Low-temperature Process Research Articles

Catalytic functionalization of MCM-41 and MCM-48 with copper by modified template ion-exchange method for low-temperature NH3-SCR process: the role of complexing agents for copper dispersion

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper by template ion-exchange (TIE) technique. A high dispersion of deposited copper species was managed by subsequent treatment of the samples with ammonia, urea, or acetonitrile solution. Copper-modified silicas were analysed in terms of their chemical composition (ICP-OES), ordering of porous structure (XRD), textural parameters (low-temperature N2 sorption), dispersion and form of introduced copper species (UV–vis-DR, XRD, H2-TPR, NH3-TPD). Mesoporous silicas modified with copper exhibited promising catalytic efficiency in selective catalytic reduction of NO with ammonia (NH3-SCR). The samples containing dispersed copper species (predominantly monomeric copper cations) presented enhanced catalytic activity compared to catalysts containing CuO aggregates. On the other hand, CuO aggregates showed greater catalytic activity in the side process of direct ammonia oxidation by oxygen present in the reaction mixture. It was demonstrated that TIE post-treatment of the samples with urea resulted in most effective improving dispersion of deposited copper and is less destructive for ordered porous structures of mesoporous silica comparing to treatment with ammonia solution.Graphical abstract

Progress in essential oil extraction and their applications in food packaging and preservation

AbstractEssential oils (EOs) are secondary metabolites synthesised by many aromatic plants, which have good antimicrobial and antioxidant activities making them popular functional agents for food preservation and packaging applications. In recent years, novel extraction techniques, such as super critical fluid extraction, pulsed electric field assisted extraction and ultrasound assisted extraction have been explored as alternatives to the conventional solvent‐based extraction methods. This review mainly discusses on recent progresses in sustainable extraction of essential oil (EO) from aromatic plants and food processing wastes and their functional properties, and applications in food preservation have also been summarised. Sustainable extraction techniques yield better‐quality EO due to low temperature and short time process compared to the conventional extraction. Despite efficacy of EOs as good active agents, their low water solubility, volatile nature, strong flavour, and susceptibility to food processing parameters are major challenges against their applications in food. These challenges can be mitigated by advanced techniques such as encapsulation and nanoemulsification of EO, which provide dual functions of enhanced applicability and improved functional properties. Incorporation of EO in the biopolymer‐based films and coatings can open avenues for sustainable food packaging and preservation.

Fabrication Strategies for 2D Halide Perovskite Towards Next-Generation Optoelectronic Applications

AbstractHalide perovskites have emerged as promising materials in high-performance optoelectronics due to their exceptional optoelectrical properties, such as long carrier lifetime and tunable bandgap. Despite the promising capabilities of three-dimensional (3D) halide perovskites in applications like solar cells and light-emitting diodes, their operational stability remains a critical challenge. This review focuses on quasi-two-dimensional (2D) halide perovskites, which offer enhanced stability through their reduced dimensionality. We discuss the unique properties of these materials, including the ability to modify optical and electronic characteristics by altering the organic cations and the layer number in the perovskite structure. Additionally, we review various fabrication techniques, highlighting the shift from traditional low-temperature solution processes to more advanced solid, liquid, and vapor-phase methods, which address the limitations of conventional fabrication and enhance material quality. This comprehensive review aims to provide insights into the development of stable and efficient 2D halide perovskite-based optoelectronic devices, paving the way for their integration into next-generation optoelectronic applications.

PROSPECTS OF THE APPLICATION OF LOW-TEMPERATURE PYROLYSIS PROCESSES FOR THE THERMAL DESTRUCTION OF HYDROCARBON-CONTAINING WASTE OF VARIOUS ORIGINS

A generalized analysis of the existing methods of utilization of hydrocarbon-containing waste of various origins and practical data on the existing experience of using low-temperature pyrolysis processes for the thermal destruction of hydrocarbon-containing municipal and oil waste are presented. A series of studies of thermochemical processes of waste destruction were conducted for both municipal solid waste and industrial waste. The common feature that unites the objects of research is their wide morphology, the presence of the predominant proportion of hydrocarbons and their derivatives. To implement the process of low-temperature pyrolysis of hydrocarbon-containing waste of various origins, a universal installation with a rotating reactor is proposed. The features of its operation, technical characteristics and advantages are presented. The prospects for further development of low-temperature pyrolysis technology for the utilization of unsorted waste groups from sorting complexes are substantiated. Bibl. 30, Fig. 2, Tab. 2.

