Susceptor Material Research Articles

Enhanced densification and phase transformations during rapid microwave sintering of alumina – yttria-stabilized zirconia ceramics

Alumina – 7.5 wt% yttria-stabilized zirconia (YSZ) ceramic composites were sintered using 24 GHz microwave heating at rates of 10 – 200 °C/min with zero isothermal hold. The starting powders were nanophase η-Al2O3 and YSZ prepared by a laser evaporation method. The final densities of the sintered samples were up to 97.5 % of the theoretical value. The samples exhibited rapid densification until transformation to the α-Al2O3 phase. The temperature of the densification rate peak (and hence of the phase transformation) decreased consistently with increasing microwave electromagnetic field intensity (varied by using different susceptor materials). The densification peak temperature difference between microwave and conventional sintering experiments exceeded 200 °C.

Thermoelectric properties of zintl antimonite compound YbCd2-xZnxSb2 prepared under microwave solid-state irradiation

We herein introduce a microwave-assisted solid state technique to synthesize zintl compounds YbCd2-xZnxSb2 (0.0 ≤ x ≤ 2.0) in short time of 10 min by utilizing an active carbon as a susceptor material. Here, we report an energy-saving preparation route using a domestic microwave oven. A microwave susceptor material rapidly heats the elemental starting materials inside an evacuated quartz ampoule resulting in near single phase compounds. By studying the crystal structure using X-Ray diffraction (XRD) and SEM-EDS, the hexagonal crystal structures of the prepared samples were identified. Thermoelectric characterizations have been performed for all obtained samples and among them the compound YbCd1.6Zn0.4Sb2 is found as the best one because it has Seebeck coefficient of −22.68 μV/k, and power factor of 8.20 μWcm−1k−2 at 523 K with carrier concentration of 3.04 × 1021 cm−3 at 300 K.

RETRACTED: Optimizing microwave energy utilization & heating efficiency: Comparative analysis of susceptor materials for enhanced microwave absorption performance

Susceptors are vital components in microwave heating systems, ensuring efficient, selective, and uniform heating while improving both energy utilization and time effectiveness in various microwave processing applications. The present investigation underlines the microwave absorption performance of various silicon carbide (SiC) susceptors during microwave hybrid heating. The current study also explores methods, including theoretical analysis, simulations, and experiments, to identify most suitable SiC susceptor materials for efficient microwave heating (high microwave absorbing and energy utilization efficiency). Among all susceptor materials, porous nitride-bonded SiC exhibited combination of high properties including permittivity (9.64), loss tangent (0.268), reflection loss (−13.32 dB) and attenuation constant (21.12 Np/m) when microwave heating carried at 1.2 kW, 900 s. Porous nitride-bonded SiC susceptor emerged as optimal choice for most appropriate susceptor material on the basis of theoretical analysis (reflection loss, impedance, microwave attenuation constant, dielectric properties) as compared to other susceptors. The microwave absorption mechanism of various SiC susceptor materials have been established and summarized. The microwave heating behaviour of various SiC susceptors with different compositions were analysed using COMSOL simulations. A higher microwave utilization efficiency was observed by COMSOL simulation for the porous nitride-bonded SiC (95 %) susceptor than dense nitride-bonded SiC (78 %), dense SiC (69 %) and dense oxide-bonded SiC (58 %). The excellent microwave absorption capability of porous nitride-bonded SiC susceptor can be ascribed to synergistic efforts of various polarization mechanisms: dipole polarization, interfacial polarization, multiple reflections and scatterings, defect-induced dipole polarization and conductive loss.

Experimental Analysis of Inductive Heating of Catalytic Beds

AbstractTo reduce CO2 emissions in the chemical industry, already established endothermic reactors should be heated with electrical energy. One promising possibility is inductive heating, in which electrical energy can be transferred to the susceptor (material to be heated). The uniform heating of the susceptor material is necessary for stable operation in chemical reactors and is therefore investigated in this work. For this purpose, a non‐reactive test setup was built that enables the investigation of inductive heating of different susceptor materials and measurement of the temperature distribution under defined non‐reactive conditions. In the first tests, temperatures of up to 800 °C were reached and an uneven heat input in a bed of stainless‐steel rings was observed.

