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1.
S. -X. Wang Z. -C. Tan Y. -S. Li L. -X. Sun Y. Li 《Journal of Thermal Analysis and Calorimetry》2008,92(2):483-487
Synthesis, characterization and thermal analysis of polyaniline (PANI)/ZrO2 composite and PANI was reported in our early work. In this present, the kinetic analysis of decomposition process for these
two materials was performed under non-isothermal conditions. The activation energies were calculated through Friedman and
Ozawa-Flynn-Wall methods, and the possible kinetic model functions have been estimated through the multiple linear regression
method. The results show that the kinetic models for the decomposition process of PANI/ZrO2 composite and PANI are all D3, and the corresponding function is ƒ(α)=1.5(1−α)2/3[1−(1-α)1/3]−1. The correlated kinetic parameters are E
a=112.7±9.2 kJ mol−1, lnA=13.9 and E
a=81.8±5.6 kJ mol−1, lnA=8.8 for PANI/ZrO2 composite and PANI, respectively. 相似文献
2.
K. Chrissafis K. M. Paraskevopoulos C. Manolikas 《Journal of Thermal Analysis and Calorimetry》2006,84(1):195-199
The
thermal effect accompanying the transition of Cu2–xSe
into a superionic conduction state was studied by non-isothermal measurements,
at different heating and cooling rates (β=1, 2.5, 5, 10 and 20°C
min–1). During heating the peak temperature
(Tp) remains almost
stable for all values of β, (136.8±0.4°C for Cu2Se
and 133.0±0.3°C for Cu1.99Se). A gradual
shift of the initiation of the transformation towards lower temperatures is
observed, as the heating rate increases. During cooling there is a significant
shift in the position of the peak maximum (Tp)
towards lower temperatures with the increase of the cooling rate. A small
hysteresis is observed, which increases with the increase of the cooling rate, β.
The mean value of transformation enthalpy was found to be 30.3±0.8
J g–1 for Cu2Se and
28.9±0.9 J g–1 for Cu1.99Se.
The transformation can be described kinetically by the model f(ǯ)=(1–ǯ)n(1+kcatX), with activation energy E=175 kJ mol–1,
exponent value n equal to 0.2, logA=20 and log(kcat)=
0.5. 相似文献
3.
In this work, a kinetic study on the thermal degradation of carbon fibre reinforced epoxy is presented. The degradation is
investigated by means of dynamic thermogravimetric analysis (TG) in air and inert atmosphere at heating rates from 0.5 to
20°C min−1 . Curves obtained by TG in air are quite different from those obtained in nitrogen. A three-step loss is observed during
dynamic TG in air while mass loss proceeded as a two step process in nitrogen at fast heating rate. To elucidate this difference,
a kinetic analysis is carried on. A kinetic model described by the Kissinger method or by the Ozawa method gives the kinetic
parameters of the composite decomposition. Apparent activation energy calculated by Kissinger method in oxidative atmosphere
for each step is between 40–50 kJ mol−1 upper than E
a calculated in inert atmosphere.
The thermo-oxidative degradation illustrated by Ozawa method shows a stable apparent activation energy (E
a ≈130 kJ mol−1 ) even though the thermal degradation in nitrogen flow presents a maximum E
a for 15% mass loss (E
a ≈60 kJ mol−1 ).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase
transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T
tr=455±10°C, Δtr
H=403±8 J mol–1 at T
tr, V→C: T
tr=320–460°C, depending on the way of preparation,Δtr
H=–3.2±0.1 kJ mol–1 at T
tr,Δtr
H=–3.4±0.9 kJ mol–1 at 40°C, S
V
Θ= 93.6±0.5 J (K mol)–1, A→C: E
A=370±10 kJ mol–1; XRD only, V→C: E
A=250±10 kJ mol–1; thermally activated, iso- and non-isothermal, XRD
2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are
presented. NCC→C: T
tr=276±10°C,Δtr
H=–15.0±3 kJ mol–1 at T
tr, T
tr – transition temperature, Δtr
H – transition enthalpy, S
Θ – standard entropy, E
A – activation energy.
