Low-Temperature Synthesis of Single-Phase Barium Strontium Titanate Thin Film with a nm-Seeding Technique and Its Dielectric Properties

Dielectric barium strontium titanate (Ba_0.5Sr_0.5TiO₃, BST) thin films containing crystalline seeds of BST nanoparticles were prepared on indium titanium oxide (ITO) glass electrodes with a complex alkoxide precursor method. BST precursor solution that dispersed the BST particles was spin-coated on the electrode and annealed at various temperatures. Thickness of the film was about 300 nm, and BST particle concentration in the film was varied from 0 to 17 mol%. An unseeded BST film was crystallized into a perovskite structure by annealing at 600C, while the seeding with the 17 mol%-BST particles promoted crystalline growth of BST perovskite and lowered crystallization temperature of the films to 525C. Measurement of dielectric properties at 1 kHz showed that the 4.9 mol% BST-seeded film annealed at 600C had a relative dielectric constant of 303, which was higher than that of the unseeded BST film.     

The Properties of Mixtures of Sodium Dodecylsulfate and Diethylsulfoxide in Water

The aqueous mixtures of sodium dodecylsulfate (SDS) and diethylsulfoxide (DESO) have been studied using conductivity, viscosity and surface tension techniques. The critical micellar concentration (cmc) was determined in the presence of DESO at 30, 40, and 50 C from conductance and surface tension measurements. The enthalpy ( G_m), entropy ( S_m) and Gibbs energy ( G_m) of micellization were determined from the temperature dependence of the cmc. The results obtained were compared with published results for aqueous solutions of SDS and dimethylsulfoxide (DMSO). The data demonstrate a more pronounced inhibitory effect of DESO on the micellization of SDS, in comparison with the effect of DMSO. On the basis of the dependences of the relative viscosities on concentration, as given by the Jones–Dole semi-empirical equation, the B-coefficients have been calculated for the post-micelle composition region.     

Structural and Microstructural Evolution During Pyrolysis of Hybrid Polydimethylsiloxane-Titania Nanocomposites

The evolution during pyrolysis of hybrid polydimethylsiloxane-titania nanocomposites has been studied as a function of the ratio between polysiloxane and titania phases. The xerogels, prepared by the sol–gel process starting from diethoxydimethylsilane and titanium isopropoxide, have been heated under argon atmosphere and the evolution with temperature has been followed by infrared and ²⁹Si solid state nuclear magnetic resonance spectroscopies, thermal analyses, X-ray diffraction, N₂ sorption measurements and scanning electron microscopy. Below 800C, the polymer-to-ceramic conversion takes place at different temperatures with changing the titania content. The stability of Si–C bonds in polydimethylsiloxane networks depends on the metal oxide amount. The high reactivity of titanium atoms towards the Si–C bonds produces Si–C bond cleavage with mild thermal treatments and in the case of 30 mol% TiO₂, leads to the ceramization of the hybrid nanocomposite at 500C. Decreasing the titania load, a shift towards higher temperatures to complete the polymer-to-ceramic conversion is observed. The structural rearrangement of the siloxane moiety produces mesoporous and microporous materials, depending on the composition; in the case of 10 and 20 mol% TiO₂ content, the samples present high specific surface area up to 1200C.The crystallization process begins at 1000C and the phase evolution depends on the composition. The phase analysis obtained from XRD spectra shows that different crystalline oxide and oxycarbide phases develop during the thermal process, as a function of the amount of available carbon, ultimately leading to the preferential crystallization of titanium carbide. Between 1000 and 1600C the amorphous silicon oxycarbide phase undergoes a continuous structural evolution caused by the decrease of carbon content in the phase, leading to almost pure silica at 1600C.     

Conductance of iron(III) laurate solutions in binary liquid mixtures

Summary The specific conductivity of iron(III) laurate solutions in binary liquid mixtures shows that the soap aggregates into micelles and CMC is found to be independent of temperature and concentration of benzene, acetone and tetrachloromethane in 1-butanol. The variation of molecular conductance,, with soap concentration, C, is expressed by the equation: = 10^AC^B. Both constants A and B vary with solvent composition but B remains constant with increase in temperature. Several parameters such as molecular conductance at infinite dilution, , dissociation constant, K, heat of dissociation, H, entropy, S and free energy, G of dissociation of soap have been evaluated and the effect of the nature of solvents has been discussed.     

