Thermal Analysis of new soil sorption regulators

After mechanochemical treatment of multicomponent mixtures complex fertilizers containing nitrogen, phosphorous, potassium and sulphur (NPKS) with higher water capacity were obtained. As raw materials some solid wastes and ammonia and potassium sulfates were used. Due to the different ratio used, new solid phases in the mixtures are formed. New solid phases are confirmed by the stages and rate of mass changes and also by the thermal effects at different temperature ranges. New phases are also confirmed by using X-ray diffraction method. On the base of data obtained mechanism of chemical transformations is proposed. It was found that the kinetics of mechanical activated mixtures decomposition is significantly influenced by the time of treatment and proceeds in few stages. The results have shown that the soluble nutrients forms ratio and sorption capacity could be controlled by the initial components ratios and treatment conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of triboactivation conditions on the synthesis in natural phosphate-ammonium sulphate system

Summary No data is available in the literature about the effects of mechano-chemical activation on the processes of chemical interaction in the Tunisia phosphorite-ammonium sulphate mixture. The purpose of this paper is to study the chemical and thermal reactions in mixtures of Tunisia phosphorite and ammonium sulphate in a mass ratio of 1:1, triboactivated in a planetary mill using different mill balls for a period of 10 h. Using chemical, thermal, X-ray powder diffraction and infrared spectroscopy to analyse the activation products, and analysing the changes occurring during the TG-DTA-DTG measurements, allowed to determine the chemical transformations in the system and to assess the degree of transformation of non-soluble forms of phosphorus from the natural phosphate into soluble. Data from the studies have registered the changes in the solids resulting form preliminary mechano-chemical activation of samples. The additional endo- and exothermic effects resulting from thermal decomposition in the temperature range of up to 1373 K are proof of the changes during the TG-DTA-DTG studies and of new interactions occurring in the system. The results from the thermal and spectroscopic methods show that triboactivation using different mill balls and modes of operation produce new compounds in the form of ortho-, pyro- and tripolyphosphates, soluble in the soil solution. The data obtained are part of the complex studies on the way to optimize the composition and conditions of triboactivation and subsequent thermal treatment aimed to produce high-efficiency slow-acting fertilizer products.     

Thermochemical investigations of natural phosphate with ammonium sulfate additive

Summary The free energy of the acidic ammonium sulfate is a good precondition its use as an additive or reagent for decomposition of natural phosphates on the way to obtain NPS or NPKS complex fertilizers. During our previous studies it was confirmed that as a result of thermo-mechanical treatment new solid phases are formed as a result of the phosphates decomposition. The aim of this study is to find out appropriate conditions for thermal treatment of Tunisia phosphorite with ammonium sulfate where the content of P₂O₅ soluble forms has its maximum. The process was investigated under dynamic thermal conditions. Structure and phase transformations of the mixtures to intermediate and final solid products are confirmed by different techniques. X-ray powder diffraction, infrared spectroscopy and electron microscopy have been applied successfully and relationship found between phase structure and thermal treatment applied. As a result of the complex studies optimal temperatures are determined. The solid products under optimal conditions contain phosphorous in soluble forms available for plants in the soil. As a final it is concluded that the final products could be used as complex mineral fertilizers.     

Thermal behavior and decomposition kinetics of composite solid propellants in the presence of amide burning rate suppressants

The employment of burning rate suppressants in the solid rocket propellant formulation is long known. Different research activities have been conducted to well understand the mechanism of suppression, but literature about the action of oxamide (OXA) and azodicarbonamide (ADA) on the thermal decomposition of composite propellant is still scarce. The focus of this study is on investigating the effect of burning rate suppressants on the thermal behavior and decomposition kinetics of composite solid propellants. Thermogravimetric analysis (TG) and differential thermal analysis have been used to identify the changes in the thermal and kinetic behaviors of coolant-based propellants. Two main decomposition stages were observed. It was found that OXA played an inhibition effect on both stages, whereas the ADA acts as a catalyst in the first stage and as coolant in the second one. The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) based on the TG data obtained at different heating rates. The mechanism of action of coolants on the decomposition of solid propellants was confirmed by the kinetic investigation as well.     

