Search

Aluminum (Al) is an attractive material for hydrogen generation through its reaction with water. This study assesses the effectiveness of aluminum hypophosphite (AHP) in inhibiting Al dust explosions and elucidates its decomposition pathway and inhibition mechanism. At a concentration of 1050 g/m3, AHP completely inhibited the maximum explosion intensity of Al dust. Its high activation energy and P–O cross-linking layer impeded heat transfer. Reactive force field molecular dynamics (ReaxFF-MD) simulations complemented that AHP decomposes into vital products such as PH 2 and H 2 PO 2. Concurrently, CHEMKIN numerical calculations highlighted the crucial role of phosphorus hydroxide (PH) radicals in the recycling and regeneration of phosphorus radicals. The reaction PO 2 + PH⇔ HOPO + P accelerated the cycling of HOPO, thereby reducing the required radicals for sustaining aluminum combustion. AHP exhibits dual-phase inhibition against Al dust explosions, thereby guaranteeing the safe operation of aluminum-based hydrogen generation systems in the hydrogen energy domain. [Display omitted] • Chosen aluminum hypophosphite validated against aluminum dust explosions. • ReaxFF simulations reveal that AHP decomposes into PH 2 and H 2 PO 2 in the gas phase. • Phosphorus-hydrogen radicals enhance the HOPO ⇔ PO 2 inhibitory cycle. [ABSTRACT FROM AUTHOR]

The study of the pyrolysis/combustion kinetics and kinetic modelling of methyl ethyl ketone peroxide (MEKPO) is of great significance for its potential engineering applications. The pyrolysis and combustion mechanisms of MEKPO are studied in this work by ReaxFF MD simulation, DFT calculations and modelling simulations. The potential energy surface (PES) of the primary pathways in MEKPO pyrolysis and combustion are established at M06–2X/6–31 +G* *// CCSD(T)/cc-PVTZ level, and the rate constants are obtained via TST/VTST. The identified pathways and rate constants are integrated to a novel kinetic model. The results of ReaxFF MD simulation and modelling simulation both indicate that MEKPO will rapidly pyrolyze into butanone primarily in the way of MEKPO→·C 4 H 9 O 3 →butanone. The most crucial intermediate species in the process of MEKPO combustion are C 2 H 4 , H 2 O 2 , CH 2 O, CH 2 CO and H 2. Although a large amount of ·HO 2 is generated during the pyrolysis of MEKPO, the key radicals for MEKPO combustion are ·H, ·O and ·OH, which can be attributed to the energy barriers for ·H, ·O and ·OH attacking H atoms are relatively low. For instance, the average energy barriers for ·HO 2, ·H, ·O, ·OH attacking H atoms of butanone are 26.5, 14.7, 11.5 and 8.4 kcal/mol, respectively. However, the ·HO 2 generated during pyrolysis has the effect of promoting the H 2 -O 2 sub-mechanism, while also facilitating the combustion of MEKPO. The study can facilitate a deeper understanding of the chemical processes occurring in the formation of air pollutants (CO/ CO 2 /C 2 H 2 /CH 2 O) in MEKPO combustion, and the threats to the environment and human health. [Display omitted] • Reaction paths of MEKPO combustion is revealed and a kinetic model is developed. • The formation of air pollutants during MEKPO combustion process is clarified. • A method that integrates ReaxFF MD simulations and DFT calculations is employed. [ABSTRACT FROM AUTHOR]