3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
E. I. Povarova A. I. Pylinina I. I. Mikhalenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(6):935-941
The dehydrogenation of propanol-2 on sodium-zirconium phosphates (NZP) with the composition Na1 − 2x
M
x
Zr2(PO4)3 (x = 0.125 and 0.25) in which Na+ ions were replaced by M2+ = Co2+, Ni2+, and Cu2+ ions was studied. The experimental reaction activation energy E
a decreased while transition through the T* = 310−340°C temperature; above this temperature, the electrophysical and crystallographic properties of the material changed.
These changes were explained by the reversible transfer of Me2+ ions from position M1 to M2 in the NZP lattice. Me2+ centers with different alcohol adsorption forms at T < T* (one-point) and T > T* (two-point) participated in the dehydrogenation reaction. For the first form, E
a and the logarithm of the preexponential factor linearly correlated with the ionic radius of M2+. The activity of M-NZP catalysts altered in repeated experiments and in cases when the direction of temperature variations
changed. 相似文献
6.
E. G. Klimchuk G. M. Avetisyan A. A. Khodak V. T. Minasyan K. G. Gazaryan A. S. Mukas'yan A. G. Merzhanov 《Russian Chemical Bulletin》1999,48(12):2245-2258
The regularities of chemical reactions in solid 8-hydroxyquinoline—chloramine B mixtures were studied under conditions of
organic self-propagating high-temperature synthesis (SHS), isothermal reaction, and thermal explosion in the 20–220 °C temperature
range. Comprehensive physicochemical analysis and microstructural study of the reaction products were carried out. The temperature
of SHS initiation (58 °C), the heat of the reaction (129±9 kJ mol−1), the stoichiometric coefficient (1), the maximum temperature (T
max=98–140 °C), and the velocity of SHS wave propagation (u=0.15–0.55 mm s−1) were determined. Depending on the ratio of the reactants (n), a low-temperature non-degeerate stable gasless mode (n≤1,T
max=115 °C,E
a=42 kcal mol−1) and a high-temperature mode (n>1,T
max=140 °C,E
a=0.4 kcal mol−1) are possible for SHS. The SHS affords monohydroxy and monochloro derivatives of 8-hydroxyquinoline, benzenesulfonamide,
NaCl, NaOH, and H2O. The mechanism of the solid-phase reaction at temperatures below 58 °C includes surface, solid-phase, and gas-phase diffusion;
that for SHS is capillary spreading of the hydroxyquinoline melt.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2271–2284, December, 1999. 相似文献
7.
Josiane de Lima Souza Marcelo Kobelnik Clóvis Augusto Ribeiro Jorge Manoel Vieira Capela Marisa Spirandeli Crespi 《Journal of Thermal Analysis and Calorimetry》2009,97(2):525-528
Poly(3-hydroxybutyrate), PHB, has been structurally modified through reaction with hydroxy acids (HA) such as tartaric acid
(TA) and malic acid (MA). The crystallization kinetic of the samples was evaluated by isoconversional method through nonlinear
fitting to obtain the estimation for activation energy (E
a
) and pre-exponential (A) values. The thermal behavior of the crystallization temperature, 44.8 and 58.9 °C at 5 °C/min, and results obtained to the
average activation energy, 73 ± 9 kJ mol−1 and 63 ± 1 kJ mol−1, to PHB/MA and PHB, respectively, are suggesting that malic acid may be deriving plasticizer units from its own PHB chain.
PHB/TA show increase in the medium value of E
a, 119 ± 2 kJ mol−1 and T
c = 48.2 °C (at 5 °C/min), indicating that tartaric acid is probably interacts in different way to the of PHB chain (E
a=73 ± 9 kJ mol−1, T
c = 44.8 °C at 5 °C/min). 相似文献
8.
