Conventional Thermal Processing Research Articles

Performance and Characterization of Additively Manufactured BST Varactor Enhanced by Photonic Thermal Processing

The demand for reconfigurable devices for emerging RF and microwave applications has been growing in recent years, with additive manufacturing and photonic thermal treatment presenting new possibilities to supplement conventional fabrication processes to meet this demand. In this paper, we present the realization and analysis of barium–strontium–titanate-(Ba0.5Sr0.5TiO3)-based ferroelectric variable capacitors (varactors), which are additively deposited on top of conventionally fabricated interdigitated capacitors and enhanced by photonic thermal processing. The ferroelectric solution with suspended BST nanoparticles is deposited on the device using an ambient spray pyrolysis method and is sintered at low temperatures using photonic thermal processing by leveraging the high surface-to-volume ratio of the BST nanoparticles. The deposited film is qualitatively characterized using SEM imaging and XRD measurements, while the varactor devices are quantitatively characterized by using high-frequency RF measurements from 300 MHz to 10 GHz under an applied DC bias voltage ranging from 0 V to 50 V. We observe a maximum tunability of 60.6% at 1 GHz under an applied electric field of 25 kV/mm (25 V/μm). These results show promise for the implementation of photonic thermal processing and additive manufacturing as a means to integrate reconfigurable ferroelectric varactors in flexible electronics or tightly packaged on-chip applications, where a limited thermal budget hinders the conventional thermal processing.

Comparison of acidified and conventional low acid thermal processing of white mushroom in glass jars as influenced by reciprocating agitation

The objective of this study was to evaluate the quality advantage that can be gained by combining acidified low-acid food thermal processing (ALTP) (pH < 4.6) and reciprocating agitation thermal processing (RATP) of mushroom. Mushroom was selected as a low acid food which is conventionally subjected to low-acid food conventional thermal processing (LACP) (pH > 4.6). Glass jars were used as containers. LACP was established to target a commercial sterilization process (Fo value of 5.0 min at 121.1 °C), while ALTP was established to get an equivalent pasteurization process (Fo value of 10.0 min at 90 °C). Heat penetration data was obtained to establish the above targeted processes and to assess the influence of processing conditions on the heating rate index and heating lag factor. Once processed, the associated quality parameters were evaluated and compared. Process variables included three processing temperatures (115, 120, 125 °C for LACP and 90, 95 and 100 °C for ALTP) and three RATP conditions (0, 1.0 and 2.0 Hz agitation). The results revealed higher rates of heat penetration and lower processing times for both LACP and ALTP processes as the reciprocation frequency increased. Quality retention advantages were realized as the process temperature was increased in each case. The best advantage was delivered with ALTP. Although the rate of heat transfer was the highest at 2.0 Hz, the best quality was observed at a moderate agitation frequency (1.0 Hz) as product texture breakdown was avoided. This is the first study that combined ALTP and RATP and compared them with LACP.

Solution infiltrated lanthanum nickelate–GDC composite cathode via flash-light sintering for intermediate temperature solid oxide fuel cells

Solid oxide fuel cells (SOFCs) require high operating temperatures to minimize the oxygen reduction reaction resistance at cathode and increase the ionic conductivity of oxygen. However, at high operating temperatures, their stability during long-term operation degrades because of material deterioration and the mutual chemical reactions occurring at the interfaces. Herein, an electrode–electrolyte composite is fabricated by solution infiltration of lanthanum nickelate (LNO) electrode material into a GDC electrolyte layer to ensure more reaction sites compared with the conventional powder mixing of the electrode and electrolyte material. Further, the conventional thermal sintering process is replaced with the flash-light sintering process. Thus, the performance of the LNO–GDC cathode cell manufactured by flash-light sintering improves owing to suppression of grain growth of the infiltrated LNO particles. The microstructures of the infiltrated solution and composite layer of the electrolyte material are analyzed using field-emission scanning electron microscopy, and the crystallinity of the LNO nanoparticles is analyzed using high-resolution transmission electron microscopy. A maximum power density of 1.1 W/cm2 is achieved, an improvement of 58 % over the LSCF cell without infiltration at 750 ℃. This study is expected to contribute to the commercialization of SOFCs by replacing conventional thermal sintering.

