Violeta Koleva

Violeta Koleva
Bulgarian Academy of Sciences | BAS · Institute of General and Inorganic Chemistry

Professor

About

95
Publications
15,160
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1,235
Citations
Citations since 2017
20 Research Items
549 Citations
2017201820192020202120222023020406080100
2017201820192020202120222023020406080100
2017201820192020202120222023020406080100
2017201820192020202120222023020406080100

Publications

Publications (95)
Article
To outline the role of dual-ion intercalation chemistry to reach sustainable energy storage, the present review aims to compare two types of batteries: widely accepted dual-ion batteries based on cationic and anionic co-intercalation versus newly emerged hybrid metal-ion batteries using the co-intercalation of cations only. Among different charge c...
Article
Full-text available
This study aims to quantify the synergistic effect of Ni2+ and Mn2+ ions on the capacitive performance of oxide, hydroxide and phosphate electrodes in alkaline electrolytes. Three types of phases containing both nickel and manganese in a ratio of one-to-one were selected due to their stability in alkaline media: oxides with ilmenite and spinel stru...
Article
This study reports an effective approach to improve dramatically the electrochemical performance of nanosized NaFePO4 with a maricite structure, which is commonly considered as electrochemically inactive due to the absence of structural channels for alkaline ions mobility. The approach is based on the complete oxidation at mild conditions (i.e. at...
Article
Full-text available
Polycrystalline samples of struvite-type MgRbAsO4·6H2O and MgTlAsO4·6H2O in both protiated and deuterated forms have been prepared for the first time by a precipitation method. Detailed analysis of their infrared (IR) and Raman (R) spectra recorded at room temperature (RT) and liquid nitrogen temperature (LNT) has been carried out and assignment of...
Article
Full-text available
Sodium manganese phospho-olivine, NaMnPO4, is considered to be a higher-voltage alternative to the presently used iron-based electrode material, NaFePO4, for sodium ion batteries. Irrespective of this advantage, the electrochemical performance of NaMnPO4 is still far from what is desired. Herein we provide the first report on the storage performanc...
Article
A new strategy for fabrication of binder- and carbon-free electrodes for Lithium ion batteries is demonstrated. The strategy is based on the employment of a nanoporous metallic structure as mechanically stable and conductive scaffold inside of which an active material is directly grown. The porous metallic structures with a pore size in the nanomet...
Article
The salts of dicarboxylic acids with alkaline earth metals are not very thoroughly studied and only a few such compounds are well known and characterized. In this work a detailed examination of the infrared spectra recorded at room temperature (RT) and at the liquid nitrogen boiling temperature (LNT) and Raman spectra (at room temperature) of the m...
Article
This study provides first data on the preparation of ammonium iron-manganese phosphates monohydrates, NH4Mn1-xFexPO4.H2O, with a dittmarite-type structure in the whole concentration range. The structure, Mn2+/Fe2+ distribution over 2a crystallographic site and morphology of the mixed dittmatite salts are assessed by means of powder X-ray diffractio...
Article
Full-text available
Fourier transform infrared (FT-IR) spectra recorded at room temperature (RT) and at the boiling temperature of liquid nitrogen (LNT), as well as Raman spectra recorded at room temperature for the cubic polymorph of magnesium cesium arsenate hexahydrate (MgCsAsO4·6H2O) and its partially deuterated analogues, were interpreted with respect to the norm...
Article
The energy storage by redox intercalation reactions is, nowadays, the most effective rechargeable ion battery. When lithium is used as intercalating agents, the high energy density is achieved at an expense of non-sustainability. The replacement of Li+ with cheaper monovalent ions enables to make greener battery alternatives. The utilization of pol...
Article
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Hybrid electrochemical supercapacitors supply a high energy density and reduced cycle stability. Herein, we provide new data on the effect of the Li+ and K+ ion from the aqueous alkaline electrolyte on the hybrid supercapacitor performance. The electrochemical cell is assembled by two dissimilar electrodes: AC versus α-Ni(OH)2 /AC composite. Two ty...
