TG MS Research Articles

Studies on evolution of nano SiC ceramics from allylborosiloxane

Allylborosiloxane preceramic oligomers with ceramic residue in the range 75–84% (at 900°C) were synthesized through the condensation of phenyl boronic acid (PBA) with allyltriethoxysilane (ALTEOS) in three different monomer feed ratios. The oligomers were characterized by GPC, IR, viscosity, TGA and TG–MS techniques. There is an increase in ceramic residue with increase in ALTEOS and maximum residue of 84% was obtained for the oligomer synthesized from PBA and ALTEOS in 1:2 ratio. The oligomers were pyrolysed at 900°C followed by heat treatment at 1500°C and 1650°C in inert atmosphere and were characterized by spectroscopic techniques. Even though SiC formation is observed at 1500°C, conversion of SiBOC/SiOC to SiC is not complete at 1500°C and the presence of silica and carbon phases are found in the ceramics. Spectral studies reveals that β-SiC with trace amount of α-SiC is formed when oligomers are heated at 1650°C in argon atmosphere.

The preparation and characterization of polymer-derived Fe/Si/C magnetoceramics

In this work, the preparation of polymer-derived Fe/Si/C ceramics was achieved by synthesis and pyrolysis of the preceramic hyperbranched polyferrocenylsilane. The Fe/Si/C ceramics obtained under various experimental conditions such as different pyrolytic temperatures, atmospheres and heating rates, were investigated by TG–MS, XRD, and XPS. Moreover, the magnetic properties of the ceramics were investigated by the vibrating sample magnetometer (VSM). Experimental results indicated that the pyrolysis of the preceramic polymer started above 250°C and completed among 800–1000°C. The crystallization of the pyrolytic product started at 500°C. Besides the heat treatment temperature, the atmosphere and heating rate also played important roles in the composition and magnetic properties of the corresponding Fe/Si/C ceramics. Fe existed as α-Fe in ceramics sintered at 900°C under N2 and NH3 atmospheres. However, the main components in ceramic product sintered under air were γ-Fe2O3 and carbon. Although all of the three ceramic products sintered under different atmosphere were ferromagnetic with low remanent magnetization and coercivity, the ceramics sintered under NH3 had the largest saturation magnetization. The saturation magnetization of the Fe/Si/C ceramics further ascended when fabricated under NH3 with a slower heating rate, in which Fe existed as α-Fe, Fe3O4 and γ′-Fe4N.

Thermoanalytical, magnetic and structural investigation of neutral Co(II) complexes with 2,2′-dipyridylamine and salicylaldehydes

Cobalt(II) complexes of 2,2′-dipyridylamine (dpamH) and substituted salicylaldehyde ligands (X-saloH, where X = 5-NO2, CH3, Br and Cl) with the general formula [Co(X-salo)2(dpamH)] (1–4), were synthesized and characterized by physicochemical methods and by spectroscopy (IR and UV–Vis). The octahedral geometry around Co2+ ion and the bidentate chelating mode of the anion X-salo− were proved by single-crystal X-ray diffraction analysis for the complexes [Co(5-CH3-salo)2(dpamH)] (2) and [Co(5-Cl-salo)2(dpamH)] (4). The variable-temperature (76–303 K) magnetic susceptibility measurements showed a paramagnetic nature of the complexes, in accordance with their molecular structure. The simultaneous TG/DTG–DTA technique was used to analyze their thermal behavior under inert atmosphere, with particular attention to determine their thermal degradation pathways, which was found to have a multi-step nature, accompanied by the release of the ligand molecules, as it is partially confirmed by analyzing the amount of gases evolved during heating under experimental conditions comparable with those of TG by using a TG–MS device. Finally, the decomposition kinetics, analyzed by applying the Vyazovkin’s advanced isoconversional method and referred to the elimination of the ligand molecules in the range 200–400 °C (process that was found to be common in all four complexes), confirmed the stability order assessed on the basis of the decomposition temperatures only.

