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Blank, Jonathan PEffect of boron additions on microstructure and mechanical properties of titanium alloys produced by the armstrong process
Doctor of Philosophy, The Ohio State University, 2008, Materials Science and Engineering
The beneficial influence of boron additions on processing, microstructure, physical and mechanical properties of various titanium alloys has been recognized since 1950’s. However, boron additions to titanium alloys to obtain specific microstructures and mechanical properties for several niche applications, including automotive and aerospace, have been actively studied during the past 25 years. The addition of boron concentrations greater than 0.05 wt.% to titanium alloys creates a dispersion of TiB. The presence of TiB enhances the tensile and fatigue strengths as well as the wear resistance as compared to the original titanium alloy. Although these improvements in mechanical properties are attractive, there are still two major obstacles in using these alloys: (1) relationship of microstructure and mechanical properties in Ti-B alloys needs further investigation to optimize the alloys for specific commercial applications; and (2) cost to benefit ratio of producing these alloys is high for a given application(s). The Armstrong process is a novel process that can produce commercially pure (CP) titanium and titanium alloy powder directly from TiCl4 (and other metal halides or as required, to obtain the desired alloy composition). The Armstrong process uses sodium as a reducing agent, with similar reactions as the Hunter process using sodium as a reducing agent and Kroll process using magnesium as a reducing agent. The Armstrong process forms CP-Ti and titanium alloyed powder, which can be directly consolidated or melted into the final product. In comparing the downstream processing steps required by the Kroll and Hunter processes with direct consolidation of Armstrong powder, several processing features or steps are eliminated: (1) restriction of batch processing of material, (2) blending of titanium sponge and master alloy material to create titanium alloys, (3) crushing of the sponge product, (4) melting, and (5) several handling steps. The main objective of this research was to characterize structure and properties of CP-Ti and Ti-B alloys produced by the Armstrong process. Particular emphasis has been placed on improved understanding of the strengthening mechanisms associated with the addition of boron to titanium alloys.

Committee:

James Williams (Advisor)

Subjects:

Textile Technology

Keywords:

Titanium; Titanium-boron; TiB; Commercially Pure Titanium; CP-Ti; Titanium microstructure; Titanium-boron microstructure; Tensile; Notched Fatigue; Fatigue Crack Growth

Ayyala Somayajula, DilipBiocompatibility of osteoblast cells on titanium implants
Master of Science in Chemical Engineering, Cleveland State University, 2008, Fenn College of Engineering
Adhesion and proliferation of UMR 106-01 osteoblast cells were studied on various surface modified titanium materials such as polished, sandblasted, anodized and alkaline treated. Anodization of polished surface in Hydrofluoric acid developed nano-tubes, while NaOH treatment produced spongy microporous morphology. Test samples were coated with non-adhesive protein bovine serum albumin and compared with fibronectin coated specimens. The adhesion study lasted for 4 hrs, where osteoblast cells were cultured in serum free medium. Polished titanium, anodized titanium and NaOH titanium have shown similar percentages of cell adherence. The proliferation study lasted for 48 hrs, where cells were initially allowed to adhere to the surface in serum free medium for 4 hrs, followed by a medium change to 10% fatal bovine serum. The specific growth rate after 48 hrs in culture on the polished surface was found to be comparable to the tissue culture plastic, which exhibited a high growth rate. No significant difference was found in cell numbers between polished, anodized and NaOH-Ti, but each has varying cell orientation on the surface. Fluorescence images stained with alkaline phosphatase revealed that polished surface had cells flattened to the surface with short filapodia. Anodized surface had cells uniformly distributed across the surface where as NaOH-Ti displayed cells in colonies. Cells were found bonding to the surface of NaOH-Ti firmly using their filapodia as an anchoring agent. These results suggest that NaOH-Ti provides support in initial hours of implantation and bolsters cell proliferation. All together this process may help to better integrate titanium implant surfaces.

Committee:

Joanne Belovich (Committee Chair); Ronald Midura (Committee Member); Surendra Tewari (Committee Member)

Subjects:

Biomedical Research; Chemical Engineering; Dental Care; Materials Science

Keywords:

UMR 106-01; osteoblast cells; titanium; polished titanium; polished and anodized titanium; polished and NaOH treated titanium

Bathini, UdaykarA Study of Microstructure, Tensile Deformation, Cyclic Fatigue and Final Fracture Behavior of Commercially Pure Titanium and a Titanium Alloy
Master of Science in Engineering, University of Akron, 2010, Civil Engineering

Rapid industrial growth and advances in the domains of engineering and related technologies during the last fifty years have led to the extensive use of traditional metals and their alloy counterparts. Titanium is one such metal which has gained wide popularity in the aerospace and defense related applications owing to a wide range of impressive mechanical properties like excellent specific strength (σUTS/ρ), stiffness, corrosion and erosion resistance, fracture toughness and capability to withstand significant temperature variations.

Two materials, namely commercial purity titanium (Grade 2), referred to henceforth as Ti- CP (Grade 2) and the “work-horse” alloy Ti-6Al-4V have been chosen for this research study. The intrinsic influence of material composition and test specimen orientation on the tensile and fatigue behavior for both Ti- CP (Grade 2) and Ti-6Al-4V have been discussed. Samples of both Ti- CP (Grade 2) and Ti-6Al-4V were prepared from the as-provided plate stock along both the longitudinal and transverse orientations. The specimens were then deformed to failure in uniaxial tension for the tensile tests and cyclically deformed at different values of maximum stress at constant load ratio of 0.1 for the high cycle fatigue tests. The microstructure, tensile properties, resultant fracture behavior of the two materials is presented in the light of results obtained from the uniaxial tensile tests. The conjoint influence of intrinsic microstructural features, nature of loading and specimen properties on the tensile properties is discussed. Also, the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of applied stress-microstructural feature interactions in governing failure for the cyclic fatigue properties for both the materials under study Ti- CP (Grade 2) and the “work-horse” alloy Ti-6Al-4V have been discussed in detail.

