Materials Science and Engineering Commons^™

Electroless And Chemical Metal Deposition On Human Tooth Enamel., Richard Doyle Christie

Masters Theses

"Initial investigations have confirmed the feasibility of depositing an adherent metal film onto tooth enamel. Such films might be used as pit and fissure sealants in preventive dentistry, with denture or orthodontic work, as an intermediate substrate with various organic or inorganic restorative materials, or other such areas. The process employs chemical solutions containing ions of the metal to be deposited and suitable reducing agent solutions.

To date, metallic copper and silver films have been plated onto teeth in vitro. The deposits are quite adherent and appear to exhibit the conductivity, crystal structure, luster, hardness, and other chemical and physical …

The Influence Of Oxygen Activity On Sintering Of Strontium Doped Lanthanum Chromite., Leslie Groupp

Masters Theses

"The influence of oxygen activity upon the sintering of lanthanum chromite (La_1-xSr_x CrO₃) with x ranging from Oto 0.2 was investigated using chemically prepared powders of <0.1 microns particle size. The results show that at a temperature of 1740 ° C densities of >92% of theoretical could be achieved if the oxygen activities were maintained in the 10^-11 to 10^-12 atm. range. If oxygen activity exceeds 10^-10 atm., densities of not >80% theoretical could be obtained. For the compositions studied, room temperature X-ray analysis of both the starting powders and sintered compacts show the compositions to be orthorhombic and single phase. The ambient lattice parameters and resistivity measurements decreased …

Variables Affecting The Rate Of Solution Of Mold Inoculants In Cast Iron, Jose Osorno Fonnegra

Masters Theses

"The purpose of this investigation was to measure the effectiveness of an inoculant alloy reacting with molten cast iron in a reaction chamber properly located in the gating system.

The chemical composition of the gray iron was held constant while several metallurgical factors were varied to produce test samples with different cementite thicknesses. These chill depths were measured as an indication of the inoculation effectiveness.

Appreciable differences in chilling tendency were observed within the different variables studied. The results indicate that pouring temperature, as well as the other variables studied, are of considerable importance when dealing with inoculation of gray …

Effect Of Temperature, Aging, And Composition On Phase Development In The System Al₂O₃-P₂O₅-H₂0., John Allan Middleton

Masters Theses

The chemical and physical conditions for the formation of various phases of aluminum phosphate were studied. Mixtures of Al₂O₃ and H₃PO₄ were aged in sealed containers and examined for phase development by X-ray diffraction. The results revealed the aging of samples to be a critical process for the formation of equilibrium phase assemblages at low temperatures, Initial composition becomes important as equilibrium is neared and at elevated temperatures when the molar ratios of Al₂O₃, P₂O₅, and H₂O determine what phases will be formed. Temperature …

Characterization Of Two Mexican Raw Dolomites For Refractory Brick Production, Rodolfo Trevino Cantu

Masters Theses

"Two Mexican dolomites were characterized in order to discover their suitability for production of refractory brick.

The results were compared with other dolomites from American Companies. Some samples were burned in a gas fired Laboratory Furnace and others were obtained in the burned state after processing in Industrial Rotary Kilns.

The characterization procedures included X-Ray Diffraction, Scanning Auger Microprobe, DTA and TGA techniques, Chemical Analysis and Bulk Density measurements.

The procedure to control the quality of the dead-burned dolomite at the industrial level was established taking as the main criteria, bulk density, hydration susceptibility, and impurity levels"--Abstract, page ii.

