دانلود رایگان مقاله سنتز، شناسایی و عملکرد نانوکامپوزیت سیمانی پیزو رسیستیو

Abstract

Smart material reinforced non-destructive structural health monitoring technique has been evolving as the most predominated route for assessing the performance of the civil structures. In the present study, multiwalled nanotubes (MWNT) were suitably incorporated into the cement matrix, which act as actively embedded sensor for monitoring real-time flaws in structures. Initially, the stable homogenous MWNT dispersion was prepared by using ionic surfactant technique with high-intensity ultrasonic agitation process. Since, a suitable and adequate synthesis procedure to incorporate MWNT in cement matrix is essential, but complicated, the role of amplitude and frequency of sonication on dispersion of nanotubes was categorically evaluated. Further, this paper focuses to find out the effect of surfactant on MWNT dispersion by using the UV Visible spectroscopy and by evaluating the effective hydro-dynamic diameter. Based on micromechanics based analytical model, the influence of the interface layer thickness and geometrical configuration of nanotubes on the electrical conductivity of cement nano-composite are also analyzed. Further, the electrical conductivity of MWNT incorporated cement system, as developed in the present study, is measured using four probe method. Piezo-resistivity of the oven dried samples is measured to evaluate the change in potential drop under cyclic loading regime. It is found that the efficiency of the piezo-resistive strain sensors greatly depends on synthesis process and the circuit system. Appropriately proportioned and properly synthesized MWNTs incorporated in cement matrix were capable of providing consistent and steady response under the variable external stress. Thus, the material can be used as embedded sensor for health monitoring and identifying initiation of any damage in reinforced concrete structure.

7. Concluding remarks

The role of ultrasonic energy and time with varying surfactant concentration on MWNTs dispersion, and piezo-resistivity of MWMTs incorporated cementitious nano-composite was studied here. It is found that the issues like process of synthesis, influence of various sonication parameters, role of ionic surfactant concentration, which are crucial to develop a composite sensor, are not adequately discussed in reported studies. In the present study, UV visible spectral description clearly depicts that longer time of sonication improves dispersion efficiency. To impart adequate ultrasonic energy and critical micelle concentration (surfactant concentration) in MWNT dispersion (for the given surfactant to MWNTs ratio of 0.5e0.6) toward uniform and stable dispersion, ultrasonic energy of 50e70% and amplitude of 50% cycle is required for centrifuged solutions, and 40% amplitude with 50% cycle is required for sonicated sample. While increasing ultrasonic energy, corresponding hydrodynamic diameter shows decreasing trend. Samples with surfactant to MWNTs ratio of 0.4e0.6 showed that the change of the sonication parameter (amplitude or cycle) did not considerably influence the hydrodynamic diameter. Due to flocculation mechanism and physical effects (temperature raise during ultrasound agitation), solutions with surfactant to MWNTs ratio of 0.7 & 0.4 (above 60% sonication parameters) showed larger hydrodynamic diameter. Also, the PDI data for sonicated sample corresponding to above d