Structure of Amorphous Fe_<80>-P_<13>-C_7 by X-Ray Diffraction

X-ray diffraction patterns have been obtained from Fe_-P_-C_7 alloy in both amorphous and liquid states. Using the common Fourier analysis, the atomic radial distribution function was evaluated from which interatomic distance and coordination number were obtained. The essential feature of the structure in the amorphous state was similar to that in the liquid state. The crystallization process of this alloy during isothermal aging at 330℃ was also studied by the same procedures. The results indicated that the initial amorphous structure changes to a second amorphous structure, which in turn, transforms to the stable crystalline phase. This crystallization product was single phase of bcc structure (a_0=2.864A). By means of the Fourier analysis, these results led to the conclusion that the initial amorphous structure re-arranges to relax the stress or anisotropic configuration of atoms arising from the rapid quenching and subsequently the crystallization of this alloy occurs by a nucleation and growth mechanism during isothermal aging

Structural Study of an Amorphous Pd_<80>-Si_<20> Alloy by X-Ray Fourier Analysis

The structure of an amorphous Pd_-Si_ alloy obtained by rapid quenching from the liquid state has been studied by X-ray diffraction . After calculating the interference function by means of the Fourier analysis, the atomic radial distribution function is obtained from which interatomic distance and coordination number are estimated. Comparing the result with that in the liquid state it is found that the general feature of the structure in the amorphous state is quite similar to that in the liquid state. Besides, the sample aged at 180℃ for 300 min is examined by the same procedures

Electrical Properties of Amorphous Cu-Zr Alloy

The electrical resistivity of amorphous Cu_-Zr_ alloy and the temperature coefficient of the resistivity are estimated to be 195μΩ・cm and -1.23×10^μΩ・cm/°K at 273°K, respectively. The Hall coefficient and the thermoelectric power are equal to +7.4×10^ m^3/AS and +0.39μV/°K, respectively. These electrical properties are similar to those for some liquid transition metals

Passivity of Extremely Corrosion Resistive Iron Alloys

This paper reviews studies on corrosion resistance of chromium bearing amorphous iron alloys and high purity-high chromium ferritic steels containing molybdenum. High corrosion resistance of these alloys have been interpreted in terms of the compositions and functions of the passive films formed on these alloys

Time-of-Flight Pulsed Neutron Diffraction of Pd_<0.8>-Si_<0.2> Amorphous Alloy Using the Electron Linac

The structure factor S(Q) of Pd_-Si_ amorphous alloy was measured over wide range of Q (=4π sin θ/λ) up to 40 A^ by time-of-flight neutron diffraction using pulsed epithermal-neutron generated from the Tohoku University electron linac. The S(Q) has definitely shown an oscillation even in range of Q≳25 A^. The 1st peak of the pair distribution function Fourier transformed from the S(Q) has been split into two sub-peaks at the position of 2.42 and 2.81 A. Combining the neutron result with the X-ray result, the 1st sub-peak was verified to correspond to Pd-Si pair and the 2nd sub-peak the mixture of Pd-Pd pair and Pd-Si pair where Pd atom was substituted with Si atom. The average numbers of the nearest neighbour atoms around the Pd atom at origin are 1.7 Si atoms in the 1st sub-peak and 10.7 Pd and 1.5 Si atoms in the 2nd sub-peak. There may be no Si-Si pair with the nearest interatomic distance in the alloy. Such a relation for atom-atom pairs is found in the crystalline Pd_3Si compound, too. The liquid structure of the alloy was also measured and concluded to be essentially close to the amorphous structure except more blurring of peaks

Influence of carrier-carrier and carrier-phonon correlations on optical absorption and gain in quantum-dot systems

A microscopic theory is used to study the optical properties of semiconductor quantum dots. The dephasing of a coherent excitation and line-shifts of the interband transitions due to carrier-carrier Coulomb interaction and carrier-phonon interaction are determined from a quantum kinetic treatment of correlation processes. We investigate the density dependence of both mechanisms and clarify the importance of various dephasing channels involving the localized and delocalized states of the system.Comment: 12 pages, 10 figure

Soft and Hard Magnetic Properties of Nanocrystalline Fe-M-B (M=Zr, Nd) Base Alloys Containing Intergranular Amorphous Phase

