Radio Frequency Induction Heating Research Articles

Magnetic Nanoparticles and Radio Frequency Induction: From Specific Heating to Magnetically Induced Catalysis

AbstractThis comprehensive review explores the potential of radio frequency (RF) induction heating in chemical reactions, explicitly focusing on magnetically induced catalysis using magnetic nanoparticles (NPs). We trace the recent historical progress of induction heating and highlight the advancements in liquid and gas‐phase reactions, particularly in its integration with heterogeneous catalysis. The review finds that induction heating profoundly impacts reaction kinetics, and selectivity, and can even reduce overpotentials in electrocatalytic processes. A final outlook unveils the challenges and opportunities associated with aspects such as fundamental research and reactor design, with a particular focus on expanding its use to higher pressures and necessary optimizations to improve energy efficiency. Moreover, it highlights the pressing need for standardized reporting in induction‐heated catalysis. The study underscores the significance of this brand‐new field in developing efficient and sustainable catalytic processes, which are essential for meeting the growing demand for clean energy and sustainable chemical production.

Radiofrequency Induction Heating for Green Chemicals Manufacture: A Systematic Model of Energy Losses and a Scale-Up Case-Study

Radiofrequency Induction Heating for Green Chemicals Manufacture: A Systematic Model of Energy Losses and a Scale-Up Case-Study

Assessment of the Impact of Nanowarming on Microstructure of Cryopreserved Fibroblast-Containing 3D Tissue Models Using Mueller Polarimetry

We studied the impact of two different thawing mechanisms on the microstructure of defrosted cryopreserved 3D tissue models using transmission Mueller microscopy and a statistical analysis of polarimetric images of thin histological sections of defrosted tissue models. The cryopreserved 3D tissue models were thawed by using either a 37 °C water bath or radio-frequency inductive heating with the magnetic nanoparticles embedded into the 3D tissue model during the preparation process. Polarimetric measurements were conducted at 700 nm and the acquired Mueller matrices of the samples were post-processed using the differential decomposition and the statistical analysis of the maps of the azimuth of the optic axis. Our results indicate the sensitivity of polarimetry to the changes in thawed tissue morphology compared to that of reference non-frozen tissue. Thus, Mueller microscopy can be used as a fast complementary technique to the currently accepted gold standard methods for the assessment of the cryopreserved tissue microstructure after thawing.

Simultaneous improvement of heating efficiency and mechanical strength of a self-healing thermoplastic polymer by hybridizing magnetic particles with conductive fibres

Radio-Frequency (RF) induction heating is a versatile in-situ method for contactless heating of structures by utilizing either magnetic hysteresis loss or eddy-current loss mechanism. Achieving high heating efficiency without degrading mechanical properties is a major challenge. Herein, a RF induction compatible self-healing composite was developed by hybridizing iron oxides (Fe3O4) nanoparticles with carbon fibre veils (CFVs) in poly(ethylene-co-methacrylic acid) (EMAA), which could possess both high magnetic and electrical properties. Owing to the multiscale conductive networks built by Fe3O4 nanoparticles and CFVs, the electrical conductivity of the nanocomposite was found to be higher than the linear combination of the individual contributions, thus creating a synergistic improvement in electrical conductivity and heating efficiency. Furthermore, single lap shear test results demonstrated that the combination of Fe3O4 nanoparticles and CFVs could significantly improve the bonding strength of EMAA polymer. Therefore, the hybridization of magnetic particles with conductive fibres offers a promising technology for a wide range of applications, such as self-healing, reversable bonding, and multiple use bonded composites.

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.

Induction Heating of Magnetically Susceptible Nanoparticles for Enhanced Hydrogenation of Oleic Acid.

Radio frequency (RF) induction heating was compared to conventional thermal heating for the hydrogenation of oleic acid to stearic acid. The RF reaction demonstrated decreased coke accumulation and increased product selectivity at comparable temperatures over mesoporous Fe3O4 catalysts composed of 28–32 nm diameter nanoparticles. The Fe3O4 supports were decorated with Pd and Pt active sites and served as the local heat generators when subjected to an alternating magnetic field. For hydrogenation over Pd/Fe3O4, both heating methods gave similar liquid product selectivities, but thermogravimetric analysis–differential scanning calorimetry measurements showed no coke accumulation for the RF-heated catalyst versus 6.5 wt % for the conventionally heated catalyst. A different trend emerged when hydrogenation over Pt/Fe3O4 was performed. Compared to conventional heating, the RF increased the selectivity to stearic acid by an additional 15%. Based on these results, RF heating acting upon a magnetically susceptible nanoparticle catalyst would also be expected to positively impact systems with high coking rates, for example, nonoxidative dehydrogenations.

