Hard and transparent glass-ceramics (GCs) from the ZnO-Al2O3-SiO2 (ZAS) system containing TiO2 as a nucleating agent often exhibit a grayish to brownish hue, limiting their use in applications requiring high-transmittance and colorless materials. This coloration arises from charge-transfer mechanisms involving Ti ions. To address this issue, the oxidizing agents CeO2, Sb2O3, and As2O3 were incorporated individually into a TiO2-nucleated ZAS base composition to promote the oxidation of Ti3+ ions to Ti4+ ions, as the latter exhibits minimal coloring effects. The experimental characterization of the glasses and GCs comprised the following steps: Differential Scanning Calorimetry, to study the influence of the optical clarifiers on the thermal behavior and crystallization kinetics; UV-Vis Spectroscopy and CIELAB color analysis to evaluate the effectiveness of the oxidizers in mitigating the color; Electron Paramagnetic Resonance to determine the oxidation states of the coloring ions; Rietveld analyses to assess the impact of microstructural factors on light absorption; and Vickers microhardness to evaluate the effect of the composition and heat treatments on the mechanical performance. The results demonstrate that As2O3 and Sb2O3 are more effective than CeO2 in reducing coloration and enhancing the transmittance in the visible range of the ZAS GCs containing TiO2 without affecting their hardness.

This study aimed to optimize the nitriding parameters for Plasma Immersion Ion Implantation (PIII) of stainless steels. UNS S32750 super duplex stainless steel, widely employed in the petrochemical industry, was subjected to PIII under varying nitriding atmospheres (mixtures of H2 and N2) and treatment pressures. The fixed PIII nitriding parameters included a temperature of 300 degrees C, a duration of 3 h, a bias voltage of approximately -10 kV, a frequency of 500 Hz, and a pulse width of 30 mu s. Following the treatments, the phases were characterized by X-ray diffraction (XRD), while the hardness and elastic modulus of the modified surfaces were evaluated via nanoindentation. Regarding the nitriding atmosphere, gas mixtures approaching a 60% N2/40% H2 (vol.) ratio yielded a higher volume fraction of nitrogen-rich expanded phases in solid solution. Furthermore, higher treatment pressures promoted the formation of these expanded phases, consequently enhancing the surface hardness up to 2.7 times the hardness value of the untreated sample. These findings stand in contrast to those found for low-energy plasma nitriding (PN) processes.

Three-point bending tests are used to estimate elastic modulus, flexural strength, and resilience modulus. Mechanical properties are indirectly obtained from experimental quantities, and the resulting property estimates will have associated uncertainties. The primary objective of this research was to apply principles of uncertainty propagation to the basic definitions of mechanical properties in order to obtain uncertainty models for the property estimates. The models were designed to be versatile, making them applicable to a wide range of materials, such as steel, ceramics, and concrete. The modeling process involved mathematical manipulations, including solving partial derivatives. Rectangular soda-lime-silica (SLS) glass samples (N = 30) were selected for validation and analysis due to their isotropic and homogeneous nature, which are critical for validating mathematical models. The statistical treatment of the experimental data was performed using Gaussian, rectangular, and Weibull distributions. Contributions of isolated uncertainties to the overall property uncertainty were characterized. A modified coefficient of variation for property estimation was proposed and evaluated with the experimental data. Finally, analytical expressions for uncertainty of the property estimates were derived, providing a robust approach to assess uncertainty in mechanical property estimates.

