Average Stretching Force Constant Research Articles

Dynamic mechanical characteristics of aged silicone rubber blend

The effect of aging on the mechanical properties of silicone rubber (SR) was investigated by means of ultrasonic, dynamic mechanical analysis, and FTIR techniques. Both longitudinal and shear (Ultrasonic wave velocities) were measured at room temperature and at frequencies of 2 MHz. Density, molar volume, ultrasonic wave velocities, tensile strength, mechanical properties, and FT–IR showed the improvement of the silicone rubber network with aging time from 0 to 70 days, while loosening of the network structure was observed at 14 days and 50 days aging. These behaviours were explained in terms of the change in cross-link density and average stretching force constant of bonds with aging. Thermogravimetric analysis and differential scanning calorimetric techniques showed quite low thermal stability and temperature performance for aged SR at 14 and 50 days than virgin SR which was confirmed by the cracks and voids appeared under scanning electron microscope.

Structural analysis on the basis of effect of molybdenum on the Pr2O3 doped lead borate glasses series-II

This paper explains the role of molybdenum on the structural analysis of the investigated rare earth ion Pr3+ doped, lead borate (75 PbO — [25 – (x+y)]B2O3—yMoO3—xPr2O3) glass matrix has been discussed using the relation between Tg and structural parameters like average cross-link density (), average stretching force constant (F) and the number of bonds per unit volume (nb). Densities, molar volume have been measured as a function of MoO3 content. Linear variation in density and in the molar volume has been observed and is credited to the role of MoO3 in the investigated glasses. Based on the properties like good stability and bond strength, investigated glasses possibly suitable for the design of optoelectronic devices.

Analysis of elastic properties of lithium substituted barium vanadate glasses to understand the structural changes

Abstract The elastic moduli of 60V2O5- (40-x) BaO-xLi2O where x = 30, 25, 20, 15, 10 (mol%) glass system was analyzed and correlated with the physical properties of glass-like molar volume and average stretching force constant. This was done to understand how the rigidity of glass is affected by the variation in Li2O content in the glass samples. This study involves the application of Makishima-Mackenzie’s theory to calculate the elastic constants of glass, like Young’s modulus, Bulk modulus, Modulus of rigidity and Poisson’s ratio and correlate them to the structural modifications in the glass with the addition of alkali oxide (Li2O) in the glass system at the expense of alkaline-earth oxide (BaO). This work was done to understand how the variation in the composition of glass affects its rigidity and elastic properties which in turn affects its structure. This study helped to tweak the mechanical properties of the current glass system by varying their chemical composition. It was found that glass with 30% Li2O has the highest value of elastic constants and therefore, maximum mechanical strength.

Theoretical Elastic Moduli of TeO2 – B2O3 – SiO2 Glasses

In this work, the elastic moduli of silica based borotellurite glass system with compositional formula; [(TeO2)0.7 (B2O3)0.3]1-x (SiO2)x with x= 0.0, 0.1, 0.2, 0.3 and 0.4 was studied using theoretical models. Makishima and Mackenzie, bond compression, Rocherulle, and ring deformation models were employed in the calculation of the elastic moduli, Poisson ratio, packing density, dissociation energy, cross-link density, average stretching force constant and the glass network ring size of the studied glasses. The values of the elastic moduli obtained from the Makishima and Mackenzie model were found to be lower than those obtained from the Rocherulle model and the value from the bond compression model was reported to be highest among the three models. In all the models, the elastic moduli increased with an increase in the concentration of silica in the glass composition. Therefore, it satisfied the original intention of improving mechanical strength to achieve high Young modulus which is considered in glasses fiber drawing/ manufacturing.

