Thermal Test Research Articles

Construction of microstructurally controllable B/BaCrO4 particles based on droplet microfluidic technology for enhanced usability and delay precision

Tuning the microstructure of composite energetic materials is an effective way to improve charging, safety, and combustion performance. In this paper, boron (B)/barium chromate (BaCrO4) composite particles with controllable microstructure were prepared using droplet microfluidic technology (DMT). Based on the theory of droplet template self-assembly, composite particles with controllable morphology, size, and composition were prepared, revealing the regulation mechanism of the particle microstructure. The composite particles prepared using DMT exhibit a uniform distribution of characteristic elements, high circularity, smooth surface, enhanced bulk density, and excellent flow properties. The thermal decomposition characteristics, safety, and combustion properties of the samples were investigated by thermal weight loss, mechanical sensitivity, and combustion tests. Thermal weight loss and mechanical sensitivity tests showed that the samples had stable thermal decomposition properties and significantly increased mechanical stability compared to the control. The combustion test results showed that the DMT-prepared samples had a short ignition response time and significantly improved delay precision. This paper presents a straightforward method for preparing B/BaCrO4 particles with high delay accuracy, which can serve as a reference for preparing other composites.

Hot compression behavior and microstructure evolution of Mg-Gd-Y-Zn-Zr alloy

In this work, the hot compression behavior and microstructure evolution of Mg-8Gd-3Y-xZn-0.6Zr (x = 0, 1.5) alloys were investigated by Gleeble-1500D thermal simulation test machine, SEM, EBSD and other equipment. The results showed that, prior to hot deformation, the grain size of Mg-8Gd-3Y-1.5Zn-0.6Zr (1.5Zn) alloy was smaller than that of Mg-8Gd-3Y-0.6Zr (0Zn) alloy. Both alloys exhibited weak texture strength with predominantly large angle grain boundaries. The true stress-strain curve of the 1.5Zn alloy distinctly revealed dynamic recrystallization features. Notably, the 1.5Zn alloy exhibited higher peak stress and thermal activation energy compared to the 0Zn alloy. Furthermore, the 1.5Zn alloy demonstrated a lower critical strain for dynamic recrystallization, suggesting a heightened likelihood and increased degree of recrystallization. After hot deformation, the Mg-8Gd-3Y-xZn-0.6Zr alloy experienced a notable reduction in grain size, particularly evident in the 1.5Zn alloy, where the grains were smaller compared to the 0Zn alloy. Moreover, the texture strength of 1.5Zn alloy was obviously weaker than that of 0Zn alloy. Dynamic precipitation and dynamic recrystallization were more likely to occur at grain boundaries. Simultaneously, the constitutive model, hot processing map and recrystallization kinetics model were constructed for Mg-8Gd-3Y-xZn-0.6Zr alloy.

Preliminary small-scaled thermal resistance testing of a masonry wall with enhanced electromagnetic shielding effectiveness

This study presents the preliminary results of a small-scale masonry wall thermal resistance (R-value) measurement. Two small-scale masonry walls were constructed using regular and antimony tin oxide (ATO)-containing bricks. ATO has shown potential for improving the protection against electromagnetic radiation penetration. R-values of the walls were measured using a FluxDAQ device equipped with a heat flux sensor and two temperature sensors for obtaining the heat flux and inside and outside temperatures during the measurement. Furthermore, the thermal conductivity (λ) of the bricks was measured by using the Fox200 Heat Flow Meter. Both results can be used for determining a walls’ thermal transmittance (U-value), which is often used for describing the energy losses and as a measure of a wall's energy efficiency. This research sought to investigate whether there is a correlation between the results obtained by the small-scale masonry wall and Fox200 device. Ultimately, this experiment aims to verify whether the small-scale masonry wall non-standard method described herein can provide approximately similar results to the standardised method.

