High-resolution Thermogravimetric Analysis Research Articles

Thermogravimetric analysis of organoclays intercalated with the surfactant octadecyltrimethylammonium bromide

High resolution thermogravimetric analysis has been used to study the thermal decomposition of montmorillonite modified with octadecyltrimethylammonium bromide. Thermal decomposition occurs in 4 steps.The first step of mass loss is observed from ambient to 100°C temperature range and is attributed to dehydration of adsorbed water. The second step of mass loss occurs between 87.9 to 135.5°C temperature range and is also attributed to dehydration of water hydrating metal cations such as Na+. The third mass loss occurs between 179.0 and 384.5°C; it is assigned to the loss of surfactant. The fourth step is ascribed to the loss of OH units due to dehydroxylation of the montmorillonite and takes place between 556.0 and 636.3°C temperature range. These TG steps are related to the arrangement of the surfactant molecules intercalating the montmorillonite. Changes in the basal spacing of the clay with surfactant are followed by X-ray diffraction. Thermal analysis provides an indication of the stability of the organo-clay.

Structure of organoclays--an X-ray diffraction and thermogravimetric analysis study.

X-ray diffraction has been used to study the changes in the surface properties of a montmorillonitic clay through the changes in the basal spacings of montmorillonite (SWy-2) and surfactant-intercalated organoclays. Variation in the d-spacing was found to be a step function of the surfactant concentration. High-resolution thermogravimetric analysis (HRTG) shows that the thermal decomposition of SWy-2-MMTs modified with the surfactant octadecyltrimethylammonium bromide takes place in four steps. A mass-loss step is observed at room temperature and is attributed to dehydration of adsorption water. A second mass-loss step is observed over the temperature range 87.9 to 135.5 degrees C and is also attributed to dehydration of water hydrating metal cations such as Na+. The third mass loss occurs from 178.9 to 384.5 degrees C and is assigned to a loss of surfactant. The fourth mass-loss step is ascribed to the loss of OH units through dehydroxylation over the temperature range 556.0 to 636.4 degrees C. A model is proposed in which, up to 0.4 CEC, a surfactant monolayer is formed between the montmorillonitic clay layers; up to 0.8 CEC, a lateral-bilayer arrangement is formed; and above 1.5 CEC, a pseudotrimolecular layer is formed, with excess surfactant adsorbed on the clay surface.

Decomposition of the synthetic hydrotalcites mountkeithite and honessite—a high resolution thermogravimetric analysis and infrared emission spectroscopic study

A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer combined with infrared emission spectroscopy has been used to study the thermal decomposition of synthetic hydrotalcites honessite (Ni 6Fe 2(SO 4)(OH) 16·4H 2O) and mountkeithite (Mg 6Fe 2(SO 4)(OH) 16·4H 2O) and the cationic mixtures of the two minerals. High resolution thermal analysis shows the decomposition takes place in five steps. A mass loss step is observed over the 125–150 °C temperature range and is attributed to the mass loss due to dehydration. A second mass loss step is observed over the 260–330 °C temperature range and is attributed to dehydroxylation. The third mass loss occurs from 350 to 460 °C, and is assigned to a loss of oxygen. The fourth mass loss step is ascribed to the loss of sulphate from the hydrotalcite and occurs over the 676–820 °C temperature range. A mechanism for the thermal decomposition is proposed based upon the loss of water, hydroxyl units, oxygen and sulphur dioxide. The changes in the chemical structures are readily followed by infrared emission spectroscopy.

Compositional analysis of thermoplastic wood composites by TGA

AbstractA method has been developed for the quantitative determination of the composition of thermoplastic wood composites. The method involves area measurements of the two peaks in the derivative curve of a tracing produced by the thermogravimetric analysis (TGA) of a thermoplastic composites sample in an inert atmosphere. This may involve the standard, constant heating rate method or the high resolution (Hi‐Res™) TGA method; both produce virtual baseline separation between wood and polyolefin peaks over a wide compositional range. Because this baseline separation suffers from a mutual effect on the thermal degradation of wood and polyolefins, best results are obtained if the parameters relating peak area with polyolefin content are different below and above 40% polyolefin content. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1484–1492, 2004

