Microwave Heating Performance Research Articles

Anti-icing and de-icing properties of composite superhydrophobic coating with microwave heating performance on asphalt pavement

Severe icing on asphalt pavements significantly impacts traffic safety and efficiency. Superhydrophobic coatings exhibit excellent hydrophobic and anti-icing properties, making them suitable for asphalt pavements. However, the formation of dense and hard ice limits their anti-icing effectiveness in cold regions. Within this paper, we have developed a novel composite superhydrophobic coating (CSC) with microwave heating performance by constructing a hierarchical structure using carbon nanotubes and incorporating micron-sized iron powder as a primary microwave-absorbing material. Scanning electron microscopy, 3D confocal microscopy, and contact angle tests reveal that the optimally mixed CSC possesses a complex micro-nano hierarchical structure, superhydrophobic properties (contact angle of 155.4°), and excellent anti-icing properties. Microwave heating results show that the CSC achieves a maximum heating rate of 1.108 ℃/s and an energy utilization efficiency of 47 %, representing improvements of 118.1 % and 18.3 % compared to uncoated specimens. Durability tests indicate that after wear, the CSC's contact angle decreases by 6.2 %, and the microwave heating rate drops by 13.7 %. Despite these reductions, the coating still maintains high hydrophobicity and microwave heating performance. While the friction coefficient of CSC-coated pavement decreases to μ=0.63, it still meets regulatory requirements. Overall, the application of CSC can effectively increase de-icing efficiency and mitigate the adverse effects of ice and snow on pavements.

Effect of silicon carbide powder on asphalt material properties and microwave-induced self-healing

Silicon carbide (SiC) powder, an excellent microwave-absorbing material, can serve as a filler in asphalt mixtures. This study compares the particle size distribution, phase composition, pore structure, specific surface area, and electromagnetic properties of SiC powder and limestone powder. Asphalt mastic and mixtures were prepared with SiC powder replacing mineral powder at ratios ranging from 0 % to 60 %. The study examines how differences in particle size gradation, mineral composition, pore structure, and specific surface area contribute to deformation resistance and improve mechanical properties through micro-level interlocking and cementation. Electromagnetic parameter variations affect microwave heating performance, with uniform distribution of absorbing fillers ensuring heating homogenization. SiC powder also enhances the self-healing index, reaching 74.4 %, and maintaining a maximum healing index of 68.1 % after four damage-healing cycles. These findings support the practical application of SiC powder in asphalt concrete, enhancing maintenance efficiency and advancing microwave heating for self-healing and hot recycling.

Comparative Evaluation of Microwave Heating Performance across Structurally Diverse Tungsten Oxides

Comparative Evaluation of Microwave Heating Performance across Structurally Diverse Tungsten Oxides

The combined effect of active packaging and relative phase sweeping on microwave heating performance in a dual-port solid-state system

The combined effect of active shielding packaging and relative phase sweeping on heating performance in a dual-port solid-state microwave heating process was evaluated. Four types of heating strategies that combine two factors (passive and active packaging and fixed and sweeping relative phase) were used in heating a tray of 300 g gellan gel sample for 3 min. The temperature distributions at the top and middle layers of the heated samples were collected and analyzed for heating uniformity index (HUI) and power absorption efficiency (PAE). The results showed that both active shielding package and relative phase sweeping can individually improve the HUI while maintaining high PAE. The packaging factor and relative phase factor showed a significant interaction effect (p = 0.0021) in influencing HUI but not PAE, highlighting the necessity of considering both factors (packaging and relative phase) when optimizing the microwave heating uniformity. The combination of active packaging and sweeping relative phase is a robust heating strategy that delivers the best heating performance that is significantly better than or similar to other combinations of packaging and relative phase strategies.

