Changes In Properties Of Glasses Research Articles

Structural investigation and effect of gamma-ray irradiation on barium borate glasses containing vanadium oxide

This work investigates the structural changes induced in barium borate glasses by gamma irradiation doses and vanadium doping using FTIR spectroscopic technique. Binary Barium borate parent glass and samples of the same composition containing different concentrations of vanadium oxide with formula xV2O5-(65-x)B2O3-35BaO (x = 0, 2, 4, 6, 8, and 10) were synthesized by melt quenching technique. FTIR spectroscopy approves the formation of both BO3 trigonal and BO4 tetrahedral structural units within the network backbone. V2O5 additions lead to borate network depolymerization by breaking B-O-B bonds and increasing V2O5 content causes systematic reductions in boroxol rings and B-O-B linkages, indicating disruption of the borate network. Gamma irradiation also damages the borate structure by cleaving B-O-B bonds in boroxol rings and BO3 units. This progressively converts BO3 to BO4 groups. Infrared spectroscopy reveals decreases in BO3 vibrations at higher doses as the network degrades. The radiation-induced network damage leads to changes in glass properties including thermal stability and hardness. A clearer understanding of borate structural modifications helps target these glasses for optical devices with controlled properties.

Optical and electrical properties of Fe3O4@MoS2 nanocomposites and doped lead boron tellurite glass

Transition metal oxide core–shell-nanostructured Fe3O4@MoS2 is attractive in photocatalytic, optoelectronics and optical applications. Magnetic Fe3O4@MoS2 core–shell nanocomposites were synthesized by a facile hydrothermal method. Transmission electron microscopy (TEM) results show that the 80-nm-diameter nanoparticles were composed of Fe3O4 core and MoS2 shell. The presence of characteristic of Fe–O and Mo–O vibrations in Fe3O4@MoS2 FT-IR spectra indicate the Fe3O4 has been composited with MoS2 successfully. The optical UV–Vis spectra of Fe3O4@MoS2 composites exhibited a strong peak at 250–300 nm due to the strong absorption of MoS2. The photoluminescence spectra of Fe3O4@MoS2 showed two peaks at 670 and 625 nm corresponding to A1 and B1 excitons of MoS2. Glass-containing nanoparticles have promising multifunctional advantages such as the simultaneous existence of magnetic, optical and photoluminescence. Glasses containing different Fe3O4@MoS2 contents were fabricated in this study by melt-quenching method. Glass network was disordered by the doping, and as the doping content increasing, the coordination numbers were changed and more non-bridging oxygen numbers were produced, these modifications on glass structure induced changes of glass properties. Compared to spectra of base glass, the UV–Vis absorption spectra of doped glasses showed a red-shift in cutoff wavelength and an absorption peak around 680 nm due to the excitation of Mo5+ (4d1) ions. The photoluminescence spectra of Fe3O4@MoS2-doped glasses present one intense peak centered around 570 nm due to the charge transfer of O2−→Mo6+ ions in MoO42− units, and the intensity of this emission peak increased with doping contents. The conductivity of base glass gets increased from 1.59 × 10−7 to 2.08 × 10−6 S cm−1 when the doping content reaches to 5%. Such improvement is mainly caused by the non-adiabatic small polaron hopping at 473 K and non-bridging oxygens production. Glass doped with 5% Fe3O4@MoS2 exhibited promising photoluminescence, optical cutoff wavelength (526 nm) and high electrical conductivity (2.08 × 10−6 S cm−1) due to the charge transfer of Fe and Mo ions and high polarization property of Fe3O4@MoS2.

The Structure-Property Relationship in Oxide Glasses: A Thermodynamic Approach

This paper considers a rigorous thermodynamic approach that can be used for calculating a variety of glass properties and the content of various structural units in glasses. Since both the properties and the structure are calculated on a unified basis, this approach enables the structureproperty relationship in glasses to be established quantitatively, and the structural units that characterise changes in glass properties to be determined.