Investigation of the effect of thermal aging and wear test parameters on the wear behavior of glass fiber (GF) reinforced epoxy composites

AbstractThis study focused on the wear behavior of unidirectional, thick GF epoxy composites produced using the autoclave method. The thermal aging process was applied for 250 and 500 cycles to understand the wear behavior of the material as it ages over time. To evaluate the wear behavior of the samples, wear tests were carried out under three different loads (10, 20, and 30 N) and three different sliding distances (150, 300, and 450 m). Taguchi‐based regression analysis was used to analyze the experimental results. The results obtained were evaluated using ANOVA tables and main and contour graphs. When the test results are examined, it is surprisingly observed that the wear resistance of the composite material increases positively with the aging effect. With thermally aging while the coefficient of friction value of composite samples increases from approximately 0.12 to 0.3, the wear volume decreases from approximately 4 to 1.3 mm3. Taguchi based regression analysis showed that the relationship between wear and thermal cycle sliding distance and load can be established by reducing the number of experiments in wear studies.Highlights Thermal aging effect on wear properties of thick GFRP was determined. Minimum wear volume and COF values were determined by applying ANOVA. It was determined that a load increment has the most impact on wear volume. Worn surface images supported the reduction in the wear rates of the thick GFRP. Empirical regression models developed for the mathematical prediction.

Uncertainty quantification with high-dimensional correlated process variations for an in-situ thermal expansion coefficient test structure

The impacts of process variations on the π-shaped thermal expansion coefficient (TEC) in-situ test structure are analyzed. Correlations among high-dimensional design parameters have to be taken into account for this type of structure, while the widely studied polynomial chaos expansion (PCE) technique is incapable of solving such problems. This paper presents a novel method for high-dimensional uncertainty quantification problems with non-Gaussian correlated variants. As a pre-processing method, the Spearman correlation coefficient and generalized lambda distribution are merged to eliminate the correlation. Then a compressed-sensing based Legendre-sparse solver is applied benefiting from the uniformly distributed parameters derived from the pre-processing and thus the cost of rebuilding correlated basis functions is eliminated. This method has demonstrated superior performance over existing methods in the analysis of TEC in-situ test structures. This analysis shows that the measurement accuracy of the test structure demonstrates good performance and is insensitive to process errors, which is consistent with experimental data. The presented technique has the potential to be applied in the design of various microelectromechanical system (MEMS) devices.

Optimizing Space Telescopes’ Thermal Performance through Uncertainty Analysis: Identification of Critical Parameters and Shaping Test Strategy Development

The integration of uncertainty analysis methodologies allows for improving design efficiency, particularly in the context of instruments that demand precise pointing accuracy, such as space telescopes. Focusing on the VINIS Earth observation telescope developed by the Instituto de Astrofísica de Canarias (IAC), this paper reports an uncertainty analysis on a thermal model aimed at improving cost savings in the future testing phases. The primary objective was to identify critical parameters impacting thermal performance and reduce overdesign. Employing the Statistical Error Analysis (SEA) method across several operational scenarios, the research identifies key factors, including the Earth’s infrared temperature and albedo, and the spacecraft’s attitude and environmental conditions, as the variables with major influences on the system’s thermal performance. Ultimately, the findings suggest that uncertainty-based analysis is a potent tool for guiding thermal control system design in space platforms, promoting efficiency and reliability. This methodology not only provides a framework for optimizing thermal design and testing in space missions but also ensures that instruments like the VINIS telescope maintain optimal operating temperatures in diverse space environments, thereby increasing mission robustness and enabling precise resource allocation.

Mechanisms and experimental study of directional thermal shock fracture of granite under bidirectional horizontal loading

The study of the mechanism of thermal shock directional fracture of rocks under bidirectional horizontal stress is important for the application of directional thermal shock fracture technology. With the engineering background of the thick igneous roof overlying the coal seam, we conducted high temperature thermal shock directional fracture tests on granite under different horizontal loads to investigate the fracture mechanism. The results show that during the directional thermal shock of granite, the heating rate of borehole surrounding rock experienced three stages of rapid increase, rapid decrease and slowly decrease. AE tests were used to characterize the typical features of rocks during thermal shock fracture: the appearance of macrocracks in the specimen was accompanied by sharp increases in the cumulative AE count and the sudden drops in b-value. The experimental results show that thermal shock can create macroscopic directional fractures within the rock. Within a certain range of horizontal stress difference, the expansion direction of thermal shock cracks could be released locally from geological stress control, i.e. expanding along the direction of the minimum horizontal dominant stress. This provides completely new thinking for the cutting of hard roof and the directional fracturing of rock. In addition, directional thermal shock caused modifications in the distribution of stress in borehole surrounding rocks. We have established a model for stress distribution around the borehole rock and given the calculation formula for the initiation stress of the rock. The studies provide significant theoretical guidance for the industrial application of directional thermal shock fracturing technology.