Understanding how the mixed alkaline-earth effect tunes transition metal oxides-tellurite glasses properties

Mixed alkaline-earth effect (MAEE) on the transition metal oxides (TMO)-tellurite glasses [TMO = MoO3, Nb2O5 and WO3] modified with BaO/MgO mix is analyzed to understand how feasible it is to tune structural and optical properties of a tellurite glass. Changes induced by the three transition metal oxides on the tellurite polyhedral produce some modifications on the cut-off wavelength, optical band gap, Urbach's energy, refractive index and permittivity values where the MAEE manifest itself in different ways. The changes in the glass structural properties are dominated by the TMO type while optical and electrical properties depend mostly on the combination between the TMO and the [BaO/(BaO + MgO)] ratio. Glass transition temperature is discussed in terms of some parameters like number of bonds per unit volume, average stretching force constant, molar volume, oxygen packing density values (OPD) and FTIR spectra. In this work we provide evidence that the behavior attributed to the relationship between structure and electrical or optical properties in pure oxide and even binary systems is not reproduced by multi-component glassy systems. A comparison between traditional and new optical methods confirm allowed direct inter-band electronic transitions in the studied glasses evidencing that the a priori parameter election is not always an accurate procedure.

Effect of lead and zinc oxides on the thermal properties of tellurite glass systems

Thermal properties of binary (PbO)x(TeO2)1-x, x = 0, 0.10, 0.15, 0.20, 0.25, 0.30 mol% and ternary [ZnO]y[(TeO2)0.7-(PbO)0.3]1-y with y = 0.15, 0.17, 0.20, 0.22, 0.25 mol% were measured. The glass systems were prepared using the conventional melt-quenching technique. The thermal properties of the glasses were investigated using differential scanning calorimetry (DSC) analysis. Thermal analysis of the glasses was realized regarding the glass transition temperature (Tg), glass crystallization temperature (Tc), and glass stability against crystallization (∆T). Quantitative analysis of the Tg of the glass samples was discussed based on the total number of bonds per unit volume and average stretching force constant of each bond in each glass composition. Debye temperature, softening temperature and thermal expansion coefficient, (αP) of the glass samples were calculated based on the measured ultrasonic velocities and densities data. The addition of PbO improved the thermal properties in the binary PbO-TeO2 glasses, while the addition of ZnO showed the different trend to the thermal properties of the ternary ZnO-PbO-TeO2 glasses.

Effect of V2O5 concentration on the structural and optical properties and DC electrical conductivity of ternary semiconducting glassy nanocomposites

Transition metal oxide–doped glassy nanocomposites of the form xV2O5-(1 − x) (0.05CdO-0.95ZnO) with x = 0.3, 0.5, 0.7, and 0.9 were prepared by the melt quenching route. Their microstructure was studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy, and optical absorption spectroscopy. The absorption bands at around 640–756 cm−1 are attributed to the antisymmetric stretching vibrations of VO2 groups. Physical attributes such as density, molar volume, oxygen molar volume, oxygen packing density, number of bonds per unit volume, and the average stretching force constant were evaluated. The XRD patterns reveal distinct diffraction peaks indicating crystallinity in the sample with x = 0.3, whereas significantly broadened patterns are observed in samples with x = 0.5, 0.7, and 0.9, reflecting a dominant amorphous nature. Different peaks in the XRD patterns indicate the formation of Zn2V2O7, ZnV2O6, CdV2O6, Cd2V2O7, and CdVO3 nanocrystallites, which are dispersed in the as-prepared glassy matrices. The optical absorption spectra show indirect transitions. With a rise in the concentration of V2O5, the optical transmission cutoff wavelength moves to higher wavelength. DC electrical conductivity was studied at various temperatures from 60–650 °C. The establishment of small polaron hopping was anticipated from the DC electrical conductivity data. DC conductivity was inferred with use of Mott's and Greaves's variable range hopping models.

DTA and FTIR of 70TeO2–(25 − x)MnO2–xV2O5–5Fe2O3 tellurite glass systems

A series of quaternary tellurite glasses in the form of 70TeO2–(25 − x)MnO2–xV2O5–Fe2O3 where (0 ≤ x ≤ 25 mol%) have been prepared by the conventional melt quenching technique. Differential thermal analysis (DTA) curves of these glasses have been investigated in the temperature range 300–1093 K and at different heating rates a = (2.5, 5, 10, 20 and 40 K min−1). The glass transition temperature (T g), the crystallization temperature (T P), the glass stability (∆T) and the activation energy for crystallization have been measured. The glass transition temperature has been analyzed according to the average cross-link density, and the average stretching force constant is present in the glass. FTIR investigations showed that the absorption bands of different modes of vibration in the manganese tellurite network were shifted toward higher wave number.

