TG DSC Research Articles

Synthesis of [Pb(H2O)6][ATZ]·H2O and its impact on potassium nitrate decomposition temperature

In this study, catalyst formation [Pb(H2O)6][ATZ]·H2O (ATZ = azo tetrazolium anion) was successfully synthesized originally; meanwhile, the single-crystal structure of the compound was cultivated and analyzed by diffraction single-crystal method. The influence of the compound in which [Pb(H2O)6][ATZ]·H2O was used as combustion catalyst on the decomposition temperature of potassium nitrate was studied by TG–DSC. The result proved that [Pb(H2O)6][ATZ]·H2O can effectively reduce the decomposition temperature. In other words, [Pb(H2O)6][ATZ]·H2O can reduce the decomposition temperature of potassium nitrate, so the addition of [Pb(H2O)6][ATZ]·H2O can make potassium nitrate better to be used in the fields of initiating explosive device and fire engineering.

Investigation on thermal stability and flame spread behavior of new and aged fine electrical wires

Thermal properties and fire propagation performance were studied for the new and aged electrical wires. Two fine electrical wires were tested using the DSC–TG and a flame spread apparatus. The main objective is to understand the thermal aging effect because the aging of electrical wire is inevitable in real service conditions. The significant discoloration occurs for PC sample during the thermal aging, while slightly changes for PN sample. The microstructure of all samples surface presents relatively smooth. The diffusion of metal from inner core to polymer insulation was discovered by the XPS. The change of these parameters including melting temperature, heat of melting, onset temperature of decomposition, mass loss, etc., is observable and complicated. The metal core also has the effect on properties of polymer insulation during the thermal aging. The difference of thermal properties between new and aged electrical wires shows that the chemical composition and structure of polymer insulation change due to thermal degradation and metal catalysis. Finally, the influence of thermal aging on the flame spread rate was also discussed. This study indicates that thermal aging coupled with the metal catalysis can promote the degradation and change the thermal or fire spread properties of polymer materials.

Effect of inhibitors on the thermodynamics and kinetics of spontaneous combustion of coal

In order to find a low-cost and better performance inhibitor, this study chose the widely used and effective inhibitors NH4HCO3, ammonium polyphosphate (APP) and waterborne polyacrylate (PA) and designed the TG–DSC and FTIR experiments of coal samples with three kinds of inhibitors to study the effects of different inhibitors on various parameters of spontaneous combustion of coal. The results showed that the mass loss rate of C&APP and C&PA was lower than that of raw coal, and the enthalpy and oxygen absorption quantity of coal obviously reduced, and the content of gas products also reduced to some extent. The two kinds of inhibitors had good retardant effect, but it was not good for C&NH4HCO3. Through the curve-fitting analysis of infrared spectrums, the intrinsic mechanism of retardant effect of PA was studied in depth, and it was found that PA can reduce the decomposition of aliphatic structure and inhibit the formation of oxygen-containing functional groups of coal. Further kinetic analysis was carried out by using the isoconversional method. It is found that adding PA increases activation energy in the oxygen absorption and mass gain stage of coal, which have retardant effect in the primary stage of spontaneous combustion of coal.

Investigation of the ignition and combustion of compressed aluminum/polytetrafluoroethylene bulk composites

The thermal pyrolysis process of mold-compressed Al/PTFE composites has been investigated. TG–DSC analysis of the Al/PTFE composites revealed a slight exothermic pre-reaction in the range 500–600 °C. Based on XRD and XPS analyses of Al/PTFE composites subjected to heat treatment at 500–600 °C, this pre-reaction is believed to be fluoridation of the alumina passivating layer on the surface of Al particles. This fluoridation has been confirmed to be a crucial factor in triggering the ignition of aluminum particles in an O2 flow at a temperature much lower than the melting point of aluminum (660 °C). The energetic properties of the Al/PTFE composites have been studied, and the compositions of their combustion residues have been analyzed by XRD. The results indicated that the energy release from the composites and the compositions of their solid combustion residues were determined by their PTFE contents. Composition analysis of these combustion residues has revealed the formation of AlF3, Al2O3, Al4C3, and amorphous carbon.