Low temperature processing and characterization of novel ceria based electrolyte composition Ce0.8−xGd0.1Bi0.1TixO2−δ (x = 0.05,0.1) for intermediate temperature SOFC application

Low temperature processing and characterization of novel ceria based electrolyte composition Ce0.8−xGd0.1Bi0.1TixO2−δ (x = 0.05,0.1) for intermediate temperature SOFC application

Performance analysis of heat pump drying system combined with rotor dehumidification for low temperature drying of mango slices

In order to solve the problems of low drying efficiency and poor drying quality existing in the current closed heat pump drying system (CHPD), a closed carbon dioxide heat pump drying system (CHPRD) with the function of combining rotor dehumidification was designed. This study investigates the drying kinetics and quality characteristics of CHPRD in low-temperature drying processes using mango as the drying material through experimental studies and theoretical analysis. The experimental results showed that the drying rate of CHPRD increased by 29% and 17.8%, the moisture removal rate per unit energy (SMER) by 14.2% and 12.5%, and the coefficient of performance (COP) by 17.3% and 12.0%, respectively, compared with that of CHPD in the low-temperature drying process with loading amounts of 400 and 450 g, respectively. In terms of drying quality, the rehydration factor (Rf ) of CHPRD-dried mango slices increased by 6.0% and 5.0%, the ascorbic acid content increased by 15.0% and 14.4%, and the color difference (ΔE) was lower by 11.0% and 5.6%, respectively. These improvements indicate that CHPRD provides better drying kinetics and higher quality of dried material. Based on the experimental data, simulation fitting was conducted, revealing that the two-term model is the best mathematical model to simulate the drying characteristics of CHPRD for mango.

Heavy metal migration and enrichment in desulfurization wastewater during low-temperature triple effect evaporation process

Zero discharge of desulfurization wastewater from coal-fired power plants has become important. Desulfurization wastewater and gypsum from different stages of the low-temperature triple-effect evaporation process of a coal-fired power plant were collected and investigated. The results showed that after low-temperature triple-effect evaporation, the concentrations of Na+, Mg2+, K+, and Cl− in the desulfurization wastewater increased by 7.91, 7.15, 8.49, and 8.35 times, respectively. With the progress of low-temperature triple effect evaporation process, the concentrations of As, Cd, Co, Cr, Cu, Mn, Se, and Zn in the wastewater after the triple effects were 5.85, 75.44, 1.28, 2.34, 13.66, 5.58, 8.59, and 4.35 times higher than those in the raw wastewater. Mn and Se exceeded the emission limits by 40 and 10 times, respectively. After triple-effect evaporation, the concentrations of As, Cd, Co, Cr, Cu, Pb, Se, and Zn in gypsum decreased to 46%, 26%, 66%, 41%, 35%, 97%, 39%, and 51% of the raw gypsum, respectively. Compared with that of other metal sulfates, the solubility of PbSO4 was extremely low under low-temperature conditions, and some PbSO4 precipitated during the triple-effect evaporation process, leading to a gradual decrease in the Pb concentration in the liquid phase. The mercury compounds in gypsum after the first and second effects were the same as those in raw gypsum, both of which were HgS and HgO. After third effect, the mercury compound in gypsum also included HgSO4. In addition, owing to the promoting effect of the pH of desulfurization wastewater approaching 5.50 on the generation of HgS, the proportion of HgS gradually increased, and the proportion of HgO gradually decreased from the raw gypsum to the third effect gypsum. Therefore, the stability of the mercury compounds in gypsum was enhanced. It can provide a good reference for the migration and enrichment of heavy metals in the low-temperature triple-effect evaporation process, which is beneficial for the clean production and efficient utilization of coal.

