Showing papers on "Thermal decomposition published in 2016"

Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry–mass spectrometry analysis

Abstract: Thermal gravimetric and differential thermal analysis (TG-DTA) coupled with quadrupole mass spectrometry (MS) and first principles calculations were employed to elucidate the chemical nature of released gases during the thermal decomposition of CH3NH3PbI3. In contrast to the common wisdom that CH3NH3PbI3 is decomposed into CH3NH2 and HI, the major gases were methyliodide (CH3I) and ammonia (NH3). We anticipate that our findings will provide new insights into further formulations of the perovskite active material and device design that can prevent methylammonium decomposition and thus increase the long-term stability of perovskite-based optoelectronic devices.

Porous Core–Shell Fe3C Embedded N-doped Carbon Nanofibers as an Effective Electrocatalysts for Oxygen Reduction Reaction

Abstract: The development of nonprecious-metal-based electrocatalysts with high oxygen reduction reaction (ORR) activity, low cost, and good durability in both alkaline and acidic media is very important for application of full cells. Herein, we developed a facile and economical strategy to obtain porous core–shell Fe3C embedded nitrogen-doped carbon nanofibers (Fe3C@NCNF-X, where X denotes pyrolysis temperature) by electrospinning of polyvinylidene fluoride (PVDF) and FeCl3 mixture, chemical vapor phase polymerization of pyrrole, and followed by pyrolysis of composite nanofibers at high temperatures. Note that the FeCl3 and polypyrrole acts as precursor for Fe3C core and N-doped carbon shell, respectively. Moreover, PVDF not only plays a role as carbon resources, but also provides porous structures due to hydrogen fluoride exposure originated from thermal decomposition of PVDF. The resultant Fe3C@NCNF-X catalysts, particularly Fe3C@NCNF-900, showed efficient electrocatalytic performance for ORR in both alkaline an...

Nitrogen and sulfur co-doped CNT-COOH as an efficient metal-free catalyst for the degradation of UV filter BP-4 based on sulfate radicals

Abstract: By using CNTs functionalized by oxygenic functional groups ( COOH or OH) as the carbon source, novel catalysts of nitrogen (N) and sulfur (S) co-doped multi-walled carbon nanotubes (CNTs) were prepared for the first time by thermal decomposition. The obtained CNTs were characterized by SEM, TEM, BET, XPS, XRD, FT-IR and Raman spectroscopy. Additionally, the new material was used as a catalyst for the activation of peroxymonosulfate (PMS) for the degradation of benzophenone-4 (BP-4). Results indicated that the COOH group plays an important role in the S doping process. Moreover, binary (N and S)-doped CNT-COOH (NS-CNT-COOH) exhibited a notably enhanced catalytic activity towards PMS for degrading BP-4. This activity level was approximately five-fold greater than that of singly (N)-doped CNT-COOH and binary (N and S)-doped CNT, and it even exceeded that of the metal catalyst CuFe2O4. The enhanced catalytic performance was attributed to the active sites generated by the introduced pyridinic and pyrrolic N atoms and thiophenic S atoms. The effects of various factors on the catalytic activity of NS-CNT-COOH were studied. Results revealed that the degradation efficiency of BP-4 increased with catalyst load, oxidant concentration and reaction temperature. In contrast, NS-CNT-COOH exhibited no remarkable catalytic activity towards peroxodisulfate (PDS) and H2O2. In the case of the NS-CNT-COOH/PMS system, a possible pathway for BP-4 degradation was proposed and based on detected intermediates. The mechanism was justified by theoretical calculations of the frontier electron densities, which have not been reported previously. Furthermore, mineralization, toxicity, stability and reusability tests suggested that the developed catalyst, NS-CNT-COOH, holds promise for practical application.

About the Compatibility between High Voltage Spinel Cathode Materials and Solid Oxide Electrolytes as a Function of Temperature.

