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Due to environmental pollution and energy crises, zero‑carbon fuel ammonia (NH 3 ) has attracted extensive attention as an alternative fuel for engines. In this paper, the effects of ammonia energy ratio (AER) and injection strategy on particulate emission characteristics of an ammonia diesel dual-fuel engine were examined by merging experimental and simulation results; additionally, soot formation and oxidation mechanism were investigated. Results showed that the reduction in particulate emission was substantially higher than the increase in AER. When AER increased to 60 %, the reduction in particulate mass concentration reached 97.5 %. The initial soot formation area gradually moved to the bottom of the piston bowl with increasing AER. When the piston reached the top dead center, the high-soot-concentration area was shifted to the center of the piston bowl as AER increased. The contents of acetylene (C 2 H 2 ) and methyl (CH 3 ) reduced considerably, which restricted the formation of soot precursors. With AER increasing, the contents of nitric oxides (NO x ) and other nitrogen-containing species increased and reacted with CH 3 and other carbon-containing species, which effectively reduced the number of C in soot formation pathway, thereby lowering particulate emissions. As AER increased, hydroxyl (OH) involved in soot formation gradually decreased, and only 14 % of OH was involved in the oxidation of n-heptane at 60 % AER, which was favorable for reducing the soot formation rate. Furthermore, OH is a substantial species in soot oxidation. The introduction of ammonia caused an increase in OH, which facilitated the removal of soot. The decrease in hydrogenium (H) hindered the hydrogen-abstraction-acetylene-addition (HACA) reaction, further limiting the soot surface growth. By optimizing the injection timing and AER, particulate emission was lowered to 4.31 × 10 -5  μg/cm 3 , and particle size was reduced by 64.2 % when AER was 60 %, injection timing was -20° CA ATDC, and injection pressure was 60 MPa., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

CO 2 hydrogenation into valuable chemical compounds can effectively address the issues of greenhouse gas emissions and energy scarcity. The activation and dissociation processes of CO 2 are crucial for its reduction reactions, but the effects of *H adatoms on the C-O cleavage are still confusing. This study investigates the H-assisted CO 2 dissociation pathways on the Pd n Pt (4- n ) /In 2 O 3 ( n = 0-4) catalysts via DFT calculation. Initially, the adsorption properties of *H 2 , *COOH, and *HCOO species are calculated. Then, two H-assisted CO 2 dissociation channels, i.e. , *CO 2 + *H → *COOH → *CO + *OH and *CO 2 + *H → *HCOO → *CHO + *O, are studied. Results show that Pt and Pd promote the CO 2 hydrogenation and C-O bond cleavage reactions, respectively. In comparison to CO 2 direct dissociation, the COOH-mediated and HCOO-mediated channels facilitate and impede the C-O bond cleavage, respectively. Overall, the Pd 3 Pt/In 2 O 3 constituent is suggested for the H-assisted CO 2 dissociation reaction. The electronic effects of the Pd n Pt (4- n ) bimetals adjust the stabilities of the intermediates and barriers of the elementary steps, and the interactions between Pd n Pt (4- n ) and In 2 O 3 provide extra sites for the adsorbates and reaction steps. This study reveals the effects of *H on the C-O bond dissociation processes and provides useful insight into designing PdPt/In 2 O 3 catalysts for CO 2 hydrogenation reactions.

Energy self-circulation systems, defined as energy systems incorporating the recycling utilization of waste biomass, have been proposed to reduce greenhouse gases emissions from livestock sector. In this study, a comprehensive review of the situation and challenges of biogas utilization in the livestock industry was provided. Moreover, two technological routes were proposed for a circular livestock system combined with Powerfuels production (CP-CLS), starting from biogas combustion for power generation and steam reforming to the sustainable development path of synthesizing, storing, and utilizing Powerfuels. The self-circulation capability and comprehensive benefits of the CP-CLS life cycle was discussed, along with future application scenarios and proposed standards for Powerfuels. To realize this potential, continuous research, development, and policy support are crucial. This study envisions the next generation of energy self-circulation systems, which expects to reduce the negative effect of livestock industry on climate change and promote sustainable development., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Existing studies indicate that future global carbon dioxide (CO 2 ) removal (CDR) efforts could largely be concentrated in Asia. However, there is limited understanding of how individual Asian countries and regions will respond to varying and uncertain scales of future CDR concerning their energy-land-water system. We address this gap by modeling various levels of CDR-reliant pathways under climate change ambitions in Asia. We find that high CDR reliance leads to residual fossil fuel and industry emissions of about 8 Gigatonnes CO 2 yr -1 (GtCO 2 yr -1 ) by 2050, compared to less than 1 GtCO 2 yr -1 under moderate-to-low CDR reliance. Moreover, expectations of multi-gigatonne CDR could delay the achievement of domestic net zero CO 2 emissions for several Asian countries and regions, and lead to higher land allocation and fertilizer demand for bioenergy crop cultivation. Here, we show that Asian countries and regions should prioritize emission reduction strategies while capitalizing on the advantages of carbon removal when it is most viable., (© 2024. The Author(s).)

The combustion processes and catalytic after-treatment of ammonia/hydrogen-fueled engines, including NO x storage and reduction (NSR) and noble-metal selective catalytic reduction (SCR), can produce the byproduct N 2 O, a potent greenhouse gas that weakens the zero-carbon attribute of these fuels. Currently, the mechanism of N 2 O formation on DeNO x catalysts remains unclear due to limited research on catalytic after-treatment for such engines and the complexity of surface catalytic reactions. To elucidate the formation of N 2 O on the DeNO x catalysts of ammonia/hydrogen fuel engines, the impact factors on N 2 O formation on platinum catalysts (typical catalysts in NSR and noble-metal SCR) were investigated using first-principles molecular dynamics (FPMD). By employing the blue-moon ensemble enhanced sampling method and the slow-growth approach for free energy surface exploration, together with density functional theory (DFT) for electronic structure analysis, a linear relationship between the spin splitting of the d states of Pt clusters and N 2 O formation energy barriers was revealed, along with the increased structural sensitivity of Pt clusters with fewer atoms. It is highlighted that the energy barrier for N 2 O formation is determined by the matching degree of energy levels between molecules and surfaces. These findings provide atomic-scale insights into N 2 O formation on DeNO x catalysts for ammonia/hydrogen-fueled engines, facilitating N 2 O emission control for carbon-free engines.