Optical and Thermal Properties of Some Tellurite Glasses

Tellurite glasses in the form (95-X) TEO<SUB>2</SUB>-5NB<SUB>2</SUB>O<SUB>5</SUB>-XTIO<SUB>2</SUB>, X= 5.0, 7.5, 10.0 and 12.5 mol % have been successfully prepared by the melt quenching technique. Density ρ and molar volume V have been measured. UV-Visible absorption spectra for the presented ternary tellurite glass systems have been measured in the wavelength range 200-850 nm. The optical band gap, E<SUB>g</SUB>, and refractive index, n, of the presented glass systems have been calculated by using the derivation absorption spectrum fitting (DASF) and absorption spectrum fitting (ASF) methods. Also, Urbach’s energy, ΔE for tellurite glass systems was obtained using the absorption spectrum fitting (ASF) method. Comparison between both methods has been presented. Differential thermal analysis (DTA) for the prepared glasses with systematic heating rate 10°C/min has been carried out. The glass transition temperature, T<SUB>g</SUB>, onset crystallization temperature, T<SUB>c</SUB>, melting temperature, T<SUB>m</SUB>, glass stability range, S, and glass factor, K<SUB>g</SUB>, of the present glasses have been measured. The average cross-link density, &macr;n<SUB>c</SUB>, number of bonds per unit volume, n<SUB>b</SUB>, and average stretching force constant, F&macr;, have been calculated.

Effect of vanadium on the optical and physical properties of lithium borate glasses

In the present studies, the effects of vanadium substitution for 30Li2O–55B2O3-(15-x) ZnO–xV2O5, (0≤x≤7.5) glass system on the physical and optical properties have been investigated. V2O5 can work as a conditional glass former and its incorporation into glass yields vanadyl ions (VO2+), which causes considerable change in the structure of glass. The glass composition can be tailored by optimizing the zinc and vanadium content so as to obtain the desirable semiconducting or optical applications. Physical parameters like density, molar volume, molar electro-negativity, oxide electro-negativity, basicity moderating parameters, ionic concentration, and inter-ionic distance are obtained for all the glass compositions. Characterization techniques like X-ray diffraction (XRD), UV–Visible and Fourier transforms infra-red spectroscopy (FTIR) are used to yield the structural and optical parameters. Average stretching force constant, network bond/volume and bulk modulus are calculated theoretically and correlated with each other. The Urbach energy as well as optical band gap shows a decreasing trend with decreasing concentration of V2O5 with respect to ZnO content.

Structural and optical properties of 30Li2O–55B2O3–5ZnO–xTiO2–(10 − x)V2O5, (0 ≤ x ≤ 10) glasses

The structural and optical properties have been investigated for the 30Li2O–55B2O3–5ZnO–xTiO2–(10−x)V2O5, (0≤x≤10) glasses using different spectroscopic characterization techniques. The relationship between optical and structural properties has been established in light of the variation of TiO2 content. The band gap shows a decreasing trend with a decrease in V2O5 content. Physical parameters like density, molar volume, ionic concentration and inter ionic distance have been obtained for all the glass compositions. Theoretical parameters like optical basicity, oxide polarizability and electronegativity have been obtained and discussed in relation to the non-bridging oxygen (NBO). Bulk modulus has been calculated theoretically and correlated with average stretching force constant and network bonds/volume.

