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Adsorption of sodium/calcium poly(acrylic acid) salts on anatase: effect of the polyelectrolyte molecular weight and neutralization

Jacquemet Christian

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 1

113--123

EN

Abstract: Interactions of poly(acrylic acid)s (PAAs) of two different molecular weights (Mw = 9,560 g×mol-1 and 4,220 g×mol-1) with surfaces of an untreated anatase TiO2 were assessed through adsorption isotherm measurements. Those dispersants were tested under different sodium-calcium neutralization states (molar ratio r = Ca2+/CO2- varying from 0 to 0.35). Their behavior towards the TiO2 surfaces can be described by the Langmuir adsorption model. For both polymers, surface coverage (Γmax) evolves linearly with the molar ratio r. For a given r value, a lower surface coverage was observed with the polymer having the highest molecular weight. The free energy of adsorption (ΔGads) of PAAs was estimated from adsorption experiment data. This calculation indicates that sorption occurs spontaneously and is unlikely to be of chemical nature. The absolute values of ΔGads are higher for the highest molecular weight polymers suggesting that they are more strongly adsorbed to anatase surfaces. The absolute values of ΔGads per mole of sodium-calcium macromolecules are found to be lower than those calculated for their homologues 100% sodium neutralized suggesting that they are bound with the solid by a fewer number of segments.

2

TiO2 waveguides thin films prepared by sol-gel method on glass substrates with and without ZnO underlayer

Bouachiba Y., Taabouche A., Bouabellou A., Hanini F., Sedrati C., Merabti H.

Materials Science Poland

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2020

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Vol. 38, No. 3

381--385

EN

TiO2 thin films have been deposited on glass substrates with and without ZnO underlayer by sol-gel dip coating process. XRD patterns show the formation of anatase phase with the diffraction lines (1 0 1) and (2 0 0) in TiO2 /glass sample. In TiO2 /(ZnO/glass) sample, TiO2 is composed of anatase phase with the diffraction line (2 0 0) but the diffraction peaks of ZnO wurtzite are also well-defined. The determination of the refractive index and the thickness of the waveguiding layers has been performed by m-lines spectroscopy. The thickness of TiO2 thin films deduced by Rutheford Backscattering Geometry (RBS) agrees well with that obtained by m-lines spectroscopy. TiO2 /glass sample exhibits one guided TE0 and TM0 polarized modes. In TiO2 /(ZnO/glass) sample, only, TE0 single mode has been excited due to cutoff condition.

3

Characterization techniques of sandwich-type TiO₂/QD composites for low-cost quantum dots' solar cell

Kwaśnicki Paweł, Jarzębski Maciej, Kardasz P., Inglot M.

Opto-Electronics Review

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2019

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Vol. 27, No. 2

105--112

EN

There is a high impact of the solar cells on energy manufacturing. For several years the energy efficiency was limited due to base-materials' structural and technological limits. High increase of energy harvesting of solar cells has been observed since the first solar cell based on dye-sensitized colloidal TiO₂ films occurred. One of the most promising solutions are used quantum dots (QD) for light energy conversion. In this paper, we described the use of selected characterization techniques for sandwich-type TiO₂/QD composites for a low-cost quantum dots' solar cell in the point of view of mass manufacturer of solar cells and research and development laboratory. Moreover, the increasing role of Raman spectroscopy and mapping for the TiO₂/QD was presented and compared with other necessity techniques for solar cell investigations such as ellipsometry, atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS).

4

Activity of phthalocyanine-sensitized TiO2-anatase in photooxidation of sulfite ions

Galbas M., Banaszczyk A., Dyrda G., Szczegot K., Słota R.

Polish Journal of Chemical Technology

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2015

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Vol. 17, nr 2

64--69

EN

Hybrid catalysts based on the TiO2 matrix impregnated with Nd, Eu and Yb diphthalocyanines proved effective in oxidation of sulfite ions under irradiation with light from the UV-visible range. Micro- and nano-crystalline anatase powders were used in preparation of the photocatalysts, which were applied in the form of a suspension in the water phase. The reaction yield was found to depend on the phthalocyanine sensitizer used and the conditions of TiO2 impregnation. The best results were obtained when micro-anatase impregnated with Yb-diphthalocyanine was used

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First-principles study of atomic structure and electronic properties of Si and F doped anatase TiO2

Li H., Chen L., Liu S., Li C., Meng J., Wang Z.

