Investigation of thermal properties of some basalt samples in Egypt

This work aims in studying the temperature dependence of the thermal properties (thermal diffusivity, k, specific heat, C _p and thermal conductivity, ) of some basalt group samples, collected from different regions in the eastern desert of Egypt. The thermal properties of these samples were measured in the temperature range from r.t. to 900 K. The average values of the thermal conductivity of these investigated samples lie in the range from 0.4·10^–3 to 2.01·10^–3 cal cm^–1 s^–1 K^–1. This means that these samples are considered as thermal insulating materials. The thermogravimetric analysis (TG) confirmed that these investigated samples are dry rocks. X-ray fluorescence (XRF) and X-ray diffraction (XRD) confirmed that these rock samples have a crystalline phase, the peaks of XRD have a small change in their location as a result of heat treatment. This behaviour was attributed to the oxidation and firing of some minerals after the heat treatment.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal,Spectral and Antimicrobial Properties of New Zinc(II) Isobutyrate Compounds: Part I. Papaverine,Phenazone

Zinc carboxylate complexes with N-donor ligands exhibit antimicrobial and antifungal effects. The preparation and thermal properties of complex compounds Zn(isobut)₂ and Zn(isobut)₂L(isobut=(CH₃)₂CHCOO^–, L=papaverine — pap, phenazone — phen) are described in this paper. The newly synthesized compounds were characterized by elemental analysis, IR spectroscopy and TG/DTG, DTA methods.During the thermal treatment it was found that the release of organicligands (pap, phen) was followed by pyrolysis of zinc(II) isobutyrate. (C₃H₇)₂CO and CO₂ were found as gaseous products and zinc oxide as the final product of thermal decomposition. Gaseous and solid products of thermal decomposition were confirmed by chemical analysis, IR spectra and X-ray powder diffraction.This revised version was published online in November 2005 with corrections to the Cover Date.     

The Thermal Degradation Mechanism and Thermal Mechanical Properties of Two High Performance Heterocyclic Polymer Fibers

The thermal mechanical properties and degradation behaviors were studied on fibers prepared from two high-performance, heterocyclic polymers, poly(p-phenylenebenzobisthiazole) (PBZT) and poly(p-phenylenebenzobisoxazole) (PBZO). Our research demonstrated that these two fibers exhibited excellent mechanical properties and outstanding thermal and thermo-oxidative stability. Their long-term mechanical tensile performance at high temperatures was found to be critically associated with the stability of the C—O or C—S linkage at the heterocyclic rings on these polymers' backbones. PBZO fibers with the C—O linkages displayed substantially higher thermal stability compared to PBZT containing C—S linkages. High resolution pyrolysis-gas chromatography/mass spectrometry provided the information of the pyrolyzates' compositions and distributions as well as their relationships with the structures of PBZT and PBZO. Based on the analysis of the compositions and distributions of all pyrolyzates at different temperatures, it was found that the thermal degradation mechanisms for both of these heterocyclic polymers were identical. Kevlar®-49 fibers were also studied under the same experimental conditions in order to make a comparison of thermo-oxidative stability and long-term mechanical performance at high temperatures with PBZO and PBZT fibers. The data of two high-performance aromatic polyimide fibers were also included as references.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermodynamic properties of liquid bismuth—Lead alloys

On liquid Bi—Pb alloys emf measurements were carried out. From the emf data the thermodynamic properties were calculated. In the temperature range between 643 to 923 K no anomalies in the thermodynamic properties were found. The emf varies linearly with temperature and the activity of Pb shows a slight negative deviation fromRaoult's law. However, when H ^M /x is plotted against (1–x) the results are two staight lines which intersect at approximately 35 at% Bi. This could be interpreted that Bi—Pb melts change from one regular behaviour to another.Herrn Prof. Dr.K. L. Komarek mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Thermal Analysis of Casein

Case in was analyzed during thermal treatment and pyrolysis. The thermal degradation process of casein was interpreted and thermostability indices, rate, order and activation energy of thermode-structive reaction of casein were determined on the basis of thermogravimetric analysis. The thermodestruction of casein has the characteristics of a first order reaction with activation energy E _a=3.87 kcal mol^–1 (16.2 kJ mol^–1).The pyrolysis of casein was investigated and we determined optimal heating temperature — 550°C and yields of biochar, pitch, pyrolysis water and gases.This revised version was published online in November 2005 with corrections to the Cover Date.     

