Dragomir Tatchev

Dragomir Tatchev
Bulgarian Academy of Sciences | BAS

About

54
Publications
9,415
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
830
Citations
Citations since 2017
18 Research Items
357 Citations
2017201820192020202120222023020406080
2017201820192020202120222023020406080
2017201820192020202120222023020406080
2017201820192020202120222023020406080
Introduction
Skills and Expertise

Publications

Publications (54)
Article
Full-text available
We report on a new approach toward a laser-assisted modification of biocompatible polydimethylsiloxane (PDMS) elastomers relevant to the fabrication of stretchable multielectrode arrays (MEAs) devices for neural interfacing technologies. These applications require high-density electrode packaging to provide a high-resolution integrating system for...
Article
A simple, alternative, catalyst preparation method was proposed in order to combine the properties of photoactive and stable TiO2 with state-of-the art of IrO2 for the oxygen evolution reaction (OER). IrO2 nanoparticles were obtained in the process of photodeposition on the surface of TiO2 powder by UV illumination from appropriate Ir salt aqueous...
Article
Full-text available
In this study two hybrid organic–inorganic ureasilicate monomers with different length of polymer segments were chosen for preparation of sol–gel material that includes two moieties blended on the molecular scale. The first monomer was obtained by crosslinking a double terminated polyoxyalkyleneamine with an isocyanate modified silicone ethoxide an...
Preprint
The Sari\c{c}i\c{c}ek howardite meteorite shower consisting of 343 documented stones occurred on 2 September 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sari\c{c}i\c{c}ek experienced a complex cosmic ray exposure history, exposed during ~12-14 Ma in a regolith near the surface of a parent asteroid, and t...
Chapter
Full-text available
The subsequent synthesis of sintered self-glazed glass-ceramics and/or glass-ceramic foams using metallurgical slag is the topic under discussion. The observed intensive sample expansion can be considered as an autocatalytic process related to the oxygen release due to thermal reduction of Fe2O3 and MnO2 present in the slag. The sintering of the sa...
Preprint
Full-text available
Herein we report on a detailed investigation of the irreversible capacity in the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl3) as electrolyte. The reaction mechanism, involving the intercalation of AlCl4 in graphite, has been fully characterized...
Article
Full-text available
The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on September 2, 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic‐ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m siz...
Article
Full-text available
Combining X-ray Absorption Fine Spectroscopy (XAFS) with Anomalous Small-Angle X-ray Scattering (ASAXS) determines the location of Cu ²⁺ ions in silicoaluminophosphate (SAPO-5) frameworks prepared by hydrothermal crystallization or impregnation. As expected, for the hydrothermally prepared sample, incorporation in the SAPO-5 framework was observed....
Article
Full-text available
Herein we report on a detailed investigation of the irreversible capacity of the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1-ethyl-3-methylimidazolium chloride: aluminum trichloride (EMIMCl:AlCl3) as electrolyte. The reaction mechanism, involving the intercalation of AlCl4- in graphite, has been fully characterize...
Poster
Full-text available
The research is focused on fundamental study of processes and effects of interaction of short and ultra-short laser irradiation with optical transparent nanocomposite biocompatible polymers. Laser generation from ultraviolet to near infrared regions of the spectrum is applied. The high optical transparency of the biopolymers in this range and the r...
Article
Full-text available
Electroless deposited ternary alloys have been reviewed in relation to the chemical state of the third element, its localisation and the possible influence of these on alloy properties. Three types of electroless Ni–W–P, Co–W–P and Ni–Zn–P coatings have been investigated. Low P deposits are nanocrystalline and those with higher P content are amorph...
Chapter
Transparent organic-inorganic ureasilicate materials (ureasils) were synthesized by hydrolysis and co-condensation of two organic – inorganic precursors, obtained by reactions between 3-isocyanatepropyltriethoxysilane (ICPTES) and double terminated polyetheramine (Jeffamine), and between ICPTES and 3-aminopropyl triethoxysilane (APTES), respectivel...
Poster
PDMS was structured by Nd:YAG laser for creating functionalized surfaces which could be used to build up microelectrode arrays.
Article
The structure of Au–Co and Au–Ni alloy coatings deposited at low current density (2–20 mA cm⁻²) from weakly acidic additive-free electrolyte with higher (16–20 g L⁻¹ Co or Ni) than usually employed (0.1–1.0 g L⁻¹) concentration of the alloying element was investigated. Under these conditions, structural effects in the coatings were observed represe...
Article
Highly ordered TiO2 nanotube arrays (TNTA) have attracted much attention due to the excellent photocatalytic, optical and electrical properties. However, their absorption range is limited to ultraviolet (UV) spectrum only due to the wide band gap (3.2 eV). One of the strategies to overcome this problem is doping with boron and nitrogen. They are pr...
Poster
