共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Kozak K. Wieczorek-Ciurowa K. Pielichowski 《Journal of Thermal Analysis and Calorimetry》1995,45(5):1245-1253
The adduct of Al(NO3)3·6CO(NH2)2 has been prepared and characterized by means of chemical analysis, IR spectroscopy, X-ray patterns and microscopy. A thermoanalytical study of Al(NO3)3·6CO(NH2)2 as well as urea, for comparison purposes, under conventional dynamic and quasi-isothermal—quasi-isobaric conditions in air has been carried out. It has been found that the adduct is thermally stable up to about 200°C, i.e. up to higher temperature than the decomposition temperature of the constituent compounds. The thermal decomposition mechanism of the adduct is complex, thus infrared spectroscopy and X-ray diffraction techniques have been used to determine the intermediate products. Aluminium oxide(III) is the final decomposition product. 相似文献
2.
D. Bontea C. Mita D. Humelnicu 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):305-311
Summary Three
silylcellulosic derivatives with different substitution degree were examined as
sorbents for uranyl ions. The adsorption rate and capacity of cellulose and
modified cellulose were investigated in aqueous media, at various pH and
temperature values. The polymer - metal complexes of UO22+
were characterized by infrared and electronic spectra, and thermogravimetry.
The thermal behavior of cellulose (C), trimethylsilyl - cellulose (tmsc, SD=
2.85) and triphenylsilyl - cellulose (TPSC1, SD=2.89 and TPSC2, SD
=2.70) and their complexes with
uranyl ions in atmospheric air has been studied between room temperature and
600 °C. The Coats-Redfern method was applied to estimate the kinetic
parameters. The results revealed that the complexation of C and TMSC with UO22+
increases the thermal stability.</p>
</p> 相似文献
3.
Tian C. M. Xie J. X. Guo H. Z. Xu J. Z. 《Journal of Thermal Analysis and Calorimetry》2003,73(3):827-834
The thermal oxidative degradation of cellulose, and of cellulose ammonium phosphate and its metal complexes products were
studied by thermal analysis, infrared spectroscopy and elemental analysis. The temperature of decomposition was lower for
metal complexes of cellulose ammonium phosphate than those samples untreated by metal ions and the values of char yield were
greater for treated cellulose than those untreated. This indicates the metal ions can catalyze the reaction of degradation
and form more char.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Thermal stabilization of TEMPO-oxidized cellulose 总被引:1,自引:0,他引:1
Hayaka Fukuzumi 《Polymer Degradation and Stability》2010,95(9):1502-76
A partially C6-carboxylated cellulose with carboxylate content of 1.68 mmol/g was prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation of a softwood bleached kraft pulp. Thermogravimetric analyses of the TEMPO-oxidized cellulose (TOC) and its related materials were studied to improve thermal stability of the TOC. Thermal decomposition (Td) points of the TOC with sodium carboxylate groups, alkali-treated TOC with free carboxyl groups of 0.23 mmol/g and the original cellulose were 222 °C, 264 °C and 275 °C, respectively. Thus, the anhydroglucuronic acid units formed by TEMPO-mediated oxidation of the native wood cellulose and present in the TOC cause the decrease in Td point by decarbonation during heating process. When carboxyl groups in the TOC were methylated with trimethylsilyl diazomethane (TMSCHN2), the Td point increased from 222 °C to 249 °C, and the peak temperature in its derivative thermogravimetric (DTG) curve increased from 273 °C to 313 °C, which was almost equal to that of the original cellulose. Thus, the methyl esterification of carboxyl groups in the TOC is effective in improving thermal stability. When sodium ions present in the TOC as counter ions of carboxylate groups were exchanged to some other metal ions, thermal stability was improved to some extent. Especially, when CaCl2, Ca(OAc)2, Ca(NO3)2 and CaI2 solutions were used in the ion-exchange treatments, the peak temperatures in the DTG curves increased to approximately 300 °C. MgCl2, NiCl2, SrCl2 and Sr(OAc)2 solutions were also effective to some extent in increasing the peak temperatures of DTG curves. Thus, thermal stability of the fibrous TOC can be improved to some extent by methyl esterification of the sodium carboxylate groups present in the original TOC with TMSCHN2 or ion-exchange treatments with some metal salt solutions. 相似文献
5.
