Non-bridging Oxygen Atoms Research Articles

Insight into carbonation reactivity of polycrystalline CS by DFT simulation

Monocalcium silicate (CS) is a promising carbon-sequestration cementitious material, but experimentally its polymorphs exhibit differing carbonation reactivity. This work utilized first-principles calculations to reveal the intrinsic mechanisms causing carbonation reactivity differences of α-CS, β-CS, and Para-CS by analyzing their crystal structure and electronic structure properties at the atomic scale. The results indicated that the order of carbonation reactivity is α-CS > Para-CS > β-CS. The carbonation of CS minerals depends on Ca-O bond breakage. Electrophilic attack associated with non-bridging oxygen atoms dominates the carbonation reaction. O-2p orbital and Ca-3d state are the main contributors to the electrophilic and nucleophilic reactivity. The crystal and electronic structure synergy enhances α-CS's carbonation reactivity. Analyzing the crystal and electronic structures showed α-CS has the lowest crystal cohesion and is structurally least stable due to its 3-member silica rings and co-edge linkage with Ca polyhedra. The larger volumes, lower bond order, and longer bond length of Ca-O polyhedra in α-CS cause weaker Ca-O bonds and more and easier Ca2+ dissolution than β- and Para- CS. The type and number of electrophilic active O sites in α-CS also facilitate Ca-O bond breaking and CO2 capture. These insightful revelations offer a systematic and efficient approach to identifying minerals demonstrating exceptional carbonation reactivity.

Optical properties and concentration dependence of BaO-GeO[formula omitted] in glass systems

We prepared novel barium germanium (BaO–GeO2) glass samples with varying BaO concentrations and investigated their physical and optical properties. We analyzed the refractive indices, glass transition temperatures (Tgs), molar volumes, and optical band gaps of the samples, which were measured and plotted against their BaO concentrations. The results showed that refractive indices, Tgs, molar volumes, and coefficients of thermal expansion increased with BaO concentration. Raman spectra showed structural network modifications and typical Germanium glass bands. The band at ∼529 cm−1 was assigned to vibration bonds of Ge(4)-O-Ge(4), and that at ∼823 cm−1 was attributed to stretching vibration of non-bridging oxygen (NBO) atoms.

Physical properties and energy storage performance of TeO2-based ferroelectric glass-ceramics

xBaO–xTiO2–(100–2x)TeO2 (BTT) glass-ceramics were prepared through a melt-quenching synthesis method. Structural and optical properties, analyzed from Raman spectroscopy and absorption (OA) measurements, revealed that the increase in the TiO2 content promoted a loss in the network connectivity because of the formation of the non-bridging oxygen atoms (NBO’s) as well as the Te–O–Te bonds’ deformation. X-ray diffraction analysis confirmed the formation of ferroelectric nanocrystals (FeNCs) with tetragonal symmetry, related to the BaTiO3 phase, in the studied compositions, whose crystallinity seems to be intensified as the TiO2 concentration increases. The room temperature energy storage performance of these BTT samples, assessed using P-E hysteresis loops, confirmed excellent energy storage response and reveals the potential of the study glass-ceramics for practical applications.

BaO–reinforced SiO2–Na2O–Ca(O/F2)–Al2O3 glasses for radiation safety: On the physical, optical, structural and radiation shielding properties

This paper reports on a study aimed at investigating the physical properties and radiation shielding capability of a low-cost, high-transparency silicate glassy system reinforced with barium oxide. The prepared glasses' elementary and modified network structures were analyzed using X-ray diffraction and Raman spectroscopy, confirming their glass nature and revealing the progressive network depolymerization with BaO inclusion. Differential scanning calorimetry was employed to determine the glass transition temperature, which showed an increase with increasing BaO content. Tauc's plot was used to study the direct optical bandgap, which was observed to increase from 3.91 to 4.75 eV with BaO content from 0 to 30 mol%, linked to an increase in the average oxygen bond chain length and non-bridging oxygen atoms' creation. The density, molar volume, and oxygen packing density of the glass were found to increase with BaO addition, indicating that barium oxide promotes the formation of a compact network structure collapsing into a closely packed arrangement. At an X-ray energy of 40 keV, the mass attenuation coefficient increased from 0.67 to 11.48 cm2/g with BaO content. To assess the efficacy of theoretical calculations, we have conducted an experimental setup to measure the linear attenuation coefficient using an 241Am (59.5 keV) radiation source. Finally, the gamma shielding effectiveness was evaluated, and the sample containing 30 mol% of BaO showed superior radiation protection compared to concrete and was comparable to RS360 commercial glass.