Nickel catalyst supported on SiC incorporated SiO2 for CO2 methanation: Positive effects of dysprosium promoter and microwaves heating method

In this work, Dy-promoted Ni/SiC-SiO2 catalysts with varied Dy loadings (0–1 %) were developed using the wet impregnation method and evaluated for their effectiveness in CO2 methanation. The characterization results reveal that Dy addition can reduce the Ni crystallite size, enhance the dispersion of active phase and increase the catalyst’s reducibility. Among the prepared catalysts, the 0.5 %Dy-10 %Ni/SiC-SiO2 demonstrated the highest CH4 selectivity (100 %) and CO2 conversion (73.9 %) at 350 °C owing to its highest basic sites and H2 chemisorption capacity. The performance of this Dy-promoted catalyst diluted with different amounts of SiC, which was employed as a microwave susceptor and high thermal conductive dilution material, was also investigated in both microwave and electric reactor. Microwave heating leads to higher CO2 conversion compared to electric heating, regardless of reaction temperature and dilution factor due to selective heating and the random occurrence of hot spots, which are usually considered as micro-plasmas in the catalyst bed. However, further increase quantity of SiC decreased both CO2 conversion and CH4 selectivity regardless of heating method. This may be attributed to the appearance of extreme overheating and the absence of gentle overheating with increased amount of SiC in the microwave and electric reactors, respectively. The temperature-programmed oxidation results demonstrated that carbon deposition on the 0.5 %Dy-10 %Ni/SiC-SiO2 catalyst during 30 h of reaction can be significantly suppressed by microwave.

Green Microwave-Assisted Cladding: Enhancing SS-304 with Ni-ZrB2 Composite Coatings

This study focuses on achieving effective deposition of a Ni and 15% ZrB2 particle mixture onto SS-304 substrate surfaces through meticulous preparation steps. Thorough cleaning of the SS-304 substrate using alcohol in an ultrasonic bath eliminated contaminants, ensuring optimal adhesion. Simultaneously, the Ni-ZrB2 mixture underwent preheating at 1200°C for 20 hours in a muffle furnace to eliminate moisture content, crucial for preventing coating defects. Uniform distribution of the preheated powder onto the substrate was crucial for consistent coating thickness. Microwave hybrid heating (MHH) using charcoal as a susceptor material overcame microwave reflection by rapidly heating the powder mixture. SEM analysis revealed a uniform dispersion of both Ni and ZrB2 particles across the substrate surface, indicating successful deposition and optimal adhesion. The cladding resulted in a significant improvement in surface hardness, with an increase of approximately 42.43%. The wear rate, measured at 0.00178 mm³/m, and the coefficient of friction, determined to be 0.246, provided crucial insights into the surface’s wear resistance and frictional behavior, confirming its suitability for applications requiring enhanced durability and performance. These findings highlight the efficacy of the microwave-assisted cladding process in enhancing SS-304 with Ni-ZrB2 composite coatings, paving the way for its utilization in various industrial applications.

Revolutionizing Surface Enhancement: Microwave-Assisted Cladding of Ni-Boron Nitride Mixture onto SS-304

This study presents a revolutionary approach to surface enhancement through microwave-assisted cladding of a Ni and 15% BN particle mixture onto SS-304 substrates. Meticulous preparation steps were undertaken, including substrate cleaning and powder preheating, to ensure optimal adhesion and coating quality. Microwave hybrid heating using charcoal as a susceptor material facilitated rapid and uniform heating of the powder mixture, while a pure graphite sheet prevented contamination during the process. The experiment was conducted using a multimode microwave applicator at specific power and frequency settings, resulting in controlled heating for optimal coating formation. The precision of the microwave-assisted cladding process was illustrated through SEM images, revealing a uniform distribution of cladding particles across the substrate. Moreover, significant improvements in surface hardness and wear resistance were observed, with a 44.67% increase in surface hardness and a low wear rate of 0.0020 mm3/m. These findings highlight the effectiveness of the developed cladding technique in enhancing the mechanical properties and wear resistance of SS-304 substrates, paving the way for its potential application in various industries requiring reliable surface protection and durability under sliding contact conditions.