Raluca Dumitru Oana Carp P. Budrugeac M. Niculescu E. Segal 《Journal of Thermal Analysis and Calorimetry》2011,103(2):591-596
The authors present their results concerning the decomposition in air of the homopolynuclear coordination compound [CoC2O4·2.5H2O]
n
. In the temperature range 20–300 °C, the heating curves TG, DTG and DTA allowed to evidence three decomposition steps. The
kinetic analysis was performed on the second step which proved to be the only workable one. The application of nonlinear regression
procedure shows that this is a complex process consisting in three successive steps. The checking of the mechanism and corresponding
kinetic parameters for quasi-isothermal data (T = 150 °C) shows that the obtained results could be used for prediction of the thermal behaviour of the investigated compound
in both isothermal and non-isothermal conditions. 相似文献
6.
Kh. M. Yakubov V. A. Logvinenko T. A. Zhemchuzhnikova Sh. Kh. Abdullaev G. V. Gavrilova A. N. Mikheev 《Journal of Thermal Analysis and Calorimetry》1985,30(5):1095-1103
The thermal analysis of acetate clusters of general formula [Fe 2 III MIIO(CH3COO)6(H2O)3]·2H2O, with M=Mn, Fe, Co or Ni, was performed in dynamic and quasi-isothermal regimes. The thermal decompositions of these compounds proceed in the interval 40–310° and consist of two endothermic and three exothermic stages. Dependence on the nature of the transition metal M is evidenced most explicitly in the parameters of the second stage, proceeding in the interval 103–170°. For this stage the sequences of thermodynamic stability and kinetic stability were established. The effect of the nature of the metal on the thermodynamic and kinetic parameters of the thermal decomposition processes involving the heteronuclear acetates was analyzed. Mechanisms for the first two stages of thermal decomposition are suggested. 相似文献
7.
S. H. Chaki Jiten P. Tailor M. P. Deshpande 《Journal of Thermal Analysis and Calorimetry》2014,117(3):1137-1144
The catalytic action of copper sulfide (CuS) micro-particles and as-synthesized nanoparticles was studied on cellulose pyrolysis. The market procured CuS powder was used as micro-particles without any treatment. The CuS nanoparticles were synthesized at ambient temperature by simple wet chemical technique. Before using the micro-particles and nanoparticles for catalytic study, they were comprehensively characterized. The thermal analysis including catalytic properties of both the micro-particles and nanoparticles of CuS on cellulose pyrolysis was studied employing thermogravimetric (TG), differential thermogravimetric, and differential thermal analysis techniques. Prior to the study as catalyst in cellulose pyrolysis, the CuS micro- and nanoparticles were characterized by thermal analysis in inert atmosphere. The TG curves showed two steps and five steps decomposition having total mass loss of 29 and 42 % in case of CuS micro- and as-synthesized nanoparticles, respectively. The catalytic study in cellulose pyrolysis showed that the decomposition commences at temperature 295 °C for pure cellulose, 270 °C for cellulose mixed with 3 % CuS micro-particles and 205 °C for cellulose mixed with 3 % CuS nanoparticles. It clearly showed that the decomposition starting temperature decreased by 65 °C in case of cellulose mixed with CuS nanoparticles compared to cellulose mixed with CuS micro-particles. Thus, CuS nanoparticles act as better catalyst then CuS micro-particles in cellulose pyrolysis. The obtained results are deliberated in details. 相似文献
8.
The derivatograph has been modified to provide a new technique with the help of which the weight change of a sample and the amount of the evolving gases can be determined as a function of the temperature of the sample under quasi-isothermal and quasi-isobaric conditions. The thermal decompositions of potassium and sodium hydrogencarbonate were investigated; it was established that under special conditions the otherwise one-step thermal decomposition of the two materials becomes a two-step process. The phenomenon involves a change only from the point of view of kinetics, for the decomposition itself does not split into two consecutive processes. 相似文献
9.
