Course Of Thermal Decomposition Research Articles

Studies on the Thermal Decomposition Course of Nitrogen-Rich Heterocyclic Esters as Potential Drug Candidates and Evaluation of Their Thermal Stability and Properties.

Drug candidates must undergo thermal evaluation as early as possible in the preclinical phase of drug development because undesirable changes in their structure and physicochemical properties may result in decreased pharmacological activity or enhanced toxicity. Hence, the detailed evaluation of nitrogen-rich heterocyclic esters as potential drug candidates, i.e., imidazolidinoannelated triazinylformic acid ethyl esters 1-3 (where R1 = 4-CH3 or 4-OCH3 or 4-Cl, and R2 = -COOC2H5) and imidazolidinoannelated triazinylacetic acid methyl esters 4-6 (where R1 = 4-CH3 or 4-OCH3 or 4-Cl, and R2 = -CH2COOCH3)-in terms of their melting points, melting enthalpy values, thermal stabilities, pyrolysis, and oxidative decomposition course-has been carried out, using the simultaneous thermal analysis methods (TG/DTG/DSC) coupled with spectroscopic techniques (FTIR and QMS). It was found that the melting process (documented as one sharp peak related to the solid-liquid phase transition) of the investigated esters proceeded without their thermal decomposition. It was confirmed that the melting points of the tested compounds increased in relation to R1 and R2 as follows: 2 (R1 = 4-OCH3; R2 = -COOC2H5) < 6 (R1 = 4-Cl; R2 = -CH2COOCH3) < 5 (R1 = 4-OCH3; R2 = -CH2COOCH3) < 3 (R1 = 4-Cl; R2 = -COOC2H5) < 1 (R1 = 4-CH3; R2 = -COOC2H5) < 4 (R1 = 4-CH3; R2 = -CH2COOCH3). All polynitrogenated heterocyclic esters proved to be thermally stable up to 250 °C in inert and oxidising conditions, although 1-3 were characterised by higher thermal stability compared to 4-6. The results confirmed that both the pyrolysis and the oxidative decomposition of heterocyclic ethyl formates/methyl acetates with para-substitutions at the phenyl moiety proceed according to the radical mechanism. In inert conditions, the pyrolysis process of the studied molecules occurred with the homolytic breaking of the C-C, C-N, and C-O bonds. This led to the emission of alcohol (ethanol in the case of 1-3 or methanol in the case of 4-6), NH3, HCN, HNCO, aldehydes, CO2, CH4, HCl, aromatics, and H2O. In turn, in the presence of air, cleavage of the C-C, C-N, and C-O bonds connected with some oxidation and combustion processes took place. This led to the emission of the corresponding alcohol depending on the analysed class of heterocyclic esters, NH3, HCN, HNCO, aldehydes, N2, NO/NO2, CO, CO2, HCl, aromatics, and H2O. Additionally, after some biological tests, it was proven that all nitrogen-rich heterocyclic esters-as potential drug candidates-are safe for erythrocytes, and some of them are able to protect red blood cells from oxidative stress-induced damage.

Searching for Optimal Measurement Parameters by Thermogravimetry for Determining the Degree of Modification of Thermally Modified Wood

When wood is thermally modified, several chemical reactions take place that change the chemical and physical properties of the wood. These changes correlate with the degree of modification, which is mostly a function of the temperature and duration of modification, and consequently with the mass loss during this process. There is a lack of standardised quality control to verify the degree of heat treatment of wood and thus its quality. One of the possible methods to check the degree of thermal modification of a particular type of wood is thermogravimetry (TG). It is based on the assumption that processes that did not take place during thermal modification continue when the TG experiment is carried out. In this method, calibration curves have to be established based on TG measurements of standard samples that have been thermally modified at different temperatures and whose mass loss during modification is known. The calibration curves show the mass loss during the TG measurement as a function of the mass loss during the previous thermal modification. The course of thermal decomposition during the TG measurements is influenced by many parameters, such as the mass of the sample, the heating rate, the atmosphere in which the measurement takes place, and the shape of the crucible in which the sample is placed. In this paper, the influence of these parameters on the calibration curves was investigated. We have focused on oak wood. The best parameters result in a calibration curve with the largest correlation coefficient R2 and the highest slope of the line k. On this basis, we can determine the mass loss during the thermal modification of unknown samples of the same wood species under the same measurement conditions.

