Chemical Energy Release Research Articles

Application of microencapsulated phase change materials for controlling exothermic reactions

Abstract Thermal runaway is a frequent source of process safety issues, and the uncontrolled release of chemical energy puts reactors at risk. The design of the exothermic reactor faces challenges due to the selective sensitivity of the product to high temperatures and the need to increase the lifetime of the catalyst, optimize the product distribution, and improve the thermodynamic properties. Phase change material (PCM) encapsulation is recommended to reduce leakage, phase separation, and volume change problems. This work introduces encapsulated PCMs to improve reactor temperature control and minimize thermal runaway in exothermic processes. The warning temperature value setting effectively inhibits fugitive exothermic reactions and enhances heat transfer. When a sufficient quantity of encapsulated PCMs is input, the response speed will automatically accelerate. Spontaneous acceleration of the reaction rate due to thermal runaway of the reaction may be completely avoided by adding a sufficient amount of encapsulated PCM. Microencapsulation is used to control volume changes and inhibit thermal reactions. Preventive strategies include cooling, depressurization, safety release, emergency resources, and reaction containment. Encapsulated PCMs improve mechanical and thermal properties, surface-to-volume ratio, heat transfer surface, thermal capacity, and efficiency.

Shock-induced energy release reaction characteristics of Nb17Zr33Ti17W33 high entropy alloy

Nb17Zr33Ti17W33 high entropy alloy is a novel class of energetic structural material. In addition to exhibiting insensitivity and mechanical strength commensurate with inert metal materials, it demonstrates the capacity to release non-self-sustained chemical energy under high-speed dynamic load. In this study, the energy release characteristics of the Nb17Zr33Ti17W33 high-entropy alloy material under impact were investigated using the dynamic energy release test method, which involves ballistic gun-induced bullet-target interaction in a quasi-closed reaction vessel. The energy release process and governing laws of the impact event have been meticulously analyzed, resulting in the development of a comprehensive impact compression chemical energy release model. The direct ballistic tests and the recovered products revealed that Nb17Zr33Ti17W33 experienced chemical reactions during the impact loading, primarily the oxidation of the Zr element, which resulted in the release of significant chemical energy. This study elucidates the deformation response mechanism of Nb17Zr33Ti17W33 under high-speed impact loading, providing a crucial reference for further insights and applications of high-entropy alloy materials.

New Materials for Alkaline Fuel Cells from Electroplating Industries Waste Solution Oxygen Reduction Reaction Catalyzed by Pd on Carbon Nanotubes, Graphene and Carbon Black

