Evolved Gas Analysis Research Articles

Probing pyrolysis conversion of separator from spent lithium-ion batteries: Thermal behavior, kinetics, evolved gas analysis and aspen plus modeling

The exponential growth in the consumption of lithium-ion batteries (LIBs) has resulted in a concomitant increase in the spent LIBs. Multi-component recycling is a highly desirable and beneficial process, yet the separator component remains overlooked. This study examined the thermal behavior, kinetics, thermodynamics, and evolved products of separator pyrolysis in N2 and CO2 atmospheres. Furthermore, the conversion was modeled using Aspen Plus and a sensitivity analysis was conducted to investigate the impact of varying operating conditions. The findings indicated that the whole degradation process could be divided into three stages: below 200 °C, 200–550 °C and 550–900 °C. The evolved products at peak temperatures of 485 °C in N2 and 500 °C in CO2 were composed of olefins and alkanes. The average apparent activation energy values were determined to be 222.78 kJ mol−1 and 159.36 kJ mol−1 in the N2 and CO2 atmospheres, respectively. Thermodynamic analysis indicated that the separator decomposition was an endothermic and non-spontaneous process. Aspen Plus modeling results were in agreement with the experimental data. The sensitivity analysis revealed that an increase in temperature lead to an increased content of lighter compounds (≤C9) and a decrease in the proportion of heavier compounds (>C10) in the pyrolysis products.

Studies on the pyrolysis and potential flame retardancy of low-substituted starch phosphates

Investigations on the pyrolysis and potential flame retardancy imparted by solvent-free and semi-dry phosphorylation of different starches using sodium orthophosphates were conducted. The samples – low-substituted starch phosphates (SP) with degrees of substitution DSP < 0.5 - were subjected to differential scanning calorimetry, thermogravimetry coupled with evolved gas analysis and pyrolysis – gas chromatography – mass spectrometry. The data obtained as well as features of charring residues examined using microscopic and spectroscopic methods were related to structural aspects of SP – analysed by means of various spectroscopic techniques - and compared with those of native starches. It was found that charring and polyphosphate formation and the thermal resistance of the solid SP residues increased significantly if the DSP was at least 0.1. Accordingly, the exothermal decomposition, the temperature-induced loss of mass and the decomposition rates of SP decreased distinctly compared to native starch. The activation temperatures of SP and the formation of low-molecular pyrolysis products including aliphatic, cyclic, and aromatic aldehydes and ketones as well as anhydrosugars decreased markedly, even at DSP < 0.1. The results confirm the potential flame-retardancy of SP achieved by flame-inhibiting effects, despite low phosphorylation degrees, in both the gas and condensed phases.

The influence of functional groups on the pyrolysis of per- and polyfluoroalkyl substances

Thermal treatment is a widely used remediation strategy for PFAS-contaminated materials such as soil, spent sorbents, and domestic waste. To better understand the effectiveness and environmental impact of thermal treatments for PFAS-contaminated materials, a fundamental understanding of PFAS thermal degradation mechanisms is required. This work aims to study the pyrolysis of six representative PFAS compounds, all of which have an eight-carbon length but with different functional groups. To assess the thermal stability and pyrolysis products of these six PFAS compounds, evolved gas analysis (EGA) was performed using thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) coupled with an infrared spectrometer (IR) and a mass spectrometer (MS), as well as pyrolysis-GCMS (Pyr-GCMS). The EGA data demonstrates that compounds with lower estimated vapor pressures were generally found to be more thermally labile, and the presence of an ionic bond necessitates higher temperatures for pyrolysis. Pyrolysis at 900 °C yielded a variety of fluorinated organic compounds at significant signals. Tetrafluoroethene constituted the majority of the Pyr-GCMS signal for all the compounds. Moreover, a significant fraction of detected products was unable to be identified, underscoring a need for better tools to help with the identification of unknowns. Pyrolysis can occur through random chain scission, scission of the functional group, scission of the terminal CF3 group, and HF elimination. Some compounds may undergo more complete beta-scission to produce smaller pyrolysis products compared to others. The presence of acidic protons within the functional group can help facilitate HF elimination, whereas the salt form of a PFAS compound is less likely to undergo HF elimination. Termination of radical intermediates can either be recombination with a CF3 radical or hydrogen abstraction (H-abstraction). Observed hydrogen-substituted products indicate that functional groups with higher hydrocarbon character may lead to more H-abstraction terminated products. Overall findings show that the functional group of a PFAS may decrease or increase its thermal stability and lead to different profiles of pyrolysis products.

