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Preparation, characterization of a ceria loaded carbon nanotubes nanocomposites photocatalyst and degradation of azo dye Acid Orange 7

Wen T., Tang Y.-B., Mo B.-Y.

Archives of Environmental Protection

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2016

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Vol. 42, no. 2

12--19

EN

A ceria loaded carbon nanotubes (CeO2/CNTs) nanocomposites photocatalyst was prepared by chemical precipitation, and the preparation conditions were optimized using an orthogonal experiment method. HR-TEM, XRD, UV-Vis/DRS, TGA and XPS were used to characterize the photocatalyst. Nitrogen adsorption-desorption was employed to determine the BET specifi c surface area. The results indicated that the photocatalyst has no obvious impurities. CeO2 was dispersed on the carbon nanotubes with a good loading effect and high loading effi ciency without agglomeration. The catalyst exhibits a strong ability to absorb light in the ultraviolet region and some ability to absorb light in the visible light region. The CeO2/CNTs nanocomposites photocatalyst was used to degrade azo dye Acid Orange 7 (40 mg/L). The optical decolorization rate was 66.58% after xenon lamp irradiation for 4 h, which is better than that of commercial CeO2 (43.13%). The results suggested that CeO2 loading on CNTs not only enhanced the optical decolorization rate but also accelerated the separation of CeO2/CNTs and water.

2

Composite oxide electrolytes for electrochemical devices

Dudek M.

Advances in Materials Science

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2008

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Vol. 8, nr 1(15)

14-26

EN

This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes, providing a brief overview of the materials having better performance than mo-nophase ones in various high temperature electrochemical devices such as: solid oxide fuel cells, sensors for automotive industry, oxygen probes for controlling metal processing. Introduction of Al2O3 inclusions into cubic yttria - zirconia solid solution (8YSZ) matrix, caused the improvement of electrical and mechanical properties compared to pure 8YSZ. The Nd2Ti2O7 secondary phase was also able to coexist with 8YSZ matrix and the frac-ture toughness KIc of 8YSZ ceramics was also significantly improved by Nd2Ti2O7 addition. Heterophase oxide ionic conductors in the system Calcium zirconate - cubic calcia zirconia solid electrolytes seem to be promising solid electrolytes for application in electrochemical probes for controlling oxygen dissolved in molten steel. The ionic conduction limit for electrolytes based on CaZrO3 is lower than that for calcia - stabilized zirconia (13CSZ). Hence CaZrO3-based materials perform better at low oxygen concentration at molten alloys. On the other hand composite layered ceramics involving Ce0.8Sm0.2O2/Bi0.8Eb0.2O2 or Ce0.9Gd0.1O2/BaCe0.8Y0.2O3/Ce0.9Gd0.1O1.95 system exhibited better electrolytic stability in gas atmos-pheres with low oxygen partial pressure at the temperatures 600-800°c. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance.

3

Ceria-yttria-based solid electrolytes for intermediate temperature solid oxide fuel cell

Dudek M., Molenda J.

Materials Science Poland

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2006

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Vol. 24, No. 1

45--52

EN

Pure ceria and ceria-yttria solid solution powders with formula Ce1-xYxO2, where 0 < x < 0.30 were prepared by the coprecipitation-calcination method. The samples were sintered at 1250-1600 °C for 2 hours. The XRD method was used to determine cell parameters of the samples. Their electrical properties were investigated by ac impedance spectroscopy in the temperature range of 100-700 °C in air. It was found that the electrical conductivity, fracture toughness, and flexural strength of the samples increase with yttria concentration and reach a maximum for Ce0.85Y0.15O2. The obtained material seems to be a promising solid electrolyte for IT-SOFC.

4

Nanocrystalline doped zirconia and ceria films for fuel cell application

Jasiński P., Jasiński G., Petrovsky V., Anderson H., U.

Elektronika : konstrukcje, technologie, zastosowania

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2006

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Vol. 47, nr 12

14-15

EN

The preparation of dense electrolyte films for Solid Oxide Fuel Cells (SOFCs) is a crucial technological process. The method has been developed, which allows preparing 1 to 10 µm thick dense and nanocrystalline films. In this process the powder is first deposited onto the surface to provide a framework of connected particles into which the polymeric precursor impregnates to form an oxide particle/organic polymer composite film. Using this technology typical SOFCs electrolyte films, doped zirconia and ceria, were prepared. In this paper the films properties were evaluated and compared. Due to nanocrystalline nature of the films the grain boundary conductivity is a significant part of electrolyte conductivity.

