Diana Nihtianova - Academia.edu (original) (raw)

Papers by Diana Nihtianova

Materials Today: Proceedings, 2022

European Journal of Pharmaceutical Sciences, 2020

Batteries & Supercaps, 2020

The integration of sodium‐ion batteries into large‐scale energy storage systems will become feasi... more The integration of sodium‐ion batteries into large‐scale energy storage systems will become feasible in the case when their performance becomes less sensitive towards ambient temperature. Herein, we demonstrate the elaboration of the oxide‐based electrode material with an optimized layered structure and composition that is designed to work at elevated temperatures. Through selective substitution of Mg2+ ions for Ni2+ in the three‐layered oxide, P3‐Na2/3Ni1/2Mn1/2O2, the oxidation state of Ni ions, the cationic distribution in the layers, the sodium intercalation capacity, and the rate capability is manipulated. The electrochemical behavior of P3‐Na2/3Ni1/3Mg1/6Mn1/2O2 is discussed on the basis of ex situ diffraction as well as microscopic and spectroscopic methods in terms of redox activity of the lattice oxygen, the reversible transfer of Mg2+ and Ni2+ ions between layers during Na+ intercalation, thermal stability of cycled electrodes, and surface reactivity of the layered oxide t...

Inorganics, 2020

Magnesium-based materials are promising as hydrogen storage media due to their high theoretical h... more Magnesium-based materials are promising as hydrogen storage media due to their high theoretical hydrogen absorption capacity, abundance and low price. The subject of this study are the hydrogen sorption characteristics of the composites 80 wt % MgH2-15 wt % Ni-5 wt % activated carbon (synthesized from polyolefin wax, a waste product of polyethylene production at low pressure which will be denoted further in the text as POW) and 90 wt % MgH2-5 wt % Ni-5 wt % POW, prepared by ball milling under argon atmosphere. Structure, phase and surface composition of the samples before and after hydrogenation are determined by XRD and TEM. The maximum absorption capacity value of the composites at a temperature 573 K and after 60 min. of hydrogenation are 5.3 wt % H2 for the material with higher Ni content and 5.5 wt % H2 for the other sample. The presence of both additives—nickel and activated carbon derived from POW—has a positive impact on hydrogenation kinetics and the capacity achieved. The ...

Dalton Transactions, 2019

The co-intercalation of Li+ and Mg2+ into magnesium manganates and lithium titanates allow using ... more The co-intercalation of Li+ and Mg2+ into magnesium manganates and lithium titanates allow using them as electrodes in hybrid Li–Mg ion cells with conventional lithium electrolyte.

Chemical Engineering Journal, 2019

Complex study of the activity, stability and sulfur resistance of Pd/La 2 O 3-CeO 2-Al 2 O 3 syst... more Complex study of the activity, stability and sulfur resistance of Pd/La 2 O 3-CeO 2-Al 2 O 3 system as monolithic catalyst for abatement of methane,

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018

In this work colloidal gold nanoparticles (GNPs) are prepared using a citrate-reduction route, in... more In this work colloidal gold nanoparticles (GNPs) are prepared using a citrate-reduction route, in which citric acid serves as reductive agent for the gold precursor HAuCl4. We demonstrate that a temperature variation on the one hand enables to tune the reaction rate of GNP formation and on the other hand allows modifying the morphology of the resulting metal nanoparticles. The use of chitosan, a biocompatible and biodegradable polymer with a multitude of functional amino and hydroxyl groups, facilitates the simultaneous synthesis and surface modification of GNPs in one pot. The resulting GNPs, which are stabilized by a network of chitosan and ß-ketoglutaric acid units, are characterized by UV-vis spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) as well as fluorescence correlation spectroscopy (FCS) and reveal an average diameter of about 10 nm at the end of the synthesis. The kinetics of GNP formation is studied by calculating

