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1.
The mixed metal oxalate precursors, calcium(II)bis(oxalato)cobaltate(II)hydrate (COC), strontium(II)bis(oxalato)cobaltate(II)pentahydrate (SOC) and barium(II)bis(oxalato)cobaltate(II)octahydrate (BOC) have been synthesized and their thermal stability was investigated. The complexes were characterized by elemental analysis, IR spectral and X-ray powder diffraction studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound COC decomposed mainly to CaC 2O 4 and Co 3O 4 at 340 °C, and a mixture of CaCO 3 and Co 3O 4 identified at 510 °C. A mixture of CaCO 3 and Ca 3Co 2O 6 along with the oxides and carbides of both the cobalt and calcium were attributed at 1000 °C as end products. DSC study in nitrogen ascertained the formation of a mixture of CaO and CoO along with a trace of carbon at 550 °C. The mixture species, SrC 2O 4, CoC 2O 4 and Co 3O 4 were generated at 255 °C in case of SOC in air, which ultimately changed to CoSrO 3, SrCO 3 and oxides of strontium and cobalt at 1000 °C. The several mixture species also generated as intermediate at 332 and 532 °C. The DSC study in nitrogen indicated the formation of CoSrO x (0.5 < x < 1) as end product. In case of BOC in air, a mixture of BaCoO 2, BaO, CoO and carbides are identified as end product at 1000 °C through the generation of several intermediate species at 350 and 530 °C. A mixture of BaO and CoO is identified as end product in DSC study in nitrogen. The kinetic parameters have been evaluated for all the dehydration and decomposition steps of all the three compounds using four non-mechanistic equations. Using seven mechanistic equations, the kind of dominance of kinetic control mechanism of the dehydration and decomposition steps are also inferred. The kinetic parameters, Δ H and Δ S of all the steps are explored from the DSC studies. Some of the decomposition products are identified by IR and X-ray powder diffraction studies. 相似文献
2.
Potassium cobalt hexacyanoferrate(II), K 2CoFe(CN) 6 · 1.4H 2O, loses its water when heated up to 170°C, and the anhydrous compound begins to decompose above 230°C. The cyanide groups are evaporated off in the temperature range 230–350°C, and the solid products thus formed are K 2CO 3, Fe 2O 3, Co 3O 4 and CoFe 2O 4. In the range 550–900°C, the cobalt-containing compounds become CoO, and K 2CO 3 probably partly decomposes to K 2O, so that the product mixture at 900°C is K 2CO 3/K 2O, Fe 2O 3 and CoO. Above this temperature, K 2CO 3 decomposes to K 2O. 相似文献
3.
The thermal decomposition of CaOsO 3 by differential thermal analyses, thermogravimetry and X-ray powder diffraction has been studied. In nitrogen CaOsO 3 decomposes at 880 ± 10°C into CaO, osmium metal and oxygen due to the reaction CaOsO 3 → CaO + Os + O 2. In static air the decomposition occurs in three stages: 2CaOsO 3 + 1/2O 2 → Ca 2Os 2O 7 (in region 775–808°C), Ca 2Os 2O 7 → Ca 2Os 2O 6,5 + 1/4O 2 (at a temperature interval of 850–1000°C) and in the third stage Ca 2Os 2O 6,5 → 2CaO + OsO 4 ÷ 1/4 O 2 (at 1005 ± 5°C). The first intermediate Ca 2Os 2O 7 is isostructural with orthorhombic Ca 2Nb 2O 7 and its cell parameters are: a0 = 3.745 Å, b0 = 25.1 Å, c0 = 5.492 Å, Z = 4, space group Cmcm or Cmc2. Ca 2Os 2O 7 exhibits metallic conductivity and its electrical resistivity is 4.6 × 10 −2 ohm-cm at 296K. 相似文献
4.
