The average magnetic moment and the magnetic moments of the sublattices of (Fe1–xMnx)3Al alloys are determined from saturation magnetization and neutron diffraction. By Mössbauer experiments the effective magnetic fields on 57Fe nuclei are measured. The distribution of Fe, Mn, and Al on the three sublattices of the DO3 structure are determined by means of neutron and X‐ray diffraction. The observed decrease of magnetic moments with increasing Mn concentration is explained by the occurrence of parasitic antiferromagnetism. Also 55Mn spin‐echo measurements show the existence of antiferromagnetically coupled magnetic moments.
The DO, order of the Heusler-type alloys is proved by X-ray diffraction. The order of the transition metal atoms and consequently the degree of the L2, order are not provable because of the impossible task of distinguishing the transition metal atoms. Using EXAFS different occupation numbers of the lattice sites are obtained. The short-range order of Co,MnSi is almost ideally that of the Heusler-type, the Fe2 4Mno 6Al alloy tends t o the disordered DO, structure. The reason behind the different order degree can be explained by the influence of clectronegativity.Die DO,-Ordnung der Heusler-Legierungen wird mittels Rontgenbeugung nachgemiesen. Die Ordnung der Obergangsmetallatome und damit der Grad der LB,-Ordnung sind nicht nachweisbar, weil es nicht moglich ist, die Obergangsmetallatome zu unterscheiden. Mit EXAFS erhrllt man unterschiedliche Besetzungszahlen der Gitterplatze. Die Nahordnung von Co,MnSi ist fast ideal vom Heusler-Typ, die Fez,aMno,fiAl-Legierung tendiert zur ungeordneten DO,-Struktur. Die Ursache fur den unterschiedlichen Ordnungsgrad kann durch den EinfluIJ der Elektronegativitat erklart werden.
The localized magnetic moments of Fe and Cr are determined by combination of saturation magnetization measurements and magnetic diffuse scattering. Power series characterizing the interactions between the different kinds of atoms in the alloys are chosen to describe the concentration dependence of the magnetic moments. The different terms are discussed on the basis of band structure models valid for dilute alloys taking into account their modification by impurity interactions.Die lokalisierten magnetischen Momente von Pe und Cr werden durch Kombination von Messungen der Sattigungsmagnetisierung und der diffusen Neutronenstreuung gemessen. Zur Beschreibung der Konzentrationsabhangigkeit der magnetischen Momente werden Potenzreihen verwendet, die die Wechselwirkungen zwischen den verschiedenen Atomsorten in den Legierungen widerspiegeln. Die einzelnen Terme werden auf der Basis von fdr verdunnte Legierungen gultigen Bandstrukturmodellen unter Berucksichtigung ihrer Modifikation durch Storstellenwechselwirkung diskutiert.
The National Center for Asphalt Technology (NCAT) has developed a test method to determine the asphalt content of hot-mix asphalt (HMA) mixtures by ignition. In the ignition method, an HMA sample is subjected to heat of 538°C (1,000°F) in a furnace to ignite and burn the asphalt cement (AC) from the aggregate. The difference in weight of the sample before and after is used to determine the asphalt content of the mixture. The aggregate recovered after ignition testing may then be used for gradation analysis. A round-robin study was completed by NCAT to determine the accuracy and precision of the ignition method. The round-robin test program is discussed, as well as the accuracy and precision values determined for the measured AC content and gradation using the ignition method. The results of the round-robin study indicate that the ignition method can measure the AC content of HMA mixtures with greater precision than solvent-extraction methods, without significantly affecting the gradation of the aggregate. This test method has shown excellent potential for replacing existing test methods for measuring asphalt content.
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