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1.
The main purpose of this work is proposing a new method of using non-isothermal formal kinetics analysis to predict the lifetime of luminescent complex materials. The Eu(III)-phenanthroline complex doped xerogel has been in situ synthesized by a catalyst-free sol-gel method. The photoluminescence spectra and TG curves of the xerogel verify the formation and decomposition of Eu(III)-phenanthroline complex in xerogel. The decomposition of the xerogel formally occurs in three steps. The Friedman and FWO isoconversional methods and multivariate non-linear regression method are used for formal kinetic analysis. The overall decomposition process below 800 °C is fitted by three-step consecutive reaction. The best fitted model for each step is Fn (n order reaction, the corresponding function f(α) is (1 − α)n). Correlation coefficient is 0.99956. The lifetime values of xerogel at different temperatures are predicted based on non-isothermal kinetic models by the 5% decomposition of europium organic complex. 相似文献
2.
Baker G.A. Pandey S. Maziarz E.P. Bright F.V. 《Journal of Sol-Gel Science and Technology》1999,15(1):37-48
We explore the potential of xerogel composites to tailor the behavior of active dopants that are sequestered within the xerogel. Toward this end, we report on the local dipolarity and dynamics of two fluorescent probes (pyrene and rhodamine 6G, R6G) each co-doped at low concentration directly into a series of binary xerogel composites. The composites that we have investigated are composed of tetraethylorthosilicate (Si(OCH2CH3)4,TEOS) plus one of several organically-modified silanes (ORMOSILs), organic oligomers, or a common surfactant. For convenience we divide these xerogel composites into two classes: (1) xerogels wherein the organic character arises from the addition of an ORMOSIL co-monomer, possessing a non-hydrolyzable organic functional group, that becomes covalently incorporated with in the xerogel and (2) xerogels wherein the organic content is adjusted by adding organic oligomers or a surfactant. Six organically-modified silylalkoxides of the form R
n
Si(OR)4–n
were investigated as ORMOSILs. Poly(ethylene glycol), Nafion, and Ionene 6,2 were tested as oligomers. Triton X-100 was used as the surfactant. To estimate the local dipolarity within these composites we used the static fluorescence from pyrene molecules that were sequestered within the composites. These experiments showed that the local dipolarity surrounding the average pyrene molecule can be tuned significantly, but this depends on the actual organic species that one uses to prepare the xerogel composite. Time-resolved fluorescence anisotropy measurements were used to quantify the R6G mobility within the same composites. These results demonstrate that certain organic additive scan be used to adjust the R6G mobility within the xerogel composite. 相似文献
3.
Poly(vinyl
chloride) (PVC), plasticized by di(2-ethylhexyl) phthalate (DEHP), medium
molecular mass polyesterurethane (PU) or by both plasticizers, was thermally
degraded under dynamic thermogravimetric conditions and the kinetics of decomposition
was studied by isoconversional methods and by non-linear regression. It has
been found that the initial decomposition temperature is higher for PVC plasticized
with PU, as compared with PVC plasticized with di(2-ethylhexyl) phthalate
(DEHP) or plasticized with PU/DEHP, and thermal degradation shows features
of a multi-step complex process. Application of polymeric plasticizer leads
to the increase and a 'smoothing' effect in the course of energy
of activation and pre-exponential factor at the initial stage of decomposition
indicating thus the hindered migration of medium molecular mass compound from
PVC matrix (in comparison with PVC containing monomeric DEHP) due to steric
hindrances as well as due to specific interactions between C=O and Cl groups
along the macrochains. Kinetic model function of the decomposition process
of PVC/DEHP and PVC/DEHP/PU blends was found to be a two-stage autocatalyzed
reaction of nth
order; autocatalytic effect is associated most likely with the role of HCl
formed during PVC decomposition. For PVC/PU blend best fit was found by non-linear
regression for a two-stage scheme in which first stage was Prout-Tompkins
model and the second was autocatalytical model of nth
order - the first one involves particle disintegration, which was promoted
by product generation at branching PVC 'pseudo-crystals' nuclei,
thus exposing more surface on which decomposition reaction proceeds. 相似文献
4.
