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1.
K. A. Aly A. Dahshan Yasser B. Saddeek 《Journal of Thermal Analysis and Calorimetry》2010,100(2):543-549
The present paper reports on the effect of MoO3 on the glass transition, thermal stability and crystallization kinetics for (40PbO–20Sb2O3–40As2O3)100−x
–(MoO3)
x
(x = 0, 0.25, 0.5, 0.75 and 1 mol%) glasses. Differential scanning calorimetry (DSC) results under non-isothermal conditions
for the studied glasses were reported and discussed. The values of the glass transition temperature (T
g) and the peak temperature of crystallization (T
p) are found to be dependent on heating rate and MoO3 content. From the compositional dependence and the heating rate dependence of T
g and T
p, the values of the activation energy for glass transition (E
g) and the activation energy for crystallization (E
c) were evaluated and discussed. Thermal stability for (40PbO–20Sb2O3–40As2O3)100−x
–(MoO3)
x
glasses has been evaluated using various thermal stability criteria such as ΔT, H
r
, H
g and S. Moreover, in the present work, the K
r(T) criterion has been considered for the evaluation of glass stability from DSC data. The stability criteria increases with
increasing MoO3 content up to x = 0.5 mol%, and decreases beyond this limit. 相似文献
2.
Balbir Singh Patial Nagesh Thakur S. K. Tripathi 《Journal of Thermal Analysis and Calorimetry》2011,106(3):845-852
Calorimetric study of Se85−x
Te15Sn
x
(x = 0, 2, 4 and 6) glassy alloys have been performed using Differential Scanning Calorimetry (DSC) under non-isothermal conditions
at four different heating rates (5, 10, 15 and 20 °C/min). The glass transition temperature and peak crystallization temperature
are found to increase with increasing heating rate. It is remarkable to note that a second glass transition region is associated
with second crystallization peak for Sn additive Se–Te investigated samples. Three approaches have been employed to study
the glass transition region. The kinetic analysis for the first crystallization peak has been taken by three different methods.
The glass transition activation energy, the activation energy of crystallization, and Avrami exponent (n) are found to be composition dependent. The crystallization ability is found to increase with increasing Sn content. From
the experimental data, the temperature difference (T
p − T
g) is found to be maximum for Se83Te15Sn2 alloy, which indicates that this alloy is thermally more stable in the composition range under investigation. 相似文献
3.
The present work demonstrates application of electrical conductivity (σ)–temperature (T) cycles to investigate thermal properties viz., crystallization and glass transition kinetics in AgI–Ag2O–V2O5–MoO3 superionic glasses. The σ–T cycles are carefully performed at various heating rates, viz., 0.5, 1, 3, 5, and 7 K/min. The conductivity in Ag+ ion conducting glasses exhibit anomalous deviation from Arrhenius behavior near glass transition temperature (T
g) followed by a drastic fall at crystallization (T
c). The temperature corresponding to maximum rate of crystallization (T
p) is obtained from the derivative of σ–1/T plots. With increasing heating rates, the characteristic temperatures (T
g, T
p) are found to be shifting monotonically toward higher temperatures. Thus, activation energy of structural relaxation E
s, crystallization E
c and other thermal stability parameters have been obtained from σ–T cycles using Kissinger equation and Moynihan formulation. For a comparative study, these kinetics parameters have also been
calculated from differential scanning calorimetry plots. The parameters obtained from both the methods are found to be comparable
within experimental error. 相似文献
4.
Glasses with compositions 60B2O3–40PbO, 60B2O3–40Bi2O3, and 60B2O3–30Bi2O3–10PbO have been prepared and studied by differential thermal analysis. The crystallization kinetics of the glasses was investigated
under non-isothermal conditions. From dependence of the glass transition temperature (T
g) on the heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the
crystallization process was determined. Thermal stability of these glasses were achieved in terms of the characteristic temperatures,
such as the glass transition temperature, T
g, the onset temperature of crystallization, T
in
, the temperature corresponding to the maximum crystallization rate, T
p, beside the kinetic parameters, K(T
g) and K(T
p). The results revealed that the 60B2O3–40PbO is more stable than the others. The crystallization mechanism is characterized for glasses. The phases at which the
glass crystallizes after the thermal process have been identified by X-ray diffraction. 相似文献
5.
