Thermal Decomposition Gas Research Articles

Thermodynamic Computational Method of Thermal Decomposition Gas Content in Transformer Oil Considering Temperature and Competitive Reaction

Thermodynamic Computational Method of Thermal Decomposition Gas Content in Transformer Oil Considering Temperature and Competitive Reaction

Kinetics and mechanism of hydrogen release from isothermal decomposition of AlH3

Aluminum trihydride is an ideal hydrogen storage material. Aluminum trihydride is prone to dehydrogenate in ambient atmosphere due to its low chemical and thermal stability. Therefore, its thermal stability has become the focus of attention during production, use, transportation, and storage. In this paper, the pressure curve of the gas produced during the thermal decomposition of AlH3 with time at 333–373 K was obtained using an isothermal thermal decomposition gas measurement device. The isothermal thermal decomposition kinetic parameters of AlH3 were calculated using Arrhenius equation and mode matching method. The results show that the decomposition of AlH3 can be divided into three stages. The time required for AlH3 to reach a certain decomposition depth at different temperatures was obtained from Semenov equation. At room temperature, the time required for the decomposition depth of AlH3 (purity>99%) to reach 0.1% is 224.7 days in a vacuum environment. Furthermore, the possible decomposition mechanism of AlH3 was proposed by X-ray diffraction, gas chromatography, and transmission electron microscopy.

Carboxymethyl cellulose/poly(vinyl alcohol) blended films reinforced by buckypapers of carbon nanotubes and 2D material (MoS2): Enhancing mechanical strength, toughness, and barrier properties

Plastic waste is one cause of climate change. To solve this problem, packaging films are increasingly produced from biodegradable polymers. Eco-friendly carboxymethyl cellulose and its blends have been developed for such a solution. Herein, a unique strategy is demonstrated to improve the mechanical and barrier properties of carboxymethyl cellulose/poly(vinyl alcohol) (CMC/PVA) blended films for the packaging of nonfood dried products. The blended films were impregnated with buckypapers containing different combinations of multiwalled carbon nanotubes, two-dimensional molybdenum disulfide (2D MoS2) nanoplatelets, and helical carbon nanotubes (HCNTs). Compared to the blend, the polymer composite films exhibit significant increases in tensile strength (~105 %, from 25.53 to 52.41 MPa), Young's modulus (~297 %, from 155.48 to 617.48 MPa), and toughness (~46 %, from 6.69 to 9.75 MJ m−3). Polymer composite films containing HCNTs in buckypapers offer the highest toughness. For barrier properties, the polymer composite films are opaque. The water vapor transmission rate of the blended films decreases (~52 %, from 13.09 to 6.25 g h−1 m−2). Moreover, the maximum thermal-degradation temperature of the blend rises from 296 to 301 °C, especially for the polymer composite films with buckypapers containing MoS2 nanosheets that contribute to the barrier effect for both water vapor and thermal-decomposition gas molecules.

Research on Thermal Aging Behavior and Thermal Decomposition of Insulating Material XLPE

In this paper, accelerated thermal aging experiment was used to simulate the thermal aging behavior of XLPE, and FT-IR, DSC, TG and other test techniques were used to characterize the materials with different aging periods. The results show that with the aging time, the oxygen-containing groups in XLPE increase, and the crosslinking degree of molecular chains decreases. At the same time, the melting peak of the endothermic peak of the material shifts and the endothermic enthalpy decreases. After aging, the high temperature resistance of XLPE decreases and decomposition occurs more easily. The thermal decomposition of XLPE before and after thermal aging was carried out at different temperatures, and the corresponding thermal decomposition gases were collected. According to GC-MS analysis, the thermal decomposition gas products were all small molecule unsaturated olefin, small molecule containing oxygen and long carbon chain containing oxygen, and the content changed significantly before and after aging.

