Browsing by Author "Tostanoski, Nicholas"
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Item Effects of Post-Treatment Abrasion on Dynamic Fatigue of Chemically Strengthened Glass(2018-05-07) Tostanoski, Nicholas; LaCourse, William; Pilgrim, Steven; McGowan, GarrettEffects of post-ion exchange abrasion on strength and fatigue of soda-lime silicate glass rods, were determined using four-point bend tests. Dynamic fatigue tests were carried out by varying the strain rate over 2 orders of magnitude in air or after a short immersion in water. Ion exchange was carried out at 450ᵒC for 4 or 16-hours. Following the ion exchange treatment, the glass rods were abraded using sand particles between 212 to 149μm and 106 to 63μm. The resulting strength (MOR) values were plotted using Weibull statistics. Dynamic fatigue plots showing the effect of stressing rate on strengths were also plotted, and the slow crack growth constant (n) was determined for each combination of ion exchange time and post-abrasion. Results indicate that the surface stresses induced by chemical strengthening reduces effects of stress-induced slow crack growth. However, anomalous, and unexpected large reductions in fatigue behavior requires that additional measurements, be carried out before any interpretations can be provided.Item 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. DavidWe 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.Item 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.