Phase separation mechanism of high-magnesium nickel slag and its applicability as magnesium phosphate cement

The focus of this work was on the process conditions of phase separation activation treatment of high-magnesium nickel slag (HMNS) and the mechanism of formation of HMNS phase separation structure, as well as the potential of HMNS as a precursor for magnesium phosphate cement (MPC). The results indicated that the phase separation structure played a crucial role in improving the pozzolanic activity of HMNS. The pozzolanic activity of the M4 sample obtained by doping with 8 wt% MgO and water quenching at 1550 °C remelting was substantially increased compared to the untreated HMNS, the dissolution of Mg element increased from 94.55 to 206.71 mg/g, Fe from 33.25 to 62.85 mg/g, Si from 24.85 to 93.48 mg/g, and Al from 10.57 to 27.93 mg/g, they were increased by 118.60%, 89.00%, 276.20% and 164.20% respectively. The main reason for the increase in HMNS pozzolanic activity was that the alkali-rich phase of the phase separation structure caused Si-O-Si to break by producing more "non-bridging" oxygen atoms (NBO), subsequently disrupting the continuity of the glass network. The obtained optimal process conditions existed for the water-quenched HMNS: water quenching at 1550 °C for HMNS with 32 wt% of MgO produced a phase separation structure in turn possesses high pozzolanic activity. Correspondingly, the compressive strength of the HMNS-based geopolymers (cured for 28 d) activated by ammonium dihydrogen phosphate reached 45 MPa, an increase of 433%, which meeted the 42.5 R grade of ordinary Portland cement (OPC) (GB175–2007). Moreover, the CO2 emissions was reduced by more than 74.4% compared to MPC.

Effect of femtosecond laser irradiation on structure‐terahertz property relationship in sodium borosilicate glasses

AbstractWe report the effect of high‐repetition rate femtosecond (fs) laser irradiation on structure‐terahertz (THz) property relationship for sodium borosilicate glasses. We have used nuclear magnetic resonance (NMR), terahertz time‐domain spectroscopy (THz‐TDS), and Raman spectroscopy to examine pristine and laser irradiated regions of these glasses to determine and quantify boron speciation, THz refractive index, n(THz), and change (Δn) in n(THz), and spectral, that is, structural, changes due to laser exposure, respectively. Our results suggest that laser irradiation‐induced Δn(THz) values are dependent upon the glass composition, structural units, connectivity, and network, for example, the corresponding K‐ and R‐values of the borosilicate glass. Depolymerized glass networks show no changes in NMR B4 signal, slight changes in Raman spectral changes related to silicate structural units, for example, increase in Q3 tetrahedra with one nonbridging oxygen (nbO) atom, and higher measurable n(THz) and Δn(THz). More polymerized glasses, on the other hand, show changes in NMR B4 signal, varying degrees of Raman spectral changes in the borate subnetwork and structural units, and lower n(THz) and Δn(THz). The THz refractive index is most sensitive to modifier ions in the glasses, which are directly responsible for nbO formation, glass structure, and network polymerization.

Investigation on high-magnesium nickel slag treated by phase-separated activation as cementitious material

High-magnesium nickel slag is a hazardous waste from nickel smelting process with low pozzolanic activity. In order to improve the pozzolanic activity of high-magnesium nickel slag, this study produced a phase separation structure of high-magnesium nickel slag by activation treatment, and studied the effect of phase separation structure on the pozzolanic activity, engineering performance and hydration mechanism of high-magnesium nickel slag as cementitious material. The results showed that the phase separation structure was crucial for the pozzolanic activity of the high-magnesium nickel slag. It was confirmed by dissolution test that the phase separation structure significantly improved the pozzolanic activity of high-magnesium nickel slag. The main reason for the increase in slag activity is that the phase-separated glass consists of a silica-rich phase and an alkali-rich phase, which is rich in Mg, Fe, etc. (network modifiers), and the modifiers break Si–O–Si by producing "non-bridging" oxygen atoms (NBO), forming more Si-O-NBO and Si–O–2NBO, which disrupt the continuity of the glass network. Compared with the untreated high-magnesium nickel slag, the compressive strength of the geopolymer prepared from the high-magnesium nickel slag with a phase separation structure (W-HMNS) was increased by 69%. Its volume stability was also much better than that of geopolymers prepared from untreated high-magnesium nickel slag. The main hydration products of phosphoric acid activated W-HMNS based geopolymers were newberyite (MgHPO4·3H2O), and a small amount of aluminosilicates and hydrated calcium silicates. Together they make up the gel phase and the crystalline phase. A large number of gel phases such as newberyite wrapped unreacted quartz and crystallized newberyite form a dense gel-crystal structure, with crystal as the skeleton and colloidal as the bonding medium, increasing the density of geopolymer, forming a denser hardening body with higher strength. These results may provide some guidance for the practical application of high-magnesium nickel slag as a raw material to prepare geopolymer, and provide a new idea for improving the reactivity of slag.