In this study, we examine the impact of structural modifications from incorporating tantalum oxide on the thermal, electrical, and mechanical properties of sodium phosphate glasses and glass‐ceramics. Although these materials are well known for optical applications, this work aims to systematically explore their macroscopic properties, which are yet to be fully characterized. Glass samples were prepared in the binary molar system (100 − x )NaPO 3 – x Ta 2 O 5 with x = {20, 30, 40, 47.5, 50}. A transparent glass‐ceramic was also produced by heat‐treating the 52.5NaPO 3 –47.5Ta 2 O 5 glass composition. Structural characterization was performed by Raman, Fourier transform infrared (FTIR), and solid‐state nuclear magnetic resonance (NMR) spectroscopies. Increasing tantalum oxide content led to a notable increase in glass transition temperature together with a reduced thermal stability against crystallization, indicating higher glass network connectivity at higher tantalum levels. Thermal analysis and X‐ray diffraction (XRD) confirmed the formation of a single crystalline phase in the glass‐ceramic, identified as the bronze‐like perovskite Na 2 Ta 8 O 21 with an average particle size of 31 nm. Electrical properties were investigated using impedance and electric modulus formalisms, revealing that higher tantalum content increases resistivity and decreases conductivity, attributed to reduced Na + ion concentration and increased atomic packing density. Interestingly, glass‐ceramics exhibited slightly higher conductivity than pristine glass. Density, Vickers hardness, Young's modulus, and nanoindentation hardness also increased significantly with higher tantalum content, while crystallization had a minimal effect on these properties. Overall, these results indicate that higher tantalum oxide content not only enhances the glass network's connectivity but also significantly influences the electrical and mechanical properties of sodium phosphate glasses and glass‐ceramics.

In this work, we added strontium ions to hydrolyzed PAN fibers to improve their thermal resistance. For comparison, we characterized hydrolyzed non-modified (PAN-H) and strontium-modified PAN fibers (PAN-H-Sr) using techniques such as XRD, FTIR, TG, DSC, and SEM. Our XRD diffractograms demonstrated that PAN-H-Sr was more crystalline, while the FTIR spectra confirmed that both fibers underwent hydrolysis by breaking nitrile group bonds, and the refractory cation was incorporated into the fiber through the O–Sr–O bond. SEM micrographs showed that the width of the PAN-H-Sr fiber decreased, and a stiffer structure was obtained. The TG and DSC analysis indicated that PAN-H-Sr presented higher thermal stability since the presence of strontium delayed the degradation reactions of PAN, and, at the end of the heat treatment, exposed a more significant residual mass equivalent to 48.55

The Plasma Immersion Ion Implantation (PIII) nitriding was used to form a modified layer rich in expanded austenite (γN) and expanded ferrite (αN) phases in super duplex steel. The thermal stability of these phases was investigated through the in situ synchrotron X-ray diffraction. All the surfaces were analyzed by SEM, EDS, and nanoindentation. During the heating stage of the thermal treatments, the crystalline structure of the γN phase expanded thermally up to a temperature of 350 °C and, above this temperature, a reduction in the lattice parameter was observed due to the diffusion of nitrogen into the substrate. During the isothermal heating, the gradual diffusion of nitrogen continued and the lattice parameter of the γN phase decreased. Increasing the treatment temperature from 450 °C to 550 °C, a greater reduction in the lattice parameter of the γN phase occured and the peaks related to the CrN, α, and αN phases became more evident in the diffractograms. This phenomenon is associated with the decomposition of the γN phase into CrN + α + αN. After the heat treatments, the thickness of the modified layers increased and the hardness values close to the surface decreased, according to the diffusion of the nitrogen to the substrate.

Transparent glass-ceramics (GCs) are promising for applications that require both optical clarity and superior mechanical strength, such as high-performance displays and ballistic armor. However, achieving this combination typically involves a trade-off, as crystallization processes that enhance mechanical properties often compromise transparency. This study investigates the optimization of mechanical properties in transparent and translucent MgO-Al2O3-SiO2 (MAS) GCs. We examine the heat treatment conditions necessary for achieving various levels of transparency and evaluate the influence of crystal size and volume fraction on Vickers hardness, indentation crack resistance, and fracture toughness (K-Ic). Our findings indicate that, depending on the composition and heat treatment conditions, even nanocrystals smaller than 100 nm can diminish transparency, rendering the GCs translucent. Translucent and opaque samples exhibit superior mechanical performance due to higher crystallized fractions and larger crystals. However, specific thermal protocols were identified to produce transparent GCs (visible light transmittance > 80% for 1.5 mm thick samples) with at least a 30% increase in K-Ic compared to their parent glasses. This study demonstrates the feasibility of balancing transparency and mechanical strength in MAS GCs through careful optimization of processing parameters.

