Simultaneous Thermogravimetry Differential Scanning Calorimetry Research Articles

Simultaneous Thermogravimetry-Differential Scanning Calorimetry (TG-DSC) in Nanoporous Materials: Examples of Data for Zeolites, Metal–Organic Frameworks (MOFs), Clay Based and Mesostructured Solids

AbstractThis article presents and discusses the results of a compilation of experimental results of thermogravimetry with simultaneous differential scanning calorimetry (TG-DSC), obtained in the same apparatus and under similar experimental conditions, for a selection of nanoporous materials with interesting properties as adsorbents and catalysts, namely clays and clay-based materials (such as pillared-clays and porous clays heterostructures), zeolites and related materials (such as titanosilicates), mesostructured silicas and MOFs. Materials functionalized with a relatively common silane, the (3-aminopropyl)triethoxysilane (APTES) were also analyzed and discussed.

Exploration of the bioenergy potential of Dactyloctenium aegyptium through pyrolysis, kinetics, and thermodynamic parameters to produce clean fuels and biochemicals

The Egyptian grass (Dactyloctenium aegyptium) is a common low-cost coarse grass which is adapted to poor soils. The biomass of the Egyptian grass may be used to produce cleaner and sustainable fuels through pyrolysis without causing any contradictory impact on the land for food. It is profound to understand the thermochemical character of the Egyptian grass biomass for its efficient thermal conversion to clean fuels and chemicals. The current study elucidated the pyrolysis process of this biomass for the very first time based on the pyrolysis data. Heat-dried powdered biomass of Dactyloctenium aegyptium was pyrolyzed at 10 min−1, 30 min−1 and 50 °C min−1 in a simultaneous Thermogravimetry–Differential Scanning Calorimetry analyzer (TGA-DSC) under nitrogen atmosphere. Isoconversional models of Kissenger-Akahira-Sunose (KSA), Flynn–Wall–Ozawa (FWO) and first and second order reaction kinetics model were used to analyze the pyrolytic kinetic parameters. The pyrolysis of D. aegyptium grass biomass was shown to be a three-stage pyrolysis process where around 50 % of the product formation was happening within a narrow temperature range of 240–360 °C with the Activation energies ranged from 167 to 267 kJ mol−1 and thermodynamic parameters including 18.25–18.63 MJ kg−1 of high heating values, 169–177 kJ mol−1 of Gibb’s free energies, and 166–256 kJ mol−1 of reaction enthalpy have shown the outstanding pyrolysis and co-pyrolysis potential of Egyptian grass to produce clean fuels.

Ordered Mesoporous Silica Prepared in Different Solvent Conditions: Application for Cu(II) and Pb(II) Adsorption.

In this work, the synthesis of ordered mesoporous silica of MCM-41 type was investigated aimed at improving its morphology by varying the synthesis conditions in a one-pot process, employing different temperatures and solvent conditions. 2-methoxyethanol was used as co-solvent to ethanol. The co-solvent ratio and the synthesis temperature were varied. The pore morphology of the materials was characterized by nitrogen porosimetry and small angle neutron scattering (SANS), and the particle morphology by transmission electron microscopy (TEM) and ultra-small angle neutron scattering (USANS). The thermal behavior was investigated by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) measurements. The SANS and N2 sorption results demonstrated that a well-ordered mesoporous structure was obtained at all conditions in the synthesis at room temperature. Addition of methoxyethanol led to an increase of the pore wall thickness. Simultaneously, an increase of methoxyethanol content led to lowering of the mean particle size from 300 to 230 nm, according to the ultra-small angle scattering data. The ordered porosity and high specific surfaces make these materials suitable for applications such as adsorbents in environmental remediation. Batch adsorption measurements of metal ion removal from aqueous solutions of Cu(II) and Pb(II) showed that the materials exhibit dominantly monolayer surface adsorption characteristics. The adsorption capacities were 9.7 mg/g for Cu(II) and 18.8 mg/g for Pb(II) at pH 5, making these materials competitive in performance to various composite materials.