Issues concerning the energy sector are the focus of international discussions; the progressive depletion of fossil reserves and the increase in energy demand have led to the rise in fuel and electricity prices. In this context, fuel cells are promising candidates for a sustainable future. Oxygen Reduction Reaction (ORR) is the bottle-neck strategic reaction ruling the fuel cell efficiency process. This reaction allows the release of chemical energy in the form of electricity without producing any waste. However, the slow kinetics of ORR require highly effective electrocatalysts for proper boosting. It is well known that best available catalysts, in terms of raw bulk elements, belong to the so-called platinum group metals (PGMs). PGMs are very expensive, hence lowering the PGM content of ORR catalysts is among the most prevalent research focuses [1,2].We propose two different ways to obtain carbon-based ORR catalyst with a low continent of PMGs. The first approach involves the use of Single-Ion catalysts designed by carbon nanotubes functionalized with palladium(II) complexes show [3]. The second approach is totally innovative and aims at recovering precious metals to reduce industrial waste and promote the development of a circular economy. Large quantities of wastewater are produced in electroplating industries. This wastewater not only has to be properly processed before it is released into the environment, but also contains metals like palladium [4]. Using carbon materials and an electroless deposition, palladium can be recovered from the wastewater of the electroplating industry. We focus on carbon black (CB) and two different types of graphene-type materials named as (G4) and (G7). It was found that CB and G4 can recover up to 97% palladium. In this way we obtained hybrid materials containing palladium that could be promising candidates for use as catalysts for the ORR in alkaline fuel cells.New catalysts were treated by preparing a nafion polymeric dispersion and tested with electroanalytical techniques. Rotating ring-disk electrode (RRDE) experiments were performed to investigate the catalytic pathway of ORR and asses the number of exchanged electrons per oxygen molecule. Results confirm that tested materials promote the four-electron reaction pathway and reduce the formation of hydrogen peroxide. These approaches provide the basis for further developments to improve the efficiency of future low-cost catalysts for alkaline fuel cells.[1] Passaponti, M.; Lari, L.; Bonechi, M.; Bruni, F.; Giurlani, W.; Sciortino, G.; Rosi, L.; Fabbri, L.; Vizza, M.; Lazarov, V.K.; et al. Optimisation Study of Co Deposition on Chars from MAP of Waste Tyres as Green Electrodes in ORR for Alkaline Fuel Cells. Energies 2020, 13, 5646, doi:10.3390/en13215646.[2] Bonechi, M.; Giurlani, W.; Vizza, M.; Savastano, M.; Stefani, A.; Bianchi, A.; Fontanesi, C.; Innocenti, M. On the Oxygen Reduction Reaction Mechanism Catalyzed by Pd Complexes on 2D Carbon. A Theoretical Study. Catalysts 2021, 11, 764, doi:10.3390/catal11070764.[3] Savastano, M.; Passaponti, M.; Giurlani, W.; Lari, L.; Calisi, N.; Delgado-Pinar, E.; Serrano, E.S.; Garcia-España, E.; Innocenti, M.; Lazarov, V.K.; et al. Linear, Tripodal, Macrocyclic: Ligand Geometry and ORR Activity of Supported Pd(II) Complexes. Inorganica Chim. Acta 2021, 518, 120250, doi:10.1016/j.ica.2021.120250.[4] De Beni, E.; Giurlani, W.; Fabbri, L.; Emanuele, R.; Santini, S.; Sarti, C.; Martellini, T.; Piciollo, E.; Cincinelli, A.; Innocenti, M. Graphene-Based Nanomaterials in the Electroplating Industry: A Suitable Choice for Heavy Metal Removal from Wastewater. Chemosphere 2022, 292, 133448, doi:10.1016/j.chemosphere.2021.133448.

Low Temperature Heat Release and ϕ-Sensitivity Characteristics of Iso-Octane/Air Mixtures

ABSTRACT Chemical energy release from high octane number fuels via low temperature heat release (LTHR) can help develop high-efficiency gasoline engines by promoting ultra-lean combustion in spark ignition engines and improving combustion control in gasoline compression ignition engines. A recently developed experimental technique that permits isolated LTHR investigations in motored engines was used to characterize the LTHR behavior of iso-octane/air mixtures ranging in strength from to at multiple inlet temperature conditions ( to °C). LTHR changes were studied by observing variations in exhaust CO emissions and exhaust temperature increase. Observed heat release results were explained using cylinder mixture pressure-temperature histories alongside supporting chemical kinetics modeling estimates of mixture reactivity in the form of chemical ignition delay (ID) time. The effects of fuel enrichment on iso-octane/air mixture reactivity were found to be non-uniform and dependent on mixtures’ thermal state trajectories in the LTHR ID peninsula. LTHR intensity measurements were used to discuss changes in mixture sensitivity at different engine inlet conditions. It was shown that by appropriately adjusting mixture thermal conditions via charge cooling from direct fuel injection and intake air heating, reactivity enhancements could be exploited maximally; and strong, positive, linear sensitivity of around 10 J per 0.1 increase in could be realized across a wide range of equivalence ratios from 0.05–1.2. It was also found that dominance of charge cooling effects at rich conditions resulted in negative and zero sensitivity regions.

Enhanced structural damage behavior of liquid-filled tank by reactive material projectile impact

A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles (RMPs) impacting liquid-filled tanks, and the corresponding hydrodynamic ram (HRAM) was studied in detail. PTFE/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering process. The projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 1250 m/s. The corresponding cavity evolution characteristics and HRAM pressure were recorded by high-speed camera and pressure acquisition system, and further compared to those of steel and aluminum projectiles. Significantly different from the conical cavity formed by the inert metal projectile, the cavity formed by the RMP appeared as an ellipsoid with a conical front. The RMPs were demonstrated to enhance the radial growth velocity of cavity, the global HRAM pressure amplitude and the front panel damage, indicating the enhanced HRAM and structural damage behavior. Furthermore, combining the impact-induced fragmentation and deflagration characteristics, the cavity evolution of RMPs under the combined effect of kinetic energy impact and chemical energy release was analyzed. The mechanism of enhanced HRAM pressure induced by the RMPs was further revealed based on the theoretical model of the initial impact wave and the impulse analysis. Finally, the linear correlation between the deformation-thickness ratio and the non-dimensional impulse for the front panel was obtained and analyzed. It was determined that the enhanced near-field impulse induced by the RMPs was the dominant reason for the enhanced structural damage behavior.

