Olivia A. Graeve

We explore the effects of lithium doping on the structure of three alkaline-earth hexaborides─CaB 6, SrB 6, and BaB 6 . Lithium incorporation was characterized using inductively coupled plasma mass spectrometry and X-ray diffraction analyses, demonstrating a systematic expansion of the cubic Pm3̅m lattice with increasing lithium concentration. Scanning and transmission electron microscopy revealed that lithium doping induces distinct surface pitting and localized lattice distortions. Solid-state 7 Li nuclear magnetic resonance (NMR) spectroscopy provided deeper insight into the lithium coordination environments. One-dimensional NMR confirmed the ionic character of lithium and demonstrated the presence of minor side products, which were largely eliminated by acid treatment of the powders. Two-dimensional exchange spectroscopy NMR identified two distinct ionic lithium environments within the BaB 6 lattice. The absence of cross-peaks with side-product signals confirmed spatial separation and chemical stability of lattice-confined lithium. Our analyses establish a foundational understanding of alkali metal doping behavior in boron-rich ceramics and highlight the structural role of lithium as a dopant in hexaboride systems, supporting future investigations into how lithium incorporation may influence electronic properties.

We describe the osteogenic potential and hemocompatibility of rare-earth-doped hydroxyapatite in a murine preosteoblastic (MC3T3-E1) cell line, aiming to assess the osteoblast differentiation effect of ytterbium-, terbium-, cerium-, and europium-doped hydroxyapatite through alkaline phosphatase activity and the expression levels of osteogenic marker genes, including Runx2, ALP, OPN, and BMP2. Our findings reveal various levels of enhancement in early osteogenic activity across the four dopants. Among the dopants tested, europium- and ytterbium-doped hydroxyapatites produce the most pronounced effects, significantly enhancing ALP activity and upregulating multiple osteogenic genes. Cathodoluminescence spectroscopy confirms successful incorporation of all rare-earth ions in the HAp lattice, while hemocompatibility and cell viability assays demonstrate that all compositions are biocompatible and safe for contact with blood, providing a comparative framework for understanding how rare-earth dopants influence early osteogenic response. These findings demonstrate the potential of Eu- and Yb-doped hydroxyapatites as bioactive materials for bone regeneration.

We report a defect-selective luminescence response in calcium-deficient hydroxyapatite (HAp) induced by electron and ion irradiation. Compacted HAp pellets prepared from hydrothermally grown nanofibers were investigated to analyze defect-related luminescence using photoluminescence (PL) and cathodoluminescence (CL) techniques, both before and after compaction. Low-energy electron beam irradiation (15 keV) produced a two-stage luminescent response, an initial enhancement arising from field-assisted activation of OH-channel vacancies (VOH and VOH + Hi), followed by an exponential decay attributed to defect annealing. Monochromatic transient CL measurements show that this rise–decay behavior is selective to the OH-related bands at 2.57 and 2.95 eV, whereas the 3.32 and 3.67 eV emissions exhibit only a monotonic exponential decay. The corresponding decay constants further indicate that the activated OH-channel vacancies anneal more rapidly than the other centers, consistent with their higher electron-capture probability and lower structural stability. In contrast, Ga+ ion irradiation (30 keV, 1.4 × 10−13 A/µm2) induced progressive monotonic luminescence quenching, primarily driven by selective annealing of oxygen vacancies in PO43− groups. These complementary pathways, electron-induced activation and ion-driven suppression, demonstrate that irradiation serves as a versatile tool for defect engineering in hydroxyapatite. Beyond providing fundamental insights into vacancy stability, these results open new routes for tailoring the optical, sensing, and bioimaging functionalities of HAp through controlled irradiation.

Recently, there has been a strong interest in understanding and developing Fe-based bulk metallic glasses (Fe-BMG), due to their distinctive set of properties that make Fe-BMG an attractive material in the development of advanced magnetic components. The design of Fe-BMG is hindered by its reliance on extensive experimentation in searching for the optimal composition, which is time-consuming and costly. New machine learning (ML) approaches offer a potential solution to aid in the discovery and development of Fe-BMG with desired properties, but understanding the development process and selecting the correct algorithm from the many options available is a challenge. This paper presents a comprehensive review of ML algorithms reported in the literature for the design of Fe-BMGs, aiming to provide an objective comparative analysis of their performance, and enabling informed decision-making in the future design of Fe-BMGs.