Unveiling the microwave heating performance of biochar as microwave absorber for microwave-assisted pyrolysis technology

Microwave (MW) heating has gained significant attention in food industries and biomass-to-biofuels through pyrolysis over conventional heating. However, constraints for promoting MW heating related to the use of different MW absorbers are still a major concern that needs to be investigated. The present study was conducted to explore the MW heating performance of biochar as a low-cost MW absorber for performing pyrolysis. Experiments were performed on biochar under different biochar dosing (25 g, 37.5 g, 50 g), MW power (400 W, 700 W, 1000 W), and particle sizes (6 mm, 8 mm, 10 mm). Results showed that MW power and biochar dosing significantly impacted average heating rate (AHR) from 17.5 to 65.4 °C/min at 400 W and 1000 W at 50 g. AHR first increased, and then no significant changes were obtained, from 37.5 to 50 g. AHR was examined by full factorial design, with 94.6% fitting actual data with predicted data. The model suggested that the particle size of biochar influenced less on AHR. Furthermore, microwave absorption efficiency and biochar weight loss were investigated, and microwave absorption efficiency decreased as MW power increased, which means 17.16% of microwave absorption efficiency was achieved at 400 W rather than 700 W and 1000 W. Biochar weight loss estimated by employing mass-balance analysis, 2–10.4% change in biochar weight loss was obtained owing to higher heating rates at higher powers and biochar dosing.

The effect mechanism of microwave enhanced aggregates on the microwave heating performance of asphalt mixtures

The use of microwave enhanced material as aggregate for asphalt mixture has emerged as a crucial focus in improving the microwave heating performance of asphalt mixture. However, there is a marginal diminishing effect in microwave heating, which limited further improvement in the microwave heating property of the asphalt mixture. In order to explain the mechanism of the marginal diminishing effect, a three-phase (microwave enhanced aggregate, ordinary aggregate, asphalt sand) microscopic model of asphalt mixture was established using MATLAB and COMSOL based on the random aggregate placement and finite translation algorithm. The distribution of electromagnetic field, temperature field and the heat transfer efficiency were analyzed to investigate the mechanism of microwave enhanced aggregates influencing microwave heating efficiency. The results show that the microwave enhanced aggregate changes the heating efficiency of non-microwave enhanced phases (ordinary aggregate, asphalt sand) as follows: firstly, the change of electromagnetic fields distribution may affect the electromagnetic loss power of non-microwave enhanced phases. The other is that the heat transfer rate from microwave enhanced aggregate to the non-microwave enhanced phase will affect the heating efficiency of asphalt mixture. However, it was found that the self-generated heat of non-microwave enhanced phase accounts for over 80% of its internal energy increment. The heat transfer rate of microwave enhanced aggregates decreased as its substitute amount increased. The decrease in impedance matching of asphalt mixture with air and heat transfer efficiency are the two main reasons for the marginal diminishing effect of asphalt mixture containing microwave enhanced aggregates.

Self-healing properties of steel slag asphalt mixture based on experimental characterization and 3D reconstruction

Asphalt pavement is susceptible to cracking which affects its service life. And self-healing technology helps to heal micro-cracks in mixture at an early stage, but its mechanism of action at the mesoscale is still unclear. Therefore, the composition of steel slag asphalt mixture (SSAM) was designed, microwave heating performance, healing performance and road performance of SSAM were investigated by laboratory experiments. Finally, the SSAM was scanned using X-ray CT for 3D reconstruction and quantitative analyses. The results show that steel slag has obvious magnetic loss characteristics; the surface temperature of SSAM designed by composition is higher under microwave heating to obtain a better healing rate, and the road performance of SSAM meets the specification requirements. The damage-healing process mainly affects voids in SSAM, and microwave healing can reduce the fractal dimension of voids to reduce the proportion of fissures; from the healing index based on voids, self-healing can reduce the average coordination number and throat number of connected voids, thereby improving the performance of SSAM by reducing permeability. The self-healing performance of SSAM is improved through its compositional design; the mesoscopic model based on void characteristics helps to refine the theory of self-healing of asphalt mixtures under microwave heating.