The water-repellence properties of superhydrophobic surfaces make them promising for many applications. However, in some extreme environments, such as high humidities and low temperatures, condensation on the surface is inevitable, which induces the loss of surface superhydrophobicity. In this study, we propose a freezing-melting strategy to achieve the dewetting transition from the Wenzel state to the Cassie-Baxter state. It requires freezing the droplet by reducing the substrate temperature and then melting the droplet by heating the substrate. The condensation-induced wetting transition from the Cassie-Baxter state to the Wenzel state is analyzed first. Two kinds of superhydrophobic surfaces, i.e., single-scale nanostructured superhydrophobic surface and hierarchical-scale micronanostructured superhydrophobic surface, are compared and their effects on the static contact states and impact processes of droplets are analyzed. The mechanism for the dewetting transition is analyzed by exploring the differences in the micro/nanostructures of the surfaces, and it is attributed to the unique structure and strength of the superhydrophobic surface. These findings will enrich our understanding of the droplet-surface interaction involving phase changes and have great application prospects for the design of superhydrophobic surfaces.

Gasoline compression ignition characterized by partially premixed and long ignition delays typically features complex flame structures such as deflagration or spontaneous ignition fronts. In this study, the flame structure and propagation characteristics of PRF90/air mixtures under compression ignition engine-relevant conditions are investigated numerically. Similar to other types of fuels, under such conditions, the propagation speed of PRF90 laminar premixed flames depends not only on the unburnt mixture properties but also on the residence time, and the transition of the flame regime depends only on the residence time. Nevertheless, due to the temperature-dependent autoignition chemistry of PRF90, flames with excessively high unburnt temperatures show different combustion behaviors after the transition from deflagration to autoignition-assisted flames. Sensitivity analysis showed that, the dominant chain branching reactions in the deflagration mode are H + O 2 = OH + O and CO + OH = CO 2 + H, and that in the autoignition-assisted flames with lower unburnt temperature are H 2 O 2 (+M) = 2OH(+M) and IC 8 H 18 + HO 2 = AC 8 H 17 + H 2 O 2 , while for higher unburnt temperatures, the reactions C 3 H 5 + HO 2 = C 2 H 3 + CH 2 O + OH and IC 8 H 18 = IC 4 H 9 + TC 4 H 9 are more important than the fuel low-temperature oxidation reactions. In addition, a criterion based on chemical explosive mode analysis is used to analyze the local combustion mode. The results show that the difference in diffusion/chemical structure at the crossover progress variables C 0 and to be used as a flame location for distinguishing propagation modes in premixed flame. However, the effects of the equivalence ratio on C are different from that on , which means that the selection of 0 and may lead to different discriminant results for stratified mixtures. Comparing the applicability of C -based and -based locations in three-dimensional gasoline compression ignition flame, it is found that the flame location based on the value of 0 are different from that on , which means that the selection of C 0 and may lead to different discriminant results for stratified mixtures. Comparing the applicability of C 0 -based and -based locations in three-dimensional gasoline compression ignition flame, it is found that the flame location based on the value of C 0 at ϕ = 1.0 can more completely reflect the flame development characteristics in stratified premixed combustion., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Anion exchange polymers (AEPs) play a crucial role in green hydrogen production through anion exchange membrane water electrolysis. The chemical stability of AEPs is paramount for stable system operation in electrolysers and other electrochemical devices. Given the instability of aryl ether-containing AEPs under high pH conditions, recent research has focused on quaternized aryl ether-free variants. The primary goal of this review is to provide a greater depth of knowledge on the synthesis of aryl ether-free AEPs targeted for electrochemical devices. Synthetic pathways that yield polyaromatic AEPs include acid-catalysed polyhydroxyalkylation, metal-promoted coupling reactions, ionene synthesis via nucleophilic substitution, alkylation of polybenzimidazole, and Diels-Alder polymerization. Polyolefinic AEPs are prepared through addition polymerization, ring-opening metathesis, radiation grafting reactions, and anionic polymerization. Discussions cover structure-property-performance relationships of AEPs in fuel cells, redox flow batteries, and water and CO 2 electrolysers, along with the current status of scale-up synthesis and commercialization.

The mechanical and physicochemical properties of diesel engine exhaust particles before and after diesel oxidation catalyst (DOC) treatment are analyzed. It is considered important to explore the interrelationships between these attributes in order to understand their relevance. Understanding of these properties provides insights into the deposition characteristics of particles within the system and the evolution of the particles after the DOC treatment, which may help the selection of appropriate aftertreatment strategies. In this paper, particle samples were collected before and after the DOC to explore the variations in the mechanical and physicochemical properties of the particles under different operating conditions. Atomic force microscopy, thermogravimetric analysis, transmission electron microscopy, and Raman spectroscopy were employed to investigate the attraction force, adhesion force, adhesion energy, oxidative reactivity, primary particle size, nanostructure, and graphitization degree of the particles. The results indicated that under post-injection conditions, the attraction force, adhesion force, and adhesion energy of the particles increased significantly. However, when the particles passed through the DOC, these properties decreased to varying degrees. By analyzing the combination of physicochemical properties, it was determined that the attraction force of the particles was primarily influenced by the primary particle size and the particle's graphite structure. The adhesion force was found to be closely related to the content of soluble organic matter. Additionally, the soluble organic matter affected the degree of particle agglomeration by altering the adhesion energy of the particles., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

An excellent textual properties and performance La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst was synthesized. The reaction mechanism of H 2 /NOx over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst was investigated by temperature programmed reduction/ desorption/ surface reaction (TPR/D/SR) technologies and in-situ diffuse reflectance Fourier transform (DRIFT) technology. The results show that cerium or palladium species are inserted into the cells of LaCoO 3 , as well as they synergetic promote the redox properties of the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst. Surface activated nitrates exist over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst, with thermal stable increasing in the order: absorbed N 2 O 4 < monodentate nitrates < chelating bidentate nitrates < nitrates unidentate < free ionic nitrates < bulk free ionic nitrates. H 2 preferentially reacted with absorbed N 2 O 4 and monodentate nitrates at low temperatures, due to their high activity. The concentration of generated NH 3 from the redox reaction of H 2 /NOx achieves the maximum value between 350 and 450 °C over the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst. Compared with the NOx adsorption process at 50 °C, monodentate nitrates and absorbed N 2 O 4 disappeared due to their low thermal stability, chelating bidentate nitrates become stronger, as well as free ionic nitrates converted to bulk free ionic nitrates with higher thermal stability at 350 °C. When H 2 is exposed to NOx species adsorbed on La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 , chelating bidentate nitrates and bulk free ionic nitrates are consumed gradually, indicating that although the bulk free ionic nitrates own high stability, it also could be consumed by involving in the H 2 /NOx reaction at 350 °C. The quantitative H 2 /NO reaction experiments confirmed the results of H 2 -TPSR and NSR. It is beneficial to the formation of NH 3 when the H 2 /NO ratio is more than 2.5. Comparing traditional Pt-BaO/Al 2 O 3 catalyst, the La 0.9 Ce 0.1 Co 0.9 Pd 0.1 O 3 -BaO/Al 2 O 3 catalyst exhibit an excellent performance, including considerable NH 3 production property, lower N 2 O selectivity, and the precious metal saving., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Engineering symmetry breaking in thermoelectric materials holds promise for achieving an optimal thermoelectric efficiency. van der Waals (vdW) layered transition metal dichalcogenides (TMDCs) provide critical opportunities for manipulating the intrinsic symmetry through in-plane symmetry breaking interlayer twists and out-of-plane symmetry breaking heterostructures. Herein, the symmetry-dependent thermoelectric properties of MoS 2 and MoSe 2 obtained via first-principles calculations are reported, yielding an advanced ZT of 2.96 at 700 K. The underlying mechanisms reveal that the in-plane symmetry breaking results in a lowest thermal conductivity of 1.96 W·m -1 ·K -1 . Additionally, the electric properties can be significantly modulated through band flattening and bandgap alteration, stemming directly from the modified interlayer electronic coupling strength owing to spatial repulsion effects. In addition, out-of-plane symmetry breaking induces band splitting, leading to a decrease in the degeneracy and complex band structures. Consequently, the power factor experiences a notable enhancement from ∼1.32 to 1.71 × 10 -2 W·m -1 ·K -2 , which is attributed to the intricate spatial configuration of charge densities and the resulting intensified intralayer electronic coupling. Upon simultaneous implementation of in-plane and out-of-plane symmetry breaking, the TMDCs exhibit an indirect bandgap to direct bandgap transition compared to the pristine structure. This work demonstrates an avenue for optimizing thermoelectric performance of TMDCs through the implementation of symmetry breaking.