A simplified approach is applied to produce B,N-co-doped TNTA. It consists in combining the electrochemical boron doping method with subsequent annealing in N2 atmosphere. This method is environment-sparing compared with ammonia atmosphere. It is handier and less expensive than many others methods to implant nitrogen in TNTA.
Article
Full-text available
Observations of the interaction of poly(dimethylsiloxane) (PDMS) sheet (210 μm thick) with KrF excimer laser irradiation (λ = 248 nm), with low energy of 50 mJ/pulse are presented. The negative ablation or swelling of the material caused by low frequency pulse irradiation is characterized by optical microscopy, μ-Raman spectrometry and X-ray micro-...
Article
Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na2O–62.9SiO2–8.5MnO–15.0Fe2O3−x (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on the...
Article
Fe–Mn–O magnetic nanocrystals precipitate in a glass system SiO2/Na2O/Fe2O3/MnO during thermal annealing for different periods of time. We report here small angle neutron scattering investigations using polarized neutrons (pSANS) on these glass samples. Analysis of scattering data reveals the formation of spherical core–shell particles. The core of...
Article
The present work reports the structural analysis of magnetic nanocrystals of Fe‐ and Mn‐containing phases formed during annealing of the glass 13.6Na2O–62.9SiO2–8.5MnO–15.0Fe2O3−x (mol%) at 823 K for different periods of time. X‐ray diffraction investigation shows the formation of a mixture of MnFe2O4 and Fe3O4 phases. Furthermore, small‐angle X‐ra...
Article
In this investigation, glasses from the system Na2O/MnO/SiO2/Fe2O3 are prepared using a conventional glass-melting technique. During annealing the glass, a nanocrystalline (Fe, Mn)-based spinel phase is precipitated. The phase composition and microstructure of the formed glass–ceramics are studied using X-ray diffraction and electron microscopy. An...
Article
Full-text available
The in situ formation of gold nanoparticles in soda lime silicate glass under constant x-ray irradiation is compared with the ex situ formation in preirradiated glasses. The ASAXS measurements confirm that pure Au particles are formed. The comparison shows that the number of particles nucleated under irradiation is about an order of magnitude highe...
Article
Oxide glass-ceramics containing ferrimagnetic nanocrystals are of fundamental and practical interest due to their electrical and magnetic properties. Depending on phase composition, size and volume fraction of the crystalline phase formed, the precipitated crystals are applied as parts of ferrofluids, in magnetic resonance imaging and as parts of b...
Article
Full-text available
The morphology of sol-gel derived dip-coated yttria-doped zirconia films containing variable amounts of yttria has been studied using in situ grazing-incidence small-angle X-ray scattering (GISAXS) whilst heated incrementally to 1000 °C. A procedure to analyse in situ GISAXS data has been devised which allows a quantitative analysis of time-depende...
Article
The primary crystallization of amorphous Ni83P17 alloy was studied by in situ anomalous small-angle scattering (ASAXS) and differential scanning calorimetry (DSC). ASAXS, DSC and X-ray diffraction experiments show that only one process, the primary crystallization, proceeds at 250 °C for annealing times up to 18 h. The volume fraction and the avera...
Article
Highly symmetrical protein cage architectures from three different iron storage proteins, heavy and light human ferritin chains (HuHFt and HuLFt) and ferritin from the hyperthemophilic bacterium Pyrococcus furiosus (PfFt), have been used as models for understanding the molecular basis of silver ion deposition and metal core formation inside the pro...
Article
The two-phase approximation in small-angle scattering is well known and is still the dominant approach to data analysis. The intensity scattered at small angles is proportional to the second power of the difference between the scattering densities of the two phases. Nevertheless, scattering contrast variation techniques are widely used, and they ar...
Article
Full-text available
Nanosized metal particles of various configurations embedded in surface regions of glass have great potential as nonlinear optical materials for photonic devices. We have prepared Ag/Au nanoparticles in core-shell configuration in soda-lime silicate glass by double-ion implantation and investigated their structural characteristics by anomalous smal...
Article
The magnetic nanoparticles of Fe <sub>3</sub> O <sub>4</sub>-γ– Fe <sub>2</sub> O <sub>3</sub> grown inside the cavity of globular proteins (apoferritin)-magnetoferritin proved to be a useful model system for studying the fundamental effects of magnetostatic interactions in nanoparticle assemblies. In this work the main focus is on structural chara...
Article
A comparison between the resonant scattering curve obtained by anomalous small-angle X-ray scattering at the X-ray absorption edge of Ni and the complementary small-angle neutron scattering curve from an Al 89 Ni 6 La 5 alloy sample is reported. The sample does not comply with the two-phase approximation. The two resulting scattering curves are app...
Article
Full-text available
We report the chemistry and photophysics of atomic gold and silver particles in inorganic glasses. By synchrotron irradiation of gold-doped soda-lime silicate glasses we could create and identify unambiguously the gold dimer as a stable and bright luminescing particle embedded in the glassy matrix. The gold dimer spectra coincide perfectly with rar...