Composition optimization and characterization of combustible cartridge cases with polyvinyl acetate (PVAc) as a binder

Combustible cartridge case samples composed of nitrocellulose (NC), polyvinyl acetate (PVAc), kraft cellulose (KC), dibutyl phthalate (DBP) and diphenylamine (DPA) were prepared to study their structures and chemical and mechanical properties. Taguchi’s experimental design method was used to design the experimental formulations. First, simultaneous thermogravimetry-differential scanning calorimetry (STA TG-DSC), scanning electron microscopy (SEM), Brunauer–Emmett–Teller analyser (BET), bomb calorimeter (BC), vacuum stability tester (VST) and a tensile testing machine (TTM) were employed to analyse the thermochemical characteristics, structure, explosion heat, chemical stability and compatibility, and mechanical strength of all formulated samples. Based on the analysis results, the weight loss of the combustible cartridge case sample obtained by the TG experiment was chosen as the quality characteristic. The results of the Taguchi analysis indicated that the optimal parameter combination was an NC/KC weight ratio of 80:20, an NC/PVAc weight ratio of 85:15, an additional DPB of 3.5 wt.% and a density of 1.25 g/cm3. The results of the chemical stability and compatibility test, explosion heat test and mechanical strength test show that the test samples prepared with the optimal parameter combination can meet the requirements of combustible cartridge cases. Furthermore, the combustion performance of the combustible cartridge case sample prepared with the optimal formula was measured by a high-temperature combustion furnace (HTCF) and burning rate measurement device (BRM). The experimental results indicated that the autoignition temperature and ash content were 231 °C and 0.28%, respectively. In addition, the burning rate increased with increasing combustion chamber pressure but was lower than that of ordinary gun propellants at the same pressure. These combustion characteristics can meet the quality requirement of combustible cartridge cases. Finally, an actual combustible cartridge case was prepared and verified. The result of the performance verification test indicated that the average ash content was 0.30%, which was similar to that of the previous test samples and met the quality requirement.

Preparation and oxidation of aluminum powders with surface alumina replaced by iron coating

ABSTRACT Aluminum powders are well known for excellent release of energy during oxidation upon heating. However, this release of energy becomes limited due to formation of dense oxide (Al2O3) layer on powder surface. In this study, reactivity of aluminum particles was improved by replacing oxide layer with metallic shell of iron using electroless plating technique. Three different bath compositions were selected for deposition of iron on aluminum particles. The surface morphology of prepared Al/Fe core–shell composite powder was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Further, iron content in the composite powder was measured quantitatively using helium gas pycnometer while elemental analysis was performed by X-ray diffraction (XRD). Finally, thermo-physical behavior of the composite powder was investigated using simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC). The results showed that the synthesized Al/Fe core–shell composite powder exhibits higher energy release in comparison to the uncoated aluminum powder upon heating in air (up to 1180 °C). The powder with the densest iron coating released the highest energy.

Synthesis and characteristics of polycarbomethylsilane via a one-pot approach

A one-pot approach was developed to synthesize polycarbomethylsilane by using dicholorodimethylsilane, titanocene dichloride, and sodium metal as the reactants. This approach was developed because polycarbomethylsilane is a well-known polymeric precursor for fabricating silicon carbide fibers. The as-synthesized product and the derived fibers were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, 29Si nuclear magnetic resonance spectroscopy, gel permeation chromatography, simultaneous thermogravimetry-differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy coupled with energy-dispersive X-ray microscopy. The results revealed that the as-synthesized product was Ti-containing polycarbomethylsilane with a linear-chain structure and possessed an appropriate molecular weight and a narrow molecular distribution. It was found that the dicholorodimethylsilane-to-titanocene dichloride molar ratio affected the characteristics of the product, such as the product yield, molecular weight, and polydispersity. Based on the experimental results and referring to the catalytic polymerization of 1-olefin, a possible heterogeneous reaction mechanism is proposed. The as-synthesized product could be electrospun into green fibers. After curing at 180 °C for 1 h in air and calcining at 1200 °C for 2 h under a N2 atmosphere, the green fibers were transformed into ceramic fibers with a diameter less than 2 μm and an aspect ratio greater than 200. The fibers were composed of β-silicon carbide and titanium carbide.

Low-Resistivity Screen-Printed Contacts on Indium Tin Oxide Layers for Silicon Solar Cells With Passivating Contacts

