ReaxFF Reactive Molecular Dynamics Research Articles

Adaptive accelerated reactive molecular dynamics driven by parallel collective variables overcoming dimensionality explosion.

ReaxFF reactive molecular dynamics has significantly advanced the exploration of chemical reaction mechanisms in complex systems. However, it faces several challenges: (1) the prevalent use of excessively high temperatures (>2000K), (2) a time scale considerably shorter than the experimental timeframes (nanoseconds vs seconds), and (3) the constraining impact of dimensionality growth due to collective variables on the expansiveness of research systems. To overcome these issues, we introduced Parallel Collective Variable-Driven Adaptive Accelerated Reaction Molecular Dynamics (PCVR), which integrates metadynamics with ReaxFF. This method incorporates bond distortion based on each bond type for customized Collective Variable (CV) parameterization, facilitating independent parallel acceleration. Simultaneously, the sampling was confined to fixed cutoff ranges for distinct bond distortions, effectively overcoming the challenge of the CV dimensionality explosion. This extension enhances the applicability of ReaxFF to non-strongly coupled systems with numerous reaction energy barriers and mitigates the system size limitations. Using accelerated reactive molecular dynamics, the oxidation of ester-based oil was simulated with 31 808 atoms at 500K for 64s. This achieved 61% efficiency compared to the original ReaxFF and was ∼37 times faster than previous methods. Unlike ReaxFF's high-temperature constraints, PCVR accurately reveals the pivotal role of oxygen in ester oxidation at industrial temperatures, producing polymers consistent with the sludge formation observed in ester degradation experiments. This method promises to advance reactive molecular dynamics by enabling simulations at lower temperatures, extending to second-level timescales, and accommodating systems with millions of atoms.

Pyrolysis and oxidation mechanisms of ethylene and ethanol blended fuel based on ReaxFF molecular dynamics simulation

To gain detailed atomic-level insights into the reaction mechanisms associated with the oxy-fuel combustion of ethylene and ethanol, ReaxFF reactive force field molecular dynamics simulations were performed to analyze the behavior of their high-temperature pyrolysis and oxidation. Results showed that the main reaction of pure ethylene involves the formation of long carbon chains by C–C polymerization in an oxygen-free environment. The polycondensation-cyclization of long carbon chains significantly contributes to the formation of polycyclic aromatic hydrocarbons (PAHs). The addition of ethanol enriches the initial reaction pathways of ethylene. For instance, ethanol participates in the following reactions: C2H4 + C2H6O → C4H10O, C2H6O + C2H4 → C2H5 + C2H5O, and C2H6O + C2H4 → C2H5 + H2O + C2H3. Ethanol inhibits the growth of long carbon chains, with a more pronounced effect at higher ethanol concentrations. In an oxygen atmosphere, the decay rate of ethylene decreases significantly, and its main reaction pathway involves dehydrogenation and oxidation with the assistance of OH, HO2, H, and O2. The final products are released in the form of CO, CO2, and H2O. In addition, the formation of soot particles is mainly divided into three steps: (i) ethylene aggregates to form long carbon chains, (ii) rearrangement and cyclization of long carbon chains, and (iii) growth of PAHs.

Catalytic hydropyrolysis of lignin: Insights into the effect of Ni catalyst and hydrogen using ReaxFF molecular dynamics simulation

Catalytic hydropyrolysis (CHP) of lignin as an emerging technology provides an efficient way of utilizing waste resources and promoting the production of alternative fuels and valuable bio-based products. The reinforcement of selective catalysts and hydrogen facilitates the overall conversion process but the mechanism remains difficult to clarify due to the complex nature of the system. This work employs a ReaxFF reactive molecular dynamics simulation method to explore the CHP of lignin dimer DMPD and the reaction mechanism at the molecular level. The results suggest that the hydropyrolysis (HP) system achieves a deoxygenation degree of 12.0 % for liquid products and the incorporation of hydrogen into pyrolysis suppresses the production of CO while promoting H2O and CH4 generation. The introduction of the Ni catalyst in the CHP system results in a liquid product yield of 68.9 wt % at 2000 K with a higher deoxygenation degree of 14.6 % due to the participation of a large amount of •H radicals species dissociated on the catalyst surface. The CHP reactions remarkably promote the production of phenols such as guaiacol and catechol and catechol is more likely to generate from the dynamic evolution of reaction intermediates. The integrated system also improves the production of H2O and light hydrocarbons like CH4 and C2H6. The first-order kinetic model reveals that the average activation energies of C-C, C-H, C-O bonds, and DMPD in the CHP system are significantly reduced to 113.12, 55.79, 59.99, and 132.17 kJ/mol in contrast to HP. The results indicate that the CHP system is more favorable for producing desirable liquid products with lower energy barriers.

