Final Reaction Product Research Articles

Mutual Transformations of Polysulfide Chromophore Species in Sodalite-Group Minerals: A DFT Study on S6 Decomposition.

It is known that various polysulfide species determine the color of sodalite-group minerals (haüyne, lazurite, and slyudyankaite), and that heating induces their transformations and color change, but the mechanisms of the transitions are unknown. A prominent example is the decay of cyclic S6 molecule. Using density-functional simulations, we explore its main decay pathways into the most probable final reaction products (the pairs of radical anions S3⋅-+S3⋅- and S2⋅-+S4⋅-). It was found that the most favorable reaction path involves initial capture of one electron by the S6 molecule, which greatly facilitates its decay of S6 and leads to the opening of the S6 cycle, and subsequent decomposition of the thus formed chain radical anion, with a limiting energy barrier of ~0.4 eV. Neutral polysulfide molecules capture one electron with a significant energy reduction. The radical anions Sn⋅- (n=2-6) are the most stable ones among corresponding species with the same n values and different charges. The capture of the second electron by S6⋅- occurs with a huge energy barrier (~2 eV). The results of the DFT calculations are in agreement with experimental data on the products of thermal conversions of extra-framework S-bearing groups in sodalite-group minerals.

Interaction mechanism of cold atmospheric plasmas and fusion peptides of spike protein in SARS-CoV-2 revealed by reactive molecular dynamics simulation

Despite the conclusion of the COVID-19 pandemic, the coronavirus-killing ability of cold atmospheric plasma (CAP) remains impressive, and investigations into its underlying mechanisms are still ongoing. The fusion peptide (FP) is a crucial site of membrane fusion and toxicity exerted by the S-protein in severe acute respiratory syndrome CoV-2 (SARS-CoV-2). In this study, reactive molecular dynamics simulations were performed to investigate the interaction mechanisms of FP and reactive oxygen species (ROS). The simulation results show that the given ROS (O atoms and OH radicals as examples) can destroy hydrophobic residues, negatively charged acidic residues, and peptide bonds through structurally altering essential sites. Furthermore, the reaction typically initiates from the H-abstraction reaction, followed by various types of oxidative modifications such as dehydrogenation, hydroxylation, carbonylation, cyclogenesis, ring cleavage, and decarboxylation, which are consistent with the experimental findings made on peptides. Therefore, it can be predicted that the membrane fusion ability of FP and the toxicity of SARS-CoV-2 will be reduced, with CAP functioning as a bactericidal disinfectant. The dose effects were also investigated, providing experimental guidance for the optimization of CAP. In this study, the interaction processes of FP and CAP are explored by revealing the chemical pathways and final reaction products from the computational data, thus providing a fundamental understanding of the mechanisms for inactivating SARS-CoV-2 by CAP.

Effect of high pressure synthesis conditions on the formation of high entropy oxides

High entropy materials are often entropy stabilized, meaning that the configurational entropy from multiple elements sharing a single lattice site stabilizes the structure. In this work, we study how high-pressure synthesis conditions can stabilize or destabilize a high entropy oxide (HEO). We study the high-pressure and high-temperature phase equilibria of two well-known families of HEOs: the rock salt structured compound (Mg,Co,Ni,Cu,Zn)O, including some cation substitutions, and the spinel structured compound (Cr,Mn,Fe,Co,Ni)3O4. Syntheses were performed at various temperatures, pressures, and oxygen activity levels, resulting in dramatically different synthesis outcomes. In particular, in the rock salt HEO, we observe the competing tenorite and wurtzite phases and the possible formation of a layered rock salt phase while the spinel HEO is highly susceptible to partial decomposition into a mixture of rock salt and corundum phases. At the highest tested pressures, 15 GPa, we discover the transformation of the spinel HEO into a metastable modified ludwigite-type structure with the nominal formula (Cr,Mn,Fe,Co,Ni)4O5. The relationship between the synthesis conditions and the final reaction product is not straightforward. Nonetheless, we conclude that high-pressure conditions provide an important opportunity to synthesize high entropy phases that cannot be formed any other way.