PL

Przygotowanie gęstych i cienkich warstw do tlenkowych ogniw paliwowych jest złożonym procesem technologicznym. Opracowana przez nas metoda umożliwia przygotowanie gęstych i nanokrystalicznych warstw o grubości 1 ...10 µm. W metodzie tej, najpierw, z zawiesiny koloidalnej nanoszona jest warstwa połączonych cząsteczek związku tworząca szkielet, który następnie jest wypełniany z użyciem ciekłego prekursora metaloorganicznego. Z wykorzystaniem tej metody przygotowane zostały warstwy domieszkowanego tlenku cyrkonu i tlenku ceru, które typowo wykorzystywane są w tlenkowych ogniwach paliwowych jako elektrolity. W artykule porównywano właściwości elektryczne tych warstw. Z powodu nanokrystalicznej struktury warstw przewodnictwo obszarów międzyziarnowych jest dominujące.

5

CeO2 oraz stabilizowany ZrO2 jako potencjalne katalizatory ketonizacji odpadowych alkoholi

Teterycz H., Klimkiewicz R., Grabowska H.

Chemia i Inżynieria Ekologiczna

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2002

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Vol. 9, nr 5/6

655-658

PL

CeO2 oraz ZrO2 domieszkowany MgO i Y2O3 zastosowano jako katalizatory w ketonizacji n-butanolu. Wobec obu katalizatorów wydajność i konwersja były zbliżone. Badania zmierzają do przeróbki odpadowych frakcji alkoholowych.

EN

CeO2 and also Zr)2 doped with MgO and Y2O3 were applied as catalysts in the ketonization of n-butanol. Over both catalysts the yields and conversions were similar. The research leads to the reprocessing of waste alcohol fractions.

6

Mikrowarstwowe kompozyty ceramiczne.

Tomaszewski H., Węglarz H., Boniecki M., Rećko W.M.

Inżynieria Materiałowa

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1998

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R. XIX, nr 5

1288-1296

PL

Kompozyty warstwowe o matrycy Y-ZrO2 lub Ce-ZrO2 z warstwami zbudowanymi z tlenku glinu lub mieszaniny tlenku glinu i dwutlenku cyrkonu grubości 10 do 70 mikrometrów wytwarzano metodą przemiennego odwirowania wodnych zawiesin proszków. W obu przypadkach (Y-ZrO2 i CeZrO2) zaobserwowano znaczny wzrost odporności na pękanie i wytrzymałości na zginanie, ale tylko dla warstw barierowych zbudowanych z tlenku glinu. W przeciwieństwie do wyników uzyskanych przez D.B. Marshalla, mechanizm odchylania spękania wydaje się być odpowiedzialny za obserwowane przyrosty własności. Jak się okazało, wielkość kąta odchylenia jest zależna od grubości warstwy tlenku glinu. Wyższe kąty odchylenia pęknięcia, oznaczające dłuższą drogę pęknięcia zaobserwowano dla grubszych warstw. Wielkości kąta odchylenia skorelowano z gradientem naprężeń wewnętrznych obecnych w warstwach tlenku glinu. Źródłem naprężeń wewnętrznych w badanych kompozytach jest różnica we współczynnikach rozszerzalności cieplnej ZrO2 i Al2O3 oraz krystalograficzna anizotropia rozszerzalności cieplnej Al2O3. Trzecim składnikiem naprężeń okazała się być różnica skurczliwości wypalania obu materiałów. Naprężenia wewnętrzne mierzono metodą piezospektroskopową wykorzystującą zjawisko fluorescencji jonu Cr do potęgi +3 będącego naturalnym zanieczyszczeniem tlenku glinu.

EN

Composites of yttria or ceria partially-stabilised zirconia with layers of either alumina or a mixture of 50% by the volume of the alumina or zirconia were produced using a colloidal technique. The method involved sequential centrifuging of solutions containing suspended solutions allowed to form layers with thickness of 10 to 70 mm. In both cases (Y-ZrO2 and Ce-ZrO2), the significant increase in the fracture toughness, work of fracture and bending strength was observed only in the case of the barrier layers made of pure alumina, not made of the mixture. On the contrary to D.B. Marshall's results, the crack deflection in the alumina layers seems to be the main mechanism responsible for the observed improvement of mechanical properties. As it was found a crack deflection angle depends on the alumina layer thickness. Higher deflection angles, what means longer way of a crack through the alumina layer, were observed for the thicker alumina layers. The crack deflection angle was correlated with the gradient of compressive residual stresses present in the alumina layers. The stresses are the result of both the thermal expansion mismatch between alumina and zirconia and the crystallographically anisotropic thermal expansion of the alumina. The shrinkage mismatch was found as the third component of stresses. The residual stress distribution has been measured by piezospectroscopy based on the optical fluorescence from Cr to the +3rd power dopants in the alumina.