Faculty Scholarship

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Nanoscale engineering of BaTiO3 using Y3+-Ta5+ dipoles
(Taylor & Francis, 2023-02) Tidrow, Steven; Pellegrino, Victoria
BaTiO3 properties can be enhanced to improve capacitor energy storage density through electric-field (E) dipole engineering at the nanoscale (E-DENS). E-DENS allows engineers to modify the internal E through dipole interactions. E-DENS of Ba[(Y3+,Ta5+)xTi1-2x]O3 with 0.0000 ≤ x ≤ 0.0500 are investigated by substituting Y3+-Ta5+ dipole pairs for Ti4+-Ti4+ non-dipolar pairs within the BaTiO3 structure. The Y3+ and Ta5+ ions are more polarizable than Ti4+ and are expected to increase the temperature at which the material becomes cubic and paraelectric. Room temperature XRD, UV-Vis-NIR, LCR, and resistivity analysis have been used to characterize Ba[(Y3+,Ta5+)xTi1-2x]O3 with 0.0000 ≤ x ≤ 0.0500.
Structure-terahertz property relationship and femtosecond laser irradiation effects in chalcogenide glasses
(Elsevier, 2023-01) Sundaram, S.K.; Tostanoski, Nicholas; Heilweil, Edwin; Wachtel, Peter; Musgraves, J. David
We report structure-terahertz (THz) property relationship for various non-oxide chalcogenide glasses including unary (vitreous selenium (Se)), binary (arsenic sulfide (As-S), arsenic selenide (As-Se), and germanium selenide (Ge-Se)), and ternary (germanium arsenic selenide (Ge-As-Se)), systems along with commercially available AMTIR-1, IRG 22, and IRG 24 Ge-As-Se glasses. This comprehensive study is the first of its kind to combine Raman spectroscopy to examine structural units, connectivity, and glass network and terahertz time-domain spectroscopy (THz-TDS) to record the THz refractive index, n(THz), across a broad THz bandwidth. THz-TDS was carried out at Alfred University (AU) and National Institute of Standards and Technology (NIST), ultimately providing confidence in n(THz) values measured at AU. Vitreous Se, = 2.0, record the minimum THz refractive index value of all Se-containing glasses. As-S and As-Se binary glasses have the highest measurable THz refractive index value at = 2.4. Ge-Se binary glasses measure increased THz refractive index as increases, with the maximum at = 2.8. Ternary Ge-As-Se glasses record the maximum THz refractive index value at = 2.5 for Ge10As30Se60. Low-repetition rate femtosecond laser irradiation (≈1 KHz, ≈40 fs, and ≈70 mW) was used to modify As-S and As-Se glass systems, where Raman and THz-TDS were used to observe minimal structural and THz refractive index values changes, respectively. Long-wave infrared (LWIR) (e.g., 10 μm)-THz (e.g., 1.0 THz) refractive index correlation is presented for all binary and ternary studied chalcogenide glasses. Such a correlation is valuable for predicting and designing chalcogenide glasses for integrated optical applications across THz and IR regions.
3D Printed Thick Reduced Graphene Oxide: Manganese Oxide/Carbon Nanotube Hybrid Electrode with Highly Ordered Microstructures for Supercapacitors
(Wiley, 2022-11) Ding, Junjun; Gao, Yuqi
High capacitance and good rate performance supercapacitors are needed to power sensors and miniaturized electrical devices. Thick electrodes are promising to increase the mass loading of active materials in supercapacitors, but the 3D geometries and microstructures in thick electrodes still hinder the development with high electron and ion exchange rate and accessible active sites. The scaffold 3D electrodes of reduced graphene oxide:manganese oxide/carbon nanotube (rGO:MnOx/CNT) are manufactured by material extrusion 3D printing (ME3DP), where the mass ratio of rGO to MnOx/CNT composites, thickness, and mass loading per unit area are controllable. The increasing amount of MnOx/CNT composites boosts the areal capacitance. Although the rate capability decays fast with the increasing of MnOx/CNT, it remains stable at different thicknesses (1.2, 1.6, and 2 mm). 2 mm thick rGO:MnOx/CNT (weight ratio 5:3) electrode exhibits an area capacitance of 302.13 mF cm−2 at a current density of 0.5 mA cm−2, due to the highly ordered rGO networks. Compared to the casted electrodes, the microstructures in the 3D printed electrode contribute to lower resistances for the charge and ion transportation.
Glasses in a Fraction of a Second
(Optica, 2022-09) Sundaram, S.K.
