Processing Temperature Research Articles

Photothermal Laser Printing of Sub-Micrometer Crystalline ZnO Structures.

During light-driven 3D additive manufacturing, an object represented in digital form is initially translated into a spatial distribution of light intensity (sequentially or in parallel), which then results in a spatial material distribution. To date, this process typically proceeds by photoexcitation of small functional molecules, leading to photochemically induced crosslinking of soft materials. Alternatively, thermal triggers can be employed, yet thermal processes are often slow and provide only low spatial localization. Nevertheless, sub-micrometer ZnO structures for functional microelectronic devices have recently been laser-printed. Herein, the photothermal laser-printing of ZnO is advanced by i) introducing single-crystalline rather than amorphous sub-micrometer ZnO shapes that crystallize in the hexagonal ZnO wurtzite structure, ii) employing dimethyl sulfoxide (DMSO) instead of water, enabling higher local process temperatures without micro-bubble formation, and iii) using substrates tailored for light absorption and heat management, resolving the challenge of light to heat conversion. Finally, the herein-demonstrated ZnO printing requires no post-processing and is a cleanroom-free technique for the fabrication of crystalline semiconductors.

CALCULATION OF THERMODYNAMIC TEMPERATURES OF CHEMICAL REACTIONS OF STEPWISE MANGANESE REDUCTION PROCESS FROM ITS DIOXIDE BY CO GAS AND GASIFICATION OF SOLID CARBON BY DEGREES OF CHEMICAL AFFINITY OF SUBSTANCES TO OXYGEN

The results of a thermodynamic analysis of the course of chemical reactions of the stepwise reduction of manganese from its dioxide by CO gas and the gasification reaction of solid carbon (Bella-Boudoir) are presented. The goals of the work are to obtain eigenexpressions for calculating the numerical values of the Gibbs free energy depending on temperature using tabulated values of the standard enthalpies of formation and entropies of inorganic substances, as well as to construct graphical dependences of the Gibbs energy on temperature using formulas from literary sources and obtained expressions. Numerical values of the boundary temperatures are obtained above which the chemical reactions of the stepwise reduction of manganese from its dioxide by CO gas and the chemical reaction of gasification of solid carbon (Bella-Boudoir) can or cannot thermodynamically proceed. Considering the complete coincidence of the obtained data on the own (obtained) expressions using two (direct and indirect) methods, it is possible to consider with a significant degree of probability the numerical values of the boundary temperature for the reactions of stepwise reduction of manganese from its dioxide and gasification of solid carbon as reliable, which indicates the possibility of the reduction of Mn2O3 from MnO2, Mn3O4 from Mn2O3 and MnO from Mn3O4 by CO gas, the Bell-Boudoir reaction and the impossibility of the reduction of manganese from MnO by CO gas at the temperatures of the actual process in reduction furnaces. This also confirms that CO gas is not a manganese reducer at the last stage of stepwise reduction of MnO according to scheme (B), refuting any theories and assumptions about the possibility of reducing Mn from MnO by CO gas.

Enhancement in Corrosion Resistance of Low-Carbon Steel via Surface Modification

This research investigated the corrosion resistance of surface layers on low-carbon steel exposed to a chloride environment at room temperature. This study systematically evaluated the effects of varying pack compositions, coating temperatures, and application durations on the characteristics of the deposited coatings. The potentiodynamic polarization corrosion test was employed to assess the wet corrosion behavior of the specimens. Elemental compositions and microstructural features were analyzed using energy-dispersive X-ray spectroscopy (EDX) in conjunction with scanning electron microscopy (SEM), providing insights into phase distribution. The chromizing, titanizing, and chromotitanizing treatments were conducted at temperatures of 900 °C, 1000 °C, and 1100 °C, respectively, with varying coating times. X-ray diffraction analysis revealed a complex arrangement of elements and compounds within the coatings, including Cr, Ti, Cr1.9Ti, FeTi, Al2O3, Cr2O3, TiO2, Cr1.36Fe0.52, and (Ti0.86)3.58. The study found that as the deposition duration increased, the coating thickness increased, comprising a thin inner layer and a substantially thicker outer layer. This layered structure resulted from the outward diffusion of Fe atoms and the inward diffusion of Cr and Ti atoms. Electrochemical analysis in a 3.5% NaCl aqueous solution indicated a marked enhancement in the corrosion resistance of the coated specimens compared to their uncoated counterparts. The potentiodynamic polarization tests confirmed that the protective coatings significantly reduced the corrosion rate, with performance influenced by both the temperature and duration of the deposition process. These findings highlighted the potential of tailored coating techniques to improve the durability and performance of low-carbon steel in corrosive environments.

