Thermogravimetry Coupled With Mass Spectrometry Research Articles

The structural evolution characteristics for high volatile bituminous coal by in-situ heating in electronical microscope

In order to visually investigate the aromatic layer arrangement and structural evolution characteristics, high volatile bituminous coal was selected and investigated by in-situ high-resolution transmission electron microscopy (HRTEM) and thermogravimetry coupled with mass spectrometry (TG-MS). HRTEM was applied to quantify the size and arrangement of aromatic layers (such as length, curvature, orientation, d002 and Lc) during in-situ heating from room temperature (RT) to 1000 ℃, thereby revealing aromatic structural evolution characteristics. TG-MS was employed to identify gaseous release characteristics from RT to 900 ℃·H2O, CO2, CH4, C3H6, benzene and H2 were monitored and measured in this study. Based on the HRTEM experimental results, it was found that with temperature increasing, the distributions of aromatic layers changed from disordered to well-aligned and then to disordered again. Among them, the naphthalene structure, the smallest aromatic layer structure identified in the HRTEM image formed by the condensation of two benzene rings, presents the most obvious variation. In addition, the relationship between aromatic structural evolution and gaseous generation was also discussed in this work. The results showed that the structural evolution of high volatile bituminous coal was complex and closely related to the gaseous generation characteristics. At the temperature of RT∼300 ℃, the decomposing of oxygen-containing functional groups caused an increase in the content of naphthalene, the layers became shorter but more disordered, d002 decreased significantly while Lc increased. Up to 400 ℃, the layers were extended and parallel, the d002 decreased and La increased, while Lc remained almost stable, demonstrating that the polymerization of smaller layers formed in the previous stage was the main reaction in this stage. 400–600 ℃ was the main pyrolysis stage with large amounts of volatile matter generated, new active sites were thus formed and reconnected, causing the growth of aromatics and improvement of the order degree. At 600 ℃∼700 ℃, the content of naphthalene increased again, which may possibly due to the decomposition of methylene-bridge bond connected between aromatic rings, accompanied by the release of CH4 and benzene. Then the layers arrangement reached the most order and the perfect crystallite structure began to be formed gradually up to 800 ℃, which is owing to the polycondensation between the aromatics accompanied with the release of H2. As the temperature rise to 1000 ℃, the value of Lc showed a significant increase and the d002 remained a slight decrease, indicating the improving of the stacking degree, however, the formation of new naphthalene through the aromatization of aliphatic rings caused the naphthalene content increase and La reduce significantly.

Surfactant-free synthesis of sub-10 nm Co3O4 in a rotating packed bed and its high catalytic activity for AP pyrolysis

Sub-10 nm Co3O4 nanoparticles with a narrow size distribution are prepared by a surfactant-free liquid precipitation method in a rotating packed bed (RPB) reactor. The mean size of the material is about 8.5 nm, and is the smallest among previous reports via surfactant-free liquid precipitation. The growth mechanisms show that the sizes of Co3O4 nanoparticles inherit from the precursory Co(OH)2. Compared to the traditional stirred tank reactor, RPB can enhance the nucleation of Co(OH)2 through enhanced micro-mixing, which leads to thinner and more uniform products. As-prepared Co3O4 can show enhanced catalytic performance for ammonium perchlorate (AP) decomposition. The peak temperatures of AP decomposition reduce to 296.8 °C, 291.8 °C, 290.0 °C, and 286.6 °C by adding 2 wt% 22.6 nm, 15.0 nm, 10.9 nm, and 8.5 nm of Co3O4 nanoparticles, respectively. Density functional theory (DFT) calculations and thermogravimetry coupled with mass spectrometry (TG-MS) analysis reveal that the size-dependent catalytic activity of Co3O4 for AP decomposition origin from varied O2 activation ability and NH3 adsorption capacity at the edge and corner sites.

