Number Of Network Bonds Research Articles

Synthesis and Characterization of Vitrimer-like Self-Healing Polymer Electrolytes for Lithium Metal Batteries

Solid-polymer electrolytes have become crucially significant with the fast-expanding energy requirements in both the academic and industrial spheres due to their better safety and energy density compared to liquid electrolytes. Despite these encouraging possibilities, a few obstacles are associated with these electrolytes, chief among them being the limited charge transport via the solid electrode-electrolyte interface. Due to the difference in electrochemical potential between the electrode and the electrolyte, this obstruction initiates electrode-electrolyte interactions through electrode volumetric changes, interface reactions, and space charge layers.One possible way to enhance the LIB performance could be by integrating a new class of covalent adaptable networks called vitrimers.The self-healing, shape memory, recyclability, and reprocessibility properties of vitrimers, a class of covalent adaptable networks (CANs), are derived from a covalent molecular network that can change its topology through molecular rearrangements while maintaining the overall number of network bonds. In this manner, Li dendrites that might develop during battery cycling could be eliminated and the electrolyte-electrode contact could be restored by vitrimers. Figure 1

Alkaline phosphate glasses and synergistic impact of germanium oxide (GeO2) additive: Mechanical and nuclear radiation shielding behaviors

In this study, mechanical and nuclear radiation shielding behaviors of highly efficient alkaline phosphate glasses with various GeO2 concentrations were evaluated for their nuclear radiation shielding applications. Moreover, the glass rigidity parameters of alkaline phosphate glasses were calculated for determination mechanical properties. The μm values were calculated using XCOM program and MCNPX simulation code. The nuclear radiation shielding properties (gamma and neutron) such as μm, HVL, TVL, MFP, Zeff, EBF, EABF, and ΣR were calculated for all alkaline phosphate glasses with various GeO2 concentrations. The results showed that μm, Zeff, and ΣR increased as the Bi2O3 concentration increased. The G14 glass sample had the minimum HVL, TVL, MFP, EBF and EABF. The G14 sample had the largest μm, Zeff, and the number of network bonds, and can be considered as an excellent attenuator for gamma and neutron shielding. The outcomes of recent investigation can be useful to understand the nature of GeO2 additive into alkaline phosphate glasses, which can be considered as a candidate shield type in medical and industrial radiation facilities.

Influence of intermediates on the optical and theoretical parameters of xLa2O3-(10-x) Y2O3 -15SrO-15CaO -10B2O3-10Al2O3-40SiO2 (2 ≤ x ≤ 8) glasses

In the present investigation, an attempt has been made to study the effect of La2O3/Y2O3 (X) ratio on the optical properties of the novel glass series xLa2O3-(10-x)Y2O3 -15SrO-15CaO -10B2O3-10Al2O3-40SiO2 (x = 2, 4, 6, 8). The glasses have been prepared via melt quenching route. Fourier transform infrared spectroscopy (FTIR) has been done to obtain the band positions and functional groups for all the pristine as well as heat treated glasses, respectively. UV-visible spectroscopy has been performed to obtain the band gap, Urbach energy and refractive indices for all the pristine as well as heat treated glasses. The parameters like density/molar volume have been calculated with the varying La2O3/Y2O3 (X) ratio. Also, some theoretical parameters like electronegativity of metal ion/oxide ion, interionic distance, ionic concentration, optical basicity and polarizability have been calculated. The parameters like average cross link density, average force stretching constant, bulk modulus and number of network bonds per unit volume have also been calculated. Furthermore, electron paramagnetic resonance (EPR) spectra have also been obtained for all the glass samples to determine the magnetic behavior as well as g values (spin Hamiltonian parameters). The optical basicity of all the glasses lies within the range of 0.621–0.631. All the pristine glasses exhibit band gap energy ranging from 5.80 to 5.89 eV.

