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1

Mechanical Properties and Sliding Wear Resistance of Suspension Plasma Sprayed YSZ Coatings

Łatka Leszek, Szala Mirosław, Macek Wojciech, Branco Ricardo

Advances in Science and Technology. Research Journal

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2020

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Vol. 14, no 4

307--314

EN

In this work, the yttria stabilised zirconia ZrO2 + 8 wt% Y2 O3 (YSZ) coatings were studied. The coatings were manufactured by using a relatively new method based on liquid feedstock, called suspension plasma spraying (SPS). The main aim of the study was to investigate the influence of one of the fundamental process parameters, stand-off distance, on the YSZ coating mechanical properties, namely adhesion, cohesion, hardness, and dry sliding wear resistance. Moreover, the coating surface morphology and microstructure were investigated. Despite the fact that in the SPS method, the heat flux into the substrate is much higher than in conventional atmospheric plasma spraying (APS), for the stand-off distances as short as 40 mm, the structure has not been damaged by thermal stresses. The results revealed that shorter spray distance leads to obtaining the coatings characterised by higher cohesion and adhesion to the substrate as well as higher hardness and resistance to sliding wear. The wear mechanism of both YSZ coatings relies on the adhesive mode, which is intensified by severe coating material delamination.

2

Effects of PVA Polymer Type and Calcination Temperature on Synthesis of Nanocrystalline Yttria Powder by Polymer Solution Route

Yang Y.-K., Lee S.-J.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1473--1476

EN

Nano-sized yttria (Y2O3) powders were synthesized by a polymer solution route using polyvinyl alcohol (PVA) as an organic carrier. The PVA polymer affected the dispersion of yttrium ions in precursor sol. In this study, three kinds of PVA polymer (different molecular weight) were applied for synthesis of yttria powder. The PVA type as well as calcination temperature had a strongly influence on the particle morphology. Single crystal nano wire particles were observed at the temperature of polymer burn out range and the size was dependent on the PVA type. The stable, fully crystallized yttria powder was obtained through the calcination at 800°C for 1 h. The yttria powder prepared with the high weight PVA (MW: 153,000) revealed a particle size of 30 nm with a surface area of 18.8 m2/g.

3

Spiekanie i mikrostruktura dwutlenku cyrkonu stabilizowanego wapniem i itrem

Bućko M.M., Morgiel J.

Materiały Ceramiczne

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2006

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R. 58, nr 4

131-136

PL

Celem prezentowanej pracy było określenie wpływu składu chemicznego roztworów stałych dwutlenku cyrkonu zawierających itr oraz wapń na spiekalność nanoproszków oraz zmiany mikrostrukturalne. Sporządzono trzy serie nanoproszków zawierających nominalnie 8, 10 oraz 12% molowych wakancji tlenowych. Odpowiedni poziom wakancji w danej serii realizowany był poprzez wprowadzenie do sieci dwutlenku cyrkonu odpowiednio zmiennych ilości tlenków itru i wapnia. Proszki te były spiekane swobodnie w temperaturach zależnych od ich składów chemicznych. Obserwacje mikroskopowe wykazały, że wielkości ziaren w spiekach były kontrolowane poziomem tlenku wapnia w roztworze stałym. Już niewielka zamiana Y2O3 itru na CaO prowadziła do znaczącego wzrostu średnich wielkości ziaren a także do wzrostu rozrzutu tych wielkości. W tworzywach stabilizowanych jedynie tlenkiem itru obserwowano typowe wzbogacenie granic międzyziarnowych w itr. Częściowa zamiana tlenku itru na tlenek wapnia skutkowała silną segregacją wapnia na granicach międzyziarnowych oraz brakiem tego efektu w przypadku itru. W materiałach zawierających tylko CaO, oprócz wzmożonej segregacji wapnia na granicach międzyziarnowych, widoczne są również kilkunanometrowe strefy wzdłuż granic międzyziarnowych wzbogacone w wapń.