Decomposition of the synthetic hydrotalcites mountkeithite and honessite?a high resolution thermogravimetric analysis and infrared emission spectroscopic study

A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer combined with infrared emission spectroscopy has been used to study the thermal decomposition of synthetic hydrotalcites honessite (Ni6Fe2(SO4)(OH)16·4H2O) and mountkeithite (Mg6Fe2(SO4)(OH)16·4H2O) and the cationic mixtures of the two minerals. High resolution thermal analysis shows the decomposition takes place in five steps. A mass loss step is observed over the 125–150 °C temperature range and is attributed to the mass loss due to dehydration. A second mass loss step is observed over the 260–330 °C temperature range and is attributed to dehydroxylation. The third mass loss occurs from 350 to 460 °C, and is assigned to a loss of oxygen. The fourth mass loss step is ascribed to the loss of sulphate from the hydrotalcite and occurs over the 676–820 °C temperature range. A mechanism for the thermal decomposition is proposed based upon the loss of water, hydroxyl units, oxygen and sulphur dioxide. The changes in the chemical structures are readily followed by infrared emission spectroscopy.

Thermal decomposition of metazeunerite—a high-resolution thermogravimetric and hot-stage Raman spectroscopic study

A combination of high-resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of metazeunerite {Cu(H 2O) 4}(H 2O) 4[(UO 2)(AsO 4)] 2. Five stages of weight loss are observed at 48, 88, 125, 882 and 913 °C. In the first three stages 2, 4 and 2 mol of water are lost. In stages 4 and 5, some As 2O 5 units are lost and it is probable that reduction of the anhydrous phase Cu[(UO 2)(AsO 4)] 2 occurs. The stages of dehydration were confirmed by the use of evolved water vapour mass spectroscopy. Changes in the structure of metazeunerite were followed by the use of Raman microscopy in conjunction with a thermal stage. Two Raman bands are observed at 818 and 811 cm −1 and are assigned to the ν 1 symmetric stretching modes of the UO 2 units. The UO 2 Raman antisymmetric stretching mode was observed at 890 cm −1. No AsO 4 stretching vibrations were observed until after two stages of dehydration of the metazeunerite. The AsO 4 ν 4 bending modes show complexity with bands observed at 463, 446, 396 and 380 cm −1. Thermal treatment results in the removal of this degeneracy. The ν 2 band of the AsO 4 units is observed at 320 cm −1. Raman bands at 275 and 235 cm −1 are attributed to the ν 2 bending modes of the (UO 2) 2+ units. The use of the hot-stage Raman microscope enables low-temperature phase changes brought about through dehydration to be studied.

Thermal decomposition of peisleyite: a thermogravimetry and hot stage Raman spectroscopic study

High resolution thermogravimetric analysis (HRTG) coupled with a gas evolution mass spectrometer was used to study the decomposition of peisleyite Na 3Al 16(SO 4)(PO 4) 10(OH) 17·20H 2O. Peisleyite, a hydrated hydroxylated multianion mineral, shows thermal decomposition in five stages, indicative of a loss of water, hydroxyl units and sulphate. Thermal analysis shows the loss of water and hydroxyl units occurs in three distinct stages; at 36, 105 and 162 °C. The high resolution thermogravimetry was complimented with hot stage Raman spectroscopy, which follows the dehydration of peisleyite. This dehydration can be followed by the decrease in intensity of the OH stretching vibrations which occur between 4000 and 2500 cm −1 and by the shift in the sulphate and phosphate peaks which occur due to changes in the mineral structure.