The development of ultrafast lasers has revolutionized the study and processing of glasses, enabling new applications and drawing closer to a full understanding of the liquid-to-glass transition.
Additive manufacturing of yttria stabilized zirconia and lithium silicate electroceramics for energy applications
(American Ceramic Society, 2022-09) Sundaram, S.K.; Zaengle, John; Allan, Shawn
Structural and Optical Properties of High Entropy (La,Lu,Y,Gd,Ce)AlO3 Perovskite Thin Films
(Wiley, 2022-08) Wu, Yiquan; Corey, Zachary; Lu, Ping; Zhang, Guangran; Sharma, Yogesh; Rutherford, Bethany; Dhole, Samyak; Roy, Pinku; Wang, Zhehui; Wang, Haiyan; Chen, Aiping; Jia, Quanxi
Mixtures of Ce-doped rare-earth aluminum perovskites are drawing a significant amount of attention as potential scintillating devices. However, the synthesis of complex perovskite systems leads to many challenges. Designing the A-site cations with an equiatomic ratio allows for the stabilization of a single-crystal phase driven by an entropic regime. This work describes the synthesis of a highly epitaxial thin film of configurationally disordered rare-earth aluminum perovskite oxide (La0.2Lu0.2Y0.2Gd0.2Ce0.2)AlO3 and characterizes the structural and optical properties. The thin films exhibit three equivalent epitaxial domains having an orthorhombic structure resulting from monoclinic distortion of the perovskite cubic cell. An excitation of 286.5 nm from Gd3+ and energy transfer to Ce3+ with 405 nm emission are observed, which represents the potential for high-energy conversion. These experimental results also offer the pathway to tunable optical properties of high-entropy rare-earth epitaxial perovskite films for a range of applications.
Structure-terahertz property relationship in sodium borosilicate glasses
(Wiley, 2022-08) Möncke, Doris; Tostanoski, Nicholas; Youngman, Randall; Sundaram, S.K.
We report, for the first time, an early evidence of structure-terahertz (THz) property relationship for two tie-lines within the sodium borosilicate glass system. The NaBSi series was chosen to study the effect of the substitution of silicon dioxide for boron oxide, whereas the BNaSi series studies the substitution of silicon dioxide for sodium oxide. Nuclear magnetic resonance, infrared absorption, and Raman spectroscopies were used to determine structural changes across both series. THz time-domain spectroscopy was used to record the refractive index over the measured bandwidth. Individual measurements at .502 THz were used as a frequency of focus for comparisons. The foundation for the proposed structure-THz property relationship is based on higher measurable THz refractive index changes correlated to a depolymerized glass network, R > .5, a network consisting of SiO4 tetrahedra and charge-deficient [BØ4]− tetrahedra-forming borosilicate danburite and reedmergnerite rings with mixed Si–O–B bridges, and the formation of nonbridging oxygen (nbO) atoms on silicate tetrahedra. A polymerized glass network, R < .5, consists of homonuclear boroxol and silica rings within sodium borate and silicate subnetworks. Calculated and experimental fractions of tetrahedral borate and silicate tetrahedra with one nbO, optical basicity, density, and network connectivity data support the structure-THz property relationship.
The intrinsic strength prediction by machine learning for refractory high entropy alloys
(Springer Nature, 2022-08) Wang, Kun; Yan, Yong-Gang
Herein, we trained machine learning (ML) model to quickly and accurately conduct the strength prediction of refractory high entropy alloys (RHEAs) matrix. Gradient Boosting (GB) regression model shows an outstanding performance against other ML models. In addition, the heat of fusion and atomic size difference is shown to be paramount to the strength of the high entropy alloys (HEAs) matrix. In addition, we discussed the contribution of each feature to the solid solution strengthening (SSS) of HEAs. The excellent predictive accuracy shows that the GB model can be efficient and reliable for the design of RHEAs with desired strength.
Future of optical glass education
(Optica Publishing Group, 2022-06) Clare, Alexis; Ballato, John; Seddon, Angela; Petit, Laeticia; Hu, Juejun; Richardson, Kathleen
In homage to the United Nations International Year of Glass 2022 (IYoG 2022), this article discusses the past, present, and future of glass education, with a focus on inorganic systems of value to optical and photonic applications.
