Wyniki wyszukiwania - Biblioteka Nauki

1

Otrzymywanie i właściwości modyfikowanych nanoporowatych adorbentów krzemionkowych

100%

Choma J. , Jaroniec M.

Ochrona Środowiska

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2003

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tom R. 25, nr 1

3-8

PL

Otrzymano uporządkowane, nanoporowate adsorbenty krzemionkowe (MCM-41) z merkaptopropylowymi oraz aminopropylowymi grupami. W procesie syntezy tych materiałów wykorzystano metodę hydrotermiczną z zastosowaniem bromku cetylotrimetyloamoniowego, jako surfaktantu, i tertaetoksysilanu, jako źródła krzemionki. Po wytrąceniu się białego osadu uporządkowanego materiału krzemionkowego dodawano 3-merkaptopropylotrietoksysilan lub 3-aminopropylotrietoksysilan, jako modyfikatory. Właściwości tak otrzymanych modyfikowanych merkaptopropylowych i aminopropylowych materiałów porównano z właściwościami niemodyfikowanego MCM-41. Otrzymane materiały badano za pomocą metody rozpraszania promieniowania rentgenowskiego (XRD), wysokorozdzielczej termograwimetrii (HRTG) i niskotemperaturowej (77 K) adsorpcji azotu. Stwierdzono, że w wyniku tak przeprowadzonej syntezy udało się wprowadzić około 12% wag. grup merkaptopropylowych oraz około 6% wag. grup aminopropylowych. Tak otrzymane modyfikowane materiały charakteryzują się uporządkowaną strukturą mezoporowatą o małej dyspersji porów a ich średnica wynosi około 3,6 - 3,8 nm. Inne parametry struktury mezoporowatej takie jak całkowita powierzchnia właściwa Sc, powierzchnia właściwa SBET, objętości pierwotnych mezoporów Vme i całkowita objętość porów Vc są wysokie i niewiele mniejsze od odpowiednich parametrów dla niemodyfikowanego MCM-41 C16. Badane modyfikowane adsorbenty MCM-41 mogą być wykorzystywane do usuwania jonów metali ciężkich z wody.

EN

Ordered nanoporous siliceous adsorbents (MCM-41) with mercaptopropyl and aminopropyl groups were synthesized. Cetyltrimethylammonium bromide as the templating surfactant and tetraethoxysilane as the silica source were used to synthesize these materials hydrothermally. After precipitation of a white powder of ordered silica, 3-mercaptopropyltriethoxysilane and 3-aminopropyltriethoxysiliane were added as modifiers. The properties of mercaptopropyl- and aminopropyl-modified materials were compared with those for the unmodified MCM-41. The resulting materials were studied by powder X-ray diffraction (XRD), high resolution thermogravimetry (HRTG) and low temperature (77 K) nitrogen adsorption. With the method of synthesis used we were able to introduce 12% of mercaptopropyl groups and 6% of aminopropyl groups. The resulting modified materials possess on ordered mesoporous structure of a small dispersion of pores, with a pore diameter ranging between 3.6 and 3.8 nm. The other structural parameters such as the total specific surface area (Sc), the BET surface area (SBET), the volume of primary mesopores (Vme) and the total pore volume (Vc) are high and not very much smaller than the corresponding parameters for the unmodified MCM-41. The modified MCM-41 adsorbents can be used for the removal of heavy metal ions from water.

2

Thermal degradation of epoxy polymers. Method of the evaluation of kinetic parameters on the base of thermogravimetric data

100%

Zakordonskiy V. P. , Hnatyshin S. Y. , Soltys M. M.

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tom Vol. 72, nr 12

2610-2620

EN

A new evaluation of kinetic parameters of the thermal degradation of cross-linked polymers is proposed. The DTG-peaks separation is the base for this method. The application of this approach to thermal degradation of epoxypolymers is discussed with respect to chemical transformations and structure of the polymer matrix.