Assessing the level of airborne polystyrene microplastics using thermogravimetry-mass spectrometry: Results for an agricultural area

The global consumption of plastic is increasing year by year. The usage of plastic materials may generate small plastic fragments known as microplastics (MPs) which affect the quality of the air we breathe. In this study, a procedure based on thermogravimetry coupled to mass spectrometry (TGA-MS) has been developed to quantify polystyrene (PS) microplastics found in the atmosphere nearby an agricultural area. The quantification of PM10 fractions of airborne PS microplastics has been scarcely studied. For this purpose, around 50 mg of the fiberglass filters used for the airborne sample collection were pyrolyzed on the TGA instrument (40–800 °C) at 10 °C min−1. At the same time, sample mass loss and MS signal intensity of typical PS pyrolysis compounds were recorded. Limits of detection and quantification were 7.7 and 25.8 ng m−3, respectively. PS microplastic has been found in the studied atmosphere area at an average of 35.97 ng m−3, the potential contamination source being mainly related to agricultural activities. This works shows the potential of the hyphenated TGA-MS methodology as a complementary technique for microplastics characterization.

Applicability of water glass for the transfer of the glass-foaming process from controlled to air atmosphere

For thermal insulation to be sustainable, its performance and production efficiency must be considered. Foamed glass prepared from the mixture of waste cathode ray tube panel glass (CRT), Mn3O4 and carbon could become such a material assuming that its production efficiency could be improved. In light of this, the aim of the study was to engineer the transfer of the foaming process from inert to air atmosphere without drastically disturbing the primary mechanism of expansion. Foaming of carbon-containing mixtures in air atmosphere is normally a challenge due to premature oxidation of carbon by the oxygen from the air. Here, we systematically investigate how the addition of water glass (WG) affects the process by thermogravimetry coupled with mass spectrometry (TG/MS) and heating-stage microscopy analysis. Further, we propose an explanation about how WG protects the carbon and show that the addition of WG allows for the process to be successfully performed in air atmosphere. Two direct sources of expansion were identified (carbon-Mn3O4 reaction and WG) and quantitatively evaluated, allowing determination of an optimal addition of WG, 12 wt %, for the foaming temperature of 800 °C. The obtained foamed glass samples have a relatively low density and degree of open porosity, which reflects in their low thermal conductivity (λ). The lowest λ obtained was 39 mW m−1 K−1 at a density of 145 kg m−3, which is comparable to the samples prepared in inert atmosphere and best commercial products.

Quantification of microplastics in a freshwater suspended organic matter using different thermoanalytical methods – outcome of an interlaboratory comparison

A sedimented freshwater suspended organic matter fortified with particles of polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) was employed in an interlaboratory comparison of thermoanalytical methods for microplastics identification and quantification. Three laboratories performed pyrolysis gas chromatography-mass spectrometry (Py-GC-MS), three others provided results using thermal extraction desorption followed by gas chromatography coupled to mass spectrometry (TED-GC-MS). One participant performed thermogravimetry-infrared spectroscopy (TGA-FTIR) and two participants used thermogravimetry coupled to mass spectrometry (TGA-MS). Further participants used differential scanning microscopy (DSC), a procedure based on micro combustion calorimetry (MCC) and a procedure based on elemental analysis. Each participant employed a different combination of sample treatment, calibration and instrumental settings for polymer identification and quantification. Though there is obviously room for improvements regarding the between-laboratory reproducibility and the harmonization of procedures it was seen that the participants performing Py-GC-MS, TED-GC-MS, and TGA-FTIR were able to correctly identify all polymers and to report reasonable quantification results in the investigated concentration range (PE: 20.0 μg/mg, PP: 5.70 μg/mg; PS: 2.20 μg/mg, PET: 18.0 μg/mg). Although for the other methods limitations exists regarding the detection of specific polymers, they showed potential as alternative approaches for polymer quantification in solid environmental matrices.

Gaseous Products Evolution Analyses for Catalytic Decomposition of AP by Graphene-Based Additives.