Porous alumina ceramic via gelcasting based on 2-hydroxyethyl methacrylate dissolved in tert-butyl alcohol

Abstract To obtain porous alumina ceramic with high strength, a novel gelcasting system based on 2-hydroxyethyl methacrylate (HEMA) dissolved in tert-butyl alcohol (TBA) was developed. The polymerization of the HEMA–TBA gelcasting system, the thermal behavior of obtained green body, and the microstructures and mechanical properties of the sintered bodies were investigated by rheometer, TG–DSC, SEM and bending strength testing, respectively. The results show that, (1) 10 mg/mL of the initiator (benzoyl peroxide) is the optimal amount for polymerization of this gelscasting system at 25 °C; (2) The alumina suspension of the HEMA–TBA gelcasting system showing shear-thinning behavior is sufficiently low for gelcasting process; (3) The bending strength of porous alumina ceramic samples, whose porosities range from 42% to 56%, is from (8±0.5) to (91±4.5) MPa.

Highly Active Monolith Catalysts of LaKCoO3 Perovskite-type Complex Oxide on Alumina-washcoated Diesel Particulate Filter and the Catalytic Performances for the Combustion of Soot

The LaKCoO3/ɤ-Al2O3/cordierite and LaCoO3/ɤ-Al2O3/cordierite monolithic catalysts were successfully prepared by impregnating the as-pretreated monolith with aqueous solution of metal salts on monolithic cordierite substrate with a dip-coating two-step method. For comparison, one-step method without the alumina sol coating was also investigated. The monolithic catalysts were characterized by means of XRD, FT-IR, BET, ICP, TG–DSC, XPS and SEM-EDS. The characterization results demonstrate the formation of a small amount of Co3O4 when a large amount of K+ was introduced into LaCoO3 for the substitution of La3+. The coating of porous hollow aluminum oxide nano-particles could enhance the surface area of monolithic cordierite by about 100 times. The active components of LaKCoO3/ɤ-Al2O3 supported catalysts can disperse on the surface of the catalysts as monolayer and be the uniform distributions of La, Co and K. The ultrasonic vibration treating results indicated that the Al2O3 washcoat and catalyst components were adhered to the substrate strongly, the average weight loss is limited to about 1.0 % of the washcoat weight after 30 min in ultrasonic bath. The TG–DSC results show the good thermal stability of the LaKCoO3 and LaCoO3 coatings on alumina-coated monolithic cordierite. The LaKCoO3/ɤ-Al2O3/cordierite catalyst gave the highest catalytic activity for soot combustion among the studied catalysts. The T10, T50, T90 over the LaKCoO3/ɤ-Al2O3/cordierite catalyst were 186.3 °C, 314.6 °C, 390.0 °C, respectively, and Sco2mwas 99.8%.

Recovery of molybdenum by solvent extraction from simulated high level liquid waste

In this study, simple and a rapid solvent extraction method is investigated to recover Mo(VI) from simulated HLLW. The (NH4)6Mo7O24·4H2O dissolved in 3 M HNO3 was treated with ascorbic acid and KSCN to form orange red colored Mo(V)-SCN. Reduction of Mo(VI) was confirmed by cyclic voltammetry. The freshly formed complex was completely extracted to ethyl acetate layer. The organic solvent could be recovered using rotary evaporator. The Mo-complex disproportionated gradually to form a yellow solid, Mo(OH)2(SCN)3·6H2O, which forms MoO3 @ 400 °C. The solid product was characterized by XRD, FT-IR, EDX, TG–DSC and SQUID measurements.

Stabilization of Cerium(III) in the Structure of Hydrotalcite-Like Layered Double Hydroxides

This research is devoted to the preparation of cerium-containing layered double hydroxides (LDHs) and exploring the possibility of stabilizing cerium in the unstable valence state (III) in their structure. It has been shown that the best result is achieved in the case of using hydrothermal treatment in the synthesis process. A sample of an LDH obtained via this method possesses characteristics typical for this class of compounds, as has been demonstrated using a set of instrumental methods (XRD, IR, TG–DSC). It has been proved by cerium L3-edge X-ray absorption spectroscopy that cerium is only partially oxidized to Ce(IV) during the synthesis process.

Thermal and evolved gas analyses of decomposition of ammonium dinitramide-based ionic liquid propellant using TG–DSC–HRTOFMS

Thermal and evolved gas analyses were carried out to assess the decomposition of an ionic liquid propellant consisting of ammonium dinitramide (ADN), methylammonium nitrate (MMAN) and urea, using thermogravimetry–differential scanning calorimetry–high-resolution time-of-flight mass spectrometry (TG–DSC–HRTOFMS). This technique simultaneously assesses the thermal and evolved gas behavior and is able to distinguish between products having similar mass-to-charge ratios, based on accurate mass determinations. ADN/MMAN and ADN/MMAN/urea mixtures were found to decompose to form NH3, H2O, HCN, CO, N2, CH2O, CH3NH2, HNCO, CO2, N2O and HNO3, and possible reaction schemes for the decomposition processes were developed. Interactions between ADN and MMAN appear to enhance the generation of N2, while the presence of urea reduces the net exothermic heat of reaction due to the endothermic pyrolysis reaction of urea to NH3 and HNCO, followed by the reaction HNCO + H2O → NH3 + CO2.

