Heating Technique Research Articles

Uncovering the Size-Dependent Thermal Solid Transformation of Akaganéite.

Investigating the structural evolution and phase transformation of iron oxides is crucial for gaining a deeper understanding of geological changes on diverse planets and preparing oxide materials suitable for industrial applications. In this study, in-situ heating techniques are employed in conjunction with transmission electron microscopy (TEM) observations and ex-situ characterization to thoroughly analyze the thermal solid-phase transformation of akaganéite 1D nanostructures with varying diameters. These findings offer compelling evidence for a size-dependent morphology evolution in akaganéite 1D nanostructures, which can be attributed to the transformation from akaganéite to maghemite (γ-Fe2O3) and subsequent crystal growth. Specifically, it is observed that akaganéite nanorods with a diameter of ∼50nm transformed into hollow polycrystalline maghemite nanorods, which demonstrated remarkable stability without arresting crystal growth under continuous heating. In contrast, smaller akaganéite nanoneedles or nanowires with a diameter ranging from 20 to 8nm displayed a propensity for forming single-crystal nanoneedles or nanowires through phase transformation and densification. By manipulating the size of the precursors, a straightforward method is developed for the synthesis of single-crystal and polycrystalline maghemite nanowires through solid-phase transformation. These significant findings provide new insights into the size-dependent structural evolution and phase transformation of iron oxides at the nanoscale.

Rapid densification of nanocrystalline zirconia: Pressureless versus pressure-assisted spark plasma sintering

Spark plasma sintering (SPS) is the most straightforward way to rapidly sinter nanoceramics, but the applied pressure prevents sintering of additively manufactured ceramics. Therefore, fast firing techniques such as “pressureless” SPS and ultra-fast high-temperature sintering, based on intense thermal radiation, are gaining interest. Here we compare pressure/current-assisted and pressureless SPS techniques for the rapid heating (∼300 °C/min, 5 min) of nanocrystalline zirconia with high sintering activity. The applied pressure and current indeed contributed to the lowestr temperatures needed for full densification of nanocrystalline zirconia, retaining very fine grain size, but also induced tetragonal phase transformations in the final sintering stages. When the radiative heat transfer was “decoupled” (pressureless SPS), a pronounced temperature difference between graphite crucible wall and simulated specimen temperature along with non-steady-state conditions during dwell were observed. Nevertheless, high heating rates facilitated fine and dense microstructures even in the absence of pressure/current.

In-plane thermal conductivity measurement of microscale polymer films using a reusable micro-thermocouple

Polymers serve as encapsulating materials for electronic devices, making it crucial to investigate their thermophysical properties. In this work, a novel 2ω method for assessing the in-plane thermal conductivity of polymer films is proposed. A reusable micro-thermocouple, serving as both a heating wire and a sensor, is used with silver paste as the interstitial material in contact with the test film. By comparing the 2ω voltages under both contact and non-contact conditions, the thermal impedance is determined. The thermal conductivity is directly calculated by determining the slope of the real part of the thermal impedance against the logarithm of frequency. Theoretical analysis shows that the influences of contact thermal resistance and radiation heat loss are negligible. To validate the accuracy of the method, measurements were repeated on polyimide and polyester films under various contact conditions. The results demonstrate consistency and align with those obtained using the laser spot periodic heating technique.

Electrochemical performance of NiAl-activated cathode for green hydrogen production

The current study presents for the first time the preparation of a NiAl (68 wt.% Ni) intermetallic compound through the induction heating technique as a cathode for alkaline water electrolysis. The high-purity target was confirmed by X-ray diffraction and scanning electron microscopy combined with energy dispersive X-ray analysis. The chemical activation of Al from the NiAl electrode was achieved in a 25% NaOH solution at 353 K for 72 h. The performance and stability tests in a 1 mol·L–1 KOH solution at 298 K demonstrated that the enhancement of the hydrogen evolution reaction was 13 times higher in the activated NiAl electrode than in the non-activated NiAl electrode. In addition, the electrochemical tests showed that the activated NiAl electrode exhibited the best HER performance. Based on the findings, it is believed that the induction heating technique is a promising route for preparing a highly active and cost-effective NiAl electrode for green hydrogen production.

