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Articles 1771 - 1800 of 2244

Full-Text Articles in Materials Science and Engineering

Diffusion And Internal Friction In Sodium-Rubidium Silicate Glasses, Gary L. Mcvay Jan 1970

Diffusion And Internal Friction In Sodium-Rubidium Silicate Glasses, Gary L. Mcvay

Doctoral Dissertations

"The internal friction and self diffusion coefficients of sodium and rubidium ions for (1 - X) Na₂O·X Rb₂O·3 SiO₂ glasses have been measured. The diffusion measurements employed radioactive isotopes and a thin sectioning technique and extended from 350 to 500°C. Internal friction measurements were made from -150 to 500°C and at frequencies of 0.05 to 6000 Hz. The maximum height for the mixed alkali internal friction peak occurs at the composition where the sodium and rubidium diffusion coefficients are equal. It is concluded that the mechanism responsible for the mixed alkali peak is a cooperative rearrangement of sodium-rubidium ions and …

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Voids In Neutron Irradiated Aluminum, Nicholas H. Packan Jan 1970

Voids In Neutron Irradiated Aluminum, Nicholas H. Packan

Doctoral Dissertations

"Void formation in high purity aluminum resulting from irradiation to fluences between 1.5 x 10¹⁹ and 1.6 x 10²² neutrons/cm² (E > 0 .1 MeV) at a temperature of 55 ± 5ºC was studied, primarily by means of transmission electron microscopy. In particular the effects of neutron fluence and flux were examined, as well as the possible influences of both preexisting and transmutation-produced impurities. A very low concentration of voids (about 10¹²/cm³) resulted from irradiation to 1.5 x 10¹⁹ neutrons/cm²; they averaged about 150 Å in diameter. Void concentrations and sizes increased with fluence, reaching values of 6 x 10¹⁴ voids/cm³ …

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Temperature Variation In Distribution Of Relaxation Times In Aluminosilicate Glasses, David Wayne Moore Jan 1970

Temperature Variation In Distribution Of Relaxation Times In Aluminosilicate Glasses, David Wayne Moore

Doctoral Dissertations

"The distribution of relaxation times for the alkali peak in a Li₂ O·A1₂O₃ ·2.0SiO₂ glass and for the mixed alkali peak in a 0.5Li₂O·0.5Na₂O·A1₂O₃·2.OSiO₂ glass was studied using the internal friction technique. A lognormal distribution of relaxation times provided the best agreement with the experimental data. The ß parameter of the lognormal distribution function, which is related to the half-height peak width, varied with temperature, indicating that the distribution of relaxation times is dependent upon the activation energy and the activation entropy of the relaxation mechanism. The major contributor to the distribution of relaxation times is a wide distribution in …

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The Deformation Mechanisms In Sublimed Magnesium Under Cyclic Loading, Babu Narian Thakur Jan 1970

The Deformation Mechanisms In Sublimed Magnesium Under Cyclic Loading, Babu Narian Thakur

Doctoral Dissertations

"A detailed study of the deformation processes in sublimed magnesium under reverse bending fatigue in air at room temperature has been undertaken utilizing the light, scanning and transmission electron microscopy. The Principal deformation modes are the basal slip and {10Ī2} twinning. The proportion of twinning increases markedly with the increasing stress level and the number of cycles. The evidence for cross slip is seen on the basal slip bands. The extrusions are seen not only along the basal slip lines but also along the {10Ī2} twin boundaries. In the later stages of fatigue, the extrusions chip off producing a notch …

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Electrode Reactions In Zinc Electrolysis, Ernest R. Cole Jan 1970

Electrode Reactions In Zinc Electrolysis, Ernest R. Cole

Doctoral Dissertations

"The effects of temperatures from 0°C to 50°C and current densities from 10 asf to 200 asf on the current efficiency in the electrolysis of pure zinc sulfate solutions (65 gpl Zn⁺⁺ - 200 gpl H₂SO₄) were determined. Pure platinum and platinum coated titanium anodes were used with an aluminum cathode. Platinum anodes were not inert at certain combinations of temperature and current density, and platinum acted as a low overvoltage impurity causing resolution of the cathode deposit. Orientation of the zinc deposits was found to vary with temperature and to have a distinct relationship to current efficiency. Preconditioning of …