Careful study of the microstructure for Ti-CP (Grade 2) material at a low magnification revealed the primary alpha (α) grains to be intermingled with small pockets of beta (β) grains. Observation at the higher allowable magnifications of the optical microscope revealed very fine alpha (α) phase lamellae located within the beta (β) grain. The microhardness and macrohardness measurements were consistent through the sheet specimen for Ti- CP (Grade 2) and slightly lower compared to Ti-6Al-4V. However, the macrohardness was marginally higher than the microhardness resulting from the presence of a large volume fraction of the soft alpha phase. The hardness values when plotted reveal marginal spatial variability. Tensile fracture of Ti-CP (Grade 2) was at an inclination to the far field tensile stress axis for both longitudinal and transverse orientations. The overload region revealed a combination of fine microscopic cracks, microscopic voids of varying size and randomly distributed through the surface, and a large population of shallow dimples, features reminiscent of locally brittle and ductile failure mechanisms. The maximum stress (σmaximum) versus fatigue life (Nf) characteristics shown by this material is quite different from those non-ferrous metals that exhibit a well-defined endurance limit. When compared at equal values of maximum stress at a load ratio of 0.1, the fatigue life of the transverse specimen is noticeably greater than the longitudinal counterpart. At equivalent values of maximum elastic strain, the transverse specimens revealed noticeably improved fatigue life as compared one-on-one to the longitudinal counterparts.

Careful observations of the Ti-6Al-4V alloy microstructure over a range of magnifications spanning very low to high magnification revealed a duplex microstructure consisting of the near equiaxed alpha (α) and transformed beta (β) phases. The primary near equiaxed shaped alpha (α) grains (light in color) was well distributed in a lamellar matrix with transformed beta (dark in color). The microhardness and macrohardness values recorded for the Ti-6Al-4V alloy reveal it to be harder than the commercially pure (Grade 2) material. However, for the Ti-6Al-4V alloy the microhardness is noticeably higher than the corresponding macrohardness value that can be ascribed to the presence of a population of processing-related artifacts and the hard beta-phase. Tensile fracture of the Ti-6Al-4V alloy was macroscopically rough and essentially normal to the far field stress axis for the longitudinal orientation and cup-and-cone morphology for the transverse orientation. However, microscopically, the surface was rough and covered with a population of macroscopic and fine microscopic cracks, voids of varying size, a population of shallow dimples of varying size and shape, features reminiscent of locally brittle and ductile failure mechanisms. When compared at equal values of maximum stress at a load ratio of 0.1, there is a marginal to no influence of microstructure on high cycle fatigue life of both orientations of the alloy.

Committee:

Anil Patnaik, Dr. (Advisor)

Subjects:

Civil Engineering; Materials Science

Keywords:

Titanium Alloy; Commercially Pure Titanium; Microstructure, Tensile Properties; Tensile Fracture; Titanium; Materials tests; Cyclic tests; Fatigue life; Fracture

Hill, Davion MMicrostructure and mechanical properties of titanium alloys reinforced with titanium boride
Doctor of Philosophy, The Ohio State University, 2006, Physics
Microstructure features in TiB-reinforced titanium alloys are correlated with mechanical properties. Both laser deposition and arc melting are used to fabricate test alloys where microstructure evolution with heat treatment is examined. SEM and TEM investigations of microstructure are coupled with 3D reconstruction to provide an adequate picture of phases in these alloys. Mechanical properties are then studied. Wear testing of several test alloys is presented, followed by hardness and modulus measurements of individual phases via micro- and nano-indentation as well as a novel micro-compression technique. Bulk mechanical properties are then tested in Ti-6Al-4V and Ti-555 (Ti-5Al-5V-5Mo-3Cr-1Fe) with varying amounts of boron. Image processing methods are then applied to high resolution back-scattered scanning electron microscope images to quantify microstructure features in the tensile test specimens, and these values are then correlated with mechanical properties.

Committee:

John Wilkins (Advisor)

Keywords:

TiB; TiB Reinforced; Titanium; alpha titanium; beta titanium; metal matrix composite; equiaxed alpha; 3D reconstruction; serial sectioning; Ti-6Al-4V; LENS; laser engineered net shape; laser deposition; hot isostatic press

Poondla, Narendra BabuA STUDY OF WELDED BUILT-UP BEAMS MADE FROM TITANIUM AND A TITANIUM ALLOY
Master of Science, University of Akron, 2010, Civil Engineering

Titanium is well recognized as a modern and high performance metal that is much stronger and lighter than the most widely used steels in the industry. There is a growing need to reduce the part weight, cost and lead time, while concurrently facilitating enhanced performance of structural parts made from titanium and titanium alloys. Structural components made from titanium have the advantage of high strength-to-weight ratio, and high stiffness-to-weight ratio. Owing to good resistance to corrosion and superior ballistic properties, titanium is used in several defense applications. This thesis presents a summary of the research conducted on welded built-up titanium beams so as to eventually facilitate the design, fabrication, and implementation of titanium in large structural members.

An alternative to machining a structural component from thick plates or billets is to fabricate beams using the built-up concept. Rolled plates and sheets of titanium alloys can be cut to size and welded together to fabricate a built-up structural component. The primary objective of this project is to investigate structural performance of built-up welded beams fabricated from commercially pure (Grade 2) titanium and a common alloy (Ti-6Al-4V) under both static and fatigue loading conditions. Six welded built-up titanium beams were fabricated and tested to experimentally and theoretically evaluate structural performance. Analysis and design approaches for static and fatigue performance of built-up beams were also studied and it is clearly demonstrated that it is feasible to fabricate large built-up titanium beams by welding parts together using GMAW-P welding process. The welds produced by this method were found to be sound and without any visible cracks. The study also revealed that there is no deleterious influence of welding on structural performance of the built-up welded beams of commercially pure titanium and Ti-6Al-4V titanium alloy.

With suitable modifications to the current AISC steel design specifications a preliminary design methodology was developed for the titanium beams. The failure loads, deflections and strains of welded built-up titanium beams are predictable to a reasonably good level of accuracy. The test beams also demonstrated significant reserve strength and ductility following yielding. The deflection curves and the load versus strain relationships obtained from the test results demonstrate a reasonably close match between the theoretical predictions and experimental test results up until the elastic limit of the material. The fatigue tests conducted for this research revealed that the welded built-up beams made from the commercially pure titanium have better life than those made from the Ti-6Al-4V. However additional work is required to develop further insight into the fatigue behavior of welded built-up titanium beams.

Finally the proposed welded built-up beam approach is anticipated to be a cost effective alternative to fabricating large structural elements and members by machining of the parts from thick plates or billets.