Si(OCH2Fc)4: Synthesis, Electrochemical Behavior, and Twin Polymerization

AbstractThe preparation and twin polymerization of the twin monomer Si(OCH2Fc)4 [Fc = Fe(η5‐C5H4)(η5‐C5H5)] (2) by the reaction of FcCH2OH (1) with SiCl4 in the presence of pyridine was explored. The electronic properties of 2 were investigated by cyclic voltammetry, square‐wave voltammetry, and UV/Vis/near‐IR spectroelectrochemistry, which showed a redox separation caused by electrostatic repulsion. Thermally induced condensation of 2 is characteristic, as evidenced by differential scanning calorimetry (DSC) and thermogravimetry coupled mass spectrometry (TG–MS). Upon heating 2 to 210 °C, twin polymerization occurred and a hybrid material was formed that showed similarities with known systems derived from 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] (SBS), such as the nanopatterning of the formed silicon dioxide, which is characteristic for twin polymerization. Electron microscopy of this material revealed the absence of typical microstructuring found for other twin polymers, and hence, the herein presented system can be characterized as a borderline system if compared to known twin monomers such as SBS. The copolymerization of 2 and SBS afforded a hybrid material from which porous carbon or silica materials containing iron oxide nanoparticles could be obtained. The oxidation state of the incorporated particles was examined by Mössbauer experiments, which confirmed that only FeIII was incorporated within the porous carbon and silica materials, respectively. The preparation of iron oxide containing porous carbon capsules was achieved by applying a mixture of 2 and SBS to silicon dioxide spheres (d = 200 nm). After twin polymerization and carbonization, porous carbon capsules with incorporated iron oxide nanostructures were obtained.

Study on pyrolytic kinetics and behavior: The co-pyrolysis of microalgae and polypropylene

In the current work, the co-pyrolysis kinetics of Dunaliella tertiolecta and PP were investigated via TGA, while TG–FTIR and TG–MS were used for the analysis of gas-phase components and volatiles transition. The TGA results show that PP with certain small particle size accelerates the pyrolysis process of the microalgae, while the existence of D. tertiolecta delayed that of PP. This significant interaction achieves maximum when mass ratio of PP and D. tertiolecta is 6:4. The activation energy estimated from FWO kinetic model also supports this interaction. The TG–FTIR and TG–MS results show that a significant decrease of CO2 occurs at PP and D. tertiolecta mass ratio of 6:4, indicating that small molecules (such as radicals) released by PP might react with CO2 produced by D. tertiolecta or carbonyl groups in the microalgae.

Coal pyrolysis characteristics by TG–MS and its late gas generation potential

As natural gas production from deep strata becomes increasingly successful in recent years, the evaluation on gas generation potential from OM (organic matter) in the deep formations is attracting increasing attention recently, especially the late gas generation potential. In this paper, a TG–MS (thermogravimetric analysis–mass spectrometry) device was applied to investigate the process and characteristics of gas generation of HCs (hydrocarbons) and non-HCs (non-hydrocarbons) during the pyrolysis processes of coal from Songliao Basin, and its late gas generation potential. The TG–MS experimental results show that: (1) during coal pyrolysis with heating rate of 10 °C/min, methane generation started at ∼300 °C, reached its peak generation at 480 °C, and ended at ∼850 °C, which was much higher than the ending generation temperatures of other HCs; (2) when investigating the methane generation characteristics through the gas generation curve by ion fragments, more accurate results are obtained with mass to charge ratio m/z = 15 than currently used m/z = 16; (3) this coal has a high late gas generation potential, with 17% additional methane generated at late generation stage after 600 °C (equivalent to a vitrinite reflectance: Ro ⩾ 2.5%), and the methane generation ended at a maturity level of 5.3% (Ro). After calibration with coal pyrolysis results, a kinetic model has been established and applied successfully to estimate gas generation timing and illustrate gas generation mechanisms of the Shahezi Formation in the Xujiaweizi Fault Depression. Based on the results derived from the proposed kinetic model, the gas generation timing for the Shahezi Formation was between ∼115 and 50 Ma, and methane appeared to be generated steadily without any major generation peak indentified during this period and the gas generation lasted for ∼65 Ma.