3

Evaporation of Zinc in an Argon - Hydrogen Mixture

100%

Matuła T.

Archives of Metallurgy and Materials

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2022

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tom Vol. 67, iss. 3

885--888

EN

Many modern processes for the production and casting of metals and their alloys are carried out in protective gas atmospheres, which protect them, for example, from oxygen pollution. This applies, for example, to titanium, magnesium or aluminum alloys. Most liquid alloys are comprised of constituents that differ in vapor pressures, resulting in harmful phenomenon during melting due to evaporation of some of its components. This harmful process may be limited by the selection of a suitable gas atmosphere in which the liquid metal treatment process is carried out. In the paper, results of study on the impact of the type of gas atmosphere on the rate of evaporation of zinc in argon - hydrogen mixtures are presented. It should be noted that such mixtures are used, for example, in metal welding processes, in which it is also possible to evaporate a component of the so-called liquid metal pool. The research results showed that the rate of zinc evaporation increases with the increase of hydrogen content in the gas atmosphere.

4

Thermogravimetric studies of exotic woods in oxidative environment

100%

Jaskolowski W. , Szajewska A.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2015

|

tom 92

5

THERMOGRAVIMETRY OF CHITOSAN WITH NANOFILLERS

100%

Puchalska A. , Mucha M.

Progress on Chemistry and Application of Chitin and its Derivatives

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2011

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tom 16

31 - 42

EN

In the present paper the degradation of chitosan and its blends with hydroxyapatite, nanoclay and nanosilver as well as the impact of those nanofillers added to chitosan on its decomposition at high temperatures are studied. The applied films of thickness 50 μm were obtained by casting the acidic solutions: chitosan and its blends with hydroxyapatite, nanoclay and nanosilver. To mix solutions with nanofillers ultrasounds were applied. To study the thermal degradation we applied thermogravimetry in dynamic and static conditions, which is a method of thermal analysis involving the continuous recording of weight loss Based on experimental data activation energies of thermal decomposition close to a maximum rate loss were calculated using different methods for chitosan and its blends with hydroxyapatite, nanoclay and nanosilver. The addition of three nanofillers mentioned above result in a visual increase of activation energy of thermal degradation process of chitosan due to slower evolution of decomposed gases from chitosan matrix reflected by a slower rate of weight loss.

6

Synthesis of WC-20 wt. % Cu composite powders by co-precipitation and carburization processes

100%

Ardestani M. , Arabi H. , Razavizadeh H. , Rezaie H. R. , Mehrjoo H.

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tom Vol. 28, No. 2

413--420

EN

WC/Cu composite powders were synthesized by co-precipitation and subsequent reduction-carburization process. The precipitates contained W-Cu compounds fabricated using a chemical procedure from a mixture of copper nitrate and ammonium paratungstate in distilled water. In order to synthesize the WCCu composite powders, dried precipitates were calcined at 823 K in air and then reduced and carburized by carbon monooxide (CO). The non-isothermal mechanism of reduction-carburization of the calcined powders in carbon monoxide was investigated by thermogravimetry, differential thermogravimetry and X-ray diffraction analyses. The optimum reduction-carburization temperature was determined as 1065 K. The microstructures of the powders were characterized by the scanning electron microscopy.

7

Preparation and characterization of multi-walled carbon nanotubes grown on transition metal catalysts

88%

Pełech I. , Narkiewicz U. , Kaczmarek A. , Jędrzejewska A.

