Showing papers on "Chromium published in 1974"

Catalytic process for reducing nitrogen oxides to nitrogen

Abstract: A catalyst compositions for reducing nitrogen oxide comprising, as its chief ingredient, an intimate mixture of A. titanium (Ti) as component A, with B. at least one metal selected from the group consisting of molybdenum (Mo), tungsten (W), iron (Fe), vanadium (V), nickel (Ni), cobalt (Co), copper (Cu), chromium (Cr), and uranium (U), as component B, in the form of their oxides, and a process for reducing nitrogen oxides to nitrogen, which comprises contacting a gaseous mixture containing nitrogen oxides and molecular oxygen and a reducing gas with aforesaid catalyst compositions at an elevated temperature.

Electron energy loss spectra and optical constants for the first transition series from 2 to 120 eV

Abstract: Energy loss spectra in the first series transition metals (Ti, V, Cr, Mn, Fe, Co, Ni) have been performed by transmission of 35 keV electrons through thin films (200 to 400 A) in the spectral range 2 to 120 eV. Experimental data processing enables to distinguish between single scattering volume losses and surface losses. Characteristic functions, such as the energy loss function, the complex dielectric constant, and the optical absorption coefficient are computed and compared with results obtained by different methods. Ces spectres de pertes d'energie des metaux de transition de la premiere serie (Ti, V, Cr, Mn, Fe, Co, Ni) ont ete obtenus par transmission d'electrons rapides (35 keV) a travers des couches minces (200 a 400 A) sur un intervalle d'energie important (2 a 120 eV). L'analyse numerique des donnees permet de distinguer les pertes par diffusion unique en volume des pertes de surface. Certaines grandeurs caracteristiques de l'echantillon comme la fonction perte d'energie, la constante dielectrique complexe et le coefficient de photo-absorption en sont deduites et comparees avec des resultats obtenus par des methodes differentes.

Thermodynamics of the carbides in the system Fe-Cr-C

Abstract: Phase relations in the Fe-Cr-C system in the temperature range 900 to 1150°C have been studied using metallographic and X-ray methods and the electron microprobe. An isothermal section of the phase diagram at 1000°C is shown. Lattice dimensions of the three carbides were determined for several values of the ratio Cr:(Fe +Cr). The solubilities of the carbides at each temperature were determined by metallographic study of quenched specimens. The distribution of Cr between austenite (γ) and the several carbides was determined by use of the electron microprobe. Data of Wada et al on the activity of carbon were used to calculate activities at the y-phase boundary and the free energy of the several carbides as a function of their chromium content. The data are treated thermodynamically on the basis of assumed random mixing of Cr and Fe atoms in each carbide. While this randomness was not definitely proved, the assumption was shown to be reasonable and the results useful. Extrapolation to 0 and 100 pct Cr gives values for the standard free energy of Cr7C3 and the hypothetical carbides Cr36C, and Fe7C3.

Structural investigations of amorphous transition element films: II. Chromium, iron, manganese and nickel

Abstract: Thin films of iron, chronium, manganese and nickel have been prepared in ultra high vacuum at 4 K and examined by scanning electron diffraction. Amorphous structures have been identified in iron, chromium and manganese and their respective interference functions found to be similar to each other and to that for cobalt. An argument is given supporting the concept of a truly amorphous phase devoid of crystalline order, as distinct from a miorocrystalline array. This argument is based not only on experimental structural results but on computer-simulated models together with magnetic and electron transport measurements. No evidence was found of an amorphous phase in clean nickel films. Some explanations are suggested for the inconsistencies between the present and earlier work, particularly in the case of nickel and iron.

Oxidation of alkanes to maleic anhydride using promoted vanadium-phosphorus catalyst

Abstract: There is provided an improved process for the vapor phase oxidation of alkanes to dicarboxylic acidanhydrides, particularly butane to maleic anhydride, which comprises using a vanadiumphosphorus-oxygen complex catalyst having a P/V atomic ratio of 0.5-2, promoted or modified with certain transition metals, preferably zirconium, chromium, iron or hafnium. Using these catalysts, the oxidation process can be carried out at lower temperatures and increased yield as compared to the unpromoted complex.