Katarína Győryová J. Chomič Erika Szunyogová Lenka Piknová V. Zeleňák Zuzana Vargová 《Journal of Thermal Analysis and Calorimetry》2006,84(3):727-732
Three
new complex compounds of general formula Zn{4-ClC6H3-2-(OH)COO}2⋅L2⋅nH2O
(where L=thiourea (tu), nicotinamide (nam),
caffeine (caf), n=2,3), were prepared and
characterized by chemical analysis, IR spectroscopy and their thermal properties
were studied by TG/DTG, DTA methods. It was found that the thermal decomposition
of hydrated compounds starts with the release of water molecules. During the
thermal decomposition of anhydrous compounds the release of organic ligands
take place followed by the decomposition of salicylate anion. Zinc oxide was
found as the final product of the thermal decomposition performed up to 650°C.
RTG powder diffraction method, IR spectra and chemical analysis were used
for the determination of products of the thermal decomposition. 相似文献
5.
Rongzu Hu Shanxiang Wu Yanjun Liang Lixia Sun Zhengquan Yang 《Journal of Thermal Analysis and Calorimetry》1995,44(4):885-902
A numerical method of computing the kinetic parameters (the activation energy (E), the preexponential constant (A) and the reaction order (n)) of exothermic decomposition of energetic materials via the exothermic rate equation is presented. The values ofE, A, andn are reported for the exothermic decomposition of six typical energetic materials, 1,6-diazido-2,5-dinitrazahexane (I), 1,5-diazido-3-nitrazapentane (II), 2,2,4,7,9,9-hexanitro-5-methyl-4,7-dinitrazadecane (III), 2,2,2-trinitroethyl-4,4,4-trinitrobutyrate (IV), 1,4-dinitro-2,3-dioxo-1,4-dinitrazacyclohexane (V) and 1,3,5-trianitro-1,3,5-triazafurazano[3,4-f]cycloheptane (VI).
相似文献6.
The triethanolamine complexes, [M(tea)2]sq·nH2O, (n=2 for Co(II), n=0 for Ni(II), Cu(II) and n=1 for Cd(II), tea=triethanolamine, sq2−=squarate), have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measurements,
UV-Vis and IR spectra, and thermal analyses techniques (TG, DTG and DTA). The Co(II), Ni(II) and Cu(II) complexes possess
octahedral geometry, while the Cd(II) complex is monocapped trigonal prismatic geometry. Dianionic squarate behaves as a counter
ion in the complexes. The thermal decomposition of these complexes takes place in three stages: (i) dehydration, (ii) release of the tea ligands and (iii) burning of organic residue. On the basis of the first DTGmax of the decomposition, the thermal stability of the anhydrous complexes follows the order: Ni(II), 289°C>Co(II), 230°C>Cu(II),
226°C>Cu(II), 170°C in static air atmosphere. The final decomposition products — the respective metal oxides — were identified
by FTIR spectroscopy. 相似文献
7.
N. Ózpozan H. Arslan T. Ózpozan M. Merdivan N. Külcü 《Journal of Thermal Analysis and Calorimetry》2000,61(3):955-965
Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order
to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two-
or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the
decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru,
NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and
0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Vignali Francesca Predieri Giovanni Feci Elisabetta Palanti Sabrina Baratto Maria Camilla Basosi Riccardo Callone Emanuela Müller Klaus 《Journal of Sol-Gel Science and Technology》2011,60(3):445-456
Interpenetration of wood samples of pine sapwood (Pinus sylvestris L.) with hybrid inorganic–organic silica xerogels bearing amine functions able to coordinate copper(II) cations has been
successfully carried out. These materials have been prepared by sol–gel processing TEOS/APTES mixtures inside the wood. Solid
state 29Si NMR data provide evidence that the interpenetrated xerogel material has the same degree of condensation of the corresponding
xerogel formed outside the wood. Copper(II) is effectively vehiculated inside the wood by coordination linkages with two ammine
functions well evidenced by ESR measurements. SEM/EDX investigations show that the chlorine/copper atomic ratio inside the
wood is lower than that of the starting salt CuCl2, suggesting an exchange reaction with silanol groups with the formation of Si–O–Cu linkages and HCl. This reaction could
be promoted by the excess of amine functions with formation of ammonium chloride species which remain onto the surface of
the wood and in the mother solution owing to a higher degree of condensation. Sodium silicate was tested in place of TEOS
in order to have a cheaper and ethanol-free formulation. However, gel penetration results significantly lower than that of
the corresponding formulation containing TEOS and preservation performance are lower than that of TEOS formulation against
brown-rot fungal decay. 相似文献
9.
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
10.