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The Oxidation Kinetics Of Liquid Lead And Lead Alloys, Thomas Edward Weyand Jan 1970

The Oxidation Kinetics Of Liquid Lead And Lead Alloys, Thomas Edward Weyand

Doctoral Dissertations

"Liquid lead and lead-silver alloys were investigated to determine the rates and products of oxidation in pure oxygen at temperatures of 350 to 600°C. The kinetic data were determined using a Cahn electro-balance. Liquid lead was found to follow a cubic rate of oxidation between 350 and 400°C. A parabolic rate was found at temperatures above 400°C. 0.496% silver and 2.258% silver alloys followed a cubic rate of oxidation from 350 to 550°C and tended to approach a parabolic rate of oxidation above this temperature. Silver additions were found to increase the rate of oxidation as compared to the pure …

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Thermal Expansion Of Tetragonal Pbo, Charles A. Sorrell Jan 1970

Thermal Expansion Of Tetragonal Pbo, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

Thermal expansion of tetragonal PbO, investigated by high‐temperature X‐ray diffraction in vacuum, is nearly isotropic, with the coefficient in the c0 direction only slightly greater than that in the a0 direction. Volume thermal expansion is only slightly greater than in massicot. Retardation of the litharge‐massicot transformation is tentatively interpreted as the result of very low oxygen partial pressures caused by catastrophic oxidation of the stainless‐steel sample holder and resulting oxygen scavenging by lead vapor. Copyright © 1970, Wiley Blackwell. All rights reserved

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Fracture Surface Energy Determinations Of High Density Polycrystalline Ceramics, Gene Arthur Pahlmann Jan 1970

Fracture Surface Energy Determinations Of High Density Polycrystalline Ceramics, Gene Arthur Pahlmann

Masters Theses

"Values of fracture surface energy were measured for steatite, zircon, mullite and four densities of alumina. Rods of these high density materials were cut into thin rectangular specimens which were notched and broken in three-point loading. The resulting load necessary for fracture of the specimens was used to calculate the fracture surface energy of the materials. The value for the steatite was around 20,000 ergs/cm². The values for the zircon and mullite were on the order of 13,000 ergs/cm², and the values for the aluminas ranged from 17,000 to 24,000 ergs/cm²"--Abstract, page ii.

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Imperfections In The Ag-In System (Alpha-Phase) And Lattice Parameters Of Cadmium Oxide, Prafulla Maganlal Vora Jan 1970

Imperfections In The Ag-In System (Alpha-Phase) And Lattice Parameters Of Cadmium Oxide, Prafulla Maganlal Vora

Masters Theses

"This thesis has been divided into two parts, namely, "Imperfections in the Ag-In System (Alpha-Phase)" and "Lattice Parameters of Cadmium Oxide." Imperfections in the Ag-In System (Alpha-Phase): It can be shown -- as in the case of the Cu-In α solid solutions -- that during quenching from the liquid state, strains are produced by the quenching process and, in addition, vacancies are quenched-in, in the Ag-In α-solid solutions. The number of vacancies present, measured by the decreased density of the alloys, is proportional to the indium content up to the solid-solubility limit. Upon heat treatment of the alloys, the thermal …

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Cathodic Behavior Of Co, Co-Fe Alloys And Some Other Metals In Acids In A Cathodic Protection Arrangement, Ram Bajaj Jan 1970

Cathodic Behavior Of Co, Co-Fe Alloys And Some Other Metals In Acids In A Cathodic Protection Arrangement, Ram Bajaj

