Use of emanation thermal analysis to characterize thermal reactivity of brannerite mineral

Emanation thermal analysis (ETA) was used to characterize the thermal reactivity of amorphous brannerite mineral of general formula U_1–xTi_2+xO₆ (locality El Cabril, near Cordoba, Spain). It was demonstrated that on sample heating up to 880°C microstructure changes taking place in the sample were accompanied by the formation of new radon diffusion paths, followed by their closing up during the final transformation of amorphous to crystalline brannerite in the range 900–1020 °C. Relative changes in structure irregularities that served as radon diffusion paths during heating and subsequent cooling of the sample to temperatures of 300, 550, 750, 880, 1020 and 1130°C, respectively, were determined from the ETA results. Mass losses in temperature ranges of 230–315, 570–760 and 840–1040°C were observed by thermogravimetry. Mass spectrometry indicated the release of CO2 mainly due to the decomposition of minor carbon amount in the brannerite mineral sample.     

Thermal behaviour of the precursors of ruthenia-titania based mixed oxides

Summary Studies on ruthenia-titania based materials have been attractive because of their catalytic properties as well as due to the possibility of solid solution formation. Samples of pure ruthenia and ruthenia containing various amounts of titania (10-70 mol%) were investigated during heating of their hydroxide precursors from 20 to 800°C in air using emanation thermal analysis (ETA), thermogravimetry (TG), and differential thermal analysis (DTA). The resulting mixed oxide type materials were characterized by X-ray diffraction (XRD), which indicate the presence of three ruthenia-titania phases. The onset temperature of the crystallization of materials was identified by ETA results, whereas DTA effects characterized the crystallization in bulk of the samples. A good agreement was found between the ETA results and other characterization techniques used. ETA results, indicating the microstructural changes in surface and subsurface of ruthenia-titania based catalytic materials, can be used for optimization of their synthesis protocols to achieve the better physical properties.     

Thermal behaviour of ground vermiculite

Thermal behaviour of natural vermiculite (Santa Olalla, Huelva, Spain) was investigated by TG, DTA, emanation thermal analysis (ETA) and high temperature XRD on heating in the temperature range from 30 to 1100°C before and after vibratory mill grinding. Microstructure changes of natural and ground vermiculite samples were characterized by using ETA under in situ conditions of heating. By comparing the ETA and XRD results it was demonstrated that a decrease of radon release rate measured by ETA characterized the decrease in the interlayer spacing of the vermiculite samples that followed the dehydration. Dedicated to the memory of Professor Dr. Ferenc Paulik who passed away on October 12, 2005.     

Comparative study of the effects of thermal and mechanical treatments on the structures of clay minerals

Controlled heating (in air) of clay minerals leads to transformations into disordered structures and recrystallization into new phases at high temperatures. These phase transformations are of topotactic nature. On the other hand, prolonged dry-grinding treatments of the same silicates causes structural amorphization with no recrystallization into new phases. The mechanical energy relaxation mechanism, invoked to explain these differences, accounts for the particle size changes and the large growth of dislocations. The latters affect sensibly the reactivity of the materials submitted to such solid-state treatments.These processes are monitored mostly by XRD, DTA and IR spectroscopy. The latter method allows to study in some silicates submitted to progressive grinding the location and nature of OH groups and water molecules.Plenary lectures.     

Thermal behavior of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> mesoporous gels

Summary Titania-based photocatalytic materials were prepared by sol-gel method using Fe³⁺ and polyethyleneglycol (PEG₆₀₀) as additives. Thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) with MS detection were used to elucidate processes that take place during heating of Fe³⁺ containing titania gels. The microstructure development of the Fe₂O₃/TiO₂ gel samples with and without PEG₆₀₀ admixtures was characterized by emanation thermal analysis (ETA) under in situ heating in air. A mathematical model was used for the evaluation of ETA results. Surface area and porosity measurements of the samples dried at 120&deg;C and the samples preheated for 1 h to 300 and 500&deg;C were compared. From the XRD measurements it was confirmed that the crystallization of anatase took place after thermal heating up to 600&deg;C.     

Thermal Reactivity of Fossilized Dinosaur Eggshells

The thermal reactivity of fossilized/petrified dinosaur eggshells excavated in China, Argentina and France has been studied by means of thermal analysis/mass spectrometry (TG-MS), X-ray diffractometry (XRD) and analytical scanning electron microscopy (SEM-EDX). The results provide more detailed information on the properties of these fossil materials and therefore allow an improved typology of this most remarkable family of creatures. This revised version was published online in August 2006 with corrections to the Cover Date.     

大黄游离羟基蒽醌的TG—DTA和XRD谱图特征分析

中药大黄属蓼科植物,性寒味苦,是中医临床常用药物,具有攻坚破积、活血化瘀、泻火凉血、清热解毒及抗菌、抗炎、调节免疫、抗肿瘤、止血和保健等作用[1].     

