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in subjects: "Sapphire"

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Radiation Response of Rhombohedral Oxides

The radiation response of three rhombohedral oxides, namely, sapphire ({alpha}-Al{sub 2}O{sub 3}), ilmenite (FeTiO{sub 3}), and geikielite (MgTiO{sub 3}), has been examined by irradiating electron transparent samples with 1 MeV Kr(+) and 1.5 MeV Xe(+)ions. The microstructural changes during irradiation were observed in situ in a high-voltage electron microscope using electron diffraction and microscopy. The irradiation conditions were designed to minimize beam heating and chemical effects due t… more

Date: December 31, 1997

Creator: Devanathan, R.; Weber, W.J.; Mitchell, J.N.; Sickafus, K.E. & Nastasi, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fundamental Mechanisms of Interface Roughness

Publication quality results were obtained for several experiments and materials systems including: (i) Patterning and smoothening of sapphire surfaces by energetic Ar+ ions. Grazing Incidence Small Angle X-ray Scattering (GISAXS) experiments were performed in the system at the National Synchrotron Light Source (NSLS) X21 beamline. Ar+ ions in the energy range from 300 eV to 1000 eV were used to produce ripples on the surfaces of single-crystal sapphire. It was found that the ripple wavelength v… more

Date: January 6, 2009

Creator: Headrick, Randall L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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And the Stereotype Award Goes to...: A Comparative Analysis of Directors using African American Stereotypes in Film

This study examines African American stereotypes in film. I studied six directors, Kathryn Bigelow, Spike Lee, the Russo Brothers, Ryan Coogler, Tate Taylor, and Dee Rees; and six films Detroit, BlacKkKlansman, Captain America: The Winter Soldier, The Help, and Mudbound. Using the framework of critical race theory and auteur theory, I compared the common themes between the films and directors. The main purpose of my study is to see if White or Black directors predominantly used African American… more

Date: December 2019

Creator: Young, Kelcei

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Hydrogenation of Dislocation-Limited Heteroepitaxial Silicon Solar Cells: Preprint

Post-deposition hydrogenation by remote plasma significantly improves performance of heteroepitaxial silicon solar cells. Heteroepitaxial deposition of thin crystal silicon on sapphire for photovoltaics (PV) is an excellent model system for the study and improvement of deposition on inexpensive Al2O3-coated (100) biaxially-textured metal foils. Without hydrogenation, PV conversion efficiencies are less than 1% on our model system. Performance is limited by carrier recombination at electrically … more

Date: June 1, 2012

Creator: Bolen, M. L.; Grover, S.; Teplin, C. W.; Bobela, D.; Branz, H. M. & Stradins, P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Substrate surface structure effects on microstructure of epitaxial films

Microstructure of epitaxial thin films grown on sapphire substrates using the metal organic chemical vapor deposition technique were found to depend on the substrates surface structure. Epitaxial TiO[sub 2] films grown on the sapphire (0001) substrates were highly-oriented polycrystal and the films on the (1120) substrates were single crystal. First-principles total energy calculations were carried out to gain atomistic understandings of sapphire surface structures and their effects on microstr… more

Date: December 1, 1992

Creator: Guo, J.; Chang, H.L.M.; Zhang, H. & Lam, D.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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[Letter from Winifred H. Mills]

A letter from Winifred H. Mills to Carl B. Compton regarding his acceptance of a teaching position at North Texas State Teachers College in Denton.

Date: August 19, 1944

Creator: Mills, Winifred H.

Item Type: Letter

Partner: UNT Libraries Special Collections

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New Optimal Sensor Suite for Ultrahigh Temperature Fossil Fuel Applications

Accomplishments during Phase II of a program to develop and demonstrate photonic sensor technology for the instrumentation of advanced powerplants are described. The goal of this project is the research and development of advanced, robust photonic sensors based on improved sapphire optical waveguides, and the identification and demonstration of applications of the new sensors in advanced fossil fuel power plants, where the new technology will contribute to improvements in process control and mo… more

Date: September 30, 2006

Creator: Coggin, John; Ivasauskas, Jonas; May, Russell G.; Miller, Michael B. & Wilson, Rena

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Design of a Thermal Imaging Diagnostic Using 90-Degree, Off-Axis, Parabolic Mirrors

Thermal imaging is an important, though challenging, diagnostic for shockwave experiments. Shock-compressed materials undergo transient temperature changes that cannot be recorded with standard (greater than ms response time) infrared detectors. A further complication arises when optical elements near the experiment are destroyed. We have designed a thermal-imaging system for studying shock temperatures produced inside a gas gun at Sandia National Laboratories. Inexpensive, diamond-turned, para… more