Materials Science Poland

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2015

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Vol. 33, No. 3

549--554

EN

Chemical doping represents one of the most effective ways in engineering electronic structures of anatase TiO2 for practical applications. Here, we investigate formation energies, geometrical structures, and electronic properties of Si-, F-doped and Si/F co-doped anatase TiO2 by using spin-polarized density functional theory calculation. We find that the co-doped TiO2 is thermodynamically more favorable than the Si- and F-doped TiO2. Structural analysis shows that atomic impurity varies crystal constants slightly. Moreover, all the three doped systems show a pronounced narrowing of band gap by 0.33 eV for the F-doped TiO2, 0.17 eV for the Si-doped TiO2, and 0.28 eV for the Si/F-co-doped TiO2, which could account for the experimentally observed redshift of optical absorption edge. Our calculations suggest that the Si/F-co-doping represents an effective way in tailoring electronic structure and optical properties of anatase TiO2.

6

Fabrication and characterization of TiO2 nanotube arrays on Ti membrane enlarged by anodic oxidation

Kim J. O., Cho C. H., Choi W. Y.

Materials Science Poland

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2015

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Vol. 33, No. 3

588--592

EN

TiO2 nanotube arrays have attracted a great deal of attention as photocatalytic and photoelectrode materials due to their large surface area, low cost and easy fabrication. Highly ordered TiO2 nanotube arrays for the photoelectrodes in dye-sensitized solar cells have been fabricated from Ti foil. However, the TiO2 nanotube arrays from Ti foil were not effective for the photocatalytic materials, because it had only one plane for the photocatalytic reaction. We have fabricated the TiO2 nanotube arrays from macroporous Ti metal membrane by anodic oxidation and tried to scale it up. Various factors were controlled to obtain the optimal microstructure of the TiO2 nanotube arrays on the surface of macroporous Ti metallic membrane. Microstructure and phase were studied by SEM and XRD, respectively. Temperature was a very important factor in anodic oxidation of large surface area. 10 μm thick TiO2 nanotube arrays on Ti metallic membrane having a large surface area were fabricated and some factors for scaling-up were discussed.

7

Crystal Structure And Optical Properties Of TiO2 Thin Films Prepared By Reactive RF Magnetron Sputtering

Goto S., Adachi Y., Matsuda K., Nose M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

965--967

EN

In sputtering deposition process of TiO2, metal Ti or sintered TiO2 target is used as deposition source. In this study, we have compared the characteristic of target materials. When TiO2 target was used, stoichiometric TiO2 films was deposited under the Ar atmosphere containing 1.0% of oxygen. The highest sputtering rate under this atmosphere was 3.9nm/min at 3.4W/cm2. But, sintered TiO2 target is fragile and cannot endure higher density of input power than 3.4W/cm2. On the other hand, Ti target needs higher oxygen concentration (8%) in sputtering gas atmosphere for obtaining rutile/anatase. Even though Ti target can be input twice power density of 7.9W/cm2, the highest deposition rate for Ti target was 1.4/nm, which was ~35% of the highest rate for TiO2 target. Then we have study out the composite target consisting of Ti plate and TiO2 chips. Using the composite target, stoichiometric TiO2 films were prepared in the rate of 9.6nm/min at 6.8 W/cm2 under the atmosphere of Ar/2.5%O2. Furthermore, we have found that the TiO2 films obtained from the composite target consisted of about 100% anatase, whereas TiO2 films obtained from other target have rutile dominant structure. The optical band gap energy of the film is determined by using the Tauc plot. The calculated band gap energies for the films deposited by Ti target and composite target were 2.95 and 3.24eV, which are equivalent to that of rutile and anatase structure, respectively.