BaF2–contained tellurite glasses: Quantitative analysis and prediction of elastic properties and ultrasonic attenuation–Part I

In this article, the semi-empirical formulas of Abd El-Moneim’s model were applied to predict the composition dependence of ultrasonic attenuation coefficient in BaF2-contained tellurite glasses, for the first time. In addition to this, the various experimental elastic moduli and Poisson’s ratio were analyzed quantitatively and predicted on the basis of the bond compression, ring deformation and Makishima-Mackenzie’s models. The results show that:•The molar volume, packing density, fractal bond connectivity, average cross-link density, number of network bonds per unit volume and average atomic ring size play a dominant role in predicting the modifier role of the alkaline earth fluoride BaF2 in binary fluorotellurite BaF2-TeO2 glasses.•The theoretically calculated values of Poisson’s ratio on the basis of the bond compression model are in a better agreement with the corresponding experimentally measured values, when compared with those theoretically calculated on the basis of Makishima-Mackenzie’s model.•The agreement between theoretical and experimental values is excellent for bulk, good for Young’s and longitudinal moduli and unsatisfactory for shear modulus. The divergence between theoretical and experimental values has been attributed to the anomalous behavior between elastic moduli and dissociation energy per unit volume of the glass.•The correlation between ultrasonic attenuation coefficient and the most significant compositional and structural parameters was achieved on the basis of Abd El-Moneim’s model.

Theoretical analysis for ultrasonic properties of vanadate-phosphate glasses over an extended range of composition: Part I

Effect of V2O5 on the physical, structural and ultrasonic properties of binary V2O5-P2O5 glasses has been comprehensively interpreted over a wide range of composition (45mol%≥V2O5≤85mol%). Elastic moduli and ultrasonic attenuation coefficient were correlated with the most significant compositional parameters, such as molar volume, excess molar volume, number of network bonds per unit volume, oxygen density, first-order stretching force constant, single bond strength, dissociation energy per unit volume and packing density of the glass. The correlation has been carried out on the basis of Abd El-Moneim's semi-empirical formulas, bond compression model and Makishima-Mackenzie's theory. One of Abd El-Moneim's semi-empirical formulas was modified, due to the anomalous behavior between ultrasonic properties and calculated dissociation energy per unit volume. On the basis of the modified semi-empirical formula, correlation between ultrasonic attenuation coefficient and molar volume is achieved through the average first-order stretching force constant of P-O-V linkages. The divergence between theoretical and experimental values of elastic moduli has been attributed to the anomalous behavior between ultrasonic properties and dissociation energy per unit volume of the glass.

Ultrasonic investigations of some bismuth borate glasses doped with Al2O3

The velocities of longitudinal and transverse ultrasonic waves in different compositions of 5Al 2O3–29Na 2O–(66 − x) B2O3−xBi2O3 glass system were measured at 4 MHz at room temperature using the pulse-echo technique. The velocity data were used to determine the elastic moduli and the dimensionality of the studied glasses. The observed changes in the elastic moduli of the glasses were related to the modifier role of Bi 2O3 content. The results revealed that the density increased with increasing Bi 2O3 content, which was attributed to the increase in the compactness and packing of the glass network. The ultrasonic data were analysed in terms of creation of new bonds of Bi 2O3 attached to the structural units of the borate network. The new bonds decreased the average crosslink density and the number of network bonds per unit volume along with a weakening of the different modes of vibrations, which in its turn decreased the ultrasonic velocity. Quantitative analysis was carried out using Makishima–Mackenzie model in order to obtain more information about the rigidity of these glasses.

Effect of P2O5 on optical parameters of (25−x) CaO–xP2O5–B2O3–SiO2–ZnO sol–gel glasses: a theoretical assessment

The present investigation is an attempt to address the effect of P2O5 on the optical properties, cross link density (nc) as well as theoretical parameters like Poisson’s ratio and bulk modulus for (25−x)%CaO−x%P2O5–60%SiO2–5%B2O3–10%ZnO (x = 5, 10, 15, 20) novel sol–gel glasses. The optical basicity, oxide polarisability, direct/indirect band gaps and theoretical elastic constants have been calculated for all the glasses. In addition to this, the cross-link density, average force stretching constant and number of network bonds per unit volume (nb) have been calculated. The values of optical basicity and polarisabilty have allowed the same trend for all these glasses. The cross-link density decreases when the P2O5 content increases from 5 to 20 %.

Elastic moduli of borosilicate glasses doped with heavy metal oxides

Comparative studies on the theoretical and experimental values of elastic moduli of the borosilicate glasses (70-x)SiO2–30B2O3–xHMOs glass system, where HMOs (heavy metal oxides) are TiO2, BaO and Bi2O3 with 0, 1, 2, 3, 4 and 5mol% of each HMO, were investigated. Elastic moduli were assessed by measuring the ultrasonic velocities. The number of network bonds per unit volume, the average of a stretching force constant, the average of cross-link density, the average of ring diameter and the theoretical bond compression bulk modulus were calculated by using a theoretical bond compression model to confirm the obtained results from the experiments. The results show that changes in the structure of the glass depend on a type and concentration of HMOs. Moreover, the experimental elastic moduli are in good agreement with the theoretical values.