An enzyme cascade biosensor based on multiwalled carbon nanotube-RuO2 nanocomposite for selective amperometric determination of lactose in milk samples

An enzyme-based electrochemical biosensor was fabricated for the sensitive determination of lactose. The utilized enzyme cascade system is composed of β-galactosidase (β-Gal) and glucose oxidase (GOx). The ruthenium(IV) oxide (RuO2) presents in MWCNT-RuO2 nanocomposite immobilized on the glassy carbon electrode acts as an electrochemical mediator, resembling a second-generation enzyme biosensor. The functional mechanism of the biosensor was discussed, explaining the chemical oxidation of H2O2, the final product of the enzymatic reaction, by RuO2 and subsequent reoxidation of generated Ru to RuO2 at the electrode surface. This shifts the oxidation of H2O2 to a lower potential magnitude of +0.40 V, enhancing the biosensor’s selectivity. The analytical figures of merit were verified for the developed lactose biosensor through repetitive measurements. The precision of the lactose biosensor was ensured with good reproducibility (RSD % = 2.68) and repeatability (RSD % = 4.12). The selectivity of the biosensor towards various saccharides and ionic species potentially present in milk samples was investigated, and no notable interference effect was detected. Moreover, the accuracy of the lactose biosensor was tested by analyzing spiked samples and a semi-skimmed milk (SS-milk) sample with certified lactose values. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be (0.036 mM) and (0.121 mM), respectively. Thanks to the short response time of the fabricated lactose biosensor, it was transferred to a screen-printed carbon electrode (SPCE) and successfully employed in flow injection analysis (FIA).

Chemoselective Adsorption of Allyl Ethers on Si(001): How the Interaction between Two Functional Groups Controls the Reactivity and Final Products of a Surface Reaction.

Selective adsorption of multifunctional molecules is rarely observed when the different functional groups react via nonactivated reaction channels. Although the latter is also the case for ether cleavage and the adsorption of C=C double bonds on the highly reactive Si(001) surface, we find that allyl ethers, which combine both functional groups, react on Si(001) selectively via the cleavage of the molecules' ether group. In addition, our XPS measurements at 90, 150, and 300 K indicate an increased reactivity of the ether group when compared to monofunctional ethers. STM investigations furthermore reveal different final adsorption configurations after ether cleavage of allyl methyl ether when compared to diethyl ether as the monofunctional reference molecule. The interaction of the two functional groups in one molecule thus leads to new reaction channels with higher reactivity for ether cleavage on Si(001). As a further consequence, the reactivity of the C=C double bond is suppressed up to room temperature, leading to the observed selective adsorption.

Strengthening the Synergy between Oxygen Vacancies in Electrocatalysts for Efficient Glycerol Electrooxidation.

Defect-engineered bimetallic oxides exhibit high potential for the electrolysis of small organic molecules. However, the ambiguity in the relationship between the defect density and electrocatalytic performance makes it challenging to control the final products of multi-step multi-electron reactions in such electrocatalytic systems. In this study, controllable kinetics reduction is used to maximize the oxygen vacancy density of a Cu─Co oxide nanosheet (CuCo2O4 NS), which is used to catalyze the glycerol electrooxidation reaction (GOR). The CuCo2O4-x NS with the highest oxygen-vacancy density (CuCo2O4-x-2) oxidizes C3 molecules to C1 molecules with selectivity of almost 100% and a Faradaic efficiency of ≈99%, showing the best oxidation performance among all the modified catalysts. Systems with multiple oxygen vacancies in close proximity to each other synergistically facilitate the cleavage of C─C bonds. Density functional theory calculations confirm the ability of closely spaced oxygen vacancies to facilitate charge transfer between the catalyst and several key glycolic-acid (GCA) intermediates of the GOR process, thereby facilitating the decomposition of C2 intermediates to C1 molecules. This study reveals qualitatively in tuning the density of oxygen vacancies for altering the reaction pathway of GOR by the synergistic effects of spatial proximity of high-density oxygen vacancies.