A quantitative evaluation method has been developed to study the effects of nanoadditives on thermal decomposition mechanisms of energetic compounds using the conventional thermogravimetry coupled with mass spectrometry (TG/MS) technique. The decomposition of ammonium perchlorate (AP) under the effect of several energetic catalysts has been investigated as a demonstration. In particular, these catalysts are transition metal (Cu2+, Co2+ and Ni2+) complexes of triaminoguanidine (TAG), using graphene oxide (GO) as dopant. They have been well-compared in terms of their catalytic effects on the concentration of the released gaseous products of AP. These detailed quantitative analyses of the gaseous products of AP provide a proof that the proton transfer between ∙O and O2 determines the catalytic decomposition pathways, which largely depend on the type of reactive centers of the catalysts. This quantitative method could be applied to evaluate the catalytic effects of any other additives on the thermal decomposition of various energetic compounds.

Melamine-functionalized graphene oxide: Synthesis, characterization and considering as pseudocapacitor electrode material with intermixed POAP polymer

In this study, Melamine functionalized graphene oxide (FGO-Melamine) was synthesized by chemical route. The prepared functionalized graphene oxide was characterized by different analytical techniques such as FT-IR, Raman spectroscopy, thermogravimetry coupled with mass spectrometry (TG-MS), X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS). To improve electrochemical properties of polyorthoaminophenol (POAP), the electropolymerized POAP/FGO-Melamine films, employed as an active electrode regarding electrochemical performance. In terms of electrochemical measurements, galvanostatic charge–discharge evaluation, EIS (electrochemical impedance spectroscopy) and CV (cyclic voltammetry) were employed for conducting an enquiry into supercapacitive performance of nanocomposite of POAP/FGO-Melamine. This graphene-based electrode showed a specific capacitance (SC) by 273 F g−1 and high energy of 37.91 W kg−1 at power density of 500 W kg−1. The novel materials synthesized in the current work show higher efficiency compared to the carbon-based ones concerning redox reactions of capacitors consisting of good stability in the existence of aqueous electrolyte, large active surface area and ease synthesis method.

VOCs reduction and inhibition mechanisms of using active carbon filler in bituminous materials

Abstract Volatile organic compounds (VOCs), which are harmful to atmospheric environment and human health, will volatilize from bituminous binder in the process of production, transportation and construction. Many inhibitors were applied to reduce the VOCs emissions for designing environment friendly bituminous material. This paper investigated the possibility of using active carbon filler to reduce the VOCs emissions from bituminous materials, by means of thermogravimetry coupled with mass spectrometry (TG-MS). Eight types of emissions were studied through ion mass spectra. The influence of active carbon on VOCs was researched by ionic density and residual volatile speed. Storage stability of modified bituminous binder had been examined as well to ensure acceptable application purpose. For further consideration, the basic properties of active carbon characterized by Scanning Electron Microscope (SEM), Surface Area and Porosity Analyzer and Fourier Transform Infrared Spectroscopy (FT-IR), for better understanding of the inhibition mechanisms. Results illustrated that adding active carbon filler into bitumen would not degrade the storage stability. Active carbon filler with porous structure can significantly reduce the VOCs emissions. The inhibition effect depends on the kind of emissions and the inhibitor's adding ratio. The influence of active carbon on VOCs reduction increased with the addition ratio and the optimum adding quantity is 5 wt%, without significant reduction of road performance. High specific surface area and developed pore structure contributed to the physical adsorption between active carbon and VOCs molecules, while organic functional groups determined the selective chemical absorption of active carbon.

Human Hair as Adsorbent of Palladium(II) in Solution: A Precursor of Well-Dispersed Size-Controlled Pd Nanoparticles

This work describes, for the first time, the preparation of palladium nanoparticles supported in thermally-treated human hair. Human hair showed to be an efficient adsorbent of Pd2+ in aqueous media, reaching nearly 100% of adsorption from a 100 ppm solution. The thermal treatment of hair containing Pd2+ at 200 oC under nitrogen atmosphere led to the formation of an N, S-containing material presenting 0.5 wt.% of palladium. The material was extensively characterized by elemental analysis (CHN and inductively coupled plasma optical emission spectroscopy (ICP OES)), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopies, and by thermogravimetry (TG), thermogravimetry coupled to mass spectrometry (TG-MS), scanning electron miscroscopy (SEM), transmission electron microscopy (TEM) and dispersive X-ray spectroscopy (EDS) analyses. It was possible to observe that the surface structure of hair was preserved during thermal treatment, presenting palladium nanoparticles with particle sizes of approximately 4 nm. This material was used as heterogeneous catalyst in a preliminary application in nitrobenzene reduction to aniline in aqueous medium using sodium borohydride.