Masters Theses

"During cathodic protection of a corroding metal, electrons are forced into the metal by a sacrificial anode, a battery or a rectifier. These electrons, which constitute the suppressing or external current, are discharged (by H⁺ of the corrosive liquid) on the local cathode of the corroding metal decreasing the emf of the local cells, and, thus, reducing the cell current or the rate of corrosion of the metal. This process was studied in detail by finding out the relationship existing between the cell and suppressing currents. The study was made using two circuits: the cell circuit (representing the local current) …

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Etch Patterns On Zone-Refined Fe, M. E. Straumonis, Chang-Soo Kim Jan 1970

Etch Patterns On Zone-Refined Fe, M. E. Straumonis, Chang-Soo Kim

Electrical and Computer Engineering Faculty Research & Creative Works

Upon dissolution of zone-refined Fe in strong acids, mainly three kinds of corrosion patterns were observed in the crystallites of the sections. Regardless of the acids, the {110} plane always appeared on the three patterns in the form of smooth and even steps, ledges, or facets. The {112}, {122}, and {123} planes were also developed but to a much lesser degree. The {100} and {111} planes were not observed because grains of the respective orientation were missing on the sections. Attempts were made to explain the formation of the planes by taking into consideration the reticular density of the planes …

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Carburization Of Type 316l Stainless Steel In Static Sodium, F. B. Litton, Arthur E. Morris Jan 1970

Carburization Of Type 316l Stainless Steel In Static Sodium, F. B. Litton, Arthur E. Morris

Materials Science and Engineering Faculty Research & Creative Works

The transport of carbon from an iron-87 wt.% carbon alloy through static sodium to Type 316L stainless steel was investigated at temperatures of interest to the liquid-metal fast-breeder reactor (LMFBR) program. The rate-controlling step for the experimental geometry employed was the diffusion of carbon in the source. © 1970.

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Exact Solution For A Model Of Dislocation Pipe Diffusion, J. Mimkes, Manfred Wuttig Jan 1970

Exact Solution For A Model Of Dislocation Pipe Diffusion, J. Mimkes, Manfred Wuttig

Materials Science and Engineering Faculty Research & Creative Works

The dislocations are treated as an ideal array of parallel pipes of radius and diffusivity Dp embedded in the bulk material of the diffusivity Db. The exact solution of this problem of diffusion along semi-infinite edge dislocations is presented for cubic, tetragonal, and hexagonal crystals. The solution makes it possible to evaluate the dislocation pipe radius a and the ratio of diffusivities from one experiment. It is applied to experimental data for self-diffusion in tellurium available in the literature. The results of the calculations are a dislocation pipe radius a=(1.5 0.5)x10-4 cm and an activation energy for the pipe diffusion …

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The Smelting Of Lead Drosses, Humberto Adolfo Arzabe Jan 1970

The Smelting Of Lead Drosses, Humberto Adolfo Arzabe

Masters Theses

"The constitution of the matte and bullion obtained by the smelting of lead drosses coming from the cooling of lead blast furnace bullion was investigated by metallographic, chemical, electron-microprobe, and X-ray means. At smelting temperatures (1200°C to 1300°C) two liquid phases are in equilibrium. A liquid lead phase with low concentrations of copper and sulfur, and a lighter liquid matte phase containing a high concentration of copper and sulfur with some dissolved lead. On cooling to room temperature the matte precipitates cuprous sulfide, a eutectic mixture of cuprous sulfide and lead sulfide with a deficiency of sulfur, and metallic lead …

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Spheroidization In Tool Steels, Sharad Gajanan Bankar Jan 1970

Spheroidization In Tool Steels, Sharad Gajanan Bankar

Masters Theses

"A carbon steel, W1, and four other alloy tool steels, namely, A2, H13, D3, and M2, were spheroidized by five different procedures. Any modification made in the treatments for an individual steel were suggested by the results obtained with these five procedures. The hardnesses and microstructures obtained were compared with steel samples annealed at a tool steel mill. The response given by different steels to various methods of spheroidization was studied. It was found that A2, W1, and D3 steels responded the best to the cycling method whereas the best response to the isothermal annealing was given by H13 and …

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Investigation Of The System Al₂O₃-Teo₂-O₂, Vera Zelenkova Sestak Jan 1970