Application of the thin layer chromatography method for the determination of the degree of hydrolysis of soy lecithin

The aim of this study was the determination of the degree of enzymatic hydrolysis of soy lecithin using thin layer chromatography in combination with a modern imaging data processing program. Hydrolysis of phospholipids was carried by the action of the enzyme phospholipase A2 (PLA2) in the presence of calcium ions for 2 h at a temperature of 50°C and pH 5.7. Chromatographic separation of the components of the reaction medium was carried out 10, 20, 30, 60, 90, and 120 min after adding the PLA2 in the chloroform: methanol: ammonium hydroxide system in a ratio of 6.5 : 2.5 : 0.4 (v/v/v). The following phospholipids and their lysoforms were identified: Rf = 0.41±0.03 for phosphatidylethanolamine (PE), Rf = 0.28±0.02 for phosphatidylcholine (PC), Rf = 0.09±0.01 for phosphatidylinositol (PI), Rf = 0.06±0.01 for phosphatidic acid (PA), Rf = 0.15±0.02 for lysophosphatidylethanolamine (LPE), Rf = 0.08±0.01 for lysophosphatidylcholine (LPC), Rf = 0.03±0.01 for lysophosphatidylinositol (LPI) and Rf = 0.02±0.01 for lysophosphatidic acid (LPA). It was shown that soy lecithin contained PC, PE, PI, and PA before the enzymatic reaction, the content of these compounds after the addition of the PLA2 decreases due to the formation of LPC, LPE, LPI, and LPA, respectively. The dependence of the degree of hydrolysis (α, %) of PC on the duration of the enzymatic reaction was obtained. It was established that the intensive conversion of PC to LPC under the action of the PLA2 occurred during 60 min (α = 82%). Further conversion of PC occurred insignificantly: 84% after 90 min and 87% after 120 min, which was due to the inhibition of enzyme activity by the final reaction product.

Chemotactic Interactions Drive Migration of Membraneless Active Droplets.

In nature, chemotactic interactions are ubiquitous and play a critical role in driving the collective behavior of living organisms. Reproducing these interactions in vitro is still a paramount challenge due to the complexity of mimicking and controlling cellular features, such as tangled metabolic networks, cytosolic macromolecular crowding, and cellular migration, on a microorganism size scale. Here, we generate enzymatically active cell-sized droplets able to move freely, and by following a chemical gradient, able to interact with the surrounding droplets in a collective manner. The enzyme within the droplets generates a pH gradient that extends outside the edge of the droplets. We discovered that the external pH gradient triggers droplet migration and controls its directionality, which is selectively toward the neighboring droplets. Hence, by changing the enzyme activity inside the droplet, we tuned the droplet migration speed. Furthermore, we showed that these cellular-like features can facilitate the reconstitution of a simple and linear protometabolic pathway and increase the final reaction product generation. Our work suggests that simple and stable membraneless droplets can reproduce complex biological phenomena, opening new perspectives as bioinspired materials and synthetic biology tools.

Dynamical evolution of CO2 and H2O on garnet electrolyte elucidated by ambient pressure X-ray spectroscopies

Garnet-type Li6.5La3Zr1.5Ta0.5O12 (LLZO) is considered a promising solid electrolyte, but the surface degradation in air hinders its application for all-solid-state battery. Recent studies have mainly focused on the final products of the LLZO surface reactions due to lacking of powerful in situ characterization methods. Here, we use ambient pressure X-ray spectroscopies to in situ investigate the dynamical evolution of LLZO surface in different gas environments. The newly developed ambient pressure mapping of resonant Auger spectroscopy clearly distinguishes the lithium containing species, including LiOH, Li2O, Li2CO3 and lattice oxygen. The reaction of CO2 with LLZO to form Li2CO3 is found to be a thermodynamically favored self-limiting reaction. On the contrary, the reaction of H2O with LLZO lags behind that of CO2, but intensifies at high pressure. More interestingly, the results provide direct spectroscopic evidence for the existence of Li+/H+ exchange and reveal the importance of the initial layer formed on clean electrolyte surface in determining their air stability. This work demonstrates that the newly developed in situ technologies pave a new way to investigate the oxygen evolution and surface degradation mechanism in energy materials.

