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Biomass pyrolysis is the most effective process to convert abundant organic matter into value-added products that could be an alternative to depleting fossil fuels. A comprehensive understanding of the biomass pyrolysis is essential in designing the experiments. However, pyrolysis is a complex process dependent on multiple feedstock characteristics, such as biomass consisting of volatile matter, moisture content, fixed carbon, and ash content, all of which can influence yield formation. On top of that, product composition can also be affected by the particle size, shape, susceptors used, and pre-treatment conditions of the feedstock. Compared to conventional pyrolysis, microwave-assisted pyrolysis (MAP) is a novel thermochemical process that improves internal heat transfer. MAP experiments complicate the operation due to additional governing factors (i.e. operating parameters) such as heating rate, temperature, and microwave power. In most instances, a single parameter or the interaction of parameters, i.e. the influence of other parameter integration, plays a crucial role in pyrolysis. Although various studies on a few operating parameters or feedstock characteristics have been discussed in the literature, a comprehensive review still needs to be provided. Consequently, this review paper deconstructed biomass and its sources, including microwave-assisted pyrolysis, and discussed the impact of operating parameters and biomass properties on pyrolysis products. This paper addresses the challenge of handling multivariate problems in MAP and delivers solutions by application of the machine learning technique to minimise experimental effort. Techno-economic analysis of the biomass pyrolysis process and suggestions for future research are also discussed. [ABSTRACT FROM AUTHOR]

The prime objective of the current research work was to understand the role of microwave-assisted pyrolysis for the upgradation of expanded polystyrene (EPS) waste into valuable aromatic hydrocarbons. Ethyl acetate solvent was used to dissolve the EPS to enhance the homogeneous dispersion of EPS with susceptor particles. Biochar obtained from the pyrolysis was used as a susceptor. The design of experiments method was used to understand the role of microwave power (300 W, 450 W, and 600 W) and susceptor quantity (5 g, 10 g, and 15 g) in the pyrolysis process. The pyrolysis was conducted till the temperature reached up to 600 °C, and this temperature was achieved in the time interval of 14–38 min based on the experimental conditions. The obtained average heating rates varied in the range of 15 to 41 °C/min to attain the pyrolysis temperature. The EPS feed was converted into char (~ 2.5 wt.%), oil (51 to 60 wt.%), and gaseous (37 to 47 wt.%) products. The specific microwave energy (J/g) was calculated to know the energy requirement; it increased with an increase in susceptor quantity and microwave power, whereas specific microwave power (W/g) was a function of microwave power and increased from 15 to 30 W/g. The predicted values calculated using the model equations closely matched the actual values showing that the developed model equations via optimization had a good fit. The obtained pyrolysis oil physicochemical properties including viscosity (1 to 1.4 cP), density (990 to 1030 kg/m3), heating value (39 to 42 MJ/kg), and flash point (98 to 101 °C) were thoroughly analyzed. The pyrolysis oil was rich in aromatic hydrocarbons and it was predominantly composed of styrene, cyclopropyl methylbenzene, and alkylbenzene derivates. [ABSTRACT FROM AUTHOR]

In this study, a novel multifunctional film known as susceptor, containing silver nanoparticles, was proposed to improve the induction welding performance of unidirectional carbon fiber-reinforced polyetherketoneketone (CF/PEKK) thermoplastic composites. A group of Ag/PEKK films was synthesized with different amounts of silver nanoparticles. Good thermal performance was obtained, including the maximum temperature and thermal growth time constant, leading to the selection of films with 60 wt.% and 70 wt.% silver nanoparticles. In addition, the mechanical performance was evaluated for single-lap joints fabricated with the selected films and stainless-steel mesh. Specifically, the highest interlaminar shear strength and single-lap shear strength of 25.2 MPa and 20.9 MPa, respectively, were achieved with a susceptor containing 60 wt.% silver nanoparticles. The mechanism of these increases in thermal and mechanical performance is discussed using numerical and experimental methods (non-destructive test and optical microscope observation). In conclusion, the multifunctional heating film incorporated into the adhesive can improve the thermal and mechanical efficiency of single-lap joints of thermoplastic composites fabricated using the induction welding method. [ABSTRACT FROM AUTHOR]

Production of dissimilar weldments using microwave hybrid heating is currently gaining immense impetus in the field of advanced welding. This is because such heat source could provide benefits like cost-effectiveness, rapid, volumetric, uniform and selective heating, and efficient throughput which would be significant to various industries. Till-date researchers have carried out joining of dissimilar general purpose engineering materials using microwave hybrid heat source. But attention has not been paid on the joining and characterization of dissimilar exotic-general purpose materials using the aforementioned heat source and the promising applications of the weldments. Therefore, the present article is focused on the joining of dissimilar materials- Inconel 625 and SS 304 alloys using selective microwave hybrid joining (SMHJ) technique. In SMHJ, nickel-based powder is used as a filler material, Silicon carbide (SiC) block and SiC powder are used as susceptor to increase the initial temperature. The developed weldments through SMHJ are characterized using various physico-chemical diagnostic methods. The results reveal the average micro-hardness of joint was found to be 303 ± 17 HV owing to the presence of various carbides and nitrides phase like NbC, Cr23C6, Cr2Ni3, Ni8Nb, and Fe3Ni2 in the joint zone which is evident from XRD. The average UTS of the joints found to be 448.6 MPa with an elongation of 10.93% and flexural strength observed to be 435 MPa. Further, fractography study reveals, the joint regions have mixed mode of failure. The failure was attributed to the existence of secondary phases in the joint zone. [ABSTRACT FROM AUTHOR]