Investigation Of The System Al₂O₃-Teo₂-O₂, Vera Zelenkova Sestak

Masters Theses

"The system Al₂O₃-TeO₂-O₂ has been investigated by X-ray diffraction and differential thermal analysis in air and in sealed silica ampoules. The tellurate, Al₂TeO₆, with tellurium in the +6 valence state, forms in air but not in vacuum at 1 mm pressure. A second phase, a tellurite, possibly Al₂Te₂O₇, forms in air or vacuum by devitrification. The glass-forming region is wider than previously stated and is more extensive in vacuum--from 50% to 98% TeO₂. Tentative phase boundaries have been placed for the system in air and vacuum"--Abstract, page ii.

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A Systematic Study Of Instrument Variables Upon The Accuracy Of Microprobe Analysis, R. A. Parr Jan 1970

A Systematic Study Of Instrument Variables Upon The Accuracy Of Microprobe Analysis, R. A. Parr

Masters Theses

"The purpose of this investigation was to study the effect of instrument parameter changes upon X-ray intensity measurements of the copper-manganese system. The parameters utilized in this study included: (1) polished, contaminated, and 600 grit surfaces ; (2) constant sample current and constant beam current modes; and (3) 15 KV, 20 KV, and 25 KV accelerating potentials. Inspection of the data disclosed three interesting points: (1) copper and manganese X-ray intensity measurements appear to be a linear function of composition in the 15 KV through 25 KV accelerating potential range; (2) electron backscatter measurements consistently show in a limited range …

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Metallographic Study Of Phase Changes In Heat Treated Ductile Iron, Mahendra Vadilal Desai Jan 1970

Metallographic Study Of Phase Changes In Heat Treated Ductile Iron, Mahendra Vadilal Desai

Masters Theses

"Continuous cast ductile iron samples were hardened. It was found that carbide dissolved in the austenite faster than graphite and that this material requires higher austenitizing temperatures and longer austenitizing time than steels. Tempered microstructures were affected by the prior austenitizing treatment and it appeared that the amount of carbon dissolved in the austenite determined the tempered microstructure. Several attempts to determine the austenite grain size indicated that it is not as easy to determine in ductile iron as in steels. Two techniques, heat etching and an isothermal transformation method, were found to reveal prior austenite grain size. It was …

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Investigations Of Several Variables In The Dwight-Lloyd Mcwane Ironmaking Process, James Orlan Hood Jr. Jan 1970

Investigations Of Several Variables In The Dwight-Lloyd Mcwane Ironmaking Process, James Orlan Hood Jr.

Masters Theses

"The Dwight- Lloyd McWane Ironmaking Process (D-LM) is the first commercial process of its particular type and one of the few commercial processes involving prereduction of iron ore in existence today. This presentation reviews some promising ironmaking processes which involve iron ore prereduction, with special attention being given the D-LM process. Although the D-LM process is continuous from iron ore to high quality molten cast iron, the research and discussion herein is limited to principal variables involved in the production of high quality carbonized pellets in the prereduction phase of the operation. The variables of process temperature and pellet carbon …

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Thermal Expansion Of Orthorhombic Pbo, Charles A. Sorrell Jan 1970

Thermal Expansion Of Orthorhombic Pbo, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

Thermal expansion of orthorhombic PbO was investigated by high‐temperature X‐ray diffraction. The coefficients in the a0, and c0 directions are equal and Pb–O chains extended in the a0 direction and bonded into layers in the b0 direction; appreciable Pb–Pb bonding is indicated. Coordination and bond distances observed in PbSiO3 and lead silicate glasses, which are similar to those of massicot, and PbnOn polymeric units reported in PbO vapor are interpreted as additional evidence of the importance of PbO chains as structural entities. Copyright © 1970, Wiley Blackwell. All rights reserved

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Some Effects Of Oh Groups On Sodium Silicate Glasses, Mokhtar Sayed Maklad Jan 1970