Study on the Effects and Mechanism of Temperature and AO Flux Density in the AO Interaction with Upilex-S Using the ReaxFF Method

Atomic oxygen (AO), which is one of the most predominant and conspicuous space environmental factors in the low earth orbit, leads to severe deterioration of polymeric materials in spacecraft. The AO flux density and ambient temperature vary while a craft orbits in space; thus, it is necessary to pay close attention to the flux density and temperature effects on the mechanism of the AO interaction with materials. In past years, polyimide has been widely used on spacecraft due to its excellent performance—that is the reason why we chose Upilex-S as the object for study. It was analyzed using the ReaxFF reactive force field molecular dynamics simulation, respectively from the aspect of impact-induced temperature variation, mass loss, reaction product and erosion yield. The results show that dense AO deposition on the surface impedes further erosion at low temperatures, and the AO interaction with Upilex-S is exacerbated as the ambient temperature increases. However, the accelerating rate is inversely proportional to the ambient temperature, which means the higher the ambient temperature is, the slower it increases. On the other hand, the interaction rate of AO induced to Upilex-S is aggravated as the flux density increases at the lower stage, while the interaction rate begins to drop as the flux density increases at the higher level. The AO erosion effect is a complicated process rather than a simple summation of single atomic oxygen interactions. Our study could be used as a technical reference for the wide usage of Upilex-S on spacecraft.

A reactive molecular dynamics simulation of the atomic oxygen impact on poly(p-phenylene-terephthalamide)

Poly(p-phenylene-terephthalamide) (PPTA) is widely used in spacecraft structures due to its excellent mechanical properties and thermal stability. The space environment resistance of PPTA is the key factor affecting its service life. However, the mechanisms of the erosion process of PPTA during Atomic oxygen (AO) impact, which is one of the main factors for polymer degradation in the low earth orbit, remain unclear. In this study, the degradation mechanisms of PPTA under the AO impact are investigated by analyzing the morphology evolution, mass loss, the distribution of temperature, and the small molecules produced with simulation time using the ReaxFF reactive force field molecular dynamics simulations. The results show that the degradation mechanism of crystalline polymers due to the AO impact is closely related to the direction of the AO incidence. Throughout the simulation, the (010) surface has more mass loss and more CO and CO2 production, showing worse degradation than the (001) surface. This is due to the different temperature distributions of the two models caused by kinetic energy transfer in different crystal orientations. The extremely high local temperature on the surface of the (010) model leads to faster disintegration of the material. The simulation results can be used to provide atomic-scale insight into the design of crystalline polymers and their composites to resist atomic oxygen erosion.

Effects of grinding-induced surface topography on the material removal mechanism of silicon chemical mechanical polishing

Ultra-precision thinning technology using workpiece self-rotational grinding followed by chemical mechanical polishing (CMP) is extensively applied in the integrated circuit manufacturing process, which enables to obtain large size ultra-thin silicon wafers with high material removal rate and low damage layer thickness. However, an in-depth understanding of the influence caused by ground surface topography on material removal mechanism in silicon CMP process has not been revealed yet. This work systematically investigates the contact characteristics of the wafer-pad interface and corrosion behaviors of the ground silicon wafer immersed in polishing solution. Firstly, some silicon wafers are ground using different wheels and subsequently polished. The material removal depth during the whole CMP process is measured. Then, the intrinsic model of polishing pad is determined via mechanical property tests. A finite element method is adopted to evaluate the contact status, displacement distortion and stress distribution at the contact region between pad and ground wafer surface. Moreover, the chemical reaction mechanism between ground silicon wafer and polishing solution is revealed by utilizing X-ray photoelectron spectroscopy and electrochemical analysis. The influence of wafer surface topography on corrosion resistance in CMP process is illustrated. Finally, corresponding experimental results are explained from an atomic scale by a ReaxFF reactive molecular dynamics simulation model. This presented study demonstrates the corrosion promotion principle of ground silicon wafer in CMP process.