Effect of Thermal Processing on Food Allergenicity: Mechanisms, Application, Influence Factor, and Future Perspective.

Thermally processed foods are essential in the human diet, and their induced allergic reactions are also very common, seriously affecting human health. This review covers the effects of thermal processing on food allergenicity, involving boiling, water/oil bath heating, roasting, autoclaving, steaming, frying, microwave heating, ohmic heating, infrared heating, and radio frequency heating. It was found that thermal processing decreased the protein electrophoretic band intensity (except for infrared heating and radio frequency heating) responsible for destruction of linear epitopes and changed the protein structure responsible for the masking of linear/conformational epitopes or the destruction of conformational epitopes, thus decreasing food allergenicity. The outcome was related to thermal processing (e.g., temperature, time) and food (e.g., types, pH) condition. Of note, as for conventional thermal processing, it is necessary to control the generation of the advanced glycation end products in roasting/baking and frying, and the increase of structural flexibility in boiling and water/oil bath heating, autoclaving, and steaming must be controlled; otherwise, it might increase food allergenicity. As for novel thermal processing, the temperature nonuniformity of microwave and radio frequency heating, low penetration of infrared heating, and unwanted metal ion production of ohmic heating must be considered; otherwise, it might be the nonuniformity and low effect of allergenicity reduction and safety problems.

Comparing the impact of conventional and non-conventional processing technologies on water-soluble vitamins and color in strawberry nectar – a pilot scale study

A comprehensive comparison was conducted on the effect of conventional thermal processing (TT), high-pressure processing (HP), pulse electric field (PF), and ohmic heating (OH) on water-soluble vitamins and color retention in strawberry nectar. The ascorbic acid (AA) content increased by 15- and 9-fold after TT and OH treatment, respectively, due to rupturing of cells under heat stress and release of intracellular AA. Dehydroascorbic acid (DHA) content did not change considerably after TT and PF treatment but significantly decreased after HP and OH treatment. TT treatment offered the highest total vitamin C retention. The B vitamins remained largely unchanged after processing, with the highest loss of 34 % for riboflavin in OH-treated samples. All the technologies resulted in similar color retention after processing. The study concludes with a standardized comparison of mainstream preservation technologies using pilot-scale equipment. Such an approach significantly increases the applicability of the results presented in the study.

Advances in Non-thermal Food Processing Methods-Principle Advantages and Limitations for the Establishment of Minimal Food Quality as well as Safety Issues: A Review

Background: The demand from consumers for safe, healthy food with a long shelf life, with no change in taste or nutritive value, has made food safety a key concern in today's world. Traditional thermal food processing technology has trouble meeting these standards. Conventional thermal and non-thermal processing has limitations and to overcome these limitations more studies are conducted regarding the novel non-thermal food processing methods. Objective: The goal of this paper was to present an overview of the research on the development of non-thermal processing techniques, such as electrofreezing, high hydrostatic pressure, pulsed electric fields, ultrasound, pulsed light, and plasma activated water, as well as their advantages and limitations. Methods: The present review aims to summarize findings related to novel non-thermal processing techniques, gathered from work published in scientific journals, related books, and book chapters from sources such as Web of Science (WoS), Google Scholar, Scopus and ScienceDirect. Results: Non-thermal treatment may result in more desirable outcomes, such as greater preservation of heat-sensitive nutrients, fewer changes in sensorial as well as physico-chemical quality of the processed foods. Conclusion: Compared to traditional heat processing, the nutritional value of foods is better preserved, and the sensory qualities of foods are less altered. These novel techniques can be combined with each other to achieve higher efficiency and overcome other limitations. More studies should be conducted regarding the combination of novel non-thermal techniques to achieve greater efficiency.

