PHYSICAL AND OPTICAL POLARIZABILITY AND TRANSPORT PROPERTIES OF BISMUTHATE GLASSES

2009 ◽  
Vol 23 (22) ◽  
pp. 2665-2679
Author(s):  
SHASHIDHAR BALE ◽  
SYED RAHMAN
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Raman Spectroscopy ◽  
Refractive Index ◽  
Glass Transition ◽  
Transition Temperature ◽  
Transport Properties ◽  
Dc Electrical Conductivity ◽  
Oxide Ion ◽  
Transition Temperature Increase

Bismuth-based glasses containing ZnO , B 2 O 3 and Li 2 O are investigated through different physical, polarizability and transport properties. Raman spectroscopy reveals that these glasses are built from [ BiO 3] and [ BiO 6] units. Zinc in tetrahedral form is also observed. Density and glass transition temperature increase with the bismuth content. The refractive index, oxide ion polarizability and optical basicity also increase with the Bi 2 O 3 content, whereas the interaction parameter decreases. The DC electrical conductivity increases and the activation energy decreases with the increase in the Li 2 O content.

scholarly journals Spectroscopic and Physical Properties of --ZnO- Glasses

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Shashidhar Bale ◽  
Syed Rahman
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Heat Capacity ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Electrical Conduction ◽  
Glass Network ◽  
Dc Electrical Conductivity ◽  
Conduction Properties

Bismuth glasses containing ZnO and Li2O were prepared by conventional melt-quench technique. ZnO is gradually substituted by Li2O, and its effect on various physical, thermal, and electrical conduction properties was studied and analyzed. Raman studies revealed that these glasses are mainly made up of [BiO3] and [BiO6] units. The density decreases and molar volume increases with the incorporation of Li2O into these glasses. MDSC studies have been performed on these glasses to determine the glass transition temperature and other related thermal parameters such as change in the glass transition temperature () and specific heat capacity difference (). These studies revealed that the glasses possess high values, and decreases with Li2O content. The trend of these properties is attributed to the changes in the glass network structure. Dc electrical conductivity revealed that the conductivity increases and activation energy decreases with Li2O content.

Study on the Crystallization Activation Energy of Poly (L-lactic acid) Nucleated with P-tert-butylcalix[8]arene

2018 ◽  
Vol 26 (2) ◽  
pp. 169-175
Author(s):  
Yaoqi Shi ◽  
Liang Wen ◽  
Zhong Xin
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crystallization Temperature ◽  
Nucleating Agent ◽  
Crystallization Activation Energy ◽  
Temperature Range ◽  
Chain Mobility

The crystallization activation energy (Δ E) of a polymer comprises the nucleation activation energy Δ F and the transport activation energy Δ E*. In this paper, the Δ E of poly (L-lactic acid) (PLLA) nucleated with nucleating agent p- tert-butylcalix[8]arene (tBC8) was calculated. The results showed that the Δ E of nucleated PLLA was 165.97 kJ/mol, which is higher than that of pure PLLA. The reason why Δ E of PLLA increased when incorporating nucleating agent was studied. The increment of glass transition temperature ( Tg) for nucleated PLLA revealed that the polymer chain mobility was restricted by tBC8, which was considered as the reason for the increase of Δ E*. Further, polyethylene glycol (PEG) was added to improve the chain mobility, thus eliminated the variation of the transport activation energy Δ E* caused by tBC8. Then the effect of the increment of crystallization temperature range on the increase of Δ F was also taken into consideration. It was concluded that both decreasing the mobility of chain segments and increasing the crystallization temperature range caused an increase of Δ E for PLLA/tBC8.

scholarly journals The Glass Transition Temperature and Temperature Dependence of Activation Energy of Viscous Flow of Ovalbumin

2016 ◽  
Vol 39 (1) ◽  
pp. 13-25
Author(s):  
Karol Monkos
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Viscous Flow ◽  
Solvent Interactions ◽  
Model Free ◽  
Free Volume Model ◽  
Wide Range ◽  
Different Temperatures

Abstract The paper presents the results of viscosity determinations on aqueous solutions of ovalbumin at a wide range of concentrations and at temperatures ranging from 5°C to 55°C. On the basis of these measurements and three models of viscosity for glass-forming liquids: Avramov’s model, free-volume model and power-law model, the activation energy of viscous flow for solutions and ovalbumin molecules, at different temperatures, was calculated. The obtained results show that activation energy monotonically decreases with increasing temperature both for solutions and ovalbumin molecules. The influence of the energy of translational heat motion, protein-protein and protein-solvent interactions, flexibility and hydrodynamic radius of ovalbumin on the rate of decrease in activation energy with temperature has been discussed. One of the parameters in the Avramov’s equation is the glass transition temperature Tg. It turns out that the Tg of ovalbumin solutions increases with increasing concentration. To obtain the glass transition temperature of the dry ovalbumin, a modified Gordon-Taylor equation is used. Thus determined the glass transition temperature for dry ovalbumin is equal to (231.8 ± 6.1) K.