Microstructures and mechanical properties of Mg-12Gd-0.8Zn-0.4Zr (GZ1208K, wt.%) alloy under different treatments (as-cast: signed as nonHIP-GZ1208K, hot isostatic pressing (HIP): signed as HIP-GZ1208K) were characterized. Based on microstructure characterization, two prismatic precipitates, β' and β 1 precipitates, and one basal precipitate, γ' precipitate, formed in both of nonHIP-GZ1208K and HIP-GZ1208K alloy. According to analysis, the area number density and the size of β' precipitate could be adjusted through HIP treatment. The area number density of β' precipitate increased after HIP treatment when aged at 32 h, and the size of β' precipitate refined in both of the HIP-GZ1208K alloy aged at 8 h and 32 h. Except the influence of HIP treatment on microstructures, the ultimate tensile strength (UTS) and elongation of nonHIP-GZ1208K alloy also improved after HIP treatment. The UTS of the GZ1208K alloy aged at 8 h increased from 348 MPa (nonHIP-) to 371 MPa (HIP-) and the elongation increased from 2.6% to 4.7%. The density of the nonHIP-GZ1208K alloy increased after HIP treatment, that is to say the casting defects could be eliminated and the compactness of microstructures could be increased under the high pressure of HIP treatment., (© 2024. The Author(s).)

Fault diagnosis can improve the safety and reliability of diesel engines. An end-to-end method based on a multi-attention convolutional neural network (MACNN) is proposed for accurate and efficient diesel engine fault diagnosis. By optimizing the arrangement and kernel size of the channel and spatial attention modules, the feature extraction capability is improved, and an improved convolutional block attention module (ICBAM) is obtained. Vibration signal features are acquired using a feature extraction model alternating between the convolutional neural network (CNN) and ICBAM. The feature map is recombined to reconstruct the sequence order information. Next, the self-attention mechanism (SAM) is applied to learn the recombined sequence features directly. A Swish activation function is introduced to solve "Dead ReLU" and improve the accuracy. A dynamic learning rate curve is designed to improve the convergence ability of the model. The diesel engine fault simulation experiment is carried out to simulate three kinds of fault types (abnormal valve clearance, abnormal rail pressure, and insufficient fuel supply), and each kind of fault varies in different degrees. The comparison results show that the accuracy of MACNN on the eight-class fault dataset at different speeds is more than 97%. The testing time of the MACNN is much less than the machine running time (for one work cycle). Therefore, the proposed end-to-end fault diagnosis method has a good application prospect.

Hypothesis: Droplet coalescence process is important in many applications and has been studied extensively when two droplets are surrounded by gas. However, the coalescence dynamics would be different when the two droplets are surrounded by an external viscous liquid. The coalescence of immiscible droplets in liquids has not been explored., Experiments: In the present research, the coalescence of two immiscible droplets in low- and high-viscosity liquids is investigated and compared with their miscible counterparts experimentally. The coalescence dynamics is investigated via high-speed imaging, and theoretical models are proposed to analyze the growth of the liquid bridge., Findings: We find that, the liquid bridge r evolves differently due to the constraint from the triple line in the bridge region, which follows r∝t 2/3 for low-viscosity surroundings. While for high-viscosity surroundings, the liquid bridge grows at a constant velocity u r which varies with the surrounding viscosity μ s as [Formula: see text] . In the later stage of the bridge growth, the bridge evolution again merges with the well-established power-law regime r∝t 1/2 , being either in low or high-viscosity liquids. Moreover, a new inertia-viscous-capillary timescale is proposed, which unifies the combined influence of inertia, viscous, and capillary forces on the evolution of the liquid bridge in liquid environments, highlighting the joint role of inertia and viscous resistance in the coalescence process., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Cu-SSZ-13 has been commercialized for selective catalytic reduction with ammonia (NH 3 -SCR) to remove NO x from diesel exhaust. As its synthesis usually requires toxic and costly organic templates, the discovery of alternative Cu-based zeolite catalysts with organotemplate-free synthesis and comparable or even superior NH 3 -SCR activity to that of Cu-SSZ-13 is of great academic and industrial significance. Herein, we demonstrated that Cu-T with an intergrowth structure of offretite ( OFF ) and erionite ( ERI ) synthesized by an organotemplate-free method showed better catalytic performance than Cu-ERI and Cu-OFF as well as Cu-SSZ-13. Structure characterizations and density functional theory calculations indicated that the intergrowth structure promoted more isolated Cu 2+ located at the 6MR of the intergrowth interface, resulting in a better hydrothermal stability of Cu-T than Cu-ERI and Cu-OFF. Strikingly, the low-temperature activity of Cu-T significantly increased after hydrothermal aging, while that of Cu-ERI and Cu-OFF substantially decreased. Based on in situ diffuse reflectance infrared Fourier transform spectra analysis and density functional theory calculations, the reason can be attributed to the fact that NH 4 NO 3 formed on the Cu x O y species within ERI polymorph of Cu-T underwent a fast SCR reaction pathway with the assistance of Brønsted acid sites at the intergrowth interfaces under standard SCR reaction conditions. Significantly, Cu-T exhibited a wider temperature window at a catalytic activity of over 90% than Cu-SSZ-13 (175-550 vs 175-500 °C for fresh and 225-500 vs 250-400 °C for hydrothermal treatment). This work provides a new direction for the design of high-performance NH 3 -SCR catalysts in terms of the interplay of the intergrowth structure of zeolites.

