Main Decomposition Products Research Articles

Characteristics of an Overstressed Discharge of Nanosecond Duration between Electrodes of Chalcopyrite in High Pressure Nitrogen

The electrical and optical characteristics of the overstressed nanosecond discharge in nitrogen at a pressure of 202 kPa, which was ignited between electrodes from chalcopyrite (CuInSe2 ), are presented. Upon sputtering of chalcopyrite electrodes, CuInSe2 compound vapors have been introduced into the discharge plasma. Chalcopyrite molecules were partially destroyed in the plasma and partially deposited in the form of thin films on a quartz substrate, which was placed near the system of discharge electrodes. The main decomposition products of a chalcopyrite molecule in an overstressed nanosecond discharge were found, which were in excited and ionized states and which, in the plasma emission spectra, were mainly represented by atoms and singly charged copper and indium ions. The spectral lines of copper and indium are proposed, which can be used to control the deposition of thin films of chalcopyrite in real time. On quartz substrates, gas-discharge method was used to synthesize thin films based on the CuInSe2 compound, which effectively absorbed light in a wide spectral range (200-800 nm), which opens up prospects for their use in photovoltaic devices.

A series of guanidine salts of 3,6-bis-nitroguanyl-1,2,4,5-tetrazine: green nitrogen-rich gas-generating agent.

Nitrogen-rich energetic materials (EMs) have been widely studied because of their high thermal stability, insensitivity, excellent detonation performance and non-toxic characteristics. In particular, these compounds are well applied as gas-generating agents (GGAs). As a nitrogen-rich heterocyclic framework, 1,2,4,5-tetrazine derivatives have shown great potential in the design of GGAs. The guanidine salts of 3,6-bis-nitroguanyl-1,2,4,5-tetrazine (DNGTz), guanidine (G2DNGTz) (1), aminoguanidine (AG2DNGTz) (2), diaminoguanidine (DAG2DNGTz) (3), and triaminoguanidine (TAG2DNGTz) (4) have been synthesized and characterized by elemental analysis and FT-IR. The crystal structures of 1 and 2 were obtained by X-ray single crystal diffraction. Crystal analysis shows that 1 and 2 arrange through zigzag-chain-like assembly and face-to-face geometries, which is helpful in decreasing mechanical sensitivity. The thermal stability and thermal decomposition kinetics of these four salts were studied by Differential Scanning Calorimetry (DSC). Furthermore, the thermogravimetry-Fourier transform infrared-mass spectrometry (TG-FTIR-MS) analysis of thermal decomposition products reveals that the main decomposition gaseous products are H2O, N2O, CO2, NO, N2 and NH3. Then, the cytotoxicity of the four salts was tested by MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) method, and it was found that salts 1–4 show slight cytotoxicity in mouse fibroblasts (L929), at a concentration of 0.125 mg ml−1. The insensitivity, low toxicity, and production of clean gases without solid residue after burning of salt 1 indicate that it can be used as a potential green energetic material for GGAs.

Thermal stability and material compatibility for hexamethyldisiloxane as the working fluids of organic Rankine cycle

