Thermal Analysis Mass Spectrometry Research Articles

Structural Study of Dried Linseed Film using Two-Stage Pyrolysis-Gas Chromatography/Mass Spectrometry.

A dried linseed film was analyzed by two-stage pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) to investigate its structure and pyrolysis mechanisms. Heating furnace temperatures appropriate to the pyrolysis were determined to be 300°C and 600°C by thermogravimetry/differential thermal analysis-mass spectrometry (TG/DTA-MS). The dried linseed film was then pyrolyzed at 300°C and 600°C. From the pyrolysis at 300°C, saturated and monoenyl fatty acids were detected, and the relative peak intensities of hexadecanoic acid and of octadecanoic acid were highest. These fatty acids are the pyrolysis products of the terminal groups. The dried linseed film is terminated with saturated and monoenyl fatty acid esters, especially with hexadecanoic acid ester and octadecanoic acid ester. From the pyrolysis at 600°C, alkenes, alkanes and fatty acids were detected. Some alkenes and alkanes have carbon chains longer than the side chains of the glycerides. The alkenes and alkanes are the pyrolysis products of the glyceride polymers generated by the autoxidative C-C cross-linking. The formation of fatty acids is also attributed to the cross-links of the glyceride polymers. These results reveal that autoxidative cross-linking proceeds through the polymerization of linseed oil.

A study on combustion of Chinese coals by TA/MS

Thermal behavior and evolution characterization under designed combustion conditions of 13 Chinese coals of different ranks were investigated by means of thermal analysis/mass spectrometry (TA/MS). The experiments were carried out in a synthetic air atmosphere (20% oxygen+80% nitrogen) with a flow rate of 150 ml min −1 and the samples were heated from 40 up to 1200 °C at a constant heating rate of 10 K min −1. The volatile products and their evolution profiles against the temperature during the combustion were identified through the on-line recorded mass spectra. The results revealed that the whole combustion procedure could be broadly divided into 4 phases and the temperature of the maximum weight loss rate shifted to lower temperatures as the coal rank decreased. In addition to the primary combustion products water and carbon dioxide, fragments with the masses m/ z 15, 55–60, 66, 67 and sulphur dioxide ( m/ z 64) were also found in the mass spectra.

The application of CRTA and linear heating thermoanalytical techniques to the study of supported cobalt oxide methane combustion catalysts

Two combined thermal analysis-mass spectrometry techniques have been used to ascertain the effects of various support materials on the preparation and subsequent combustion activity of supported cobalt oxide catalysts. Both techniques used small sample masses in order to minimise temperature and pressure gradients throughout the sample during reaction as the sample temperature was increased at a linear heating rate. Temperature-programmed reduction (TPR) techniques employed not only reveal reduction, but also distinguish it from the adsorption (or evolution) of the H 2 and the loss of absorbed water. The thermally induced decomposition of supported and unsupported cobalt nitrate hexahydrate was studied using a solid insertion probe mass spectrometer (SIP-MS) system operating under high vacuum. The support material was found to affect the decomposition process significantly. In particular, the decomposition of cobalt nitrate dispersed on γ-Al 2O 3 occurred via a markedly altered process in comparison with the unsupported nitrate. The ZrO 2 and CeO 2 supports both exhibited less pronounced effects on the decomposition process. After calcination of dispersed cobalt nitrate species, methane combustion activity was found to be much lower for alumina-supported samples relative to the other supports used. A combined temperature-programmed reduction–mass spectrometry (TPR–MS) technique was used to elucidate a correlation between catalyst activity and reducibility. The reduction of a Co 3O 4/CeO 2 catalyst was also studied under constant rate thermal analysis (CRTA) conditions.

The structure of bone studied with synchrotron X-ray diffraction, X-ray absorption spectroscopy and thermal analysis

Bone samples of different origins and two bone substituent materials were studied with modern solid-state chemical methods: combined thermogravimetry–differential thermal analysis–mass spectrometry (TG-DTA-MS), X-ray powder diffraction (synchrotron), X-ray absorption spectroscopy (EXAFS, Ca K-edge, synchrotron), and infrared spectroscopy. The results complement those from medical histology. The mineral phase consists of disordered apatite with no indication for another calcium phosphate phase. Size and morphology of the bone mineral particles are independent of the nature of the bone sample, but there are significant differences in the overall composition of the bone samples and in the carbonate content of the mineral phase. It is concluded that the biological resorption of living bone (remodeling) is closely related to morphology and composition of its mineral phase.

