Thermal analysis of Moroccan phosphates 'Youssoufia' in an oxidative atmosphere by TG and DSC

A non-isothermal experimental study using thermogravimetry (TG) and differential scanning calorimetry (DSC) was conducted for investigation the oxidation reactivity of natural phosphate and its demineralised products. The analyses were carried out in oxygen atmosphere and at different heating rate (5, 10, 20, 30, 50, 60°C min-1) up to 1000°C. The results indicated that the material washed with HCl from the original phosphate, mainly apatite and carbonates of calcium and magnesium, as well as with HCl/HF, silicates minreals, had an inhibition effect during oxidation reactions of organic material. The increase of the heating rate shifted the reactions to higher temperatures. In addition, kinetic parameters were determined by assuming a single first-order kinetic model, using the Coats-Redfern method. The influences of demineralization process of natural phosphate and the heating rate were examined and discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal behaviour of intercalated 8-hydroxyquinoline (oxine) in montmorillonite clay

The composite montmorillonite-8-hydroxyquinoline (Swy-1-8-HQ) was prepared by two different processes and studied by using thermogravimetric analysis (TG/DTG and DSC), as well as helpful techniques as fluorescence in the UV-visible region and X-ray diffraction. The composites developed fluorescent appearance, however with quantum poor efficiency and they exhibited distinct TG and DSC thermal behavior. The fluorescence data of spectra associated to the TG/DT curves allowed to suggest that the 8-HQ was present in the composites in two different circumstances: 1 - intercalated in the interlayer spaces (Swy-1-8-HQ2), rigidly associated to the substrate feasible as a monolayer with the aromatic rings parallel to the silica layer; and/or, 2 - adsorbed on the surface (Swy-1-8-HQ1), either as a bilayer formation or tilting of the molecules to the silicate layer sheet. All results confirmed above are in agreement with X-ray diffraction patterns, once the interlayer space increases when 8-HQ is incorporated. The experimental results confirm the formation of the composites in agreement with the method used in the preparation. This revised version was published online in August 2006 with corrections to the Cover Date.     

A thermochemical investigation of guest-host interactions in labile Werner clathrates of the [Ni(4-EtPy)4(NCS)2]·G type (G = Methyl derivatives of benzene)

The stoichiometry of thermal decomposition has been studied for (I): [Ni(4-EtPy)₄(NCS)₂] as a host complex as well as for its clathrates [Ni(4-EtPy)₄(NCS)₂]·G where guest molecule G - toluene, (II): T, (III): o-xylene (o-X) and (IV): p-xylene (p-X). The loss of volatile components proceeds in three steps (−2L, −1L, −1L) for I and in four steps (−G, −2L, −1L, −1L) for II, III and IV. DSC and X-ray powder measurements indicated a phase transition in all compounds under study. However, this process is overlapped by the escape of G in II and III. The differences in enthalpy changes are associated with different guest-host interactions in the particular clathrates.     

聚缩水甘油硝酸酯的热安定性和相容性研究

采用DSC、TG热分析方法研究了聚缩水甘油硝酸酯(PolyGLYN)的热安定性和与1,3,5-三硝基-1,3,5-三氮杂环己烷(RDX)间的相容性.结果表明,PolyGLYN在100℃以前较为稳定.当加热速率趋于零时PolyGLYN的热分解峰温为196.4℃,由Ozawa法计算的热分解表观活化能为182.0 kJ·mol-1,分别比RDX的低15.1℃和高22.2 kJ·mol-1.PolyGLYN热稳定性与RDX接近,两者之间的相容性较好.     

2,4-二硝基咪唑铅配合物Pb(DNI)2(H2O)4的热分解

应用TG, TG-DSC-FTIR-MS联用技术和热裂解原位RSFT-IR技术研究了2,4-二硝基咪唑铅(PDNI)的热分解机理. 结果表明, PDNI在102 ℃附近脱除分子内配位水, 生成Pb(DNI)2; 在284 ℃附近C—NO2断裂, 生成NO2, 咪唑环开环, 伴随发生强烈的氧化放热反应, 生成CO2, N2O和铅盐与咪唑残余基团形成的复杂混合物或多聚烃类化合物; 在300～400 ℃范围内, PDNI继续缓慢分解, 生成CO2, N2O和Pb[NCO]2; 升温至410 ℃以上, PDNI分解生成CO和Pb[CN]2.     