The oxidation-resistance mechanism of WTaNbTiAl refractory high entropy alloy
(Elsevier, 2022-08) Wang, Kun; Yan, Yonggang; McGarrity, Kade; Delia, Daniel; Fekety, Curtis
The WTaNbTiAl alloy demonstrated excellent oxidation resistance with a 31.83 mg/cm2 of specific mass gain after 48 h oxidation at 1000 °C in the air environment. Based on the multi-scale microstructural characterizations, a diffusion-controlled three-layers oxide scale model was proposed to explain the oxidation kinetics of this RHEA. In addition, thermodynamic calculation results shed light on the formation mechanism of the oxides based on the standard free energy of formation. The present work uncovered the oxidation-resistance mechanism of WTaNbTiAl RHEA via delicate microstructural analysis of oxides, which assists to guide the design of oxidation-resistant high entropy alloys.
Glass as a State of Matter—The “newer” Glass Families from Organic, Metallic, Ionic to Non-silicate Oxide and Non-oxide Glasses
(Mineralogical Society of America, 2022-05) Möncke, Doris; Topper, Brian; Clare, Alexis G.
In theory, any molten material can form a glass when quenched fast enough. Most natural glasses are based on silicates and for thousands of years only alkali/alkaline earth silicate and lead-silicate glasses were prepared by humankind. After exploratory glass experiments by Lomonosov (18th ct) and Harcourt (19th ct), who introduced 20 more elements into glasses, it was Otto Schott who, in the years 1879–1881, melted his way through the periodic table of the elements so that Ernst Abbe could study all types of borate and phosphate glasses for their optical properties. This research also led to the development of the laboratory ware, low alkali borosilicate glasses. Today, not only can the glass former silicate be replaced, partially or fully, by other glass formers such as oxides of boron, phosphorous, tellurium or antimony, but also the oxygen anions can be substituted by fluorine or nitrogen. Chalcogens, the heavier ions in the group of oxygen in the periodic table (S, Se, Te), on their own or when paired with arsenic or germanium, can function as glass formers. Sulfate, nitrate, tungstate and acetate glasses lack the conventional anion and cation classification, as do metallic or organic glasses. The latter can occur naturally—amber predates anthropogenic glass manufacture by more than 200 million years. In this chapter, we are going to provide an overview of the different glass families, how the structure and properties of these different glass types differ from silicate glasses but also what similarities are dictated by the glassy state. Applications and technological aspects are discussed briefly for each glass family.
Luminescence and Scintillation in the Niobium Doped Oxyfluoride Rb4Ge5O9F6:Nb
(MDPI, 2022-06) Misture, Scott; Carone, Darren; Klepov, Vladislav; Schaeperkoetter, Joseph; Jacobsohn, Luiz; Aziziha, Mina; Schorne-Pinto, Juliano; Thomson, Stuart; Hines, Adrian; Besmann, Theodore; zur Loye, Hans-Conrad
A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b = 11.7265(2) Å, and c = 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9 units connected by GeO3F3 octahedra. In its pure form, Rb4Ge5O9F6 shows neither luminescence nor scintillation but when doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.9960(3) Å, b = 11.7464(6) Å, and c = 19.3341(9) Å. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggest that the niobium is located in an octahedral coordination environment. Optical measurements inform us that the niobium dopant acts as the activator. The synthesis, structure, and optical properties are reported, including radioluminescence (RL) measurements under X-ray irradiation.
Synthesis, Processing and the Effect of Thermal Treatment on the Solubility, Antioxidant Potential and Cytocompatibility of Y2O3 and CeO2 doped SiO2-SrO-Na2O Glass-Ceramics
(SAGE, 2022-04) Wren, Anthony; Keenan, Timothy; Placek, Lana; Coughlan, Aisling
Thermal treatment of a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramic series (where x = 0.08 and MO = Y2O3 or CeO2) was conducted in order to synthesize yttrium (Y3+) and cerium (Ce3+) crystalline species that may act as radical oxygen specie (ROS) scavengers. The prominent phase for the Control is a sodium-strontium-silicate while the experimental glass-ceramics (HY, YCe, and HCe) present sodium-Y/Ce-silicate and oxide phases. Disk shrinkage during thermal processing ranges from 1–7% for Control, HY, YCe, and HCe in both diameter and thickness. Solubility studies determined that the release of Si4+ and Na+ are greatest from the Control disks which peaks at 1550 µg/mL. Release from the Y3+ and Ce3+ glass-ceramics reached 320 µg/mL for Si4+ and 630 µg/mL for Na+. The range of antioxidant capacity (ABTS assay) for all samples was 0.31–3.9 mMTE. No significant reduction in MC 3T3 Osteoblast cell viability was observed for any composition tested.