Changes in composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe oilfield in the course of thermal decomposition

The relevance. The need to obtain information on heat treatment effect on composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe field (Republic of Tatarstan) to solve the problems associated with their negative impact on oil refining. The aim. To characterize the composition of nitrogenous organic bases, isolated from the resins of bituminous oil of the Nurlatskoe field, and the products of their thermal cracking. Methods. Complex formation, extraction, liquid adsorption chromatography, potentiometric titration, 1H NMR spectroscopy, structural group analysis, combined gas chromatography-mass spectrometry. Results. Based on a comparative study of the composition and structure of nitrogenous bases of the initial and thermally treated resins of the bituminous oil from the Nurlatskoe field, the authors found out that they both contain high- and low-molecular nitrogenous bases with predominance of high-molecular compounds precipitated by hydrogen chloride. As a result of thermal exposure, the number of such bases increases due to an increase in the proportion of compounds with shorter alkyl substituents in their composition. The method of structural group analysis was used to show that the main directions of thermal transformations of high- and low-molecular bases of resins in Nurlatskoe oil are destruction of alkyl substituents and cyclization of shortened alkyl chains with formation of naphthenic rings. Among the lowest molecular weight bases of the initial resins and thermolysate the authors have identified alkyl-substituted quinolines, benzoquinolines, azapyrenes, thiophenoquinolines, and benzothiophenoquinolines with similar molecular weight distributions. During the thermolysis of resins, the relative content of low molecular weight homologues in the identified nitrogenous bases increases. The share of structures with reduced chromatographic mobility caused by a decrease in the degree of spatial screening of a nitrogen atom increases among similar homologues.

Experimental Studies on the Thermal Properties and Decomposition Course of a Novel Class of Heterocyclic Anticancer Drug Candidates

The experimental studies on the thermal properties and decomposition course of a novel class of potential anticancer drugs (1-5) containing in their heterobicyclic structures the asymmetrical triazine template were performed with the use of differential scanning calorimetry (DSC) and simultaneous thermogravimetry/differential scanning calorimetry (TG/DTG/DSC) coupled online with Fourier transform infrared spectroscopy (FTIR) and quadrupole mass spectrometry (QMS) in inert and oxidizing conditions. All the compounds were thermally characterized in detail for the first time in this article. The DSC studies proved that the melting points of the tested compounds depended on the position and type of the substituent at the phenyl moiety, whereas they did not depend on the furnace atmosphere. All the tested polynitrogenated heterocycles proved to be molecules with high thermal stability in both atmospheres, and most of them (1, 3-5) were more stable in oxidizing conditions, which indicated the formation of a more thermally stable form of the compounds when interacting with oxygen. The simultaneous TG/FTIR/QMS analyses confirmed that their pyrolysis process occurred in one main stage resulting in the emission of volatiles such as NH3, HNCO, HCN, CO, CO2, H2O, NO2, aromatic amine derivatives, alkenes (for compounds 1-5), and HCl (for the compound 5). On the other hand, the oxidative decomposition process was more complicated and proceeded in two main stages leading to the emission of NH3, CO2, CO, HCN, HNCO, H2O, some aromatics (for compounds 1-5), HCl (for compounds 3-5) as well as the additional volatiles such as N2, NO2, NH2OH, and (CN)2. The type of the formed volatiles indicated that the decomposition process of the studied heterocycles under the influence of heating was initiated by the radical mechanism. Their decomposition was related to the symmetric cleavage of C-N and C-C bonds (inert conditions) and additional reaction of the volatiles and residues with oxygen (oxidizing conditions).

