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1.
《Materials Chemistry》1982,7(4):479-498
The grinding under constant temperature and vapour pressure of Cd(OH)2 brings about rapid dehydration into CdO.The evolution v.s. grinding time of the half bredth of hydroxide and oxide X-ray diffraction lines shows three steps. The part of diminution in particle size or distortions of the structure but also of the mechanical dehydration in these modifications is discussed.The X-ray line profiles Fourier analysis shows that (i) whatever temperature and vapour pressure imposed during the grinding, the particles sizes of the oxide product by mechanical dehydration is close to that of the oxide obtained by thermal dehydration under vacuum. (ii) The distortions of the structure don't depend on the dehydration process, they are similar in the two types of oxide but they are influenced by the vapour pressure. 相似文献
2.
Grinding a mixture of hydrous amorphous chromium oxide (Cr2O3·nH2O), vanadium oxide (V2O5) and antimony oxide (Sb2O5) was conducted by using a planetary ball mill, to investigate their mechanochemical reactions to form chromium vanadium oxide (CrVO4) and chromium antimony oxide (CrSbO4). The synthesis reactions proceed with an increase in grinding periods of time. The ground samples consist of agglomerates with particle size of about ten nanometers. The synthesized CrVO4 sample exhibits a rutile-type tetragonal crystal structure, which is a high pressure phase. Additionally, solid solutions, CrV1−xSbxO4 (x=0∼1, Δx=0.25), have been synthesized mechanochemically from the mixtures of Cr2O3·nH2O, V2O5 and Sb2O5. 相似文献
3.
Rare earth cobalties, LnCoO3, can be conveniently prepared by the thermal decomposition of the precursor LnCo(C2O4)3·nH2O (La, Ce, n=9; Pr, Nd, n=8). CeCo(C2O4)3·8H2O, unlike the other oxalato compounds thermally decompose to a mixture of CeO2 and Co3O4. Although LnCoO3are formed from the precursors at a temperature lower than 800°C, thermal analysis of a mixture of La2(C2O4)3·10H2O and CoC2O4·2H2O at 900·C shows the residue containing mainly La2O3 and Co3O4 with a small amount of LaCoO3. 相似文献
4.
《Journal of solid state chemistry》2004,177(4-5):1312-1320
The thermal behavior, thermostructural and morphological changes, of rare earth phosphate powders RePO4·nH2O (Re=La, Ce or Y) was investigated up to 1500°C using high temperature X-ray diffraction, FT-infrared and Raman spectroscopies and thermogravimetry coupled with differential thermal analysis. The hydration water of the compounds was zeolitic (for Re=La or Ce) or coordinated (for Re=Y) and was associated with a divariant or a monovariant equilibrium of dehydration, respectively. The high temperature anhydrous monoclinic phase LaPO4 or CePO4 formed irreversibly at about 750°C after the total dehydration of the hexagonal hydrated structure while the dehydration of the monoclinic YPO4·2H2O phase began from about 190°C with its simultaneous decomposition into tetragonal YPO4. A polytrioxophosphate secondary minor phase Re(PO3)3 resulting from adsorbed H3PO4 was formed at 950°C and decomposed at 1350°C. The particle morphology did not change with the temperature but grain coalescence occurred below 1000°C. 相似文献
5.
Chun-Yan Sun Lin-Hua Xie Bo Gao Zhong-Min Su 《Journal of solid state chemistry》2006,179(7):2093-2100
Three new extended frameworks built from paratungstate and transition metals have been synthesized and characterized. In the compound Na8[{Cd (H2O)2}(H2W12O42)]·32H2O (1), two neighboring paratungstate-B ions [H2W12O42]10− are linked by [Cd(H2O)2]2+ units, leading to the formation of infinite one-dimensional (1D) anion chain [{Cd(H2O)2}(H2W12O42)]n8n−. The anion [{Co(H2O)3}{Co(H2O)4}(H2W12O42)]n6n− of the compound Na6[{Co(H2O)3}{Co(H2O)4}(H2W12O42)]·29H2O (2) shows a layer-like (2D) structure in which paratungstate-B units are linked by CoO6 octahedra, while the anion [{Co(H2O)3}3(H2W12O42)]n4n− of the compound (H3O+)3[{Na(H2O)4}{Co(H2O)4}3(H2W12O42)]·24.5H2O (3) is a three-dimensional (3D) anionic polymer that consists of paratungstate-B units linked by CoO6 octahedra. Compound 3 can reversibly adsorb and desorb water molecules leading to the color reversibly change from pink to violet. The preliminary magnetic measurement and electrochemical properties of compounds are performed. The crystal structure of unexpected product Na4[NiW6O24H6]·13H2O (4) is described here for the rare report of crystal structure information on the Anderson-type polyoxotungstate which has nickel as a heteroatom. 相似文献
6.