Study of rigidity of semiconducting vanadate glasses and its importance in use of coatings

The elastic moduli of some multicomponent vanadate based glasses were analysed in terms of the bond compression model by some physical parameters such as, the density, average stretching force constant and average atomic ring size. These parameters were calculated for all the glass series and for all the glass composition to estimate the rigidity of these glasses. The results showed that the average force constant and the elastic moduli of these glasses are sensitive to the decrease in PbO content. This behaviour was attributed to the increase in the molar volume and the role of different modifiers. These parameters along with the coordination number of the glasses affect the glass transition temperature. The correlation between the elastic moduli and thermal properties of these samples showed that 0·25MoO3–0.25PbO–0·5V2O5 glass is the most rigid and has an applicable glass transition temperature for coating.

Thermal properties of quaternary TeO2–ZnO–Nb2O5–Gd2O3 glasses

Quaternary tellurite glass systems in the form 75TeO2–15ZnO–(10−x) Nb2O5–xGd2O3 (x=0.5, 1.0, 1.5, 2.0 and 2.5mol%) have been prepared by the melt quenching technique. Density, molar volume and oxygen packing density of every glass composition have been measured and calculated. Differential thermal analyses (DTA) have been carried out on the prepared glass systems in the temperature range 300–800K at heating rate 5, 10, 15, and 20°C/min. The glass transition, Tg and crystallization, Tc temperatures values were measured by using DTA. Kinetics parameters like activation energy of relaxation structure Et, activation energy of crystallization, Ec and order of crystallization have been calculated for every glass composition. Structural parameters like number of bonds per unit volume (nb) and average stretching force constant (F¯) have been calculated to interpret the experimental data.

Theoretical analysis of constants of elasticity of lead calcium alumino-borosilicate glass system

This paper reports on the constants of elasticity of xPbO-RNa2B4O7-(100 − R − x) CAS with 0 ≤ x ≤ 50, and 50 ≤ R ≤ 75 mol % glass system (CAS is calcium alumino silicate glasses). The constants of elasticity were calculated in terms of the bond compression model and Makishima-Mackenzie model. The average cross-link density, the number of network bonds per unit volume, the average stretching-force constant, and the ratio of the estimated bulk modulus (Kbc) to the experimentally determined (Ke), have been calculated and discussed in terms of the bond compression model to analyze the role of PbO. Young’s modulus, the packing density and dissociation energy have been calculated and analyzed according to the Makishima-Mackenzie model. The dimensionality of the glassy network has been calculated in terms of the d ratio (4C44/C12) and discussed in terms of the cross-link density of these glasses. C12 = C11−2C44, C11 and C44 are the longitudinal and shear elastic constant. The results show good agreement between the experimental and theoretical data for the representation of the constants of elasticity of borosilicate glasses.

Correlation between the dimensionality and the constants of elasticity of rare-earth doped borate glasses

This work was devoted to explore the correlation between the dimensionality and the computed theoretically constants of elasticity of borate based glasses doped with rareearth oxides. The dimensionality of the glassy network has been calculated in terms of the d ratio which is equal to 4 C 44 /K e and discussed in terms of the crosslink density and number of network bonds per unit volume of these glasses. Constants of elasticity were calculated in terms of the bond compression model and the Makishima-Mackenzie model. The average crosslink density, the number of networ k bonds per unit volume, the average stretchingforce constant, and the ratio of the estimated bulk modulus (Kbc) to the experimentally determined (Ke) have been calculated and discussed in terms of the bondcompre ssion model. Young's modulus, the packing density, and the dissociation energy have been calculated and analyzed in terms of the Makishima-Mackenzie model. The results showed that the computed elastic moduli and the dimensionality of the borate glasses containing La2O3 or Gd2O3 are strongly dependent on the concentration of the structural units of the constituent oxides and types of bonds between these units.

Effect of zinc on the physical properties of borate glasses

This manuscript presents a theoretical analysis of the elastic properties of ZnO−Na2O−Al2O3−B2O3 (in molar %) glass. The elastic moduli were calculated in terms of Makishima–Mackenzie theory and bond compression model. Addition effect of ZnO on the elastic moduli was investigated according to bond compression model in terms of the number of network bonds, the mean cross-link density, average stretching force constant, atomic ring size, and the ratio Kbc/Ke of the glass systems. Young's modulus, packing density and Poisson's ratio have been calculated and analyzed according to Makishima–Mackenzie model. The results indicate that the elastic moduli and the dimensionality of these glasses are sensitive to the increase in the zinc oxide content.