The complexes, M[M(C 2O 4) 3]· xH 2 O, where x=4 for M=Cr(III), x=2 for M=Sb(III) and x=9 for M=La(III) have been synthesized and their thermal stability was investigated. The complexes were characterized by elemental analysis, IR and electronic spectral data, conductivity measurement and powder X-ray diffraction (XRD) studies. The chromium(III)tris(oxalato)chromate(III)tetrahydrate (COT), Cr[Cr(C 2 O 4) 3]·4H 2O, released water in a stepwise fashion. Removal of the last trace of water was accompanied by a partial decomposition of the oxalate group. Thermal investigation using TG, DTG and DTA techniques in air produced Cr 2O 3 at 858°C through the intermediate formation of Cr 2O 3 and CrC 2O 4 at around 460°C. While DSC study in nitrogen up to 670°C produced a mixture of Cr 2O 3 and CrC 2O 4. In antimony(III)tris(oxalato)antimonate(III)dihydrate (AOD), Sb[Sb(C 2O 4) 3]·3H 2O the dehydration took place during the decomposition of precursor at 170–290°C and finally at ca. 610°C Sb 2 O 5 along with trace amounts of Sb 2O 4 were produced. Trace amount of Sb 2O 3 and Sb along with Sb 2O is proposed as the end product at 670°C of AOD in nitrogen. The oxide La 2O 3 is formed at 838°C from the study with TG, DTG and DTA in air of lanthanum(III)tris(oxalato)lanthanum(III)nonahydrate (LON), La[La(C 2O 4) 3]·9H 2O. Intermediate dioxycarbonate, La 2O 2CO 3 was generated at 526°C prior to its decomposition to lanthanum oxide in air; whereas in N 2 the formation of La 2(CO 3) 3 at 651°C was proposed. The thermal parameters have been evaluated for each step of the dehydration and decomposition of COT, AOD and LON using five non-mechanistic equations i.e. Flynn and Wall, Freeman and Carroll, Modified Freeman and Carroll, Coats–Redfern and MacCallum–Tanner equations. Kinetic parameters, such as, E*, ko, Δ H*, Δ S* etc. were also supplemented by DSC studies in nitrogen for all the three complexes. Some of the intermediate species have been identified by analytical and powder XRD studies. Tentative schemes has been proposed for the decomposition of all three compounds in air and nitrogen. 相似文献
5.
The role of Na 2O- and Li 2O-doping on the thermal decomposition of Co 3O 4 to CoO and the re-oxidation of cobaltous to cobaltic oxide has been investigated using DTA, with controlled rates of heating and cooling, IR and X-ray diffraction spectrometry techniques. The DTA investigation revealed that both Li2O and Na2O increased the thermal stability of Co3O4. However, the effect was much more pronounced in the case of lithium oxide. Doping Co3O4 with 1.5 mole% Li2O was found to prevent any thermal decomposition of cobaltic oxide even by heating at 1100°C. The maximum thermal stabilization effect induced by doping with sodium oxide (4.5 mole%) was 30%. The sodium oxide- and lithium oxide-doping enhanced the reactivity of the produced CoO towards the re-oxidation by O2 yielding Co3O4. The X-ray diffraction and IR spectrometric investigations showed that part of Li2O and Na2O was effectively incorporated in the Co3O4 lattice, affecting the thermal stabilization of the solid, and another part of the dopant oxide interacted with the produced CoO and also with Co3O4 giving a new sodium cobalt compound, and with Co3O4 producing, also, a new lithium cobalt oxide phase. However, the amount of Li2O dissolved in the Co3O4 lattice was greater than that of Na2O. The sudden cooling of doped solids, from 1000°C to room temperature, favoured the formation of the new sodium cobalt oxide compound, and exerted no effect on the production of the new lithium cobalt oxide phase. The characteristic d spacings and IR absorption bands of these new compounds have been determined. The possible mechanisms of dissolution of Li2O and Na2O in cobaltic oxide lattice are discussed. 相似文献
6.
Thermal events encountered throughout the heat treatment of praseodymium acetate, Pr(CH 3COO) 3·H 2O, were studied in nitrogen and air atmospheres. The samples calcined at the 300–700 °C temperature range were characterized using XRD, IR and N 2 adsorption. Moreover, in situ electrical conductivity was employed to follow up the formation of the different decomposition intermediates. The results indicated that the anhydrous salt decomposes to the final product, PrO 1.833, through the formation of the following intermediates: Pr(OH)(CH 3COO) 2, PrO(CH 3COO) and Pr 2O 2(CO 3). PrO 1.833 formed at 500, 600, and 700 °C possesses a surface area of 17, 16 and 10 m 2/g and crystallites size of 14, 17 and 30 nm, respectively. 相似文献
7.