Potentiometric Investigation of Fluoride Complexes of Zirconium(IV) and Hafnium(IV) in 1 <Emphasis Type="Italic">M</Emphasis> (H,Na)ClO<Subscript>4</Subscript> Medium Using a Fluoride Ion Selective Electrode

The stability constants of zirconium(IV) and hafnium(IV) fluoride complexes in 1 M (H,Na)ClO₄ medium were measured potentiometrically at 293 K for the first time using a fluoride ion selective electrode (F-ISE). This technique has been recommended by IUPAC as the best tool for studying fluoride complexes. A number of precautions were taken to ensure the stabilization of zirconium or hafnium in 1 M (H,Na)ClO₄ medium and to prevent the formation of polynuclear hydroxo complexes. The formation of only mononuclear complexes was indicated. The average log values of the overall stability constants of zirconium(IV)-fluoride complexes, ₁, ₂, ₃ and ₄ were computed by varying the concentration of metal ion and were found to be 8.49 ± 0.11, 15.76 ± 0.15, 21.57 ± 0.10, and 26.68 ± 0.16, respectively, whereas the corresponding values for hafnium(IV)-fluoride complexes were 8.22 ± 0.06, 15.48 ± 0.15, 21.76 ± 0.14, and 27.42 ± 0.15, respectively. The thermodynamic stability constant, ₁, calculated for these complexes follows the same trend as expected from the linear correlation based on the Brown Sylva Ellies (BSE) model for metal-fluoride complexes provided the effective charge on Zr is taken as +4.1 instead of the formal charge of +4. Without considering this adjustment of formal charge, an attempt has also been made to explain the trend in ₁ values of group(IV) metal-fluoride complexes based on electronegativity values. A good linear correlation was obtained that could explain the ability of these group(IV) ions to form different fluoride complexes with varying number of fluoride ions.     

Study of the Surface Tensions of Cyclohexane or Methylcyclohexane with Some Cyclic Ethers

Experimental surface tensions, measured with a drop volume tensiometer and the corresponding surface tension deviations for the binary mixtures of cyclohexane or methylcyclohexane with a cyclic ether (tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran or 2,5-dimethyltetrahydrofuran) are given at 25 and 40 C. The results have been discussed in terms of lyophobicity and molecular interactions using the extended Langmuir isotherm. The model proposed by Patterson and Rastogi has been used to calculate the surface tensions of the pure components and of their mixtures at 25C; these calculations have been compared with the experimental results.     

Thermodynamics of 2,2′,2′'-terpyridinecopper(II) complexes in aqueous solution

Summary The thermodynamic quantities relative to the protonation and the complexation of 2,2,2'-terpyridine with copper(II) ion have been determined at 25° and I=0.1 mol dm^–3 (NaNO₃). The G data was obtained by potentiometric measurements; a copper selective electrode was employed for the study of the complexation equilibria. The H values have been determined by direct calorimetry.The hydrolytic species, existing at pH>6 and their relative G and H values have also been obtained.From the thermodynamic data the importance of enthalpy and entropy terms in stabilizing the complexes is assessed.Moreover some considerations on the chelating effect are reported.Presented in part at 2 Congresso Nazionale di Chimica Analitica, Catania (1977).     

Electronic effect of the 1-[η5-cyclgpentadienyl-η5-(3)-1,2-dicarbollyliron(II)] group

Conclusions The Taft method was used to determine the electronic effect of the 1-[⁵-cyclopenta-dienyl-⁵-(3)-1,2-dicarbollyliron(II) ] group which displays strong electron-donor properties: _I=–0.22 and _R=–0.20.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1449–1451, June, 1985.     

Various dynamic behavior of Ag+-induced oscillations in uncatalyzed bromate oscillators

Silver ion induces the uncatalyzed bromate oscillators /aromatics-bromate-acid/on a variety of dynamic behavior, including high frequency and complex oscillations. The behavior of a reacting system depends on the chemical composition of the armatics, the time of addition of Ag⁺, and the concentration of Ag⁺. The chemistry underlying the phenomena is discussed.