Isotopic and geochemical modeling approach to evaluate abiotic nitrite reduction by ferrous iron

Nitrite reduction has often been treated as a biotic process in water treatment systems, but it also occurs abiotically, and it is difficult to distinguish both reactions as they can co-occur at field-scale. The potential reduction of NO2− was tested in 3 anaerobic experimental scenarios using a NO2− bearing solution amended with: i) siderite (FeCO3) (Sid experiment); ii) Fe(II) solution from FeCl2.4H2O(s) (DFe experiment); and iii) siderite mixed with Fe(II) solution (Sid+DFe experiment). Non-sterilized batch experiments were carried out in anaerobic conditions with an initial ratio of nitrogen to dissolved iron of 5 in DFe and Sid+DFe (Sid had no initially dissolved Fe(II)) and 1000 mg L−1 of siderite in Sid and Sid+DFe experiments. At the end of the experiments, the NO2− removed was 3% for Sid, 54% for DFe and 84% for Sid+DFe. The NO2− concentration decrease over time was characterized by an enrichment in the δ15NNO2 of the unreacted NO2−, increasing from −26.9 ‰ to −26.4 ‰ (Sid), −18.0 ‰ (DFe) and −15.9 ‰ (Sid+DFe). The calculated ε15NNO2 for Sid was −11.8 ‰, whereas for DFe was −12.0 ‰ and Sid+DFe was −13.0 ‰, suggesting a common NO2− degradation mechanism in all experiments. The Rayleigh distillation equation showed that the generated N2O was the final product of the abiotic nitrite reduction reaction, and the calculated N2O site preference (SP) was 22.5 ± 0.7 ‰ for DFe and 23.5 ± 0.5 ‰ for Sid+DFe. The continuous N2O measurement showed that only 25.3 ± 5.1% in DFe and 31.0 ± 6.3% in Sid+DFe of the generated N2O in water was recovered in the headspace vials, suggesting that a large portion of the produced N2O(aq) in solution did not diffuse from water. The coupled NO2− reduction and Fe(II) oxidation followed a second-order kinetic reaction with a rate equal to (9.39 ± 0.36)·10−4·[NO2−]·[Fe(II)] (mol L−1 s−1) in all experiments. The experimental conditions supported by the Rayleigh distillation equation using the experimentally calculated ε15N values, coupled with NO2− isotopic data and N2O SP values, showed that biological denitrification had a negligible influence on nitrite reduction and that chemodenitrification was the main NO2− attenuation pathway. A geochemical model coupling the kinetic chemodenitrification, isotope fractionation, aqueous speciation in equilibrium and precipitation and dissolution of calcite has been implemented and reproduced the experimental results. The geochemical model developed in our study can be applied to similar experimental studies and to field-scale studies to predict the efficiency of abiotic nitrite reduction treatments using Fe(II).

Tailoring the dimensionality of metal complexes via ligand modifications.

A series of CuII complexes obtained under the same reaction conditions has been analyzed to gain insight into the effect of the ligand composition on the final reaction product. Dipodal ligands containing N-donor imidazole rings and a benzene ring as a spacer with different numbers of methyl substituents on the aromatic rings were selected for the study such as 1,3-bis(imidazol-1-ylmethyl)benzene (L1), 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene (L2), 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (L3), 1,3-bis(2-methylimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (L4). L4 has not been reported previously and was synthesized for this study. The formed metal complexes show the presence of polymeric (ligand with no or one methyl substituent; 1-4), or discrete motifs (3- or 5-methyl substituents; 5-7). The new metal complexes 3, 5 and 6 were analyzed using single-crystal X-ray diffraction and powder diffraction. In addition, the structural analyses were supported by computational methods.