Performance of Steel Beams reinforced by CFRP Sheets with Fire-Retardant Coating

The objective of this study was to determine the physical, mechanical, and chemical aspects of bonding and priming Fire-Retardant Coatings (FRCs) to steel surfaces before and after fire testing. Carbon Fiber Reinforced Polymers (CFRP) have been used to strengthen steel components. Certain types of polymer systems have demonstrated high fire retardancy without additives, while others require additives to achieve optimum fire resistance. A wide range of compounds are available to enhance the fire retardant properties of these materials, characterized by their chemical nature and behavior (such as halogenated, metal complex, silicon-based, and phosphorus additives) and mode of action (either condensed or gas-phase active systems).This article provides a comprehensive overview of fire retardant additives for CFRP used in various large-scale applications, including the aerospace, automotive, railway, electronics, and civil engineering industries, as well as their fire retardant mechanisms at the microscopic, macroscopic, and nanoscale levels. In addition to fire retardant properties, this study also discusses the effects of additives on other material parameters and coatings, such as glass transition temperature, mechanical performance, and FRP processability. The primary focus is on thermoset systems, with a brief mention of thermoplastics according to the matrix compounds relevant to the FRP market size. Test results show that the direct velocity ultrasonic value varied between 3.016 and 3.618 km/s, giving an estimated compressive strength of 15.974 MPa. The standard deviation was 0.533 km/s with a relative standard deviation of 16.407%.

Development and characterization of active gelatin-chitosan packaging incorporated with guava leaf extract for extending meat shelf life

Biopolymer films (biofilms) were evaluated for suitability in meat packaging applications. Polyesters, proteins, and carbohydrates are among the most commonly utilized materials for producing bioplastics due to their mechanical properties, which closely resemble those of conventional plastics. However, these properties are significantly influenced by the film's composition, molecular weight, solvent type, pH, component concentration, and processing temperature. Conventional plastic films, including microplastics, are non-bioactive and contribute to persistent pollution. This underscores the importance of developing novel materials that incorporate bioactive plant compounds to endow plastic films with antimicrobial and antioxidant functionalities. In this study, two gelatin-chitosan films were fabricated: one without any extract and another incorporating guava leaf extract. These films were characterized to determine their optical, mechanical, morphological, and thermal properties. Additionally, a microbiological analysis was conducted to assess the impact of polymeric biofilm packaging on the shelf life of beef. Both films exhibited favorable tensile strength values (24.74 – 27.12 MPa), high transparency (0.79 – 1.18), and effective barrier properties against water vapor (8.95 – 9.29 × 10⁻⁸ g·mm·Pa⁻1·h⁻1·m⁻2) and oxygen (9.7–9.10 × 10⁻1⁸ m³·m⁻2·s⁻1·Pa⁻1). During storage, the biofilm containing guava leaf extract demonstrated a reduction in microbial growth, and this enhanced the beef’s color stability. In conclusion, biopolymeric films incorporating guava leaf extract demonstrated notable antioxidants and antimicrobial properties, effectively inhibiting microbial growth, preserving the physical quality of beef, and significantly extending its shelf life under refrigerated conditions.

A green approach for delignification of corn husks and their application as an unpowered thermo-responsive sensor