Ionic Thermal Current In Sodium-Rubidium Silicate Glasses., Chi-Ming Hong

Masters Theses

"The ionic thermal current (ITC) method has been employed to study alkali ion motion in a sodium silicate glass and two sodium-rubidium silicate glasses over the temperature range 110 ° K to 400 ° K. T wo peaks and three peaks were observed in a l.0Na₂O-3.0SiO₂ glass and a 0.75Na₂O-0.25Rb₂O-3.0SiO₂ glass, respectively. Only one peak and a high temperature shoulder were observed in the 0.50Na₂O-0.50Rb₂O-3.0SiO₂ glass. These peaks were attributed to orientation and space charge polarization with each peak associated with a particular movement of the sodium …

The Spheriodization Of Tool Steels., Siri Ram Rai

Masters Theses

"Four different tool steels--AISI 01, Sl, A9 and Tl5--were obtained in the 1/2-inch diameter hot rolled and air-cooled condition from the steel mill. The lower critical temperatures of these steels were determined. The spheroidization of each steel by three different spheroidizing procedures was evaluated with the use of hardness testing and metallographic techniques. Isothermal annealing completely spheroidized each steel yielding coarse carbides and low hardness. Cyclic annealing was an effective spheroidization procedure only for 01 and Tl5 steels. Hardening and tempering resulted in rather fine spheroidized structures in these steels. The total time consumed to produce the best spheroidized structures …

Phase Equilibria Near The Solidus Temperature For Iron-Rich Fe-Cu-C Alloys., Kenneth L. Metz Jr.

Masters Theses

"The effect of copper on the solidification temperature of graphite-saturated iron-rich alloys was determined with the use of cooling curves. The ternary invariant temperature for the alloy was found to be 1172°c with the use of heating curves. At 1172°c, graphite, austenite, an iron rich liquid, and a copper-rich liquid are in equilibrium. The composition of the metallic phases was determined by weight gain, chemical analysis, and the electron microprobe. In addition, the composition of the iron-rich liquid was calculated from thermodynamic data. Isothermal sections of the iron-rich corner of the system were constructed for several temperatures in the range …

Esca Characterization Of Flotation Products From A Lead-Zinc-Copper Concentrator On The New Lead Belt Of Southeast Missouri., Kevin Leroy Purdy

Masters Theses

"Electron spectroscopy for chemical analysis (ESCA) was used to determine the surface characteristics of products from an operating Pb-Zn-Cu concentrator on the New Lead Belt of southeast Missouri and pure galena and sphalerite samples treated with flotation reagents in concentrations similar to those used in the mills. The emphasis was on the action of surface modifiers such as Na₂Cr₂O7, starch, SO₂, CuSO₄ and NaCN in sphalerite flotation and in the galena-chalcopyrite separation. The objective of the investigation was to monitor the relative oxidation states of the mineral and reagent constituents and correlate these …

A Study Of The Feasibility In Obtaining The Kinetics Of Various Ordering Phenomena Of The Iron Aluminum System Utilizing The Mössbauer Effect, Lloyd Rollan Chapman

Masters Theses

"The determination of the kinetics of ordering for various ordering phenomena of the Iron-Aluminum system utilizing exclusively the Mössbauer effect technique is shown to be infeasible for all but a highly restrictive consideration from experimental as well as theoretical evidence. Also, the possible use of the Mössbauer effect for the analysis of other ordered systems is discussed.

An alternative method for the acquisition of the needed information utilizing diffraction and Mossbauer techniques is presented recognizing the need for a computer fitting analysis of the complex Mössbauer effect spectra. However, at this stage of investigation, no experimental work has been performed …

Detection Of Impurities In Zinc Sulfate Electrolytes By Cyclic Voltammetry Techniques., Bruce Alan Lamping

Masters Theses

"A cyclic voltammetric technique has been developed for quantitatively detecting the presence of active chemical species present in zinc sulfate electrolytes. The experimental apparatus consisted of a pyrex "H" cell, an Al cathode encased in a Teflon holder, a carbon anode and a mercurous sulfate reference electrode. Voltammograms were obtained from industrial, purified neutral leach solution (Cominco Ltd., Trail, B.C.) acidified to give a final concentration of 0.77 M Zn⁺⁺, 1 M H₂SO₄. The polarization curves were then evaluated and used as a reference standard to compare with results obtained when various organic and …

Amine Flotation Of Feldspar From Magnetite Concentrate., Gary William Hudiburgh Jr.

Masters Theses

"The gangue in some magnetite ore bodies contains feldspar; the alkali content of the feldspar reduces the usefulness of these iron ores. One method of decreasing the feldspar content in magnetite concentrate is froth flotation.