A Novel Framework for Consequence Prediction of Battery Thermal Runaway Failure Hazards

Lithium-ion batteries (LIBs) are widely utilized for energy storage in a broad range of applications, such as handheld electronics, emobility, spaceflight vehicles, etc. Thermal runaway (TR) and subsequent combustion of LIBs represent several significant hazards to consumers, including substantial energy release, jet flames, toxic gases, airborne particulates, and secondary explosions. Numerous experimental investigations in the literature have measured the energy release and chemical composition of off-gasses during LIB TR, but little theoretical work has been completed to this end. The current study focuses on prediction of product chemical composition, flame temperature, and energy release for LIBs undergoing TR failure through implementation of chemical equilibrium analyses (CEA). Theoretical calculations for various LIB electrolyte decomposition and combustion scenarios were compared to data available in the literature. Excellent agreement was observed between predicted and experimental measured heats of combustion for plain LIB electrolytes, indicating the global thermodynamic properties are well captured by the modeling approach. Theoretical product gas production (i.e., moles of gas per mole of electrolyte) and composition were compared to experimentally measured values from accelerated rate calorimetry experiments. The results indicate that general trends are well captured by the CEA modeling approach developed here and that the standard experimental protocols documented within the literature can be improved. Similar theoretical predictions for battery failure experiments (product gas composition and energy release) are also presented. The novel modeling framework presented here can be used in future work to evaluate LIB failure hazards for existing systems and to evaluate the safety of future designs. In addition, this modeling approach provides unique insight into how adjusting global battery chemistry (cathode, electrolyte, etc.) changes the potential hazards produced battery thermal runaway and failure. Figure 1

Experimental investigation on the performance of the variable cross section rotating detonation engine

Optimizing the structure of the rotating detonation engine (RDE) is an effective way of improving its performance. In this paper, a variable cross section RDE with convergent-channel combustor (CC-RDE) is designed and compared with annular-channel combustor (AC-RDE). The operation range, propagation characteristics of rotating detonation waves (RDWs), and working performance were analyzed. In this study, the combustor outlet blockage ratios of both RDEs were equal, both being 0.35. The results show that the CC-RDE increased the propellant flow velocity, thus increasing the chemical reaction rate, and led to a comparative increase in RDW intensity of up to 185.4%. However, the higher the RDW intensity, the more likely the air plenum and the combustor were to be coupled, which shortened the range of stable operation. The RDW position under two RDEs were approximately 100 mm away from the combustor inlet. The percentages of pressure feedback and pressure pulsation in the air plenum were defined to evaluate the extent of pressure feedback. The results show that a higher RDW intensity in the CC-RDE led to a greater pressure pulsation in the air plenum. When the unstable mode appeared, the pressure feedback further increased. The heat flux of the combustor was also measured to assess the thermal environment of the RDE. The rates of chemical reaction and energy release were higher when the CC-RDE was used, and the average heat flux increased by 40.2% compared with that of the AC-RDE. Moreover, the specific thrust of the CC-RDE was increased by 40.3%.

Investigation on auto-ignition and chemical energy release characteristics of pilot hydrogen in supersonic combustion flow

