Enthalpy Research Articles

Construction of a β-cyclodextrin-based colloid containing silicon, phosphorus and nitrogen components: Toward enhancing flame retardancy of flax fabrics

Natural cellulose fabrics, as one of the combustibles prone to causing indoor fires, are modified with flame retardants encouraged by the fire protection industry. Herein, a bio-based colloid named ASDPC was prepared by 3-aminopropyltriethoxysilane, diethylenetriaminepentakis(methylphosphonic acid) and β-cyclodextrin, and used to enhance the flame retardancy of flax fabrics via the pad-dry-cure method. The treated flax fabrics named ASDPC-FF showed good flame retardancy with a damaged length of only 6.4 cm in the vertical burning test and a limiting oxygen index value of up to 33.8 %. Meanwhile, ASDPC-FF exhibited thermal stability and combustion behavior distinct from untreated flax fabrics. Thermogravimetric analysis presented that the char residue produced by ASDPC-FF at 800 °C was as high as 36.2 %. Cone calorimetry test indicated that the peak heat release rate and total heat release of ASDPC-FF decreased by approximately 89.0 % and 35.7 %, respectively. Furthermore, compared to untreated flax fabrics, condensed-phase and gas-phase studies found that ASDPC-FF turned into expanded char and produced fewer gaseous volatiles containing C-H, CO and C-O-C at high temperatures. More importantly, ASDPC-FF remained self-extinguishing after 25 laundering cycles with flame retardancy surpassing untreated flax fabrics. In summary, this work provides a novel route for expanding the manufacture of flame-retardant flax fabrics.

Applying neural network model to real-time frosting detection and intelligent defrosting control for air source heat pump

Periodic defrosting is essential for efficient operation of air source heat pump to avoid the attenuation of performance caused by frosting. However, the mal-defrosting phenomena in practice, which are no defrosting progress when necessary and unnecessary defrosting operation under no frosting, happen occasionally. To improve the accuracy of defrosting, a convolutional neural network model based on deep learning with YOLOv5 is introduced for frosting detection in this paper. Firstly, the evaluation method of frosting degree combining fractal dimension and heating capacity attenuation is constructed. Then, an image dataset is built based on frosting degree evaluation. The optimized YOLOv5-frost network is constructed, which improves the accuracy of frosting detection by iterative training. Thirdly, a novel defrosting control method based on YOLOv5-frost network is proposed, in which the defrosting initiation and termination points are investigated. Finally, comparative experiments are conducted between the proposed defrosting control method and traditional methods. The results indicate that the mal-defrosting phenomena are effectively avoided under the proposed method. The COP and total heating capacity are increased by 11.83 % and 7.42 % respectively, as well as the defrosting frequency and energy consumption are decreased by 75.00 % and 88.24 %, respectively. Additionally, the time consumption, memory overhead, and central processing unit overhead of the proposed method are 2.72 %, 71.58 %, and 74.07 % of those for the traditional methods, respectively. The performance of air source heat pump unit in real-time frosting detection and on-demand defrosting in complex conditions can be effectively improved with the proposed method.

Chemical Looping Ammonia Decomposition Mediated by Alkali Metal and Amide Pairs for H2 Production and Thermal Energy Storage

AbstractAmmonia decomposition to H2 (ADH) is one of the key reactions in the ammonia‐based energy system. Recent research has been focused on developing more active and affordable catalysts, however, few can operate below 500 °C and typically require the expensive metal ruthenium. Herein, a fundamentally different thermal ADH via a chemical looping process (CLADH) mediated by alkali metal and its amide pairs, which can work under lower temperatures than the catalytic process, is reported. This CLADH consists of two steps: 1) Ammoniation step ̶ NH3 reacts with Na or K to generate NaNH2 or KNH2, respectively, accompanied by releasing one‐third of H2 in NH3 at room temperature; 2) Decomposition step ̶ NaNH2 or KNH2 decomposes to N2 and H2 with the regeneration of Na or K which can be performed above 275 °C. Additionally, due to the significant enthalpy change in the two‐step reactions of this CLADH, −78.0 kJ mol−1 for the first step and 123.9 kJ mol−1 for the second, using the Na and NaNH2 pair—suggest potential for thermal energy storage. This work not only reports an alternative route to produce H2 from NH3, but also unravels the potential of chemical looping process for thermal energy storage.