The utilization of microwave hybrid heating in the field of low-temperature joining presents a notable benefit of delivering both selective and uniform heating, a feature that is not commonly observed in traditional welding methods. This work utilized numerical simulation to predict the heating effects of three susceptors. Furthermore, the impacts of susceptor variants on the interface morphology, mechanical properties, and fracture morphology of the Sn-3.0 Ag-0.5 Cu joint were studied. In the current study, the normal MHH technique was utilized with parameters of 900 W and 240 s to achieve successful joint production. According to the numerical simulation, the heating rate of carbon powder as a susceptor was found to be greater than that of graphite, while silicon carbide susceptor exhibited the slowest heating rate. Nevertheless, the combustion of carbon powder during the MHH process poses a potential risk to the integrity of the microwave cavity. As a result, graphite powder was selected as a more suitable susceptor. The experimental findings indicate that the shear strength of the joint with silicon carbide and charcoal as the susceptor is 75.4 % and 91.0 % of that with graphite as the susceptor, respectively. The fracture modes of the three samples with various susceptors are mixed fracture.

This paper aims to focus on the current developments of Microwave Hybrid Heating (MHH) as a promising alternative method in soldering, characterization of solder joint properties related to the MHH and comparison with the conventional methods. A brief introduction to conventional heating, microwave heating and the concept of MHH in soldering is described in the earlier topic of this review. Further investigation on wettability, phase, and structural evaluation, interfacial intermetallic compounds (IMC) morphology, and tensile properties are presented and discussed in parallel with previous work (in the last decade) and the current works. The essential value of this review is to provide an in-depth understanding of MHH for an alternative soldering approach by compiling all the most recent research, technical setup, and key discoveries. This helps the electronic packaging sector, which is dealing with difficulties in meeting the growing demands for downsizing and adding multifunctionality in a single electronic device. Hence, any necessary advancement in this sector will help in future efforts to advance the soldering industry.

The susceptor and susceptor thickness significantly influence the microwave heating process. This work theoretically investigates the effects of two different susceptors with various thicknesses on microwave heating of raw meat. A susceptor with low dielectric loss (alumina) and a susceptor with high dielectric loss (SiC) are used for present study to investigate the effect of dielectric loss during microwave heating. The addition of the alumina susceptor either enhances or diminishes the heating rate of resonating samples depending on thickness, while the addition of the SiC susceptor improves the heating uniformity of resonating samples. The addition of susceptors on thick samples shows different characteristics from resonating samples. High heating rate and heating uniformity are the two major criteria for several microwave heating applications. Hence, the optimum susceptor thicknesses for specific sample dimensions are determined based on either high heating rate or heating uniformity. [ABSTRACT FROM AUTHOR]

Microwave energy heating is one of the methods to improve product quality, faster processing, eco-friendliness, and cost and energy savings. The unique heating ability leads to explore this heat treatment method by exploiting its process parameters to improve its effectiveness. This research aimed to predict the effect of microwave heat treatment on aluminium alloy 6063-T6 sheets using fuzzy logic. Microwave heat-treatment trials are designed using the Design of Experiment (DOE) method. The input parameters are heating time, susceptor, and insulator. The non-heated and heated aluminium 'specimen's mechanical properties have been tested using a hardness and tensile testing machine. The experimental results are used to develop a Mamdani fuzzy logic model system. The results indicate that the mechanical properties in terms of tensile Load, and hardness of the specimen have improved after being microwave heat-treated for a short time. The susceptor material and insulator can assist in the microwave processing of materials. The percentage difference between the experimental and simulation values are 0.27 and 6.31%, respectively, for tensile Load and hardness. The experimental and predicted results are still compatible with a small percentage of errors. The fuzzy model can be used to predict the parameters.

An intermediate stage in the net casting that can potentially limit the features of the final metallic product, called dewaxing, is highly dependent on features of pattern wax. The general process of dewaxing, involved in investment casting for the reuse of the wax, requires a high amount of energy and entails high processing time through conventional heating methods thus resulting in a lower rate of processing at a bulk scale production. In this research, the pattern wax blends, containing polyethylene, ethylene–vinyl acetate, bitumen, and paraffin wax, were investigated for their microwave processing time in the presence of susceptor material (polyaniline). Polyaniline in wax blends was incorporated as a microwave susceptor in concentrations of 0.15, 0.45, 0.75, 1.5, 3, 5, and 10 wt%. Advancements in processing properties of pattern wax blends, using microwave dewaxing technology, were observed along with the improvement in melting behavior of pattern wax blends owing to the creation of heat-sensitive sites due to the addition of a susceptor. The decrease in complete flow time was observed from 202 to 55 s by the addition of 10 wt% of polyaniline in wax. A ceramic die and stand to hold the die at a hotspot in microwaves were designed for experiments. FTIR-ATR, rheological, TGA, DSC, mechanical (UTM), and morphological analysis (SEM and OM) were performed to investigate the behavior of pattern wax blends under the application of microwave heating. An inverse trend was observed in processing time with susceptor loading in microwaves. [ABSTRACT FROM AUTHOR]