Investigation on Thermal Decomposition of FeS2 and BaO2 Mixtures Part II

The thermal decomposition of FeS₂ and BaO₂ mixtures (mol ratio from 2 to 8) was studied in oxygen containing gas medium using dynamic heating rate. The solid decomposition products have been investigated with X-ray power diffraction and Mössbauer spectrometer. The thermal process has two main stages. In the presence of BaO₂ the mixtures have a lower initial temperature of iron sulfide burning. The same time by the increasing of BaO₂ content in the mixtures the diffusion difficulties are withdrawn in higher temperature ranges. It is proved that as intermediates BaSO₄, nonstoichiometric sulfide, barium ferrites and Fe₂O₃ are formed. The content of many solid phases in the final product is in relationship with the initial ratio of BaO₂ and FeS₂.     

Structural studies of apatite-type oxide ion conductors doped with cobalt

A series of Co doped lanthanum silicate apatite-type phases, La9.83Si4.5Co1.5O26, La9.66Si5CoO26, La10Si5CoO26.5 and La8BaCoSi6O26, have been synthesised, and neutron diffraction, EXAFS and XANES used to investigate their structures in detail. All compositions were shown to possess the hexagonal apatite structure, and the results confirmed that cobalt can be doped onto both the La and Si sites within the structure depending on the starting composition. The Co doping is shown to cause considerable local distortions within the apatite structure. In the case of Si site doping two compositions showed anisotropic peak broadening, which has been attributed to incommensurate ordering of oxygen within the apatite channels.     

Structural Peculiarities of Anomalous Electrolytic Palladium Deposits Prepared under Hydride Formation Conditions

The peculiarities of bulk and surface structures of electrolytic palladium deposits formed under hydride formation conditions are studied by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy techniques. For anomalous deposits with high hydrogen capacities, the evolution of the XRD behavior is traced as a function of thermal treatment. The material is shown to comprise two cubic phases with different lattice parameters.     

Direct determination of total mercury in phosphate rock using alkaline fusion digestion

The aim of this work was to develop a new method to determine the mercury (Hg) concentrations in phosphate rock using a dedicated analytical instrument (the DMA80 Tricell by Milestone) that employs an integrated sequence of thermal decomposition followed by catalyst conversion, amalgamation and atomic absorption spectrophotometry. However, this instrument underestimates Hg concentrations when phosphorite and apatite rocks are investigated with a classic thermal decomposition treatment that complies with US EPA method 7473.     

Relation between kinetic parameters for reactions of organic matter degradation in waste environmental matrix

The organic fraction of urban solid residues disposed of in sanitary landfills during the decomposition yields biogas and leachate, which are sources of pollution. Leachate is a resultant liquid from the decomposition of substances contained in solid residues and it contains in its composition organic and inorganic substances. Literature shows an increase in the use of thermoanalytical techniques to study the samples with environmental interest, this way thermogravimetry is used in this research. Thermogravimetric studies (TG curves) carried out on leachate and residues shows similarities in the thermal behavior, although presenting complex composition. Residue samples were collected from landfills, composting plants, sewage treatment stations, leachate, which after treatment, were submitted for thermal analysis. Kinetic parameters were determined using the Flynn–Wall–Ozawa method. In this case they show little divergence between the kinetic parameter that can be attributed to different decomposition reaction and presence of organic compounds in different phases of the decomposition with structures modified during degradation process and also due to experimental conditions of analysis.     

Mechano-chemical Activation of Dolomite

Mechano-chemical activation is a widely used method for increasing the reaction activity of solids and, consequently, to accelerate solid phase reactions and to reduce the temperature of the subsequent thermal decomposition. Thermal decomposition of triboactivated calcium carbonate is a subject of different studies while dolomite decomposition has limited data. The present work represents a study of thermal stability and phase transitions of mechano-chemical activated dolomite under different conditions, namely using various amounts and kind of milling balls and the duration of activation. Temperatures of decomposition of MgCO₃ and CaCO₃ are specified. The study includes the determination of the thermal stability and the rate of thermal decomposition of activated dolomite. This revised version was published online in July 2006 with corrections to the Cover Date.     

大豆蛋白动态超高压微射流均质中机械力化学效应

以大豆蛋白为对象, 研究大豆蛋白在动态超高压均质过程中存在的机械力化学效应, 同时探究机械力化学效应对大豆蛋白热稳定性的影响. 结果表明, 在动态超高压微射流均质的机械力作用下, 蛋白颗粒粒度变小, 粒度分布范围变窄, 蛋白内部的二硫键和疏水基团被破坏, 致使巯基和疏水基团暴露, 并随着工作压力的增大破坏作用力增强. 同时经过机械力化学效应改性的大豆蛋白热稳定性增强, 并随着工作压力的增加改善效果增强.     

