共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Dabkowska 《Journal of Thermal Analysis and Calorimetry》1990,36(4):1319-1330
The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln2(C7H10O4)3.nH2O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.
Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln2(C7H10O4)3 nH2O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.相似文献
2.
The thermal behaviour of the intercalation complex of a dickite from Tarifa, Spain, with dimethylsulfoxide was studied by
high-temperature X-ray diffraction, differential thermal analysis and thermogravimetry, and attenuated total reflectance infrared
spectroscopy. The ATR-FTIR study indicated that the heating between room temperature and 75°C produced the elimination of
adsorbed molecules. Above this temperature the elimination of intercalated molecules occurs through several stages. Loss of
6.5% of the intercalated DMSO first causes a slight contraction of the basal spacing at 90şC due to a rearrangement of the
DMSO molecules in the interlayers positions. This contraction is followed by the formation of a single layer complex and the
restoring of the dickite structure, at 300°C, when the loss of intercalated species have been completed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
H. Langfelderová 《Journal of Thermal Analysis and Calorimetry》1994,41(4):955-970
Dehydration steps of aquacopper(II) complexes with homogeneous and heterogeneous coordination sphere are investigated from the view point of structural changes taking place under their heating to the decomposition temperature and during the dehydration. The role of loosening of intra-and intermolecular hydrogen bonds in the decomposition reaction for the structure changes of the remainder, the structural presumptions of the reactants for lower hydrates formation are discussed. Activation parameters of dehydration were found to be the lower, the smaller are the structure differences between the reactants and products. They do not reflect the bond length central atomvolatile ligand, much more the overall structure differences between the starting and resulting compounds. From all data on crystal and molecular structures of dehydrated compounds is the reaction pathway best indicated by anisotropic temperature parameters of donor atoms corrected for the thermal movement of the central atom: the higher these values in the bond direction are, the lower the values of activation energies of dehydration are. 相似文献
4.
Fourier-transform infrared (FTIR) spectroscopy has been applied in combination with wide-angle X-ray diffraction and measurements of strength, fluidity, yellowness, birefringence, and moisture regain to detect microstructural changes in lyocell fibres, a regenerated cellulose fibre, subjected to direct heat and annealing treatments. TMA, and SEM were used to show the effect of direct heat and annealing on lyocell fibres. The FTIR spectroscopy results show that a decrease in intermolecular hydrogen bonding occurs at 70 and 80 °C for annealed and directly heated samples, respectively. The results demonstrate increase of the intensity of O–H stretching vibrations, this associated with hydrogen bonds reforming around 130 °C. Lyocell fibres shrink with direct heating in the temperature range 130–160 °C. The crystallinity decreases gradually with increasing temperature. There is no significant change in colour of the samples annealed up to 150 °C. A continuous increase in the fluidity occurs for the annealed samples in the range 150–230 °C. The tenacity and breaking extension of heated samples decrease with increasing temperature. The lower annealing temperatures cause no observable change in the smooth and void-free surface, but in the annealing temperature range 170–230 °C, substantial non-uniformity is apparent on the surface of the fibres. 相似文献
5.
The thermal degradation behaviour and the gaseous products of FEP-g-polystyrene sulfonic acid membranes prepared by radiation-induced grafting of styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films and the subsequent sulfonation were studied using thermal gravimetric analysis coupled with Fourier transform infrared spectrometry (TGA/FTIR). The membranes were found to have a three-step degradation behaviour due to water removal, elimination of sulfonic acid groups and decomposition of the FEP matrix. The evolving gaseous products were identified using FTIR analysis. The degree of grafting was found to have a strong effect on the weight loss in the membranes, whilst the degradation temperatures of the individual membrane components were shown to be independent of the degree of grafting. 相似文献
6.
A. Miyake A. Kimura Y. Satoh R. Shimizu M. Inano T. Ogawa 《Journal of Thermal Analysis and Calorimetry》2006,85(3):633-636
In order to obtain a better
understanding of the thermal hazard of hydrazine and nitric acid mixtures
which are used in plutonium and uranium recovery by extraction (PUREX) process
during recycling of spent fuel in nuclear plant, DSC was carried out for the
mixed system made by the small scale reaction calorimeter super-CRC in various
conditions. It was found that the concentration of the nitric acid has a strong
influence on the thermal behavior of the mixed system, and hydrazine nitrate
which is formed in the reaction in the mixture was determined by DSC with
FTIR analysis. 相似文献
7.
8.
1,3-propanediaminotetramethylenephosphonic acid (PDTMP, H8L) was prepared and its complexes with some lanthanide ions (La(III), Eu(III), Gd(III) and Sm(III)) were isolated. The IR
spectra and thermal stabilities of PDTMP and its complexes were studied. All the complexes contain physically and coordinately
bound water molecules, which are released from the solid samples below 370°C. On heating PDTMP decomposes to phosphorus oxides,
while its anhydrous complexes decompose to lanthanide oxides, and cyclic and linear polyphosphates between 400 and 1000°C.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Use was made of thermal and other techniques to characterise three native asphalt samples. The purpose was to support archaeological
investigations reconstructing their thermal history and composition. The first sample (from a Roman quarry in central Italy)
proved to have 37% impurities, no sign of oxidation or degradation and to have never been heated to above 100°C. The second
sample (from a Roman ship sunk south of France) was pure, but partially oxidised, with a saturated fraction in its structure.