Influence of pre-oxidation on kerogen concentrate (KC) pyrolysis

In this study, the rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using TG/DTG technique. The rate of pyrolysis after preoxidation step performed at low temperature (below 230°C), was also studied. The determined pyrolysis activation energy increases with increasing paraffinic structure in the KC: an opposite effect was determined in the case of oxidation. Comparison of the reaction rate constants of the pyrolysis as well as the oxidation of untreated and pre-oxidized KC samples indicated the basis of the proposed thermal method for kerogen type determination.

---

Zusammenfassung Mittels TG/DTG wird die Pyrolyse- und Oxidationsgeschwindigkeit von 8 verschiedenen Ölschieferkerogenkonzentraten (KC) untersucht, ebenso die Pyrolysegeschwindigkeit nach einem Präoxidationsschritt bei niedriger Temperatur (unter 230°C). Die Pyrolyse-Aktivierungsenergie steigt mit zunehmender Paraffinstruktur im KC, ein entgegengesetzter Effekt kann bei der Oxidation beobachtet werden. Ein Vergleich der Reaktionsgeschwindigkeit von Pyrolyse und Oxidation sowohl bei unbehandelten als auch voroxidierten KC-Proben zeigt auf die Basis der empfohlenen thermischen Methode bei Bestimmungen von kerogenen Substanzen.

     

Study of curing behaviour and thermal properties of elastomer-modified bismaleimide resin

Bismaleimide resin (Compimide 353) was modified with the liquid elastomer carboxyl-terminated acrylonitrile butadiene (CTBN). The prereaction synthesis and curing of the CTBN-bismaleimide resin is discussed. The structure of the modified resin was identified by IR and NMR spectroscopy. The basic curing mechanism is also discussed. DSC and TG were used to study the curing behaviour and kinetic parameters, viz. the order of reaction, energy of activation and preexponential factor. Adhesive properties such as lap shear strength and peel strength at room temperature and elevated temperature were evaluated and are discussed.     

Partial thermal reduction of ammonium paratungstate tetrahydrate

Thermal decomposition of ammonium paratungstate tetrahydrate, (NH₄)₁₀[H₂W₁₂O₄₂]·4H₂O has been followed by simultaneous TG/DTA and online evolved gas analysis (TG/DTA-MS) in flowing 10% H₂/Ar directly up to 900°C. Solid intermediate products have been structurally evaluated by FTIR spectroscopy and powder X-ray diffraction (XRD). A previously unexplained exothermic heat effect has been detected at 700–750°C. On the basis of TG/DTA as well as H₂O and NH₃ evolution curves and XRD patterns, it has been assigned to the formation and crystallization heat of γ-tungsten-oxide (WO_2.72/W₁₈O₄₉) from β-tungsten-oxide (WO_2.9/W₂₀O₅₈) and residual ammonium tungsten bronze.     

Dehydration studies of Co(II), Cu(II) and Zn(II) methanesulfonates

The dehydration process of Co(II), Cu(II) and Zn(II) methanesulfonates was studied by thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) techniques in dynamic N₂ atmosphere. The TG/DTG curves show that all of them contain four crystallization water molecules, which are lost in two steps. The peak temperature and dehydration enthalpies ΔH were measured from DSC curves for each compound. The effect of procedural variables on the TG and DSC curves was investigated. In this work, the procedural variables included heating rate, Al pan state (unsealed and sealed) and sample mass.     

Pectin based cerium (IV) and thorium (IV) phosphates as novel hybrid fibrous ion exchangers synthesis,characterization and thermal behaviour

Summary Pectin based cerium (IV) and thorium (IV) phosphates have been synthesized as new phases of hybrid fibrous ion exchangers. Both materials were characterized using X-ray diffraction, infrared (IR) spectra, thermogravimetric analysis (TG), differntial thermogravimetry (DTG), differntial thermal analysis (DTA) and scanning electron microscopy (SEM), as well as the determination of their ion exchange capacity, elution and pH titration. The X-ray study reveals the amorphous nature of the materials, while SEM studies confirm the fibrous nature of the materials. The thermal studies of these materials indicate that both of them are highly stable on heating as they retain about 97% of their ion-exchange capacity (i.e.c.) on heating up to 100°C and about 81% on heating up to 200°C.     