Zinc titanates nanopowders: synthesis and characterization

Zinc titanates nanopowders viz.; Zn2TiO4, ZnTi3O8 and ZnTiO3 were synthesized through the thermal decomposition course of ZnC2O4.2H2O-TiO2 precursors mixture (1:1 mole ratio), prepared via a new co-precipitation method up to 900 °C. Thermogravimetric measurement (TG) was utilized to characterize the precursors mixture decomposition while x-ray diffraction (XRD), Fourier transform infra-red (FT-IR) were used to characterize the decomposition products as well as the phase transitions at different temperatures. XRD revealed the starting of titanates formation at 700 °C via detecting Zn2TiO4 along with ZnO and TiO2 (anatase) diffraction peaks. By increasing the calcination temperature to 800 °C, the ZnO content vanished with the appearing of Zn2Ti3O8 besides ZnTi2O4 and impurities of TiO2 (anatase). Finally at 900 °C, the Zn2Ti3O8 content was decomposed into ZnTiO3. Nitrogen adsorption-desorption isotherm of the calcined precursors mixture at 900 °C indicated low specific surface area of 7.1 m2 g−1 in accordance with the agglomeration nature estimated via transmission electron microscopy (TEM) study. The conductivity measurements showed semiconducting behavior of the prepared titanates with ferroelectric transition in the range 200 °C–308 °C. The obtained low dielectric value suggests the uses of present titanates as a co-fired ceramic or resonator ceramics.

Time-resolved study of thermal decomposition process of (NH4)2[PtCl6]: Intermediates and Pt nucleation

Evolution in crystal, electronic and local atomic structures of Pt in ammonium hexachloroplatinate in the course of thermal decomposition in inert and reducing atmospheres have been studied by Powder X-Ray Diffraction (PXRD) and Quick X-ray Absorption Fine Structure (QXAFS) at Pt L3-edge for deeper understanding the thermally-induced solid state reaction and the formation of metallic nanoparticles. A three-step thermal decomposition mechanism of (NH4)2[PtCl6] in the inert atmosphere with the intermediate products Pt(NH3)2Cl2 and PtCl2 has been found instead one-[G.Meyer, A.Möller, J. Less. Common. Met. 170 (1991) 327–331] and two-step one [Q.Kong, F.Baudelet, J.Han, S.Chagnot, L.Barthe, J.Headspith, R. Goldsbrough, F.E.Picca, O.Spalla, Sci. Rep. 2 (2012) 1018–1025] considered early. In the reducing atmosphere, the thermal decomposition is a two-step process with the formation of the intermediate PtCl2. The best approach to determining the number of thermal decomposition steps turned out to be the express-analysis of QXAFS spectra offered in the papers, based on the simultaneous presentation of the most important parameters extracted from X-ray Absorption Near Edge Structure (XANES) and Fourier transformed Extended XAFS (EXAFS). This express-analysis was tested by comparison with results of various approaches such as conventional EXAFS fitting, linear combination fit (LCF), Multivariate Curve Resolution Alternating Least Squares method (MCR ALS).

Time-resolved study of Pd-Os and Pt-Os nanoalloys formation through thermal decomposition of [Pd(NH3)4][OsCl6] and [Pt(NH3)4][OsCl6] complex salts