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(--) , . , Ag⁺ Ag⁺. .

     

The solvent eluotropic strength on carbon adsorbents

Summary Two theoretical approaches are discussed to calculate the solvent strength () on carbon materials. One is based on the adsorbate-adsorbent interfacial tension and the other uses the theory of solubility parameters. It is shown that there is good agreement between these approaches. Experimental values are compared with theoretical ones and there is again a good agreement. Solvents having small and highly polar molecules have small values. Solvents having large and aromatic molecules have high values. Binary solvent mixtures can be classified in two groups depending on the rate of change of with the mole fraction of the strongest solvent in the mixture.Dedicated to Professor Dr. István Halász for his 60th birthday.     

Volumetric Parameters of Interaction of Monosaccharides (D-xylose,D-arabinose,D-glucose,D-galactose) with NaI in Water at 298.15 K

Densities for monosaccharide (D-xylose, D-arabinose, D-glucose, D-galactose)–NaI–water solutions were measured at 298.15 K and were used to calculate the apparent molar volumes of these saccharides and NaI. Infinite dilution apparent molar volumes for the saccharides (V_,S) in aqueous NaI and those for NaI (V_,E) in aqueous saccharide solutions and partial molar volumes of the saccharides (V_S) and NaI (V_E) at each composition have been evaluated, together with the standard transfer volumes of the saccharides (_tr V_S) from water to aqueous NaI and those of NaI (_trV_E) from water to aqueous saccharide solutions. It was shown that the _tr V_S and _trV_E values are positive and increase with increasing co-solute molalities. Volumetric parameters indicating the interactions of NaI with saccharides in water were also obtained and applied to explore the interactions between saccharides and NaI in water. A comparison of the _ES value for NaI with those for NaCl and NaBr showed that for a given saccharide, except for glucose, the _ES value for NaBr is the largest of three sodium halides (NaCl, NaBr and NaI). These were interpreted in terms of the apparent molar electrostriction volumes ( V_e) and the structure interaction model.     

X-ray diffraction study of 1,2-bis(methylidene-2,2-dimethyl-hydrazino)ethylene — product of the oxidation of 1,1,2-trisubstituted hydrazines [1,1-dimethyl-2-(2-cyanoethyl)hydrazine]

It was established by x-ray diffraction analysis of crystals with the composition C₁₀H₁₄N₆ [a=14.869(2), b=11.405(2), c=7.585(1) Å, =107.53(1), d_calc=1.18 g·cm^–3, Z=4, and space group P2₁/c] that the molecule has a linear rather than a cyclic structure and is 1,2-bis(methylidene-2,2-dimethylhydrazino)ethylene rather than 1,4-bis(dimethylamino)-2,5-dicyano-1,4-dihydropyrazine as previously assumed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 541–544, April, 1978.     

Influence of carbon dioxide and carbon monoxide on the kinetics of propylene polymerization

Retardation effect of the carbon oxides on propylene polymerization, catalyzed by the TiCl₃/AlEt₂Cl system, can be described in terms of a Langmuir type equation as selective adsorption of the carbon oxides on the polymerization sites.

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, TiCl₃/AlEt₂Cl, , .

     

Physicochemical Properties of Ampicillin and Amoxicillin as Biologically Active Ligands with Some Alkali Earth,Transition Metal,and Lanthanide Ions in Aqueous and Mixed Solvents at 20, 30, and 40<Superscript>∘</Superscript>C

The acid-base equilibria of ampicillin and amoxicillin were investigated in pure water and different solvent + water mixtures (solvent = methanol, ethanol, acetone, dimethylformamide, and dimethyl sulfoxide) at a constant ionic strength (I = 0.1 mol-dm^–3 KNO₃) and organic solvent volume fractions of 10, 20, and 30%. The effect of temperature on these equilibria was studied at 20, 30, and 40C. Thermodynamic functions of these ligands were calculated and discussed in terms of G, H, and S. The number of ionizable protons was determined using conductometric titrations. The formation constant of the complexes, which form by reaction of the ligands with Mg(II), Ca(II), Zn(II), Cu(II), Ni(II), Co(II), Ce(III), Pr(III), Eu(III), Gd(III), Ho(III), Er(III), and Yb(III), are determined. The relative stability of the alkali earth, transition, and lanthanide elements are compared with each other and discussed in terms of the ionic radius and the electronic structure of the outer shell of that ion. The results obtained are discussed in terms of macroscopic properties of the mixed solvents and the possible variation in microheterogenity of the solvation shells around the solute.     