In situ preparation of MoS2@Fe3O4 by radiation method and its application in flame retardancy, mechanical properties, and friction properties of EVA composites

In recent years, there has been significant interest in using two-dimensional MoS2 to enhance flame retardancy, which has proven challenging. MoS2@Fe3O4 nanosheets were successfully synthesized via a one-step method called radiation reduction to boost MoS2’s flame retardant properties. Incorporating these MoS2@Fe3O4 nanocomposites notably improved the flame retardancy of ethylene vinyl acetate copolymer (EVA). Compared to pure EVA, EVA nanocomposites with 1 part of MoS2@Fe3O4 showed a 17.4% reduction in peak heat release rate, 40.4% decrease in total heat release, and 52.9% reduction in total smoke release, with scaly residue content improving from 0.4% to 12.6%. Additionally, MoS2@Fe3O4 incorporation enhanced the mechanical and friction properties of EVA composites, increasing tensile strength by 25.7% and elongation at break by 10.4% compared to pure EVA. This study presents an effective and simple method for producing modified MoS2 nanosheets that enhance flame retardancy, as well as mechanical and friction properties of EVA composites.

Encapsulating montmorillonite and ammonium polyphosphate in one polyurea microcapsule to improve flame‐retardant and mechanical properties of polypropylene composites

AbstractAmmonium polyphosphate (APP) and montmorillonite (MMT) have been widely used in the flame‐retardant of polypropylene (PP), but the low synergistic flame‐retardant efficiency and their poor compatibility with PP matrix need to be greatly improved. In this work, APP and MMT were encapsulated in the one microcapsule (PU@A‐M) at the determined optimal ratio through the “bridging” reactions of diethylenetriamine (DETA) with APP and MMT. Compared with the PP/A + M composites with the physical mixture of APP and MMT, the limiting oxygen index, peak of heat release rate, total heat release, and total smoke production of PP/PU@A‐M were decreased by 5.7%, 48.8%, 3.1%, and 20%, respectively. The well‐dispersed PU@A‐M with charring‐forming agent (CFA) generated continuous and compact char layers with COP, COSi, and SiOP crosslinking structure. Furthermore, the tensile strength and elongation at break of PP/PU@A‐M were enhanced by 4.8% and 36.9%, respectively, as compared with PP/A + M because of good dispersibility and compatibility of PU@A‐M in PP matrix.

Core-shell V2O5- Gum ghatti grafted poly (acrylamide-co-methacrylic acid) adsorbent for the removal of methylene blue dye in water: Kinetic, equilibrium and thermodynamic studies

Herein, vanadium pentoxide (V2O5) encapsulated Gum ghatti grafted poly(acrylamide-co- methacrylic acid) adsorbent was synthesized to remove methylene blue dye from water. The materials were characterized by FTIR, TEM, SEM, Raman and XRD analysis. Batch adsorption studies were performed on the materials. Several variables' effects on methylene blue removal, including pH, contact time, initial dye concentration, and adsorbent dosage, were examined. Kinetics and thermodynamic analysis were also carried out for the adsorbent-adsorbate interaction to determine the maximum adsorption and mechanism for adsorption. By using UV-Vis spectrophotometric analysis, the dye concentration was evaluated both before and after adsorption. Langmuir, Freundlich, and Dubini-Radushkevic's isotherm models were used to analyze the adsorption data. Results showed a maximum adsorption efficiency of 92 % at a pH of 9 and 0.2 g as the maximum adsorbent dosage. The study followed the Langmuir isotherm model with a correlation coefficient (R2) of 0.9995. The results from the kinetic studies show a pseudo-second-order mechanism. The negative values of the Gibbs free energy change ΔG° ranging from −10.57 KJmol−1 to −9.64 Kmol−1 within the temperatures of 298 K to 313 K is an indication of a spontaneous process. A negative enthalpy change (ΔH° = −29.05 KJmol−1) shows an exothermic process and a negative entropy change (ΔS° = −0.06 KJmol−1) represents a highly ordered system. ANOVA in Microsoft Excel and other statistical analyses were used to evaluate the effects of time, pH, concentration, dose, temperature, and other factors on the effectiveness of dye adsorption. Importantly, every parameter that was investigated showed statistically significant impacts on the removal of dye (p < 0.05), revealing their important impact on the adsorption process.