Abstract: The reactivity of mixtures of high voltage spinel cathode materials Li2NiMn3O8, Li2FeMn3O8, and LiCoMnO4 cosintered with Li1.5Al0.5Ti1.5(PO4)3 and Li6.6La3Zr1.6Ta0.4O12 electrolytes is studied by thermal analysis using X-ray-diffraction and differential thermoanalysis and thermogravimetry coupled with mass spectrometry. The results are compared with predicted decomposition reactions from first-principles calculations. Decomposition of the mixtures begins at 600 °C, significantly lower than the decomposition temperature of any component, especially the electrolytes. For the cathode + Li6.6La3Zr1.6Ta0.4O12 mixtures, lithium and oxygen from the electrolyte react with the cathodes to form highly stable Li2MnO3 and then decompose to form stable and often insulating phases such as La2Zr2O7, La2O3, La3TaO7, TiO2, and LaMnO3 which are likely to increase the interfacial impedance of a cathode composite. The decomposition reactions are identified with high fidelity by first-principles calculations. For the cathode ...

Kinetics of ZIF-8 Thermal Decomposition in Inert, Oxidizing, and Reducing Environments

Abstract: Zeolitic imidazolate frameworks (ZIFs) have been foregrounded as structures with exceptional, intrinsic chemical and thermal stability. However, there has yet to be a systematic study of the isothermal stability of ZIFs, specifically the well-studied ZIF-8. In this work, ZIF-8 isothermal TGA decomposition kinetics were studied in air, argon, H2/CO2, and nitrogen environments by exposing ZIF-8 to each gas for 20 h at temperatures of 200, 250, and 300 °C, respectively. ZIF-8 crystallinity was preserved under the experimental isothermal conditions at 200 °C in each atmosphere, but crystallinity was increasingly eliminated at higher temperatures. Decomposition kinetics data show that the rate of ZIF-8 carbonization significantly increases at temperatures above 200 °C irrespective of environment. ZIF-8 decomposition in the H2/CO2 reducing mixture exhibits the slowest decomposition kinetics at all temperatures and the greatest morphological change. At 300 °C, oxidative effects enhance ZIF-8 decomposition in air...

Monodisperse magnetite nanoparticles with nearly ideal saturation magnetization

Abstract: We present a scalable thermolysis and high temperature oxidation procedure for synthesizing monodisperse magnetite nanoparticles with saturation magnetization of up to 80 emu g−1 (412 kA m−1), 92% of bulk magnetite. Diameters in the 15–30 nm size range are produced from iron oleate via the thermolysis method at 324 °C and varying oleic acid ratios for size control (6.7–7.6 equivalents per Fe). The influence of the iron oleate synthesis procedure on the quality of resulting nanoparticles is examined and the structure of the iron oleate is proposed to have a triironoxonium core [Fe3O+] based on magnetic susceptibility measurements. The thermolysis method is shown to initially give wustite nanoparticles, which are oxidized in situ at 318 °C using 1% oxygen in argon to form highly magnetic magnetite nanoparticles. The use of 1% oxygen offers broad application as a safe and efficient reagent for the high temperature oxidation of nanoparticles. Special consideration to the reproducibility of nanoparticle diameter and monodispersity has uncovered critical factors. Additionally, the reduction of Fe(III) to Fe(II) is shown to occur during the heat up stage of thermolysis, beginning at less than 180 °C and being complete by 320 °C. Evidence for the reduction occurring by the oxidative decarboxylation of oleic acid is presented. Decomposition of the remaining oleic acid is shown to occur by a ketonization reaction producing oleone. The nucleation event and growth of particles is examined by TEM. Comparison of the solvents 1-octadecene and octadecane are presented demonstrating the effect on the reduction of Fe(III) during heat up, the large difference in particle size, and effects on the oxidation rate of iron oxide nanoparticles. Determination of Fe(II) content in magnetic iron oxide nanoparticles by titration is presented.

Superparamagnetic Fe3O4 Nanoparticles: Synthesis by Thermal Decomposition of Iron(III) Glucuronate and Application in Magnetic Resonance Imaging.