Simulations on the oxidation of Al-Mg alloy nanoparticles using the ReaxFF reactive force field

Nanoalloy holds multiple complex morphologies in combustion. However, the underlying mechanism, which is crucial to advance technical application of the nanoalloy, remains a challenging mystery. Herein, we performed a ReaxFF reactive molecular dynamics simulation on Al-Mg alloy nanoparticles (AMNPs) as a case study to further analyze oxidation behavior. Results showed that the evolution of AMNPs in combustion can be divided into three stages: (1) AMNPs first undergo phase separation and aggregate into Mg and Al phases; (2) Mg atoms rapidly diffuse to the surface and are oxidized; (3) Oxygen atoms diffuse inward and oxidize Al atoms. The inward diffusion of oxygen atoms is particularly hindered at the interface between Mg oxide shell and Al oxide layer. AMNPs prefer to form internal hollow structures at lower temperature and high oxygen concentration. The outward diffusion of Mg atoms causes the core to be gradually hollowed out. The spilled Mg atoms are oxidized and attached to the surface of alumina. The structure of Mg oxide (surface layer)-Al oxide (middle layer)-hollow (core) is finally formed. In addition, micro-explosion and external Mg oxide shell inhibit the agglomeration of nanoparticles. The study provides insight into the complex interactions between Al-Mg nanoalloy and oxygen.

Modulation Effect of Substrate Interactions on Nucleation and Growth of MoS2 on Silica

Chemical vapor deposition is a well-established bottom-up technique to produce a high-quality single-crystal MoS2 film. In this technique, the substrate (e.g., silica) plays a crucial role in the segregation and chemical interaction of precursors to form grain-sized MoS2. However, the mechanisms of the surface interactions that influence the properties of MoS2 during growth are still poorly understood. Here, we combine ReaxFF reactive molecular dynamics simulations, density functional theory (DFT) calculations, and experimental growth of MoS2 to provide an atomic insight into the coupling between the surface chemistry and the MoS2 nucleation and growth on a silica surface. Our experimental results show that the dehydroxylated surface stays mainly inert during the MoO3 flow, while the presence of hydroxyl groups leads to MoO3 nucleation on the substrate. ReaxFF and DFT simulations further confirm that the reaction between MoO3 and the hydroxylated surface is both thermodynamically and kinetically driven, indicating that hydroxyl groups formed on silica enhance the chemical reactivity of the surface toward MoO3 molecules and promote the growth. Additionally, the MoS2 growth on the hydroxylated silica support initiates with MoO3 nucleation followed by the chalcogen–surface interactions. Moreover, the existence of the substrate catalyzes the growth by lowering the growth temperature, providing an effective way for energy saving and cost reduction. These results demonstrate the intricate role of surface engineering in controlling and promoting large-area MoS2 growth.

Thermal decomposition mechanism investigation of hyperbranched polyglycerols by TGA-FTIR-GC/MS techniques and ReaxFF reactive molecular dynamics simulations

Molecular structure of hyperbranched polyglycerols (hbPGs) strongly affected the thermal stability as the critical heat transfer medium to maintain thermal homeostasis during working of heat engine. Here, thermogravimetric analysis (TGA)-fourier-transform infrared spectroscopy (FTIR)-gas chromatography (GC)-mass spectroscopy (MS) and reactive force-field (ReaxFF) techniques were utilized to identify major thermal decomposition products and explore the molecular mechanism. TGA-FTIR-GC/MS results showed that the major products were CO, CO2, water molecules and C3 organic moieties. To perform ReaxFF molecular dynamic simulation, timestep-dependent images revealed that C3 molecules were mainly originated from glycerol units and hydroxyl groups played an essential role in catalyzing thermal decomposition. To examine our hypothesis, different methoxylation levels of hbPGs were prepared, and TGA analysis of these methoxylated hbPGs polymers clearly corroborated that lower percentage of hydroxyl groups in the hbPGs can significantly increase maximum peak temperature from ∼400 °C to ∼460 °C. Our investigation clearly provided the molecular mechanism of hbPGs thermal decomposition and identified a potential way to improve thermal stability of hbPGs.

