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The Na3RE(PO4)2 phosphates (where RE: La, Ce, Nd, Gd or Er) were obtained by precipitation from sols under mild hydrothermal conditions. Characterization of the powders was carried out by XRD, SEM, ICP/OES and DSC/TG methods. The resulted molar ratio of Na:RE:P in the precipitates was equal 3:1:2 and proved the successful synthesis of Na3RE(PO4)2 compounds. The powders consisted of non-agglomerated spindle or flower-like shaped grains with the size up to 5 microns. The most of the obtained powders have a trigonal structure, which is a characteristic feature of high-temperature polymorphs of Na3RE(PO4)2. An exception is the Na3La(PO4)2 compound, which crystallized in an unidentified type of structure. Under heating, the Na3RE(PO4)2 phosphates change their structure. Their polymorphic transformation path, i.e. temperatures of transitions and their structural changes, is dependent on RE3+ radius size. For La, Ce and Nd compounds heated at high temperatures, only orthorhombic polymorphs have been observed, whereas monoclinic or orthorhombic polymorphs of Na3Er(PO4)2 and Na3Gd(PO4)2 phosphates can form in the course of sintering. [ABSTRACT FROM AUTHOR]

Phase equilibria in the ErPO4–KPO3–Er(PO3)3 partial system were established, and the primary crystallization fields of the phosphates occurring in the composition range of ErPO4, KErP2O7, KPO3, Er(PO3)3, KEr(PO3)4 were defined. Two polythermal binary cross-sections, KErP2O7–Er(PO3)3 and KErP2O7–KEr(PO3)4, which are quasi-binary only in the subsolidus region (i.e. below 855 °C and 640 °C, respectively), were determined, and their phase diagrams were elaborated. Three invariant points, two ternary peritectics P1 (855 °C) and P2 (640 °C) as well as one ternary eutectic E (530 °C) were found in the ErPO4–KPO3–Er(PO3)3 system. Alloy crystallization ends with the solidification of the ternary eutectic (KErP2O7 + KEr(PO3)4 + KPO3). The studies were carried out by thermoanalytical methods (DSC/TG) and powder X-ray diffraction analysis (PXRD). [ABSTRACT FROM AUTHOR]

Three-layer YO, CeO, SiO-AlO and SiO-AlO-YO-CeO coatings were deposited by sol-gel method on the FeCrAl alloy foil substrate. The protective properties of the coatings during high-temperature cyclic oxidation and the changes in the topography of the surface, the structure, and chemical composition of the FeCrAl alloy surface layer were examined. It has been shown that small additions of cerium and yttrium affect the morphology of the growing AlO scale. After 10 oxidation cycles in air ( T = 900 °C, t = 120 h, one cycle = 12 h), the smallest change in the mass of the samples was observed for YO and SiO-AlO-YO-CeO coatings with an appropriate yttrium and cerium content. The protection effectiveness of the coatings to that of uncoated substrate after 10 oxidation cycles ranges from 28 to 66 %. The oxidation scale thickness ( h) and the designated value of the parabolic rate constant ( k ) depended on the yttrium and cerium content in the coating. [ABSTRACT FROM AUTHOR]

Mn-Zn ferrite was prepared from the solution after acid leaching of spent batteries by co-precipitation method using ammonia oxalate, sodium carbonate and sodium hydroxide as precipitating agents. The co-precipitation process was performed at temperature of over 50 °C by continuous magnetic stirring. The precipitates were pre-sintered at 850 °C in air. Dilatometric study has revealed that lowest shrinkage (only 5.6%) showed a material obtained from an oxalate precipitant. After pressing and high-temperature sintering at 1325 °C, it showed both insufficient density and the presence of pores, which contribute to the deterioration in the magnetic properties of the ferrites: the low magnetic permeability value and high magnetic losses. Ferrite prepared from hydroxide and carbonate precipitant showed a much higher shrinkage, sintered density and much higher magnetic permeability compared with the ferrite prepared from oxalate precursor. [ABSTRACT FROM AUTHOR]