Xuehang Wu Wenwei Wu Xuemin Cui Sen Liao 《Journal of Thermal Analysis and Calorimetry》2012,109(1):163-169
The MnV2O6·4H2O with rod-like morphologies was synthesized by solid-state reaction at low heat using MnSO4·H2O and NH4VO3 as raw materials. XRD analysis showed that MnV2O6·4H2O was a compound with monoclinic structure. Magnetic characterization indicated that MnV2O6·4H2O and its calcined products behaved weak magnetic properties. The thermal process of MnV2O6·4H2O experienced three steps, which involves the dehydration of the two waters of crystallization at first, and then dehydration of other two waters of crystallization, and at last melting of MnV2O6. In the DSC curve, the three endothermic peaks were corresponding to the two steps thermal decomposition of MnV2O6·4H2O and melting of MnV2O6, respectively. Based on the Kissinger equation, the average values of the activation energies associated with the thermal decomposition of MnV2O6·4H2O were determined to be 55.27 and 98.30?kJ?mol?1 for the first and second dehydration steps, respectively. Besides, the thermodynamic function of transition state complexes (??H ??, ??G ?? , and ??S ?? ) of the decomposition reaction of MnV2O6·4H2O were determined. 相似文献
7.
《Journal of Inorganic and Nuclear Chemistry》1978,40(8):1501-1505
Rare earth trisoxalatochromates (III), LnCr(C2O4)3·nH2O (n = 9 for La, and n = 8 for Ce, Pr and Nd) have been isolated and characterized by a number of physicochemical studies. These compounds (except for Ce) serve as precursors for the rare earth chromates (V) and chromites (III). LnCrO4 may be obtained by heating LnCr(C2O4)3·nH2O at 520°C for 4 hr and LnCrO3 at 900°C for a similar period. CeCr(C2O4)3. 8H2O decomposes to a mixture of CeO2 and Cr2O3. The EPR spectra of LaCrO4 are consistent with a tetrahedral geometry of the CrO4 group. Although the unit cell of LaCrO4 is monoclinic and of NdCrO4 is tetragonal, compounds of composition La1−xNdxCrO4 show the presence of only monoclinic phase for x up to 0.23. The electronic spectra of LnCrO3 are compatible with the perovskite structure of these compounds. 相似文献
8.
《Journal of Electroanalytical Chemistry》1983,143(1-2):291-321
All three isomeric 1-methylpyridiniumcarboxaldehydes are present in aqueous solutions predominantly in the hydrated form (PyCH(OH)2). At pH smaller than about 7, the protonated form of the free aldehyde is reduced in two one-electron steps following the sequence H+, e, H+, e. At pH greater than about 8 the free aldehydic form is reduced in two one-electron steps following the sequence, e, H+, e, H+. Up to pH about 10 the reducible species is formed by dehydration of PyCH(OH)2, at higher pH by elimination of hydroxide ion from PyCH(OH)O−.The increase in polarographic reduction current between pH about 8 and 10 is due to a base-catalyzed dehydration, involving a rate-determining formation of PyCH(OH)O−. The polarographic dissociation curve (i1 vs. pH) is in this case shifted to lower pH-values when compared with the conditional dissociation curve ([PyCH(OH)2] vs. pH). Such behavior shows that the effective reduction of the conjugate base of an electroinactive acid (PyCH(OH)2) occurs.The increase in polarographic reduction current at pH smaller than about 1 is due to an acid-catalyzed dehydration involving formation of PyCH(OH)(OH2+). The rate of protonation governs the limiting current, since the increase in current with increasing acidity occurs in a region one to two acidity units higher than pK1 values obtained spectrophotometrically, using acidity functions HC(OH)2. The free carbonyl species produced by dehydration is reduced following a sequence H+, e, H+, e. 相似文献
9.