Criteria-based assessment of analgesic activity of condensed 3-aminothieno[2,3-b]pyridines and 1,4-dihydropyridines derivatives based on dataexperimental studies

BACKGROUND: An urgent task in pharmacology is to identify highly effective drugs with analgesic and anti-inflammatory activity. Heterocyclic cyanothioacetamide compounds are of considerable interest. Most authors evaluate the results of studies with separate private indicators of analgesic activity, and their comprehensive criterion assessment is insufficiently defined.
 AIM: Development of a criterion assessment in the study of analgesic activity and the establishment of its generalized criteria for samples of chemical compounds of medicinal products.
 MATERIALS AND METHODS: The experiments were performed on 390 male rats weighing 250–280 g in the laboratory of the Department of Fundamental and Clinical Pharmacology of St. Luke Lugansk State Medical University. Intact, control and reference (comparison group) groups of ten animals in each group were formed for each pharmacological test. In the intact group, the rats were unharmed. The control group received 2 mL of 0.9% sodium chloride solution intragastrically before each pharmacological test to establish analgesic activity. The reference group was injected with sodium metamizole at a dose of 7 mg/kg intragastrally once 1.5 h before modelling an acute pain reaction. Ten experimental groups were also formed, in which rats were injected with appropriate samples of new original studied derivatives of condensed 3-aminothieno[2,3-b]pyridines and 1,4-dihydropyridine intragastrically at a dose of 5 mg/kg 1.5 h before modelling acute pain syndrome. Tests for orofacial trigeminal pain, thermal immersion and hot plate were simulated. The indicators of the analgesic effect were the frequency of scratching movements in the orofacial trigeminal pain test and a statistically significant increase in the latent reaction period after the administration of the studied substances in the thermal immersion tests of the tail and hot plate.
 RESULTS: The studied samples with ciphers AZ-023, AZ-331 and AZ-383 showed maximum analgesic activity. The proposed criterion of analgesic activity in the experimental groups receiving thienopyridine derivatives with the AZ-023 cipher, according to the results of three tests, was 50.1, exceeding the indicator in the comparison group by 42 times. The values of this criterion in the experimental groups that received new 1,4-dihydropyridine derivatives with laboratory ciphers AZ-331 and AZ-383 for preventive purposes were the maximum in this series of experiments (64.3 and 68.4), which is 53–57 times higher than that of sodium metamizole.
 CONCLUSION: The methodology for assessing analgesic activity can be improved based on a criteria-based approach with the aggregation of particular indicators into an abstract model that allows quantifying the degree of analgesic activity. An integral criterion for the analgesic activity of cyanothioacetamide derivatives based on experimental data is proposed. In the future, the proposed approach can be used in studies of various analgesic samples.

The effect of water activity on thermal resistance of Salmonella in chocolate products with different fat contents

Several instances of Salmonella outbreaks have been documented in association with chocolates. Conching, an important chocolate manufacturing step, may be designed for control of Salmonella if proper product temperature is maintained for sufficient time. A better understanding of thermal inactivation kinetics of Salmonella in different chocolate products is, however, highly desirable in evaluating the effectiveness of an existing conching process for Salmonella reduction or assessing the need for modification of manufacturing operations. Our previous study on milk chocolate (41.8% fat content) noted that aw and temperature are two key factors influencing Salmonella inactivation in a thermal process. In this research we studied the effect of different fat levels on Salmonella inactivation in chocolates at 80 °C. White and dark chocolates (fat content: 53.0% and 74.3%) were used in this study. The samples were conditioned to three water activity (aw) levels, 0.23, 0.33, and 0.43, at room temperature. The changes of aw in these samples were quantified when heated to 70 °C and 80 °C to reflect the real relative humidity conditions during the process. The data indicated an increase in the aw in the chocolate products, correlating with elevated temperatures. The thermal inactivation tests showed that D-values (time to achieve one log reduction at a fixed temperature) of Salmonella were between 33.9 and 46.5 min when treated at 80 °C, the corresponding aw,80 °C were 0.29 and 0.28 in white and dark chocolate samples, respectively. Our data suggests that the higher fat content contributed to a less increase in aw, leading to a higher heat tolerance of bacteria in the chocolates. The research results may offer useful insights for the chocolate manufactures to utilize conching process for the pathogen control of chocolate products made with different recipes.

