Search results for "Barium"
showing 10 items of 262 documents
CoOx catalysts supported on alumina and alumina-baria: influence of the support on the cobalt species and their activity in NO reduction by C3H6 in l…
2003
Abstract CoO x catalysts (Co 1 and 3 wt.%) were prepared by incipient-wetness impregnation of the supports, Al 2 O 3 and Al 2 O 3 (80 wt.%)-BaO (20 wt.%), and calcined at 500 and 800 °C. The samples were characterized by X-ray diffraction (XRD) and BET techniques. H 2 -temperature programmed reduction (TPR) and UV-Vis diffuse reflectance spectroscopy (DRS) spectra were recorded with the aim to identify the different Co species formed. The presence of Co 2+ species tetrahedrally and octahedrally coordinated appears strongly influenced by the nature of the support and the cobalt content. Co 3 O 4 particles were detected after calcination at 500 °C, a successive treatment at 800 °C promotes th…
A study of the behaviour of Pt supported on CeO2–ZrO2/Al2O3–BaO as NO storage–reduction catalyst for the treatment of lean burn engine emissions
2002
Abstract The behaviour of a Pt(1 wt.%) supported on CeO2–ZrO2(20 wt.%)/Al2O3(64 wt.%)–BaO(16 wt.%) as a novel NOx storage–reduction catalyst is studied by reactivity tests and DRIFT experiments and compared with that of Pt(1%)–BaO(15 wt.%) on alumina. The former catalyst, designed as a hydrothermally stable sample, is composed of an alumina modified with Ba ions and an overlayer of ceria-zirconia. The results pointed out that during the calcination barium ions migrates over the surface of the catalyst which thus show a good NOx storage–reduction behaviour comparable with that of Pt–BaO on alumina, although Ba ions result much better dispersed.
Thermal stability, structural properties and catalytic activity of Pd catalysts supported on Al2O3–CeO2–BaO mixed oxides prepared by sol–gel method
2003
Abstract Al2O3–CeO2–BaO oxides with constant Al/Ba mass ratio and increasing cerium content were prepared, using the sol–gel procedure, and calcined at 1000 °C for 5 h. The influence of barium oxide on the thermal stability and on the morphological and structural properties of the corresponding supports, in terms of increasing surface area of alumina and ceria dispersion, was studied. The corresponding Pd (1 wt.%) catalysts were prepared by a stepwise impregnation method with a solution of palladium acetylacetonate in benzene. Palladium was introduced in two sequential steps by impregnation 0.5 wt.% of Pd each time. The structural and textural properties of the materials were studied by X-r…
Ultrasonication as a Method of Investigation of the Mechanical Properties of Doped Hafnium Barium Titanate
2012
The purpose of this study was to fabricate dense ceramic specimens from the system of BaTiO3-BaHfO3 and then to perform mechanical tests. The effect of Hf content on a microstructure and mechanical properties of the BaTiO3-BaHfO3 solid solution was investigated at room temperature. To determine the elastic constants (the Young′s modulus E, the shear modulus G, bulk modulus K and the Poisson′s ratio v) of BaHfxTi1-xO3 a method of measurement of the longitudinal (VL ) and transverse (VT ) ultrasonic wave velocities for this type of material was developed.
Multi-elemental determination of heavy elements in plastics using X-ray fluorescence after destruction of the polymer by molten sodium hydroxide
1992
In this paper a method is proposed for the multielemental analysis of Sb(III), Ba, Cd, Cr(III), Hg, Pb and As(III) in plastics, using X-ray fluorescence after alkaline decomposition and preconcentration by (co)precipitation. The organic matrix is destroyed by decomposition with sodium hydroxide melted in a silver crucible by the open system technique, using sodium nitrate as auxiliary oxidant. The variables which influence preconcentration are optimized: digestion time, pH, salinity, carrier and sodium diethyldithiocarbamate (DDTC) and sodium rhodizonate (R) as precipitants. The calibration curves were linear up to 200 μg of the element present, except for lead (150 μg) antimony(III) (100 μ…
Remarks on the type material of Linaria cavanillesii Chav. (Antirrhineae, Veronicaceae)
2013
ABSTRACT Some aspects concerning the type material of Linaria cavanillesii Chav. (Antirrhineae, Veronicaceae), which are conserved in different herbaria, are discussed. This name had previously been lectotypified on Tournefort's collections that are kept at the herbarium P, though they had been regarded erroneously as syntypes. Evidence is shown on the existence of a duplicate of the lectotype (isolectotype), which is conserved among the Salvador herbarium at BC (Institut Botanic de Barcelona), as well as of syntypes deposited in MA on which the illustration by Cavanilles cited in the protologue was drawn. Historical data are reported on collection sites and dates for all cited syntypes of …
Valorisation of industrial iron oxide waste to produce magnetic barium hexaferrite
2016
Barium M-type hexagonal ferrite (BaM, BaFe12O19) is an immensely important magnetic material, which we have successfully made from the simple valorisation of Fe-rich industrial waste from steel wire drawing, with addition of BaCO3 and heating in air to 1000 degrees C. The optimum ratio of Fe. Ba (producing 86 wt% BaM) was found to be 11: 1 (non-stoichiometric), and secondary phases of alpha-Fe2O3 (non-magnetic) and ZnFe2O4 (poorly antiferromagnetic) were always present. This material consisted of small submicron platelets. A hard magnetic ferrite was produced with Ms=48.6 A m(2) kg(-1) and H-c=211.5 kA m(-1). The highest density was achieved by sintering samples with Fe: Ba ratios of 11: 1 …
Influence of barium and cerium oxides on alumina supported Pd catalysts for hydrocarbon combustion
2002
Abstract The effects of baria and ceria additions to alumina-supported palladium catalysts have been investigated. Two series of binary Al 2 O 3 –BaO and ternary oxides Al 2 O 3 –CeO 2 –BaO were prepared using a sol–gel method and then characterized, after high-temperature treatments, by XRD, BET, TG, TEM and EDXS analyses. The influence of baria and ceria on the thermal stability and morphology of the supports was examined. A baria content of 12 wt.% appears the most effective for alumina stabilization. Palladium catalysts were prepared by impregnation method using Pd(NH 3 ) 4 (NO 3 ) 2 and were characterized by XRD and TEM. The catalysts showed high activity in the total oxidation of meth…
About the mechanism of the solid-way synthesis of barium metatitanate. Industrial consequences
1990
Abstract Barium metatitanate BaTiO 3 is the main component of the dielectric material of class 2 ceramic capacitors. The solid state reaction between BaCO 3 and TiO 2 is still one of the main industrial ways for the BaTiO 3 preparation. The aim of the paper is to propose a coherent set of interfacial reactions in order to explain all the experimental results previously published about this well known solid state reaction. The paper gives at first a summary of the main experimental results. Then all the interfacial reactions at the various stages of the advancement are proposed. All these reactions involve the same main point defects in BaTiO 3 which are barium and oxygen vacancies. It has b…
Determination of gunshot residues by neutron activation analysis
1973
Systematic investigations of gunshot residues, deposited around the bullet hole, have been carried out. The traces were produced by firing on filter papers from distances of 5 to 200 cm using one rifle and three pistols as arms. Antimony, lead and barium were quantitatively determined after irradiating the samples in the nuclear reactor TRIGA Mainz by measurement of gamma-lines of122mSb,122Sb,207mPo and139Ba. The determinations were made purely instrumentally and-where the half lives were long enough-also after chemical separation of the nuclides. The amount of the elements were determined in dependence of the firing distance and of the area around the bullet hole.