A new flexible 3D porous metal-organic framework (MOF) with 1D open nanotube,[Co2(μ5-CTAI)(dpe)(H2O)2]n·6n(H2O)(1) (CTA=cyclohexane-1,2,4,5-tetracarboxylic acid,dpe=1,2-di(4-pyridyl) ethylene) has been prepared and structurally characterized.Meanwhile,each 1D nanotubes filled with 1D water chain with dimension of 13.711 × 12.275 2.Compound 1 represents a new example that collapse/deform upon dehydration/hydration and shows adsorb H 2 O selectively over organic solvents. 相似文献
10.
K. Nahdi M. Férid Malika Trabelsi Ayadi 《Journal of Thermal Analysis and Calorimetry》2009,96(2):455-461
The aim of this work is to highlight the importance of controlling the residual water vapour pressure above the sample as
well as the rate of the thermal decomposition during the thermal dehydration of cerium cyclotriphosphate trihydrate CeP3O9·3H2O.
For this reason, the dehydration of the titled compound was followed by both techniques: the constant rate thermal analysis
at P
H2O = 5 hPa and the conventional TG-DTA in air. 相似文献
11.
N.Z. Lyakhov A.P. Chupakhin V.P. Isupov V.V. Boldyrev 《Journal of solid state chemistry》1978,26(2):173-178
The dependence of the growth rate vg of nuclei during CuSO4·5H2O dehydration upon water vapor pressure PH2O has been investigated. At small PH2O (less than 1 Torr at 50°C), vg falls rapidly with decreasing PH2O, and simultaneously vg anisotropy disappears. At PH2O = 1–9 Torr, vg for elliptic and round nuclei is constant and independent of PH2O. The influence of initially keeping the samples in water vapor upon the kinetics of the following dehydration has been studied. Treatment by water vapor leads to slowing of dehydration and increasing its degree of transformation. On the basis of data obtained a kinetic interpretation of the Topley-Smith effect has been proposed. 相似文献
12.
Zhipeng Chen Qian Chai Sen Liao Yu He Wenwei Wu Bin Li 《Journal of Thermal Analysis and Calorimetry》2012,108(3):1235-1242
The single phase ??-LiZnPO4·H2O was directly synthesized via solid-state reaction at room temperature using LiH2PO4·H2O, ZnSO4·7H2O, and Na2CO3 as raw materials. XRD analysis showed that ??-LiZnPO4·H2O was a compound with orthorhombic structure. The thermal process of ??-LiZnPO4·H2O experienced two steps, which involved the dehydration of one crystal water molecule at first, and then the crystallization of LiZnPO4. The DTA curve had the one endothermic peak and one exothermic peak, respectively, corresponding to dehydration of ??-LiZnPO4·H2O and crystallization of LiZnPO4. Based on the iterative iso-conversional procedure, the average values of the activation energies associated with the thermal dehydration of ??-LiZnPO4·H2O, was determined to be 86.59?kJ?mol?1. Dehydration of the crystal water molecule of ??-LiZnPO4·H2O is single-step reaction mechanism. A method of multiple rate iso-temperature was used to define the most probable mechanism g(??) of the dehydration step. The dehydration step is contracting cylinder model (g(??)?=?1?(1???)1/2) and is controlled by phase boundary reaction mechanism. The pre-exponential factor A was obtained on the basis of E a and g(??). Besides, the thermodynamic parameters (??S ??, ??H ??, and ??G ??) of the dehydration reaction of ??-LiZnPO4·H2O were determined. 相似文献
13.
