Maria Gancheva (Mancheva)

Maria Gancheva (Mancheva)
Bulgarian Academy of Sciences | BAS · Institute of General and Inorganic Chemistry

PhD

About

39
Publications
10,252
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444
Citations
Additional affiliations
February 2002 - July 2015
Bulgarian Academy of Sciences
Position
  • Research Assistant
Education
February 2002 - April 2007
Institute of General and Inorganic Chemistry, Bulgarian Academy of Science
Field of study

Publications

Publications (39)
Article
MgMoO4 with hexagonal particles were prepared by combining high energy ball milling with heat treatment technique. The influence of the mechanochemical activation/heat-treatment on the phase, structural and morphology transformation were investigated by X-ray powder diffraction analysis (XRD), infrared spectroscopy (IR), differential scanning calor...
Article
Dy³⁺ doped glasses from the oxide system CaOGeO2Li2OB2O3 with different compositions were prepared by melt quenching technique. The obtained glass samples were characterized by X-ray diffraction (XRD), Differential thermal analyses (DTA), Infrared spectroscopy (IR) and Photoluminescence (PL) measurements. The X-ray analysis reveals amorphous nature...
Article
Europium doped glasses with three different compositions and different dopant concentrations were prepared from the CaO-GeO2-Li2O-B2O3 system. The influences of Eu³⁺ ions concentration on the thermal stability of the glasses were investigated by DTA analyses. The IR spectra display variations in the glass structures depending on the glass compositi...
Article
Full-text available
Terbium doped glasses with three different compositions from the system CaO-GeO2-Li2O-B2O3 and different dopant concentrations were prepared. DTA analyses show weak influence of the rare earth ion on the glass thermal properties. The FTIR spectra revealed variations between glass structures. Excitation and emission spectra of the doped glasses poss...
Article
Full-text available
We report on the fabrication of highly porous metal-oxide nanostructures by pulsed laser deposition performed in air at atmospheric pressure. The depositions were performed by ablating synthesized ZnO and a mixed target of ZnO and TiO 2 as initial materials. The attention was focused on the structure, morphology, optical and photocatalytic properti...
Article
CaWO4 nanoparticles were successfully obtained by direct mechanochemical synthesis. In the search of new and advanced catalysts, the CaWO4 has been modified by Pd and characterized by various techniques such as: N2-physisorption, XRD, IR, TEM, XPS, TPR and TPD. The results from the instrumental methods confirmed that CaWO4 can be formed at room tem...
Article
Glasses with different compositions were prepared from the oxide system CaO-GeO2-Li2O-B2O3 in order to find out compositions, where after thermal treatment of the initial glasses crystallize Ca2GeO4, Ca5Ge3O11 or Li2CaGeO4 as a main phase. Glass-ceramics were obtained and crystallizing phases were determined. Ca2GeO4, Ca5Ge3O11 and Li2CaGeO4 region...
Article
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Powder samples of Ca 2 GeO 4 doped with 0.2, 0.5, 1, 2 and 3 at% Dy 3+ were prepared using conventional solid state synthesis technique. XRD analyses show obtaining of the pure phase at all dopant concentrations. Emission and excitation spectra contain the characteristic peaks of Dy 3+ ion. The Dy 3+ excitation spectrum in the range from 300 to 500...
Article
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High-energy milling has been employed for the preparation of CuWO 4 nanopowders using the planetary ball and the shaker mills. The phase formations after each milling stage have been characterized by X-ray diffraction analysis (XRD) and infrared spectroscopy (IR). The optical band gap and the morphology of the obtained CuWO 4 have been also studied...
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A study of the photocatalytic activity of commercial and mechanically activated zinc oxide powders has been carried out based on the example of the decomposition of Brilliant Green. The goal of this work was to study the effect of the grinding time (0, 1, 3, 5, and 7 min) on the structure of zinc oxide and its photocatalytic activity under visible...
Article
Проведено исследование фотокаталитической активности коммерческих и механоактивированных порош- ков оксида цинка на примере разложения бриллиантового зеленого. Целью работы явилось исследование влияния времени измельчения (0, 1, 3, 5, 7min) на структуру оксида цинка и его фотокаталитическую активность в видимом и ультрафиолетовом (УФ) излучении. Ус...
Article
Zinc oxide particles with various morphologies were successfully prepared via three synthesis methods: precipitation; tribophysical treatment and sonochemistry. The as-synthesized samples were characterized by X-ray diffraction (XRD); infrared spectroscopy (IR); scanning electron microscope (SEM); BET specific surface area; electron-paramagnetic re...