Mesophasic properties of low molecular weight analogues of nematogenic polycarbonates

The mesophasic behaviour of the following compounds has been investigated by DSC, X-ray diffraction and optical microscopy methods: CH₃(CH₂)₄-CO-R-A _n -R-CO-(CH₂)₄-CH₃,n=9 14, 16 CH₃(CH₂)₄-CO-R-B _n -R-CO-(CH₂)₄-CH₃,n=2, 3A _n=-CO-O-(CH₂)_n–4-O-CO-,B _n =-CO-(OCH₂CH₂) _n -O-CO-,R=-O-Ø-C(CH₃)=N-N=(CH₃)C-Ø-O-,Ø=-C₆H₄ They have been assumed to be low molecular weight models of homologous nematogenic polymers.All the examined compounds exhibit nematic mesomorphism. On complete analogy with the corresponding polymers, the thermodynamic data relative to the nematic-isotropic phase transition show a very reduced, if any, odd-even fluctuation. These data are compared with those obtained for very similar compounds, both polymeric and non-polymeric, containing ester linkages between the rigid and flexible groups, to provide evidence of the reliability of the dimeric compounds as models of the polymeric homologues.

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Zusammenfassung Das mesophasische Verhalten der folgenden Verbindungen wurde mittels DSC, Röntgendiffraktion und optischer Mikroskopie untersucht: CH₃(CH₂)₄-CO-R-A _n -R-CO-(CH₂)₄-CH₃;n=914, 16 CH₃(CH₂)₄-CO-R-B _n -R-CO-(CH₂)₄-CH₃;n=2, 3A _n =-CO-O-(CH₂)_n-4-O-CO-;B _n =-CO-(OCH₂CH₂)_n-O-CO-;R=-O-C₆H₄-C(CH₃)=N-N=(CH₃)C-C₆H₄-O-. Die Verbindungen wurden als Modelle homologer nematogener Polymere mit niedrigem Molekulargewicht angesehen. Alle untersuchten Verbindungen zeigen einen nematischen Mesomorphismus. Analog zu den entsprechenden Polymeren zeigen die sich auf den nematisch-isotropen Phasenübergang beziehenden thermodynamischen Daten eine, wenn überhaupt, sehr reduzierte ungerade-gerade Fluktuation. Diese Daten werden mit denen verglichen, die für sehr ähnliche, sowohl polymère als auch nicht-polymere Verbindungen mit Esterbindungen zwischen den starren und flexiblen Gruppen erhalten wurden, um Beweise für die Zuverlässigkeit der auf dimeren Verbindungen aufbauenden Modelle für polymère Homologe zu erhalten.

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, : CH₃(CH₂)₄-CO-R-A _n -R-CO-(CH₂)₄-CH₃ n=914,16 CH₃(CH₂)₄-CO-R-B _n -R-CO-(CH₂)₄-CH₃ n=2, 3A _n =-CO-O-(CH₂) _n–4-O-CO-;B _n =-CO-(OCH₂CN₂) _n -O-COR =-O--C(CH₃)=N-N=(CH₃)C--O- =C₆H₄ , . . — , , , - . , , ,

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The financial assistance of the Ministero Pubblica Istruzione is acknowledged.     

Oxidation Behavior of Si–Nb–C–O Ceramics Prepared by the Pyrolysis of Methyltriethoxysilane Based Organic-Inorganic Hybrid Gel

The oxidative structural characterization of Si–Nb–C–O ceramic prepared by the heat-treatment of transition metal containing polymethylsilsesquioxane hybrid was investigated. The heating temperature for the pyrolysis of precursor hybrid gels strongly affected the oxidation behavior of the resultant ceramics. The hybrid gel pyrolyzed at 600C was rapidly oxidized, while the hybrid gel pyrolyzed at 1000C showed the higher resistance to oxidation. In the hybrid pyrolyzed at 600C, new Si–O–Nb oxygen-bridged heterometal bonds were formed after oxidation, which was confirmed by FT-IR spectra. On the other hand, silica and oxycarbide protective layer was formed on the oxidized surface of the hybrid heated at 1000C, as suggested by X-ray photoelectron spectroscopy (XPS). Raman spectra showed a large luminescence background, G and D bands before oxidation. After oxidation, however, the luminescence background disappeared and G band was more symmetric than that of non-oxidative product. This strongly suggested the predominant oxidation of radical and related unstable carbon species in the ceramics.     