Mirjana V. ?iljegovi? Goran R. ?trbac Fedor Skuban Svetlana R. Luki?-Petrovi? 《Journal of Thermal Analysis and Calorimetry》2011,105(3):947-951
Thermal properties of glasses from the system Bi
x
(As2S3)100−x
were studied by differential scanning calorimetry of a representative series of samples with x = 0.5, 2, 4, 6, 8, and 10 at.% Bi by determining the characteristic temperatures (T
g, T
onset, T
c, T
m) and enthalpies (H
c, H
m) of the processes taking place in the samples during their thermal treatment. Analysis of DSC recordings for the samples
at the same heating rate allowed characterization of the phase transition temperature T
g as a function of the content of doping atoms in accordance with the criteria of chemical bonds formation in amorphous materials.
Samples with 4 and 6 at.% Bi were thermally treated at different heating rates with the aim of determining, among the others,
the parameters of their thermal stability. The assessment was done based on three different criteria. A higher tendency toward
crystallization was observed with the glasses having a higher Bi content. Also, a trend of T
g shifting toward higher values, observed with increase in the heating rate, is in concordance with the Lasocka equation. 相似文献
6.
M. M. A. Imran D. Bhandari N. S. Saxena 《Journal of Thermal Analysis and Calorimetry》2001,65(1):257-274
Results of phase transformations, enthalpy released and specific heat of Ge22Se78–xBix(x=0, 4 and 8) chalcogenide glasses, using differential scanning calorimetry (DSC), under non-isothermal condition have been reported and discussed. The glass transition temperature, T
g, is found to increase with an average coordination number and heating rates. Following Gibbs—Dimarzio equation, the calculated values of T
g (i.e. 462.7, 469.7 and 484.4 K) and the experimental values (i.e. 463.1, 467.3 and 484.5 K) increase with Bi concentration. Both values of T
g, at a heating rate of 5 K min–1, are found to be in good agreement. The glass transition activation energy increases i.e. 102±2, 109±3 and 115±8 kJ mol–1 with Bi concentration. The demand for thermal stability has been ensured through the temperature difference T
c–T
g and the enthalpy released during the crystallization process. Below T
g, specific heat has been observed to be temperature independent but highly compositional dependent. The growth kinetic has been investigated using the Kissinger, Ozawa, Matusita and modified JMA equations. Results indicate that the crystallization ability is enhanced, the activation energy of crystallization increases with increasing the Bi content and the crystal growth of these glasses occur in 3 dimensions.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
7.
Linli Xu Kai Xu Dehong Chen Qiukai Zheng Feiyue Liu Mingcai Chen 《Journal of Thermal Analysis and Calorimetry》2009,96(3):733-740
The effects of non-isothermal and isothermal crystallization on the formation of α- and β-phase in isotactic polypropylene
(iPP) with different content of β-nucleating agent are investigated by differential scanning calorimetry (DSC). On non-isothermal
crystallization, the content of β-phase and regularity of its crystals are depended on both cooling rate and the content of
β-nucleating agent. The faster cooling rate is, the lower of melting peak temperature (Tmp) and crystallization peak temperature (Tcp) of α- and β-phase are. The enthalpy of fusion (∆H) of β-phase increases with cooling rate in a certain range for the sample
with 0.1 wt% β-nucleating agent (G1) and decreases for that with 0.3 wt% β-nucleating agent (G3). On isothermal crystallization, the enthalpy of fusion of β-phase in G1 is higher than in G3 which is related to the efficiency of nucleation in different concentration of nucleating center in two samples. 相似文献
8.
Thermal behavior of xGa2O3–(50 − x)PbO–50P2O5 (x = 0, 10, 20, and 30 mol.% Ga2O3) and xGa2O3–(70 − x)PbO–30P2O5 (x = 0, 10, 20, 30, and 40 mol.% Ga2O3) glassy materials were studied by thermo-mechanical analysis (TMA) and differential thermal analysis (DTA). Replacement of
PbO for Ga2O3 is accompanied by increasing glass-transition temperature (263 ≤ T
g/°C ≤ 535), deformation temperature (363 ≤ T
d/°C ≤ 672), crystallization temperature (396 ≤ T
c/°C ≤ 640) and decreasing of coefficient of thermal expansion (5.1 ≤ CTE/ppm K−1 ≤ 16.7). Values of Hruby parameter were determined (0.1 ≤ K
H ≤ 1.3). The thermal stability of prepared glasses increases with increasing of concentration of Ga2O3. 相似文献
9.