With the introduction of increasingly strict emission regulations, reducing nitrogen oxide (NO x ) emissions and nitrous oxide (N 2 O) production from diesel engines have become the focus of research. At high temperature, the reaction of NO 2 in the catalyst generates the intermediate product NH 4 NO 3 , which first crystallizes below 300 °C. These crystals tend to block the pores and inhibit the reaction. Subsequently, N 2 O is produced through the decomposition of NH 4 NO 3 , leading to additional pollution. Therefore, the concentration of NO 2 has a direct impact on both the NO x conversion efficiency and the generation of N 2 O, requiring consideration of the optimal proportion of NO 2 in SCR. Considering these two factors, it is concluded that the optimal amount of NO 2 varies with temperature. To improve the NO x conversion rate of the Cu-SSZ-13 catalyst at low temperatures and reduce N 2 O generation, the optimal NO 2 ratio of the Cu-SSZ-13 catalyst under various operating conditions is studied using numerical simulations. As the temperature rises, the optimal NO 2 /NO x ratio first increases and then decreases. Under the optimal NO 2 /NO x ratio, the NOx conversion rate significantly increases, while N 2 O generation decreases considerably. The optimal NO 2 /NO x ratio also provides suggestions for the optimization of the DOC-DPF-DCR system., (© 2024 Wiley-VCH GmbH.)

Hypothesis: The coalescence of droplets with liquid-gas interfaces of different surface tensions is common in nature and industrial applications, where the Marangoni-driven film spreading is an essential process. Unlike immiscible fluids governed by triple contact line dynamics, the mixing between two miscible fluids strongly couples with the film spreading process, which are expected to manifest distinct power-law relations for the temporal increase in the film radius., Experiments: We experimentally investigate the Marangoni-driven film spreading phenomenon for a droplet with lower surface tension dropping onto a miscible, thin liquid layer. The temporal growth of the film radius was detected by using a novel deep convolutional neural network, the U 2 -net method. Scaling analysis was performed to interpret the spreading dynamics of the film., Findings: We find that the film radius exhibits a three-stage power-law relation over time, with the exponent varying from 1/2 to 1/8, and back to 1/2. The diffusion-affected Marangoni stresses in these three stages were derived, and two estimations of viscous stress were considered. Through estimating and balancing the viscous stress with the Marangoni stress, the three-stage power-law relation was derived and validated., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Carbon dioxide removal (CDR) is necessary for reaching net zero emissions, with studies showing potential deployment at multi-GtCO 2 scale by 2050. However, excessive reliance on future CDR entails serious risks, including delayed emissions cuts, lock-in of fossil infrastructure, and threats to sustainability from increased resource competition. This study highlights an alternative pathway─prioritizing near-term non-CDR mitigation and minimizing CDR dependence. We impose a 1 GtCO 2 limit on global novel CDR deployment by 2050, forcing aggressive early emissions reductions compared to 8-22 GtCO 2 in higher CDR scenarios. Our results reveal that this low CDR pathway significantly decreases fossil fuel use, greenhouse gas (GHG) emissions, and air pollutants compared to higher CDR pathways. Driving rapid energy transitions eases pressures on land (including food cropland), water, and fertilizer resources required for energy and negative emissions. However, these sustainability gains come with higher mitigation costs from greater near-term low/zero-carbon technology deployment for decarbonization. Overall, this work provides strong evidence for maximizing non-CDR strategies such as renewables, electrification, carbon neutral/negative fuels, and efficiency now rather than betting on uncertain future CDR scaling. Ambitious near-term mitigation in this decade is essential to prevent lock-in and offer the best chance of successful deep decarbonization. Our constrained CDR scenario offers a robust pathway to achieving net zero emissions with limited sustainability impacts.

Droplet impact on soft surfaces (PDMS) was experimentally studied with particular interest in the complete rebound of droplets. This study focuses on the effect of liquid viscosity and the elastic modulus of the substrate on the critical rebound Weber number, maximum spreading, and contact time. Specifically, the lower and upper critical Weber numbers increase with an increasing droplet viscosity. With decreasing PDMS elastic modulus, the upper critical Weber number increases, while the lower critical Weber number decreases. The PDMS elastic modulus does not significantly affect the maximum spreading time and contact time. An interesting phenomenon of discontinuous contact time was experimentally observed and was theoretically interpreted.

The transport of water and protons in the cathode catalyst layer (CCL) of proton exchange membrane (PEM) fuel cells is critical for cell performance, but the underlying mechanism is still unclear. Herein, the ionomer structure and the distribution/transport characteristics of water and protons in CCLs are investigated via all-atom molecular dynamics simulations. The results show that at low water contents, isolated water clusters form in ionomer pores, while proton transport is mainly via the charged sites of the ionomer side chains and the Grotthuss mechanism. Moreover, with increasing water content, water clusters are interconnected to form continuous water channels, which provide effective paths for proton transfer via the vehicular and Grotthuss mechanisms. Increasing the ionomer mass content can enhance the dense arrangement of the ionomer, which, in turn, increases the density of charge sites and improves the proton transport efficiency. When the ionomer mass content is high, the clustering effect reduces the space for water diffusion, increases the proton transport path, and finally decreases the proton transport efficiency. By providing physics insights into the proton transport mechanism, this study is helpful for the structural design and performance improvement of CCLs of PEM fuel cells., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Competing Interests: Conflict of interest The authors declare that they have no conflict of interest.

1,4-Butanediol (BDO) is an important chemical raw material for a series of high-value-added products. And the ethynylation of formaldehyde is the key step for the production of BDO by the Reppe process. However, little work has been done to reveal the reaction mechanism. In this work, the reaction mechanism for the ethynylation of formaldehyde process on copper-terminated Cu 2 O(100) surfaces was investigated with density functional theory (DFT). The reaction network of the ethynylation of formaldehyde was constructed first and the adsorption properties of the related species were calculated. Then the energy barrier and reaction energy of the related reactions and the geometric configuration were calculated. It is a consecutive reaction including two processes. For the propargyl alcohol (PA) formation process, the most favorable pathway is the direct addition of acetylene to formaldehyde followed by a hydrogen transfer reaction. And the rate control step is the hydrogen transfer reaction with an energy barrier of 1.43 eV. For the 1,4-butynediol (BYD) formation process, the most competitive pathway is the addition of PA to CH 2 OH, including formaldehyde hydrogenation to form CH 2 OH, coupling addition, and dehydrogenation reaction. The rate control step of this pathway is the dehydrogenation reaction with an energy barrier of 1.51 eV.

Hypothesis: Immiscible liquids are commonly used to achieve unique functions in many applications, where the breakup of compound droplets in airflow is an important process. Due to the existence of the liquid-liquid interface, compound droplets are expected to form different deformation and breakup morphologies compared with single-component droplets., Experiments: We investigate experimentally the deformation and breakup of compound droplets in airflow. The deformation characteristics of compound droplets are quantitatively analyzed and compared with single-component droplets. Theoretical models are proposed to analyze the transition between breakup morphologies., Findings: The breakup modes of compound droplets are classified into shell retraction, shell breakup, and core-shell breakup based on the location where the breakup occurs. The comparison with single-component droplets reveals that the compound droplet is stretched more in the flow direction and expands less in the cross-flow direction, and these differences occur when the core of the compound droplet protrudes into the airflow. The transition conditions between different breakup modes are obtained theoretically. In addition, the eccentricity of the compound droplet can lead to the formation of the thick ligament or the two stamens in the droplet middle., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Competing Interests: Conflict of interest The authors declare that they have no conflict of interest.