Feedstock recycling of single-use garment simultaneously using CO2 and MSW incinerator bottom ash

This study is aimed at proposing a feedstock recycling approach to make value-added monomer from single-use garment like stocking waste (SW) using incinerator bottom ash catalyst (IBAC). SW is made mainly of nylon 6 (>80 wt%) with minor components such as polyurethane. Thermochemical SW decomposition pathways are identified by evolved gas analysis and single-shot pyrolysis analysis, confirming that caprolactam (a value-added chemical re-used for manufacturing nylon 6) is the major product. IBAC is composed mainly of alkaline metal oxides (e.g., CaO). The use of IBAC in thermochemical SW conversion at 500 °C under CO2 atmosphere increases the yield of caprolactam reaching 70.8 wt% (20 % higher than non-catalytic SW conversion (59.2 wt%)). Moreover, the caprolactam yield corrected to the nylon 6 content of SW is 86.8 wt%. The enhancement of caprolactam production by IBAC in CO2 is most likely due to the synergistical effect of IBAC and CO2 on promoting the molecular interaction of amide groups present on SW. It is hoped that this study brings the idea of new applications of concurrently reusing textile waste (e.g., SW) and municipal solid waste-treatment byproduct (e.g., IBAC).

Organic Carbon and Ca‐Rich Carbonate Detections in Soils of the Northern Plains, Mars: Evaluation of Unreported Data From the Mars Phoenix Scout's Thermal Evolved Gas Analyzer (TEGA)

AbstractThe Thermal Evolved Gas Analyzer (TEGA) analysis of surface and icy subsurface Phoenix landing site soils consisted of low (300–700°C) and high (&gt;700°C) temperature CO2 evolutions that were attributed to organic carbon (83–1,484 μgC/g) and Ca‐rich carbonate (1.1–2.6 wt.%). Total carbon abundances ranged from 1,143 to 4,905 µgC/g, which is the highest soil carbon concentration so far detected on Mars. Low temperature CO2 was attributed to oxidized organic C (e.g., oxalates, acetates), while hydrocarbon combustion was indicated in two soils by the detection of coevolved CO2 and O2 (perchlorate). Combustion reactions may have prevented the detection of hydrocarbon masses in the Phoenix landing site soils. Organic C was likely derived from meteoritic and igneous/hydrothermal sources, but microbiological sources cannot be excluded. CO2 evolved at high temperatures was consistent with Ca‐rich carbonate along with possible minor contributions from macromolecular organic carbon and mineral/glass vesicle CO2. Carbon detected in the Phoenix landing site soil and other landing site soils and sands (e.g., Gale/Jezero craters) would be consistent with global organic C and carbonate in soils and sand across Mars. However, oxidizing water thin films derived from the near‐surface ice in the Phoenix soils favor Ca‐carbonate over Fe‐carbonate, which is likely more stable in the ice‐free regions of Mars (e.g., Gale/Jezero craters). The global carbon budget on Mars inferred from these results emphasizes that Mars Sample Return should yield carbon bearing soil/rock that would allow the identification of the origin of carbon and any possible connections to ancient martian microbiology.

Advanced multifunctional fabrics enabled by bioinspired coatings

The demand for textiles with functional properties has been increasing over the past few decades, driven by both civilian and military applications. In this study, we present a method to impart flame retardant (FR) and insect repellent (IR) properties to nylon-cotton blends. Flame retardancy was achieved by covalently attaching phytic acid, a bio-derived material, to the hydroxyl groups of cotton in nyco fabrics. Subsequently, these FR-treated nyco fabrics were coated with an acylate-based monomer along with permethrin to confer insect-repellent properties. FTIR-ATR spectroscopy confirmed the presence of weight of phytic acid on nyco fabric and the weight gain from this was 6 % with respect to initial fabric weight. The multifunctional fabrics exhibited a 200 % increase in char formation upon thermal degradation compared to untreated nyco. Moreover, the multifunctional fabrics demonstrated self-extinguishing properties with a char length of <15 cm, whereas untreated fabrics burned completely. In cone calorimeter experiments, FR-treated fabrics showed a reduction of over 25 % in total heat release compared to untreated controls. The addition of FR facilitates char formation and the release of non-flammable gases such as water vapor (H2O), carbon dioxide (CO2), and ammonia (NH3), suggesting a condensed phase mechanism of FR action as evident from TGA-FTIR evolved gas analysis. The insect repellent properties (IR) were evaluated using a tube test method as described by the World Health Organization, revealing a knockdown rate exceeding 98 % for fabrics treated with insect repellent.