Sintering activation energy and low-temperature sinterable process of Boron-lanthanide glass/Li2Zn3Ti4O12 ceramic composite systems for LTCC technology

This work investigates the characteristics of wettability, activation energy for sintering, evolution of phase structure, and behavior during the low-temperature sintering process of B2O3-La2O3-MgO-TiO2 (BLMT) glass/Li2Zn3Ti4O12 ceramic composites for low temperature co-fried ceramics technology (LTCC). As the BLMT glass content increases from 0 to 10 wt%, the average sintering activation energy (Ea) of the composite decreases from 450 ± 8 to 356 ± 37 kJ/mol. There are two phases the primary Li2Zn3Ti4O12 phase and the secondary LaBO3 phase, the latter precipitates from the BLMT glass after sintering at 700 °C. This indicates that BLMT glass promotes the sintering of Li2Zn3Ti4O12 ceramic below 900 °C. In composites containing 20 wt% or more glass, sintering is governed by both liquid-phase sintering and reactive viscous sintering. As the BLMT glass content increases, the impact of viscous flow on the densification process becomes more pronounced. Simultaneously, when the glass content is greater than 20 wt%, the glass precipitates LaBO3, TiO2, and MgLaB5O10 phases between 700 and 750 °C. After 850 °C, the glass melts and reacts with Li2Zn3Ti4O12 phase to produce a new TiO2 phase. Accordingly, the activation energy (Ea) of sintering the composite material increases from 393 ± 17 to 667 ± 1 kJ/mol.

Including detailed chemistry features in the modeling of emerging low-temperature reactive flows: A review on the application to diluted and MILD combustion systems

Developing and optimizing new reactive systems with carbon-neutral fuels like biofuels, e-fuel, hydrogen, or ammonia is crucial for sustainable energy. This requires advanced technologies capable of fuel flexibility, high efficiency, and minimal pollutant emissions. However, these energy carriers still produce pollutants, especially NOx. To address this, engineers aim to lower combustion process temperatures by adopting different strategies such as burned gas recirculation, staging or increasing the air-to-fuel ratio. Yet, lean flames, though effective at emission reduction, are prone to instability and extinction, posing safety and mechanical risks. Emerging technologies like MILD Combustion, based on burned gas recirculation and reactant dilutions offer interesting solutions. The review article begins by synthesizing experimental studies and numerical simulations of MILD turbulent combustion. It then explores fundamental phenomena specific to diluted combustion (where MILD regimes are included as sub-sets), including autoignition and flame propagation. Using high-fidelity simulations and advanced experiments, it examines flow and mixing roles in reactive zones stabilization. Moving forward, the review paper addresses the inclusion of detailed chemical properties in modeling turbulent combustion systems. Scientific challenges revolve around modeling the intricate interactions between combustion chemistry and flow turbulence while maintaining computational efficiency compatible with industrial constraints. To address this, various simplified chemistry methods – such as reduced, tabulated, or optimized chemistry – have been developed. Additionally, turbulence/chemistry coupling modeling remains unresolved in simulations, with three main routes – geometrical, statistical, or reactor-based approaches – available for turbulent combustion modeling. The state-of-the-art in simplified chemistry and turbulent combustion modeling for low-temperature regimes is then focused on capturing MILD regimes, where there is a crucial impact of dilution by burnt gases, heat transfer, and turbulence mixing on the chemical flame structure. Recent advancements enabled by machine learning and deep learning algorithms are also highlighted. Lastly, the article underscores the critical need for data to validate models, emphasizing the importance of scale-bridging experiments.