The amine flotation of feldspar from magnetite concentrate was investigated using zeta potential measurements, Hallimond tube flotation tests and laboratory-scale flotation tests. The zeta potential of various feldspars (microcline, albite, anorthite, oligoclase and anorthoclase) were determined as a function of pH; the point of zero charge ranged from pH 1.4 to 2.5. Hallimond tube flotation tests using two amine reagents were conducted on the feldspars. …

Kiss Gating In Sand-Cast Aluminum Alloys., Michael Lynn Holt

Masters Theses

"This thesis describes the optimum conditions necessary for the production of macrosound plate castings of sand-cast aluminum alloys by the kiss gating process. Castings of alloys of different freezing ranges in the Al-Si-Cu system (alloys 195, 319, 380, and 384) were produced and examined visually to evaluate the effectiveness of various gating systems and superheats on the production of macrosound castings.

For the aluminum alloys used in this investigation, the optimum conditions leading to the production of macrosound castings without the use of risers are one or a combination of the following: (l) wider freezing ranges; (2) pressurized gating systems; …

Effect Of Nodule Count And Cooling Rate On The Matrix Of Nodular Iron., Subrata Sen Gupta

Masters Theses

"The objective of this investigation was to establish the relationship between the nodule count, the matrix structure, and the cooling rate through the eutectoid in nodular iron. The chemical composition of the nodular iron was held constant while various inoculation methods, inoculants, and mold designs, including chills, were used to vary the solidification time and cooling rate through the eutectoid range. This produced variations in both the matrix structure and the nodule count.

The nodule count has a power relationship with the percent pearlite in the matrix at fixed cooling rates: Percent pearlite = K (Nodule count)^-n where the …

Effect Of Dissolved Water On Physical Properties Of Silver Borate Glasses, E Richard Reynolds

Masters Theses

"The effect of dissolved water on borate glasses containing 4-20 mol % Ag₂O was investigated. Water was dissolved in the glasses by bubbling with a carrier gas (oxygen) containing different partial pressures of water vapor. A minimum in water solubility was found at 11 mol % Ag₂O. Water contents in excess of 0.5 mol % H₂O did not have a great effect on the transition temperature or the dilatometric softening point. Below 15 mol % Ag₂O, the water content had no effect on the thermal expansion coefficients. Beyond 15 mol % Ag …

Magnetostrictive Aftereffects In A Dilute 50fe-50ni-C Alloy, Raj N. Master

Masters Theses

"Crystallographically equivalent interstitial sites are energetically equivalent when the host crystal is free of any fields. This situation is shown in Fig. Pl from which it may be appreciated that the difference of the free energy of the "crystal" with an interstitial "I" located in "x" and "y" sites, respectively, is equal to zero. This energy equivalence of the various interstitial sites is destroyed when the host crystal is subjected to fields such as strain fields, magnetization fields or a combination of both as may be appreciated from Figs. P2 through P4. In this case, the interstitials will preferentially occupy …

Determination Of Oxygen Chemical Diffusion Coefficients In Single Crystal Strontium Titanate By Capacitance Manometry, Douglas Bugh Schwarz

Masters Theses

"The use of the tensi-volumetric apparatus to study the non-stoichiometric behavior of strontium titanate was discussed. Oxidation kinetics of reduced single crystal strontium titanate were measured with an ultrasensitive capacitance manometer as the sample absorbed oxygen in response to a changing oxygen activity.

The oxidation kinetics were found to fit a solution to Fick's second law for rectangularly shaped samples....

The procedure selected for measurement of the oxidation kinetics, and the method of obtaining diffusion coefficients from the oxidation data was discussed along with potential sources of error of the system"--Abstract, page ii.

Synthesis Of Fused Silica By Flame Hydrolysis, James Edward Rourke

Masters Theses

"Apparatus to synthesize and dope high purity, optical quality fused silica by flame hydrolysis was constructed. Fused silica samples containing 0, <35, 35 and 90 ppm niobium were synthesized and characterized by the following properties: purity, refractive index, radiation damage resistance, and transmission spectra. The properties of the undoped sample were shown to be comparable to those of available commercial fused silica. Deviations in the properties of the doped samples from those of the undoped samples were explained in terms of the niobium content"--Abstract, page ii.