Impacts of thermal aging and water absorption on the surface electrical and chemical properties of cycloaliphatic epoxy resin

New techniques for measuring surface degradation are applied to the study of surface tracking resistance of materials intended for outdoor use. Cycloaliphatic epoxy resin (CAE) with 200 pph silica powder was aged under accelerated conditions for 100 h (100 to 250/spl deg/C) and then its tracking resistance was assessed. The tracking resistance of CAE that was exposed to water absorption (0 to 3.3%) also is evaluated. Changes on the surface layer (1 to 10 /spl mu/m) with thermal treatment are revealed by employing scanning electron microscopy (SEM)-energy dispersive X-ray (EDX) analysis, attenuated total reflection (ATR)-Fourier transform infrared (FTIR), reflective visible spectroscopy and thermal gravimetry (TG)-differential thermal analysis (DTA) mass spectrometry (MS). The tracking resistance of CAE aged above 170/spl deg/C is particularly reduced. Surface resistivity declines with rising temperature of thermal aging. The lowering of surface resistivity enlarges the leakage current passing at the aged surface layer and increases the surface temperature of CAE. This would accelerate thermal aging. It also is shown that absorbed water in CAE decreases tracking resistance. The effect of absorbed water during the initial stage of a tracking test is described. Under saline pollution and moisture, thermal aging affects not only surface tracking but also electrochemical erosion derived from sodium hydroxide which forms through electrolysis of sodium chloride. Electrochemical erosion enhances water uptake for CAE, which can lead to tracking resulting from absorbed water.

Thermal deblocking of masked low molecular isocyanates: I. Aliphatic isocyanates

The thermal deblocking of masked isocyanate model substances was investigated by means of simultaneous thermal analysis and quadrupole mass spectrometry system (STA/QMS). The results were compared with additional measurements carried out by differential scanning calorimetry (DSC) and temperature dependent Fourier transform infrared spectroscopy (FTIR). The measured values which were determined as the deblocking temperature depend on the method of investigation. Thermogravimetric and mass spectrometric data depend on the volatility of the components and could differ from those observed by DSC and/or FTIR. Furthermore, the mechanism of deblocking is very complex. Secondary reactions obviously play an important role.

水酸化ストロンチウム浴中で生成するアルミニウム化成皮膜の二次処理による高耐食性化

It is known that the coatings produced by MBV method and Alojin method are inferior with point of anticorrosion, because those coatings have characteristic of thin amorphous coatings and much cracks on the surface of coating. Manufacture of the thick coating which was superior in corrosion-resistance is needed, and this study has attempted to obtain chemical conversion coatings in 0.01 mol/l Sr(OH)2 bath with boehmite process. The major component of first coating was Al(OH)3, because Al(OH)3 was remade in supersaturated sodium aluminate solution and the first coatings were examined by secondary treatment. The chemical structure, and its composition of each chemical coatings were investigated by X-ray diffraction analysis (XRD), scanning electron microscope (SEM), thermal analysis and secondary ion mass spectrometry. It is found that the first coating formed by dipped at 70°C for 60 min. was thickness of about 10 μm. The structure of first coating has two layers: one crystal layer was growing from uniform amorphous layer and another amorphous layer was thickness of about 3 μm. Crystallinity of the crystal layer (Gibsite) was enhanced by secondary treatment, the amorphous layer was double thickness compared with first coating, which was confirmed by measure of XRD and SEM. This secondary treatment coatings showed excellent corrosion-resistance (10 times or more). The mechanism of corrosion protection by secondary coating had been attributed to reason that the dissolution of aluminum decreased with coating of thick and uniform amorphous layer.