Hot‐stage Raman spectroscopic study of the thermal decomposition of saléeite

AbstractHot‐stage Raman spectroscopy was used to study the changes in structure of the mineral saléeite, Mg(UO2)2(PO4)2·10H2O, during dehydration. Raman spectra were obtained using a Renishaw Raman microscope coupled with a Linkam thermal stage. Temperatures for Raman spectroscopic analysis were selected by studying the high‐resolution thermogravimetric analysis of saléeite. Five stages of dehydration are observed at 43, 73, 87, 231 and 376°C with the loss of 3, 3, 2, 1 and 1 mol of water, respectively. Three antisymmetric PO4 stretching vibrations are observed at 1007, 994 and 980 cm−1. No symmetric stretching vibration is observed until after significant dehydration has occurred at 75°C, when a low‐intensity band at 927 cm−1 is observed. Two bands at 843 and 827 cm−1 are attributed to the symmetric stretching modes of the two UO2 vibrational modes resulting from the two non‐equivalent UO bonds. The low‐intensity band at 894 cm−1 is assigned to the UO2 antisymmetric stretching mode. The complexity that is observed in the ν3 antisymmetric stretching region of the PO4 units is also observed in the PO4 ν2 bending region. Four bands are observed at 471, 446, 405 and 376 cm−1. Two bands observed at 283 and 234 cm−1 are assigned to the (UO2)2+ bending modes. After dehydration, it is suggested that the structure loses its distortion, takes on a tetragonal structure and hence the Raman spectra become less complex upon thermal treatment. Copyright © 2004 John Wiley & Sons, Ltd.

Thermal decomposition of synthetic hydrotalcites reevesite and pyroaurite

A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of synthetic hydrotalcites reevesite (Ni6Fe2(CO3)(OH)16·4H2O) and pyroaurite (Mg6Fe2(SO4,CO3)(OH)16·4H2O) and the cationic mixtures of the two minerals. XRD patterns show the hydrotalcites are layered structures with interspacing distances of around 8.0. A. A linear relationship is observed for the d(001) spacing as Ni is replaced by Mg in the progression from reevesite to pyroaurite. The significance of this result means the interlayer spacing in these hydrotalcites is cation dependent. High resolution thermal analysis shows the decomposition takes place in 3 steps. A mechanism for the thermal decomposition is proposed based upon the loss of water, hydroxyl units, oxygen and carbon dioxide.

A versatile synthetic approach to periodic mesoporous organosilicas

A synthetic protocol for the preparation of a variety of high-quality periodic mesoporous organosilicas (PMOs) is presented. These nanostructured organosilicas have been synthesized by the acid-catalyzed hydrolysis and condensation of bis(triethoxysilyl) precursors containing different organic bridging groups. Polyoxyethylene(10) stearyl ether (Brij 76) is employed as the structure director using the surfactant template approach. Methylene, ethylene, ethenylene, and phenylene-bridged PMOs have been synthesized. Surfactant extraction is accomplished by refluxing the mesoscopic composite precipitates in acidified ethanol. The resulting PMOs have been characterized by nitrogen gas sorption, powder X-ray diffraction, 13C and 29Si solid-state NMR, and high-resolution thermogravimetric analysis. These organosilicas exhibit large surface areas, narrow pore size distributions, and large total pore volumes. This is the first report of a synthetic protocol with the versatility to make high-quality PMOs containing aliphatic, aromatic, or olefinic carbon functional groups. This versatility is discussed in terms of template and precursor structures under the acidic reaction conditions.

A Raman spectroscopic study of thermally treated glushinskite—the natural magnesium oxalate dihydrate

Raman spectroscopy has been used to study the thermal transformations of natural magnesium oxalate dihydrate known in mineralogy as glushinskite. The data obtained by Raman spectroscopy was supplemented with that of infrared emission spectroscopy. The vibrational spectroscopic data was complimented with high resolution thermogravimetric analysis combined with evolved gas mass spectrometry. TG–MS identified two mass loss steps at 146 and 397 °C. In the first mass loss step water is evolved only, in the second step carbon dioxide is evolved. The combination of Raman microscopy and a thermal stage clearly identifies the changes in the molecular structure with thermal treatment. Glushinskite is the dihydrate phase in the temperature range up to the pre-dehydration temperature of 146 °C. Above 397 °C, magnesium oxide is formed. Infrared emission spectroscopy shows that this mineral decomposes at around 400 °C. Changes in the position and intensity of the CO and CC stretching vibrations in the Raman spectra indicate the temperature range at which these phase changes occur.

