Author
W.J. Sime
Bio: W.J. Sime is an academic researcher from Obafemi Awolowo University. The author has contributed to research in topics: Lead(II) oxide & Lead oxide. The author has an hindex of 1, co-authored 1 publications receiving 22 citations.
Topics: Lead(II) oxide, Lead oxide
Papers
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TL;DR: In this paper, the R theory of amphiphybrid mesophases has been used in the interpretation of phase transitions in molten carboxylate systems, and the results of the analysis were shown to be useful in the analysis of phase transition in lead dodecanoate/lead oxide.
22 citations
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TL;DR: The thermal behavior of di-, tri-and tetravalent metal soaps (carboxylates) is reviewed in this paper, with reference to both the phase behaviour and thermal decomposition.
100 citations
TL;DR: In this article, a detailed review of the phase and structural properties of metal carboxylates is presented along with proposed theories and molecular models for odd-even alternation, chain length effects, phase structures and mesophase formation.
Abstract: Investigations on the phase behaviors and structural properties of mono-, di- and poly-valent metal carboxylates are reviewed with reference to developments in experimental and theoretical concepts surrounding their liquid crystalline properties. The main methods of structural investigation such as X-ray diffraction, infrared and 13C-NMR spectroscopies are examined in detail on the basis of common synthetic routes leading to the isolation of pure compounds. A detailed review of the thermal behaviors of several metal carboxylates is presented along with proposed theories and molecular models for odd–even alternation, chain length effects, phase structures and mesophase formation. Theories explaining the effects of metal ion radii and chain unsaturation are also discussed. Proposed degradation mechanisms resulting in the formation of various products and kinetic studies are also considered. Though this review highlights a number of investigations on the structural and phase properties of the mostly widely studied carboxylates, the results presented here strongly indicate that there is room for further studies on some of these systems.
35 citations
TL;DR: In this paper, the thermal decomposition of lead(II) dodecanoate, tetradecanoate, and octadecanate has been studied thermogravimetrically in the temperature range 298-1073 K by the modified method of Freeman and Carroll.
18 citations
TL;DR: In this article, a phase diagram has been constructed for the lead-dodecanoate system and the total entropy change accompanying the transformation from crystal → liquid phase is the same for all the compositions studied.
15 citations
TL;DR: In this paper, an inert platinized platinum wire bathed with a gaseous mixture of oxygen and water served as a hydroxide electrode in potentiometric determinations of the hydroxides activity in the melts.
Abstract: The complexation between lead(II) and hydroxide has been studied in molten (K,Na)NO3 at 280 °C by various techniques. An inert platinized platinum wire bathed with a gaseous mixture of oxygen and water served as a hydroxide electrode in potentiometric determinations of the hydroxide activity in the melts. Only PbOH+ and Pb2OH3+ can be detected at the low hydroxide concentrations used. Raman spectra and 1H NMR experiments gave strong indications that hydroxide retains the proton also when coordinated to lead(II). Oxide ions added to the melts readily transform into hydroxide even at very low water activities. Studies of the solubility of Pb(NO3)2 in melts with various concentrations of dissolved PbO show the formation of [PbOH+]q-species at fairly high hydroxide concentrations. Liquid X-ray scattering data yield q= 2 at these hydroxide concentrations, i.e. Pb2(OH)2+2 is the predominant complex ion. The Pb—O and Pb—Pb distances are 2.7 and 3.4 A, respectively. The short Pb—Pb distance is the same as that observed in the halide species Pb2X3+, and it is suggested that the complex is stabilized by a Pb—Pb interaction.
15 citations