High entropy alloy cladding on mild steel substrate using microwave energy at 2.45 GHz: An insight from multi-physics simulation study to experimental investigations

Microwave hybrid heating (MHH) has emerged as a novel technology for cladding high-entropy alloy (HEA) powders on metallic substrates. The existence of a multi-material system (Al, Co, Cr, Ni, and Ti powder) in HEA provides difficulties in microwave cladding. These problems are addressed in the current study by employing silicon carbide as a susceptor material for MHH to microwave-clad AlCoCrNiTi HEA on a mild steel substrate. A multi-physics model of the microwave cladding setup was constructed to investigate the cladding properties. The model was verified using experimental data, and simulation was used to examine the electric field, resistive losses, energy distributions, and temperature-time profile. The simulation results indicated that the electric field intensity, resistive losses, and energy distribution were at their maximum near the susceptor and the cladded surface. As a result, the HEA-cladded surface reached a temperature of 1030 °C at the central plane. This is comparable to the experimental temperature of 1041 °C in 41 min, which shows an error of <10 %. From the microstructural investigation, the HEA powder exhibited a flaky microstructure and a uniform distribution of all the constituents, resulting in a solid metallurgical link between the HEA powder and substrate. The surface hardness of mild steel components was enhanced intensely by three times with the inclusion of AlCoCrNiTi HEA cladding.

Susceptor based design strategies for enhancing microwave hybrid heating capability via experimental analysis, 3D multi-physics simulation and parametric optimization

Microwave processing has gained remarkable recognition based upon volumetric processing that is energy efficient. Susceptor-assisted microwave heating is a fast-emerging technology because of its advantages over traditional microwave processing. Susceptor help to speed up microwave processing by offering two-way heating with less heat loss from the material's surface. The present investigation brings out ways (theoretical, simulation and experimental) to select appropriate susceptor material by considering different types of microwaves absorbing material (alumina, yttria stabilized zirconia, boron nitride and silicon carbide) for efficient microwave heating. Theoretical analysis (dielectric properties, penetration depth, absorption loss and reflection loss) suggests silicon carbide (SiC) to be the most suitable susceptor. COMSOL Multiphysics based simulation in conjunction with experimental results were utilized for critical understanding of SiC susceptor heating. The influence of physical parameters: microwave input power, microwave frequency, placement of susceptor inside cavity and dimension of susceptor on electric field distribution and temperature profile of SiC susceptor are also investigated and presented in detail. Among all susceptor materials, SiC exhibited highest heating rate in similar operating parameters. The temperature obtained for SiC susceptor during microwave heating without casket (80 °C) was significantly lower than that with casket insulation (1003 °C). A susceptor of 10 mm thickness with cross-section of 625 mm2 was found to be the optimum dimension for SiC susceptor. The maximum temperature obtained by the SiC susceptor was 658 °C, 1003 °C, 1182 °C and 1380 °C for input power of 800 W, 1200 W, 1600 W and 2000 W respectively. Simulation data were validated with experimental results. The results exhibit a good agreement between simulation results and experimental data.

Joining of INCONEL-625 by microwave hybrid heating and its performance analysis

Welding is a process in joining of two or more metals which is done by using or without using of filler materials. Domestic microwave ovens have been in use since last century. Now a day’s microwave technology could be employed to process materials. The investigation is carried out to compare the performance of Joint formed by Microwave hybrid heating with respect to tungsten inert gas (TIG) welding. Radiations emitted from microwave are used to join INCONEL-625 by employing INCONEL-625 powder of grain size 40μm as interface material. Graphite, Silicon carbide (SiC) and Charcoal was used as a susceptor material. And thin graphite sheet is used as separator. Traditional TIG welding machine is used to join INCONEL625 plates with INCONEL-625 wire as filler material. Scanning electron microscope (SEM) characterization joints after welding shows complete melting of INCONEL-625 powder particles and good metallurgical bonding with surface. X-ray diffraction (XRD) reveals the formation of niobium and chromium carbides and intermetallic phases. Joining of same INCONEL-625 plates by using TIG welding has successfully conducted. The novelty of this study is to develop new material joining approach by microwave heating. The comparative study showed material diffusion in microwave hybrid heating is much greater than that of TIG welding. Weld formed by microwave heating is more effective that of TIG welding.