Article
Full-text available
The metal ions substituttion in phospho-olivines is an effective way for improving their performance as electrode materials in lithium ion and alternative sodium ion batteries. In this contribution, we examine in details the crystal structure of Mg-substituted NaMnPO4. The preferential occupancy of the alkaline M1 position by Mg2+ ions has been fou...
Article
Infrared and Raman spectra of Mg2KH(PO4)2·15H2O and Mg2KH(AsO4)2·15H2O and a series of their partially deuterated analogues were recorded and analyzed. Compounds of the type Mg2KH(XO4)2·15H2O (X = P, As) are little-known and a rare case of phosphate and arsenate salts containing dimer units [H(XO4)2] in the crystal structure. The analysis of their...
Article
Full-text available
Molten salt reactions between dittmarite-type NH4FePO4.H2O and different lithium eutectic compositions are systematically investigated in order to obtain at low temperature olivine-type LiFePO4 which is valuable electrode material for lithium-ion batteries. Nanosized LiFePO4 powder is successfully prepared by topotactic reactions using LiCl-LiOH eu...
Article
This study provides new data on the fabrication of hybrid battery-supercapacitor with an excellent cycling stability based on composites of α-Ni(OH)2 and activated carbon (AC). The α-phase, Ni(OH)2.0.3H2O, consists of charged Ni(OH)2-x layers, SO²⁻4 anions being intercalated in the interlayer spaces. The hydroxide has a mesoporous structure and con...
Article
Full-text available
In this work, we present first data on the infrared and Raman spectroscopic characteristics, thermal analysis and solid-state transformations of Mg2KH(AsO4)2·15H2O, which is a unique example of an acid salt containing dimeric units [H(AsO4)2] in its crystal structure. The infrared and Raman spectra recorded at ambient conditions have been studied,...
Article
In this contribution we provide novel data on the reversible lithium and sodium ions intercalation into a sodium-manganese phospho-olivine NaMnPO4, when it is used as a cathode in model lithium-ion cells. The ion-exchange reaction involving the participation of KMnPO4.H2O dittmarite as precursor was chosen for the preparation of NaMnPO4. The NaMnPO...
Article
Full-text available
In this work we investigated the isomorphic substitution and thermal decomposition of sedimentary fluor apatite (FAp) (with Ca/P ratio > 1.67) from Tunisia after high-energy-milling (HEM) activation at different times from 10 to 600 min. The chemical composition of the material includes: 29.6 % P2O 5total and 46.5 % CaO (main components) and 3.5 %...
Poster
Full-text available
Vanadium(V) oxide-based materials have the potential to broaden the color palette displayed by inorganic electrochromics, and thus to extend the range of their functions. The present contribution is focused on the electrochromic properties of thin films with compositions Na0.33V2O5·nH2O (n = 1 and 1.3) prepared by chemical bath deposition method. T...
Article
Full-text available
Abstract: Electrochromic sodium intercalated vanadium(V) oxide xerogels thin films with composition Na0.33V2O5∙H2O have been deposited on electroconductive FTO glass substrates by a simple chemical bath method. The deposition of the homogenous thin films is performed from an aqueous solution containing sodium metavanadate and diethyl sulfate at 85...
Article
The crystal structure of magnesium potassium arsenate hexahydrate, MgKAsO4·6H2O, was refined from powder diffraction data. MgKAsO4·6H2O crystallizes in the orthorhombic space group Pmn21 with Z = 2, as the biomineral struvite. Complete dehydration of MgKAsO4·6H2O proceeds in a single step, with one endothermic peak at 87.9 °C (Tonset). The infrared...
