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1.
The influences of atmospheric CO2 and H2O on the kinetics of the thermal decomposition of zinc carbonate hydroxide, Zn5(CO3)2(OH)6, were investigated by means of controlled rate evolved gas analysis (CREGA) coupled with TG. Although CO2 and H2O were evolved simultaneously in a single mass-loss step of the thermal decomposition, different effects of those evolved
gases on the kinetic rate behavior were observed. No distinguished effect of atmospheric CO2 was detected within the possible range of self-generated CO2 concentration. On the other hand, apparent acceleration effect by the increase in the concentration of atmospheric H2O was observed as the reduction of reaction temperature during the course of constant rate thermal decomposition. The catalytic
effect was characterized by the decrease in the apparent activation energy for the established reaction with increasing the
concentration of atmospheric H2O, accompanied by the partially compensating decrease in the pre-exponential factor. 相似文献
2.
The effect of atmospheric water vapor on the kinetic rate behavior of the thermal decomposition of copper(II) carbonate hydroxide,
Cu2CO3(OH)2, was investigated by means of TG-DTA coupled with a programmable humidity controller. With increasing water vapor pressure
p(H2O) from 0.8 to 10.6 kPa, a systematic reduction of the reaction temperature of the thermal decomposition was observed as the
continuous trend from the previous works at the lower p(H2O). Through a comparative kinetic analysis of the reaction at different p(H2O), a catalytic action of the atmospheric water vapor on the nucleation process at the first half of the reaction was identified
as the possible origin of the reduction of the reaction temperature. 相似文献
3.
《Journal of Coordination Chemistry》2012,65(18):1727-1734
Reaction of urea with sodium tetrachloroaurate(III) dihydrate and zinc(II) chloride has been investigated at room and elevated temperature (~90°C) producing three new compounds: [Au(urea)4]Cl3·2H2O, [Au2(NH2)2Cl2(NCO)(OH)]·H2O and 2ZnCO3·3Zn(OH)2. The infrared spectra were recorded and the observed bands were assigned. The binuclear gold complex and basic zinc carbonate basic were also investigated by thermal analysis, and general mechanisms describing their decompositions are suggested. 相似文献
4.
Sara J. Palmer H. J. Spratt R. L. Frost 《Journal of Thermal Analysis and Calorimetry》2009,95(1):123-129
Thermal analysis complimented with evolved gas mass spectrometry has been applied to hydrotalcites containing carbonate prepared
by coprecipitation and with varying divalent/trivalent cation ratios. The resulting materials were characterised by XRD, and
TG/DTG to determine the stability of the hydrotalcites synthesised. Hydrotalcites of formula Mg4(Fe,Al)2(OH)12(CO3)·4H2O, Mg6(Fe,Al)2(OH)16(CO3)·5H2O, and Mg8(Fe,Al)2(OH)20(CO3)·8H2O were formed by intercalation with the carbonate anion as a function of the divalent/trivalent cationic ratio.
XRD showed slight variations in the d-spacing between the hydrotalcites. The thermal decomposition of carbonate hydrotalcites
consists of two decomposition steps between 300 and 400°C, attributed to the simultaneous dehydroxylation and decarbonation
of the hydrotalcite lattice. Water loss ascribed to dehydroxylation occurs in two decomposition steps, where the first step
is due to the partial dehydroxylation of the lattice, while the second step is due to the loss of water interacting with the
interlayer anions. Dehydroxylation results in the collapse of the hydrotalcite structure to that of its corresponding metal
oxides and spinels, including MgO, MgAl2O4, and MgFeAlO4. 相似文献
5.
An instrument of controlled rate evolved gas analysis (CREGA) coupled with TG‐DTA was constructed for analyzing the influences of product gases on the kinetics and mechanism of the thermal decomposition of solids that produce more than one gaseous products at the same stage of reaction. The thermal decomposition of synthetic malachite, Cu2(OH)2CO3, was subjected to the measurements of CREGA‐TG under controlled concentrations of H2O and CO2 in the reaction atmosphere with taking account of self‐generated H2O and CO2 during the course of reaction. By a series of CREGA‐TG measurements carried out under various atmospheric conditions, it was reconfirmed that the reaction is accelerated and decelerated by the effects of atmospheric H2O and CO2, respectively. From the kinetic analysis of the CREGA‐TG curves and results of high temperature X‐ray diffraction measurements under various reaction atmospheres, it was revealed that the anomalous effects of atmospheric H2O on the reactivity and on the reaction rate of the thermal decomposition of synthetic malachite appear at the early stage of the reaction. Usefulness of the CREGA‐TG technique for measuring the kinetic rate data for the thermal decomposition of solids was demonstrated in the present study, by emphasizing the importance of quantitative control of self‐generated reaction atmosphere. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 346–354, 2005 相似文献
6.