Bael (Aegle marmelos) beverage pasteurization by non-isothermal heating with continuous microwave to achieve microbial safety

The efficacy of conventional thermal (batch) and continuous microwave (MW) heating to pasteurize bael beverage was examined by inactivating Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium, Saccharomyces cerevisiae, their cocktail, and native microbial groups. Continuous-MW was operated at 2 kW power and 45–80 °C final temperature. For 25–90 °C beverage temperature, the fluid followed a laminar flow. Data were appropriately modelled using first-order kinetics. MW-heating effectively inactivated all microorganisms. S. cerevisiae was most resistant towards thermal inactivation under single (D70 °C = 0.03 min) and cocktail scenario (D80 °C = 0.014 min) and towards MW under cocktail scenario (DMW_67.5 °C = 0.23 min). The resistance towards temperature rise was highest by L. monocytogenes. Based on lower zMW-values, the thermal sensitivity of microbes improved under MW heating. Morphological alteration in microbial cells of S. cerevisiae &L. monocytogens reveals that the lethality of MW inactivation is mainly based on its thermal effects. Industrial relevanceBael fruit is a nutritious tropical fruit whose beverage is relished by consumers for its refreshing flavour and numerous health benefits. The food sector is presently concentrating on creating innovative, minimally processed goods that are ready-to-eat or handy, shelf-stable, and of higher quality. As an alternative to conventional thermal processing, several novel and sustainable processing methods are now being investigated. To determine if microwave processing is a suitable substitute for thermal processing, the inactivation of artificially inoculated microorganisms, their cocktail, and indigenous microorganisms in the bael beverage were examined in this work. Kinetic study, beverage rheology and changes in cell morphology were also studied. The study's findings indicate that continuous microwave technology can be a more suitable method of pasteurizing fruit beverages than conventional heating due to its >7 log reduction in a shorter time. Except for a few differences, the inactivation mechanisms of thermal and microwave are comparable.

Application of radio frequency energy in processing of fruit and vegetable products.

Thermal processing is commonly employed to ensure the quality and extend the shelf-life of fruits and vegetables. Radio frequency (RF) heating has been used as a promising alternative treatment to replace conventional thermal processing methods with advantages of rapid, volumetric, and deep penetration heating characteristics. This article provides comprehensive information regarding RF heating uniformity and applications in processing of fruit and vegetable products, including disinfestation, blanching, drying, and pasteurization. The dielectric properties of fruits and vegetables and their products have also been summarized. In addition, recommendations for future research on RF heating are proposed to enhance practical applications for fruits and vegetables processing in future.

Ultra-antiwetting Membrane for Hypersaline Water Crystallization in Membrane Distillation.

Membrane distillation (MD) has great potential in the management of hypersaline water for zero liquid discharge (ZLD) due to its high salinity tolerance. However, the membrane wetting issue significantly restricts its practical application. In this study, a composite membrane tailored for extreme concentrations and even crystallization of hypersaline water is synthesized by coating a commercial hydrophobic porous membrane with a composite film containing a dense polyamide layer, a cation exchange layer (CEL), and an anion exchange layer (AEL). When used in direct contact MD for treating a 100 g L-1 NaCl hypersaline solution, the membrane achieves supersaturation of feed solution and a salt crystal yield of 38.0%, with the permeate concentration at <5 mg L-1. The composite membrane also demonstrates ultrahigh antiwetting stability in 360 h of long-term operation. Moreover, ion diffusion analysis reveals that the ultrahigh wetting resistance of the composite membrane is attributed to the bipolar AEL and CEL that eliminate ion crossover. The literature review elucidates that the composite membrane is superior to state-of-the-art membranes. This study demonstrates the great potential of the composite membrane for direct crystallization of hypersaline water, offering a promising approach to filling the gap between reverse osmosis and conventional thermal desalination processes for ZLD application.

Surfactant Directionally Assembled at the Electrode-Electrolyte Interface for Facilitating Electrocatalytic Aldehyde Hydrogenation.