Deuterium lattice location in Cr and W

Abstract: Direct determination of the lattice location of implanted deuterium in single-crystal chromium has been made for the first time. Ion-channeling measurements of the angular distributions along the $〈100〉$ axial and {100} planar directions indicate that implanted D occupies the octahedral position in bcc Cr. This contrasts to the expected tetrahedral interstitial position recently observed under the same conditions for bcc W. These results further clarify the apparent anomaly in the thermodynamic data for hydrogen solubility in Cr.

The Isothermal Decomposition of Austenite in Simple Chromium Steels

Abstract: Two high-purity steels containing 12 and 5% chromium with 0.2% carbon have been isothermally transformed in the temperature range 775-600°C. The various ferrite and carbide morphologies encountered...

Proces for selective removal of nitrogen oxides from waste gases

Abstract: A process for the selective removal of nitrogen oxides from waste gases containing nitrogen oxides, which comprises contacting the waste gases with a metal oxide catalyst having the following formula: V.sub.x A.sub.y O.sub.z wherein V is vanadium; A is at least one element selected from the group consisting of copper, zinc, tin, lead, titanium, phosphorus, chromium, iron, cobalt and nickel; x and y are each a numeral of 0.5 to 12; and z is a numeral of 1 to 60, at a temperature of 150° to 800° C in the presence of ammonia.

Copper base alloy

Abstract: An improved phosphor-bronze copper alloy having good hot workability and mechanical properties, and method of processing same. A preferred alloy contains from 2 to 11 percent tin, from 0.01 to 0.3 percent phosphorus, from 0.2 to 0.8 percent chromium and from 0.3 to 2.0 percent each of iron and/or cobalt.

Compositions for alloying metal

Abstract: A method, compositions and articles are described for the direct addition of alloying metal to a molten metal to be alloyed, which provide more rapid dissolution of the alloying metal in the molten metal than has been possible heretofore. The alloying metal is added to the molten metal to be alloyed in finely particulate form in intimate admixture with a flux suitable for the purpose and finely particulate phenolic resin. The phenolic resin, in particle form, and preferably in the form of low density microballoons, is employed in an amount such that the ratio of the volume of the metalflux mixture to the volume of the microballoons is in the range from about 2:1 to about 12:1. The flux-alloying metal mixture contains about 3 to about 10% flux and about 90 to about 97% alloying metal, by weight of the flux-metal mixture. The compositions may be added to the molten metal bath in powder or lump form or may be incorporated in articles such as bags or briquettes containing the compositions. The method, compositions and articles are particularly useful for alloying aluminum and especially for the addition of manganese or chromium to aluminum. The preferred fluxes for alloying aluminum are non-hygroscopic metal salts, particularly chlorides and fluorides; a flux composed of 40% sodium chloride, 40% potassium chloride and 20% cryolite being especially useful for the addition of manganese or chromium to aluminum.

THe corrosion of chromium, iron, and stainless steel in liquid sodium

Abstract: The corrosion products NaCrO/sub 2/ and Na/sub 4/FeO/sub 3/ were observed on the surfaces of chromium, iron, and stainless steel after exposure to liquid sodium at 600 deg C and above. The products were identified by x-ray diffraction without the removal of the covering sodium layer. (8 figures) (auth)

Trivalent chromium electroplating baths and electroplating therefrom

Abstract: It is known to attempt to plate chromium from a solution containing trivalent chromium salts and organic complexants. The invention provides an aqueous chromium electroplating system containing trivalent chromium, together with both a formate or acetate and a bromide. Optionally the solution also contains ammonium, borate, chloride, sulphate and alkali metal ions and a wetting agent. The invention has the advantage of providing a solution with commercially acceptable covering and throwing power whose effluent can easily be purified to acceptable standards.