This study investigates auto-ignition and heat release characteristics of pilot hydrogen chemical energy in a scramjet combustor equipped with a single cavity. Experiments are conducted in a direct-connected facility simulating Mach 6.0 flight conditions with a total temperature of 1350 K and total pressure of 1.75 MPa. Data are obtained from schlieren imaging, hydroxyl planar laser-induced fluorescence, flame emission, and 10-kHz static pressure transducers. The present investigation extends the pilot hydrogen ignition delay experimental dataset and clarifies the instabilities present in the ignition process. The results show that the supersonic internal flow of a confined cavity exhibits self-oscillating behavior with a dominant frequency of approximately 141.3 Hz. The primary chemical reaction occurs at mid-cavity, where the chemical energy of the pilot hydrogen begins to be converted into heat energy, then approaches the cavity ramp before finally being distributed across the whole cavity. The combustion mode is the cavity-stabilized scramjet mode. The distribution of hydroxyl radicals varies significantly because the combustion in the cavity is unsteady. The ignition delay time increases as the injection pressure rises. However, an injection pressure of 4.0 MPa produces an ignition delay of 24.7 ms, which is apparently shorter than the delay under an injection pressure of 3.5 MPa and similar to that under an injection pressure of 3.0 MPa. The injection of pilot hydrogen under high pressures induces greater heat release and more intense blockage effects, thus enhancing the probability of successful ignition and stable combustion.

Engineered Surface Chemistry and Enhanced Energetic Performance of Aluminum Nanoparticles by Nonthermal Hydrogen Plasma Treatment.

Extracting the maximum chemical energy from aluminum nanoparticles (Al NPs) during oxidation is essential for their use in energetic applications. However, the shell of native Al2O3 limits the release of chemical energy by acting as a diffusion barrier and dead weight. Engineering the surface properties of Al NPs by modifying their shell chemistry can reduce the inhibiting effects of the oxide shell on the rate and heat release of oxidation. Here, we employ nonthermal hydrogen plasma at high power and a short time to alter the shell chemistry by doping it with Al-H, as examined and confirmed by HRTEM, FTIR, and XPS. Thermal analysis (TGA/DSC) shows that Al NPs with modified surfaces exhibit augmented oxidation and heat release (33% higher than those of untreated Al NPs). The results demonstrate the promising effect of nonthermal hydrogen plasma in engineering the shell chemistry of Al NPs to improve their overall energetic performance during oxidation.

Penetration behavior of reactive projectiles impacting TC4 plates

The reactive projectile presents a tremendous potential to induce the combined damage effect of kinetic energy and chemical energy to the plate. A series of ballistic impact experiments and numerical simulation studies were carried out to study the penetration behavior of reactive projectile against TC4 plate. The experimental results showed that with the impact velocity of the reactive projectile increasing from 537m/s to 682m/s, the damage mode of the plate gradually changes from bulge, cross crack to plug. According to the experimental results, the ballistic limit velocity of reactive projectile perpendicular penetrating 5mm TC4 is 648.33m/s. The numerical simulation results showed that the reactive projectile reaches GPa high pressure within a few microseconds when it impacted with the plate. During reactive projectile penetrating TC4 plate, the chemical energy release significantly improves the projectile penetrating ability, and the contribution of chemical energy to projectile penetrating can reach 55.07%.

Enhancing the mechanical and energy release performance of nano-aluminum@fluororubber (nAl@F2311) core–shell microstructured composite materials

Aluminum (Al)-based reactive materials have recently attracted much attention due to their excellent chemical energy release characteristics. However, there still exists a great challenge to improve the mechanical properties and energy density of Al-based reactive materials. In this work, we reported that core–shell nano-aluminum@fluororubber (nAl@F2311) composites with good mechanical properties and high energy release characteristics were designed and fabricated by the electrical exploding wires method. The results showed that Al nanospheres were coated by F2311 uniformly to form the nAl@F2311 core–shell microstructure with high Al contents. Quasi-static/Split Hopkinson Pressure Bar dynamic compression test results showed axial splitting failure mode of nAl@F2311 composites. nAl@F2311-10 composites with 90 wt. % Al contents had higher compressive strength, with quasi-static and dynamic compressive strength of 117.6 and 304.6 MPa, respectively. nAl@F2311-15 composites with 85 wt. % Al contents had a lower ignition threshold. Furthermore, the impact-induced energy release test showed higher fluorine contents will accelerate energy release, reduce impact ignition threshold, and improve the reaction efficiency of nAl@F2311 composites. The high reaction efficiency (97.79%) of the nAl@F2311-15 composites was obtained at an impact velocity of 1090 m/s. This offered a concept-of-proof work to design and fabrication of nanostructured reaction materials, which had high strength and energy release performance.

Reaction mechanism and electronic properties of host-guest energetic material CL-20/HA under high pressure by quantum-based molecular dynamics simulations.