Journal of Solid State Chemistry, 2017

The present contribution provides new structural and spectroscopic data on the formation of solid... more The present contribution provides new structural and spectroscopic data on the formation of solid solutions between hydrated and dehydrated sulfate salts of sodium-nickel and sodium-manganese in a whole concentration range: Na 2 Ni 1-x Mn x (SO 4) 2 •yH 2 O, 0 d x d 1.0. Using powder XRD, electron paramagnetic resonance spectroscopy (EPR), IR and Raman spectroscopy it has been found that double sodium-nickel and sodium-manganese salts form solid solutions Na 2 Ni 1x Mn x (SO 4) 2 •4H 2 O with a blödite-type of structure within a broad concentration range of 0 d x d 0.49, while the manganese rich compositions Na 2 Ni 1-x Mn x (SO 4) 2 •2H 2 O (0.97 d x d 1.0) crystallize in the kröhnkite-type of structure. The Ni-based blödites Na 2 Ni 1-x Mn x (SO 4) 2 •4H 2 O dehydrate between 140 and 260 o C into anhydrous salts Na 2 Ni 1-x Mn x (SO 4) 2 , 0 d x d 0.44, with a structure where Ni 1-x Mn x O 6 octahedra are bridged into pairs by edge-and corner sharing SO 4 2groups. Both TEM and EPR methods show that the Ni 2+ and Mn 2+ ions are homogenously distributed over three crystallographic positions of the large monoclinic cell. The dehydration of the kröhnkite phase Na 2 Ni 1-x Mn x (SO 4) 2 •2H 2 O yields the alluaudite phase Na 2+G Mn 2-G/2 (SO 4) 3 , where the Na-to-Mn ratio decreases and all Ni 2+ dopants are released from the structure. The process of the dehydration is discussed in terms of structural aspects taking into account the distortion degree of the Ni,MnO 6 and SO 4 polyhedra.

Topics in Catalysis, 2016

Alumina supported Cu-Mn mixed oxide with Cu/Mn molar ratio 2:1 was used as a support of gold and ... more Alumina supported Cu-Mn mixed oxide with Cu/Mn molar ratio 2:1 was used as a support of gold and silver catalysts for oxidation of CO, methanol and dimethylether. Different techniques (XRD, HRTEM, XPS, FTIR, EPR, and TPR) were used to investigate structurereactivity relationship. A strong effect of the nature of the promoters on the catalytic behaviour was observed. Superior catalytic activity in oxidation of CO was measured after addition of Au, while modification by Ag affected very slightly the CO oxidation activity of Cu/Mn 2:1 sample. Both Au and Ag have beneficial effect on CH 3 OH oxidation activity of Cu-Mn mixed oxides. The combination of the good redox properties of Cu-Mn mixed oxides and gold nanoparticles has proved to be an advantageous approach for developing new catalytic formulations with high effectiveness to eliminate different type pollutants in waste gases from formaldehyde production. The use of high surface area support is beneficial for the stabilization of gold particles in a highly dispersed state and contributes for economic viability in case of practical applications, because of the composition of this catalytic system, that is mostly alumina (80%).

The Journal of Physical Chemistry C, 2017

Sodium-deficient nickel-manganese oxides with a layered type of structure are, nowadays, of great... more Sodium-deficient nickel-manganese oxides with a layered type of structure are, nowadays, of great interest as electrode materials for both lithium-and sodium-ion batteries, since they are able to intercalate lithium and sodium ions reversibly within a broad concentration range. Herein we report new data on the effects of the particle sizes and of the electrolyte salt on the intercalation properties of Na 2/3 Ni 0.5 Mn 0.5 O 2 with a P3-type of structure. The morphology of layered Na 2/3 Ni 0.5 Mn 0.5 O 2 oxides has been varied by changing the type of the precursor used: from Na-Ni-Mn acetates to Na-Ni-Mn mixed nitrate-acetates. The structure, particle dimensions

Journal of Polymer Research, 2016

Hybrid fillers have been prepared by impregnation of conductive carbon black with different amoun... more Hybrid fillers have been prepared by impregnation of conductive carbon black with different amounts of silicasol, equivalent to 3 % and 7 % silica, respectively. The fillers have been characterized and their effect upon the microwave properties of natural rubber based composites has been also investigated. The results obtained show that, the silica (dielectric) phase is distributed both over the surface and inside the carbon black aggregates (conductive phase). Thus, the interaction between the particles of the conductive filler (building of conductive pathways) is restricted. It has been established that the microwave properties studied are dependent on the ratio between the filler's phases. The composites filled with the hybrid filler comprising the highest amount of silica possess the best total shielding effectiveness and absorptive shielding effectiveness. In all cases absorption is the mechanism prevailing in effectiveness. Thus, the fillers obtained allow an easy control and tailoring of the elastomer based electromagnetic interference shielding materials. The investigations carried out reveal the good potential of the composites studied for finding applications as antennas, automobiles, sensors and military-related applications.

$Research paper thumbnail of Structural insights intoM2O–Al2O3–WO3(M= Na, K) system by electron diffraction tomography$

Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, 2015

TheM2O–Al2O3–WO3(M= alkaline metals) system has attracted the attention of the scientific communi... more TheM2O–Al2O3–WO3(M= alkaline metals) system has attracted the attention of the scientific community because some of its members showed potential applications as single crystalline media for tunable solid-state lasers. These materials behave as promising laser host materials due to their high and continuous transparency in the wide range of the near-IR region. A systematic investigation of these phases is nonetheless hampered because it is impossible to produce large crystals and only in a few cases a pure synthetic product can be achieved. Despite substantial advances in X-ray powder diffraction methods, structure investigation on nanoscale is still challenging, especially when the sample is polycrystalline and the structures are affected by pseudo-symmetry. Electron diffraction has the advantage of collecting data from single nanoscopic crystals, but it is frequently limited by incompleteness and dynamical effects. Automated diffraction tomography (ADT) recently emerged as an alter...