Studies on the separation of calcium and neodymium ions by using ethylenediaminetetraacetic acid (H4EDTA) as a complexing agent were performed. This research was undertaken due to the possibility of H4EDTA applying to isolate rare earth elements from the solution after acidic leaching of phosphogypsum, and because of the similarity of coordination properties of calcium and lanthanides ions. The experiment was carried out in model systems containing Ca2+ and Nd3+ ions in hydrochloric or sulphuric acid. The content of calcium and neodymium metals, phase composition and thermal behaviour of the obtained products were determined by ICP-OES, FTIR, XRD and TG/DTA techniques. During the separation process, the precipitates of a light pink colour were obtained. The obtained results show that the neodymium ethylenediaminetetraacetate has been successfully formed and that the isolation of neodymium ions was more efficient in chloride medium. The precipitate included 72.2 and 3.9% of the starting amount of neodymium and calcium used in the experiment, respectively. However, in sulphates medium, these amounts were equal to 73.8 and 53.5%, respectively. Moreover, the obtained powder was polluted with sulphates. The addition of the EDTA in an excess (15%) contributed only to an increase in calcium content in the complex. [ABSTRACT FROM AUTHOR]

The characterization of three commercial powders of niobium(V) oxide received from two producers was made. The thermal behavior of NbO up to melting point and its microstructure were studied using X-ray powder diffraction, thermoanalytical methods (DSC/TG), infrared spectroscopy (IR) and scanning microscopy. Analysis of the obtained results revealed that the starting structure of niobium(V) oxide and its thermal behavior depend on the origin of niobia. Depending on the origin of the powder and of its thermal treatment, three polymorphs of NbO can be observed. Sintering of powders above 1200 °C results in the formation of single phase, H-NbO. [ABSTRACT FROM AUTHOR]

One-layer protective coatings made up of SiO-AlO or SiO-AlO-CeO oxides were synthesized on a FeCrAl alloy substrate by the sol-gel method from sols containing tetraethyl orthosilicate, aluminum tri- sec-butoxide and cerium(III) 2,4-pentanedionate as the precursors. Coating solutions with the Si:Al:Ce molar ratio of 3:1:0, 3:1:0.1; 3:1:0.01, and 3:1:0.001 were used. The composition and morphology of the obtained gels were examined by TG/DSC, XRD, and SEM techniques. It was found that a small addition of cerium affected the morphology of the forming coatings and improved the FeCrAl alloy resistance to high-temperature oxidation (in air at T = 900 °C for t = 100 h). The oxidation of all the investigated samples conformed to the parabolic rate. The protection effectiveness of the one-layer coatings after 100 h of high-temperature oxidation was as high as 70 %. [ABSTRACT FROM AUTHOR]

The phase equilibria in the samarium(III) chloride-thallium chloride pseudobinary system were established by means of differential scanning calorimetry (DSC). The DSC investigations were performed on samples with different compositions in whole mole fraction x(SmCl) range. Experiments were carried out at heating and cooling rates ranging from 1 to 5 K min. This system has an eutectic character and includes three intermediate compounds: congruently melting TlSmCl ( T = 790 K) and incongruently melting TlSmCl ( T = 754 K) and TlSmCl ( T = 774 K). The dependence of heat capacity of TlSmCl on temperature has been measured for temperature range 300-900 K. The SmCl-TlCl pseudobinary system was optimized by CALPHAD method using the available experimental data. The dependencies of mixing enthalpy and mixing entropy on mole fraction x(SmCl) were estimated. The dependencies of formation Gibbs energy on temperature and temperature range of existence of all solid compounds have been calculated and discussed. [ABSTRACT FROM AUTHOR]

Phase diagram of HoBr-KBr pseudo-binary system was established by differential scanning calorimetry (DSC) method. This system includes two intermediate compounds: KHoBr and KHoBr. KHoBr undergoes a solid-solid phase transition at 689 K and melts congruently at 992 K, while KHoBr melts incongruently at 736 K. In the HoBr-KBr, system two eutectics occur. The eutectic mixture e melts at 875 K; its composition is x(HoBr) = 0.162. The other eutectic e with composition of x(HoBr) = 0.455 melts at 699 K. The heat capacity (solid and liquid phase) of congruently melting compound formed in this system was measured by DSC in the 300-1273 K range. The specific conductivity of HoBr-KBr liquid mixtures was measured down to temperatures below solidification over the entire composition range. The obtained results are discussed in term of possible complexes formation. [ABSTRACT FROM AUTHOR]