Se80?x Te20Zn x (x?=?2, 4, 6, 8, and 10) glasses have been prepared using conventional melt quenching technique. The kinetics of phase transformations (glass transition and crystallization) have been studied using differential scanning calorimetry (DSC) under non-isothermal condition at five different heating rates in these glasses. The activation energy of glass transition (E t), activation energy of crystallization (E c), Avrami exponent (n), dimensionality of growth (m), and frequency factor (K o) have been investigated for the better understanding of growth mechanism using different theoretical models. The activation energy is found to be highly dependent on Zn concentration. The rate of crystallization is found to be lowest for Se70Te20Zn10 glassy alloy. The thermal stability of these glasses has been investigated using various stability parameters. The values of these parameters were obtained using characteristic temperatures, such as glass transition temperature T g, onset crystallization temperature T c, and peak crystallization temperature T p. In addition to this, enthalpy-released during crystallization has also been determined. The values of stability parameters show that the thermal stability increases with the increase in Zn concentration in the investigated glassy samples. 相似文献
10.
A number of samples of sodium and silver phosphate glasses doped with
various compositions of some transition metals viz. iron, manganese and zinc
chlorides alongwith undoped samples of sodium and silver phosphate glasses
were synthesized and characterized by X-ray diffraction, IR spectral, electrical
conductivity and differential scanning calorimetry (DSC). The glass transition
temperature (T
g)
and crystallization temperature (T
c)
values obtained from DSC curves were found to increase with increasing concentration
of the dopant Fe/Mn/Zn chlorides in both sodium and silver phosphate glasses
and the following sequence is observed:
T
g(–FeCl3)>T
g(–MnCl2)>T
g(–ZnCl2)
T
c(–FeCl3)>T
c(–MnCl2)>T
c(–ZnCl2)
The increase in T
g
and T
c values indicate
enhanced chemical durability of the doped glasses. The electrical conductivity
values and the results of FTIR spectral studies have been correlated with
the structural changes in the glass matrix by the addition of different transition
metal cations as dopants. 相似文献
11.
P. Mošner K. Vosejpková L. Koudelka L. Beneš 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1129-1135
The effect of TeO2 additions on the thermal behaviour of zinc borophosphate glasses were studied in the compositional series (100 − x)[0.5ZnO–0.1B2O3–0.4P2O5]–xTeO2 by differential scanning calorimetry, thermodilatometry and heating microscopy thermal analysis. The addition of TeO2 to the starting borophosphate glass resulted in a linear increase of glass transition temperature and dilatometric softening
temperature, whereas the thermal expansion coefficient decreased. Most of glasses crystallize under heating within the temperature
range of 440–640 °C. The crystallization temperature steeply decreases with increasing TeO2 content. The lowest tendency towards crystallization was observed for the glasses containing 50 and 60 mol% TeO2. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were Zn2P2O7, BPO4 and α-TeO2. Annealing of the powdered 50ZnO–10B2O3–40P2O5 glass leads at first to the formation of an unknown crystalline phase, which is gradually transformed to Zn2P2O7 and BPO4 during subsequent heating. 相似文献
12.
Phase behavior and crystal morphology in poly(ethylene succinate) biodegradably modified with tannin
Siti Nurkhamidah Eamor M. Woo I-Han Huang Chean C. Su 《Colloid and polymer science》2011,289(14):1563-1578
Specific interactions, growth kinetics, and dendritic morphology in poly(ethylene succinate) (PESu) biodegradably modified
with various contents of tannic acid (TA) were characterized using differential scanning analysis, Fourier-transform infrared
(FTIR) spectroscopy, polarized-light optical microscopy, and atomic force microscopy. Strong interactions and highly retarded
growth between PESu and a macromolecular ester with polyphenol groups, TA, interaction-induced highly retarded growth rates
for the PESu/TA (80:20) composition are proven to lead to single-crystal-like dendrites when crystallized at high crystallization
temperature (T
c). At T
c = 70 °C, the growth rate for neat PESu is 12 μm/min while it is dramatically depressed to one tenth-fold at 1.5 μm/min with
20 wt.% TA in the blend. Strong specific interactions between the carbonyl group of polyesters and the phenolic hydroxyl group
of TA are confirmed by (1) the blend’s glass transition temperature (T
g)–composition relationship exhibits a sigmoidal curve, well fitted by the Kwei T
g model for miscible blends with large negative q = −90; (2) thermal analysis on crystal melting revealed an interaction parameter χ = −0.64 between PESu and TA; and (3) IR peak shifting analyzed using two-dimensional FTIR technique. A comparative blend
of another polyester poly(hexamethylene sebacate) with TA, lacking the specific interactions, does not exhibit such single
crystals upon similar melt crystallization. 相似文献
13.
