Showing papers on "Thermogravimetric analysis published in 1985"
TL;DR: In this article, a thermogravimetric analyzer (TGA) was used to study the reaction between SO 2 and calcium oxide, produced from calcining reagent grade calcium hydroxide.
91 citations
TL;DR: In this article, a pyrolytic study of a variety of lignins prepared from hardwood and softwood species, and of selected commercial lignin, was performed using isothermal and dynamic thermogravimetric analysis.
Abstract: A pyrolytic study of a variety of lignins prepared from hardwood and softwood species, and of selected commercial lignins, was performed using isothermal and dynamic thermogravimetric analysis and pyrolysis-gas chromatography. The lignins were evaluated according to weight loss, rate of weight loss, and products formed during the pyrolysis in an inert atmosphere. These data were then compared to nitrobenzene oxidation data. Infrared spectroscopy was used to determine structural changes of lignin during initial weight loss in the temperature range of 250° to 320°C. Structural changes appear to occur without any appreciable weight loss. Lignin's thermal behavior during pyrolysis depends upon the degree of condensation present in the initial lignin. Thermogravimetric analysis is shown to be a simple and accurate method to determine the extent of lignin condensation. The yield of monomeric phenols is also dependent on the degree of lignin condensation.
74 citations
TL;DR: In this article, a polycrystalline silicon of reasonable purity has been prepared by metallothermic reduction of purified rice-husk white ash (amorphous silica) by using calcium.
Abstract: Polycrystalline silicon of reasonable purity has been prepared by metallothermic reduction of purified rice-husk white ash (amorphous silica) by using calcium. The mechanism of reduction of the silica with calcium was investigated using simultaneous thermogravimetric analysis and differential thermal analysis, which revealed the reduction temperature to be around 720‡ C. The paper also discusses the method of preparation of silicon and its purification procedure. Characterization of the silicon sample thus prepared was made by X-ray diffraction, scanning electron microscopy and emission spectrography.
70 citations
56 citations
TL;DR: The thermogravimetric picture of hydrated ordinary portland cement includes up to seven separate reactions as discussed by the authors, including five dehydration reactions, a dehydroxylation reaction, and a decarbonation reaction.
43 citations
TL;DR: In this article, an easy-install combination between a thermoanalytical and spectroscopical method aiming at the quantification and identification of the thermal decomposition products is demonstrated for an epoxy resin sample.
32 citations
TL;DR: In this article, the bimetallic catalysts consisted of (i) unalloyed Pd phase detected by x-ray diffraction and thermogravimetric measurements, and (ii) alloy phase detecting by thermogravenetric measurements.
Abstract: Pd-Co catalysts on activated graphite support are more active in some liquid phase hydrogenations than any of the unalloyed metals. The bimetallic catalysts consisted of (i) unalloyed Pd phase detected by x-ray diffraction and thermogravimetric measurements, and (ii) alloy phase detected by thermogravimetric measurements.
32 citations
Journal Article•
TL;DR: In this article, the authors carried out thermal analysis of nonwood plants (bagasse, rice straw, and rice hulls) by using differential thermal and thermogravimetric (TG) analysis under oxidizing and inert atmospheres.
Abstract: Thermal analysis of nonwood plants (bagasse, rice straw, and rice hulls) was carried by using differential thermal (DT) and thermogravimetric (TG) analysis under oxidizing and inert atmospheres. Degradation patterns were different, depending on the kind of material and on the pyrolytic atmosphere. Thermal curves of rice straw and hulls were very similar, but bagasse showed a different curve. Degradation of bagasse is similar to hardwood. The rate of thermal degradation of nonwood plants is faster than wood because of their porous structure. Kinetic studies were based on weight loss obtained from TG analysis. A dual mechanism concept, similar to wood, was found for nonwood plants. Two values of activation energy were obtained with a transition temperature at 335 C. Rice straw and hulls have low values of activation energy due to their porous structure and presence of high percentage of silica, while activation energies of bagasse are close to that of hardwood. The presence of inorganic impurities in the cellulosic material has an effect on the kinetics of thermal decomposition.
28 citations
01 Dec 1985
TL;DR: In this article, a series of linear aromatic polyimide films have been synthesized and characterized with the objective of obtaining maximum optical transparency, and two approaches have been used as part of this structure-property relationship study.