European Powder Diffraction Conference; August 2010, Darmstadt, Germany, 2011

J. Mater. Chem. A, 2014

The capability of sodium deficient nickel manganese oxides to participate in reactions of Li+inte... more The capability of sodium deficient nickel manganese oxides to participate in reactions of Li+intercalation and Na+/Li+exchange allows their use as low-cost electrode materials in lithium cells.

Three different synthesis techniques were applied in order to prepare ZnO powder samples with dif... more Three different synthesis techniques were applied in order to prepare ZnO powder samples with different crystallite size. The first method is thermal decomposition of Zn(NO 3) 2 .6H 2 O. The second synthesis method is a sucrose-assisted solution combustion method. The third technique used is ultrasound assisted precipitation. A short-time thermal treatment is used to obtain ZnO materials with the required mean crystallite size. Materials were studied by means of powder XRD and TEM. The detailed morphology of the materials was first studied by XRD utilizing the special features of Fullprof program. This study revealed that different synthesis methods lead to products with different morphology. Materials obtained by the first method have an average crystallite size of 130-150 nm with irregular but isometric shape of the crystallites, while those obtained by the second method are almost spherical particles with size of about 30-40 nm. Regardless of the similar average crystallite size of the material obtained by the third method, its morphology is spindle-like, derived from different broadening of the XRD lines. The results from XRD analyses were confirmed by TEM observations. The influence of crystal morphology on the performance of ZnO as a main active material in zinc electrodes is discussed.

New perovskite-based compounds with general formula PbBaFe 2-x Mn x O 5 id-state reaction under a... more New perovskite-based compounds with general formula PbBaFe 2-x Mn x O 5 id-state reaction under argon atmosphere. The compounds were characterized by X-ray powder diffraction, TEM (SAED) and 57 Fe Mössbauer spectroscopy. The crystal structure of PbBaFeMnO 5 and PbBaFe 0.5 Mn 1.5 O 5 members of the series is determined by Rietveld refinement method. The basic crystallographic sections in orientations [100] and [010] are obtained by SAED method. The Rietveld refinement results are in good agreement with the SAED data. The compounds crystallize in the orthorhombic space group Pnma with unit cell parameters p , p , and p (a p-the parameter of the perovskite subcell). The crystal structure of the studied phases consists of perovskite blocks separated by ½[110] p (-101) p (p-the perovskite subcell) crystallographic shear planes. Inside the blocks the octahedral B-position is occupied by Fe 3+ and Mn 3+ ions and the twelve coordinated A-position is fully occupied by Ba 2+ ions. The perovskite blocks are connected to each other by double chains of edge-sharing (Fe, Mn)O 5 distorted tetragonal pyramids running along the b-axis. The double chains delimit six-sided tunnels fully occupied by Pb 2+ cations. The pyramidal chains adopt two mirror-related configurations ("left" L and "right" R) and layers consisting of chains of the same configuration alternate along the c-axis in-L-R-L-R-sequence. The Mössbauer spectroscopy reveals a transition from magnetic ordering to paramagnetic state in PbBaFe 1.5 Mn 0.5 O 5 at room temperature with the substitution of Fe 3+ by Mn 3+ cations. The measurements at 77 K show that the Mn 3+ cations replace the Fe 3+ cations for the octahedral (1) and the pyramidal (2) sites in equal proportions.

CrystEngComm, 2014

ABSTRACT We have demonstrated the capability of dittmarite-type precursors to act as structure an... more ABSTRACT 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 are considered: potassium and ammonium manganese phosphate monohydrates, M′MnPO4·H2O (M′ = K, NH4). Both KMnPO4·H2O and NH4MnPO4·H2O precursors interact with the eutectic LiCl–LiNO3 composition before its melting, leading to the formation of the target LiMnPO4. The reaction of KMnPO4·H2O with LiCl–LiNO3 takes place by a topotactic mechanism including a fast ion exchange of K+ for Li+ and H2O release, as a result of which nanostructured LiMnPO4 is formed. The NH4MnPO4·H2O precursor reacts with the lithium salts by massive evolution of H2O, NH3, NO and N2O gasses, resulting in fragmentation of the pristine plate-like aggregates into well-shaped and dispersed particles with nanosizes of about 20–50 nm.