Characterization of Magnetic Susceptor Heating Rate Due to Hysteresis Losses in Thermoplastic Welding

Welding techniques are emerging as a new method to join thermoplastic composite parts. They present a fast and efficient alternative to adhesives and mechanical fasteners. Induction welding is a welding technique that relies on the application of an oscillating magnetic field on the joining interface, where a material called a magnetic susceptor generates heat by interacting with the applied magnetic field. In this work, susceptors relying on magnetic hysteresis losses made of polyetherimide (PEI) and nickel (Ni) particles are investigated with varying Ni concentration. The materials are mixed using an internal mixer and pressed to form films approximately 500μm thick. To characterize the heating rates of the susceptor materials, samples are placed on an induction coil – a water-cooled copper tube in which AC current (frequency 388kHz), generates an alternating magnetic field – and the temperature evolution is measured using a thermal camera. An increasing concentration of Ni particles results in increased heating rate and maximum temperature reached by the samples. The temperature-time experimental curves are compared with theoretical heating curves to verify if the model can be used to predict the temperature evolution at the joining interface during a welding process.

Challenges and opportunities in the production of sustainable hydrogen from lignocellulosic biomass using microwave-assisted pyrolysis: A review

Hydrogen is the potential future resource to cater the energy and chemical requirements. Microwave-assisted pyrolysis (MAP) could be the potential technology to obtain green hydrogen from lignocellulosic biomass waste. The proximate and elemental composition varies with the type of lignocellulosic biomass, which influences the yield of hydrogen. In MAP, the operating parameters including microwave power, heating rate, temperature, and susceptor play an important role in hydrogen production. Cellulose, hemicellulose, and lignin present in the lignocellulosic biomass undergo decomposition when they are subjected to MAP. Most importantly, the susceptor material added to the feedstock induces the plasma, which would help the cleavage of the bonds to form hydrogen gas. When the microwave power intensity is high, then the generation of hydrogen would be high. During the MAP, the formed char from the biomass would act as susceptor cum catalyst, hence it further speeds up the hydrogen generation pathways. The energy and time required for the MAP are very less compared to conventional pyrolysis. The present review manuscript would help the research community to understand the possible applications of MAP for hydrogen production.

Influence of process parameters on microhardness and porosity of Al 2024 microwave cast

A new approach to metal casting has been developed that uses microwave radiation at 2.45 GHz to melt and heat the metal. At microwave powers of 600, 800, and 1000 W, AA2024 is employed as a charge material. Three susceptor materials WC and Silicon Carbide—are used in the process, and the solidification takes place in two stages, one in a closed cavity and the other in an open one. It was discovered that tightly cast samples 15 and 9 had smaller equiaxed grains and micro indentation hardness testing. Intermetallic phases of Al2Mg3 and MgZn2 were detected in these cast samples, however, cast specimen 18 includes intermetallic stages of Al2Mg3, Magnesium Zinc, and Al2Mg3. This study discovered that the solidification atmosphere, microwave power, and susceptors affect grains and intermetallic precipitates. In this study, the micro indentation hardness (HV)of cast sample 18 is about 166 HV, larger than the other casts. The hardness, porosity, and XRD characterization of the generated casts is examined. Rapid solidification and increasing microwave power affect the composition, distribution and size of eutectic stages, leading to a rise in micro indentation hardness.