JWST imaging of the closest globular clusters

We present observations of the two closest globular clusters, NGC 6121 and NGC 6397, taken with the NIRISS detector of JWST. The combination of our new JWST data with archival Hubble Space Telescope (HST) images allows us to compute proper motions, disentangle cluster members from field objects, and probe the main sequence (MS) of the clusters down to <0.1 M⊙ as well as the brighter part of the white-dwarf sequence. We show that theoretical isochrones fall short in modeling the low-mass MS and discuss possible explanations for the observed discrepancies. Our analysis suggests that the lowest-mass members of both clusters are significantly more metal-rich and oxygen-poor than their higher-mass counterparts. It is unclear whether the difference is caused by a genuine mass-dependent chemical heterogeneity, low-temperature atmospheric processes altering the observed abundances, or systematic shortcomings in the models. We computed the present-day local luminosity and mass functions of the two clusters; our data reveal a strong flattening of the mass function indicative of a significant preferential loss of low-mass stars in agreement with previous dynamical models for these two clusters. We have made our NIRISS astro-photometric catalogs and stacked images publicly available to the community.

Low temperature combustion and ash deposition characteristics of palm oil and forest replanting waste

This study evaluation and analysis the low-temperature combustion characteristics and ash deposition of palm oil waste, including palm kernel shell (PKS) and empty fruit bunch (EFB), as well as forestry waste in the form of rubber wood (RBW) and replanting waste (RPW). The experiments were conducted using a drop tube furnace at 900 ᵒC, which is considered a low temperature compared to the operating temperature of pulverized coal. The thermogravimetric method (TGA) was applied to understand the combustion properties of the biomass, while the ash deposition tendency was assessed through empirical calculations, combustion experiments, and direct observation of the ash produced. The results showed that RBW had the best combustion performance compared to the other samples. Although RPW has the highest ash fusion temperature value among all samples, with a value above 1200 ᵒC, the low-melting-point mineral phase such as fairchildite, produced at low-temperature combustion at 24.74%, increases the risk of ash sticking to metal surfaces. PKS and EFB produce very high albite mineral content of more than 60%, which has a low melting point and could potentially cause ash deposition problems. On the other hand, RBW, with a dominant content of SiO2 (21.79%), Al2O3 (20.24%), and MgO (8.03%), produces minerals dominated by quartz at up to 78% and magnesioferrite at more than 5%, both of which have a high melting point that tends to produce harmless ash. These findings provide insight into the potential of utilizing biomass in low-temperature combustion processes, which is a way of reducing waste and lowering greenhouse gas emissions.

Improved Subthreshold Characteristics of Epi-Silicon FinFET via Fin Surface Passivation Technologies

As demand for advanced integrated circuits (ICs) continues to grow, fin field-effect transistors (FinFETs) have remained highly influential in the IC market because of their mature fabrication process and powerful driving capabilities. However, the ion bombardment that occurs during the reactive ion etching (RIE) process used to form the fin structure increases the fin’s surface roughness and results in a high interfacial state density (D it ), which hinders further improvement in the subthreshold swing (SS) of FinFETs. To overcome this issue, this study proposes two oxidative trimming methods for use on the fin structures to improve their interface quality. It is found that conventional thermal oxidation and low-temperature oxidation processes reduced the channel D it by 73.31% vs 71.17%, respectively. Furthermore, the corresponding SS values of the device improved to 72.76 and 71.72 mV dec−1, respectively. The technical solutions proposed in this paper represent a promising approach for performance optimization of FinFETs and other advanced devices.

Flexible and Flame Retardant Cotton Fiber-reinforced CS/CNF/EP Composites For a Sensitive Fire Warning

Enhancing fire safety performance in resin-based composites is critical for mitigating fire hazards. Composites that provide early warnings during initial fire stages and maintain prolonged alarm capabilities under flame exposure are essential for minimizing injuries and property damage. This study employs chitosan (CS) as a cross-linking and char-forming agent, while carbon nanofiber (CNF) acts as a flame retardant and conductive component. Cotton fiber-reinforced chitosan/carbon nanofiber composites with varying epoxy and CNF contents (CS/CNF/EP) were prepared through a straightforward low-temperature curing process (40 °C, 4 h). Crosslinking polymerization between chitosan and epoxy was confirmed via Fourier Transform Infrared Spectroscopy (FTIR). The presence of the tough structure of CS and the rigid structure of EP results in a synergistic toughening and reinforcement effect in the CS/CNF/EP composites. Additionally, due to the carbon facilitating properties of CS and the enhanced conductivity of CNF, the composites exhibit a sensitive fire alarm functionality. At 35 % epoxy content, the CS/CNF/EP composites demonstrated exceptional properties, including mechanical flexibility (tensile strength of 7.09 MPa and breaking elongation of 129.05 %) and outstanding flame retardancy (LOI of 32.3 % and UL-94 V-0 rating). These composites provided a rapid alarm (∼1 s), sustaining a 263 s warning under flame exposure and over 35 min post-flame removal. These findings indicate that CS/CNF/EP composites, integrating mechanical flexibility, flame retardancy, and superior fire warning properties, present significant potential applications in fire safety engineering.