Natural fluid-deposited graphite; mineralogical characteristics and mechanisms of formation

This paper focuses on the similarities and differences between metamorphic graphite (formed in situ from organic matter) and fluid-deposited graphite. We discuss the formation of fluid-deposited graphite in terms of the source of carbon, the characteristics of the C-bearing fluids (the C-O-H system), the mechanisms of carbon mobilization, and the mechanisms of carbon precipitation. New and existing analytical data are compiled on the physical and chemical characteristics of fluid-deposited graphite obtained by the following techniques: optical microscopy, differential thermal analysis, thermogravimetry, X-ray diffraction, Raman spectroscopy, and stable isotope mass spectrometry. Our discussions focus on major, that is, volumetrically significant, worldwide concentrations of graphite.

Synthesis and characterizations of hydroxy-aluminum cross-linked montmorillonite

Cross-linked montmorillonite was prepared by reacting homoionic sodium form of bentonite (Na-M) from Istenmezeje (Hungary) with high molecular weight polyhydroxy-aluminum complex. The complex was prepared by controlled hydrolysis of alumina macrocation. The intercalated clay (Na-Al-M) was thermally treated to convert the hydroxy cations to oxide pillars. The pillared products were characterized by X-ray powder diffraction (XRD), Fourie transform infrared spectroscopy (FTIR), (thermogravimetry (TG), differential thermal analysis (DTA) and thermal analysis-mass spectrometry (TA-MS) methods. The specific surface area as well as pore size and pore structure distribution of samples were measured by nitrogen, water and carbon tetrachloride adsorption, and the heat of immersion was also determined. The pillared products were characterized by d(001) reflections of 19 A, which is stable even at 500°C. The interaction of polymer alumina caused several changes in the obtained FTIR spectra due to the formation of different new bonds. The rate of dehydroxylation of the pillared product is very moderate, the water release occurred in different temperature ranges according to TA-MS results. Dehydration starts at interfaces and at the wall of pores, occurring nearly with uniform rate at 250-500°C. DTA curve indicates the formation of a new phase at 950°C. The obtained surface area of the pillared product by nitrogen adsorption becomes larger (208 m2 g-1) with respect to the non pillared clay, which decreases less than 10% upto 700°C. The pillared sample has a definite pore structure, the quantity of micropores (0-40 A) decreased with increasing of macropores (>1000 A). The obtained domestic pillared montmorillonite possesses a high degree of thermal stability and may be used as adsorbent.

Oxidation of Single Crystals of Hafnium Carbide in a Temperature Range of 600° to 900°3C

The isothermal oxidation of HfC single crystals with (100) orientation was carried out using an electromicrobalance at temperatures of 600° to 900°3C at an oxygen pressure of 2 to 8 kPa. Nonisothermal oxidation was performed by a simultaneous thermogravimetry—differential thermal analysis—mass spectrometry analysis. A polished cross section of the oxidized crystal was observed by backscattered electron imaging in a scanning electron microscope. Quantitative chemical analysis for Hf, O, and C and their elemental profiles in the HfC and oxide scale was carried out by wavelength dispersive X‐ray microanalysis. It was found that the oxide scale consists of two regions, zones 1 and 2, both of which showed the existence of carbon. The carbon content at the middle point of zone 1 was about twice that in zone 2, which contained 7 to 14 at.% carbon. Zone 1 showed an almost compact and pore‐free phase; its thickness remained constant (1 to 2 μm) after a prolonged time. The thickness of zone 2 increased linearly with time. The oxidation mechanism including interfacial reaction responsible for the deposition of carbon is discussed.

The effect of low-concentration SO 2 on the adsorption of NO from gas over activated carbon

The effect of low-concentration SO 2 on the adsorption of NO over activated carbon was studied using adsorption-desorption profiles obtained during thermal analysis-mass spectrometry. Using three different gas mixtures and adsorption temperatures between 293 and 413 K with NO and SO 2 as the reactants, it was determined that NO 2 and SO 2 were the primary adsorbed species. The uptake of NO 2 decreased with increasing temperature, whereas the uptake of SO 2 was independent of temperature. Except at the highest adsorption temperatures, the amount of NO 2 adsorbed was greater than that of SO 2 adsorbed. The presence of SO 2 inhibited adsorption of NO 2, but the co-adsorption of NO 2 promoted the adsorption of SO 2. These data point to the possibility that the SO 2 binding sites on the carbon are associated with the reaction NO + 1 2 O 2 → NO 2, and to the different adsorption mechanisms which control NO 2 and SO 2 uptake.

