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Cure Kinetics and Processing Parameters of Neat and Reinforced High Performance Epoxy Resins: Evaluation of Techniques

Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC). … more

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Date: December 1999

Creator: Bilyeu, Bryan

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Preparation and Characterization of a Treated Montmorillonite Clay and Epoxy Nanocomposite

Montmorillonite reinforced polymers are a new development in the area of nanocomposite materials. Since reinforcement of epoxy is important to the development of high strength adhesives and composite matrices, the introduction of montmorillonite to epoxy is of interest. Compositional effects on epoxy reactivity, on molecular relaxation, and on mechanical properties were investigated. Change in reactivity was determined by Differential Scanning Calorimetry. Tensile properties at room temperature… more

Date: December 2000

Creator: Butzloff, Peter Robert

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Epoxy + Liquid Crystalline Epoxy Coreacted Networks

Molecular reinforcement through in-situ polymerization of liquid crystalline epoxies (LCEs) and a non-liquid crystalline epoxy has been investigated. Three LCEs: diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) and digylcidyl ether of 4-hydroxyphenyl-4"-hydroxybiphenyl-4'-carboxylate (DGE-HHC), were synthesized and blended with diglycidyl ether of bisphenol F (DGEBP-F) and subsequently cured with anhydride and amine curing agents. Curing kinetics were determined using differential scanning… more

Date: December 2000

Creator: Punchaipetch, Prakaipetch

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Thermal, Electrical, and Structural Analysis of Graphite Foam

A graphite foam was developed at Oak Ridge National Laboratory (ORNL) by Dr. James Klett and license was granted to POCO Graphite, Inc. to manufacture and market the product as PocoFoam. Unlike many processes currently used to manufacture carbon foams, this process yields a highly graphitic structure and overcomes many limitations, such as oxidation stabilization, that are routinely encountered in the development of carbon foam materials. The structure, thermal properties, electrical resistiv… more

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Date: August 2001

Creator: Morgan, Dwayne Russell

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Polyamide-imide and Montmorillonite Nanocomposites

Solvent suspensions of a high performance polymer, Polyamide-imide (PAI) are widely used in magnetic wire coatings. Here we investigate the effect that the introduction of montmorillonite (MMT) has on PAI. MMT was introduced into an uncured PAI suspension; the sample was then cured by step-wise heat treatment. Polarized optical microscopy was used to choose the best suitable MMT for PAI matrix and to study the distribution of MMT in PAI matrix. Concentration dependent dispersion effect was stud… more

Date: August 2001

Creator: Ranade, Ajit

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Characterizaton of Triethoxyfluorosilane and Tetraethoxysilane Based Aerogels

Aerogels are highly porous, low dielectric constant (low k) materials being considered by the semiconductor industry as an interlayer dielectric. Low k materials are needed to overcome capacitance problems that limit device feature sizes. Precursors triethoxyfluorosilane (TEFS) and tetraethoxysilane (TEOS) were used to prepare bulk aerogels. Samples were prepared by sol-gel methods, and then carbon dioxide supercritically-dried. Effects of varying the water to precursor ratio were studied with … more

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Date: December 2001

Creator: Roepsch, Jodi Ann

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Hypotheses for Scratch Behavior of Polymer Systems that Recover

Scratch recovery is a desirable property of many polymer systems. The reason why some materials have demonstrated excellent scratch recovery while others do not has been a mystery. Explaining the scratch resistance based upon the hardness of a material or its crosslink density is incorrect. In this thesis, novel polymers were tested in an attempt to discover materials that show excellent scratch recovery - one of the most important parameters in determining the wear of a material. Several hypo… more

Date: May 2002

Creator: Bujard, Bernard

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Influence of design and coatings on the mechanical reliability of semiconductor wafers.

We investigate some of the mechanical design factors of wafers and the effect on strength. Thin, solid, pre-stressed films are proposed as a means to improve the bulk mechanical properties of a wafer. Three-point bending was used to evaluate the laser scribe density and chemical processing effect on wafer strength. Drop and strike tests were employed to investigate the edge bevel profile effect on the mechanical properties of the wafer. To characterize the effect of thin films on stren… more

Date: August 2002

Creator: Yoder, Karl J.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Mechanical Properties of Polymer Modified Mortar

The mechanical properties of the polymer-modified mortar are markedly improved over conventional cement mortar. We utilized recycled ABS in powder form and a polymer latex emulsion, polymer percentage ranges from 0 to 25 percent by polymer/cement ratio were investigated. The mechanical properties investigated were compression strength and adhesion strength. Compression strength effects did not have an impact on adhesion strength. Adhesion strength was calculated with pullout testing apparatus … more

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Date: August 2002

Creator: Palos, Artemio

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Application of Thermomechanical Characterization Techniques to Bismuth Telluride Based Thermoelectric Materials

The thermoelectric properties of bismuth telluride based thermoelectric (TE) materials are well-characterized, but comparatively little has been published on the thermomechanical properties. In this paper, dynamic mechanical analysis (DMA) and differential scanning calorimetry data for bismuth telluride based TE materials is presented. The TE materials' tan delta values, indicative of viscoelastic energy dissipation modes, approached that of glassy or crystalline polymers, were greater than ten… more

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Date: August 2002

Creator: White, John B.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

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

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: 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

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: Thesis or Dissertation

Partner: UNT Libraries

open access

Structure property and deformation analysis of polypropylene montmorillonite nanocomposites.

