No abstract is provided for this article.
Sensor characteristics of V2O5 dispersed on oxide supports such as Al2O3, TiO2 and ZrO2 with respect to various gases and vapours including liquefied petroleum gas (LPG) have been investigated. Of all the systems studied, 20 mol% V2O5 dispersed on ZrO2 shows the highest sensitivity for LPG, the log sensitivity—log concentration (in ppm) plots being linear up to 1000 ppm or more. The sensitivity is not affected by humidity or recycling. Addition of P2O5 to V2O5 however destroys the sensitivity. Considering all aspects, 20 mol% V2O5/ZrO2 is suggested for use as a practical LPG sensor. ESR spectroscopy indicates the formation of V4+ species on exposure of V2O5/ZrO2 or TiO2 to LPG. In-situ high-temperature x-ray diffraction measurements show the formation of an unusual monoclinic form of VO2 on exposure to LPG at 625 K which gets oxidized back to V2O5 on exposure to air.
No abstract is provided for this article.
No abstract is provided for this article.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCrystallography and defect chemistry of solid solutions of vanadium and titanium oxidesR. E. Loehman, C. N. Ramachandra Rao, and Jurgen M. HonigCite this: J. Phys. Chem. 1969, 73, 6, 1781–1784Publication Date (Print):June 1, 1969Publication History Published online1 May 2002Published inissue 1 June 1969https://pubs.acs.org/doi/10.1021/j100726a025https://doi.org/10.1021/j100726a025research-articleACS PublicationsRequest reuse permissionsArticle Views464Altmetric-Citations60LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts
On the basis of dielectric hysteresis, electrical conductivity and pyroelectric current measurements, some polycrystalline rare earth orthochromites are suspected to be associated with ferroelectric phenomena which are not compatible with the assignment of a centrosymmetric space group (Pbnm).
Preparation and characterization of the fullerenes, C60 and C70, are described in detail, including the design of the generators fabricated locally. The characterization techniques employed are UV-visible, IR, Raman and C-13 NMR spectroscopies, scanning as well as transmission electron microscopy and mass spectrometry. The electron energy level diagram of C60 as well as the one-electron reductions of C60 and C70 leading to various anions are discussed. Electronic absorption spectra of C60- and C60(2-) are reported. Phase transitions from the plastic to the crystalline states of C60 and C70 are examined. Based on a C-13 NMR study in a mixture of nematic liquid crystals, it has been demonstrated that C60 retains its extraordinary symmetry in solution phase as well. Interaction of C60 and C70 with strong electron-donor molecules has been investigated employing cyclic voltammetry. Superconductivity of K(x)C60 has been studied by non-resonant microwave absorption; Na(x)C60 as well as K(c)C70 are shown to be non-superconducting. Doping C60 with iodine does not make it superconducting. Interaction of C60 with SbCl5 and liquid Br2 gives rise to halogenated products.
Charge ordering in rare earth manganates of the typeLn 0.5 A 0.5MnO3(Ln=rare earth,A=alkaline earth) is highly sensitive to the average radius of theA-site cations, 〈rA 〉. In the small 〈rA 〉 regime (e.g., Y0.5Ca0.5MnO3), charge ordering occurs in the paramagnetic state, the transformation to an antiferro-magnetic state occurring at still lower temperatures. At moderate 〈rA 〉 values (e.g., Nd0.5Sr0.5MnO3), a ferromagnetic metallic state transforms to a charge-ordered antiferromagnetic state with cooling. These two distinct types of charge ordering and associated properties are explained in terms of the variation of the exchange couplingsJ FMandJ AFMwith 〈rA 〉 and the invariance of the single-ion Jahn–Teller energy with 〈rA 〉. A qualitative temperature–〈rA 〉 phase diagram, consistent with the experimental observations, has been constructed to describe the properties of the manganates in the different 〈rA 〉 regimes.
V2O5 supported on ZrO2is found to be an excellent sensor for n-propane–butane mixtures at 625 K; in-situ X-ray diffraction studies show that V2O5 is reduced to VO2 with a metastable monoclinic structure on contact with the hydrocarbons and is oxidised back to the parent oxide on exposure to air.
We have carried out fluorination on La2NiO4 and La2CuO4+δ. Only a small fraction of fluorine enters the bulk; the rest resides on the surface. The cuprate after fluorination exhibits greater departures from tetragonal symmetry than the parent material and transforms at ∼40 K to the superconducting state. By contrast, the nickelate deviates less from tetragonal symmetry upon fluorination; no superconductivity was observed down to 4.2 K.
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