Two tert-butylammonium decavanadate(V) salts with the formulae [(CH 3) 3CNH 3] 6[V 10O 28] · 8H 2O (1) and [(CH 3) 3CNH 3] 4[H 2V 10O 28] (2), have been synthesized and their crystal structures have been determined by means of single-crystal X-ray diffraction. The crystal structure of compound 1 is stabilized by electrostatic forces and an extensive network of hydrogen contacts involving anions, cations and water molecules. The anions and cations of this compound are arranged in layers perpendicular to the [010] direction following the sequence, cation-anion-cation. In the crystal structure of compound (2), each dihydrogen decavanadate(V) anion is joined to three adjacent polyanions by means of O(6)---H ··· O(4) hydrogen contacts forming layers parallel to the plane (
01) and the hydrophobic groups of the cations are disposed in layers parallel to the anionic sheets. The thermal behaviour of both compounds has been studied. Compound 1 is an octahydrate and its thermal decomposition begins at 70°C with the loss of water of crystallization, while compound 2 is anhydrous and is consequently more stable, with decomposition starting at 200°C. 相似文献
8.
The effects of doping of Co 3O 4with MgO (0.4–6 mol%) and V 2O 5 (0.20–0.75 mol%) on its surface and catalytic properties were investigated using nitrogen adsorption at −196°C and decomposition of H 2O 2 at 30–50°C. Pure and doped samples were prepared by thermal decomposition in air at 500–900°C, of pure basic cobalt carbonate and basic carbonate treated with different proportions of magnesium nitrate and ammonium vanadate. The results revealed that, V 2O 5 doping followed by precalcination at 500–900°C did not much modify the specific surface area of the treated Co 3O 4 solid. Treatment of Co 3O 4 with MgO at 500–900°C resulted in a significant increase in the specific surface area of cobaltic oxide. The catalytic activity in H 2O 2 decomposition, of Co 3O 4 was found to suffer a considerable increase by treatment with MgO. The maximum increase in the catalytic reaction rate constant ( k) measured at 40°C on Co 3O 4 due to doping with 3 mol% MgO attained 218, 590 and 275% for the catalysts precalcined at 500, 700 and 900°C, respectively. V 2O 5-doping of Co 3O 4 brought about a significant progressive decrease in its catalytic activity. The maximum decrease in the reaction rate constant measured at 40°C over the 0.75 mol% V 2O 5-doped Co 3O 4 solid attained 68 and 93% for the catalyst samples precalcined at 500 and 900°C, respectively. The doping process did not modify the activation energy of the catalyzed reaction but much modified the concentration of catalytically active constituents without changing their energetic nature. MgO-doping increased the concentration of CO 3+–CO 2+ ion pairs and created Mg 2+–CO 3+ ion pairs increasing thus the number of active constituents involved in the catalytic decomposition of H 2O 2. V 2O 5-doping exerted an opposite effect via decreasing the number of CO 3+–CO 2+ ion pairs besides the possible formation of cobalt vanadate. 相似文献
9.
Four polyoxometalate complexes, (CPFX·HCl)3H4SiW12O40, (CPFX·HCl)3H3PW12O40, (CPFX·HCl)3H3PMo12O40 and (CPFX·HCl)4H4SiMo12O40, were prepared from ciprofloxacin hydrochloride(CPFX·HCl) reacting with HnXM12O40·nH2O(X=P,Si; M=W,Mo) in an aqueous solution, and characterized by elemental analysis, IR spectrometry and TG-DTA. The IR spectrum confirms the presence of Keggin-type anions of heteropoly acids and the characteristic functional groups of ciprofloxacin. The TG/DTA curves show that their thermal decomposition is a multi-step process including simultaneous collapse of the Keggin-type structure. At first, these compounds had a mass loss of water molecules, then several other mass losses occurred due to the decomposition of ciprofloxacin hydrochloride and its fragments with the degradation of Keggin anions. The end product of decomposition is the mixture of WO3(or MoO3) and SiO2(or P2O5), identified by X-ray diffraction and IR spectroscopy. The possible thermal decomposition mechanisms of these complexes are proposed. This study exemplified that the thermal stability of the complexes containing tungsten is much better than that of the complexes containing molybdenum. 相似文献
10.
The compound [Zn(H 2O) 4] 2[H 2As 6V 15O 42(H 2O)]·2H 2O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a= b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å 3, Z=3 and R1( wR2)=0.0512 (0.1171). The crystal structure is constructed from [H 2As 6V 15O 42(H 2O)] 4− anions and [Zn(H 2O) 4] 2+ cations linked through hydrogen bonds into a network. The [H 2As 6V 15O 42(H 2O)] 6− cluster consists of 15 VO 5 square pyramids linked by three As 2O 5 handle-like units. 相似文献
11.
