Thermal Reaction Research Articles

Injectable Salecan/hyaluronic acid-based hydrogels with antibacterial, rapid self-healing, pH-responsive and controllable drug release capability for infected wound repair

Designing materials for wound dressings with superior therapeutic benefits, self-healing and injectable characteristics is important in clinical practice. Herein, a new self-healing injectable hydrogel was prepared via thermal treatment and dynamic Schiff base reaction by mixing oxidized hyaluronic acid (OHA) and hydrazided Salecan (Sal-ADH). The versatility of the wound dressing was confirmed by studying the inherent rheological properties, high swelling rate, sustained-release behavior of the drug, pH/hyaluronidase-dependent biodegradation, in vitro antimicrobial as well as in vivo wound healing performance. The presence of the antimicrobial drug polyhexamethylene biguanide (PHMB) conferred good antimicrobial properties to the Sal-ADH/OHA/PHMB (SOP) hydrogel, which could effectively prevent wound infection (the width of the inhibition circle of SOP-0.20 hydrogel was 4.97 mm, 5.93 mm for Staphylococcus aureus and Escherichia coli, respectively). The findings suggested that SOP hydrogel exhibited remarkable self-healing and injectability properties, as well as excellent hemostasis and biocompatibility. In vivo experiments indicated that the application of SOP hydrogels would obviously accelerate wound healing and attenuate the inflammatory response while increasing collagen deposition and angiogenesis. Altogether, antibacterial SOP hydrogels with moderate mechanical properties, pH-responsive release, excellent injectability, exceptional self-healing ability and anti-inflammatory effects could expand potential applications of injectable hydrogels in the biomedical field.

Data and modeling sensitivity analysis for molten salt fast reactor benchmark – Static calculations

The Molten Salt Reactor (MSR) idea is increasingly being recognized in the nuclear field due to its potential safety, sustainability, and economic efficiency advantages. The Molten Salt Fast Reactor (MSFR) benchmark, introduced in 2019, highlighted variations in results tied to different neutron cross-section libraries. This study investigates the impact of utilizing the ENDF/B-VIII.0 and JEFF-3.3 cross-section libraries for MSFR benchmark assessment compared to the ENDF/B-VII.1 database. Monte Carlo based open source code OpenMC is used for the analyses. Rigorous sensitivity analyses assess the influence of individual components, including the cross-section database, resonance elastic scattering, and Thermal Scattering Law (TSL). Beyond the criticality assessments, parameters such as delayed neutron fraction, temperature coefficient of reactivity, and neutron spectrum are compared for different cross-section libraries. Our analyses reveal that incorporating new evaluations for 233U (n,γ) and fission cross-sections in ENDF/B-VIII.0 significantly alters criticality results, i.e., more than 1700 pcm difference is seen between libraries. Similarly, critical concentration using ENDF/B-VII.1 and JEFF-3.3 is over-predicted by approximately 3%. The variations in Thermal Scattering Law (TSL) files do not yield substantial differences in outcomes due to the fast spectrum of the reactor. In some cases, the treatment of resonance elastic scattering leads to reactivity differences greater than 50 pcm. The benchmark compares 233U-started and Minor Actinide (MA)-started core. From the reactor physics point of view, the MA-started core leads to a 29% higher (n, γ) reaction rate than the 233U-started core. A 3–4% smaller value of thermal reactivity coefficient is obtained using the ENDF/B-VIII.0 library compared to the ENDF/B-VII.1 value. Using the ENDF/B-VIII.0 for the MSFR benchmark signifies using newer and better data for the GEN-IV reactors neutron physics calculations.