Study on mechanisms of methane/hydrogen blended combustion using reactive molecular dynamics simulation

Methane is an ideal alternative to other fossil fuels but requires great bond strength to bond dissociation, which leads to poor ignition performance. Hydrogen, as a promising and environmental-friendly fuel, has a very high calorific value, the addition of which is considered as an effective approach to enhance the methane combustion. In this study, the ReaxFF reactive force field molecular dynamics (ReaxFF-MD) simulation is used to study the process of methane/hydrogen blended combustion with various amounts of hydrogen addition. The results show that the addition of hydrogen can promote the methane combustion by accelerating the consumption of methane. In addition, the instant when methane starts to participate in the reaction is advanced. However, with the increase of hydrogen content, the promoting effect of methane combustion weakens as the temperature increases. It is found that the enhanced OH production resulted from the hydrogen addition not only promotes the initiation but also affects the intermediate and final products of methane combustion. Furthermore, compared with pure methane combustion, the addition of hydrogen significantly lowers the activation energy by up to 50% but the enhancement is becoming weaker with the increasing amount of hydrogen addition. This research provides atomistic insights into the methane/hydrogen blended combustion that could potentially benefit its practical application.

Decomposition mechanism of hydrofluorocarbon (HFC-245fa) in supercritical water: A ReaxFF-MD and DFT study

In this work, the concept of using supercritical water to treat Hydrofluorocarbons (HFCs) refrigerants waste is proposed. Taking 1,1,1,3,3-Pentafluoropropane (HFC-245fa) as the research object, based on the ReaxFF reactive force field molecular dynamics method and density function theory, the decomposition mechanism of HFC-245fa in supercritical water, the effects of temperature, HFC-245fa mass concentration and oxygen addition on the decomposition of HFC-245fa in supercritical water and decomposition mechanism were studied. The results show that the main stable products of HFC-245fa decomposition in supercritical water are HF, CO2, CO and H2. In supercritical water, ·F radicals can easily combine with H2O molecules and then rapidly decompose to generate HF molecules and ·OH radicals. The hydrogen extraction reaction of ·H radicals with H atoms in HFC-245fa molecules and H2O molecules has relatively low energy barrier. ·OH radicals can also participate in the dehydrogenation reaction, promoting the further dehydrogenation of HFC-245fa molecules and their molecular fragments. Moreover, it can combine with carbon-containing molecular fragments to promote the conversion of C element to CO and CO2. The lower concentration of HFC-245fa promotes the conversion of C element and generation of H2. The addition of oxygen facilitates the generation of ·OH radicals and promotes the conversion of C element to CO2, but reduces the generation of CO and H2. Under the condition of HFC-245fa mass concentration of 13.0%, the calculated formation apparent activation energies of HF, CO and CO2, H2 are 196.3, 368.5 and 249.0 kJ·mol−1, respectively.

ReaxFF reactive molecular dynamics study on electrochemistry of H2/CO hybrid fuel in Ni/YSZ anode

Fuel flexibility, e.g. using reformate or syngas fuel directly, is one of the most advantages of solid oxide fuel cells (SOFC). However, the electrochemical mechanism of the H2/CO mixture, which is common and key in hydrocarbon fuel-fed SOFC, is unclear and relatively rarely studied at present. This article makes Reactive Force-Field (ReaxFF) reactive molecular dynamics (RMD) simulations on the electrochemical co-oxidation of H2/CO hybrid fuel in Ni (nickel)/YSZ (yttria-stabilized zirconia) anode. The RMD simulations at different fuel gas components show that in the H2/CO/Ni/YSZ system the H2 conversion rate maintains the maximum (100%), and the conversion rate of CO improves compared with that of pure CO fuel in the case of 30%H2−70%CO. Two ways of CO2 generation are found: one is that the CO(Ni) species formed by the adsorption and activation of CO on the Ni surface is oxidized by the lattice oxygen; the other is the oxidation of CO(Ni) by spillover atomic oxygen, which is adsorbed on the Ni surface. It is worth noting that the effect of oxygen vacancies on the oxidation of CO is more significant than that of H2. A viewpoint is proposed to explain how H2 enhances the oxidation of CO. The results help understand the electrochemistry of H2/CO involved fuel in the context of SOFC operations.