Poly(vinyl alcohol) films were grafted with two monomers (acrylic acid and N-vinyl imidazole) using the gamma irradiation technique. The melting temperature (Tm) and glass transition temperature (Tg) of the grafted membranes were determined with respect to the grafting yield. The ability of these membranes to separate cobalt from nickel has been investigated. The diffusion of cobalt and nickel ions from the feed compartment to the receiver compartment depends on the grafting yield and the pH of the feed solution. Cobalt ions do not diffuse through the membrane when the pH of the feed solution is >4.5. Thus, the prepared membranes could be considered for the separation of cobalt ions from nickel ions. The temperature of thermal decomposition of pure PVA-g-AAc/Zol membrane, PVA-g-AAc/Zol membranes containing cobalt ions, and PVA-g-AAc/Zol membranes containing nickel ions are determined using TGA analyzer; it was shown that the presence of cobalt and nickel increases the decomposition temperature. Also the membranes bonded with cobalt ions are more stable than the membranes containing nickel ions. 相似文献
10.
The thermal decomposition of thiobenzpiperidides and some derivatives containing substituents on the benzene nucleus was studied.
By thermal analysis was put in evidence the influence of the nature and position of the substituents on the decomposition
process.
Kinetic parameters in non-isothermal and quasi-isothermal conditions (CRTA) were calculated.
The chromatographic analysis, associated with mass spectrometry, proved that the initiation of the complex decomposition process
is the result of the polar bond break.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
The influence of water vapour on the course of the thermal decompositions of pure calcite, magnesite and dolomite, and of these materials mixed with 2% sodium chloride, was studied partly under dynamic, and partly under quasi-isothermal heating conditions. The sample holders used were of four different types, i.e. the carbon dioxide in direct contact with the solid phase of the sample was at different partial pressures. The investigations were carried out in the presence of dried air as well as in air of 60% and 100% humidity content. It is stated that the presence of water vapour increases the decomposition temperature of the first stage of dolomite decomposition (by about 20–50°C) but reduces it in the second stage (by about 5–10°C), as it does in the decomposition of calcite and magnesite. It was also found that the presence of sodium chloride and water vapour together reduces the temperature of both decomposition stages of dolomite. 相似文献
12.
Forozan Gholamian Masoud Salavati-Niasari Davood Ghanbari Mohammad Sabet 《Journal of Cluster Science》2013,24(1):73-84
Flower-like magnesium hydroxide (Mg(OH)2) nanostructures were synthesized via a simple hydrothermal reaction at relatively low temperature. The Mg(OH)2 nanostructures were then added to acrylonitrile–butadiene–styrene (ABS) and cellulose acetate (CA) polymers. The effect of Mg(OH)2 nanostructures on the thermal stability of the polymeric matrixes has been investigated. The thermal decomposition of the nanocomposites shifts towards higher temperature in the presence of the Mg(OH)2. The enhancement of thermal stability of nanocomposites is due to endothermically decomposition of magnesium hydroxide that releases of water and dilutes combustible gases. Nanostructures and nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), UL-94 test and limiting oxygen index (LOI) analysis. 相似文献
13.
The influence of sodium chloride on the course of thermal decomposition of calcite, magnesite and dolomite was studied partly under dynamic, and partly under quasi-isothermal heating conditions. Four different types of sample holders were applied in the experiment, i.e., the partial pressure of carbon dioxide was also different in the four cases. It was found that the presence of sodium chloride reduced the decomposition temperature in every case. The extent of this reduction amounted to about 10°C in the case of calcite, 40–80°C in the case of magnesite, and 10–40°C and 10–20°C for the first and second decomposition stages, respectively, of dolomite. 相似文献
14.
Veronika Vágvölgyi M. Hales R. L. Frost A. Locke J. Kristóf Erzsébet Horváth 《Journal of Thermal Analysis and Calorimetry》2008,94(2):523-528
The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including
hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process
for the removal of atmospheric CO2.
The conventional thermal analysis of synthetic nesquehonite proves that dehydration takes place in two steps at 157, 179°C
and decarbonation at 416 and 487°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the
second quasi-isothermal at 108 and 145°C. In the CRTA experiment carbon dioxide is evolved at 376°C. CRTA technology offers
better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite
via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample
as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature
reveal partial collapse of the nesquehonite structure. 相似文献
15.