The world is adopting biodegradable materials to replace existing petroleum-based plastics, owing to their toxicity and unfriendly environmental aspects. Biodegradable corn husk (CH) is considered a promising alternative due to its environmental friendliness and widespread availability as agricultural waste. In this work, a green process for the delignification of corn husk was developed and preparation of CH-based reversible thermo-responsive delignified corn husk (RTDCH) sensors was done which exhibit different colors corresponding to particular temperature ranges. These RTDCH sensors employed with reversible thermo-responsive nanoparticles (RTNPs) were characterized thoroughly using X-ray Diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), and Fourier transform spectroscopy (FTIR), which ensures their successful synthesis. Upon deploying them for sensing temperatures from 20 to 80℃, different color displays appeared rapidly within 5seconds, which helps to identify the particular temperature range. The RTDCH exhibited excellent reusability for several cycles and maintained consistency in color displays at certain exposed temperatures. The RTDCH, being unpowered, fast responsive, accurate, biodegradable, economical, and scalable production feasibilities, has the necessary traits to become practical at the industrial level. Such materials have tremendous potential for the food industry, scientific laboratories, and monitoring the temperature of industrial processes. The strategy adopted in this work is crucial since it is paving the way for the development of advanced functional materials from natural wastes through green synthesis approaches.

On the Synergistic Interplay Between Annealing Temperature and Time and Additive Concentration for Efficient and Stable FAPbI3 Perovskite Solar Cells

Formamidinium-based lead triiodide perovskite (FAPI) is the workhorse candidate for highly efficient perovskite solar cells owing to its ideal bandgap and phase purity. An essential condition to that is the formation of a pure α-black phase, commonly triggered by external additives such as methylammonium chloride (MACl). This results in the suppression of unwanted crystallization phases and defect reduction. However, there is no consensus on the exact experimental conditions (i.e. annealing time, temperature and concentration) for processing of the additives neither a defined relationship between them nor the resulting film morphology, leading to scattered knowledge on it and lack of thin film reproducibility. Here, we provide a systematic investigation on the simultaneous effect of MACl concentration, annealing time, and annealing temperature on the FAPI crystallization, and ultimately FAPI perovskite solar cell efficiency and stability. Finally, the optimized combination of such parameters, based on tests with 230 devices, leads to the realization of 22.7% efficient inverted FAPI perovskite solar cells with enhanced stability.

Waste management of straw to manufacture biochar: An alternative reinforcing filler for natural rubber biocomposites

To achieve climate neutrality, alternative processes and materials should be proposed to replace those currently in use, which excessively burden the environment. Fossil fuels are non-renewable, and their resources are slowly being depleted, leading to increased prices.The aim of this work was to determine the potential of using agro-industrial residues in the form of oat straw for the production of biochar and its utilization as a filler in natural rubber biocomposites. The process of pyrolysis of plant material was used to obtain biochar with a high carbon content and a characteristic structure, which can affect selected rubber properties. The influence of the applied temperature of the pyrolysis process on the properties of the filler was determined. In this work, analysis techniques were used to enable the evaluation of both filler activity and specific properties of the final vulcanizates. The course of straw pyrolysis process, the carbon content in the fillers, and the size distribution of the bio-additive were examined. The structural, morphological, dispersion, processing, and functional properties of the compositions were examined. The reference in assessing the impact of the produced bio-additive on the properties of the product were composites filled with a commercial carbon black.The conducted research proved that the pyrolysis of straw at a temperature of 600°C was as effective as that carried out at a higher temperature, with comparable weight loss for both samples. The increase in torque was the highest in the case of biochar samples (torque gain 4,4-6,5 dNm), indicating greater intensity of the cross-linking process after the use of this type of additive. This was also confirmed by differential scanning calorimetry. Moreover, the obtained biocomposites were characterized by much higher strength parameters (tensile strength 18,3-21,3MPa) than conventional composites. Unfortunately, vulcanizates containing biochar as a filler exhibited poor resistance to thermo-oxidative aging (aging factor 0,24-0,54).

Research on the oxidation process of micro-boron below the melting point temperature

The ignition and combustion characteristics of boron and the energy release rate of boron-based fuel are closely related to the surface oxide layer of boron. To understand the oxidation process of boron below its melting point, the slow oxidation process of boron under different temperature and humidity storage conditions and the fast oxidation process under high-temperature conditions were investigated. The results indicate that the surface oxide layer mainly comprises boron (B), boron suboxides (BxOy), and boron trioxide (B2O3). When the degree of oxidation is low, BxOy and B are the main components. After deep oxidation, BxOy almost disappeared. The thickness and composition of the surface oxide layer vary with changes in environmental temperature, humidity, and aging time. The effect of temperature increase on the growth rate of the oxide layer thickness is significantly greater than that of moisture. With the prolongation of boron aging treatment time, the onset, end, and maximum weight gain rate temperatures of the boron thermal oxidation process all slightly decrease. As the ambient temperature increases, the formation of the oxide layer transitions from a unidirectional diffusion mechanism of oxygen into the interior of boron particles to a bidirectional diffusion mechanism of molten oxide and oxygen.