TG–MS analysis of nitrogen transformation during combustion of biomass with municipal sewage sludge

Municipal sewage sludge can be chosen as an inhibitor to solve the problems related to alkali metal during biomass combustion. Emission of NO x and N2O is an important factor for the co-combustion of biomass with municipal sewage sludge. Thermogravimetry–mass spectrometry was adopted to study nitrogen transformation during the co-combustion of the blends. In this paper, the release characteristics of nitrogen-containing species of the blends during heating process are mainly studied. The yields of main nitrogenous gases (HCN, NH3, NO and HNCO) decrease by mixing biomass with municipal sewage sludge during the heating process. The decrease rate is significant when municipal sewage sludge share changes from 0 to 30 %. The co-combustion of corn straw and cotton stalk mixed with sludge releases less nitrogenous gases than that of wheat straw mixed with sludge.

Synthesis, thermal study and some properties of Gd(III), Tb(III), Dy(III) and Er(III) complexes with 4,4′-bipyridine and dibromoacetates

New complexes with formulae: Ln(4-bpy)(CBr2HCOO)3·3H2O (where Ln(III) = Gd, Tb, Dy) and Er(4-bpy)1.5(CBr2HCOO)3·3H2O, were prepared and characterized by chemical, elemental analysis and IR spectroscopy. The nature of metal–ligand coordination was studied. All of them are crystalline. Gd(III), Tb(III) and Dy(III) complexes are isostructural in one group. Conductivity studies (in methanol, dimethyloformamide and dimethylsulfoxide) were also discussed. The thermal properties of complexes in the solid state were studied using TG–DTG techniques under dynamic flowing air atmosphere. TG–MS system was used for Tb(III) (as an example of isostructural compound) and Er(III) complexes to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis in dynamic flowing air atmosphere.

Gas evolution characteristics during pyrolysis and catalytic pyrolysis of coals by TG–MS and in a high-frequency furnace

Abstract Pyrolysis and catalytic pyrolysis behaviors of two kinds of coals with different ranks were determined by thermogravimetric analyzer–mass spectrometry (TG–MS) and a high-frequency furnace. A quantitative method of on-line gas analysis was proposed using quadrupole mass spectrometry. The effects of pyrolysis temperature (650–800 °C) and Na 2 CO 3 loading amount (0–15 wt.%) on the gaseous compounds evolution were investigated. The results show that loading Na 2 CO 3 on coal was favorable for gas production in pyrolysis process. The yields of light gas species in the high-frequency furnace were lower than those in TG–MS. By comparing the pyrolysis yields of gas and solid in the high-frequency furnace and TG–MS, it was concluded that heating methods had great effects on the reaction mechanism and product distribution of pyrolysis and catalytic pyrolysis of coals. Moreover, the evolution processes of gaseous compounds were related to the presence of different functional groups in the solid samples.

Thermal decomposition of three kinds of sludge by TG–MS and PY–GC/MS

The larger volatiles content of industrial sludge compared with sewage sludge would improve the economic benefit of pyrolysis treating process. Two kinds of industrial sludge discharged by waste metalworking liquid treatment plant were used to compare with sewage sludge for their thermal decomposition characteristics by using TG–MS and Py–GC/MS methods. The results show that the abundant amount of waste base oil in waste metalworking liquids caused the DTG peaks of BS and PCS around 330 and 440 °C. The formation of calcium stearate coating layer has caused the increasing content of Aliphatics group in BS pyrolysate from 300 to 500 °C, accompany with two delayed CO2 releasing peaks. In another hand, the presence of plant debris in SS has caused the persistently Aliphatics group content decreasing of SS. It can be concluded that different wastewater characteristics and treating methods have caused several distinctions among the thermal decompositions of three samples. The high content of Aliphatics and hydrocarbons in BS and PCS pyrolysate indicated that pyrolyzing this kind of industrial sludge could obtain high valuable bio-oil and adsorbent char.

