Alloys in and near the ε single phase region found by Morral In the iron-aluminum-carbon system were prepared and their ferromagnetic and structural properties determined„ The ε phase has been described as chiefly Fe₃Al plus 15 atomic percent carbon with the possibility of varying the Fe:Al ratio from approximately 2 to 3.5. The face-centred cubic ε phase was found to be highly ordered with iron at the face centre positions, aluminum at the cube corners and carbon in the body-centred position. The lattice parameter varies with carbon content from 3.73 to 3.76 A°. Keeping the amount of carbon constant at 14.6 atomic percent the alloys with the Fe:Al ratio less than 3 have their saturation magnetization increasing with increasing iron by an amount corresponding to the estimated increase of 5.4 Bohr magnetons per iron atom. However, for values of the ratio greater than 3 the magnetization is decreased with increasing iron. The amount of this decrease is not certain but it is thought to be of the order of 8 Bohr magnetons per iron atom in excess of that required to give Fe:Al equal to 3. Increasing the carbon content with the Fe:Al ratio kept at 2.9 ± .1 also decreases the magnetization by an amount corresponding to an estimated 8.5 Bohr magnetons per carbon atom. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Binary alloys of manganese and boron and ternary alloys of manganese and boron with aluminum, zinc, tin and indium were prepared. Their structures were determined from x-ray powder photographs, and their ferromagnetic properties were measured with a Sucksmith rinf balance, using a powerful electromagnet. The orthorhombic phase MnB had a ferromagnetic Bohr magneton number of 1.73 per molecule and a Curie point of 309°C. Most of the ternary alloys were slightly ferromagnetic, but no strongly ferromagnetic single phase regions were found. Paramagnetic measurements on Heusler alloys showed that they followed the Curie-Weiss law for the restricted range of temperature in which measurements could be made. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering (Metallurgy and Materials Engineering). Johannesburg, March 2014 / This study investigated the C-Ni-V ternary phase diagram and identification of possible abrasive-resistance alloys. Twenty-four alloys were made from the elemental components and were arc-melted under an argon atmosphere, using Ti as an oxygen-getter. These alloys were analysed in both the as-cast condition, and after annealing for 1000oC and water quenching. Microstructural characterization was carried out in a SEM with EDX, and was done to confirm the phases. The results were used to plot a solidification projection and all binary phases extended into ternary, except for ~Ni8V, ~NiV3 and ~V2C which were not found, due to the sample compositions chosen. The extensions of the binary phases were: ~Ni3V: ~15 at.% C; ~Ni2V: ~20 at.% C; σ′: ~18 at.% C; (Ni): ~27 at.% C; ~V8C7: ~2 at.% Ni; ~V6C5: ~2 at.% Ni and ~VC: ~2 at.% Ni. The liquidus surface was derived, and three ternary invariant reactions were identified. The isothermal section at 1000oC was also constructed. Hardness of the alloys was studied in both conditions. Alloys with (Ni) (188-402HV5) were found to be ductile with low hardness. Alloys containing (V), ~Ni3V and ~Ni2V were identified as hard phases (533-1052 HV5). Alloys with σ′ phase were very hard (1065-1266 HV5) extremely brittle with cracks. Fracture toughness of the C-Ni-V alloys 0.9-5.2 (MPa.m-1/2) were comparable with ceramics 0.5-5.3(MPa.m-1/2). The wear behaviour of the alloys was characterized by sliding the carbide alloys against a Cr-steel ball in a pin-on-disc configuration. There were several co-existing wear mechanisms: abrasion, adhesion and the formation of a thin tribolayers. The wear coefficients for a 10N contact load after a sliding wear path of 300m varied between 0.1 x 10-6and 7.6 x 10-6(mm3/Nm), which was not as good as WC-Co hard metals, but close. / MT2017

No description available.