Study on the influence of high rate charge and discharge on thermal runaway behavior of lithium-ion battery

With the development of the new energy industry, battery life and rapid charge-discharge capacity have attracted much attention. At the same time, the high temperature inside the cell during high-rate charging and discharging may increase the probability of the battery thermal runaway. This paper studied the thermal runaway reaction of Li-ion batteries under different state of charge (SOC) and charge rates using a self-made experimental platform. The experimental phenomena and the changes in the temperature field were recorded. The key parameters, such as trigger temperature (T1, Lithium battery back thermal runaway triggers temperature), maximum temperature (Tmax),voltage, and mass loss (ML) of thermal runaway, were measured. The morphology changes of electrode materials, the battery remains, and the dynamics of thermal runaway reaction after high rate charge and discharge were further analyzed. The results show that for the 4 C-100 % battery, the T1 and Ea are reduced by 22.6 ℃ and 82.2 %, and the Tmax and maximum mass loss rate (MLRmax) are increased by 218.14 ℃ and five times, compared with the 1 C-50 % battery. With the increase of charge-discharge rate, the thermal stability of the battery decreases, and the gravity degree of accident increases.

Understanding flame behaviors under gradient magnetic fields: The dynamics of non-reacting gas jets

Gradient magnetic fields impact fluid dynamics through Kelvin forces, altering flame behavior. Key complexities such as the interaction of magnetic fields with thermal gradients and chemical reactions within flames remain largely unexplored. By isolating variables such as heat release and thermal convection, this study aims to delve into fundamental mechanisms by which gradient magnetic fields affect the fluid dynamics of flames. This research adopts nitrogen, helium, argon and oxygen as jet gases, focusing exclusively on the fluid dynamics of non-reacting flow. Experimental techniques and Computational Fluid Dynamics (CFD) simulations are employed to explore the effects of varying gas species and magnetic field strengths. Results demonstrate that gas density significantly impacts jet behavior, with paramagnetic oxygen concentrating in areas of stronger magnetic fields, and other gases like helium, nitrogen, and argon showing distinct behaviors based on their molar mass. The study also establishes an optimized energy conservation equation that accurately predict jet height, considering factors such as buoyant and Kelvin forces. By studying the flow behavior of non-reacting gases under magnetic fields, the results are ultimately extended to estimate flame heights and elucidate the mechanisms of air-to-fuel diffusion.

Influence of hot-pressing temperature and density on the physical and mechanical properties of bamboo scrimber

Bamboo scrimber (BS) has been widely used as a high-performance engineering composite in construction and outdoor applications, typically employing a thermosetting adhesive that requires hot-pressing. Previous studies have focused on the effects of resin content and BS curing temperature, often overlooking the self-bonding of bamboo during the hot-pressing process. This study investigated the impact of hot-pressing temperature and density on the physical and mechanical properties of BS containing phenol–formaldehyde resin, with a particular focus on regulating BS self-bonding by adjusting these parameters. The study also examined the effects on the chemical composition and pore structure of BS. The results showed that increasing the hot-pressing temperature from 140 to 180 °C broke unstable bonds in the hemicellulose, cellulose, and lignin components of the BS, leading to new crosslinks through dehydration and thermal degradation reactions. This process enhanced self-bonding, improved water resistance, and resulted in different surface colors. Raising the density from 0.9 to 1.3 g/cm3 made the density distribution of BS more uniform and reduced the size and number of internal pores. These characteristics promoted interfacial bonding and impeded water flow through the material, thereby enhancing its water resistance and mechanical properties. This study elucidates the mechanism behind the performance enhancement of BS and offers insights for its low-cost and environmentally friendly production.

Copper-Catalyzed Enantioselective Dehydro-Diels-Alder Reaction: Atom-Economical Synthesis of Axially Chiral Carbazoles.

The dehydro-Diels-Alder (DDA) reaction is a powerful method for the construction of aromatic compounds. However, the enantioselective DDA reaction has been rarely developed, probably due to the competitive thermal reaction. Herein, we report a copper-catalyzed enantioselective DDA reaction through vinyl cation pathway. The reaction leads to the atom-economical synthesis of axially chiral phenyl and indolyl carbazoles in generally excellent yields with good to excellent atroposelectivities. This methodology represents the first example of non-noble metal-catalyzed enantioselective DDA reaction. Notably, new chiral ligand and organocatalyst derived from the constructed axially chiral carbazole are demonstrated to be useful in asymmetric catalysis.