Article
Full-text available
The theory of small-angle scattering is reviewed with special attention paid to the anomalous scattering and multiphase systems. A general equation is derived that describes the scattering of a multiphase system as a sum of scattering functions of each of the phases, as if it scattered alone in a two-phase system, and interphase interference scatte...
Article
Primary crystallisation of Ni P particles in hypoeutectic Ni P amorphous alloy is investigated. Small angle scattering with polarized neutrons is used to find simultaneously the particle size distribution and the size dependence of the particle composition. The size distribution consists of a peak at particle radius of 1 nm and a tail spanning from...
Article
Full-text available
Primary crystallization of Ni(P) particles in hypoeutectic Ni - P amorphous alloy obtained by electroless deposition has been investigated with ASAXS. The particle size distribution, the size dependence of the particle composition and the amorphous matrix composition were found simultaneously. The size distribution consists of a peak at particle ra...
Article
The initial phase arising at the interface with aluminum substrate during electroless deposition of amorphous high phosphorus (16–19 at.%) Ni–Cu–P alloy with alloyed copper 1.7–3.4 at.% is studied. Stripped deposit foils are inspected by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy coupled with energy dispersive X-ray ana...
Article
Full-text available
Electroless deposition onto polycrystalline (Cu, Au) and amorphous (Ni-P) substrates was applied to prepare Co-W-P coatings of two types: crystalline (hexagonal close packed, hcp), with low phosphorus content about 2.4-2.7 atom %, and amorphous, with P concentration within 7.4-8.3 atom %. Tungsten content varied typically in the narrow range of 2.9...
Article
Several aspects of the application of the maximum-entropy method (MEM) to the determination of particle size distributions by small-angle scattering (SAS) are discussed. The `historic' version of the MEM produces completely satisfying results. Limiting the data error from below (i.e. imposing a minimal relative error) is proposed as a solution of s...
Article
The extension of the small angle scattering technique with polarized neutrons invokes the necessity of new tools for data analysis. Up to ve scattering curves can be derived from a single experiment. It is shown that for the case of a dilute system of particles in a matrix, the maximum entropy method can be modi ed to analyse any combination of the...
Article
A juxtaposition of two methods both presenting the rates of change during crystallization of amorphous alloys and being based on different effects of the occurring transformation is presented. Magnetothermal analysis is sensitive to the precipitation of strong magnetic phase. Differential dilatometric technique is displaying the rate of length chan...
Article
Full-text available
Electro-or electrolessly deposited Ni-P amorphous coatings exhibit some degree of inhomogeneity. This can affect the nucleation process during crystallization of the alloy and therefore its thermal stability. Pure Ni or Ni-rich particles precipitate in the alloy upon annealing and deteriorate its valuable paramagnetic behavior. The composition or d...
Article
The microstructure of amorphous Ni–P and Ni–Me–P materials and especially its change during the heat treatment is of great importance for their magnetic, mechanical and corrosion behavior. A new magnetic phase analysis method (magnetothermal) is presented that reveals the precipitation of nanoparticles with strong magnetic properties during phase t...
Article
Full-text available
The impact of zinc incorporation on the chemical composition of electroless Ni-Zn-P coatings and the elements distribution through the thickness was studied. Ni-Zn-P alloy was deposited on various metal substrates (Al, Fe, Au) with and without electroless Ni-P underlayer. The employed bath formulation and the substrates with a Ni-P intermediate lay...
Article
A new magnetic phase analysis method is presented and its application to a certain class of amorphous alloys is thoroughly discussed. Special attention is paid to the size of clusters with strong magnetic properties that form the separating phase. This magnetothermal (MT) method reveals the formation or disappearance of a phase with strong magnetic...
Article
Absolute calibration relates the measured (arbitrary) intensity to the differential scattering cross- section of the sample, which contains all of the quantitative information specific to the investigated material. The absolute calibration is a requirement to deduce the quantitative structural model on nano-scale in case of more complex and nano-st...
Article
Proteins are well known to form crystals and show promise as templates for making nanoparticles. We exploit these properties to create 3 dimensional protein based nanoparticle arrays. In previous studies a magnetic protein, magnetoferritin, was formed by replacing the core of the natural iron storage protein molecule ferritin with a ferrimagnetic o...

Network

Cited By

Projects

Project (1)
Project
The main aim of this project is to create a common theory, explaining the various cases of sinter-crystallization, which is based on the crystallization ability of parent glasses and on the size of used fraction. (https://sinter-crystallization.akaramanov.com)