Committee:

Anil Patnaik, Dr (Advisor); Tirumalai Srivatsan, Dr. (Advisor); Dr. Craig Menzemer, PhD (Committee Member)

Subjects:

Civil Engineering

Keywords:

Titanium; Static Tests; Ti-6Al-4V; Fatigue Tests; Welded Built-Up Beams; Commercially Pure Titanium; Structural guidelines for Titanium

Barry, Erin PatriciaThree-Dimensional Reconstruction of Microstructures in α + β Titanium Alloys
Master of Science, The Ohio State University, 2008, Materials Science and Engineering

Titanium and its alloys are comparatively recent newcomers to the metallurgical market. They are gaining widespread acceptance for use in the recreational, aerospace, biomedical, petro-chemical, and commercial processing industries due to their combination of unique and advantageous properties, including high strength, low density, and superior corrosion resistance to most aggressive agents. The material properties of titanium and its alloys can be optimized and tailored by engineering the microstructure via control of chemistry, processing route, and heat treatment. The morphology of the two crystallographic allotropic phases can be manipulated to refine the structure and produce desirable mechanical property combinations. Microstructural constitution of the titanium alloys is classified according to the dominant phase within the alloy; alpha + beta (α + β) titanium alloys are the most widely used alloys. The temperature of the final heat treatment of the α/β components is governed by the service requirements. In order to evaluate the behavior of these alloys for future applications, it is imperative that the microstructural features and characteristics be quantified and examined on a spatial dimension. The Robo-Met.3D is a high precision robotic serial sectioning device that can fulfill this need.

Initially, several months were spent resolving problems with the functioning of the Robo.Met.3D. Two-dimensional (2-D) stereology was done on Timetal 550 using automated batch processing with Adobe Photoshop and Fovea Pro. Images from different locations on the gage were obtained and compared. Final data demonstrated quantitative differences which were the result of the heat treatment. Discrepancies and inconsistencies in the data were identified as limiting factors in the reproducibility of the procedure in future work.

Serial sectioning using focused ion beam (FIB) was performed using Timetal 550, and three-dimensional (3-D) reconstruction was done using IMOD. Robo-Met.3D procedures and algorithms were identified for serial sectioning collection for titanium alloys using Ti-6Al-4V.

Recommendations for future work include developing more efficient procedures for coloring in the microstructural features in the Adobe Photoshop CS™. A new procedure is needed to mount and polish the sample to prevent sample curvature due to the polishing step. Also, the small size of the secondary alpha (α) presents a challenge when examining microstructural features; however, it is imperative that these features be examined in the future to determine their effect on mechanical properties.

Committee:

Hamish Fraser (Advisor); Yunzhi Wang (Committee Member)

Subjects:

Materials Science

Keywords:

titanium alloys; stereology; titanium microstructure; robo-met.3D

Ngendahimana, AimableInvestigation of Novel Routes in the Synthesis of TiNF and Compounds in the Ti-N-O-F System
Master of Science in Chemistry, Youngstown State University, 2010, Department of Chemistry
Titanium nitride fluoride, TiNF, an anion exchange derivative of titanium dioxide, has been a target for synthetic inorganic chemists for some time. No true TiNF compound has been reported to date. A novel route for the synthesis of a TiNF phase has been outlined and tested. The method involves the use of a titanium complex as a precursor for the formation of TiNF and/or a Titanium Oxynitride Fluoride, 'Ti-N-O-F'. A suitable precursor, bis (diethylamidofluoro) titanium [F2(Et2N)2Ti]4 was identified, synthesized, its single crystal structure was determined, and it was used to test the proposed synthetic route towards TiNF. In this work, we propose that titanium complexes of the general formula [F2(Et2N)2Ti]4 undergo a thermal decomposition reaction involving a β-elimination of volatile ethylene from the amide ligands and subsequent loss of equally volatile ammonium fluoride, thus leaving at the end of the thermal decomposition as the only non-volatile product TiNF after all other products escape as gases or highly volatile solids. In the presence of fortuitous air and moisture the non-volatile TiNF is expected to undergo partial hydrolysis to form a 'Ti-N-O-F' phase. The thermal decomposition reaction of TiF2(NEt2)2 has been investigated via Thermal Gravimetric Analysis and the properties of the non-volatile product were analyzed using Powder X-Ray Diffraction, Electron Microscopy and X-Ray Photoelectron Spectroscopy. In a second synthesis route, doping of TiO2 with nitrogen has been achieved by reacting TiO2 with urea. The amount of nitrogen doped into TiO2 using urea is 8.62% by atomic concentration which is about twice the amount of nitrogen doped into TiO2 using other known methods.

Committee:

Timothy Wagner, PhD (Advisor); Allen Hunter, PhD (Committee Member); Clovis Linkous, PhD (Committee Member)

Subjects:

Chemistry; Materials Science

Keywords:

titanium nitride fluoride; Bis(diethylamidofluoro) titanium

Douglass, D. L.The kinetics and mechanism of the conversion of titanium dioxide to titanium nitride /
Doctor of Philosophy, The Ohio State University, 1958, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Titanium dioxide;Titanium nitride

Norfleet, David MSample size effects related to nickel, titanium and nickel-titanium at the micron size scale
Doctor of Philosophy, The Ohio State University, 2007, Materials Science and Engineering
Micron-sized compression specimens, fabricated using a focused ion beam (FIB), indicate a dramatic strengthening effect as sample dimensions are reduced from 20μm to sub-micron diameters in nickel and gold microcrystals. To understand this effect, novel microscopy techniques were utilized to study the mechanical properties and dislocation substructures from microcrystals of pure nickel, Ti-6wt.%Al, Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti-6242) and Ti-50.8at.%Ni. The dislocation behavior that governs plasticity is quite different between each of these materials and as such produces different size effects at small sizes. The nickel compression results indicate a dramatic increase in strength as sample dimensions are reduced. Quantitative dislocation density measurements performed on slip-plane TEM foils extracted from nickel microcrystals indicate an increase in stored dislocation density at smaller sizes. However, hardening contributions from forest-hardening and source truncation hardening were insufficient in explaining the high observed flow stresses. This result suggests that other hardening mechanism are operating in the nickel microcrystals. The titanium alloys exhibit a much less dramatic strengthening effect compared to the nickel microcrystals. The titanium microcrystals, at all sample sizes tested (1-60μm), are stronger than bulk compression specimens. Even at the 60μm sizes bulk behavior is not observed, while at only 20 microns nickel microcrystals exhibit bulk properties. Transmission electron microscopy (TEM) investigations indicate several dislocation pile-ups of both screw and edge character at the microcrystal surfaces. These pile-ups appear to be related to ion damage induced by the fabrication of these samples, resulting in a strengthening effect that follows a Hall-Petch relationship. Nickel-Titanium alloys deform through a phase transformation, as well as dislocation motion. The microcrystal compression results indicate no observable size effect related to the strength of the 5μm and 20μm crystals. TEM studies indicate an increase in dislocation activity, <100>{110}, with the number of loading cycles. However, determining the relationship between plasticity and the martensitic transformation was inconclusive.