The organic Rankine cycle (ORC) is one of the most suitable methods to generate electricity for renewable energy and industrial waste heat recovery systems. High temperature ORCs have recently attracted much interest because of the improved theoretical thermal efficiency. For high temperature ORCs, the working fluids need high critical temperature, low flammability and good thermal stability. Siloxanes are considered as the promising working fluids for high temperature ORCs in previous studies because of their high critical temperature, low flammability and environmental friendliness. The thermal stability and material compatibility of working fluid is the primary limitation for the working fluid selection at high temperatures. However, the results about thermal stability and material compatibility of siloxanes are scarce in previous studies. In this paper, the thermal stability and material compatibility of siloxanes were studied with hexamethyldisiloxane (MM) as a representative fluid. A test system and an experimental method were designed to identify the compositions of decomposition products. The masses of liquid samples were measured before and after tests to confirm the mass fractions of gaseous and liquid compositions in decomposition products. Liquid decomposition products, such as octamethyltrisiloxane (MDM) and tetramethylsilane, were found to be the main decomposition products of MM. The possible decomposition paths of MM were analyzed by the results of decomposition product composition analysis. The decomposition ratios of MM at 220, 240, 260, 280 and 300°C were measured after decomposition for 24 h. The decomposition could be detected at 240°C, which was lower than the critical temperature of MM. Thus, the thermal stability of MM should be emphasized for supercritical ORCs if the decomposition of MM is unacceptable in ORC systems. The air was confirmed to have big effects on MM decomposition and could change the reaction paths of MM decomposition. Thus, air dissolved in the liquid working fluid should be removed before filling the working fluid into ORC systems. The material compatibility of MM with metal samples was measured experimentally. 304 stainless steel and copper were chosen as test metal materials and the metal samples were processed into the shapes for the tensile experiments. The experimental temperature was 220°C, which was considered as a thermal stable temperature for MM. The material compatibility experimental periods in this study were 10 days, which were long enough in previous studies. The experimental results showed that the mass and hardness relative changes in both metal samples were very small and could be negligible. However, the tensile strength changes in the copper samples were obviously bigger than those in 304 stainless steel samples. Thus, 304 stainless steel has better compatibility with MM than copper as the metal material in systems at 220°C. The material compatibility of n-pentane with metal samples at 220°C was also measured using the same test system and method to be a comparison. The results showed that the tensile strength changes in metal samples with n-pentane were much bigger than those with MM. Thus, MM exhibited better compatibility with metal materials than n-pentane at 220°C as ORC working fluids.

Thermal decomposition properties of fluoronitriles-N2 gas mixture as alternative gas for SF6

We explored the thermal decomposition properties of Fluoronitriles-N2 (C4F7N-N2) gas mixture using as SF6 substitute gas in GIE. The yield of main decomposition products of 10 %C4F7N-90 %N2 gas mixture under different overheating temperature and gas pressure conditions were detected and analyzed. We found that thermal decomposition of C4F7N-N2 mainly produces C3F6, C3F8, CF4, CF3CN, (CN)2 and COF2. C3F6 is the first detected by-product at 350℃, while CF4 and C3F8 were generated at temperatures higher than 500℃. The yield and formation rate of C3F6, (CN)2 increases with temperatures lower than 450℃ then decreases at higher temperatures, while the generation of C3F8, CF4, CF3CN and COF2 has positive correlation with temperature. C4F7N-N2 gas mixture has great thermal stability at high pressure. The increase of gas pressure could effectively reduce the decomposition of C4F7N, which ensures the insulation strength of gas mixture.

Nanometer Ammonium Perchlorate and Ammonium Nitrate Prepared with 2D Network Structure via Rapid Freezing Technology.

Nanometer (nano) ammonium perchlorate (AP) and ammonium nitrate (AN) were prepared with 2D network structures by the ultra-low temperature spray method. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis/infrared spectrometry (TG-IR) were employed to probe the micron structure, crystal phase, and thermal decomposition of nano AP and nano AN. SEM images revealed that the sizes of nano AP and AN were in the nanometer scale (<100 nm) in one dimension. XRD patterns showed that the crystal phases of nano AP and AN were in accordance with those of raw AP and raw AN, respectively. DSC traces indicated that the thermal decomposition process of AP depended on its particle size, while the thermolysis of AN was independent of the particle size of AN. TG-IR analyses illustrated that the decomposition products of nano AP were NO2, N2O, HCl and H2O, with a small amount of NOCl, and the main decomposition products of nano AN were N2O and H2O, with a small amount of NH3. The results of mechanical sensitivity tests indicated that nano AP was more sensitive than raw AP and both nano AN and raw AN were very insensitive to impact and friction stimuli.