A comparative study on the slow pyrolysis of Miscanthus (Miscanthus×giganteus Greef et Deu.) cultivated on agricultural and contaminated soils: Assessment of distribution of final products

This study aims to investigate the slow pyrolysis behavior of uncontaminated (MSC-I - reference) and heavy metals contaminated (MSC-R) samples with heavy metals from the tailings of a Pb-Zn-Cu flotation mine, consisting of whole stems of Miscanthus. Physicochemical properties of raw materials were investigated through instrumental characterization techniques (Atomic Absorption Spectrometry (AAS), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD)), while the pyrolysis process was monitored by simultaneous thermal analysis techniques (thermogravimetry (TG) – derivative thermogravimetry (DTG)), coupled with Mass spectrometry (MS), for evolved gas analysis. After determination of the lignocellulose content (cellulose, hemicellulose, and lignin) and extractive of the MSC-I and MSC-R samples, it was found that Pb, Zn, Fe, and Mn in MSC-R lead to very fast decomposition of extractive fraction, which facilitates their distribution in formed bio-char, together with lignin char-participation, acting catalytically. It was established that a much greater fraction of extractives decomposition products and non-volatile heavy metals are incorporated in MSC-R bio-char increasing its yield (23 %), compared to MSC-I bio-char yield (21.5 %). It was identified that MSC-R has increased production of H2, CO, and CO2, while decreased production of CH4, influenced by Fe (Fe has a significant positive effect on CO2 evaluation during MSC-R pyrolysis, enhancing decarboxylation process). It was established that CH4 reforming reactions catalyzed by iron additionally affect methane reduction, and increase production of H2, compared to the reference sample. Isoconversional kinetic analysis showed that pyrolysis reactions profile was strongly conditioned by the presence of heavy metals, such as Cd, Pb, and Zn, because they affect the modification of biomass lignocellulosic structure. Also, it was found that small amounts of Cd present in MSC-R can increase pyrolysis activation energy of three pseudo-components, and inhibit their deoxygenation, thus increasing yield of bio-char.

Material Characterization of Silicones for Additive Manufacturing.

Three-dimensional printing is ideally suited to produce unique and complex shapes. In this study, the material properties of polysiloxanes, commonly named silicones, produced additively by two different methods, namely, multi-jet fusion (MJF) and material extrusion (ME) with liquid printing heads, are investigated. The chemical composition was compared via Fourier-transform infrared spectroscopy, evolved gas analysis mass spectrometry, pyrolysis gas chromatography coupled to mass spectrometry, and thermogravimetry (TGA). Density and low-temperature flexibility, mechanical properties and crosslink distance via freezing point depression were measured before and after post-treatment at elevated temperatures. The results show significant differences in the chemical composition, material properties, as well as surface quality of the tested products produced by the two manufacturing routes. Chemical analysis indicates that the investigated MJF materials contain acrylate moieties, possibly isobornyl acrylate linking branches. The hardness of the MJF samples is associated with crosslinking density. In the ashes after TGA, traces of phosphorus were found, which could originate from initiators or catalysts of the curing process. The ME materials contain fillers, most probably silica, that differ in their amount. It is possible that silica also plays a role in the processing to stabilize the extrusion strand. For the harder material, a higher crosslink density was found, which was supported also by the other tested properties. The MJF samples have smooth surfaces, while the ME samples show grooved surface structures typical for the material extrusion process. Post-treatment did not improve the material properties. In the MJF samples, significant color changes were observed.