Andogová E. Györyová K. Nour El-Dien F. A. 《Journal of Thermal Analysis and Calorimetry》2002,69(1):245-253
Four new complex compounds were prepared by the reaction of zinc bromobutyrate and organic ligands. The general formula of the synthetized complex compounds are (2-Brbut)2ZnL and (4-Brbut)2ZnL2nH2O (but=butyrate, L=theobromine (tbr), theophylline (tph), methyl-3-pyridyl carbamate (mpc), n=0-1). The compounds were characterized by chemical analysis and IR spectroscopy. The thermal behaviour of the zinc(II) complexes was studied by thermal analysis. Thermal decomposition in the case of hydrated compounds starts with the release of water molecules. Then molecules of organic ligands and the bromobutyrate anion are released and decomposed. CH3CH2CH=O, CO, CH2=CHCH=O, CH2O and ZnBr2 were found as gaseous products of thermal decomposition during heating up to 700°C. IR, mass spectroscopy, X-ray powder diffraction and chemical analysis were used for the determination of solid and gaseous intermediates and products of the thermal decomposition.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
11.
For the reaction of Al(III) with organic chelating reagents to form of the complex AlL
n± a general acid base catalysis was detected. A reaction model is given. The general acid catalysis is only present if at least one kinetic pathway of complex dissociation reacts with participation of protons. This depends on the kind of the chelating reagent. 相似文献
12.
A. Miyake K. Nomura Y. Mizuta M. Sumino 《Journal of Thermal Analysis and Calorimetry》2008,92(2):407-411
To understand better the thermal decomposition characteristics of organic peroxides, a C80 heat flux calorimeter was used
and the decomposition pattern of cumene hydroperoxide and di-tert-butylperoxide were classified as auto-catalytic and n
th order reaction, respectively. Based on the scanning results with the C80 at several differing rates of heating, the thermal
decomposition behavior of organic peroxides under isothermal storage at lower temperature was simulated with a model-free
simulation. Simulated results showed that the calculated conversion of cumene hydroperoxide as a function of time was in good
agreement with experimental data obtained with the TAM-III high sensitivity thermal activity monitor. 相似文献
13.
Chomič J. Györyová K. Szunyogová E. Kováéová J. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):33-41
Five new complex compounds of general formula Zn(Hsal)2·L2·nH2O (where Hsal=OHC6H4COO-, L=thiourea (tu), nicotinamide (nam), caffeine (caf), theobromine (tbr), n=2-4), were prepared and characterized by chemical analysis, IR spectroscopy and studied by methods of thermal analysis (TG/DTG,
DTA). It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During
the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of
salicylate anion. Zinc oxide was found as the final product of the thermal decomposition heated up to 800°C. RTG powder diffraction
method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
T. Vlase N. Doca Gabriela Vlase C. Bolcu F. Borcan 《Journal of Thermal Analysis and Calorimetry》2008,92(1):15-18
In the present work a comparative kinetic study was performed on the thermal behavior of three antioxidants of IRGANOX-type
(L101, L109 and L115) in dynamic air atmosphere under non-isothermal conditions.
The TG-DTG data were obtained at heating rates of 5, 7, 10 and 15 K min−1. The kinetic parameters were obtained by processing these data with strategies corresponding to Flynn-Wall-Ozava (FWO), Friedman
(FR), Budrugeac-Segal (BS) and non-parametric kinetic (NPK) methods.
The thermal degradation by all the three compounds take place in melted state, so that any kinetic models regarding the decomposition
of solids are inapplicable. Only with the NPK method it was possible a separation between the two functions of the reaction
rate.
For the temperature dependence, f(T), an Arrhenius-type model was searched; for the conversion dependence, the Ŝestak-Berggren equation was suggested in order
to discriminate between physical (m) and chemical (n or p) steps of a complex thermodegradation process. 相似文献
15.
Zh. Bo J. H. Yan X. D. Li Y. Chi K. F. Cen B. G. Chéron 《Plasma Chemistry and Plasma Processing》2007,27(5):546-558
The combined effects of oxygen and water vapor on three typical volatile organic compounds, i.e. tetrachloromethane, n-butane and toluene, decomposition efficiency under gliding arc gas discharge conditions are studied. The electron density
and the density of the reactive radicals such as O and OH are modified by addition of oxygen and water vapor. Consequently,
the decomposition process can be enhanced or suppressed, depending on the involved chemical structures and reaction channels.
The addition of oxygen and water vapor suppresses the tetrachloromethane decomposition which indicates that this process is
mainly controlled by the electron dissociation reactions. By contrast, the n-butane and toluene decompositions are enhanced, which shows that they can be mainly ascribed to the radical induced reactions.