Coupled numerical modelling and experimental analysis of domestic induction heating systems

Continuous demands on resources of energy heighten the need for better and smarter use of available resources. Induction heating (IH) is a technology that is proved to be more efficient in many industrial applications compared to direct resistive heating. Also, IH can be used in domestic devices, as it provides clean and contactless regime of heating. In this paper, a fully coupled numerical approach of a domestic IH system for water boiling is presented. The approach couples the modelling of magnetic field generated in the system with both heat transfer and fluid flow phenomena. The nonlinear and temperature-dependent characteristics of materials are accounted for in the coupled numerical approach. The numerical approach is validated by experimental measurements that are implemented for four case studies. In addition, a detailed parametric study is presented to investigate the effects of different design parameters. The results provide a picture of the nonlinear, complex, transient buoyancy-driven fluid motion. It is found that the heating efficiency is highly affected by different design parameters such as susceptor material, thickness, and offset distance from the bowl base. These effects are highly nonlinear due to the inclusion of nonlinear magnetic and thermal characteristics. The results also highlight the importance of the investigation of IH systems as integrated systems, in contrast to most of existing similar studies. By this holistic approach, different thermal processes and effects of different design parameters are involved, and consequently the heating efficiency can be clearly assessed.

Comparative performance of various susceptor materials and vertical cavity shapes for selective microwave hybrid heating (SMHH)

The microwave processing of materials is gaining popularity over the past decade due to its unique heating abilities. The microwave hybrid heating (MHH) technique has effectively processed bulk metallic materials. MHH is assisted by susceptor material which forces metals to absorb microwave radiations. Further, MHH is modified to selective microwave hybrid heating (SMHH) to increase the efficiency of the process. This work examines the performance of Graphite and Charcoal susceptors with a conical vertical cavity for SMHH using FEM simulation. It is observed that the maximum temperature achieved by Graphite was 215 °C at an exposure time of 300 s, whereas, for Charcoal susceptor, it is 655 °C. Further, the effect of different vertical cavity shapes (cylindrical and conical) on the SMHH technique is presented for Charcoal susceptor. For an exposure time of 300 s, the temperature rise in the conical and cylindrical cavity is 655 °C and 319 °C, respectively. From resistive heat flow, time-temperature profile and temperature distribution, it is clear how SMHH is significantly effective for a conical vertical cavity having Charcoal susceptor. In addition, the performance of the conical vertical cavity having Charcoal susceptor was validated through experimental study. The real-time temperature profile was determined through testo 885/testo 890 thermal imaging camera. The observed maximum temperature of the susceptor after heating for 300 s was 639.9 °C.

Gas-solid contactors and catalytic reactors with direct microwave heating: Current status and perspectives

Microwave heating (MWH) transforms energy from an electromagnetic wave to heat. In contrast to conventional heating (CH) mechanisms that use slower heat transfer processes via conduction, convection or radiation, microwaves (MW) directly interact with MW susceptor materials and induce a rapid conversion of the electromagnetic energy into heat. This rapid heating provides MWH with distinct features that can be leveraged to increase conversion, selectivity and/or energy efficiency of chemical processes. Here we discuss recent significant advances reported in MWH processes involving gas-solid interactions. Special attention is devoted to key aspects such as the methodologies to accurately determine local temperatures under the influence of electromagnetic (EM). Other relevant aspects such as the consideration of the solid catalyst dielectric properties or the design of novel gas-solid contactor configurations will be discussed. Emerging aspects such as the potential of MWH to minimize secondary by-products in high temperature reactions or to efficiently perform in transient processes, e.g. adsorption-desorption cycles, are highlighted. Finally, current challenges and perspectives towards a wide application of MWH in gas solid contactors will be critically discussed.

Microstructural and mechanical properties of mild steel pipes joined using selective microwave hybrid heating

Microwave joining is an eco-friendly non-conventional technique resulting in fine grain structure, overall improvement in quality, and performance of the processed materials with up to 90 % less energy consumption than conventional processes. Due to problems including difficulty in positioning the susceptor material in the joint region and reduced solid cross-section area of hollow pipes, an efficient and precise process for microwave joining metallic pipes is yet to be developed. The present work is an attempt to join mild steel (MS) pipes placed horizontally in a conventional microwave oven. COMSOL Multiphysics software has been used to simulate the microwave joined MS pipes, wherein the temperature distribution in the specimen inside the microwave cavity was analyzed. The MS pipe was successfully joined at an exposure time of 900 s with nickel powder as an interfacial material. Characterization of the welded joint has been carried out using microstructural and mechanical properties. A fully dense and homogeneous microstructure with good metallurgical bonding was revealed through scanning electron microscopy (SEM). The Vicker's microhardness of joined specimen was 262 ± 10 HV at the joint zone, while the heat affected zone (HAZ) was 240 ± 10 HV. The joined specimen exhibited an ultimate tensile strength of 217 ± 8 MPa with an elongation of 4.4 ± 0.7 %.