Sibel Kasap Huseyin Tel Sabriye Piskin 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):537-544
A spherical polyacrylonitrile–TiO2 composite adsorbent was prepared and its strontium removal potential was investigated. The Langmuir equation fixed well the
equilibrium data. The value of ∆H° = 8.943 kJ/mol and ∆G° = 6.291 kJ/mol at 298 K indicate that the adsorption of strontium onto TiO2/PAN composite adsorbent is an endothermic and non-spontaneous reaction. The kinetic process was described by a pseudo-second-order
rate model very well. 相似文献
9.
Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters
(ΔG
o, ΔH, ΔS) for the formation of the citrate complexes with the Mn2+, Co2+, Ni2+ and Zn2+ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic
strength of 100 mM was maintained with NaClO4. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes
have been discussed. 相似文献
10.
Yttrium
orthoborate crystallizes in the vaterite-type structure and has two polymorphous
forms, viz. a low- und a high temperature one. DTA measurements of YBO3
confirmed a reversible phase transition with a large thermal hysteresis. The
phase transition has been accurately characterized by the application of different
heating and cooling rates (β). Consequently, the extrapolation of the
experimental data to zero β yields the transition points at 986.9°C
for the heating up and at 596.5°C for the cooling down cycle. These values
correspond to samples just after treatment at 1350°C. For samples with
a different ‘thermal history’ other phase transition temperatures
are observed, (e.g. after having performed several heating and cooling cycles).
The linear relationship between the associated DTA signal ΔT=T
onset–T
offset and the square root
of the heating rate β was confirmed, but the relation between T
onset and square root of β
is not found here.
From the empirical data a good linear fitting
between T
onset and
ln(β+1) can be derived.
From the kinetic analysis (Kissinger
method) of the phase transformation of YBO3 an apparent
activation energy of about 1386 kJ mol–1
for heating and of about 568 kJ mol–1 for
cooling can be determined 相似文献
11.
S. F. Santos M. C. de Andrade J. A. Sampaio A. B. da Luz T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2007,87(3):743-746
TiO2–CeO2 oxides
for application as ceramic pigments were synthesized by the Pechini method.
In the present work the polymeric network of the pigment precursor was studied
using thermal analysis. Results obtained using TG and DTA showed the occurrence
of three main mass loss stages and profiles associated to the decomposition
of the organic matter and crystallization. The kinetics of the degradation
was evaluated by means of TG applying different heating rates. The activation
energies (E
a) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of E
a
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled. 相似文献
12.
The effects of temperature and common ions on binding of puerarin to bovine serum albumin (BSA) are investigated. The binding
constants (K
a) between puerarin and BSA are 1.13×104 L⋅mol−1 (20 °C) and 1.54×104 L⋅mol−1 (30 °C), and the number of binding sites (n) is (0.95±0.02). However, at a higher temperature (40 °C) the stability of the puerarin–BSA system decreases, which results
in a lower binding constant (1.58×103 L⋅mol−1) and number of binding sites (n=0.73) of the puerarin–BSA system. However, the presence of Cu2+ and Fe3+ ions increases the binding constants and the number of binding sites in the puerarin–BSA complex. 相似文献
13.
Paolo Ferruti Elisabetta Ranucci Sabrina Bianchi Luigi Falciola Patrizia R. Mussini Manuela Rossi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(7):2316-2327
An amphoteric polyamidoamine (PAA)‐based hydrogel, named INT‐PAA1, with a novel molecular architecture was prepared and studied as a Co2+‐, Ni2+‐, and Cu2+‐sorbing material. This hydrogel was obtained by the synthesis of a PAA in the presence of a second presynthesized PAA carrying many primary amino groups as side substituents, which acted as a macromolecular crosslinking agent. Therefore, it had an intersegmented structure. INT‐PAA1 exhibited a remarkable sorption capacity and sorption rate for Co2+, Ni2+, and Cu2+ that were advantageously in situ monitored by cyclic voltammetry. An extended X‐ray absorption fine structure spectroscopy characterization of the Co2+/INT‐PAA1 complex was also performed. The very fast and quantitative metal‐ion uptake, made apparent by an intense coloring of the hydrogel, showed remarkable potential for environmental applications such as heavy‐metal detection, recovery, and elimination. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2316–2327, 2006 相似文献
14.
