Kinetics of phase formation in a Li2CO3-TiO2-Fe2O3 system during radiation-thermal synthesis

Суржиков, А. П.; Vasendina, E. A.; Lysenko, Elena; Nikolaev, E. V.

doi:10.1134/s207511331402021x

“…It has been proven that the electron irradiation significantly speeds up the synthesis process of reactions at low temperatures for different oxide systems (NaFeO2, BaTiO3, NiFe2O4, LiFe5O8, MnFe2O4, ZnFe2O4, among others) (Surzhikov et al, 2014). According to Ranjan and Sasselov (2016), UV photons are very energetic to change the structure of molecules by splitting bonds (photolysis), exciting molecules into a higher level of energy (photoexcitation) or ionization of molecules (photo-ionization).…”

Section: Uv-assisted Thermal Synthesismentioning

confidence: 99%

Development of a novel photocatalyst for the photocatalytic treatment of industrial wastewater

Nasirian¹

2021

Preprint

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Heterogeneous semiconductor photocatalysts have been shown to be efficient for the degradation of refractory organics into simple compounds. Among all photocatalysts, TiO2 is the most used one. Two issues that arise with the use of unmodified TiO2 as a photocatalyst are the unwanted fast recombination of electron/hole pairs and the lower effectiveness in the presence of visible light irradiation. Doping a transition metal or a non-metal into TiO2 and its combination with another photocatalyst have been used to enhance its photoactivity. This study is to develop a new photocatalyst by the combination of TiO2 with another semiconductor oxide (Fe2O3) and its doping with transition metal such as Ag. Combined photocatalysts of Fe2O3 /TiO2 (with different mass ratio of Fe:TiO2) is synthesized and then silver ion is doped to combine photocatalysts (with different mass ratio of Ag:TiO2) to produce a new composite photocatalyst of Ag/TiO2/Fe2O3. A new method of UV-assisted thermal synthesis is also employed to prepare the new composite photocatalyst. Methyl orange (MO) and Congo red (CR), as model pollutants, are used to test the developed photocatalyst. In addition, nitrogen-doped titanium dioxide photocatalyst (N-TiO2) with heterojunction structures is synthesized by three different approaches including new UV-assisted thermal synthesis, annealing, and microwave techniques. The novel UV-assisted thermal synthesis has produced encouraging results as a preparation method to prepare N-TiO2 at lower temperature and atmospheric pressure as well as a lower cost. Design of Experiment (DOE) along with response surface methodology (RSM) is used to optimize the photocatalytic activity of N-TiO2 as well as the affecting parameters (wavelength, light intensity, pH, and initial TOC) for decomposition of organics. The structure of all synthesized composite photocatalysts are investigated by X-ray diffraction (XRD). Scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) is employed to evaluate surface characteristics and elemental analysis of synthesized photocatalysts. Specific surface area of photocatalysts is measured based on Brunauer, Emmett and Teller (BET) technique. Results show that bare TiO2 has the lowest photocatalytic activity in degradation of organics. When silver is doped to TiO2, the degradation of MO is slightly enhanced at specific mass ratio. The presence of Fe2O3 in the new composite causes a red shift and enhances the potential to absorb higher range of visible light. Results from XRD confirmed that Fe3+ substitutes with Ti4+ in the crystal lattice of TiO2 and crystal defect occurs. The degradation of MO in presence of Ag/TiO2/Fe2O3 (Ag/TiO2=0.005 w:w and Fe:TiO2= 0.01 w:w) reached to 95.6% under sunlight in three hours with a red shift towards visible light. It is observed that there is an optimum specific surface area of photocatalysts by doping and combining photocatalysts.

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“…At high UV light intensity, collisions are more frequent, more particles are activated, and consequently, the speed of reaction will be increased (Ranjan and Sasselov, 2016). It has been already confirmed that the high intensity of electron irradiation expressively increased the speed of reactions at lower temperatures for different oxide systems such as NaFeO2, BaTiO3, NiFe2O4, LiFe5O8, MnFe2O4, and ZnFe2O4 (Surzhikov et al, 2014). UV photons are very strong to alter the structure of molecules by breaking down bonds in photolysis reactions, exciting molecules into a higher level of energy (photoexcitation), or ionization of molecules (photo-ionization) (Ranjan and Sasselov, 2016).…”

Section: Uv-assisted Thermal Synthesismentioning

confidence: 92%

“…Based on the Arrhenius law, by increasing the temperature of reactants, the constant rate of the reaction also increases. It has been proven that the electron irradiation significantly speeds up the synthetic process at low temperatures for various oxide systems (NaFeO2, BaTiO3, NiFe2O4, LiFe5O8, MnFe2O4, ZnFe2O4, among others) (Surzhikov et al, 2014).…”