Non-porous and porous materials prepared by cross-linking of polyhydromethylsiloxane with silazane compounds

In the work, polyhydromethylsiloxane (PHMS) was cross-linked with two vinylsilazanes: 1,1,3,3-tetramethyl-1,3-divinyldisilazane (ViSiNSiVi) or 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasilazane ((ViSiN)4) in the presence of Karstedt’s catalyst. When the reactions were carried out in solvent-free conditions non-porous polysiloxane-silazane networks were obtained. The processes conducted in high internal phase emulsion (HIPE) resulted in macroporous materials. Their non-porous or porous morphology was established by SEM studies. They were also analyzed by elemental analysis, swelling measurements, FTIR and 29Si MAS-NMR spectroscopies and thermogravimetry coupled with mass spectrometry (TG/MS). Results showed that the non-porous networks contained high amounts of silazane moieties and were fairly hydrolytically stable. In contrast, contents of silazane units in most porous materials were low. Moreover, hydrolysis of SiH groups of PHMS followed by condensation of the resulting SiOH groups took place in HIPE conditions. This led to additional cross-linking of PHMS by siloxane bonds. During preparation of porous systems using ViSiNSiVi, hydrolysis of silazane bonds (SiN) also occurred. All the materials studied in the work contained reactive SiH groups and therefore exhibit a great potential for various applications. Presence of nitrogen atoms in their structure as well as porosity may be additional advantages.

Evolution of pore structure, submaceral composition and produced gases of two Chinese coals during thermal treatment

To better understand coal performance during underground coal gasification, coal combustion and in-situ enhancement of coalbed methane recovery by heating, the variable gases generation and pore structure of subbituminous coal and bituminous coal with thermal treatment related to organic petrology are investigated. Multiple experiments including organic petrology analysis from an optical microscope, gases analysis from thermogravimetry coupled with mass spectrometry (TG-MS), pore structure analysis using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) were constructed to simulate the thermal treatment of coal at elevated temperatures. The coal petrology results exhibit that the submacerals that contribute to the gases generation were significantly reduced when temperature was over 400°C, especially for collinite, cutinite, resinite and telalginite. And there was only a slight difference in CO2 content between subbituminous coal and bituminous coal, which was reduced in the bituminous coal. On the other hand, thermal decomposition of functional groups of submacerals at over 400°C also creates more seepage pores and fractures. Pore structure analysis indicates that the adsorption pores were observed with aggregates of plate-like particles leading to slit-shaped pores below 200°C. However, the massive seepage pores and fissures (over 35.42% in volume) were created in the high-temperature-treated coals, especially between 400°C and 600°C. Furthermore, the dominant seepage pores and fissures formed at high temperature (>400°C) are due to the pyrolysis of semifusinite and collinite submacerals. These investigations may serve to characterize gases generation and pore evolution of coal during thermal treatment.

Mechanistic and Kinetic Analysis of Na2SO4-Modified Laterite Decomposition by Thermogravimetry Coupled with Mass Spectrometry.

Nickel laterites cannot be effectively used in physical methods because of their poor crystallinity and fine grain size. Na2SO4 is the most efficient additive for grade enrichment and Ni recovery. However, how Na2SO4 affects the selective reduction of laterite ores has not been clearly investigated. This study investigated the decomposition of laterite with and without the addition of Na2SO4 in an argon atmosphere using thermogravimetry coupled with mass spectrometry (TG-MS). Approximately 25 mg of samples with 20 wt% Na2SO4 was pyrolyzed under a 100 ml/min Ar flow at a heating rate of 10°C/min from room temperature to 1300°C. The kinetic study was based on derivative thermogravimetric (DTG) curves. The evolution of the pyrolysis gas composition was detected by mass spectrometry, and the decomposition products were analyzed by X-ray diffraction (XRD). The decomposition behavior of laterite with the addition of Na2SO4 was similar to that of pure laterite below 800°C during the first three stages. However, in the fourth stage, the dolomite decomposed at 897°C, which is approximately 200°C lower than the decomposition of pure laterite. In the last stage, the laterite decomposed and emitted SO2 in the presence of Na2SO4 with an activation energy of 91.37 kJ/mol. The decomposition of laterite with and without the addition of Na2SO4 can be described by one first-order reaction. Moreover, the use of Na2SO4 as the modification agent can reduce the activation energy of laterite decomposition; thus, the reaction rate can be accelerated, and the reaction temperature can be markedly reduced.