Timothy Biswick Alexandra Pacu?a Jerzy Podobinski 《Journal of solid state chemistry》2007,180(4):1171-1179
The steps associated with the thermal decomposition of Zn5(OH)8(NO3)2·2H2O and ZnOHNO3·H2O are re-examined. Previous reports have suggested that Zn5(OH)8(NO3)2·2H2O decomposes to ZnO via two intermediates, Zn5(OH)8(NO3)2 and Zn3(OH)4(NO3)2 whereas ZnOHNO3·H2O has been reported to decompose to ZnO via a Zn3(OH)4(NO3)2 intermediate. In this study, we demonstrate using TG, mass spectral analysis of evolved gases and in situ variable temperature powder X-ray diffraction analysis that, in fact, in the decomposition of Zn5(OH)8(NO3)2·2H2O an anhydrous zinc nitrate intermediate is also involved. We, additionally, show that the decomposition of ZnOHNO3·H2O to ZnO also involves the formation of an anhydrous zinc nitrate intermediate. The anhydrous zinc nitrate formed in both cases is poorly crystallised and this observation may explain why this phase could not be observed by PXRD analysis in the previous studies. 相似文献
7.
Timothy Biswick William Jones Aleksandra Pacuła Ewa Serwicka Jerzy Podobinski 《Solid State Sciences》2009,11(2):330-335
Zinc hydroxy acetate, Zn5(OH)8(CH3CO2)2·4H2O, has been prepared by the precipitation method. It has been demonstrated by FTIR analysis that, contrary to previous reports, the interaction of the acetate anion with the matrix cation is ionic. TG analysis, mass spectral analysis of the evolved gases, and in situ variable temperature PXRD and FTIR analysis have shown that decomposition of the material to ZnO involves the formation of Zn5(OH)8(CH3CO2), Zn3(OH)4(CH3CO2)2 and anhydrous zinc acetate (Zn(CH3CO2)2) as some of the acetate-containing intermediate solid products. The acetate anion is finally lost, at temperatures below 400 °C, as acetic anhydride, (CH3CO)2O. 相似文献
8.
Fabrication of mesoporous ZnO nanosheets from precursor templates grown in aqueous solutions 总被引:1,自引:0,他引:1
Keita Kakiuchi Eiji Hosono Toshio Kimura Hiroaki Imai Shinobu Fujihara 《Journal of Sol-Gel Science and Technology》2006,39(1):63-72
Mesoporous ZnO nanosheets were successfully prepared by pyrolytic transformation of zinc carbonate hydroxide hydrate, Zn4CO3(OH)6·H2O. The nanosheets were initially formed as assemblies on glass substrates during chemical bath deposition (CBD) in aqueous
solutions of urea and zinc acetate dihydrate, zinc chloride, zinc nitrate hexahydrate, or zinc sulfate heptahydrate at 80°C.
It was key to induce heterogeneous nucleation of Zn4CO3(OH)6·H2O by promoting a gradual hydrolysis reaction of urea and controlling the degree of supersaturation of zinc hydroxide species.
Morphology of Zn4CO3(OH)6·H2O was largely influenced by the anions present in the CBD solutions. The Zn4CO3(OH)6·H2O nanosheets were transformed into wurtzite ZnO by heating at 300°C in air without losing the microstructural feature. 相似文献
9.
P. S. Sokolov A. N. Baranov A. S. Alikhanyan M. I. Nikitin Zh. V. Dobrokhotova 《Russian Journal of Inorganic Chemistry》2007,52(12):1963-1967
The gas phase over nanocomposites consisting of zinc carbonate hydroxide (ZCH) Zn2(OH)2CO3 · xH2O(x = 1, 3) dispersed in a NaCl matrix has been characterized by high-temperature mass spectrometry and on-line FTIR spectroscopy coupled with thermal analysis. Volatile zinc-sodium chloro complexes are in equilibrium with ZCH-rich nanocomposites at 20–700°C under mass spectrometric conditions. This is evidence that sodium chloride reacts readily with zinc oxide nanoparticles. The thermal events in the ZCH-NaCl (Li2CO3) system have been investigated by differential scanning calorimetry. 相似文献
10.
