Mechanism Of Thermolysis Research Articles

Structures of hexamethyl-[1,1′-biphenyl]-4,4′-diammonium salts

The crystal structures of nine hexamethyl-[1,1′-biphenyl]-4,4′-diammonium (HMB) salts are described: the iodide (2), triiodide (3), succinate (4), fumarate (5), tetravanadate (6), hydroterephthalate (7) and perylenetetracarboxylate (8), as well as pentamethyl-[1,1′-biphenyl]-4,4′-diammonium iodide (1) and the metal–organic framework sodium diacetylenedisalicylate–HMB (9). HMB carbonate (10) has been synthesized as an important intermediate for a promising anti-metal–organic framework (`anti-MOF'). All the described compounds are characterized by high solubility in water. The results suggest that, during crystallization, crystallohydrates are formed from water. Compounds 6 and 9 are characterized by the presence of a rigid framework; compound 6 has an open framework structure filled with water molecules. Synchronous thermal analyses of compounds 2, 4, 6, 7, 8 and 10 allowed the identification of similarities in the mechanisms of thermolysis. At about 80–180°C, the loss of crystallization water molecules occurs. Between 180 and 250°C, a methyl group (methyl cation) is split off from the quaternary ammonium salt to form tetramethylbenzidinium. In the case of the iodides and salts of organic acids, the second thermolysis product is the methyl ester of this acid (methyliodide, dimethyl carbonate), which easily evaporates. In the range 240–355°C, tetramethylbenzidinium evaporates without decomposition.

Facial Telangiectasia Treated with Narrow Band Intense Pulsed Light (IPL): A Case Report

Introduction: Facial telangiectasia (FT) are superficial cutaneous vessels that can result in noticeable aesthetical imperfections. They can vary in size, location, color, and pattern. Recently, a laser with broadband light was effective for vascular disease, in 2020 a retrospective study reported patients FT treated with IPL using 530-650nm and 900-1200nm show a better result after 4 weeks of interval treatment. Case Illustration: Male, 50 years old, complains of discoloration around the nose. The complaint began for the past 2 years and is more visible around the nose. Vital signs and physical examination within normal limits. Dermatological status in the nasal is found a dilated vessels around 0.5-1.0 mm, discoloration erythematous to violaceous vessels, and spider web shaped. The patient was diagnosed with facial telangiectasia C1 and treated using intense pulsed light 600nm after the first session showed significant results. Discussion: The recommendation for FT is using narrow-band laser, such as Intense Pulsed Light (IPL) that uses a flashlamp to emit polychromatic light across a broad wavelength spectrum of approximately 400–1400 nm that can penetrate the skin from superficial to deeper vessels, uses the mechanism of photo thermolysis by targeting chromophores within the vessels with minimum side effects. Conclusion: Adequate therapy using IPL gives a good result with one session of treatment in the right patient according to the grading of Facial Telangiectasia.

New Mechanistic Insights into the Primary Thermolysis Reactions of 1,3,4,6-Tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) from Predictive Local Coupled Cluster Calculations.

