Kinetic study of the crystallization processes of some decorative ceramic glazes

A kinetic study of the crystallization processes was performed for some decorative ceramic glazes in the PbO-SiO₂-Na₂O-K₂O-CaO(BaO)-Al₂O₃-B₂O₃ system with addition of 10% TiO₂ and ZnO. The crystallization kinetics has been studied in non-isothermal conditions using DTA technique. The apparent activation energies of the crystallization processes were calculated using the Kissinger method. The main crystalline phase, which provides the decorative effect, is rutile. This has been identified by X-ray diffraction and it is clearly visible in the optical microscopy images taken in transmitted light, as needle-like or even prismatic crystals arranged in radial-fibrous aggregates.     

Coordination of solvent molecules to VO(acac)<Subscript>2</Subscript> complexes in solution studied by hyperfine sublevel correlation spectroscopy and pulsed electron nuclear double resonance

Interactions and binding sites of the solvent molecules chloroform and ethanol to bis(acetylacetonate)oxovanadium(IV) (VO(acac)₂) complexes in (frozen) solutions have been investigated by pulsed electron nuclear double resonance, sum peak electron spin echo envelope modulation and hyperfine sublevel correlation spectroscopy. The experimental proton hyperfine coupling data of coordinating solvent molecules have been interpreted using quantum chemical calculations (density functional theory). Experimental and computed hyperfine couplings indicate that ethanol coordinates to vanadium in the equatorial plane of VO(acac)₂ and chloroform interacts via hydrogen bonding to oxygens of the acac ligands.     

Microwave-Assisted Preparation of Trifluoroacetaldehyde (Fluoral): Isolation and Applications

A novel method for the preparation of trifluoroacetaldehyde (fluoral, TFAc, CF₃CHO) from commercially available trifluoroacetaldehyde ethylhemiacetal (TFAE) by microwave irradiation is described. The isolation, characterization and reaction of fluoral with various nucleophiles were studied to verify the diverse applicability of this new method.     

Thermal behaviour of the homopolynuclear glyoxylate complex combinations with Cu(II) and Cr(III)

Homopolynuclear complexes of Cu(II) respectively Cr(III) with the glyoxylate dianion, C₂H₂O₄ ^2-, have been studied in non-isothermal regime in air and nitrogen. The results of the non-isothermal analysis performed for the synthesised complexes, Cu(C₂H₂O₄)·0.5H₂O, respectively [Cr₂(OH)₂(C₂H₂O₄)₂(OH₂)₄]·2H₂O, correlated with the results of the IR and TG analysis of the compounds obtained by thermal treatment from the initial complexes and the results of the GLC and XR analysis have led to the establishment of the thermal decomposition mechanisms for the two studied complexes. The decomposition mechanisms confirm the stoichiometric and structural formulae proposed for the two synthesised homopolynuclear complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of steroids. XLI. Ion-pair high-performance liquid chromatographic separation of quaternary ammonium steroids on silica.

A normal-phase ion-pair chromatographic system has been developed for the high-performance liquid chromatographic investigation of pipecuronium bromide (2 beta,16 beta-bis-(N'-dimethyl-l-piperazinyl)-3 alpha,17 beta-diacetoxy-5 alpha-androstane dibromide) and related quaternary ammonium steroids. The use of silica as the stationary phase and a 96:4 mixture of acetonitrile and water containing 0.1 mol/dm3 sodium perchlorate as the eluent with detection at 213 nm enable the potential impurities as well as the hydrolytic and oxidative degradation products of pipecuronium bromide to be separated and detected down to the 0.01% level. The above system is also applicable to the high-performance liquid chromatographic investigation of other quaternary ammonium steroids (pancuronium bromide, vecuronium bromide).     

A Levi–Civita functional equation on semigroups

Aequationes mathematicae - Let S be a semigroup. We describe the solutions $$f,g:S \rightarrow \mathbb {C}$$ of the functional equation $$\begin{aligned} f(xy) = f(x)g(y) + g(x)f(y) - g(x)g(y), \...     

Isolated subgroups of finite abelian groups

Czechoslovak Mathematical Journal - We say that a subgroup H is isolated in a group G if for every x ∈ G we have either x ∈ H or 〈x〉 ∩ H = 1. We describe the set of...     