In this study, a series of reversible thermochromic microencapsulated phase change materials (TC-MPCMs), exhibiting excellent thermal energy storage performance, were designed and fabricated successfully. The core of TC-MPCMs was comprised of crystal violet lactone employed as thermochromic colorant, bisphenol A as developer and 1-tetradecanol as co-solvent, respectively. The effects of shell materials on reversible thermochromic properties, thermal performance and thermal stability of TC-MPCMs were investigated systematically as well. These influencing factors of encapsulation process such as the dripping speeds, SMA emulsifier and pH were carried out to optimize the encapsulation parameters. Additionally, the TC-MPCMs modified with fabricated silver nano-particles displayed excellent thermal properties, heat transfer and antibacterial activity. Both the microscopic morphology and microstructure of TC-MPCMs were characterized and discussed systematically. The thermal distribution on the TC-MPCMs was exhibited via the infrared camera. The performance of fusion, crystallization, enthalpy and thermal stability of various capsules were measured and studied as well. In the end, ultraviolet–visible spectrophotometry was employed to investigate the antibacterial activity of Ag-TC-MPCMs(B). Furthermore, the TC-MPCMs(B) and Ag-TC-MPCMs(B) exhibited excellent thermal stability and the cyclic durability. [ABSTRACT FROM AUTHOR]

In this study, a series of reversible thermochromic microencapsulated phase change materials (TC-MPCMs), exhibiting excellent latent heat storage-release performance, were designed and fabricated successfully. The characterization and microstructure regulation of TC-MPCMs were conducted systematically as well. The core of TC-MPCMs was comprised of crystal violet lactone employed as thermochromic colorant, bisphenol A employed as developer and 1-tetradecanol employed as co-solvent, respectively. These influencing factors of encapsulation process such as the amount of emulsifier, stirring rate, feeding weight of core/shell ratio, acid resistance and thermal cyclic durability were carried out to clarify the effect of various experimental conditions. The surface morphology, shell thickness and core–shell structure of TC-MPCMs were characterized via optical microscope (OM), thermal field emission scanning electronic microscope (TFE-SEM), transmission electron microscope (TEM), respectively. From different scanning calorimetry (DSC) analysis, the performance of temperature of fusion and crystallization and enthalpy of TC-MPCMs under various conditions were measured as well. The results of thermogravimetric (TG) analysis illustrated the influence on thermal stability of TC-MPCMs. In addition, Lab color space obtained by colorimeter is certainly intuitive to observe the colorimetric characteristics of TC-MPCMs as well. More importantly, the reversible thermochromic property associated with phase state of the 1-tetradecanol could also provide a visual evidence of energy storage or release performance of the TC-MPCMs. Furthermore, The TC-MPCMs exhibited excellent stability even after 100th thermal cycling test without any obvious performance degradation, including the morphology, phase change properties and thermal stability. In the end, the fire fighter protective clothing containing TC-MPCMs was designed and fabricated, which could provide adequate thermal protection in the various fire environments. Thus, TC-MPCMs developed in this work showed great potential applications in thermal protective clothing and other thermal regulation fields. [ABSTRACT FROM AUTHOR]

In this paper, chitosan-based polyurethane (c-PU) microencapsulated phase change materials (MicroPCMs) were prepared via the interfacial polymerization reaction of hexamethylene diisocyanate and chitosan accompanied by the charge attraction-assisted. The utilization of natural non-toxic chitosan in MicroPCMs expanded the application of chitosan and guided a new approach to preparing green shell. And the morphology of MicroPCMs with different reaction ration, surfactant and the pH value of reaction system were systematically investigated. The MicroPCMs with c-PU shell exhibited outstanding latent thermal performance (Δ H m = 106.3 J/g, Δ H c = −105.1 J/g), high energy storage efficiency (E = 71.4%), excellent thermal stability and cyclic durability. The c-PU MicroPCMs with reversible photochromic show promising application in the fields of anti-counterfeiting technology and flexible wearable UV protective clothing. [Display omitted] • Chitosan-based polyurethane MicroPCMs were fabricated via interfacial polymerization. • The MicroPCMs exhibited outstanding thermal performance and cyclic durability. • The MicroPCMs with reversible photochromic extended the application of phase change materials. [ABSTRACT FROM AUTHOR]

