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Fractography and Mechanical Properties of Laminated Alumina and Yttria Stabilized Zirconia

Description: Yttria stabilized zirconia (YSZ) is a polymorph with possible phase transformation toughening occurring during impact. The fractography and mechanical properties of laminated alumina and YSZ were studied in this thesis. Five sample types were studied in this thesis: (5:5) Al2O3/YSZ (a sequence of 5 alumina tapes stacked on 5 YSZ tapes), (5:5) Al2O3/YSZ (1 wt.% Pure ZrO2), (7:3) Al2O3/YSZ, Al2O3, and YSZ. Scanning electron microscopy (SEM) and X-ray microscopy (XRM) were used to study morphology… more
Date: December 2021
Creator: Cotton, Shomari Johnny
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

High Temperature Water as an Etch and Clean for SiO2 and Si3N4

Description: An environmentally friendly, and contamination free process for etching and cleaning semiconductors is critical to future of the IC industry. Under the right conditions, water has the ability to meet these requirements. Water becomes more reactive as a function of temperature in part because the number of hydronium and hydroxyl ions increase. As water approaches its boiling point, the concentration of these species increases over seven times their concentrations at room temperature. At 150 °C, … more
Date: December 2018
Creator: Barclay, Joshua David
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Processing-Structure-Property Relationships of Spark Plasma Sintered Boron Carbide and Titanium Diboride Ceramic Composites

Description: The aim of this study was to understand the processing – structure – property relationships in spark plasma sintered (SPS) boron carbide (B4C) and B4C-titanium diboride (TiB2) ceramic composites. SPS allowed for consolidation of both B4C and B4C-TiB2 composites without sintering additives, residual phases, e.g., graphite, and excessive grain growth due to long sintering times. A selection of composite compositions in 20% TiB2 feedstock powder increments from 0% to 100%, was sintered at 1900°C… more
Date: May 2018
Creator: Rubink, William S.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Modified epoxy coatings on mild steel: A study of tribology and surface energy.

Description: A commercial epoxy was modified by adding fluorinated poly (aryl ether ketone) and in turn metal micro powders (Ni, Al, Zn, and Ag) and coated on mild steel. Two curing agents were used; triethylenetetramine (curing temperatures: 30 oC and 70 oC) and hexamethylenediamine (curing temperature: 80 oC). Variation in tribological properties (dynamic friction and wear) and surface energies with varying metal powders and curing agents was evaluated. When cured at 30 oC, friction and wear decreased sig… more
Date: August 2009
Creator: Dutta, Madhuri
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Processing-Structure Relationships of Reactive Spark Plasma Sintered Diamond Composites

Description: Traditional lightweight armor ceramics such as boron carbide (B4C) and silicon carbide (SiC) are used alone or together in varying amounts to create monolithic protective plates. These materials exhibit relatively small differences in hardness, flexure strength, and fracture toughness. Many of the routes taken during the synthesis of the powder and sintering of the plates using traditional ceramic processing techniques have long processing times, tend to leave asperities within the microstruc… more
Date: August 2022
Creator: Garcia, Christian
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

P-type Doping of Pulsed Laser Deposited WS2 with Nb

Description: Layered transition metal dichalcogenides (TMDs) are potentially ideal semiconducting materials due to their in-plane carrier transport and tunable bandgaps, which are favorable properties for electrical and optoelectronic applications. However, the ability to make p-n junctions is the foundation of semiconductor devices, and therefore the ability to achieve reproducible p- and n-type doping in TMD semiconducting materials is critical. In this work, p-type substitutional doping of pulsed laser d… more
Date: December 2017
Creator: Egede, Eforma Justin
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Measurement of Lattice Strain and Relaxation Effects in Strained Silicon Using X-ray Diffraction and Convergent Beam Electron Diffraction

Description: The semiconductor industry has decreased silicon-based device feature sizes dramatically over the last two decades for improved performance. However, current technology has approached the limit of achievable enhancement via this method. Therefore, other techniques, including introducing stress into the silicon structure, are being used to further advance device performance. While these methods produce successful results, there is not a proven reliable method for stress and strain measurements o… more
Date: August 2007
Creator: Diercks, David Robert
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Development and Thermo-Mechanical Testing of Low Hysteresis Shape Memory Alloy for Satellite Actuators

Description: Shape memory alloys (SMAs) have gained much attention as a powerful source of actuation due to their improved performance, reduced size, and reduced complexity between components as well as having a high work output density. Their primary mechanism of actuation relies on a non-diffusional cyclic phase transformation from martensite to austenite, where the amount of thermal energy needed per cycle is directly associated with the hysteresis width between the austenite final and martensite final t… more
Date: December 2022
Creator: Montagnoli, Andre Luiz
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Effects of Plasma, Temperature and Chemical Reactions on Porous Low Dielectric Films for Semiconductor Devices