Thermal Decomposition Mechanism of Nitroglycerin by ReaxFF Reactive Molecular Dynamics Simulations

ABSTRACT The decomposition processes of nitroglycerin (NG) at various temperatures (2500, 2750, 3000, 3250 and 3500 K) are simulated by the reactive molecular dynamics simulations with ReaxFF-lg. The initial decomposition pathway of NG, the evolution of the main products and the reaction kinetic parameters for the different stages are analyzed. The results show that the main initial decomposition mechanisms of NG are O-NO2 bond dissociation and the hydrogen capture reaction of NO2. The main products of NG thermal decomposition are NO2, NO, HNO, CO2, N2, and H2O, while CO2, N2, and H2O are the final products. As the temperature increases, the processes of O-NO2 bond dissociation and the hydrogen capture reaction of NO2 accelerate, resulting in accelerated decomposition of NG. The reaction kinetic parameters are calculated for three different reaction stages. The activation energy and the pre-exponential factor obtained in the initial decomposition stage are 69.58 kcal mol−1 and 32.53 s−1. The activation energy and the pre-exponential factor obtained in the intermediate decomposition stage are 111.78 kcal mol−1 and 29.12 s−1. At 3250 K, the rate constants of N2 and CO2 reach maximum while the rate constant of H2O increases continuously with increasing temperature. Accordingly, the mechanism of initial thermal decomposition of NG under the high temperatures is proposed detailedly.

Diagnosing the bioactive compounds in Iraqi garlic (Allium sativum) by GC-MS and HPLC

This study including diagnosing the bioactive compounds releasing from an action of alliinase with alliin in the Iraqi garlic by GC-MS and HPLC technique. The bioactive compounds resulting from the garlic by GC-MS were heptane,2,4-dimethyl,cyclopropyl bromide, octane,5-ethyl-2-methyl, diallyl disulphide,trisulfide,di-2-propenyl,tetrasulfide,di-2-propenyl,3-vinyl-1,2-dithiacyclohex-4-ene,3-vinyl-1,2 dithiacyclo hex-5-ene and eicosane at different percentages through periods of time ranged between 5-30 minutes when following its activity by GC-MS. The best time for an activity was found at 30 minutes. Diallyl disulphide was the highest percent of 51.92% and tetrasulfide, di-2-propenyl at percent of 19.49%, as well as standard allicin and prepared allicin that is the main product of the enzymatic decomposition was diagnosed by HPLC technique of Iraqi garlic at the same periods with high concentration 39.244%.

Electrospinning Preparation of NC/GAP/Submicron-HNS Energetic Composite Fiber and its Properties.

In this work, novel three-dimensional nitrocellulose/glycidyl azide polymer/submicron-2,2′, 4,4′, 6,6′-hexanitro-stilbene (NC/GAP/submicron-HNS) composite fibers were prepared by the electrospinning method. As-prepared NC/GAP/submicron-HNS fibers were continuous and possessed a large specific surface area. The structure of fibers was characterized by energy-dispersive X-ray, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy (IR). The results showed that HNS submicron particles were uniformly loaded on the surface of NC/GAP fibers and incorporated with it. Thermal analyses were performed. Such NC/GAP/submicron-HNS fibers showed a low activation energy of 204 kJ·mol–1 and large rate constant of 1.74 s–1, indicating high reactivity and fast reaction rate. The result of TG-IR analysis revealed that the main decomposition products of NC/GAP/submicron-HNS were CO2, CO, H2O, N2O, few NO, and fragments such as −CH2O– and −CH–, which were low-signature gases. An evaluation on the energy performance disclosed that the standard specific impulse (Isp) of NC/GAP/submicron-HNS fibers was 2032 N·s·kg–1, which was higher than 2014 N·s·kg–1 of NC/GAP. This meant the addition of HNS submicron particles to the NC/GAP fiber was favorable to the improvement of energy performance. Additionally, introduction of submicron-HNS made the energetic fibers becoming very insensitive to impact action. It was expected that as-prepared NC/GAP/submicron-HNS membranes were promising materials applied for solid rocket propellant.

Decomposition behavior and mechanism of epoxy resin from waste integrated circuits under supercritical water condition.