Hypothesis: The impact of droplets is prevalent in numerous applications, and jetting during droplet impact is a critical process controlling the dispersal and transport of liquid. New jetting dynamics are expected in different conditions of droplet impact on super-hydrophobic surfaces, such as new jetting phenomena, mechanisms, and regimes., Experiments: In this experimental study of droplet impact on super-hydrophobic surfaces, the Weber number and the Ohnesorge number are varied in a wide range, and the impact process is analyzed theoretically., Findings: We identify a new type of singular jets, i.e., singular jets induced by horizontal inertia (HI singular jets), besides the previously studied singular jets induced by capillary deformation (CD singular jets). For CD singular jets, the formation of the cavity is due to the propagation of capillary waves on the droplet surface; while for HI singular jets, the cavity formation is due to the large horizontal inertia of the toroidal edge during the retraction of the droplet after the maximum spreading. Key steps of the impact process are analyzed quantitatively, including the spreading of the droplet, the formation and the collapse of the spire, the formation and retraction of the cavity, and finally the formation of singular jets. A regime map for the formation of singular jets is obtained, and scaling relationships for the transition conditions between different regimes are analyzed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

M-N-C was recently reported to be a high activity catalyst for hydroformylation compared with a metal nanocluster. However, the nature of M-N-C sites and the dominant path of propylene hydroformylation on M-N-C sites with different structures are poorly understood. In this work, five different Co-N-C models (Co-N 3 -C, Co-N 4 -C, 0N-bridged Co 2 -N 6 -C, 1N-bridged Co 2 -N 7 -C and 2N-bridged Co 2 -N 6 -C) were constructed to simulate the Co active sites with different coordination that may exist on the surface of MOF-derived Co-based carbon materials. DFT combined with kinetic Monte Carlo (kMC) methods were used to study the catalytic performance for hydroformylation of different Co-N-C models. The results of the DFT calculations show that the coordination number and mode of N atoms could regulate the electronic density of the Co sites. The electronic density of the Co sites further affects the catalytic activity. The higher the electronic density is, the lower the energy barrier for partial hydrogenation of propylene and CO insertion reactions. Besides, the catalytic activity is also affected by the strong interaction in closer neighboring Co atoms in some Co 2 -N x -C models. The strong interaction affects the adsorption state and energy of species, which also reduces the overall reaction energy barrier. The kMC simulation results further showed that the dominant path of propylene hydroformylation was the n -butylaldehyde path for the 0N-bridged model, and the isobutylaldehyde path for Co-N 3 -C and 2N-bridged models.

Superhydrophobic surfaces can exhibit icephobicity in many ways due to their large contact angles and small rolling angles. The melting process of frozen droplets on superhydrophobic surfaces is still unclear, hindering the understanding of surface icephobicity. In this experimental study of the melting process of frozen sessile droplets on superhydrophobic surfaces, we find two types of melting morphologies with opposite vortex directions on a single-scale nanostructured (SN) superhydrophobic substrate and a hierarchical-scale micronanostructured (HMN) superhydrophobic substrate. Melting pattern visualizations and flow field measurements showed Marangoni convection and natural convection occurring in the melting sessile droplets. For the HMN superhydrophobic substrate, the internal flow was found to be dominated by Marangoni convection due to the temperature gradient along the surface of the droplet. For the SN superhydrophobic substrate, Marangoni convection was inhibited by the superhydrophobic particles at the surface of the droplet, which were shed from the fragile superhydrophobic substrate during the freezing-melting process, as confirmed by surface characterizations of the substrate and flow measurements of a water pool. These results will help researchers better understand the melting process of frozen droplets and in designing novel icephobic surfaces for numerous applications.

Microporous zeolites that can act as heterogeneous catalysts have continued to attract a great deal of academic and industrial interest, but current progress in their synthesis and application is restricted to single-phase zeolites, severely underestimating the potential of intergrowth frameworks. Compared with single-phase zeolites, intergrowth zeolites possess unique properties, such as different diffusion pathways and molecular confinement, or special crystalline pore environments for binding metal active sites. This review first focuses on the structural features and synthetic details of all the intergrowth zeolites, especially providing some insightful discussion of several potential frameworks. Subsequently, characterization methods for intergrowth zeolites are introduced, and highlighting fundamental features of these crystals. Then, the applications of intergrowth zeolites in several of the most active areas of catalysis are presented, including selective catalytic reduction of NOx by ammonia (NH 3 -SCR), methanol to olefins (MTO), petrochemicals and refining, fine chemicals production, and biomass conversion on Beta, and the relationship between structure and catalytic activity was profiled from the perspective of intergrowth grain boundary structure. Finally, the synthesis, characterization, and catalysis of intergrowth zeolites are summarized in a comprehensive discussion, and a brief outlook on the current challenges and future directions of intergrowth zeolites is indicated.

The kinetics of intermolecular chain transfer to polymer (CTP) and chain transfer to monomer (CTM), as well as backbiting in solution copolymerization of ethylene and vinyl acetate (VAc), are calculated by density functional theory. An intrinsic rate coefficient for each reaction type, whose Arrhenius parameters are expressed as functions of unreacted monomer composition, is extracted from calculated elementary reactions, and hence it applies to a wide range of fragment compositions of EVA. Backbiting controls the generation of midchain radicals (MCRs) on the backbone, and its rate maximizes at a medium fraction of VAc in the unreacted monomers. CTP plays an insignificant role in MCR generation even at high conversion rates due to its low pre-exponential factor. The concentration of MCRs is quantified and is close to that of ECRs at high conversions and high fractions of VAc in monomers. Additionally, branching characteristics are explored; concentrations of short-chain branching (SCB) and long-chain branching (LCB) are about 0.7-2.5 and 0.1-0.4%, respectively, and drop with VAc fraction rapidly. The role of the migration of MCRs is highlighted, which transforms about 10% of SCB points into LCB points. Disagreeing with insights from laboratory experiments, it is the migration, rather than CTP, which increases the LCB concentration at high conversions.