Quick charging adsorption-based thermal energy storage system

This work presents the computational modeling of a fast-charging battery-like thermal energy storage system using a heat exchanger with adsorbent-coated microchannels and a condenser. The utilization of microchannels leads to an extreme asymmetry in the operation of the energy storage system, where the charging time becomes <10 % of the total cycle time. When the system is charged with a 90 °C heat source, it can recover heat at the same temperature for ten times longer. Using silica gel as the adsorbent and water as the medium, this system can store up to 70 kWh m−3 of heat, which is >3.5 times energy over the conventional thermal energy storage options, including latent and sensible heat techniques. Additional advantages of this system include a perfectly scalable operation, flexibility to use diverse adsorbents and refrigerants and location independence, warranting a detailed experimental validation.

Effects of heating on bioceramic sealers: a scoping review of chemo-physical properties and clinical implications.

This scoping review aims to summarize current research to assess the impact of heating on the chemo-physical properties of bioceramic sealers. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews guidelines, a comprehensive literature search was conducted in April 2024 across PubMed and Scopus databases. Inclusion criteria referred to all study types evaluating the effect of heating temperature on bioceramic sealers' properties, with no language or time restrictions applied. Studies were independently screened by two reviewers, and relevant data were extracted and synthesized qualitatively. Out of 91 initially identified studies, 19 met the eligibility criteria for inclusion in the qualitative synthesis. The selected studies ranged from 2014 to 2024 and comprised laboratory-based investigations. Various bioceramic sealers, including EndoSequence BC Sealer, BioRoot RCS, and TotalFill BC, were analyzed across different heating techniques. The findings revealed divergent responses of bioceramic sealers to heat, with some demonstrating stability while others exhibited alterations in properties such as flow, setting time, and chemical composition. The impact of heat on bioceramic sealers depends on the sealer's composition and laboratory setting. While some sealers are affected significantly, others remain stable. Clinicians should carefully consider these factors when bioceramic sealers are used with warm obturation techniques, but caution is needed as real-world conditions may vary. Integrating laboratory results with clinical evidence is essential for improving treatment efficacy and patient care.

Methods for the Inactivation of Mycobacterium tuberculosis: a Systematic Review of the Literature.

To systematize published laboratory methods to inactivate Mycobacterium tuberculosis (MTB) and to describe their effectiveness. We carried out a review of the scientific literature to identify the publications that reported methods for the inactivation of MTB, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. The search addressed inactivation methodologies used in Public health laboratories for the treatment of biological material and only included studies reporting the efficacy of the method. The database used were PubMed (National Library of Medicine) and LILACS (Latin American and Caribbean Literature in Health Sciences). We evaluated the quality of the studies with the JBI (Joanna Briggs Institute) Critical Instrument Appraisal Checklist. We included 14 publications meeting the established inclusion and exclusion criteria. These 14 studies actually described a total of 35 inactivation methods. Most of them combined heat treatment with some chemical or enzymatic agent, and there were very few applying a single strategy. Twenty-four (68.57%) methods demonstrated significant efficacy in inactivating MTB. The systematic review identified 35 methods of inactivation of MTB, published in 14 studies. Most of the methods combined physical treatment techniques, especially heat, with chemical and/or enzymatic treatment techniques, obtaining mostly good results in preventing the reproduction of the microorganism. PROSPERO (International Prospective Register of Ongoing Systematic Reviews) (Code CRD42024503621).

Analysis of the Effects of Microwave Combined Induction Heating on Steamed Pork with Rice Powder.