Abstract: Several series of linear aromatic polyimide films have been synthesized and characterized with the objective of obtaining maximum optical transparency. Two approaches have been used as part of this structure-property relationship study. The first approach is to vary the molecular structure so as to separate chromophoric centers and reduce electronic interactions between polymer chains to lower the intensity of color in the resulting polymer films. A second and concurrent approach is to perform polymerizations with highly purified monomers. Glass transition temperatures of thermally cured polyimide films are obtained by thermomechanical analysis and thermal decomposition temperatures are determined by thermogravimetric analysis. Transmittance UV-visible spectra of the polyimide films are compared to that of a commercial polyimide film. Fully imidized films are tested for solubility in common organic solvents. The more transparent films prepared in this study are evaluated for use on second-surface mirror thermal control coating systems. Lightly colored to colorless films are characterized by UV-visible spectroscopy before and after exposure to 300 equivalent solar hours UV irradiation and varying doses of 1 MeV electron irradiation. The effects of monomer purity, casting solvent and cure atmosphere on polyimide film transparency are also investigated.
26 citations
TL;DR: In this article, the pyrolysis of glucose, maltose, cellobiose, amylose and cellulose was studied by thermogravimetry between 250-400°C at atmospheric pressure in helium.
26 citations
TL;DR: In this paper, the thermal behavior of acrylamide-maleic anhydride copolymers was studied by thermogravimetric (TG and DTG) analysis.
Abstract: The thermal behaviour of acrylamide-maleic anhydride copolymers was studied by thermogravimetric (TG and DTG) analysis. The obtained data permitted the calculation of activation energies and reaction orders of the decomposition steps by the Coats-Redfern and Freeman-Carroll methods.
TL;DR: In this article, the synthesis and characterization of six bismaleimide resins containing amide linkages in their backbones was described and the effect of structure on thermal behavior was investigated by introducing phosphine oxide, fluorene, ether, methylene, m-phenylene and sulphone groups into the backbone.
TL;DR: In this paper, the thermogravimetric analysis, differential scanning calorimetry, and limiting oxygen index measurements were performed on polypropylene-g-poly(methacrylic acid) fibers.
Abstract: Thermal behavior of polypropylene-g-poly(methacrylic acid) fibers prepared by graft copolymerization of methacrylic acid onto polypropylene fibers, using simultaneous-irradiation technique, was evaluated by thermogravimetric analysis, differential scanning calorimetry, and limiting oxygen index measurements. In general, the thermal properties of polypropylene fiber were markedly improved by the grafting of methacrylic acid. The inherent crystallinity of polypropylene, as deduced from DSC, did not show any change in the grafted fibers, suggesting that the grafting occurs in the amorphous region, without disrupting the crystalline part of the polymer. The LOI of grafted fibers showed an increase over the original fiber.
TL;DR: In this article, a slow thermal decomposition of amorphous Ce(OH) 4 at a constant rate and low water vapor pressure (12 N m −2 ) was followed by thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy studies.
TL;DR: In this paper, the effect of NO contaminant on the thermal decomposition of chromia gel has been thoroughly investigated and physicochemically characterized by means of infrared and X-ray diffraction techniques.
01 Dec 1985-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the intrinsic kinetics of the hydrogen reduction of cuprous sulfide (Cu2S) have been measured in the temperature range 823 to 1023 K using a thermogravimetric analysis method.
Abstract: Intrinsic kinetics of the hydrogen reduction of cuprous sulfide (Cu2S) have been measured. Experiments were carried out in the temperature range 823 to 1023 K using a thermogravimetric analysis method. The reaction was studied in detail using both thin pellets and powder samples. The reaction followed first-order kinetics with respect to the solid reactant concentration as well as the hydrogen concentration. An activation energy of 92.0 kJ/mol (22.0 kcal/g-mole) was obtained for the reaction. Copper produced from the reaction formed filaments which sintered above about 1000 K.
TL;DR: In this article, experimental techniques and theoretical analyses of thermogravimetry as applied to the thermal decomposition of polymers are reviewed and it is concluded that little useful mechanistic information can be derived simply by measuring weight loss during heating.
TL;DR: In this article, the authors explored the potential of an isothermal TGA via evaluation of several freshly processed, unhydrogenated soybean oils and found that the rate of oxidation at 150 C is directly proportional to the specific surface area of an oil.
Abstract: A method for evaluating the oxidative stability of oils based on heating the sample in an oven and periodically testing for weight gain has been known for over 100 years. Thermogravimetric analysis (TGA) with its highly sensitive recording electrobalance turns this simple method into a powerful technique for studying the relative thermooxidative stabilities of oils. This paper explores the potential of an isothermal TGA via evaluation of several freshly processed, unhydrogenated soybean oils. The objective was to define the parameters of the TGA experiment for fast routine measurement and to compare isothermal and dynamic experiments. The consideration of influence of temperature, specific surface area, air flow rate, sample volatilization and nature of the sample pan on the induction period (IP), which is a measure of the oil’s resistance to oxidation, revealed that the temperature and specific surface area are the major parameters that affect the oxidation process. The Arrhenius plot in the range of 80–150 C has shown that the overall activation energy of the oxidation process for three freshly processed oils lies within the range of 21–22 kcal/mole. The rate of oxidation at 150 C is directly proportional to the specific surface area of an oil, suggesting that the rate of oxygen diffusion determines reaction rates at this temperature. A coefficient of variation of the IP better than 2% was found in a routine experiment (10 mg sample, 150 C, 60 ml/min air flow rate, aluminum pan) for typical oils which had an IP range of 25–31 min.