Poster
Full-text available
Vanadium oxide-based materials are very promising electrochromic materials since they have the potential to broaden the color palette displayed by inorganic electrochromics, and thus to extend the range of their functions. The one-stage chemical deposition on FTO substrates from a bath containing NaVO3 and (C2H5)2SO4 at 85 °C yields xerogel thin fi...
Article
Full-text available
We have demonstrated the capability of dittmarite-type precursors to act as structure and morphology directed agents for a facile synthesis of electrochemically active lithium manganese phospho-olivine nanostructures which are of interest as positive electrode materials for lithium ion batteries. Two types of compounds from the dittmarite series ar...
Article
Full-text available
A new and simple chemical method for deposition of thin films of ammonium intercalated V2O5·nH2O xerogels has been designed. The chemical deposition has been performed in aqueous solutions of ammonium metavanadate and acetic acid at temperatures between 50 and 85 °C. Depending on the vanadium concentration and deposition temperature xerogels with d...
Article
We have examined the influence of the deposition temperature and deposition time on the electrochromic activity of nanostructured (NH4)0.3V2O5·1.25H2O thin films prepared by the newly developed chemical bath deposition method. The film structure is characterized by XRD powder diffraction, IR spectroscopy, and TG-DTA techniques. SEM and AFM observat...
Article
Full-text available
The phase formation in the systems NH4MnPO4.H2O-LiCl-LiNO3 and NH4MnPO4.H2O-NaCH3COO.3H2O is systematically investigated in order to obtain at low-temperature olivine-type LiMnPO4 and NaMnPO4 which are of great interest as cathode materials for lithium and sodium ion batteries. The experimental conditions such as molar ratio between reagents, tempe...
Article
Full-text available
We report precursor-based methods for low-temperature synthesis of two structure modifications of NaMnPO4. The maricite phase is thermodynamically more stable, while the olivine phase is of great interest as a positive-electrode material for lithium and sodium ion batteries. The advantage of synthetic procedures is the formation of defectless NaMnP...
Poster
Full-text available
Abstract: Electrochromic sodium intercalated vanadium(V) oxide xerogels thin films with composition Na0.33V2O5∙H2O have been deposited on electroconductive FTO glass substrates by a simple chemical bath method. The deposition of the homogenous thin films is performed from an aqueous solution containing sodium metavanadate and diethyl sulfate at 85...
Poster
Full-text available
Vanadium(V) oxide xerogels are promising materials for application in different electrochromic devices. The present contribution is focused on the effect of thermal annealing at 250 and 400 ºC on the electrochromic properties of as-deposited Na0.33V2O5∙H2O thin films. The structure and morphology of the annealed films is examined by XRD, IR spectro...
Article
Full-text available
Infrared and Raman spectra of cubic magnesium caesium phosphate hexahydrate, MgCsPO4·6H2O (cF100),and its partially deuterated analogues were analyzed and compared to the previously studied spectraof the hexagonal analogue, MgCsPO4·6H2O (hP50). The vibrational spectra of the cubic and hexagonal dimorphic analogues are similar, especially in the reg...
Article
Full-text available
The infrared, far-infrared and Raman spectra of acid phosphate salts of the type M(H2PO4)2·2H2O (M = Mg, Mn, Co, Ni, Zn, Cd) in both protiated and deuterated forms have been recorded at ambient and liquid nitrogen temperature. The vibrational spectra have been interpreted with respect to the vibrations of the H2PO4− ions. Strong vibrational couplin...
Article
A new chemical method for fast deposition of electrochromically active thin films of birnessite-type potassium manganese oxide (K0.27MnO2·xH2O) has been developed. The chemical deposition has been performed at room temperature by a reaction of aqueous solutions of potassium permanganate and manganese(II) chloride. The prepared thin films have thick...
Article
Full-text available
The infrared and Raman spectra of protiated and deuterated crystalline Co(H2PO4)2·2H2O are presented and discussed with respect to the internal vibrations of the H2PO4− ions, the OH stretching vibrations and the water librations. A detailed interpretation of the vibrational spectra is proposed on the basis of the isotopic and temperature shifts of...