Structural study and thermal behavior of novel interaction product of 4-amino-5-(furan-2-yl)-4H-1,2,4-triazole-3-thione with molecular iodine

Abstract

As a part of investigation of thyreostatic activity of mercapto-substituted triazoles, the structure, spectroscopic properties of 4-amino-5-(furan-2-yl)-4H-1,2,4-triazole-3-thione were obtained. 4-amino-5-(furan-2-yl)-4H-1,2,4-triazole-3-thione forms steady charge-transfer complex in dilute chloroform solution, coordinating one iodine molecule (lgβ?=?3.47). The reaction product of 4-amino-5-(furan-2-yl)-4H-1,2,4-triazole-3-thione is presented by uncharged adduct: C₆H₆N₄OS·I₂. The crystal structure of the adduct was studied in detail by single crystal X-ray diffraction. The results of thermogravimetric analysis revealed the stability of adduct in a solid state at the temperature range 50–500?°C.     

Multiple melting behaviour of poly(3-hydroxybutyrate-co-hydroxyvalerate) using step-scan DSC

Melting behaviour and crystal morphology of poly(3-hydroxybutyrate) (PHB) and its copolymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with various hydroxyvalerate (HV) contents [5 wt.% (PHB5V), 8 wt.% (PHB8V) and 12 wt.% (PHB12V)] have been investigated by conventional DSC, step-scan differential scanning calorimetry (SDSC), wide angle X-ray diffraction (WAXRD) and hot stage polarised optical microscopy (HSPOM). Crystallisation behaviour of PHB and its copolymers were investigated by isothermal crystallisation kinetics. Thermal properties were investigated after isothermal crystallisation treatment. Multiple melting peak behaviour was observed for all polymers. SDSC data revealed that PHB and its copolymers undergo melting-recrystallisation-remelting during heating, as evidenced by exothermic peaks in the IsoK baseline (C_p,IsoK, non-reversing signal). An increase in degree of crystallinity due to significant melt-recrystallisation was observed for isothermally crystallised polymers. SDSC proved a convenient and precise method for measurement of the apparent thermodynamic specific heat (C_p,ATD, reversing signal). PHB and PHBV showed different crystal morphologies for similar crystallisation condition. HSPOM results showed that the crystallisation rates reduced and sizes of spherulites were significantly increased as HV content increased.     

Oxidation behaviour of precipitation hardened steel TG,X-Ray,XRD and SEM study

In the present work the oxidation behavior of ageing treated steel was examined up to 1000°C in different environments (O₂ and CO₂) and with different heating rates. The examination was conducted by means of thermogravimetric analysis, scanning electron microscopy and X-ray diffraction. In this study it was deduced that in the case of O₂ an oxide scale is formed on top of the steel. The oxidation is uniform and the growth of the scale is more intent at low heating rate. It consist of different Fe, Mn, Mo and Cr oxides which are adjusted in the form of layers. This phenomenon was explained by the different diffusion coefficients of each metal in the already formed scale. Regarding the oxidation in CO₂, the scale formation takes place at a lower temperature than in the case of O₂. Hence the examined substrate is more vulnerable in CO₂.     

Evaluation of thermal behavior of latex membranes from genetically improved rubber tree (Hevea brasiliensis)

Thermal stability, thermal decomposition process, residual mass, temperature of glass transition (T_g) and temperature dependence of storage modulus (E’), were determined for latex membranes prepared from six clones of Hevea brasiliensis: IAC 331, IAC 332, IAC 333 and IAC 334 grown at experimental plantations of Instituto Agronômico de Campinas (IAC) in Votuporanga, São Paulo State, Brazil. Latex membranes from GT1 and RRIM 600 Asian matrix clones were used as references. The thermal behavior of latex membranes from genetically improved rubber trees was characterized using thermogravimetry/derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The thermal behavior of latex from clones studied in the present work showed similar features of the clones previously reported (IAC 40, IAC 300, IAC 301, IAC 328, IAC 329 and IAC 330), with mass loss in four consecutive steps, except IAC 333, which showed an additional mass loss step.     