Cadmium oxide as a substitute for sodium phosphate structural units: structure and properties

Amorphous glasses in the system xCdO-(100-x)(yNa2O + zP2O5), (x = 0, 10, 20, 30, 40, 42.5, 45, y = z) mol% are prepared by a fast quenching technique. Addition of CdO at the expense of equal amounts of both P2O5 and Na2O causes a substantial influence on the distinctive feature of the measured Raman spectra. The concentration of nonbridging oxygen atoms (NBO) rises with increasing CdO content. The numerical data from the deconvolution of Raman spectra revealed that Q3 (branching group) and Q2 (metaphosphate group) decline while Q1 (pyrophosphate group or end group) increases. The rise in the number of NBO in terms of Q1 is supported by the change in molar volume, free volume, and packing density. This result is compatible with Raman and NMR spectroscopic observations. Increased CdO content causes a rise in the O/P ratio, which causes an increase in NBO in the glass network which lowers the glass’s hardness number.

Impact of MnO on the structural, physicochemical, and dissolution properties of phosphate-based glasses

In this work, manganese was suggested to improve the durability of 50P2O5–33·33K2O–(11·11−x/2) CaO−(5·56−x/2) MgO –xMnO glasses with 0≤x≤ 2 mol%. Indeed, its effect on the glass structure, thermal properties, physicochemical properties, and in particular, dissolution behaviours have been studied. The conventional melt-quenching technique was used to produce glasses at 1000°C and they were characterised by differential thermal analysis, density and molar volume measurements, x-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. Dissolution behaviours were tracked by measuring weight loss and pH. Molar volume measurements showed that phosphate glasses become more compact by incorporating MnO. Structural characterisation using Raman and infrared spectra proved that the glass network is composed mainly of metaphosphate chains. The dissolution results showed that incorporating manganese was an effective method to change the phosphate glasses’ chemical durability due to their ionic crosslinking between the nonbridging oxygen atoms of the phosphate chains, corresponding to the change in thermal properties (Tg, Tc and Tf).

One‐Step Preparation of Glass‐Ceramics from a Ferrochrome Slag and an Electrolytic Manganese Slag

Electrolytic manganese slag materials can be used in the preparation of glass‐ceramics. Herein, glass‐ceramics with excellent properties are obtained by melting electrolytic manganese slag and ferrochrome slag as raw materials. The effects of the addition of ferrochrome slag on the recrystallization of the base glass and the physicochemical properties of the glass‐ceramic are especially investigated. With the addition of ferrochrome slag, the introduced Cr2O3 may play a role in the deconstruction of the glass network and is more likely to produce a spinel phase as a way to promote the heterogeneous nucleation of the diopside phase. The sample with a ferrochrome slag addition of 12 wt% shows the optimal recrystallization ability. Furthermore, the ratio of nonbridging oxygen atoms (NBO) to the total amount of oxygen atoms (T) is the highest (NBO/T = 1.90). Also, the bending strength and the density of the samples reach 96.08 MPa and 3.05 g cm−3, respectively, and the acid and alkali resistance become 98.16% and 99.48%, respectively. Moreover, the glass‐ceramic structure did effectively stabilize and solidify the harmful heavy metal elements. This study has provided innovative ideas for an efficient, harmless, and low‐cost treatment of electrolytic manganese slag in the preparation of glass‐ceramics.