Preparation,Mechanical Properties and Thermal Degradation Kinetics of a Novel Poly(ester-ether-imide) Elastomer Based on N′,N-Bis(2-hydroxyethyl)-Pyromellitimide Unit

A novel poly(ester-ether-imide) (PEEI) based on N′,N-bis(2-hydroxyethyl)-pyromellitimide unit was synthesized via a conventional two-stage procedure with 1,4-butanediol (BD), dimethyl terephthalate (DMT) and poly(tetramethylene glycol) (PTMG1000). The structures of imide dihydric alcohol and PEEI were confirmed by FT-IR and ¹H-NMR spectra, respectively. The thermal properties and mechanical properties were investigated. The results show PEEI possesses good mechanical properties and excellent thermal stability with the 5% weight loss temperature of the PEEI at 367.3°C, and melting temperature of hard segments (T_mh) at 209.7°C. In addition, the kinetic parameters of thermal degradation of the PEEI were studied by thermogravimetric analysis (TGA) at different heating rates. The activation energy of the solid-state process was determined to be 174.83 and 175.83 kJ/mol using Kissinger and Flynn–Wall–Ozawa methods, respectively. The degradation mechanism model of PEEI was determined bythe Coats-Redfern method. Compared with the values obtained from the Kissinger and Flynn–Wall–Ozawa methods, the actual reaction mechanism of the novel PEEI is a F₁ type (Random nucleation with one nucleus on the individual particle nucleation) and growth model with integral g(a)=?ln(1?a)).     

Thermal behavior of poly(vinylbenzyl chloride)‐grafted poly(ethylene‐co‐tetrafluoroethylene) films

The effect of the degree of grafting (DOG) on the thermal behavior of poly(vinylbenzyl chloride)‐grafted poly(ethylene‐co‐tetrafluoroethylene) (ETFE‐g‐PVBC) films was investigated by differential scanning calorimetry (DSC), X‐ray diffraction (XRD), dynamic mechanical analysis ( DMA), FT‐IR, and thermogravimetric analysis (TGA) instruments. Several ETFE‐g‐PVBC films with various degrees of grafting, including 10, 24, 41, 60, and 94%, were prepared using a radiation grafting technique. The DSC and XRD results of the ETFE‐g‐PVBC films revealed that the crystallinity of the films decreased as the DOG increased. The DMA and FT‐IR results of the films indicated that a crosslinking reaction occurred at temperatures above 250 °C. In the thermal properties of the grafted films, an increase in the DOG led to an increase in the decomposition temperature. The activation energy (E_a) of the thermal decomposition was calculated using Kissinger's equation from TGA results. The E_a value of the PVBC graft chain was found to increase as the DOG increased, indicating that the crosslinking reaction of ETFE‐g‐PVBC films increased with an increase in the DOG during the thermal degradation process. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 517–525     

On the linearity of the energy of activation in theEyring theory of kinetics

Summary A result obtained earlier implies that — if theEyring theory is correct — the energy of the transition state is less thanU+E _a whereU is the sum of the internal energies of the chemical reactants andE _a is the energy of activation. The energy of the transition state for the forward reaction is not equal to that of the inverse reaction; it varies linearly with the temperature.

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Zur Linearität der Aktivierungsenergie in derEyringschen Theorie

Zusammenfassung Aus einem früher erhaltenen Ergebnis folgt, daß — Richtigkeit derEyring-Theorie vorausgesetzt — die Energie des Übergangszustands geringer ist alsU+E _a (U: Summe der inneren Energien der Reaktanden;E _a: Aktivierungsenergie). Die Energie des Übergangszustands ist für Hin- und Rückreaktion unterschiedlich und hängt linear von der Temperatur ab.