Microwave energy heating is one of the methods to improve product quality, faster processing, eco-friendliness, and cost and energy savings. The unique heating ability leads to explore this heat treatment method by exploiting its process parameters to improve its effectiveness. This research aimed to predict the effect of microwave heat treatment on aluminium alloy 6063-T6 sheets using fuzzy logic. Microwave heat-treatment trials are designed using the Design of Experiment (DOE) method. The input parameters are heating time, susceptor, and insulator. The non-heated and heated aluminium 'specimen's mechanical properties have been tested using a hardness and tensile testing machine. The experimental results are used to develop a Mamdani fuzzy logic model system. The results indicate that the mechanical properties in terms of tensile Load, and hardness of the specimen have improved after being microwave heat-treated for a short time. The susceptor material and insulator can assist in the microwave processing of materials. The percentage difference between the experimental and simulation values are 0.27 and 6.31%, respectively, for tensile Load and hardness. The experimental and predicted results are still compatible with a small percentage of errors. The fuzzy model can be used to predict the parameters. [ABSTRACT FROM AUTHOR]

As a new non-contact heating technology, induction heating technology has very broad application prospects in the field of fluid food heating. However, its application is inevitably affected by the heat concentration caused by uneven energy distribution. The uneven temperature distribution of the heating process will lead to the decrease in the quality of heating products. Therefore, based on the previous research, in order to improve the uniformity of heat distribution in the heating process, this study selected the susceptor with the greatest potential for efficient and the most uniform heating fluid to carry out the coupling simulation of electromagnetic heat transfer. The susceptor was simulated and optimized in three aspects: different power comparisons, the influence of structural change on temperature distribution uniformity, and the influence of physical property change of metal material on temperature distribution uniformity. The results show that the simulation results are in good agreement with the experimental results, and the error between the experimental and simulation values of the outlet temperature at Kelvin temperature is less than 0.18%. The change of geometric structure had a great influence on the uniformity of temperature distribution, and the uniformity of temperature distribution was inversely proportional to the conductivity. During the simulation, the temperature of the fluid heated by the susceptor was increased from 284.75 K to about 333K. The temperature distribution of the fluid at the outlet of the susceptor was uniform, and the temperature difference was about 1 K. [ABSTRACT FROM AUTHOR]

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 N p /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. [Display omitted] • Experimental & simulation used to estimate potential of various susceptors for effective microwave heating. • Polarization mechanisms for effective microwave heating of various susceptors discussed. • Microwave absorption properties & utilization efficiency quantitatively shown by COMSOL. • Among all susceptors, porous nitride-bonded SiC exhibited the maximum heating rate (97.73 °C/min). • Highest energy utilization efficiency (95 %) obtained with porous nitride-bonded SiC susceptor. [ABSTRACT FROM AUTHOR]

Due to their excellent dielectric properties and the rapid response to microwave irradiation, silicon carbide nanowhiskers (SiCNWs) were employed as microwave susceptor in this study to absorb microwave and locally melt the surrounding polypropylene (PP) substrates for the joining of PP substrates. Complete welded joint is formed after the melted PP was cooled and resolidified. Other than microwave susceptor, SiCNWs also acted as the nanofillers in strengthening the welded joint through the formation of SiCNWs reinforced PP nanocomposite at the interface of PP substrates. Besides, the effect of microwave power on the microwave welding of PP substrates using SiCNWs as susceptor was studied and reported. It was found that the tensile strength and modulus of elasticity of the welded joint improved as microwave power increased. However, it deteriorates the flexibility of the welded joint as high stiffness SiCNWs were incorporated deeper into the PP matrix which restricted the PP chain mobility. Aside from microwave power, clamping pressure is also critical in determining the mechanical properties of a welded joint. When compared to unclamped welded joint, the tensile strength, modulus of elasticity and flexibility of welded joint subjected to clamping pressure improved drastically. Moreover, the tensile strength of welded joint increased when the clamping pressure was increased from P1 to P3, but decreased when the clamping pressure was further increased to P4 due to the occurrence of flashing at welded joint. The formation mechanism of SiCNWs reinforced PP welded joint was also proposed in this study. Compared to conventional welding, this welding process is easy, straightforward and is able to produce welded joint with outstanding mechanical properties via precise controlling of the processing parameters. Thus, microwave welding is thought to offer an option for the joining of thermoplastics and other applications. [ABSTRACT FROM AUTHOR]

In the current study, metal matrix composites of iron-based alloy (SS316) are successfully cast by the application of a novel processing route of microwave hybrid heating (MHH). The castings of iron-base alloy (SS316) powder and reinforced with 10 wt.% EWAC1004 (Ni-based) + 3 wt.% WC-12Co are developed in the domestic microwave oven power of 900 W and frequency 2.45 GHz. The mechanical and metallurgical properties of the prepared casts are investigated. The value of the mean particle size of the powder used is found to be 40 μm. Scanning electron microscopy (SEM), optical microscopy (OM), X-Ray diffraction (XRD), and Vickers's microhardness tester are used for the characterization of so developed composites samples. The microstructure is reported as elongated columnar grains or lathlike structure with uniform melting of the iron-based (SS316) matrix has been achieved. The XRD confirmed the presence of typical carbides and intermetallic. The average micro-hardness of the reinforced composites is reported as 420 ± 90 HV0.3. The achieved microhardness of cast samples is 2 times the commercially received SS316. The micro-hardness obtained on the surface of the carbide phase is 648.16 HV0.3. The porosity of the prepared cast is found to be less than 2% which is approximately 3 times less as compared to commercially received SS316. The relative density of the microwave cast SS316 without reinforcement is found to be maximum with the value of 98%. The value of grain size of the microwave-casted composite samples is reduced to 23 microns (μm) [ABSTRACT FROM AUTHOR]