Integrated circuits (IC), a kind of widely used electronic component, is paid great attention to recover valuable materials and remove hazardous materials after being discarded. However, refractory epoxy resin as packaging material is tightly covered on waste IC. It is difficult to remove epoxy resin and recover metals environmentally friendly by traditional methods. In this study, decomposition of epoxy resin from waste IC in supercritical water (SCW) was investigated. The epoxy resin could be efficiently decomposed under SCW condition. High temperature and long operation time of SCW treatment was positive for decomposition efficiency. The main decomposition intermediates and products were phenol and its derivatives. The decomposition mechanism of epoxy resin in supercritical water belongs to complex free radical reaction. Seven proposed pathways for the formation of key intermediates were investigated, with the kinetic and thermodynamic parameters obtained by density functional theory calculations. The analyzation provided assistance in the optimization of SCW treatment. Epoxy resin conversion rate could reach 95.51% under the condition of 500 ℃, 23 MPa and 90 min, then metals could be easily separated and recovered from solid residue. Thus, SCW treatment presents an efficient and green process for the recycle of waste IC.

Reactive molecular dynamics simulation of the thermal decomposition mechanisms of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11]dodecane (TEX)

4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11]dodecane (TEX) is a new type of cage-structured explosive with good explosive performance, good thermal stability and low production cost. TEX has high application value in casting and press-packed explosives. A TEX supercell model was constructed using the reaction molecular dynamics (MD) method. Based on the ReaxFF/lg reactive force field, an MD simulation of the thermal decomposition process of TEX explosives at different temperatures (2000 K, 2500 K, 3000 K, and 3500 K) was performed. The calculations were carried out to analyze the initial reaction pathways, small molecule products, destruction of the TEX cage structure and formation of clusters. The structural characteristics and elemental composition of the clusters were studied, and the reaction kinetic parameters of TEX at different reaction stages were calculated. During the thermal decomposition process, the NNO2 bond in the TEX molecular structure breaks first, then the adjacent CO bond is stretched, and finally the cage structure is gradually destroyed. The main decomposition products are small molecules (NO2, NO, H2O, CO2, N2, H2, HNO2 and HNO) and clusters (C12H12N6O12 and C18H13N7O14). The effect of temperature on the clusters is twofold. On the one hand, when the temperature is low, the cage structure of the TEX molecule is difficult to destroy and is not conducive to cluster growth. On the other hand, when the temperature is high, clusters are generated in the TEX supercell system but are subsequently rapidly decomposed. Throughout the whole process, H, N and O will gradually escape from the cluster, but O is more confined to the cluster, which will affect the subsequent autoxidation process of TEX to some extent.

The Destruction of Carbon Tetrachloride Dissolved in Water in a Dielectric Barrier Discharge in Oxygen

The kinetics of decomposition of tetrachloromethane (TCM) in its aqueous solutions and the kinetics of decomposition products formation was investigated under the action of DBD at atmospheric pressure in oxygen in a falling-flow reactor. The range of initial concentrations of TCM was 25–325 μmol/l, the discharge power—2–11 W and O2 flow rates—1–3 cm3/s. It is shown that the kinetics of the TCM decomposition can be described by the equation of pseudo-first kinetic order. The rate constant depended weakly on the discharge parameters and was ~ 5 s−1. The energy efficiency of the decomposition, depending on the parameters, was 0.1–1.3 molecules per 100 eV. When the residence time of the solution with the discharge zone is more than 1 s, it is possible to achieve almost 100% degree of TCM decomposition. It is shown that the main products of the TCM decomposition in the liquid phase are aldehydes and Cl− ions, and in the gas phase—the molecules CO and CO2. The results for energy efficiency are compared with the results obtained in other AOP’s processes (Fenton process, photocatalytic process, the radiation process by the action of high-energy electron flux). It is shown that the action of the DBD is more effective than the action of the above processes.