Effect of lossy thin-walled cylindrical food containers on microwave heating performance

Cylindrical containers are commonly used in microwave food processing applications. However, due to the shape effect, microwave energy mainly focuses in the center of the sample within the container, leading to a nonuniform temperature gradient between the inner and outer layers of the sample. Employing a lossy container may be an effective method to address this issue because the heat conduction from the container's wall or the microwave's interaction with the container edge can compensate for the lack of heating in the outer layer. Multiphysics modeling is a powerful tool for uncovering the effect of the lossy container on microwave heating performance. However, noncompliance between the fine and coarse mesh elements at the thin-walled boundary of the container will generate a huge number of irregular meshes, which will not only lead to excessive computational costs but also lead to the possibility of calculation error of the boundary flux. To overcome this difficulty, a fast simulation method based on transformation optics is proposed to analyze the effect of lossy containers on microwave food processing performance in this paper. By using the proposed method, the calculation efficiency can be increased by up to 800% with comparable or even better accuracy than the traditional method. Meanwhile, the results show that the lossy container can improve the temperature uniformity around microwaved food but it will slightly reduce the heating efficiency due to energy loss within the container. This paper offers an efficient and fast way to analyze microwave food heating processes with a thin-wall structure. Furthermore, the discussion on the feasibility of using lossy containers to improve the microwave heating uniformity will also contribute to the further application of microwave cylindrical food processing. • Microwave heating models with lossy thin-walled cylindrical containers were realized by transformation optics. • Compared with traditional method, this method can improve the computing efficiency by 8 times with a wall thickness of 1 mm. • The influence of container's material, size and wall thickness on microwave heating is analyzed. • Employing lossy container can weak the phenomenon of thermal focus during microwave heating cylinder food.

Microwave heating of carbon materials for on-demand thermal patterning via tunable electromagnetic resonators

Recently, thermal manipulation in carbon materials has drawn much interest in multiple domains. Compared with existing conductive heating techniques, microwave heating has many advantages such as non-contact heating, fast and accurate temperature response, low energy consumption, etc. However, it is still challenging to realize real-time on-demand thermal manipulation in carbon materials with microwaves, due to the lack of effective control methods on electromagnetic (EM) properties. Here, for the first time, we report a solution to this problem by employing tunable EM resonators. Specifically, EM resonators with electrically tunable lumped elements were designed to couple microwave energy into the carbon material, realizing a pixel-controlled microwave heating performance. Through carefully designing the structure of the EM resonators, the local energy concentration on the tunable lumped elements was remarkably alleviated. Experimental results indicated that the microwave absorbance can be tuned from 12.1% to 99.6%, leading to a tunable heating rate ranging from 1.3 °C/min to 13.5 °C/min under fixed microwave power of 600 W. Moreover, a pixelated thermal manipulation was demonstrated through a thermal display of Arabic numerals. Our work may open new avenues for thermal manipulation in carbon materials and can be applied to complex thermal tasks such as customized materials processing, thermal display, deicing and defrosting, etc.

Preparation and anti-icing performance of acrylic superhydrophobic asphalt pavement coating with microwave heating function

In winter, icing greatly reduces the friction performance of pavement and brings a high safety hazard to road traffic. We prepared a superhydrophobic coating (SHC) with a microwave heating function to minimize pavement icing risk. The static contact angle of the water droplet on the SHC is 161.2°. The freezing time of water droplets on asphalt mixture coated with SHC is 1.63 times longer than that of asphalt mixture without coating. SHC can significantly delay the freezing process of water. The normal adhesion strength of 10 mm ice layer on the asphalt mixture coated with the SHC at −5 °C is only 14.3 % of that on the asphalt mixture without coating. It confirms that the SHC dramatically reduces the normal adhesion strength of the ice layer on asphalt pavement. In addition, the microwave heating rate of the asphalt mixture coated with SHC is 48.37 % faster than that of the asphalt mixture without coating. Carbon nanotube particles directly contact the ice on the SHC surface. Besides, carbon nanotube particles also have high microwave heat conversion efficiency and high thermal conductivity. The ice layer on the surface of the asphalt mixture coated with SHC can be melted and removed within 80 sec, which is 42.86 % faster than the ice removal time of asphalt mixture without coating. Carbon nanotube particles on the SHC surface were directly heated by microwaves and melted the ice layer rapidly. The acrylic coating on the asphalt mixture surface has an excellent thermal insulation performance. The load wheel rolling experiment was conducted to simulate the traffic wheel friction. The static contact angle of the water droplet on the SHC keeps at 147°, and the microwave heating performance of the SHC has no significant changes before and after 500 rolling times. This implies that the SHC has sustainable superhydrophobic properties and can melt the ice layer under microwave heating even after the traffic wheel friction. The SHC is of great significance for improving the driving safety of asphalt pavement.