Kobalt(III)ammin-derivate einiger Reineckesalz-Analoga mit Xylidinen

Zusammenfassung Es wurden 34 neue Komplexsalze durch doppelte Umsetzung aus wäßr.-alkohol. Lösungen der folgenden Reineckeat-Analoga: [Cr(NCS)₄(m-xylidin)₂]^–, [Cr(NCS)₄(p-xyl)₂]^– und Hexammin-, Monoacido-pentammin- und Diacido-tetramminkobalt(III)-komplexsalze erhalten. Es wurden in einigen Fällen Unterschiede in physiko-chemischen Eigenschaften, wie Farbtönung, Kristallform, Löslichkeit und papierchromatographischeR _f-Werte, bei den stellungsisomeren Salzen vom Typus: Kation · [Cr(NCS)₄(xyl)₂] und auch bei den Koordinationsisomerpaaren: [Co(DH)₂(m-xyl)₂] [Cr(NCS)₄(p-xyl)₂] und [Co(DH)₂(p-xyl)₂] [Cr(NCS)₄(m-xyl)₂] usw. beobachtet.

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Cobalt(III)ammine derivatives of some reineckate analogues with xylidines

34 new complex salts were prepared by double conversion of the reineckate analogues [Cr(NCS)₄(m-xylidine)₂]^–, [Cr(NCS)₄(p-xyl)₂]^–, with the hexammine-, monoacido-pentammine- and diacidotetrammine-complexes of Co(III). In some of the position and coordination isomeres differences of the standard physico-chemical properties, i.e. color, crystal form, solubility and paper chromatographyR _f-values were observed.

     

Etude des métastannates de cadmium par spectrographie d'absorption infrarouge entre 5 et 40μ. Solutions solides entre l'oxyde d'étain et Poxyde de cadmium

Résumé Par chauffage à 1000° de mélanges d'oxyde stannique et d'oxyde de cadmium en proportions diverses, comme par déshydratation de précipités mixtes des hydroxydes correspondants, il se forme une série de solutions solides de l'oxyde de cadmium dans l'oxyde d'étain. Elles sont solubles dans l'acide chlorhydrique et présentent un spectre d'absorption infrarouge caractéristique que l'on a comparé avec celui des 2 métastannates de cadmium CdSnO₃, l'un de type ilménite, l'autre de type perovskite.

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Summary By heating various mixture of stannic oxide and cadmium oxide to 1000° C, a series of solid solutions of cadmium oxide in stannic oxide results as is the case when mixed precipitates of the corresponding hydroxides are dehydrated. They are soluble in hydrochloric acid and yield a characteristic infrared absorption spectrum that was compared with that of the two cadmium métastannates CdSnO₃, one of the ilmenite type, the other of the perovskite type.

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Zusammenfassung Erhitzt man verschieden zusammengesetzte Gemische von Zinnoxid und Cadmiumoxid auf 1000° C oder werden Mischfällungen der entsprechenden Hydroxide dehydratisiert, so entsteht eine Reihe fester Lösungen von Cadmiumoxid in Zinnoxid. Sie sind in Salzsäure löslich und zeigen ein charakteristisches Absorptionsspektrum im IR. Dieses wurde mit dem Spektrum zweier Cadmium-Metastannate (CdSnO₃) vom Typus des Ilmenits bzw. Perovskits verglichen.

     

Orientation control of perovskite thin films on glass substrates by the application of a seed layer prepared from oxide nanosheets

Orientation control of perovskite compounds was investigated by the application of a seed layer prepared from oxide nanosheets. An aqueous suspension of oxide nanosheets was prepared by the exfoliation of a layered compound of KCa₂Nb₃O₁₀ oxide grains. A seed layer composed of (TBA)Ca₂Nb₃O₁₀ nanosheets (TBA = tetrabutylammonium) was formed on a glass substrate by simply dip coating it in the suspension. Two kinds of perovskite compounds, LaNiO₃ (LNO) and Pb(Zr,Ti)O₃ (PZT) with a preferred orientation of (00l) were successfully grown on this seeded glass substrate. In this study, the relation between lattice mismatch and electrical properties is investigated. A large, oriented PZT film with a size of 5 ×4 cm shows an improved P-E hysteresis behavior by use of this orientation control.