Description: Low-dielectric (k) films are one of the performance drivers for continued scaling of integrated circuit devices. These films are needed in microelectronic device interconnects to lower power consumption and minimize cross talk between metal lines that "interconnect" transistors. Low-k materials currently in production for the 45 and 65 nm node are most often organosilicate glasses (OSG) with dielectric constants near 2.8 and nominal porosities of 8-10%. The next generation of low-k materials wi… more
Date: December 2010
Creator: Osei-Yiadom, Eric
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Adherence/Diffusion Barrier Layers for Copper Metallization: Amorphous Carbon:Silicon Polymerized Films

Description: Semiconductor circuitry feature miniaturization continues in response to Moore 's Law pushing the limits of aluminum and forcing the transition to Cu due to its lower resistivity and electromigration. Copper diffuses into silicon dioxide under thermal and electrical stresses, requiring the use of barriers to inhibit diffusion, adding to the insulator thickness and delay time, or replacement of SiO2 with new insulator materials that can inhibit diffusion while enabling Cu wetting. This stu… more
Date: May 2004
Creator: Pritchett, Merry
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

An Assessment of Uncommon Titanium Binary Systems: Ti-Zn, Ti-Cu, and Ti-Sb

Description: The current study focuses on phase stability and evolution in the titanium-zinc titanium-copper and titanium-antimony systems. The study utilized the Laser Engineering Net Shaping (LENS™) processing technique to deposit compositionally graded samples of three binary system in order to allow the assessment of phase stability and evolution as a function of composition and temperature the material is subjected to. Through LENS™ processing it was possible to create graded samples from Ti-xSb (up … more
Date: May 2015
Creator: Brice, David
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Molecular Dynamics Simulations of the Structures of Europium Containing Silicate and Cerium Containing Aluminophosphate Glasses

Description: Rare earth ion doped glasses find applications in optical and photonic devices such as optical windows, laser, and optical amplifiers, and as model systems for immobilization of nuclear waste. Macroscopic properties of these materials, such as luminescence efficiency and phase stability, depend strongly on the atomic structure of these glasses. In this thesis, I have studied the atomic level structure of rare earth doped silicate and aluminophosphate glasses by using molecular dynamics simulati… more
Date: August 2012
Creator: Kokou, Leopold Lambert Yaovi
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Friction Stir Welding of Dissimilar Metals

Description: Dissimilar metals joining have been used in many industry fields for various applications due to their technique and beneficial advantages, such as aluminum-steel and magnesium-steel joints for reducing automobile weight, aluminum-copper joint for reducing material cost in electrical components, steel-copper joints for usage in nuclear power plant, etc. The challenges in achieving dissimilar joints are as below. (1) Big difference in physical properties such as melting point and coefficient of … more
Date: December 2018
Creator: Wang, Tianhao
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Thermodynamics, Kinetics and Mechanical Behavior of Model Metallic Glasses

Description: The thermophysical properties and deformation behavior of a systematic series of model metallic glasses was investigated. For Zr-based metallic glasses with all metallic constituents, the activation energy of glass transition was determined to be in the range of 74-173 kJ/mol while the activation energy of crystallization was in the range of 155-170 kJ/mol. The reduced glass transition temperature was roughly the same for all the alloys (~ 0.6) while the supercooled liquid region was in the ran… more
This item is restricted from view until January 1, 2026.
Date: December 2023
Creator: Akhtar, Mst Alpona
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Carrier Mobility, Charge Trapping Effects on the Efficiency of Heavily Doped Organic Light-Emitting Diodes, and EU(lll) Based Red OLEDs

Description: Transient electroluminescence (EL) was used to measure the onset of emission delay in OLEDs based on transition metal, phosphorescent bis[3,5-bis(2-pyridyl)-1,2,4-triazolato] platinum(ΙΙ) and rare earth, phosphorescent Eu(hfa)3 with 4'-(p-tolyl)-2,2":6',2" terpyridine (ttrpy) doped into 4,4'-bis(carbazol-9-yl) triphenylamine (CBP), from which the carrier mobility was determined. For the Pt(ptp)2 doped CBP films in OLEDs with the structure: ITO/NPB (40nm)/mcp (10nm)/65% Pt(ptp)2:CBP (2… more
Date: August 2010
Creator: Lin, Ming-Te
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

The Electron Emission Characteristics of Aluminum, Molybdenum and Carbon Nanotubes Studied by Field Emission and Photoemission.

Description: The electron emission characteristics of aluminum, molybdenum and carbon nanotubes were studied. The experiments were setup to study the emission behavior as a function of temperature and exposure to oxygen. Changes in the surface work function as a result of thermal annealing were monitored with low energy ultra-violet photoelectron spectroscopy for flat samples while field emission energy distributions were used on tip samples. The change in the field emission from fabricated single tips expo… more
Date: December 2002
Creator: Sosa, Edward Delarosa
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Hydrophobic, fluorinated silica xerogel for low-k applications.