Waste-glass fume synthesized using plasma spheroidization technology: Reactivity in cement pastes and mortars

Using silica-based nanoparticles is one way to stimulate the hydration reactivity and improve the rheological properties of concrete, given their fineness and spherical shape. Based on its high content in amorphous silica ((SiO2>70wt.%), waste glass is an excellent material for valorization into pozzolanic nanoparticles or the so-called “glass fume” (GF). GF, produced using the radiofrequency induction-coupled-plasma (RF ICP) spheroidization technology, mainly consists of spherical and amorphous nanoparticles (dia. of 30–200nm). Given the scarcity and high cost silica fume (SF), its use in producing high-strength concrete is now limited. GF produced using the scalable plasma spheroidization process is currently being tested in cement-based products as an alternative for SF.The GF was characterized with field-emission-gun scanning electron microscopy (FEGSEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) specific surface, acoustic particle sizer (APS), X-ray fluorescence (XRF) and thermogravimetry coupled to mass spectrometry (TGA-MS). The hydration of GF in cement pastes and mortars was monitored in this study. The cement pastes were characterized at early age with isothermal calorimetry and as a function of curing time with X-ray diffraction (XRD) as well as with thermogravimetric analysis (TGA) and variable pressure scanning electron microscopy (VPSEM). Mortars were tested for compressive strength and their microstructure was observed with VPSEM. Also, their hydration was monitored with the electrical conductivity. The results indicate that GF offers nucleation sites for portlandite, alkalis for the activation of the cement hydration at early age, and a pozzolanic behavior for the long-term evolution of mortar properties. In mortars, the GF yielded compressive strengths equivalent to those obtained with SF used as a comparison. The GF mortars required a lower superplasticizer (SP) dosage than the SF mortar because of the ball-bearing effect induced by GF’s complete spherical morphology. In addition to spherical nanoparticles, SF contains silica-based nanofilaments, which affect the rheology of fresh cement-based materials.

Semi-pilot scale sewage sludge pyrolysis and characterization of obtained fractions by thermal analysis

Sewage sludge pyrolysis is an alternative to incineration and presents as advantages the generation of three fractions: gas (non-condensable volatiles), liquid (condensable volatiles) and solid (carbonaceous coke). In this context, the purpose of the present study is to quantify and to characterize by thermal analysis the fractions produced by sewage sludge pyrolysis in semi-pilot scale. The semi-pilot pyrolysis was performed in two steps, the first dynamic up to 500 °C, followed by an isothermal step at this temperature for 3 h. The solid and liquid fractions produced were analyzed by TG/DTG/DTA, and the volatiles were analyzed by thermogravimetry coupled to mass spectrometry (TG-MS). The influence of different pyrolysis conditions (dynamic and isothermal) was verified by differential thermal analysis (DTA) characterization and by the higher heating value (HHV) of the liquid fractions produced by sludge pyrolysis. In total, 60.1, 28.6 and 11.3 % of the sludge initial mass were obtained, respectively, as solid, liquid and gas pyrolytic fractions. The liquid fraction was composed of aqueous and oily phases. By TG-MS, the volatile compounds detected in pyrolysis were as follows: H2O, C3H6, CO2, NO2, C4H8, SO2, C6H6 and C7H8. The aliquots obtained at higher time periods by isothermal pyrolysis at 500 °C showed higher DTA exothermic peaks and higher HHV values as well. Sewage sludge isothermal pyrolysis at 500 °C produces a liquid fraction with HHV of 36.2 MJ kg−1, indicating that it can be used as renewable energy source. A good correlation exists between total DTA peak area of the oily fractions obtained from sewage sludge pyrolysis and respective HHV values, indicating that it can be used to estimate these values from corresponding DTA curves.