Leveraging Advanced Analytical Chemistry Techniques to Probe Thermo-Electrochemical Aging Effects in Lithium-Ion Battery Electrolytes

As lithium-ion and other battery chemistries gain market traction for grid and industrial-scale applications, pressure is mounting to develop more robust, longer lasting cells that can operate for hundreds of cycles at variable temperatures without sacrificing performance or safety. Electrolyte design is crucial to this effort and requires deep understanding of the correlated physical, chemical, and electrochemical factors that dictate long-term electrolyte performance. In this presentation, I will discuss the value of combined analytical chemistry techniques (solid- and liquid- state NMR, GCMS, and ICPMS) to resolve molecular-level impacts of thermally- and electrochemically- induced aging of lithium-ion electrolytes. In a model electrolyte, High Resolution (HR)-GCMS enables identification of subtle changes in solvent and additive chemistry while NMR reveals the formation of lithium-salt breakdown products. These findings are instructive for battery cycling as demonstrated by full chemical analysis of electrolyte extracted from aged lithium-ion cells, including evolved gas analysis, electrolyte deformulation, and SEI characterization. These cutting-edge analytical chemistry techniques are powerful and underutilized tools for detecting and mitigating failure modes in liquid electrolytes.

Thermal Studies of Fractionated Lignite and Brown Coal Fly Ashes.

Coal fly ash (CFA), a by-product of coal combustion, is a valuable raw material for various applications. However, the heterogeneous nature of the composition and properties of CFA provides challenges to its effective usage and utilisation. This study investigates the thermal behaviour of the fly ashes of lignite (FA1) and brown coal (FA2) and their fractions obtained by dry aerodynamic separation. Thermal analysis techniques, including thermogravimetry (TG), differential scanning calorimetry (DSC), and evolved gas analysis (EGA), were used to characterise the behaviour of the fly ash fractions while heating up to 1250 °C. The results reveal distinct differences in the thermal behaviour between ash types and among their different size fractions. For the FA1 ashes, the concentration of calcium-rich compounds and the level of recrystallisation at 950 °C increased with the decrease in particle size. The most abundant detected newly formed minerals were anhydrite, gehlenite, and anorthite, while coarser fractions were rich in quartz and mullite. For the FA2 ashes, the temperature of the onset of melting and agglomeration decreased with decreasing particle size and was already observed at 995 °C. Coarser fractions mostly remain unchanged, with a slight increase in quartz, mullite, and hematite content. Recrystallisation takes place in less extension compared to the FA1 ashes. The findings demonstrate that the aerodynamic separation of fly ashes into different size fractions can produce materials with varied thermal properties and reactivity, which can be used for specific applications. This study highlights the importance of thermal analysis in characterising fly ash properties and understanding their potential for utilisation in various applications involving thermal treatment or exposure to high-temperature conditions. Further research on advanced separation techniques and the in-depth characterisation of fly ash fractions is necessary to obtain materials with desired thermal properties and identify their most beneficial applications.

Accessing the Low-Polar Molecular Composition of Boreal and Arctic Peat-Burning Organic Aerosol via Thermal Analysis and Ultrahigh-Resolution Mass Spectrometry: Structural Motifs and Their Formation.

Peatland fires emit organic carbon-rich particulate matter into the atmosphere. Boreal and Arctic peatlands are becoming more vulnerable to wildfires, resulting in a need for better understanding of the emissions of these special fires. Extractable, nonpolar, and low-polar organic aerosol species emitted from laboratory-based boreal and Arctic peat-burning experiments are analyzed by direct-infusion atmospheric pressure photoionization (APPI) ultrahigh-resolution mass spectrometry (UHRMS) and compared to time-resolved APPI UHRMS evolved gas analysis from the thermal analysis of peat under inert nitrogen (pyrolysis) and oxidative atmosphere. The chemical composition is characterized on a molecular level, revealing abundant aromatic compounds that partially contain oxygen, nitrogen, or sulfur and are formed at characteristic temperatures. Two main structural motifs are identified, single core and multicore, and their temperature-dependent formation is assigned to the thermal degradation of the lignocellulose building blocks and other parts of peat.

Thermal Kinetics and Nitriding Effect of Ammonia-Based Direct Reduction of Iron Oxides.