Development and characterization of carbon fiber reinforcement in Aluminium metal matrix composites

Abstract Carbon fibers (CF) possess exceptional mechanical properties and the highest degree of chemical stability. However, carbon reinforcement in metal matrix composites is extremely scarce due to production difficulties, particularly in obtaining a uniform distribution. Carbon fiber reinforced composites are typically made using high temperature processing processes. However, the fibers must be coated with Ni or Cu in order to achieve effective particle dispersion; otherwise, there is a larger likelihood of intermetallic compound formation, which reduces the chances for enhanced properties. In this work, the metallurgical, mechanical, and tribological characteristics of the carbon fiber reinforcement in AA 7050 are examined. Uncoated carbon fibers are reinforced into the Aluminium matrix using a low temperature processing technique known as powder metallurgy. The AA 7050 matrix reinforced with carbon fibers at various weight percentages between 0 and 1.5. The samples undergone mechanical and metallurgical testing in accordance with ASTM guidelines. The findings indicate that the 0.25 weight percent carbon fiber reinforcement in the matrix increased the material’s hardness by 30% over the monolithic alloy, making it an excellent alternative for structural applications.

Evaluation on the effect of modified treatment of spent coffee grounds on the concrete performance

To evaluate the change of low-temperature hydrothermal process on the characteristics of spent coffee grounds (SCG) and the performance after incorporation into concrete, the experiment of hydrothermal temperature and times was designed and carried out to incorporate the prepared spent coffee grounds hydrothermal biochar (SCG-HTC) as fine aggregate into concrete in the study. The study carried out to assess the varying SCG-HTC characteristics, SCG-HTC concrete performances and economic benefits through a methodological approach covering microstructure, workability, mechanical and thermal performance. The effects of hydrothermal times and temperature on the characteristics of SCG-HTC and the performance of SCG-HTC concrete were revealed. The results showed that the increase of both hydrothermal times and temperature significantly enriched the pore structure of SCG-HTC and changed the morphology of SCG-HTC particles. With the increase of hydrothermal temperature and times, the workability of SCG-HTC concrete gradually deteriorated, the mechanical performance first increased and then decreased, the thermal insulation performance and the ability to resist temperature changes improved. The appropriate substitution amount of SCG-HTC was not more than 15 %, and the cost of concrete could be reduced by 5 %∼7 %.

Deconvolution of high and low-temperature alteration processes along the contact zones of basaltic-dike intrusions in basaltic host rocks of different permeabilities – implications for geothermal exploration

Magmatic intrusions serve as crucial heat sources for geothermal systems, facilitating mass transfer, mineral transformations, and elemental exchange, which result in the formation of contact aureoles. While these processes have been extensively studied in large intrusive complexes in ancient geological formations, understanding of their occurrence in active geothermal systems remains limited. The extreme conditions present in active volcanic systems often obscure the geochemical processes occurring within host rock/intrusion zones. Uncertainties persist regarding whether relatively small dike intrusions (∼0.5 m thick) possess sufficient heat content to induce textural or geochemical changes in the surrounding wall rock, and what implications this may hold for future exploratory drilling projects. The analyses in this study were conducted on two distinct outcrops, each featuring 50-cm thick basaltic intrusions within both high- and low-permeability basaltic host rocks. The low permeability host rock hosts high-temperature mineral phases (>800 °C), such as sanidine + hedenbergite + albite-rich plagioclase in the contact zone, which we interpret to have formed during partial melting. Immobile, incompatible trace elements (such as Zr, Nb and La) retain the signatures of partial melting in both outcrops. We demonstrate that low degree partial melting (F ≈ 3–10 %) results in a compositional shift in the host rock from basalt to dacite and/or trachyandesite. Thermal modelling suggests that these small dikes, along with their partial melts in the contact zone, form over a very short period of time (< 1 day), but can elevate the ambient temperature. This type of events play an important role in the development of active geothermal systems. In theory, these small dikes do not pose a significant risk during geothermal drilling, unless they are too small to be detected during geophysical exploration.