The microstructure and thermal properties of lyocell and other regenerated cellulose fibres (viscose and modal) were analysed using DSC, TG and FTIR. The FTIR spectral analysis showed that lyocell is the most crystalline fibre and is composed principally of crystalline cellulose II and amorphous cellulose. Likewise, the thermal analysis showed that lyocell has a higher thermal stability than viscose and modal fibres, as the difference between the onset temperature for its decomposition process was as high as 20 °C. 相似文献
16.
Maurizio Avella Roberto Avolio Irene Bonadies Cosimo Carfagna Maria Emanuela Errico Gennaro Gentile 《Journal of Thermal Analysis and Calorimetry》2010,102(3):975-982
Dynamic thermogravimetric analysis under nitrogen flow was used to investigate the thermal decomposition process of high-density
poly(ethylene) (HDPE)-based composites reinforced with cellulose fibers obtained from the recycling of multilayer carton scraps,
as a function of the cellulose content and the compatibilization. The Friedman, Flynn–Wall–Ozawa, and Coats–Redfern methods
were used to determine the apparent activation energy (E
a) of the thermal degradation of the cellulose component into the composites. E
a has been found dependent on the cellulose amount and on the cellulose/polymer matrix interfacial adhesion. In particular,
it has been evidenced an increase of the cellulose thermal stability as a consequence of the improved interfacial adhesion
between the components in NFR composites. 相似文献
17.
Controlled rate thermal analysis of hydromagnesite 总被引:1,自引:0,他引:1
Veronika Vágvölgyi R. L. Frost M. Hales A. Locke J. Kristóf Erzsébet Horváth 《Journal of Thermal Analysis and Calorimetry》2008,92(3):893-897
The reaction of magnesium minerals such as brucite with CO2 is important in the sequestration of CO2. The study of the thermal stability of hydromagnesite and diagenetically related compounds is of fundamental importance to
this sequestration. The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous
carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration
process for the removal of atmospheric CO2. This work makes a comparison of the dynamic and controlled rate thermal analysis of hydromagnesite and nesquehonite. The
dynamic thermal analysis of synthetic hydromagnesite proves that dehydration takes place in two steps at 135 and 184°C, dehydroxylation
at 412°C and decarbonation at 474°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the
second quasi-isothermal at 108 and 145°C, respectively. In the CRTA experiment both water and carbon dioxide are evolved in
an isothermal decomposition at 376°C.
CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates
such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer
of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of
non-isothermal nature reveal partial nesquehonite structure. 相似文献
18.
H. E. Zorel Jr. M. S. Crespi C. A. Ribeiro 《Journal of Thermal Analysis and Calorimetry》2004,75(2):545-550
Crystalline PbTiO3 was obtained through the thermal decomposition of 8-hydroxyquinolinate of lead(II) and that of titanium(IV), which was monitored
by TG/DTG/DTA under different atmospheric conditions and with varying heating rates. The compound was prepared from adding
8-hydroxyquinoline solution in the solution of metallic ions Pb(II):Ti(IV) (1:1) under constant stirring at 3°C, having the
pH adjusted to 10. The results of these investigations show that different thermal behavior related to the precursor occurred
and also the consequent formation of residues which have different crystallinities. No carbonate residues from the thermal
decomposition could be determined by XRD and IR. Only PbTiO3 was observed and confirmed by DSC at 470°C, temperature lower than the tetragonal-cubic transition.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
O.Toft Srensen 《Thermochimica Acta》1981,50(1-3):163-175
20.
J. J. Suñol D. Miralpeix J. Saurina F. Carrillo X. Colom 《Journal of Thermal Analysis and Calorimetry》2005,80(1):117-121
Summary New regenerated cellulose fibers were developed during the last decades as environmentally friendly systems. In this work, three fibers: lyocell, modal and viscose were subjected to an enzymatic treatment. Likewise, different lyocell fibers were washed in a Na2CO3 solution under severe conditions. Analysis was performed by means of differential scanning calorimetry, thermogravimetry and scanning electron microscopy. In all samples, at low temperature, water desorption was detected. Furthermore, thermal analysis shows wide exothermic processes that began between 250 and 300°C corresponding to the main thermal degradation and it is associated to a depolymerization and decomposition of the regenerated cellulose. It is accompanied with mass more than 60% mass loss. Kinetic analysis was performed and activation energy values 152-202 kJ mol-1 of the main degradation process are in agreement with literature values of cellulose samples. 相似文献