The novel host-guest material 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)/hydroxylamine (HA) improves the detonation energy of CL-20 explosives without compromising its safety. However, the reaction mechanism of CL-20/HA under high pressure is not yet fully understood for the complex host-guest structure. A multiscale shock simulation technique by quantum-based molecular dynamics was performed to investigate the reaction mechanism of CL-20/HA under shock with different velocities along different directions, focusing on charge transfer, electronic properties, reaction path and product evolution. The structural changes caused by both insertion of HA and charge overlap between CL-20 and HA are responsible for the electronic changes and gap decrease. Directional charge transfer was observed between CL-20 and HA molecular fragments during shock in all shock loading directions, causing the CL-20 molecular group to become electrically non-neutral. The C-N bond in the CL-20 cage then broke, leading to the release of nitro and nitrous oxide at high temperatures and pressures. The HA molecules or free H atoms from HA could bond with the O atom in the nitro group, leading to the N-O bond cleavage. Some free H atoms could act as an intermediary, connecting two CL-20 molecules and forming dimeric molecules briefly. Compared with the pure CL-20 system, HA can inhibit the reaction of CL-20 in the CL-20/HA system to some extent during the initial shock stage. A further understanding of the chemical reaction mechanism and energy release in dense host-guest materials can be advanced by focusing on the microscopic internal effects of the guest molecule on the host molecule reactions.

Effect of absorption depth on chemical energy release from laser ablation of ADN-based liquid propellants

Ammonium dinitramide is a new green oxidant, which has been widely used in the field of liquid propulsion. In order to study the influence of doping laser absorber on the propulsion performance of liquid targets, the mixed solution of ammonium dinitramide and ionic liquid 1-allyl-3-methylimidazolium dicyandiamide was used as the ablation target, and the infrared dye was used as the laser absorber to change the doping content of infrared dye and laser energy density. The results show that the light absorption performance of liquid propellant is obviously improved with the increase of infrared dye content. The absorption coefficient and absorption depth of liquid propellant with infrared dye content of 0.6wt% are 425.19 cm−1 and 23.52 μm, respectively. The propellant with lower absorption depth produces high values of impulse bit, specific impulse, impulse coupling coefficient and ablation efficiency under the ablation of high laser energy density. The propellant sample doped with 0.6wt% infrared dye yielded the highest impulse bit of 114.32 μN·s, largest specific impulse of 84.14 s, highest impulse coupling coefficient of 1.07 mN·s·J−1, and the maximal ablation efficiency of 44% at the laser energy density of 21.51 J·cm−2. Furthermore, the effects of laser energy density and absorption depth on the chemical energy release of liquid propellant were studied. It was found that the maximum contribution of chemical energy to kinetic energy of ammonium dinitramide based liquid propellant is 93.93%. In general, improving the absorption performance of propellant can significantly enhance the energy release of energetic propellant. Which has guiding significance for propellant design and selection.

Energy, exergy and economic (3E) evaluations of a novel power generation system combining supercritical water gasification of coal with chemical heat recovery

Supercritical water gasification (SCWG) is a promising clean coal utilization technology. A proposed power system with integrated coal SCWG, supercritical turbine, gas turbine and chemical heat recovery is proposed in this paper. And the power system with integrated combined cycle and parallel heat recovery is re-proposed for structure simplification and efficiency enhancement. With a gasification condition of 660℃/250 bar, and a coal-water-slurry concentration of 11.3 %, the efficiencies of the proposed system and the system with parallel heat recovery are 49.06 % and 47.93 %, respectively. The power efficiency of the proposed system is greatly improved compared with the traditional systems. This is mainly due to the reasonable use of the pressure energy of the gasification product through the supercritical turbine, the release and use of high level chemical energy stored in the syngas in the gas turbine, and chemical heat recovery of the sensible heat of the flue gas from the gas turbine. Exergy and economic analyses are also performed. The levelized cost of electricity (LCOE) of the proposed power system is 0.2963 ¥/kWh. The power system proposed herein can be considered as one of the suitable options to achieve the carbon peak and carbon neutrality goals.