SHOCK-TUBE EXPERIMENTAL STUDY AND KINETIC MODELING OF JP-10 PYROLYSIS

Pyrolysis of JP-10 hydrocarbon fuel was studied in a single-pulse shock tube over temperature range from 1150 K to 1300 K. The main decomposition products were identified by gas chromatography as ethylene, acetylene, propylene, $n$-butene, 1,3-butadiene, cyclopentadiene, cyclopentene, benzene, toluene, and a small amount of methane, ethane, xylene and 1-methylcyclopentene. By summation of all product concentrations in each run, the rate coefficient of JP-10 pyrolysis was experimentally determined. Comparative rate measurements were used to eliminate the effects of shock's non-ideality and boundary layer. A small amount of the internal standard compound, whose rate expression for decomposition is well established, was added in the test gas mixtures, and the reaction temperatures were determined according to the decomposition extents of the internal standard compound under the same experimental conditions in a shock tube. The reaction temperatures determined from the decomposition extents of the internal standard compound are usually less than those at the region 5 behind reflected shock calculated by shock velocity measurements. The temperatures determined by two methods are consistent between 1150 K and 1300 K, the difference is within 20 K, and the difference increases with the temperature increase. Based on the experimental study, kinetic modeling of JP-10 pyrolysis was carried out according to San Diego Mechanism. The yields of three main products, ethylene, acetylene and 1,3-butadiene, have a good agreement between the experimental and the simulation results,while the experimental results of cyclopentene yield are much higher than simulation,indicating that both fully and partially ring-opening reactions in JP-10 pyrolysis are important decomposition reaction pathways.

Study on the thermal decomposition mechanism of graphene oxide functionalized with triaminoguanidine (GO-TAG) by molecular reactive dynamics and experiments.

Graphene oxide (GO) has a catalytic effect on the thermal decomposition of energetic materials above the melting point. To further enhance the catalytic activity of GO, it has been functionalized with the high nitrogen ligand triaminoguanidine (TAG). However, theoretical studies on the reactivity of functionalized GO (e.g., GO-TAG) have not been carried out. Therefore, the thermal decomposition of each TAG, GO and GO-TAG is studied by molecular dynamic simulations using a reactive force-field (ReaxFF) with experimental verification, and the results are reported herein. The results show that the GO nanolayer has a tendency to aggregate into a large carbon cluster during its degradation. The main decomposition products of TAG are NH3, N2 and H2. For GO-TAG, the main decomposition products are H2O, NH3, N2 and H2. GO has a significant acceleration effect on the decomposition process of TAG by decreasing the decomposition temperature of TAG. This phenomenon is in agreement with the experimental results. The initial decomposition of TAG is mainly caused by hydrogen transfer in the molecule. The edge carbon atoms of GO promote the decomposition of TAG molecules and reduce the decomposition activation energy of TAG by 15.4 kJ mol−1. Therefore, TAG will quickly decompose due to the catalytic effect of GO. This process produces a “new” GO that catalyzes the decomposition of components such as TAG. At the same time, many free radicals (HN2, H2N and free H) are generated during the decomposition of TAG to catalyze the decomposition of other components, which in turn, enhance the catalytic capability of GO.

Characteristics and properties of nitrocellulose/glycidyl azide polymer/2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane nanocomposites synthesized using a sol–gel supercritical method