Description: A new hydrophobic hybrid silica film was synthesized by introducing one silicon precursor (as modifiers) into another precursor (network former). Hybrid films have improved properties. Hydrolysis and condensation of dimethyldiethoxysilane (DMDES) (solvent (EtOH) to DMDES molar ratio R = 4, water to DMDES molar ratio r = 4, 0.01 N HCl catalyst) was analyzed using high-resolution liquid 29Si NMR. It was found that after several hours, DMDES hydrolyzed and condensed into linear and cyclic species.… more
Date: May 2004
Creator: Zhang, Zhengping
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Low Temperature Polymeric Precursor Derived Zinc Oxide Thin Films

Description: Zinc oxide (ZnO) is a versatile environmentally benign II-VI direct wide band gap semiconductor with several technologically plausible applications such as transparent conducting oxide in flat panel and flexible displays. Hence, ZnO thin films have to be processed below the glass transition temperatures of polymeric substrates used in flexible displays. ZnO thin films were synthesized via aqueous polymeric precursor process by different metallic salt routes using ethylene glycol, glycerol, citr… more
Date: December 2006
Creator: Choppali, Uma
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Supercritical CO2 foamed biodegradable polymer blends of polycaprolactone and Mater-Bi.

Description: Supercritical CO2 foam processing of biopolymers represents a green processing route to environmentally friendly media and packaging foams. Mater-Bi, a multiconstituent biopolymer of polyester, starch and vegetable oils has shown much promise for biodegradation. The polymer, however, is not foamable with CO2 so blended with another polymer which is. Polycaprolactone is a biopolymer with potential of 4000% change in volume with CO2. Thus we investigate blends of Mater-Bi (MB) and polycaprolacton… more
Date: December 2007
Creator: Ogunsona, Emmanuel Olusegun
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting

Description: There is a wide range of applications for 3D printing technology with an additive manufacturing such as aerospace, automotive, marine and oil/gas, medical, consumer, electronics, building construction, and many others. There have been many pros and cons for 3D additive manufacturing. Even though 3D printing technology has many advantages: freedom to design and innovate without penalties, rapid iteration through design permutations, excellence mass customization, elimination of tolling, green ma… more
Date: December 2015
Creator: Mun, Jiwon
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Dynamic Adhesion and Self-cleaning Mechanisms of Gecko Setae and Spatulae

Description: Geckos can freely climb on walls and ceilings against their body weight at speed of over 1ms-1. Switching between attachment and detachment seem simple and easy for geckos, without considering the surface to be dry or wet, smooth or rough, dirty or clean. In addition, gecko can shed dirt particles during use, keeping the adhesive pads clean. Mimicking this biological system can lead to a new class of dry adhesives for various applications. However, gecko’s unique dry self-cleaning mechanism rem… more
Date: December 2013
Creator: Xu, Quan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Structures of Multicomponent Silicate and Borosilicate Glasses from Molecular Dynamics Simulations: Effects of Iron Redox Ratio and Cation Field Strength

Description: Multicomponent silicate and borosilicate glasses find wide technological applications ranging from optical fibers, biomedicine to nuclear waste disposal. As a common component of earth's mantle and nuclear waste, iron is a frequent encounter in silicate and borosilicate melts and glasses. The redox ratio in glass matrix defined by the ratio of ferrous and ferric ions is dependent on factors such as temperature, pressure, and oxygen fugacity. Understanding their roles on the short- and medium-ra… more
This item is restricted from view until June 1, 2024.
Date: May 2023
Creator: Tuheen, Manzila Islam
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Nanohybrids Based on Solid and Foam Polyurethanes

Description: Polymer nanocomposites are a going part of Materials Science and Engineering. These new composite materials exhibit dimensional and thermal stability of inorganic materials and toughness and dielectric properties of polymers. Development of nanocomposites become an important approach to create high-performance composite materials. In this study silica, fly ash, silica nanotubes and carbon black particles have been added to modify polyurethane foam and thermoplastic polyurethanes. It has been fo… more
Date: May 2015
Creator: Bo, Chong
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Wettability of Silicon, Silicon Dioxide, and Organosilicate Glass

Description: Wetting of a substance has been widely investigated since it has many applications to many different fields. Wetting principles can be applied to better select cleans for front end of line (FEOL) and back end of line (BEOL) cleaning processes. These principles can also be used to help determine processes that best repel water from a semiconductor device. It is known that the value of the dielectric constant in an insulator increases when water is absorbed. These contact angle experiments will d… more
Date: December 2009
Creator: Martinez, Nelson
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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