Study of the structure and thermal behaviour of intercalated kaolinites

Intercalation complexes of three different Hungarian kaolinites with hydrazine and potassium acetate were investigated by FT-IR (DRIFT) spectrometry, X-ray diffraction, and thermogravimetry combined with mass spectrometry. Differences were found in the thermal behaviour of the complexes as well as in the rehydration — reexpansion patterns of the heated intercalates. An XRD method is proposed for the distinction of kaolinite and 7.2 Å halloysite present in the same mineral.The authors wish to thank Dr. E. Máttyás for providing the kaolinite samples and for carrying out their chemical analysis. Financial support from the Hungarian Scientific Research Fund under grant No. OTKA-014179 is gratefully acknowledged.     

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].     

Effect of nano-barium titanate on thermal stability of ferrite filled poly-ether-ether-ketone (PEEK) composites

The reinforcement of nano-barium titanate in ferrite filled poly-ether-ether-ketone (PEEK) composites caused a shift in the decomposition temperature, at which maximum mass loss occurred, to higher side and enhancement in char yield in thermogravimetric analysis. Loss tangent and glass transition temperature of ferrite filled PEEK composites were also found to be increased with the reinforcement of nano barium titanate. The effect of nano barium titanate on the melting behaviour of ferrite filled PEEK composites was negligible. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis of (2E)-2-(tetrafluoroethylidene)-3,3-bis(trifluoromethyl)-2,3-dihydrothiazolo[3,2-a]benzimidazole

The reaction of benzimidazoline-2-thione with perfluoro-2-methylpent-2-ene in the presence of triethylamine afforded (2E)-2-(tetrafluoroethylidene)-3,3-bis(trifluoromethyl)-2,3-dihydrothiazolo[3,2-a]benzimidazole whose structure was confirmed by X-ray diffraction analysis. The reaction pathways are discussed.     

Kinetic Analyis of TG Data XXXV. Spectroscopic and thermal studies of some cobalt(III) chelates with ethylenediamine

A number of 30 [Co(en)₃ ]Y₃ , [Co(en)₂ X₂ ]Y and [Co(en)₂ X(amine)]Y₂ type complexes (X =Cl, Br; Y =Cl, Br, I, NCO, NCS, NO₃ , ClO₄ , etc.; amine =aromatic and alkylamines) were obtained from trans-[Co(en)₂ Cl₂ ]Cl by double decomposition and by substitution reactions, respectively. The structure of the complexes was proved by means of far and middle FTIR spectra. The thermal decomposition was studied by TG, DTA and DSC measurements. Mass spectra were also recorded. In the case of [Co(en)₃ ]Y₃ complexes the nitrate, perchlorate and dimesoperiodates decompose suddenly, frequently explosion like. The halides and thiocyanates seem to substitute an ethylenediamine ligand, yielding a rather unstable intermediate. The pyrolysis of [Co(en)₂ X₂ ]Y type derivatives yields no relatively stable intermediates, but the decomposition temperatures may be correlated with the nature of Y and with the cis or trans configuration of the compound. With the [Co(en)₂ X(amine)]Y₂ type complexes one observes the formation of [Co(en)₂ XY]Y as intermediate product. From the TG curves kinetic parameters were derived for some dehydration and deamination processes, by using the nomogram method. The validity of a non-linear kinetic compensation law was observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Thermoanalytical Study of Copper(I) Thiocarbamide Compounds

Hydrated isostructural 1:3 complexes of copper(I) chloride and bromide with thiourea were synthesised and their thermal decomposition studied by simultaneous TG/DTA complemented by ex situ FTIR and XRD studies. The decomposition of Cu(tu)₃Cl·H₂O is initiated by dehydration around 100°C, followed by a total multi-step degradation of the structure in the temperature range of 200–600°C. The counter ion has some influence on the temperatures and composition of the solid residue. The results were compared with those obtained with the 1:1 complex Cu(tu)Cl·1/2H₂O. This revised version was published online in August 2006 with corrections to the Cover Date.