Ammonia is a promising alternative hydrogen carrier that can be utilized for the solid-state reduction of iron oxides for sustainable ironmaking due to its easy transportation and high energy density. The main challenge for its utilization on an industrial scale is to understand the reaction kinetics under different process conditions and the associated nitrogen incorporation in the reduced material that originates from ammonia decomposition. In this work, the effect of temperature on the reduction efficiency and nitride formation is investigated through phase, local chemistry, and gas evolution analysis. The effects of inherent reactions and diffusion on phase formation and chemistry evolution are discussed in relation to the reduction temperature. The work also discusses nitrogen incorporation into the material through both spontaneous and in-process nitriding, which fundamentally affects the structure and chemistry of the reduced material. Finally, the effect of nitrogen incorporation on the reoxidation tendency of the ammonia-based reduced material is investigated and compared with that of the hydrogen-based reduced counterpart. The results provide a fundamental understanding of the reduction and nitriding for iron oxides exposed to ammonia at temperatures from 500 to 800 °C, serving as a basis for exploitation and upscaling of ammonia-based direct reduction for future green steel production.

Theoretical and experimental characterization of trivalent lanthanide (La-Eu) aquacomplexes with losartan

In this work, losartan compounds with trivalent ions La(III), Ce(III), Pr(III), Nd(III), Sm(III), and Eu(III) were synthesized in the solid-state. The thermal and spectroscopic study of the compounds was performed using TG-DSC, FTIR, DRX, and evolved gas analysis (EGA) by TG-DSC/FTIR. The theoretical and experimental spectroscopic data suggested the possible modes of coordination of the ligand with the metal ions by the tetrazole ring. Thermogravimetric analyses provide information on the thermal stability, water coordination, and stoichiometry of the compounds. The minimum formulae of the compounds is [Ln(Los)3(H2O)x], where Ln=La and Ce/x = 7; and Pr, Nd, Sm, Eu/x = 6. TG-DSC coupled to FTIR in an air atmosphere suggested the release of H2O, CO2, CO, MeOH, NH3, and -NCO during the thermal decomposition of losartan from lanthanides. Amorphous compounds were obtained, and their poor solubility suggests their potential use as prodrugs in the solid-state.

Probing thermodynamics of radiogenic helium and defects in δ-plutonium alloys and interactions with adsorbed environmental gases

Differential scanning calorimetry coupled with simultaneous evolved gas analysis (DSC-EGA) on aged δ-Pu samples shows that most radiogenic helium remains trapped within the Pu matrix at temperatures very close to, or slightly above, the melting temperature. Our results indicate that helium release from 50-year-old δ-Pu occurs as a burst just below the melting temperature (>0.994 Tm), with subsequent pressure oscillations as temperature increases. Subordinate quantities of H2 were also released along with helium. The helium emission tails off and ceases above ∼720 – 750°C. In a δ-Pu alloy aged 6 years, the initial helium burst occurs slightly above melting (∼1.015 – 1.042 Tm), with a discrete, larger helium spike occurring between 670 and 686°C. The proximity of helium release to the liquidus transition presented challenges in the deconvolution of overlapping process enthalpies, the liquidus endotherm, and the exotherm resulting from bubble collapse, annealing and gas expulsion. Helium’s strong affinity for vacancy binding in a 2He-vac configuration is predicted by Density Functional Theory (DFT) modeling. The measured stored energy associated with the He release events in a 50-year-old δ alloy is on the order of ∼10–11 J/g, which is significantly higher than stored energies measured in the sub-solidus regimes (∼2 J/g) that are related to the solid-state annealing of processing- and radiation-induced defects. This implies that aged δ Pu alloys have a remarkable resilience to accommodate the lattice strain produced by the internal pressure of the helium bubbles and provides further insight into the thermodynamic behavior of aged δ Pu.

Structural Characterisation of End-of-Life Cement–Asbestos Materials from Lithuania

Asbestos is a widely used name for natural silicate minerals with fibrous properties. Asbestos minerals were one of the most popular and cheapest raw materials used in the construction industry in the past when they was used in the form of cement–asbestos composite material. Nowadays, we know that asbestos possesses carcinogenic properties. Due to this fact, asbestos was banned in many countries including Lithuania. All asbestos-containing materials are considered waste and stored in special landfills, which causes significant environmental pollution. One of the methods proposed to solve the asbestos problem may be thermal treatment. In the present study, asbestos-containing wastes in the form of cement–asbestos materials were examined. These asbestos-containing materials were characterised via chemical analysis (XRF) connected with mineralogical phase analysis with powder X-ray diffraction (XRD) as well as scanning electron microscopy (SEM). The thermal decomposition of samples was studied via differential thermal analysis (DTA) and thermogravimetric measurements with evolved gas analysis (TG–EGA). It was found that thermal treatment is a possible way to destroy asbestos contained in cement–asbestos wastes and convert it into new mineral phases. The work also compared the obtained characteristics of asbestos waste with the characteristics of waste produced in other countries.