Observation of Quiet‐Time Mid‐Latitude Joule Heating and Comparisons With the TIEGCM Simulation

AbstractJoule heating is a major energy sink in the solar wind‐magnetosphere‐ionosphere system and modeling it is key to understanding the impact of space weather on the neutral atmosphere. Ion drifts and neutral wind velocities are key parameters when modeling Joule heating, however there is limited validation of the modeled ion and neutral velocities at mid‐latitudes. We use the Blackstone Super Dual Auroral Radar Network radar and the Michigan North American Thermosphere Ionosphere Observing Network Fabry‐Perot interferometer to obtain the local nightside ion and neutral velocities at ∼40° geographic latitude during the nighttime of 16 July 2014. Despite being a geomagnetically quiet period, we observe significant sub‐auroral ion flows in excess of 200 ms−1. We calculate an enhancement to the local Joule heating rate due to these ion flows and find that the neutrals impart a significant increase or decrease to the total Joule heating rate of &gt;75% depending on their direction. We compare our observations to outputs from the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM). At such a low geomagnetic activity however, TIEGCM was not able to model significant sub‐auroral ion flows and any resulting Joule heating enhancements equivalent to our observations. We found that the neutral winds were the primary contributor to the Joule heating rates modeled by TIEGCM rather than the ions as suggested by our observations.

Sustainably sourced and DOPO-derived triols as hardeners for epoxy thermosets: A promising solution to synchronously improve flame retardancy, mechanical strength and toughness

The flammability and brittleness of the diglycidyl ether of bisphenol A (DGEBA)-type epoxy resin greatly restrict its application in electronic appliances and structural materials. However, the synchronous improvement in the flame retardancy, mechanical strength, and toughness of DGEBA-type epoxy thermosets remains a significant challenge. To overcome this challenge, in this study, a sustainably sourced and DOPO-derived triol (DOPO-GL-DCDA) was synthesized from a bio-based material, glycerol 1, 3-diglycerolate diacrylate (GL-DCDA). A series of epoxy thermosets with different phosphorus contents were prepared by introducing DOPO-GL-DCDA into the DGEBA matrix. EP/DOPO-GL-DCDA demonstrated excellent flame retardancy and mechanical properties without compromising transparency. Specifically, EP/DOPO-GL-DCDA-1.0P exhibited a limit oxygen index (LOI) of 34.0 % and a UL-94 V-0 rating, and the total heat release (THR) and peak heat release rate (PHRR) of EP/DOPO-GL-DCDA-1.5P decreased by 36.6 % and 46.8 %, respectively, compared with those of pure EP. In addition, compared with those of pure EP, the tensile strength, impact strength, fracture toughness (KIC), and fracture energy (GIC) of EP/DOPO-GL-DCDA-1.5P increased by 62.8 %, 69.9 %, 62.9 %, and 99.0 %, respectively. Moreover, EP/DOPO-GL-DCDA had better dielectric properties than pure EP. Under the premise of maintaining transparency, this work provided a promising solution to synchronously improve the flame retardancy, mechanical strength, and toughness of epoxy thermosets.

Determination of the coefficient of thermal effusivity ε for a semi-confined rod

The article provides methods and formulas for calculating the coefficient of thermal effusivity ε (coefficient of heat accumulation) of solid bodies using known solutions of direct heat conduction problem. The work describes a method by which the final formulas are simplified to algebraic equations using the relative temperature θM of heating semi-confined rod from the end. The temperature Tc at the beginning of the rod is measured — x0 and time — τ0 from the start of heating. For calculation, the amount of heat Q accumulated during heating by a heater with a constant temperature at the end of the rod is used for the entire heating time. The technique is physically implemented during the experiment by bringing the ends of two semi-confined rods into contact. A flat, low-inertia electric heater is placed between the rods. The amount of heat ∆Q used in the calculations is half of the total heat of the heater for the entire heating time.