Remarkable microwave heating performance of MWCNTs/polypropylene composites verified by electromagnetic-thermal coupling experiment and simulation

To explore the microwave heating technology of thermoplastic materials, multiple-walled carbon nanotube (MWCNT)/polypropylene (PP) composites with mass content of MWCNT ranging from 0.5 wt% to 6 wt% had been fabricated by melt blending. The as-prepared samples were heated in a commercial microwave oven with microwave frequency of 2.45 GHz for 5 s and their surface temperatures were recorded via an infrared thermal imager. The temperature of these samples reached its highest point when the mass content of MWCNT was 3 wt% and it could be heated to 290 °C in 5 s. The composites were also characterized by scanning electron microcopy (SEM), four-point probe method and vector network analyzer (VNA) to study the morphology, electrical performance and S-parameter respectively. The dc conductivity and morphology of the sample indicates that the effective three-dimensional conductive network is formed when the mass content of MWCNT is 1 wt%, and the microwave energy is converted into heat mainly in the form of conduction loss. Microwave heating mechanism of MWCNT/PP composites was studied by EM-thermal coupling and analyzing the absorbance (A), reflectance (R) and transmittance (T) calculated by S-parameters. The simulation results of EM-thermal coupling are consistent with the experimental results. The absorbance shows the samples' absorption of microwave energy and it has the same variation trend as the samples’ temperature, which indicates that the microwave heating property of MWCNTs/PP composites can be estimated by its absorbance. Therefore, MWCNT can be considered as a potential microwave absorber for thermoplastic materials and its best content can be well estimated.

Three-dimensional mesostructure model of coupled electromagnetic and heat transfer for microwave heating on steel slag asphalt mixtures

Steel slag as a special type of aggregate in asphalt mixture owns excellent potential for microwave heating. To gain high heating performance, the determinant of the optimal content of steel slag in asphalt mixture becomes a key problem. This paper develops a numerical model of the mesostructure of the three-phase asphalt mixture (aggregate, steel slag, and asphalt mortar) with coupled electromagnetic field and heat transfer process. Firstly, the model generates spherical aggregates by the random placement method based on the given grading. Then, the limestone aggregate particles are replaced by steel slag with the same volume. Finally, microwave heating analysis of asphalt mixtures with different steel slag contents is performed by FEM. The comparison between our numerical simulations and the reported experimental data demonstrates that the proposed model is reliable and effective. This research can characterize well the heat transfer among components of asphalt mixture during microwave heating and show the details of the inner temperature distribution. The results also indicate that the microwave heating performance of asphalt mixture enhances with the increase of steel slag content. However, excessive steel slag content can lead to overheating in most areas of the asphalt mixture, and the temperature distribution is more uniform and suitable when steel slag replaces coarse aggregate (4.75 – 9.5 mm) with an equal volume about 60 %.

Development of a novel silica-based microwave receptor for high temperature processes

A novel silica-based microwave receptor was developed via a fluidized bed chemical vapor deposition (FBCVD) technique. In this study, the silica sand particles were successfully coated in an induction heating-assisted reactor, with carbon produced from thermal degradation of methane (TDM) at various reaction temperatures and times. The effect of FBCVD reaction parameters, temperature and reaction time, on the amount of carbon deposition, and the composition, coherence and thickness of the carbon coating layer were investigated using thermogravimetric and morphological analysis, respectively. The microwave heating performance of such developed receptors was further investigated in an innovative single-mode microwave apparatus and was subsequently compared with the relevant performance of sand and graphite particle mixtures. The developed microwave receptor stipulates low level of carbon content and high layer uniformity, extreme microwave heating rate, high durability, and excellent potential for application in gas-solid fluidized bed reactors as heat generator and catalyst support/promoter simultaneously.