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.

Correlation between acoustical and compositional parameters of borate and tellurite glasses

A new semi-empirical relation was presented to correlate the measured ultrasonic attenuation coefficient at room temperature with the packing density, dissociation energy per unit volume and first-order stretching force constant of the glass. A comprehensive study was carried out to examine the validity of this relation as well as Makishima and Mackenzie theory for TiO2-doped 30CaO–30Al2O3–40B2O3 and x1 Ag2O-x2 V2O5-(1−x1−x2) TeO2 glass systems. It has been found that the correlation between ultrasonic attenuation coefficient and both packing density and dissociation energy per unit volume was achieved through first-order stretching force constant of the glass. Also, the theoretically calculated values of bulk modulus are in a good agreement with the corresponding experimentally measured values. Moreover, fractal bond connectivity and number of network bonds per unit volume play an important role in determining the changes in the structural and acoustical properties of the investigated glasses.

Influence of MoO3 on the Structure of Lithium Aluminum Phosphate Glasses

IR spectroscopy, density and ultrasonic velocity measurements have been carried out for aluminum lithium phosphate glasses with and without MoO3. The observed changes in the FTIR spectra of the glasses were related to the modifier/former role of molybdenum ions. The results revealed that the density increases with increasing MoO3 content, which was attributed to the increase in the compactness and packing of the glass network. The ultrasonic data were analyzed in terms of creation of new bonds of MoO3 attached to phosphate units. The new bonds increased the average crosslink density and the number of network bonds per unit volume along with a strengthening of the different modes of vibrations which in its turn increased the ultrasonic velocity, the rigidity and hence the elastic moduli of the glasses.

Ultrasonic, FTIR and thermal investigations of SiO2–Na2O–CaO–P2O5 glasses doped with CeO2

The longitudinal and shear ultrasonic wave velocities for different compositions of SiO2–Na2O–CaO–P2O5 glasses were measured at room temperature (305 K) using a pulse-echo method at a frequency of 4 MHz. The elastic moduli, Poisson's ratio, microhardness, Debye temperature and other ultrasonic parameters were obtained from experimental data and analyzed using bond compression theory. By calculating the number of network bonds per unit volume, the average stretching constant, and the average ring size, information about the structure of the glass can be deduced. Structural changes after doping with CeO2 were investigated by FTIR spectroscopy, and by measurements of the thermal expansion coefficient, glass transition and softening temperature to throw more light on the characterization of these glasses.

Elastic and structural properties of vanadium–lithium–borate glasses

The ternary xV2O5–(40 − x)Li2O–60B2O3 glass system, where x = 1, 2, 3, 4 and 6 mol%, was prepared by normal quenching. Ultrasonic velocities and attenuation were measured at room temperature using a pulse-echo technique. Various parameters, such as elastic moduli, micro-hardness, Poisson's ratio and Debye temperature, were determined from the measured densities and velocities. The composition dependence of these parameters, in addition to the glass-transition temperature, suggested that vanadium ions were incorporated into these glasses as a network modifier, resulting in the reconversion of BO4 tetrahedra to BO3 triangles by the breaking of B–O–B linkages and the formation of nonbridging oxygens (NBOs). The outcome was a reduction in network connectivity and rigidity with increasing V2O5 content. The results are explained quantitatively in terms of fractal bond connectivity, average atomic volume, network dimensionality, packing density, number of network bonds per unit volume, cross-link density and atomic ring size. The Makishima and Mackenzie model appears to be valid for the studied glasses when the fate of BO4 tetrahedra and creation of NBOs are taken into account.

Structural role of RO and Al 2O 3 in borate glasses using an ultrasonic technique

The ternary alkaline earth aluminoborate glasses RO–Al 2O 3–B 2O 3, where R = Mg, Ca, Sr, have been prepared by the normal quenching method. Ultrasonic velocities and attenuation were measured in these glasses using the pulse-echo technique to explore the structural role of RO and Al 2O 3 in these glasses. From the measured densities and velocities, various parameters such as elastic moduli, microhardness and Poisson’s ratio have been determined. Results obtained are discussed in terms of the field strength of the interstitial cation, molar ratio (Al 2O 3/RO), fraction of four coordinated boron atoms, number of network bonds per unit volume, average cross-link density and fractal bond connectivity of the network. It was found that the network connectivity of these glasses increases in the order Mg > Ca > Sr. Makishima and Mackenzie theory has been applied to correlate the experimental and theoretical data and good correlation was observed.