Electrocatalytic hydrogenation of unsaturated aldehydes to unsaturated alcohols is a promising alternative to conventional thermal processes. Both the catalyst and electrolyte deeply impact the performance. Designing the electrode-electrolyte interface remains challenging due to its compositional and structural complexity. Here, we employ the electrocatalytic hydrogenation of 5-hydroxymethylfurfural (HMF) as a reaction model. The typical cationic surfactant, cetyltrimethylammonium bromide (CTAB), and its analogs are employed as electrolyte additives to tune the interfacial microenvironment, delivering high-efficiency hydrogenation of HMF and inhibition of the hydrogen evolution reaction (HER). The surfactants experience a conformational transformation from stochastic distribution to directional assembly under applied potential. This oriented arrangement hampers the transfer of water molecules to the interface and promotes the enrichment of reactants. In addition, near 100 % 2,5-bis(hydroxymethyl)furan (BHMF) selectivity is achieved, and the faradaic efficiency (FE) of the BHMF is improved from 61 % to 74 % at -100 mA cm-2. Notably, the microenvironmental modulation strategy applies to a range of electrocatalytic hydrogenation reactions involving aldehyde substrates. This work paves the way for engineering advanced electrode-electrolyte interfaces and boosting unsaturated alcohol electrosynthesis efficiency.

Design of Mixed-Matrix MOF Membranes with Asymmetric Filler Density and Intrinsic MOF/Polymer Compatibility for Enhanced Molecular Sieving.

The separation of high-value-added chemicals from organic solvents is important for many industries. Membrane-based nanofiltration offers a more energy-efficient separation than the conventional thermal processes. Conceivably, mixed-matrix membranes (MMMs), encompassing metal-organic frameworks (MOFs) as fillers, are poised to promote selective separation via molecular sieving, synergistically combining polymers flexibility and fine-tuned porosity of MOFs. Nevertheless, conventional direct mixing of MOFs with polymer solutions results in underutilization of the MOF fillers owing to their uniform cross-sectional distribution. Therefore, in this work, a multizoning technique is proposed to produce MMMs with an asymmetric-filler density, in which the MOF fillers are distributed only on the surface of the membrane, and a seamless interface at the nanoscale. The design strategy demonstrates five times higher MOF surface coverage, which results in a solvent permeance five times higher than that of conventional MMMs while maintaining high selectivity. Practically, MOFs are paired with polymers of similar chemical nature to enhance their adhesion without the need for surface modification. The approach offers permanently accessible MOF porosity, which translates to effective molecular sieving, as exemplified by the polybenzimidazole and Zr-BI-fcu-MOF system. The findings pave the way for the development of composite materials with a seamless interface.

Methanol-based thermochemical energy storage (TCES) for district heating networks

With increasing volatility in natural gas markets and the need for residential heat, research for alternative thermal systems based on green hydrogen-based fuels is necessary. Massive implementation of hydrogen in the current fleet presents a challenge for the decarbonisation of conventional thermal processes. This paper presents the integration of green methanol from a seasonal thermochemical energy storage system (TCES) coupled with district heating networks (DHN). It allows for a solar-based storage and low-temperature heat generation from the exothermic discharge reaction. The system uses concentrated solar thermal energy to decompose methanol into syngas at moderate temperatures (<315 °C), reducing GHG emissions from combustion to meet residential heat. Its potential is assessed through an analysis of 458 rural municipalities in Spain, achieving a substitution of 3.1 % of the natural gas demand. The system allows the production of green fuels from syngas using an open-loop approach, offering new market pathways in primary sector. In a closed-loop configuration, roundtrip efficiencies exceeding 60 % and chemical conversion efficiencies exceeding 70 % are reached, resulting in a global efficiency of 12 % for the DHN and methanol-TCES. The results show a levelized cost of stored energy highly competitive with other storage systems (<200€/MWh), given its simplicity.

Rapid thermal process for fabricating α-alumina tight ultrafiltration membrane with narrow pore size distribution

The development of tight ceramic ultrafiltration membranes for water purification facilitates is challenging because of high fabrication costs and low permeate flux. In this study, a low-energy rapid thermal process (RTP) was comprehensively investigated for fabricating of high-precision, permeable α-alumina tight ultrafiltration membranes. Compared to the conventional thermal process (CTP), RTP offers an ultra-fast heating rate and shorter holding time, effectively mitigating grain growth and pore aggregation. Moreover, the decomposition of organic matter is delayed during RTP, providing a lower interfacial energy that enables direct formation of α-alumina at a low temperature of 750 °C. During a secondary subsequent RTP, the residual phase is fully converted to α-alumina by the in-situ seeding effect. By utilizing RTP, we successfully prepared α-alumina ultrafiltration membranes within 30 min by calcination, with an average pore size of approximately 6 nm, a narrow pore distribution coefficient of 1.12, and high permeance of 219 L−1·m−2·h−1·bar−1.