Article
Full-text available
Thin yellow-orange films of sodium vanadium oxide bronzes have been prepared from a sodium–vanadium solution (1:1) at 75 °C and pH = 3. The composition, structure and morphology of the films have been studied by XRD, IR spectroscopy, TG and SEM–EDX analyses. It has been established that the prepared films are a phase mixture of hydrated NaV6O15 (pr...
Article
Vibrational Spectroscopy j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / v i b s p e c a b s t r a c t The IR spectra of natural Tunisian phosphorite before and after high energy milling recorded at ambient and liquid nitrogen temperatures are presented and thoroughly interpreted in respect to the vibrations of the m...
Article
Full-text available
LiFe1−x Mn x PO4 solid solutions in the whole concentration range (0≤x≤1) are obtained at 500°C by a phosphate–formate precursor method. The method is based on the formation of homogeneous lithium–iron–manganese phosphate–formate precursors by freeze-drying of aqueous solutions containing Li(I), Fe(II), Mn(II), phosphate, and formate ions. Thermal...
Presentation
Electrochromic thin films were deposited on electroconductive FTO - layered glass substrates using dip coating method. Substrates were subsequently immersed in aqueous solutions of MnCl2 and KMnO4 in order to obtain thin films with different thicknesses. The obtained thin films were characterized using several methods. X-ray investigations were mad...
Article
Full-text available
The infrared and Raman spectra of magnesium rubidium phosphate hexahydrate MgRbPO4 • 6H2O and magnesium thallium phosphate hexahydrate, MgTlPO4 • 6H2O were recorded at room temperature (RT) and the boiling temperature of liquid nitrogen (LNT). To facilitate their analysis, also recorded were the spectra of partially deuterated analogues with varyin...
Article
Full-text available
Dittmarite-type compound KMnPO(4)·H(2)O was used as a new precursor for the synthesis of nanostructured LiMnPO(4) phospho-olivines with a plate-like morphology at low temperature (about 200 °C) and a short reaction time (90-180 min). The dehydration of KMnPO(4)·H(2)O was studied by DTA and TG analysis. Structural and morphological characterization...
Article
Full-text available
Single phases of olivine-type LiCoPO4 and LiNiPO4 were synthesized by thermal treatment of homogeneous lithium–metal–phosphate–formate precursors obtained by freeze drying of aqueous solutions of the corresponding metal formates and LiH2PO4. The structure, thermal behavior, and morphology of the precursors were studied by IR spectroscopy, DTA, and...
Article
The electrochemical performance of carbon-coated nanocrystalline LiFePO 4 prepared by a freeze-drying method is examined. This method is based on the thermal decomposition of homogeneous phosphate-formate precursors. Structural and morphological characterization of LiFePO 4 is carried out by powder XRD, BET measurements, SEM and XPS analyses. The e...
Article
The preparation of homogeneous phosphate–formate precursors by freeze-drying of solutions containing lithium, Mn(II), phosphate and formate ions ensures production of stoichiometric, well crystallized, defectless and nano-sized LiMnPO4 powders at temperatures above 400◦C. A systematic study of the influence of the synthesis conditions on the structu...
Article
High-pressure modification of LiNiPO4 with a Na2CrO4-type structure was obtained at ambient pressure and low temperature from a mixed LiNi–phosphate–formate precursor, LiNiPO4Hx(HCOO)x·yH2O (where x ≈ 1.2 and y ≈ 2.5). The structural and thermal characterization of the precursor and the LiNiPO4 compositions were carried out by powder XRD analysis,...
Article
Mixed phosphate-formate precursors, LiFePO4Hx(HCOO)x·yH2O (x ∼ 1, 1 < y < 1.3 and x < y), were prepared by freeze-drying of solutions containing Li+, Fe2+, PO43− and HCOO− in a ratio of 1:1:1:2. Fe(HCOO)2·2H2O was used as an iron source. The concentration of the freeze-dried solutions allows affecting the morphology of phosphate-formate precursors....