Beta zeolites have been widely used in acid-catalyzed reactions because of their excellent properties. An in-depth study of the position, quantity, and distribution of beta zeolites substituted by Al is significant to understand the catalytic performance of the active site of zeolite catalysts. The distribution of Al in H-BEA and the structure of silanol nests in dealuminated BEA at different Si/Al ratios and synthesis temperatures were studied by the DFT method. T1, T2, T7, and T9 sites were chosen to be simulated. The synthesis temperature can change the distribution of Al and the proportion of T sites at different Si/Al ratios. The proportion of T7 and T9 is more than 70% at different Si/Al ratios of H-BEA and decreases with the synthesis temperature. T1 and T2 sites begin to appear when Si/Al < 20 and the proportion of T1 and T2 sites is less than 20%. When Si/Al < 8, the substitution energy of the AlSiAl structure, which has Si(2Al, 2Si) species, is obviously lower than that of the normal structure, which indicates that the Al-O-Si-O-Al species will appear in H-BEA. The Al(T7)Si(T5)Al(T9)Si(T5)Al(T7) and Al(T1)Si(T1)Al(T9) groups can not only stabilize H-BEA but also play an essential role in the formation of Si(2Al, 2Si) species. For dealuminated BEA zeolites, the silanol nest forms four hydrogen bonds through four silanols. The orientation of silanol groups in the silanol nest formed after dealumination at different T sites is different. The T7 and T9 sites in H-BEA are more likely to undergo dealumination. By contrast, the dealumination of the T1 and T2 sites is a challenge.

Volatile organic compounds (VOCs) harm the environment and human health and have been of wide concern and purified efficiently by catalytic oxidation. Spinel oxides, mainly composed of transition metal elements with low price and extensive sources, have been widely investigated as efficient and stable catalysts for VOCs oxidation due to their adjustable element composition, flexible structure, and high thermal/chemical stability. However, it is necessary to dissect the design of the spinel in a targeted way to satisfy the removal of different types of VOCs. This article systematically summarizes the recent advances regarding the application of spinel oxides for VOCs catalytic oxidation. Specifically, the design strategies of spinel oxides were first introduced to clarify their effect on the structure and properties of the catalyst. Then the reaction mechanism and degradation pathway of different kinds of VOCs on the spinel oxides were in detail summarized, and the characteristic requirements of the spinel oxides for various VOCs purification were analyzed. Furthermore, the practice applications were also discussed. Finally, the prospects were proposed to guide the rational design of spinel-based catalysts for VOCs purification and intensify the understanding of reaction mechanisms.

Benzene (C 6 H 6 ) and 1,3-cyclopentadiene (c-C 5 H 6 ) are critical intermediate species in the combustion of fossil fuel and the formation of polycyclic aromatic hydrocarbons (PAHs). This study investigates the underlying mechanisms of pyrolysis and oxidation of C 6 H 6 and c-C 5 H 6 in the presence of O 2 , NO and NO 2 , respectively, under combustion conditions via ReaxFF molecular dynamics simulations. The size growth in the pyrolysis system is accompanied by an amorphous nature as well as an increase in the C/H ratio. In the oxidation sytems, NO 2 is the most effective in the oxidation of both C 6 H 6 and c-C 5 H 6 , followed by NO and O 2 . In the presence of NO x , O and N radicals generated in the high-temperature decomposition reactions of NO and NO 2 are actively involved in the addition and H-abstraction reactions of C 6 H 6 and c-C 5 H 6 . Remarkably, the decomposition of NO 2 dramatically increases the number of O radicals in the system, which significantly accelerates the ring-opening of C 6 H 6 and c-C 5 H 6 by O-addition and forms linear-C 6 H 6 O and C 5 H 6 O species, respectively. Afterwards, the formation of -CH 2 - by H-transfer plays an essential role in the decomposition of linear-C 6 H 6 O and -C 5 H 6 O. Reaction pathways of O and N radicals with C 6 H 6 and c-C 5 H 6 are reported in detail. The O and N-addition of C 6 H 6 facilitate the decomposition to resonance-stabilized cyclopentadienyl radicals after the restructuring of the C-C bond.

By the fine manipulation of the exceptional long-range germanium-telluride (Ge─Te) bonding through charge transfer engineering, we have achieved exceptional thermoelectric (TE) and mechanical properties in lead-free GeTe. This chemical bonding mechanism along with a semiordered zigzag nanostructure generates a notable increase of the average zT to a record value of ~1.73 in the temperature range of 323 to 773 K with ultrahigh maximum zT  ~ 2.7. In addition, we significantly enhanced the Vickers microhardness numbers ( H ) to an extraordinarily high value of 247 v and effectively eliminated the thermal expansion fluctuation at the phase transition, which was problematic for application, by the present charge transfer engineering process and concomitant formation of microstructures. We further fabricated a single-leg TE generator and obtained a conversion efficiency of ~13.4% at the temperature difference of 463 K on a commercial instrument, which is located at the pinnacle of TE conversion.H v and effectively eliminated the thermal expansion fluctuation at the phase transition, which was problematic for application, by the present charge transfer engineering process and concomitant formation of microstructures. We further fabricated a single-leg TE generator and obtained a conversion efficiency of ~13.4% at the temperature difference of 463 K on a commercial instrument, which is located at the pinnacle of TE conversion.

The detailed kinetic mechanisms for the reactions of hydrogen cyanide (HCN) and hydrogen isocyanide (HNC) with the methyl radical (CH 3 ) are discussed. These are important reactions in combustion and Titan's atmosphere chemistry and were investigated at the CCSD(T)/cc-pVQZ//M06-2X/6-311++G(2df,2p) level of theory. The multiwell and multichannel potential energy surface (PES) was constructed. The rate constants were determined by using variational transition state theory (VTST) and Master Equation/Rice-Ramsperger-Kassell-Marcus (ME/RRKM) method over a temperature range of 300-2000 K and a pressure range of 1-10 000 torr. Corrections of the Eckart tunneling effect were included and the calculated results were in good agreement with the literature. A clear dependence of the reaction mechanism on temperature and pressure was revealed via detailed kinetic and species analysis. For the HCN reaction, the channel of C-addition forms an intermediate that is dominant at low temperatures and high pressures, leading to the total rate constant exhibiting a pressure dependence, but this dependence disappears at high temperatures. The H-abstraction channel is more competitive with increasing temperatures, but it is still not dominant. For the HNC reaction, the C-addition channel is dominant, and CH 3 CN and H constitute almost all the products. The proposed temperature and pressure-dependent rate constants can be used in the combustion and atmospheric model development for related systems.

Solid oxide electrochemical cells (SOCs) hold potential as a critical component in the future landscape of renewable energy storage and conversion systems. However, the commercialization of SOCs still requires further breakthroughs in new material development and engineering designs to achieve high performance and durability. In this study, a data-driven powder-to-power framework has been presented, fully digitizing the morphology evolution of heterogeneous electrodes from fabrication to long-term operation. This framework enables accurate performance prediction over the full life cycle. The intrinsic correlation between microstructural parameters and electrode durability is elucidated through parameter analysis. Rational control of the ion-conducting phase volume fraction can effectively suppress Ni coarsening and mitigate the excessive ohmic loss caused by Ni migration. The initial and degraded electrode performances are attributed to the interplay of multiple parameters. A practical optimization strategy to enhance the initial performance and durability of the electrode is proposed through the construction of the surrogate model and the application of the optimization algorithm. The optimal electrode parameters are determined to accommodate various maximum operation time requirements. By implementing the data-driven powder-to-power framework, it is possible to reduce the degradation rate of Ni-based electrodes from 2.132% to 0.703% kh -1 with a required maximum operation time of over 50,000 h., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2023 Science China Press. Published by Elsevier B.V. All rights reserved.)