The phase transition at T
p (~109 °C) of RbH2PO4 and its composite with SiO2 has been investigated by thermal analysis here. In the case of neat RbH2PO4, there is a linear relationship between endothermic peak temperature (T
m) and square root of heating rate (Φ
1/2), from which the onset temperature of phase transition can be determined. Besides, Kissinger method and another calculation
method were employed to obtain the activation energy of phase transition. The detailed deduction process was presented in
this paper, and the estimated activation energies are E
1 ≈ 126.3 kJ/mol and E
2 ≈ 129.2 kJ/mol, respectively. On the other hand, the heterogeneous doping of RbH2PO4 with SiO2 as dopant facilitates its proton conduction and leads to the disappearance of jump in conductivity at T
p. The heats of transition in the composites decrease gradually with increasing the molar fraction of SiO2 additives. In the cooling process, a new and broad exothermic peak appeared between ~95 and ~110 °C, and its intensity also
changes with the SiO2 amount. These phenomena might be related to the formation of amorphous phase of RbH2PO4 on the surface of SiO2 particles due to the strong interface interaction. 相似文献
15.
V. I. Ovcharenko S. V. Fokin G. V. Romanenko A. S. Bogomyakov D. S. Yachevskii D. L. Chizhov V. N. Charushin O. N. Chupakhin 《Russian Chemical Bulletin》2010,59(6):1162-1174
Dinuclear heterospin complexes of CuII and MnII 1,1,1,7,7,7-hexafluoroheptane-2,4,6-trionates ([Cu2L2] and [Mn2L2], respectively) with nitronyl nitroxides 2-R-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide 1-oxyls (NIT-R, R = H, Me, Et, m-C5H4N, m-NCC6H4, p-NCC6H4, PzMe) and the diradical NIT-Pz-(CH2)4-Pz-NIT (Pz is 1,4-pyrazolylene) were synthesized and structurally characterized. In the complexes under study, the CuII atom
tends to have the square-pyramidal coordination environment, and the MnII atom is in an octahedral environment. The magnetochemical
investigation of the compounds in the temperature range of 2–300 K showed that the antiferromagnetic exchange coupling dominates
in the [Cu2L2] molecules, whereas this coupling in [Mn2L2] is manifested in the experimental plot μeff(T) at T < 100 K. The magnetic properties of the heterospin complexes of [Cu2L2] with NIT-R are also determined by the intramatrix antiferromagnetic exchange coupling. For the complexes of [Mn2L2] with NIT-R, the coordination mode of the nitroxide plays a decisive role. 相似文献
16.
《Radiation Physics and Chemistry》2004,69(3):211-216
The temperature dependence of the rate constant for the reactions of HO2 with OH, H, Fe2+ and Cu2+ has been determined using pulse radiolysis technique. The following rate constants, k (dm3 mol−1 s−1) at 20°C and activation energies, Ea (kJ mol−1) have been found. The reaction with OH was studied in the temperature range 20–296°C (k=7.0×109, Ea=7.4) and the reaction with H in the temperature range 5–149°C (k=8.5×109, Ea=17.5). The reaction with Fe2+ was studied in the temperature range 16–118°C (k=7.9×105, Ea=36.8) and the reaction with Cu2+ in the temperature range 17–211°C (k=1.1×108, Ea=14.9). 相似文献
17.
Abstact The reduction process of silica supported cobalt catalyst was studied by thermal analysis technique. The reduction of the
catalyst proceeds in two steps:
which was validated by the TPR and in-situ XRD experiments. The kinetic parameters of the reduction process were obtained with a comparative method. For the first step,
the activation energy, E
a, and the pre-exponential factor, A, were found to be 104.35 kJ mol−1 and 1.18·106∼2.45·109 s−1 respectively. The kinetic model was random nucleation and growth and the most probable mechanism function was found to be
f(α)=3/2(1−α)[−ln(1−α)]1/3 or in the integral form: g(α)=[−ln(1−α)]2/3. For the second step, the activation energy, E
a, and the pre-exponential factor, A, were found to be 118.20 kJ mol−1 and 1.75·107∼2.45 · 109s−1 respectively. The kinetic model was a second order reaction and the probable mechanism function was f(α)=(1−α)2 or in the integral form: g(α)=[1−α]−1−1. 相似文献
18.
