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Thermal decomposition of bis 2-amino-5-phenyl-1,3,4-thiadiazole copper(II) sulphate has been studied by TG, DTA and DTG. The electrical conductivity of the compound in the solid state have also been measured at different temperatures. It is believed that decomposition is a nucleation controlled process and starts at the site of defects.

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Investigations of the thermal stability of detonating fuse containing 10 g pentaerythrol tetranitrate (PETN) revealed that the cord burnt under unconfinement at 403 K. Under confinement in a steel pipe or copper tube there was a partial detonation at 403 K. In order to characterize the thermal stability of PETN and pyrotechnic composition used in fuse head of electric detonators differential thermal analysis (DTA) was used.

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Abstract  

α-Hemihydrate was allowed to hydrate in the presence of tartaric, succinic, malic or citric acids at room temperature at a water/ binder ratio of 0.35. Hydration of hemihydrate leading to the crystallisation of calcium sulphate dihydrate is an exothermic process. The temperature rise during hydration was measured as a function of time using a semi-adiabatic method. The temperature rise–time curves are similar for all investigated systems but with different induction period. The results showed that calcium sulphate dihydrate crystallisation is a nucleation controlled process and different acids are chemisorbed at the surface of forming nuclei to different extent. Processes taking place during nucleation may control the morphology of resultant crystals. Infrared spectral and differential scanning calorimetric studies confirmed the adsorption of carboxylic acids at the surface of dihydrate crystals.

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Reaction between two oxides leading to the formation of a new compound through a change in weight can be studied by TG methods. However, for catalyst preparations, in most of the cases the starting materials are not oxides. The more common methods of coprecipitation or kneading of the precipitated oxides are employed. In such cases the TG and DTG curve of the composites are of a complex nature for several possible reasons including the formation of new compounds. The interpretation of the conventional DTG curve of such a sample and identification of temperature regions for any new thermal activity thus presents problems. For such studies the use of a derived derivative thermogravimetric curve is suggested as described in this paper. This curve indicates the differences between the experimental thermal behaviour of the composite vis-a-vis theoretical thermal behaviour of the composite computed from the thermal behaviour of its constituents. The regions of a new thermal activity can be readily located and interpretated. Two systems are described, MgO-Cr2O3 and MgO-Fe2O3.

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The hydrated oxides which are formed by the addition of ammonium bi-carbonate to a solution of Zn(NO3)2 and Fe(NO3)3, and drying the precipitates at 110° are zinc hydroxy carbonate(I) and iron(III) oxide gel(II), respectively. A new, derived derivative thermogravimetric curve along with conventional DTA and DTG methods have been used to study the reaction between (I) and (II) in two components system.

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Cereal Research Communications
Authors: S. Sareen, R. Munjal, N. Singh, B. Singh, R. Verma, B. Meena, J. Shoran, A. Sarial, and S. Singh

Terminal heat, which is referred as increase in temperature during grain filling, is one of the important stress factors for wheat production. Current estimates indicate that wheat crop grown on around 13.5mha in India is affected by heat stress. In order to meet the challenges of high temperature ahead of global warming, concerted efforts are needed to evaluate germplasm for heat tolerance and identify and develop genotypes suitable for such stressed environments. The advanced wheat genotypes developed for stress and normal environments by different research centers were evaluated across 7 locations representing varied agroclimatic zones during 2007–08 and 2008–09 to study their adaptability for heat stress and non-stress environments. The additive main effects and multiplicative interaction analysis for G × E interactions revealed differences amongst locations to phenology and grain yield. Genotype RAJ 4083 developed for cultivation under late sown conditions in peninsular zone was also found adaptable to timely sown conditions. Similarly, HD 2733 a cultivar of NEPZ timely sown conditions and PBW 574 an advanced breeding line of NWPZ late sown conditions was found adapted to Peninsular zone. The cultivar RAJ 3765 showed specific adaptability to Pantnagar in NWPZ. Genotype NW 3069 developed for NEPZ timely sown conditions have shown adaptability to number of locations; timely sown conditions at Karnal and Hisar in NWPZ and Niphad in PZ. Likewise, WH 1022 developed for NEPZ late sown conditions exhibited specific adaptability to all timely sown locations in NWPZ.

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DTA techniques were employed to study the thermal and structural characteristics of hydrated aluminium oxides and aluminous clays of the Pipra pelitic rocks from district Sidhi, India. Detailed microscopic investigations, X-ray and chemical analyses reveal that these clays were derived by the localized weathering of arkosic metasediments. The chemical and normative behaviours have confirmed their formation by the isochemical metamorphism of arkose, aided by a little granitization and followed by minor retrogression. A tentative correlation between the thermal and structural changes of these oxides and clay minerals at various transition temperatures has nicely displayed the presence of kaolinite, diaspore and gibbsite. The exothermic curves of kaolinite confirm the recrystallization. The presence of kaolinite in the clay fractions indicates the detrital origin.

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The thermal behaviours of polystyrene (PS), polymethylacrylate (PMA), polyacrylonitrile (PAN), polystyrene-co-methylacrylate [P(S: MA)](alternate and random), polystyrene-co-acrylonitrile [P(S: AN)] (alternate) and a terpolymer of styrene, methylacrylate and acrylonitrile [P(S: MA: AN)] are discussed on the basis of non-isothermal thermogravimetric studies. The thermal stabilities of the copolymers have been found to be intermediate between of those of the individual homopolymers. The stability of the [P(S: AN)] copolymer is higher than those of the individual homopolymers. The activation energy values are also in accordance with the thermal behaviours of these polymers.

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Solvent free reactions

Reactions of nitrophenols in 8-hydroxyquinoline–benzoic acid eutectic melt

Journal of Thermal Analysis and Calorimetry
Authors: Preeti Gupta, Tanvi Agrawal, S. S. Das, and N. B. Singh

Abstract

Reactions of nitrophenols have been studied in the eutectic melt of 8-hydroxyquinoline–benzoic acid, where it reacted with 8-hydroxyquinoline. The reactions were also carried out in solution. The reaction products obtained from both the methods were characterized by FT-IR, differential scanning calorimetry, X-ray diffraction technique and microstructural investigations. The reaction products obtained from eutectic melt were analyzed for C, H, N. The results showed that reaction products obtained from both the methods are same. An attempt has been made to propose the overall mechanism of the reaction in the eutectic melt.

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