Theoretical studies of the decomposition mechanism of energetic materials quite often scrutinize only the primary thermolysis reactions. However, the secondary reactions are crucial, inter alia, for proper building of the combustion models and understanding the autocatalytic processes. In the present study, we applied predictive DLPNO-CCSD(T) calculations to elucidate the kinetics and decomposition mechanism of a novel promising energetic material, 1,3,4,6-tetranitrooctahydroimidazo [4,5-d] imidazole (BCHMX). We identified eight previously unknown BCHMX conformers, both cis and trans in accordance to the spatial position of the H atoms bonded to a carbon bridge. Among them, the relative enthalpies of cis isomers lie in the narrow range ∼10 kJ mol-1 rendering them thermally accessible in the course of decomposition. The radical N-NO2 bond cleavage via one of the novel conformers is the dominant primary decomposition channel of BCHMX with the kinetic parameters Ea = 168.4 kJ mol-1 and log(A, s-1) = 18.5. We also resolved several contradictory assumptions on the mechanism and key intermediates of BCHMX thermolysis. To get a deeper understanding of the decomposition mechanism, we examined a series of unimolecular and bimolecular secondary channels of BCHMX. Among the former reactions, the C-C bond unzipping followed by another radical elimination of a nitro group is the most energetically favorable pathway with an activation barrier ∼113 kJ mol-1. However, contrary to the literature assumptions, the bimolecular H atom abstraction from a pristine BCHMX molecule by a primary nitramine radical product, not the nitro one, followed by another NO2 radical elimination, is the most important bimolecular secondary thermolysis reaction of BCHMX at lower temperatures. The isokinetic temperature of the bimolecular and unimolecular secondary reactions is ∼620 K. Unimolecular reactions might be important in dilute solutions, where bimolecular reactions are suppressed. The secondary reactions considered in the present work might be pertinent in the case of related energetic nitramines (e.g., RDX, HMX, and CL-20).

Multi-aspect and comprehensive atomic insight: the whole process of thermolysis of HMX/Poly-NIMMO-based plastic bonded explosive.

Based on the reactive molecular dynamics, the whole process of thermolysis of HMX/Poly-NIMMO-based PBX was studied in detail at the micro scale, which provided a novel atomic insight into the thermolysis mechanism of HMX/Poly-NIMMO. Further, it was compared with the HMX single substance system to explore the influence of binder on thermolysis of HMX. According to the findings, the activation energy required by pyrolysis of HMX in the mixed system is much less than that required by the pure HMX system at both phases. From the point of view of reaction energy, poly-NIMMO promoted the thermolysis of HMX. Especially, the mechanism analysis confirmed this point. The nitro and hydroxyl groups detached from Poly-NIMMO will react with HMX, and the generated HNO2 will further accelerate the decomposition process of nitrogen heterocycles. In addition, the number of the final products H2O and H2 in the two-component system increased greatly, but the number of CO2 and N2 molecules had not changed much, and C clusters were formed in the system. The evolution trend of bond number further verified the above analysis. While the maximum cluster number does drop with increasing temperature at first, after a particular temperature threshold is reached, it remains unchanged. In a nutshell, poly-NIMMO will hasten HMX's thermolysis and reduce the system's stability when subjected to heat.

Are there differences in the adaptive profile of hair sheep and their crosses with wool breeds?

This study aimed to evaluate and compare the physiological performance of different genetic groups of sheep, by physiological variables and serum hormone levels, in a hot weather environment. Thirty sheep from five genetic groups were used: Santa Inês (SI), ½ Dorper + ½ Santa Inês (DO), ½ Ilê de France + ½ Santa Inês (IF), ½ Suffolk + ½ Santa Inês (SK), and ½ Texel + ½ Santa Inês (TX). The readings and records of physiological parameters (respiratory rate (RR), rectal temperature (RT), auricular cavity temperature (ACT), and surface temperature (ST)) were carried out at 7:00 am, 1:00pm, and 7:00pm, in 12 non-consecutive days. The collections of blood samples for hormone analysis (triiodothyronine (T3), thyroxine (T4), and cortisol (CORT)) is in four consecutive days. The environmental conditions of the experimental period caused a thermal discomfort in the sheep, but not a state of thermal stress. The thermolysis mechanisms, sensitive (ST and ACT) and latent (RR) processes, were enough to maintain their homeostasis (RT). The results showed that crossbred breeds presented a higher metabolism and were more efficient at dissipating heat through thermolysis than the SI breed. The crossbred breeds were efficient at dissipating heat through the elevation of body surface temperature and respiratory rate, mainly SK and TX, i.e., crossbred breeds, despite the wool cover, used thermoregulatory mechanisms that promoted lower variation of RT. The analysis of variance showed significant effects (P < 0.05) to the time factor in the responses of T4 and T3, and to the breed factor in the responses of CORT, T4, and T3. We did not observe interaction between the factors to any of the hormonal variables. Therefore, we can state that the effect of time was independent of breed and vice versa. Thyroid hormones presented lower blood concentration in the mornings (4.03 ± 0.82, T4; 65.08 ± 10.6, T3), increasing their concentration in the afternoon (4.60 ± 1.03, T4; 70.16 ± 14.17, T3). The thyroid hormones presented a normal circadian rhythm, with the exception of SK. Air temperature (AT) showed greater correlation with physiological variables than enthalpy (H) did, in the experimental conditions. However, H showed correlation with T4 and T3. The adaptive profile of the genetic groups under study are different, but the IF genetic group showed better performance under environmental conditions.