The development of high efficiency oxygen evolution electrocatalyst is of great significance for water splitting reaction. Herein, an efficient cone-structured NiFe-LDH/Nicone/Ti catalyst is fabricated by electrodeposition method towards enhanced oxygen evolution reaction (OER). The featured tip curvature of nanocone structure can accelerate the reaction kinetics of OER by offering a field-enhanced aggregation of local hydroxide ion reactant on the catalyst surface, and thus improves the performance of the NiFe catalyst. Accordingly, NiFe-LDH/Nicone/Ti requires only a low overpotential of 292 mV to achieve 50 mA cm -2 , and with high stability under continuous high-current operations. In addition, the alkali-electrolyzer using NiFe-LDH/Nicone/Ti electrode exhibits good performance with a voltage of 1.73 V at 50 mA cm -2 and displays excellent stability in long-term stability test. This cone-structured catalyst design with field-enhanced local hydroxide ion aggregation effect provides a promising method for the development of highly active OER electrocatalysts., (© 2023 IOP Publishing Ltd.)

Next-generation ultrahigh power density proton exchange membrane fuel cells rely not only on high-performance membrane electrode assembly (MEA) but also on an optimal cell structure. To this end, this work comprehensively investigates the cell performance under various structures, and it is revealed that there is unexploited performance improvement in structure design because its positive effect enhancing gas supply is often inhibited by worse proton/electron conduction. Utilizing fine channel/rib or the porous flow field is feasible to eliminate the gas diffusion layer (GDL) and hence increase the power density significantly due to the decrease of cell thickness and gas/electron transfer resistances. The cell structure combining fine channel/rib, GDL elimination and double-cell structure is believed to increase the power density from 4.4 to 6.52 kW L -1 with the existing MEA, showing nearly equal importance with the new MEA development in achieving the target of 9.0 kW L -1 ., (© 2023 Wiley-VCH GmbH.)

Proton exchange membrane (PEM) fuel cell has been regarded as a promising approach to the decarbonization and diversification of energy sources. In recent years, durability and cost issues of PEM fuel cells are increasingly significant with the rapid increase of power density. However, the failure to maintain the cell consistency, as one major cause of the above issue, has attracted little attention. Therefore, this study intends to figure out the underlying cause of cell inconsistency and provide solutions to it from the perspective of multi-physics transport coupled with electrochemical reactions. The PEM fuel cells with electrodes under two compression modes are firstly discussed to fully explain the relationship of cell performance and consistency to electrode structure and multi-physics transport. The result indicates that one main cause of cell inconsistency is the intrinsic conflict between the separated transport and cooperated consumption of oxygen and electron throughout the active area. Then, a mixed-pathway electrode design is proposed to reduce the cell inconsistency by enhancing the mixed transport of oxygen and electron in the electrode. It is found that the mixing of pathways in electrodes at under-rib region is more effective than that at the under-channel region, and can achieve an up to 40% reduction of the cell inconsistency with little (3.3%) sacrificed performance. In addition, all the investigations are implemented based on a self-developed digitalization platform that reconstructs the complex physical-chemical system of PEM fuel cells. The fully observable physical information of the digitalized cells provides strong support to the related analysis., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2023 Science China Press. Published by Elsevier B.V. All rights reserved.)

Engine fault detection is conducive to improving equipment reliability and reducing maintenance costs. In practical scenarios, high-quality data is difficult to obtain. Usually, only single-sensor data is available. This paper proposes a fault detection method combining Variational Mode Decomposition (VMD) and Random Forest (RF). At first, the spectral energy distribution is obtained by decomposing and statistic the engine data of multiple working conditions. Based on the spectral energy distribution, the overall optimal mode number was identified, and the quadratic penalty term was optimized using SNR. The improved VMD (IVMD) improves mode aliasing and iterative efficiency and unifies feature dimensions. Decomposition of real signals demonstrates the effectiveness. The paper designs a feature vector composed of seven types of attributes, including unit bandwidth energy, center frequency, maximum singular value and so on. The feature vector is then fed to RF for classification. Features are selected in order of importance to classification to improve the training efficiency. By comparing with various algorithms, the proposed method has higher accuracy and faster training efficiency in single-speed, multi-speed and cross-speed single-sensor data diagnosis. The results show that the method has application prospects with little training data and low hardware requirements.

The flow field structure of a proton exchange membrane fuel cell (PEMFC) is a determining factor for improving the cell power density. In this study, a universal alternating flow field design for the first time is proposed, which arranges structural units with different flow resistances in an alternating way to significantly improve the gas transfer rate into the electrode, with the advantages of easy machining and low pumping loss. Based on the design, it is proposed and tested large-scale fuel cells with three novel flow fields by combining a parallel channel, baffled channel, serpentine channel, and narrowed channel. The results show that the design can significantly enhance the gas supply efficiency and that the novel baffled flow field improves the PEMFC performance by 23% with low pumping loss. The design employed in the study offers additional options for flow field optimization and contributes to the early achievement of next-generation ultrahigh power density fuel cells., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