     

Thermal and electrical behavior of hybrid thermosets based on epoxy and maleimide resins cured with p-aminobenzoic acid

Two thermoset systems based on maleimides and diglycidyl ether of bisphenol A (DGEBA) cured with p-aminobenzoic acid were characterized in terms of thermal and electrical behavior. Thermal characterization has been undertaken by means of thermogravimetric analysis in nitrogen atmosphere up to 600°C using simultaneous thermogravimetric/Fourier transform infrared/mass spectrometry (TG/FT-IR/MS) analysis. In the first stage of thermal degradation, the global kinetic parameters [activation energy (E_a) and preexponential factor (log A₁ (s⁻¹))] were calculated using the isoconversional method of Friedman. The energies variation as well as the shape of the differential thermal analysis curves suggests that the thermal decomposition process occurred in multiple stages. The evolved gases analysis was conducted by simultaneous TG/FT-IR/MS coupled techniques. Dielectric relaxation spectroscopy characterization was also made.     

Study of The Thermal Decomposition of Some New Cyanine Dispersed Dyes

The structure of the studied compounds was confirmed by elemental analysis, IR and NMR. TG and DTG data were used to study the kinetics of the thermal decomposition process of some new cyanine dispersed dyes derived from 2-[(p-chloro)-styryl]-6-[5-(3-aryl-rhodanine)]-1,2-dihydropyridine. The reaction was found to follow first order mechanism. The activation energy E_a was calculated and used to calculate the thermodynamic parameters enthalpy change (H^*), entropy change (S^*), and free energy change (G^*), related to the thermal decomposition process. Two different calculation methods including Coats—Redfern and Chatterjee were applied to evaluate thekinetic and thermodynamic parameters. Quantum study was performed to support both the structure and the thermal data.This revised version was published online in November 2005 with corrections to the Cover Date.     

über den Zusammenhang zwischen dem Molekulargewicht und der ViskositÄtszahl von Lösungen kurzkettiger PolyÄthylenglykole

Zusammenfassung Es wird der Zusammenhang zwischen der ViskositÄtszahl von Lösungen linearer Kettenmolekel (PolyÄthylenglykole) und dem Molekulargewicht dieser Molekeln gemessen. Bei gro\en Molekulargewichten können die Me\ergebnisse durch die Gleichung []=kM ^a mit konstanten Werten fürk unda beschrieben werden. Bei kleinen Molekulargewichten mu\ diese Gleichung zur Beschreibung der Me\ergebnisse modifiziert werden, man mu\ mitMeyerhoff berücksichtigen, da\ sich bei kleinen Molekulargewichten mit abnehmendem Molekulargewicht nicht nur die Grö\e, sondern auch die Form der gelösten Molekel Ändert. Aus dem Zusammenhang zwischen der ViskositÄtszahl und dem Molekulargewicht bei kleinen Molekulargewichten kann die Behinderung der Drehbarkeit der einzelnen Kettenglieder berechnet werden. Diese Behinderung, dargestellt durch den Parameter — ist von Lösungsmittel zu Lösungsmittel verschieden. Ihre AbhÄngigkeit von anderen Eigenschaften der Lösung und der Lösungsmittelmolekeln wird untersucht.

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Summary The dependence of the intrinsic viscosity of a solution of linear chain molecules (polyethylene glycols) from the molecular weight of these molecules have been measured. At higher molecular weights the results can be described by the famous equation []=k· M ^a . Therek anda have constant values. At lower molecular weights, the experimental results can be described by a modified equation according the purpose ofMeyerhoff, who says, that at lower molecular weights with decreasing molecular weight decrease the dimension of the chain molecules and change the form of these molecules.With the result of the measurements at lower molecular weights one can also calculate the hindrance of rotation of the chain molecules. This hindrance — represented by the parameter — changes from solvent to solvent, their dependence from other properties of the solutions and the molecules of the solvent are discussed.