The interaction between sludge and microplastics during thermal hydrolysis of sludge

In municipal wastewater treatment plants (WWTPs), large number of microplastics (MPs) accumulated in wastewater migrated into sludge. Thermal hydrolysis of sludge (THS) was one of the most promising processes for promoting changes in molecular structure of MPs. The physicochemical properties and degradative pathways of polyethylene (PE) and polyethylene terephthalate (PET) in THS under different temperatures were studied in this paper. It was found that there was a mutual promotion relationship between sludge degradation and MPs aging. The presence of PE and PET MPs not only increased organics and nitrogen concentrations of sludge filtrate, but also enhanced the transformation of organics like proteins. Sludge accelerated the aging of PE and PET MPs. The friability of PE and PET MPs was increased with more surface fragmentation and breakage under the temperature of 120 ℃−180 ℃. Moreover, PE and PET MPs occurred thermal oxidation and reduction reactions with significant chemical structure changes at 160 °C and 140 °C, respectively. Pristine PE and PET had multiple carbon and oxygen active sites. During THS reaction, not only PE and PET reacted hydrolysis/decomposition to produce short-chain hydroxyl-terminated compounds, but also hydrothermal shear broke the polymer molecules and formed carboxyl-terminated and olefin-terminated low-carbon chains. This study provided some promising sign for in situ microplastic removal during sludge treatments.

Optimization Analysis of In-Situ Conversion and Displacement in Continental Shale Reservoirs.

In the context of growing global energy demands and the need for efficient extraction techniques, this research, based on numerical analysis, addresses the high-energy demands of in situ conversion by introducing a two-stage development strategy. The strategy begins with an initial continuous heating stage, followed by a thermal stabilization stage. It culminates in a hydrocarbon production stage, which is divided into primary recovery and water injection-enhanced recovery. The findings demonstrate that the reservoir temperature continues to increase even after the stop of heating. Consequently, the reactions within the reservoir persist, leading to increased hydrocarbon generation. The heating stage also helps restore reservoir pressure, enabling high production rates of hydrocarbons during the first year of primary recovery. However, natural depletion subsequently occurs, requiring an enhanced oil recovery (EOR) method. While water injection is a viable EOR method, it proves less effective due to high water breakthroughs in the producer well. Additionally, a comprehensive analysis reveals that hydrocarbon generation and production are closely related to the calibration of energy input and the duration of injection. These results underscore the critical importance of precise energy management and injection timing in optimizing hydrocarbon recovery. By enhancing our understanding of the thermal dynamics and reaction kinetics within the reservoir, this research contributes to the development of more efficient and sustainable extraction technologies, ultimately improving the feasibility of commercial shale oil production.

Combined kinetic analysis of thermal degradation characteristics and reaction mechanism of thin intumescent fire-retardant coating of steel structure

To determine the thermal kinetic triplets and elucidate the reaction mechanism of thin intumescent fire-retardant coatings (IFR) of steel structures, one efficient combined kinetic approach was implemented in this study. Thermogravimetric experiments were conducted in air atmosphere at four heating rates, and the whole IFR thermal degradation process was divided into two stages. The average activation energy values derived by model-free methods were 78.9 kJ/mol and 175.16 kJ/mol for Stage I (0<α < 0.2) and Stage II (0.2<α < 0.9), respectively. Furthermore, the linear Coats-Redfern (CR) and non-linear Masterplots models were applied to identify the possible reaction mechanism. It was found that the F3/2 mechanistic model was better suited to the main thermal degradation process. Then model reconstruction based on the F3/2 mechanism model was performed. The results showed that the reconstructed model had a strict linear relationship in the independence analysis and KCE analysis, along with a good agreement between the theoretical and experimental results. The current study provided new insights into the systematic thermal degradation mechanism of IFR, and the proposed kinetic model would be helpful for the thermal protection prediction for steel structure during fire.