Thermogravimetry–Mass Spectrometry Analysis of Nitrogen Transformation during Oxy-fuel Combustion of Coal and Biomass Mixtures

The nitrogen transformation during the oxy-fuel combustion of coal and biomass mixtures was studied through thermogravimetry–mass spectrometry (TG–MS). Influence factors, such as atmosphere and biomass share, were selected to study the release of four nitrogenous gases HCN, HNCO, NH3, and NO. With the presence of ≥20% O2, the combustion of Datong coal and biomass mixtures releases less HCN, NH3, and NO and more HNCO in the O2/CO2 atmosphere compared to the O2/N2 atmosphere. HCN and HNCO compete mutually during the formation of nitrogenous gases. The mixtures of Datong coal and biomass release more nitrogenous gases than Datong coal alone in both O2/CO2 and O2/N2 atmospheres during the devolatilization. With the O2 concentration in the O2/CO2 atmosphere increasing from 20 to 100%, the relative yields of NH3, HCN, and HNCO produced from the mixtures decrease, while the NO yield increases. The HNCO yield changes greatly with the increase of the O2 concentration because of the oxidation by OH. Increasing the biomass share in the mixtures improves the relative yields of nitrogenous gases. The biomass share can greatly affect the HCN and HNCO yields, owing to the different forms of N-containing structures between coal and biomass.

Synthesis and characterization of a novel copper chromite catalyst for the thermal decomposition of ammonium perchlorate

A novel copper chromite based burning rate catalyst for composite solid propellants was synthesized by the thermal decomposition of basic copper ethylamine chromate. Thermal decomposition of the precursor to copper chromite was followed by TG–DSC techniques and the volatile products formed were characterized by TG–MS analysis. Copper content, surface area and Lewis acid sites of the new catalyst are higher than that in the standard copper chromite. XRD analysis showed the presence of CuCrO2 phases along with CuO and CuCr2O4. SEM analysis revealed the presence of rod shaped nanoparticles of copper chromite having diameter of 20–30nm and length of 200–300nm. The improved surface properties as well as the synergetic action of three phases of oxides, viz., CuO, CuCr2O4 and CuCrO2 in the system increase the catalytic activity of new catalyst resulting in a reduction of 60°C in the decomposition temperature of ammonium perchlorate.

Comparison of chemical composition of enamel and dentine in human, bovine, porcine and ovine teeth

ObjectiveThe aim of this paper was to compare the chemical composition of human teeth with other mammal species that are likely candidates for replacing them in studies that test dental material. DesignDentine and enamel fragments extracted from 400 sound human, bovine, porcine and ovine – 100 teeth per species – incisors and molars were mechanically ground up to a final particle size of less than 100μm. C/N analysis, thermogravimetric analysis coupled to mass spectrometry (TG–MS), and wavelength dispersive X-ray fluorescence (WDXRF) were used to analyse the samples’ composition. ResultsElemental analysis showed more organic carbon and nitrogen in dentine than in enamel. Human enamel was the most highly mineralised, with C and N values close to hydroxyapatite. Bovine dentine and enamel were the most similar to human. TG–MS: in all species, enamel contained less carbon and organic matter than dentine. Thermal decomposition of human enamel showed great similarity to synthetic hydroxyapatite, and large differences from bovine, ovine and porcine enamel. Thermal decomposition showed the greatest similarity between human and bovine dentine. WDXRF: Dentine contained larger quantities of Mg, S, Sr and Zn than enamel. Enamel contained larger quantities of P, Ca, Cl, Cu, K and Ca/P ratio than dentine. Human enamel and dentine contained a higher Ca/P ratio, larger quantities of Cl and Cu and lower quantities of Mg, S, Zn than the animal species. ConclusionsElemental analysis, TG–MS and WDXRF have shown that human and bovine enamel and dentine show the greatest similarity among the species analysed.