Experimental Study of the Thermal Decomposition Properties of Binary Imidazole Ionic Liquid Mixtures

Ionic liquids (ILs) have a wide range of applications, owing to their negligible vapor pressure, high electrical conductivity, and low melting point. However, the thermal hazards of ILs and their mixtures are also non-negligible. In this study, the thermal hazards of various binary imidazolium ionic liquids (BIIL) mixtures were investigated. The effects of parent salt components and molar ratios on the thermal decomposition temperature (T_d) and flashpoint temperature (T_f) are investigated. It is found that both T_d and T_f increase as the proportion of highly thermally stable components in BIIL mixtures increases. Furthermore, the decomposition process of BIIL mixtures can be divided into two stages. For most molar ratios, the T_f of the BIIL mixtures is in the first stage of thermal decomposition. When the proportion of highly thermally stable components is relatively high, T_f is in the second stage of thermal decomposition. The flammability is attributed to the produced combustible gases during the thermal decomposition process. This work would be reasonably expected to provide some guidance for the safety design and application of IL mixtures for engineering.     

Thermal Analysis of Polymer-silicate Nanocomposites

The thermal behavior of epoxy-smectite nanocomposites (hybrids) is examined by non-isothermal thermogravimetry (TG, DTG and DTA) in air atmosphere. It has been shown that the thermal stability of hybrids is much greater than that of epoxy resin and strongly depends on both the smectite loading and the type of the gallery cations of organically modified smectites. The kinetics of degradation of nanocomposites is significantly influenced by the presence of smectites and proceeds in three stages. Stage I is attributed to the effect of quaternized ammonium ion exchanged smectite, as stages II and III are associated with the decomposition of the bulk epoxy resin. Because of the interfacial interactions and thesilicate-polymer multilayered nanoscale organization, the nanocomposites act as excellent heat insulator and mass transport barrier, which shift the thermal decomposition peaks towards much higher temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of thermal behavior of α-PbO2, using TG and DSC

Using two techniques of thermogravimetry and differential scanning calorimetry under O₂ gas atmosphere from 25 to 600°C, the thermal behavior of laboratory-produced compound lead(IV) oxide α-PbO₂ was investigated. The identity of products at different stages were confirmed by XRD technique. Both techniques produced similar results supporting the same decomposition stages for the compound. Three distinct energy changes were observed, namely, two endothermic and one exothermic in DSC. The amount of ΔH for each peak is also reported.     

Decomposition pathway of diaquabis(N,N'-dimethyl-1,2-ethanediamine)Ni(II) acesulfamate

Summary Prediction of the thermal decomposition pathway of the metal complexes is very important from the theoretical and experimental point of view to determine the properties and structural differences of complexes. In the prediction of the decomposition pathways of complexes, besides the thermal analysis techniques, some ancillary techniques e.g. mass spectroscopy is also used in recent years. In the light of the molecular structures and fragmentation components, it is believed that the thermal decomposition pathway of most molecules is similar to the ionisation mechanism occurring in the mass spectrometer ionisation process. In this study, the thermal decomposition pathway of [Ni(dmen)₂(H₂O)₂](acs)₂ complex have been predicted by the help of thermal analysis data (TG, DTG and DTA) and mass spectroscopic fragmentation pattern. The complex was decomposed in four stages: a) dehydration between 84-132°C, b) loss of N,N'-dimethylethylenediamine (dmen) ligand, c) decomposition of remained dmen and acesulfamato (acs) by releasing SO₂, d) burning of the organic residue to resulting in NiO. The volatile products observed in the thermal decomposition process were also observed in the mass spectrometer ionisation process except molecular peak and it was concluded that the ionisation and thermal decomposition pathway of the complex resembles each other.     

Studies on SO 4 2− Ion Incorporation into Apatite Structure

Calcium sulphate-apatites were synthesised by precipitation from aqueous solutions with different fluorine content and analyzed by chemical, x-ray diffraction (XRD), Raman, and Fourier transform infrared (FTIR) analyses. Their thermal stability was studied by differential scanning calorimetry (TG/DSC) and high-temperature XRD. It was established that the introduction of SO 4 2 m into apatite structure and the thermal changes depend on the fluorine content in the apatite structure. At temperatures above 600;C the structure of apatite reorganizes and CaSO 4 forms a separate phase.     