This research aimed to create a new Li metasilicate-based glass-ceramic for dental use, prioritizing improved chemical durability (CD) and machinability while preserving good glass-forming ability (GFA) and adequate mechanical properties. Characterization also involved examining fracture strength (Sf) and fracture toughness (KIC). The experimental approach involved precise microstructural adjustments through designed compositional changes and controlled thermal treatments. Four compositions underwent scrutiny using mechanical tests, microscopy, differential scanning calorimetry, and X-ray diffraction to analyze the impact of lithium metasilicate (LS) and disilicate (LS2) crystals on these properties. Machinability was evaluated by weight loss measurements during controlled grinding experiments. The developed GCs exhibited interconnected acicular LS and LS2 crystals, which resulted in favorable Sf ∼300 MPa and KIC ∼ 1.7 MPa.m1/2 (SEVNB). Although the KIC was smaller than that of an experimental LS-LS2 GC (285 MPa and 3 MPa.m1/2(double torsion)) used as a reference, the chemical durability (126 μg/cm2 for ML14F GC) improved by nearly 50% compared to the reference (∼ 220 μg/cm2). This study introduced three new GCs with LS as the major phase (rather than the traditional LS2), showcasing commendable GFA, chemical durability and machinability, with satisfactory flexural strength and fracture toughness.

In this work, glass samples were obtained by melt-quenching in the binary system (100-x)KPO3-xNb2O5 with x = 20, 30, 40, and 50 mol%. Thermal properties investigated by DSC together with structural investigations by Raman spectroscopy allowed to understand the structural effect of Nb2O5 incorporation in the potassium phosphate glass network. A transparent glass-ceramic has also been produced by heat treatment of the 50KPO3-50Nb2O5 glass sample. Density, molar volume, atomic packing, and refractive index were determined and increased with Nb2O5 content. Chemical resistance in several corrosive aqueous solutions was found to increase with Nb2O5 content and crystallization. Vickers hardness as well as elastic modulus and hardness obtained from nanoindentation experiments also strongly increased with higher niobium contents, indicating that not only optical properties but also chemical and mechanical properties are improved with niobium incorporation in the phosphate glass network.

Under nitrogen plasma immersion ion implantation, the energy density per pulse EPulse/A was found to be proportional to the amount of the N-expanded austenite phase (γN) in a superaustenitic stainless steel, as previously seen for an austenitic-ferritic alloy. Since γN occurs in a range of stoichiometries, the parameter was also contrasted with the ion fluence Γ, which affects the retained dose. Γ varies inversely with EPulse/A and influences oppositely the properties of the modified surfaces. The temperature was the same among the treatments (320 °C) to rule out thermal diffusion as an extra variable. The increase of EPulse/A (for applied voltages 6.2-10.4kV) produces thicker layers (1.4-2.2 μm), as an increase in lattice defects and stresses enhances N-diffusion, while high Γ values favor the N-saturation at the top surface for the opposite reason. The lowest Epulse/A (6.2-9.5kV) result in brittle cases with a possible thin nitrides layer on top, whereas γN prevails in the ductile layer produced by the highest one (10.4kV). The N-concentration governs the strength against plastic deformation: hardness varies up to 32% from the highest (6.2kV) to the lowest Γ treatment (10.4kV). In summary, the correlation of Epulse/A with Γ is indispensable for controlling properties of the modified surfaces for performance purposes.