This study investigates the application of microwave combined induction heating (MCIH) to steam ready-to-eat pork with rice powder, emphasizing the advantages of rapid and uniform heating. The experimental setup included a mixture of 180 g pork strips, 30 g rice powder, and 10 g water in a CPET tray using MCIH with 1080 W microwave (MW) and 130 °C induction heating (IH) for 150 s. The results showed a quick temperature increase rate of 0.56 °C/s that achieved pasteurization against a variety of pathogenic bacteria, such as Listeria monocytogenes, but not Clostridium botulinum, by lethality calculation. Compared to typical electric cooker steaming, MCIH significantly shortened cooking time (8.6 times faster). To address rice starch gelatinization, two-stage heating techniques to steam pork with rice powder were MCIH: 150 s, and then IH: 60 s (MW1), and MCIH: 180 s, and then IH: 30 s (MW2), with no significant differences seen in color or the nine-point taste scale between treatment groups. MCIH groups had smaller shear forces than control. After MCIH cooking, no microbial counts were detected in the MW1 and MW2 groups initially, and the pork with rice powder had a shelf life of 14 days at 4 °C based on aerobic plate count assay.

Impact of external moisture on quantitative analysis of coal and rapid drying by a CO2 laser to improve prediction accuracy based on laser induced breakdown spectroscopy

For high-accuracy determination of ash, fixed carbon, and volatile matter in coal, generally, the impact of external moisture content in coal must be considered and removed in quantitative modeling based on laser-induced breakdown spectroscopy (LIBS). Herein, the ash, fixed carbon, and volatile of coals with moisture contents from 3% to 15% are quantitatively assessed using partial least squares based on principal component analysis (PCA-PLS), and the predictive limit of this model for moist coals is explored based on LIBS. To validate the industrial feasibility of the method, an infrared CO2 laser based heating technique is employed to rapidly dry the moist coals before laser ablation. The results demonstrate that root mean square error of prediction (RMSEP) of all ash, volatile carbon, and fixed carbon become higher with moisture content increase. Nevertheless, as the moisture content reaches 3%, the prediction model retains an acceptable predictive capability with mean absolute error (MAE) of ash, volatile matter, and fixed carbon of 1.85%, 1.5%, and 1.79%, respectively. When the IR laser for drying is employed to irradiating for 40 ms, external water in coal with an original moisture content of 15% can be quickly removed, resulting in a decrease in RMSEP of ash, volatile matter, and fixed carbon from 3.06%, 5.42%, and 6.22% to 1.47%, 3.16%, and 3.34%, respectively. This method provides a potential technical solution for the use of infrared laser-assisted LIBS real-time online rapid detection of indicators in raw coal with high moisture content.

Enhanced energy efficiency and fast co-pyrolysis characteristics of biogas residues and long-flame coal using infrared heating and TG-FTIR-MS

Co-pyrolysis may enhance the energy efficiency of anaerobic digestion waste (biogas residues), while simultaneously facilitating the clean utilization of coal. A thermogravimetric analyzer (TG), TG-FTIR-MS, and infrared heating technique were employed to investigate the rapid co-pyrolysis properties of long-flame coal (LFC) and biogas residues (BR) in this study. Meanwhile, the effects of temperature on the co-pyrolysis product distributions and compositions were studied in reactors that were heated with electric heating and rapid infrared heating. The co-pyrolysis of LFC and BR had the potential to decrease greenhouse gas emissions, as indicated by the TG-FTIR/MS findings. The co-pyrolysis kinetics were calculated using two models (KAS and FWO); the average Eα values are 176.09 and 187.26 kJ/mol, respectively. Tar yields increased initially in IH (electric heating) and EH (infrared heating) reactors, before declining as the temperature rose. The tar yields are greatest for EH at 500 °C (16.12 wt%) and IH at 600 °C (16.02 wt%). Tar yields generated via infrared heating were greatly higher than those generated by EH at 600–700 ℃. IH has a higher tar yield due to the fact that there are significant synergistic effects between coal and lignin, protein, and lipid at high temperatures. The GC-MS results indicate that IH has promoted the aromatization and ketonization reactions. Moreover, more monocyclic aromatic and bicyclic aromatic products are generated by infrared heating, suggesting an indication of tar quality improvement. An elevated co-pyrolysis temperature results in a greater degree of graphitization in char.

