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1.
A new thallium(I) uranate(VI) of composition Tl4UO5 was isolated and characterised by X-ray, i. r. and chemical analyses. The compound dissociated into thallium(I) oxide and Tl2UO4 on heating to 230°C and its subsequent thermal behaviour depended on the volatilisation and oxidation characteristics of the thallium(I) oxide released.  相似文献   

2.
Seven ternary oxides; Li4UO5, Li2UO4, Li22U18O65, Li2U1.75O6.25, Li2U2O7, Li2U3O10 and Li2U6O19 in the system Li–U(VI)–O were prepared by solid-state reaction route and characterized by X-ray diffraction method. Specific heats of these compounds were measured by differential scanning calorimetry in the temperature range from 300 to 860 K. The specific heats show a decreasing trend with increase in UO3(s) content in these lithium uranates. However, the specific heat per gram atom shows an increasing trend with decrease in number of oxygen atoms in the formula unit.  相似文献   

3.
Thermal decomposition of ammonium uranates precipitated from uranyl nitrate solutions on addition of aqueous ammonium hydroxide under various conditions has been examined by thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy and X-ray diffraction study. The TG curves of all precipitates show the weight-loss corresponding to the calculated value as UO3·NH3·H2O. The DTA curves of the precipitates give the endotherms at about 130, 210 and 590 °C and the exotherms at 340–420 °C. As a result, it is found that ammonium uranates thermally decompose to amorphous UO3 at about 400 °C, and transform to U3O8 via β-UO3.  相似文献   

4.
The thermal decomposition of UO2NH4PO4 · 3H2O and UO2HPO4 · 4H2O was studied in the temperature range 25–1600?C. Both compounds gave U2O3P2O7 around 900?C after a two step dehydration and an orthophosphate-pyrophosphate transformation. UO2NH4PO4 · 3H2O did not form any pure intermediates, but (UO2)2P2O7 could be prepared from UO2HPO4 · 4H2O. In air, U2O3P2O7 lost phosphorus above 1250?C. In argon, (UO)2P2O7 was first formed between 1000 and 1290?C and this product only lost phosphorus at still higher temperatures. (UO)2P2O7 was also obtained by reduction of (UO2)2P2O7 or U2O3P2O7 at 700?C in H2 or with carbon black in argon above 1000?C. It oxidised in air above 250?C with the formation of U2O3P2O7.  相似文献   

5.
The oxidation of UO2 was investigated by TG, DSC and X-ray diffraction . UO2 samples were prepared by the reduction of UO3 at PH2 + PN2 = 100 + 50 mm Hg and 5°C min?1 up to 800°C. In order to obtain six UO2 samples with different preparative histories, UNH, UAH and ADU were used as starting materials and their thermal decomposition was carried out at 450–625°C for 0–9 h at an air flow rate of 100 ml min?1. α-UO3, γ-UO3, UO3 - 2 H2O, and their mixtures were obtained. The reduction of UO3 gave β-UO2+x with different x values from 0.030 to 0.055. The oxidation carried out at PO2 = 150 mm Hg was found to consist of oxygen uptake at room temperature. UO2 - U3O7 (Step I) and U3O7 → U3O8 (Step II). TG and DSC curves of the oxidation showed two plateaus and two exothermic peaks corresponding to Steps I and II. In the case of two of the samples, the DSC peak of Step II split into two substeps, which were assumed to be due to the different reactivities of U3O- formed from α-CO3 and that from other types of UO3. The increase in O/U ratio due to the oxygen uptake at room temperature changed from 0.010 to 0.042 except for a sample prepared from ADU which showed an extraordinarily large value of 0.445. TG curves showed an increase in O/U from room temperature to near 250°C for Step I and the plateau at 250–350°C where O/U was about 2.42, and showed a sharp increase in O/U above 350°C for Step II and the plateau above 100°C where O/U was 2.72–2.75. It is thought that the prepared UO2 had a defective structure with a large interstitial volume to accommodate the excess oxygen.  相似文献   

6.
Conclusions As a result of an investigation of the heterogeneous equilibria in M2O-Tl2O3-H2O systems, where M=Tl(I), Li, Na, K, Rb, and Cs, at 25°C it was established that the components only react in systems with thallium(I) and sodium hydroxides with the formation of thallium(I) orthothallate and restricted solid solutions between thallium oxide and the orthothallate based on thallium oxide and sodium hydroxythallate Na3Tl(OH)6, respectively.At elevated temperatures of 150 and 200°C it was established that potassium metathallate is formed in the K2O-Tl2O3-H2O system while sodium metathallate NaTlO2 and a hydrated thallate of the composition 4Na2O·Tl2O3·(3–4)H2O are formed in the Na2O-Tl2O3-H2O system at 150°C. The thallates Tl3TlO3, Na3Tl(OH)6, NaTlO2, and KTlO2 have been isolated in a pure form and identified.The amphoteric nature of thallium oxide has been proven.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1689–1693, August, 1984.  相似文献   