A “one‐pot” method for synthesizing zinc tryptophan and its derivatives as highly efficient PVC thermal stabilizer with excellent mechanical properties

AbstractZinc Tryptophan (Trp‐Zn) and zinc N‐(salicylic) tryptophan (SalTrp‐Zn) were synthesized from tryptophan, zinc acetate, and salicylic aldehyde by one‐pot method, respectively. The structure was analyzed by FT‐IR, 1H NMR, and elemental analysis. PVC samples were prepared by stirring method and solvent film process, and then the thermal properties of PVC samples were studied by thermal aging chamber test, Congo red test, electrical conductivity test, and thermogravimetric analysis (TGA). The thermal stability of Trp‐Zn and SalTrp‐Zn stabilized PVC samples was better than calcium and zinc soaps used in industry. The thermal stability time was up to 80 min, and it was a long‐acting thermal stabilizer. After the addition of CaSt2 and Trp‐Zn stabilizer in different proportions, the thermal stability of PVC was obviously improved, and the initial whiteness of the film was improved after the combination of Trp‐Zn/SalTrp‐Zn. In addition, the tensile test verified that the PVC samples stabilized by Trp‐Zn and SalTrp‐Zn had the highest elongation at break. The addition of Trp‐Zn can reduce the elastic modulus of PVC, effectively improve the mechanical properties of PVC, and make the PVC film have better toughness and elasticity. Through DMA and EDS tests, it can be seen that Trp, SalTrp‐Zn had good compatibility with PVC and DOP. The quantum chemical calculation of Trp‐Zn, SalTrp‐Zn and vinyl chloride models was carried out, and the thermal stability mechanism of thermal stabilizer on PVC was analyzed accurately, mainly the absorption mechanism of HCl and the substitution mechanism of unstable chlorine atoms.

Investigating the Effect of ABS on the Mechanical Properties, Morphology, Printability, and 4D Printing of PETG‐ABS Blends

AbstractIn this study, Acrylonitrile butadiene styrene (ABS) with three different ratios of 30%, 50%, and 70% is used to enhance the shape memory and mechanical properties of Polyethylene terephthalate glycol (PETG). Additionally, morphology, printability, and dynamic thermomechanical analysis are also examined. The thermal test results show that PETG‐ABS compounds have two transition temperatures in the range of 80 and 110 °C, which are related to the components. By changing the weight percentage of PETG from 30 to 70%, three morphologies of matrix‐droplet, sea‐island, and combination of co‐continuous and matrix‐droplet are observed. The results of the mechanical properties show an increase in strength with the increase of ABS, which can be justified due to the higher strength of ABS compared to PETG. The highest tensile strength of 32.48 MPa and 15.16% elongation is obtained for PETG‐ABS(30‐70) and PETG‐ABS(70‐30), respectively. Due to the better shape memory performance of PETG, PETG‐ABS(50‐50) and PETG‐ABS(70‐30) have complete shape recovery, and with the increase of PETG, the shape recovery rate also increased. This diversity in morphology, mechanical properties, and shape memory effect is one of the goals of this research which is well fulfilled.