Combustion characteristics and quantitative determination of energy release of Epoxy-Al active materials projectile hypervelocity impact steel targets in vacuum environment

Epoxy resin is often used to intermediate of structural materials or adhesives as an important raw material and product of modern industry by low density, high strength and easy molding, which plays an important role in the field of composite materials. However, the current research mainly focuses on the mechanical properties of epoxy matrix composites under quasi-static and low strain rate loading, and there is little research on the properties of Epoxy-metal composites under high-speed loading. In this paper, Epoxy-Al5μm (70 wt%/wt30%) samples were prepared by adding active metal aluminum powder to epoxy resin and vacuum curing. The reaction-release energy and combustion characteristics of Epoxy-Al active materials projectile hypervelocity (2.85–3.46 km/s) impact steel targets in vacuum environment were studied by two-stage light gas gun loaded combined with a high-speed camera, an infrared thermal imager, a transient overpressure testing system and a transient optical fiber pyrometer. The results show that the Epoxy-Al material exhibits strong chemical energy release and combustion characteristics under hypervelocity impact load. The energy release can reach 21.36 kJ/g, which is much higher than the existing PTFE/Al active materials (8.23 kJ/g). The whole reaction process can be divided into three stages: accelerated reaction stage, decelerated reaction stage and after effect stage, a stable combustion phenomenon exists in the deceleration reaction period. In the accelerated reaction stage, the average reaction speed of the Epoxy-Al projectile is 1.4 km/s and the maximum temperature is 1650 K.

Exploring the controlling mechanisms for gradient evolution in unsteady detonation flows

Proper characterization of the transient interaction between shock front motion and chemical energy release is the key for further understanding of unsteady detonation dynamics. We have shown that the gradients could be the adequate intermediate quantities to reflect the transient interaction between shock front motion and chemical energy release through the Lagrangian particle analysis of the simulated direct detonation initiation (DDI) process in H2–O2–Ar mixtures. Specifically, the “shock change equations” are verified to describe the direct relation between the shock front motion and the gradients immediately behind the shock. Moreover, given the time derivatives of shock speed, the gradient evolution in the induction zone can be reproduced by the gradient evolution equations that are deduced from the Euler equations, no matter if the shock front undergoes rapid deceleration or acceleration. While in the reaction zone where the heat release is significant, it is demonstrated that the evolutions of velocity, pressure, and their gradients can be described by the Zel'dovich–von Neumann–Döring model with a constant wave speed that is below the Chapman–Jouguet speed, no matter if the shock front undergoes rapid deceleration or acceleration. These two distinct controlling mechanisms are verified in both planar and spherical DDI processes, showing their general applicability. This work suggests a new perspective, in terms of gradient evolution, for further understanding the unsteady detonation dynamics.

Research on Impact‐Induced Reactive Characteristics of Reactive Materials Under Low Air Pressure

AbstractReactive materials (RMs) are usually prepared from metal/non‐metal mixed powders through hot processing. The main feature of the material is that it will react and release energy when impacted. However, the impact‐induced chemical energy release during impact has a complicated mechanism and needs to be further explored. This work investigated the impact‐induced chemical process by split Hopkinson pressure bar and low‐pressure experimental system, different atmospheric pressure environment has been simulated. Moreover, High‐speed photography was used to reveal the macroscopic ignition phenomena. Furthermore, X‐ray diffraction (XRD) was used to study the material composition of raw and recovered specimens. The results of the experiments described here clearly show that metal reacts with oxygen and PTFE at atmospheric environment, which reaction produces are metal oxides and metal‐fluoropolymers. However, the material only undergoes fluorination reaction at low pressure, which reaction produces only has metal‐fluoropolymers. Meanwhile, the reactive ratio of the material increases with the pressure increase, furthermore, the maximum reaction ratio of the material in an atmospheric pressure environment is about 29.5 %, which reaction ratio is 4.7 times more than the pressure of 750 Pa.

