Wyniki wyszukiwania - BazTech

1

Microstructure, mechanical and thermal properties of YSZ thermal barrier coatings deposited by axial suspension plasma spraying

Poliarus Olena, Morgiel Jerzy, Żórawski Wojciech, Góral Anna, Pomorska Małgorzata, Wojciechowski Krzysztof T., Cherniushok Oleksandr

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 2

art. no., e89, 2023

EN

Yttrium-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are indispensable elements of present-day turbine propulsion systems. The ones deposited with atmospheric plasma spraying (APS) are characterized by required low thermal conductivity, but they are unable to survive frequent thermomechanical loading and therefore their application is limited to parts remaining stationary. Expanding capability of TBCs is sought in various areas, but the one realized through modification of most proliferated apparatus used for plasma spraying (PS) (from radial to axial injection) and substituting micrometric powders with the nano-structured suspension needs least changes in the industry established procedures and offers the highest property improvement. The present experiment covered the deposition of ZrO2-8Y2O3 YSZ TBC using both atmospheric and suspension PS processes. They were performed with commercial micrometric and nano-structured YSZ (8% Y2O3) powders. The coatings morphology and microstructure were characterized with 3D profilometry, scanning and transmission electron microscopy (SEM/TEM) methods. Finally, the coating’s hardness and heat conductivity were measured. This complex approach allowed to state that PS of micrometric t’-ZrO2 powder having an admixture of m-ZrO2 phase is capable of only partial improvement in its homogenization. However, the suspension PS process of nano-structured powder eliminated any traces of the monoclinic phase from the coating. The TEM microstructure observations indicated that the suspension PS coating is built by in-flight solidified droplets as well as by the melted ones flattened on arrival. A surface layer of liquefied material on solid droplets increases their adhesion to surface asperities promoting pseudo-columnar growth of the coating. The preservation of monotonic slow increase of thermal conductivity during heating of the suspension PS coating means, that its pseudo-columnar microstructure is better suited to withstand high strains during such treatment.

2

Influence of solid loading in the gel-casting process on the microstructure and properties of porous YSZ ceramics

Wang Chang-An, Hao Bianlei, Hu Liangfa, Lang Ying

Materiały Ceramiczne

|

2019

|

T. 71, nr 4

356--361

EN

With the development of hypersonic space vehicles for near space, high requirements have been put forward to heat insulation materials. In this work, porous yttria-stabilized zirconia (8 mol%Y2O3-ZrO2, YSZ) ceramics with different solid loading were fabricated by tert-butyl alcohol (TBA)-based gel-casting process. After sintered at the same conditions (1550 °C for 2 h), the sintered YSZ ceramics with different porosity, open porosity, pore size distribution and microstructure were obtained. The relationships between compressive strength and microstructure, room-temperature thermal conductivity and microstructure were discussed, respectively. Porous YSZ ceramics with porosity ranging from 56.4% to 66.9% were fabricated by adjusting the solid loading in the initial slurry. A uniform pore size distribution was observed in each sample. The compressive strength of porous YSZ ceramics was 26.8-35.0 MPa. The room-temperature thermal conductivity of porous YSZ ceramics was between 0.205 W/(mK) and 0.337 W/(mK). Moreover, the compressive strength and the thermal conductivity at room temperature of the porous YSZ ceramics decreased with the increase of porosity, respectively.

PL

Wraz z rozwojem hipersonicznych pojazdów kosmicznych do bliskiej przestrzeni kosmicznej stawiane są wysokie wymagania dotyczące materiałów termoizolacyjnych. W tej pracy porowate materiały ceramiczne z tlenku cyrkonu stabilizowanego tlenkiem cyrkonu (8% mol. Y2O3-ZrO2, YSZ) o różnej zawartości fazy stałej wytworzono metodą odlewania żelowego na bazie alkoholu tert-butylowego (TBA). Po spiekaniu w tych samych warunkach (1550 °C przez 2 godz.) otrzymano spiekaną ceramikę YSZ o różnej porowatości, porowatości otwartej, rozkładzie wielkości porów i mikrostrukturze. Omówiono zależności między wytrzymałością na ściskanie a mikrostrukturą oraz przewodnością cieplną w temperaturze pokojowej i mikrostrukturą. Porowatą ceramikę YSZ o porowatości w zakresie od 56,4% do 66,9% wytworzono przez dostosowanie udziału fazy stałej w wyjściowej zawiesinie. W każdej próbce zaobserwowano jednorodny rozkład wielkości porów. Wytrzymałość na ściskanie porowatej ceramiki YSZ wynosiła 26,8-35,0 MPa. Przewodność cieplna porowatej ceramiki YSZ w temperaturze pokojowej wynosiła od 0,205 W/(mK) do 0,337 W/(m•K). Ponadto wytrzymałość na ściskanie i przewodność cieplna w temperaturze pokojowej porowatej ceramiki YSZ zmniejszały się odpowiednio wraz ze wzrostem porowatości.

3

Microstructure and Properties of YSZ Coatings Prepared by Plasma Spray Physical Vapor Deposition for Biomedical Application

Barczyk J., Dercz G., Matuła I., Góral M., Maszybrocka J., Bochenek D., Gurdziel W.