Development of a complementary-frequency strategy to improve microwave heating of gellan gel in a solid-state system

As a helpful step towards the future development of a solid-state microwave system that can dynamically control microwave source parameters to deliver better heating performance, a complementary-frequency heating strategy has been developed and will be discussed here. The proposed complementary-frequency heating strategy is based on potential microwave heating uniformity enhancement through microwave frequency shifting during heating has shown promise to improve the microwave heating performance. The average temperature and heating uniformity results of this strategy were compared to conventional heating strategies like Fixed-Frequency and Sweeping-Frequency strategies. Typically, the Complementary-Frequency strategy could selectively use specific frequencies in the microwave heating process. These frequencies could be identified based on their associated complementary temperature profile of the top surface of the food product collected by a thermal imaging camera and sequenced in a specific order dictated by a predefined algorithm. The results indicated that both the Sweeping-Frequency and the Complementary-Frequency strategies could uniformly heat food products more than the Fixed-Frequency strategy. Meanwhile, the Complementary-Frequency strategy can trade-off microwave power absorption efficiency and heating uniformity to deliver a higher heating rate than the Sweeping-Frequency strategy does. • Complementary heating patterns were utilized to develop the frequency-shifting strategy. • The Complementary-Frequency strategy can be developed to balance efficiency and uniformity. • The Complementary-Frequency strategy could improve the microwave heating performance.

A core-shell liquid metal-Cu nanoparticle with glutathione consumption via an in situ replacement strategy for tumor combination treatment of chemodynamic, microwave dynamic and microwave thermal therapy.

The presence of high content glutathione (GSH) provides an effective "protective shield" for tumor cells, which undoubtedly is a huge impediment to reactive oxygen species (ROS)-based treatment. Fortunately, divalent copper (Cu2+) can not only consume GSH, destroying the protection mechanism of GSH, but also can be reduced to Cu+ with excellent Fenton-like reaction activity. Hence, capitalizing on the properties of liquid metals, we introduced Cu with three different valances via an in situ replacement reaction. A stable core-shell liquid-metal based "Cu storage pool" was obtained. It can effectively deplete GSH within the cells, and simultaneously produce ·OH through a Fenton-like reaction, further improving the effect of chemodynamic therapy (CDT). Under microwave irradiation, it is also capable of producing a large amount of ROS to promote tumor treatment. In addition, the loading of ionic liquid endows LZC@IL nanoparticles with certain microwave heating performance, which is able to augment microwave thermal therapy (MWTT). With the combination of CDT, microwave dynamic therapy (MDT) and MWTT, LZC@IL has an excellent effect on tumor elimination. This work offers a new idea for the application of liquid metals and the combined treatment of tumors, which has potential application value.

Mechanistic and Machine Learning Modeling of Microwave Heating Process in Domestic Ovens: A Review.

The domestic microwave oven has been popularly used at home in heating foods for its rapid heating rate and high power efficiency. However, non-uniform heating by microwave is the major drawback that can lead to severe food safety and quality issues. In order to alleviate this problem, modeling of microwave heating process in domestic ovens has been employed to simulate and understand the complicated interactions between microwaves and food products. This paper extensively reviews the mechanistic models with different geometric dimensions and physics/kinetics that simulated the microwave heating process. The model implementation and validation strategies related to the model accuracy and efficiency are also discussed. With the emergence of the machine learning technique, this paper also discusses the recent development of hybrid models that integrate machine learning with mechanistic models in improving microwave heating performance. Besides, pure machine learning models using only experimental data as input are also covered. Further research is needed to improve the model accuracy, efficiency, and ease of use to enable the industrial application of the models in the development of microwave systems and food products.

Double pendulum mode stirrer for improved multimode microwave heating performance

This is a common way to improve the uniformity of microwave heating by using a mode stirrer. However, the conventional mode stirrer is a reciprocating periodic motion, which in some cases does not effectively improve the uniformity of microwave heating. In this study, a mode stirrer with double pendulum structure was creatively proposed. Due to the chaotic characteristics of the double pendulum motion process, the mode stirrer process is no longer a traditional periodic motion, and this chaotic stirrer process will affect the uniformity of heating. Based on the finite element method combined with the implicit function and level set method, the microwave heating process with double pendulum mode stirrer was calculated, and the multiphysics coupling simulation of structure-electromagnetic-heat transfer was realized. The heating performance under different double pendulum mode stirrers was studied and compared with the heating results of the single pendulum mode stirrer. The results show that the double pendulum mode stirrer with a specific initial position can effectively improve the heating uniformity without reducing the heating efficiency.