Article
The Fourier transform infrared and Raman spectra of the struvite analogue, hexagonal magnesium caesium phosphate hexahydrate, MgCsPO4·6H2O (hP50) and of its partially deuterated analogues were recorded from room temperature (RT) down to the boiling temperature of liquid nitrogen (LNT). The existence of strong hydrogen bonds between water molecules...
Article
Full-text available
Infrared and Raman spectra of Mn(H2PO4)2·2H2O and of series of deuterated analogues recorded at room temperature (RT) and at the boiling temperature of liquid nitrogen (LNT) have been presented and analyzed with respect to the OH vibrations. In the OH stretching mode region ABC bands behaviour is observed in accordance with the structural data for...
Article
Infrared and Raman spectra of Mn(H2PO4)2·2H2O and of series of deuterated analogues recorded at room temperature (RT) and the boiling temperature of liquid nitrogen (LNT) have been presented and analyzed in detail in respect to the internal vibrations of the H2PO4- ions and the external modes of the water molecules. Some vibrational couplings of th...
Article
The compounds M[PO2(OH)2]2·2H2O (M=Mg, Mn, Fe, Co, Ni, Zn, Cd) were prepared from super-saturated aqueous solutions at room temperature. Single-crystal X-ray structure investigations of members with M=Ni, Zn, Cd were performed at 295 and 120K. The space-group symmetry is P21/n, Z=2. The unit-cell parameters are at 295/120K for M=Ni: a=7.240(2)/7.20...
Article
The IR and Raman spectra of the isostructural M'M''PO4.H2O compounds (M'=K+, NH4+; M''=Mn2+, Co2+, Ni2+) are reported and discussed with respect to the normal vibrations of the PO(4)3- ions. The vibrational behavior of PO4(3-) is in agreement with its low site symmetry Cs in the lattices-the symmetric nu1 and nu2 modes are activated in the IR spect...
Article
It has been established that M(H2PO4)2·2H2O (M = Mn, Co, Ni) are paramagnetics between 173 and 353 K with weak antiferromagnetic exchange interaction between the metal ions. In situ magnetic measurements during the thermal decomposition of the salts show that the oxidation state and the octahedral coordination of M2+ are preserved. From the data ob...
Article
The vibrational behavior of the uncoupled nu(OD) modes and of the water librations in dittmarite-type compounds M'M''PO4.H2O (M'=K+, NH4+; M''=Mn2+, Co2+, Ni2+) is analyzed in terms of the influence of two types of metal-water interactions (M+-H2O and M2+-H2O), the hydrogen bonding and the repulsion potential of the lattices. The M+-H2O interaction...
Article
Full-text available
The IR and Raman spectra of calcium hydrogen triacetate monohydrate, CaH(CH3COO)3 · H2O, (Speakman’s classification: B type acid salt) in the 4000-400 cm–1 frequency region are presented and discussed with respect to the fundamental vibrations of acetic acid species (CH3COO– and CH3COOH) and hydrogen bond vibrations due to both hydroxyl groups of C...
Article
BeSeO4.2H2O and BeSeO4 have been studied röntgenographically: BeSeO4.2H2O forms orthorhombic crystals with lattice constants: a = 5.843(2) Å; b = 9.790(3) Å; c = 4.692(1) Å; V = 268.4(1) Å3. The crystals of BeSeO4 are tetragonal: a = 4.648(1) Å; c = 7.084 (3) Å; V = 153.1(1) Å3, SG I. The thermal dehydration of BeSeO4.4H2O has been studied by TG, D...
Article
The infrared spectra of related compounds with kröhnkite-type chains Na2Me(SeO4)2·2H2O (Me=Mn, Co, Ni, Cu, Zn, Cd) containing matrix-isolated SO42− guest ions are reported and discussed with respect to the SO stretching modes ν3 and ν1. Due to the low site symmetry C1 of the SO42− guest ions three bands for ν3 and one band for ν1 are seen in all s...