Электризация поверхности кварцевых стекол электронными пучками

To establish the effect of subthreshold defect formation on the charge accumulation in quartz glasses, a comprehensive study of the process of their electrization by electron beams was carried out. Earlier it was shown that the process of radiative electrization of quartz glasses consists of two stages. The short-term stage of charging can be explained by the accumulation of charge on the initial trap centers, and the long-term component can be caused by the generation of deep trap centers capable of capturing electrons. In the studied quartz samples, the trapping centers can be three-coordinated silicon atoms (E'-centers). The presence of two stages of the charging process is confirmed by two different methods for determining the surface potential. Despite the increase in the surface potential during irradiation and the resulting decrease in the energy of the incident electrons, an increase in the intensity of the cathodoluminescent signal is observed. Such an increase in intensity can be caused by an increase in the number of luminescent defects in quartz, a two-coordinated silicon atom or a non-bridging oxygen atom, as well as by charge accumulation at competing nonradiative trap centers.

Methods to functionalize gold nanoparticles with tandem-phosphorothioate DNA: role of physicochemical properties of the phosphorothioate backbone in DNA adsorption to gold nanoparticles.

Perception of the differences in the physicochemical properties of phosphorothioate DNA (PS-DNA) and phosphodiester DNA (PO-DNA) greatly aids in understanding the AuNP-DNA binding process. Replacing one non-bridging oxygen atom of the anionic phosphodiester backbone with a sulfur atom leads to a major change in the DNA adsorption mechanism of AuNPs. In this work, we investigated and compared salt-aging, low pH-assisted, and freeze-thaw methods for conjugating phosphorothioate-modified oligonucleotides to AuNPs. The results obtained clearly demonstrate that only the pH-assisted method can successfully bind tandem phosphorothioate DNA to gold nanoparticles and sufficiently maintain the colloidal stability of AuNPs. When a phosphate group is converted to a phosphorothioate group, the negative charge of the phosphate group is located on the sulfur atom. Due to the soft nature of sulfur (a very weak H-bond acceptor), the negative charge on the sulfur atom cannot be shielded even with the gradual addition of salt to increase the ionic strength, so, the pH-assisted based method is the best for the functionalization of AuNPs with tandem-PS DNA.

Physical and optical properties of MoO3 doped B2O3-CdO-Al2O3-CaF2 glasses

The glass samples with precise composition 60B2O3-20CdO-5Al2O3-(15-x) CaF2-(x)MoO3 (where × = 0, 0.5, 1, 1.5, 2) was prepared by using standard melt quenching method. The physical and optical characteristics of the glass samples were identified by making use density and UV spectra. In the investigated compositions, the increase of non-bridging oxygen atoms, due to the conversion of Mo6+ ions to Mo5+ ions, with increased MoO3 content resulting in lowering the optical band gaps is noticed. The non-bridging oxygen levels will go up with an increase in BO4 units, improving the compositions density inturn raises refractive index and other physical parameters. Because of more density and refractive index these glass materials can have its applications in the area of radiation shielding and optical communications.

Rapid wet chemical synthesis of bioactive glass with high yield by probe sonication.

Bioactive glasses (BGs) are inorganic biomaterials which possess favourable properties for bone repair and regeneration. The biological properties of the BGs depend on their physical features. This manuscript describes a simple methodology for rapid synthesis of BG nanoparticles (NPs) with tailored physical properties using ultrasonic disruption produced by an ultrasonic probe. The ultrasonic probe generates stable and transient cavitation which increases the mass transfer and accelerates the chemical reaction. This approach is relatively green as it evades the use of the drastic acidic conditions required for hydrolysis. The prepared BG NPs were characterized by Fourier transform infra-red (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), particle size analysis (PSA), nitrogen adsorption/desorption and BET surface area analysis, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), and in situ high temperature synchrotron XRD. The effects of ultrasonic irradiation time, and amplitude on the surface properties were investigated and the results confirmed that both parameters, especially amplitude, have significant effects on the physical properties of the prepared BG NPs. The XPS results showed that both, amplitude and time have a pronounced effect on the bridging and non-bridging oxygen atoms bonded to the Si centre in the BG samples, which play an important role in the bioactivity of the BG NPs. The in situ high temperature XRD patterns indicated a gradual phase transformation for the BG samples synthesized at different ultrasonic irradiation times and amplitudes. The TEM images showed that uniform nano-sized BG particles were obtained at 50% amplitude in only 10 minutes. A bimodal particle size distribution was observed with an increasing reaction time, up to 30 minutes, due to an increase in the formation of vortices at the interface where nucleation starts. All the prepared samples exhibited a glassy structure with the composition 70SiO2 : 25CaO : 5P2O5 and were highly bioactive. The proposed method would give a quick route for the synthesis of bioactive glasses and other ceramics with controlled physical properties.