Thermal studies of isoniazid and mixtures with rifampicin

Rifampicin–Isoniazid mixture is a frequently used product in the treatment of tuberculosis. Rifampicin exhibits polymorphism and exists in two polymorphic forms: the stable form I and the metastable form II. The aim of this work was to evaluate the thermal behavior of the binary mixtures of polymorphs I and II of rifampicin and isoniazid by using DSC. Mixtures of different forms (rifampicin form I and II) showed interaction with isoniazid indicating that the mixtures are less stable compared to the drug alone. Interaction was observed in case of both polymorphs of rifampicin.     

Thermochemistry of triboactivated natural and NH<Subscript>4</Subscript>-exchanged clinoptilolite mixed with Tunisian apatite

Mechanical tribo- and thermo-chemical methods applied for remodeling phosphate raw materials manifest a number of advantages over the conventional technologies. They are related to the reduction of soil contamination and minimization of the released gas emissions in the environment and generate solid wastes. In this work, natural and NH₄-exchanged clinoptilolite are used for increasing the transition of P₂O₅ into assimilated by plants form during tribochemical activation (TCA). Better nutrients assimilation as well as green production could be achieved by applying such a treatment based on the ion-exchange reactions taking place in the soil. The occurring upon TCA structural changes and phase transformations of the used Tunisian phosphorite, natural and NH₄-exchanged clinoptilolite as well as their mixtures are investigated by means of X-ray powder diffraction, IR spectroscopy, and thermal analysis. The thermal method gives evidence for solid phase reactions and increased reactivity as a result of the tribochemical treatment. This treatment leads also to minimization of the size of crystallites, amorfization of the samples, and increasing amount of hydroxyl and carbonate ions in the apatite structure. Treated samples are highly soluble. In addition, conditions for almost complete solubility of P₂O₅ were found. This study shows that some of the produced compositions are suitable for fertilizers or soil conditioners.     

Pharmaceutical compatibility of dexamethasone with excipients commonly used in solid oral dosage forms

Dexamethasone is a glucocorticoid drug used for the treatment of acute and chronic inflammatory conditions, autoimmune diseases, some cancers, and several other pathologies. It is widely marketed worldwide especially under solid dosage forms. This study aimed to assess its compatibility with solid pharmaceutical excipients. Compatibility study was conducted through the preparation of binary mixtures (1:1, w/w) of dexamethasone with 12 selected excipients. Binary mixtures were analyzed by thermoanalytical techniques (thermogravimetric and differential thermal analysis), Fourier transform infrared spectroscopy, and X-ray diffraction. TG curves pointed only slight anticipations of dexamethasone decomposition. DTA curves showed interactions signs with microcrystalline cellulose 101 and 102, magnesium stearate, mannitol, and polyvinylpyrrolidone. Drug infrared absorption profile was not affected by the mixture with most excipients. X-ray diffractograms of all binary mixtures did not exhibit signs of interactions with changes of dexamethasone crystalline state. These results pointed that the interactions found by DTA technique were probably heat-induced. Therefore, the above-mentioned excipients should be carefully used in solid dosage forms with heat-based manufacturing processes.

     

Thermal Decomposition and Melting of A New Carboxyindole Derivative

GV150526A is a novel 2-carboxyindole derivative, recently synthesized by GlaxoWellcome, which is used in treatment or prevention of CNS disorders resulting from neurotoxic damage. It has been prepared in three forms, F1, F2 and F3, having significantly different hydration/dehydration behavior and/or diffraction patterns. Here, we extend the thermal analysis of these polymorphs above 200°C, where all forms are fully dehydrated and the main thermal phenomena are decomposition and melting. Simultaneous TG/DSC measurements have been repeated in wet and dry nitrogen atmospheres over a wide range of heating rates. Form F3 displays a qualitatively different behavior relative to F1 and F2. This fact is interpreted as an evidence of a mechanism of decomposition which sets F3 apart from F1 andF2. The thermal data are summarized by simple heuristic equations and few ‘apparent’enthalpies. This revised version was published online in August 2006 with corrections to the Cover Date.