Reversible Photooxygenation of Anthracene Carboxyimide for Singlet Oxygen Formation: Mechanistic Study and Efficient Nitrite Detection.

Polycyclic aromatic endoperoxides are important sources of singlet oxygen (1O2) and their formation from polyacenes is well established. Anthracene carboxyimides are of particular interest as they exhibit excellent antitumor activity and possess unique photochemical properties. However, the photooxygenation of the synthetically versatile anthracene carboxyimide moiety has not been reported due to its competing [4+4] photodimerization reaction. Herein, we describe the reversible photo-oxidation of an anthracene carboxyimide. X-ray crystallographic analysis surprisingly revealed the formation of a racemic mixture of chiral hydroperoxides, rather than the expected endoperoxide. The photoproduct undergoes both photo- and thermolysis to form 1O2. Activation parameters were derived for the thermolysis and the mechanisms of photooxygenation and thermolysis are discussed. The anthracene carboxyimide also showed high selectivity and sensitivity for nitrite anions in acidic aqueous media and possessed stimuli-responsive behaviour.

Biochar synthesis from mineral and ash-rich waste biomass, part 2: characterization of biochar and co-pyrolysis mechanism for carbon sequestration

The increase in mineral and ash-rich waste biomass (MWB) generation in emerging economies poses critical environmental problems and bottlenecks the solid waste and wastewater treatment systems. Transforming these MWB such as sewage sludge from wastewater treatment (SSW) to biochar can be a sustainable method for their disposal and resource recovery. However, such biochar has limited applicability due to the relatively low organic content and possibly contaminated nature of SSW. This may be offset through combined pyrolysis with other MWB, which can also support municipal solid waste management. Studies on this MWB co-pyrolysis are lacking and have not yet seen successful long-term implementation. This work is the second part of authors’ research encompassing an analytical and lab-scale investigation of biochar production from MWB through pyrolysis for the case of Chennai city, India. Here, the physicochemical properties of biochar derived from lab-scale co-pyrolysis of SSW with other MWB such as anaerobic digestate from waste to energy plants of food, kitchen or market waste fermentation, and banana peduncles (BP) collected from vegetable markets and their thermolysis mechanism are comprehensively investigated for purpose of carbon sequestration. Also, a novel preliminary investigation of the effect of sample weight (scaling effect) on the analytical pyrolysis of biomass (BP as model substrate) is undertaken to elucidate its impact on the heat of pyrolysis and carbon distribution in resultant biochar. The maximum carbon sequestration potential of the derived biochar types is 0.22 kg CO2 kg−1 biomass. The co-pyrolysis of MWB is exothermic and governed by the synergetic effects of the components in blends with emission profiles following the order CO2 > CH4 > CO > NH3. Co-pyrolysis reduced the heavy metal enrichment in SSW biochar. The derived biochars can be an immediate source of N, P and S in nutrient-deficient acidic soils. The biochar has only up to 4-ring polyaromatic compounds and a residence time longer than 1 h at 500 °C is necessary to improve carbonization. The heat released during analytical pyrolysis of the model biomass and distribution of carbon in the resultant biochar are significantly influenced by scaling effects, drawing attention to the need for a more detailed scaling investigation of biomass pyrolysis.