A comprehensive study of melt foaming in E‐glass batch‐to‐melt conversion process: Effects of sulfate content and chemistry of raw materials

AbstractControl of sulfate‐induced melt fining without excessive foaming is one of the critical steps in maintaining the stability of E‐glass fiber manufacturing processes. Besides, the efficiency of combustion or energy utilization is directly affected by the extent of the melt‐foaming. A fundamental understanding of key factors affecting melt foaming under the simulated oxy‐fuel combustion environment will enable commercial E‐glass fiber production to optimize both batch chemistry and operation conditions to achieve adequate furnace control. In this study, six types of E‐glass batches with the same target glass composition were prepared by using four different CaO sources; calcined limes with different SO3 contents, limestone, limestone with sodium sulfate, and a mixture of limestone and calcined lime. All batch samples were examined by HTMOS‐EGA system (high temperature melting observation system with evolved gas analysis). HTMOS enables monitoring batch‐to‐melt conversation steps by using a high‐resolution camera and EGA detects the evolved reaction gaseous, such as CO, CO2, and SO2 via an Fourier transform infrared (FTIR) gas analyzer. Gases of water vapor, N2, and O2 were introduced accordingly into the fused quartz crucible to simulate similar oxy‐fuel atmosphere of the furnace operation. This study aimed to investigate the effects of different SO3 contents in batches and different raw material chemistries on the foam formation in E‐glass melts under the oxy‐fuel atmosphere. Different raw materials were characterized by mineralogical analysis, chemical analysis, particle size distribution, chemical oxygen demanding (COD) level, and Brunauer–Emmett–Teller (BET) analysis. Although some of the batches contained the same SO3 content, different foam formations resulted from the effect of the batch chemistry. Our detailed HTMOS‐EGA investigations show that not only SO3 content in the batch affects foam formation in E‐glass melts, but also raw material chemistry and particle size have strong effects on the melt foaming in E‐glass batch melting, especially for those of ingredients having hydroxide phases and/or finer particles with higher specific areas.

Pyrolysis mechanism and evolved gas analysis of a promising energetic carbamate-functionalized microcrystalline cellulose nitrate

The present study aims to elucidate the decomposition mechanism and gas evolution characteristics of a promising energy-rich carbamated microcrystalline cellulose nitrate (M3CN). The molecular structure and morphological characteristics of starting microcrystalline cellulose carbamate (MCCC) and its nitrated derivative were examined using FTIR and SEM techniques. Thermal analysis using TGA and DSC revealed distinct decomposition behaviors for MCCC and M3CN. MCCC exhibited endothermic decomposition linked to the degradation of the cellulosic structure. In contrast, an exothermic decomposition event was observed for M3CN, attributed to the cleavage of energetic groups within the nitrated cellulosic chains. Furthermore, the hyphenated TG-FTIR analysis confirmed that the primary gaseous products emitted during the pyrolysis of M3CN included NO, N2O, NO2, CO2, H2O, CH4, HCHO, HCN, and CHNO. The findings of this study enhance our understanding of the pyrolysis mechanism in cellulose-based energetic materials, providing a significant reference for forthcoming research and explorations in this field.

Analysis of gas evolution in the heart, liver, and kidney of turtles presenting with gas embolic pathology based on ultrasonography

Human-caused disturbances of sea turtles can result in them presenting with gas embolic pathology which often leads to severe injury or death. While gas embolism has been previously observed in turtles using MRI and x-ray/CT, as well as ultrasound to a lesser degree, how the distribution of gas evolves in different organs over time, and its possible correlation to outcome, is poorly understood. We hypothesize that ultrasound imaging of the heart, kidney, and liver over time can help differentiate pathology resolution or worsening trajectory and may help refine veterinarians’ treatment algorithm in this population. The liver, kidney, and heart of 100 by-caught turtles were imaged, and gas amount in each ultrasound scan was graded on a scale from 0 (no gas) to 5 (gas completely shadowing organ anatomy). Turtles scanned on the boat had higher grades in all organs compared to turtles first scanned at shore which was on average 163 minutes later. Average pixel brightness in the top half of cardiac scans increased with grade as expected, apart from grade 5 likely due shadowing. Ultrasound brightness could become a quantitative metric for veterinarians to determine which turtles need hyperbaric oxygen treatment and which can be released.