Closing the loop in space 3D printing: Effect of vacuum, recycling, and UV aging on high performance thermoplastics produced via filament extrusion additive manufacturing

The outlook for space exploration, and the long-term sustainable presence of humans in space, rely upon the advancement of in-situ manufacturing capabilities. In-space additive manufacturing (AM) has gained significant attention due to its potential to produce spare parts in-situ and facilitate repairs for extending space missions. However, to date, there is no AM system capable of processing high-performance engineering thermoplastic polymers within uncontrolled space conditions (i.e., reduced gravity, vacuum, and radiation environment). Additionally, the effect of ultra-violet (UV) radiation on printed parts has remained unexplored. In this work, a custom-built filament extrusion AM breadboard has been developed and tested enabling the fabrication of engineering thermoplastic polymers, whereby the machine was placed inside a vacuum chamber to partly mimic the harsh space environment. Mechanical (tensile and flexural) and thermal (thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis) tests were conducted on the printed specimens before and after exposure to UV aging. Moreover, the printed geometries underwent a recycling process involved the shredding of the pristine 3D-printed polymeric samples, the drying of the obtained granulates and finally the extrusion of 3D-printable filaments. The polymeric recycled 3D-printed specimens were then subjected to further mechanical and thermal testing, offering valuable insights into the feasibility of in-space AM and the potential to augment the circularity of the printed parts. The results of the mechanical and thermal tests, together with the effect of vacuum printing, UV aging, and recycling, are provided within the manuscript. This work cements the basic building blocks to sustainably advance on-orbit and in-space infrastructure, and paves the way for long-term human space missions.

Cooling performance measurements of different types of cooling vests using thermal manikin

This study compared the effectiveness of five commercially available cooling vests using three distinct thermal manikin test protocols. In addition, the constraints associated with each test protocol were elucidated, facilitating the identification of suitable evaluation methods for the different cooling vests. The cooling performances of the vests were evaluated using three thermal manikin test scenarios, incorporating the adaptations from Ciuha et al. (Ergonomics 64:625–639, 2021) and ASTM F2371-16, along with a modified protocol simulating the hot and humid weather in a South Korean summer. The results revealed substantial variations in the cooling performance across different test protocols, highlighting the importance of carefully selecting thermal manikin test methods. Moreover, the specific cooling vests exhibited immeasurable performance in certain test methods, which presents the limitations inherent in each testing scenario. For example, when evaluated with a non-sweating thermal manikin, the air-cooling vests exhibited the worst cooling performance, showing an average cooling rate of 1.0 W and cooling durations of five minutes. In contrast, the same vests demonstrated superior performance when assessed using the ASTM F2371-16 method, revealing an effective cooling rate of 114.8 W and sustained cooling durations exceeding eight hours. These results emphasize the lack of a one-size-fits-all evaluation method for cooling vests and the need for accessible guidelines to inform decision-makers aiming to enhance workplace safety and comfort.

The influence of sodium silicate water glass content on the structure and properties of silicate thermal insulation coating

Thermal insulation slurry was fabricated using sodium silicate water glass (SSWG) as the film-forming material and hollow glass microspheres (HGM) as thermal insulation fillers. The thermal insulation slurry was coated on 316L stainless steel to fabricate a silicate thermal insulation coating. The results show that SiO2 phase is formed by SSWG in the thermal insulation coating after sintering at 680 ℃. Through polymerization and dehydration reactions between Si-OH groups, the Si-O three-dimensional network structure develops at 680 ℃. The optimal value of SSWG to aggregate mass ratios is 2.00. Under this condition, the silicate thermal insulation coating exhibitssmoothsurface, continuous and dense microstructure, high Shore hardness of50.1 HSD,remarkablethermal insulation efficiency of21 %at260 ℃, andexcellentresistance to drop and thermal shock tests without anynoticeablecracks or detachment.

Robust ultrablack film deposited on large-curvature magnesium alloy by atomic layer deposition

A broadband absorber composed of a TiAlC/SiO2 film stack prepared by atomic layer deposition was presented, which could be uniformly coated on magnesium alloys with large curvature, achieving an average absorption as high as 99.4% within the wavelength range from 400 to 1000 nm. An Al2O3/TiO2 interlayer was deposited on magnesium alloys prior to the deposition of ultrablack films, which effectively prevented corrosion of magnesium caused by Al3+ and Cl− by-products in the TiAlC film. With the presence of this interlayer, the ultrablack film on the surface of the magnesium alloy exhibited good adhesion and abrasion resistance. Furthermore, after undergoing damp heat and thermal cycling tests, the absorptions of the ultrablack film-coated magnesium alloys remained at 99.1% and 99.0%, respectively, which indicated that the film is promising for application in precision optics under harsh environmental conditions.