The formation mechanisms of Pd-Os and Pt-Os alloys in the course of thermal decomposition of iso-formular and isostructural complex salts [Pd(NH3)4][OsCl6] and [Pt(NH3)4][OsCl6] in an inert atmosphere have been studied by in-situ QXAFS, XPS and PXRD. The mechanisms of thermal decomposition of the precursors are found to differ from each other, but the detected intermediate products show no significant effect on the local atomic structure around Os, Pt/Pd in their final products. A crystalline beta-trans-[Pd(NH3)2Cl2] intermediate of the first step of thermal decomposition of [Pd(NH3)4][OsCl6] makes the anion [OsCl6]2− transform differently than that of [Pt(NH3)4][OsCl6]. It transforms into a short-lived [Os(NH3)xCl6-x] (2≤x≤4), and then to a distorted octahedron [OsCl6]2−, similar to the high-temperature modification of OsCl4. In case of [Pt(NH3)4][OsCl6], the intermediate [Os(NH3)2Cl4] modifies into four chlorine coordinated Os,{OsCl4}0/1−. Consecutive reduction of Pd(II)/Pt(II) and Os(IV) to the metals defines the homophilic atomic order with the fcc-Pd covered by a random Pd-Os alloy layer and Os on the surface, that is supported by High-Resolution Transmission Electron Mictroscopy (HRTEM) and Scanning TEM (STEM) energy dispersive X-ray (EDX) data, and the diffusion direction going from the surface (hcp-Os) to bulk (fcc-Pd/Pt). As a result, the heterogeneous alloys are formed with a very similar electronic and local atomic structure of Os and Pd/Pt. Upon alloying, the Os 5d5/2,3/2 and Pt 5d5/2,3/2 levels are depleted in the Pt-Os alloys compared to dispersed hcp-Os, fcc-Pt, and Pt foil. This is an unusual behaviour for Os and Pt, calling into question the versatility of d-band theory in bimetallic Os-alloys. The spin-orbit effect at the Os site has been found for both the Pd-Os and Pt-Os alloys, but it is about 4 times less compared to the complex salts. The obtained values for the complex compounds are comparable with those for the iridates, proposed as materials with spin-orbit-induced properties.

Surface compositional changes upon heating cobalt oxalate dihydrate in vacuum

X-ray photoelectron spectroscopy (XPS) was chosen to explore changes occurring in the surface composition, structural and chemical state of atoms during the course of thermal decomposition of CoC2O4·2H2O under ultra-high vacuum conditions. Accordingly, a large set of high-resolution core-level and Auger spectra was recorded as a function of temperature and time. Some Co-related XPS characteristics, including Auger parameter, were found to be sensitive to the local chemical and structural environment of Co atoms, demonstrating non-monotonic variation in the temperature range of intense dehydration. Isothermal decomposition was shown to proceed via formation of a two-phase system composed of metallic Co and oxygen-deficient oxalate and could be described by Avrami–Erofeev or Prout-Tompkins kinetic models. The long-term isothermal decomposition of the oxalate at 380 °C produced nearly oxygen-free Co covered by a substantial amount of carbon in carbidic form (~19 at%) and as graphitic overlayer (~26 at%). On the contrary, heating of the oxalate to 500 °C produced Co particles covered by surface CoO (~29 mol%) with traces of carbidic and graphitic carbon. XRD, TG and DTA coupled with mass spectrometry were employed as complementary techniques.

Delving into Autocatalytic Liquid-State Thermal Decomposition of Novel Energetic 1,3,5-Triazines with Azido, Trinitroethyl, and Nitramino Groups.

Thermal decomposition of 1,3,5-triazines with azido, trinitroethyl, and nitramino groups, the three important energetic functionalities, has been studied with a range of thermal analysis tools. The involved compounds melt under heating with the following mass loss and heat and gas release in the course of thermal decomposition. Model-fitting kinetic analysis resulted in formal reaction schemes with two general stages. In case of the least energetic 6-azido-2,4-bis(2,2,2-trinitroethylamino)-1,3,5-triazine, the first reaction is a first-order reaction followed by a third-order reaction. Alternatively, for 6-azido-2,4-bis(2,2,2-trinitroethylnitramino)-1,3,5-triazine and 2,4,6-tris(2,2,2-trinitroethylnitramino)-1,3,5-triazine, the first step comprises the autocatalytic reaction. The activation energy for the first decomposition step drops from 141 to 122 kJ mol-1 due to the inductive influence of a β-nitramino group. The second general reaction for all species obeys the third-order reaction model with activation energies in the range 112-126 kJ mol-1. On the basis of the analysis of the kinetic data and temporal behavior of the evolved gases, a similar primary decomposition channel, the homolytic cleavage of a C-NO2 bond, has been proposed for all investigated substances.