PL

W procesie nanoszenia TiO2 metodą rozpylania, jako tarczy używano metalicznego Ti lub spiekanego TiO2. W pracy dokonano porównania obu materiałów. W przypadku zastosowania jako tarczy TiO2 przy nanoszeniu w atmosferze Ar zawierającym 1,0% tlenu otrzymano stechiometryczną warstwę TiO2. Największa uzyskana szybkość rozpylania w tej atmosferze wyniosła 3,9 nm/min przy gęstości mocy wejściowej 3,4 W/cm2. Jednak spiekany TiO2 jest kruchy i nie wytrzymuje gęstości mocy wejściowej powyżej 3,4 W/cm2. Z drugiej strony, przy rozpylaniu z tarczy Ti konieczne jest zwiększone stężenie tlenu (8%) w atmosferze aby otrzymać fazę rutyl/anataz. Mimo że tarcza Ti wytrzymuje gęstość mocy dwa razy wyższą niż TiO2 (7,9 W/cm2), największa uzyskana szybkość rozpylania wynosiła 1,4 nm/min, co stanowi ~35% najwyższej szybkości uzyskanej dla tarczy TiO2. Zbadano także tarczę kompozytową składające się z płyty Ti oraz wiórów TiO2. W przypadku zastosowania tarczy kompozytowej, szybkość rozpylania wyniosła 9,6 nm/min przy mocy 6,8 W/cm2 w atmosferze Ar/2,5%O2. Dodatkowo, warstwy TiO2 otrzymane z tarczy kompozytowej zawierały około 100% anatazu, podczas gdy w przypadku warstw otrzymanych z pozostałych tarcz dominowała faza rutylu. Szerokość przerwy energetycznej wyznaczono na podstawie wykresu Tauca. Obliczone wartości przerwy energetycznej wynosiły 2,95 eV dla podłoża Ti i 3,24 eV dla podłoża kompozytowego, co odpowiada wartością przerw odpowiednio dla rutylu i anatazu.

8

Structural and optical properties of TiO2 thin films grown by sol-gel dip coating process

Bouachiba Y, Bouabellou A, Hanini F, Kermiche F, Taabouche A, Boukheddaden K

Materials Science Poland

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2014

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Vol. 32, No. 1

1--6

EN

The mono and bi-layer TiO2 thin films have been prepared by sol-gel method on glass. X-Ray diffraction, Raman spectroscopy, atomic force microscopy, spectroscopic ellipsometry and m-lines spectroscopy techniques have been used to characterize the TiO2 films. The mono-layer film is found to be amorphous, while the bi-layer film shows the presence of anatase phase. The bi-layer film exhibits more homogeneous surface with less roughness. The thickness effect on the refractive index, extinction ceofficient, packing density and optical band gap is analysed. The waveguiding measurements of the bi-layer film exhibit single-guided TE0 and TM0 polarized modes from which we can measure the refractive index and the film thickness.

9

Study of the anatase to rutile transformation kinetics of the modified TiO2

Grzmil B., Gleń M., Kic B., Lubkowski K.

Polish Journal of Chemical Technology

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2013

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Vol. 15, nr 2

73–80

EN

TiO2 attracts much interest because of its many potential applications. The use of titanium dioxide strongly depends on its polymorphic form: brookite, anatase, or rutile. Only rutile and anatase play an important role in industry. Anatase as a metastable form undergoes a non-reversible transformation into rutile. Understanding the kinetics of phase transformation and the processes of crystal growth of a material is essential for controlling its structure and, thus, its specific properties. The main purpose of this paper is to explain the anatase to rutile recrystallization kinetics in the modified TiO2 calcined from industrial hydrated titanium dioxide. The apparent activation energy of anatase to rutile transformation and the average size of titanium dioxide crystallites were determined for the unmodified TiO2 and TiO2 modified with P, K, Al, B, Zn, Zr, Ce, Sn, or Sb introduced in the amount of 0.5 mol% and 1.0 mol% when recalculated for their oxides. The growth of TiO2 crystallites during calcination was strongly inhibited by P, Ce and Zr, and inhibited to a lesser degree by Al, Sn and Sb. B and Zn did not affect the investigated process and K accelerated crystallites growth. The values of apparent activation energy depending on a modifier formed a relationship: Al

10

Evaluation of the Photocatalytic Properties of Textile Fabrics Modifed with Titanium Dioxide of Anatase Structute

Siwińska-Stefańska K., Ciesielczyk F., Jesionowski T., Sójka-Ledakowicz J., Lota W., Walawska A.