EN

The aim of the present work was to investigate an effect of yttria and calcia additions to zirconia solid solutions both on the powder sinterability and microstructure of sintered bodies. Three series of the samples, which contained nominally 8, 10 or 12 % oxygen vacancies, were prepared by introducing yttria and calcia to zirconia in the appropriate proportions. The powders were pressureless sintered at temperatures depended on their chemical composition. Microstructural observations indicated that the grain size in the sintered samples was controlled by the amount of calcia in zirconia solid solution. A small exchange of yttria for calcia led to the significant grain growth and to the increased of the grain size dispersion. The TEM/EDS investigations showed the typical enrichment of the grain boundaries by yttrium in the zirconia material stabilized with yttria. The exchange of yttria for calcia caused the strong calcium segregation and remained yttrium without segregation at the grain boundaries. In the sample stabilized only with calcia, the additional wide areas along the grain boundary with calcium content higher than that in the grain interior were observed.

4

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.

5

Hydrosulfurization of Methanol on Y2O3-TiO2-ZrO2 Catalysts

Szalaty-Bujakowska A., Kujawa J., Ziółek M., Fiedorow R.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 5

789-796

EN

Y2O3-TiO2-ZrO2 catalysts, where the contribution of oxide components ranges from 0 to 100 mol %, have been studied for their catalytic performance in methanol hydrosulfurization. Their activity and selectivity have shown a strong dependence on acid-base properties which, in turn, changed with catalyst composition. High yttria content favors selectivity to methanethiol, while catalysts highly active for the formation of dimethylsulfide were those containing 8 mol % Y2O3. The latter composition, which boosted selectivity to (CH3)2S, has created favorable conditions for the generation of acid centers in chemically mixed oxides as concluded on the ground of ESR studies and acidity measurements.

6

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.

7

Zirconia based nanomaterials: elaboration, characterization and transport properties.

Monty C., Bousseta H., Rouanet A., Sibieude F., Amdouni-Cheikh A., Madani A., Roucau C., Snoeck E., Brun N., Georgescu C., Lelievre D., Piticescu R.R., Carry C., Begin-Colin S., Gandhi A.S., Jayaram V.

Inżynieria Materiałowa

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1999

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R. XX, nr 1

29-31

EN

Yttria doped zirconia nanophases ('0D-NANOS' as ultrafine powders) yttria doped zirconia/alumina nanocomposites ('3D-NANOS' as ribbons), have been obtained using high concentration solar image furnaces. The two techniques used (vaporization-condensation and splat-cooling) are described. Ribbons were grinded by various routes. The nanostructure of these nanomaterials was characterized using X-ray diffraction (X-D) and High Resolution Electron Microscopy (HREM). Oxygen transport properties were investigated by Impedance Spectrometry (IS). Bulk conductivity was compared to data obtained from single crystals and literature data. The grain boundary contribution has been found higher than the volume one is a typical case of 4% mol yttria doped zirconia. Oxygen transport mechanisms are discussed.

PL

W piecach słonecznych o wysokiej zdolności koncentracji energii uzyskano nanometryczny proszek tlenku cyrkonu domieszkowanego itrem ('OD-NANOS w postaci ultradrobnego proszku) oraz domieszkowany itrem nanometryczny kompozyt tlenek cyrkonu/Al2O3 ('3D-NANOS w postaci taśm). Opisano dwie zastosowane metody (odparowanie-kondensacja i ultraszybkie chłodzenie). Taśmy były mielone w młynach kulowych w celu uzyskania proszku. Lity materiał uzyskano spiekając ultradrobne proszki otrzymane różnymi metodami. Nanostrukturę tak uzyskanych próbek charakteryzowano stosując metody dyfrakcji promieniowania rentgenowskiego (X-D) i mikroskopię elektronową wysokiej rozdzielczości (XREM). Zjawiska transportu tlenu badano metodą spektroskopii impedancyjnej (IS). Przewodność właściwą próbek spiekanych porównano z wynikami uzyskanymi dla pojedynczych kryształów oraz danymi literaturowymi. Stwierdzono, że udział granic ziarn w badanych materiałach jest wyższy niż w typowym przypadku 4% mol tlenku cyrkonu domieszkowanego itrem. Przedyskutowano także mechanizmy transportu tlenu.

8

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.

9

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.