Electrical and thermal properties of PANI–Mmt nanocomposites in strongly acidic aqueous media

Polymer nanocomposite have presented a growing importance in many uses such as the higher protection of steel from corrosion, lifelong thermal and electrical performance of their nanocomposite due to their morphological improvements with nanocharges hence become an alternative to pure polymers. The nanocomposites are mixed materials synthesized by polymeric matrix with small percentage of montmorillonites (Mmt) as inorganic reinforcement which can be recycled and not toxic. The dispersion of Mmt is facilitated by the organophilisation of their structure by alkylammonium. It is a question of following the evolution of the electrical conductivity and thermal stability of nanocomposite according to time for samples aged in strongly acidic solutions at various temperatures. Fractions of products will be taken regularly and characterized by FTIR–UV, RX and GPC. Conductivity will be followed by the four probe method. The study will be followed by the evaluation of morphology by microscopy and the thermal stability by DSC–TG.

Synthesis of layered double hydroxide from asbestos-containing waste and its adsorption property

Asbestos-containing waste is potentially harmful, and this study proposed a method to prepare layered double hydroxide using acid leaching solution of asbestos-containing waste as resource. This method can effectively reduce the harmful effects of asbestos-containing waste, and the product has wider application prospects. The as-prepared layered double hydroxide is examined by XRD, SEM, FT-IR, TG–DSC and N2 adsorption/desorption isotherms. XRD characterization showed that the layered double hydroxide has been successfully prepared, and other characterizations confirmed the layered double hydroxide prepared from asbestos-containing waste has similar physical and chemical properties to the layered double hydroxide synthesized by traditional resource. Moreover, the adsorption capacities of the layered double hydroxide prepared from asbestos-containing waste for Congo Red and Cr(VI) are 112.3 and 29.8 mg/g, respectively, suggesting its promising application for waste water purification. In addition to that, the acid-treated derivatives of asbestos-containing waste can be used in other fields, such as adsorbent, catalyst carrier.

Effect of Small Molecular Organic Acids on the Structure and Catalytic Performance of Sol–Gel Prepared Cobalt Cerium Oxides towards Toluene Combustion

Cobalt cerium oxide catalysts with small molecular organic acids (SOAs) as chelating agents were prepared via the sol–gel method and investigated for the complete oxidation of toluene. Four kinds of natural SOAs, i.e. malic acid (MA), citric acid (CA), glycolic acid (GA), and tartaric acid (TA), were selected. The effect of organic acids on the composition, structure, morphology and catalytic performance of metal oxides is discussed in details. The cobalt cerium oxides catalysts were characterized by various techniques, including TG–DSC, XRD, SEM–EDS, N2–adsorption and desorption, XPS, and H2–TPR analyses. The results show that the nature of organic acids influenced the hydrolysis, condensation and calcination processes, as well as strongly affected the textural and physicochemical properties of the metal oxides synthesized. The best catalytic activity was obtained with the CoCe–MA catalyst, and the toluene conversion reached 90% at 242 °C. This outstanding catalytic activity could be related to its textural, redox properties and unique surface compositions and oxidation states. In addition, the CoCe–MA catalyst also showed excellent stability in long–time activity test.

Investigation the catalytic profile of Eu and Pr doped CeO2 nanoparticles for the thermal behavior of AP

In these studies we report the catalytic proficiency of two Eu and Pr doped CeO2 nanoparticles on the thermal behaviour of powder AP and CSPs samples. A co-precipitation method was used for synthesizing Eu and Pr doped CeO2 nanoparticles and they were characterized by XRD, FTIR, and SEM with EDX. The catalytic proficiency of both Eu and Pr doped CeO2 nanoparticles were investigated by utilizing TG–DSC technique. The FWO, KAS, and Starink methods were used to determine activation energies of all catalyzed AP and CSPs samples. The catalytic proficiency increased by addition of Eu and Pr doped CeO2 nanoparticles and decomposition temperature decreased in the presence of catalyst. The activation energy decreased by the addition of Eu and Pr doped CeO2 nanoparticles in AP and CSPs, the burning rate of CSPs found to increase by the addition of Eu and Pr doped CeO2 nanoparticles. The Pr doped CeO2 nanoparticles showed good catalytic efficiency on AP and CSPs that reduced the decomposition temperature around 70 °C for AP and 20 °C for CSPs. The activation energy of CSPs catalyzed by Pr doped CeO2 nanoparticles reported 150.12, 147.60, and 146.83 kJ mol−1 by FWO, KAS, and Starink method respectively which decreases in existence of catalyst in CSPs.