A DOPO-eugenol linear siloxane as a highly effective liquid flame retardant also imparting improved mechanical properties to an epoxy amine network

A liquid bio-derived eugenol-containing phosphorus silicone hybrid molecule (EGDS-DOPO) that endows excellent flame-retardancy and enhanced mechanical performance to an epoxy amine network at low levels of addition was successfully synthesized and characterised. The EGDS-DOPO significantly improved the flame retardancy requiring only 5 wt% of EGDS-DOPO to achieve a limiting oxygen index (LOI) of 34.9 % and a UL 94 V-0 rating. Cone calorimetry measurements reveal a reduction of the peak heat release rate, the total heat release, and total smoke production by 62.2 %, 34.0 % and 47.5 %, respectively when EGDS-DOPO concentration was 20 wt%, compared to the unmodified epoxy network. Viscosity remained low throughout cure, and despite some retardation of reactivity, the epoxy amine resin remains fast curing and suitable for liquid moulding composite fabrication technologies. Moreover, the modified EGDS-DOPO epoxy networks display a glass transition temperature (Tg) between 218.5 °C and 174.1 °C, a hydrophobic surface with water contact angle of 97.5°–106.6°, a low moisture ingress of 2.35 %–2.91 %, and improved overall mechanical properties in flexure (maximum 39.8 % increase in flexural strength and 27.0 % in flexural modulus), compression (maximum 24.5 % and 35.0 % increase in compressive strength and modulus, respectively), and fracture toughness (maximum 28.0 %).

Conversion of PET bottles into carbonaceous adsorbents for Pb(II) removal from aqueous solutions via KOH activation

In this study, we present a novel approach to repurpose waste Polyethylene terephthalate (PET), a prominent contributor to global plastic usage, for the synthesis of efficient adsorbents via facial pyrolysis. The as-synthesized adsorbents were applied for the removal of lead (Pb(II)) ions in aqueous solution. Controlled batch experiments at pH 5 with 0.075 g of adsorbent at room temperature (20 °C) were conducted to measure Pb(II) adsorption capacities (mg/g) and fitted on isotherm models (Langmuir, Freundlich, and Temkin) and kinetics models (Pseudo-First order, Pseudo-Second order, and Elovich). Thermodynamic experiments conducted at four different temperatures (293 K, 303 K, 313 K, and 323 K) provided enthalpy, entropy, and Gibbs free energy change parameters, explaining the Pb(II) adsorption behaviors on PET-based adsorbents. The activation process involving KOH, followed by carbonization, yielded adsorbents with exceptional surface areas, pore volumes, and elevated oxygen contents (up to 22.8 %). The best adsorbent exhibited superior performance, achieving a maximum adsorption capacity of 219.7 mg/g within a rapid equilibrium time of 15 min. The adsorption behavior adhered well to the Langmuir isotherm model (R2 = 0.999) and Pseudo-Second Order kinetics model (R2 = 0.999). Furthermore, C600K600 displayed outstanding reusability, with negligible efficiency reduction (<5 %) even after five consecutive cycles. These results underscore the successful conversion of PET waste into a low-cost and highly effective adsorbent, offering a promising solution for sustainable waste management.

Regional-Scale Assessment of the Potential for Shallow Geothermal Energy Development Using Vertical Ground Source Heat Pumps

Shallow geothermal energy (SGE) is a widely prevalent geological resource underground, and its utilization offer significant energy conservation and emission reduction benefits, contributing to the achievement of carbon neutrality goals. Assessing the development potential of regional SGE can ensure sustainable development of these resources and prevent adverse effects induced by overexploitation. Jiangsu Province, a developed region in the eastern coastal area of China, has a strong demand for cooling and heating in urban buildings. The primary form of utilizing SGE in this area is through vertical ground source heat pumps (VGSHP). Based on the analysis of the impact of regional geological conditions on the development of SGE, this study specifically evaluated the suitability of developing SGE through VGSHP. After excluding areas unsuitable for development, the heat exchange capacity, heating or cooling area per unit area, and energy conservation and emission reduction benefits of VGSHP were calculated. The results indicate that the area suitable and moderately suitable for developing SGE through VGSHP in Jiangsu Province amounts to 76,453 km2. The total heat exchange capacity for summer is 1.21 × 109 kW, which can provide cooling for an area of 1.21 × 1010 m2. The total heat exchange capacity for winter is 8.70 × 108 kW, which can provide heating for an area of 1.09 × 1010 m2. The annual available resource amount is 2.68 × 1012 kWh, equivalent to 3.30 × 108 tons of standard coal, and a CO2 reduction of 7.86 × 108 tons.