Décomposition thermique du sulfite de fer(II) anhydre

Résumé Sous azote ou sous vide, le sulfite ferreux anhydre se décompose vers 210° en magnétite, pyrite et dioxyde de soufre. Concurremment une réaction de dismutation intervient avec formation de FeSO₄, Fe₃O₄ et FeS₂. Lorsque la température atteint 320°, la pyrite et le sulfate réagissent ensemble pour donner Fe_1–xS, Fe₃O₄ et SO₂. Au-delà de 370° le sulfure ferreux non-stchiométrique commence à réagir à son tour avec le sulfate restant pour former de la magnetite et du dioxyde de soufre.

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In nitrogen or under vacuum, anhydrous iron(II) sulfite decomposes near 210° to magnetite, pyrite and sulfur dioxide. A parallel disproportionation reaction occurs with formation of FeSO₄, Fe₃O₄ and FeS₂. When the temperature reaches 320°, pyrite and sulfate react together to give Fe_1–xS, Fe₃O₄ and SO₂. Above 370° the non-stoichiometric ferrous sulfide begins to react with the remaining sulfate to give magnetite and sulfur dioxide.

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Zusammenfassung Unter Stickstoff oder im Vakuum zersetzt sich das wasserfreie Eisen(II)-sulfit in der Nähe von 210 °C zu Magnetit, Pyrit und Schwefeldioxid. Parallel hierzu findet eine Disproportionierung unter Bildung von FeSO₄, Fe₃O₄ und FeS₂ statt. Wenn die Temperatur 320 °C erreicht, reagieren Pyrit und Sulfat unter Bildung von Fe_1–xS, Fe₃O₄ und SO₂ Oberhalb von 370 °C beginnt das nichtstöchiometrische Eisensulfit seinerseits mit dem restlichen Sulfat zu reagieren um Magnetit und Schwefeldioxid zu ergeben.

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(II) 210° , . FeSO₄, Fe₃O₄ FeS₂. 320°, , Fe_1–xS, Fe₃O₄ SO₂. 370° .

     

The Effects of Temperature of Condensation on the Thermal Stability and Morphology of 1,4-Phenylenediamine-1-Propylsilica Xerogels

1,4-phenylenediamine-1-propylsilica hybrid xerogels were obtained for two composition at different temperatures of gelation, from 5 up to 70C. The morphological effects produced by the different gelation temperatures were investigated by using N₂ adsorption-desorption isotherms and scanning electron microscopy. The thermal stability of the organic groups and their distribution on the xerogel matrix, i.e. the fraction of the organic groups that were trapped in closed pores, formed during the xerogel synthesis, and the fraction of organic groups present on the surface, were obtained by using infrared thermal analysis. The higher porosity of the xerogels and the higher thermal stability of the organic groups were achieved for samples gelled at 25C.     

Microstructure Control of RF and Carbon Aerogels Prepared by Sol-Gel Process

A novel sol–gel process has been successfully developed for preparing strontium bismuth tantalate (SrBi₂Ta₂O₉, known as SBT) with ethylene alcohol as a solvent and acetic acid as a catalyst. The size of phase-pure SBT nanoparticles could be 4 nm in diameter by avoiding the formation of the fluorite phase at the low temperatures (550–600C). The behavior of the crystallization in SBT is investigated by XRD, TG-DTA, FT-IR and TEM. The nanoparticle size as a function of the annealing temperature is also investigated. By fitting the Arrhenius curve, we obtain the crystalline and vitreous growth activation energies, i.e, E_a1 = 0.709 eV and E_a2 = 0.093 eV. The two other fitting parameters, transition temperature T₀ = 814 K (541C) and transition width = 0.022, directly show the behavior of the phase transition from vitreous phase to crystalline phase.