Optical band gap, glass transition temperature and structural studies of (100 − 2 x)TeO 2– xAg 2O– xWO 3 glass system

Optical absorption, differential scanning calorimetry (DSC) and Raman studies have been carried out on (100 − 2 x)TeO 2– xAg 2O– xWO 3 (7.5 ≤ x ≤ 30) glass system. The Raman spectra showed that the structure of glass network consists of [TeO 4], [TeO 3]/[TeO 3+1], [WO 4] units. The glass transition temperature ( T g ) values were measured from DSC thermogram and the variation in T g has been discussed in terms of physical parameters like number of bonds per unit volume ( n b ), average cross-link density ( n c ¯ ), average stretching force constant ( F ¯ ), oxygen molar volume ( V o ) and oxygen packing density (OPD) values. The cut-off wavelength ( λ c), optical band gap ( E opt ), Urbach energy (Δ E) and refractive index ( n) values were calculated from optical absorption data. The observed decrease in optical band gap ( E opt ), Urbach energy (Δ E) and increase in refractive index ( n) values have been discussed in terms of structural changes brought about by WO 3 and Ag 2O incorporation in to TeO 2 network.

The acoustic properties of borosilicate glass affected by oxide of rare earth gadolinium

SiO 2–Na 2O–B 2O 3 glasses doped with different mol% content of Gd 2O 3 have been prepared by rapid-quenching method. Longitudinal and transverse ultrasonic wave velocities have been measured using the pulse-echo method at 4 MHz frequency at room temperature. Elastic moduli, Debye temperature, softening temperature and Poisson’s ratio have been obtained as a function of Gd 2O 3 modifier content and are found to be rather sensitive to the glass composition. Information about the structure of the glass can be deduced after calculating the average stretching force constant and the average ring size. A comparison between the experimental elastic moduli data obtained in this study and those calculated theoretically by other models has been discussed.

Preparation and structural studies in the (70 − x)TeO2–20WO3–10Li2O–xLn2O3 glasses

Quaternary tellurite glass systems (70 − x)TeO2–20WO3–10Li2O–xLn2O3 where x = 0, 1, 3 and 5 mol% and Ln are La, Pr, Nd, Sm, Er and Yb, respectively, have been prepared by the melt quenching technique. Densities of the obtained glasses were measured and the molar volume was calculated. IR absorption spectra of the present glass systems were determined at room temperature over the range of wavenumbers from 400–1,600 cm−1. Raman spectra of the present glass samples were measured in the range of 30–1,030 cm−1. Density, molar volume, IR and Raman spectra of the glasses were discussed by calculating average cross-link density, packing density, theoretically calculated Poisson’s ratio and number of bonds per unit volume of the studied glasses. Also, the quantitative interpretations were based on concentration of ions per unit volume of Te, Ln and O, short distance in nanometre between ions for (Te–O) of TeO4 and TeO3 groups, (W–O) of WO4, WO6 groups and calculated wavenumber, $$ \bar{\upsilon } $$ , for TeO4 and TeO3, respectively. The average stretching force constant that present in these quaternary glasses has been calculated in order to interpret the data obtained.

Structural Analysis of Some Alkali Diborate Glasses

This manuscript presents a theoretical analysis of the correlation between the computed bulk modulus and the structure of a series of multicomponent sodium diborate based glasses in terms of the bond compression model. The main parameters in the analysis were the computed elastic moduli, the average stretching force constant and the average atomic ring size. These parameters were calculated for every glass series and for every glass composition. The results showed that the average force constant and the elastic moduli of these glasses are sensitive to the decrease in the sodium diborate content. This behaviour was attributed to the increase in the molar volume, and to the role of the dierent modifiers.