The thermal decomposition of natural iowaite of formula Mg6Fe2(Cl,(CO3)0.5)(OH)16·4H2O was studied by using a combination of thermogravimetry and evolved gas mass spectrometry. Thermal decomposition occurs over
a number of mass loss steps at 60°C attributed to dehydration, 266 and 308°C assigned to dehydroxylation of ferric ions, at
551°C attributed to decarbonation and dehydroxylation, and 644, 703 and 761°C attributed to further dehydroxylation. The mass
spectrum of carbon dioxide exhibits a maximum at 523°C. The use of TG coupled to MS shows the complexity of the thermal decomposition
of iowaite.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
Prateek Bhojane Armel Le Bail Parasharam M. Shirage 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(1):61-64
The successful attempt to solve the crystal structure of Co(CO3)0.5(OH)·0.11H2O (denoted CCH ), based on synchrotron powder diffraction data, leads to a drastic revision of the chemical formula to Co6(CO3)2(OH)8·H2O [hexacobalt(II) bis(carbonate) octahydroxide monohydrate] and to a hexagonal cell instead of the orthorhombic cell suggested previously [Porta et al. (1992). J. Chem. Soc. Faraday Trans. 88 , 311–319]. This results in a new structure‐type related to malachite involving infinite chains of [CoO6] octahedra sharing edges along a short c axis, delimiting tunnels having a three‐branched star section. All reports discussing cobalt hydroxycarbonates ( CCH ) without any structural knowledge and especially its topotactic decomposition into Co3O4 have, as a result, to be reconsidered. 相似文献
12.
Marques R. F. C. Zorel H. E. Crespi M. S. Jafelicci M. Paiva-Santos C. O. Varanda L. C. Godoi R. H. M. 《Journal of Thermal Analysis and Calorimetry》1999,56(1):143-149
The compound obtained via state solid reaction of the La2O3 and SrO oxides and expose the room atmosphere shows the crystallographic data of the compound reported as La2SrOx. However, thermogravimetric, differential thermal analysis and XRD with controlled temperature indicated that the stoichiometry
of the compound is 2La(OH)3-SrCO3, which structural parameters were determined by using the Rietveld method. It was verified that when the compound exposed
at room atmosphere, the mixture oxide absorbs H2O and CO2 producing hydroxide and carbonate of lanthanum and strontium, respectively, which thermal decomposition occurs by the same
steps, producing the La2O3-SrO.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
J. M. Bouzaid R. L. Frost A. W. Musumeci W. N. Martens 《Journal of Thermal Analysis and Calorimetry》2006,86(3):745-749
The thermal
stability and thermal decomposition pathways for synthetic woodallite have
been determined using thermogravimetry in conjunction with evolved gas mass
spectrometry. Chemical analysis showed the formula of the synthesised woodallite
to be Mg6.28Cr1.72Cl(OH)16(CO3)0.36⋅8.3H2O and X-ray diffraction confirms the layered
LDH structure. Dehydration of the woodallite occurred at 65°C. Dehydroxylation
occurred at 302 and 338°C. Both steps were associated with the loss of
carbonate. Hydrogen chloride gas was evolved over a wide temperature range
centred on 507°C. The products of the thermal decomposition were MgO and
a spinel MgCr2O4. Experimentally
it was found to be difficult to eliminate CO2 from
inclusion in the interlayer during the synthesis of the woodallite compound
and in this way the synthesised woodallite resembled the natural mineral. 相似文献
14.
《Journal of Coordination Chemistry》2012,65(4):353-358
Abstract Reaction of copper and of copper in presence of zinc with glycylglycine H2Gg, H2NCH2CONHCH2COOH (in ratios 1:2 and 1:1:2, respectively), and an excess of hydrogen peroxide results in the formation of a novel peroxy complex [Cu(O2 2-) (H2Gg)2].2H2O and a mixed metal peroxo carbonate complex [Cu, Zn(O2 2-(CO3)(H2O)4], respectively. A notable feature of the reaction is the facile decomposition of the peptide bond at room temperature on addition of zinc to the system. 相似文献
15.
Thierry Chartier Lionel Lostec Christian Gault Christian Chatillon 《Journal of Sol-Gel Science and Technology》2002,23(1):27-37
Desorption and vaporisation from MAS-L (MgO-Al2O3-SiO2-Li2O) sol-gel powders are observed during heat treatment from room temperature to 1000°C using thermogravimetry and Knudsen-cell mass spectrometry. The vaporisation gaseous products are H2O, CO2, NO, NO2 and LiNO2. Volatile hydroxides are not observed, but the evolution of the partial pressure of H2O(g) with temperature, when compared with equilibrium thermodynamic calculations, reveals that LiOH (solid or liquid) is present as an independent bulk phase and that Li2O is likely to be combined with another compound. The hydroxide Mg(OH)2 is formed from the physically adsorbed and/or condensed water inside the porosity. From the evolution of the CO2(g) partial pressure, independent carbonated bulk phases could not be detected, although the measured partial pressures crossed the pressure range of thermodynamic stability of known carbonate phases. Besides, both decompositions of LiOH and of nitrates were seen to contribute to the loss of lithium during heat treatment. 相似文献
16.