Thesis (Nucl. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005. / Includes bibliographical references. / Shadow corrosion of zirconium alloy fuel cladding in BWR environments, the phenomenon in which accelerated corrosion is experienced when the cladding surface is in close proximity to other metals, has become a potentially life-limiting issue for BWR fuel. Recent results from experimentation at MIT, Halden, and Studvik suggest that a galvanic coupling drives the phenomenon between the cladding and the adjacent material. However, the actual processes involved are not understood. One key parameter that would help in the understanding of the phenomenon would be a measurement of the actual corrosion current between fuel cladding and adjacent materials in the actual in-reactor environment. The limitations placed on the bum-up of uranium oxide fuel correlates to the amount of corrosion seen through a directly measurable oxide thickness on the waterside of the zirconium alloy cladding. This oxide corrosion product directly correlates to distance from structural components, leading to the effect commonly referred to as shadow corrosion. In recent experiments, Studvik determined that there are large ECP differences associated with Inconel and zirconium alloys that correlate to increased galvanic current density when the materials are coupled. / (cont.) In this thesis research, four electrode pairs were used to measure galvanic current densities in the irradiation environment: Pt-Pt, Zircaloy 2 (Zr-2)-Pt, Inconel (X-750)-Pt, and Zr-2-X-750. To determine the changes in the coolant water conductivity due to the presence of radiolysis products, electrochemical potential measurements of Pt-Pt coupled electrodes were analyzed. Finally, attempts to characterize the observed oxide behavior using measurements from Electrochemical Impedance Spectroscopy (EIS), also known as Alternating Current Impedance, were conducted. Through the measurements taken, analysis of the mechanisms potentially causing the shadow corrosion phenomenon was conducted. The results of the observations included: -- Measurement of increased conductivity of coolant water correlating to increases in reactor power. -- Measurement of increased galvanic current measurements correlating to increases in reactor power. / by Nicole M. Treeman. / Nucl.E.and S.M.

To date there has been much work carried out in the field of surface science to gain a better understanding of the fundamentals of a wide range of catalytic systems and reactions. The central theme of this thesis relates to cobalt based Fischer-Tropsch synthesis (FTS) with particular focus on the structure, composition and surface chemistry of CoPd bimetallic systems and on the interaction of Co with oxide support materials. In the work described in this thesis MEIS and STM are used to examine the growth of Co on Pd{111} and to characterise the structure of CoPd alloys created by thermal treatment of thin Co films. MEIS investigations indicate that Co grows initially as an fcc overlayer, but beyond a few layers, a stacking fault exists resulting in hcp growth. On annealing between 550 and 700 K, a previously unreported ordered surface alloy is observed giving rise to a p(2 x 1) structure which is concluded to be the surface termination of an ordered CoPd bulk alloy. At higher annealing temperatures, long range Moiré structure is observed by STM which MEIS reveals to correspond to a Pd-rich alloy. MEIS is used to investigate adsorbate induced segregation effects at CoPd surfaces on Pd{111}. The adsorption of O2, CO, H2 and CO/H2 mixtures (syngas) were all examined on a range of bimetallic surfaces. Oxygen adsorption on CoPd alloys strongly segregates cobalt to the surface as a result of the facile oxidation reaction. The behaviour of the components of syngas was more complex with the most noticeable effects being observed on surfaces which were more defect rich. The growth, annealing behaviour and adsorption properties of Co particles on oxide and mixed oxide surfaces are examined using MEIS and TPD.

LD2668 .T4 1947 A3 / Master of Science

No description available.

The design and analysis of a low-frequency, resonant, tonpilz type, rare earth iron underwater sound transducer using rods of Tb.27Dy.73Fe1.95 are described. An equivalent circuit is presented which predicts the performance of the transducer in the presence of eddy currents and demagnetization. The effect of eddy currents on the impedance of a rod is discussed. The predicted performance of a laminated transducer is compared with that of an unlaminated transducer. The performance of the rare earth iron transducer is compared with the performance of the same transducer with identical ceramic active elements. Data on transmitting current response, transmitting voltage response, free field voltage sensitivity, coupling coefficient, efficiency, and linearity are presented. Advantages, disadvantages, and possible uses of rare earth iron material are discussed.

No description available.