Radio-frequency induction heating powered low-temperature catalytic CO2 conversion via bi-reforming of methane

Radio-frequency (RF) induction heating of nanoparticles has unfolded novel routes to heterogeneous catalytic chemical reactions. It offers contactless, direct, time- and energy-saving heating with high-achieved catalytic activity. Herein, the tailored chemical synthesis of mono-metallic Cu, binary Cu-Ni, Cu-Co, and ternary Cu-Ni-Co catalysts was evaluated for CO2 conversion via bi-reforming of methane (combined steam- and dry-reforming processes) under induction heating. All prepared catalysts were activated under RF heating to convert CO2 and co-reactants i.e., H2O (steam) and methane into syngas (H2 and CO) at a relatively low temperature of 400 °C. The Cu-Co sample delivered the highest catalytic performance and stability under all tested conditions. Experimental results elaborated that the concomitant presence of a magnetic element and an electrically conductive component in the catalyst system facilitates highly effective heating occurring via both hysteresis loss and Joule effects mechanisms. On account of Joule heating, the Cu-Co catalyst preserved its excellent stability for at least 50 h over the stream test at a reaction temperature higher than its Curie temperature (TC). The findings provide significant insights into the catalyst development for RF-assisted chemical reactions that are not needed to be heavily dependent on the use of strong magnetic metals or high input current to obtain desired reactant conversions.

Catalytic Depolymerization of Waste Polyolefins by Induction Heating: Selective Alkane/Alkene Production.

Low- and high-density polyethylene (LDPE/HDPE) have been selectively depolymerized, without added H2, to C2–C20 + alkanes/alkenes via energy-efficient radio frequency induction heating, coupled with dual-functional heterogeneous Fe3O4 and Ni- or Pt-based catalysts. Fe3O4 was used to locally generate heat when exposed to magnetic fields. Initial results indicate that zeolite-based Ni catalysts are more selective to light olefins, while Ni supported on ceria catalysts are more selective to C7–C14 alkanes/alkenes. LDPE conversions up to 94% were obtained with minimal aromatic, coke, or methane formation which are typically observed with thermal heating. Two depolymerization mechanisms, a reverse Cossee–Arlman mechanism or a random cleavage process, were proposed to account for the different selectivities. The depolymerization process was also tested on commercial LDPE (grocery bags), polystyrene, and virgin HDPE using the Ni on Fe3O4 catalyst, with the LDPE resulting in similar product conversion (∼48%) and selectivity as for virgin LDPE.

Aspects of rf-heating and gas-phase doping of large scale silicon crystals grown by the Float Zone technique

Float Zone growth of silicon crystals is known as the method for providing excellent material properties. Basic principle of this technique is the radiofrequency induction heating, main aspects of this method will be discussed in this article. In contrast to other methods, one of the advantages of the Float Zone technique is the possibility for in-situ doping via gas phase. Experimental results on this topic will be shown and discussed.

Ex-situ up-conversion of biomass pyrolysis bio-oil vapors using Pt/Al2O3 nanostructured catalyst synergistically heated with steel balls via induction

Radiofrequency-driven hydrodeoxygenation of sawdust pyrolysis vapor and the coking performance of the catalysts were investigated using Pt/Al2O3 commercial pellets mixed with steel balls inside an alumina tube. The radio-frequency induction heating of the catalyst bed was compared with a conventional method of heating using electric tape engulfing the catalyst bed reactor. Partial deoxygenation of the oil was successfully achieved in the catalytic upgrading of pyrolysis oil at 234°C, with the use of the induction heater. The molar O/C ratio of the oil decreased from 1.36 to 0.51. No deoxygenation of the oil was observed using the electric tape control under identical conditions as both carbon and oxygen appeared to be removed at approximately equal rates, with the carbon being deposited in the form of coke onto the catalyst instead of being recovered in the liquid.

Optimisation of the synthesis of ZrC coatings in a radio frequency induction-heating chemical vapour deposition system using response surface methodology

A chemical vapour deposition process using radio frequency induction heating operating at atmospheric pressure was developed for the deposition of ZrC coatings. The precursors utilised in this process were zirconium tetrachloride and methane as zirconium and carbon sources respectively, in an excess of hydrogen. Additionally, a stream of argon was used to, first, remove oxygen from the reactor and then to sweep the vapourised ZrCl4 at 300°C to the reaction chamber. The ZrC coatings were deposited on graphite substrates at substrate temperatures in the range of 1200°C–1600°C. The molar ratio of CH4/ZrCl4 was varied from 6.04 to 24.44. Before the start of the deposition process, thermodynamic feasibility analysis for the growth of ZrC at atmospheric pressure was also carried out. Response surface methodology was applied to optimise the process parameters for the deposition of ZrC coatings. A central composite design was used to investigate the effects of temperature and molar ratio of CH4/ZrCl4 on the growth rate, atomic ratio of C/Zr and crystallite size of ZrC coatings. Quadratic statistical models for growth rate and crystallite size were established. The atomic ratio of C/Zr followed a linear trend. It was found that an increase in substrate temperature and CH4/ZrCl4 ratio resulted in increased growth rate of ZrC coatings. The carbon content (and concomitantly the atomic ratio of C/Zr) in the deposited coatings increased with temperature and molar ratio of CH4/ZrCl4. The substrate temperature of 1353.3°C and the CH4/ZrCl4 molar ratio of 10.41 were determined as the optimal condition for growing near-stoichiometry ZrC coatings. The values were 1.03, 6.05μm/h and 29.8nm for C/Zr atomic percentage ratio, growth rate and average crystallite size respectively.

