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Preventing Thermal Degradation of Pvc Insulation by Mixtures of Cross-Linking Agents and Antioxidants

Description: Poly(vinyl chloride)(PVC) wire and cable insulation has poor thermal stability, causing the plasticizer to separate from the PVC chain and produce an oily residue, lowering the tensile elongation at break and thus increasing brittleness. We have added 4 wt.% of three different types of cross-linking agents and antioxidants, as well as mixtures of both, to improve the thermal stability of the plasticizer and tensile properties of PVC after thermal exposure. We performed tensile tests, tribologic… more
Date: May 2018
Creator: Kim, Taehwan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Improving the Long-term Performance of PVC Compositions

Description: PVC are extensively applied in many fields, such as cables, pipes, vehicles, shoes, toys and infusion bags. Generally, plasticizers are blended with PVC to improve the ability of process in industrial production; however, the toxic plasticizers will gradually migrate to the surface of products and such a leakage results in brittleness of plasticized PVC and environmental pollution. In other words, humans are frequently exposed to the potential risks. According to previous researches, cross-link… more
Date: December 2016
Creator: Yang, Yu Chia
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Engineering the Uniform Lying Helical Structure in Chiral Nematic Liquid Crystal Phase: From Morphology Transition to Dimension Control

Description: Chiral nematic liquid crystals or cholesteric liquid crystals (CLC) can be obtained by adding a chiral dopant into a nematic liquid crystal. Liquid crystal molecules spontaneously rotate along a long axis to form helical structures in CLC system. Both pitch size and orientation of the helical structure is determined by the boundary conditions and can be further tuned by external stimuli. Particularly, the uniform lying helical structure of CLC has attracted intensive attention due to its beam s… more
Date: May 2021
Creator: Jia, Zhixuan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Process Improvement of Surface Preparation of Structuraly Bonded Helicopter Detail Parts

Description: The objective of this study was to increase the bond strength at the surface interface of a thin stainless-steel panel for structural bonding on a helicopter. To achieve this objective, six activation methods for applying the coating to the panel in the surface preparation process are presented and explored. Adhesion and roughness tests were conducted to determine which method consistently initiates the etch and improves the bond at the surface. Based on the test results, three methods proved t… more
Date: December 2018
Creator: Tafoya, Keirsten Breann
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Effect of Friction-stir Processing on the Wear Behavior of Titanium (Ti-1Al-8V-5Fe) and Stainless Steel (A-286) Alloys

Description: The effect of friction stir processing (FSP) on the mechanical wear behavior was investigated for Ti-1Al-8V-5Fe (Ti-185) and stainless steel (Incoloy® A-286) alloys. The Ti-185 and A-286 alloys were tested in different processing conditions, including as rolled (AR), AR+FSP, and AR+FSP+aged. A high frequency reciprocating rig was used to simulate fretting-type wear of these alloys at room temperature. The Vickers micro-hardness and wear rates were calculated and compared for each processing co… more
Date: May 2015
Creator: Tinubu, Olusegun Olukunle
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Effects of HALSs and Nano-ZnO Worked as UV Stabilizers of Polypropylene

Description: This work reports the outdoor weathering performance of ultraviolet (UV)-stabilized polypropylene (PP) products (using PP resins from Encore Wire). Different hindered amine light stabilizers (HALSs) and nano-ZnO were used to stabilize PP-film-based formulations that were exposed under UV light for 6 weeks simulating for in harsh outdoor weather of Dallas, Texas, USA in 2016. Characterization of the exposed PP film products was done in terms of mechanical and friction spectroscopic properties. T… more
Date: December 2017
Creator: Lu, Xinyao
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Solid Lubrication Mechanisms in Laser Deposited Nickel-titanium-carbon Metal Matrix Composites