Nitrocellulose/glycidyl azide polymer/2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane nanocomposites, in which 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane nanoparticles uniformly embedded in nitrocellulose/glycidyl azide polymer matrix, were synthesized using a sol–gel supercritical method. The micron morphology, crystal phase, molecular structure, specific surface area, and surface elements were characterized using scanning electron microscopy, X-ray diffractometry, infrared, Brunauer–Emmett–Teller, and X-ray photoelectron spectroscopy analyses, respectively. Thermal analyses were performed, and the kinetic and thermodynamic parameters, such as activation energy, per-exponent factor, rate constant, activation heat, activation free energy, and activation entropy, were calculated. The decomposition products of the nitrocellulose/glycidyl azide polymer matrix and nitrocellulose/glycidyl azide polymer/2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane were also investigated by differential scanning calorimetry–infrared analysis. The result indicated that the main decomposition product of nitrocellulose/glycidyl azide polymer is carbon dioxide and the –N3 group in glycidyl azide polymer decomposed to nitrogen without being detected by infrared spectrometer; the main decomposition products of nitrocellulose/glycidyl azide polymer/2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane are carbon dioxide, nitrous oxide, and water, and few carbon monoxide, methane, and nitrogen oxide are also detected. Energy performances of nitrocellulose/glycidyl azide polymer matrix and nitrocellulose/glycidyl azide polymer/2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane nanocomposites were evaluated, that is, the parameters such as standard specific impulse, characteristic speed, combustion chamber temperature, average molecular weight of combustion products, and explosion heat were calculated. The results illustrated that as the weight percentage of nitrocellulose increases, the values of standard specific impulse, characteristic speed, average molecular weight of combustion products, combustion chamber temperature, and explosion heat increase. This was ascribed to that the oxygen balance of glycidyl azide polymer is substantially lower than that of nitrocellulose, which results in that the chemical energy of glycidyl azide polymer does not release sufficiently. Additionally, as weight percentage of glycidyl azide polymer increases, the impact and friction sensitivity of the composites decrease obviously. This means that glycidyl azide polymer is much more insensitive than nitrocellulose.

Influence of trace water on decomposition mechanism of c-C4F8 as environmental friendly insulating gas at high temperature

Fluorocarbon gas has excellent environmental characteristics and insulation properties and has the potential of replacing SF6 for medium-voltage electrical equipment. While c-C4F8 will decompose under discharge or overheating faults conditions. At present, studies on the decomposition characteristics of c-C4F8 have made some achievements, but little attention has been paid to the influence of temperature and trace water. In this paper, the interaction between OH· and H· produced by H2O and c-C4F8 is analyzed based on the density functional theory (DFT) and plasma discharge decomposition experiment. The decomposition path, reaction enthalpy and activation energy, and the impact of temperature on the reaction path is discussed. It is found that the decomposition of c-C4F8 requires an endothermic heat of about 420 kJ/mol, and the decomposition of c-C4F8 to C2F4 is more likely to occur at high temperature. The H· and OH· generated by trace water will promote the decomposition of c-C4F8, which produces HF and low fluoride particles. The main decomposition products of c-C4F8 in the trace water environment are C2F4, CF4, CF3OH, CF3H, C2F6, CF2O and HF. Among them, CF2O and HF are toxic and corrosive substances, which pose a threat to the safety of operation and maintenance personnel. Relevant research results not only reveal the decomposition mechanism of c-C4F8, but also provide guidance for the application of c-C4F8 gas mixture.

3-D lanthanide coordination polymers with the flexible 1,3-phenylenediacetate linker: Spectroscopic, structural and thermal investigations

Four isostructural lanthanide coordination polymers of the formula [Ln2(1,3-pda)3(H2O)]·H2O where Ln = Gd(1), Dy(2), Er(3), Lu(4) and 1,3-pda = 1,3-phenylenediacetate were hydrothermally synthesized and characterized by vibrational spectroscopy, thermal analysis, powder and single-crystal X-ray diffraction methods. All 1,3-phenylenediacetates act as μ4-linkers and connect the eight-coordinate lanthanide ions into the 3-D coordination networks. Carboxylate groups in the ligands molecules exhibit diverse conformations: both trans or trans and cis. Changes of Ln–O bond lengths among the investigated compounds point out to the lanthanide contraction. Infrared and Raman spectra confirmed that both carboxylic groups of ligand were deprotonated. The presence of the band of non-hydrogen bonded hydroxyl group from water molecule in the infrared spectra was discussed. Thermal behaviour of the complexes was investigated by the TG-DSC and TG-FTIR methods. The investigated complexes are thermally stable in air and nitrogen atmosphere up to 106–135 °C. Further heating of the complexes leads to dehydration and decomposition. Water, carbon oxides, m-xylene and methane are main volatile products of complexes thermal decomposition in nitrogen.