Temperature distribution characteristics of linear fires in utility tunnels under the influence of sealing ratios and vertical positions of the fire source

This study delves into two key factors affecting fire development process and longitudinal ceiling temperature attenuation characteristics in a utility tunnel: the sealing ratios and the vertical positions of the linear fire source. The evolution process of linear fire is typically divided into five stages. In the stable combustion stage, the flame height at the end of the liner fire source is observed to be higher than that at the center. During the rapid loss stage of mass, the mass loss rate peaks and then stabilizes for a period of time, the maximum peak growth rate is 1.35 (the fire source is located at position 02), the duration shortens as the distance between the liner fire source and the ceiling decreases and the sealing ratio increases. When the sealing ratio is 100 %, the maximum temperature growth rate is 2.25 with the change of fire source position. The ceiling temperature in the upper part of the linear fire zone is lower in the center and higher on both sides, however, the distribution is asymmetric. A mathematical model of longitudinal ceiling temperature attenuation is established. The results may provide guidance for the control of linear fires in long-narrow confined spaces.

Pressureless synthesis and consolidation of the entropy-stabilized (Hf0.25Zr0.25Ti0.25V0.25)B2-B4C composite by ultra-fast high-temperature sintering (UHS)

Entropy-stabilized Ultra High-Temperature Ceramics (UHTC) offer a groundbreaking solution to the challenges of extreme environments, showcasing enhanced mechanical properties, thermal stability, and resistance to oxidation at high temperatures. The consolidation of UHTC by ultra-fast high-temperature sintering (UHS) significantly reduces processing times and temperature and can produce dense high-performance ceramics with superior mechanical properties. This study reports the pressureless synthesis and consolidation of the entropy-stabilized (Hf0.25Zr0.25Ti0.25V0.25)B2-B4C composite through UHS within 1minute, starting from transition metal diboride powders. B4C acts as an effective sintering aid, promoting the densification of the system and the formation of a nearly single-phase hexagonal diboride with a diboride-eutectic phase. Furthermore, a secondary minor hexagonal phase rich in V and Zr is formed close to the eutectic regions. Sintering currents of 40A were necessary to reach densities higher than 90% under pressureless conditions, achieving nano hardness higher than 27.3GPa, comparable with high-entropy diborides produced by Spark Plasma Sintering. The study highlights the entropy-stabilized phase formation, diffusion, densification, and grain mechanisms involved during UHS. The work contributes to understanding entropy-stabilized ceramics produced by UHS as a faster and less energy-consuming process than more conventional sintering methods.

From biogas to biomethane: Evaluating the role of microalgae in sustainable energy production – A review

Methane, predominantly derived from fossil resources, is a highly utilised energy source due to its high energy density. However, the rapid consumption of fossil fuels has precipitated anthropogenic climate change and resource depletion, compelling the necessity for a transition towards sustainable and climate-compatible energy sources. This review examines biogas upgrading technologies, encompassing physical, chemical, and biological methods, with a particular focus on photosynthetic CO2 fixation to enhance methane purity and meet biomethane purity standards. Biological processes, in particular those utilising microalgae, demonstrate considerable potential for CO2 sequestration and have the capacity to reduce emissions while simultaneously generating valuable byproducts. The review investigates key process parameters, including pH, liquid-to-gas (L/G) ratio, temperature, and gas retention time (GRT), along with the removal efficiency of CO2. The mass transfer of CO2 and the role of microorganisms are also examined. Furthermore, biological, and chemical/physical upgrading technologies are economically and ecologically compared.