TL;DR: In this paper, a new technique was described to predict the parameters that govern the performance of the in-situ combustion process using thermogravimetric analysis and differential scanning calorimetry.
Abstract: This paper describes a new technique to predict the parameters that govern the performance of the in-situ combustion process. This prediction is accomplished by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the crude-oil combustion. The effect of surface area on the in-situ combustion-tube runs was also investigated.
TL;DR: The results of the differential thermal analysis (DTAt) and the thermal gravimetric analysis (TGA) of four different metal oxides and their respective Ag-MeO materials indicated that the thermochemical properties are directly influenced by the metal oxide components as discussed by the authors.
Abstract: The results of the differential thermal analysis (DTAt and the thermal gravimetric analysis (TGA) of four different metal oxides and their respective Ag-MeO materials indicated that the thermochemical properties of the Ag-MeO materials are directly influenced by the metal oxide components. The energies required to bring the different Ag-MeO materials into different thermal states were calculated, diseussed, and compared. This investigation postulates two hypotheses. First, the arc erosion loss of a contact material depends on the erosion mode. If the predominate mode is splattering, then the Ag-CdO material may be the superior to pure silver because it requires more heat to reach an equivalent thermal state. Second, the oxide, the function of which is to weaken the contact welding, tends to remain on the surface thus increasing the contact resistance. Cadmium, due to its low boiling point, evaporates from the surface. These unique properties may account for the superiority of Ag-CdO as a contact material over other single oxides.
TL;DR: In this article, carbonate apatites precipitated from an aqueous solution and containing Mg 2+ and Sr 2+ ion were studied by thermogravimetric, infrared absorption, and X-ray diffraction methods.
TL;DR: In this article, five types of Polish bituminous coal of different grades were analyzed using, simultaneously, thermogravimetric analysis (TGA), DTG, differential thermal analysis (DTA), and evolving gas analysis (EGA) to investigate the non-isothermal coal oxidation.
01 Jan 1985
TL;DR: In this article, the influence of different precursors on the amount of incorporated metal and its dispersion in the final product was studied by means of thermogravimetric analysis, and the reduction performed at a convenient temperature chosen from the TG data.
TL;DR: In this paper, the thermal decomposition of Thioped, a liquid polysulfide polymer based on dichloroethyl formal, was studied using pyrolysis-GC-MS.
Abstract: The thermal decomposition of Thioped, a liquid polysulfide polymer based on dichloroethyl formal, was studied using pyrolysis–GC–MS. The nature and composition of the products of pyrolysis at 358 and 485°C are given. A striking feature of the product analysis is the presence of several disulfide compounds only at the higher decomposition temperature. The pyrolysis-GC of other liquid polysulfide polymers (LP-2, LP-32, LP-3, and LP-33) showed that molecular weight had only marginal effect on the product composition. Ionic and radical mechanisms were considered to account for the product formation. Isothermal and dynamic thermogravimetric studies were carried out to differentiate between the two mechanisms. The results were found to be in agreement with a free radical mechanism, with cleavage of the formal CO linkage as the preferred mode of initiation. The overall activation energy for the decomposition was found to be 190 kJ mol−1.
TL;DR: In this article, the heat of ammonium azide sublimation was investigated over the temperature range 360-389 K in a continuous flow of dry argon by thermogravimetry (TG).
TL;DR: In this article, the enthalpies of the thermal decomposition of alkylammonium chlorides were derived and based on them the energy of formation and the crystal lattice of the salts were also estimated.
TL;DR: In this paper, a slow thermal decomposition of CeO 2 · x H 2 O at a constant rate and a low water vapour pressure of 8 × 10 −2 Torr (non-conventional procedure) is described.
TL;DR: In this article, the authors combined thermogravimetry and infrared spectroscopy in a unique method to provide quantitative and qualitative analyses of polymers, including the amounts of additives, polymers and inorganic fillers.
TL;DR: In this paper, the main decomposition processes were examined and the thermogravimetric residues analysed by IR and X-ray powder spectra, and were found to be constituted by the respective pyrophosphates, which are thermally very stable.