Research on Thermal Aging Behavior and Thermal Decomposition of Insulating Material XLPE

In this paper, accelerated thermal aging experiment was used to simulate the thermal aging behavior of XLPE, and FT-IR, DSC, TG and other test techniques were used to characterize the materials with different aging periods. The results show that with the aging time, the oxygen-containing groups in XLPE increase, and the crosslinking degree of molecular chains decreases. At the same time, the melting peak of the endothermic peak of the material shifts and the endothermic enthalpy decreases. After aging, the high temperature resistance of XLPE decreases and decomposition occurs more easily. The thermal decomposition of XLPE before and after thermal aging was carried out at different temperatures, and the corresponding thermal decomposition gases were collected. According to GC-MS analysis, the thermal decomposition gas products were all small molecule unsaturated olefin, small molecule containing oxygen and long carbon chain containing oxygen, and the content changed significantly before and after aging.

The effect of oxygen on the thermal stability and decomposition behaviours of 1,3-dimethylimidazolium nitrate for application using STA, ARC and FTIR

The thermal decomposition and runaway reaction of 1,3-dimethylimidazolium nitrate ([Mmim]NO3), a typical nitrate IL, were studied by a simultaneous thermogravimetric analyzer (STA) and accelerating rate calorimeter (ARC). The STA results show that the thermal decomposition of [Mmim]NO3 is divided into two stages, and the decomposition behaviour is similar in nitrogen or oxygen. The experimental results under adiabatic conditions indicate that [Mmim]NO3 has higher Tmax and Pmax than other imidazolium ILs, which reflects the greater explosion hazard of [Mmim]NO3. The apparent activation energies of [Mmim]NO3 were 86 kJ/mol and 83 kJ/mol, as calculated by the F-W-O and K-A-S methods. The complete thermal decomposition gas products of [Mmim]NO3 were analyzed by thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR), and the gas released by thermal decomposition of [Mmim]NO3 does not react with oxygen. Therefore, the decomposition reaction of [Mmim]NO3 was not positively related to the concentration of oxygen, which indicated that [Mmim]NO3 could play an active role in the reactions in the presence of oxygen. The results of this study may provide theoretical and experimental basis for [Mmim]NO3 safety precautions in storage and transportation.

Application of a high-resolution terahertz gas spectroscopy method to compositional analysis of thermal decomposition products of human fluids (urine)

Subject of study. In this study, the compositions of thermal decomposition products of samples of human fluids (urine) of cancer patients obtained before and after chemotherapy were investigated to identify the markers reflecting the influence of platinum-based chemotherapy, including its nephrotoxic influence, on the human body. Method. Molecular absorption spectroscopy, including nonstationary spectroscopy in the terahertz frequency range, is a prospective approach to investigation of multicomponent gas mixtures of different origins, including those of biological origin. The rotational spectrum lines and low-frequency vibrational spectra of molecules are in the terahertz frequency range (0.100–10 THz). When radiation transmitted through a gaseous sample is detected, the absorption lines, which are a unique characteristic of specific substances, are recorded in the spectrum. These absorption lines indicate the presence of the corresponding substances in the investigated multicomponent gas mixture; thus, this technique allows the identification of potential markers for pathologies and diseases as well as markers characterizing the effects of various exposure types on the human body, including the effect of drugs. Main results. A complex of metabolites resulting from the thermal decomposition of the sample was identified. The contents of gaseous thermal decomposition products of urine obtained from sick and conditionally healthy volunteers were compared. In addition, the contents of thermal decomposition products of urine obtained from the cancer patients before and after chemotherapy were compared. Practical significance. The proposed approach is advantageous for the development of a noninvasive investigation method that facilitates the assessment of chemotherapy effects on the human body.

Nondestructive silicon wafer recovery by a novel method of solvothermal swelling coupled with thermal decomposition