Analyses of the latter sample, obtained from the eye of a Thracian bronze head, revealed that the asphalt had been heated
to over 100°C and then mixed with natural wax. 相似文献
10.
The effects of temperature on the stability of a soil humic acid were studied in the present work. Solid samples of Gohy-573 humic acid (HA) and dissolved ones in aqueous solution (pH 6.0, 0.1 mol L−1 NaClO4) were investigated in order to understand the impact of temperature on the chemical properties of the material. The methods applied to solid samples in the present investigation were thermogravimetric analysis (TGA), temperature-programmed desorption coupled with mass spectrometry (TPD-MS), and in situ diffuse reflectance infrared Fourier transformed spectroscopy (in situ DRIFTS). Humic acid samples were studied in the 25-800 °C range, with focus on thermal/chemical processes up to 250 °C. The reversibility of the changes observed was investigated by cyclic changes to specified temperature ranges (40-110 °C). All measurements were conducted under inert-gas atmosphere in order to avoid samples combustion at increased temperatures. Aqueous solutions were analyzed by UV-vis absorption spectroscopy after storage at temperatures up to 95 °C, and storage times up to 1 week. For temperatures below 100 °C experiments on solid and aqueous samples have shown results which were consistent to each other. The amount of water desorbed is temperature dependent and up to 70 °C this process was totally reversible. Above 70 °C an irreversible loss of water was also observed, which according to UV-vis spectroscopy corresponds to water produced by condensation leading to more condensed polyaromatic structures. The water released up to 110 °C was about 7 wt% of the total mass of the dried humic acid, where less than 50% corresponded to reversibly adsorbed water. At higher temperatures (>110 °C), gradual decomposition resulting in the formation of carbon dioxide (110-240 °C), and carbon monoxide (140-240 °C) takes place. Hence, thermal treatment of Gohy-573 humic acid above 70 °C results in irreversible structural changes, that could affect chemical properties (e.g., complex formation) of the material. 相似文献
11.
F. A. Al-Newaiser S. A. Al-Thabaiti A. O. Al-Youbi A. Y. Obaid M. A. Gabal 《Chemical Papers》2007,61(5):370-375
The thermal decomposition behavior in air of SrC2O4 · 1.25H2O was studied up to the formation of SrO using DTA-TG-DTG techniques. The decomposition proceeds through four well-defined
steps. The first two steps are attributed to the dehydration of the salt, while the third and fourth ones are assigned to
the decomposition of the anhydrous strontium oxalate into SrCO3 and the decomposition of SrCO3 to SrO, respectively. The exothermic DTA peak found at around 300°C is ascribed to the recrystallization of the anhydrous
strontium oxalate. On the other hand, the endothermic DTA peak observed at 910°C can be attributed to the transition of orthorhombic-hexagonal
phase of SrCO3. The kinetics of the thermal decomposition of anhydrous strontium oxalate and strontium carbonate, which are formed as stable
intermediates, have been studied using non-isothermal TG technique. Analysis of kinetic data was carried out assuming various
solid-state reaction models and applying three different computational methods. The data analysis according to the composite
method showed that the anhydrous oxalate decomposition is best described by the two-dimensional diffusion-controlled mechanism
(D2), while the decomposition of strontium carbonate is best fitted by means of the three-dimensional phase boundary-controlled
mechanism (R3). The values of activation parameters obtained using different methods were compared and discussed. 相似文献
12.
Methods of DTA, TG, X-ray phase analysis and IR spectroscopy were used to study the thermal dehydration and decomposition of Ni2+ and Zn2+ peroxotitanates to the corresponding metatitanates. The course of the process was established and the intermediate phases were identified. The information obtained was utilized to determine the optimum temperatures of heating the initial peroxotitanates for conversion to metatitanates with a fairly high degree of crystallinity (for ZnTiO3 the optimum temperature is 600°C, while for NiTiO3 it is 550°C). 相似文献
13.
杂多酸在活性炭上的固载化Ⅲ.活性炭在酸性介质中对钨硅杂多酸(SiW_(12))的吸附 总被引:1,自引:0,他引:1
在氢离子浓度均为3mol/L的硫酸,盐酸,磷酸,醋酸水溶液中和冰醋酸中研究了具有Keggin结构的硅钨杂多酸(SiW_(12))在不同来源活性炭上的吸附作用。各活性炭对SiW_(12)吸附等温线的形式是不相同的,吸附剂载体的微孔结构以及杂多酸的溶剂化起着重要的作用。并且在无机酸介质中,杂多酸的吸附量比在水溶液中成规律性地增加,且与酸强度成正比关系。在有机酸介质中,吸附作用比较复杂。根据所得结果,提出了在酸性介质中杂多酸在活性炭表面的吸附模型。 相似文献
14.