Date: September 1, 2006

Creator: Malone, Robert M.; Becker, Steven A.; Dolan, Daniel H.; Hacking, Richard G.; Hickman, Randy J.; Kaufman, Morris I. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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AC microcalorimetry of adsorbates on evaporated metal films: Orientational ordering of H₂ multilayers

We have improved and extended a novel ac calorimetric technique for measuring the heat capacity of adsorbates on evaporated metal films. Metallic substrates are of particular interest in current studies of the thermodynamics of adsorbed molecules. The method described in the present work is only calorimetric technique which allows measurements of molecules on simple metallic surfaces. Among other improvements, we have achieved significant progress in the preparation and characterization of the … more

Date: November 1, 1991

Creator: Phelps, R.B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Prism-film coupling in anisotropic planar waveguides of epitaxial (101) rutile thin films

We report optical waveguiding in single-crystal, epitaxial (101) oriented rutile (TiO[sub 2]) thin films grown on (1120) sapphire ([alpha]-Al[sub 2]O[sub 3]) substrates using the MOCVD technique. The propagation-constants for asymmetric planar waveguides composed of an anisotropic dielectric media applicable to these films are derived. Modifications to the prism-film coupling theory for this anisotropic case are also discussed. By application of this model to (101) oriented rutile thin films, w… more

Date: April 1, 1993

Creator: Foster, C. M.; Chan, S. K.; Chang, H. L. M.; Chiarello, R. P. & Lam, D. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Response of sapphire thermocurrent dosimeters to fast neutrons

The response of sapphire (Al/sub 2/O/sub 3/) thermocurrent (TC) dosimeters to 14 MeV neutrons is about 10% of the response to cesium gamma rays on an equivalent tissue rad basis. The addition of proton radiator covers of methyl methacrylate increases this response to about 15%. The magnitude of the thermocurrent peak at 260/sup 0/ (peak 3) allows measurement of gamma ray exposures of 10 mR with a signal to noise ratio of about unity.

Date: January 1, 1975

Creator: Pearson, D. W. & Moran, P. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A Ti:Sapphire laser for the new polarized electron source

The SLAC polarized electron source uses a laser driven photo cathode gun. We have developed a Titanium Sapphire laser at SLAC to replace the dye laser currently used for the source. The new laser is designed to operate at wavelengths between 750 and 850 nm while producing 400mJ of energy in 1.6 ns pulses at 120 Hz. Installation on the accelerator is expected in January of 1993.

Date: October 1, 1992

Creator: Frisch, Josef; Woods, Mike B. & Zolotorev, Max

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Thermocurrent dosimetry with high purity aluminum oxide

The application of thermocurrent (TC) to ionizing radiation dosimetry was studied. It was shown that TC in alumina (Al/sub 2/O/sub 3/) has properties that are suited to personnel dosimetry and environmental monitoring. TC dosimeters were made from thin disks of alumina. Aluminum electrodes were evaporated on each side: on one face a high voltage electrode and on the opposite face a measuring electrode encircled by a guard ring. Exposure to ionizing radiation resulted in stored electrons and hol… more

Date: January 1, 1976

Creator: Fullerton, G. D.; Cameron, J. R. & Moran, P. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Healing of lithographically introduced flaws in glass and glass containing ceramics

The morphological evolution of cylindrical pores or channels'' and crack-like cavities in glass and glass-containing ceramics at elevated temperatures was studied. The systems studied were: Coming 7056 alkali borosilicate glass, soda-lime glass (microscope slides), a commercially available 96% Al[sub 2]O[sub 3]with [approx]5--10% intergranular glass, 96% Al[sub 2]O[sub 3] bonded to sapphire, and a model sapphire/glass/sapphire system fabricated by diffusion bonding etched and unetched pieces of… more

Date: December 1, 1992

Creator: Ackler, H. D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Science & Technology Review October 2006

This months issue has the following articles: (1) Innovative Solutions Reap Rewards--Commentary by George H. Miller; (2) Surveillance on the Fly--An airborne surveillance system can track up to 8,000 moving objects in an area the size of a small city; (3) A Detector Radioactive Particles Can't Evade--An ultrahigh-resolution spectrometer can detect the minute thermal energy deposited by a single gamma ray or neutron; (4) Babel Speeds Communication among Programming Languages--The Babel program a… more

Date: September 1, 2006

Creator: Radousky, H B

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Epitaxial film growth study of single crystal V/Ce prepared by molecular-beam epitaxy on sapphire

The growth of epitaxial films of cerium (Ce)/vanadium (V)/on single crystal sapphires (..cap alpha..-Al/sub 2/O/sub 3/) was studied by in-situ reflection high energy electron diffraction and x-ray scattering. For the first time Ce(111) single crystal films was grown on V(110)/Al/sub 2/O/sub 3/(1120) in the Frank-van der Merwe mode. A new epitaxial orientation, different from the well known Nishiyama-Wasserman or Kurdjumov-Sachs orientations is found in the present study. Subsequent V(110) layer… more