Committee:

Michael Mills (Advisor)

Subjects:

Engineering, Materials Science

Keywords:

sample size effects; intrinsic size effects; FIB; titanium; nickel; nickel-titanium; TEM; density measurements; plastic deformation

Matic, NikolaSURFACE SCIENCE ASPECTS OF ELECTROCATALYSIS
Doctor of Philosophy, Case Western Reserve University, 2014, Chemistry
A multilayer system denoted as Pt/TiN/Ti/Si(111) was created in UHV. Chemical and physical properties of these layers were studied with XPS and ARXPS. Results of the analysis shows that a ca. 1nm thick titanium nitride layer between platinum and silicon was sufficient to stop diffusion of Pt to Si at room temperature. Nature of the interaction of thin layers of Pt on titanium nitride showed that initially deposited monolayer of Pt produced Pt/Ti intermetallic compound while properties of subsequent layers suggested metallic Pt. Relevance and conclusions were discussed in relation to titanium nitride as a catalyst support in PEM fuel cells. Hydroxylamine was successfully deposited in UHV on well characterized clean and oxygen covered Pt(100). RAIRS analysis suggests specific orientation of hydroxylamine molecule on clean Pt(100) and non-specific adsorption in case of oxygen covered Pt(100). Subsequent heating was followed by desorption in case of clean Pt(100) and by chemical reaction in case of oxygen covered Pt(100).Relevance and conclusions were discussed in relation to nitrogen cycle and electrocatalytic denitrification.

Committee:

Daniel Scherson (Advisor); Carlos Crespo (Committee Chair); Alfred Anderson (Committee Member); Gary Chottiner (Committee Member); Frank Ernst (Committee Member)

Subjects:

Chemistry; Physical Chemistry; Physics

Keywords:

Artificial photosynthesis; titanium nitride diffusion barrier for silicon and platinum; titanium nitride as a catalyst support; PEM catalyst support; Hydroxylamine adsorption on Pt 100; RAIRS of Hydroxylamine; Hydroxylamine in UHV; Nitrogen cycle

Riggs, Mark R.TIG Welding of Nickel Titanium to 304 Stainless Steel
Master of Science, The Ohio State University, 2014, Mechanical Engineering
Nickel-titanium is a shape memory alloy capable of producing high stresses with an 8% maximum recoverable strain. The rotation of a nickel-titanium (NiTi) torque tube can be controlled by thermally cycling the material through its critical martensite and austenite temperatures. Transforming the phase of NiTi corresponds to a change in its crystalline structure and a macroscopic change in shape. This change in shape, through a controlled thermal input, lends itself well to powering a solid-state actuator. Shape memory alloys can in some cases replace traditional actuators, for instance in harsh aerospace environments where lightweight operation is critical. NiTi is effective as a solid-state actuator, but it is very difficult to machine. The poor machinability of NiTi drives the cost and complexity of system integration to the point where its widespread use is hindered. The general solution is to join NiTi to a structural material and machine the structural material for system integration. Several types of joining methods have been studied such as ultrasonic soldering, adhesives, and laser welding. This study focuses on tungsten inert gas (TIG) welded joints between 304 stainless steel and NiTi tubing. A nickel filler is used in TIG welding of NiTi to 304SS to prevent brittle intermetallics formed by titanium and iron in the weld pool. The thickness of the nickel filler and the current required to create a strong TIG weld in torsion failure is investigated in a Taguchi L9 full factorial test matrix. Based on ultimate failure torque test results and welding observations, a 0.050'' filler thickness with an 85 A starting current was chosen for thermocycling tests with a constant load. The chosen joint parameters produce an average ultimate failure torque of 371 in-lb (41.9 N-m) with a shear strength of 41 ksi (282 MPa). EDS analysis of 0.025'' and 0.075'' filler thickness welds confirm observations from welding and test data with a crack caused by TiFe intermetallics in the 0.025'' filler weld and minimal weld penetration on the 304SS interface with the 0.075'' filler thickness. Results from dye penetrant tests, ultimate failure test data, and sectioned weld analysis were used to gain understanding of TIG welding NiTi to 304SS.

Committee:

Marcelo Dapino, Dr. (Advisor); Mark Walter, Dr. (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

nickel; titanium; nickel-titanium; TIG; tungsten inert gas welding; Mark Riggs; Dapino; Ohio State; Mechanical Engineering; nickel filler; joining; structural material; tungsten inert gas; Marcelo Dapino; torque tube

Ki, Jun-WanTitanium Sponge on Titanium Substrate for Titanium Electrolytic Capacitor Anodes
Doctor of Philosophy, Case Western Reserve University, 2005, Materials Science and Engineering
Capacitors are energy storage devices capable of supplying electric energy. Volumetric and gravimetric energy storage efficiencies are some of the important criteria for evaluating electrolytic capacitors as energy storage devices. High energy density capacitors can be achieved by anodic growth of a dielectric film on surface enhanced valve-metal. Electrodes with high surface area accessible along with wide and short conduction paths (electrolyte) have advantages as power devices. Surface-enhanced metal substrates can be made by various methods. One method is by oxidation followed by reduction. Oxidation of a metal and reduction of oxide are generally associated with volume changes. During growth of an oxide scale on a metal substrate, the volume expansion of an attached oxide scale can only occur in the thickness direction. During subsequent reduction of the oxide volume shrinkage occurs. It can take place along all directions, in particular in the plane of the oxide scale. This shrinkage leads to pores in the metal layer that is formed by the reduction of the oxide scale. Therefore, a layer of titanium sponge can be obtained by the oxidation plus reduction method. The titanium sponge layer can be anodized in order to grow a thin dielectric film on the surface of the sponge metal. In this way it is made into a capacitor anode. Reduction of titanium oxide scale with magnesium or calcium produces titanium sponge with different morphologies. Magnesium-reduced sponge has a higher degree of porosity than calcium-reduced sponge. The different morphologies of the reduced oxide scale result from different reduction behaviors in the presence of magnesium or calcium. Possible mechanisms are suggested to explain how magnesium and calcium affect the reduction behavior of titanium oxide. Because titanium anodic films tend to have high leakage current, titanium is not used for commercial electrolytic capacitor anodes. Nitrogen and oxygen doping of titanium surface layer enables the growth of a doped anodic titanium film and can decrease leakage current of titanium anodic film. Leakage current of titanium anodic film decreases with higher [N + O] doping level. TEM micrograph shows that such doped titanium anodic film has an improved micro-structure.