Flow injection-thermal analysis-mass spectrometry: Application to studies of carbon gasification reactions

Flow injection combined with thermal analysis-mass spectrometry is a useful technique for studying gasification reactions. It provides a rapid, powerful method of separating the variables of a particular reaction, such as reactant concentration, reactant composition and temperature, studying their influence on the reaction products and differential thermal analysis. The present work illustrates the technique using the following examples: (1) the reaction of NO with carbon, and (2) the reaction of NH 3 and NO over carbon. In both cases, > 99% isotopically pure 13C was used, so that N 2 and CO, and also N 2O and CO 2 could be mass-resolved. The results also illustrate the application of the technique to the study of the effect of oxygen concentration and gasification temperature on the formation of N 2O and N 2 during the NO-carbon reaction. The results show that the N 2O:N 2 ratio increases with oxygen concentration while the N 2O concentration decreases with increasing temperature.

97/00262 Studies on brown coal liquefaction (23). Effect of oxidation of fine particle pyrite catalyst on coal liquefaction

Thermal analysis-mass spectrometry (TA-MS) has been used to study the reactions of Al Maghara coal and its low temperature ash (LTA) under combustion-related conditions. The TA-MS profile of the coal gives information on combustion performance (ignition, peak combustion and burnout temperatures) and on chemical changes to the volatile matter (H2O, SO2, CO2 and NO2), char and minerals. X-ray diffraction identified pyrite as the major mineral component in the coal. The major and only feature of the TA-MS profile of the LTA is SO2 evolution associated with decomposition of pyrite and iron sulphates. The high sulphur content of Al Maghara coal is a severe obstacle to its use in combustion. Cleaning of the coal to reduce the sulphur to an acceptable level is considered to be essential.

Temperature-Programmed Desorption Mass Spectrometry (TPDMS) of Dispersed Oxides

Temperature-programmed desorption mass spectrometry (TPDMS) is discussed with reference to studies of modified pyrogenic oxides. Simple theoretical models are presented in order to allow an approximate analytical treatment of TPDMS data. The ‘unimolecular’ decomposition of alkoxide groups was studied. The rate constants of the reactions were derived from TPDMS measurements. The kinetics of thermal transformations of phosphorous and phosphoric acids on a pyrogenic silica surface were investigated by TPDMS. Oxidation–reduction reactions in samples containing phosphorous acid resulted in the removal of molecular phosphorus (P4). Two stages of phosphorus evolution were observed which were attributed to the disproportion of phosphorus in the surface monolayer (high-temperature stage) and in the bulk layers (low-temperature stage). The biologically active samples obtained by adsorption of cyanocobalamine, glucose and raffinose on ultrafine oxide surfaces were studied via a combination of temperature-programmed desorption and solid-state thermal analysis mass spectrometry (TPD/TA MS). The role of the charged cobalt atom and of the propionamide and benzimide groups in the adsorption mechanism is discussed. It was shown that the adsorption of cyanocobalamine on the silica surface transformed the propionamide group to a weakly bound form. TPD/TA MS data were obtained confirming the stable adsorption of glucose and raffinose on an ultrafine pyrogenic silica surface modified by amino groups.

Thermal degradation and combustion process of liquid crystalline polyesters studied by directly coupled thermal analysis-mass spectrometry

Thermal degradation and combustion processes of commercial liquid crystalline polyesters (LCPs) were studied by directly coupled thermal analysis-mass spectrometry (TA-MS) under inert and quasi-air atmosphere. The first major degradation step of LCPs was the ester linkage rupture reaction. In the case of fully aromatic LCPs, this process was little influenced by 20% oxygen atmosphere. The main evolved gaseous products at this step were CO, CO 2, H 2O and phenol for fully aromatic LCP samples, in addition, aliphatic products for a semi-aromatic LCP sample. Evolution of CO 2 was followed by that of flammable organic products for fully aromatic LCPs, while flammable organic products evolved prior to CO 2 for semi-aromatic LCP. The flame resistant and self-extinguishing mechanisms of LCPs are discussed on the basis of their thermal degradation behavior.