Bifunctional Au-Sn-SiO2 catalysts promote the direct upgrading of glycerol to methyl lactate.

Valuable alkyl lactates can be obtained from (waste) glycerol, through a two-step process that entails (i) the oxidation of glycerol to dihydroxyacetone (DHA) catalyzed by support Au nanoparticles and (ii) a rearrangement of DHA with an alcohol effectively catalyzed by Sn-based heterogeneous catalysts. To solve selectivity and processing issues we propose to run the process as a cascade reaction, in one step, and with a single bifunctional catalyst. Tackling the challenge associated with the preparation of such bifunctional catalysts, here, an aerosol-assisted sol-gel route is exploited. The catalysts feature small Au nanoparticles (3-4 nm) embedded at the surface of mesoporous Sn-doped silica microspheres. The preparation successfully leads to insert both active sites in their most active forms, and in close proximity. With the bifunctional catalysts, the yield for the final product of the cascade reaction (methyl lactate) is higher than the DHA yield when only the first reaction is carried out. This highlights a beneficial substrate channeling effect which alleviates side reactions. Interestingly, the bifunctional catalysts also markedly outcompeted mechanical mixtures of the corresponding monofunctional Au- and Sn-based catalysts. Thus, the spatial proximity between the two active sites in bifunctional catalysts is identified as a key to stir the cascade reaction towards high lactate yield.

Synthesis, Characterization, Antiglycation Evaluation, Molecular Docking, and ADMET Studies of 4-Thiazolidinone Derivatives.

The design and development of new small-molecule glycation inhibitors are essential for preventing various chronic diseases, including diabetes mellitus, immunoinflammation, cardiovascular, and neurodegenerative diseases. 4-Thiazolidinone or thiazolidine-4-one is a well-known heterocyclic compound with the potential to inhibit the formation of advanced glycation end products. In the present work, we report the synthesis and characterization of four new 5-arylidene 3-cyclopropyl-2-(phenylimino)thiazolidin-4-one (1-4) compounds and their human serum albumin glycation inhibitory activity. One of the compounds 5-(2H-1,3-benzodioxol-5-ylmethylidene)-3-cyclopropyl-2-(phenylimino)-1,3-thiazolidin-4-one (3) showed potent inhibition in the synthesis of initial, intermediary, and final products of glycation reactions. Besides, conformational changes in the α-helix and β-sheet (due to hyperglycemia) were also found to be reversed upon the addition of (3). Experimental findings were complemented by computational [molecular docking, ADME/Tox, and density functional theory (DFT)] studies. The docking scores of the compounds were in order 1 > 3 > 2 > 4, indicating the importance of the polar group at the 5-arylidene moiety. The results of ADME/Tox and DFT calculations revealed the safe nature of the compounds with high drug-likeness and stability. Overall, we speculate that the results of this study could provide valuable insights into the biological activity of 4-thiazolidinones.

Sustainable PET Waste Recycling: Labels from PET Water Bottles Used as a Catalyst for the Chemical Recycling of the Same Bottles.

We report using a waste material, poly(ethylene terephthalate) (PET) water bottle labels, for the chemical recycling of the same PET water bottles. The solid fillers used for the manufacturing of the packaging labels were recovered by thermolysis in an electrical furnace at 600, 800, and 1000 °C with 13.5, 12.0, and 10.4 wt % recovery. Characterization of the solid residue showed the presence of calcium carbonate, calcium oxide, and titanium dioxide, which are typical fillers used for packaging film manufacturing, such as water bottle labels. These solid residues were then used as a catalyst for PET depolymerization by glycolysis, in which the catalyst recovered from bottle labels and shredded PET reacted in the presence of excess ethylene glycol at 200 °C. The reaction mixtures were analyzed for PET conversion and the yield of the bis(2-hydroxyethyl)terephthalate (BHET) monomer as the final product of the glycolysis reaction to determine the efficiency of the catalyst. Our results show that the catalyst prepared at 800 °C (Cat-800) has the best performance and provides a 100% PET conversion with a 95.8% BHET yield with a 1.0 wt % loading in 1.5 h. The catalyst from the PET water bottle labels is nontoxic, readily available, cost-effective, environmentally friendly, and can be used as a model for the self-sufficient chemical recycling of PET via glycolysis.