Committee:

Gerhard Welsch (Advisor)

Subjects:

Engineering, Materials Science

Keywords:

Capacitor; Electrolytic capacitor; Dielectric film; Anodic film; Anodic titanium oxide film; Metal Sponge; Surface Enhancement; Titanium Oxide

Bloss, Matthew CUltrasonic metal welding: the weldability of stainless steel, titanium, and nickel-based superalloys
Master of Science, The Ohio State University, 2008, Welding Engineering
Ultrasonic metal welding (UMW) is a solid-state joining process in which materials are held together under moderate forces while applying localized high frequency shear vibrations, creating a true metallurgical bond. While ultrasonics have been applied extensively to joining soft materials, such as copper and aluminum, applications for joining more advanced materials are limited. UMW has generally not been considered for more advanced materials due to poor tooling life and inadequate ultrasonic power levels. In a relatively short period of time, developments in UMW equipment and potential tool materials, may allow UMW to be applied to these more advanced metals. Using commercially-available ultrasonic spot welding equipment, the ultrasonic weldability of 304 and 410 stainless steel, commercially pure and 6Al-4V titanium, and Nickel-base superalloys 625 and 718 was investigated. Tool materials developed for friction-stir weld tooling were used to develop new ultrasonic tools. Tool textures and designs were also evaluated.

Committee:

Karl Graff (Advisor)

Keywords:

Ultrasonic Metal Welding; Materials Joining; Solid State; Welding; Titanium; Stainless Steel; Nickel; Tungsten; Ultrasonic Tool; Weldability; Ultrasonics

Corwin, Peter ESynthesis and Characterization of Titanium Zirconium Based Alloys for Capacitor Use
Master of Sciences (Engineering), Case Western Reserve University, 2013, Materials Science and Engineering
This work seeks to characterize a series of Ti-Zr binary alloys and a ternary Ti-Zr-Be alloy as anode materials for electrolytic capacitors. Specifically, this work attempts to improve the electrical behavior by reducing leakage through anodically grown oxide film on binary alloys via microstructure modifications. It also examines creep of Ti25Zr38Be37 metallic glass for surface enhancement. A variety of mechanical and electrical properties were measured. Leakage current through the anodic dielectric was found to decrease with increasing zirconium content. Alloy treatments which produce concentration gradients (a, a+ß fields) increased dielectric leakage; treatments maintaining uniform composition (as cast, wrought) retain low dielectric leakage current. UTS was fit to a solid solution model which compares well with related literature. Estimates of viscosity for Ti25Zr38Be37 metallic glass were made at various temperatures and resulting surface texturing examined. Long term creep rate change was fit to exponential decay with a time constant of 7.9x103s.

Committee:

Gerhard Welsch (Advisor); John Lewandowski (Committee Member); Mark DeGuire (Committee Member)

Subjects:

Materials Science; Metallurgy

Keywords:

Titanium; Zirconium; Beryllium; Ti; Zr; Be; Metallic Glass; Creep; Leakage; Microstructure

Jia, HuiyingAnodized TiO2 Nanotube Film For Controllable Drug Delivery
Master of Science, Miami University, 2013, Chemical, Paper & Biomedical Engineering
TiO2 nanotubes have great potential to improve the performance of Ti implants as a surface coating due to their high surface area, ability to promote bone growth and biocompatibility. However, there are two issues needed to be solved before further advancing TiO2 nanotubes technology as drug carrier: uncontrolled drug release and poor mechanical properties. In this study, a drug carrier using composite of biodegradable polymer/TiO2 nanotubes is engineered. Ibuprofen, carprofen and lidocaine were selected as test drugs. A simple characterization method is developed to investigate the infiltration of polymer into TiO2 nanotubes. The synthesized drug carrier demonstrated much better sustained drug release profile, greatly improved mechanical strength and flexibility compared to pure TiO2 nanotubes coating. It has also been found that the drug release kinetics using the synthesized drug carrier is controlled mainly by the drug solubility, polymer degradation and electrostatic force between drug and polymer which are pH dependent.

Committee:

Lei Kerr (Advisor); Shashi Lalvani (Committee Member); Catherine Almquist (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Titanium dioxide nanotubes; drug delivery; biodegradable polymer; PLGA

Wang, JunweiChemical doping of metal oxide nanomaterials and characterization of their physical-chemical properties
Doctor of Philosophy, Case Western Reserve University, 2012, Chemistry

Energy and environment are vital to every aspect of our daily lives. It is paramount to have a new source of energy before the exhaustion of fossil fuels to prevent a setback in the standard of living in which we have grown accustomed to and to have emission of greenhouse gases under control to deflect tremendous global ecological tragedy. Photocatalysis using solar energy is considered by many as the most promising solution for both energy and environment. Among all the photocatalysts under research, titanium dioxide (TiO2) remains one of the most studied for decades. Reducing its bandgap via doping is crucial to harvest visible-light, which accounts for 48% of the total solar energy. In addition, it is very important to keep the particle size small to avoid recombination of the photo-generated electrons and holes.

In this dissertation, metal and / or non-metal elements have been used as dopants to modify the electronic structure of TiO2. Special synthesis techniques have been chosen so that the particle size is in the nano-regime. Various techniques such as X-ray diffraction patterns (XRD), Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy (UV-DRS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) have been used to obtain detailed information of the crystal structure, light-absorbing property, organic remains, particle appearance, size distribution and elemental compositions, respectively. Based on the characterization results, we have successfully introduced doping levels into TiO2 to reduce its band gap and thus made the prepared materials visible-light reactive. The sizes of the products are controlled in nano-scale. For all the photocatalysts tested, the performance for the decomposition of methylene blue can be ranked as follows: Ga,N-TiO2 > N-TiO2 > Co,N-TiO2 > Fe-TiO2 Fe,N-TiO2. Furthermore, there have been other important discoveries such as the observation of phenomena similar to that of nitrogen fixation in the Fe-TiO2 experiment and the observation of the surprising reducing properties of commercial material Cab-o-sil.

