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  Partner: UNT College of Arts and Sciences
 Department: Chemistry
 Collection: UNT Scholarly Works
Rediscovery of the Elements: Hafnium

Rediscovery of the Elements: Hafnium

Date: Autumn 2011
Creator: Marshall, James L., 1940- & Marshall, Virginia R.
Description: Article describing the search for element 72, the scientists involved, and the nationalist politics surrounding the discovery. Tourist information is included for areas significant to the history of hafnium.
Contributing Partner: UNT College of Arts and Sciences
The 2011 Beta Eta Spring Banquet. Celebration of Rediscovery of the Elements

The 2011 Beta Eta Spring Banquet. Celebration of Rediscovery of the Elements

Date: Summer 2011
Creator: Marshall, James L., 1940-
Description: Article describing an Eta Beta celebration of the completion of James and Virginia Marshall's "Rediscovery of the Elements." Photographs from the event are included. Three separate articles appear on the right side of the page.
Contributing Partner: UNT College of Arts and Sciences
The Gas That Wouldn't Burn

The Gas That Wouldn't Burn

Date: Summer 2012
Creator: Marshall, James L., 1940- & Marshall, Virginia R.
Description: Article describing how Alpha Chi Sigma members were involved with the events described on a pictured Kansas historical marker relating to the discovery of helium in a deposit of natural gas.
Contributing Partner: UNT College of Arts and Sciences
Rediscovery of the Elements: The Noble Gases--Rayleigh and Ramsay

Rediscovery of the Elements: The Noble Gases--Rayleigh and Ramsay

Date: Autumn 2012
Creator: Marshall, James L., 1940- & Marshall, Virginia R.
Description: Article describing the discovery of argon, helium, and other inert gases by Lord Rayleigh, Sir William Ramsay, and other collaborators. Ramsay also characterized the noble gases and classified them within the structure of the Periodic Table of Elements.
Contributing Partner: UNT College of Arts and Sciences
Ring of Fire

Ring of Fire

Date: Autumn 2012
Creator: Marshall, James L., 1940- & Marshall, Virginia R.
Description: Front cover of the fall 2012 issue of The Hexagon, which features an image of the "ring of fire" that occurred during the annular eclipse on May 20, 2012. The photograph was taken in Brownfield, Texas a few minutes before sunset. The inside cover contains a table of contents, a staff list, an editorial, and details about the cover photograph.
Contributing Partner: UNT College of Arts and Sciences
Charge transfer equilibria in ambient-exposed epitaxial graphene on (0001) 6 H-SiC

Charge transfer equilibria in ambient-exposed epitaxial graphene on (0001) 6 H-SiC

Date: June 5, 2012
Creator: Sidorov, Anton N.; Gaskill, D. Kurt.; Buongiorno Nardelli, Marco; Tedesco, Joseph L.; Myers-Ward, Rachel L.; Eddy, Charles R. et al
Description: This article discusses charge transfer equilibria in ambient-exposed epitaxial graphene on (0001) 6 H-SiC. Abstract: The transport properties of electronic materials have been long interpreted independently from both the underlying bulk-like behavior of the substrate or the influence of ambient gases. This is no longer the case for ultra-thin graphene whose properties are dominated by the interfaces between the active material and its surroundings. Here, the authors show that the graphene interactions with its environments are critical for the electrostatic and electrochemical equilibrium of the active device layers and their transport properties. Based on the prototypical case of epitaxial graphene on (0001) 6 H-SiC and using a combination of 'in-situ' thermoelectric power and resistance measurements and simulations from first principles, the authors demonstrate that the cooperative occurrence of an electrochemically mediated charge transfer from the graphene to air, combined with the peculiar electronic structure of the graphene/SiC interface, explains the wide variation of measured conductivity and charge carrier type found in prior reports.
Contributing Partner: UNT College of Arts and Sciences
Activation of water on the TiO2 (110) surface: The case of Ti adatoms