Electrocatalysis Boosts the Methanol Thermocatalytic Dehydrogenation for High-Purity H2 and CO Production.

Hydrogen production from methanol represents an energy-sustainable way to produce ethanol, but it normally results in heavy CO2 emissions. The selective conversion of methanol into H2 and valuable chemical feedstocks offers a promising strategy; however, it is limited by the harsh operating conditions and low conversion efficiency. Herein, we realize efficient high-purity H2 and CO production from methanol by coupling the thermocatalytic methanol dehydrogenation with electrocatalytic hydrogen oxidation on a bifunctional Ru/C catalyst. Electrocatalysis enables the acceleration of C-H cleavage and reduces the partial pressure of hydrogen at the anode, which drives the chemical equilibrium and significantly enhances methanol dehydrogenation. Furthermore, a bilayer Ru/C + Pd/C electrode is designed to mitigate CO poisoning and facilitate hydrogen oxidation. As a result, a high yield of H2 (558.54 mmol h-1 g-1) with high purity (99.9%) was achieved by integrating an applied cell voltage of 0.4 V at 200 °C, superior to the conventional thermal and electrocatalytic processes, and CO is the main product at the anode. This work presents a new avenue for efficient H2 production together with valuable chemical synthesis from methanol.

Rapid Thermal Processing and Improved Photocatalysis of Bi2O3-BaTiO3 Heterojunction

Bi2O3-BaTiO3 heterojunction with high photocatalysis efficiency was directly synthesized by rapid thermal processing (RTP). Bi2O3 and BaTiO3 were mixed in ratio and treated by RTP and conventional thermal processing (CTP), respectively. RTP samples have obvious Bi2O3 diffraction peaks, while CTP samples show pure BaTiO3 tetragonal perovskite. More small particles and layered existed in RTP samples. Photodegradation of MB solutions shows that RTP can promote photocatalytic efficiency. Its main lies in the following points: RTP can remove grain boundary defects by strengthening the bond grains; RTP can limit the solution region of the two substances to a certain range to get the best built-in electric field width; and RTP can strengthen the tetragonal BaTiO3 phase to hasten ion movement. Therefore, RTP can achieve much higher photocatalytic efficiency by improving the build heterojunction. This work provides a direct and efficient route to get improvement and high performance of heterojunction.

Predicting dielectric properties of fruit juices at 915 and 2450 MHz using machine learning and physicochemical measurements

Microwave-assisted thermal processing can provide superior quality for fruit-based products when compared to conventional thermal processing. Understanding the temperature-dependent dielectric properties of liquid foods is needed for the analysis and optimization of the microwave applicator chamber since they govern the heating rate and temperature distribution. While literature offers correlations for specific products, there is a scarcity of methods capable of accommodating variability in composition or predicting behavior for broader product groups. In this study, we measured the dielectric properties (dielectric constant and loss factor) of eight fruit juices (passion fruit, melon, pineapple, cashew, orange, lemon, acerola, and guava) using an open-ended coaxial-line technique for temperatures ranging from 5 to 90 °C at commercial frequencies of 915 and 2450 MHz, alongside electrical conductivity. These properties were successfully correlated with the temperature for each individual juice; then, machine learning techniques (random forest, gradient boosting machine, and multilayer perceptron) were used to predict the properties of this diverse group of eight juices based on various physicochemical measurements. These techniques revealed temperature and electrical conductivity as the most critical predictors, while total solids, pH, acidity, ashes, and select color parameters also emerged as significant variables. These findings demonstrate that the integration of physicochemical analyses with machine learning tools offers an objective approach to correlate and predict dielectric properties for a group of food products, facilitating adjustments in product composition without additional measurements, thus enhancing the efficiency and accuracy of microwave-assisted thermal processing simulations and optimizations.

