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1.
Summary The solubility isotherm of the system Tb2O3-SeO2-H2O at 100° was studied. The compounds of the three-component system were identified by the Schreinemakers’ method as well as by chemical and X-ray phase analyses. Simultaneous TG and DTA analyses of all compounds of the system were made. The mechanism of thermal decomposition was described. 相似文献
2.
The solubilities of the systems CeO2-SeO2-H2O and Ce2O3-SeO2-H2O were studied at 100°C. The field of crystallization of Ce(SeO3)2 was established in the system CeO2-SeO2-H2O, and fields of crystallization of Ce2(SeO3)3 and Ce2(SeO3)3H2SeO3 were established in the system Ce2O3-SeO2-H2O. The compound obtained were identified by means of chemical, X-ray and derivatograph analysis. The mechanism of thermal
dissociation of Ce(SeO3)2, Ce2(SeO3)3 and Ce2(SeO3)3·H2SeO3 was studied.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
The solubility isotherm of the three-component system Yb2O3-SeO2-H2O at 100°C was studied. There are two fields of crystallization in the solubility diagram at this temperature - a small one
of Yb2(SeO3)3·4H2O and a large one of YbH(SeO3)2·2H2O. These compounds were identified by the Schreinemakers' method, and by chemical and X-ray analyses as well. Simultaneous
TG and DTA curves of the two compounds obtained were made and the mechanism of the thermal decomposition was described.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
The solubility isotherm of the system Eu2O3-SeO2-H2O was studied at 100°C. Certain amounts of the obtained selenites (normal and acid) were subjected to thermal analysis. The
intermediate phases were isolated and chemical and X-ray phase analysis was made. The scheme of thermal decomposition was
determined.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
The solubility of the system CdO-SeO2-H2O was studied at 25 and 100°C. The fields of crystallization of α-CdSeO3, 3CdSeO3·H2SeO3 and CdSeO3·SeO2 were established at 25°C. At 100°C crystallize α-CdSeO3, 3CdSeO3·SeO2, 2CdSeO3·SeO2 and CdSeO3·SeO2. The compounds obtained were identified by means of chemical, X-ray and crystal-optical analysis. The mechanism of thermal
dissociation of α-CdSeO3, 3CdSeO3·H2SeO3 and CdSeO3·SeO2 was studied.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
The selenites of scandium are used as new materials in producing instrument and semi-conductor engineering. Like tellurites,
they can also be applied as materials for making lasers. The process of producing scandium selenides by the reduction of the
corresponding selenites has the advantage of taking place at relatively low temperatures and high rate. In this respect, it
is necessary to command methods of obtaining high-purity selenites and to obtain data concerning their thermal stability.
A physicochemical study of the system Sc2O3-SeO2-H2O was carried out at 100°C in order to find solutions to these problems. The possible compounds in the system at a given temperature
were obtained. The compounds were identified by the Schreinemakers' method and also by chemical and X-ray phase analyses.
The mechanism of thermal decomposition was determined by means of a derivatograph.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
TG and DTA have been carried out on new anhydrous rare-earth selenites R2SeaO3+2a (a=3.5,4) in order to establish their stability. Decomposition occurs in three steps attributed to successive losses of SeO2. The first process gives rise to other new group of selenites of composition R2Se3O9, which crystallize in two different forms depending on the rare-earth element. The second process leads to isomorphous compounds R2SeO5. The final product of thermal degradation is R2O3. All products were characterized by chemical analysis and X-ray powder diffraction methods. 相似文献
8.
The solubility isotherm of the system La2O3—SeO2—H2O at 100°C was studied. The compounds of the three-component system were identified by the Schreinemakers method as well as by chemical and X-ray phase analyses. Simultaneous TG and DTA analyses of all compounds of the system were made by using a derivatograph. The mechanism of thermal decomposition was described.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
9.
O. V. Andreev M. N. Bochkarev N. M. Volodin T. V. Nekrasova A. V. Protchenko 《Russian Chemical Bulletin》1993,42(8):1292-1293
Samarium monosulfide in a state amorphous to X-rays was prepared by the successive interaction of lithium naphthalenide with samarium diiodide and a solution of sulfur in THF in inert atmosphere or under reduced pressure under standard (normal) conditions. Samarium monosulfide was transferred to the polycrystalline state (a=5.95 Å, NaCl-like structure) by annealing in a vacuum (<0.1 Pa) or in an inert atmosphere at 500–600 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1361–1363, August, 1993. 相似文献
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11.