Valuable renewable carbon biorefinery products can be obtained by using agro-residual biomass as a feedstock. Bio-oil, gas, and char products can be obtained from Microwave-assisted pyrolysis (MAP) by converting agro-residual waste. In MAP, the process variables like microwave power, temperature, heating rate, raw materials, susceptors, and catalysts play an important role to alter the product spectrum. The temperature, heating rate, and pyrolysis time can be tuned to obtain the desired products during biomass decomposition. The obtained carbonaceous products can be used as intermediated feedstocks to synthesize a variety of end products. Hence, in this review, the application of MAP for the conversion of agro-residual waste is discussed. Special focus is given to the interaction of microwaves with susceptors. This manuscript provides background, current status, progress, and future scope of MAP technology for waste valorization. The objectives of the review are to address (i) The necessity of environmental protection, (ii) The role of biorefinery in the biomass conversion, (iii) The advancements in the MAP for the resource recovery, (iv) The mechanism of heat generation from microwaves, (v) The effects of process parameters, susceptors, and catalysts in MAP, (vi) The interactions of biomass and susceptors during the pyrolysis, (vii) The formation of valuable renewable carbon products and (viii) The future scope and challenges for the integration of MAP in solid waste management. [Display omitted] [ABSTRACT FROM AUTHOR]

In microwave (MW) sintering, samples directly heat by absorption of the electromagnetic field, leading to a fast volumetric heating. Thus, the materials are heated thanks to their own dielectric properties. In multimode cavities, samples are always heated with a sintering cell in order to get an insulation of the samples and a heating homogeneity. However, to date, very limited research has been carried out to study the effects of materials used in the sintering cell. In this paper the microstructure and densification of Al 2 O 3 and 3Y-TZP were investigated and compared between three different sintering cells. The used sintering cell contains three main elements: thermal insulators, a SiC susceptor and a protective mullite tube. Higher final densities (98.3 ± 0.6% and 98.6 ± 0.6% of T.D. for Al 2 O 3 and 3Y-TZP respectively), lower densification temperatures and better microstructure homogeneity were obtained by using the sintering cell containing both mullite tube and SiC susceptor. But, sintering using the sintering cell without the SiC susceptor was also possible, especially for the lowest lossy material, i.e. , Al 2 O 3. This can be explained by a possible susceptor effect of the mullite tube. However, the microstructural observations showed a difference of homogeneity in the microstructure for Al 2 O 3 and 3Y-TZP with some sintering cells. It can be linked to the difference of dielectric properties of the two materials. The influence of the sintering cell is less critical for 3Y-TZP, which couples better with MW than Al 2 O 3. It was also observed that densification curves were switched to higher temperatures during sintering with the presence of SiC susceptor and without mullite tube. These results were justified by an error in the temperature measurement of the IR-pyrometer. [ABSTRACT FROM AUTHOR]

In contrast to conventional casting, casting using in situ microwave route is an advanced and promising technique of bulk metal casting wherein bulk metal is heated and melted in microwave radiations at 2.45 GHz. In this present work, AA-6063 is used as a charge material at three microwave powers of 600 W, 750 W and 900 W. The process uses three susceptor materials—stone charcoal, wood charcoal and SiC—and solidification is done at two levels as closed and open cavity. The optimization of the process parameters has been done through Taguchi technique. Microstructure and microindentation hardness studies of the developed casts divulged that smaller equiaxed grains could be obtained in densely cast samples 15 and 9. In these cast samples, the presence of intermetallic phases of Al2Mg3, MgZn2, Mg2Si, Al2Mg was observed; however, the cast sample 18 contains intermetallic phases of Al2Mg, MgZn and Al2Mg3. It was found from this work that the grain structure and intermetallic precipitates in the developed cast depend primarily on solidification environment, microwave power and susceptors. Microindentation hardness of the cast sample 18 in the present study was about 166 HV that is higher than the other developed casts. The characterization of developed casts in terms of microstructure, elemental analysis, porosity, XRD and fractography is analyzed. The results reveal that the rapid solidification and increased microwave power alter elemental composition, distribution and size of eutectic phases resulting in increase in the microindentation hardness. [ABSTRACT FROM AUTHOR]

The microwave-assisted conversion of municipal solid waste (MSW) into value-added products would be a promising option to tackle MSW piles. The present work was intended to understand the effect of microwave power (300,450, and 600 W) and graphite susceptor loading (10, 30, and 50 g) on MSW valorization. Response surface methodology was used to analyze the impact of input variables on product yields and energy consumption. The heating rate increased, and microwave energy consumption decreased with the increase in microwave power. An increase in susceptor quantity resulted in a reduction in heating rates and also energy consumption. Nearly 84-88 wt% of MSW was converted into gases (42-60%), oil (26-42%), and char (12-16%) products. The carbon number distribution of oil fraction is in the range of C5 to C20 with a high yield of carbon content (74-91%). A high yield of aromatic hydrocarbons (84.5%) was obtained at 600 W microwave power and 30 g of the susceptor. The char fraction is rich in carbon content (80-90%) with a reasonable pore area (111-152 m²/g). This work demonstrated the feasibility of MSW upgradation into value-added chemicals, materials, and energy-rich fuel products. [ABSTRACT FROM AUTHOR]