Committee:

Clemens Burda (Advisor)

Subjects:

Chemistry

Keywords:

doped titanium dioxide; photocatalysis; nanomaterial

RODRIGUEZ-LATTUADA, SYLIAN JOYIN SITU GENERATED SORBENTS FOR MERCURY CAPTURE IN COMBUSTOR EXHAUSTS: ROLE OF OTHER PARTICLES AND WATER VAPOR
MS, University of Cincinnati, 2001, Engineering : Environmental Engineering
Mercury emissions from combustion exhausts have been reported to be a great concern, taking into account the risk to public health, due to its high volatility, tendency to bio-accumulate and toxic properties. Several control methodologies have been used, but low capture efficiencies are usually obtained with conventional air pollution control devices. Titanium oxide-based sorbents offer a low cost alternative, have demonstrated to be very effective at capturing Hg, and under controlled conditions, this appeared to work with efficiencies as high as 96%. More realistic environments were investigated in this study to test the effectiveness of the novel sorbent injection technology. As a model of fly ash in combustion exhausts, silica particles were introduced into the reaction system, to investigate their influence on mercury capture. Mercury removal efficiencies were remarkably improved by increasing the molar ratio of titania/silica. A steady state was observed when particles were separately generated, which was explained by two effects: 1) a shielding effect by silica particles and 2) a Ti-Si competition for water molecules. The importance of the point of injection of a sorbent precursor in a real combustion system was also discussed. The role of water vapor on the removal efficiency of Hg was also investigated to evaluate the initial reaction rates of mercury oxidation. As the water vapor concentration increased, more OH - radical species were generated on the surface of the titania particle, increasing the number of active sites for the photo-oxidation. Therefore the initial reaction rates of Hg were shown to occur faster, improving the mercury capture in the first minutes of reaction. A kinetic model containing three parameters was developed to accurately describe the experimental data for the photo-oxidation of mercury by UV irradiated titania particles. Parallel studies were conducted with novel iodine sorbent processes at room temperature for their feasibility for mercury capture in gas streams. Rather high capture efficiencies (> 98%) of elemental mercury were obtained using the potassium iodide sorbent particles, due to the submicrometer particles with high surface area in which Hg vapors were condensed and oxidized. Agglomerated sorbent particles with high surface area per unit mass were generated by nebulizing potassium iodide solutions. It was also demonstrated by a series of experiments that commercially available KI crystals and iodine gas removed Hg 0 , showing the potential to scale up for applicability in pilot systems.

Committee:

Dr. Pratim Biswas (Advisor)

Subjects:

Engineering, Environmental

Keywords:

coal combustion; mercury; sorbent; potassium iodide; titanium oxide

SUBRAMANIAM, SRINIVASEFFECTS OF PROCESSING ON PTCR BARIUM TITANATE SYSTEMS WITH BARIUM OXIDE AND TITANIUM OXIDE ADDITIONS IN THE NEAR STOICHIOMETRIC REGION
MS, University of Cincinnati, 2003, Engineering : Materials Science
Barium oxide and titanium oxide additions were made to modify base Ba-excess and Ti-excess BaTiO3 powders towards the near stoichiometric region, to understand and control microstructure evolution and PTCR properties in these materials during processing. Microstructure and properties exhibited by these systems were compared with stoichiometric blended systems in literature which exhibit high density uniform fine grained microstructures. TiO2 additions do not have any effect on the solution behavior of the system being insoluble in aqueous media in the observed pH ranges. BaO additions modify the solution behavior of the system increasing the pH of the solution. TEM studies on powders with TiO2 additions show double-layer formations on the particle surfaces suggesting Barium dissolution from the BaTiO3 particle surfaces. Powders with BaO additions exhibit a single layer formation on the particle surfaces suggestive of BaO dissolution and redeposition occurring during milling and drying. Dissolution of BaO additions in solution considerably reduces dissolution from BaTiO3 particle surfaces. Surface states were however found to play a lesser role on microstructure and property evolution with high temperature processes dominating grain growth and densification in these systems. Near stoichiometric systems prepared through oxide additions have bimodal microstructures with the absence of second phase regions across the range of sintering temperatures used in this study. Inhomogenities in the system coupled with modified surface states and localized variations in the material may be responsible for this behavior. These systems exhibit a minimal PTC rise (=2 orders) when compared with Ti-excess systems which exhibit a PTC rise of ~4 orders. Higher porosity coupled with low grain boundary coherence and large amounts of second phase in the grain boundary regions appear to be responsible for the enhanced PTC properties suggesting these mechanisms and their control to be dominant in obtaining high-rise PTC systems.

Committee:

Dr. Rodney Roseman (Advisor)

Subjects:

Engineering, Materials Science

Keywords:

titanium oxide; barium oxide; barium titanate; PTCR; processing

Pawar, VishalUse of laminar ESP for the capture of titanium dioxide particles
Master of Science (MS), Ohio University, 2004, Mechanical Engineering (Engineering)
Use of laminar ESP for the capture of titanium dioxide particles

Committee:

David Bayless (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

Laminar ESP; Titanium Dioxide Particles

Rymer, Dawn LeeThe atmospheric chemical vapor deposition of titanium nitride on polyimide substrates
Master of Science (MS), Ohio University, 1995, Chemical Engineering (Engineering)

The atmospheric chemical vapor deposition of titanium nitride on polyimide substrates

Committee:

Daniel Gulino (Advisor)

Subjects:

Engineering, Chemical

Keywords:

Atmospheric Chemical Vapor Deposition Titanium Nitride; Polyimide Substrates

McGovern, William RobertCharacterization of carbon-molecule-metal junctions by cyclic voltammetry, raman spectroscopy and X-Ray photoelectron spectroscopy
Doctor of Philosophy, The Ohio State University, 2005, Chemistry
Nitroazobenzene (NAB) diazonium salts were reduced with cyclic voltammetry scans to derivatize pyrolyzed photoresist (PPF) surfaces. This process resulted in covalently bonded NAB on the PPF surface, as shown by XPS and Raman spectroscopy. Junction top contacts were fabricated by using various deposition conditions and metal layers including titanium, copper, aluminum, silver and gold. Junction low voltage resistance, current density and properties of aging molecular junctions will be discussed, along with their role in electron injection for NAB. The PPF/NAB/Ti/Au junctions are examples of monolayer molecular electronic devices with covalent bonding between the contacts and the molecular layer. Electron transfer through the molecular layer was found to be a strong function of molecular structure as well as molecular thickness. The pressure in the electron beam chamber during metal deposition was found to have a large effect on junction resistance in titanium junctions, and to a lesser extent with copper junctions. Both high and low oxide junctions are discussed with titanium being the most commonly used metal. Electronic and Raman characterization of different metal top contact molecular junctions was performed. Raman intensity ratios were used to characterize reduction of the NAB molecular layer with different metal top contacts. XPS characterization was used to show the surface bonding between the molecule and metal contact, as well as oxide characterization in the junction metal contact. Depth profiling using Argon ion sputtering was used to determine depth-resolved composition inside fabricated molecular junctions. Five different metals were used with PPF/NAB(3.7nm). Aluminum junctions were shown to have low conductivity, and high resistance compared to other metals. Titanium junctions deposited at high oxide conditions exhibited semiconductor properties with asymmetric i/V curves that included hysteresis and rectification. At lower deposition pressures, Ti, Cu, Ag and Au all showed symmetric, conductive i/V curves. Ti, Cu and Ag were found to form covalent metal-N bonds at the NAB/metal interface. At higher deposition pressures, the metal oxides present in the top contact contributed significantly to the observed i/V curves for Al, Ti, and to a lesser extent with Cu.