Study on Thermal Oxygen Aging Characteristics and Degradation Kinetics of PMR350 Resin.

The thermal stability and aging kinetics of polyimides have garnered significant research attention. As a newly developed class of high thermal stability polyimide, the thermal aging characteristics and degradation kinetics of phenylene-capped polyimide prepolymer (PMR350) have not yet been reported. In this article, the thermo-oxidative stability of PMR350 was investigated systematically. The thermal degradation kinetics of PMR350 resin under different atmospheres were also analyzed using the Flynn-Wall-Ozawa method, the Kissinger-Akahira-Sunose method, and the Friedman method. Thermogravimetric analysis (TGA) results revealed that the 5% thermal decomposition temperature (Td5%) of PMR350 in a nitrogen atmosphere was 29 °C higher than that in air, and the maximum thermal degradation rate was 0.0025%/°C, which is only one-seventh of that observed in air. Isothermal oxidative aging results indicated that the weight loss rate of PMR350 and the time-dependence relationship follow a first-order exponential growth function. PMR350 resin thermal decomposition reaction under air atmosphere includes one stage, with a degradation activation energy of approximately 57 kJ/mol. The reaction model g(α) fits the F2 model, and the integral form is given by g(α) = 1/(1 - α). In contrast, the thermal decomposition reaction under a nitrogen atmosphere consists of two stages, with degradation activation energies of 240 kJ/mol and 200 kJ/mol, respectively. The reaction models g(α) correspond to the A2 and D3 models, with the integral forms represented as g(α) = [-ln(1 - α)]2 and g(α) = [1 - (1 - α)1/3]2 due to the oxygen accelerating thermal degradation from multiple perspectives. Moreover, PMR350 resin maintained high hardness and modulus even after thermal aging at 350 °C for 300 h. The results indicate that the resin exhibits excellent resistance to thermal and oxygen aging. This study represents the first systematic analysis of the thermal stability characteristics of PMR350 resin, offering essential theoretical insights and data support for understanding the mechanisms of thermal stability modification in PMR350 and its engineering applications.

Microwave vacuum pyrolysis rapidly transforms bamboo into solid biofuel: Predicting fuel performances by response surface methodology

Microwave vacuum pyrolysis presents significant advantages in biochar refining and industrial upgrading. In this study, bamboo charcoal (BC) was produced rapidly by microwave vacuum pyrolysis, the microwave pyrolysis and conventional pyrolysis characteristics of bamboo were compared, and the potential of response surface methodology (RSM) to predict the fuel performances was investigated. The results indicated that microwave pyrolysis significantly reduced the heating time, and also effectively lowered the threshold of thermal decomposition reaction. Besides, as the microwave power and radiation time rose, the fixed carbon, ash, higher heating value, energy density, and fuel ratio of BCs increased, while the yield, H/C, O/C, volatile, and energy yield decreased. The quadratic models have high correlation coefficients for these characteristics, which can be used for the prediction of subsequent BCs production. When the microwave power was 1666 W and the radiation time was 13.3 min, the prepared BC exhibited the highest yield while maintaining a fixed carbon content of over 85 %. This research provided a green way for the transformation and upgrading of BCs industry, and also showed that the most cost-effective production strategy can be formulated through RSM.

Investigation of kinetics, reaction mechanisms, thermodynamics, and synergetic effects in co-pyrolysis of wood sawdust and linear low-density polyethylene using the thermogravimetric approach.