H2S and SO2 adsorption on Pt-MoS2 adsorbent for partial discharge elimination: A DFT study

Abstract SF6 inevitably decomposes to various decomposition products under partial discharge in SF6-insulated equipment. Therefore, in order to ensure the running stability of the equipment, Pt-MoS2 monolayer adsorbent material was proposed to remove the main decomposition products: H2S and SO2, based on the density functional theory (DFT) calculation. The adsorption energy, charge transfer and structural parameters, density of states, and electron density difference were calculated to find the most stable adsorption structure and analyze the interaction mechanism of Pt-MoS2 monolayer to SO2 and H2S. It was found that Pt-MoS2 monolayer shows strong interaction to H2S and SO2 due the strong chemical activity of doped Pt atom. This study provides a theoretical basis to prepare Pt-MoS2 adsorbents for the SF6 decomposition components removal.

Possible carbon-carbon bond formation during decomposition? Characterization and identification of new decomposition products in lithium ion battery electrolytes by means of SPME-GC-MS

Commercially available lithium ion batteries (LIBs) of the 18650 cell format were aged with different cycling protocols. After cell opening and electrolyte extraction, the obtained electrolyte was characterized with respect to the occurring organic aging products. Therefore, gas chromatography - mass spectrometry (GC-MS) with standard liquid injection as well as solid phase microextraction (SPME) was applied. The composition of the pristine electrolyte and the main decomposition products have already been discussed in a preceding study. However, the SPME method provides access to study aging products, which are present in lower concentrations. Structural elucidation was done for several signals of interest. For ongoing validation of previously unknown compounds, selected standards were synthesized in order to compare fragment patterns and retention times. Three carbonates with butoxy-moieties were identified, although the longest carbon chain in the constituents of this specific electrolyte are the C2 chains of ethyl methyl carbonate (EMC) and ethylene carbonate (EC). Furthermore, the longest chain in standard carbonate based electrolytes in general is the C3-chain of propylene carbonate (PC). Thus, the formation of a carbon-carbon bond during cycling of LIB electrolytes has to be considered. In addition to the well-known transesterification reactions the occurrence of this type of reaction leads to a variety of new carbonate based decomposition products. Hence, their presence has to be taken into account with respect to possible influences on the interphases formed at the electrode/electrolyte interfaces.

Thermal behaviour of bambus[6]uril and its chloride caviplex

The present paper presents the thermal behaviour of methyl-bambus[6]uril in its anion-free and chlorine-included form. Our study was based on thermogravimetry associated to Fourier-transform infrared spectroscopy and differential scanning calorimetry. The compounds decompose after $$300\,^{\circ }\hbox {C}$$ and both forms of this macrocycle, contain four hydration water molecules. The main decomposition products are $$\hbox {H}_2\hbox {O}$$ , $$\hbox {CO}_2$$ , $$\hbox {NH}_3$$ and isocyanic acid as we could detect by FTIR spectroscopy. Finally, we verified that the caviplex loses its chloride ion after $$270\ ^{\circ }\hbox {C}$$ and may produce the anion-free macrocyle upon heating.

Insights on decomposition process of c-C4F8 and c-C4F8/N2 mixture as substitutes for SF6.

In recent years, many scholars have carried out studies on c-C4F8 and its gas mixture and found it has potential to be used as an environment-friendly insulating medium to replace SF6 in medium-voltage equipment. In this paper, the c-C4F8 and c-C4F8/N2 gas mixture models were built to study its decomposition process by the combination of reactive molecular dynamics method and density functional theory. The yield of the main decomposition products, the reaction pathways and enthalpy under different temperatures were explored. It was found that the decomposition of c-C4F8/N2 mainly produces CF2, F, CF3, CF, C, CF4 and C2F4. c-C4F8 can decompose to C2F4 by absorbing 43.28 kcal/mol, which is the main decomposition path and this process easily occurs under high temperature. There is a dynamic equilibrium process among the various produced radicals, which ensures the insulation performance of system to a certain extent. The decomposition performance of c-C4F8/N2 mixture is better than that of pure c-C4F8 at the same temperature. Relevant results provide guidance for engineering application of the c-C4F8/N2 gas mixture.