Thermal behavior and thermolysis mechanisms of graphene oxide-intercalated energetic complexes of carbohydrazide

Graphene-based carbohydrazide coordination polymers are beneficial for improving solid propellants’ energy level and safety, so the study of their thermal decomposition mechanism is promoted for their wide application. In this paper, graphene oxide (GO) intercalated transition metal (Cu2+, Co2+, and Ni2+) complexes of carbohydrazide (CHZ) have been evaluated by using DSC/TGA apparatus and the TG-FTIR technique. Both isoconversional and combined kinetic methods were employed to calculate the kinetic parameters. The components inside GOCHZ-M would react with each other to cause a large mass loss rate and lead to a larger heat-releasing value than pure GO. The types of metal ions could affect their reaction model. Compared with GO, G-CHZ-Co shows a two-sided effect (stabilization and catalytic) on its decomposition. For G-CHZ-Co, the reaction model of each peak is close to the random 2d nucleation and nucleus growth model.

Multi-aspect simulation insight on thermolysis mechanism and interaction of NTO/HMX-based plastic-bonded explosives: a new conception of the mixed explosive model.

Reactive molecular dynamics (RMDs) calculations were used to determine, for the first time, the process of thermolysis of the mixed explosives, including 3-nitro-1,2,4-triazol-5-one (NTO) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoline (HMX). Significantly, this is the first time that a layered model for mixed explosives, which is an extreme innovation of mixed explosive models was adopted. It is shown that a large amount of NO2 in the HMX and OH groups generated by the decomposition of HNO2 has a favorable effect on the thermolysis of NTO, as further validated by a reduction in the activation energy of NTO/HMX. The amount of H2O and N2 in the resulting products increased significantly, but the amount of NH3 changed slightly. The analysis results correspond to the change in chemical bonds. Whenever there is an increase in temperature, the time for the maximum number of clusters to appear is shortened accordingly. In addition, the acidity of NTO has been considered. An independent gradient model based on Hirshfeld partition (IGMH) and atoms in molecule (AIM) analysis of NTO/HMX was implemented. The relatively strong hydrogen bonds indicate that HMX can inhibit the acidity of NTO and is beneficial for the wide application of NTO/HMX-based plastic-bonded explosives (PBXs).

Suckling behavior, performance, and Kleiber index in calves of different genetic groups under shaded and unshaded environments.

The aim of this study was to evaluate the effect of heat stress on the suckling behavior and performance of Nelore (NE), ½ Nelore × ½ Angus (NA), and ½ Nelore × ½ Pantaneiro (NP) crossbred calves, in environments shaded or unshaded, using the temperature-humidity index (THI) and Kleiber index (KI) equations. Twenty-five animals were evaluated, from 30days of age distributed as follows: 9 NE, 8 NA, and 8 NP calves, from 7:00 A.M. to 5:00 P.M., under shaded and unshaded environments. Data were collected on number of suckling episodes per day (NS), mean suckling duration (MSD), surface body temperature (SBT), THI, weight gain, and KI. THI showed difference (P < 0.05) between environments, being lower in the shaded area. NA cattle had higher SBT (33.00 ± 2.31), differing (P < 0.05) from NE (31.71 ± 1.65) and NP (31.38 ± 1.99), and lower (P < 0.05) suckling activity, suggesting reduced thermal comfort. However, their weight gain and KI were higher, differing (P < 0.05) from the other genetic groups. NE and NP cattle did not differ (P > 0.05) in weight gain and KI. Thus, the results suggest that NA calves, despite the greater thermal discomfort, used thermolysis mechanisms to maintain higher weight gain and feed efficiency (KI) than the other groups. NP showed greater thermal adaptability, in addition to weight gain and KI similar to NE cattle.