Thermodynamic activities and phase boundaries for the alloys of the Ni3Al-Ni3Ti pseudobinary section in the Ni-Al-Ti system

The pseudobinary section Ni3Al-Ni3Ti of the ternary Ni-Al-Ti system has been investigated by ther-mal analysis and Knudsen effusion mass spectrometry. The solidus of the pseudobinary section and the thermodynamic activities of Ni and Al have been determined in the alloys Ni0.75A10.25-xTix of the compositionsx = 0.00 to 0.21. Moreover, the thermodynamic activities of Ni and Ti in Ni3Ti (x = 0.25) as well as the Gibbs energy of mixing of the Ni0.75Ti0.25 phase resulted. The ionization cross-sectional ratio Σ(Ni)/Σ(Ti) = 0.77 has been evaluated for the electron impact energy of 50 eV.

Reaction studies of an Egyptian coal under combustion-related conditions by thermal analysis-mass spectrometry

Abstract Thermal analysis-mass spectrometry (TA-MS) has been used to study the reactions of Al Maghara coal and its low temperature ash (LTA) under combustion-related conditions. The TA-MS profile of the coal gives information on combustion performance (ignition, peak combustion and burnout temperatures) and on chemical changes to the volatile matter (H 2 O, SO 2 , CO 2 and NO 2 ), char and minerals. X-ray diffraction identified pyrite as the major mineral component in the coal. The major and only feature of the TA-MS profile of the LTA is SO 2 evolution associated with decomposition of pyrite and iron sulphates. The high sulphur content of Al Maghara coal is a severe obstacle to its use in combustion. Cleaning of the coal to reduce the sulphur to an acceptable level is considered to be essential.

State Analysis of Carbonaceous Components in Coal Fly Ash by Simultaneous Thermal Analysis-Mass Spectrometry

The state of carbonaceous components in coal fly ash fractionated by particle size and density was investigated by means of simultaneous thermal analysis-mass spectrometry in an inert atmosphere (He) and a quasi air atmosphere (O2/He=20/80 vol%). The carbonaceous components were characterized by their thermal degradation behavior and evolved gas species observed in each condition. Their components were proved to exist in three different states: the fractions with larger particle size (>20 μm) and medium density (2.0 – 2.4 g/cm3) mostly consist of elemental carbon, the smaller particle size fractions (<5 μm) organic and elemental carbon, and the higher density fractions (2.8 – 3.2 g/cm3) carbonate. In addition to the carbonaceous components, the existence of sulfate and hydroxide was suggested.

Thermal degradation of different fire retardant polyurethane foams

The thermal behaviour of four different flame retarded polyurethane foams has been investigated. For this reason simultaneous thermal analysis/mass spectrometry (TA/MS) as well as incineration experiments on laboratory scale were carried out. Additionally the evolved gases during TA/MS measurement were adsorbed on XAD-resin and identified by means of GC-MS analysis. The results were compared to those of the incineration experiments and the degradation pathways of the flame retardants are discussed.

Thermal degradation of glycidyl methacrylate-styrene copolymers

The thermal degradation of copolymers of glycidyl methacrylate and styrene was studied by thermal volatilisation analysis (TVA), thermogravimetry (TG) and pyrolysis mass spectrometry. The apparent activation energies for the decomposition of copolymers were calculated from the results of TG experiments. The condensable volatile products from the TVA experiments have been identified after separation by subambient thermal volatilisation analysis (SATVA). The cold ring fraction was examined by IR spectroscopy. The copolymers are intermediate in stability between polystyrene and poly(glycidyl methacrylate). The degradation products are mainly those expected by comparison with those obtained from the homopolymers. A mechanism of thermal degradation has been suggested.