Veronika Vágvölgyi M. Hales W. Martens J. Kristóf Erzsébet Horváth R. L. Frost 《Journal of Thermal Analysis and Calorimetry》2008,92(3):911-916
The understanding of the thermal stability of zinc carbonates and the relative stability of hydrous carbonates including hydrozincite
and hydromagnesite is extremely important to the sequestration process for the removal of atmospheric CO2. The hydration-carbonation or hydration-and-carbonation reaction path in the ZnO-CO2-H2O system at ambient temperature and atmospheric CO2 is of environmental significance from the standpoint of carbon balance and the removal of green house gases from the atmosphere.
The dynamic thermal analysis of hydrozincite shows a 22.1% mass loss at 247°C. The controlled rate thermal analysis (CRTA)
pattern of hydrozincite shows dehydration at 38°C, some dehydroxylation at 170°C and dehydroxylation and decarbonation in
a long isothermal step at 190°C. The CRTA pattern of smithsonite shows a long isothermal decomposition with loss of CO2 at 226°C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of zinc
carbonate minerals 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. The CRTA technology offers a mechanism for
the study of the thermal decomposition and relative stability of minerals such as hydrozincite and smithsonite. 相似文献
17.
Ray L. Frost Sara J. Palmer Ross E. Pogson 《Journal of Thermal Analysis and Calorimetry》2012,107(3):905-909
Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral crandallite CaAl3(PO4)2(OH)5·(H2O) and to ascertain the thermal stability of this ‘cave’ mineral. X-ray diffraction proves the presence of the mineral and
identifies the products of the thermal decomposition. The mineral crandallite is formed through the reaction of calcite with
bat guano. Thermal analysis shows that the mineral starts to decompose through dehydration at low temperatures at around 139 °C
and the dehydroxylation occurs over the temperature range 200–700 °C with loss of the OH units. The critical temperature for
OH loss is around 416 °C and above this temperature the mineral structure is altered. Some minor loss of carbonate impurity
occurs at 788 °C. This study shows the mineral is unstable above 139 °C. This temperature is well above the temperature in
the caves of 15 °C maximum. A chemical reaction for the synthesis of crandallite is offered and the mechanism for the thermal
decomposition is given. 相似文献
18.
Twenty-four nanocomposites built from layered double hydroxides and bicyclic and tricyclic carboxylates have been synthesised for the first time. Eight carboxylates were successfully intercalated into [LiAl2(OH)6]Cl·yH2O, [Ca2Al(OH)6]NO3·yH2O, and [Mg2Al(OH)6]NO3·yH2O, and the products fully characterised. Guest species incorporated include 1-adamantane carboxylate (1-AC) and 5-norbornene-2-endo-3-exo-dicarboxylate. In some cases, carbonate anions were co-intercalated with the organic guest, and in others poorly crystalline aluminium hydroxides formed as by-products. Sharper resonances were observed in the 13C solid-state NMR spectra of the 1-AC intercalates than in the spectrum of pure 1-AC, suggesting increased order in the arrangement of the cyclic cages in the intercalates. Where possible, time-resolved in situ X-ray diffraction was employed to study the nanoscopic steps involved in the intercalation reactions. These investigations showed that the reactions are one-step processes, proceeding directly to the fully exchanged intercalate with no intermediate phases. The intercalation processes were found to be nucleation controlled. 相似文献
19.
R. L. Frost J. M. Bouzaid A. W. Musumeci J. T. Kloprogge W. N. Martens 《Journal of Thermal Analysis and Calorimetry》2006,86(2):437-441
The thermal
stability and thermal decomposition pathways for synthetic iowaite have been
determined using thermogravimetry in conjunction with evolved gas mass spectrometry.
Chemical analysis showed the formula of the synthesised iowaite to be Mg6.27Fe1.73(Cl)1.07(OH)16(CO3)0.336.1H2O
and X-ray diffraction confirms the layered structure. Dehydration of the iowaite
occurred at 35 and 79°C. Dehydroxylation occurred at 254 and 291°C.
Both steps were associated with the loss of CO2. Hydrogen
chloride gas was evolved in two steps at 368 and 434°C. The products of
the thermal decomposition were MgO and a spinel MgFe2O4.
Experimentally it was found to be difficult to eliminate CO2
from inclusion in the interlayer during the synthesis of the iowaite compound
and in this way the synthesised iowaite resembled the natural mineral. 相似文献
20.
The thermal stability of carbonate precursors of yttrium oxide was studied by thermal and thermogravimetric analyses, specifically,
with evolved gas mass spectroscopy, on TA Instruments equipment. The thermolysis of Y2(CO3)3 · nH2O (n = 2.46) is a complex process and comprises several stages of elimination of water (90–285°C) and carbon dioxide. 相似文献