The influence of alkali cations on mix design of geopolymers is essential for their mechanical, thermal, and electrical performance. This research investigated the influence of alkali cation type on microscale characteristics and mechanical, dielectric, and thermal properties of fly ash-based geopolymer matrices. The geopolymers were elaborated via class F fly ash from the thermal plant Jorf Lasfar, El Jadida (Morocco), and several alkaline solutions. Morphological, structural, mechanical, dielectric, and thermal characteristics of materials synthesized via fly ash with different proportions of KOH and NaOH aged 28 days were evaluated. The physicochemical properties of class F fly ash-based geopolymers were assessed using X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX) analyses. Based on readings of the results obtained, XRD and FTIR analysis detected the creation of semicrystalline potassium/sodium aluminate-silicate hydrate (KASH/NASH) gel in the elaborated matrices after the geopolymerization reaction. The SEM analysis proved the formation of alkali alumina-silicate hydrate gel in the raw material particles after the polycondensation stage. Experimental compressive strength data indicated that the highest compressive strength (39 MPa) was produced by the alkaline activator (75% KOH/25% NaOH). The dielectric parameters values of the elaborated materials changed depending of the mass ratios KOH/NaOH. Dielectric findings demonstrated that geopolymers containing 100% NaOH have better dielectric performances. The fire resistance study revealed that the geopolymer binders induced by KOH are stable up to 600°C. Based on these results, it can be deduced that the formulated geopolymer concrete possesses good mechanical, dielectric, and fire resistance properties.
The aim of this paper is to provide a theoretical analysis on the mechanical power of the mass spring's system. Some tests are conducted to experimentally evaluate the theoretical analysis and to investigate the mechanical energy ability of this concept. The authors suggest a system used for applications of energy harvesting from roads. The system is able to transform the kinetic energy produced by the passage of vehicles on the road for electrical energy based on the mass-spring using two technologies. The hybrid system has two goals. First, supply the entourage by a mechanism to produce significant electrical power used mainly for public lighting. A device is also provided for storing electrical energy for later use, for home lighting at night or in the case of bad weather. Second, the piezoelectric subsystem controls the spring's health through analyzing the amplitude and shape of the voltage generated by a piezoelectric material. Finally, an experimental validation of the designed smart speed bump is presented.
With recent advancements in energy conversion mechanisms, piezoelectric ceramics (1–x)PbMg1/3 Nb2/3Ο3-xPbTiΟ3 (1–x)PMN-xPT have demonstrated their abilities for converting mechanical vibrations into electricity. Three (1–x)PMN-xPT compositions were used in the present work with (x = 0.25, 0.31 and 0.33). The purpose of this paper is to investigate their piezoelectric performance as generators for energy harvesting applications. The energy harvester is numerically analyzed in this work. It consists of a piezoelectric bimorph clamped at one end to vibrating machinery, and a proof mass mounted on its other end. The energy harvester is also analyzed and experimental measurements of the harvested power are compared to the simulation results. A good agreement was observed between the experimental and the simulations results. According the application to exploit the vibrations of a hot air extractor, the results show that the harvested energy density of solid ceramics (1–x)PMN-xPT is 0.043 W/m2.
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