The solubility of the system Pr2O3-SeO2-H2O at 100°C was studied. The fields of crystallization of Pr2(SeO3)3·H2O, PrH(SeO3)2, Pr(HSeO3)3 were established. The compounds obtained were identified by means of chemical, X-ray and thermal analysis. The thermal decomposition of Pr2(SeO3)3·H2O, PrH(SeO3)2, and Pr(HSeO3)3 was determined.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
12.
L. T. Vlaev Svetlana D. Genieva Velyana G. Georgieva 《Journal of Thermal Analysis and Calorimetry》2006,86(2):449-456
The solubility of NiSeO3–SeO2–H2O
system in the temperature region 298–573 K was studied. The compounds
of the three-component system were identified by the Schreinemakers’
method. The phase diagram of nickel(II) selenites was drawn and the crystallization
fields for the different phases were determined. Depending on the conditions
for hydrothermal synthesis, NiSeO3·2H2O,
α-NiSeO3·1/3H2O,
β-NiSeO3·1/3H2O,
NiSeO3 and NiSe2O5
were obtained. The different phases were proved and characterized by chemical,
powder X-ray diffraction and thermal analyses as well as IR spectroscopy. 相似文献
13.
The solubility of MnSeO3-SeO2-H2O system was studied in the temperature region 25–300°C. The compounds of the three-component system were identified by the
Schreinemaker’s method. The phase diagram of manganese(II) selenites was drawn and the crystallization fields for the different
phases were determined. Depending on the conditions for hydrothermal synthesis, MnSeO3·H2O, MnSeO3·3/4H2O, MnSeO3·l/3H2O and MnSe2O5 were obtained. The different phases were proven and characterized by chemical, powder X-ray diffraction and thermal analyses,
as well as IR spectroscopy. The kinetics of dehydration and decomposition of MnSeO3·H2O was studied under non-isothermal heating. Based on 4 calculation procedures and 27 kinetic equations, the values of activation
energy and pre-exponential factor in Arrhenius equation were calculated for both processes. 相似文献
14.
A. R. Marquesi J. R. J. Delben A. A. S. T. Delben 《Journal of Thermal Analysis and Calorimetry》2009,96(2):403-406
New oxyfluoride glasses based on the system ZrO2-Pr2O3-ZrF4-BaF2 were obtained, and the glass forming ability of this system was evaluated. The effects of glass composition on both thermal
stability and the crystalline phases formed upon heat treatment were determined by the DSC and XRD methods, respectively.
The composition with higher thermal stability and better glass forming ability contained 2 mol% of oxides. 相似文献
15.
Feng ML Prosvirin AV Mao JG Dunbar KR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(32):8312-8323
Six new divalent metal selenites have been synthesized by hydro-/solvothermal methods which leads to the incorporation of the organic template as a cation or a ligand. The structure of [H(2)pip][Cu(SeO(3))(2)] (1) (pip=piperazine) features 1D anionic chains of [Cu(SeO(3))(2)](2-) which are cross-linked by the template cations through hydrogen bonds into a 2D layer. In [Cu(C(3)H(4)N(2))(SeO(3))] (2) the organic template is coordinated to the copper(II) ion of the inorganic Cu(SeO(3)) layer. The isostructural compounds [H(2)en][M(HSeO(3))(2)Cl(2)] (en=ethylenediamine; M=Cu (3), Co (4)) contain layers of [MCl(2)(HSeO(3))(2)](2-) units (M=Cu, Co), which are cross-linked by the template cations via hydrogen bonds into a 3D network. The structure of [H(2)en][Cu(2)(SeO(3))(2)(HSeO(3))](2)H(2)O (5), consists of a pillared layered architecture in which the Cu(SeO(3)) layers are further interconnected by bridging hydrogen selenite groups (the pillar). The compound [H(2)pip][Cu(2)(Se(2)O(5))(3)] (6), which crystallizes as a 3D open framework represents the first organically templated metal diselenite. These new compounds are thermally stable up to at least 170 degrees C. All of the compounds exhibit fairly strong antiferromagnetic interactions. More interestingly, compounds 3 and 4 behave as a weak ferromagnets below the critical temperatures of T(c)=12 and 8 K, respectively, and both of them exhibit spin-flop phase transitions around 800+/-100 Oe. 相似文献
16.