Promoted micropollutant degradation and structural evolution of natural organic matter by a novel S(IV)-based water treatment strategy

The ubiquity of various organic micropollutants in global water and wastewater has raised considerable concern about their cost-efficient elimination. This study reported that the novel UV365/FeTiOX/S(IV) system could accomplish superior abatement of different micropollutants (e.g., carbamazepine, CMZ) in 30–45 min with excellent reusability and stability of FeTiOX. In addition, this system functioned effectively to remove roxarsone and As(III)/As(V) by catalytic oxidation and adsorption, respectively. Mechanistic investigations suggested the dual roles of S(IV) in enhancing pollutant oxidation, i.e., promoted Fe(II)/Fe(III) cycle and photocatalysis. These processes facilitated the continuous generation of multiple oxidizing intermediates (e.g., hydroxyl radicals, sulfate radicals, and singlet oxygen), in which the last one was first proposed as the main contributor in iron-mediated S(IV)-based oxidation processes. Based on the product identification, the transformation pathways of four different micropollutants were tentatively unraveled. The in silico prediction suggested the lower environmental risks of the final reaction products than the precursors. Particularly, the structural alteration of humic acid was analyzed, indicating an increased O/C ratio after oxidative treatment. Overall, this study has implications for developing an efficient oxidation technique for removing multiple micropollutants in water and facilitating the mechanistic reactivity modulation of the S(IV)-based oxidation strategies in water treatment.

Reinterpret the heterogeneous reaction of α-Fe2O3 and NO2 with 2D-COS: The role of SDS, UV and SO2

Heterogeneous reaction of mineral aerosols and atmospheric polluting gases play an important role in atmospheric chemistry. In this study, the reactions of NO2 with or without SO2 mixture gas on the surface of α-Fe2O3 particles under dry conditions were studied. The effects of sodium dodecyl sulfate (SDS) and the heterogeneous reaction under both dark and UV irradiation conditions were investigated. The infrared spectrum analyzed by the two-dimensional correlation spectroscopy (2D-COS) was used to obtain the products formation sequences. The results showed that UV irradiation can promote the production of nitrate. The 2D-COS analysis indicated SDS changed the sequence order of nitrate and nitrite species during reactions. In oxidation conditions, the final product of heterogeneous reaction of NO2 and α-Fe2O3 was monodentate nitrate. Only the heterogenous reaction of NO2 and α-Fe2O3 containing SDS (FOS) without UV light, the final product was bidentate nitrate. SDS was the catalysis agent supply and photoresist to the system. With surface active compounds, the environmental lifetime of heterogeneous reactions between trace gases and aerosols extends. Surfactants, ultraviolet light, and the types of gases involved in the reaction all have complex effects on the aerosol aging process. This study provided a reference for subsequent heterogeneous reaction studies and the formation of aerosols.

Real-Time Mass Spectrometric Detection of Reaction Intermediates Formed during Laser-Induced UV/H2O2 Advanced Oxidation of 2-Methylbenzoisothiazol-3-one.