Abstract: Monodisperse superparamagnetic Fe3O4 nanoparticles coated with oleic acid were prepared by thermal decomposition of Fe(III) glucuronate. The shape, size, and particle size distribution were controlled by varying the reaction parameters, such as the reaction temperature, concentration of the stabilizer, and type of high-boiling-point solvents. Magnetite particles were characterized by transmission electron microscopy (TEM), as well as electron diffraction (SAED), X-ray diffraction (XRD), dynamic light scattering (DLS), and magnetometer measurements. The particle coating was analyzed by atomic absorption spectroscopy (AAS) and attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) spectroscopy. To make the Fe3O4 nanoparticles dispersible in water, the particle surface was modified with α-carboxyl-ω-bis(ethane-2,1-diyl)phosphonic acid-terminated poly(3-O-methacryloyl-α-D-glucopyranose) (PMG–P). For future practical biomedical applications, nontoxicity plays a key role, and the PMG–P...

Cobalt ferrite nanoparticles via a template-free hydrothermal route as an efficient nano-adsorbent for potential textile dye removal

Abstract: We have reported herein the preparation of a pure cobalt ferrite (CoFe2O4) nanostructure, as an efficient nano-adsorbent, via a template-free hydrothermal and post thermal conversion route. We prepared micro-spherical particles of a cobalt carbonate/iron carbonate (CoCO3/FeCO3) composite precursor using the hydrothermal reaction of cobalt sulfate, iron sulfate, ascorbic acid, and ammonium carbonate at 140 °C for 3 h. Various parameters influencing the hydrothermal reaction have been studied. Thermal decomposition of the carbonate composite precursors prepared using different Co2+ : Fe2+ molar ratios generated various impure products. However, the CoCO3/FeCO3 composite precursor synthesized employing a 0.4Co2+ : 0.6Fe2+ molar ratio produced a pure spinel CoFe2O4 nanostructure with an average crystallite size of 9.5–21.6 nm on calcination in the temperature range of 400–600 °C for 2 h. The products were identified using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (HR-TEM), nitrogen physical adsorption (BET), zeta potential and thermal analysis. The as-prepared spinel CoFe2O4 product showed a high adsorption capacity (91.7 mg g−1) toward Reactive Red 195 (RR195) dye in 20 min. The adsorption results fitted well the pseudo-second-order kinetics and could be well described by the Langmuir isotherm model. The RR195 dye adsorption was spontaneous, exothermic, and a physisorption process, implied from the calculated thermodynamic constants: ΔG0 (from −0.022 to −0.711 kJ mol−1), and ΔH0 (−7.55 kJ mol−1). It is concluded that the suggested CoFe2O4 nanostructure can be employed as an efficient nano-adsorbent for the removal of RR195 textile dye from aqueous solutions.

New Superefficiently Flame-Retardant Bioplastic Poly(lactic acid): Flammability, Thermal Decomposition Behavior, and Tensile Properties

Abstract: In this study, a superefficiently flame-retardant bioplastic poly(lactic acid) was developed by incorporating gas–solid biphase flame-retardant N,N′-diallyl-P-phenylphosphonicdiamide (P-AA), into PLA matrix. The flame retardancy of PLA/P-AA was investigated by limiting oxygen index (LOI), vertical burning test (UL94), and cone calorimeter test. Surprisingly, it was noted that only 0.5 wt % loading of P-AA increased LOI value of PLA from 20.5 to 28.4 and passed UL 94 V-0 rating at 3.2 mm thickness. In order to understand the effect of P-AA on the thermal decomposition behavior of PLA, a comprehensive study was investigated in this paper, including (i) adopting modified Coats–Redfern method to study the thermal decomposition kinetics of PLA and PLA/P-AA systems, and (ii) characterizing the evolved gaseous products and the residues in the condensed phase by thermogravimetry linked Fourier transform infrared spectroscopy (TGA–FTIR) and variable temperature Fourier transform infrared spectroscopy (VT-FTIR) tec...

Characterization of Cobalt Oxide Nanoparticles Prepared by the Thermal Decomposition of [Co(NH3)5(H2O)](NO3)3 Complex and Study of Their Photocatalytic Activity.