Combustion and NO Emission of Shenmu Char in a 2 MW Circulating Fluidized Bed

The combustion and NO emission characteristics of Shenmu coal and char were investigated with a thermogravimetry–mass spectrometry (TG–MS) system and on a pilot platform of a 2 MW circulating fluidized bed (CFB), respectively. Unlike Shenmu coal, the disadvantages of Shenmu char combustion include late ignition, poor combustion stability, and poor burnout. Despite its well-developed pore structure, there is less volatile content and more carbon crystal for Shenmu char, resulting in lower combustion reactivity compared to Shenmu coal. The combustion of Shenmu char has a higher dependence upon the combustion temperature, and it improves when the combustion temperature exceeds 900 °C. NO emission from the combustion of Shenmu char decreases with an increase in the combustion temperature, which is in contrast with the combustion of Shenmu coal. However, with an increase in the excess air ratio and a decrease in the secondary air ratio and the height of the secondary air port, NO emission from the combustion of both Shenmu char and coal increases.

Combustion mechanism of asphalt binder with TG–MS technique based on components separation

To investigate the combustion mechanism of asphalt in this study, asphalt binder was separated into four components, namely, saturate, aromatic, resin, and asphaltene. Thermo-gravimetric analysis coupled with mass spectrometry (TG–MS) was implemented to analyze the combustion behavior of the four components of asphalt in a simulated air environment. The Coats–Redfern Integral Model (CRIM) and Distributed Activation Energy Model (DAEM) were used to calculate the activation energies of the four components during the combustion process, respectively. During the combustion of each component, TG–MS was employed to investigate the weight loss and to identify the products. According to the mass loss rates at different temperature range, the combustion process was divided into several stages at a heating rate of 15K/min. DAEM was utilized to calculate nine activation energies during the entire combustion process at three heating rates of 10, 15, and 20K/min, respectively. Comparison of the activation energies obtained with the two methods indicates that the four components have entirely different combustion mechanisms, which demonstrates the importance of the component separation in the investigation of the combustion mechanism of asphalt.

Tracking of the behaviour of lidocaine base containing hydroxypropylcellulose free films with thermoanalytical method

The excipients proved to exert strong effects on the physicochemical properties of the tested systems, and it is very important to study them intensively in preformulation studies in pharmaceutical technology. In our earlier paper, we already described the structure of Klucel®-containing films with various physicochemical examinations (tensile strength, surface properties and positron annihilation lifetime spectroscopy). The aim of our present investigations was to study the thermal behaviour of the film-forming polymers with two different chain lengths, of the taste-enhancing and plasticizing excipients and also of the films prepared from them. The thermal behaviour of Klucel® LF and Klucel® MF film-forming polymers was found to differ only in the range of 340–400 °C, which is due to the different chain lengths of the polymer molecules. Among the active ingredients and excipients used, glycerol had the smallest while xylitol showed the greatest thermal stability. The shape of the TG curves shows that the decomposition process changes with the increase in the concentration of the excipients. The TG curves open up more, which is probably due to the fact that the molecules built-in among the polymer chains loosen the structure, which in turn is decomposed more easily. The TG–MS examinations revealed that during decomposition, carbon dioxide was formed in the highest concentration and that acetic acid, isopropyl alcohol and acetone also developed. The shape of the TG curves shows that in the case of the 5 and 10 % systems, the presence of lidocaine did not result in a significant difference in thermal stability.