We report the influence of vacancy point defects on the conductivity and piezoelectricity of hydroxyapatite (HAp) nanofibers. A combination of experimental techniques, including conductive atomic force microscopy, electrostatic force microscopy, and switching spectroscopy piezoresponse force microscopy, along with computational modeling, was employed to elucidate the conduction mechanisms and charge accumulation effects in HAp. Our findings demonstrate that oxygen and calcium vacancy defects play a crucial role in the conduction mechanism of HAp nanofibers, specifically through charge-trapping and detrapping processes, as well as in charge accumulation and the piezoelectric response. The Poole-Frenkel conduction mechanism was confirmed by fitting experimental current-voltage data to a theoretical model, revealing a dielectric constant consistent with previously reported theoretical values. These insights contribute to a deeper understanding of the role of point defects in the electrical and piezoelectric properties of HAp, which is essential for optimizing its performance in biomedical applications.

Image-to-image translation is a task in the field of computer vision that has been gaining importance in recent years, with the objective of transforming an image from one visual domain to another without losing coherence. This process has applications in various tasks, such as style transfer, and in different fields, including medicine. One area where image translation has great potential is materials science, where obtaining a series of images of a material using scanning electron microscopy can be a complex process. In this context, image-to-image translation emerges as an alternative for generating synthetic images of a material’s microstructure, based on specific visual information obtained by the scanning electron microscopy process. In this work, we present a comparison of the performance of different conditional generative architectures for obtaining synthetic images from edge maps. These edge maps are obtained through image pre-processing algorithms such as the Laplacian and Canny edge detectors, complemented with image manipulation and correction techniques. To evaluate the performance of the conditional generative adversarial networks, metrics such as the structural similarity index (SSIM) and peak signal-to-noise ratio (PSNR) are employed. The results demonstrate that both the choice of edge detection algorithm and the correction techniques significantly impact the model’s ability to generate synthetic images with high fidelity.

We present a direct electrospinning fabrication technique for the manufacture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylene oxide) (PEDOT:PSS/PEO) polymer fibers containing embedded cubic lanthanum hexaboride (LaB 6 ) particles. We focus on the impact of relative humidity on the formation of uniform polymer fibers and show that a relative humidity of 5% is optimal, resulting in an average fiber thickness of 266 ± 88 nm. As the relative humidity is increased, the fibers contain beads as a consequence of Rayleigh instabilities. The addition of lanthanum hexaboride cubic particles to the polymer solution before electrospinning results in the encapsulation of the LaB 6 particles inside the fibers. We investigate the effect of LaB 6 particle size on morphology and observe that particles of ∼500 nm yield a fiber-cube-fiber morphology, while 2 μm particles result in fewer embedded cubes along the length of the polymer fibers. This phenomenon likely arises from electrodynamic interactions between the LaB 6 particles in the polymer solution and the electric field lines generated during electrospinning between the spinneret and the collector. Our results display the versatility of the electrospinning technique in the fabrication of unique polymer/hexaboride composite fibers.

Abstract This study describe the design and catalytic activity of enzymatic nanoreactors based on copper oxide nanoparticles surface‐functionalized with laccase (CuO‐Lac) from Coriolopsis gallica . Transmission electron micrographs show complete laccase coverage on the nanoparticle surfaces. In addition, the catalytic rate ( k cat ) of the immobilized laccase is two‐fold higher at an optimized pH, when compared with free laccase, while the affinity constant ( K M ) is not significantly affected. Importantly, the total turnover number (TNN) of the CuO‐Lac nanoreactors reaches 358 ± 9 × 10 6 mol ABTS/mol laccase, which is four times higher than the TTN obtained for the free enzyme (88 ± 3 × 10 6 ). Thus, our nanoreactors exhibit a significant improvement in laccase catalytic performance. Inductively coupled plasma mass spectrometry was used to confirm the loss of copper ions from free laccase during the catalytic cycle, suggesting that the CuO nanoparticles act as a copper ion source that prevents enzyme inactivation. This work contributes to an improved understanding of the CuO‐laccase interface and confirms that CuO nanoparticles serve as copper sources for laccase during catalysis.