Durable Cr-substituted (Ba,Cs)1.33(Cr,Ti)8O16 hollandite waste forms with high Cs loading
(Wiley, 2022-02) Misture, Scott; Zhao, Mingyang; Birkner, Nancy; Schaeperkoetter, Joseph; Koch, Robert; Russell, Patrick; Besmann, Theodore; Amoroso, Jake; Brinkman, Kyle
A series of Cr-substituted hollandite solid solution BaxCsyCr2x+yTi8−2x−yO16 over a broad range of Cs content (x + y = 1.33, 0 ≤ x and y ≤ 1.33) were systematically investigated. A monoclinic-to-tetragonal phase transition was induced by increasing Cs content in the tunnel sites of the hollandite structure, and all members of the series show structure modulations related to the ordering of the Ba/Cs and vacancies along the tunnels. The thermodynamic stability of the Cr-substituted hollandite samples was measured via high-temperature oxide melt solution calorimetry, which included making the first measurements of the enthalpies of drop solution for Cs2O and BaO in sodium molybdate solvent at 800°C. Thermodynamic stability increased with increasing Cs content for the series of Cr-substituted hollandite, which also exhibited a greater thermodynamic stability compared to other substituted hollandite analogs including Zn, Ga, Fe, and Al variants. The leaching performance, also known as aqueous durability, demonstrated that the fractional Cs release in the Cr hollandite samples is much lower than in other hollandite systems. After 7 days of leaching at 90°C, the lowest Cs release was observed in the sample with the highest Cs content, approximately 22 wt.% Cs. The Cs release could be further suppressed, by approximately 3× if the sample was further densified and sintered. The Cs release results correlated inversely to the thermodynamic stability, suggesting that the thermodynamic stability may be used in future materials design for nuclear waste immobilization.
Novel transparent MgGa2O4 and Ni2+-doped MgGa2O4 ceramics
(Springer, 2022-01) Wu, Yiquan; Zhang, Guangran; Goldstein, Adrian
In this study we fabricated, for the first time, magnesium gallate (MgGa2O4, a partially inverted spinel) transparent ceramics, both undoped and doped with 1 at% Ni. The specimens were derived from in-house prepared powder, with a crystallite size of ∼10 nm (by wet chemistry) and densified by pulsed electric current sintering (PECS; peak temperature 950 °C for 90 min). Densification levels of 99.84% and 99.52% of theoretical density were attained for doped and undoped materials, respectively. Doping with Ni was seen to marginally improve the densification level. Quite transparent specimens were produced: the best showing transmission of ∼89% of the theoretical level (thickness t = 0.85 mm). The absorption spectra revealed that the dopant was accumulated as Ni2+ in the octahedral sites of the lattice, as occurs in single-crystal specimens. After excitation at 980 nm, the doped disks exhibited a wide fluorescence band centered at 1264 nm.
Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics
(Springer, 2022-01) Möncke, Doris; Wójcik, Natalia A.; Tagiara, Nagia S.; Kamitsos, Efstratios I.; Ali, Sharafat; Ryl, Jacek; Barczyński, Ryszard J.
Electrical properties of beryllium-alumino-tellurite glasses and glass–ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass–ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.
Tunable Large-Scale Compressive Strain Sensor Based on Carbon Nanotube/Polydimethylsiloxane Foam Composites by Additive Manufacturing
(Wiley, 2021-12) Ding, Junjun; Liu, Chao; Le, Linh; Zhang, Mingshao
The compressive strain sensor is an extensively used flexible electronic device because of its capability to convert mechanical deformation to an electrical signal. However, the difficulty in tuning the performance of the strain sensor limits its further applications. Herein, the approach of fabricating a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) compressive strain sensor, which has both tunable mechanical and electrical performances, is presented. CNT plays the role of reinforcement due to its outstanding mechanical strength and electrical conductivity. PDMS is a widely used matrix because of its softness and nontoxicity. The material extrusion 3D printing method is used to fabricate the composites, due to its advantages of design flexibility and compatibility with liquid-based materials. The foam microstructure formed by removing sodium chloride provides a large-scale deformation of at least 50% compressive strain and excellent elasticity. The strain sensor works durably over 10 000 cycles, with a gauge factor (GF) of 17.4. The compressive strain sensor in detecting both large- and small-scale human motions due to the tunability of CNT/PDMS composites is also tested.