The capability for contact formation on indium tin oxide layers of different low-temperature screen printing silver pastes after thermal curing and photonic sintering is evaluated in detail. The 80-nm-thick indium tin oxide layers used in this study are sputtered at three different oxygen gas flows and, consequently, differ by their electrical and optical properties. All pastes are analyzed by means of simultaneous thermogravimetry-differential scanning calorimetry. After printing and contact formation processing, the lateral resistivity of the metal contacts and their contact resistivity to the indium tin oxide layers are determined. Furthermore, the microstructure of the metal electrodes is investigated to gain a deeper understanding of the underlying contact formation mechanisms. Besides low-temperature curing at Tcuring, low = 180-220°C, as conventionally applied to silicon heterojunction solar cells, photonic sintering and thermal curing at medium temperatures Tcuring, mid = 250-350°C are utilized. The higher curing temperatures in the range of Tcuring, mid enhance the sintering and densification processes of the different pastes, and thereby, lateral resistivities of 2.4-3.5 μΩ·cm and contact resistivities of 1.0-2.5 mΩ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are achieved. The results indicate a promising industry-relevant non-firing-through metallization approach for, e.g., poly-silicon-based structures like tunnel oxide passivating contacts, which allow comparatively high temperatures for contact formation processing. With thermal curing at Tcuring, low and photonic sintering, both compatible with temperature-sensitive silicon heterojunction solar cells, lateral finger resistivities of 6.5-9.4 μΩ·cm and contact resistivities of 1.2-2.5 mΩ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are achieved. Thereby, photonic sintering has the potential of a significantly reduced process time from several minutes down to 1-4 ms.

Thermodynamics and Kinetics Parameters of Eichhornia crassipes Biomass for Bioenergy.

Eichhornia crassipes is an aquatic plant well known for its role in soil reclamation due to the containment of valuable nutrients. Moreover, its biomass is an abundant and low-cost biological resource. Pyrolysis of a biomass offers one of the cleanest methods to harness the bioenergy stored in the biomass. The present study was focused on evaluating the bioenergy potential of Eichhornia crassipes via pyrolysis. Biomass of E. crassipes was collected from a municipal wastewater pond. Oven dried powdered biomass of E. crassipes was subjected to pyrolysis at three heating rates including 10, 30 and 50 °C min-1 in a simultaneous Thermogravimetry-Differential Scanning Calorimetry analyzer under an inert environment containing nitrogen. Data obtained were subjected to isoconversional models of Kissenger-Akahira-Sunose (KSA) and Flynn-Wall-Ozawa (FWO) to understand the reaction chemistry. Kinetic parameters have shown that the pyrolysis followed first-order reaction kinetics. The average values of activation energies (129.71-133.03 kJ mol-1) and thermodynamic parameters including high heating values (18.12 MJ kg-1), Gibb's free energies (171-180 kJ mol-1) and enthalpy of reaction (124-127 kJ mol-1) have shown the remarkable bioenergy potential of this biomass. This low-cost biomass may be used to produce liquids, gases, and biochar in a costefficient and environmentally friendly way via pyrolysis or co-pyrolysis in the future.

Template-assisted synthesis of 3D ordered macroporous structured CuO as catalyst for ammonium perchlorate

Three-dimensionally ordered macroporous (3DOM) CuO is prepared by colloidal crystal templated method. The obtained 3DOM structure with about 230[Formula: see text]nm pore diameter is composed of small CuO windows. The special structured CuO is used as a catalyst for thermal decomposition of ammonium perchlorate (AP) and its catalytic activity is measured by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) techniques. Test results show that thermal decomposition performance is significantly improved after adding 2[Formula: see text]wt.% 3DOM CuO.

Effect of carbothermal reduction on the microstructures of porous carbons from the mixture of coal-tar pitch and nano-MgO

Porous carbons were prepared by pyrolysis of the mixture of coal-tar pitch and nano-MgO, and the effect of carbothermal reduction between nano-MgO and carbons on their microstructures was studied. Pyrolysis behavior of the mixture was characterized by simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC) and X-ray diffraction (XRD). In addition, the microstructures of resulting porous carbons were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and nitrogen adsorption-desorption measurement. Results show that the carbothermal reduction occurs when the temperature is beyond 1300°C, greatly influencing the microstructures of the resulting porous carbons. With the increasing of temperature, the porous carbon prepared possesses a thinner thickness of pore wall and a higher specific surface area with a less mesopore volume. When the temperature arrives at 1800°C, the porous carbon prepared exhibits three-dimensional network structures consisting of few-layered graphene sheets.

Thermal behavior of glycolic acid, sodium glycolate and its compounds with some bivalent transition metal ions in the solid state

Synthesis, characterization and thermal behavior of some transition metal glycolates, M(C2H3O3)2 [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)], as well as the thermal behavior of glycolic acid and its sodium salt (NaC2H3O3) were investigated employing simultaneous thermogravimetry and differential thermal analysis, infrared spectroscopy (FTIR), simultaneous thermogravimetry–differential scanning calorimetry coupled to FTIR (evolved gas analysis), complexometry and high-resolution electrospray ionization mass spectrometry. The lowest energy model structure of each complex has been proposed by using the density functional theory at the B3LYP/6-311++g(d) level of theory. The results provided information concerning the composition, dehydration, thermal stability, thermal decomposition and identification of the gaseous products evolved during the thermal decomposition of these compounds in dynamic dry air atmosphere.