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Auszugsweise vorgetragen auf der Informationsveranstaltung des Deutschen Kunststoff-Instituts am 10. Juli 1963 in Darmstadt und auf der Tagung der Deutschen Physikalischen Gesellschaft am 13. September 1963 in Hamburg.

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Herrn Prof. Dr.K.-H. Hellwege danke ich für die Förderung und Diskussion dieser Arbeit.

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Die Arbeit wurde dankenswerterweise unterstützt vom Land Baden-Württemberg durch GewÄhrung eines Forschungszuschusses und von den Farbwerken Hoechst AG, Werk Gendorf/Obb. durch überlassung der PolyÄthylenglykole.     

Die Bildungskonstanten der Wasserstoff—Fluor-Komplexe in konzentrierten Salzlösungen

Zusammenfassung Die Bildungskonstanten von HF und HF2^–in NaClO₄-Medien wurden aus Messungen mit einer Chinhydron- und einer LaF₃-Membranelektrode bestimmt. Die Bildungskonstanten bei den Ionenstärken 1–, 2–, 3– und 4M werden mit Hilfe einesDebye—Hückel-Ansatzes als Funktion der Ionenstärke dargestellt. Durch Extrapolation auf unendliche Verdünnung werden die thermodynamischen Bildungskonstanten bei 25°C erhalten. Die mit Hilfe der Chinhydronelektrode und der LaF₃-Membranelektrode erhaltenen Ergebnisse werden verglichen und kritisch gewertet.

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Stability constants of hydrogen fluorides in concentrated salt media; Measurements with aLaF ₃-membrane electrode

Formation constants of HF and HF2^– in NaClO₄ media were determined from measurements with a quinhydrone and a LaF₃-membrane electrode. The formation constants at 1,2,3, and 4M ionic strength are presented as a function of the ionic strength through aDebye—Hückel approximation. Extrapolation to infinite dilution gives the thermodynamic stability constants at 25°C. The results obtained from measurements with a quinhydrone and a LaF₃-membrane electrode are compared and critically evaluated.

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Mit 3 Abbildung     

CEPA calculations on open-shell molecules. V. The vibration frequencies of SF and SCl

Ab initio calculations for the ² ground states of SF and SCl have been performed on Hartree-Fock level and with inclusion of valence shell correlation effects by means of the CI and CEPA approaches. The calculated properties are: Equilibrium distances, vibration frequencies, and dipole moment curves in the vicinity of the respective equilibrium geometries. Our best estimates for the 0 1 infrared absorption frequencies _o for SF and SCl are 786 cm^–1 and 520 cm^–1, respectively, both with an uncertainty of about 10 cm^–1. This confirms a recent experimental value obtained by Willner for SF (791 cm^–1), but indicates that for SCl both experimental values reported previously in the literature (617 cm^–1 and 574 cm^–1) are wrong. The S—F and S—Cl bonds in SF and SCl are very similar to the ones in SF₂ and SCl₂, being essentially single p-bonds in either case. In the analogous oxygen-halogen molecules the situation is different, the O—F and O—Cl bonds in the diatomic radicals OF and OCl have partial double bond character and are much stronger than those in OF₂ and OCl₂ or in HOF and HOCl.     

The monostandard method in thermal neutron activation analysis of geological, biological and environmental materials

Summary A simple method is decribed for instrumental multielement thermal neutron activation analysis using a monostandard. For geological and air dust samples, iron is used as a comparator, while sodium has advantages for biological materials.To test the capabilities of this method, the values of the effective cross sections of the 23 elements determined were evaluated in a reactor site with an almost pure thermal neutron flux of about 9·10¹² n·cm^–2·s^–1 and an epithermal neutron contribution of less than 0.03%. The values obtained were found to agree mostly well with the best literature values of thermal neutron cross sections. The results of an analysis by activation in the same site agree well with the relative method using multielement standards and for several standard reference materials with certified element contents. A comparison of the element contents obtained by the monostandard and relative methods together with corresponding precisions and accuracies is given.