Thermally induced growth of ZnO nanocrystals on mixed metal oxide surfaces.

An in situ method for the growth of ZnO nanocrystals on Zn/Al mixed metal oxide (MMO) surfaces is presented. The key to this method is the thermal treatment of Zn/Al layered double hydroxides (Zn/Al LDHs) in the presence of nitrate anions, which results in partial demixing of the LDH/MMO structure and the subsequent crystallization of ZnO crystals on the surface of the forming MMO layers. In a first experimental series, thermal treatment of Zn/Al LDHs with different fractions of nitrate and carbonate in the interlayer space was examined by thermogravimetry coupled with mass spectrometry (TG-MS) and in situ XRD. In a second experimental series, Zn/Al LDHs with only carbonate in the interlayer space were thermally treated in the presence of different amounts of an external nitrate source (NH4NO3). All obtained Zn/Al MMO samples were analysed by electron microscopy, nitrogen physisorption and powder X-ray diffraction. The gas phase formed during nitrate decomposition turned out to be responsible for the formation of crystalline ZnO nanoparticles. Accordingly, both interlayer nitrate and the presence of ammonium nitrate led to the formation of supported ZnO nanocrystals with mean diameters between 100 and 400 nm, and both methods offer the possibility to tailor the amount and size of the ZnO crystals by means of the amount of nitrate.

Aggregate structure evolution of low-rank coals during pyrolysis by in-situ X-ray diffraction

Two competitive processes, i.e. decomposition and condensation, exist in coal pyrolysis. Although a number of approaches have been used to investigate its mechanism, the ex-situ analysis methods cannot reveal the real pyrolysis process because of the complexity of coal pyrolysis. In the present study, the evolution characteristics and mechanism of the aggregate structure of four low-rank coals during pyrolysis process were investigated by the combination of in-situ X-ray diffraction (XRD) and thermogravimetry coupled with mass spectrometry (TG/MS). All the four samples had similar pathways of structural evolution during heat treatment up to 900°C, which can be divided into four distinct stages based on the X-ray structural parameters (d002, Lc, La). The relationship between the structure evolution of coals and gas generation during pyrolysis was investigated. Stage 1 was characterized by obvious increase of d002 and decrease of Lc and La, indicating the imperfection of the aggregate structure due to the swell of small molecules in the interlayer stacking structure and the broken of the hydrogen bonds. Minor changes of these parameters in stage 2 demonstrated the stability of aromatic layers during the main pyrolysis stage. Stage 3 was identified by the distinct decrease of d002 and increase of Lc and La, reflecting the development of aggregate structure, which is accompanied by the evolution of H2. In the last stage, d002, Lc and La showed minor changes.

Metallic oxides as fire retardants and smoke suppressants in flexible poly(vinyl chloride)

AbstractCombustion and smoke emission properties of PVC compounds, modified with copper (II), molybdenum, and zinc oxides, were studied using cone calorimeter, limiting oxygen index (LOI) and thermogravimetry coupled with mass spectrometry (TG/MS). Results showed that the metal oxides have a very significant effect on the combustion and smoke suppression properties of the PVC compounds. The results also confirmed the anticipation mechanisms of the dehydrochlorination reactions, reductive coupling, and elimination of benzene resulting from the presence of copper (II), molybdenum, and zinc, indicated by the increasing content of postcombustion char residue and the significant reduction in benzene production, indicated by the MS measurements performed. The results also provide indications that the combination of the copper (II) and molybdenum oxides is the one with the best balance of combustion properties, as it reduced the heat released and promoted the suppression of smoke more efficiently. The formulations containing ZnO, because of their strong Lewis acid character, indicated a less pronounced reduction of smoke released during the combustion process, when compared with copper (II) and molybdenum oxides. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Use of Thermogravimetry/Mass Spectrometry Analysis to Explain the Origin of Volatiles Produced during Biomass Pyrolysis