Hydrophobic reversible thermochromic MicroPCMs with amino resins shell. • The effect of TDI modification on performance of TC-MPCMs was discussed in detail. • HTC-MPCMs possess hydrophobic surface (WCA = 148.5°). • HTC-MPCMs possess excellent latent heat storage capability and cyclic durability. The microstructure and composition of shell of reversible thermochromic microcapsulated phase change materials (TC-MPCMs) are crucial for their performance. High reaction activity between isocyanate group of TDI and active hydrogen of hydroxymethyl amino resin is conducive for TC-MPCMs to obtaining hydrophobic performance. Thus, a new type of TC-MPCMs with hydrophobic amino resins shell is developed via surface modifying using the prefabricated MF resin-encapsulated TC-PCMs as template. The experimental results shown the water contact angles (WCA) of the surface of modified microcapsules increased from 0° to 148.5°, suggesting that shell surface turned hydrophobic. The TC-MPCMs with hydrophobicity possessed good thermal properties (△H m = 100.0 J·g−1, △H c = 100.2 J·g−1), thermal stability, satisfactory thermal cyclic durability and reversible thermochromic performance. That might be beneficial for broadening its practical application value in the field of latent thermal energy storage. [ABSTRACT FROM AUTHOR]

Aiming at the characteristics of melamine-formadehyde resin with poor toughness and high brittleness owing to its unique structure of trizine ring, long-chain alkanol etherified melamine-formaldehyde prepolymer was selected as shell material to synthesize MicroPCMs. The study mainly explored the effect of etherification and relevant influencing factors in the etherification process on performance of microcapsules. Through a series of characterization, the alkyl chain of dodecanol can be grafted into the methylolated melamine-formaldehyde prepolymer via etherification, contributing to enhancing the adsorption of core material and encapsulation effect of microcapsules. The optimal molar ratio of melamine, formaldehyde and n-dodecanol was 1:7:2 in etherification process. N-dodecanol-etherified melamine-formaldehyde prepolymer was synthesized via one-step method as shell material for encapsulation n-dodecanol to obtain MicroPCMs4-2. The MicroPCMs4-2 finally obtained presented complete microstructure, uniform particle size distribution, well dispersibility and satisfactory thermal energy storage performance with high enthalpy value (△H m = 166.1 J/g, △H c = 160.2 J/g) and effective loading (72.2%) for potential applications to thermal-regulating textiles and energy storage fibers. Image 1 • Long-chain alkanol successfully etherified MF resin via one-step method. • Etherification contributed to improve the encapsulation efficiency of microcapsules. • The long-chain alkanol for etherification can be consistent with core materials. • MicroPCMs4-2 had perfect energy storage performance and mechanical properties. [ABSTRACT FROM AUTHOR]

Spiropyran (SP) materials have attracted considerable interest owing to sensitive and efficient photochromic properties, but it is a challenge to obtain photochromic materials with excellent sensitive UV-responsivity and photodegradation resistance durability. In this study, a series of comb-like acrylate polymer nanoparticle latexes containing SP are fabricated via miniemulsion polymerization. The influence of the length of the alkyl side chain of comb-like acrylate polymer on some photochromic properties of SP is investigated. Compared with the short-side chain poly(butyl acrylate) (PBA) nanoparticles latexes, the comb-like acrylate polymer nanoparticle latexes with longer side chain possess better photoresponsivity and more excellent photodegradation resistance because the strong interaction and chain flexibility of comb-like alkyl side chain provide effective spaces for the SP→MC or MC→SP photochemical isomerization. The investigations of photochromic nanoparticle latexes guide an approach to reversible optical data storage, multipurpose photo-responsive sensing system and show promising application in the field of ultraviolet intensity indicator and flexible wearable UV protective clothing. [Display omitted] • Photochromic nanoparticles were prepared by miniemulsion polymerization. • The comb-like polymer was selected as the carrier of photochromic materials. • The effect of alkyl side chain length of comb-like polymer on photochromic properties was studied. [ABSTRACT FROM AUTHOR]