This article deals with the investigations on mullite ceramics formation from Kyanite sample- an alumino-silicate mineral with microwave heating. In the present investigation kyanite was heated in microwave sintering furnace with calcined alumina, silicon carbide, zirconium dioxide and binder for mullite formation as well as for the preparation of zirconia toughened mullite product. The results of these studies reveal that how a small amount of zirconium dioxide helps in toughening the mullite formation for refractory and ceramics applications. The results shows that microwave heating method is one of the most novel and eco-friendly process for such toughened mullite formation, well within very short period of time. The observations with mullite formation and zirconia toughened mullite formation were observed with the structural data using X-ray diffraction data, field effect scanning electron microscope and energy dispersive spectroscopy. Future studies are still in process. [ABSTRACT FROM AUTHOR]

The feasibility of fabrication of 304 stainless steel through microwave energy using new technique which includes susceptor is conveyed throughout this paper work. The intersection was welded in household IFB microwave oven multimode operated at frequency of 2.45GHz and 900W. Mixture of Nickel-cobalt based fine powder with resin was placed uniting the clean surfaces and using the atmospheric conditions, samples were exposed to microwave radiation for obtaining the joint. Welded joints were analysed by tensile test, X-ray diffraction (xrd) for intermetallic compounds, Micro structural analysis, Field emission scanning electron microscopy (Fe-sem), Porosity test, Micro hardness test and surface temperature measurement. Tensile strength found 390Mpa which is about 70% of the base metal. Micro structure images showed the welded edges were fused properly & got melted on sides of the parent material and porosity found to be negligible through Fe-sem result. The average observed microhardness on weld metal area and base metal were to be 65-66 HRB and 71-72 HRB respectively. The surface temperature of weld zone area was found to be 926oC. [ABSTRACT FROM AUTHOR]

The joining of aluminum (Al) to magnesium (Mg) alloys is a challenge due to the detrimental effects of formation of hard and brittle intermetallic compounds. This work investigates the joining of AA6061-T6 to AZ31B by microwave hybrid heating using zinc (Zn) powder, especially in the effect of susceptors on microstructure. It was observed that formation of Al-Mg intermetallic compounds was hindered, and a good metallurgical joint was achieved. A distinct reaction zone was formed between the Zn interlayer and AZ31B. The use of graphite susceptor exhibited faster joint formation than when activated charcoal was used. However, graphite susceptor formed irregular reaction zone, whereas activated charcoal produced an uniform reaction zone. Elemental analysis concluded the formation of a solid solution of Mg + MgZn on the reaction zone. The width of the Mg-Zn reaction layer increased with the increase in microwave exposure time. Toward the AA6061- Zn faying surface of the interlayer, a Zn solid solution was formed having no intermetallic compounds and no reaction layer. Zn solid solution zone compromised the mechanical strength of the joint. The optimum value of microwave exposure time, clamping pressure and epoxy% was studied to achieve the highest joint strength. [ABSTRACT FROM AUTHOR]

This research develops a specific methodology for de-waxing and firing refractory lining molds to obtain cast jewelry pieces using microwave technology. These processes, in the traditional technique, require slow and progressive thermal curves with a duration of 7 to 12 h using electric muffles. The hypothesis of this proposal is based on the fact that the 40 % of water necessary for the elaboration of refractory pastes is a perfect ally for an effective dielectric heating by microwaves and, therefore, this technology would be viable for the production of metal jewelry. In order to carry out the study, it was necessary to design a method based on appropriate time/power ramps so that these negatives gradually lose the contained water, without the thermal expansion generating cracks or crumbling of the mold due to non-uniform humidity profiles. In the research it was determined that microwave heating is effective for these compounds, however, with advanced dehydration, their microwave absorption capacity is exponentially devaluated, making it essential to use a susceptor that makes it possible to increase their temperature. For this purpose, a muffle doped with SiC was fabricated to subject the samples to hybrid microwave heating after dehydration, making it possible to design gradual thermal curves until the firing was completed. The quality of the thermal processing was evaluated by subjecting the samples to mechanical stress using a centrifugal machine for the injection of the molten metal. At the end of the study, 99 % wax collection and effective recording quality for artistic models were obtained with a reduction of 66 % with respect to the time used in the traditional technique. The results of this research demonstrate that the viability of microwaves as an energy source contributes to simplify and economize the production of metal jewelry [ABSTRACT FROM AUTHOR]