Age related changes in the thermal transition of Turkey leg flexor tendon collagen

A differential scanning calorimetric, thermogravimetric and electron microscopic investigation has been carried out on the uncalcified areas of turkey leg flexor tendon as a function of age. Rehydrated samples exhibit an increase of thermal stability with age. The H_D values drop from about 11 cal·g^–1 in the first weeks of life down to 7 cal·g^–1 after the 11th week.At about 11 weeks, the collagen fibril diameter distribution passes from unimodal to multimodal. The DSC curves as well as the TG-DTG curves recorded from dried samples do not show any appreciable difference with ageing. The variations in thermal behaviour of rehydrated samples and fibril diameter distribution could be related to modifications in water binding with ageing.The Authors are grateful to Dr. G. Fabris for discussion and help in the selection of the samples. They also wish to thank Mr. G. Pizzuto for excellent technical assistance. The financial support by Consiglio Nazionale delle Ricerche is gratefully acknowledged.     

Characterization of some new alkali metal molybdate hydrates by thermal and X-ray methods

Preparation and characterization of four new hydrated alkali metal molybdates Na₂Mo₄O₁₃·6H₂O, K₂Mo₄O₁₃·3H₂O, Rb₂Mo₄O₁₃·2H₂O and Cs₂Mo₄O₁₃·2H₂O are described. The compounds were prepared by crystallizing the solution obtained by dissolving MoO₃ and corresponding alkali metal carbonates A₂CO₃ or molybdate A₂MoO₄ in stoichiometric amount in distilled water. The hydrated molybdates were characterized by thermal (TG/DTA) and X-ray diffraction (XRD) methods. The number of water molecules in the compounds were determined from their TG /DTA curves recorded in air and identification of their dehydration products was done by XRD. The cell parameters of the compounds were obtained by indexing their XRD patterns. Attempt to prepare the corresponding hydrated compound of lithium was not successful. This revised version was published online in July 2006 with corrections to the Cover Date.     

Applications of Micro-Thermal Analysis

Micro-thermal analysis combines the imaging facility of scanning probe microscopy with the ability to characterize, with high spatial resolution, the thermal behavior of materials. A sample may be visualized according to its surface topography and also its relative thermal conductivity. Areas of interest may then be selected and localized thermal analysis (TMA and modulated temperature DTA) performed. Applications of this new technique to study semiconductors, polymer blends and biological specimens are described. This revised version was published online in August 2006 with corrections to the Cover Date.     

Utilization of Thermal Analysis to Establish the Optimal Conditions for Regeneration of Activated Carbons

Thermoanalytical methods (TG, DTG and DTA) were used to determine the temperature interval (140–350°C) in which p-nitroaniline undergoes thermal desorption from the surface of activated carbons obtained from the shells of oxidized plum stones and impregnated with aqueous solutions of Cu, Fe and Ti salts, which simulate the processes of activated carbon regeneration. It was established that the impregnation of the activated carbons facilitated the regeneration processes in the sense that they can occur at lower temperatures: 135–320 (Cu), 150–340 (Ti) and 130–320°C (Fe). The utilized activated carbons were preliminarily characterized by BET surface area, DSC and scanning electron microscopic methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of natural and ion exchanged vermiculite by emanation thermal analysis,TG, DTA and XRD

Emanation thermal analysis (ETA), thermogravimetry, DTA and XRD were used in thermal characterization of natural vermiculite (Santa Olalla, Huelva, Spain) and of Na^+- and - exchanged vermiculite samples during heating in air in the range 25-1100°C. A good agreement between the results of these methods was found. Changes in the radon release rate measured by ETA, which reflected the decrease and collapse of the interlayer space after the release of water as well as the formation of new crystalline phases were evaluated using a mathematical model. The model used for the evaluation was found suitable for the quantitative characterization of microstructure changes during in situ conditions of heating of vermiculite samples. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition of cycloadducts of vinylnaphthalenes with electron-deficient dienophiles

Light transmittance was measured during heating of thin NaPO₃ glass plates at different heating rates. According to the results, the crystallization of orthorhombic textured NaPO₃ glass proceeds from sample surfaces into their interior due to the foregoing surface nucleation. The glass surface crystallization process resulted in the sigmoidal decrease of the optical transmittance. Elaborated data lead to the activation energy of glass surface crystallization of the value of 182.8 kJ mol ^-1.     

Radiation analytical material characterization of diamond layers deposited onto tungsten carbide

The characterization of diamonds deposited onto WC single crystals by means of the CVD-method is reported. Investigations were performed by scanning electron microscopy, X-ray diffraction methods and the Kossel reflection technique. Single diamond crystals were deposited in the form of icosahedrons. An orientation correlation between substrate single crystal and diamond crystals could not be proved. In the paper presented, reasons will be given for this fact.     