Fabrication of binder-free TiO2 P 25 films on flexible PET/ITO substrate for photoanode in dye-sensitized solar cells

In this work, TiO2 P 25 films for photoanode in dye-sensitized solar cells (DSSCs) have been fabricated using a flexible PET/ITO substrate with a low-temperature heating technique. Ammonium hydroxide/ethanol solution was used as an alternative binding agent to fabricate TiO2 paste, which can be removed at low-temperature heating. The conventional screen print method is still used in DSSC fabrication because it is a very cheap and easy technique. A hot-pressing method is also used to improve the quality of TiO2 films and the performance of DSSCs. The encapsulation technique used in the assembly of DSSC is expected to increase the stability of DSSC devices to prevent electrolyte leakage. The resulting TiO2 film shows the highest DSSC performance using the hot-pressing and encapsulation method with PCE 0.29%. The encapsulation technique increased the stability of DSSC devices with more extended durability than without encapsulation.

Advanced FEM Insights into Pressure-Assisted Warm Single-Point Incremental Forming of Ti-6Al-4V Titanium Alloy Sheet Metal

This study employs the finite element (FE) method to analyze the Incremental Sheet Forming (ISF) process of Ti-6Al-4V titanium alloy. The numerical modeling of pressure-assisted warm forming of Ti-6Al-4V sheets with combined oil-heating and friction stir rotation-assisted heating of the workpiece is presented in this article. The thermo-mechanical FE-based numerical model took into account the characteristics of the mechanical properties of the sheet along with the temperature. The experimental conditions were replicated in FEM simulations conducted in Abaqus/Explicit, which incorporated boundary conditions and evaluated various mesh sizes for enhanced accuracy and efficiency. The simulation outcomes were compared with actual experimental results to validate the FE-based model’s predictive capacity. The maximum temperature of the tool measured using infrared camera was approximately 326 °C. Different mesh sizes were considered. The results of FEM modeling were experimentally validated based on axial forming force and thickness distribution measured using the ARGUS optical measuring system for non-contact acquisition of deformations. The greatest agreement between FEM results and the experimental result of the axial component of forming force was obtained for finite elements with a size of 1 mm. The maximum values of the axial component of forming force determined experimentally and numerically differ by approximately 8%. The variations of the forming force components and thickness distribution predicted by FEM are in good agreement with experimental measurements. The numerical model overestimated the wall thickness with an error of approximately 5%. By focusing on the heating techniques applied to Ti-6Al-4V titanium alloy sheet, this comparative analysis underlines the adaptability and precision of numerical analysis applied in modeling advanced manufacturing processes.

A new approach based on a concurrent cooling method during GTAW and DC-LSND welding to mitigate residual stresses in Al 6061-T6

Welding often induces residual stresses and undesired distortion in components. The negative impacts of these detrimental residual stresses have prompted researchers to explore methods for preventing or mitigating these stresses. Altering the temperature history can influence residual stress, and employing cold or heating techniques during welding has the potential to reduce harmful residual stress. In this study, the dynamically controlled low-stress no-distortion (DC-LSND) method with TIG welding was utilized to reduce the residual stresses in Al alloy 6061-T6. The methodology was simulated using Abaqus software, and the simulation results were validated with experimental data. The Al alloy served as the base metal, alloy (ER-4043) as the filler, and dry ice as the coolant. In the finite element analysis, the longitudinal residual stress at the center of the weld line in TIG welding was calculated to be 77 MPa. In the DC-LSND welding method, this value approached zero. Experimental measurements revealed residual stresses in the center of the welding line to be 183 MPa in conventional welding and 130 MPa in DC-LSND welding. According to the DC-LSND results, a 100% reduction in residual stresses was achieved in the finite element method. In the experimental test, a reduction of approximately 30% in residual stress was observed. The method developed in this research is recommended for application in welding metals and alloys where phase changes do not occur.