Influences of modified Chaplygin dark fluid around a black hole

In this work, we study a static, spherically charged AdS black hole within a modified cosmological Chaplygin gas (MCG), adhering to the calorific equation of state, as a unified dark fluid model of dark energy and dark matter. We explore the influence of model parameters on several characteristics of the MCG-motivated charged AdS black hole (MCG-AdSBH), including the geodesic structure and some astrophysical phenomena such as null trajectories, shadow silhouettes, light deflection angles, and the determination of greybody bounds. We then discuss how the model parameters affect the Hawking temperature, remnant radius, and evaporation process of the MCG-AdSBH. Quasinormal modes are also investigated using the eikonal approximation method. Constraints on the MCG-AdSBH parameters are derived from EHT observations of M87* and Sgr A*, suggesting that MCG-AdSBH could be strong candidates for astrophysical black hole.

Interfacial structure and mechanical properties of contact-reaction TC4/TC4 joint brazed with copper filler

TC4 alloy was brazed by contact reaction brazing without flux in vacuum brazing furnace with copper foil as intermediate layer. The variation of microstructure and strength of the sandwich TC4/Cu/TC4 brazed joints with different brazing temperature were discussed. The results showed that the joint consisted of diffusion zone (β-Ti), interface zone (Ti2Cu) and center zone (a large amount of complex Ti-Cu compounds) with low brazing temperature (920 ℃). With the increase of temperature, the center zone firstly disappeared, then the interface zone, finally leaving the diffusion zone and little of interface zone (1010 ℃). After the compression shear testing, it showed that with the increasing brazing temperature, the shear strength of the joints raised, the maximum shear strength can reach 735MPa at 980 ℃. Although further increasing the brazing temperature increases the joint strength, the high processing temperature (above the α→β phase transus temperature of about 985 ℃) deteriorates the properties of the TC4 base metal. The fracture mode with low brazing temperature presented cleavage fracture while the fracture mode with high brazing temperature appeared quasi-cleavage fracture.

Study of the Straw Compaction Degree as a Function of Moisture Content, Particle Size and Process Temperature

Study of the Straw Compaction Degree as a Function of Moisture Content, Particle Size and Process Temperature

Unveiling the Corrosion Mechanism of the NixSey Intermetallic Compound in Water-Based Solution.

In this study, Ni-Se intermetallic compound coatings were fabricated using electrodeposition at various process temperatures (40-70 °C). The results show that increasing the process temperature promotes the deposition of Se, which leads to a transition in the crystal phase of the samples from the Ni0.85Se phase, prepared under low-temperature conditions, to a NiSe2 phase. The dissolution rate of Se in pure water from Ni-Se coatings is inversely related to the incorporated Se content, which indicates that the Ni0.85Se phase has a higher natural corrosion rate compared to the NiSe2 phase. Under the influence of an electric field, the corrosion behavior of Ni-Se coatings is dominated by a two-stage reaction involving Se transformation and dissolution. Coatings with a predominant Ni0.85Se phase exhibit more severe corrosion behavior compared to those with a predominant NiSe2 phase, which suggests that the corrosion reaction is enhanced by the electric field. However, because coatings with a predominant NiSe2 phase contain a higher proportion of Se22- ions, the dissolution reaction of SeOx, generated during the electrochemical reaction, is retarded, thereby inhibiting the progression of the corrosion reaction. Consequently, coatings with a predominant NiSe2 phase exhibit relatively better corrosion resistance in a water-based electrolyte.

Characterisation of zinc phosphate coating deposited on carbon steel wire rod using an accelerator-side and iron-side phosphating solution

ABSTRACT Accelerator-side phosphating solutions are widely used for zinc phosphate conversion coating on carbon steel wire rods to impart good lubrication and corrosion resistance during wire drawing of steel. But on the accelerator side, the use of nitrite and nitrate as accelerator agents has challenges of high process temperature, liberation of nitrous gases and high sludge generation. For these challenges, the iron-side phosphating process is used as one of the solutions where the bath is maintained at a higher iron level and aeration is done to oxidise ferrous iron instead of an accelerator. In the literature, details of different processes and bath composition are available but their effects on the characteristics of zinc phosphate coating deposited on the carbon steel wire rod are not available. In this paper, zinc phosphate coating was deposited on different grades and sizes of wire rods using accelerator-side and iron-side phosphate solutions and their effect on coating weight and other coating characteristics was studied using SEM, EDS and Tafel polarisation experiments.