This study is focused on creating value addition to kitchen waste (KW) by converting it into valuable product resources via microwave pyrolysis. The effect of the following on product yields and energy efficiency were examined in this study: (i) microwave power (140–700 W), (ii) KW: susceptor ratio (20:0 to 20:20 (g/g)), and (iii) pyrolysis temperature (200–600 °C). The KW was pyrolyzed without the addition of a susceptor and char formed during pyrolysis acted as a susceptor and enhanced pyrolysis energy efficiency (78%). An increase in microwave power has significantly increased the heating rate from 4 to 85 °C/min, and KW has produced 73 wt% of bio-oil and gases even at low microwave power (140 W). An increase in pyrolysis temperature promoted thermal cracking of KW, which resulted in decreased char yields (64–27 wt%), and an increase in gas yields (12–45 wt%). Bio-oil contains a significant amount of phenolics (35–50%) and its selectivity varied significantly with the variables probed. The selectivity of furan derivatives has dramatically decreased from 45 to 20% with the increase in pyrolysis temperature. This work demonstrated the feasibility of valorization of kitchen waste into various value-added products. [Display omitted] s [ABSTRACT FROM AUTHOR]

The current work is focused to investigate the synergetic interactions between biomass (groundnut shell, bagasse, rice husk, Prosopis juliflora, mixed wood sawdust) and hydro-rich plastics (Low-density polyethylene (LDPE) and Polyisoprene (PIP)) in microwave co-pyrolysis. The heating value of co-pyrolysis oil (38–42 MJ kg−1) was enhanced dramatically compared to biomass pyrolysis oil (20–28 MJ kg−1). Among biomasses studied, the energy yield of bio-oil obtained from rice husk with LDPE mixture is higher (42%). Whereas bio-oil from polyisoprene and groundnut shell mixture has the highest energy yield (78%). Each gram of co-pyrolysis feedstock consumed 12–18 kJ of incident microwave energy. An increase in overall energy efficiency in co-pyrolysis (62–70%) is observed compared to that of biomass pyrolysis (46–57%). Actual mass yield (31–47 wt%) of co-pyrolysis bio-crude is lower than its predicted value (42–57 wt%) due to the formation of lighter gases. In the combinations of and hydrogen-rich plastics considered in this study, it was found that co-pyrolysis of LDPE: bagasse has produced bio-crude with the highest yield of aliphatic hydrocarbons (25.78%), and co-pyrolysis of LDPE: rice husk has produced bio-crude with high selectivity of aromatics (11.7%). The extent of de-oxygenation was promoted in the co-pyrolysis due to synergy. [Display omitted] • Superior quality bio-crude (38–42 MJ kg−1) was obtained via co-pyrolysis. • Co-pyrolysis promoted high yield of hydrocarbons (29% and 56%) in the liquid fraction. • High oil energy yield (∼42%) with bagasse/rice husk co-pyrolysis with LDPE was obtained. • High energy yield oil (78%) was obtained with PIP and groundnut shell co-pyrolysis. • Energy efficiency of co-pyrolysis (63–68%) is higher than biomass pyrolysis (51–57%). [ABSTRACT FROM AUTHOR]

We present a new approach to the study of microwave efficiency (MW) and microwave susceptors in the process of obtaining high quality nanopowders. Susceptors accelerate the processing of various poorly absorbent materials in the microwave field, reduce processing time and energy consumption. We calculated the electric field by a three-dimensional modelling of a microwave applicator designed to obtain nanopowders. The main objective is to optimize the technology of nanopowder production, by using raw materials and catalysts to ensure low processing temperatures. The performance of nanopowders was evaluated by physical-chemical, morphological, phase methods. [ABSTRACT FROM AUTHOR]

This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X‐ray fluorescence, loss on ignition (LOI), X‐ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre‐sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X‐ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. [ABSTRACT FROM AUTHOR]

[Display omitted] Petroleum refining generates hazardous sludge with polyaromatic hydrocarbons and heavy metals. The main objective of the study was to evaluate the performance of microwave pyrolysis for the recovery of oil from furnace oil sludge. The characteristics of furnace oil tank bottom sludge such as pH, moisture, viscosity, and volatile hydrocarbon content were determined. Thermal Gravimetric Analysis has been done to determine the cracking and degradation range of oily sludge. Gas Chromatography-Mass Spectrometry was used to fingerprint the hydrocarbon. Pyrolysis experiments were conducted in lab-scale pyrolysis set up with different susceptors and sludge in a specific weight ratio. The process parameters like microwave power, sludge: susceptor ratio were optimized to increase the oil yield. Graphite mixed sludge in 1:5 ratio at 450 W power shown higher oil yield. The calorific value of oil and char were determined as 44,442.9 and 16,686.58 kJ /kg. Physicochemical characteristics of oil such as flash point, density, and kinematic viscosity are 94 °C, 874.9, kg/m3, and 4.063 cSt. Cetane index and sulfur content were measured as 40.9, 6.85 g/kg respectively. The gas analysis had shown the presence of H 2 , CO 2 , CO, and CH 4 compounds. Char contains a higher percentage of carbon, Fe, Al, Ni, Pb, Cd, and S compounds. [ABSTRACT FROM AUTHOR]

