John S. Mccloy

John S. Mccloy
Washington State University | WSU · School of Mechanical and Materials Engineering

PhD

About

265
Publications
62,785
Reads
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3,505
Citations
Citations since 2016
165 Research Items
2917 Citations
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
Additional affiliations
August 2018 - present
Washington State University
Position
  • Professor (Full)
August 2018 - present
Washington State University
Position
  • Professor (Full)
August 2013 - August 2018
Washington State University
Position
  • Professor (Associate)
Education
September 2005 - May 2008
The University of Arizona
Field of study
  • Materials Science and Engineering
September 2000 - May 2004
The University of Arizona
Field of study
  • Cultural Anthropology
September 1992 - June 1996
Massachusetts Institute of Technology
Field of study
  • Materials Science and Engineering

Publications

Publications (265)
Article
X-ray nano-computed tomography (nano-CT) is a powerful technique to characterize and visualize 3 dimensional (3D) phenomena in complex glasses at the nanoscale. This technique can offer a unique opportunity to explore the intricate morphology of multicomponent glass and glass-ceramic samples, due to its low X-ray energy and high spatial resolution...
Article
The presence of sulfur-containing molten salt phases during vitrification is a particular problem which can be detrimental to the melter. Borosilicate compositions were designed to explore both the effects of a fixed amount of Cr, as Cr2O3 or Na2CrO4, and the impact of Al2O3, on sulfur solubility as determined by progressively adding elemental S. T...
Article
The article demonstrates the complete process of I2(g) capture using Ag-exchanged faujasite (AgX) and Ag-exchanged mordenite (AgZ) zeolite sorbents, the recovery of Ag for recyclability of iodine capture in a Na2S solution, and the immobilization of iodide (from the elution process) into an iodosodalite waste form, which is chemically and environme...
Article
Transition-metal ions (Ni, Cu, and Zn) in β-Ga 2 O 3 crystals form deep acceptor levels in the lower half of the bandgap. In the present study, we characterize the Ni acceptors in a Czochralski-grown crystal and find that their (0/−) level is approximately 1.40 eV above the maximum of the valence band. Both Ni 2+ (3d 8) and Ni 3+ (3d 7) acceptors a...
Article
Herein we utilize polarized photoluminescence (PL) microscopy and spectral analysis to locate and characterize many different types of µm-scale extended defects present in melt-grown bulk crystals and metal-organic vapor-phase epitaxy (MOVPE)-grown epitaxial thin films of β-Ga 2 O 3 and β-(Al,Ga) 2 O 3 . These include pits, divots, mounds, scratche...
Article
Full-text available
CdTe:Cl doped single crystals were grown under conditions of tellurium excess by using an accelerated crucible rotation technique, modified vertical Bridgman (ACRT-MVB) method. Chlorine dopant levels were kept at 4.4 × 1019 at·cm−3, for all growths, while the Te excess level varied from 3.5 to 15% by weight. The relationship between the detector pe...
Presentation
Full-text available
ISTR2022 is postponded Scope and background The International Symposium on Technetium and Rhenium – Science and Utilization (ISTR) aims at covering all aspects of Technetium and Rhenium chemistry, from the role of Tc in the nuclear fuel cycle to nuclear medicine applications, extending to catalysis chemistry of Re in the industry. Like the very su...
Presentation
Full-text available
The International Symposium on Technetium and Rhenium – Science and Utilization (ISTR) aims at covering all aspects of Technetium and Rhenium chemistry, from the role of Tc in the nuclear fuel cycle to nuclear medicine applications, extending to catalysis chemistry of Re in the industry. Like the very successful earlier meetings in this series of s...
Article
With plenty of charges and rich functional groups, bovine serum albumin (BSA) protein provides effective transport for multiple metallic ions inside blood vessels. Inspired by the unique ionic transport function, we develop a BSA protein coating to stabilize Li anode, regulate Li+ transport, and resolve the Li dendrite growth for Li metal batteries...
Presentation
Full-text available
The International Symposium on Technetium and Rhenium – Science and Utilization (ISTR) aims at covering all aspects of Technetium and Rhenium chemistry, from the role of Tc in the nuclear fuel cycle to nuclear medicine applications, extending to catalysis chemistry of Re in the industry. Like the very successful earlier meetings in this series of s...
Article
Full-text available
There is wide industrial interest in developing robust models of long‐term (>100 years) glass durability. Archeological glass analogues, glasses of similar composition and alteration conditions to those being tested for durability, can be used to evaluate, and inform such models. Two such analogue glasses from a 1500‐year‐old vitrified hillfort nea...