Structural analysis of alkali borate glasses

This paper reports on the elastic properties of alkali borate glass systems (R 2O–B 2O 3, R=K, Rb, Cs). The elastic moduli were calculated in terms of Makishima–Mackenzie model and a model by Bridge et al. The average cross-link density, number of network bonds per unit volume, average stretching force constant, atomic ring size, and the ratio K bc/ K e, have been calculated and discussed according to bond compression model to analyze the borate anomaly. Young's modulus, packing density and Poisson's ratio have been calculated and analyzed according to Makishima–Mackenzie model. Debye temperature has been calculated and discussed in terms of the cross-link density of these glasses. The borate anomaly was discussed in terms of experimentally derived Debye temperature and theoretically calculated elastic moduli. The results showed good agreement between experimental and theoretical data for the borate anomaly representation.

Ultrasonic and structural studies on TiO2-doped CaO–Al2O3–B2O3 glasses

TiO2-doped 30CaO–30Al2O3–40B2O3 glasses have been prepared by the melt quenching method over a wide range of composition (TiO2 = 5, 10, 15, and 20 mol%). The longitudinal velocity and attenuation of ultrasonic waves were measured in these glasses at room temperature using the pulse-echo technique. The acoustic impedance and longitudinal modulus were calculated and are discussed quantitatively in terms of the structural parameters, such as packing density, dissociation energy per unit volume, field strength of the modifiers, number of network bonds per unit volume, average cross-link density and the number of two-well systems (loss centers) per unit volume of the glass. The composition dependence of these parameters suggested that Al2O3 associates itself with CaO to form AlO4 tetrahedra and Ti4+ ions are incorporated in the network as TiO6 octahedra. This leads to an increase in the three-dimensional linkage and rigidity of the network. Moreover, the theoretical elastic moduli were calculated for these glasses from the chemical composition and the experimentally determined density using the Makishima and Mackenzie model. Results showed that the model is valid for the studied glasses. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Quantitative analysis of elastic moduli and structure of B 2O 3–SiO 2 and Na 2O–B 2O 3–SiO 2 glasses

The average cross-link density n ̄ c , number of network bonds per unit volume n b, average stretching force constant F ̄ and atomic ring size ℓ have been calculated for the binary B 2O 3–SiO 2 and ternary Na 2O–B 2O 3–SiO 2 glass systems. These data have been used to calculate the bond compression bulk modulus K bc and Poisson's ratio σ cal for each glass sample. The variation of these parameters and the ratio K bc/ K e with composition were discussed quantitatively in terms of the change in structure of the glass network. The result showed that the connectivity and hence the rigidity of the B 2O 3–SiO 2 glasses decreases with increasing B 2O 3 concentration. Whereas increasing of Na 2O modifier in Na 2O–B 2O 3–SiO 2 glasses increase the cross-link density due to the transformation of three-fold-coordinated boron atoms into four-fold-coordinated ones. This in turn raises the resistance of the network to deformation and increases the observed density and elastic moduli of this glass system. Moreover, the theoretical elastic moduli have been obtained for each glass sample and compared with the corresponding experimental values. The results showed excellent agreement for the majority of the samples examined.

A new structural parameter of polymers–the relative number of network bonds per unit volume

AbstractIn this paper we define a new structural parameter of polymers, and show how this may be employed. This parameter, for which only the structure and the density are needed, is the relative number of network bonds per unit volume; it is written Ner (basis 1 cm3), and it is used in conjunction with the average connectivity or connection number CN of the network atoms, where the word connection also refers only to network bonds. The relationship of these two numbers makes it possible to present a unified picture of all polymers, organic and inorganic, including such highly condensed networks as diamond. By plotting Ner against CN, the region in which inorganic and organic polymers occur can be seen. This is called the polymer zone, and it is evident that carbon polymers occupy only a small part of it. From this graph, an arbitrary measure of bond packing efficiency can be deduced for carbon polymers. In addition, the process of graphitization and carbonization can be followed graphically within the polymer zone. Ner is also related to certain physical properties such as bulk modulus, hardness, and cubical coefficient of expansion, which depend (among other things) on the tightness of bond arrangement. The resultant correlations can be used to predict the value of Ner required to achieve given values of these properties for the more rigid structures.