A New And Direct Process For The Reduction Of Lead Sulfide, Rolando Oscar Fernandez

Masters Theses

"The direct reduction of lead sulfide concentrates by iron was investigated. An oxygen-bearing flux was shown to be a necessary ingredient for complete reduction of the concentrate. The effects of time and temperature on lead recovery were studied. Only a trace amount of sulfur dioxide is evolved during reduction, which is in agreement with thermochemical calculations"--Abstract, page ii.

Characterization Of A Mexican Halloysitic Clay And Behavior In Dry Pressing, Jesus L. Derat

Masters Theses

"A Mexican clay, intended to be used as refractory raw material, was identified. Problems encountered in the characterization of halloysitic clays are discussed and emphasis is made on the use of the electron microscope (scanning or transmission type) as a definite evidence of the existence of halloysite due to its unique morphology within the kaolinite group of clay minerals.

Beneficiation of this particular clay was carried out on a small scale hydrocyclone equipment and the results are discussed.

In an attempt to increase the green density in dry pressing of this halloysitic clay, mixtures with grog were prepared using different …

The Effect Of Gating On Soundness Of Al-Alloy Permanent Mold Castings, Dinesh Shantilal Patel

Masters Theses

"This thesis describes the step by step approach to the design of a gating system for the production of sound plate castings in permanent molds. Castings of different thicknesses were produced, utilizing various gating systems, and examined radiographically to evaluate the effectiveness of these gating systems in the production of sound castings. A gating system which allows metal to enter the mold cavity with no turbulence and which establishes proper temperature gradients in the casting will produce sound permanent mold castings"--Abstract, page ii.

Sintering And Microstructure Control Of A Ferrimagnetic Mn-Zn Ferrite Spinel, Joel Keith Michel

Masters Theses

"The effect of minor additions of CaO dopant to a manganese zinc ferrite – Zn_.25Mn_.75 Fe_2.17 O_4.0 - on its grain growth and densification kinetics in air at 1250°C., 1300°C., and 1350°C. was studied. Grain growth was controlled over a range of dopant levels. At a sintering temperature of 1350°C. and time of six hours a ferrite with the smallest dopant addition was sintered to the highest density - 98% of theoretical. Under the same sintering conditions ferrites with higher dopant levels also sintered with normal growth but sintered to lower densities.

Due to discontinuous …

Precipitation Of Carbon From Martensite In Ductile Iron, Devendra Ratilal Majmundar

Masters Theses

"Since metallographic studies of quenched and tempered cast iron have indicated that the carbon might precipitate directly as graphite rather than as carbides which are found in steels, this investigation used the Debye-Scherrer x-ray diffraction technique to examine electrolytically extracted residues from quenched and tempered ductile cast iron samples to determine if cementite was present. The precipitation of carbon in quenched samples of this ductile cast iron was found to be similar to the precipitation process in steels. Cementite was identified during the early stages of the tempering process when the tempering temperature was 800 degrees F, 900 degrees F, …

The Effect Of Porosity On Strength Degradation In Thermally Shocked Alumina, Russell David Smith

Masters Theses

"Strength degradation and crack propagation in Al₂O₃ are shown to depend on the initial strength and porosity of the material. Specimens were fabricated containing between 0 and 5% induced cylindrical, two dimensional, and spherical porosity. The strengths of the various porosity samples decreased discontinuously at a critical quenching temperature. No difference was observed in the critical temperature for the various aluminas; initial strength decrease occurred between 165°C and 175°C temperature differential. The strength retained after thermal shock decreased with increasing initial strength. The degree of damage sustained upon shocking was also characterized by crack density and crack …