Article
β-Ga2O3 is an emergent ultrawide bandgap material, which has been recently studied with respect to alumina alloying in order to tailor the bandgap for thin film or bulk applications. In this work, bulk Czochralski and vertical gradient freeze crystals of 6 – 8 mol.% Sc2O3 alloyed β-Ga2O3 (SGO) – β-(Sc0.06Ga0.94)2O3 to β-(Sc0.08Ga0.92)2O3 – were obt...
Article
This study shows the effects of nuclear waste glass production on Monofrax® K‐3 refractory corrosion. A continuously fed research‐scale melter (RSM) containing a Fe‐ and Ni‐rich simulated nuclear waste feed with borosilicate glass‐forming chemicals was cyclically melted at 1150°C and idled at 1050°C for a total of 11 weeks. Chemical maps using scan...
Article
Full-text available
Understanding the impact of individual compositional components on the devitrification of complex multicomponent glasses, e.g., 10–50+ oxides, typically requires numerous studies to examine each component's impact. Here we apply exploratory data analysis to a heterogeneous data set of silicate glasses to determine the cations' individual and intera...
Article
Full-text available
Owing to its good chemical and thermal durability at high temperatures, MonofraxTM K-3 refractory is widely used in nuclear waste vitrification as a lining material in the melting vessels. However, the corrosion of K-3 refractory during the vitrification of nuclear waste is a serious problem because it affects the safety, performance, and lifetime...
Article
Full-text available
Dark and clear silicate glasses formed during an iron age vitrification event ≈ 1500 years ago at the Broborg hillfort near Uppsala, Sweden have been analyzed using a scanning electron microscope equipped with a micro-X-ray fluorescence (μXRF) spectrometer. Correlated µXRF and electron beam-induced energy dispersive spectrometry (EDS) X-ray maps we...
Article
It was discovered around 250 years ago that some of the rock material in the walls of some hillforts had been subjected to such high temperature that it had vitrified. This prompted a debate as to the reason for it that is still going on today: did the vitrification come about as a result of hostile action, by accident, or for the purpose of constr...
Article
Full-text available
This study presents the successful implementation of eco-friendly recycled powders (RPs) in concrete based on extensive experimental data to promote the reuse of these RPs as supplementary cementitious materials to lower cement demand and reduce associated CO2 emissions. The fine fraction of recycled concrete aggregate and brick waste was used to p...
Article
Full-text available
Calcium rare earth silicate oxyapatites, (Ca 2 RE 8 (SiO 4) 6 O 2), are of interest as components of glass-ceramic nuclear waste forms. To assess their long-term behavior in a geologic repository, it is essential to determine their structure and thermo-dynamic stability at relevant conditions. In this work, we performed detailed structural and ther...
Article
OVERVIEW On Earth, natural glasses are typically produced by rapid cooling of melts, and as in the case of minerals and rocks, natural glasses can provide key information on the evolution of the Earth. However, natural glasses are products not solely terrestrial, and different formation mechanisms give rise to a variety of natural amorphous materia...
Article
In this work, bulk Czochralski-grown single crystals of 10 mol. % Al 2 O 3 alloyed β-Ga 2 O 3 —monoclinic 10% AGO or β-(Al 0.1 Ga 0.9 ) 2 O 3 —are obtained, which show +0.20 eV increase in the bandgap compared with unintentionally doped β-Ga 2 O 3 . Further, growths of 33% AGO—β-(Al 0.33 Ga 0.67 ) 2 O 3 —and 50% AGO—β-(Al 0.5 Ga 0.5 ) 2 O 3 or β-Al...
Article
In this work, we quantify electronic and ionic contributions to conductivity in the bulk and depletion widths of back-to-back sputtered Pt Schottky contacts on single crystals of β-Ga 2 O 3 . We also demonstrate asymmetric changes to these contacts induced by DC bias at temperatures as low as 200 °C, which has obvious bearing on the performance and...
Article
Full-text available
In this work, a systematic photoluminescence (PL) study on three series of gallium oxide/aluminum gallium oxide films and bulk single crystals is performed including comparing doping, epitaxial substrates, and aluminum concentration. It is observed that blue/green emission intensity strongly correlates with extended structural defects rather than t...
Article
β-Ga2O3 is an ultrawide band gap semiconductor with emerging applications in power electronics. The introduction of acceptor dopants yields semi-insulating substrates necessary for thin-film devices. In the present work, exposure of Cu-doped β-Ga2O3 to UV light >4 eV is shown to cause large, persistent photoinduced darkening at room temperature. El...
Article
Caustic scrubbers are proposed to remove vaporized iodine from nuclear fuel reprocessing plants. Resulting caustic slurries of radioactive iodine (¹²⁹I) and other anions can be captured and immobilized into the cage structures of sodalite-type minerals. Here, mixed-anion sodalites were hydrothermally synthesized from a simulated caustic scrubber so...