Activation of water on the TiO2 (110) surface: The case of Ti adatoms

Date: February 8, 2012
Creator: Miao, Meng; Liu, Yingchun; Wang, Qi; Wu, Tao; Huang, Liping; Gubbins, Keith E. et al
Description: This article discusses the activation of water on the TiO2 (110) surface. Abstract: Using first-principles calculations the authors have studied the reactions of water over Ti adatoms on the (110) surface of rutile TiO2. The authors' results provide fundamental insights into the microscopic mechanisms that drive this reaction at the atomic level and assess the possibility of using this system to activate the water dissociation reaction. In particular, the authors show that a single water molecule dissociates exothermically with a small energy barrier of 0.17 eV. After dissociation, both H⁺ and OH⁻ ions bind strongly to the Ti adatom, which serves as an effective reactive center on the TiO2 surface. Finally, clustering of Ti adatoms does not improve the redox activity of the system and results in a slightly higher energy barrier for water dissociation.
Contributing Partner: UNT College of Arts and Sciences
Multiple coexisting intercalation structures of sodium in epitaxial graphene-SiC interfaces

Multiple coexisting intercalation structures of sodium in epitaxial graphene-SiC interfaces

Date: March 9, 2012
Creator: Sandin, Andreas; Jayasekera, Thushari; Rowe, J.E.; Kim, Ki Wook; Buongiorno Nardelli, Marco & Dougherty, Daniel B.
Description: In this article, the authors show using scanning tunneling microscopy, spectroscopy, and ab initio calculations that two intercalation structures coexist for Na in epitaxial graphene on SiC(0001). Intercalation takes place at room temperature, and Na electron dopes the graphene. It inserts in between single-layer graphene and the interfacial layer and also penetrates beneath the interfacial layer and decouples it to form a second graphene layer. Decoupling is accelerated by annealing and is verified by Na deposition onto the interface layer combined with computational modeling of the two new decoupled buffer layer structures.
Contributing Partner: UNT College of Arts and Sciences
Phonon engineering in nanostructures: Controlling interfacial thermal resistance in multilayer-graphene/dielectric heterojunctions

Phonon engineering in nanostructures: Controlling interfacial thermal resistance in multilayer-graphene/dielectric heterojunctions

Date: September 13, 2012
Creator: Mao, R.; Kong, B.D.; Kim, K.W.; Jayasekera, T.; Calzolari, Arrigo & Buongiorno Nardelli, Marco
Description: This article discusses phonon engineering in nanostructures: Controlling interfacial thermal resistance in multilayer-graphene/dielectric heterojunctions. Using calculations from first principles and the Landauer approach for phonon transport, the authors study the Kapitza resistance in selected multilayer graphene/dielectric heterojunctions (hexagonal BN and wurtzite SiC) and demonstrate (i) the resistance variability (~50 - 700 x 10(-10) m2K/W) induced by vertical coupling, dimensionality, and atomistic structure of the system and (ii) the ability of understanding the intensity of the thermal transmittance in terms of the phonon distribution at the interface. The authors results pave the way to the fundamental understanding of active phonon engineering by microscopic geometry design.
Contributing Partner: UNT College of Arts and Sciences
Complex Materials for Molecular Spintronics Applications: Cobalt Bis(dioxolene) Valence Tautomers, from Molecules to Polymers

Complex Materials for Molecular Spintronics Applications: Cobalt Bis(dioxolene) Valence Tautomers, from Molecules to Polymers

Date: October 16, 2012
Creator: Calzolari, Arrigo; Chen, Yifeng; Lewis, Geoffrey F.; Dougherty, Daniel B.; Shultz, David A. & Buongiorno Nardelli, Marco
Description: This article discusses complex materials for molecular spintronics applications. Abstract: Using first principles calculations, the authors predict a complex multifunctional behavior in cobalt bis(dioxolene) valence tautomeric compounds. Molecular spin-state switching is shown to dramatically alter electronic properties and corresponding transport properties. This spin state dependence has been demonstrated for technologically relevant coordination polymers of valence tautomers as well as for novel conjugated polymers with valence tautomeric functionalization. As a result, these materials are proposed as promising candidates for spintronic devices that can couple magnetic bistability with novel electrical and spin conduction properties. The authors' findings pave the way to the fundamental understanding and future design of active multifunctional organic materials for spintronics applications.
Contributing Partner: UNT College of Arts and Sciences