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nr 1

117-122

EN

Transition metal catalysts (mainly: iron, cobalt and nickel) on various supports are successfully used in a largescale production of carbon nanotubes (CNTs), but after the synthesis it is necessary to perform very aggressive purification treatments that cause damages of CNTs and are not always effective. In this work a preparation of unsupported catalysts and their application to the multi-walled carbon nanotubes synthesis is presented. Iron, cobalt and bimetallic iron-cobalt catalysts were obtained by co-precipitation of iron and cobalt ions followed by solid state reactions. Although metal particles were not supported on the hard-to-reduce oxides, these catalysts showed nanometric dimensions. The catalysts were used for the growth of multi-walled carbon nanotubes by the chemical vapor deposition method. The syntheses were conducted under ethylene - argon atmosphere at 700°C. The obtained catalysts and carbon materials after the synthesis were characterized using transmission electron microscopy (TEM), X-ray diffraction method (XRD), Raman spectroscopy and thermogravimetric analysis (TG). The effect of the kind of catalyst on the properties of the obtained carbon material has been described.

8

THERMAL DEGRADATION OF DOUBLE CROSSLINKED HYDROGEL CHITOSAN MEMBRANES

88%

Pieróg M. , Ostrowska-Czubenko J. , Gierszewska-Drużyńska M.

Progress on Chemistry and Application of Chitin and its Derivatives

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2012

|

tom 17

71 - 78

EN

The thermal degradation behaviour of uncrosslinked and crosslinked chitosan membranes were studied by means of dynamic thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) over the temperature range 25-500ºC in nitrogen atmosphere. Modified chitosan membranes were prepared using a crosslinking method based on covalent crosslinking of chitosan with glutaraldehyde and subsequent ionic crosslinking with sodium citrate, sulfuric acid, sulfosuccinic acid and tripolyphosphate, respectively. Chemical structure of modified chitosan membranes before and after their thermal degradation was characterized by FTIR spectroscopy. Both TGA and DSC experiments as well as spectral results (FTIR spectra of thermal degradation residues) indicated some differences in the mechanism of thermal degradation of uncrosslinked and crosslinked chitosan membranes.

9

Magnetic studies of 0.7(Fe2O3)/0.3(ZnO) nanocomposites in nanopowder form and dispersed in polymer matrix

88%

Typek J. , Wardal K. , Zolnierkiewicz G. , Szymczyk A. , Guskos N. , Narkiewicz U. , Piesowicz E.

Materials Science Poland

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2016

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tom Vol. 34, No. 2

286--296

EN

Magnetic properties of 0.7(Fe2O3)/0.3(ZnO) nanocomposite synthesized by traditional wet chemistry method and containing only two phases: ZnO (nonmagnetic) and Zn Fe2O4 (magnetic, with nanocrystallites of average size 12 nm, but forming large agglomerates, up to 100 nm in size) were studied by DC magnetization and ferromagnetic resonance (FMR). The investigated nanocomposite was either in a form of nanopowder or dispersed at concentration of 0.1 wt.% in poly(ethylene naphthalate-block-tetramethylene oxide) PTMO-b-PEN polymer matrix. Similarities and differences in magnetic behavior of these two samples revealed by the study of static magnetization and FMR spectra have been discussed relative to different morphologies and the associated variation of interparticle interactions. Moreover, thermal and thermo-oxidative stability of the nanocomposite and the neat polymer have been studied by thermogravimetric method.

10

Preparation and characterization of multi-walled carbon nanotubes grown on transition metal catalysts

88%

Pełech I. , Narkiewicz U. , Kaczmarek A. , Jędrzejewska A.

Polish Journal of Chemical Technology

|

2014

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tom Vol. 16, nr 1

117-122

EN

Transition metal catalysts (mainly: iron, cobalt and nickel) on various supports are successfully used in a largescale production of carbon nanotubes (CNTs), but after the synthesis it is necessary to perform very aggressive purification treatments that cause damages of CNTs and are not always effective. In this work a preparation of unsupported catalysts and their application to the multi-walled carbon nanotubes synthesis is presented. Iron, cobalt and bimetallic iron-cobalt catalysts were obtained by co-precipitation of iron and cobalt ions followed by solid state reactions. Although metal particles were not supported on the hard-to-reduce oxides, these catalysts showed nanometric dimensions. The catalysts were used for the growth of multi-walled carbon nanotubes by the chemical vapor deposition method. The syntheses were conducted under ethylene - argon atmosphere at 700°C. The obtained catalysts and carbon materials after the synthesis were characterized using transmission electron microscopy (TEM), X-ray diffraction method (XRD), Raman spectroscopy and thermogravimetric analysis (TG). The effect of the kind of catalyst on the properties of the obtained carbon material has been described.