Structural, spectroscopic, and radiation shielding properties of Pb2+‐doped borate and phosphate glasses

AbstractLead‐containing alkali/alkaline‐earth borate and barium lead phosphate glasses were prepared by melt‐quenching for a detailed investigation of the Pb2+ ions’ optical properties. UV–Vis absorption and photoluminescence spectroscopy reveal variations in the s–p transition of Pb2+, which are shown to correlate with the optical basicity of the host glass in both borates and phosphates. Pb2+ emission differs significantly for borate and phosphate glasses, as the nature of the charged sites available to accommodate Pb2+ cations vary. Optical basicity values were determined from the composition (Λth) and the measured refractive index (Λn). The UV‐cutoff shifts toward higher wavelengths with increasing optical basicity and lead content. In borate glasses, the frequency of the stretching modes due to nonbridging oxygen atoms of trigonal metaborate species is identified to be inversely proportional to the excitation wavelength (directly proportional to the excitation energy) of Pb2+. Lead‐containing alkali and alkaline‐earth borate glasses show additional correlations between the Pb2+ emission wavelength and the weighted average of the field strength of the modifier(s). Complementary to the investigation of optical properties, radiation and neutron shielding parameters were calculated, suggesting the potential utility of some of the studied compositions for radiation shielding applications.

Effect of sulphate ions on the physical and optical properties of zinc phosphate glasses containing Sm3+ ions

Lithium based zinc-phosphate containing Sm2O3 glasses of the system (5-x) Li2SO4 − 20Li2O − 45P2O5 − 30ZnO - xSm2O3, (where x = 0, 0.1, 0.5, 1, 2 and 3 mol%) were prepared by melt quenching technique. The amorphous nature of the prepared glasses is ascertained by X-ray diffraction. The density and molar volume are found to vary non-linearly with Sm2O3 content. The addition of modifier oxides such as Li2O to P2O5 glass would break P-O-P bonds and resulting in the creation of non-bridging oxygen’s. The creation of non-bridging oxygen atoms makes the structure less rigid and would leads to the formation of weaker phosphate structural entities. This would lead to the formation of voids between the phosphate groups. The addition of alkali and samarium content in the phosphate glasses is accountable for the collective number of the non– bonded oxygens and this may cause a non-linear variation in the volume of the network structure which in turn lead to non-linear variation in the density. The optical spectrum consists of a characteristic Ultraviolet absorption bands of Sm3+ ions in the range 200–400 nm and other strong bands at 940 nm and 1100 nm which are considered to originate from the transitions of ground state to the different excited states. The optical band gap energies were determined from both ultraviolet band edges and Tauc’s plots. The band gap energy varies non-linearly with Sm2O3 content. The non-linear variation in density, molar volume and band gap energy discloses the intermediate-range structure composed of PO4and ZnO4tetrahedra and are discussed in view of the polymeric chain of phosphate network structure.

Structure and related properties of amorphous magnesium aluminosilicates

The structure of the magnesium aluminosilicate glasses ${(\mathrm{MgO})}_{x}{({\mathrm{Al}}_{2}{\mathrm{O}}_{3})}_{y}{({\mathrm{SiO}}_{2})}_{1\ensuremath{-}x\ensuremath{-}y}$, where $0\ensuremath{\le}x<1$, $0\ensuremath{\le}y<1$ and $x+y<1$, was explored by neutron and x-ray diffraction, aided by the results from $^{27}\mathrm{Al}$ magic angle spinning nuclear magnetic resonance spectroscopy. A wide composition range was investigated, using aerodynamic levitation with laser heating to extend the glass-forming region well into the peraluminous regime where $R=x/y<1$. The results were interpreted with the aid of an analytical model for the composition-dependent structure where magnesium ions do not contribute towards the glass network. The model delivers Al-O bond distances typical of fourfold and fivefold coordinated aluminum atoms. It also delivers Mg-O coordination numbers of 4.46(9) and 5.39(10) for magnesium in a predominantly network-modifying versus charge-compensating role, corresponding to Mg-O bond distances of 2.024(10) and 2.120(20) \AA{}, respectively. The more compact coordination environment of the network modifier is related to an enhanced probability of magnesium finding nonbridging oxygen (NBO) atoms as the nearest neighbors. Structural change is observed along the tectosilicate tie line in the transformation from a ``normal'' to ``anomalous'' glass, where the mechanism of deformation under sharp-contact loading changes from shear flow to densification. A minimum in the composition dependence of the glass hardness is related to a minimum in the Al-O coordination number and to a competition between the availability of NBO atoms, which break the connectivity of the tetrahedral network, versus high cation field-strength ${\mathrm{Mg}}^{2+}$ and fivefold and sixfold coordinated ${\mathrm{Al}}^{3+}$ ions, which cross-link the pieces of the network thus fragmented.