The Influence of Gamma Radiation on the Glass Transition of Hydroxyapatite/Poly L-Lactide Composite

2007 ◽  
Vol 555 ◽  
pp. 497-502
Author(s):  
Dejan Miličević ◽  
S. Trifunović ◽  
N. Ignjatović ◽  
E. Suljovrujić
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Structural Relaxation ◽  
Absorbed Dose ◽  
Gel Permeation Chromatography ◽  
Chain Scission ◽  
Scanning Calorimetry ◽  
Dsc Measurements

Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma irradiation has been successfully employed in the modification/sterilization of such porous composites and that it has advantages over other procedures. In this study, differential scanning calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass transition behavior and structural relaxation, as well as to estimate the activation energy for this process. The apparent activation energy ΔH* for structural relaxation in the glass transition region was determined on the basis of the heating rate dependence of the glass transition temperature Tg. Furthermore, the results were correlated with those obtained by gel permeation chromatography (GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is the main reason for the decrease of the glass transition temperature and/or activation energy with the absorbed dose.

Synthesis and Gas Transport Properties of New High Glass Transition Temperature Ring-Opened Polynorbornenes

2002 ◽  
Vol 35 (12) ◽  
pp. 4677-4684 ◽  
Author(s):  
Armando Pineda Contreras ◽  
Mikhail A. Tlenkopatchev ◽  
Maria del Mar López-González ◽  
Evaristo Riande
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Transport Properties ◽  
Gas Transport ◽  
High Glass Transition Temperature ◽  
Gas Transport Properties

On the Possibility to Observe a Compensation Effect around the Glass Transition Temperature

2006 ◽  
Vol 514-516 ◽  
pp. 1462-1466
Author(s):  
Rodica M. Neagu ◽  
José N. Marat-Mendes ◽  
Eugen R. Neagu
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Compensation Effect ◽  
Depolarization Current ◽  
Exponential Factor ◽  
Relaxation Parameters ◽  
Maximum Current ◽  
Thermally Stimulated Depolarization

Compensation has been reported for the relaxation parameters: the activation energy W and the pre-exponential factor τ0, determined from the Thermal Sampling of Thermally Stimulated Depolarization Current technique. Below the glass transition it is assumed that the relaxation time follows an Arrhenius equation. In the vicinity of glass transition temperature an experimental thermogram may be analyzed using the Vogel-Fulcher-Tamman-Hesse (VFTH) or the Williams- Landel -Ferry equation. In this article we use the VFTH relationship to study the compensation effect in the range of glass transition. For an elementary peak obtained by TS there is a relationship between the activation energy W, the temperature of the maximum current Tm, the VFTH temperature, the compensation temperature Tc and the compensation time τ c. We employ this relationship for a basic analysis of the compensation effect in the temperature range around Tg. By numerical simulations, and assuming parameters similar to those measured experimentally, we show that it is possible to observe a compensation point in some well defined conditions

Structural and Physical Characterization of Li2O:P2O5:MO3 (M = Cr2, Mo, W) Ion Conducting Glasses

1992 ◽  
Vol 293 ◽  
Author(s):  
B.V.R. Chowdari ◽  
K.L. Tan ◽  
W.T. Chia
Keyword(s):  
Raman Spectroscopy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Photoelectron Spectroscopy ◽  
Oxygen Species ◽  
X Ray ◽  
Ion Conducting ◽  
Phosphate Groups ◽  
Glass Compositions

AbstractThe conductivity of the Li2O:P2O5:MO3 (M = Cr2, Mo, W) glasses increases as P2O5 is progressively substituted by MO3 and as the Li2O content increases. Amongst the glass compositions studied, the 0.50Li2O:0.20P2O5:0.30WO3 glass has the highest conductivity at 25°C of 2. 1×10−6 ×−1 cm−1. The glass transition temperature of the glasses increases initially with network former substitution, reaches a maximum at around MO3/P2O5 = 1, and decreases with further substitution. X-ray photoelectron spectroscopy reveals the presence of M ions in more than one oxidation state and oxygen species such as P=O, P-O-P, P-O, M-O-M, M-O and P-O-M. Raman spectroscopy shows that the Li2O:P2O5:MoO3 and Li2O:P2O5:WO3 glasses consist of PO4, MoO4 (WO4) and MoO6 (WO6) polyhedra while the Li2O:P2O5:Cr2O3 glasses consist of the PO4 and CrO6 polyhedra only. The phosphate groups are preferentially modified by Li2O in comparison with the tungstate, molybdate and chromate groups. The increasing number of non-bridging oxygen atoms per phosphate group may be related to the increasing conductivity with the progressive substitution of MO3 for P2O5.

Preparation and Characterization of TeO2 Based Glasses

2005 ◽  
Vol 480-481 ◽  
pp. 315-322 ◽  
Author(s):  
J. Pedlíková ◽  
J. Zavadil ◽  
Olga Prochazková ◽  
J. Kaluzny
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Low Temperature ◽  
Absorption Edge ◽  
Electronic Transitions ◽  
Transmission Range ◽  
Dc Electrical Conductivity ◽  
Pacs Codes ◽  
Low Temperature Photoluminescence

Binary and ternary TeO2 based oxy-chloride glass systems have been prepared and characterised by absorption and low-temperature photoluminescence spectroscopy, and by the measurements of dc electrical conductivity. Prepared glasses exhibit transmittance 75-80% in a broad transmission range 0.3 – 6.5µm with modest shift of upper absorption edge to longer wavelength as heavier ions are introduced into the system. Electronic transitions between 4f-4f inner shells of Pr3+ ions embedded into the host glass have been investigated in a wide temperature range as a function of used precursors used for doping. The temperature dependence of dc electrical conductivity exhibits Arrhenius plots with the single activation energy. PACS codes 81.05.Kf, 78.20.Ci, 78.55.Hx

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