A linear relationship exists between the glass transition temperature (T
g) and the quadrupole splitting (Δ) of Fe(III). The linear relationship, termed ‘T
g-Δ rule’, has been verified in 60CaO·(40-x)Al2O3·xFe2O3, 60CaO·10BaO·(30-x) Al2O3·xFe2O3, 60CaO·(40-x)Ga2O3·xFe2O3, and 50CaO·(50-x)Ga2O3·xFe2O3 glasses. In these glasses, both theT
g and Δ decrease linearly with an increasing content of Fe2O3 (≈40 mol%). The slope of the straight line, obtained from the plot of theT
g vs. Δ, was calculated to be 670≈700, °C/(mm·s−1), revealing that the Fe(III) constitutes the skeleton of aluminoferrate and galloferrate glasses. 相似文献
14.
Silicate-phosphate glasses of SiO2–P2O5–K2O–MgO–CaO system containing manganese cations were investigated to obtain information about the influence of manganese ions
on the thermal behavior of such glasses. Amorphous state of glasses and the course of phase transformation and crystallization
taking place during their heating were investigated by DSC, XRD, and FTIR methods. It was shown that an increasing content
of manganese replacing calcium and magnesium in the structure of analyzed glasses causes decrease of glass transition temperature
(T
g) and heat capacity change (Δc
p) accompanying the glass transformation. Simultaneously, thermal stability of the glasses increased. Products of multistage
crystallization of glasses containing up to 8 mol% of MnO2 were: marokite (CaMn2O4), phosphate of Ca9MgK(PO4)7 type, and diopside (CaMgSi2O6). Product of crystallization of glasses containing higher amount of manganese was braunite (Mn7O8SiO4). This was accompanied by change of structure of magnesium calcium silicates from diopside-type structure to akermanite-type
silicates (Ca2MgSi2O7). The data interpretation was based on bonds and chemical interactions of the individual components forming the glass structure. 相似文献
15.
Yanchun Li Yi Cheng Yinghua Ye Ruiqi Shen 《Journal of Thermal Analysis and Calorimetry》2010,102(2):605-608
The relative errors (e%) in the determination of the activation energy from the slope of the Kissinger straight line ln(β/βT
p2) vs. 1/T
p (β is the heating rate) are in-depth discussion. Our work shows that the relative errors is a function containing the factors
of x
p and Δx
p, not only x
p (x
p = E/RT
p, E is the activation energy, T
p is the temperature corresponding to maximum process rate, R is the gas constant). The relative error between E
k and E
p will be smaller with the increase of the value of x and/or with the decrease of the value of Δx. For a set of different heating rates in thermal analysis experiments, the low and close heating rates are proposed from
the kinetic theory. 相似文献
16.
The crystallization kinetics of Cu50Zr43Al7 and (Cu50Zr43Al7)95Be5 metallic glasses was studied using differential scanning calorimetry (DSC) at four different heating rates under non-isothermal condition. The glass transition temperature T g, the onset temperature of crystallization T x, and the peak temperature of crystallization T p of the two metallic glasses were determined from DSC curves. The values of various kinetic parameters such as the activation energy of glass transition E g, activation energy of crystallization E p, Avrami exponent n and dimensionality of growth m were evaluated from the dependence of T g and T p on the heating rate. The values of E g and E p, calculated from many different models, are found to be in good agreement with each other. The average values of the Avrami exponent n are (2.8 ± 0.4) for Cu50Zr43Al7 metallic glass and (4.2 ± 0.3) for (Cu50Zr43Al7)95Be5 metallic glass, which are consistent with the mechanism of two-dimensional growth and three-dimensional growth, respectively. Finally, the parameter H r, S, and crystallization enthalpy ΔH c are introduced to estimate the glass-forming ability and thermal stability of metallic glasses. The result shows that the addition of Be improves the glass-forming ability and thermal stability of Cu50Zr43Al7 metallic glass. 相似文献
17.