Pyrolysis and kinetic analyses of Camel grass (Cymbopogon schoenanthus) for bioenergy

The aim of this work was to study the thermal degradation of grass (Cymbopogon schoenanthus) under an inert environment at three heating rates, including 10, 30, and 50°Cmin−1 in order to evaluate its bioenergy potential. Pyrolysis experiments were performed in a simultaneous Thermogravimetry–Differential Scanning Calorimetry analyzer. Thermal data were used to analyze kinetic parameters through isoconversional models of Flynn-Wall-Ozawa (FWO) and Kissenger-Akahira-Sunose (KSA) methods. The pre-exponential factors values have shown the reaction to follow first order kinetics. Activation energy values were shown to be 84–193 and 96–192kJmol−1 as calculated by KSA and FWO methods, respectively. Differences between activation energy and enthalpy of reaction values (∼5 to 6kJmol−1) showed product formation is favorable. The Gibb’s free energy (173–177kJmol−1) and High Heating Value (15.00MJkg−1) have shown the considerable bioenergy potential of this low-cost biomass.

An Approach to the Estimation of Adsorption Enthalpies of Polycyclic Aromatic Hydrocarbons on Particle Surfaces.

Current atmospheric models incorporate the values of vaporization enthalpies, ΔHvap, obtained for neat standards, thus disregarding the matrix effects on volatilization. To test the adequacy of this approximation, this study measured enthalpies of vaporization for five polycyclic aromatic hydrocarbons (PAHs) in the form of neat standards (ΔHvap) as well as adsorbed on the surface of silica, graphite, and graphene particles (ΔHvap(eff)), by using simultaneous thermogravimetry-differential scanning calorimetry (TGA-DSC). Measurement of the corresponding activation energy values, Ea(vap) and Ea vap(eff), by TGA using a derivative method was shown to be the most reliable and practical way to assess ΔHvap and ΔHvap(eff). Enthalpies of adsorption (ΔHads) were then calculated from the differences between Ea(vap) and Ea vap(eff), thus paving a way to modeling the solid-gas phase partitioning in atmospheric particulate matter (PM). The PAH adsorption on silica particle surfaces (representing n-π* interactions) resulted in negative values of ΔHads, indicating significant interactions. For graphite particles, positive ΔHads values were obtained; i.e., PAHs did not interact with the particle surface as strongly as observed for PM. PAHs on the surface of graphene particles evaporated in two stages, with the bulk of the mass loss occurring at temperatures lower than those with the neat standard, just as on graphite. Yet, unlike graphite, a small PAH fraction did not evaporate until higher temperatures compared to case of the neat standards and other particle surfaces (37.4-145.7 K), signifying negative, more PM-relevant values of ΔHads, apparently reflecting π-π* interactions and ranging between -7.6 and +32.6 kJ mol(-1), i.e., even larger than for silica, -3.3 to +8.3 kJ mol(-1). Thus, current atmospheric models may underestimate the partitioning of organic species in the particle phase unless matrix adsorption is taken into account.

Synthesis, characterization and thermal behavior of 2,4-dinitrophenoxy ethanol as a suitable plasticizer for propellants formulations

2,4-Dinitrophenoxy ethanol (DNE) can be considered as a suitable plasticizer for propellants based on cellulose acetate. It was synthesized in two forms, raw and pure products, which were analyzed by FTIR spectroscopy, 1H-NMR and 13C-NMR spectroscopy, elemental analysis, gas chromatography, mass spectrometry and high-performance liquid chromatography. Thermal stabilities of the products, impurities in the raw products and the effect of DNE on the thermal behavior of cellulose acetate were investigated using simultaneous thermogravimetry–differential scanning calorimetry. The results suggest that the raw product containing a small amount of impurity has better thermal stability than the pure product.

Solid-state thermal and spectroscopic studies of the anti-inflammatory drug sulindac using UV–Vis, MIR, NIR, DSC, simultaneous TG–DSC, and the coupled techniques TG-EGA-MIR and DSC–optical microscopy

Simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC), differential scanning calorimetry–optical microscopy (DSC–optical microscopy), online coupled thermogravimetry–infrared spectroscopy evolved gas analyses (TG-EGA-MIR), and spectroscopic techniques were used to study the non-steroidal anti-inflammatory drug sulindac in polymorphic form II. The TG–DSC curves, which were performed with the aid of DSC–optical microscopy, provided information concerning the thermal stability and decomposition profiles of the compound. From the TG-EGA-MIR coupled technique, it was possible to identify formaldehyde as a volatile compound that was released during thermal decomposition. A complete spectroscopic characterization in the ultraviolet, visible, near- and middle-infrared regions was performed in order to understand the spectroscopic properties of sulindac form II.