• 86.11% of Si-wafers in commercial PV module can be reclaimed without damage. • The formation of gas release channels contributes to the nondestructive recovery. • PV backsheet removal avoids the fluorine-containing gas emission. • Solvothermal swelling strategy provides significant time and organic solvent savings. • The reclaimed silicon wafer meets the requirements of new PV module fabrication. End-of-life (EoL) photovoltaic (PV) waste is becoming a severe environmental issue worldwide. Developing technologies to reclaim nondestructive and reusable silicon wafers (Si-wafers) is the most appealing way to solve this problem, saving ~40% on PV module production costs, but it remains a great challenge. Herein, we develop a novel method of coupling solvothermal swelling with thermal decomposition (SSTD) for structure-intact Si-wafers recovery. Laboratory-scale studies reveal that undamaged Si-wafers can be easily obtained by conducting a solvothermal swelling process in advance to build channels for the quick, horizontal release of ethylene-vinyl acetate (EVA) thermal decomposition gas. Using scaling-up equipment, 86.11% of Si-wafers in commercial PV module are reclaimed without any damage, nearly 10-fold higher than that of thermal decomposition alone (9.26%). Moreover, PV backsheet can be depolymerized with specially designed solvents (toluene-ethanol), greatly facilitating swelling by exposing EVA directly to toluene vapor and reducing the emission of fluorine-containing gas pollutants. The reclaimed Si-wafers are comparable to the originals, with the following properties: interstitial oxygen, <6 × 10 17 atoms·cm −3 ; substitutional carbon, <5 × 10 17 atoms·cm −3 ; resistivity, 1.84 Ω·cm; and minority carrier lifetime, 3.92 μs.

Terahertz high-resolution spectroscopy of thermal decomposition gas products of diabetic and non-diabetic blood plasma and kidney tissue pellets.

.Significance. One of the modern trends in medical diagnostics is based on metabolomics, an approach allowing determination of metabolites which can be the specific features of disease. High-resolution gas spectroscopy allows investigation of the gas metabolite content of samples of biological origin. We present the elaboration of a method of studying diabetic and non-diabetic biological samples, prepared as pellets, by terahertz (THz) high-resolution spectroscopy.Aim: The main idea of the work is studying the content of thermal decomposition gas products of diabetic and non-diabetic dried blood plasma and kidney tissues for revealing the set of gas-markers that characterized the diabetes by the THz high-resolution spectroscopy method.Approach: We present an approach to study the diabetic and non-diabetic blood plasma (human and rats) and kidney tissues (rats), using high-resolution spectroscopy based on the non-stationary effect of THz frequency range. The methods of preparing the blood and kidney tissue samples as pellets and of vaporizing the samples were developed.Results: The measurements of rotational absorption spectra of vapors at heating the pellets prepared from blood and kidney tissue were carried out in 118 to 178 GHz frequency range. The absorption lines appearing in spectra of the sample vapors were detected and identified. The molecular contents of thermal decomposition products differed for non-diabetic and diabetic samples; e.g., main marker is acetone appearing in the diabetic blood (human and rats) and in the diabetic kidney tissue.Conclusions: Our paper illustrates the potential ability for determining the metabolite content of biological samples for diagnostics and prognosis of diseases for clinical medicine.

Mathematical Model of the Motion of Gaseous Thermal Decomposition Products of Composites in a Porous Frame under Strong Heat Flows

The paper describes theoretical issues of the motion of gaseous thermal decomposition products of composite materials in a porous frame structure under the effect of intensive heat flows of different nature. The developed model was verified using benchmark filtration problems and its performance was tested for gas motion using the sample with the porosity that varied in coordinates.

Isothermal decomposition kinetics and possible decomposition process of pentaerythritol tetranitrate

ABSTRACT The isothermal decomposition kinetics of pentaerythritol tetranitrate (PETN) was studied through a self-established isothermal thermal decomposition gas metering device. The pressure versus time curves of the gas generated by PETN decomposition under different temperature conditions were divided into two parts, showing the remarkable effect of temperature and melting point on PETN decomposition. Model-fitting calculation result showed that the decomposition of PETN at 90–110°C conformed to the No. 8 model, namely, the anti-Jander equation, and a corresponding activation energy Ea of 107.1 kJ·mol−1 with ln(A/s−1) = 6.97. Within a temperature range of 112–130°C, the decomposition model of PETN conformed to the No. 28 model with reaction order n = 4. The device was simultaneously used to predict the time of PETN to reach a certain decomposition extent. Results showed that the time of PETN was extrapolated to 54.4 years when the extent of reaction reached 0.1% at ambient temperature (25°C). Furthermore, Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize PETN decomposition residues with different decomposition depths to understand the decomposition process.

Selective Phenol Recovery by Catalytic Cracking of Thermal Decomposition Gas from Epoxy-Based Carbon-Fiber-Reinforced Plastic

In order to promote the recycling of carbon fiber reinforced plastic (CFRP), catalytic cracking of hazardous gases generated by thermal decomposition from epoxy-based CFRP composites was performed....