7.
In the CrUO system, besides the phases reported earlier, a triuranate CrU3O10-x (x ~ 0.3) could be identified. It is unstable above 70o°C and decomposes to a mixture of CrUO4 and U3O8. Under reducing atmospheres up to 1600°C, the uranium—chromium—oxygen system gives a mixture of Cr2O3 and UO2. No new phase could be identified. The compound CrUO4 is unstable under reducing conditions and decomposes to a mixture of Cr2O3 and UO2.  相似文献   

8.
The thermal decomposition of (UO2)3(PO4)2 and U(HPO4)2 ·xH2O in the temperature range 25–1600?, was investigated. (UO2)3(PO4)2 decomposed first to 1/3[U3O8 + 3U2O3P2O7] and then to U3O5P2O7 before a loss of phosphorus was observed above 1350?. Decomposition in air and in inert atmospheres was nearly identical. Reduction with H2 or with carbon black in argon gave U3O5P2O7 and [UO2 + + (UO)2P2O7] before pure UO2 was formed. U(HPO4)2 ·xH2O decomposed to UP2O7 in argon. It oxidized partly in air before the same product was obtained. The high temperature stability of UP2O7 and U3(PO4)4 was also investigated.  相似文献   

9.
The effect of the mechanoactivation on UO3 and U3O8 in agate or stainless steel vessels in air or in toluene is studied. UO2(OH)2 is the main product of UO3·H2O activation in steel vessel in air. The presence of toluene leads to strong amorphization and dispersity increase and, probably, to the formation of U2O5. The activation of U3O8 leads to its reduction to U3O7 which relative content in the reaction mixture depends on the mechanoactivation conditions.  相似文献   

10.
Previously unknown individual crystalline compounds MIIIU3O10.5·6H2O were obtained by the reaction of synthetic schoepite UO3·2.25H2O with aqueous solutions of La, Ce, Pr, Nd, and Sm nitrates in hydrothermal conditions at 200°C. Their composition and structure were determined, and the processes of dehydration and thermal decomposition were studied by the methods of chemical analysis, X-ray diffraction, IR spectroscopy, and scanning calorimetry.  相似文献   

11.
Six thallium(I) molybdates with numerous allotropic modifications have been found in the binary system Tl2OMoO3; Tl4MoO5, Tl2Mo2O7, Tl8Mo10O34 (three forms), and Tl2Mo7O22 (two forms) melt incongruently; Tl2MoO4 and Tl2Mo4O13 which are trimorphic melt congruently. For the most part, the compounds were characterized by their powder diagram and by their IR spectrum which allowed comparisons with alkaline molybdates.  相似文献   

12.
The cesium uranates Cs2UO4, Cs2U2O7, Cs4U5O17 and Cs2U4O12 were studied using X-ray Diffraction (XRD), neutron diffraction, X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS) in an attempt to couple the crystallographic structure to the uranium valence state using the local uranium environment. The diffraction spectra were used for Rietveld refinement to determine the atomic positions and interatomic distances. These distances were subsequently used in Bond Valence Sum (BVS) calculations to determine the uranium valences. The XAS spectra give direct information on the local uranium environment regarding the U-O distances and the arrangement of the oxygen atoms around the central uranium. The difference between the monovalent uranates and the multivalent Cs2U4O12 is clearly established in all spectra, as well as in the crystal structures. The different valences present can be assigned to individual uranium lattice sites, but some amount of disorder is required to balance the charges.  相似文献   

13.
As cesium hexanitratouranium(IV), Cs2U(NO3)6, has the same Cs:U stoichiometry as that of Cs2UO4, thermal decomposition of this nitrato complex in air and nitrogen was studied in detail as a possible alternate method of preparing pure Cs2UO4. The volatility of cesium nitrate, which is one of the intermediate products, changed this Cs:U ratio during thermal decomposition. Hence, only Cs2U2O7 was obtained on heating the sample to 775 K or higher. A scheme for the thermal decomposition of Cs2U(NO3)6 is given by combining the observed TG, XRD and IR data.  相似文献   

14.
Li2U3O10 · 6H2O crystal hydrate was synthesized by the reaction between synthetic schoepite UO3 · 2.25H2O and aqueous lithium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the obtained compound were established, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and scanning calorimetry.  相似文献   

15.
Summary Electronic absorption spectra have been measured by diffuse reflectance for MgUO4–x, MgU3O9, CaUo)4–x, Ca2UO5, Ca3UO6, Ca2U3O11, CaU2O7, CaU4O12, SrUO3, SrUO4, SrUO3.67, Sr2U3O11, SrU4O12.8, Sr2UO5, Sr3UO6, BaUO4, Ba3UO6, BaU2O7, Ba2U2O7 and Ba2U3O11.Measurements in the near i.r. region of the spectrum have identified transitions arising within the manifold of the 5f electronic levels which indicate the presence of uranium(V) in certain compounds. The portion of the spectrum between 20 000 and 30 000 cm–1 is shown to contain charge-transfer transitions and, in certain instances, vibrational progressions which are characteristic of the symmetry of the UO6 octahedron in the solid state structure.  相似文献   

16.