Understanding the multiscale structure and in vitro digestibility changes of corn starch-ferulic acid complexes induced by high hydrostatic pressure

High hydrostatic pressure (HHP) was used to synthesize corn starch (CS) and ferulic acid (FA) complex (CS-FA). Its effects on the structure of the complex at multiple scales and its digestibility were examined. The results demonstrated that HHP significantly influenced the digestibility of the CS-FA complex, decreasing the content of rapidly digestible starch (RDS) while increasing slowly digestible starch (SDS) and resistant starch (RS). Notably, the combined SDS and RS content in the HHP-treated CS-FA complex with 2.0 % FA addition (38.13 %) was significantly higher (p < 0.05) than those in the CS-FA complex without HHP treatment (29.21 %) and pure CS (21.72 %). The results indicated that HHP treatment reduced the enthalpy change (ΔH), number of short-range order structures, and relative crystallinity (RC) while increasing the average particle size of these CS-FA complexes. This treatment also increased the proportion of amorphous starch regions and the degree of agglomeration between the starch and FA. HHP treatment-induced CS-FA complexes exhibited a denser fractal structure and higher short-range order, affecting the interaction sites between the starch and digestive enzymes. These findings suggest the potential application of HHP treatment and FA in modulating the postprandial glycemic response to starchy food.

Thermodynamics of gaseous strontium and calcium cerates studied by Knudsen effusion mass spectrometry and estimation of relative electron ionization cross-section for CeO2(g).

Ceria-based systems are of great interest because of their unique properties. Such systems may be used as anode materials for SOFCs or in oxygen sensors. Theexploitation of these materials often requires high temperatures. In such conditions, the partial or complete evaporation of materials is possible. Therefore, knowledge of the values of partial pressures and thermodynamic properties is essential to predict and/or prevent possible consequences and accidents. Knudsen effusion mass spectrometry was used to determine partial pressures of vapor species over the SrO-CeO2 and CaO-CeO2 systems. Measurements of partial pressures were performed with a MS-1301 mass spectrometer. Vaporization was carried out using molybdenum or tungsten effusion cells. A theoretical study of gaseous strontium and calcium cerates was performed by several quantum chemical methods: density functional theory (DFT) M06, DFT PBE0, and MP2. The minimum value of relative electron ionization cross-section for CeO2 was estimated. In the temperature range of 2218-2249 K above the SrO-CeO2 system and of 2128-2208 K above the CaO-CeO2 system, gaseous M, MO, MO, CeO2, O, O2 and MCeO3 (M = Sr, Ca) were found. Energetically favorable structures of gaseous SrCeO3 and CaCeO3 were found, and vibrational frequencies were evaluated in the "rigid rotor-harmonic oscillator" approximation. On the basis of the equilibrium constants of gaseous reaction MO + CeO2 = MCeO3, the standard formation enthalpy of gaseous SrCeO3 (-913 ± 26 kJ/mol) and of gaseous CaCeO3 (-917 ± 26 kJ/mol) at 298 K were determined. The estimated value of relative electron ionization cross-section for CeO2 is in agreement with the general rule applicable for dioxides. The stability of SrCeO3 and CaCeO3 gaseous species was confirmed by KEMS. Gas-phase reactions involving gaseous SrO (CaO) and CeO2 with gaseous SrCeO3(CaCeO3) were studied. Enthalpy of formation reaction of gaseous SrCeO3(CaCeO3) from gaseous SrO (CaO) were evaluated theoretically, and the obtained value is in agreement with the experimental one.