ReaxFF/lg molecular dynamics study on thermolysis mechanism of NTO/HTPB plastic bonded explosive

3-nitro-1,2,4-triazol-5-one (NTO), a very promising high-energy density energy material, has been extensively used in plastic bonded explosive (PBX). However, the potential mechanism of thermal decomposition of PBX systems composed of NTO and the ordinary binder Hydroxyl-terminated polybutadiene (HTPB) is not yet understood. Therefore, in this paper, the mechanism of thermal decomposition of the NTO/HTPB hybrid system was investigated at five temperatures in the range of 2500–3500 K using a reactive molecular dynamics approach (ReaxFF/lg). The results show that the intermolecular reaction paths of NTO in the hybrid system are still reactions such as dehydrogenation and denitrification reaction, etc. The incorporation of HTPB introduces a large amount of H and OH into the hybrid system, and these radicals react with NTO and the decomposition products of NTO. For example, A large amount of chemical reaction with HNO2 promote the thermal decomposition of NTO. The number of hydrogen transfer reactions between NTO molecules is all reduced to different degrees in the mixed system. The comparison of the number of products is shown that the content of H2O increases greatly and the curve reaches the peak in a shorter time, and the decomposition reaction rate of the system is faster, while the content of N2 decreases substantially. The changes of clusters at five temperatures were analyzed, and the maximum number of clusters increased with the increase of temperature in a certain temperature range, and the high temperature played a certain degree of inhibition on the formation of clusters. The ratio of the number of H, O and N atoms to C atoms in the clusters at each temperature was O/C > H/C > N/C. In addition, The natural logarithm of pre-exponential factor (lnA) of the initial and intermediate decomposition stages of the hybrid system were 24.25 and 28.10, respectively, and the activation energies (Ea) were 68.3786 KJ/mol and 59.6588 KJ/mol, respectively. Comparing the activation energy of NTO-only monoplasmic systems, both were reduced to varying degrees. Therefore, the incorporation of HTPB would contribute to the thermal decomposition of NTO and reduce the insensitivity of the system to thermal stimuli.

Quantum chemical investigation of the 1‐methyl‐ and 1‐neopentyl‐2‐methoxydiazene‐1‐oxides thermal decomposition mechanisms

AbstractThe thermolysis mechanism of two members of the 2‐alkoxydiazene‐1‐oxide class of compounds – 1‐methyl‐2‐methoxydiazene‐1‐oxide (1) and 2‐methoxy‐1‐neopentyldiazene‐1‐oxide (2) was studied by quantum chemical methods. Calculations were performed using coupled clusters method at the CCSD and CCSD(T) level using the aug‐cc‐pVDZ and aug‐cc‐pVTZ basis sets. It was shown that the mechanism of thermal decomposition of compounds 1 and 2 is similar and occurs via two competing channels – via homolytic N‐OCH3 bond cleavage and via intramolecular nucleophilic substitution at the methoxyl carbon atom. The calculated values of the activation enthalpies for both compounds are close (ΔНа‡ is in the range of 200–210 kJ/mol) and practically coincide with the experimental activation energies obtained earlier. The main thermolysis products predicted theoretically correspond to the thermal decomposition products of compounds 1 and 2 that have been observed experimentally.

Pyrolysis process and mechanism for calcium elimination of used lubricating oil

The present work is mainly focused on the mechanism for used lubricating oils (ULOs) elimination of calcium using calcium dodecyl benzenesulfonate (Ca-DDBS) as a model compound for the first time. Intermediate and final products formed during thermal degradation in air and N2 atmosphere were determined by combining TG-DSC, XRD, TG-MS, and TG-IR techniques. Bond dissociation energies (BDEs) of Ca-DDBS were calculated systematically using the Gaussian 16 program, and primary, secondary decomposition intermediates and transition states of decomposition reactions have been optimized using the B3LYP method. More importantly, the thermolysis mechanism of Ca-DDBS was determined by combining quantum-chemical calculations and experimental results. Results disclosed that the thermolysis process of Ca-DDBS involves a cascade process with multiple steps, each having its individual characteristics. The model compound first initiates thermolysis through the homolytic cleavage of the C-S bond. Through the pyrolysis mechanism, it is speculated that the solid product of thermal decomposition is a mixture of CaSO4, CaSO3, and CaO, owing to the interconversion of decomposition products, which is also confirmed by XRD analysis. Finally, the decomposition process of the model compound in base oil was similar to that of monomers in air. Significantly, this study provides important theoretical support for the resource utilization of ULOs.

