Infrared absorption study of metal oxides in the low frequency region (700-240 cm−1)
01 May 1964-Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (Elsevier)-Vol. 20, Iss: 5, pp 799-808
TL;DR: In this article, the characteristic frequencies of 52 metals have been studied in the region 700-240 cm−1 and a particle size of 10 μ or smaller was found to give the best representative spectrum.
Abstract: The characteristic frequencies of oxides of 52 metals have been studied in the region 700-240 cm−1. Data for oxides of metals of different valence states and the frequencies of polymorphic forms of several oxides are presented. A particle size of 10 μ or smaller was found to give the best representative spectrum.
TL;DR: In this paper, it was shown that bidentate acetates replace the OR groups and are directly bounded to the titanium, leading to Ti(OR) x (Ac) y. oligomers.
Abstract: Monolithic TiO 2 gels can be reproducibly obtained when the hydrolysis of titanium alkoxides is performed in the presence of acetic acid. This carboxilic acid does not act only as an acid catalyst, but also as a ligand and changes the alkoxide precursor at a molecular level therefore modifying the whole hydrolysis condensation process. Infra-red experiments show that bidentate acetates replace OR groups and are directly bounded to the titanium. Both, chelating and bridging acetates, are observed, leading to Ti(OR) x (Ac) y . oligomers. Hydrolysis of this new molecular precursor removes first (OR) groups and bridging acetates. Chelating acetates are still observed in the gel. They can only be removed upon heating above 200 °C.
TL;DR: In this article, the long wavelength optical phonons of ionic crystals give rise to dipole-dipole forces, whose long range nature causes the vibrations to depend on the size and shape of the crystal sample.
Abstract: The long wavelength optical phonons of ionic crystals give rise to dipole-dipole forces, whose long range nature causes the vibrations to depend on the size and shape of the crystal sample. This dependence affects significantly most spectral properties of all crystals whose dimensions are of the order of or shorter than the wavelength of reststrahlen (characteristically several tens of micrometres). In experimental work in which the infrared properties of ionic crystals were examined on small samples, in powder form or in colloidal suspension or in the shape of thin layers, the peculiarities due to size and shape were not always properly recognized. The infrared frequencies of the material which are derived with disregard to these peculiarities may be in error by some tens of wavenumbers. In the experimental section of the review we interpret the general characteristics of the experimental spectra and analyse in detail some representative infrared measurements in the light of the theory. The theory of optical vibrations which takes account of the finiteness of the specimen is formulated firstly in general terms and then by special reference to samples which have one, two or three dimensions short (slab, cylinder and sphere-like geometries). Synthetic spectra are drawn whose characteristic features are interpreted in terms of bulk and surface modes. In the theory retardation effects, i.e. the coupling between lattice and electromagnetic waves, are also included, and the quantized modes are combinations of these, i.e. polaritons. For tiny crystallites of such size that the characteristic infrared radiation wavelength is much larger than the sample size, retardation effects can be neglected. The theory becomes much simpler and the spectrum sharper. Some of the absorption peaks are due to optical surface modes, and their positions are simply related to the characteristic shapes of the crystallites. The theory is so presented as to provide a practical aid in the correlation of spectra with sample shape. The consequences on the spectra of other, less common variables of experiments, for example, the refractive index of the environments, are also calculated. The role of optical surface modes in Raman - and electron - scattering is then discussed. Simple geometrical arrangements of small sized crystals enable the spectra of surface modes to be scanned.
TL;DR: In this article, the vibrational spectra for polycrystalline powders of AgO and Ag2O are discussed in relation to its crystal structure, and were found to be consistent with factor group analysis predictions.
Abstract: FT-IR and Raman spectra for polycrystalline powders of silver (I, III) oxide, AgO, and silver (I) oxide, Ag2O, are reported. The vibrational spectra for each oxide are discussed in relation to its crystal structure, and were found to be consistent with factor group analysis predictions. Infrared and Raman spectroscopy, in conjunction with powder XRD, were also used to follow the thermal decomposition of AgO powder in air. Supplementary studies employing differential scanning calorimetry (DSC) and temperature programmed reaction (TPR), provided additional information relevant to the decomposition process. In agreement with mechanisms previously reported, AgO was thermally reduced to metallic silver ia two non-reversible steps, with the intermediate formation of Ag2O. The transformation of AgO to Ag2O occurred with heating in the 373–473 K region, while the product of this reaction remained stable to temperatures in excess of 623 K. Complete thermal decomposition of the Ag2O intermediate to Ag and O2 occurred at 673 K.