Thermal Decomposition of Polychlorobiphenyls and Their Derivatives

The thermal stability and composition of the gas phase of Sovol technical mixture of polychlorobiphenyls was studied by synchronous thermal analysis and mass spectrometry in comparison with the derivatives synthesized by the reaction of the congeners with sodium methoxide or with polyethylene glycol in the presence of alkali. The obtained mixtures of methoxy + hydroxy + methoxyhydroxy or hydroxy + poly(ethylene glycol)oxy derivatives of polychlorobiphenyls are less stable thermally than the congeners of the Sovol mixture. In pyrolysis of a mixture of methoxy, hydroxy, and methoxyhydroxy derivatives, the vaporization is accompanied by decomposition with the formation of simple volatile substances. No vaporization is observed in the course of oxidative thermal decomposition of a mixture of hydroxy and poly(ethylene glycol)oxy derivatives. Thermal decomposition of the derivatives requires lower power consumption compared to polychlorobiphenyls and is characterized by decreased emission of hazardous chlorinated compounds.

Insight on spectral, thermal and biological behaviour of some Cu(II) complexes with saturated pentaazamacrocyclic ligands bearing amino acid residues

A novel series of Cu(II) complexes with formula M(HLn)(ClO4)2·mH2O [HLn: 13-membered pentaazamacrocyclic ligand resulted from condensation of N,N′-bis(2-aminoethyl)ethane-1,2-diamine, l-tyrosine (HL1)/l-tryptophan (HL2)/l-phenylalanine (HL3) and formaldehyde] were synthesized by one-pot method. Techniques such as ESI–MS, IR, UV–Vis and EPR spectroscopy provided data characterizing the complexes as mononuclear species. The course of thermal decomposition was followed using TG/DSC–MS analysis in air atmosphere. The TG curves showed a gradual decomposition in several stages that comprise dehydration, decomposition of perchlorate ions as well as fragmentation and oxidative degradation of the organic part. The intermediates formed after first stage of water elimination are stable on 40, 15 and 80 °C interval for complexes (1), (2) and (3), respectively. The compounds were tested on the eukaryotic unicellular organism Saccharomyces cerevisiae, showing variable actions in terms of toxicity, cellular uptake and capacity to alleviate growth defects associated with Cu, Zn-superoxide dismutase (SOD1) depletion.

Forward Looking Analysis Approach to Assess Copper Acetate Thermal Decomposition Reaction Mechanism

Thermal decomposition course of copper acetate monohydrate was monitored by combining diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) coupled with μ gas chromatography-mass spectrometry (μGC-MS) with other analytical techniques (thermogravimetry analysis and in situ X-ray diffraction). Non-isothermal kinetic was examined in air and Ar. A complete analysis of the evolution of infrared spectra matched with crystalline phase transition data during the course of reaction allows access to significant and accurate information about molecular dynamics. While thermogravimetry gives broad conclusion about two steps reaction (dehydration and decarboxylation), in line approach (in situ X-ray and in situ DRIFT coupled to μGC-MS) is proposed as an example of a new robust and forward-looking analysis. While decomposition mechanism of copper acetate monohydrate is still not well elucidated yet previously, the present in-line characterization results lead to accurate data making the corresponding mechanism explicit.

Features of propagation of droplets of water and special water-based compositions in a sample of forest fuel material

The article presents the results of experimental studies of water droplets propagation through the sample of typical forest fuel materials: needles, leaves, and their mixture. Different conditions are considered: without any additional energy supply, with heating, in the course of intensive thermal decomposition and flaming combustion. Three methods of registration are applied: thermocouple measurements, control of the weight of the sample as a whole and of its individual layers, and high-speed video recording. Water-based compositions with special additives (bentonite, bischofite, and foaming agents) typical for forest fire extinguishing systems are used. The experiments are carried out using aerosol and single water drops, as well as a small group of the latter. It is shown that the mechanisms, conditions and characteristics of droplet propagation through the layers of needles, leaves and their mixtures differ significantly. The scientific novelty of the work is the determining of the values of all the key characteristics of these processes in the conditions of intensive pyrolysis of the material, as well as through its inert layers.