Date: November 1, 1986

Creator: Homma, Hitoshi; Yang, Kai-Y. & Schuller, Ivan K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Low-frequency nuclear quadrupole resonance with a dc SQUID

Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and applicati… more

Date: July 1, 1991

Creator: Chang, J. W.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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A high repetition rate beam profile monitor

A high repetition rate beam profile monitor is needed to measure the momentum distribution of each bunch in a 200 bunch train at the Brookhaven Accelerator Test Facility. We have designed a monitor using secondary emission from a microstrip delay line. The delay line converts position information into discrete time delays synchronous with the sampling rate of a fast transient digitizer. We present the results of initial electrical testing here.

Date: January 1, 1991

Creator: Rogers, J.T.; Warren, J.B. (Brookhaven National Lab., Upton, NY (United States)) & Gray, A. (State Univ. of New York, Stony Brook, NY (United States). Dept. of Physics)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Heat capacity measurements of atoms and molecules adsorbed on evaporated metal films

Investigations of the properties of absorbed monolayers have received great experimental and theoretical attention recently, both because of the importance of surface processes in practical applications such as catalysis, and the importance of such systems to the understanding of the fundamentals of thermodynamics in two dimensions. We have adapted the composite bolometer technology to the construction of microcalorimeters. For these calorimeters, the adsorption substrate is an evaporated film … more

Date: May 1, 1989

Creator: Kenny, T.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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X-Ray Diffraction From Ion Implanted Zones

Measurements of x-ray profiles and diffuse scattering from (111), (100) single crystal Niobium films implanted with Nitrogen to average levels of 5 and 0.5 atomic percent are discussed. Theoretical analysis of the asymmetric profiles are used to determine the strain profile in the implanted films. The measured strain profile results from two factors: (1) depth distribution of implants and knock-on damage and (2) elastic constraints. Residual elastic strains develop due to the constraints impose… more

Date: 1988~

Creator: Rao, Satish I.; Houska, Charles R.; Grabowski, K.; Claussen, J.; Ice, G. & Habenschuss, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Infrared detection with high-{Tc} bolometers and response of Nb tunnel junctions to picosecond voltage pulses

Oxide superconductors with high critical temperature {Tc} make sensitive thermometers for several types of infrared bolometers. The authors built composite bolometers with YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thermometers on sapphire substrates which have higher sensitivity than competing thermal detectors which operate at temperatures above 77 K. A 1 x 1 mm bolometer with gold black serving as the radiation absorber has useful sensitivity for wavelengths 20--100 {mu}m. A 3 x 3 mm bolomete… more

Date: May 1, 1993

Creator: Verghese, S.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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Joining of alumina via copper/niobium/copper interlayers

Alumina has been joined at 1150 degrees C and 1400 degrees C using multilayer copper/niobium/copper interlayers. Four-point bend strengths are sensitive to processing temperature, bonding pressure, and furnace environment (ambient oxygen partial pressure). Under optimum conditions, joints with reproducibly high room temperature strengths (approximately equal 240 plus/minus 20 MPa) can be produced; most failures occur within the ceramic. Joints made with sapphire show that during bonding an init… more

Date: March 15, 2000

Creator: Marks, Robert A.; Chapman, Daniel R.; Danielson, David T. & Glaeser, Andreas M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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First principles energetic calculations of sapphire (0001) and (1 1 02) surfaces

Various crystallographic faces of sapphire, the undoped single crystal {alpha}-Al{sub 2}O{sub 3}, have been widely used as substrates fro depositing thin films of metals, semiconductors, and insulators for basic scientific studies and for microelectronic applications. Epitaxial TiO{sub 2} and VO{sub 2} thin films were successfully grown on (0001), (1102) and (1120) surfaces of sapphire substrates by the Metal Organic Chemical Vapor Deposition (MOCVD) technique in our experimental program. The p… more

Date: March 1, 1992

Creator: Guo, J.; Ellis, D.E. & Lam, D.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Hardness of ion implanted ceramics

It has been established that the wear behavior of ceramic materials can be modified through ion implantation. Studies have been done to characterize the effect of implantation on the structure and composition of ceramic surfaces. To understand how these changes affect the wear properties of the ceramic, other mechanical properties must be measured. To accomplish this, a commercially available ultra low load hardness tester has been used to characterize Al/sub 2/O/sub 3/ with different implanted… more

Date: January 1, 1985

Creator: Oliver, W. C.; McHargue, C. J.; Farlow, G. C. & White, C. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department