Effect of SS-316L and nickel-based interface powders on joint characteristics of microwave welded SS-316L plates

Microwave energy has been exploited as a rapid and volumetric heating source in various manufacturing applications, such as microwave joining. This study used stainless steel (SS-316L) plates to be microwave-joined at 2.45 GHz. The microwave hybrid heating (MHH) technique was used to prepare joints inside a microwave applicator using nickel-based (EWAC 1004EN) and SS-316L interfacing powders at 900 W. Microstructural and mechanical characterizations of the developed joints were performed to understand the effect of the interface powder on weld quality. Microstructural observations revealed adequate metallurgical bonding between interfacing powders and bulk metal with columnar and dendritic grains (EWAC-based joint) and equiaxed grains (SS-316L-based joint). The phase analysis revealed the presence of intermetallic phases such as iron-nickel, chromium carbide, and chromium iron carbide in EWAC-based joint and iron-nickel, nickel-chromium, and chromium carbide in SS-316L-based joint, which contribute to enhanced joint microhardness compared to base alloys. A larger grain size, more low-angle boundaries, and higher misorientation angles were found in the EWAC-based joint. Furthermore, the average ultimate tensile strength of SS-316L-based joints was 26% higher, with a 6.9% enhanced elongation, than that of EWAC-based joints. The EWAC-based joint exhibited better corrosion resistance than that of SS-316L-based joint.

Oxidation behavior and atomic structural transition of size-selected coalescence-resistant tantalum nanoclusters

Herein a series of size-selected Ta N (N = 147, 309, 561, 923, 1415, 2057, 6525, 10 000, 20 000) clusters are generated using a gas-phase condensation cluster beam source equipped with a lateral time-of-flight mass-selector. Aberration-corrected scanning transmission electron microscopy (AC-STEM) imaging reveals good thermal stability of Ta N clusters in this study. The oxidation-induced amorphization is observed from AC-STEM imaging and further demonstrated through x-ray photoelectron spectroscopy and energy-dispersive spectroscopy. The oxidized Ta predominantly exists in the +5 oxidation state and the maximum spontaneous oxidation depth of the Ta cluster is observed to be 5 nm under prolonged atmosphere exposure. Furthermore, the size-dependent sintering and crystallization processes of oxidized Ta N clusters are observed with an in situ heating technique, and eventually, ordered structures are restored. As the temperature reaches 1300 °C, a fraction of oxidized Ta309 clusters exhibit decahedral and icosahedral structures. However, the five-fold symmetry structures are absent in larger clusters, instead, these clusters exhibit ordered structures resembling those of the crystalline Ta2O5 films. Notably, the sintering and crystallization process occurs at temperatures significantly lower than the melting point of Ta and Ta2O5, and the ordered structures resulting from annealing remain well-preserved after six months of exposure to ambient conditions.

Flexural behavior of SS316-based metal matrix composite prepared through microwave heating

SS316 is the most commonly used material among the existing stainless steels. SS316-based composite materials provide tailor-made stuff to the various automotive and machinery components due to their competent properties. In the current work, SS316, EWAC, and Cr7C3 powders have been selected for the development of cast specimens in the domestic microwave applicator. The cast of the SS316+15EWAC+5Cr7C3, SS316+15EWAC+10Cr7C3, and SS316+15EWAC+15Cr7C3 compositions has been prepared using a novel technique of microwave hybrid heating. The sample size of 30 × 6 mm2 has been used for flexural strength analysis. The flexural modulus, flexural strength, maximum load, strain at break, and strain at peak load have been tested on a universal testing machine. The maximum values of flexural strength, flexural modulus, peak load, and microhardness were found 469.86 MPa, 10,2321.79 MPa, 4510.65 N, and 585.93 ± 203.33 HV respectively for SS316+15EWAC+15Cr7C3 cast, and maximum strain at peak load and the maximum strain at breaking load were 3.07 and 4.29% respectively for SS316+15EWAC+10Cr7C3 cast. The highest microhardness of 615 HV has been obtained at the carbide phase in the case of SS316+15EWAC+15Cr7C3 cast. The XRD presented the leading peaks of σ-Fe, μ-Fe3Ni2, τ-Cr23C6, α-MoNi4, γ-Mo2C, and β-Fe5C2. The microstructural morphology of the composite casting revealed the proper coalescence of the matrix, homogeneous dispersion of reinforcements, dendrites formation, and equiaxed grain growth. Overall the metallurgical and mechanical properties of the composite cast were improved.