Artificial neural networks as a supporting tool for compatibility study based on thermogravimetric data

This paper focuses on applying of artificial neural networks (ANNs) for the incompatibility detection between an active pharmaceutical ingredient (API) and excipients on the basis of thermogravimetric data. In binary model mixtures, caffeine was used as API mixed with selected excipients. The interpretation of ANN results was based on the assumption that the model mixtures with relatively high content of API (70 and 90%), should undergo similar course of thermal decomposition and be placed in nearby neurons, as opposed to mixtures where excipient predominated. When different behaviour of model mixtures was observed, the incompatibility between mixture ingredients was determined. The results indicate ANNs combined with thermogravimetry to be a simple diagnostic tool that visualizes the behaviour of ingredients in binary mixtures by placing them in different neurons of the topological map so as to determine incompatibility occurrence. The findings were confirmed with complementary techniques − DSC, FTIR and XRPD.

Combustion Characteristics of HAN-based Green Propellant Assisted with Nanoporous Active Carbons

Combustion of hydroxylammonium nitrate (95 wt.% HAN) ‒ water solution in presence of high specific surface area activated carbons is investigated in a constant-pressure bomb within the pressure range of 1‒6 MPa. The linear burning rate increased for the system of HAN admixed with activated carbons compared to those of the HAN alone. Moreover, the thermal decomposition of HAN (95 wt.%) ‒ water solution spiked with activated carbons was assessed by DTA – TG method. In the presence of activated carbons, the ability to trigger the decomposition at a lower temperature (86 °C vs 185 °C) was observed. The volatile products formed in the course of thermal decomposition of HAN, spiked with activated carbons were characterized by electron ionization mass spectrometry analysis. Primary products of HAN decomposition: m/z = 33 (NH2OH) and m/z = 63 (HNO3), which are further responsible for the formation of secondary products such as N2O, NO, HNO2, NO2, O2 etc. Significant reduction of NOx emissions during thermal decomposition of HAN (95 wt.%) ‒ water solution was observed (ca. 30%) in presence of activated carbons.

The effect of wax coating, aluminum and ammonium perchlorate on impact sensitivity of HMX

Abstract Interaction of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)/ammonium perchlorate (AP) and its effect on mechanical sensitivity may result in some restrictions for the application of AP/HMX system in high energetic weapon system. In this work, impact sensitivity test is used to study the effects of wax coating of HMX, AP and aluminum (Al) powder on sensitivity properties of HMX/AP/Al mixtures. Thermogravimetry-differential scanning calorimetry (TG-DSC) analysis has been developed to investigate the mechanism of interaction between HMX and AP during the course of thermal decomposition of HMX/AP/Al mixtures. The results show that severe interaction effect exists between AP and HMX, which causes the impact sensitivity ( H 50 ) to become smaller. The impact energy ( E 50 ) of mixture can be improved under the circumstances of effective separating HMX from AP by surface coating with Wax. AP may firstly engender low-temperature decomposition under the circumstance of external heat or mechanical impact, which causes the exothermic peak of HMX forward shift about 28 °C. The gaseous product releasing from thermal decomposition of HMX accelerates further decomposition of AP. For HMX/AP composite system, the interactive catalysis effect between AP and HMX can be eliminated mostly by adding a great deal of Al powder (i.e. above 30%).

Structural properties and thermal stability of cobalt- and chromium-doped α-MnO2 nanorods.