Committee:

Richard McCreery (Advisor)

Keywords:

Metal; Metal Oxide; Electronic Characterization; Cyclic Voltammetry; Carbon/Molecule/Metal Electronic Junctions; Low Temperature Voltammetry; XPS; Raman Spectroscopy; copper; aluminum; silver; gold; chromium; titanium

Foltz, John WendellThe Relationships Between Microstructure, Tensile Properties and Fatigue Life in Ti-5Al-5V-5Mo-3Cr-0.4Fe (Ti-5553)
Doctor of Philosophy, The Ohio State University, 2010, Materials Science and Engineering

β-titanium alloys are being increasingly used in airframes as a way to decrease the weight of the aircraft. As a result of this movement, Ti-5Al-5V-5Mo-3Cr-0.4Fe (Timetal 555), a high-strength β titanium alloy, is being used on the current generation of landing gear. This alloy features good combinations of strength, ductility, toughness and fatigue life in α+β processed conditions, but little is known about β-processed conditions. Recent work by the Center for the Accelerated Maturation of Materials (CAMM) research group at The Ohio State University has improved the tensile property knowledge base for β-processed conditions in this alloy, and this thesis augments the aforementioned development with description of how microstructure affects fatigue life.

In this work, β-processed microstructures have been produced in a GleebleTM thermomechanical simulator and subsequently characterized with a combination of electron and optical microscopy techniques. Four-point bending fatigue tests have been carried out on the material to characterize fatigue life. All the microstructural conditions have been fatigue tested with the maximum test stress equal to 90% of the measured yield strength. The subsequent results from tensile tests, fatigue tests, and microstructural quantification have been analyzed using Bayesian neural networks in an attempt to predict fatigue life using microstructural and tensile inputs. Good correlation has been developed between lifetime predictions and experimental results using microstructure and tensile inputs. Trained Bayesian neural networks have also been used in a predictive fashion to explore functional dependencies between these inputs and fatigue life.

In this work, one section discusses the thermal treatments that led to the observed microstructures, and the possible sequence of precipitation that led to these microstructures. The thesis then describes the implications of microstructure on fatigue life and implications of tensile properties on fatigue life. Several additional experiments are then described that highlight possible causes for the observed dependence of microstructure on fatigue life, including fractographic evidence to provide support of microstructural dependencies.

Committee:

James Williams (Advisor); Hamish Fraser (Committee Member); Katharine Flores (Committee Member)

Subjects:

Materials Science

Keywords:

titanium; fatigue; beta alloy; microstructure; neural network; fracture; tensile properties; bayesian;

ALMQUIST, CATHERINE L. BOTHETHE SYNTHESIS AND CHARACTERIZATION OF NANOSTRUCTURED TITANIUM DIOXIDE PHOTOCATALYSTS AND THEIR PERFORMANCE IN SELECTED ENVIRONMENTAL AND INDUSTRIAL APPLICATIONS
PhD, University of Cincinnati, 2001, Engineering : Environmental Engineering
Although there has been much interest in photocatalysis, there are currently few commercial applications of photocatalysis currently in use because of two developmental challenges: 1) a relatively low quantum efficiency, and 2) the requirement of near ultraviolet light energy (λ< 380 nm). In this investigation, methods to enhance the quantum efficiency were investigated. The photo-oxidation of phenol was selected to compare the efficiency of the photocatalytic process under varying photocatalyst and reaction conditions. Research efforts focused on the effects of dissolved oxygen in the reaction slurry and particle size of the TiO 2 powders on the photo-oxidation rate of phenol in water. The results show that the rate of photo-oxidation of phenol in water is a strong function of dissolved oxygen when the water contains less oxygen that air-saturated water, and under conditions of relatively high organic concentrations (1 mM or greater), the solubility of oxygen in water may limit the photo-oxidation rate of phenol. The rate of photo-oxidation of phenol decreased sharply with decreasing particle size of TiO 2 when the primary particle size was less than 30 nm. Both optical properties (light absorption and light scattering efficiencies) and charge dynamics change in this range of particle sizes, causing the sharp decrease in the photo-oxidation rate as particle size decreases from 30 nm. At particle sizes greater than 30 nm, however, surface area plays a key role in photocatalysis, and a maximum photo-oxidation rate of phenol was observed at particle sizes of approximately 30 nm. Several iron-doped TiO 2 powders were synthesized using a flame-aerosol method. The iron concentration and point of iron introduction into the flame were varied. The results show diminished apparent photoactivity when the iron is introduced to the flame pre-mixed with the TiO 2 precursor, but very little change in photoactivity at iron concentrations up to 1 percent when the iron and TiO 2 precursors were introduced separately into the flame. The incorporation of the iron in the crystal lattice occurs when the precursors are pre-mixed prior to the flame, and under such conditions, a lower anatase fraction and less crystallinity was observed in the TiO 2 powder, significantly contributing to the observed decrease in photo-activity. No significant changes in anatase fraction and crystallinity were observed when the precursors were introduced to the flame separately, thus the photo-activity of TiO 2 was maintained. Finally, photocatalysis was investigated in two specific applications: 1) the photo-oxidation of MTBE in ground water, and 2) the partial photo-oxidation of cyclohexane to produce cyclohexanol and cyclohexanone. A falling film reactor design was used to compare the MTBE photo-oxidation rates in synthetically-contaminated and in actual field samples of MTBE-contaminated ground water. The MTBE photo-oxidation rate was much faster in synthetically-contaminated water than in the field samples, and competitive adsorption between MTBE, aromatic species, dissolved metals and ions, and oxygen in the field samples was the likely reason for the observed differences. The role of competitive adsorption was highlighted in the study on the partial photo-oxidation of cyclohexane. It was shown that competitive adsorption can affect both product selectivity and product formation rate in the photo-oxidation of cyclohexane.