Article
Low melting point glass systems were explored as candidates for binders of solid oxide nuclear wastes which include volatile elements such as radioactive iodine. The base glass systems considered were ZnO–Bi2O3–B2O3 and ZnO–Bi2O3–SiO2, with specific compositions selected for synthesis trials based on available phase diagrams and a desire to explore...
Article
Nuclear fuels containing uranium oxide, plus fission and activation products, will continue to undergo radioactive decay and also fission after removal from the reactor. These nuclear materials will undergo exposure to heat and persistent irradiation by alpha particles and neutrons. Vacancies and larger open volume defects, sometimes filled by heli...
Article
Electron paramagnetic resonance (EPR) and optical absorption are used to characterize Cu2+ (3d9) and Cu3+ (3d8) ions in Cu-doped β-Ga2O3. These Cu ions are singly ionized acceptors and neutral acceptors, respectively (in semiconductor notation, they are Cu− and Cu0 acceptors). Two distinct Cu2+ EPR spectra are observed in the as-grown crystals. We...
Article
Full-text available
Raman spectroscopy is one of the most useful techniques for studying the structure of UO2 and changes due to specific defects caused by doping, changes in stoichiometry, irradiation, or heating under oxidizing conditions. In this paper, we illustrate several aspects of the application of Raman techniques to the study of UO2, including the use of wa...
Preprint
Full-text available
In this review, we provide a perspective on the science and technology of vitrification of waste. First, we provide a background on the general classes of wastes for which vitrification is currently used for immobilization or is proposed, including nuclear and industrial hazardous wastes. Next, we summarize the issues surrounding solubility of wast...
Preprint
https://arxiv.org/abs/2201.03673 β-Ga2O3 materials with alumina alloying should allow even larger ultra-wide bandgaps, and bulk crystals are desired with high alumina contents to better lattice match Al-containing β-Ga2O3 epitaxial films. In this work, bulk Czochralski-grown single crystals of 10 mol.% Al2O3 alloyed β-Ga2O3 (β-Al0.2Ga1.8O3, i.e.,...
Article
Full-text available
Spinel crystallization is known to be detrimental to the operation of Joule heated ceramic melters during the vitrification of iron-rich high-level nuclear wastes (HLW) into borosilicate glasses. The literature on this subject focuses on tackling the problem by developing empirical constraints to design compositions, which limit the fraction of spi...
Preprint
https://arxiv.org/abs/2201.01861 Beta-Ga2O3 is an ultra-wide bandgap semiconductor with emerging applications in power electronics. The introduction of acceptor dopants yields semi-insulating substrates necessary for thin-film devices. In the present work, exposure of Cu-doped Ga2O3 to UV light > 4 eV is shown to cause large, persistent photo-indu...
Chapter
CdTe and its alloy CdZnTe possess optimal physical properties for room-temperature high-resolution X-ray and gamma-ray detector applications in areas of homeland security and medical imaging. Melt growth and Te-rich flux growth are primary methods employed to produce bulk single crystals of CdTe/CZT. Reduction of performance-limiting defects includ...
Chapter
Cd-Zn-Te/CdTe is material of choice for room temperature X-ray and gamma-ray detector applications, spanning security, medical and astronomical imaging. However, potential applications of this material are limited by unfavorable thermo-physical properties that make the crystal growth of large volume material challenging (particularly at faster grow...
Article
Full-text available
Non-ideal thermodynamics of solid solutions can greatly impact materials degradation behavior. We have investigated an actinide silicate solid solution system (USiO 4 –ThSiO 4 ), demonstrating that thermodynamic non-ideality follows a distinctive, atomic-scale disordering process, which is usually considered as a random distribution. Neutron total...
Article
Full-text available
Laboratory testing used to assess the long-term chemical durability of nuclear waste forms may not be applicable to disposal because the accelerated conditions may not represent disposal conditions. To address this, we examine the corrosion of vitrified archeological materials excavated from the near surface of a ~1500-year old Iron Age Swedish hil...
Article
β-Ga2O3 has demonstrated insulating properties with Mg, Fe, and Zn acceptor doping. Here we investigate Cu doping (0.25 at.%) in bulk Czochralski (CZ) and vertical gradient freeze (VGF) β-Ga2O3, with significant Cu incorporation, even with the expected Cu evaporation. Representative crystals were assessed for orientation, purity, optical, and elect...
Article
Highly alkaline wastes known as bauxite residue are the abundant byproducts of refining bauxite into alumina through the Bayer process, and worldwide estimates of these bauxite residue stockpiles exceed 3 billion tons, with hundreds of millions of tons produced annually. Bauxite residue utilization and remediation are significantly complicated by t...