Section: The Novel Uv-assisted Thermal Synthesis As An Alternative To the Hydrothermal Methodsmentioning

confidence: 99%

Development of a novel photocatalyst for the photocatalytic treatment of industrial wastewater

Nasirian¹

2021

Preprint

2

0

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Heterogeneous semiconductor photocatalysts have been shown to be efficient for the degradation of refractory organics into simple compounds. Among all photocatalysts, TiO2 is the most used one. Two issues that arise with the use of unmodified TiO2 as a photocatalyst are the unwanted fast recombination of electron/hole pairs and the lower effectiveness in the presence of visible light irradiation. Doping a transition metal or a non-metal into TiO2 and its combination with another photocatalyst have been used to enhance its photoactivity. This study is to develop a new photocatalyst by the combination of TiO2 with another semiconductor oxide (Fe2O3) and its doping with transition metal such as Ag. Combined photocatalysts of Fe2O3 /TiO2 (with different mass ratio of Fe:TiO2) is synthesized and then silver ion is doped to combine photocatalysts (with different mass ratio of Ag:TiO2) to produce a new composite photocatalyst of Ag/TiO2/Fe2O3. A new method of UV-assisted thermal synthesis is also employed to prepare the new composite photocatalyst. Methyl orange (MO) and Congo red (CR), as model pollutants, are used to test the developed photocatalyst. In addition, nitrogen-doped titanium dioxide photocatalyst (N-TiO2) with heterojunction structures is synthesized by three different approaches including new UV-assisted thermal synthesis, annealing, and microwave techniques. The novel UV-assisted thermal synthesis has produced encouraging results as a preparation method to prepare N-TiO2 at lower temperature and atmospheric pressure as well as a lower cost. Design of Experiment (DOE) along with response surface methodology (RSM) is used to optimize the photocatalytic activity of N-TiO2 as well as the affecting parameters (wavelength, light intensity, pH, and initial TOC) for decomposition of organics. The structure of all synthesized composite photocatalysts are investigated by X-ray diffraction (XRD). Scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) is employed to evaluate surface characteristics and elemental analysis of synthesized photocatalysts. Specific surface area of photocatalysts is measured based on Brunauer, Emmett and Teller (BET) technique. Results show that bare TiO2 has the lowest photocatalytic activity in degradation of organics. When silver is doped to TiO2, the degradation of MO is slightly enhanced at specific mass ratio. The presence of Fe2O3 in the new composite causes a red shift and enhances the potential to absorb higher range of visible light. Results from XRD confirmed that Fe3+ substitutes with Ti4+ in the crystal lattice of TiO2 and crystal defect occurs. The degradation of MO in presence of Ag/TiO2/Fe2O3 (Ag/TiO2=0.005 w:w and Fe:TiO2= 0.01 w:w) reached to 95.6% under sunlight in three hours with a red shift towards visible light. It is observed that there is an optimum specific surface area of photocatalysts by doping and combining photocatalysts.

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“…Radiation methods for sintering and modifying materials are being intensively developed at the present time. It is known application of radiation heating by an electron beam for the synthesis and sintering of ferrites [1][2][3][4][5][6][7] and zirconium ceramics [8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Modification of Strength Properties of Oxide Materials by Ion Irradiation

Ghyngazov

¹

,

Kostenko

²

,

Shevelev

³

et al. 2018

KEM

0

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The effect of ion irradiation on the strength characteristics of magnesium oxide and ceramics based on zirconia is studied. The MgO samples were a single crystal grown in an artificial manner. Samples of zirconium ceramics were prepared by ceramic technology. Irradiation of MgO crystals was carried out by Si+ ions (E = 150 keV), Fe+ (E = 70 keV), C+ (E = 50 keV) at room temperature. The fluence varied within the range (1016–1017) сm–2. The modification of the investigated types of ceramics was carried out by ions Al+ (Е = 60 keV), Ar+ (Е= 60 keV), N+ (E = 50 keV). We used ion beams of microsecond duration and moderate power (the current density in the pulse was 3 10-3 A/cm2). Fluence was 1017 cm-2. The irradiation of the ceramics with an ion beam C+ (E = 50 keV) was also performed with nanosecond duration (τ = 50 ns). It is established that ionic irradiation of magnesium oxide leads to an increase in crack resistance and a critical stress intensity factor. Irradiation of ceramics leads to hardening of its near-surface layers.

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Kinetics of phase formation in a Li2CO3-TiO2-Fe2O3 system during radiation-thermal synthesis

Cited by 13 publications

References 9 publications

Development of a novel photocatalyst for the photocatalytic treatment of industrial wastewater

Development of a novel photocatalyst for the photocatalytic treatment of industrial wastewater

Development of a novel photocatalyst for the photocatalytic treatment of industrial wastewater

Modification of Strength Properties of Oxide Materials by Ion Irradiation

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