Determination of toxic products emissions of polymers thermal decomposition using fluidised bed reactor and FTIR analysis

Abstract The paper presents original method of quantitative and qualitative determination of gaseous products of polymers thermal decomposition. It is used to determine the toxic potential of emitted gases, based on their emission E (g/g) by determining the FED dose or toxicological index WLC50M. The method is based on the use of a fluidized bed reactor equipped with a resistive heating jacket, which allows to conduct decomposition of a tested material at a strictly assumed temperature. To identify the types of gaseous compounds and their emission, infrared spectroscopy with Fourier transformation, FTIR was used. The proposed method of measuring the thermal decomposition products concentrations allows mimic the conditions of the fire at different stages of its development. FTIR spectra are recorded every 5 s, which enables identifying toxic gases as a function of burning time, in a precisely determined temperature. Using the library of reference spectra it is possible to determine both inorganic and organic compounds concentrations present in thermal decomposition products of the tested composites. The use of a fluidized bed reactor together with the FTIR analyser operating on-line allows for a much more accurate determination of the emissions of organic and inorganic gaseous products at the assumed temperature, compared to the methods currently used. Silicone rubber composites filled with polyhedral oligomeric silsesquioxanes (POSS) were used for the tests. The effect of POSS, also in a synergistic system with melamine polyphosphate (MPP) on toxicity of gaseous thermal decomposition products of tested composites at temperatures of 500, 600, 700 and 800 °C was determined.

Construction of Bimetallic ZIF-Derived Co-Ni LDHs on the Surfaces of GO or CNTs with a Recyclable Method: Toward Reduced Toxicity of Gaseous Thermal Decomposition Products of Unsaturated Polyester Resin.

This work proposed an idea of recycling in preparing Co-Ni layered double hydroxide (LDH)-derived flame retardants. A novel and feasible method was developed to synthesize CO-Ni LDH-decorated graphene oxide (GO) and carbon nanotubes (CNTs), by sacrificing bimetal zeolitic imidazolate frameworks (ZIFs). Organic ligands that departed from ZIFs were recyclable and can be reused to synthesize ZIFs. ZIFs, as transitional objects, in situ synthesized on the surfaces of GO or CNTs directly suppressed the re-stacking of the carbides and facilitated the preparation of GO@LDHs and CNTs@LDHs. As-prepared hybrids catalytically reduced toxic CO yield during the thermal decomposition of unsaturated polyester resin (UPR). What is more, the release behaviors of aromatic compounds were also suppressed during the pyrolysis process of UPR composites. The addition of GO@LDHs and CNTs@LDHs obviously inhibited the heat release and smoke emission behaviors of the UPR matrix during combustion. Mechanical properties of the UPR matrix also improved by inclusion of the carbides derivatives. This work paved a feasible method to prepare well-dispersed carbides@Co-Ni LDH nanocomposites with a more environmentally friendly method.

A review of methods for measuring microplastics in aquatic environments.

An increasing number of reports have been published concerning microplastic (MP) pollution in aquatic environments. Methods used in these studies continue to be updated and lack standardization, so that an up-to-date review pertaining methods for MP research is needed. This critical review examines the analytical methods, including sampling, identification, and quantitation, for MP research. Samples are generally collected from water, sediment, and biota gastrointestinal tract. Manta nets or trawls are prevalently used in surface water sampling, while direct shoveling or box-corer grab are commonly applied in sediment sampling. Microplastics in biota are generally obtained by dissecting organisms and separating livers, gills, and guts. Density separation is frequently chosen to separate MPs from sample matrices. Chemical digestion can dissolve other organic materials and isolate MPs for further identification. Visual sorting should be combined with chemical composition analysis to better identify the polymer type. Pyrolysis or thermal decomposition gas chromatography coupled with mass spectrometry, Fourier transform infrared spectroscopy, and Raman spectroscopy are currently the main technologies for MP identification. Units prevalently used to express MP abundance in water, sediment, and biota are "particles per m3," "particles per m2," and "particles per individual," respectively. As MP abundances often varied with the methods used, we recommend that analytical protocols of MPs should better be standardized and optimized. Despite the important progress in analysis of MPs, detection technologies for identifying nano-sized plastic particles are still lacking, and therefore should be developed swiftly.