Knowledge on short-lived reaction intermediates is often essential for mechanistic investigations of organic reactions and for reaction optimization. Unfortunately, most conventional analytical methods are too slow to allow the detection of short-lived reaction intermediates. Herein, a direct laser desorption/ionization method coupled with linear quadrupole ion trap/orbitrap high-resolution tandem mass spectrometry was used for the detection and structural characterization of several previously proposed but undetected reaction intermediates formed during laser-induced UV/H2O2 advanced oxidation of 2-methylbenzoisothiazol-3-one. The elemental compositions of most detected (ionized) compounds were determined. Tandem mass spectrometry experiments based on gas-phase collision-activated dissociation (CAD) were conducted to gain information on the ion structures. The mechanisms of the CAD reactions were explored using high-level quantum chemical calculations to support the structures proposed for the neutral reaction intermediates formed during the laser-induced UV/H2O2 advanced oxidation of 2-methylbenzoisothiazol-3-one. In the negative-ion mode experiments, anions corresponding to three reaction intermediates were detected and structurally characterized: 1-hydroxy-2-methyl-1,2-dihydro-3H-1λ4-benzo[d]isothiazol-3-one, 2-(methylcarbamoyl)benzenesulfinic acid, and 2-(dihydroxy(oxo)-λ6-sulfaneyl)-N-methylbenzamide. One of the final products, 2-(methylcarbamoyl)benzenesulfonic acid, was also detected and characterized. In positive-ion mode experiments, cations corresponding to the reactant, 2-methylbenzoisothiazol-3-one, as well as an intermediate reaction product and the two final reaction products, 2-methylbenzo[d]isothiazol-3(2H)-one 1-oxide, N-methylsaccharine, and 2-(methylcarbamoyl)benzenesulfonic acid, respectively, were detected and identified. This research substantially improved the understanding on the reaction intermediates formed during laser-induced UV/H2O2 advanced oxidation of 2-methylbenzoisothiazol-3-one, which facilitates the delineation of the reaction mechanisms occurring in these processes.

Tip-Induced Dissociation of Diethyl Ether on Si(001)─Influence of Molecular Structure on Final Reaction Products

Tip-Induced Dissociation of Diethyl Ether on Si(001)─Influence of Molecular Structure on Final Reaction Products

Synthesis in Nb + 2Si Mixtures Produced in Different Modes of Discrete Mechanical Activation

An experimental study is performed of the two-stage mechanochemical synthesis of niobium silicide. Theoretical estimates are made on the basis of the resulting macrokinetic model. The initial Nb + 2Si mixture is mechanically activated in the first stage, and the NbSi2 product is synthesized in the second. The effect the period of mechanical treatment has on the activated mixture’s morphology, temperature, and rate of burning is studied, along with the phase composition of the final reaction product. Kinetic constants are calculated that describe the dynamics of the two-stage mechanochemical synthesis of niobium silicide.

Mechanistic elucidation of shock response of bis(1,2,4-oxadiazole)bis(methylene) dinitrate (BOM): A ReaxFF molecular dynamics investigation

The use of trinitrotoluene (TNT) in industrial processes or military operations presents a significant threat to both the environment and human health due to its toxicity. Recently, it has been discovered that bis(1,2,4-oxadiazole)bis(methylene) dinitrate (BOM) can be an appropriate substitute of TNT due to its low sensitivity, high detonation velocity, and nearly insignificant impact on the surrounding environment. In this study, we utilize molecular dynamics (MD) simulations with a ReaxFF force field to investigate the thermomechanical and chemical response of BOM to shock loading. We simulate shocks using the Hugoniostat technique and observe shock-induced, volume-expanding exothermic reactions following a short induction time for strong enough insults. We analyze the shock behavior at various pressures to determine the conditions necessary to initiate detonation and evaluate the consequent events of detonation. A transition between unreacted and reacted materials has been observed and several detonation properties, such as detonation pressure and velocity, have been calculated at the Chapman–Jouguet state. We elucidate the reaction initiation pathways by predicting the intermediates and final products of the exothermic reaction. The quantity of intermediates and products has been studied for different applied shock loadings to understand the effect of loadings on chemical reactions. This study illustrates how reactive MD simulations can be used to characterize the physics and chemistry of high-energy materials subjected to shock loading, and we believe that our research can assist to shed light on numerous features of BOM that may establish it as a viable alternative to TNT.