Committee:

Dr. Pratim Biswas (Advisor)

Subjects:

Engineering, Environmental

Keywords:

TITANIUM DIOXIDE; PHOTOCATALYST

Gao, TongzhaiAnticorrosive Organic/Inorganic Hybrid Coatings
Doctor of Philosophy, University of Akron, 2014, Polymer Engineering
Organic/inorganic hybrid coating system was developed for anticorrosion applications using polyurea, polyurethane or epoxide as the organic phase and polysiloxane, formed by sol-gel process, as the inorganic phase. Polyurea/polysiloxane hybrid coatings were formulated and moisture cured using HDI isocyanurate, alkoxysilane-functionalized HDI isocyanurate, and tetraethyl orthosilicate (TEOS) oligomers. Two urethanes were prepared using the same components as abovementioned in addition to the oligoesters derived from either cyclohexane diacids (CHDA) and 2-butyl-2-ethyl-1,3-propanediol (BEPD) or adipic acid (AA), isophthalic acid (IPA), 1,6-hexanediol (HD), and trimethylol propane (TMP). Accelerated weathering and outdoor exposure were performed to study the weatherability of the polyurethane/polysiloxane hybrid coating system. FTIR and solid-state 13C NMR revealed that the degradation of the hybrid coatings occurred at the urethane and ester functionalities of the organic phase. DMA and DSC analyses showed the glass transition temperature increased and broadened after weathering. SEM was employed to observe the change of morphology of the hybrid coatings and correlated with the gloss variation after weathering. Rutile TiO2 was formulated into polyurethane/polysiloxane hybrid coatings in order to investigate the effect of pigmentation on the coating properties and the sol-gel precursor. Chemical interaction between the TiO2 and the sol-gel precursor was investigated using solid-state 29Si NMR and XPS. The morphology, mechanical, viscoelastic, thermal properties of the pigmented coatings were evaluated as a function of pigmentation volume concentration (PVC). Using AFM and SEM, the pigment were observed to be well dispersed in the polymer matrix. The thermal stability, the tensile modulus and strength of the coatings were enhanced with increasing PVC, whereas the pull-off adhesion and flexibility were reduced with increasing PVC. Finally, the pigmented coatings were evaluated by electrochemical impedance spectroscopy (EIS) and the results showed that 10 wt% pigmentation improved the corrosion resistance of the entire coating system. The effect of pigmentation on epoxide/polysiloxane hybrid coatings was also investigated. The epoxide was successfully modified using 3-(triethoxysilyl) propyl isocyanate (TEOSPI) as indicated by FTIR and NMR. Good dispersion of the pigment particles was achieved as revealed by the SEM images. The tensile modulus, tensile strength, pencil hardness and thermal stability of the hybrid coatings were improved while the flexibility and pull-off adhesion were deteriorated when increasing PVC.

Committee:

Mark Soucek, Dr. (Advisor); Avraam Isayev, Dr. (Committee Member); Xiong Gong, Dr. (Committee Member); Chrys Wesdemiotis, Dr. (Committee Member); David Perry, Dr. (Committee Member)

Subjects:

Polymers

Keywords:

hybrid coatings; sol-gel process; accelerated weathering; outdoor exposure; pigmentation; titanium dioxide; corrosion resistance

Sosa, John ManuelDevelopment of Tools for 2D and 3D Microstructural Characterization and Their Application to Titanium Alloy Microstructures
Doctor of Philosophy, The Ohio State University, 2015, Materials Science and Engineering
Stereology, the science of estimating three-dimensional quantities from two-dimensionally acquired measurements, has historically been the sole technique for microstructural quantification. Over the last decade, 3D characterization has begun to replace stereology with direct 3D quantification. While direct 3D quantification offers several advantages over stereology such as the absence of sectioning variation and superior quantification of complex shapes, it is not without its limitations. Many in the 3D materials science community recognize the limited statistical confidence in most reconstructed volumes. Therefore, one objective of this work involved the use statistical tools such as random sampling and bootstrapping to establish quantitative relationships between sampled volume size and measurement precision for a variety of metrics across several microstructures. These quantitative relationships offered a unique opportunity. By determining analogous relationships between the precisions of two-dimensionally acquired metrics versus the amount of sampled area, a comparison between the representative area element (RAE) and representative volume element (RVE) has be made for a given precision. Such a comparison has served to advance the understanding of the influence of sectioning variation on stereological precision. Quantified relationships for several titanium microstructures will be presented along with a methodology to determine such relationships in other microstructures. In addition to exploring the influence of sectioning variation on various stereological metrics, 3D characterization can serve to either validate or invalidate stereological assumptions. A common stereological metric is the mean linear intercept. Measured from a series of random lines placed within a segmented microstructure, the mean linear intercept has been employed to estimate three-dimensional quantities such as the mean diameter of spheroidal precipitates and mean width of plate-like features. In both cases, the constitutive equations rely of several assumptions regarding the shape and size distribution of the intercepted features. For features such as equiaxed-a and a-laths in a+ß titanium alloys, this thesis will explore the validity of these assumptions and determined the sensitivity of stereological quantification to deviations from such assumptions. Three-dimensional materials characterization has undoubtedly advanced the understanding of numerous materials science phenomena and revealed the complexity of various microstructural features. The increasing number of applications of 3D characterization has established a series of processing procedures, the majority of which involve post-acquisition processing and analysis. As data acquisition techniques continue to advance and emerge, the need for more robust, materials science focused, analytical 3D software has become evident. This has led to the development of an all-inclusive, user-friendly software package known as MIPAR™ (Materials Image Processing and Automated Reconstruction). MIPAR™ was written and developed within the MATLAB™ environment, but is deployable as a standalone cross-platform application. MIPAR™ is structured around a modular layout. With a total of five modules, MIPAR™ was designed to handle all post-acquisition stages of 3D characterization: alignment, pre-processing, segmentation, visualization, and quantification. Its development has both driven the implementation of several 2D/3D filtering, segmentation, and quantification tools, and yielded a framework which can easily absorb additional processing techniques and serve as a launching platform for efficient algorithm development, implementation, and deployment. In this work, MIPAR™, and the developed algorithms which it contains, have been applied for the 2D and 3D characterization of various titanium alloys. In the area of 3D characterization, results of MIPAR’s application have included validation of long-standing stereological relationships, the emergence of an assumption-free metric for estimating plate-like feature thickness, and the successful segmentation of challenging microstructural features known as a-colonies. With regard to 2D characterization, MIPAR™ has proven an effective platform for rapid microstructural characterization, where the results have been correlated with local mechanical properties and revealed a strong relationship between a-lath thickness and the degree of local strain. Furthermore, an advanced algorithm has been developed and applied for the segmentation of different phases from atomic-resolution electron micrographs and has also permitted a quantification of their structural interface width. This thesis was able to accomplish many of its objectives and in some cases close areas of formerly open research. However, many areas still offer exciting opportunities for future work. The subjects of such work will be discussed in detail throughout the subsequent chapters.

Committee:

Hamish Fraser (Advisor); David McComb (Committee Member); Michael Mills (Committee Member)

Subjects:

Materials Science; Metallurgy

Keywords:

3D; three-dimensional; characterization; titanium

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