Effect of the SiO2/GeO2 ratio in the Na2O-B2O3-SiO2-GeO2 system on the characteristics of porous glasses

Results from a study of glasses of the Na2O-B2O3-SiO2-GeO2 system and porous materials obtained from them are presented. Conclusions about the appearance of highly coordinated germanium atoms in the network of the initial glasses with a decrease in the SiO2/GeO2 ratio and simultaneous decrease in the number of non-bridging oxygen atoms are drawn according to the results of Raman spectroscopy. The characteristics of the porous materials were determined by the nitrogen adsorption/desorption method. It is noted that the growth of the specific surface area and pore volume depends on the structural features of the initial glass. The porous characteristics of glass are shown to be directly dependent on the number of six-coordinated germanium atoms and inversely dependent on the number of non-bridging oxygen atoms. It is shown that the replacement of silicon oxide with germanium oxide in the Na2O-B2O3-SiO2 system leads to an increase in the pore diameter, which may be due to the absence of a secondary germanium residue.

Physical, structural, thermal, and mechanical features combined with neutron and gamma radiation attenuation qualities of Sm2O3 doped transparent borate-rich glasses

Current work presents the synthesis of B2O3–Gd2O3–Li2O–Na2O–LiF‒Sm2O3 glass system via melt-quench approach and scrutiny of its mechanical, thermal, structural, physical, and nuclear radiation attenuation aspects. Raman scattering and Fourier transform infrared spectra revealed B–O stretching modes of BO4 groups linked to BO3 units with nonbridging oxygen atoms and BO3 and BO4 units' existence in the glass structure. By differential scanning calorimetry, glass transition and crystallization temperatures are identified. Relevant analysis showed all glasses' good thermal stability where glass transition temperature varied at 372–407 °C range. ΣR (fast neutron removal cross-section) and for energy 0.025 eV neutrons σT (total cross-section) are computed. In all glasses, 49.25 B2O3–10Gd2O3–10Li2O–10Na2O–20LiF-0.75Sm2O3 (mol%) sample holds higher ΣR (= 0.10207 cm−1). 48B2O3–10Gd2O3–10Li2O–10Na2O–20LiF–2Sm2O3 (mol%) glass possesses greater σT (= 736.675 cm−1) for thermal neutrons, hinting at added Sm2O3's favorable influence as Sm owns a better ability for neutron absorption than B. By Phy-X/PSD, μ/ρ (mass attenuation coefficient) is obtained at photon energy extent 15 keV‒15 MeV. Sm2O3 inclusion from 0 to 2 mol% minorly enhanced the μ/ρ values. Buildup factors estimated via geometric progression fitting method at 1–40 mean free path and energy 0.015–15 MeV span are maximal at medium energy region owing to Compton scattering process. 48B2O3–10Gd2O3–10Li2O–10Na2O–20LiF–2Sm2O3 (mol%) sample shows superior γ-ray blocking capacity in all glasses, suggesting Sm2O3's positive effect. Elastic moduli and Poisson's ratio are computed theoretically by bond compression and Makishima–Mackenzie models. It is identified that all glasses could tolerate longitudinal stress over shear stress.

The structure of glasses M2O-B2O3 (М – Li, Na, K): Estimation of thermodynamic characteristics of alkali borates and physicochemical modeling

The paper presents results of structural calculations carried out on the alkali borate glasses using physicochemical modeling based on Gibbs energy minimisation. Standard heat capacity, entropy and enthalpy of formation values for lithium, sodium and potassium borates are estimated by regression analysis for use as the input data for the models taking into account the error of the initial data. The correction of the physicochemical model was made using results of Raman spectroscopy. The dependence of the maximum of the “borate anomaly” on the number of non-bridging oxygen atoms was shown. It was found that the most obvious changes in the dependence of properties occur in the regions of N1 and N2 compositions, which are characterized by the appearance of asymmetric triangles BØ2O− and BØO22− in glasses, correspondingly.