Charge transfer transitions in glasses - Attempt of a systematic review
(Elsevier, 2021-09) Möncke, Doris; Ehrt, Doris
In glasses, even low levels of dopants or impurities can give rise to very intense and broad charge transfer transitions from ligands (e.g. oxygen or fluorine ions) to the metal ion (L→M), absorbing strongly in the short wavelength ultraviolet. In an attempt of a systematic review of charge transfer transitions, we compile data of various glass systems with high intrinsic transmission that allow the observation of charge transfer (CT) transitions involving cations of different electronic configurations. Various glasses of different composition were selected as matrices, including fluoroaluminate glasses with low P2O5 content (FP10 = 35AlF3–10MgF2–30CaF2–15SrF2–10Sr(PO3)2), phosphate [SrP = Sr(PO3)2, NSP = Na2O-40SrO-50P2O5], silicate (NS = 15Na2O–85SiO2, DS = 33Na2O–67SiO2), aluminosilicate (BCAS = 10BaO–10CaO–15Al2O3–65SiO2) and borosilicate (NBS1 = 16Na2O–10B2O3–74SiO2, NBS2 = 4Na2O–1Al2O3–21B2O3–74SiO2, Duran = 5Na2O/K2O–1Al2O3–12B2O3–82SiO2) compositions. All glasses were prepared from very high purity materials and doped with various metal ions. Charge transfer transitions of electrons to or from these cations induce absorption and photoluminescence phenomena in the ultraviolet and visible spectral region, which were recorded by optical spectroscopy. Charge transfer transitions were considered for empty valence orbitals, that is, for the high valent 3d, 4d and 5d ions, and for Zn2+, Ag+, Cu+ with full d10 orbitals. 3d, 4d and 5d ions with partially filled valence orbitals that could be stabilized in the named glasses are studied as well. Doping concentrations for these allowed transitions typically ranged from 5 to 5000 wt-ppm of metal ions, with some samples also displaying higher dopant levels. Inter valence charge transfer (IVCT) transitions directly from one metal ion to a neighboring metal ion (M→M) of the same element or metal to metal charge transfer (MM-CT) between ions of different elements can also induce strong visible absorption and deep coloring for which some examples will be discussed.
Network former mixing effects in alkali germanotellurite glasses: A vibrational spectroscopic study
(Elsevier, 2021-06) Möncke, Doris; Tagiara, Nagia S.; Chatzipanagis, Konstantinos I.; Bradtmüller, Henrik; Rodrigues, Ana C. M.; Kamitsos, Efstratios I.
Alkali germanotellurite glasses of composition 0.3M2O–0.7[(1-x)GeO2–xTeO2], M=Li, Na and 0 ≤ x ≤ 1, were investigated by Raman and infrared vibrational spectroscopic techniques to search for the origins of the alkali ion-dependent network former mixing (NFM) effect in these ion-conducting glasses. The vibrational spectra measured on mixed network-former glasses, and the spectral comparison between equimolar-mixed glasses (x = 0.5) and pellet-mixtures of the endmember glasses, 0.3M2O–0.7GeO2 and 0.3M2O–0.7TeO2, provided evidence for the formation of hetero-atomic Ge–O–Te linkages and structural rearrangements in the germanate and tellurite components of the glass. The mixing-induced structural rearrangements were expressed in terms of chemical equilibria between the network-building units and were used to make qualitative predictions for changes in the network cross-linking density and the related network-strain energy, as well as in the binding energy part of the activation energy for ion conduction. Thus, it is proposed that the mixing-induced structural modifications in the germanate and tellurite parts of glass cause the cancelation of changes in the binding energy and the network-strain energy contributions to the activation energy for ion transport. These qualitative predictions were discussed in the context of the previously found absence of an NFM effect in ionic conductivity for M=Na and the presence of a weak positive NFM effect for M=Li.
rGO–CMC fiber supercapacitors with core-sheath structure manufactured by coaxial extrusion printing
(Springer Nature, 2021-08) Ding, Junjun; Gao Yuqi
Fiber-shaped supercapacitors are attractive as an energy storage unit due to their excellent flexibility. However, fabricating robust fibers with large yields remains a challenge. In this work, we prepare flexible core-sheath fibers via coaxial extrusion printing. Carboxymethylcellulose sodium salt (CMC) slurry with controlled rheological properties is extruded from the outer channel, while the graphene oxide (GO) slurry is extruded from the inner channel simultaneously. The followed freeze-drying process protects GO sheets from agglomeration, providing more efficient chemical reduction. The reduced GO (rGO) sheets are separated and expanded to fill in the CMC sheath, which eliminates the delamination between the CMC sheath and rGO core. We study the influences of the freeze-drying process on the fiber microstructures, and explore the slurry design, fiber quality, reduction condition, and electrochemical performance. The fabrication method allows scalable manufacturing of the core-sheath electrodes and fiber-shaped supercapacitors with more efficient conductive networks.

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