Some Effects Of Oh Groups On Sodium Silicate Glasses, Mokhtar Sayed Maklad

Doctoral Dissertations

"Glasses of various compositions in the Na₂O-SiO₂ system were prepared with different levels of OH concentration. Phase separation kinetics, thermal expansion, radiation induced optical absorption, and internal friction of these glasses were studied. The increase in OH content in these glasses was found to (a) enhance the rate of phase separation; (b) increase thermal expansion above the glass temperature and change the dilatometric softening temperature in a way that depends on microstructure; (c) increase the radiation induced optical absorption bands associated with positive hole centers and decrease those associated with electron trap centers; and, (d) decrease the low temperature alkali …

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Cation Grain-Boundary Diffusion In Sodium Chloride, K. R. Riggs, Manfred Wuttig Dec 1969

Cation Grain-Boundary Diffusion In Sodium Chloride, K. R. Riggs, Manfred Wuttig

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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A Crystallization Study Of A Tetrasilicic Fluormica Glass, William H. Daniels Jan 1969

A Crystallization Study Of A Tetrasilicic Fluormica Glass, William H. Daniels

Doctoral Dissertations

"The transformation of a synthetic mica composition K₂Mg₅Si₈O₂₀F₄ from amorphous to crystalline structure was studied isothermally at selected temperatures from 560°C to 1150°C. thermal changes associated with the transformation were followed by differential thermal analysis techniques. Structural changes promoted by the isothermal treatments were observed by density measurements, Debye-Scherrer X-ray diffraction techniques, electron replication microscopy, and electron scanning microscopy. Isothermal treatment at 450°C for 9 hours produces structural ordering in quenched K₂Mg₅Si₈O₂₀F₄ glass. Fluorine exerts a significant influence on the transformation temperature; decreasing amounts of fluorine producing increasing transformation temperatures. The crystallizing phase rapidly attains a limiting particle size and …

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Grain Boundary Self-Diffusion In Sodium Chloride, Kenneth Ray Riggs Jan 1969

Grain Boundary Self-Diffusion In Sodium Chloride, Kenneth Ray Riggs

Doctoral Dissertations

"The diffusion of ²²sodium and ³⁶chlorine along tilt and twist grain boundaries in pure and calcium chloride doped sodium chloride bicrystals was investigated. No enhanced diffusion of ²²sodium along the grain boundaries was observed. Between 400°C and 500°C the chlorine grain boundary diffusion parameter, D'Δ, is described by D'Δ = (D'Δ)₀exp (-Qb/kT), where (D'Δ)₀ is approximately 10⁻⁷ cm³/sec and Qb is 1.15 ± .30 eV. The grain boundary angle, the grain boundary character (tilt or twist), and the calcium chloride concentration appear to have no pronounced effect upon the observed chlorine grain boundary diffusion. The ionic movement …

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Phase Equilibria And Thermodynamic Studies In The System Ca0-Fe0-Fe₂0₃₋Si0₂, Muharrem Timucin Jan 1969

Phase Equilibria And Thermodynamic Studies In The System Ca0-Fe0-Fe₂0₃₋Si0₂, Muharrem Timucin

Doctoral Dissertations

"A study of phase relations and thermodynamic properties of phases in the system CaO-FeO-Fe₂O₃-SiO₂ was conducted at 1450°C and 1550°C. The region of stability of the different phases was determined by microscopic examination of the specimens. The thermodynamic properties of liquid were determined by analyses of quenched samples equilibrated at oxygen pressures from about 10⁻¹¹ to 1 atm. Isothermal phase diagrams were constructed from data for 0, 5, 10, 20, and 30 weight percent silica sections of the CaO-FeO-Fe₂O₃-SiO₂ system, and the effect of temperature and increased silica additions on the oxygen solubility of the liquid oxides was measured. Multicomponent …

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X-Ray Determination Of Lattice Parameters And Thermal Expansion Coefficients Of Aluminum, Silver And Molybdenum At Cryogenic Temperatures, Claude Lowell Woodard Jan 1969