Isobaric variations of the characteristic temperatures Tg and Tmax, obtained on uniform cooling and heating of glasses, are investigated in terms of their dependence on the relevant experimental variables, using a single retardation time model. The corresponding partial derivatives of Tg and Tmax are derived as functions of the partition parameter x (ranging between zero and unity), which determines the relative contributions of temperature and structure to the retardation time. It is shown that the variation of Tg with the cooling rate is independent of x. In contrast, Tmax critically depends on x, and its value as well as those of its three partial derivatives are linear functions of x?1. The variations of Tmax are analyzed in terms of a set of reduced variables, leading to simple reduction rules between any two of the experimental variables when the third is kept invariant. The reduction rules are further substantiated by investigating the behavior of glasses in two-step thermal cycles, which result in a unique set of inter-relationships between any pair of the partial derivatives of Tmax, whatever the value of x. The results are discussed in terms of their relevance to the behavior of real glasses. 相似文献
18.
Carrying out crystallization studies for both Se0.95In0.05 and Se0.90In0.10 chalcogenide glasses under non-isothermal conditions at different heating rates, it was realized that a rate controlling
process occurs where random nucleation of one- to two-dimensional growth is accompanied with the introduction of up to 10 at%
In into glassy Se matrix. The crystallization kinetics together with its dimensionality has been studied using the four currently
used isoconversional models (Kissinger–Akahira–Sunose, Ozawa–Flynn–Wall, Tang, and Starink). The activation energy of crystallization
(E
c) has been determined using these indicated four models where a satisfactory concurrence is achieved. The value of E
c shows a decrease while increasing both the In-content as well as the extent of crystallization. 相似文献
19.
Tho Thieu Duc Prasada Rao Rayavarapu Stefan Adams 《Journal of Solid State Electrochemistry》2010,14(10):1781-1786
(LiBr)
x
[(Li2O)0.6(P2O5)0.4](1 − x) glasses with 0 ≤ x ≤ 0.2 are prepared by melt quenching. Glass transition temperature (T
g), ionic conductivity (σ), and its activation energy (E
a) are determined experimentally and correlated to molecular dynamics (MD) simulations with an optimized potential, fitted
to match bond lengths, coordination numbers, and ionic conductivity. Based on equilibrated MD configurations, ion transport
pathways are modelled in detail by the bond valence approach to clarify the influence of the halide dopant concentration on
the glass structure and its consequence for Li ion mobility. Results of experimental and computational studies are compared
with our previous report on the (LiCl)
x
[(Li2O)0.6(P2O5)0.4](1 − x) system. Both T
g and σ values are higher for LiBr-doped glasses than for LiCl-doped glasses, but the effect of halide doping is unusually small. 相似文献
20.
Sudip K. Mukhopadhyay 《Transition Metal Chemistry》2008,33(6):739-743
The kinetics of the interaction of diethyldithiocarbamate (Et2DTC) with [Pt(dach)(H2O)2]2+ (dach = cis-1,2-diaminocyclohexane) have been studied spectrophotometrically as a function of [Pt(dach)(H2O)2
2+], [Et2DTC] and temperature at a particular pH (4.0). The reaction proceeds via rapid outer sphere association complex formation
followed by two slow consecutive steps. The first step involves the transformation of the outer sphere complex into an inner
sphere complex containing a Pt–S bond and one aqua ligand, while the second step involves chelation when the second aqua ligand
is replaced. The association equilibrium constant K
E and two rate constants k
1 and k
2 have been evaluated. Activation parameters for both the steps have been calculated (∆H
1
# = 66.8 ± 3.7 kJ mol−1, ∆S
1# = −81 ± 12 JK−1 mol−1 and ∆H
2# = 95.1 ± 2.8 kJ mol−1, ∆S
2# = −34.4 ± 9.1 JK−1 mol−1). The low enthalpy of activation and negative entropy of activation indicate an associative mode of activation for both the
steps. 相似文献