Article
The infrared spectra of related compounds with kröhnkite-type chains Na2Me(XO4)2·2H2O (Me=Mn, Co, Ni, Cu, Zn, Cd, and X=S, Se) containing matrix-isolated X′O42− guest ions and HDO molecules are presented and discussed in the region of the OD stretching modes. The strength of the hydrogen bonds formed in the compounds under study are discussed in te...
Article
Full-text available
Synthetic malachite, hydrozincite and five monophasic mixed copper-zinc hydroxycarbonates have been studied by Fourier transform infrared (FTIR) spectroscopy at ambient and liquid nitrogen temperature in the region of 4000-400 cm(-1). The analysis of the spectra reveals that the samples containing up to 20% zinc retain the malachite lattice, thus f...
Article
We have investigated the vibrational behavior of the S–O stretching modes ν3 and ν1 of the matrix-isolated SO42− guest ions isomorphously incorporated in selenate matrices of different crystal structure types: MeSeO4·6H2O (Me=Mg, Co, Ni, Zn), MeSeO4·5H2O (Me=Mn, Co, Cu, Zn) and MeSeO4·4H2O (Me=Co, Ni). The spectra of the SO42− guest ions exhibit le...
Article
The infrared and Raman spectra of Mg(CH3COO)2·4H2O, Zn(CH3COO)2·2H2O and the double salt MgZn(CH3COO)4·4H2O have been recorded and discussed with respect to the internal modes of the acetate ions and the water molecules. MgZn(CH3COO)4·4H2O crystallizes in the triclinic system with lattice parameters: a=10.441(3)Å,b=10.353(3)Å,c=8.949(3)Å,α=105.67(2...
Article
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The surface changes of alumina due to supported nickel oxide species (samples are prepared by step-wise pore volume impregnation with formate solutions) are studied in the high frequency region (OH stretches) by the method of in situ FTIR spectroscopy. A hypothesis is made that the nickel species deposite predominatingly on the surface neutral OH g...
Article
The infrared (IR) spectra of Co(HCOO)2 x 2H2O, Ni(HCOO)2 x 2H2O and Cu2Co(Ni)1-x (HCOO)2 x 2H2O mixed crystals (0 < x < or = 0.5) have been recorded and the internal modes of the formate groups and the water molecules are discussed. The analysis of the spectra of the mixed crystals reveals that when copper ions replace cobalt and nickel ions in Co(...
Article
The infrared spectra of isotopically dilute (matrix-isolated HDO molecules) isostructural compounds M(HCOO) 2·2H 2O (M=Mn,Fe,Co,Ni,Zn,Cu) are presented and discussed in the region of the OD stretching modes. According to the structural data the compounds under study are divided into two groups: in M(HCOO) 2·2H 2O (M=Mn,Ni,Zn) the H 2O(1) molecules...
Article
The infrared (IR) spectra of Mg(HCOO)2·2H2O and Mg1−xCux(HCOO)2·2H2O mixed crystals (00) evidences for the formation of linear hydrogen bonds. The IR spectra of Mg1−xCux(HCOO)2·2H2O mixed crystals show that the regions of 3200–3400cm−1 (νOH), 2300–2500cm−1 (νOD of matrix-isolated HDO), 500–950cm−1 (water librations) are mostly sensitive to the coor...
Article
The thermal dehydration of copper and manganese selenate hydrates has been studied by TG, DTA and DSC. The enthalpies of dehydration stages as well as the enthalpies of formation of CuSeO4·5H2O, CuSeO4·H2O, MnSeO4·5H2O, MnSeO4·2H2O and MnSeO4·H2O have been determined. The comparatively lower temperature of CuSeO4·H2O dehydration as compared to the...