Mechanism of thermolysis of hydrazino-dinitroethylenes

Promising energetic materials – 1,1-diamino-2,2-dinitroethylene (DADNE) derivatives, in which one or two hydrogen atoms are replaced by –NH2 group, were studied by quantum-chemical calculations using hybrid functional PBE0 with cc-pVDZ basis set and coupled cluster method CCSD with aug-cc-pVDZ basis set. A number of thermolysis primary steps were investigated and it was shown that the addition of –NH2 group leads to a change in the mechanism of rate-limiting step. The main channels for DADNE are transfer of hydrogen to carbon and various transformations of aci-forms; for hydrazino derivatives hydrogen transfer to carbon is the only main channel and the following transformations are NO2 radical separation and transfer of another one hydrogen atom to an oxygen and elimination of HNO2 molecule.

Chemical interplay between components in overall thermolysis of CL-20/N2O revealed by ReaxFF molecular dynamics simulations

Understanding of the interplay reactions between components in CL-20 bicomponent crystals is fundamental for synthesis and applications of new CL-20 cocrystals and host-guest materials. This paper reports the thermal decomposition of CL-20/N2O host-guest crystal investigated using ReaxFF MD simulations under both isothermal and adiabatic conditions. The isothermal thermolysis simulation at low temperature of 800 ​K and adiabatic decomposition simulation initiated at 800 ​K were performed to reveal as much as the real and overall scenario of CL-20/N2O thermolysis. Two reference systems of ε-CL-20 and CL-20/H2O were employed for clear depiction of reaction mechanism. Permitted by VARxMD for reaction details and facilitated by the three-stage classification, the overall scenario of CL-20/N2O thermolysis and deep insight about the interplay reaction details between host CL-20 and guest N2O were obtained. The dominating of host CL-20 decomposition during entire thermolysis of CL-20/N2O is similar with that of CL-20/HMX and CL-20/TNT. However, the branching ratios of major reaction pathways of CL-20 initial decomposition were altered. The decomposition kinetics in initial thermolysis of CL-20/N2O was found significantly slowed when compared with ε-CL-20, which is caused by the guest N2O molecules that capture the NO2 intermediates generated from host CL-20 decomposition and prevent NO2 from their active participation in further decomposition of the system. It should be noted that the early formation of N2 from guest N2O in CL-20/N2O decomposition accelerates self-heating at certain extent and provides extra oxidative NO3, which slightly compensates to the slowed kinetics in the initial stage. The acceleration effect of guest oxidant N2O on CL-20/N2O decomposition will sustain through the ​oxygen migration of guest N2O in later secondary reactions to form more NOx than that of CL-20/H2O, consequently reducing the reaction zone of CL-20/N2O thermolysis. What was obtained in this work demonstrates that ReaxFF MD simulations combined with the analysis scheme of three-stage classification can facilitate the depiction of thermolysis mechanism of CL-20 bicomponent crystals and be useful in searching for leading candidates of guest molecules for CL-20 host-guest materials.

Radicals and molecular products from the gas-phase pyrolysis of lignin model compounds: Coniferyl alcohol, theory and experiment