Abstract: In this work, thermal decomposition of the [Co(NH3)5(H2O)](NO3)3 precursor complex was investigated under solid state conditions. Thermal analysis (TG/DTA) showed that the complexwas easily decomposed into the Co3O4 nanoparticles at low temperature (175 °C) without using any expensive and toxic solvent or a complicated equipment. The obtained product was identified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). Optical and magnetic properties of the products were studied by UV-visible spectroscopy and a vibrating sample magnetometer (VSM), respectively. FT-IR, XRD and EDX analyses confirmed the formation of highly pure spinel-type Co3O4 phase with cubic structure. SEM and TEM images showed that the Co3O4 nanoparticles have a sphere-like morphology with an average size of 17.5 nm. The optical absorption spectrum of the Co3O4 nanoparticles showed two band gaps of 2.20 and 3.45 eV, which in turn confirmed the semiconducting properties. The magnetic measurement showed a weak ferromagnetic order at room temperature. Photocatalytic degradation of methylene blue (MB) demonstrated that the as-prepared Co3O4 nanoparticles have good photocatalytic activity under visible-light irradiation.

Impact of halogen-free flame retardant with varied phosphorus chemical surrounding on the properties of diglycidyl ether of bisphenol-A type epoxy resin: synthesis, fire behaviour, flame-retardant mechanism and mechanical properties

Abstract: This work aimed to investigate the effect of two types of phosphorus-containing flame retardants (P-FRs) with different chemical surroundings (phenylphosphonate-based (PO–Ph) and phenylphosphoric-based (PO–OPh)) on the flame-retardant efficiency for diglycidyl ester of bisphenol-A type epoxy (EP) resin. The two series of P-FRs which were named as FPx and FPOx (x = 1, 2 and 3), respectively, showed reactivity with epoxy group that was examined by differential scanning calorimetry (DSC) and variable temperature FTIR spectroscopy (VT-FTIR). A comparative study between the FPx and FPOx (x = 1, 2 and 3) containing flame-retardant epoxy was carried out via investigating their flammability, thermal stability and mechanical properties. The most significant difference in flame retardancy between them was that FPx (x = 1, 2 and 3) endowed EP with a V-0 rating in UL 94 test at 5 wt% loading, while FPOx (x = 1, 2 and 3) showed no rating at such loading. Importantly, it is found that there was almost 10 times difference in the flame-retardant efficiency for EP between FPx and FPOx, though they had similar chemically molecular structures. Moreover, TGA-FTIR and TGA-MS coupling techniques (TGA, thermogravimetric analysis; MS, mass spectroscopy) were employed to study the thermal decomposition of FP1 and FPO1; the impacts of FP1 and FPO1 on the thermal decomposition of EP were studied by TGA-FTIR as well. Furthermore, an online temperature detection experiment was designed to collect the temperatures by thermocouples and infrared thermometers in the UL 94 test. Based on the above results, the flame-retardant mechanisms of FP1 and FPO1 in EP are discussed. In addition, the impact of P-FRs on mechanical properties of EP was studied by means of tensile test and dynamic mechanical analysis.

A controlled, template-free, and hydrothermal synthesis route to sphere-like α-Fe2O3 nanostructures for textile dye removal

Abstract: Iron carbonate nanospheres were synthesized via hydrothermal treatment of aqueous solutions of iron sulfate, ascorbic acid and ammonium carbonate with a molar ratio of 1:1:3, respectively, at 140 °C for 1.5 h. Pure α-Fe2O3 nanoparticles with an average crystallite size of 10.5–32 nm were produced by thermal decomposition of FeCO3 at 400–600 °C for 2 h. The compositions of the products were identified by means of XRD, FE-SEM, HR-TEM, FT-IR, BET, zeta potential and thermal analysis. The adsorption properties of α-Fe2O3 were evaluated using reactive red 195 (RR195) dye. Various parameters influencing the adsorption process were investigated, using a batch technique. The results show that α-Fe2O3 nanoparticles show good adsorption capacity and the dye removal percentage reaches about 98.77% in 10 min. Plus, increasing the surface area of the α-Fe2O3 nanoparticles from 107.7 to 165.6 m2 g−1 increases the adsorption capacity from 4.7 to 20.5 mg g−1. Moreover, the adsorption data fit the Langmuir isotherm model well and the thermodynamic parameters exhibited an endothermic and spontaneous nature for the adsorption of RR195 dye on the hematite adsorbent.