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Die Monostandardmethode bei der Aktivierungsanalyse mit thermischen Neutronen von geologischem, biologischem und Umweltmaterial

Zusammenfassung Die Monostandardmethode wurde erstmals auf die Aktivierungsanalyse mit rein thermischen Neutronen aus der thermischen Säule des Reaktors FRJ-2 (mit epithermischen Anteilen von < 0,03%) angewendet. Hier sind die theoretischen Verhältnisse und damit auch Gleichungen besonders einfach. — Die bei einem Neutronenfluß von 9·10¹² n·cm^–2·s^–1 ermittelten effektiven Neutroneneinfangquerschnitte stimmen häufig gut mit den Literaturwerten überein. — Für geologische Proben wurde Eisen, für biologisches Material Natrium als Komparator, d.h. Monoelementstandard, verwendet. Es konnten über zwanzig Elemente in Andesit, Granit, Flugstaubasche, Luftstaub, Pflanzenmaterial und Obstblättern bestimmt werden.

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Dedicated to Professor Dr. Kurt Starke, University of Marburg/ Lahn on the occasion of his 70 th birthday

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Fourth Communication on Improvement of Instrumental Analysis for Service Analysis

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Guest Scientist from Egypt.

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Guest Scientist under IAEA-Fellowship from the Faculty of Chemistry, University of Sofia, Bulgaria

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This paper is an extract of the more detailed Report Jül-1822 (ISSN 0366-0885), January 1983.     

Heteroorganic betaines. 6. Structure and reactivity of silicon-containing organophosphorus betaines with the –S—Si—C—P+ fragment: a DFT study

The structures of silicon-containing organophosphorus betaines ^–S—SiR¹ ₂—CR² ₂—P⁺R³ ₃ and their ylide isomers were calculated using the density functional approach with the gradient-corrected PBE functional and extended TZ2P basis set. Three possible pathways of thermal decomposition of these betaines were analyzed. These are (i) cleavage of the central C—Si bond with the formation of a Wittig ylide and silanethione, (ii) intramolecular nucleophilic S _N-substitution with elimination of phosphine PR³ ₃ and the formation of silathiirane (the Corey—Chaikovscky transformation), and (iii) a Wittig-type decomposition followed by the formation of substituted silaethylene.The structures of products and transition states of these reactions were calculated. The cis-gauche conformation of the ^–S—Si—C—P⁺ fragment of betaines was found to be the most stable. This is in agreement with the results of X-ray diffraction study and can be rationalized by strong Coulomb attraction between the cationic and anionic centers. The betaines are stable toward retro-Wittig thermal decomposition. The Corey—Chaikovscky formation of thiirane is preferable under conditions of thermal decomposition. Retro-Wittig-type decomposition of betaines followed by the formation of silanethione is favored by intra- and intermolecular coordination of donor ligands.     

Die Kristallstruktur von Hf2Hg

Zusammenfassung Im System Hafnium-Quecksilber wurde im Temperaturbereich zwischen 500° C und 800° C nur eine Verbindung Hf₂Hg gefunden. Für diese Verbindung wird eine tetragonale Elementarzelle mita=3,34₅ Å,c=11,49₆ Å,c/a=3,436, Raumgruppe D _4h ¹⁷ –I 4/mmm vom MoSi₂-Typ vorgeschlagen.

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Investigations in the system hafnium—mercury have shown the existence of only one intermetallic compound Hf₂Hg. The structure is supposed to be tetragonal of the MoSi₂-type,a=3.34₅ Å,c=11.49₆ Å,c/a=3.436, belonging to the space group D _4h ¹⁷ –I 4/mmm.