The phase equilibria occurring in the ErPO-KPO system were investigated by thermoanalytical, X-ray powder diffraction and FTIR methods. On the basis of the obtained results, its phase diagram was proposed. This system includes one intermediate compound, KErPO. This phosphate decomposes peritectically at about 1025 °C and occurs in two polymorphic forms; transformation β/α-KErPO proceeds at about 358 °C. The binary erbium end potassium diphosphate, KErPO, was obtained by the ceramic and modified Pechini methods. Structural properties were characterized by X-ray powder diffraction and FTIR spectroscopy. [ABSTRACT FROM AUTHOR]

Mn-Zn ferrites were obtained by the sol-gel autocombustion methods. The effect of the precursor used in the sol-gel autocombustion synthesis on the ferrite's microstructure was examined. The as-obtained powders were characterized by XRD, FTIR, SEM, and TG/DTA. All ferrite powders obtained from different organic precursors, after gel autocombustion, were pure spinel phase, without secondary phases. The average crystallite size, estimated from Scherrer equation, was the smallest for ferrite obtained from a mixture of fuels/precursors (citric acid and EDTA). This ferrite powder has sponge-like microstructure with large pores, but it is less agglomerated than the material obtained from glycine as the fuel. [ABSTRACT FROM AUTHOR]

The phase equilibria occurring in the ErPO-KPO system were investigated by the thermal analysis, FTIR, and X-ray powder diffraction methods. On the basis of obtained results, the related phase diagram is proposed. This system includes one intermediate compound, KEr(PO); the double phosphate melts incongruently at 1355 °C and occurs in two polymorphic forms; transformation β/α-KEr(PO) proceeds at 420 °C. The eutectic occurs at the composition of 58.5 wt% KPO, 41.5 wt% ErPO at 1317 °C. [ABSTRACT FROM AUTHOR]

The organic-inorganic coordination polymer of the general formula {[NiL][Co(NCS)]} (where L = 5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) has been synthesized and characterized by IR, UV-Vis, DSC/TG, DTA/TG/MS methods. The magnetic behaviour of this complex has also been investigated within the temperature range 1.8-300 K. The IR spectrum indicates the presence of bridging M-NCS-M′ ligands. The absorption bands of UV-Vis spectrum confirm that the coordination environment of nickel(II) ions changes from square planar for [NiL](ClO) to octahedral for {[NiL][Co(NCS)]}. The obtained compound is stable at room temperature, but within the range 246-282 °C decomposes in a three-stage process. The first step is associated with decomposition of the coordination polymer to the cationic [NiL] and anionic [Co(NCS)] units; the next two stages correspond to gradual decomposition of the macrocyclic ring. The value of molar magnetic susceptibility (χ T = 2.16 cm molK) indicates that the compound is paramagnetic. [ABSTRACT FROM AUTHOR]

Ce2O3-K2O-P2O5 ternary system has been investigated by thermoanalytical methods (DTA, DSC), powder X-ray diffraction, XPS and IR spectroscopy. The existence of three double potassium-cerium(III) phosphates has been confirmed and a new binary phosphate K4Ce2P4O15 has been found. Phase diagram and isothermal section at room temperature of the system Ce2O3-K2O-P2O5 have been presented. [ABSTRACT FROM AUTHOR]

Effect of the synthesis conditions of Pechini technique on crystallinity and purity of Na3Ce(PO4)2 compound was investigated. Nano-sized cerium-sodium phosphate obtained when EDTA was used as an additional chelating agent for Ln3+. The total enthalpy change of Na3Ce(PO4)2 phase transition was determined as 14.2±0.7 kJ mol−1 for sample synthesized by conventional solid-solid reaction. The phase transition process was confirmed to occur at 1060°C or in temperature range 920–1060°C depending on thermal treatment of powders. [ABSTRACT FROM AUTHOR]