Article
In this Letter, we investigate the atomic and electronic structure of a Hf-doped beta-gallium oxide (β-Ga2O3) single crystal using high resolution scanning transmission electron microscopy imaging and electron energy loss spectroscopy. Ultraviolet-visible (UV-Vis)-near-infrared absorption measurements and density functional theory calculations are...
Article
In alkali aluminosilicate glasses, additions of 4+ cations like Zr and Ti are often added to promote crystallization. In this study, Zr, Ti, or Sn are progressively substituted for Si in nepheline (NaAlSiO4) glass to determine their impact on the crystallization behavior. For glasses homogeneous on quenching, up to NaAlZr0.075Si0.925O4, NaAlSn0.100...
Article
Zinc-doped monoclinic gallium oxide (β-Ga2O3:Zn) has semi-insulating properties that could make it a preferred material as a substrate for power devices. Infrared and UV/Visible spectroscopy were used to investigate the defect properties of bulk β-Ga2O3:Zn crystals. As-grown crystals contain a single O-H stretching mode at 3486.7 cm⁻¹ due to a neut...
Article
In this study, the formation and character of gallium vacancies (VGa) and their complexes in near surface and bulk regions of single crystal β-Ga2O3 were explored using unintentionally doped single crystals grown by the Czochralski method. As-grown and O2 annealed (up to 1550 °C) samples were investigated using positron annihilation spectroscopy (P...
Article
Ga2O3 has several soluble deep acceptors that impart insulating behavior. Here, we investigate Zn doping (0.25 at. %) in bulk Czochralski and vertical gradient freeze β-Ga2O3. Representative crystals were assessed for orientation (electron backscatter diffraction and Raman spectroscopy), purity (glow discharge mass spectrometry and secondary ion ma...
Article
Knowledge of the origin of deep levels and their impact on electrical properties is critical for device applications of β-Ga 2 O 3. By annealing under an oxygen (O 2) atmosphere, the resistivity in shallow-donor (zirconium) doped β-Ga 2 O 3 :Zr single crystals is found to increase by more than 10 orders of magnitude to (7 ± 4) × 10 10 cm, which is...
Article
Electron paramagnetic resonance (EPR) is used to identify and characterize neutral zinc acceptors in Zn-doped β-Ga2O3 crystals. Two EPR spectra are observed at low temperatures, one from Zn ions at tetrahedral Ga(1) sites (the Zn0Ga1 acceptor) and one from Zn ions at octahedral Ga(2) sites (the Zn0Ga2 acceptor). These Zn acceptors are small polaron...
Article
In the composition space for Hanford low-activity nuclear waste glass, the waste loading of some formulations is limited by poor incorporation of sulfate. In particular, certain elements identified in previous studies tend to raise or lower sulfate solubility in borosilicate glass. The aim of the current study is to understand how vanadium and chro...
Article
Full-text available
Disposal of spent nuclear fuel poses significant challenges, as the UO2 and fission products are under constant irradiation and must be safely stored for millennia. CeO2 is a non-radioactive analog for UO2 for studying microstructure and its evolution. Many techniques have been applied to uranium and cerium oxides to investigate point defects. Posi...
Article
Full-text available
The structures of a series of Na2O–FeO–Fe2O3–SiO2 melts with Si/Fe = 1, 2, or 3 have been characterized via synchrotron X-ray total scattering using aerodynamic levitation, a containerless technique, paired with laser heating. The melt structure has been simulated using empirical potential structure refinement (EPSR) based on X-ray scattering data...
Article
Glass-ceramic (GC) materials have the formability advantages of glasses and the opportunity for controlled crystallization of functional ceramic phases. Here, we obtain GCs containing the hard magnetic phase Sr-hexaferrite (SrFe12O19) from a borate glass. Ten compositions in the B2O3-Fe2O3-SrO system were explored, varying B2O3 and Sr/Fe ratio. Com...
Article
Full-text available
European Bronze and Iron Age vitrified hillforts have been known since the 1700s, but archaeological interpretations regarding their function and use are still debated. We carried out a series of experiments to constrain conditions that led to the vitrification of the inner wall rocks in the hillfort at Broborg, Sweden. Potential source rocks were...
Article
Cost-effective and highly efficient Fe-N‑C single-atom catalysts (SACs) have been known as the most promising potential Pt substitutes for the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel...
Article
Fluorine and other halides commonly exist in nuclear waste forms, and due to their volatile nature, halide retention poses an issue affecting waste loading during vitrification. The compositional effect on fluorine incorporation in aluminosilicate glasses is investigated through molecular dynamics simulations. Oxygen and fluorine coordination numbe...