Z. Fengqui H. Rongzu S. Jirong G. Hongxu 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(7):1034-1036
The kinetic parameters of the exothermic decomposition of the title compound in a temperatureprogrammed mode have been studied
by means of DSC. The DSC data obtained are fitted to the integral, differential, and exothermic rate equations by the linear
least-squares, iterative, combined dichotomous, and least-squares methods, respectively. After establishing the most probable
general expression of differential and integral mechanism functions by the logical choice method, the corresponding values
of the apparent activation energy (E
a), preexponential factor (A), and reaction order (n) are obtained by the exothermic rate equation. The results show that the empirical kinetic model function in differential
form and the values of E
a and A of this reaction are (1 − α)−4.08, 149.95 kJ mol−1, and 1014.06 s−1, respectively. With the help of the heating rate and kinetic parameters obtained, the kinetic equation of the exothermic
decomposition of the title compound is proposed. The critical temperature of thermal explosion of the compound is 155.71°C.
The above-mentioned kinetic parameters are quite useful for analyzing and evaluating the stability and thermal explosion rule
of the title compound.
The text was submitted by the authors in English. 相似文献
19.
The solid state thermal behavior of trans-[Co(bpb)(amine)2]NCS⋅H2O complexes where (bpb)=[N,N’-bis(2-pyridinecarboxamido-N)-1,2-benzene], and amine=pyrrolidine (prldn)(1), and benzylamine (bzlan) (2), and trans-[Co(bpb)(piperidine)2]ClO4⋅H2O (3) (mixed with KSCN), has been studied using thermoanalytical techniques, infrared spectroscopy, and pyrolysis coupled
to both infrared and mass spectrometry, PY/FTIR and PY/MS. The deamination-anation reaction is clearly observed for all three
complexes. The estimated values of E
a for the deamination-anation are: E
a(1)=246.8 kJ mol−1, E
a(2)=255.7 kJ mol−1, E
a(3)=234.7 kJmol−1. The trend in E
a values is rationalized based on the ligand field strength of the amines and the structural effects. A novel decarbonylation
of the amide CO group from the equatorial ligand is observed after the release of one amine molecule. This process has been
monitored for complex (1) by FTIR in the carbonyl region and by mass spectrometry for the detection of CO2 at 280°C. The activation energy of this process is estimated for complex (1) (662.5 kJ mol−1). The reaction scheme for the observed reactions is proposed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
H. X. Ma B. Yan Z. N. Li J. R. Song R. Z. Hu 《Journal of Thermal Analysis and Calorimetry》2009,95(2):437-444
The title compound 3,3-dinitroazetidinium (DNAZ) 3,5-dinitrosalicylate (3,5-DNSA) was prepared and the crystal structure has
been determined by a four-circle X-ray diffractometer. The thermal behavior of the title compound was studied under a non-isothermal
condition by DSC and TG/DTG techniques. The kinetic parameters were obtained from analysis of the TG curves by Kissinger method,
Ozawa method, the differential method and the integral method. The kinetic model function in differential form and the value
of E
a and A of the decomposition reaction of the title compound are f(α)=4α3/4, 130.83 kJ mol−1 and 1013.80s−1, respectively. The critical temperature of thermal explosion of the title compound is 147.55 °C. The values of ΔS
≠, ΔH
≠ and ΔG
≠ of this reaction are −1.35 J mol−1 K−1, 122.42 and 122.97 kJ mol−1, respectively. The specific heat capacity of the title compound was determined with a continuous C
p mode of mircocalorimeter. Using the relationship between C
p and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic
time-to-explosion) was obtained. 相似文献