Superb enhancement of thermal decomposition of ammonium perchlorate in the presence of methyl viologen salts: A TG-DSC/MS and kinetic study

Different salts of 1,1′-dimethyl-4,4′-bipyridinium which known as methyl viologen compounds (MVX2) (where X= iodide (I‾, MVI2), perchlorate (ClO4‾, MVC2) and tetraphenylborate anion (BPh4‾, MVT2)) were prepared and characterized using 1H NMR, 13C NMR, elemental analysis and mass spectroscopy. The impact of these viologen salts on the thermal decomposition of ammonium perchlorate was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mass spectroscopy. The obtained results revealed that the high-temperature decomposition (HTD) temperature of MVX2:AP mixtures (5:100 (w/w)) significantly decreases by 121 ◦C, 151 ◦C and 112 ◦C compared to pure AP in MVC2, MCI2 and MVT2, respectively. Moreover, the apparent released heat of AP decomposition in these mixtures grows up from 574.2 J g−1 for the pure AP to 2108, 1965 and 1564 J g−1 for MVC2, MCI2 and MVT2, respectively. Furthermore, the calculation of the kinetic parameters confirms that the activation energy of HTD of AP was significantly decreased from 142.9 to 124.9, 138.9 and 131.2 KJ mol−1, upon mixing with MVC2, MVI2 and MVT2 respectively. The rate constant of AP decomposition at the peak temperatures of these mixtures was higher than that at the peak temperature of pure AP. The evolved gas analysis using mass spectrometry shows that the decomposition of pure AP mainly results in ClO3, ClO2, HClO4, ClO, Cl2, HCl, N2O and O2, while the major gaseous products of the 5:100 (w/w) mixture of MVX2 salts with AP were detected as N2, NO, N2O, O2, Cl2, ClO, ClO2, ClO3, HClO4, HCl and 4, 4′-Bipyridine (Bpy). The amounts of Bpy in decomposition products of AP/MVX2 mixtures follow the order of MVC2>MVI2>MVT2, which surprisingly is in accordance with the catalytic activity of these compounds.

Revealing Molecular-Scale Structural Changes in Polymer Nanocomposites during Thermo-Oxidative Degradation Using Evolved Gas Analysis with High-Resolution Time-of-Flight Mass Spectrometry Combined with Principal Component Analysis and Kendrick Mass Defect Analysis.

This study introduces a novel method that utilizes evolved gas analysis with time-of-flight mass spectrometry (EGA-TOFMS) coupled with principal component analysis (PCA) and Kendrick mass defect (KMD) analysis, called EGA-PCA-KMD, to analyze complex structural changes in polymer materials during thermo-oxidative degradation. While EGA-TOFMS captures exact mass data related to the degradation components in the temperature-dependent mass spectra of the evolved products, numerous high-resolution mass spectra with large amounts of ion signals and varying intensities provide challenges for interpretation. To address this, we employed mathematical decomposition through PCA to selectively extract information about the ion series specific to the products that evolved from the degradation components. Additionally, KMD analysis was applied to the attribution of the exact mass signals extracted from the PCA, which categorizes and visualizes depending on the molecular compositions in a two-dimensional plot. The complex structural changes of the triblock copolymer thermoplastic elastomer and its nanocomposites containing nanodiamonds during thermo-oxidative degradation were elucidated using EGA-PCA-KMD to demonstrate the effectiveness of this characterization technique for polymer degradation. Furthermore, it is revealed that the formation of rigid matrix-filler interfacial interaction via the π-π stacking and chemical bonds in the nanocomposites contributes to improvement in the stability toward thermo-oxidative degradation. Our results highlight the benefits of EGA-PCA-KMD and provide valuable insights into polymer degradation.