저항가열 방식을 적용한 승화법에 의한 SiC 결정 성장에 대한 연구

SiC 결정은 전력반도체 소자용 소재로서 지금까지 외국은 물론 국내에서도 많은 연구가 이루어지고 있으며, 지금까지 고주파 유도가열 방식을 이용한 승화법으로 성장되어 왔다. 그러나, SiC 단결정은 결정 성장 계면에서의 온도 안정성에 따라 쉽게 다른 다형으로 성장하기 때문에, 고품질의 결정을 얻기 위해서는 결정성장 계면에서의 안정적인 온도 구배가 필요하다. 본 논문에서는 저항가열 방식을 이용한 승화법 성장 장치를 이용하여 종자결정을 사용하지 않은 상태에서 SIC 다결정상을 성장하여 보고, 성장 양상에 대하여 고찰하고자 하였다. SiC 다결정상은 성장속도 0.02~0.5 mm/hr로 성장되었으며, 성장된 SiC 다결정상의 두께는 0.25 mm~0.5 mm이고, 이 때 도가니 하부의 온도는 <TEX>$2100{\sim}2300^{\circ}C$</TEX>, 성장 압력은 10~760 torr의 범위에서 조절되었다. 성장된 다결정상 결정은 광학현미경으로 관찰하여, 성장 거동을 고찰하였다. SiC crystals are well known for their true potential as high power devices and their crystal growth activity is actively carried out in domestic as well as in abroad. Until now the process to grow this crystal has been done by sublimation technique using radio frequency induction heating method. However in order to get better quality of SiC crystals, the stability of temperature is needed because SiC crystal tends to transform to other polytypes. So, the possibility of SiC crytals growth was evaluated by different heating method. This study aimed to observe whether the resistant heating method would show stable growth and better quality of SiC single crystal than that of RF induction heating. As a result, polycrystalline SiC crystals were grown by the growth rate of 0.02~0.5 mm/hr under the condition of <TEX>$2100{\sim}2300^{\circ}C$</TEX> at the bottom side of the crucible and 10~760 torr. The polycrystalline SiC crystals with 0.25 and 0.5 mm in thickness were grown successfully without seed and characterized by optical stereo microscopic observation.

Growth of threaded AlN whiskers by a physical vapor transport method

Threaded aluminum nitride (AlN) whiskers are grown by a physical vapor transport method in a radio-frequency induction heating furnace. The resultant whiskers are characterized by X-ray diffraction, Raman scattering, scanning electron microscopy, transmission electron microscopy and photoluminescence. The analysis shows that the whiskers are single-crystalline, wurtzite AlN. The threaded AlN whiskers are 0.5 μm∼100 μm in diameter and several millimeters in length in the fiber direction, and have lots of tiny sawteeth on the surface. The morphology of this threaded AlN whisker is beneficial for bonding when the whisker is used in composite. The growth of the whiskers is dominated by the vapor—solid (VS) mechanism, and the particular morphology might result from an oscillating condition produced in the radio-frequency induction heating furnace.

Isothermal Bainite Transformation in Low Silicon TRIP Steel with Phosphorus Addition

The low silicon transformation-induced plasticity (TRIP) steel with phosphorus addition is consisted of the microstructure of retained austenite, ferrite and bainite which produced by intercritical annealing and isothermal bainite transformation followed by rapid cooling. In this study, isothermal bainite transformation of different experimental parameters in low silicon TRIP steel with phosphorus addition was investigated in laboratory. The addition of cheap element phosphorus, which has the same effect of silicon in retard the kinetics of carbide formation during isothermal bainite transformation, can reduce the silicon content, improve surface quality, solve galvanizing problem and reduce costs. The effect of bainite isothermal temperature, intercritical annealing temperature and heating rates were investigated by dilatometric experiment on a push-rod Formastor-FII high-speed dilatometer with radio frequency induction heating. The high resolution observations, composition analysis and elements distribution of microstructure were carried out using the electron scanning microscopy of a field emission electron probe microanalyzer (JEOL JXA-8530F) operating at 20KV accelerating voltage.

Modified Seed Growth of Iron Oxide Nanoparticles in Benzyl Alcohol - Optimization for Heating and Broad Stability in Biomedical Applications.