Highly operative removal of amoxicillin (AMX) from aqueous solution by MnFe2O4 nanoparticles and carboxy methyl cellulose (CMC) composite

In recent work, manganese ferrite (MnFe2O4) nanoparticles and manganese ferrite carboxy methyl cellulose (MnFe2O4/CMC) composite were synthesized using Salvadora persica extract (SPE). Characterization of green synthesized nanoparticles and composite was performed by different techniques such as FTIR, SEM, UV–visible spectroscopy, XRD, and EDX. These techniques evaluated the size, shape, composition, morphology, and crystallinity of bimetallic nanoparticles (BMNPs) and nano-composites (NCs). These techniques demonstrated the presence of oxygen with metals, 3.28 nm size of MnFe2O4 and CMC hump between the 22-26° and the spherical, cubic, and mostly irregular shape of MnFe2O4 nanoparticles and rougher surface of MnFe2O4/CMC composite. Nanoparticles and nanocomposites were utilized for the degradation of Amoxicillin (AMX). The maximum degradation of AMX occurred at optimum conditions such as adsorbent dosage (6 mg MnFe2O4, 2 mg MnFe2O4/CMC), pH (4,6) within 60 min at 5 mg/L initial AMX concentration. Results revealed that the catalytic activity of NCs (97 %) was more than BMNPs (93 %) which may be attributed to the incorporation of reduced Carboxy Methyl Cellulose (CMC). It reduced the e-hole recombination rate and enhanced the AMX degradation at ambient conditions. The nature of adsorption was illustrated by Langmuir and Freundlich models and results demonstrated that the Freundlich model followed more closely. Thermodynamics parameters described the endothermic and spontaneous nature of the adsorption process, negative Gibbs energy variation, and positive entropy and enthalpy change. The recovery and reusability of BMNPs and NCs were investigated and concluded that MnFe2O4 and NCs can be used many times for the AMX adsorption process.

Green flame-retardant rigid polyurethane foam with cobalt hydroxystannate to improve the thermal stability, flame retardancy and smoke suppression properties

The ecological benefits and concerns surrounding fossil fuels had led to increased interest in bio-based rigid polyurethane foam (RPUF). Nonetheless, due to its flammability, it had limited application in various fields. To solve this problem, a green bio-flame retardant, cobalt hydroxystannate (CoSn(OH)6), was prepared and compounded with montmorillonite (MMT) and chick feather protein (CF), and applied to RPUF, which not only realized the regeneration of resources, but also provided RPUF with better thermal stability, flame retardancy and smoke suppression properties. The experimental results showed that when 3 wt% CoSn(OH)6 was added, the RPUF (CF1/MMT3/Co3) had the greatest activation energy. In addition, the peak heat release rate (PHRR) and total heat release (THR) of CF1/MMT3/Co3 decreased by 12.73%, and 11.16% respectively, compared with no CoSn(OH)6. In addition, its Ds decreased by 28.9% and the light transmittance increased by 17.6% compared with the RPUF without CoSn(OH)6. At the same time, its peak smoke production rate (PSPR) and the total smoke release (TSR) decreased by 25% and 18%. And CF1/MMT3/Co3 also had the lowest fire risk evaluation index. This study presented possibilities for practical utilization of the RPUF substances founded on bio-based flame inhibitors.

Construction of a durable, halogen-free, and phosphorus-free flame retardant cotton fabric system with hydrophobic properties by phase separation and interface polymerization

Inspired by the synthesis of polyurethane, a multifunctional fabric with hydrophobic and long-lasting flame retardancy was prepared through the phase separation and interfacial reaction process between PEI (polyethyleneimine)/BX (borax) aqueous solution and isocyanate terminated polydimethylsiloxane (PDMS-NCO) in tetrahydrofuran solution. The limit oxygen index of the treated fabric increased from 18.0 % to 33.7 %, and the total heat release decreased by 34.2 %. The enhancement of flame retardant performance and thermal stability is attributed to the enhanced char-forming capacity. After 50 cycles of water washing, the cotton fabric can still pass the vertical flammability test because of the curing effect of PDMS-NCO on functional additives. Furthermore, SEM analysis revealed that the formation of nano-rough structures on the fibers was promoted by phase separation, thus leading an increased water contact angle of sample to 139°. The materials utilized in this modified process do not contain elements such as F, Cl, Br, and P, indicating its potential as an environmentally friendly methodology for fabric functionalization.