This paper reviews our recent results of the soft and hard magnetic properties of nanocrystalline Fe-rich Fe-M-B (M=Nd or Zr) base alloys containing an intergranular amorphous phase. Based on the previous results that the soft magnetic alloys in Fe-Si-B-Nb-Cu and Fe-Zr-B systems do not have zero magnetostriction (λ_s), the effect of the additional Al or Si on the λ_s and magnetic properties was examined for the nanocrystalline Fe-Zr-B-Al and Fe-Zr-B-Si alloys. The soft magnetic properties of high Bs above 1.5 T and high μ_e above 1.5x10^4 combined with zero λ_s were obtained for the Fe_Zr_7B_3Al_2 and Fe_Zr_7B_3Si_4 alloys annealed for 3.6 ks in the annealing temperature (Ta) range of 823 to 923 K. This is in contrast to the previous result that the good soft magnetic properties of the nanocrystalline Fe_Zr_7B_3 alloy are obtained in the narrow Ta range around 923 K. The remarkable extension of the Ta range seems to be attributed to the zero λ_s. The replacement of Zr by Nd in the Fe_M_7B_3 alloys was found to cause rather good hard magnetic properties of 1.3 T for Br. 260 kA/m for iHc and 146 kJ/m^3 for (BH)_ in a triplex nanostructure of bcc-Fe with a size of 20 nm, tetragonal Fe_Nd_2B with a size of 15 nm and intergranular amorphous phase with a thickness of 5 to 10 nm. The hard magnetic properties are obtained for the nanostructure containing 80 % soft magnetic phases and 20 % Fe_Nd_2B in volume. The notable result is presumably due to the effective action of the intergranular amorphous network phase which can act as a resistance against the nucleation of the reversion of magnetic domain walls leading to the increase in iHc as well as an exchange magnetic coupling medium between bcc-Fe and bcc-Fe or tetragonal Fe_Nd_2B phases leading to the high Br. This presumption is also supported from the result that no good hard magnetic properties are obtained for the over annealed sample without intergranular amorphous phase as well as for the use of the sample which does not consist of a mostly single amorphous phase in the as-quenched state. Thus, the soft and hard magnetic properties for the Fe-M-B alloys are obtained only in the optimal nanostructures. The fabrication of a new nanostructure is expected to cause the appearance of other function properties even at compositions where no useful properties have not been obtained

ESCA Study of the Passive Film on an Extremely Corrosion-Resistant Amorphous Iron Alloy

X-ray photoelectron spectroscopy was applied to study the composition of the passive film formed on an extremely corrosion resistant amorphous Fe-10at.%Cr-13at.%P-7at.%C alloy in 1 N HCl. The passive film consists mainly of hydrated chromium oxyhydroxide which is a common major constituent of passive films on crystalline stainless steels. The extremely high corrosion resistance of the amorphous alloy can only in part be attributed to the formation of a protective hydrated chromium oxyhydroxide film

Invar-Type New Ferromagnetic Amorphous Fe-B Alloys(Physics)

Measurements of magnetization, electrical resistivity, thermal expansion and differential thermal change were made on amorphous Fe_B_x (9≦X≦21) alloys prepared by rapid quenching from the liquid state. With decreasing boron content in the alloys, the Curie temperature falls remarkably, while the magnetic moment increases sluggishly. The thermal expansion curves exhibit the invar characteristics below the Curie temperature due to a large positive spontaneous volume magnetostriction, and the reduced magnetization curves decrease much more rapidly with increasing temperature than those of other ferromagnetic amorphous alloys

Structural Study of an Amorphous Bi-Fe-Ca-O Thin Film by the Anomalous X-ray Scattering

The structure of the amorphous Bi-Fe-Ca-O film with 0.3 m thick grown on the Si single crystal was studied by the anomalous x-ray scattering (AXS) method. This relatively new method using the anomalous dispersion effect of a specific constituent element in a film reduces the difficulty in the subtraction process of a substrate intensity for estimating the net intensity of a thin film, which becomes a main cause of errors of the resultant data in the conventional method. The environmental radial distribution functions around Bi and Fe in the amorphous Bi-Fe-Ca-O film were determined, from which the structural features were obtained