Source/Drain Epitaxy for Nanosheet-Based CFET Devices

This work reports the progress in source/drain (S/D) epitaxy development for nanosheet-based monolithic complementary field effect transistors (mCFET). S/D processes which were set-up for bulk finFET devices can be easily transferred to mCFET devices. Owing to the complicated integration and small dimensions of the highly scaled structures however, more attention is required for the pre-epi cleaning of the exposed channel interfaces and for the additional defectivity that arises from the merging of individual epitaxial growth fronts. Low-temperature epi processes can be structurally integrated in mCFET devices, to further reduce the transistor access resistance components and comply with thermal budget limitations.

Experimental and first-principles novel insights of atomic collapsed structure and composition-driven ω-precipitates

A complex ω phase transition is often observed in titanium alloys; nevertheless, the underlying knowledge of ω-embrittlement are not yet fully understood and require deeper insight. In this study, the ωT and ωH phases, as well as their interfacial structures, have been systematically investigated to examine compositional partitioning and to estimate Z values. A combination of aberration-corrected HAADF-S/TEM advanced characterization techniques, together with first-principles density functional theory calculations were performed under various heat treatment conditions. The results revealed that the low-temperature ageing process suppresses ω-assisted secondary α precipitations at ωT/β interfaces, whereas high-temperature ageing process promotes ω-assisted secondary α precipitations at ωH/β interface, due to relatively higher concentrations of Mo and Al contents. The interfacial energies (γ{ωβ}) between β and ω phases increase with decreasing local compositions of Mo and Al, suggesting increased stability of the ω phase and decreased stability of the β phase. Furthermore, the formation energies of β and ω phases were computed with Mo content at different Al composition, results indicate that the ω phase transition process is affected by the reduced Al content. The observations of this work provide deeper understanding of the ω phase transition mechanism in titanium alloys.

Improved Performance of Bifacial Photovoltaic Modules with Low-Temperature Processed Textured Rear Reflector

Improved Performance of Bifacial Photovoltaic Modules with Low-Temperature Processed Textured Rear Reflector

Cross-sectional surface analysis of magnetic domains, microstructures, and magnetic properties of the low-temperature phase MnBi prepared by low-temperature vacuum sintering

In this work, the low-temperature phase MnBi prepared by a low-temperature vacuum sintering process at 325 °C was studied. We found a significant increase in the energy product from 2.63 MGOe in the 12-h sintered sample to 3.64 MGOe in the 48-h sintered sample. This improvement is attributed to the solid-liquid diffusion process. Cross-sectional scanning electron microscopy (SEM) reveals that MnBi forms at the external surface of Mn particles and along interior surfaces, notably within cracks. Transmission electron microscopy further demonstrates that the Mn ratio increases and Bi decreases with distance from the crack. The selected area diffraction showed variations in the Mn ratio with distance from cracks and identified both Bi and MnBi phases in the MnBi layer. Magnetic force microscopy (MFM) analysis exhibited large phase shifts indicating repulsive or attractive forces in single ferromagnetic domains. This provides valuable insight into magnetic domains in the MnBi regions near Mn cracks. The MnBi formation model, developed for the vicinity of single cracks with uniform MnBi content, partly explains the magnetic interactions and phase shifts observed near these cracks. These findings provide significant insights into the MnBi microstructural and magnetic properties, potentially useful in tailoring and engineering magnetic structures.