Despite manufacturers' goal of molding single component products from plastics, the structures of some of the products are far too complex to be molded as a single piece. Therefore, assembly of subcomponents into the final products is important for the manufacturing of many plastic-based products. To date, welding is the most efficient joining method for plastics. In this study, multiwalled carbon nanotubes were proposed as the susceptor for the microwave welding of high-density polyethylene considering multiwalled carbon nanotube is a good microwave absorber. multiwalled carbon nanotubes were first dispersed in ethanol in an ultrasonic bath to obtain a homogeneous dispersion. Multiwalled carbon nanotubes dispersion was dropped on the targeted area of the prepared dumbbell-shaped sample and dried in an oven at 45°C for 30 min. The sample was then subjected to 800 W microwave irradiation in the domestic microwave oven. The strength of the weld was tested by using tensile testing. Besides, the cross section of the welded joint was characterized by using scanning electron microscopy. The effect of microwave heating duration and the multiwalled carbon nanotube concentration in the dispersion were studied. It was found that the joint strength increased as the heating duration increase from 2 s to 8 s but decreased when the heating duration was further extended to 10 s. Scanning electron microscopic images showed that voids were formed at the joint interface when 10 s was used and resulted in the lowering of joint strength. In the study of the effect of the multiwalled carbon nanotube concentration in the dispersion, joint strength increased when the multiwalled carbon nanotubes concentration increased from 0.25 wt% to 0.75 wt%. However, the joint strength of sample with 1.00 wt% multiwalled carbon nanotube concentration decreased. The presence of a thick unwelded multiwalled carbon nanotubes layer at the joint interface for sample with 1.00 wt% multiwalled carbon nanotubes concentration as shown in scanning electron microscopic image was believed to cause the lowering of joint strength. [ABSTRACT FROM AUTHOR]

Crude oil sludge is one of the key waste streams of the refinery, and it contains valuable hydrocarbons that can be potentially converted to fuels and petrochemicals. This study is unique in evaluating the effects of activated carbon susceptor (ACS) and catalysts to selectively recover hydrocarbons from crude sludge via microwave-assisted pyrolysis (MAP). Two different sludge samples received from the refinery, viz., sludge from storage tank bottoms (sludge 1) and mixed sludge (sludge 2), were characterized. Sludge 1 was rich in volatile matter and hydrocarbons, while sludge 2 contained a significant amount of ash, nitrogen, sulfur and iron. At 600 W microwave power with 10 % ACS loading, maximum oil yield of 87.3 wt.% was obtained from sludge 1, while it was 41.2 wt.% from sludge 2. An increase in yield of gaseous products with a concomitant decrease in oil yield was observed when the sample heating rates were increased by using high microwave power or high loading of ACS. MAP of crude sludge at 600 W with 10 % ACS produced char and oil with higher heating values (HHV) of 26 and 42.4 MJ kg−1, respectively. For the first time, ex situ catalytic upgradation with H-ZSM-5 and regenerated fluid catalytic cracking (FCC) catalyst was employed to produce refinery blendstocks from crude sludge through MAP. Catalytic upgradation resulted in significant deoxygenation of pyrolysates with low oxygen content (<5%), and high carbon (80−85 wt.%) and hydrogen (12−14 wt.%) content in the oil fraction. The HHV of the upgraded oil was 44−45 MJ kg−1. Importantly, the selectivity to hydrocarbons in the diesel range (C8 to C20) increased by more than 10 % in the oil fraction containing paraffins, iso-paraffins, and aromatic hydrocarbons. This study proves that a liquid fuel, resembling refinery blendstock, can be generated from crude oil sludge by adopting this process. [ABSTRACT FROM AUTHOR]

In the present study, 17 wt % TiN reinforced α-β SiAlON composites were sintered at low temperature by susceptor-assisted microwave heating. The effect of TiN addition on dielectrical properties of starting powders, as well as the influence of sintering temperature on phase evolution, microstructure development and mechanical properties of α/β-SiAlON-TiN composites were investigated. The obtained results showed that TiN addition increased the microwave absorbing properties which is reflected in the peak sintering temperature. Thus, the α:β ratio decreased and mechanical properties were improved, especially the fracture toughness of the composites. Furthermore, an estimate of energy consumption during microwave assisted sintering at the laboratory scale is presented. As a result, the highest values for relative density (97.1%), Vickers hardness (13.35 ± 0.47 GPa), and fracture toughness (7.52 ± 0.54 MPa m1/2) were obtained by microwave sintering for 30 min at 1300 °C. Image 1 [ABSTRACT FROM AUTHOR]

Despite manufacturers' goal of molding single component products from plastics, the structures of some of the products are far too complex to be molded as a single piece. Therefore, assembly of subcomponents into the final products is important for the manufacturing of many plastic-based products. To date, welding is the most efficient joining method for plastics. In this study, multiwalled carbon nanotubes were proposed as the susceptor for the microwave welding of highdensity polyethylene considering multiwalled carbon nanotube is a good microwave absorber. multiwalled carbon nanotubes were first dispersed in ethanol in an ultrasonic bath to obtain a homogeneous dispersion. Multiwalled carbon nanotubes dispersion was dropped on the targeted area of the prepared dumbbell-shaped sample and dried in an oven at 45°C for 30 min. The sample was then subjected to 800W microwave irradiation in the domestic microwave oven. The strength of the weld was tested by using tensile testing. Besides, the cross section of the welded joint was characterized by using scanning electron microscopy. The effect of microwave heating duration and the multiwalled carbon nanotube concentration in the dispersion were studied. It was found that the joint strength increased as the heating duration increase from 2 s to 8 s but decreased when the heating duration was further extended to 10 s. Scanning electron microscopic images showed that voids were formed at the joint interface when 10 s was used and resulted in the lowering of joint strength. In the study of the effect of the multiwalled carbon nanotube concentration in the dispersion, joint strength increased when the multiwalled carbon nanotubes concentration increased from 0.25 wt% to 0.75 wt%. However, the joint strength of sample with 1.00 wt% multiwalled carbon nanotube concentration decreased. The presence of a thick unwelded multiwalled carbon nanotubes layer at the joint interface for sample with 1.00 wt% multiwalled carbon nanotubes concentration as shown in scanning electron microscopic image was believed to cause the lowering of joint strength. [ABSTRACT FROM AUTHOR]