11

The influence of iron nanocrystallite size on a nitriding process rate

88%

Pelka R. , Glinka P. , Arabczyk W.

Materials Science Poland

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2008

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tom Vol. 26, No. 2

349--356

EN

In the course of nitriding process of nanocrystalline iron promoted with aluminum and calcium oxides, nitrides such as Fe4N and Fe3-2N were fabricated. The process rate was studied making use of a flow differential tubular reactor with thermogravimetric measurement of mass changes. Nanocrystalline iron was reduced under hydrogen atmosphere at 500 oC and 800 oC. Average crystallite sizes determined by the XRD method after reduction performed at 500 oC as well as at 800 oC and after passivation were 18 and 42 nm, respectively. The nitriding process rate as well as catalytic ammonia decomposition rate were limited by the ammonia dissociative adsorption rate on the surface of iron and were dependent on the ratio of the crystallite surface area to crystallite volume. Obtained results were explained based on the adsorption range model.

12

Flame resistant cellulosic substrate using banana pseudostem sap

88%

Basak S. , Samanta K. K. , Saxena S. , Chattopadhyay S. K. , Narkar R. , Mahangade R. , Hadge G. B.

Polish Journal of Chemical Technology

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2015

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tom Vol. 17, nr 1

123--133

EN

Flame retardancy was imparted in cellulosic cotton textile using banana pseudostem sap (BPS), an eco-friendly natural product. The extracted sap was made alkaline and applied in pre-mordanted bleached and mercerized cotton fabrics. Flame retardant properties of both the control and the treated fabrics were analysed in terms of limiting oxygen index (LOI), horizontal and vertical flammability. Fabrics treated with the non-diluted BPS were found to have good flame retardant property with LOI of 30 compared to the control fabric with LOI of 18, i.e., an increase of 1.6 times. In the vertical flammability test, the BPS treated fabric showed flame for a few seconds and then, got extinguished. In the horizontal flammability test, the treated fabric showed no flame, but was burning only with an afterglow with a propagation rate of 7.5 mm/min, which was almost 10 times lower than that noted with the control fabric. The thermal degradation and the pyrolysis of the fabric samples were studied using a thermogravimetric analysis (TGA), and the chemical composition by FTIR, SEM and EDX, besides the pure BPS being characterized by EDX and mass spectroscopy. The fabric after the treatment was found to produce stable natural khaki colour, and there was no significant degradation in mechanical strengths. Based on the results, the mechanism of imparting flame retardancy to cellulosic textile and the formation of natural colour on it using the proposed BPS treatment have been postulated.

13

Synthesis and crystal structure of chlorate-enclathrated in aluminogermanate sodalite Na8[AlGeO4]6(ClO3)2

88%

Borhade A. V. , Dholi A. G.

Materials Science Poland

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2013

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tom Vol. 31, No. 2

246--252

EN

Encapsulation of chlorate in sodalite with aluminogermanate host framework has been obtained by one pot hydrothermal synthesis at 393 K. The crystal structure of Na8[AlGeO4]6(ClO3)2; sodalite was refined from X-ray powder data in the space group P43n: a = 9.169 Å, where Al-O-Ge angle is 137.6. The 27Al MAS NMR study confirmed alternate Ge and Al ordering of the sodalite framework, while 23Na gave insight into the structure and dynamics of the cage fillings. Infrared spectrum confirmed the encapsulation of chlorate as well as the framework formation of aluminogermanate sodalite. SEM study showed the retention of cubical morphology of the aluminogermanate sodalite. Thermogravimetric analysis provided information on the extent of chlorate entrapment, stability within the sodalite cages and decomposition properties.