A safer, symmetric all-organic battery based on temperature-responsive polymers as both cathode and anode

All-organic batteries that employ organic compounds as the cathode- and anode-active materials have emerged as a promising rechargeable battery chemistry system due to their environmental friendliness, sustainability, flexibility and wide raw materials availability. Just like current lithium-ion batteries, if operated improperly, there are also safe concerns mainly caused by thermal runaway in all-organic batteries. However, the safety protection for all-organic batteries has not been explored by far. In this work, a novel type of temperature-responsive symmetric all-organic battery with overheating self-protection function is proposed based on poly(3-octylthiophene) (P3OT) as both cathode- and anode-active materials. P3OT is anchored on carbon nanotube (CNT) surface to boost its p- and n-type redox activity. Rewarded by this, the resulting all-organic battery delivers a reversible capacity of 97.2 mAh g−1 at 50 mA g−1 between 0.01 and 2 V and exhibits an outstanding cycling stability. More importantly, when being charged under overheating conditions, the designed all-organic battery can always maintain the low state-of-charge. It can provide an early warning of battery overheating, and mitigate the release of chemical energy if the battery finally goes to fire. During the discharge process, the all-organic battery will be rapidly switched off, thus avoiding continuous battery damage. The thermal protection is proved to be derived from the thermal dedoping of PF6- from cathode-active P3OT. In addition, the all-organic battery is able to resume its normal function when battery temperature is dropped to room temperature.

Mesoscale study on explosion-induced formation and thermochemical response of PTFE/Al granular jet

The dynamic formation, shock-induced inhomogeneous temperature rise and corresponding chemical reaction behaviors of PTFE/Al reactive liner shaped charge jet (RLSCJ) are investigated by the combination of mesoscale simulation, reaction kinetics and chemical energy release test. A two-dimensional granular model is developed with the randomly normal distribution of aluminum particle sizes and the particle delivery program. Then, the granular model is employed to study the shock-induced thermal behavior during the formation and extension processes of RLSCJ, as well as the temperature history curves of aluminum particles. The simulation results visualize the motion and temperature responses of the RLSCJ at the grain level, and further indicate that the aluminum particles are more likely to gather in the last two-thirds of the jet along its axis. Further analysis shows that the shock, collision, friction and deformation behaviors are all responsible for the steep temperature rise of the reactive jet. In addition, a shock-induced chemical reaction extent model of RLSCJ is built based on the combination of the Arrhenius model and the Avrami-Erofeev kinetic model, by which the chemical reaction growth behavior during the formation and extension stages is described quantitatively. The model indicates the reaction extent highly corresponds to the aluminum particle temperature history at the formation and extension stages. At last, a manometry chamber and the corresponding energy release model are used together to study the macroscopic chemical energy release characteristics of RLSCJ, by which the reaction extent model is verified.

Laser ignition and combustion characteristics of B-Al compound powder without and with HMX: A comparative study

A micro-sized B-Al alloy has application potential to be an energetic material for metal fuel. To understand the combustion mechanism of micro-sized B-Al compound powder and explosives containing B-Al (30 wt.%), the ignition and combustion characteristics of B-Al compound powder without and with HMX (cyclotetramethylenetetranitramine) under different pressures (0.4, 0.8, 1.2, 1.5 and 1.8 MPa) and atmospheres (60% O+240% N2, 80% O+220% N2 and 100% O2) were studied via a laser ignition experimental system. The images and characteristic parameters of the ignition and combustion process with different conditions for the B-Al compound powder without and with HMX were obtained. The effects of atmosphere and pressure on the ignition and combustion characteristics of the B-Al compound powder without and with HMX were discussed through a comparative analysis. For the condensed combustion products (CCPs), the phase crystal structures were analysed with X-ray diffraction (XRD), the micro-morphology of the surface was observed with scanning electron microscopy (SEM), and the micro-area elementary composition was analysed with X-ray energy dispersive spectrum (EDS). The results show that whether the increase in pressure or oxygen concentration, the ignition delay time (tid) and combustion time (tct) of samples without and with HMX decrease, while the maximum spectral intensity (Imax) and the maximum combustion temperature (Tmax) increase. According to the flame morphology, the combustion of the B-Al compound powder is weaker, while that of the B-Al powder with HMX is more intense, and the flame area is larger, which produces a large amount of smoke and presents a deflagration phenomenon. Specially, for various B-Al powder (B/Al = 3/7, 1/1 and 7/3) with HMX under high pressures (1.2, 1.5 and 1.8 MPa), the higher ratio of B leads to shorter combustion time and stronger spectral intensity. Unreacted B, Al and their final oxides, B2O3 and Al2O3, were detected in the CCPs of both samples without and with HMX. In addition, the CCPs like BN, AlN and Al5O6N were also detected. The experimental results can help us better understand the chemical reaction mechanism and energy release characteristics of HMX-based explosives containing B-Al.