Samples of γ-Mn 2O 3 with various iron contents are obtained by co-precipitation from appropriate amounts of manganese sulphate and ferric nitrate solutions by a concentrated (2.5 N) boiling solution of sodium hydroxide. Thermal analysis, X-ray diffraction and IR spectroscopy of the specimens reveal that the presence of iron in γ-Mn 2O 3 up to 15 to 25 at.% leads to formation of a single phase γ-Mn 2O 3 solid solution, which is partly reduced to Mn 3O 4 around 680 °C and finally transforms to the -Mn 2O 3 phase on heating at or above 950 °C. With increasing iron concentration beyond 25 at.%, the formation of a ferrite phase has been detected in addition to the γ-Mn 2O 3 solid solution. However, this ferrite phase is thermally unstable and breaks down on heating around 600°C. 相似文献
12.
The structural development of the NiFe 2O 4 nanocrystals dispersed in a silica matrix was followed by IR and EPR spectroscopies of the dried gel 10NiO–10Fe 2O 3–90SiO 2 after heat treatment. The dried gel obtained at 200°C was amorphous, in which Fe 3+ and Ni 2+ ions were distributed in the pores of silica matrix. When the dried gel was heat treated at 400°C, NiFe 2O 4 clusters were partially formed, showing an enhanced interaction with the silica matrix. NiFe 2O 4 clusters were completely formed in silica matrix when the heat treatment was increased to 600°C, at which the interactions between the clusters and silica matrix reached a maximum. The formation reaction of NiFe 2O 4 clusters was accompanied by a rearrangement of the silica matrix network. Further increase of the heat treatment temperature to 800°C led to superparamagnetic single domain NiFe 2O 4 nanocrystals (ca. 4 nm) dispersed in the silica matrix with the elimination of the interactions between magnetic nanocrystals and silica matrix. 相似文献
13.
New physical property data are reported for the compounds VCl 2 and VCl 3. Both compounds hydrolyse and oxidise in acidic aqueous solution, the former rapidly and the latter slowly. They are slightly soluble in organic solvents and the solutions are stable when protected from moisture and oxygen of the air. Heated in air, VCl 2 begins to oxidise to V 2O 5, around 300°, but some formation and volatilisation of VOCl 3 occurs; under similar conditions VCl 3 is converted to volatile VOCl 3 around 250°. Heated in argon, VCl 2 volatilises at 1000°, whereas VCl 3 first disproportionates at 600° to volatile VCl 4 and solid VCl 2, and the latter volatilises as the temperature is raised to 1000°. X-ray diffraction data are given for VCl 2. 相似文献
14.
The solid state formation of lithium manganese oxides has been studied from the thermal decomposition of mixtures Li 2CO 3–Mn 3O 4 with XLi (lithium cationic fraction)=0.33 (LiMn 2O 4), 0.50 (LiMnO 2) and 0.66 (Li 2MnO 3). The analysis of the reactivity has been performed mainly by thermoanalytical (TG/DSC) and diffractometric (XRPD) techniques either on physical mixtures and on mixtures subjected to mechanical activation by high energy milling. At XLi=0.33, the cubic lithium manganese spinel oxide (LiMn 2O 4) forms in air. TG measurements showed that the reaction starts at a considerably lower temperature in the activated mixture. By variable temperature X-ray diffraction it has been assessed that, upon mechanical activation, LiMn 2O 4 forms directly and its formation is completed within 700 °C whereas, starting from a physical mixture, the formation goes through Mn 2O 3 and is complete only at 800 °C. At T>820 °C LiMn 2O 4 reversibly decomposes to LiMnO 2 and Mn 3O 4 with an enthalpy of 30.05 kJ mol −1 of LiMn 2O 4. At XLi=0.50, by annealing under nitrogen flow for 6 h at 650 °C the activated mixture, the orthorhombic LiMnO 2 is formed. Such a formation goes through a mixture of LiMnO 2 and LiMn 2O 4. The enthalpy of LiMnO 2 solid state formation from the activated mixture has been determined to be 57.4 kJ mol −1 of LiMnO 2. At XLi=0.66 in air the mechanical activation considerably lowers the temperature within the monoclinic phase Li 2MnO 3 forms. Besides the reaction enthalpy could be determined as 40.13 kJ mol −1 of Li 2MnO 3. The reaction, when performed under nitrogen flow, goes through the formation of LiMnO 2. Such a first stage of the reaction is affected by the temperature of reaction rather than by mechanical activation. The activation greatly enhances the second stage of the reaction leading from LiMnO 2 to Li 2MnO 3. 相似文献
15.