Polymer-soluble thermostable phosphate-ester copper complexes for near-infrared absorbing dyes with weak absorbance in the visible region

Near-infrared absorbing dyes must be thermally stable above their processing temperatures. Here, polymer-soluble thermostable phosphate-ester copper complexes that meet these requirements are reported for use as near-infrared absorbing dyes with a wide absorption range from 700 to 1200 nm, and a weak absorbance in the visible region. C5–C12 alkyl phosphate-ester copper complexes were synthesized and their thermal stabilities were evaluated by thermogravimetric analysis. The previously reported acetoxy-butyl-phosphate copper complex, which contains an ester group, was also synthesized for comparison. The mass of the alkyl-phosphate-ester copper complexes remained constant up to 170 °C, whereas that of the acetoxy-butyl-phosphate copper complex started to decrease below 100 °C. Some copper complexes showed decomposition temperatures above 250 °C. The thermal-decomposition behavior of the n-pentyl-phosphate copper complex, cyclohexyl-phosphate copper complex and 2-ethylhexyl-phosphate copper complex was investigated by thermal-decomposition gas analysis measured by purge-and-trap gas chromatography/mass spectrometry. Cleavage of the O–C bond was the main decomposition reaction for both complexes. The difference in the thermal stabilities of the cyclohexyl-phosphate copper complex and other alkyl-phosphate-ester copper complexes is presumed to result from their different tendencies towards cleavage of the O–C bond. The absorption spectra of the 2-ethylhexyl-phosphate copper complex and the isodecyl-phosphate copper complex showed a broad absorbance from 700 to 1200 nm and a weak absorbance in the visible region. Therefore, these compounds are suitable for window materials that require heat-shielding properties and transparency. The spectra also indicated that the structures of these copper complexes are similar regardless of the substituent on the ligand.

Thermal and structural studies of sol–gel-derived yttria-doped ZrO2 nanoparticles

This investigation focuses on the role of different atmosphere conditions (air and vacuum) during annealing at different temperatures of sol–gel-derived zirconia ZrO2 (stabilised by yttria in 5 mol%) nanocrystals (5YSZ). Prepared samples were characterised by powder X-ray diffraction (PXRD), simultaneous differential thermal and thermogravimetric analysis, evolved gas analysis coupled with mass spectrometry (EGA-MS), Fourier transform infrared spectroscopy (FT-IR) and micro-Raman spectroscopy. The results of thermal analysis and PXRD analysis show the zirconia crystallisation onset at temperature not lower than 400 °C, while EGA-MS analysis further identified gaseous thermal decomposition products. Average crystallite size of the 5YSZ annealed in air at 400, 600, 700 and 800 °C was calculated to be 10, 15, 22 and 33 nm, respectively. On the other hand, crystallite size remains significantly lower when the heat treatment was conducted in vacuum, i.e. in the range 4–13 nm. Annealing atmosphere affects crystallisation, resulting in lower thermal treatment requirements and enabling controlled crystallite growth. PXRD, FT-IR and micro-Raman spectroscopy showed nanocrystalline 5YSZ samples were successfully stabilised in the tetragonal phase and preserved phase stability over the investigated wide thermal treatment range. Due to the yield of stable particle with small size at lower temperatures, the vacuum-prepared 5YSZ coatings are considered as highly applicable for steel corrosion protection.

Numerical Analysis of Heat Transfer in Fire-Protective Coatings Deformable upon Heating

Numerical studies of heat transfer in fire-protective coatings deformable (intumescent) upon heating have been conducted. The optimum combination of the computation-scheme parameters providing stability, convergence and satisfactory accuracy of solutions has been determined. An effect of basic characteristics of materials in real range of their change that made it possible to estimate the degree of influence of properties on the fire-protective efficiency of coatings and the level of warm-up (flame resistance) of structures to be protected with them has been studied. The possibility of using developed models and techniques to estimate and provide the required level of fire safety of polymer-based materials (in particular, elastomers and structures and products on their basis) is considered. The results of estimating the mass rate of evolving gaseous thermal-decomposition products that determine, in a considerable extent, the material combustibility have been presented. The numerical analysis results have demonstrated the potentiality of reducing the combustibility of such materials and increasing limits of their fire resistance at the expense of organizing the intumescence of a material upon heating by means of modification of their initial formulations as well as with the aid of an additional layer made of the intumescent coating compatible with an elastomer.