Abstract We demonstrate that doping hydroxyapatite (HAp) with Cr 3+ ions induces oxygen vacancies, contributing to paramagnetism. Cathodoluminescence and photoluminescence analyses reveal increased oxygen vacancy formation in $${\text{O}}{\text{H}}^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>OH</mml:mtext> <mml:mo>-</mml:mo> </mml:msup> </mml:math> and $${\text{P}}{\text{O}}_{4}^{3-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mtext>PO</mml:mtext> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:mo>-</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> groups with rising Cr 3+ concentrations, highlighted by stronger cathodoluminescence emissions at 2.57 and 2.95 eV and the photoluminescence emission at 3.32 eV. Raman spectroscopy shows new modes at 900 and 970 cm −1 , indicating distortion of the v 1 vibrational mode due to Cr 3+ substitution at Ca(II) sites of the HAp lattice. X-ray photoelectron spectroscopy confirms Cr 3+ in the HAp:Cr. Magnetometry reveals a shift from diamagnetism in pure HAp to increasing paramagnetism in HAp:Cr with higher Cr 3+ content, achieving 0.0460 emu/g at 10 kOe with concentrations higher than 2.9 at.%. This paramagnetism is attributed to Cr 3+ ions and singly ionized oxygen vacancies $$V^{\prime}_{{\text{O}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>V</mml:mi> <mml:mtext>O</mml:mtext> <mml:mo>′</mml:mo> </mml:msubsup> </mml:math> aligning along an external magnetic field, with $$V^{\prime}_{{\text{O}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>V</mml:mi> <mml:mtext>O</mml:mtext> <mml:mo>′</mml:mo> </mml:msubsup> </mml:math> formation linked to $${\text{PO}}_{4}^{{3}-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mtext>PO</mml:mtext> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:mo>-</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> replacement by $${\text{PO}}_{3}^{{2}-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mtext>PO</mml:mtext> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> <mml:mo>-</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> in HAp.

Previous research has shown that gendered societal expectations are adopted by students as seemingly personal and individualistic self‐assessments and preferences, which then lead to gender‐normative choices about college majors and careers. This study examines one seemingly objective mechanism, which millions use each year for guidance on college majors and careers. We examine two Career Assessment Tools (CATs) with deep institutional presence: O*NET and Traitify. Analyzing an exemplar case of engineering majors, we find that CATs are less likely to recommend engineering occupations to women, even after controlling for GPA, satisfaction with the major, and planned persistence. Even in our sample of engineering majors, CATs apparently use small differences in students' gender‐normative self‐expressive preferences to drive sharply different occupational recommendations, thereby solidifying pathways toward gender‐segregated occupations and reinforcing men's dominance of engineering. If women similar to our study participants take CATs, they are likely to be steered away from engineering occupations or majors. More broadly, CATs illustrate how taken‐for‐granted, seemingly neutral technologies can reinforce gender segregation.

We present a luminescence study investigating the dissolution of rare-earth-doped hydroxyapatite scaffolds in simulated body fluid (SBF), aiming to assess the luminescence stability of Tb-, Ce-, and Eu-doped scaffolds over time. Our findings reveal a consistent decrease in luminescence emission intensity across all samples over a four-week period in which the scaffolds were immersed in the SBF. In addition, energy-dispersive spectroscopy confirms a decrease in rare-earth ion concentration in the scaffolds with respect to time, whereas fluorescence spectroscopy shows the presence of rare-earth ions in the SBF, indicating the partial dissolution of the scaffolds over time. The use of rare-earth ions as luminescence markers provides insights into the mechanisms of apatite formation in hydroxyapatites. Thus, these scaffolds may find wider use in regenerative medicine, particularly in targeted drug delivery systems, where their luminescent properties have the potential to noninvasively track drug release.

We report compression tests on micropillars manufactured from bulk specimens of partially devitrified SAM2×5 (Fe 49.7 Cr 17.7 Mn 1.9 Mo 7.4 W 1.6 B 15.2 C 3.8 Si 2.4 ). Yield strength values of ≈6 GPa are obtained. Such a high strength can be attributed to the higher glass transition temperature (883 K) of this material, which impedes the multiplication of shear bands under loading, and to the presence of hard crystalline domains that result from devitrification of the amorphous powders during powder consolidation. The Vickers hardness of the specimens is found to be strongly correlated to the processing temperature and, hence to the volume of crystalline phases present in the specimens. As the processing temperature is increased, there is a reduction in free volume from the structural relaxation process in the amorphous alloy, leading to the eventual nucleation of crystalline phases of BCC Fe, Cr 2 B, Cr 21.30 Fe 1.7 C 6 , or Fe 23 B 2 C 4 , during the densification process. These results shed light on the relationship between nanocrystalline domains and the mechanical behavior of Fe‐based amorphous/crystalline composites.