Article
Full-text available
A strong chromatographic effect has been established during copper-managenese formate impregnation of γ-Al2O3. The samples obtained have been characterized by adsorption, IR, X-ray and magnetochemistry methods.
Article
It has been established that two series of mixed crystals are formed in the Cu(HCOO) 2-Mn(HCOO) 2-2H 2O system at 25°C. The thermal decompositions of Cu xMn 1- x(HCOO) 2·2H 2O mixed crystals (0≤ x≤0.5) have been studied. On the basis of the methods used (TG, DTA, and X-ray diffraction analysis), it has been established that homogeneous and heteroge...
Article
The dehydration of CoSeO4·6H2O, CoSeO4·5H2O CoSeO4·4H2O and CoSeO4·H2O has been studied by TG and DTA and DSC. The dehydration of CoSeO4·6H2O occurs in steps and intermediate hydrates CoSeO4·5H2O, CoSeO4·4H2O, CoSeO4·2H2O and CoSeO4·H2O are formed. The enthalpies of dehydration of the observed dehydration processes have been determined. The enthalp...
Article
The infrared spectra of Ba2Cu(HCOO)6·4H2O and its deuterated analogues have been recorded and the internal modes of the formate groups and water molecules are reported. Some of the internal formate modes (v4, v3 and v2) reflect the existence of three crystallographically independent formate ions. The frequency separations between the asymmetric and...
Article
The thermal dehydration of NiSeO4·6H2O, NiSeO4·4H2O and NiSeO4·H2O has been studied by TG, DTA and DSC. The dehydration of NiSeO4·6H2O depends on both the heating rate and the sample mass. The following intermediate hydrates are produced: NiSeO4·5H2O; NiSeO4·4H2O; NiSeO4·2H2O; NiSeO4·H2O and NiSeO4·0.5H2O. The enthalpies of dehydration of these sta...
Article
It has been established that the double salts Ba2Me(HCOO)6. 4 H2O (Me = Co, Ni, Zn) are isostructural with Ba2Cu(HCOO)6. 4 H2O (trinclinic space group P1 = C1i). The infrared spectra of the double salts and their deuterated analogues have been recorded and the internal modes of the formate groups and the water molecules are reported. The analysis o...
Article
The thermal dehydration of MgSeO4·6H2O, MgSeO4·4H2O and MgSeO4·2H2O has been studied by TG, DTA and DSC. The dehydrations occur in steps and the intermediate hydrates MgSeO4·5H2O, MgSeO4·4H2O, MgSeO4·2H2O and MgSeO4·H2O are produced. The enthalpies of dehydration of the observed stages have been determined. The enthalpies of formation of MgSeO4·6H2...
Article
The thermal dehydration of ZnSeO4 · 6 H2O, ZnSeO4 · 5 H2O, and ZnSeO4 · 3 H2O has been studied by TG, DTA, and DSC-analyses. It has been established that the dehydration of ZnSeO4 · 6 H2O occurs stepwise and as intermidiate hydrates ZnSeO4 · 5 H2O, ZnSeO4 · 3 H2O and ZnSeO4 · H2O are produced. The enthalpy of dehydration of the observed phase trans...
Article
The dehydration of MgSeO4. 6 H2O has been studied using an X-ray powder diffraction method at elevated temperatures. Five different solid phases have been identified in the temperature interval of 20–450 °C: MgSeO4. 6 H2O; MgSeO4. 5 H2O (with a small amount of MgSeO4. 4 H2O), MgSeO4. 2 H2O, amorphous MgSeO4 and crystalline MgSeO4. MgSeO4. 5 H2O cry...
Article
Full-text available
A DTA and DSC study was made of the thermal dehydration and decomposition of Mg(IO3)2·4H2O and Mg(IO3)2·4D2O. The data obtained show that the dehydration takes place in one stage. The ΔH deho obtained were used to calculate ΔH fo, and comparisons were made with the literature data. It was confirmed that the thermal decomposition passes through an...