Sustainable biomimetic solar distillation with edge crystallization for passive salt collection and zero brine discharge

The urgency of addressing water scarcity and exponential population rise has necessitated the use of sustainable desalination for clean water production, while conventional thermal desalination processes consume fossil fuel with brine rejection. As a promising solution to sustainable solar thermal distillation, we report a scalable mangrove-mimicked device for direct solar vapor generation and passive salt collection without brine discharge. Capillarity-driven salty water supply and continuous vapor generation are ensured by anti-corrosion porous wicking stem and multi-layer leaves, which are made of low-cost superhydrophilic nanostructured titanium meshes. Precipitated salt at the leaf edge forms porous patch during daytime evaporation and get peeled by gravity during night when saline water rewets the leaves, and these salt patches can enhance vaporization by 1.6 times as indicated by our findings. The proposed solar vapor generator achieves a stable photothermal efficiency around 94% under one sun when treating synthetic seawater with a salinity of 3.5 wt.%. Under outdoor conditions, it can produce 2.2 L m−2 of freshwater per day from real seawater, which is sufficient for individual drinking needs. This kind of biomimetic solar distillation devices have demonstrated great capability in clean water production and passive salt collection to tackle global water and environmental challenges.

In‐Liquid Plasma Catalysis: Tools for Sustainable H2‐free Heavy Oils Upgrading

AbstractNon‐thermal plasma (NTP) catalysis, mirroring the trend towards non‐conventional electron‐mediated molecular activation, unfolds novel routes for chemical reactions. Operating at ambient pressure, lower temperatures, and energized by electricity that can powered by renewable sources, NTP offers a cost‐effective and efficient means of sustainable fuel production. This approach has the potential to revolutionize the oil and gas industry, meeting current energy demands while circumventing the challenges posed by conventional thermal catalysis processes, thereby enhancing environmental sustainability and energy security. Through an exploration of the synergistic effects between plasma, catalysis, and hydrocarbon molecules, this concept paper emphasizes the significant advancements made in in‐liquid plasma catalysis strategies for fuel production from heavy oil upgrading. We also provide insights into the heterogeneous catalyst design and the role of plasma gas as an additional catalyst for achieving efficient and sustainable energy solutions. The prospects of in‐liquid plasma catalysis, emphasizing its transformative role in shaping the energy future, are also discussed.

Cu2ZnSnS4 formation by laser annealing in controlled atmosphere

Laser annealing is an attractive process to form high-quality semiconductor films because of localized annealing area and short annealing time. In a previous study, a Cu2ZnSnS4 (CZTS) polycrystalline semiconductor film was realized using laser annealing in air as a light absorption layer for solar cells, although the crystallization was not sufficient in comparison with CZTS formed by the conventional thermal sulfurization process. In this study, we demonstrate a newly developed gas-atmosphere-controlled laser annealing system. A Cu–Zn–Sn–S-based precursor was formed, followed by laser annealing of the system. Laser annealing in air, Ar, and 5% H2S/Ar gas was performed to investigate the influence of the gas species on the crystallization of the precursor. A 5% H2S/Ar atmosphere promoted the crystallization of CZTS with the suppression of S desorption and Cu sulfide formation, while air and Ar atmospheres allowed the formation of Cu sulfide.

CO2 laser assisted processing of (Ho0.05Y0.95)2Ti2O7 coatings for infrared photonics

We demonstrated CO2 laser assisted processing of highly transparent (Ho0.05Y0.95)2Ti2O7 nanocrystalline coatings. The amorphous coating of the thickness of 577 nm was prepared by subsequent spin-coating of a colloidal solution followed by densification at 700°C in a radiation furnace. The densified coating was irradiated by a laser beam of a power density of 20 mW/mm2 for 60 s to induce the crystallization process. The nanocrystals formation caused the densification of the coatings reducing the thickness to 490 nm and increased the refractive index to 2.088. The coating exhibited strong luminescence at 2.1 and 2.95 μm corresponding to 5I7→5I8 and 5I6→5I7 electronic transitions, respectively. The corresponding time-resolved luminesce records showed the single-exponential decay course reaching the values of 8.4 ms and 0.221 ms for the emissions recorded at 2.1 and 2.95 μm, respectively. The demonstrated process can be used to prepare a luminescent coating with tailored properties. CO2 laser assisted processing can be used in a manner of direct laser writing for the preparation of integrated optical waveguides and amplifiers as a powerful alternative to conventional thermal processing.