Thermolytic Synthesis of Imprinted Amines in Bulk Silica

The synthesis of bulk, hydrophilic imprinted silica is reported via a novel method relying on the thermolysis of carbamates. This method is used to synthesize single-site materials consisting of either isolated primary amines or multiple organized primary amines within an imprinted site. Materials are characterized by multinuclear solid-state NMR spectroscopy, high-resolution thermogravimetric analysis, and potentiometric titration. Diffuse-reflectance UV/Vis and solid-state fluorescence spectroscopies of probe molecule-bound materials are used to demonstrate the site-isolated and polar nature of the imprinted sites resulting from this process. The polar nature is due to hydrophilic silanol groups ingenerate to the framework of the material. These permit the partitioning of polar reagents, such as 1,3,5-trinitrobenzenesulfonic acid (TNBS), which are unable to access the imprinted sites when framework silanols are end-capped with hydrophobic trimethylsilyl functionality. The latter observation provides a mechanism to elucidate diminished reactivity of TNBS with lysine residues that are buried within the hydrophobic pocket of a protein.

Thermal decomposition of the natural hydrotalcites carrboydite and hydrohonessite

A combination of high-resolution thermogravimetric analysis (HRTGA) coupled to a gas evolution mass spectrometer combined with infrared emission spectroscopy has been used to study the thermal decomposition of two Australian hydrotalcites carrboydite (Ni 6Al 2(SO 4,CO 3)(OH) 16·4H 2O) and hydrohonessite (Ni 6Fe 2(SO 4,CO 3)(OH) 16·7H 2O). High-resolution thermal analysis shows the decomposition takes place in five steps. Each step is related to the loss of water, hydroxyl units, carbonate and sulphate. Infrared emission spectroscopy clearly identifies the presence of these molecular species and the temperature at which they are lost. Minor amounts of carbonate are observed in the minerals. Water is in two states in the structure, namely weakly hydrogen bonded and strongly hydrogen bonded. The symmetry of the sulphate anion is reduced through this hydrogen bonding.

Thermal treatment of weddellite—a Raman and infrared emission spectroscopic study

Thermal transformations of natural calcium oxalate dihydrate known in mineralogy as weddellite have been undertaken using a combination of Raman microscopy and infrared emission spectroscopy. The vibrational spectroscopic data was complimented with high resolution thermogravimetric analysis combined with evolved gas mass spectrometry. TG–MS identified three mass loss steps at 114, 422 and 592 °C. In the first mass loss step water is evolved only, in the second and third steps carbon dioxide is evolved. The combination of Raman microscopy and a thermal stage clearly identifies the changes in the molecular structure with thermal treatment. Weddellite is the phase in the temperature range up to the pre-dehydration temperature of 97 °C. At this temperature, the phase formed is whewellite (calcium oxalate monohydrate) and above 114 °C the phase is the anhydrous calcium oxalate. Above 422 °C, calcium carbonate is formed. Infrared emission spectroscopy shows that this mineral decomposes at around 650 °C. Changes in the position and intensity of the CO and CC stretching vibrations in the Raman spectra indicate the temperature range at which these phase changes occur.

High‐resolution thermogravimetry/coupled mass spectrometry analysis of flame‐retardant rubber

AbstractA bromobutyl rubber composition containing a variety of conventional flame retardants, such as Saytex (decabromodiphenyl oxide), Sb2O3, chlorinated paraffin wax, and polychloroprene rubber, was prepared and used to coat nylon 6 fabric in a laboratory‐coating device. An attempt was made to evaluate the decomposition profile, the evolved gases, and the kinetics of the decomposition process at a dynamic heating rate with high‐resolution thermogravimetric analysis (HR‐TGA). HR‐TGA was used with mass spectrometry for evolved gas analysis (EGA). The HR‐TGA results were compared with results from conventional thermogravimetric analysis (TGA) at a constant heating rate; the former offered sharp transitions, an economic timescale, and an accurate activation energy. The resolution optimization for stability analysis and the effect of its variation on the kinetic parameters offered better results for HR‐TGA than conventional TGA. A lifetime and temperature relationship was evaluated in HR‐TGA with Toop's method, and it was observed that the shelf life decreased sharply with temperature. The effluents HBr, HCl, Br ·, and Cl ·, generated between 210 and 496°C during EGA, were correlated with the thermal stability and fire‐retardancy behavior of the material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2051–2057, 2003

Thermal decomposition of the vivianite arsenates—implications for soil remediation

The presence of arsenate compounds in soils and mineral dump leachates is common. One potential method for the removal of the arsenates from soils is through thermal treatment. High-resolution thermogravimetric analysis has been used to follow this thermal decomposition of selected vivianite arsenates. This decomposition occurs as a series of steps. The first two steps involve dehydration with 6 mol of water lost in the first step and two in the second. The third major weight loss step occurs in the 750–800 °C temperature range with de-arsenation. The application of infrared emission spectroscopy confirms the loss of water by around 250 °C and the loss of arsenic as arsenic pentoxide is observed by the loss of AsO stretching bands at around 826 cm −1. Thermal activation of arsenic contaminated soils may provide a method of decontamination.