The molecular dynamics simulation of lignite combustion process in O2/CO2 atmosphere with ReaxFF force field

Pressurized oxy-fuel combustion is a complex process consisting of free radical collisions and reactions. ReaxFF reactive Molecular Dynamics (MD) simulation method is a useful tool to investigate the chemical events in coal combustion at atomistic level. In this work, the impact of operating conditions on the distribution of main fragments and the reaction mechanisms were examined using a lignite coal model with ReaxFF force field to simulate the process of oxy-fuel combustion under pressures. The ReaxFF MD simulations found that the decomposition of coal molecular structure would be enhanced by increasing the pressure/density, oxygen concentration and temperature. The variety of initial reactions increased with temperature. Increasing pressure promoted the effective collision of molecules and the coal structure was more likely to be attacked by oxidants, so the chemical bonds in coal molecule broke earlier and the consumption of O2 increased at higher pressure. The dehydrogenation reaction on the macromolecular structure of coal and small fragments was also promoted after increasing pressure/density. However, the number of fragments decreased as the pressure/density continued to grow, because large fragments further decomposed or some small molecular benzene ring structures with less than 6C atoms were re-polymerized. The dehydrogenation reaction of coal molecule and small fragments was promoted after increasing the pressure. O2 attacked the benzene ring structure, the C atom on the outer side of the coal, and the carbon-containing fragments in the system, indicating that the increase of O2 concentration promoted the ring opening and oxidation reactions, thereby promoting the decomposition and combustion of coal. The work in this paper has confirmed the findings obtained by other oxy-fuel experimental work from the microscopic point of view.

Atomic-scale study on particle movement mechanism during silicon substrate cleaning using ReaxFF MD

The cleaning of silicon wafer surfaces in the integrated circuits manufacturing has not yet been studied at the atomic scale, making it difficult to optimize. In this study, the atomistic mechanism of nanoparticle movement during the cleaning process of the substrate after chemical mechanical polishing (CMP) was investigated using ReaxFF reactive molecular dynamics simulations. The redeposition and removal processes of the silica nanoparticles on the Si (100) substrate with different ambient humidity and substrate state were simulated. Results indicated that water generally plays a positive role in cleaning process, preventing the silica nanoparticles from approaching the substrate and promoting the fracture of interfacial chemical bonds, and it also mitigates the substrate damage caused by particle removal. Aqueous H2O2 influences the substrate state by increasing the oxidizability and hydroxylation level of the substrate surface, which changes the interaction force between the substrate and the nanoparticles, thus impacting particle redeposition process. Additionally, the peroxide facilitates the formation of Si–O–Si bonds and inhibits the removal of the nanoparticles. This work provides atomistic insights into the wafer cleaning process, which is of great significance for the solution design.

Detailed mechanisms of amoxicillin decomposition in supercritical water by ReaxFF reactive molecular dynamics simulation

The abuse of antibiotics in China has aroused widespread concern, and the resistance genes of antibiotics in the natural environment seriously threaten human health. The supercritical water gasification (SCWG) technology is a clean and efficient technology for the treatment of antibiotic wastewater. In this paper, amoxicillin is selected as the representative antibiotic in wastewater, and the detailed mechanisms of amoxicillin decomposition in supercritical water (SCW) are studied by ReaxFF reactive molecular dynamics (MD) simulation. The results show that the decomposition process of amoxicillin in SCW includes carbon ring opening, carbon chain breaking and small molecular compounds conversion. The molecular vibration leads to the breaking of CN and CS bonds. The OH radical is vital to the ring opening of benzene ring and the breaking of carbon chain. However, the yield of NO increases with increasing OH radical concentrations. The ReacNetGenerator tool is used for the first time to analyze the migration path of nitrogen and sulfur in the SCWG system. It shows that H2 has a great effect on the transformation of sulfur, and OH radicals dominate the transformation of nitrogen. Decreasing the reaction time and the concentration of OH radicals result in inhibiting the NO production. This study will provide a theoretical guidance for understanding SCWG process of antibiotic-containing wastewater.

A complete thermal decomposition mechanism study of an energetic‐energetic CL‐20/DNT cocrystal at different extreme temperatures by using ReaxFF reactive molecular dynamics simulations

2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is a high energetic material (HEM) and have unique features including, high density, high explosion, and better oxidizer to fuel ratio, which makes it prominent as compared tp other explosive materials such as; RDX and HMX. Although; CL-20 has attractive detonation properties but due to its thermal sensitivity its uses are very limited. In modern years, cocrystallization was considered as an effective, unique, and novel methodology to reduce the sensitivity of HEMs. In this study, we reported the detailed thermal decomposition mechanism of the CL-20/DNT cocrystal at different extreme temperatures was studied by using the ReaxFF/lg reactive molecular dynamics (MD) simulations. In the thermal decomposition analysis of CL-20/DNT cocrystal, initial, intermediates, final products, total number of species, potential energy, decomposition mechanism, reaction kinetics, cluster growth, and bond cleavage/bond formation were studied. The results of CL-20/DNT decomposition analysis were compared to pure ε-CL-20 decomposition analysis where the findings reflected that the CL-20/DNT cocrystal performed better than pure CL-20 in terms of sensitivity, potential energy, total number of species, number of carbon clusters, and explosion energy. Furthermore, the decomposition mechanism provides the exact information about the thermal stability, evolution of hot spots, reaction zones formation, and reaction kinetics. This study will provide a strong basis and open up a new direction to find the decomposition mechanisms of high energetic cocrystals.