Development of an induction heating reactor for rapid catalytic CF4 decomposition

A novel catalytic reactor configuration based on the induction heating technique is proposed for the decomposition of CF4. To demonstrate the feasibility of this concept, a commercial catalyst and induction heating module are employed. The experimental results demonstrated that the reactor provides a fast response time (approximately 3 min) in the decomposition of CF4 (roughly 100 ppm), without the requirement for insulation or preheating. In addition, introduction of the induction heating technique was found to allow precise temperature control. Furthermore, empirical guidelines for optimizing the catalyst bed are established in terms of two design factors, namely the length/diameter ratio (≥ 1.48) of the catalyst bed, and 1/3 of the blending of an additional inductive heating medium in the catalyst bed. The fast response time exhibited by this system is expected to permit connection of the reactor with electric power generated by renewable energy.

Mid-infrared interferometry with non-adiabatic tapered ZBLAN optical fiber

This work illustrates, to the best of our knowledge, the first non-adiabatic tapered single-mode zirconium fluoride optical fiber sensor in the mid-infrared spectral range. It is designed and fabricated via pulling and heating technique. A waist diameter d w = 25 µm with no visible crystallization is achieved, overcoming the typical fluoride glass challenges associated with crystallization, narrow temperature fabrication window, and low glass transition temperature. The performance of the non-adiabatic tapered optical fiber is theoretically and experimentally investigated, demonstrating its high potential for a wide range of sensing applications in the mid-infrared spectral range.

Sliding wear study of the Inconel-625 clad deposits by microwave heating on SS-304

In this present study, the Inconel-625 powder was used for the surface modification of SS-304 alloy by utilizing the concept of a hybrid microwave heating technique. The XRD analysis shows the presence of various carbide and Laves phases in addition to a Ni-Cr-Fe-based face-centred-cubic matrix in the modified clad layer. The microstructural analysis revealed that the developed clad was metallurgically bonded with the substrate and free from any interfacial cracks. The modified layer mainly consists of two regions: cellular (matrix) regions and grain boundaries (GBs) regions. The average porosity in the modified clad layer was evaluated to be about 1.65%. The average microhardness (440 ± 45 HV) of the modified clad layer was observed to be about 2.1 times the base metal microhardness (210 ± 10 HV). The clad specimens exhibited a considerably lower wear rate (about 2.8 times less weight loss) than the substrate SS-304 during the dry sliding wear test. The shallow grooves, craters, and material debonding were the typical fracture features associated with the clad surfaces during rubbing when examined under a scanning electron machine apparatus.

Performance improvement of metal hydride hydrogen compressors using electromagnetic induction heating

While there are some hydrogen refueling stations (HRS) functioning in different parts of the world, their use is not widespread enough, primarily due to their expensive cost. Hydrogen compression is a main contributor to the capital and operation costs of the HRS. By improving H2 compression technology, it is possible to optimize the infrastructure for refueling with hydrogen in terms of cost and performance. The use of metal hydride hydrogen compressors (MHHCs), which have the potential to be inexpensive and have the ability to use waste heat and renewable energy sources for the H2 compression, is a promising solution to overcome this issue. The duration of the H2 compression cycle is nevertheless a serious challenge due to the metal hydride (MH) bed's low heat conductivity. As a heating technique to improve the performance of MHHCs, electromagnetic induction (EMI) is examined numerically for the first time in this work. The dynamic behavior of a two-stage MHHC with each MH reactor having an external heat exchanger and being ringed by a copper coil traversed by an alternating current is described by a two-dimensional mathematical model, which was established and successfully verified by the reference data. Numerical simulations were performed with the help of this model, and the findings showed that the EMI heating method is faster than the heat transfer fluid (HTF) heating technique. For instance, at a delivery temperature of 373 K and a supply pressure of 20 bar, it is possible to produce 106 NL H2 per kilogram of HPMH at a pressure of 97 bar with a 74 % shorter compression time than with the HTF heating technique.