Iron oxide nanoparticles have received sustained interest for biomedical applications as synthetic approaches are continually developed for control of nanoparticle properties. However, many approaches focus solely on the material, rather than the complete optimization of synthesis and functionalization together to enhance translation into biological systems. Presented herein is a modified seed growth method designed for obtaining optimal nanoparticle properties and ease of surface functionalization for long term stability. With a one or two addition process, iron oxide nanoparticles were produced in crystallite sizes ranging from 5–15 nm using only benzyl alcohol and an iron precursor. In the functionalization process, concentration variations were required for stabilizing different nanoparticle sizes. Radio frequency induction heating experiments of various crystallite and hydrodynamic sizes verified that the heating efficiency greatly increased while approaching the 15 nm crystallite, and suggested an important role of the overall particle size on heating efficiency. Initial in vitro experiments with the functionalized nanoparticles showed success in providing hyperthermia-induced tumour cell killing without an increase in the temperature of the cell suspension medium. This demonstrates the potential for nanoparticle-based hyperthermia to provide a therapeutic effect while limiting normal tissue damage.

Graphene Synthesis via Magnetic Inductive Heating of Copper Substrates

Scaling graphene growth using an oven to heat large substrates becomes less energy efficient as system size is increased. We report a route to graphene synthesis in which radio frequency (RF) magnetic fields inductively heat metal foils, yielding graphene of quality comparable to or higher than that of current chemical vapor deposition techniques. RF induction heating allows for rapid temperature ramp up/down, with great potential for large scale and rapid manufacturing of graphene with much better energy efficiency. Back-gated field effect transistors on a SiO2/Si substrate showed carrier mobility up to ∼14 000 cm(2) V(-1) s(-1) measured under ambient conditions. Many advantages of RF heating are outlined, and some fundamental aspects of this approach are discussed.

Isothermal Bainite Transformation in Aluminium Bearing TRIP Steel

In this work, the bainite transformation during isothermality of aluminium bearing TRIP steel was studied by dilatometric experiment on a pushrod Formastor-F highspeed dilatometer with radio frequency induction heating. The aluminium bearing TRIP steel consisted of the microstructure of austenite, ferrite and bainite in the form of laths which produced by intercritical annealing and isothermal transformation followed by rapid cooling. The effect of intercritical annealing temperature and isothermal transformation temperature were studied by dilatometric experiment and JEOL JXA-8530F Electron Probe Microscopic Analyzer (EPMA).

Batch welding of aligned carbon nanotube onto metal electrodes

A novel batch welding of aligned carbon nanotubes (CNTs) onto metallic electrodes is developed by radio frequency induction heating. The experiments had achieved optimum contact between CNTs and metal electrodes, two hundred samples had the same trend of reduction of contact resistance after heating process, and this reduction was irreversible, which demonstrated good reproducibility of induction heating for CNT welding. Because of its non-contact and selective heating, induction heating provide a potential approach to reproducible large-scale fabrication and wide applications of CNTs devices.

Heat explosion approach to radiofrequency heating of a conductor film on silicon substrate: Application for silicide film formation

A qualitative analysis of the kinetics of phase formation in a conductor film/Si substrate system by radiofrequency (RF) heating is presented. The analysis is done by using the mathematical approach of the heat explosion theory. It is shown that the system can experience heating at constant temperature or a sudden temperature increase, i.e. heat explosion. The relation between the parameters of the system in the heat explosion regime is presented in a simple analytical form. It was found that measurable quantities, such as film thickness, sheet resistance, specimen dimensions and applied magnetic field, determine whether the process occurs in the constant heating or heat explosion stages. The model was tested for the Ta–Ti–Si system by considering some of the mentioned measurable quantities which were obtained by RF induction heating of Ta–Ti film on Si(1 1 1) and Si(1 0 0) substrates. The agreement of theory with experiment is reasonable. Concentration of Ta in the conductor film, film thickness and the orientation of the Si substrate might influence the reaction rate. On Si(1 1 1) substrates the reaction goes to completion, whereas on Si(1 0 0) intermediate phases remain. This observation was explained in terms of an interface reaction-controlled process of Si atoms transferring from the substrate to the film.

Wafer level bonding using localized radio-frequency induction heating

A wafer level bonding technique by localized induction heating has been developed and demonstrated in this paper. A suitable fabrication process scheme has also been established for the localized induction heating and bonding. It takes only about 20 seconds to complete the bonding process. The temperatures of solder loops and the central area of solder loops are above 300°C and below 70°C, respectively. Due to the solder reflow, robust and hermetic glass wafer bonding is accomplished, and the average tensile strength is 6.42 MPa. Under-heated or over-heated bonding has been found to result in cracks at bonding interfaces and sputtering layer, which degrades the bonding qualities.