在氢离子浓度均为3mol/L的硫酸,盐酸,磷酸,醋酸水溶液中和冰醋酸中研究了具有Keggin结构的硅钨杂多酸(SiW12)在不同来源活性炭上的吸附作用,各活性炭对SiW12吸附等温线的形式是不相同的,吸附剂载体的微孔结构以及杂多酸的溶剂化起着重要的,工且在无机酸介质中,杂多酸的吸附量比在水溶液中成规律地增加,且与酸强度正比关系,在有机酸介质中,吸附作用比较复杂,根据所得结果,提出了在酸性中杂多酸在 相似文献
15.
E. Morillo J. L. Pérez-Rodríguez C. Real P. J. Sánchez-Soto 《Journal of Thermal Analysis and Calorimetry》1995,44(2):313-327
In the present investigation, DTA and TG techniques were used to study the thermal behaviour of montmorillonite treated with solutions of the pesticide aminotriazole (AMT), in nitrogen flow. These techniques have been complemented by mass spectrometry of the evolved gases (EGA-MS). AMT is adsorbed in the interlamellar space of montmorillonite as a cation. Results obtained in this study show that this provokes a shift of the dehydroxylation peak of montmorillonite to lower temperatures than those of the untreated clay. Montmorillonite protects the adsorbedAMT, delaying its first decomposition step, and catalysesAMT final decomposition at lower temperatures. The DTA curve of montmorillonite-AMT mechanical mixture differs from the sum of those of the clay mineral and the pesticide heated individually. Montmorillonite dehydroxylation occurs at lower temperature, indicating a complex formation betweenAMT and the mineral during the heating process. However the DTA of the mixture is different from that of the complex previously studied, indicating that in the complex obtained by heating the physical mixtureAMT is adsorbed as neutral molecule or as a product of its decomposition. 相似文献
16.
Differential scanning calorimeter (DSC) has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively. Dehydration of CAH10 and C2AH8 (whereH=H2O) occur at 160–180°C and 200–280°C respectively. These two phases are unstable and ultimately get transformed to AH3 and C3AH6. Dehydration of AH3 and C3AH6 occur between 290 and 350°C and overlap at lower scanning rate. The activation energy for dehydration of the stable AH3 and C2AH6 phases has been found to be 107.16 and 35.58 kJ mol–1 respectively. The compressive strength of the hydrated calcium aluminates has been determined. The result shows that in the case of CA, almost 90% of ultimate strength has been attained in 1 day whereas in CA2, ultimate strength has been attained in 14 days and in C12A7 in 1 day. DSC results have been correlated with the rate of strength developments. 相似文献
17.
Bang-Chein Ho Yu-Der Lee Wei-Kuo Chin 《Journal of polymer science. Part A, Polymer chemistry》1992,30(11):2389-2397
The thermal degradation of polymethacrylic acid was found to have two separate decomposition regions. The first decomposition region, due to anhydride formation primarily, was caused by the conversion of polymethacrylic acid to polymethacrylic anhydride. This reaction followed first-order kinetics and had an activation energy of 40.5 kcal/mol. The second decomposition region was the thermal degradation for the corresponding polymethacrylic anhydride. In this region, the fragmentation of anhydride rings structure in polymethacrylic anhydride constitutes the major decomposition reaction with an activation energy of 37.4 kcal/mol. © 1992 John Wiley & Sons, Inc. 相似文献
18.
《Journal of Chemical Sciences》1988,100(1):27-29
The electroanalytical behaviour of 5-nitroorotic acid has been studied at several pH values, using several techniques (DC
and DP polarography and CV).
The 5-nitroorotic acid undergoes five irreversible diffusion-controlled reduction waves over entire pH range considered. The
optimum conditions for determination of 5-nitroorotic acid-with the above technique are also studied. 相似文献
19.
D. Wyrzykowski E. Hebanowska G. Nowak-Wiczk M. Makowski L. Chmurzyński 《Journal of Thermal Analysis and Calorimetry》2011,104(2):731-735
Thermal decomposition of citric acid, trans- and cis-aconitic acid has been studied using the TG-MS, TG-FTIR and DSC techniques. The measurements were carried out in an argon
atmosphere over a temperature range of 293–673 K. The influence of the acid structures and configurational geometry on stability
of the transition products and pathways of thermal transformations of the studied compounds studied is discussed. 相似文献
20.
L. A. Perez-Maqueda C. Maqueda J. L. Perez-Rodriguez J. Subrt Z. Cerny V. Balek 《Journal of Thermal Analysis and Calorimetry》2012,107(2):431-438
Acid leaching of vermiculite is an interesting procedure to prepare high surface area porous silica. Thermal behaviour of
unground and ground vermiculite leached with HCl solutions has been studied by TG, DTA, ETA and high temperature XRD. Important
differences have been observed in the thermal behaviour of unground and ground vermiculite after the acid treatments. Thus,
for the acid-treated unground vermiculite, dehydrated vermiculite, enstatite and cristobalite were formed during the heating,
while for the acid-treated ground vermiculite only iron oxides and cristobalite phases were observed. Structural modifications
due to acid treatment were responsible for changes in the transport properties determined by ETA for the vermiculite samples. 相似文献