Thermal decomposition of bromine gordaite: NaZn4(OH)6(SO4)Br·6H2O

A new compound, NaZn4(OH)6(SO4)Br·6H2O named “Br-gordaite”, was obtained by mixing of ZnO with a solution of ZnSO4 and NaBr. The Br− ion occupies the Cl− ion tetrahedral position of the brucite-like layer of the gordaite structure without any other changes relating to the structure and chemical composition. The thermal decomposition of the new phase was studied by DSC–TG(DTG)–MS in regard to the thermal events and mass loss during volatile releasing, while phase composition and chemical composition of the initial and heating products were studied by XRD and SEM–EDAX, respectively. All processes are endothermic: (1) dehydration (20–185 °C), (2) dehydroxylation (185–320 °C), (3) evolving of bromine (400–600 °C) and (4) evolving of SO3 (770–1165 °C). One-stage releasing of bromine from the “Br-gordaite” was observed at 400–600 °C. Bromine-containing intermediate crystalline phases were not detected by XRD during the “Br-gordaite” decomposition. The presence of bromine in the solid residue at 340 °C was established by chemical analysis, while after 600 °C the bromine was no longer present. The final products of the thermal decomposition of “Br-gordaite” are ZnO and traces of Na2Zn(SO4)2. The thermal behavior and the obtained thermal decomposition products of the “Br-gordaite” were compared with other minerals with Zn octahedral–tetrahedral hydroxide layer.

Synthesis and electrical properties of antimony–doped tin oxide–coated TiO2 by polymeric precursor method

Antimony–doped tin oxide–coated TiO2 (TiO2@SbxSn1-xO2 or TiO2@ATO) composite was fabricated by a facile polymeric precursor (Pechini) method, with the percent yield up to 90%. Different doping amount of antimony was used to investigate the effect on conductivity of the TiO2@ATO composite. Various characterization methods including XRD, SEM, HRTEM, XPS, UV–vis, FTIR and TG–DSC, have been applied to get deep insights into the structure, morphology and the enhanced conductivity. The composite with the lowest resistivity (4.2 Ω cm) shows a core–shell structure with the shell thickness of ∼18 nm and the ATO average nanoparticle size of 9.63 nm. Finally, a possible formation mechanism of the composite was proposed.

Thermal profile of 4,4′-dinitrocarbanilide determined by thermogravimetry–differential scanning calorimetry–mass spectrometry (TG–DSC–MS) and pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS)

Nicarbazin is an anticoccidial used in poultry production. Its residue of concern left in chicken meat is 4,4′-dinitrocarbanilide (DNC) whose content can be reduced through meat thermal processing. Thermal analysis techniques can be considered to elucidate how DNC degradation proceeds. This study aimed to investigate the thermal behavior of DNC using TG–DSC–MS and Py–GC–MS. TG–DSC–MS data showed that DNC decomposition occurs in a single step (252–280 °C) as an endothermic event (ΔH of 670 J g−1). Fragments detected at m/z 43, 44 and 65 indicated the release of isocyanic acid, carbon dioxide and 4-nitroaniline as breakdown products. In addition, Py–GC–MS analysis confirmed that DNC is thermally degraded above 250 °C generating 4-nitrophenyl isocyanate and 4-nitroaniline as the major pyrolysis products. Findings obtained from thermal analysis herein are useful to better comprehend the DNC disappearance after submitting chicken meat to heat processing.

Stability and Bioavailability Enhancement of Telmisartan Ternary Solid Dispersions: the Synergistic Effect of Polymers and Drug-Polymer(s) Interactions.