Fibres & Textiles in Eastern Europe

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2011

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Vol. 19, no. 2 (85)

76-83

EN

Te efect of surface modifcation with selected alkoxysilanes on the photocatalytic properties of TiO2 used in the reaction of formaldehyde photodegradation to UV radiation was investigated. Titanium dioxide - TytanpolŽ A-11, a pigment of anatase structure of the untreated surface, was used. Silane coupling agents were hydrolysed and then deposited directly on the surface of the TiO2. Te alkoxysilanes - 3-ethacryloxypropyltrimethoxysilane, vinyltrimethoxysilane or N-2-(aminoethyl)-3-aminopropyltrimethoxysilane were applied in the amounts of 0.5, 1 or 3 wt. parts per 100 wt. parts of TiO2. Te unmodifed and modifed titanium dioxide were used for the dip-coating of textile fabrics, and their photocatalytic properties were tested using UV radiation with TiO2 as a photocatalyst. Te results proved the very good photooxidative activity of TiO2 introduced into the structure of polyester fabric.

11

Ti02 photoinduced processes in environmental purification

Mańczyk K., Trzebicka B., Malaga K., Dworak A.

Polish Journal of Applied Chemistry

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2009

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Vol. 53. nr 4

323-336

EN

The article presents and reviews up to date the properties and application areas of photocatalytic TiO:. The focus is on mechanisms responsible for the formation of self cleaning surfaces, superhydrophilic layers, deodorizing effect, dirt mineralization, sterilization of water and air purification. The review demonstrates that the two most promising and cost-effective purification processes involving TiO; are photocatalysis and photoinduced superhydrophilicity.

12

Effect of calcination temperature on photocatalytic activity of TiO2. Photodecomposition of mono- and polyazo dyes in water

Mozia S.

Polish Journal of Chemical Technology

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2008

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Vol. 10, nr 3

42-49

EN

The presented studies have focused on the influence of TiO2 properties, such as crystalline phase, crystallite size and surface area, on the effectiveness of degradation of azo dyes in water under UV irradiation. Two monoazo dyes: Acid Red 18 (AR18, C20H11N2Na3O10S3) and Acid Yellow 36 (AY36, C18H14N3NaO3S), and one polyazo dye Direct Green 99 (DG99, C44H28N12Na4O14S4) were applied as model compounds. The photocatalysts were prepared from a crude titanium dioxide obtained directly from the production line (sulfate technology) at the Chemical Factory "Police" (Poland). The crude TiO2 was calcinated in air for 1-4h at the temperatures ranging from 600 to 800°C. The BET specific surface area of TiO2 decreased gradually with increasing the calcination temperature. The crude TiO2 exhibited specific surface area of 277 m2/g. In case of the catalysts heated at 600, 700 and 800°C the BET surface area amounted to 62.3-53.3, 33.4-26.8 and 8.9-8.3 m2/g, for the calcination time of 1-4h, respectively. The crystallite size of anatase increased with increasing heat treatment temperature and ranged from 19 to 53 nm, for the temperatures of 600-800°C, respectively. The catalysts annealed at 600 and 700°C contained primarily anatase phase (94-97%), whereas the photocatalysts heated at 800°C were composed mainly of rutile (97-99%). The highest effectiveness of azo dyes degradation was obtained in case of the photocatalyst calcinated for 1h at 700°C. The photocatalyst was composed mainly of anatase (97%) with crystallite size of 27 nm. The most effectively photodegraded was AR18, having the molecular weight of 640.4 g/mol. The most difficult to degrade was AY36 exhibiting the lowest molecular weight from all the dyes used (375.4 g/mol).