Novel eco-friendly bio-nano flame retardant via the electrostatic-driven hybridization of natural halloysite nanotubes and phytic acid for superior fire safety of epoxy composites

Driven by increasingly stringent safety regulations and enhanced fire hazards awareness, rationally designing a highly flame-retardant and eco-friendly polymer composites has become critically significant, but remains challenging. Herein, to endow epoxy resin (EP) composites with exceptional fire safety while maintaining its desirable performances, a novel bio-nano flame retardant GPP@HNTs was successfully prepared via the electrostatic-driven hybridization of two natural-available green materials, halloysite nanotubes (HNTs) and phytic acid (PA). It was found that the GPP@HNTs can uniformly disperse in EP matrix due to its strong interfacial interaction with EP. In compassion with EP, the flame retardancy of GPP@HNTs/EP composites was effectively enhanced, reaching UL-94 V-0 rating and exhibiting a 42.55 % increase of LOI value, 32.76 % decrease in peak heat release rate (PHRR), 25.92 % reduction in total heat release (THR). Furthermore, the GPP@HNTs/EP composites also present excellent thermal stability and mechanical properties. Such a facile yet efficient hybridization design of bio-nano flame retardant paves the way for wide practical applications of the flame-retardant and mechanically robust EP composites in various industrial fields.

Unlocking thermochemical CO2/H2O splitting by understanding the solid-state enthalpy and entropy of material reduction process

Two-step redox thermochemical cycles, capable of directly converting CO2 and H2O respectively into CO and H2, offer a promising synthesis route towards green carbon-neutral fuels. The performance of such two-step cycles depends highly on the thermodynamic properties of splitting materials, particularly the solid-state enthalpy (Δhsolid) and entropy (Δssolid) changes during the reduction process. Here, we report an investigation into the roles of the Δhsolid and Δssolid. We shall show that a high Δssolid relaxes both reduction temperature and oxygen pressure, but increases oxidant consumption. Conversely, an increase in Δhsolid enhances reduction resistance while promotes oxidation reactions. There are therefore no perfect materials, and a trade-off is needed for an optimal solution. We also defined a thermodynamic region based on Δhsolid and Δssolid and typical operating conditions, and showed that higher values of both Δhsolid and Δssolid provided a larger reaction space. While lower Δhsolid and negative Δssolid may be more suitable for isothermal cycles. Our analyses also suggest future efforts in searching for splitting materials with a high Δssolid within an appropriate range of Δhsolid (280–460 kJ/mol).

Effects of ferritin iron loading, subunit composition, and the NCOA4-iron sulfur cluster on ferritin-NCOA4 interactions: An isothermal titration calorimetry study

Ferritin is a 24-mer protein nanocage that stores iron and regulates intracellular iron homeostasis. The nuclear receptor coactivator-4 (NCOA4) binds specifically to ferritin H subunits and facilitates the autophagic trafficking of ferritin to the lysosome for degradation and iron release. Using isothermal titration calorimetry (ITC), we studied the thermodynamics of the interactions between ferritin and the soluble fragment of NCOA4 (residues 383–522), focusing on the effects of the recently identified FeS cluster bound to NCOA4, ferritin subunit composition, and ferritin‑iron loading. Our findings show that in the presence of the FeS cluster, the binding is driven by a more favorable enthalpy change and a decrease in entropy change, indicating a key role for the FeS cluster in the structural organization and stability of the complex. The ferritin iron core further enhances this association, increasing binding enthalpy and stabilizing the NCOA4-ferritin complex. The ferritin subunit composition primarily affects binding stoichiometry of the reaction based on the number of H subunits in the ferritin H/L oligomer. Our results demonstrate that both the FeS cluster and the ferritin iron core significantly affect the binding thermodynamics of the NCOA4-ferritin interactions, suggesting regulatory roles for the FeS cluster and ferritin iron content in ferritinophagy.