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1

Characterization of zirconia-magnesia-yttria materials used as catalysts for esters and alcohols fractions transformations by ketonization

Klimkiewicz R., Teterycz H., Sikora E., Rakoczy J., Biskupski A., Trawczyński J.

Polish Journal of Chemical Technology

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2005

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Vol. 7, nr 1

29-32

EN

In former publications the application of the monophase material Zr(0.89)-Mg(0.10)-Y(0.01)-O as a catalyst of the waste alcohol and ester fractions ketonization was described. In the present work various compositions of the Zr-Mg-Y-O type respecting the reaction group: Zr(0.89)-Mg(0.10)-Y(0.01)-O(CL) synthesized from chlorides, Zr-Mg-Y-O(SULPH) from zirconium sulfate, mixed oxide ZrO2+Y2O(3BOG) and its derivative Zr-Mg-Y-O(BOG) are characterized. The catalytic properties of the materials were characterized with the use of n-butanol test, isopropanol test, cyclohexene + H2 test as well as TPD NH3, and FT-IR (pyridine) spectroscopy. Zr-Mg-Y-O(SULPH) catalyst obtained from the sulfate precursor, as compared to Zr(0.89)-Mg(0.10)-Y(0.01)-O(CL), revealed a much lower selectivity of the reaction of the primary and secondary alcohols into ketones. The surfaces of Zr(0.89)-Mg(0.10)-Y(0.01)-O(CL) and ZrO2 + Y2O(3BOG) materials, although they contained comparable numbers of the Lewis acidic centers (164 and 126 žmol Py/g, respectively), differed considerably as for the selectivity in the reaction of n-butyl alcohol condensation: ZrO2,+Y2O(3BOG) was not a selective catalyst of the ketonization. Under the conditions of the cyclohexene + H2 test over ZrO2 + Y2O(3BOG) the reaction proceeded towards isomerization and cracking, while Zr(0.89)-Mg(0.10)-Y(0.01)-O(CL) catalyzed hydrogenation. The application of Zr-Mg-Y-O(BOG) material of the lower Lewis acidity (62 žmol Py/g) did not result in the higher selectivity of the ketonization. However, the result of the cyclohexene + H2 test changed. Thus, a considerable number of the Lewis acidic centers (such as ZrO2+Y2O(3BOG) was not the only necessary condition for the bimolecular condensation of the primary alcohols and/or aldehydes or for esters transformation. The search for materials should be conducted towards the syntheses of the catalysts of the dehydrogenation properties and containing in their structure oxygen vacancies which could form the Lewis acidic centers.

2

Microstructure- transport property relation in yttria-doped zirconia

Rizea A., Chirlesan G., Kusinski J., Petot-Ervas G., Petot C.

Inżynieria Materiałowa

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2004

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R. XXV, nr 3

430-433

EN

Transmission electron microscopy, XPS analysis, electrical conductivity and diffusion measurements have allowed us to show the microstructure-transport property relation in ZrO2- 9.0mol% Y2O3 (YSZ) and Al2O3-YSZ composites. Samples with no detectable amorphous grain boundary precipitates show the highest grain boundary electrical conductivity (...gb) and oxygen diffusion coefficient (Do) values, which decrease in presence of alumina additions. On the contrary, alumina additions = or<2 mol%) lead to an increase of the transport properties of samples showing grain boundary glassy films. These results were attributed to a decrease of the grain boundary wettability by the glassy phase when the alumina amount increases. Furthermore, the same grain boundary activation energy found for the different samples show that only "clean" grain boundaries contribute to the transport processes.

3

Relation between microstructure and grain boundary conductivity in yttria-doped zirconia.

Rizea A., Petot C., Petot-Ervas G., Kusinski J.

Inżynieria Materiałowa

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2001

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R. XXII, nr 5

784-786

EN

The microstructure grain boundary relation in yttria-doped zirconia has been investigated on polycrystals sintered from powders prepared through two different processing routes. Samples with no evidence for continuous glassy boundary films show the highest grain boundary conductivities (sigma gb) which decrease in presence of alumina additions. On the contrary, samples with boundary glassy films show an increase of sigma gb for small alumina additions (< or = 2 mole%) do likely to a change in the glass phase composition. The same sigma gb activation energy found for the different samples suggests that only "clean" grain-boundaries contribute to the transport processes.

4

Pokrycia ceramiczne na bazie ZrO2 jako bariery cieplne na denku tłoka silnika wysokoprężnego.

Napadłek W., Niezgoda T., Majewski T., Derewońko A., Babul T.

Inżynieria Materiałowa

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2000

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R. XXI, nr 6

361-364

PL

W referacie przedstawiono wyniki badań adiabatyzacji komory spalania poprzez zastosowanie termoizolacyjnych powłok ceramicznych na bazie ZrO2+Y2O3 nanoszonych na denko tłoka. Badane powłoki zostały wykonane metodą natryskiwania plazmowego oraz metodą nanoszenia gazodetonacyjnego. Przedstawiono również wyniki symulacji komputerowej stanu naprężeń oraz rozkładu temperatur w skojarzeniu tłok-pierścienie tłokowe-tuleja cylindrowa silnika wysokoprężnego, przeprowadzonej przy pomocy programu Patran-Nastran 7.0A.

EN

Results of investigations of thermal insulation of combustion chamber with use by thermo-insulating ceramic coats on the base of ZrO2+Y2O3 on the piston crowns are presented in the paper. Test coats were produced by plasma spraying method and by means of gas-detonation method. results of computer simulation of stress state and temperature distribution in the piston-cylinder sleeve system of diesel engine that was conducted using Patran/Nastran 7.0A programme are given also in the work.

5

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.

6

Development of the phase composition in the carbothermally derived beta-sialon ceramics.

Sopicka-Lizer M., Metselaar R.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

735-738

EN

Carbothermally derived beta-sialon powders with different phase composition were presureless sintered with or without yttria additives. Then they were isothermally annealed in nitrogen. XRD study has shown changes in the phase composition after sintering and annealing at 1450 degrees centigrade. Development of the phase composition was dependent on the composition of the starting beta-sialon powders (presence of AlN or 15R phase) and yttria admixture. It has been found that sintering of carbothermally derived powders shifted the composition of the ceramics towards beta-sialon with higher z-value. Further annealing in nitrogen could lead to decomposition of sialon polytypoid phases and was accompanied by slow oxidation at low oxygen partial pressure.