Phase Transformations In The System Zro₂-Cao, Damri Sukhotanang

Masters Theses

"Thermal expansion, thermal hysteresis, and the monoclinic tetragonal phase transformation of ZrO₂ have been studied with high temperature x-ray diffractometry. The initial transformation temperature in pure ZrO₂, on heating, is about 1150ºC. The transformation occurs over a 100ºC temperature range and thermal hysteresis occurs on heating and cooling. The mechanism of the transformation is related to preferred vibrational modes of atoms on the A_O -C_O plane of the monoclinic structure. Because the monoclinic B_O axis is parallel with the tetragonal [110] axis, structural relationships can be seen to be a controlling factor in the transformation. Initiation of …

A Mass Spectrometric Characterization Of Positive Ions Created In Simple Vacuum Diodes Incorporating Oxide Cathodes With Supplementary Analysis Of Background Gases, Larry A. Addington

Masters Theses

"Simple diodes were constructed utilizing oxide cathodes and nickel anodes. The cathodes were obtained by applying a mixture of barium, strontium, and calcium carbonates to a nickel filament and decomposing them to yield the oxides. The products of decomposition were analyzed by monitoring the composition of the background gases in the vacuum chamber. A portion of the flux of positive ions bombarding the cathode during diode operation was analyzed. It was possible to determine the region of origin of the ions and their potential energy at the time of formation. Positive ions of chlorine, fluorine, sodium, potassium, and rubidium were …

A Study Of The System Lithia - Silica, Roy Richard Ramey

Masters Theses

"X-ray intensity and d-spacing measurements were performed upon samples in the system Li₂O-SiO₂. Samples ranged from 0.0 to 28.0 mole percent lithia and were fired for 72 hours at temperatures from 920ºC to 1400ºC. Atomic absorption analyses were made upon the fired samples. Non-equilibrium conditions were prevalent and results are inclusive. Quartz is the stable phase in the high silica field at temperatures below 1050ºC with cristobalite stable above that. The quartz - cristobalite transformation occurs at 950ºC with the cristobalite transforming into tridymite at 1010ºC. There was wide scattering of data at 1000ºC and below. There was no correlation …

Thermal Expansion Of Nickel And Iron, And The Influence Of Nitrogen On The Lattice Parameter Of Iron At The Curie Temperature, Jinn-Wen Hwang

Masters Theses

"By precise X-ray measurements, the lattice parameter of pure nickel (Fisher Co., reagent grade) was found to be 3.52389 Å at 25ºC. At the same temperature, the lattice parameters of iron samples were found to be: 2.86621 Å, 2.86624 Å and 2.86614 Å for purities of 99.999%, 99.985% and 99.9%, respectively. By measuring high angle back reflection lines, the linear coefficients of thermal expansion of both nickel and iron were precisely determined. Both, high purity nickel and iron, exhibited anomalies in their expansion coefficients near their Curie points. This is in agreement with some of the previously reported data. Some …

Mechanism Of Ual₃ To Ual₄ Transformation, Ling Ping Lee

Masters Theses

"The UAl₄ compound which forms during the peritectic reaction, Liquid + UAl₃ - UAl₄ , has a long needle-like shape and a characteristic morphology of fish-tail when cut along the long axis. It has an internal core of another phase when cut perpendicular to the needle axis. Because of the interesting similarity between UAl₃ and UAl₄ crystal structures, the peculiar UAl₄ morphology could be explained. The mechanism of UAl₃ to UAl₄ transformation is identified as shear and diffusion controlled transformation"--Abstract, page ii.

An Investigation Of Stage I Fatigue Crack Growth In Fcc, Bcc, And Hcp Metals, Marion Anthony Russo

Masters Theses

"The objectives of this investigation were to 1) determine if Stage I mode or fatigue crack growth could be extended beyond the 45 degree maximum shear plane in metals having a face-centered, body-centered and hexagonal close pack crystal structure; 2) identify the crystallographic planes or crack propagation in Stage I growth in each crystal structure; 3) characterize the fracture surface topography or Stage I growth in each crystal structure. The test material used for this investigation consisted of alpha brass (70% Cu, 30% Zn), Armco iron and commercially pure titanium which are representative of FCC, BCC, and HCP crystal structures …