This study focused on investigating thermal degradation behaviors, kinetics, reaction mechanisms, synergistic effects, and thermodynamic parameters of wood sawdust (WSD), linear low-density polyethylene (LLDPE), and their blends (LW1:3, LW1:1, and LW3:1) during co-pyrolysis in a thermogravimetric analyzer (TGA). Thermal behavior exhibited a LW1:3 blend (25 wt.% LLDPE) showing significant mass loss at lower temperatures (150 to 300°C) compared to the individual feedstocks, such as 150 to 400°C and 300 to 520°C for WSD and LLDPE, respectively. The iso-conversional methods (KAS, FWO, and FM) were used to determine the kinetic parameters (Ea and A), and the activation energy drop was highest for the LW1:3 blend. According to the master plots, the third-order reaction (O3), nucleation (P2/3), and diffusional model (D4) were the predominant reaction mechanisms for the co-pyrolysis of the LW1:3, LW1:1, and LW3:1 blend, respectively. The thermodynamic parameters demonstrate that a small amount of plastic addition into WSD can improve the reactivity of the blend, shorten the reaction time, and cause less energy-intensive reactions. The values of ΔH, ΔG, and ΔS also confirmed the co-pyrolysis process's spontaneity and endothermic nature. The Fourier transforms infrared spectrometer (FTIR) spectra of raw feedstock, blends, and their biochar revealed some of the peaks were shifted, the intensity was reduced, and disappearance can happen when the temperature was increased. Using the experimental and theoretical/predicted activation energies, the parity chart illustrates the synergistic effects of co-pyrolysis of different blends, and the LW1:3 blend has a favorable synergistic impact. These results could be helpful in process optimization and designing an effective reactor system for co-pyrolysis.

Density functional theory studies on combustion oxidative decomposition mechanism of 3,3,3-trifluoropropene

The environmentally friendly refrigerant 3,3,3-trifluoropropene (HFO-1243zf) suitable for refrigeration and heat pump systems has flammability. Based on density functional theory, the oxidation decomposition mechanism of 3,3,3-trifluoropropene was studied, including the main initial oxidation decomposition and subsequent reactions. The results indicate that among the initial thermal decomposition reactions, the reaction with the lowest energy barrier is simultaneous elimination of HF, followed by CC bond breaking to form ∙CF3. In the H abstraction reaction, the reaction energy barrier of H atom capture by ∙F is the lowest. In F abstraction reaction, the ∙H is the most active. In the addition reaction, the reaction energy barrier of ∙F is the lowest. The energy barriers of reactions involving different free radicals, from high to low, are: thermal decomposition, F abstraction, H abstraction and addition reaction. The subsequent reactions mainly involve the generation pathways of ∙CF3 and the formation of stable products.

Comparison of thermo-catalytic and photo-assisted thermo-catalytic conversion of glucose to HMF with Cr-MOFs@ZrO2

Abstract Thermo-catalytic and photo-assisted thermo-catalytic are two effective pathways for conversion of glucose. Thermo-catalytic and photo-assisted thermo-catalytic conversion of glucose was studied with Cr-MOFs@ZrO2 as catalysts in nitrogen atmosphere at 150 °C. Cr-MOFs@ZrO2 possesses simultaneously Lewis acid sites as well as Brønsted acid sites, and also has strong Brønsted acidity, so it can exhibit good thermos-catalytic performanc. When the glucose was 3 g/L, the reaction was carried out at 150 °C for 2 h with DMF as solvent, the glucose conversion was 97.9% while the HMF yield was 38%. The yield of HMF can be increased to 51.1% by adding 500w xenon lamp irradiation on the basis of thermal catalytic reaction condition. A comparison of the two reactions revealed that light-assisted thermal catalysis was more favorable for the reaction.