The solid-state reactions of TlNO3 with V2O5 in the molar ratios of 6∶5 and 2∶3 were studied by DTA, DTG and TG in the temperature ranges 20–550° and 20–400°, respectively, in a nitrogen atmosphere. For the molar ratio of 6∶5, thallium pentavanadate (Tl3V5O14) was formed as the final product of reaction at 550°. The reaction proceeds stepwise, and Tl2V6O16 and TlVO3 were identified as intermediates. For the molar ratio of 2∶3, impure thallium hexavanadate (Tl2V6O16) was obtained as the final product of reaction.

  相似文献   

17.
π-Complexes of Heavy Metals. X. Synthesis and Crystal Structure of {[(1,3,5-(CH3)3C6H3)2Tl][AlCl4]}2: an Arene Stabilized Dimeric Thallium(I) Tetrachloroaluminate From a solution of AlCl3 and TlCl in mesitylene, the bis(arene)thallium complex {[(1,3,5-(CH3)3C6H3)2Tl][AlCl4]}2 ( 1 ) (space group P21/c with a = 19.575(4) Å, b = 12.436(2) Å, c = 19.415(4) Å, β = 101.69(3)° at T = ?90 ± 1°C; Z = 4) will crystallize at low temperature. This compound can be described as a dimeric thallium(I) tetrachloroaluminate with a sceleton similar to that of (TeI4)4, shielded by four arenes, in pairs coordinated at the thallium atoms. In the solid state the complete configuration has point group symmetry 1 (C1). Tl? Cl distances ranging from 3.292(3) to 3.679(3) Å point out an ionic bonding situation between arene2Tl+ and AlCl4? fragments. The strengths of the η6 like Tl-arene interactions are characterized by distances Tl(1)–C of 3.250 Å and 3.315 Å, and Tl(2)? C of 3.285 Å and 3.328 Å and a temperature of release of all arene molecules of 61°C, which has been determined by differential thermal analysis, to yield pure thallium(I) tetrachloroaluminate.  相似文献   

18.
By powder X-ray diffraction the crystal structure of catena-(2-thiobarbiturato)dithallium(I) C4H2N2O2STl2 (C4H4N2O2S is 2-thiobarbituric acid, H2TBA), Tl2TBA, is determined. Crystallographic data for Tl2TBA are as follows: a = 15.1039(3) Å, b = 12.0818(2) Å, c = 3.86455(6) Å, β = 97.203(1)°, V = 741.34(2) Å3, space group P21/n, Z = 4. There are two non-equivalent thallium atoms in the structure. The Tl1 polyhedron is a distorted trigonal prism due to the shortened Tl-S contact (3.634 Å), and the Tl2 polyhedron is a distorted square antiprism.  相似文献   

19.
Investigations on the Structure of Thallium(I) Halide Mercurates(II) Tl4HgBr6 crystallizes tetragonal with a = 8.978, c = 8.812 Å and Z = 2 in the space group P4/mnc. Singlecrystal methods revealed isolated HgBr6-octahedra, compressed alonged the [001] axis, with thallium atoms between them. The results have been extended to clarify the structures of the isomorphous compounds (NH4)4HgBr6 (a = 9.011, c = 8.660 Å), Tl4HgJ6 (a = 9.529, c = 9.387 Å) and Tl4HgCl2Br4 (a = 8.896, c = 8.735 Å). It was impossible to obtain Tl4HgCl6; all attempts resulted in the formation of Tl10Hg3Cl16, which crystallizes tetragonal (a = 8.477, c = 23.699 Å).  相似文献   

20.
The crystal and molecular structures of thallium(I) thiobarbiturate C4H3N2O2STl (C4H4N2O2S is 2-thiobarbituric acid, Н2ТВА) have been determined. Crystallographic data for Tl(НТВА) are a = 11.2414(7) Å, b = 3.8444(3) Å, с = 14.8381(9) Å, β = 99.452(2)°, V = 649.00(7) Å3, space group P2/с, Z = 4. Each of the two independent thallium ions is bonded to four oxygen and two sulfur atoms to form a distorted tetrahedron. N?H…O and C?H…S hydrogen bonds form a branched three-dimensional network. The structure is also stabilized by π?π interaction between heterocyclic НТВА- ions. The IR spectra of Tl(НТВА) agree with X-ray powder diffraction data. The compound is also stable below 280°C, and Tl2SO4 is one of the thermolysis products in an oxidative medium in the region of 500?650°C.  相似文献   

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