This research aims to evaluate the efficiency of cavitary varnishes containing experimental bioglasses in the occlusion of dentinal tubules. One hundred and sixty-eight cervical buccal dentin samples were obtained from bovine teeth. Samples were randomized into the following groups: I. Distilled Water (DW); II. Cavity Varnish (CV); III. Colgate® Sensitive Pro-Relief™ (CS); IV. 45S5 Bioglass (45S5); V. KSr Bioglass strontium potassium (KSr); VI. P Bioglass phosphorus (P); and VII. PSi Bioglass phosphorus silica (PSi). The treatments were applied to the surfaces of the samples, which were then subjected to simulated brushing. The samples were analyzed for a) characterization of bioactive glasses; b) surface roughness; c) descriptive analysis of the dentin surface; d) total versus occluded number of dentinal tubules; e) diameter of the dentinal tubules; f) chemical composition of the dentin surfaces, and g) dentin permeability. All groups treated with biomaterials without the brushing challenge showed an increase in roughness and (total or partial) occlusion of the dentinal tubules. The PSi group had the best values for occlusion, while the KSr group had the highest calcium and phosphorus concentrations. After the brushing challenge the roughness was controlled by the presence of biomaterials; 45S5, KSr, and PSi showed occlusion of the dentin tubules. All bioactive glasses showed reduced tooth permeability compared to distilled water. The PSi group had the smallest tubule diameter and highest phosphorus concentration. KSr and PSi bioglasses are promising materials for dentin occlusion and remineralization and are promising new biomaterials for the treatment of dentin hypersensitivity.

The H-cathodic charging applied to a superaustenitic stainless steel produces a metastable H-expanded phase by interstitial solid solution, which discloses parallels with the austenite N-expanded (S-phase). The similar to 1 mu m modified layer comprises a high expansion region yH followed by a low expansion ye domain, the former presenting a lattice param-eter 3% higher than the austenite y. The complete decay yH-> ye-> y occurs around 1-day time. The mechanical properties change accordingly: hardness increases twofold and elastic modulus 17% with H-inlet, returning progressively to the pristine values after hydrogen diffuses out from the modified layer, mainly towards the outer surface. This is consistent with a competitive effect, where the solid solution strengthening overcomes the H-enhanced plasticity in the initial period of decomposition. Moreover, the prevalence of one of these phenomena in plastic deformations is strain-rate dependent: high strain rates result in hindered dislocation mobility, whereas the material discloses embrittlement under low strains. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Obtaining thermal parameters based in the analysis only on the amplitude or phase of the photoacoustic (PA) signal from photothermal measurements is useful and valid once classical theoretical expectations are that the same parameters are contained in the photoacoustic signal. This work studies the issue of disagreement between experimentally measured amplitude and phase for AISI 316 samples with the expected theoretical result from the classical model. The results of the thermal parameters obtained from individual amplitude analysis are inconsistent with phase analysis. This work aims to show a way to get a unique value of thermal parameters from simultaneous analysis of the amplitude and phase of the PA signal. Also, the fractional models were applied to improve the fit of experimental data and provided results closed with the expected thermal diffusivity value.

Borosilicate glass-ceramics are promising materials for sealing applications in solid oxide fuel cells (SOFC). This work synthesized glass and glass-ceramics of the 18CaO-27SrO-10B2O3-45SiO2 composition containing 0, 2, and 4% TiO2 (mol) by conventional melting/quenching and characterized by structural and thermal techniques. The 11B-NMR and 29Si-NMR spectra indicate no significant change in the relative concentration of the tetrahedral (B-IV) and trigonal (B-III) boron populations of all glasses, with the presence of Q2, Q3, and Q4 species. The crystalline phases of CaSiO3, SrB2Si2O8, and Sr2SiO4 precipitated in all the compositions. The thermal expansion coefficients of the glasses and corresponding glass-ceramics are compatible with those of the other stack components, and their glass transition temperatures are below the operating temperature of SOFCs (R-.1 800-950 degrees C), thus can provide a hermetic seal. The sintering temperature of the T2 and T4 glasses is lower than 1000 degrees C, an essential characteristic for their application. However, the T4 glass exhibited even better sintering characteristics, making it a potential candidate for sealing.