Understanding the Mechanisms of SiC-Water Reaction during Nanoscale Scratching without Chemical Reagents.

Microcracks inevitably appear on the SiC wafer surface during conventional thinning. It is generally believed that the damage-free surfaces obtained during chemical reactions are an effective means of inhibiting and eliminating microcracks. In our previous study, we found that SiC reacted with water (SiC–water reaction) to obtain a smooth surface. In this study, we analyzed the interfacial interaction mechanisms between a 4H-SiC wafer surface (000) and diamond indenter during nanoscale scratching using distilled water and without using an acid–base etching solution. To this end, experiments and ReaxFF reactive molecular dynamics simulations were performed. The results showed that amorphous SiO2 was generated on the SiC surface under the repeated mechanical action of the diamond abrasive indenter during the nanoscale scratching process. The SiC–water reaction was mainly dependent on the load and contact state when the removal size of SiC was controlled at the nanoscale and the removal mode was controlled at the plastic stage, which was not significantly affected by temperature and speed. Therefore, the reaction between water and SiC on the wafer surface could be controlled by effectively regulating the load, speed, and contact area. Microcracks can be avoided, and damage-free thinning of SiC wafers can be achieved by controlling the SiC–water reaction on the SiC wafer surface.

Pyrolysis mechanism of tetrahydrotricyclopentadiene by ReaxFF reactive molecular dynamics simulations

Tetrahydrotricyclopentadiene (THTCPD) has high density and volumetric heat, but its viscosity is also high, resisting its ignition and combustion, which somewhat limits its applications. Therefore, it is crucial to understand the mechanism of THTCPD pyrolysis. In this study, the ReaxFF reactive molecular dynamics simulations were performed to investigate the thermal dissociation of THTCPD. The detailed description of THTCPD pyrolysis behavior was obtained from the aspects of initial reactions, main species distributions and intermolecular reactions. Initiation of the THTCPD decomposition is mainly through CC bond fission of the bicycloheptyl structure in the middle, leading to the formation of highly active C15H22 diradicals. To give a better description of the pyrolysis behavior, main products related intermolecular reactions should be considered in the mechanism. The simulated pre-exponential factor A (2.30 × 1015 s−1) and activation energy E (55.72 kcal/mol) captured from simulations are found to be reasonably consistent with the experimental values.

A reactive force field molecular dynamics study on the inception mechanism of titanium tetraisopropoxide (TTIP) conversion to titanium clusters

We performed ReaxFF reactive molecular dynamics simulations to investigate the inception mechanism of TTIP precursor droplet conversion to Ti-containing clusters in 1000 K–2500 K with or without gaseous O2 molecules. A new Ti/C/H/O ReaxFF force field has been developed. Key intermediate titanium species and the initial decomposition pathways of TTIP are identified. The effects of temperature, O2 concentration and high-temperature residence time on the conversion of TTIP to incipient titanium clusters are investigated. Results suggest that high pyrolysis temperature does not necessarily promote the formation of incipient Ti-containing clusters, due to less stable TiO bonds at high temperatures. Ti2OxCyHz species appear earlier than TiO2 during TTIP pyrolysis, while TiO2 forms earlier than Ti2OxCyHz species and has much higher concentration with ambient O2. Decreasing high-temperature residence time boosts the formation of Ti-containing clusters by facilitating the condensation of TiO2 vapors. The growth pattern of the incipient titanium clusters is elucidated as formation of TiO bond with TiOxCyHz species or titanium clusters followed by continuous breakage of TiO or CO bonds to release hydrocarbon moieties.

A reactive molecular dynamics study of bi-modal particle size distribution in binder-jetting additive manufacturing using stainless-steel powders

The binder-jetting additive manufacturing using a bimodal particle size distribution is modelled using the ReaxFF reactive molecular dynamics method, which provides an atomistic-level insight into the mechanical and chemical property evolution.