Article
Mechanochemical activation is the most commonly applied approach for improving the photocatalytic properties of commercial zinc oxide. Here we show that ZnO obtained by two-pathway decomposition of basic zinc carbonate also possesses a very good photocatalytic activity. Nanosized ZnO powders were successfully prepared by thermal and mechanochemical...
Article
Full-text available
The synthesis of MgWO4 nanopowders was achieved by mechanically activated and following thermal treatment at 850 °C of two mixtures, containing the pure oxides (MgO/WO3) and magnesium carbonate trihydrate and tungsten oxide (MgCO3·3H2O/WO3) as precursors. The obtained samples have been analyzed by the X-ray powder diffraction, infrared spectroscopy...
Article
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This article presents data referring to the mechanochemical activated synthesis of amorphous and crystalline LaBWO 6. A stoichiometric mixture of La 2 O 3 , B 2 O 3 and WO 3 of a 1:1:2 molar ratio was subjected to intense mechanical treatment in air using a planetary ball mill (Fritsch-Premium line-Pulversette No. 7). The obtained samples were anal...
Article
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Zinc oxide (ZnO) was mechanically activated in air using a planetary ball mill upon varying the milling speed and time. The obtained samples were analyzed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and UV-Vis diffusion reflectance spectroscopy. The photocatalytic activity of the mechanically treated ZnO powders was inve...
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Full-text available
Zinc oxide (ZnO) was mechanically activated in air using a planetary ball mill using varying milling speeds and time. The obtained samples were analyzed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and UV-Vis diffusion reflectance spectroscopy. The photocatalytic activity of the mechanically treated ZnO powders were inves...
Article
The nanocrystalline ZnO powders were obtained by mechanochemical treatment of zinc carbonate hydroxide. The mechanical activation was carried out in a planetary ball mill (Fritsch–Premium line–Pulversette No 7) by varying of the milling speed. The phase and structural transformation was investigated by X-ray diffraction (XRD) and infrared spectrosc...
Article
The nanocrystalline ZnO powders were obtained by mechanochemical treatment of zinc carbonate hydroxide. The mechanical activation was carried out in a planetary ball mill (Fritsch–Premium line–Pulversette No 7) by varying of the milling speed. The phase and structural transformation was investigated by X-ray diffraction (XRD) and infrared spectrosc...
Article
The aim of this study is to investigate the change in the coloring of the silver containing float glasses by additional heat-treatment up to 950°C and second ion-exchange in the salt containing copper ions. The X-ray diffraction (XRD), Microprobe analysis and UV-Vis spectroscopy were used for the samples characterization. The brown silver glasses w...
Article
Full-text available
ZrMo2O7(OH)2·2H2O was obtained from ZrOCl2·2H2O and Na2MoO4·2H2O by a coprecipitation method. The phase and structural changes occurred during the heat-treatment of ZrMo2O7(OH)2·2H2O were investigated by XRD, IR and XPS analysis. The sequence of phase transformation can be divided into three stages: (1) transformation of ZrMo2O7(OH)2·2H2O to orthor...
Article
Single nanocrystalline ZnWO4 powders were successfully synthesized by ball milling at room temperature. A stoichiometric mixture of ZnO and WO3 in a 1:1 molar ratio was subjected to intense mechanical treatment in air using a planetary ball mill (Fritsch – Premium line – Pulversette No. 7) for a period varying from 5 to 300 min. The influence of th...
Article
Full-text available
The photocatalytic and optical properties of ZnO powders obtained by mechanochemical treatment of zinc car-bonate hydroxide are presented in this article. The mechanochemical activation was carried out in a planetary ball mill (Fritsch–Premium line–Pulversette No 7) by varying the speed of milling and milling time. The phase and structural transfor...
Article
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Purpose: The main purpose of this paper is presenting the results obtained in years 2007 – 2010 in frame of the project Marie Curie Transfer of Knowledge – CastModel. The project was focused, among others, at elaborating new, environmentally friendly cast alloys based on the Al-Zn system. Particularly, efforts were aimed at improving ductility of t...
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This study is a continuation of our previous investigation for fast preparation of the ZrMo2O8. The melt quenching method and mechanochemically assisted solid state synthesis were applied to investigate morphology of the obtained product. A stoichiometric mixture of ZrO2 and MoO3 in a 1:2 molar ratio was melted above the peritectic temperature (at...