Description: A Ni/TiC/C metal matrix composite (MMC) has been processed using the laser engineered net shaping (LENS) process from commercially available powders with a Ni-3Ti-20C (atomic %) composition. This processing route produces the in-situ formation of homogeneously distributed eutectic and primary titanium carbide and graphite precipitates throughout the Ni matrix. The composite exhibits promising tribological properties when tested in dry sliding conditions with a low steady state coefficient of fr… more
Date: December 2012
Creator: Mogonye, Jon-Erik
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Laser Powder Bed Fusion of H13 Tool Steel: Experiments, Process Optimization and Microstructural Characterization

Description: This work focused on laser powder bed fusion (LPBF) of H13 tool steel to examine microstructure and melt pool morphology. Experiments were conducted with varying laser power (P) in the range of 90-180 W and scan speed (v) in the range of 500-1000 mm/s. layer thickness (l) and hatch spacing (h) were kept constant. Volumetric energy density (γ) was calculated using the above process parameters. In order to find a relation between the recorded density and top surface roughness with changing proces… more
Date: May 2023
Creator: Channa Reddy, Sumanth Kumar Reddy
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Design and Performance of Metal Matrix Composite Composed of Porous Boron Carbide Created by Magnetic Field-Assisted Freeze Casting Infiltrated with Aluminum (A356)

Description: Magnetic field-assisted freeze-casting was used to create porous B4C ceramic preforms. An optimum slurry consisted of a mixture of B4C powders with 6 wt.% Er2O3 powder in an H2O-PVA solution and was cooled at a rate of 1 °C/min from room temperature to -30 °C resulting in porous green state ceramic preform with vertical channels. The Er2O3 powder was added to improve the magnetic response of the slurry. The preform was then sublimated to remove H2O and then sintered. The sintered ceramic prefor… more
Date: May 2022
Creator: Gamboa, Gerardo
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Laser Surface Modification on Az31b Mg Alloy for Bio-wettability

Description: Laser surface modification of AZ31B Magnesium alloy changes surface composition and roughness to provide improved surface bio-wettability. Laser processing resulted in phase transformation and grain refinement due to rapid quenching effect. Furthermore, instantaneous heating and vaporization resulted in removal of material, leading the textured surface generation. A study was conducted on a continuum-wave diode-pumped ytterbium laser to create multiple tracks for determining the resulting bio-w… more
Date: December 2013
Creator: Ho, YeeHsien
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Laser Deposition, Heat-treatment, and Characterization of the Binary Ti-xmn System

Description: The present research seeks to characterization of an additively manufactured and heat-treated Ti-xMn gradient alloy, a binary system that has largely been unexplored. In order to rapidly assess this binary system, compositionally graded Ti-xMn (0<x<15 wt%) specimens were fabricated using the LENS (Laser Engineered Net Shaping) and were subsequently heat-treated and characterized using a wide range of techniques. Microstructural changes with respect to the change in thermal treatments, hardness … more
Date: August 2013
Creator: Avasarala, Chandana
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Scuffing and Wear Prevention in Low Viscosity Hydrocarbon Fuels

Description: To design high pressure fuel system components that resist wear and scuffing failure when operated in low viscosity fuels, a comprehensive study on the tribological performance of various existing coating materials is necessary. This thesis aims to provide the relative performance of a variety of coating materials across different fuel environments by testing them in conditions that model those experienced in fuel pumps. The relative performance of these coatings are then indexed across a varie… more
Date: August 2022
Creator: Dockins, Maddox Wade
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

Processing-Structure-Property Relationships of Reactive Spark Plasma Sintered Boron Carbide-Titanium Diboride Composites

Description: Sintering parameter effects on the microstructure of boron carbide and boron carbide/titanium diboride composites are investigated. The resulting microstructure and composition are characterized by scanning electron microscopy (SEM), x-ray microscopy (XRM) and x-ray diffraction (XRD). Starting powder size distribution effects on microstructure are present and effect the mechanical properties. Reactive spark plasma sintering introduces boron nitride (BN) intergranular films (IGF's) and their eff… more
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Date: August 2019
Creator: Lide, Hunter
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Additive Manufacturing of AZ31B Magnesium Alloy via Friction Stir Deposition