The thermal dehydration reaction of potassium titanium oxalate, K2TiO(C2O4)2·2H2O, has been studied by means of thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) in nitrogen atmosphere at different heating rates. K2TiO(C2O4)2·2H2O dehydrates in a single step through a practically irreversible process. The activation energy involved and its dependence on the conversion degree were estimated by evaluating the thermogravimetric data according to model-free methods, and values of activation energy were determined for the dehydration reaction. Activation energy values were also evaluated from DSC data using isoconversional methods. The complexity of the dehydration of K2TiO(C2O4)2·2H2O is illustrated by the dependence of E on the extent of conversion, ?? (0.05??????????0.95). 相似文献
14.
The thermal decomposition of rare earth caproates with general formula Ln(C5H11COO)3 nH2O, (where Ln=Y, La-Pr, n=l; Ln=Nd-Er, n=2; Ln=Tm-Lu, n=3) were studied in an air atmosphere. On heating, the hydrated caproates are dehydrated in one step and then the anhydrous complexes decompose to the oxides (Ln2O3, Pr6O11) with formation of the intermediate Ln2O2CO3 (La, Pr-Gd) or directly to the oxides Ln2O3, CeO2, Tb4O7(Y, Ce, Tb-Lu). Caproates of rare earth elements are liquefied during dehydration. 相似文献
15.
3-Phenylpropenal benzoylhydrazone (HL) reacts with cobalt, nickel, and copper chlorides, nitrates, and acetates to give coordination compounds MX2 · nH2O [M = Co, Ni, Cu; X = Cl, NO3, HL = C6H5CH=CHCH=NNHC(O)C6H5; n = 0, 2] and ML2 · nH2O (M = Co, Ni, Cu; n = 1–3). Complexes MALCI (M = Co, Ni, Cu) were obtained by these reactions in the presence of amines (A = C5H5N, 2-CH3C5H4N, 3-CH3C5H4N, 4-CH3C5H4N). All the compounds have a monomeric structure. Azomethine (HL) in them behaves as a bidentate N,O-ligand. Thermolysis of the complexes involves the stages of dehydration (70–90°C), deaquation (145–155°C) or deamination (145–185°C), and complete thermal decomposition (330–490°C). 相似文献
16.
Konstantina E. Chrysomallidou Spyros P. Perlepes Aris Terzis Catherine P. Raptopoulou 《Polyhedron》2010
Reactions of malonic acid (H2mal) with PrCl3·6H2O afforded the known complex [Pr2(mal)3(H2O)6]n (1), and compounds [Pr2(mal)3(H2O)6]n·2nH2O (2·2nH2O), [PrCl(mal)(H2O)3]n·0.5nH2O (3·0.5nH2O) and [Pr(mal)(Hmal)(H2O)3]n·nH2O (4·nH2O) using various reaction ratios, reaction media (H2O, MeOH) and pH values. Analogous reactions with CeCl3·7H2O afforded compounds [Ce2(mal)3(H2O)6]n (5), [CeCl(mal)(H2O)3]n·nH2O (6·nH2O) and [Ce(mal)(Hmal)(H2O)3]n·nH2O (7·nH2O). Compounds 2·2nH2O and 3·0.5nH2O were characterized by X-ray crystallography, and 4–7 by microanalytical and spectroscopic data. The malonate(-2) ligand adopts three different coordination modes in the structures of 1–3, i.e., the μ2-κO:κO′:κO″ and the μ4-κ2O:κO′:κ2O″:κO? in 1 and 2 leading to a 3D network structure, and the μ3-κ2O:κO′:κ2O″:κO? in 3 promoting an 1D structure. The thermal decomposition of 1 and 3·0.5nH2O was monitored by TG/DTA and TG/DTG measurements. The structural features of 1–3 are discussed in terms of known malonato(-2) LnIII and CaII complexes. The bioinorganic chemistry relevance of our results is discussed. 相似文献
17.