The stabilities of the hydrated uranyl phosphates (UO 2) 3(PO 4) 2 · 4 H 2O, UO 2HPO 4 · 4 H 2O, and UO 2(H 2PO 4) · 3 H 2O have been reinvestigated. The compounds identified by thermal analysis have been prepared isothermally and characterized by their strongest X-ray reflections. During dehydration, oxygen was not evolved and the crystalline compounds (UO 2) 3(PO 4) 2, (UO 2) 2P 2O 7, UO 2(PO 3) 2, and probably (UO 2) 3P 4O) 13 were found. At still higher temperatures, the uranyl phosphates are reduced. The decomposition products lose phosphorus oxide above 1300–1400°C. The present results are summarized in a tentative pseudo-binary phase diagram UOx(x = 3 to 2)—UO2(PO3)2. 相似文献
16.
Thermal decomposition processes for cyclohexanediaminetetraacetic acid (CDTA-H 4) complexes of palladium, [Pd(CDTA-H 2)] and [Pd(CDTA-H 4)Cl 2]·2 HCl·2 H 2O have been studied using TG—DTA techniques. Infrared spectroscopy and X-ray diffraction have been also used for the characterization of intermediate and final products. In the decomposition of the dichloro complex, chloride ions are released simultaneously to a ring closure reaction in which CDTA becomes tetradentate. For both compounds, the final product in the decomposition is PdO, as confirmed by the X-ray difraction pattern of a sample heated at 600°C. 相似文献
17.
通过水热方法合成了2个由多铌酸盐和过渡金属配合物形成的有机-无机杂化配合物[Cu(TETA)] 4[VNb 12(VO) 4O 40][OH]·10H 2O(1)和[Cu(TETA)] 4[VNb 12(VO) 6O 40][OH] 5·5H 2O(2)(TETA=三亚乙基四胺). 化合物1和2的多阴离子分别是由4个{VO 5}帽和6个{VO 5}帽加盖在Keggin型多铌酸盐的方形缺口上形成的, 它们通过多酸阴离子中Nb-O t (O t =端氧)与[Cu(TETA)] 2+配合物的金属中心配位构筑形成三维结构. 价键计算结果表明, Keggin中心的钒为+5价, 帽位的钒为+4价, X射线光电子能谱分析(XPS)结果也证实了这一结论. 通过单晶X射线衍射分析、红外光谱(IR)、粉末X射线衍射(PXRD)、热重(TG)分析和元素分析对这2个化合物的结构和性质进行了表征. 相似文献
18.
TG, DTG and DTA have been used in non-isothermal investigations of binary systems of Ni 2O 3 and La 2O 3 with barium perchlorate trihydrate, BP·3 H 2O, in various molar ratios, carried out under an air (static) atmosphere from ambient to 1000°C. Ni 2O 3 catalysed the dehydration process of BP·3 H 2O and lowered its Tf by 20°C. The discontinuity on the TG curve due to an incomplete perchlorate—chlorate reaction vanished in the presence of either of the oxides: a mechanism is proposed. La 2O 3 lowered Tf by 50°C; Ti for the decomposition of BP was lowered by 150 and 100°C in the presence of La 2O 3 and Ni 2O 3, respectively. X-Ray diffractometry did not reveal any reaction between BP and the two oxides. Kinetic parameters for the decomposition steps in the presence of either of the oxides have been determined. 相似文献
19.
Dibromoacetic anhydride was prepared by reacting dibromoacetic acid with phosphorus(V) oxide in carbon tetrachloride at 85°C for 11 h. It reacts with Bi 2O 3 and CrO 3 in CCl 4 on prolonged refluxing forming Bi(CHBr 2COO) 3 and Cr (CHBr 2COO) 3, respectively. These new compounds were characterized by elemental analyses, IR, 1H NMR and mass spectroscopy. 相似文献
20.
Two new compounds, (Hbpy) 3(bpy) 2[K(Mo 8O 26)]·2H 2O (1) and H 3(bpy) 5[K(Mo 8O 26)]·H 2O(2) (bpy = 4,4′-bipyridine) have been synthesized under hydrothermal condition by using nearly the same starting materials, and characterized by elemental analyses, IR, TGA, XPS and single crystal X-ray diffractions. The crystal structure analyses reveal that the two compounds possess unusual networks constructed from octamolybdates, potassium ions and organic groups. Both 1 and 2 consist of an identical inorganic chain , and they have analogous structures to each other with slightly different packing modes of the organic groups and water molecules and exhibit unusual three-dimensional (3D) supramolecular networks through extensive multi-point C–HO and N–HO hydrogen-bonding interactions. 相似文献
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