14

Heavy metals complexes of poly(sodium 4-styrenesulfonate) — thermogravimetric studies

75%

Korus I.

Polimery

|

2012

|

tom T. 57, nr 4

290-295

EN

The paper analyzes thermal properties of poly(sodium 4-styrenesulfonate) bound with different metal ions [Cu(II), Ni(II), Zn(II), Pb(II), Cr(III)] and in the acidic form. Solid samples of polyelectrolyte bound with different counter-ions were prepared and their mass losses in the temperature range of 25—1000 °C were recorded. TG and DTG curves were used to estimate the activation energy of thermal degradation of sulfonic groups bound with different counter-ions. For studied polyelectrolyte counter-ions, the sulfonic group thermal stability increases in the following sequence: H << Ni << Cu << Na << Zn << Pb << Cr(III).

PL

Oddziaływania polimer-metal stanowią podstawę ultrafiltracji wspomaganej polimerami (ang. polymer enhanced ultrafiltration, PEUF) — techniki separacji umożliwiającej zatrzymywanie jonów metali na membranie ultrafiltracyjnej po uprzednim związaniu ich z makrocząsteczką polimeru. Jednym z polimerów o doświadczalnie potwierdzonej skuteczności takiego działania jest poli(4-styrenosulfonian sodu) (PSSS). Przedstawiono wyniki badań termograwimetrycznych próbek poli(4-styrenosulfonianu sodu) związanego z jonami metali [Cu(II), Ni(II), Zn(II), Pb(II), Cr(III)] oraz PSSS w postaci wodorowej i sodowej. Zarejestrowano krzywe TG i DTG suszonych na powietrzu próbek PSSS w różnej postaci jonowej (rys. 1). Rozkład termiczny badanych próbek (prowadzony w atmosferze powietrza) przebiegał trójstopniowo, z wyjątkiem postaci sodowej, w przypadku której zarejestrowano 4 etapy rozkładu (tabela 1). Pierwszy etap rozkładu próbek, odnotowany do temperatury 200—300 °C, był związany z utratą wody hydratacyjnej. Kolejny etap ubytku masy wynikał z rozkładu grupy sulfonowej i występował w różnych zakresach temperatury, w zależności od postaci jonowej polimeru. Stosując 3 metody, opierając się na równaniach (1)—(5), oszacowano energię aktywacji Ea rozkładu grupy sulfonowej polielektrolitu połączonej z badanymi jonami (rys. 2—4, tabela 2). Stwierdzono wzrost stabilności termicznej grupy sulfonowej, zależny od rodzaju przeciwjonu, w kolejności: H << Ni << Cu << Na << Zn << Pb << Cr(III). Ostatni etap dekompozycji przebiegał w temp. >>500 °C i był efektem rozkładu matrycy polimerowej. Masy próbek po zakończonym procesie rozkładu wskazywały na obecność w mineralnej pozostałości siarczanów (Na, Pb) lub tlenków (Cu, Zn, Ni, Cr) metali.

15

Wpływ temperatury redukcji na powierzchnię właściwą i aktywną preredukowanego katalizatora żelazowego do syntezy amoniaku

75%

Jasińska I. , Lubkowski K. , Arabczyk W.

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tom T. 82, nr 3

230-233

16

Reduction of Lead Oxide by Fine-Grained Carbonaceous Materials

75%

Matuła T. , Siwiec G.

Archives of Metallurgy and Materials

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2019

|

tom Vol. 64, iss. 2

647--652

EN

As part of the presented work, tests were carried out to check the possibility of replacing of conventional reducers used in the lead pyrometallurgical processes by cheaper, but equally effective substitutes. For research of lead oxide reduction, the following fine-grained carbonaceous materials were used, ie anthracite dust and coal flotation concentrate, as well as traditional used coke breeze for comparison. The obtained test results indicate a similar ability to reduce the lead oxide of all studied carbonaceous materials.

