Comparative Study on Microwave Absorbing Heating Characteristics and Microwave Deicing Performance of Airport Pavement Modified Concrete

In this paper, the airport pavement concrete has been taken as the main research object, three kinds of absorbing materials, namely silicon carbide (SiC), iron oxide (Fe3O4) and graphite, have been respectively mixed into the concrete, and an open microwave testing system has been established. Based on this system, the basic mechanical properties, microwave heating characteristics, microwave deicing effect and its influencing factors of modified concrete are systematically studied. In addition, a comparative analysis of the influence mechanism of different absorbing materials on the strength and absorbing performance of pavement concrete is carried out. The results showed that the addition of SiC, Fe3O4, and graphite could effectively enhance the microwave effect of pavement concrete, and the more the addition, the more obvious the improvement. Furthermore, under the same mixing amount, the degree of improvement of microwave deicing performance of each absorbing material from large to small is graphite, Fe3O4, SiC. However, the addition of graphite will form several weak links in concrete, thereby reducing its overall mechanical properties. SiC can slightly improve the mechanical properties of pavement concrete, but it has no significant effect on the microwave absorption properties. With the addition of Fe3O4, the strength of concrete changes little, and the effect of microwave absorbing heating and microwave deicing is remarkable. In general, the comprehensive performance of microwave deicing of Fe3O4 modified concrete is optimal. This study has high scientific and practical significance, and can be widely applied to deicing projects on airports and high-grade highways.

Microwave Assisted Alkaline Pretreatment of Algae Waste in the Production of Cellulosic Bioethanol

Biomass pretreatment has an important role in the production of cellulosic bioethanol. In this study, the effectiveness of microwave assisted alkaline pretreatment of algae waste was analysed. After pretreatment, the product was hydrolysed using sulphuric acid. The effects of microwave power, irradiating time, solid–liquid ratio and NaOH concentration were examined. Under the best conditions, the fermentable sugars were converted to cellulosic bioethanol using Saccharomyces Cerevisiae with a bioethanol yield of 1.93 ± 0.01 g/g and a fermentation efficiency of 40.4%. The reducing sugars concentration was 30% higher than that obtained from conventional hydrolysis without pretreatment. The obtained results suggest that microwave assisted alkaline pretreatment is effective in improving the production of cellulosic bioethanol of algae waste compared to that without microwave effect. Considering energy consumption, low microwave power and short microwave irradiation time are favourable for this pretreatment.

Microwave Heating of Liquid Crystals and Ethanol-Hexane Mixed Solution and Its Features (Review)

Microwave heating is widely used to accelerate organic reactions in the chemistry field. However, the effect of microwaves on chemical reaction has not yet been well characterized at the molecular level. In this review chapter, microwave heating processes of liquid crystals and an ethanol-hexane mixed solution under microwave irradiation were experimentally and theoretically investigated using in situ microwave irradiation nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulation, respectively. The temperature of the solution under microwave irradiation was estimated from a chemical shift calibrated temperature (CSC-temperature) which was determined from the temperature dependence of the 1H chemical shift. The CSC-temperatures of CH2 and CH3 non-polar protons of ethanol reflect the bulk temperature of a solution by the thermal microwave effect. The lower CSC-temperature of the OH polar protons in ethanol and much higher CSC-temperature of H-C=N (7′) and CH3-O (α’) protons of N-(4-methoxybenzyliden)-4-butylaniline with respect to the bulk temperature are attributed to the non-thermal microwave effects. According to the MD simulation under microwave irradiation, the number of hydrogen bonds increased in the ethanol-hexane mixed solution as a result of a non-thermal microwave effect. It is concluded that a coherently ordered low entropy state of polar molecules is induced by a non-thermal microwave effect. The ordered state induces molecular interaction, which may accelerate the chemical reaction rate between molecules with polar groups.

Microwave Desorption Mechanism and Microwave Effect based on SO2 Chemical Dissociation and Mass Transfer of Basic Aluminium Sulfate Desulfurization Rich Liquid

A microwave liquid-phase desorption technique for enhancing mass transfer with chemical dissociation had been proposed for the first time. In this paper, the static desorption system of basic aluminium sulfate...

Microwave Synthesis of CaTiO3 Nanoparticles by the Sol-Gel Method

A technique for the microwave-activated synthesis of calcium titanate nanopowder was proposed. The microwave effect used in the synthesis of CaTiO3 samples when using sodium carbonate as a precipitant allowed obtaining a chemically homogeneous nanopowder with a significant reduction of the process time. References1. Zhang Q., Saito F. Effect of Fe2O3 crystallite sizeon its mechanochemical reaction with La2O3 to formLaFeO3. Journal of Materials Science. 2001;36(9):2287–2290. DOI: https://doi.org/10.1023/a:10175208069222. Bayraktar D., Clemens F., Diethelm S., et al.Production and properties of substituted LaFeO3‑perovskitetubular membranes for partial oxidation ofmethane to syngas. Journal of the European CeramicSociety. 2007;27(6): 2455–2461. DOI: https://doi.org/10.1016/j.jeurceramsoc.2006.10.0043. Reznichenko V. A., Averin V. V., Olyunina T. V.Titanaty. Nauchnye osnovy, tekhnologiya, proizvodstvo[Titanates. Scientific foundations, technology, production].Moscow: Nauka Publ.; 2010. 72 p. (In Russ.)4. Suzdalev I. P. Nanotekhnologiya: fiziko-khimiyananoklasterov, nanostruktur i nanomaterialov[Nanotechnology: physical chemistry of nanoclusters,nanostructures and nanomaterials]. Moscow:KomKniga Publ.; 2006. 592 p. (In Russ.)5. Gusev A. I. Nanomaterialy, nanostruktury,nanotekhnologii [Nanomaterials, nanostructures,nanotechnology]. Moscow: Fizmatlit Publ.; 2007. 416 p.6. International Center for Diffraction Data.7. X-ray diffraction date cards, ASTM

The Effect of Microwave on the Crystallization Behavior of CMAS System Glass-Ceramics

The microwave sintering of glass-ceramics, non-thermal microwave effect, and crystal growth mechanism remain important challenges in materials science. In this study, we focus on developing approaches to affect crystal growth in the glass network of glass-ceramics by microwave heating, rather than performing a single study on the crystal structure and type. Raman spectroscopy is used to detect the structure of the glass network. We demonstrated that the non-thermal microwave effect promoted the diffusion of metal ions, which promoted the aggregation and precipitation of metal ions in the glass network to form crystals. The samples produced by microwave heating contain more non-bridging oxygen bonds than conventional sintered samples; therefore, the non-thermal microwave effect has a depolymerization effect on the glass network of the sample. Under the influence of microwave field, many metal ions precipitate, which precipitates many crystal nuclei. In addition, many active metal ions are captured during the crystal nucleus growth, which shortens the sintering process of glass-ceramics.