Enhanced photocatalytic performance of colored Ti2O3–Ti3O5–TiO2 heterostructure for the degradation of antibiotic ofloxacin and bactericidal effect

Removing emergent contaminants, such as pharmaceuticals, and inhibiting bacteria by photocatalysis represents an interesting alternative for water remediation. We report the effective preparation of colored powders containing Ti2O3, Ti3O5, and TiO2, by a simple thermal oxidation reaction of a Ti2O3 precursor from 400 °C to 800 °C. The material obtained at 500 °C (P500 sample) exhibited the highest photocatalytic performance under simulated solar light, reaching 54% degradation of antibiotic ofloxacin and a bacteria inactivation of 51% and 62% for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. The superoxide anion radical was the main specie contributing to the photodegradation of ofloxacin, while the hydroxyl radical showed negligible effect. A synergy between the physicochemical properties of the phases in the P500 sample contributes to the electrons transfer, visible light absorption capability and generation of reactive oxygen species, resulting in its remarkable photoactivity. The comparison in terms of surface-specific activity revealed that the P500 sample is more efficient than commercially available TiO2 P25. This fact opens the option of using commercially available Ti2O3 and TiO2 P25 to obtain composites for promoting photoinduced reactions using natural solar light.

Pemanfaatan Limbah Karbon-Aktif Melalui Reaktivitasi Termal Sebagai Adsorben Ion Kadmiun pada Lindi TPA

The leachate produced at the Kawatuna landfill, managed without proper waste treatment systems, has been found to contain heavy metals like cadmium (Cd), which contaminate groundwater and pose significant health risks. This study investigates the reduction of Cd ions in leachate through adsorption using activated carbon (AC) waste. The AC waste was reactivated via thermal methods, including phosphoric acid immersion, heating, and washing. Morphological analysis was conducted using scanning electron microscopy (SEM), and adsorption efficacy was evaluated with atomic absorption spectroscopy (AAS). The findings indicate that AC waste with a pore diameter of 2.95 µm can be effectively reused as an adsorbent through thermal reactivation. Specifically, AC treated with H3PO4 immersion and heating exhibited a pore diameter of 3.24 µm, while heating and washing resulted in a pore diameter of 2.29 µm. The Cd concentration in leachate treated with AC immersed in H3PO4 followed by heating showed a modest reduction, whereas the heating and washing treatment led to a significant decrease in Cd levels, achieving an adsorption capacity of 3.92 mg/L within 50 min. This method presents a viable alternative for managing landfill leachate at the Kawatuna site.

Effect of sequential delivery of 1- and 2-MHz bipolar microneedling radiofrequency energy on thermal tissue reactions in a minipig model.

Bipolar microneedling radiofrequency (RF) treatment generates different patterns of thermal reactions, depending on the skin impedance and RF treatment parameters, including the frequency, power, conduction time, settings of sub-pulse packs, and penetrating depth and type of microneedles used. We compared the effect of sequential delivery of 1- and 2-MHz bipolar RF energy to in vivo minipig skin on thermal tissue reaction. RF treatments at frequencies of 1 and 2MHz were sequentially delivered to minipigs' skin in vivo. A histological study was performed to analyze RF-induced skin reactions at 1-h and at 3-, 7-, and 14-days post-treatment. The skin specimens demonstrated that the two different frequencies of RF treatment generated mixed patterns of the peri-electrode coagulative necrosis (PECN) according to the experimental settings and tissue impedance. In the PECN zone, the tissue coagulation induced by the first RF treatment was surrounded by the effect of the later RF treatment at the other RF frequency. In the inter-electrode non-necrotic thermal reaction zone, the effect of the latter RF treatment was widespread and deep through the dermis, which had received RF treatment at the other frequency first. The delivery of pulsed-type RF energy at sub-pulse packs of 6 or 10 provided effective RF delivery over long conduction time without excessive thermal damage of the epidermis. Nonetheless, by sequential delivery of two different RF frequencies, RF-induced tissue reactions were found to be markedly enhanced. The sequential delivery of 1- and 2-MHz RF energy induces novel histological patterns of tissue reactions, which can synergistically enhance the thermostimulatory effects of each RF setting. Moreover, variations in patterns of tissue reactions can be generated by regulating the order of frequencies and the number of sub-pulse packs of RF used.