17

Thermal Impact on Heavy Metal Bioavailability in Burnt Rocks of Waste Heap of Chervonohradska Coal-preparation Plant (Lviv Region, Ukraine)

75%

Kochmar I. , Karabyn V. , Stepova K. , Stadnik V. , Sozanskyi M.

Geomatics and Environmental Engineering

|

2024

|

tom Vol. 18, no. 1

117--133

EN

For effective waste management of mining industries is important to investigate their physical and mineralogical changes. For this purpose, X-raydiffraction (XRD), thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) methods were used. Changes in the contents of mobile forms of heavy metals in rocks were investigated using an acetate-ammonium buffer solution with a pH of 4.8 after burning rocks at a temperature of 800–850°C. The obtained data indicated the significant role of the mineral composition in the thermal behavior of the rock samples and the subsequent influence of the thermal processes on the changes in the bioavailability of heavy metals.

18

Preliminary characteristics of some bottom sediments of the Baltic Sea

75%

Szponar Z. , Rzechula J. , Pielak A.

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1985

|

tom 20

19

Free radical formation in salicylic acid and heating parameters – application of EPR, UV-Vis, TGA and colorimetry examination to optimize thermal sterilization

75%

Ramos P. , Pilawa B.

|

tom 77

|

nr 3

431-441

EN

Salicylic acid heated at different temperatures and times was examined by an X-band (9.3 GHz) EPR spectroscopy, UV-Vis spectrophotometry, TGA and colorimetry test to optimize its thermal sterilization process. Free radical formation (~1018 spin/g) during thermal sterilization of salicylic acid according to the pharmaceutical norms at temperature 120oC and time of 120 minutes was compared with those for heating at the new tested temperatures and times: 130oC and 60 minutes, and 140oC and 30 minutes. It was obtained that the relatively lower free radical concentrations characterized salicylic acid heated at temperatures (times): 120oC (120 minutes), and 130oC (60 minutes), than at temperature (time) 140oC (30 minutes). So treatment at temperature 120oC during 120 minutes, and temperature 130oC during 60 minutes, were recommended as the optimal for thermal sterilization of salicylic acid. Salicylic acid should not be sterilized at temperature 140oC during 30 minutes, because of the highest free radical formation. Free radical systems of thermally treated salicylic acid revealed complex character. Fast spin-lattice relaxation processes existed in heated salicylic acid. Strong dipolar interactions characterized all the heated salicylic acid samples. EPR spectroscopy, UV-Vis spectrophotometry, thermogravimetry, and color measurement may be helpful besides microbiological analysis to optimize thermal sterilization conditions of salicylic acid.

20

Wpływ soli i tlenków na wysokotemperaturowe utlenianie sproszkowanego tantalu i wolframu

75%

Magdziarz A. , Kalicka Z.

Rudy i Metale Nieżelazne

|

2008

|

tom R. 53, nr 2

99-102

PL

W artykule przedstawiono wyniki badań wysokotemperaturowego utleniania w powietrzu mieszaniny sproszkowanego tantalu i wolframu z chlorkami i siarczanami metali alkalicznych oraz tlenkami MoO3 i V2O5. Proces badano metodą termograwimetryczną w zakresie temperatur 20-1100 stopni Celsjusza. Dla wybranych próbek wykonano analizę fazową powstałych produktów utleniania. Wykazano, że jedynie mieszanina Na2SO4 z V2O5 powoduje zwiększenie szybkości utleniania sproszkowanego tantalu.

EN

The high-temperature oxidation of a fine tantalum and tungsten powder mixed with alkaline metals chlorides, sulphates and MoO3, V2O5 oxides was investigated in the air. Thermoanalytical diagrams were recorded within the temperature range from 20 to 1100 degrees of Celsius. Phase composition of the oxidized samples was established by XRD analysis. It was stated that only Na2SO4 mixed with V2O5 increases the oxidation rate of a powdered tantalum.