Thermal transformations of tile clay before and after kaolin addition

The use of clays for ceramic filter processing may reduce its cost, leading to different applications, as water treatment. In this work, a low cost tile clay mixed with kaolin, for use in ceramic filters, were evaluated. Mineralogical and thermal changes occurring during sintering were characterized by differential thermal analysis, thermogravimetry, thermomechanical analysis and X-ray diffraction. An increase in the initial melting temperature of samples due to kaolin addition was observed. Mullite formation in kaolin was observed by DTA and in other samples by XRD. TMA analysis permitted the observation of pre-sintering step, around 850°C. This step is difficult to observe in other types of analysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of mechanical grinding on the reaction pathway and kinetics of the thermal decomposition of hydromagnesite

Effect of mechanical grinding of hydromagnesite on the reaction pathway and kinetic behaviors of the thermal decomposition process was investigated by means of thermoanalytical techniques, together with crystallographic and morphological measurements. A crystalline hydromagnesite, the as-received sample, was decomposed in two distinguished mass loss steps of overlapped dehydration-dehydroxylation and dehydroxylation-decarbonation via an amorphous intermediate of carbonate compound. Thermal decomposition of an amorphous hydromagnesite, obtained by mechanical grinding of the as-received sample, was characterized by three well-separated decomposition processes of dehydration, dehydroxylation and decarbonation. The kinetic behaviors of the respective decomposition steps were estimated separately using a mathematical deconvolution of the partially overlapped reaction steps. From the formal kinetic analyses of the respective reaction processes, it was revealed that the dehydration and dehydroxylation processes indicate the decelerate rate behaviors controlled by diffusion, while the rate behavior of nucleation limited type is predominant for the decarbonation process.     

Formation of clay intercalates with organic bilayers in hydrocarbon polymers

The formation of clay intercalates with three different kinds of organic ammonium salts, when mixed in the presence of synthetic or natural polyisoprene rubber, has been investigated. X‐ray diffraction and transmission electron microscopy (TEM) experiments have shown that intercalates with organic bilayers, rather than with interdigitated organic monolayers, are obtained only for the ammonium salts presenting two long alkyl chains and only in the presence of the natural rubber (NR). These results have been qualitatively rationalized on the basis of suitable interlayer densities. Both monolayer and bilayer clay intercalates remain stable for short‐term heating procedures at temperatures lower than 250°C. For treatments at higher temperatures, where the decomposition of the organic ammonium salt occurs, both kinds of clay intercalates maintain intralayer crystalline order. However, the decomposition of the organic modifier leads to the formation of pristine and exfoliated clay for the intercalates with organic monolayers and bilayers, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and thermal stability of xylene-formaldehyde resins

o-,p- andm-xylene have been condensed with formaldehyde using paratoluene sulphonic acid as a catalyst and acetic acid/acetic anhydride as a solvent. The xylene-formaldehyde resins thus obtained have been characterised by IR and NMR spectra. The average molecular weight of the resin samples was determined by vapour pressure osmometry. Kinetic parameters were determined by differential thermal analysis, thermogravimetry and differential scanning calorimetry.     

Characterization of new natural cellulosic fiber from the Ipomoea staphylina plant

Natural fibers extracted from plants play a major role as reinforcement in polymer composite materials due to their superior properties. This work aims to comprehensively characterize the physical and chemical properties of Ipomoea staphylina fibers (ISFs), which are extracted from the stem of the Ipomoea staphylina plant. The ISFs show cellulose content (72.76 wt%), hemicelluloses content (13.6 wt%), density (1401 kg cm^?3), and tensile strength of 173–658 MPa with a strain rate of 2.03–6.63%. The thermal stability of ISFs illustrate that the fibers are stable up to a temperature of 311°C with kinetic activation energy of 99.82 kJ mol^?1.     

Thermal behavior of a mineral mixture of sepiolite and dolomite

An industrial raw material taken from Beypazarı (Ankara, Turkey) region was heated at different temperatures in the 100–1100°C interval for 2 h. The volumetric percentage of particles having diameter below 2 μm in an aqueous suspension of the material held 24 h were determined as 85% by the particle size distribution analysis. The mineralogical composition of the material was obtained as mass% of 81% sepiolite, 15% dolomite, and 4% interparticle water by using the X-ray diffraction (XRD) and thermal analysis (TG, DTA) data. The temperature ranges were determined for the dehydrations of the interparticle water and the zeolitic water as 25–340°C, for the dehydration of the bound water as 340–580°C, and for the dehydroxylation of the hydroxyls as 800–833°C in the sepiolite. The zig-zag changes in the specific surface area (S/m² g⁻¹) and specific micro-and mesopore volume (V/cm³ g⁻¹) with the temperature increases were discussed according to the dehydrations and dehydroxylation of the sepiolite.