Evaluation of physical variables, thermal nociceptive threshold testing and pharmacokinetics during placement of transdermal buprenorphine matrix-type patch in healthy adult horses.

Matrix type transdermal buprenorphine patches have not been investigated in horses and may provide an effective means of providing continuous pain control for extended period and eliminating venous catheterization. Assessment of the physiological variables (heart rate, respiratory rate, body temperature) and thermal nociceptive threshold testing, and describing the pharmacokinetic profile of transdermal buprenorphine matrix-type patch (20 μg h-1 and 40 μg h-1 dosing) in healthy adult horses. Randomised experimental study with a Latin-square design. Six adult healthy horses received each of the three treatments with a minimum 10 day washout period. BUP0 horses did not receive a patch (control). BUP20 horses received one patch (20 μg h-1) applied on the ventral aspect of the tail base resulting in a dose of 0.03-0.04 μg kg-1 h-1. BUP40 horses received two patches placed alongside each other (40 μg h-1) on the tail base resulting in a dose of 0.07-0.09 μg kg-1 h-1. Whole blood samples (for determination of buprenorphine concentration), physiological variables and thermal threshold testing were performed before (0 h) and at 2, 4, 8, 12, 16, 24, 32, 40, 48, 56, 64, 72, and 96 h after patch application. The patches were removed 72 h following placement and were analyzed for residual buprenorphine content. Between the three groups, there was no change in physiological variables across timepoints as compared to baseline (p > 0.1). With the higher dose, there was a significant increase in thermal thresholds from baseline values from 2 h until 48 h and these values were significantly higher than the group receiving the lower patch dose for multiple timepoints up to 40 h. 40 μg h-1 patch led to consistent measurable plasma concentrations starting at 2 h up to 96 h, with the mean plasma concentrations of > 0.1 ng/ml from 4 h to 40 h. 20 μg h-1 and 40 μg h-1 patch doses were well tolerated by all horses. At higher dose, plasma buprenorphine concentrations were more consistently measurable and blunted thermal thresholds for 48 h vs. 32 h with 20 μg h-1 dosing as compared to control.

Research on vibration characteristics of rocket engine flow pipeline

PurposeAbnormal vibrations often occur in the liquid oxygen kerosene transmission pipelines of rocket engines, which seriously threaten their safety. Improper handling can result in failed rocket launches and significant economic losses. Therefore, this paper aims to examine vibrations in transmission pipelines.Design/methodology/approachIn this study, a three-dimensional high-pressure pipeline model composed of corrugated pipes, multi-section bent pipes, and other auxiliary structures was established. The fluid–solid coupling method was used to analyse vibration characteristics of the pipeline under various external excitations. The simulation results were visualised using MATLAB, and their validity was verified via a thermal test.FindingsIn this study, the vibration mechanism of a complex high-pressure pipeline was examined via a visualisation method. The results showed that the low-frequency vibration of the pipe was caused by fluid self-excited pressure pulsation, whereas the vibration of the engine system caused a high-frequency vibration of the pipeline. The excitation of external pressure pulses did not significantly affect the vibrations of the pipelines. The visualisation results indicated that the severe vibration position of the pipeline thermal test is mainly concentrated between the inlet and outlet and between the two bellows.Practical implicationsThe results of this study aid in understanding the causes of abnormal vibrations in rocket engine pipelines.Originality/valueThe causes of different vibration frequencies in the complex pipelines of rocket engines and the propagation characteristics of external vibration excitation were obtained.

On the Thermal Shock Resistance and Failure Mechanism of the Pt-Modified Aluminide Bond Coating

The failure mechanism of the Pt-modified aluminide (Pt-Al) bond coating (β-(Ni, Pt)Al coating) in a simulated service environment has seldom been investigated. Based on a self-developed thermal barrier coating service environment simulator, a thermal shock experiment of single-phase Pt-Al bond coating on DD419 substrate at a temperature of 1170 °C was conducted combined with a real-time monitoring infrared thermal imager. The lifespan and failure mechanism of the coating are analyzed in detail. The results reveal that specimens of the Pt-Al bond coating, subjected to three repeated tests, exhibit failure after 650, 528, and 793 thermal shock cycles at 1170 °C, respectively. After failure, the contents of Pt and Al elements in the peeled region are lower than those in the unpeeled area, and a diffusion zone emerges in the bond coating. The failure mechanism of the Pt-Al bond coating during the thermal shock test can be attributed to three main aspects: (1) the diffusion and consumption of the Pt element reduced the oxidation resistance of the Pt-Al bond coating; (2) the diffusion and depletion of elemental Al causes a phase change in the coating, leading to the failure of the coating; (3) thermal stresses are generated in the Pt-Al bonded coating during the thermal shock test, which ultimately leads to wrinkling.