α-MnO2 nanorods were synthesized via the hydrothermal decomposition of KMnO4 in an acidic environment in the presence of Co2+ and Cr3+ ions. Reactions were carried out at three different temperatures: 90, 130 and 170 °C. All prepared samples exhibit a tetragonal MnO2 crystalline phase. SEM–EDS analysis shows that cobalt cations are incorporated to a higher degree into the MnO2 framework than chromium ions, and that the content of the dopant ions decreases with increasing reaction temperature. The oxidation of Co2+ to Co3+ during the reaction was proved by an XANES study, while EXAFS results confirm that both dopant ions substitute Mn4+ in the center of an octahedron. The K/Mn ratio in the doped samples synthesized at 170 °C is significantly lower than in the undoped samples. Analysis of an individual cobalt-doped α-MnO2 nanorod with HAADF-STEM reveals that the distribution of cobalt through the cross-section of the nanorod is uniform. The course of thermal decomposition of the doped nanorods is similar to that of the undoped ones. Dopant ions do not preserve the MnO2 phase at higher temperatures nor do they destabilize the cryptomelane structure.

The effect of starch-g-copolymers structure on the oxidative behavior studied by the TG/DSC/FTIR-coupled method

The effect of starch-g-copolymers structure on the thermal decomposition course under oxidative conditions by using the simultaneous TG/DSC/FTIR technique has been investigated. To those studies, two types of starch-g-copolymers obtained under the graft copolymerization process of aromatic acrylate monomers such as phenyl acrylate and benzyl acrylate onto starch have been chosen. The TG/DSC investigations confirmed that the course of the decomposition process of all studied copolymers under the heating and in the presence of air was similar and run through three large stages. TG/FTIR studies indicated on the same decomposition mechanism under the first decomposition stage, however, on the completely different decomposition mechanism under the second decomposition stage of the copolymers which was directly dependent on the structure of grafted polymer. In addition, it was also proved that the percent grafting of the copolymers has not influenced on its decomposition course and its decomposition mechanism. The grafting percent influenced only on the Δm in each decomposition stage and on the intensity in the emission of the volatile species.

Formation and thermal decomposition of oxynitride germanium compounds

The formation of a previously unknown salt with the stoichiometry Li5GeNO3 was found during studies on the reactivity of lithium metagermanate with lithium nitride, germanium oxynitride, and LiGeNO and Li3GeNO2 with lithium oxide. The possibility of existence of anion GeNO35− with mixed oxygen‐nitrogen coordination shell of germanium had been predicted on the basis of analogies occurring among known silicon and germanium compounds. The course of thermal decomposition of the new salt was determined.

Synthesis, characterization and mechanisms of one-part geopolymeric cement by calcining low-quality kaolin with alkali

Precursors for the preparation of one-part geopolymers were synthesized by calcining low-quality kaolin, which containing a lot of quartz, with NaOH or Na2CO3, then the cement pastes of ground precursor powders were synthesized by only adding water and cured at 80 °C for 3 days followed by curing at ambient environment for 25 days. The geopolymeric cement pastes obtained reasonable dry compressive strengths, though they were not quite resistant to water. Alkalis seriously alter the thermal decomposition course of kaolin, and the octahedral-coordinated Al in kaolin also turns into tetrahedral-coordinated Al according to Fourier transform infrared spectroscopy analysis. By using X-ray diffractions, it is discovered that nearly all minerals convert into X-ray amorphous substances and nepheline when the low-quality kaolin is thermally treated with alkalis at 950 °C though most kinds of minerals except kaolinite are stable after the thermal treatment without alkali at 750 °C. P-zeolite is produced during the hydration of the precursors, and the optimized precursor shows partly dissolving characteristics in water under scanning electronic microscope. It is supposed that the hydrolysis of sodium silicates and glassy substances induces the crystallization of P-zeolite and facilitates the hydrated pastes cementing, on the other hand, the delayed hydrolysis of sodium silicates with high SiO2/Na2O ratio after solidification might make the one-part geopolymers expand and reduce the softening coefficients.