We describe the triboluminescence response of undoped (BaAl 2 Si 2 O 8, h –BAS) and Eu-doped ( h –BAS:Eu) barium hexacelsian powders and show that the triboluminescence behavior is dependent on the formation of barium vacancies. X-ray photoelectron spectroscopy of the h –BAS:Eu powders confirms the presence of Eu 3+ and Eu 2+ in the compound, leading to the formation of significant vacancy point defects in excess of those found in h –BAS as a result of the charge imbalance caused by the substitution of Eu 3+ in Ba 2+ sites. From electron paramagnetic resonance measurements and density functional theory (DFT) calculations, we demonstrate that the vacancy defects correspond to singly ionized barium vacancies. DFT-calculated thermodynamic transitions and electronic structure calculations reveal deep energy levels within the compound’s energy band gap, with a strong emission at 3.33 eV correlated to an electron exchange between the conduction band minimum and a barium vacancy center. Time-resolved triboluminescence spectra show that the increased concentration of barium vacancies in h –BAS:Eu enhances the signal by about 75% compared to the signal from h –BAS. These results play an important role in the understanding of fundamental mechanisms behind the triboluminescence response of ceramic materials as well as the role of different types of defects in this process.

Initiatives and Assessment.Ms. Trahan leads planning and development of new student success initiatives

We present the effect of sodium ions (Na + ) on the nucleation process and phase selectivity for the formation of hexagonal molybdenum trioxide crystals ( h -MoO 3 ). The phase selectivity during the reaction is attributed to the interaction of Na + with the molecules in our precursor solution formed by metallic molybdenum dissolved in a mixture of hydrochloric and nitric acids. The vibrational characteristics of the precursor solutions were studied by Raman spectroscopy in combination with density functional theory modeling, showing the presence of [MoO 2 Cl 3 (H 2 O)] − ions within the solutions. The symmetric stretching vibration of the Mo–O bonds found at 962 cm –1 in [MoO 2 Cl 3 (H 2 O)] − proved that the addition of Na + (in the form of dissolved NaCl) to the precursor solutions resulted only in an electrostatic interaction with the aquo (H 2 O) and chloro (Cl – ) ligands in the complex. After heating the precursor solutions, X-ray diffraction, Raman spectroscopy, and scanning electron microscopy of the obtained powders showed that adding NaCl contributed to the phase selectivity of the reaction, with the Na + ions playing a vital role in the formation of h -MoO 3 over other crystalline phases. Based on the nature of the molybdenum complexes found in the precursor solutions and the structural characteristics of the powders, a formation mechanism to obtain h -MoO 3 is proposed. Additionally, the phase stability of h -MoO 3 crystals was studied by calorimetry techniques, showing that h -MoO 3 transforms to α-MoO 3 at ∼649 K. These results provide important insights into phase control to selectively form hexagonal MoO 3 .

Tantalum carbide (TaC) and hafnium carbide (HfC) have some of the highest melting temperatures among the transition metal carbides, borides, and nitrides, making them promising materials for high‐speed flight and high‐temperature structural applications. Solid solutions of TaC and HfC are of particular interest due to their enhanced oxidation resistance compared to pure TaC or HfC. This study looks at the effect of Hf content on the oxidation resistance of TaC–HfC sintered specimens. Five compositions are fabricated into bulk samples using spark plasma sintering (2173 K, 50 MPa, 10 min hold). Oxidation behavior of a subset of the compositions (100 vol% TaC, 80 vol% TaC + 20 vol% HfC, and 50 vol% TaC + 50 vol% HfC) is analyzed using an oxyacetylene torch for 60 s. The TaC–HfC samples exhibit a reduction in the oxide scale thickness and the mass ablation rate with increasing HfC content. The improved oxidation resistance can be attributed to the formation of a Hf 6 Ta 2 O 17 phase. This phase enhances oxidation resistance by reducing oxygen diffusion and serving as a protective layer for the unoxidized material. The superior oxidation resistance of TaC–HfC samples makes these materials strong contenders for the development of high‐speed flight coatings.

In this review, two interrelated areas are focused on for the development of novel amorphous metallic alloys, namely, materials processing and machine learning techniques for the design of new alloy compositions. Findings, barriers, and opportunities are described, targeting powder production and sintering, additive manufacturing, and postprocessing techniques, followed by the latest developments in artificial intelligence algorithms for both the design of new alloys and for alloy classification tasks.