Thermogravimetry and differential thermal analysis were used to study hydrated sodium peroxide and the so-called anhydrous commercial product. Prolonged dehydration of the octahydrate under vacuum led to the partial formation of Na2O2-H2O2 compounds as well as the dihydrate and monohydrate The DTA curves for commercial sodium peroxide heated in air or other gases, showed the partial formation of Na2O2·2H2O2·nH2O and of NaHCO4·H2O by the action of the gases on the NaO2 contained in the Na2O2. 相似文献
18.
Spectral characteristics of (H2O)n, (O2)m(H2O)n, and (O)i(H2O)n cluster systems, where m≤2, i≤4, and 10 ≤ n ≤ 50, are studied with the molecular dynamics method using a flexible molecule model. The IR absorption spectra are changed substantially as a result of O2 molecule dissociation, and in the presence of atomic oxygen in the clusters, the spectra are characterized by a deep minimum at 520 cm?1. The absorption of oxygen causes a marked reduction in reflection coefficient R of monochromatic IR radiation. The number of peaks in the R(ω) spectra decreases to two in the case of molecular oxygen absorption and is no larger than four in the case of atomic oxygen absorption. The absorption of atomic oxygen by the clusters is also accompanied by a significant increase in the dissipation of energy accumulated by the clusters. This effect weakens when molecular oxygen is absorbed. An increase in atomic oxygen concentration in the clusters renders their radiation harder. 相似文献
19.
V. L. Volkov G. S. Zakharova L. A. Perelyaeva 《Russian Journal of Inorganic Chemistry》2006,51(1):41-45
New layered nanocomposites of V2O5 · nH2O xerogels with poly(vinyl alcohol) (PVA), pyrocatechol (PC), and hydroquinone (HQ) were synthesized with the compositions (C2H3)0.32V2O4.90 · nH2O, (C6H4)xV2O4.60 · nH2O, and (C6H4)0.17V2O4.94 · nH2O and the interlayer distances d 001 = 11.73, 12.85, and 15.28 ± 0.05 Å, respectively. IR and Raman spectroscopy was used to analyze which structural changes occur in the V-O layers of the xerogel upon composite formation. X-ray photoelectron spectroscopy showed V4+ and V5+ ions in the layers with binding energies lower than in V2O5 · nH2O. The electrical conductivity of the nanofilms and the thermal properties of the nanopowders were studied. 相似文献
20.
D. Brandová M. Trojan F. Paulik J. Paulik M. Arnold 《Journal of Thermal Analysis and Calorimetry》1990,36(3):881-889
The dehydration and condensation reactions taking place during the calcination of Mn1/2Ca1/2(H2PO4)2.2H2O has been followed by means of thermal analyses under quasi-isothermal-isobaric conditions. Isothermal calcination of starting binary dihydrogenphosphate has been also carried out in an electric oven at various temperatures. The reaction products obtained were analyzed by chromatography, IR-spectroscopy, X-ray diffraction analysis, and electron microscopy. The compositions of the calcinates were determined through extraction. The effect of the partial pressure of water vapour has been followed on course, of the condensation reactions and of the formation of the main product: binary cyclotetraphosphate (tetrametaphosphate) MnCaP4O12.
Zusammenfassung Dehydratations- und Kondensationsreaktion während der Kalzinierung von Mn1/2Ca1/2(H2PO4)2.2H2O wurden unter quasi-isothermen-isobaren Bedingungen mittels Thermoanalyse untersucht. Die isotherme Kalzinierung der binären Dihydrogenphosphat-Ausgangssubstanz wurde bei verschiedenen Temperaturen auch in einem Elektroofen durchgefährt. Erhaltene Reaktionsprodukte wurden mittels Chromatographie, IR-Spektroskopie, Röntgendiffraktionsanalyse und Elektronenmikroskopie untersucht. Die Zusammensetzung der Kalzinierungsprodukte wurde über Auslaugen bestimmt. Weiterhin wurde der Einfluß des partiellen Druckes von Wasser auf den Verlauf der Kondensationsreaktionen und die Bildung des Hauptproduktes {binäres Cyclotetraphosphat (Tetramethaphosphat) MnCaP4O12} untersucht.相似文献