X-Ray Determination Of Lattice Parameters And Thermal Expansion Coefficients Of Aluminum, Silver And Molybdenum At Cryogenic Temperatures, Claude Lowell Woodard

Doctoral Dissertations

"A multiple exposure back reflection diffraction camera was designed to mount on the vacuum jacket of a pressurized helium gas "Cryomite". With this design it is possible to obtain six diffraction exposures on a single film at any temperature in the range of 180 to 25°K. temperatures within this range are reached in short intervals and exposure periods are less than 30 minutes in a 2.875 inch (73.03 mm) diameter camera. Some of the advantages of this design are; direct measurements, multiple exposures on a single film, short exposures, direct compensation of film length changes due to evacuation or processing …

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Effect Of Hydrostatic Pressure On Anelastic Stress Relaxation In A Mixed-Alkali Silicate Glass, Young-Gil (Gilbert Y.) Kim Jan 1969

Effect Of Hydrostatic Pressure On Anelastic Stress Relaxation In A Mixed-Alkali Silicate Glass, Young-Gil (Gilbert Y.) Kim

Masters Theses

"The effect of hydrostatic pressure on the anelastic stress relaxation of a mixed-alkali silicate glass (0.05 Na₂O, 0.95 K₂O, 3 SiO₂) was studied at 75°C between ambient pressure and 6 kbar. The activation volume of diffusion was found to be - 4.2 cm³/mole. It is proposed that a reequilibration of the defect population at pressure gives rise to the negative activation volume of diffusion"--Abstract, page ii.

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The Electrodeposition Of Zinc; Changes In Current Efficiency And Surface Structure Resulting From Various Addition Agents, Haruhisa Fukubayashi Jan 1969

The Electrodeposition Of Zinc; Changes In Current Efficiency And Surface Structure Resulting From Various Addition Agents, Haruhisa Fukubayashi

Masters Theses

"An examination of the surface structure of zinc electrodeposited from an acid-sulfate solution was made by scanning electron microscopy techniques. The current efficiencies were also determined, to a lesser extent, in order to correlate the results with the surface structures. Commercial and pure zinc oxide were used to prepare the neutral zinc sulfate solutions. The starting solutions were in a range of acid and zinc concentrations commonly used in commercial practice. Changes in morphology resulting from addition agents such as animal glue, gum arabic, and sodium silicate are compared"--Abstract, page ii.

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Precipitation Hardening Of A Mg - 3.5 Wt. % Th - 1. Wt. % Mn Alloy, Adolf Chun-Chiung Huang Jan 1969

Precipitation Hardening Of A Mg - 3.5 Wt. % Th - 1. Wt. % Mn Alloy, Adolf Chun-Chiung Huang

Masters Theses

"The precipitation process in a Mg - 3.5 wt. % Th - 1. wt. % Mn alloy during aging at 260⁰, 350⁰ and 400⁰C was determined principally by transmission electron microscopy. At 350⁰ and 400⁰C, general precipitation of the equilibrium Mg₄Th phase moderately hardens the alloy. No transition lattice of this phase was seen. The Mg₄Th precipitate forms initially as disc shaped plates parallel either to the prism or basal plane of the matrix...During prolonged aging at 400⁰C the plates lengthen into long laths on either of the above planes in the close packed direction...At 260⁰C an unidentified G. P. …

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Thermal-Fatigue Of Type 304 Stainless Steel, Gajinder Bir Singh Arora Jan 1969

Thermal-Fatigue Of Type 304 Stainless Steel, Gajinder Bir Singh Arora

Masters Theses

"Thermal fatigue resistance of unrestrained samples of type 304 stainless steel has been investigated under different test conditions. The following studies are reported: (a) effects of heating and cooling rates on the initiation of cracks, (b) effects of upper and lower cycle temperatures on the initiation of cracks, (c) effect of water quenching and (d) the manner in which cracks initiated and propagated. It is shown that under cyclic conditions involving maximum temperatures up to 1000°C, the thermal fatigue life of the material decreases rapidly with rise in the maximum temperature of the cycle. The increase in the lower cycle …

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