Effects of Copper Content and Thermo-Mechanical Treatment on Microstructure and Mechanical Properties of AlMgSi(Cu) Alloys

This study presents the results of research on the influence of different contents of copper in aluminium alloys based on the 6xxx series on mechanical and structural properties. The investigation started with the alloying, and casting four billet variants with different copper content—0.8% Cu; 2B—1% Cu; 3A—1.2% Cu; and 3B—1.4% Cu. The prepared materials were homogenised and extruded on a 500T horizontal press with two different process temperatures and ram speeds ranging from 1 mm/s to 9 mm/s. After heat treating to the T6 and T5 tempers, their mechanical properties were tested. On this basis, the two most promising alloys 2A and 3B were selected and subjected to further tests. After extrusion and heat treatment of the profiles (to F, T1, T2, T5, and T5510), their mechanical properties were determined to select the preferred process parameters. Finally, a structural test based on crystallographic orientation based on the EBSD technique and TEM observations allowed for the characterisation of grain size, dispersoids, and phase analysis. Bright-field (BF) analysis allowed us to compare the deformed areas for T1, T5, and T5510 temperatures. The results showed significant growth in the mechanical properties of all the subjected alloys, and the best properties were shown for a Cu content of 1.4% with a tensile strength of 460 MPa and an elongation of 16% (T5510 tempering). The structural test showed an average grain size of 18 µm to 23 µm and solid solution decomposition differences for different heat-treating parameters.

Rheological and Mechanical Properties and Spinning Behavior of a Starch-Based Biodegradable Polymer

Over the last few years, the interest in biodegradable polymers has been increasing for several reasons, mainly because of the concerns about environmental protection and the reduction of emissions, especially those related to non-renewable fossil-based resources. Therefore, special attention has increased for the development of environment-friendly polymers such as biodegradable/compostable polymers, especially when they come from renewable resources, since this would help in further reducing energy consumption during their life cycle, as well as the overall environmental impact. Thus, every biopolymer should be accurately investigated in terms of its processability and main technological properties in order to find the most suitable applications. In this work, a starch-derived MaterBi® sample was characterized from the rheological and mechanical point of view, with particular focus on its ability to be processed under non-isothermal elongational flow. The role of processing parameters, such as the temperature and humidity content, was investigated, and a significant influence was found from the processing temperature. Fiber spinning was also performed, finding a good spinnability of the extrudates; in this context, the influence of the draw ratio was investigated as well, with significant effects on the main mechanical properties of the fibers.

Machining Eco-Friendly Jute Fiber-Reinforced Epoxy Composites Using Specially Produced Cryo-Treated and Untreated Cutting Tools

In recent years, consumers have become increasingly interested in natural, biodegradable and eco-friendly composites. Eco-friendly composites manufactured using natural reinforcing filling materials stand out with properties such as cost effectiveness and easy accessibility. For these reasons, in this research, a composite workpiece was specially manufactured using eco-friendly jute fibers. Two cost-effective cutting tools were specially produced to ensure high-quality machining of this composite workpiece. One of these specially manufactured cutting tools was subjected to DC&T (deep cryogenic treatment and tempering) processes to improve its performance. At the end of the research, when the lowest and highest Fd (delamination factor) values obtained with DC&T-T1 and T1 cutting tools were compared, it was observed that 5.49% and 6.23% better results were obtained with the DC&T-T1 cutting tool, respectively. From the analysis of the S/N (signal-to-noise) ratios obtained using Fd values, it was found that the most appropriate machining parameters for the composite workpiece used in this investigation were the DC&T-T1 cutting tool, a 2000 rev/min spindle speed and a 100 mm/min feed rate. Through ANOVAs (analyses of variance), it was discovered that the most significant parameter having an impact on the Fd values was the spindle speed, with a rate of 53.01%. Considering the lowest and highest Ra (average surface roughness) values obtained using DC&T-T1 and T1 cutting tools, it was seen that 19.42% and 16.91% better results were obtained using the DC&T-T1 cutting tool, respectively. In the S/N ratio analysis results obtained using Ra values, it was revealed that the most appropriate machining parameters for the composite workpiece used in this investigation were the DC&T-T1 cutting tool, a 2000 rev/min spindle speed and a 100 mm/min feed rate. In the ANOVAs, it was revealed that the most significant parameter having an effect on the Ra values was the feed rate at 37.86%.