TL;DR: In this paper, the temperature dependence of the fractionation factor α, for oxygen isotopic exchange between silicates, magnetite and water from a theoretical point of view, was discussed, and it was shown that for anhydrous silicates and magnetite 1000lnα (mineral water) = −3.7 + B/T 2, where B is a constant, for the temperature interval 500° to 800°C.
Abstract: We discuss the temperature dependence of the fractionation factor α, for oxygen isotopic exchange between silicates, magnetite and water from a theoretical point of view. It is shown that for anhydrous silicates and magnetite 1000lnα (mineral water) = −3.7 + B/T 2 , where B is a constant, for the temperature interval 500° to 800°C. Using the results of laboratory experiments and natural observed fractionations, we have derived isotopic fractionation equations for quartz, feldspar, muscovite and magnetite-water systems, which in certain cases are considerably different from already published equations.
TL;DR: The No. 10123 1quart "Success" can as discussed by the authors dispenses solvent by finger pressure on the valve, which then closes upon release of the pressure, as indicated in the accompanying figure.
Abstract: use and allows it to dispense no more solvent than is needed when the swab-stick is dipped into it like a pen into an inkwell. Available in 4 oz., 6 oz., and 8 oz. sizes, the price ranges from $3. 50 to $3. 75. This same company also advertises a model No. 10123 1quart "Success" can which dispenses solvent by finger pressure on the valve, which then closes upon release of the pressure, as indicated in the accompanying figure. There is also a plunger can of I-pint size that dispenses solvent by pressure on the plunger. Price for the first type of can is about $8, for the second, about $7.
TL;DR: In this article, the infrared spectra from 300-880 cm−1 of 208 inorganic substances are reported, nearly all of which are salts containing polyatomic ions, and a list of characteristic frequencies is given for twenty ions.
Abstract: The infrared spectra from 300–880 cm−1 of 208 inorganic substances are reported. Nearly all are salts containing polyatomic ions. Spectral curves are presented for 140 of the compounds, and a list of characteristic frequencies is given for twenty ions. Among other matters discussed are: (a) the non-reproducibility of some of the spectra, and reasons for this, (b) absorption due to the torsional oscillation of water molecules, and (c) some vibrational assignments for MnO4−1 and CrO42−1.
TL;DR: Burns and Bredig as mentioned in this paper showed that a phase identical with the new high-pressure polymorph, which had been shown to be stable only in the region above 10,000 bars, had been formed by simple grinding.
Abstract: THE mechanical action of simple laboratory grinders, mortars and similar devices has occasionally been used to assist in chemical reactions in addition to performing their primary physical functions. Among these chemical reactions are phase transformations. That the effect is due to some kind of a pressure component in the mechanical action may appear obvious, but the magnitude of the pressures is not readily appreciated, nor can it be calculated or measured. However, in the course of work in this laboratory on the high-pressure polymorphism of lead dioxide (PbO2), the information that a phase identical with the new high-pressure polymorph, which had been shown to be stable only in the region above 10,000 bars, had been formed by simple grinding1 was noted with no little surprise. The observation was promptly confirmed by grinding a small amount (2 gm.) of the common rutile form (I) of lead dioxide in a mechanical mortar and pestle combination of laboratory pattern. Grinding in air for a few hours converted an estimated one-third to the denser orthorhombic form (II). After preliminary work, it transpired that nothing new in principle had been added to some similar results which had been reported by Burns and Bredig2 on the transformation of calcite to aragonite by grinding in a mortar. The high-pressure phase was formed from the low-pressure one, the amount of change was dependent on time, and subsequent heating would form the low-pressure phase. A significant difference is that phase equilibrium and thermochemical studies3 place the calcite–aragonite transformation at about 3,000 bars at room temperature, which is considerably lower than the 10,000 bars necessary for the lead oxide I ⇌ II transformation.
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