Novel crosslinkable epoxy resins containing phenylacetylene and azobenzene groups: From thermal crosslinking to flame retardance

Several kinds of novel flame-retardant-free and thermo-crosslinkable epoxy resins (EPs) containing azobenzene or/and phenylacetylene groups have been synthesized and characterized, and the flame retardant properties as a result of thermal crosslinking during combustion were investigated in detail. Crosslinking behaviors were tested by simultaneous thermogravimetry–differential scanning calorimetry (TGA–DSC). Thermal stabilities were investigated by thermogravimetric analysis (TGA). Flame retardance of the resulting EPs was evaluated through LOI tests, and combustion behaviors were studied via cone calorimetry and micro-combustion calorimetry (MCC), which further confirmed that flame retardance of these EPs was significantly improved, despite the absence of conventional flame retardant. Py–GC/MS analysis was used to investigate the degradation mechanism of these epoxy resins, and the results confirmed that the flame-retardant activity of epoxy resins mainly took effect in the condensed phase. The chemical constitution of the char layers were investigated by XPS and Raman spectrum. The co-crosslinking behavior between azobenzene and phenylacetylene groups was predicted and confirmed, which led to the most compact char layer, therefore resulted in the best flame retardance of these EPs.

Flame retardant properties of the bark powder of Anadenanthera peregrina var. falcata (Benth.) Altschul (angico) studied by coupled thermogravimetry–Fourier transform infrared spectroscopy

In this research, the bark powder of Anadenanthera peregrina var. falcata (angico) was characterized by means of simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC) and differential scanning calorimetry (DSC) in order to investigate the chemical features responsible for the flame retardant properties of this plant. The TG–DSC and DSC data evidenced that dehydration occurs between 40 and 140°C and that the anhydrous solid is stable up to 195°C, when thermal decomposition begins. Coupled thermogravimetry–Fourier transform infrared spectroscopy (TG–FTIR) techniques were used to identify the volatile products evolved during the decomposition of the sample, showing that water and carbon dioxide are the majority products formed by its decomposition even at temperatures as low as 200°C. The strong endothermic peak associated with the release of water provides a reasonable explanation for the fire retardant properties of angico.

Synergistic Effect between Aluminum Hypophosphite and Alkyl-Substituted Phosphinate in Flame-Retarded Polyamide 6

A novel binary flame-retardant system was formed by introducing aluminum hypophosphite (AP) and aluminum isobutylphosphinate (APBu) together for PA6. The optimum flame retardant formulation was 1:1 (AP:APBu, 15 wt % in total), and the resulting flame-retardant PA6 could achieve a LOI value of 28.3 vol % and UL-94 V-0 rating. Cone calorimeter testing showed the samples containing binary flame retardants became less flammable with lower peak heat release rate (PHRR, 259 kW/m2). Dynamic oscillatory rheology and simultaneous thermogravimetry–differential scanning calorimetry results proved that cross-linking reactions existed in the samples containing AP. Morphology of the char layers was analyzed via SEM and laser Raman spectroscopy, and the results demonstrated the samples containing both AP and APBu formed more effective char. These results revealed that flame-retardant synergism existed between AP and APBu when they were combined to flame retard PA6. Consequently, a brief synergistic mechanism in this sys...

Study on the structure and properties of core–shell Fe/Al composite powder synthesized by MOCVD in fluidized bed

Core–shell Fe/Al composite powder with different thicknesses of Fe layer has been prepared by MOCVD in a fluidized bed reactor. The products were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX) and simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC). The results show that a compact nano-Fe layer is covered on the surface of Al to form core–shell Fe/Al composite powder. Nano-Fe layer thickness can be controlled by adjusting deposition time. The Fe layer thickness is evaluated by weight increase in TG curve at the temperature range of 350–550°C in air atmosphere. Combustion properties of Fe/Al composite powder have great improvement compared with raw Al.

Study of some volatile compounds evolved from the thermal decomposition of atenolol

Simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC) and coupled thermogravimetry–infrared spectroscopy (TG–FTIR) analyses were used to study the antihypertensive drug atenolol. The TG–DSC curves provided information concerning the thermal stability and decomposition profiles of the compound. From the TG–FTIR coupled techniques, it was possible to identify ammonia and isopropylamine as possible volatile compounds released during the thermal decomposition of the drug.