Assembly of nano-domain buildings blocks of copper oxalate with a cubic morphology

ABSTRACTMetallic copper nanostructured particles were synthesised by thermal decomposition of a CuC2O4 precursor obtained via the precipitation reaction between Cu(NO3)2·6H2O and Na2C2O4 in the present of hydroxyl propyl methyl cellulose (HPMC). X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and thermogravimetric analysis (TG) were used to characterise the particles and their evolution during the transformation to metallic copper. We highlight the nanostructured nature of the oxalate precursor, which is made up of anisotropic nanosized buildings blocks (25nm by 40nm). These produce an anisotropy in the oxalate particle and influence the decomposition pathway. The results show the evolution of the nanostructure as a function of degree of reaction and a possible kinetic model is discussed.

Synthesis of carbon-encapsulated magnetic nanoparticles by a grain-boundary-reaction

AbstractCarbon-encapsulated ferric magnetic nanoparticles were prepared by the grain-boundary-reaction of ultrafine goethite particles. The mechanism of the grain-boundary-reaction was studied with high-resolution transmission electronic microscope, X-ray diffraction and thermo gravimetric analysis. The magnetic properties are measured with a vibrating sample magnetometer. The diameter of carbon-encapsulated ferric magnetic nanoparticles is 30~60 nm, and the coercive force and saturate magnetization are 315 Oe and 30 emu /(g powder), respectively. These composite particles are very stable in air.

Thermal analysis of goethite

Differential scanning calorimetry shows two endotherms at 75 and 225°C for synthetic goethite. The latter endotherm is strongly asymmetric on the low temperature side. The endotherms were attributed to the loss of water and the dehydroxylation of the goethite. The temperature of the endotherms and the enthalpy of the phase change were found to be linear functions of the percentage of aluminium substitution into the goethite. High-resolution thermogravimetric analysis of goethite showed three mass loss steps, occurring at ~175, 196 and 263°C. The temperatures of these mass loss steps and the percentage of mass loss were also linearly related to the degree of Al substitution. The use of infrared emission spectroscopy confirmed the temperature of dehydroxylation. The observation of the low temperature dehydroxylation of goethite and its relation to ancient aboriginal cave art is discussed.

Nanoporous Organosilicas: Periodic Materials Synthesized with Surfactant Templates in Acidic Media

Nanoporous organosilicas have been synthesized by the acid-catalyzed hydrolysis and condensation of bis(triethoxysilyl)ethane (BTSE) using a hydrothermal approach. Cetyltrimethylammonium chloride (CTAC), polyoxyethylene(10) cetyl ether (Brij 56), and polyoxythylene(10) stearyl ether (Brij 76) were employed as structure directors using the surfactant template method. The surfactants were extracted from the nanoscopic composite precipitates with acidified ethanol. The resulting nanoporous organosilicas have been characterized by nitrogen gas sorption, powder X-ray diffraction, and high-resolution thermogravimetric analysis. While the organosilicas synthesized with CTAC exhibit large surface areas (1000 m2/g) and pore volumes (1.0 cm3/g), they form relatively disordered matrixes as evidenced by broad pore size distributions and X-ray diffraction patterns. Brij 56 gives periodic nanoporous organosilicas with pore diameters 36−39 Å. The use of brij 76 as the structure director gave better quality organosilicas, with large surface areas, sharp pore size distributions, and pore diameters of 43−45 Å. X-ray diffraction patterns exhibit three well-defined peaks typical of hexagonal (p6mm) mesoporous materials. The effects of initial HCl concentrations on the chemical and structural properties of the final products are examined.