The purpose of this study was to investigate the synergistic effect of polymers and drug-polymer(s) interactions on the improved stability and bioavailability of telmisartan (TEL) ternary solid dispersions. As a water-insoluble drug, 40 and 160mg doses of TEL tablets exhibited bioavailabilities of 42% and 58%, respectively. Through polymer screening, PVP K30 and/or Soluplus were selected and used at different concentrations to prepare TEL amorphous solid dispersions by solvent evaporation. Compared to pure TEL and TEL-PVP K30/Soluplus binary solid dispersions, TEL-PVP K30-Soluplus ternary solid dispersions demonstrated significant advantages, including higher dissolution (over 90% release at 60min), better amorphous stability (physically stable in 90days), and improved oral bioavailability (Cmax of 5535.819 ± 325.67ng/mL and tmax of 1h). These advantages were related to the complementarity of PVP K30 and Soluplus on TEL. PVP K30 had a better activity to solubilize TEL and achieved a high TEL initial concentration in dissolution media. Simultaneously, the ability of Soluplus to assist in the maintenance of supersaturation played an important role. PVP K30 and Soluplus together inhibited crystallization of the drug at different stages. The existence and intensity of drug-polymer interactions were also determined by DSC (Tg determination) and FT-IR. At the molecular level, a hypothesis was also proposed that the enhancements resulted from the contribution of the synergistic effect between PVP K30 and Soluplus. These results suggested that two polymers, in a combination and via a synergistic effect, could further enhance the bioavailability and amorphous stability of ternary solid dispersions.

Flame-Retardant Mechanism of Layered Double Hydroxides in Asphalt Binder.

The flame retardancy of asphalt binders with layered double hydroxides (LDHs) was investigated using limiting oxygen index (LOI) and cone calorimeter tests. The flame-retardant mechanism of the LDHs was also studied with thermogravimetry and differential scanning calorimetry (TG–DSC), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The cone calorimeter testing results indicated that 2 wt.% of the LDHs can decease the peak heat and smoke release rate of asphalt binders. Because a low dose of LDHs can be well dispersed in asphalt binder and favor the formation of polyaromatic structures during combustion, the thermal oxidation resistance and compactness of the char layer can be improved. The LOI of asphalt binder can be increased and the heat and smoke release during combustion can be decreased with 25 wt.% LDHs. The decomposition of LDHs can absorb the heat release of the initial two stages of asphalt combustion and reduce the burning rate of asphalt. Due to the loss of loosely bound water in the LDHs during the blending process and the decrease of dispersibility at a high LDH dose, the improvement of thermal stability is limited.

Growth, optical, mechanical, thermo-physical, laser damage threshold (LDT) and Z-scan studies on dilithium succinate single crystal for optical limiting applications

Dilithium Succinate (DLiS), a third order non-linear optical single crystal was grown efficaciously by adopting slow evaporation technique (SEST) at 303 K. DLiS crystal crystallizes into rhombohedral system with unit cell parameters a = 12.05 A, b = 12.05 A, c = 10.65 A with V = 1339 A3. ICP-OES analysis ratifies the presence of alkali metal lithium in the synthesized material. In order to evaluate the mechanical nature of the crystal Vicker’s microhardness study was carried out and diverse universalistic hardness parameters like fracture toughness (Kc), brittleness index (Bi), yield strength (σv) and stiffness constant (C11) are calculated. Reverse indentation size effect (RISE) was demonstrated using Hays-Kendall approach (HK) and proportion resistance model (PSR). TG–DSC studies depicts the thermal stability and disintegration of the grown crystal. Photoacoustic study reveals the thermal effusivity, thermal conductivity and thermal diffusivity for the grown crystal and their results are compared. The grown crystal exhibits negative photoconductivity. The result found from Z-scan technique bestow the grown crystal is a versed material for photonic device applications. The laser damage threshold (LDT) value of the grown crystal is higher than KDP and urea.

Preparation, structure and luminescent performance of Na2SiF6:Re3+ (Re3+ = Eu3+, Tb3+, Ce3+) powders

A series of Na2SiF6:xRe3+ (Re3+ = Eu3+, Tb3+, Ce3+) phosphors were prepared by co-precipitation method. The structure and luminescence performance of the materials were characterized by XRD, TG–DSC, TEM, HRTEM, EDS, FT-IR, fluorescence spectra and the calculated CIE coordinates. The results show that under the excitation of specific UV light, Na2SiF6:xEu3+, Na2SiF6:yTb3+ and Na2SiF6:zCe3+ single-doping materials exhibit the characteristic emission of Eu3+ (5D0 → 7F2, red), Tb3+ (5D4 → 7F5, green) and Ce3+ (5d → 4f, blue), respectively. In the Na2SiF6:xEu3+–yTb3+–zCe3+ three-doping system, Na2SiF6:0.03Eu3+–0.07Tb3+–0.07Ce3+ material is representative. With the increase of exciting wavelength of UV light, the emission color of the material realizes tunable from white light to cool white light, warm white light and red orange light. And the luminescence of the material is closest to the ideal white light under excitation of UV light at 290 nm. So this phosphor can be promised as a single-component tunable white phosphor for application in white LEDs.