0 at 100 degrees C. Based on the above results and the previous outstanding work for synthesis of monodispersed inorganic nanoparticles, the formation mechanism of the monodispersed ZnS quantum dots was proposed. Additionally, UV-vis absorption and photoluminescence (PL) spectra for Mn2+ and Eu3+ doped ZnS QDs were used to investigate their optical properties. Effects of Mn2+ and Eu3+ doping ratio on their optical properties were studied. The optimized doping ratio of Mn2+ and Eu3+ was 4.0 mol.% and 5.0 mol.%, respectively.
