An investigation was conducted to determine if Sn atoms could be substituted for Si atoms in the compound Cr₃Si. Prom size factor considerations, the feasibility that this substitution should occur seemed reasonable. However, attempts to make the substitution were unsuccessful. A model of the Cr₃O-type compounds, of which Cr₃Si is a representative, is proposed. From this model substitution of a Sn atom for a Si atom would require the formation of a double bond. The possibility of this double bond being unable to form may explain the unsuccessful attempts to make the above substitution. / Master of Science

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 160-164).

Thesis (Ph. D.)--University of Alabama at Birmingham, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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M.Sc. / The aim of this study is to show that there exists a parallelism between the effect of the concentration of the itinerant electrons per atoom, and the applied hydrostatic pressure, p, on the magnetic phase diagram of a Cr + 0.2 at.% Ir alloy. This Cr-Ir alloy was chosen, because it contains all possible magnetic phases that can exist in a Cr alloy.

The behavior of Fe-Cr alloys under irradiation is in part controlled by the characteristics of point defects generated by high energy collision. Radiation enhanced diffusion and radiation induced precipitation are among the mechanisms that lead to changes in the microstructure under irradiation, and are thus controlling effects such as swelling and a' precipitation. Point defects in Fe-Cr alloys are diverse in nature due to their interaction with a variety of local solute configurations. Ab initio results indicate that the magnetic structure of the alloy is critical in determining its energetics. The ability to model these properties with classic potentials is still to be proven. In this work a detailed comparison between ab initio and classic values of a variety of point defects configurations is performed, testing in this way the extent to which classic potentials can be reliably used for radiation damage studies, and evaluating the dependence of point defect formation energies on Cr concentration.

Ph.D. / A comprehensive experimental study of the effects of the spin-density-wave (SDW) on the physical properties of antiferromagnetic , doped with Mn and V, and Cr-Re alloys is reported. The purpose of the study is twofold: c c Al Cr − 1 (i) To gain insight in the anomalous behaviour of the magnetic phase diagram reported for the binary Cr-Al system. (ii) To investigate SDW effects on the anharmonic behaviour of the lattice vibrations of Cr alloys with a member of the transition metals of group-7 in the periodic table. The investigation entails the following measurements: thermal expansion in the temperature range 77 – 450 K for all the specimens, velocity of sound in the temperature range 4 – 300 K for the Cr-Al-V alloys, ultrasonic wave velocity for the Cr-Re alloys as a function of applied pressure (up to 0.242 GPa) at different temperatures and electrical resistivity in the temperature range 77 – 450 K for the Cr-Re alloys. Concentration-temperature magnetic phase diagrams of the (Mn, V) alloy systems were constructed from the measurements. Alloying with Mn, to increase the electron concentration, is observed to drive an incommensurate (I) SDW alloy towards a commensurate (C) SDW state. This results in a triple point, where the ISDW, CSDW and paramagnetic (P) phases coexist on the magnetic phase diagram. A hysteretic first-order ISDW-CSDW/CSDWISDW phase transition line is then observed on the phase diagram for Mn concentrations above the triple point concentration. Adding V, in order to decrease the electron concentration, to an ISDW alloy is found to have the opposite effect. It drives such a system deeper into the region of the ISDW c c Al Cr − 1 c c Al Cr − 1 phase. A CSDW alloy is, on the other hand, driven towards the triple point by addition of V, instead of Mn. c c Al Cr − 1 Theoretical analysis of the magnetic phase diagrams of the (Mn, V) systems confirms a previous suggestion that the Al impurity acts as an electron acceptor in the Cr matrix for c c Al Cr − 1 2 < c at.% Al, as opposed to an electron donor for at.% Al. 2 > c The high-pressure ultrasonic studies on the Cr-Re alloys were used to construct their pressure-temperature ( T p − ) magnetic phase diagrams. Applying hydrostatic pressure to a CSDW Cr-Re alloy induces a hysteretic first-order CSDW-ISDW phase transition at a certain critical pressure, resulting in a triple point on the phase diagram. An interesting aspect of the observations on the Cr-Re alloys is the suggestion of a new phase line, separating pressureinduced and temperature-induced ISDW phases, on the T p − T p − phase diagram. Acoustic-mode Grüneisen parameters, which quantify the lattice anharmonicity, were calculated for the Cr-Re alloys from the high-pressure ultrasonic measurements. The results indicate exceptionally large interactions between the SDW and the long-wavelength longitudinal phonons in Cr-Re alloys. These effects are particularly large in the vicinity of the Néel phase transition temperature. Interactions of the SDW with the shear mode phonons are on the other hand relatively much smaller. The work on the Cr-Re alloys is considered to finally complete studies of the lattice anharmonicity of Cr alloy systems with elements of all the important groups of the periodic table. It now paves the way for developing microscopic theories to explain the unique behaviour of the magneto-elasticity of dilute Cr alloys. / Prof. H.L. Alberts Dr. A.R.E. Prinsloo