Correlation of silica glass properties with the infrared spectra

Infrared (IR) spectroscopy has been used to interpret structural changes in silica glasses. Specifically, a shift of the Si–O stretching band in IR spectra is used to monitor changes in average Si–O–Si bond angle in the glass structure. A similar structural change is induced by the change of fictive temperature, hydrostatic pressure or compressive stress, with the average Si–O–Si bond angle decreasing with the increase of these parameters. It is anticipated that these similar structural changes would produce a similar change in glass properties. In order to confirm this expectation, HF etch rates of silica glasses were measured as a function of fictive temperature and stress. The experimental results on HF etch rates, together with changes in other glass properties in the literature, were compared with the change in glass structure revealed by IR spectroscopy. It was found that the similar structural change is accompanied by the consistent changes in a variety of glass properties. Monitoring the IR spectra of a silica glass sample, therefore, can be used to deduce changes in glass properties.

A structural model for phosphate glasses

Abstract The structural component of the network-former oxide in phosphate glasses has a decreasing number of links between the PO4 tetrahedra. However, in addition to the common depolymerization process, further structural principles are in effect. In the present paper, it is proposed that all of the terminal oxygen atoms, including those doubly bonded within the PO4 branching groups, tend to coordinate a network-modifier cation. In a first range, that leads to an effect which can be called a re-polymerization based on modifier oxide additions. Due to the surfeit of terminal oxygen atoms in phosphate glasses with small metal oxide content, the modifier cations, Me, occupy places with high MeO coordination numbers surrounded by terminal oxygen atoms on MeOP bridges. The system tends to stabilize at the point at which all of the terminal oxygen atoms occupy MeOP positions. For even higher concentrations of metal oxide, the coordination number of modifying cations around terminal oxygens exceeds unity, and a modified random network ensues. The model is used for the explanation of the behaviour of packing densities and MeO coordination numbers. The phenomenon of drastic changes of glass properties at about 20 mol% metal oxide content has been related to a network reconstruction based on the change in the type of linkage between the metal cations and the PO4 middle groups.

NMR study of structure of sodium boroaluminate glass at high sodium content

Nuclear magnetic resonance has been used to study the structure of sodium boroluminate (NABAL) glasses with varying sodium oxide content. A structural change is found at high sodium oxide content which is in the region where abrupt changes in glass properties have been found by different workers. A structural model is suggested based on the results of computer simulation and measurements of activation energy. The model is suggestive in explaining the abrupt changes observed in different kinds of measurements, such as conductivity.

Properties of Na2O�3SiO2 glasses impregnated with ethyl alcohol

Na2O·3SiO2 glasses impregnated with up to 8.5 wt% ethanol were prepared under high pressure and hydrothermal conditions and their properties such as hardness, fracture toughness and density were measured. Both hardness and density increased initially with increasing ethanol content up to 1∼2 wt% ethanol and then decreased with further increase in ethanol content, while fracture toughness decreased monotonically. This initial increase of hardness and density of ethanol-impregnated glasses is in contrast to the behaviour of glasses with high water content, which showed a steadily decreasing hardness and density with increasing water content. A structural study using IR and X-ray diffraction analyses was also made and changes in properties of glasses with increasing ethanol was related to the formation of Si-O-C bonds and the precipitation of sodium carbonate crystal.

Ferromagnetic resonance and spin wave excitations in metallic glasses: The effects of thermal ageing and long-range magnetic ordering

New ferromagnetic resonance experiments under degenerate resonance conditions are reported for FeNiPB metallic glass ribbons in annealed and polished samples. An interpretation of these experimental results in terms of established theories in Ferromagnetic and Spin Wave Resonance Spectroscopy (FSWR) is proposed. The spin-wave analysis is used to interpret the effects of magnetic anisotropy on the lineshapes of metallic glasses before and after annealing. The conclusion is reached that a model of dipolar-coupled regions which assume a common resonance frequency band is appropriate in ferromagnetic metallic glasses. The role of surface pits scattering, microheterogeneities in chemical composition, clustering processes and long-range magnetic ordering in these systems is discussed in relation to the changes of glass properties by annealing. We also conclude that FSWR techniques are more sensitive than differential scanning calorimetry, X-ray scattering and static, magnetic techniques which are currently used to study structural relaxation in glasses.