Photocatalytic activity, DFT/ TD-DFT, and spectrophotometric studies of a synthesized charge transfer complex of p- toluidine with 1,2,4,5-benzenetetracarboxylic acid in various polar solvents

The hydrogen bound charge transfer (CT) complex of p-toluidine (PT) and 1,2,4,5-benzenetetracarboxylic acid (BTC) was synthesized and subsequently characterized using a range of spectrum approaches such as FTIR, TGA / DTA, SC-XRD, and spectrophotometric examinations. Crystallographic evidence suggests that a strong hydrogen bond (N+____ H----O–) connects the cation and anion. This occurs when a proton is transported from the acceptor to the donor. The FTIR spectrum displays the proton transfer band, which is the region where neither the donor (PT) nor the acceptor (BTC) exhibits any absorption. A spectroscopic analysis showed that the CT complex (CTC) containing hydrogen bond has 1:1 stoichiometry. Benesi- Heildebrand equation was used for calculating the formation constant (KCT), molar extinction coefficient (ԑCT) and also to derive values for other physical parameters, such as energy of interaction (ECT), ionization potential (ID), free energy (ΔG°), resonance energy (RN) and oscillator strength (f). Thermal testing confirms that the newly synthesized CTC is stable at room temperature. DFT (Density Functional Theory) and TD-DFT (Time-Dependent Density Functional Theory) calculations at the B3LYP/6-311G++ level of theory were used to investigate the optimized geometry of the synthesized CTC and reactants (PT and BTC), with comparable theoretical data to support the experimental results. Furthermore, employing Hershfeld surfaces and the corresponding 2D fingerprint plots, the study of intermolecular interactions that maintain the crystal packing has been carried out. We also proved the CTC's efficiency as a photocatalyst for methylene blue (MB) breakdown, achieving 81 % photodegradation under UV–Vis light for 130 min. The scavenging analysis further demonstrates that holes and hydroxyl radicals are the photochemically active species responsible for dye particle disintegration.

Mechanochemical evolution of coal microscopic groups: A new pathway for mechanical forces acting on coal spontaneous combustion

Coal spontaneous combustion (CSC) remains a significant threat to regional ecological environments. As coal mining operations extend deeper into the earth, the increasingly complex mechanical force conditions in deep-seated mines escalate the potential risk of CSC. Mechanical forces such as ground stress and mechanical cutting are traditionally believed to be linked to CSC through the following pathway: mechanical forces act → mechanical energy is input → mechanical crushing and pulverization occur → coal–oxygen contact area increases → CSC accelerates. Noteworthily, these forces do more than just physically break coal; they also trigger a mechanochemical effect (MCE) that alters coal's microscopic chemistry. However, an independent evaluation of its influence on CSC was lacking. This study characterized coal's microscopic chemical group responses to the MCE. It was found that the MCE led to the degradation of aliphatic side chains while enhancing the polycondensation of aromatic ring structures, indicating a synergistic effect. Additionally, an increase in oxygen-containing functional groups, such as alkyl/aryl ethers, suggested enhanced interactions of the coal microscopic groups with oxygen due to mechanical forces. Based on these findings, an MCE-modified coal macromolecular model was developed and molecular quantum mechanical calculations were conducted. The results indicated that the MCE boosted coal macromolecule reactivity, thus facilitating easier activation. These conclusions were validated through modern thermal analysis tests. Finally, this study proposed a new pathway of mechanical forces acting on CSC: mechanical forces act → mechanical energy is input → the MCE occurs → evolutions of the microscopic groups within coal are induced → Activity of coal molecules is enhanced → CSC accelerates.