In this study, the oxidation behaviors of soot particles from diesel engine when using neat diesel fuel (DF) and lubricating base oil-blended fuel (BBF) were investigated. The changes in the average particle size and nanostructure parameters during soot oxidation process were analyzed. Exhaust particulate matter (PM) samples were collected from a four-stroke, four-cylinder and turbo0charged diesel engine operated under 1200 rpm and 200 Nm. DF and BBF Soot samples with different oxidation weight losses of 20 %, 40 %, and 60 % were obtained by thermogravimetric isothermal oxidation experiments at 600 °C, and the particle size and nanostructure parameters (fringe length, L a ; fringe tortuosity, T f ) were characterized using high-resolution transmission electron microscopy (HRTEM). Results show that the DF soot particles exhibited an oxidation mode that was initially dominated by surface oxidation and gradually deviated to internal oxidation. Combustion of the base oil increased the soot internal oxidation tendency. HRTEM results showed that as the soot oxidation progressed, the primary particles showed a shell-core, onion-like and hollow structure gradually. The L a of the primary particles gradually increased, and the T f gradually decreased, indicating that the soot layer crystallites were rearranged during the oxidation process, which resulted in a disordered nanostructure that transitioned to a more graphitized nanostructure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The purpose of the present study is to better understand the reaction kinetics of diesel exhaust soot during oxidation process. A thermogravimetric analyzer was used to oxidize real diesel exhaust soot generated from a Euro VI diesel engine under non-isothermal conditions. The Friedman-Reich-Levi method and the Sestak-Berggren model were used to determine the oxidation kinetics. Raman spectroscopy and high-resolution transmission electron microscopy were employed to follow the changes of the soot structure during oxidation. The activation energy gradually increased with increasing conversion level during soot oxidation. The oxidation process of diesel exhaust soot could be described as three-step kinetics, and the calculated conversions fitted the experimental results very well. The kinetic predictions of diesel soot oxidation that were obtained using the proposed kinetic models were more accurate and precise than those with the common first-order model. The structural order increased as oxidation progressed, which was responsible for the increased activation energy. The structural ordering was principally caused by the preferential oxidation of the disordered fraction in the diesel soot, especially for the amorphous carbon, which was oxidized in the initial stage of the oxidation reaction., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Hypothesis: Droplet coalescence is a common phenomenon and plays an important role in many applications. When two liquid droplets are brought into contact, a liquid bridge forms and expands quickly. Different from miscible droplets, an extra immiscible interface exists throughout the coalescence of immiscible droplets and is expected to affect the evolution of the liquid bridge, which has not been investigated. We hypothesized that the liquid bridge of immiscible droplets exhibits a different growth dynamics., Experiments: We experimentally study the coalescence dynamics of immiscible droplets. The evolution of the liquid bridge is measured and compared with miscible droplets. We also propose a theoretical model to analyze the effects of immiscibility., Findings: We find that immiscibility plays different roles in the viscous-dominated and inertia-dominated regimes. In the initial viscous-dominated regime, the coalescence of immiscible droplets follows the linear evolution of the bridge radius as that of miscible droplets. However, in the later inertia-dominated regime, the coalescence of immiscible droplets is slower than that of miscible droplets due to the water-oil interface. By developing a theoretical model based on the force balance, we show that this slower motion is due to the immiscible interface and the extra interfacial tension. In addition, a modified Ohnesorge number is proposed to characterize the transition from the viscous-dominated regime to the inertia-dominated regime., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Fuel aromatic content (AC) is one of the main reasons for PM (particulate matter) emissions from ocean-going ships. The present study investigates the influence of AC on physicochemical characteristics of soot particles from marine auxiliary diesel engine. The TEM (transmission electron microscopy), Raman spectroscopy, FTIR (Fourier transform infrared spectroscopy), and TGA (thermalgravimetric analyzer) are employed to jointly characterize samples. The results reveal that soot particles from high-AC fuel have bigger d p (primary particle size), longer fringe length (La), and higher graphitization degree, all of which have significant impacts on chemical properties such as more VOF (volatile organic fraction), higher concentrations of aromatic C-H and C=C groups. These are mainly due to several aromatic rings decomposed from aromatic components could promote the growth of carbon layer, and incomplete pyrolysis productions are also present in soot particles. The relative amounts of aromatic C-H and C=C are well correlated with d p and La, respectively., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This paper investigates the impact of metallic lubricant additives on the morphology, nanostructure, graphitization degree, and oxidation reactivity of diesel exhaust particles. The experiments were conducted on a turbocharged heavy-duty diesel engine. Four typical lubricant oil additives, including Ca-based, Zn-based, Mo-based and ashless additives, were mixed into diesel at 0.5% and 1.0% by mass. Analytical characterization equipment used in this study includes a high resolution transmission electron microscopy (HRTEM), a Raman spectroscopy, and a Thermogravimetric analyzer (TGA). Results showed that the lubricant additives significantly changed the soot properties. Diesel fuels blended with ashless and Zn-based additives led to a more disordered nanostructure of diesel particles, thereby improving their oxidation reactivity. When Ca and Mo additives participated in combustion, the oxidation mass loss curve of soot particles shifted to a higher temperature range due to the combined effect of the physical and chemical characteristics of soot particles and the catalytic oxidation of metallic ash. Although Ca, Mo, and other metals in lubricant additives could promote the soot oxidation, the changes in the physicochemical properties of soot particles (including increased fringe length, reduced fringe tortuosity, and higher graphitization degree) rendered it more difficult to oxidize., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The impact of droplets on a liquid pool is ubiquitous in nature and important in many industrial applications. A droplet impacting on a liquid pool can result in the pinch-off of a regular bubble or entrap a large bubble under certain impact conditions. In this study, the cavity deformation and the bubble entrapment during the impact of droplets on a liquid pool are studied by combined experimental measurements and numerical simulations. The time evolution of the free surface profile obtained in the numerical simulation is in good agreement with the experimental results. The cavity created by the droplet impact affects the pinch-off of regular bubbles and the entrapment of large bubbles. The regular bubble pinch-off is the direct consequence of the capillary wave propagating downward along the interface of the cavity and merging at the bottom of the cavity. In contrast, the large bubble entrapment is due to the merging of the liquid crowns at the mouth of the cavity. Gravity and environmental pressure play important roles in cavity deformation and bubble entrapment after droplet impact on liquid pools. The maximum depth of the cavity decreases as the gravitational effect becomes stronger. The phenomenon of regular bubble pinch-off may disappear as the gravity decreases. We find that the regular bubble pinch-off can transform into large bubble entrapment when increasing environmental pressure. The size of the large bubble entrapped decreases with increasing the environmental pressure due to the larger difference in the pressure and the vorticity around the liquid crown at increased environmental pressure. Finally, the regime map of bubble entrapment after the droplet impact is obtained.

Two kinds of C 8 isomers, di-n-butyl ether (DNBE) and 1-octanol, as potential oxygen-containing alternative fuels, show important value in the trade-off between efficiency and emission. In the present work, the effects of DNBE/1-octanol with different proportions (0, 10%, and 20%) blended into diesel on the combustion characteristics, fuel economy, and emission characteristics in a six-cylinder heavy-duty diesel engine were studied at low, medium, and high loads. 1-Octanol with a 20% blending ratio showed different combustion characteristics in the cylinder compared with the other fuels. The economic analysis showed that the brake specific fuel consumption of DNBE-diesel blend fuels was higher than that of 1-octanol-diesel blend fuels, while brake thermal efficiency was the opposite tendency. The emissions of nitrogen oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) were affected by the types of blend fuels, blending ratios, and loads. In comparison with 1-octanol-diesel blend fuels, the addition of DNBE in diesel promoted the emission of nitrogen oxides, but inhibited the emissions of soot, HC, and CO. DNBE- and 1-octanol-diesel blend fuels increased the weighted brake specific fuel consumption but decreased the weighted brake thermal efficiency compared with diesel in the World Harmonized Stationary Cycle test cycle of Euro VI regulation. The weighted NOx, HC, soot, and CO emissions of blend fuels depended on the types of blend fuels and blend ratios. The weighted NOx, HC, and soot emissions were reduced by blending 1-octanol into diesel, while the weighted CO emission was increased. The weighted CO and soot emissions of diesel blended with DNBE were reduced than that of diesel., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)