Due to the unusual crystallization of (nominally) stoichiometric BaSi2O5 (BS2) glass, which shows unexpected and diverse crystal phases, a series of six glasses with different chemicals and melting procedures were prepared in three laboratories and characterized before and after crystallization by differential scanning calorimetry, density measurements, X-ray diffraction, FTIR, and Raman spectroscopy. The aim of this study was to assess whether there is systematic behavior in the crystallization pathways in relation to precursor chemicals, impurities, and hydroxyl content of this glass. Small glass monoliths were treated at the first DSC crystallization peak and quenched to determine which phases formed in the early-stages of crystallization. The glass transition temperatures (T-g) divide these six glasses between those with a T-g near 690 ? versus those near 700 ?. The DSC peak crystallization temperatures varied even more; from 855 to 917 ?. In these six glasses, our results are best explained by a combination of metastable high-BaSi2O5 and Ba6Si10O26. Monotonic trends in crystallization show that the DSC signal from the Ba-rich phases increases as the Tg and the crystallization temperatures increase. The BS2 glasses with both the lowest Tg and lowest DSC crystallization temperatures show the most barium disilicate crystal. This leads to the conclusion that the metastable monoclinic high-BaSi(2)O(5 )is favored in these conditions. The small differences in glass synthesis conditions and chemicals used strongly influence the relative proportions of phases which crystallize and their kinetics. In-situ and ex-situ diffraction measurements confirm the conclusions above. The structural distinctions between the barium silicate crystals and the BS2 supercooled liquid, and the implications for the role of structural polymerization are discussed. We conclude that high-BaSi2O5 or Ba6Si10O26 are the predominant phases in the earliest stages of crystallization. This study highlights the extreme sensitivity of BS2 glass crystallization kinetics and pathways to minor differences in composition and synthesis conditions and explains the different conclusions reached by distinct authors that worked on the crystallization of BS2 glasses.

This work investigated the variation in fracture strength and toughness of stoichiometric lithium disilicate (LS2) glass-ceramics as a function of crystal size (d) and crystallized volume fraction (f), with three average crystal sizes (8, 13 and 34 mu m) and a wide range of crystallized fractions (0-100 %). The fracture strength and toughness increased with increasing the crystallized volume fraction. For constant crystallized fraction, KIC increased with crystal size, indicating an R-curve behavior. The mean free path between the crystals limits the maximum size of the critical defect and is the crucial feature controlling fracture strength. Finally, we verified that the contribution to the toughness of R-curve mechanisms in this glass-ceramic is proportional to (f.d)1/2, which agrees with R-curve models for ceramics.

The existence and formation of expanded austenite in ferritic stainless steels remains a subject of debate. This research article aims to provide comprehensive insights into the formation and decomposition of expanded austenite through in situ structure analyses during thermal treatments of ferritic steels. To achieve this objective, we employed the Plasma Immersion Ion Implantation (PIII) technique for nitriding in conjunction with in situ synchrotron X-ray diffraction (ISS-XRD) for microstructural analyses during the thermal treatment of the samples. The PIII was carried out at a low temperature (300–400 °C) to promote the formation of metastable phases. The ISS-XRD analyses were carried out at 450 °C, which is in the working temperature range of the ferritic steel UNS S44400, which has applications, for instance, in the coating of petroleum distillation towers. Nitrogen-expanded ferrite (αN) and nitrogen-expanded austenite (γN) metastable phases were formed by nitriding in the modified layers. The production of the αN or γN phase in a ferritic matrix during nitriding has a direct relationship with the nitrogen concentration attained on the treated surfaces, which depends on the ion fluence imposed during the PIII treatment. During the thermal evolution of crystallographic phase analyses by ISS-XRD, after nitriding, structure evolution occurs mainly by nitrogen diffusion. In the nitrided samples prepared under the highest ion fluences—longer treatment times and frequencies (PIII 300 °C 6 h and PIII 400 °C 3 h) containing a significant amount of γN—a transition from the γN phase to the α and CrN phases and the formation of oxides occurred.