Effect of the shape of particles on the characteristics of the ignition of coal–water fuel

A solution to the problem of the ignition of a coal–water fuel particle under the conditions of radiation-convective heat exchange with the environment was proposed. The mathematical simulation was carried out taking into account the combined occurrence of a set of physical and chemical processes (thermal conductivity, the evaporation of water, the thermal decomposition of the organic matter of a coal component, the filtration of water vapor and gaseous thermal decomposition products to the surface, and the chemical interaction of water vapor with the solid and gaseous products of the pyrolysis of coal) in the initial and slightly dried parts of the fuel. The effect of the configuration of a particle on the delay times of ignition was established based on an example of two typical shapes (sphere and cube).

High Performing Hollow Silicon Nanotube Anodes for Lithium Ion Batteries

Silicon has attracted considerable interest as a as a high energy density anode replacement to graphite for lithium ion batteries due to this high theoretical capacity of 4200 mAh/g. The material however suffers from colossal volume expansion (400%) related stresses during cycling leading to pulverization and cracking of the electrode. Over the past few years different approaches have been developed to address the issue caused by the formation of various zintle phases of Li – Si system during the lithiation and alloying process. These approaches involve the use of silicon nanoparticles[1], composite structures of amorphous silicon[2], in-situ and ex-situ active – inactive matrices[3], electrodeposited thin films and VACNT-Si heterostructures[4-6]. Amongst these, silicon nanoparticles and nanotubes have shown the ability to withstand the large internal stresses and strain mismatch generated during the expansion process and hence, serve as stable architectures for exploration and exploitation as an anode in Li/Li+battery. Previously we have demonstrated a simple and large scale synthesis approach for the generation of hollow silicon nanotubes (h-SiNTs) using Inorganic nanowire (I-NW) templates and chemical vapor deposition of amorphous Si which show excellent and stable cycling capacities (2420mAh/g @ 300mA/g) for the Li/Li+system. However, the system shows a high first cycle irreversible (FIR) loss (24%-27%) due to the SEI formation and relatively low columbic efficiency of 98.0% In the present work, we have studied the effect of optimizing the time of deposition of Si during the CVD on the FIR loss and loading density. These hollow Si nanotubes were then coated with a thin layer of carbon by gaseous thermal decomposition at 700oC and further washing with suitable reagents to remove the unwanted phases on the surface. Slurry based electrodes of hollow nanostructures (carbon coated and reagent washed) mixed with binder and conductive additives were then fabricated and tested in a half cell configuration against lithium foil between the voltage range 0.01V – 1V vs. Li/Li+in 1M LiPF6 (dissolved in EC:DEC:FEC=45:45:10) electrolyte. We have demonstrated the increase in loading density of the active material in the electrode by increasing the time of deposition thus, leading to increase in the thickness of the hollow Si nanotube wall. Subsequently, the FIR loss decreases to 15% with the increase in the time of Si – CVD deposition due to the reduction in the specific surface area of the hollow SiNTs however, without affecting the stability of the nanostructured electrodes. The carbon coated hollow SiNTs (Figure 1) showed a first cycle capacity of 1780 mAh/g (at 300mA/g) with FIR loss of only 14.2% and a columbic efficiency of 99.9%. The reagent washed carbon coated hollow SiNTs further exhibited a first cycle capacity of 1800mAh/g (at 300mAh/g) with an FIR loss of only 13% and a columbic efficiency of 99.92%. Materials phase, morphology and surface analysis was conducted on the electrodes before and after electrochemical testing to confirm the stability of the nanostructures on long term cycling. SEM analysis was conducted on the electrode in lithiated state to study the effect of volume expansion on the morphology and configuration of the electrodes. Results of these studies will be presented and discussed. Acknowledgement: The authors gratefully acknowledge financial support of the DOE-BATT (DE-AC02-05CHl1231) and NSF (CBET-0933141) programs. The authors also acknowledge the Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) for support of this research.