Pyrolysis of alternative biomasses, which contributes to the recovery of arid soils and does not compete with alimentary biomass, could increase use of biomass as feedstock in energy production facilities. In this sense, in order to optimize this thermal process and gain better insight the origin and evolution of the main produced volatiles, nonisothermal thermogravimetry coupled to mass spectrometry (TG/MS) has been applied for samples of two biomasses [Leucaena Leucocephala (Leucaena) and Chamaecytisus Palmensis (Tagasaste)], which find application as energy crops and contribute to soil restoration. In a first stage, autocatalytic kinetics has been used in order to obtain the mass loss rate profiles (DTG) of each biomass pseudocomponent (hemicellulose, cellulose, lignin, and extractives) during pyrolysis. In a second stage, the experimental mass spectrometry signals of the main volatiles (CO, CO2, and H2O) have been simulated using a linear combination of the previously calculated DTG profiles. The accu...

Mineralogical and Mössbauer spectroscopic study of a diopside occurring in the marbles of Andranondambo, southern Madagascar

Dark pyroxene crystals found in a calcite vein cutting across marbles and skarns at Andranondambo, southern Madagascar, were investigated with various techniques in order to characterize and identify the mineral phase. Methods applied include powder X-ray diffraction, thin-section microscopy, electron-microprobe analysis, densimetry, and thermogravimetry coupled to mass spectrometry (TGA-MS), FTIR, and Mossbauer spectroscopy. The chemical composition of the mineral phase was determined as {Ca 0 . 9 8 ,Na 0 . 0 3 }[Mg 0 . 6 8 ,Fe 2 + 0 . 0 7 Fe 3 + 0 . 0 3 ,Al 0 . 1 6 ,Ti 0 . 0 4 ](Si 1 . 7 7 ,Al 0 . 2 3 )O 6 . The refined unit-cell parameters are: a = 9.719(2) A, b = 8.838(2) A, c = 5.287(1) A, p = 106.05(2)°. and V = 436.33(6) A 3 . The refractive indices are: α = 1.690 ′ 0.002, β = 1.700 ′ 0.002, and γ = 1.712 ′ 0.002. The density is 3.370 (55) g/cm 3 . The mean refractive index calculated from the chemical composition yields a Mandarino compatibility index of K = -0.0167. From the various analytical data, we were able to conclude that the mineral corresponds to Fe- and Ti-bearing aluminian diopside. TGA-MS data suggest the presence of calcite solid inclusions and minor H 2 O and CO 2 fluid inclusions. Chemical analyses of the calcite host matrix revealed clear rare earth element enrichment. Mossbauer spectra obtained at varying temperatures show the presence of Fe 2 + and Fe 3 + . Both exhibit broad quadrupole-splitting distributions, indicating widely fluctuating chemical and structural environments for the probe Fe nuclei. The broad temperature range (80-470 K) over which the spectra were collected resulted in a precise determination of the Fe 2 + /Fe t o t ratio as 0.68, which is consistent with the chemical composition as determined from the microprobe analyses. For comparison, the Mossbauer spectra of two specimens of the type locality of aluminian diopside (the mineral formerly named fassaite) were analyzed as well and found to be consistent with those obtained for the Madagascar crystals. The relation between mineral paragenesis and local geological features is briefly discussed.

Thermal Characterization of Materials Using Evolved Gas Analysis

Thermal analysis combined with evolved gas analysis has been used for some time. Thermogravimetry (TG) coupled with Fourier transform infrared (FTIR) spectroscopy(TG/FTIR), Thermogravimetry (TG) coupled with mass spectrometry (TG/MS), and Thermogravimetry (TG) coupled with GC/MS offers structural identification of compounds evolving during thermal processes. These evolved gas analysis (EGA) techniques allow to evaluate the chemical pathway of the degradation reaction by determining the decomposition products. In this paper the TG/FTIR, TG/MS, and Pyrolysis/GC-MS systems will be described and their applications in the study of several materials will be discussed, including the analysis of the degradation mechanisms of organically modified clays, polymers, and coal blends.