Especially, in a moist atmosphere the OH radicals are supposed to play the most important role in the n-butane decomposition process. 相似文献
16.
(R)-6,6‘-Bis(triethoxysilylethen-2-yl)-2,2-‘binaphtho-20-crown-6(precursor,R-2) derived form(R)-2,2-BINOL derivative was synthesized by Pd-catelyzed Heck reaction of (R)-6-6‘-dibromo-2,2‘-binaphtoh-20-crown-6(R-1) intermediate with vinyltriethoxysilane. The hydrolysis and polycondensatlon ofthe precursor gave rise to the corresponding xerogei. Both pre cursor and xerogei were analysed by NMR, FT-IR, UV, CD spectra, fluorescent spectroscopy, polarimetry and elemental analysis. The precursor and xerogei can emit strong blue fluorescenee and are expected to have the potential appficatiou inthe separation of chiral molecules as fluorescent sensor. The precursor exhibits strong Cotton effect in its circular dichroism (CD) spectrum indicating that it is a highly rigid structure. 相似文献
17.
A. B. Shishmakov M. S. Molochnikov D. O. Antonov O. V. Koryakova A. S. Seleznev L. A. Petrov 《Russian Journal of Applied Chemistry》2013,86(3):297-303
A Cu(II)-containing binary xerogel TiO2-SiO2 was synthesized by joint hydrolysis of tetrabutoxytitanium, teraethoxysilane and copper(II) chloride dissolved in their mixture. The synthesis was performed in a vapor of 10% aqueous ammonia under static conditions. EPR spectroscopy was used to examine the state of Cu(II) in the xerogel matrix. Data on specific features of the behavior of saccharose within xerogel pores under heating were obtained. The catalytic activity of the xerogel was tested by the kinetic method on model reactions of hydrogen peroxide decomposition and oxidative dehydrogenation of trimethylhydroquinone. 相似文献
18.
Praveen K. Tandon Manisha Purwar Priy B. Dwivedi Manish Srivastava 《Transition Metal Chemistry》2008,33(6):791-795
Oxidation of benzaldehyde and p-nitro-benzaldehyde by cerium(IV) sulphate in aqueous sulphuric acid is strongly catalyzed by iridium(III) chloride. The complex
formed between cerium(IV) and the organic substrate in the first equilibrium step gives another complex in the presence of
iridium(III), which ultimately gives the corresponding aromatic acids as the product of oxidation. The order of the reaction
follows first-order kinetics at low concentrations to zero order at higher concentrations of both the oxidant and organic
substrate. The rate is directly proportional to the concentration of catalyst, but decreases sharply with increasing H+ ions and cerium(III) concentrations, while change in ionic strength of the medium or the concentration of acetic acid and
Cl− ions has no effect on the rate. 相似文献
19.
K. Chrissafis E. Pavlidou K. M. Paraskevopoulos T. Beslikas N. Nianias D. Bikiaris 《Journal of Thermal Analysis and Calorimetry》2011,105(1):313-323
Nanocomposites of poly(l-lactic acid) (PLLA) containing 2.5 wt% of fumed silica nanoparticles (SiO2) and organically modified montmorillonite (OMMT) were prepared by solved evaporation method. From SEM micrographs it was
observed that both nanoparticles were well dispersed into PLLA matrix. All nanocomposites exhibited higher mechanical properties
compared to neat PLLA, except elongation at break, indicating that nanoparticles can act as efficient reinforcing agents.
Nanoparticles affect, also, the thermal properties of PLLA and especially the crystallization rate, which in all nanocomposites
is faster than that of neat PLLA. From the thermogravimetric curves it can be seen that neat PLLA nanocomposites present a
relatively better thermostability than PLLA, and this was also verified from the calculation of activation energy (E). From the variation of E with increasing degree of conversion it was found that PLLA/nanocomposites decomposition takes place with a complex reaction
mechanism, with the participation of two different mechanisms. The combination of models, nth order and nth order with autocatalysis (Fn–Cn), for PLLA and PLLA/OMMT as well as the combination of Fn–Fn for PLLA/SiO2 give the better results. For the PLLA/OMMT the values of the E for both mechanisms are higher than neat PLLA. For the PLLA/SiO2 nanocomposite the value of the E is higher than the corresponding value for PLLA, for the first area of mass loss, while the E of the second mechanism has a lower value. 相似文献
20.
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