Hydropower plants are experiencing huge revenue losses due to the failure of hydro turbines caused by cavitation. Surface modification could be a feasible solution to tackle this problem. Microwave processing of metallic materials to coat/clad has gained popularity in recent years. In the current study, microwave exposure time by analyzing susceptor temperature is optimized to get sound clads. Nickel-based and Cr3C2-reinforced clad on SS-316 substrate is developed for cavitation erosion resistance. The clads have been developed in a domestic microwave oven of 2.45 GHz and 900 W. The Ni + 30% Cr3C2 developed clad has been characterized through various standard mechanical and metallurgical techniques like X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, Vicker's micro-hardness, porosity measurement, and flexural study. The presence of various carbide and intermetallic phases Cr2Ni3, Cr7C3, CrSi, SiO2, and FeNi3 is confirmed from the X-ray diffraction pattern. The distribution of hard carbide phases into soft matrix is confirmed from the microstructural investigation. Vicker's microhardness study confirms the enhanced average microhardness of the clad region by 2.5 times of the substrate. The analysis of porosity shows significantly less (0.98%) porosity. The flexural study of developed clads by using three-point bending test is evaluated and flexural strength and deformation index values of developed clads of 814 ± 11.5 MPa and 2.29 × 10−4 mm N−1 respectively are observed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Graphene oxide (GO) was reduced by a hybrid microwave heating (HWH) method. • The C/O atomic ratio of GO increases from 1.8 to 17.84 in HWH process. • More relative amount of carboxyls and epoxides can be removed in HWH process. • The high reduction efficiency is attributed to a mixed heating mode in HWH process. • The reduction efficiency is affected by the mass ratio of susceptor to GO. Abstract Due to the poor microwave absorption ability of graphene oxide (GO), direct reduction of GO by solid-state microwave irradiation is inefficient. In this study, GO was reduced effectively by a hybrid microwave heating (HWH) method by using mildly reduced graphene oxide (MG) membrane as a external susceptor, in which MG was obtained by annealing of GO at 300 °C for 1 h under nitrogen by a conventional heating method. When the mass ratio of MG to GO is 0.045, the C/O atomic ratio of GO increases from 1.8 to 17.84 by microwave irradiation under argon at 2000 W for 30 s. However, when GO was irradiated solely under the same conditions, the ratio of C/O was unchanged (1.88). For comparison, the MG was further irradiated by microwave at 2000 W for 30 s, its C/O ratio is enhanced from 4.17 to 8.46, demonstrating the higher reduction efficiency due to a mixed heating mode in the HWH process. The conventional heating of GO occurs during the initial stage and a two-way heating mode during the later stage, in which MG heats the GO from the surface and the microwave heating from the GO itself. Therefore, more amount of carboxyls and epoxides can be removed in the HWH process to achieve higher C/O ratio compared with that of the product obtained by direct microwave irradiation of MG. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microwave pyrolysis of lignin performed with activated carbon, charcoal and graphite. • High yield and selectivity of simple phenols over guaiacols and syringols. • Maximum bio-oil yield of 66 wt% obtained with 10 g:90 g lignin:activated carbon. • Maximum selectivity of 79% for phenol and 34% for cresol achieved in bio-oil. • Effects of bound moisture in the susceptor on heating rate and product distribution elucidated. Abstract With an objective to improve the yield and selectivity of phenols in pyrolysis bio-oil from lignin, this study investigates the effects of mass ratio of lignin-to-susceptor and different types of susceptors (activated carbons of different particle sizes, charcoal and graphite) in microwave pyrolysis. Pyrolysis was carried out in a batch microwave reactor, and the temperature profiles at different operating conditions were captured. Increasing the mass of susceptor with respect to lignin enhanced the bio-oil yield, and maximum yield of 66 wt% with >90% selectivity to phenols was obtained with 10 g lignin:90 g activated carbon. Moisture present in the susceptor is shown to control the pyrolysis severity and lead to better phenol yields. This was verified by the high yield of hydrogen gas formed due to the steam-assisted cracking of lignin. With highly porous activated carbon, 80% selectivity of phenol was obtained, albeit with a low yield of bio-oil. [ABSTRACT FROM AUTHOR]

Application of microwave energy for processing of bulk metals is effectively utilized to join Inconel-625 plates through hybrid heating technique using Inconel-625 powder as an interface filler material. Post welding characterization of microwave developed joints through X-ray diffraction shows the development of carbides of niobium and chromium as well as intermetallic phases along with the primary γ-phase face-centered cubic matrix. Microstructural examination reveals the formation of Laves phase along the grain boundaries in the fusion zone. Microwave-induced joints exhibit average microhardness of 245 ± 20 HV and 0.7% porosity in the fusion zone. Average ultimate tensile strength and flexural strength of the developed joints were estimated at 375 and 377 MPa respectively. Average impact toughness of microwave-induced joints is observed to be 18 J. [ABSTRACT FROM AUTHOR]