Description: Additive friction stir deposition (AFSD) of AZ31B magnesium alloy was conducted to examine evolution of grain structure, phases, and crystallographic texture. AFSD was carried out using a hollow tool made from tool steel at a constant rotational velocity of 400 rpm on the AZ31B base plate. Bar stock of AZ31B was utilized as a feed material. The linear velocity of the tool was varied in the range of 4.2-6.3 mm/s. The feed rate of the material had to be maintained at a half value compared to the … more
Date: December 2021
Creator: Patil, Shreyash Manojkumar
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

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

Influence of Externally Applied Magnetic Field on the Mechanical Behavior of Paramagnetic Materials

Description: Current ways to alter the microstructure of materials are usually through heat treatments, alloying, and other physical metallurgical methods. Recent efforts in the 21st century are focused on altering the microstructure of a material without physical contact which can be achieved through exposure to a magnetic field (MF). The motivation of this research is to study the quantum effects by subjecting solid-state metals to exposure of MFs. Many of the popular metals currently used in industry are… more
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Date: December 2022
Creator: Reeder, Jessica Phoebe
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

Dislocation Dynamics Simulations of Plasticity in Cu Thin Films

Description: Strong size effects in plastic deformation of thin films have been experimentally observed, indicating non-traditional deformation mechanisms. These observations require improved understanding of the behavior of dislocation in small size materials, as they are the primary plastic deformation carrier. Dislocation dynamics (DD) is a computational method that is capable of directly simulating the motion and interaction of dislocations in crystalline materials. This provides a convenient approach t… more
Date: August 2013
Creator: Wu, Han
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Synchrotron Radiation X-Ray Diffraction of Nickel-Titanium Shape Memory Alloy Wires During Mechanical Deformation

Description: Shape memory alloys (SMAs) are a new generation material which exhibits unique nonlinear deformations due to a phase transformation which allows it to return to its original shape after removal of stress or a change in temperature. It shows a shape memory effect (martensitic condition) and pseudoelasticity (austenitic condition) properties depends on various heat treatment conditions. The reason for these properties depends on phase transformation through temperature changes or applied stress. … more
Date: December 2015
Creator: Zhang, Baozhuo
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

The Effect of Processing Conditions on the Surface Morphology of Few-Layered WS2 Thin Films

Description: Recent progress in layered transition metal dichalcogenides (TMDs) has led to various promising electronic and optoelectronic applications. However, the structure of materials plays a critical role in electronic and optoelectronic devices, and determines performance. Electronic and optoelectronic devices typically consist of multiple layers that form electrical homojunctions or heterojunctions. Therefore, in a device it can be expected that a WS2 layer may serve as the substrate for a subseque… more
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: May 2019
Creator: Cai, Bimin
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

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

Defining a Relationship between the Flexibility of Materials and Other Properties

Description: Brittleness of a polymeric material has a direct relationship with the material's performance and furthermore shares an inverse relationship with that material's flexibility. The concept of flexibility of materials has been understood but merely explained with a hand-waving manner. Thus, it has never been defined by a calculation, thereby lacking the ability to determine a definite quantitative value for this characteristic. Herein, an equation is presented and proven which makes determining th… more
Date: May 2018
Creator: Osmanson, Allison Theresa
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Scratch Modeling of Polymeric Materials with Molecular Dynamics

Description: It is impossible to determine the amount of money that is spent every replacing products damaged from wear, but it is safe to assume that it is in the millions of dollars. With metallic materials, liquid lubricants are often used to prevent wear from materials rubbing against one another. However, with polymeric materials, liquid lubricants cause swelling, creating an increase in friction and therefore increasing the wear. Therefore, a different method or methods to mitigate wear in polymers sh… more
Date: August 2012
Creator: Hilbig, Travis
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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