L. T. Vlaev S. D. Genieva G. G. Gospodinov 《Journal of Thermal Analysis and Calorimetry》2005,81(2):469-475
Summary The solubility of CoSeO3-SeO2-H2O system in the temperature region 298-573 K was studied. The phase diagram of cobalt(II)selenites was drawn and the crystallization fields for the different phases were determined. Depending on the conditions for hydrothermal synthesis, CoSeO3×2H2O, α-CoSeO3×1/3H2O, β-CoSeO3×1/3H2O, CoSeO3, Co(HSeO3)2×2H2O and CoSe2O5 were obtained. The different phases were proved and characterized by chemical and X-ray analyses, as well as IR spectroscopy. 相似文献
17.
Abdirahman Saeed Dominique M. R. Georget Andrew G. Mayes 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5848-5855
There is widespread interest in responsive polymers that show cloud point behavior, but little attention is paid to their solid state thermal properties. To manufacture products based on such polymers, it may be necessary to subject them to high temperatures; hence, it is important to investigate their thermal behavior. In this study, we characterized a family of poly(N‐isopropylacrylamide‐co‐hydroxymethylacrylamide) copolymers. Although poly(N‐isopropylacrylamide) shows very high thermal stability (up to 360 °C), introduction of hydroxy side chains leads to a significant reduction in stability and new degradation processes become apparent. Thermogravimetric analysis and fourier transform infrared spectroscopy (FT‐IR) indicate that the first degradation process involves a chemical dehydration step (110–240 °C), supported by the nonreversing heat flow response in modulated temperature differential scanning calorimetry. Water loss scales with the fraction of hydroxy monomer in the copolymer. Glass transition temperatures (Tg) are higher than the temperatures causing dehydration; hence, these values relate to newly‐formed copolymer structures produced by controlled heating under nitrogen. Fourier transform‐Raman (FT‐Raman) spectra suggest that this transition involves imine formation. The Tg increases as the fraction of hydroxy groups in the original copolymer increases. Further heating leads to degradation and mass loss, and more complex changes in the FT‐IR spectra, consistent with formation of unsaturated species. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
18.
O. V. Andreev M. N. Bochkarev T. V. Nekrasova A. V. Protchenko 《Russian Chemical Bulletin》1995,44(2):233-235
X-ray amorphous samarium(II) sulfide was prepared by the reaction of H2S with samarium(II) bis[bis(trimethylsilyl)amide] (1) in THF at 10–2 Torr. Compound1 was prepared by two methods: 1) the reaction of SmI2 with lithium bis(trimethylsilyl)amide and 2) the reaction of samarium naphthalide with bis(trimethylsilyl)amine. SmS was transformed to the polycrystalline state with the lattice parametera = 5.92 Å by annealing at 400–500 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 241–243, February, 1995. 相似文献
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20.
Adrian Olejnik Paulina Kosmela Łukasz Piszczyk 《Journal of polymer science. Part A, Polymer chemistry》2021,59(11):1095-1108
In the present work, a thorough thermogravimetric (TG) analysis of bio-based polyurethane–polyisocyanurate (PUR–PIR) foams in both nitrogen and oxygen atmosphere is performed. A sustainable element of the foam is a biopolyol obtained via acid-catalyzed liquefaction of Zostera marina and Enteromorpha Algae biomass. Based on isoconversional analysis and apparent activation energies, several conclusions are obtained. In contradiction to the common understanding, biopolyol based foams exhibit enhanced stability in both oxidative atmosphere and in nitrogen compared to purely petrochemical foams. Relationships between thermal stability and structure of the foams are established. Enhanced stability of bio-based foams in oxygen is attributed to two factors. First is an increased cross-linking density due to higher hydroxyl number of biopolyol compared to petrochemical one. Possibly the presence of more amount of aromatic compounds in the structure of polyols that come from lignin or aromatic ketones contribute to further enhancement of thermal stability. Those results suggest that the studied biobased foams are prospective alternatives to standard petrochemical PUR foams. 相似文献