Thermal stability of imidazolium-based ionic liquids investigated by TG and FTIR techniques

Abstract: Thermal stability and thermal decomposition kinetics of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) were investigated using isothermal and non-isothermal thermo-gravimetric analysis. The results indicated that isothermal test in the air showed that after storage at 180 and 300 °C both for 10 h, the conversion rate of [bmim]BF4 was 1.28 and 2.57 %, respectively. When stored at less than 300 °C, all bands of IR spectra are nearly unchanged. It suggests that [bmim]BF4 basically is stable. When isothermal stored at 350 °C for 2 h, the ATR–FTIR spectra show that the relative intensity of BF 4 −1 anion near band of 1058 cm−1 fell by 36.7 %. Due to the intensity of the absorption band declined significantly in the range of 300–350 °C, the anion of BF 4 −1 was possibly dissociated by the action of air and heat; thus, at the time [bmim]BF4 is not stable. The average apparent activation energy of thermal degradation obtained by multiple scanning methods is 105.6 kJ mol−1. Moreover, mass spectrometric analysis also shows that the z/m of [bmim+] is 139.1; in the thermal degradation process, the possibility of generating a dimer between imidazolium cation exists.

Heat-Initiated Chemical Functionalization of Graphene.

Abstract: A heat-initiated chemical reaction was developed to functionalize CVD-grown graphene at wafer scale and the reaction was universally extended to carbon nanotubes, and other precursors that could be thermally converted to active radicals. The chemical reaction can occur in absence of oxygen and water vapor when the temperature is above the decomposition temperature of the reactants. The chemical reaction was also found to be substrate-dependent due to surface doping and inhomogeneity. A large-scale graphene pattern was demonstrated by combing with microfluidic technique. This heat-initiated solid-phase chemical reaction provides a facile and environmentally friendly approach to functionalize carbon nanomaterials with various functional groups.

Impact of halogen-free flame retardant with varied phosphorus´s chemical surrounding on the properties of diglycidyl ether of bisphenol-A type epoxy resin: synthesis, fire behaviour, flame-retardant mechanism and mechanical properties

Abstract: This work aimed to investigate the effect of two types of phosphorus-containing flame retardants (P-FRs) with different chemical surroundings (phenylphosphonate-based (PO?Ph) and phenylphosphoric-based (PO?OPh)) on the flame-retardant efficiency for diglycidyl ester of bisphenol-A type epoxy (EP) resin. The two series of P-FRs which were named as FPx and FPOx (x = 1, 2 and 3), respectively, showed reactivity with epoxy group that was examined by differential scanning calorimetry (DSC) and variable temperature FTIR spectroscopy (VT-FTIR). A comparative study between the FPx and FPOx (x = 1, 2 and 3) containing flame-retardant epoxy was carried out via investigating their flammability, thermal stability and mechanical properties. The most significant difference in flame retardancy between them was that FPx (x = 1, 2 and 3) endowed EP with a V-0 rating in UL 94 test at 5 wt% loading, while FPOx (x = 1, 2 and 3) showed no rating at such loading. Importantly, it is found that there was almost 10 times difference in the flame-retardant efficiency for EP between FPx and FPOx, though they had similar chemically molecular structures. Moreover, TGA-FTIR and TGA-MS coupling techniques (TGA, thermogravimetric analysis; MS, mass spectroscopy) were employed to study the thermal decomposition of FP1 and FPO1; the impacts of FP1 and FPO1 on the thermal decomposition of EP were studied by TGA-FTIR as well. Furthermore, an online temperature detection experiment was designed to collect the temperatures by thermocouples and infrared thermometers in the UL 94 test. Based on the above results, the flame-retardant mechanisms of FP1 and FPO1 in EP are discussed. In addition, the impact of P-FRs on mechanical properties of EP was studied by means of tensile test and dynamic mechanical analysis.