Reflected impedanceometry: a contact-free technique for measuring induced magnetic hysteresis and eddy current heating

Reflected Impedanceometry is a new technique that can remotely measure the power absorbed during radiofrequency induction heating. It measures the total system impedance from the phase difference between current and voltage in the electromagnetic field work coil and uses the characteristic impedance of the work coil circuit to infer the heating power transferred into a susceptor bed. Induction heating of susceptor materials within alternating magnetic fields occurs by magnetic hysteresis, eddy currents, Néel relaxation or Brownian relaxation. It shows potential for replacing fossil fuels with renewable electricity in carbon-intensive industrial applications but requires advances in measurement techniques. Previously developed methods for measuring heating power, such as pick-up coils, are limited to applications involving magnetic materials. Results presented here show that reflected impedanceometry accurately measures heating power for both magnetic hysteresis and eddy currents, fulfilling the requirement for measuring induction heating power.

Assessment of microwave susceptors for optimum temperature rise using parametric numerical simulation

Microwave hybrid heating or indirect microwave heating has been an important development in the processing of metals using microwave energy. In this method of heating, a “susceptor” is used to absorb and convert microwave energy into thermal energy which is utilized for materials processing. Few of these processing applications are sintering, joining, cladding, casting, and composite development. However, the precise selection of a susceptor for a given process is challenging and requires a thorough understanding of the microwave heating phenomenon. In addition, predicting temperature rise in a microwave cavity is a complex task. Numerical simulation can serve to solve these two significant problems. In this work, parametric simulation of microwave heating of three major susceptor materials; silicon carbide, alumina, and coal has been carried out using a multiphysics approach. Initially, a model was developed to validate the simulation procedure. The results were in good agreement with the available data in published literature. Thereafter, the effect of microwave power, position of susceptor block, and time of irradiation on temperature rise in these materials were investigated. On comparing these susceptor blocks after altering the parametric combinations, coal exhibited the formation of hot spots and uneven temperature field with a maximum temperature of 901°C. On the contrary, the temperature attained in silicon carbide (529°C) and alumina (616°C) were lower but distributed in a relatively uniform field across the block. Regression models have also been built to correlate maximum temperature achieved with the parametric variation of parameters. It has been found that microwave power and the time of microwave irradiation have a significant coactive effect on the maximum temperature reached by the material. While the rise in the position of the susceptor block from the base leads to an adverse effect on the temperature rise. The study demonstrates that indirect microwave heating can be harnessed using the proper selection of susceptors as per the temperature requirement of the process. The regression models can be used for the accurate prediction of temperature attainment for given power input, position, and time.

A comparative study of interface material through selective microwave hybrid heating for joining metal plates

The development of joints using microwave hybrid heating (MHH) received extensive attention over conventional heating due to its uniform heating, environment friendly characteristics. For effective microwave joining of bulk metals, joint region was targeted selectively naming it as selective microwave hybrid heating (SMHH). Microwave joining of stainless steel using Nickel as interface material is explored extensively through MHH; however no comparative study showing better interface material for microwave joining of Stainless steel is reported. In the present study, SS304-SS304 lap joint is simulated for two different interface materials that are nickel and Inconel-718 for an exposure time of 22 min. These joints were developed using pulverized charcoal as a susceptor material and at the power output of 700 W. Microwave hybrid heating has been simulated by implementing different assumptions and boundary conditions at better mesh quality. A time-temperature curve, resistive heating, electric field distribution, and temperature profile along different directions are those parameters that have been discussed to examine better interface material. From the results, it is observed that Inconel-718 shows better resistive heating when compared to nickel interface material, however electric field distribution remains similar for both interface materials. Further, the time-temperature profile revealed that the time taken for Inconel-718 interface material to reach fusion zone is lesser than Nickel interface material.