by Kwong Wai Kuen = 鋁銘金屬間化合物的製造和性能測試 / 鄺偉權. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Kwong Wai Kuen = Lü ming jin shu jian hua he wu de zhi zao he xing neng ce shi / Kuang Weiquan. / Acknowledgement --- p.i / Abstract --- p.ii / 摘要 --- p.iii / List of tables --- p.iv / List of figures --- p.v / Table of contents --- p.xi / Chapter Chapter 1 --- Background / Chapter 1.1 --- Introduction --- p.1-1 / Chapter 1.2 --- Aluminum --- p.1-1 / Chapter 1.3 --- Chromium --- p.1-3 / Chapter 1.4 --- Intermetallics --- p.1-4 / Chapter 1.4.1 --- Alloys and intermetallics --- p.1-4 / Chapter 1.4.2 --- Properties of intermetallics --- p.1-5 / Chapter 1.4.3 --- Intermetallics 一 past to present --- p.1-6 / Chapter 1.4.4 --- Commonly used intermetallics --- p.1-7 / Chapter 1.4.5 --- Prospects of intermetallic compounds --- p.1-9 / Chapter 1.5 --- Previous works --- p.1-11 / Chapter 1.6 --- Current work --- p.1-12 / Chapter 1.7 --- Outline of thesis --- p.1-12 / References --- p.1-14 / Tables and figures --- p.1-17 / Chapter Chapter 2 --- Methodology and Instrumentation / Chapter 2.1 --- Experimental approaches --- p.2-1 / Chapter 2.2 --- Sample preparation --- p.2-2 / Chapter 2.2.1 --- Powder mixture --- p.2-2 / Chapter 2.2.2 --- Cold-pressing --- p.2-2 / Chapter 2.2.3 --- Pressureless sintering --- p.2-2 / Chapter 2.2.4 --- Hot-pressing --- p.2-3 / Chapter 2.2.5 --- Arc-melting --- p.2-4 / Chapter 2.3 --- Sample characterization --- p.2-5 / Chapter 2.3.1 --- DTA --- p.2-5 / Chapter 2.3.2 --- TMA --- p.2-5 / Chapter 2.3.3 --- Density measurement --- p.2-6 / Chapter 2.3.4 --- Microhardness measurement --- p.2-7 / Chapter 2.3.5 --- Scanning electron microscopy --- p.2-8 / Chapter 2.3.6 --- X-ray powder diffractometry --- p.2-9 / References --- p.2-10 / Figures --- p.2-11 / Chapter Chapter 3 --- Thermal analysis of Al-Cr powder mixtures / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.2 --- Experiments --- p.3-1 / Chapter 3.3 --- Results and discussions --- p.3-2 / Chapter 3.3.1 --- DTA results --- p.3-2 / Chapter 3.3.2 --- Al-23wt%Cr --- p.3-2 / Chapter 3.3.3 --- Al-28wt%Cr and Al-33wt%Cr --- p.3-5 / Chapter 3.3.4 --- Al-46wt%Cr --- p.3-8 / Chapter 3.3.5 --- Al-55wt%Cr --- p.3-9 / Chapter 3.3.6 --- Al-79wt%Cr --- p.3-10 / Chapter 3.4 --- Reaction mechanisms in the formation of Al-Cr intermetallic compounds --- p.3-12 / Chapter 3.5 --- Summary --- p.3-12 / References --- p.3-14 / Tables and figures --- p.3-15 / Chapter Chapter 4 --- Fabrication of Al-Cr samples by hot-pressing and by arc-melting / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.1.1 --- Hot-pressing method --- p.4-1 / Chapter 4.1.2 --- Arc-melting method --- p.4-2 / Chapter 4.2 --- Experiments --- p.4-2 / Chapter 4.3 --- Results and discussions --- p.4-3 / Chapter 4.3.1 --- Hot-pressing method for some specific compositions --- p.4-3 / Chapter 4.3.2 --- Hot-pressing method to produce low Cr content (LC) samples --- p.4-5 / Chapter 4.3.3 --- Effects of hot-pressed time and temperature --- p.4-6 / Chapter 4.3.4 --- Arc-melting method for some specific compositions --- p.4-8 / Chapter 4.3.5 --- Arc-melting method to produce LC samples --- p.4-10 / Chapter 4.4 --- Summary --- p.4-11 / Reference --- p.4-12 / Tables and figures --- p.4-13 / Chapter Chapter 5 --- Thermal expansion coefficients of arc-melted Al-Cr samples / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.1.1 --- Thermal expansion --- p.5-1 / Chapter 5.1.2 --- Relations between thermal expansion and structural material --- p.5-1 / Chapter 5.2 --- Experiments --- p.5-2 / Chapter 5.3 --- Results and discussions --- p.5-3 / Chapter 5.3.1 --- TMA results of A1 and Cr --- p.5-3 / Chapter 5.3.2 --- TMA for Al-Cr IMCs --- p.5-3 / Chapter 5.4 --- Summary --- p.5-4 / References --- p.5-6 / Figures --- p.5-7 / Chapter Chapter 6 --- Physical properties of Al-Cr intermetallic compounds / Chapter 6.1 --- Introduction --- p.6-1 / Chapter 6.2 --- Results and discussion --- p.6-1 / Chapter 6.2.1 --- Hot-pressed samples --- p.6-1 / Chapter 6.2.1.1 --- Hot-pressed LC samples --- p.6-2 / Chapter 6.2.1.2 --- Effects of hot-pressing temperature and time --- p.6-3 / Chapter 6.2.2 --- Arc-melted samples --- p.6-4 / Chapter 6.2.3 --- Comparison between the hot-pressed sample and the arc-melted sample --- p.6-6 / Chapter 6.3 --- Summary --- p.6-7 / Tables and figures --- p.6-9 / Chapter Chapter 7 --- Conclusions / Chapter 7.1 --- Summary --- p.7-1 / Chapter 7.2 --- Future works --- p.7-2