Coniferyl alcohol (CFA) is one of lignin’s main building blocks and a relevant model compound. Two aspects of CFA pyrolysis are studied in the current work to gain insight into the molecular mechanism of lignin thermolysis: (i) the nature of intermediate radicals generated from vacuum pyrolysis of CFA, and (ii) the product distribution from pyrolysis of CFA dispersed into the gas phase. Low temperature matrix isolation electron paramagnetic resonance (LTMI-EPR) spectroscopy is employed to investigate the intermediate radicals associated with gas phase low-pressure pyrolysis of CFA. An anisotropic EPR spectrum of radicals trapped at liquid nitrogen temperature was registered throughout the studied temperature range (400–700 °C) characterized by high g-value (≤ 2.0100), and broad EPR line-width (~13.5–13.0 G) prescribed to a mixture of O-centered radicals produced from cleavage of O−CH3 and O−H terminal bonds. Thermal annealing of frozen radicals suggested a major contribution of methylperoxyl (CH3O2) radicals produced by the liberated CH3 and trace amounts of oxygen. The pyrolysis of CFA, for the first time, was conducted in a dispersed, gas-phase conditions to minimize the heterogeneous secondary reactions mediated by particle surfaces typical for condensed-phase pyrolysis in conventional reactors. Several unique products including polyhydroxylated derivatives of mandelic acid and some carboxylic compounds were identified in addition to those normally produced during the conventional pyrolysis - coniferyl aldehyde, vanillin (and its oxidized form homovanilic acid), eugenol and its isomers. A comprehensive analysis of product formation mechanisms, particularly the pathways for generating abundant hydroxylated compounds is performed and the role of trace oxygen is studied at the wB97XD and M06-2X hybrid density functional theory levels.

Mechanism of thermolysis of hydroxylamino-dinitroethylenes

Mechanism of thermolysis of hydroxylamino-dinitroethylenes

Initial Steps and Thermochemistry of Unimolecular Decomposition of Oxadiazole Energetic Materials: Quantum Chemistry Modeling.

In order to resolve the existing discrepancies in the mechanism and key intermediates of oxadiazole thermolysis, the initial decomposition pathways of oxadiazoles have been studied comprehensively using the M062X method for optimization and CBS-QB3 and DLPNO-CCSD(T) methods for energies. The transformation from the furoxan ring to nitro group was suggested as a potential decay channel of furoxan compounds. Results of thermochemistry calculations showed that the preferred decomposition reaction of oxadiazoles is the ring-opening through the cleavage of the O-C or O-N bond. The introduction of the nitro group has little effect on the preferential path of oxadiazole thermal decomposition, but a great impact on the energy barrier. The lowest energy barrier and bond dissociation energy of NO2 loss of azoles were comprehensively studied based on the quantum chemistry calculations. The initial decay steps of 3,4-dinitrofurazanfuroxan and benzotrifuroxan were also studied to give insights into the mechanism of primary stages of thermal decomposition of oxadiazoles.

Mechanistic study of the gas-phase chemistry during the spray deposition of Zn(O,S) films by mass spectrometry

The mass spectrometer, is a powerful tool to identify species and investigate reactions in the gas phase. In this work, the mechanism of aerosol assisted chemical vapor deposition (AACVD) of Zn(O,S) films prepared from H2S and zinc acetylacetonate (Zn(acac)2) precursor solutions is elucidated by mass spectrometry. The thermochemical behavior of Zn(acac)2 is investigated by characterizing the influence of the solvent (H2O or ethanol), the pH value of the precursor solution and the effect of the reactant H2S, and by tracking gaseous intermediate products using mass spectrometry. Based on these results, a proton-promoted thermolysis mechanism for the AACVD Zn(O,S) film formation is then proposed, which is initiated by the hydrolysis with H2O as the first stage, followed either by the rearrangement with an intramolecular proton or by the reaction with an extramolecular proton to produce ZnO or Zn(O,S). A real time mass tracking of the AACVD process reveals that only an adequate amount of H2S promotes the chemical gas-phase decomposition and sulfurization process, while an excess of H2S depletes the gaseous Zn(acac)2 concentration and consequently reduces the film growth rate. The knowledge of the thermal decomposition process helps to optimize synthesis conditions and to adjust film properties to meet the requirement of the application in chalcopyrite or kesterite thin film solar cells.

Alternative mechanism of thermolysis of diaminodinitroethylene (FOX-7)

Alternative mechanism of thermolysis of diaminodinitroethylene (FOX-7)