Synthesis of TaB2-TaC nanocomposite powders by a boro-carbothermal reduction route

This paper introduces the boron/carbon thermal reduction reaction, represented by the equation 2Ta2O5+ B4C + 11 C = 2TaB2 + 2TaC + 10CO (g), as a novel reaction pathway for synthesizing TaB2₋TaC composite powders. Subsequently, the SPS technique is employed for the fabrication of TaB2-TaC composite ceramics via sintering. The article begins by elucidating the fundamental process of this reaction and constructing a phase diagram through thermodynamic calculations. The experimental results demonstrate that adjusting the synthesis temperature and the proportion of the boron source in the raw materials enables effective control over the ratio of the two phases within the composite materials, allowing the TaB2 phase content to be tailored within the range of 38.1–60 %. Moreover, elevating the synthesis temperature and increasing the proportion of the boron source effectively mitigate the C,O impurity content in the composite powders and facilitate the TaB2 step-growth process. It is noteworthy that the hardness of TaB2-TaC composite ceramics sintered at 2000°C using the optimized complex-phase powder as the precursor reaches 21.7±0.5 GPa, and the fracture toughness attains 5.2±0.2 MPa⋅m1/2.

Silica-Ti3C2Tx MXene Nanoarchitectures with Simultaneous Adsorption and Photothermal Properties.

Layered Ti3C2Tx MXene has been successfully intercalated and exfoliated with the simultaneous generation of a 3D silica network by treating its cationic surfactant intercalation compound (MXene-CTAB) with an alkoxysilane (TMOS), resulting in a MXene-silica nanoarchitecture, which has high porosity and specific surface area, together with the intrinsic properties of MXene (e.g., photothermal response). The ability of these innovative MXene silica materials to induce thermal activation reactions of previously adsorbed compounds is demonstrated here using NIR laser irradiation. For this purpose, the pinacol rearrangement reaction has been selected as a first model example, testing the effectiveness of NIR laser-assisted photothermal irradiation in these processes. This work shows that Ti3C2Tx-based nanoarchitectures open new avenues for applications that rely on the combined properties inherent to their integrated nanocomponents, which could be extended to the broader MXene family.

Effects of ammonia energy ratio and PODE injection timing on combustion and emissions in a PODE/ammonia RCCI engine

The application of ammonia as an alternative carbon-free fuel has attracted increasing attention. In this paper, the effects and mechanisms of ammonia energy ratio (AER) and polyoxymethylene dimethyl ethers (PODE) injection timing on the combustion and emissions characteristics of a PODE/ammonia RCCI engine are investigated by both experimental and numerical methods. Results show that increasing AER from 10% to 40% leads to the delayed low temperature heat release (LTHR) due to reduced OH radical generated by PODE and the competition between PODE and ammonia for OH radical consumption. The larger AER increases the indicated thermal efficiency (ITE) by lowering combustion temperature and reducing heat transfer losses at the cost of higher hydrocarbon (HC), carbon monoxide (CO), and unburned NH3 emissions. The reduction of fuel-based nitrogen oxide (NOx) emissions with a larger AER is attributed to the enhanced in-cylinder thermal denitrification reactions. The delayed start of injection (SOI) from −60 °CA ATDC to −45 °CA ATDC leads to the higher peak in-cylinder pressure and temperature, resulting in the larger heat transfer losses and lower ITE. The impact of retarding SOI on NOx is insignificant under the combined effect of more thermal NO formation, less fuel-based NO generation, and weakened denitrification reactions. Additionally, nitrous oxide (N2O) shows dominant effects on the total greenhouse gas (GHG) emissions, and increasing AER or advancing injection timing produces more GHG. Under low loads and low AERs, although the introduction of ammonia helps to improve ITE, more researches are required to further reduce exhaust emissions.