     

Use of emanation thermal analysis in the study of thermal behaviour of inorganic materials

Emanation thermal analysis [1, 2] (ETA) is based on the measurement of the inert gas release from samples previously labelled. The high detection sensitivity of radioactive nuclides used for the measurement makes it possible to use very low concentrations of the inert gases (10^–14 at %) so that no influence of the inert gases on the properties of the solids can be supposed.

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Zusammenfassung Emanations — Thermoanalyse [1, 2] (ETA) basiert auf der Messung von freigesetztem inerten Gas aus zufor markierten Proben. Die große Nachweisempfindlichkeit der bei der Messung verwendeten radioaktiven Nuklide ermöglicht die Anwendung sehr niedriger konzentrationen (10^–14 Atom%) für das inerte Gas. Somit kann angenommen werden, daß die Eigenscahften des Feststoffes durch das inerte Gas nicht beeinflußt werden.

     

Spektroskopische Untersuchungen zur Struktur von SiF4·2 Amin-Addukten

Zusammenfassung Die Addukte von SiF₄ mit 2 Molekülen NH₃, ND₃, N₂H₄ und CH₃NH₂ wurden IR- und Raman-spektroskopisch untersucht. Schwingungsspektren,¹⁹F-Breitband-KMR und chemische Eigenschaften stehen mit einercis-oktaedrischen Struktur im Einklang, in der vermutlich durch Dipol—Dipol-Wechselwirkungen einzelne Komplexmoleküle zu polymeren Einheiten zusammentreten.

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Complexes of SiF₄ with 2 molecules of NH₃, ND₃, N₂H₄, and CH₃NH₂ were investigated by IR and Raman spectroscopy. The results as well as¹⁹F broadline nmr and chemical properties support acis-octahedral structure. Probably dipol—dipol interactions are responsible for the association of the complex molecule. *** DIRECT SUPPORT *** A3615111 00003

     

Effect of tetra‐n‐butylammonium bromide salt on the cationic polymerization of dimethylketene and on the thermal properties of the obtained polyketones

The cationic polymerization of dimethylketene is achieved in dichloromethane at ?30 °C, using a stoichiometric mixture of aluminum bromide (AlBr₃) and tetra‐n‐butylammonium bromide (n‐Bu₄N⁺Br^?) as initiator. Characterizations by ¹H and ¹³C NMR show that the resulting polymers have a perfect polyketonic microstructure. Capillary viscosity, DSC, and SEC analysis show that for a constant monomer/initiator ratio, polymers synthesized in the presence of tetra‐n‐butylammonium bromide are more crystalline and have better properties than those produced only with AlBr₃. Melting temperatures, inherent viscosities and average molecular weights are systematically higher. A good linearity is observed between ln (inherent viscosity) versus ln for the system with n‐Bu₄N⁺Br^?, showing a good control of the molecular weight by the initial feed ratio. The effect of this compound suggests a reversible equilibrium between active and dormant species, which limits the transfer and/or termination reactions, and enables a better control of the cationic polymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1493–1499     

Heat Capacities and Thermodynamic Properties of Fenpropathrin (C22H23O3N)

The heat capacities of fenpropathrin in the temperature range from 80 to 400 K were measured with a precise automatic adiabatic calorimeter. The fenpropathrin sample was prepared with the purity of 0.9916 mole fraction. A solid—liquid fusion phase transition was observed in the experimental temperature range. The melting point, T_m, enthalpy and entropy of fusion, _fusH_m, _fusS_m, were determined to be 322.48±0.01 K, 18.57±0.29 kJ mol^–1 and 57.59±1.01 J mol^–1 K^–1, respectively. The thermodynamic functions of fenpropathrin, H_(T)—H_(298.15), S_(T)—S_(298.15) and G_(T)—G_(298.15), were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min^–1 confirmed that the thermal decomposition of the sample starts at ca. 450 K and terminates at ca. 575 K. The maximum decomposition rate was obtained at 558 K. The purity of the sample was determined by a fractional melting method.This revised version was published online in November 2005 with corrections to the Cover Date.