Research on microwave heating performance of modified steel slag asphalt mixture

Aiming at the change law of the flexural and tensile strength of the modified steel slag asphalt mixture during microwave heating, the results of this paper are as follows: the microwave heating process can achieve the recovery of the flexural and tensile properties of the modified steel slag asphalt mixture. The number of point bending failure tests continues to increase, and the recovery rate of bending and tensile properties of beams made of modified steel slag asphalt mixture will slowly decrease until the test piece is completely destroyed. The flexural and tensile strength of beams made by microwave heating asphalt mixture cannot be fully recovered, but different asphalt mixtures have different recovery effects. Compared with the ordinary basalt asphalt mixture, the steel slag asphalt mixture before modification has the same bending and tensile repair effect after microwave heating, while the modified steel slag asphalt mixture has the first bending and tensile repair effect after microwave heating increased by 23%.

Effect of moisture and freeze-thaw damage on microwave healing of asphalt mixes

Microwave heating/healing is a kind of maintenance technique to repair micro-cracks in asphalt mixes. This method was conducted mostly on unaged materials, and the effects of moisture and freeze-thaw damages have not completely been studied. The fluidity of the asphalt binder, accomplished by heating, increases the ability of binder to fill micro-cracks and heal the asphalt mixes. Moisture and freeze-thaw damage increase the modulus of asphalt binder resulting decrease of fluidity of material. In contrast, moisture and freeze-thaw damages could reduce the ability of mixes to heal. In this research, mixes were prepared using neat and activated carbon modified asphalt binders. In order to assess the microwave heating properties, mixes were subjected to different levels of moisture and freeze-thaw conditions. The microwave heating performance was investigated under electromagnetic radiation. It was found that activated carbon is a proper binder-based additive that increases electromagnetic absorption of asphalt mixes. Indirect Tensile (IDT) and Semi-Circular Bending (SCB) specimens were fabricated, and different levels of moisture and freeze-thaw cycles were applied. For quantification of microwave healing capability of damaged asphalt concrete mixes, the cyclic fracture-healing tests were conducted on IDT and SCB specimens. Individual and combined effects of mechanical damage, fracture temperature, notch length, moisture, and freeze-thaw cycles on microwave healing performance of asphalt concrete mixes were investigated. Results showed that moisture and freeze-thaw damages have adverse effects on microwave healing performance of asphalt concrete mixes. Increased critical factors caused further detrimental effects on microwave healing performance of mixes.

Investigation of the Microwave Absorption of Asphalt Mixtures Containing Magnetite Powder

This article is intended to investigate the microwave heating performance of asphalt mixtures containing magnetite powders (MPAM). For this purpose, the surface temperatures of asphalt mixtures containing different dosages of magnetite powders were measured during microwave heating. The low-temperature bending test and water sensitivity test were also conducted to evaluate the performance of MPAM. Heating rate and reflection loss of different thicknesses of MPAM were determined using a microwave heating test and arch reflectivity test, respectively. The results showed that because its main components are triiron tetroxide and iron oxide, which have excellent microwave-absorbing properties, magnetite powders can be used as microwave absorbers to improve the ability of microwave absorption and increase the heating rate of asphalt mixtures. The heating rate of the asphalt mixtures increased with the increase of the amount of magnetite powder. The addition of magnetite powder improved the low-temperature properties of the asphalt mixture, but it reduced the water stability of the asphalt mixture. Considering that the microwave-absorbing asphalt mixture used for melting snow and ice should have good water stability, the recommended dosage of magnetite powders was 60%. The microwave-absorbing properties of MPAM were related to its thickness in the pavement structure and frequency of microwaves. In order to greatly enhance the absorbing efficiency, future work should be focused on matching thickness and matching frequency.