Data
a b s t r a c t This study presents two new approaches: the melt quenching method (up–down) and mechanochemical activation (down–up) for the preparation of single ZrMo 2 O 8 polymorphs. A stoichiometric mixture of ZrO 2 and MoO 3 in a 1:2 molar ratio was subjected to melt quenching with different cooling rates and intense mechanical treatment in ai...
Data
a b s t r a c t We report a novel approach for fabrication of cubic ZrWMoO 8 applying a melt quenching method. The stoichiometric mixture of ZrO 2 , WO 3 and MoO 3 in a 1:1:1 M ratio was melted and quenched at room temperature by pouring the melts between two metal plates. The quenched sample was characterized by X-ray diffraction (XRD), differenti...
Article
Full-text available
Orthorhombic (α) MoO3 and monoclinic (β) MoO3 were successfully synthesized by cation-exchange of sodium molybdate solution applying three different routes: i) pure precursor molybdic acid solution (H2MoO4), ii) addition of HNO3 to a precursor and iii) addition of 35% H2O2 to a precursor. By route i) pure orthorhombic (α) MoO3 was synthesized. Pure...
Article
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The present study is based on experiments using Zn-nitrate and Zn-acetate as precursors along with several variants of sol-gel technique which are widely popularized in the literature. The purpose is to check their applicability to ZnO-TiO 2 and ZnO-V 2 O 5 binary mxtures as well as their photocatalytic activity towards model solutions. Comparative...
Article
Heterogeneous catalytic oxidation of methanol on Au/CeO(2) catalyst in the temperature range 20-300 degrees C at a space velocity 10 000h(-1) was studied. A very high activity of the catalyst with respect to the complete oxidation of methanol to carbon dioxide was observed. The degree of conversion at 60 degrees C is higher than 90% at 60 degrees C...
Article
Full-text available
The powder of MoO3 with orthorhombic symmetry was subjected to intense mechanical treatment in air using a plan-etary ball mill (Fritsch 7) for up to 10 h. The phase, morphology and structural transformations were monitored by X-ray diffrac-tion (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR). MoO3 cannot be amorphized and...
Article
Metastable orthorhombic (γ) ZrW2O8 was obtained by fast cooling of the melt of a stoichiometric mixture of ZrO2 and WO3. Heating of the as-quenched sample at 600 °C for 15 h led to the full transition of the orthorhombic (γ) to the cubic (α) ZrW2O8 polymorph. The average crystallite sizes of the obtained ZrW2O8 phases were in the range of 50−80 nm....
Data
Full-text available
The possibilities of mechanochemical activation as a successful route for direct synthesis of NiWO 4 have been studied. A stoichiometric mixture of NiO and WO 3 in a 1:1 molar ratio was subjected to intense mechanical treatment in air using a planetary ball mill for different periods of time. The phase and structural transformations were monitored...
Article
The possibilities of mechanochemical activation as a successful route for direct synthesis of NiWO4 have been studied. A stoichiometric mixture of NiO and WO3 in a 1:1 molar ratio was subjected to intense mechanical treatment in air using a planetary ball mill for different periods of time. The phase and structural transformations were monitored by...
Article
The aim of this study is to establish the possibilities of mechanomechanical activation as a successful route for the preparation of NiMoO4 catalysts. A stoichiometric mixture of NiO and MoO3 in a 1:1 molar ratio was subjected to intense mechanical treatment in air using a planetary ball mill for different periods of time. The phase and structural...

Projects

Projects (2)
Project
The main goal of the project is preparation of new glass-ceramic luminescent materials, containing Ca2GeO4, Li2CaGeO4 or Ca5Ge3O11 phases doped by Tb3+, Eu3+ and Dy3+ ions. The planed studies are pioneer since obtaining of oxide glass-ceramic with luminescent properties from germanate systems has not been described in the literature. The problem is actual because finding of new promising luminescent materials is relevant to ecology, energy saving and improvement of the human life.
Project
The main aim of the project is to obtain new multicomponent glasses in the systems WO3-La2O3-B2O3-Nb2O5 and WO3-ZnO-B2O3-Nb2O5 doped with Eu3+, as a transparent active media for optical application. The actuality of this research is determined by the urgent need of new matrixes for light-emitting diodes (led). Compared to the conventional light sources, LEDs are one of today's most energy-efficient, environmental friendly and rapidly developing lighting technologies, which has the potential to fundamentally change the future of lighting.