Nanocomposites with expandable smectites such as montmorillonite layered silicates (MLS) in polymer matrices have attracted extensive application interest. Numerous MLS concentrations have been used with no particular justification. Here, we investigate the effects of MLS dispersion within the matrix and on mechanical performance. The latter is resolved through a three-prong investigation on rate dependent tensile results, time dependent creep results and the influence of a sharp notch in polyp… more

Date: May 2003

Creator: Hernandez-Luna, Alejandro

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Characterization of Methyltrimethoxysilane Sol-Gel Polymerization and the Resulting Aerogels.

Methyl-functionalized porous silica is of considerable interest as a low dielectric constant film for semiconductor devices. The structural development of these materials appears to affect their gelation behaviors and impact their mechanical properties and shrinkage during processing. 29Si solution NMR was used to follow the structural evolution of MTMS (methyltrimethoxysilane) polymerization to gelation or precipitation, and thus to better understand the species that affect these properties an… more

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Date: August 2003

Creator: Dong, Hanjiang

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

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

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: Thesis or Dissertation

Partner: UNT Libraries

open access

Hydrophobic, fluorinated silica xerogel for low-k applications.

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: Thesis or Dissertation

Partner: UNT Libraries

Effect of Silyation on Organosilcate Glass Films

Photoresist stripping with oxygen plasma ashing destroys the functional groups in organosilicate glass films and induce moisture uptake, causing low-k dielectric degradation. In this study, hexamethyldisilazane (HMDS), triethylchlorosilane and tripropylchlorosilane are used to repair the damage to organosilicate glass by the O2 plasma ashing process. The optimization of the surface functionalization of the organosilicate glass by the silanes and the thermal stability of the functionalized surfa… more

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Date: August 2004

Creator: Kadam, Poonam

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Synthesis and characterization of crystalline assembly of poly Nisopropylacry-lamide)-co-acrylic acid nanoparticles.

In this study, crystalline poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAm-co-AAc) nanoparticle network in organic solvents was obtained by self assembling precursor particles in acetone/epichlorohydrin mixture at room temperature followed by inter-sphere crosslinking at ~98 °C. The crystals thus formed can endure solvent exchanges or large distortions under a temporary compressing force with the reoccurrence of crystalline structures. In acetone, the crystals were stable, independent of te… more

Date: December 2004

Creator: Zhou, Bo

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Charge Interaction Effects in Epoxy with Cation Exchanged Montmorillonite Clay and Carbon Nanotubes.

The influence of charge heterogeneity in nanoparticles such as montmorillonite layered silicates (MLS) and hybrid systems of MLS + carbon nanotubes was investigated in cured and uncured epoxy. Epoxy nanocomposites made with cation-exchanged montmorillonite clay were found to form agglomerates near a critical concentration. Using differential scanning calorimetry it was determined that the mixing temperature of the epoxy + MLS mixture prior to the addition of the curing agent critically influenc… more

Date: May 2005

Creator: Butzloff, Peter Robert

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Saturation and foaming of thermoplastic nanocomposites using supercritical CO2.

Polystyrene (PS) nanocomposite foams were prepared using supercritical fluid (SCF) CO2 as a solvent and blowing agent. PS was first in-situ polymerized with a range of concentrations of montmorillonite layered silicate (MLS). The polymerized samples were then compression molded into 1 to 2mm thick laminates. The laminates were foamed in a batch supercritical CO2 process at various temperatures and pressures from 60°-85°C and 7.6-12MPa. The resulting foams were analyzed by scanning electron micr… more

Date: May 2005

Creator: Strauss, William C.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

A magnetorheological study of single-walled and multi-walled carbon nanotube dispersions in mineral oil and epoxy resin.

Single wall carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) were dispersed in mineral oil and epoxy resin. The magnetorheological properties of these dispersions were studied using a parallel plate rheometer. Strain sweeps, frequency sweeps, magneto sweeps and steady shear tests were conducted in various magnetic fields. G', G", h* and ty increased with increasing magnetic field, which was partially attributed to the increasing degree of the alignment of nanotubes in a strong… more

Date: May 2005

Creator: Yang, Zhengtao

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Synthesis and Characterization of Crystalline Assemblies of Functionalized Hydrogel Nanoparticles

Two series monodispersed nanoparticles of hydroxylpropyl cellulose (HPC) and functionalized poly-N-isopropylamide (PNIPAM) particles have been synthesized and used as building blocks for creating three-dimensional networks, with two levels of structural hierarchy. The first level is HPC nanoparticles were made from methacrylated or degradable cross-linker attached HPC. These nanoparticles could be stabilized at room temperature by residual methacrylate or degradable groups are present both with… more

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Date: December 2005

Creator: Cai, Tong

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Supercritical CO2 foamed biodegradable polymer blends of polycaprolactone and Mater-Bi.

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: Thesis or Dissertation

Partner: UNT Libraries

open access

Trapping of hydrogen in Hf-based high κ dielectric thin films for advanced CMOS applications.

In recent years, advanced high κ gate dielectrics are under serious consideration to replace SiO2 and SiON in semiconductor industry. Hafnium-based dielectrics such as hafnium oxides, oxynitrides and Hf-based silicates/nitrided silicates are emerging as some of the most promising alternatives to SiO2/SiON gate dielectrics in complementary metal oxide semiconductor (CMOS) devices. Extensive efforts have been taken to understand the effects of hydrogen impurities in semiconductors and its behavi… more

Date: December 2007

Creator: Ukirde, Vaishali

Item Type: Thesis or Dissertation

Partner: UNT Libraries