Low-temperature preparation of belite from lime sludge and nanosilica through solid-state reaction

Belite or β-dicalcium silicate (β-C2S, Ca2SiO4), one of the main compounds in Portland cement clinker, is conventionally produced by sintering beyond the temperature of 1,200 °C using limestone and quartz. This study is aimed to synthesis belite from lime sludge, a residual solid waste from paper and pulp industry, with nanosilica at relatively low temperature through solid-state reaction. The precursors and synthesized final products are characterized using TG–MS–DTA, FTIR, XRD, SEM, TEM/EDAX and BET analysis. It is observed that the thermal process toward the formation of belite of mechanically activated dissimilar-sized precursors reduced the sintering temperature of the reaction significantly and belite is obtained without the use of any chemical stabilizers and calcination of lime sludge.

Equivalent characteristic spectrum analysis in TG–MS system

A novel method of equivalent characteristic spectrum analysis (ECSA) was developed to analyze the mass spectrum of TG–MS system according to the operating principle of TG–MS coupling system. In ECSA, the characteristic spectra and the relative sensitivity were calibrated for all tested gases. This method effectively separated the mass spectrum, eliminated the mass discrimination and temperature-dependent effect, even if there were some overlaps at characteristic peak. Based on the decomposition of CaCO3 and CaC2O4, actual flow rate and concentration of individual component in evolved gas have been dynamically determined. The analyzed mass flow rates of evolved gases agree well with ECSA and the experimental data from TG analysis. Moreover, the stability of calibration and quantitative analysis by ECSA method were discussed.

Pyrolysis mechanism and electrical properties of 3D-hybrid organic–inorganic materials based on zirconium oxides-hydroxides, 3-butenoates and vinyltrimethoxysilane

This report is focused on the quantitative thermogravimetric–mass spectrometric (TG–MS) analyses and the electrical response of two hybrid organic–inorganic materials (HYP and HYPC), obtained reacting together nanoclusters of zirconium oxides-hydroxides with 3-butenoates and cross-linked with vinyltrimethoxysilane. HYP was cured at 363 K, while HYPC at 403 K. Condensation of the silanol groups, producing shrinkage, alcoholation and the release of 3-butenoic acid and methyl 3-butenoate are the main processes involved in the early stages of pyrolysis from 323 to 633 K. The nominal formula for the two samples with a fair degree of approximation was obtained by elemental analysis and quantitative TG–MS measurements. Morphology of HYP and HYPC is determined by high-resolution transmission electron microscopy. In both HYP and HYPC, the electric response is characterized by a molecular dipole relaxation detected at higher frequencies and an inter-domain polarization phenomenon revealed at the lower frequencies, due to the presence of charged interfaces between nanodomains with different permittivities. HYP material showed a further dipole relaxation at intermediate frequencies, which assists the charge migration process. HYPC, containing a smaller density of 3-butenoate groups, reveals a long-range charge migration event of mobile species by hopping processes between relatively stiff sites.

Thermooxidative degradation of polyoxymethylene homo- and copolymer nanocomposites with hydroxyapatite: Kinetic and thermoanalytical study

In this paper thermooxidative degradation process of polyoxymethylene homo- and copolymer (POM)/hydroxyapatite nanocomposites has been studied. Kinetic analysis by Friedman, Ozawa–Flynn–Wall and multiple non-linear regression methods, as well as thermoanalytical studies using TG–MS and TG–FTIR method, were performed. TG results show that thermal stability of POM matrix significantly decreases with an increase of HAp nanoparticles concentration. The presence of higher HAp concentration changes mechanism of POM degradation, including its kinetics, which was demonstrated by a change of kinetic model from autocatalytic to phase-boundary or nth order reaction one. Hyphenated TG–MS and TG–FTIR data show that the main degradation product in the presence of higher amounts of HAp is formaldehyde, and formation of other degradation products – typical for POM thermoxidative degradation – is considerably diminished. Finally, mechanism of POM degradation in the presence of stoichiometric hydroxyapatite has been postulated.