The melt and quench technique was used to create a new TeO2-Li2O-MoO3 glass system with the objective of providing alternative and new shielding materials for radiation safety purposes. The synthesized glasses were studied by means of their physical, thermal, and radiation shielding characteristics. It was demonstrated using Raman and FTIR spectroscopy that the insertion of Li2O and MoO3 resulted in a superimposed reduction of all Te units, including TeO3+1 and TeO3 with non-bridging oxygen, via the formation of Te(short)-O-Mo and a coordination change from MoO4 to MoO6. The densities of the prepared glasses were relatively high, having values between 4.48 and 5.11 g/cm3. Compared with TeO2-pure glass, the values for Tg and Tx substantially decrease with Li2O and MoO3 insertion. However, among prepared samples, there is only a small fluctuation in both characteristic temperatures, suggesting high thermal/composition stability. FLUKA simulations were used to estimate the photon, proton, electron, alpha-particle, and carbon ion shielding parameters for beam energies ranging from 15 to 15,000 keV. With changes in the chemical designation of the synthesized glasses, the mass attenuation coefficient of photons and stopping powers of charged radiation changed, gradually increasing with glass density and decreasing with Li2O and MoO3 insertion. In addition, the ability of the glasses to moderate fast neutrons declined with increases in the MoO3 and Li2O weight contents. On the contrary, the total cross section of thermal neutrons improved as glass density decreased and Li2O and MoO3 content increased. The synthesized glasses, through the evaluated parameters, showed better radiation shielding capacity compared to existing shields such as concrete and commercial RS-series glass shields.

Barium disilicate (BaO.2SiO 2 =BS2) glass is one of the few stoichiometric glasses that nucleates internally, homogeneously via thermal treatment. This system has been scarcely assessed in microstructure-property studies. Here we address fracture strength and toughness (K IC ) variation as a function of crystallized volume fraction and crystal size, as well as the possible effect of residual stresses (RS) in BS2 glass-ceramics (GCs) by independently varying these two microstructural parameters. K IC increased with spherulite size and crystallized volume fraction. K IC variation with crystallized volume fraction was similar for GCs with different crystal sizes. Combination of the current findings on BaO.2SiO 2 (crystals under tensile RS) with previous studies of Li 2 O.2SiO 2 GCs (compressive RS) indicates that crystallization of a tougher phase – not type of residual stress in the crystals – is the crucial parameter controlling fracture toughness and strength. These findings are quite useful to design novel strong and tough GCs.

Dentin hypersensitivity (DH) is characterized by pain caused by an external stimulus on exposed dentin. Different therapeutic approaches have been proposed to mitigate this problem; however, none of them provide permanent pain relief. In this study, we synthesized and characterized experimental bioactive glasses containing 3.07 mol% SrO or 3.36 mol% K2O (both equivalent to 5 wt% in the glass), and evaluated their effect on dentin permeability to verify their potential to treat DH. The experimental materials were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction to confirm the respective structures and chemical compositions. The reduction in the hydraulic conductance of dentin was evaluated at the three stages: minimum permeability; maximum permeability (24% ethylenediaminetetraacetic acid [EDTA] treatment); and final dentin permeability after treatment with the bioactive glasses. They all promoted a reduction in dentin permeability, with a significant difference for each sample and posttreatment group. Also, a significant reduction in dentin permeability was observed even after a simulated toothbrushing test, demonstrating effective action of these materials against DH. Besides, incorporating 3.07 mol% SrO was a positive factor. Therefore, strontium's desensitizing and re-mineralizing properties can be further exploited in bioactive glasses to promote a synergistic effect to treat DH.