Archives of Metallurgy and Materials

|

2019

|

Vol. 64, iss. 2

779--783

EN

This paper presents the study of microstructure and properties of 8 mol% yttrium stabilized zirconia coating fabricated by Plasma Spray Physical Vapor Deposition technique on commercial pure titanium. The coating was characterized by X-ray diffraction, high resolution scanning electron microscope, profilometer, nanoindentation and nanomachining tests. The X-ray phase analysis exhibit the tetragonal Zr0.935 Y0.065O1.968, TiO and α-Ti phases. The Rietveld refinement technique were indicated the changes of crystal structure of the produced coatings. The characteristic structure of columns were observed in High Resolutions Scanning Electron Microscopy. Moreover, the obtained coating had various development of surfaces, thickness was equal to 3.1(1) μm and roughness 0.40(7) μm. Furthermore, the production coatings did not show microcracks, delamination and crumbing. The performed experiment encourages carried out us to tests for osseointegration.

4

Impedance spectroscopy study of electrode- electrolyte system in solid oxide fuel cells

Krauz M., Radecka M., Rękas M.

Materiały Ceramiczne

|

2011

|

T. 63, nr 1

157-163

EN

Planar electrolyte-supported solid oxide fuel cells were studied. Dense membranes of the dimensions: 100 x 100 mm and a thickness of 130 žm, made from yttria-stabilized zirconia (both tetragonal and cubic) were used as solid electrolytes. Ni-zirconia cermet and La0.8Sr0.2MnO3 layers were deposited on the surfaces of the electrolyte as the anode and the cathode, respectively. Electrochemical impedance spectroscopy was used in order to characterize the electrical properties of the solid electrolyte membranes and the electrolyte-anode and electrolyte-cathode systems. It was found that an equivalent circuit is composed of two series of resistor- constant phase element connected in parallel. No additional elements in the equivalent circuit originated from either the anode or the cathode layers have been observed with respect to the single electrolyte sample.

PL

Zbadano płaskie stałotlenkowe ogniwa paliwowe osadzone na elektrolicie. Jako elektrolit stały wykorzystano gęste membrany o wymiarach 100 x 100 mm i grubości 130 žm, wykonane z dwutlenku cyrkonu stabilizowanego tlenkiem itru, zarówno tetragonalnego jaki i regularnego. Cermet Ni-ZrO2 i warstwy La0.8Sr0.2MnO3 osadzano na powierzchniach elektrolitu, odpowiednio jako anodę i katodę. Wykorzystano elektrochemiczną spektroskopię impedancyjną, aby scharakteryzować właściwości elektryczne membran elektrolitu stałego i układów elektrolit-anoda i elektrolit-katoda. Stwierdzono, że obwód równoważny zbudowany jest z dwóch serii elementów rezystor-faza stała, połączonych równolegle. W odniesieniu do próbki pojedynczego elektrolitu nie zaobserwowano żadnych dodatkowych elementów obwodu równoważnego pochodzących od warstw anody ani katody.

5

Application of microelectrodes for investigation of the oxygen electrode reaction in selected solid electrolytes

Raźniak A., Tomczyk P.

Materials Science Poland

|

2008

|

Vol. 26, No. 1

195--206

EN

In a solid oxide fuel cell (SOFC), the most often used solid electrolyte is yttria stabilized zirconia. Usually, SOFC of a tubular geometry operates at ca. 1000 °C. To decrease the temperature of the cell, it is necessary to reduce the thickness of electrolyte or replace yttrium-stabilized zirconium with an other electrolyte of a much higher ionic conductivity. A potential candidate for an electrolyte in intermediate temperature SOFC is gadolinia doped ceria. The largest energetic losses in a fuel cell of this type, apart of ohmic polarizations, are attributed to slow kinetics of the cathodic process. In this work, investigated oxygen electrode reaction for two various electrolytes: yttria stabilized zirconia and gadolinia doped ceria. The measurements were conducted using microelectrodes for which analysis of kinetic parameters of the electrode reaction is easier. Gold electrodes were applied in the experiments. Although Au is a good electrocatalyst for oxygen reduction, almost no research has been done for this metal so far. The performance of the electrode and results of impedance measurements have been presented and discussed.

6

The temperature - and stress fields of valves of IC engine

Jaskólski J., Krzyżak R.

Journal of KONES

|

2007

|

Vol. 14, No. 3

245-252

EN

The paper concerns building up one exhaust valve of composite-steel and two intake ceramics-steel valves of a hypothetical adiabatic engine. The input temperatures were computed using three diverse FORTRAN95 programs, solving a shortened optical integral equation with radiative transfer, transient differential equation while starting and switching off the engine and a rod like diff. Equation with 'progonka' (Thomas) solution. The ANSYS11 programme was fed up with the output of the programs. It turns out that, generally, a mineralogical, crystal-chemical approach to the joining of materials results in stresses known from the common metal engines. Such problems as CTE enhancing (partly hypothetical) by means of doping the anionic compounds by cationic ones, swelling of structures, compressibility versus coefficient of thermal expansion (CTE) , compatibility of crystal motifs while joining, thermal shock resistance, switching the bonds, mechanical longevity, radiation protection etc were addressed. It turns out that true nature of the temperature and stress field, especially of the exhaust valve is closer to the FORTRAN temperature computation than, e.g. From the heat film coefficients (ANSYS11).

7

Application of Nasicon and YSZ for the construction of CO2 and SOx potentiometric gas sensors

Pasierb P.

Materials Science Poland

|

2006

|

Vol. 24, No. 1

279--284

EN

Solid-state potentiometric CO2 and SOx sensors were fabricated using Nasicon (Na3Zr2Si2PO12) or YSZ (ZrO2 + 8 mole % of Y2O3) solid electrolytes, with fused carbonates or sulphates as sensing electrodes and Na2Ti6O13-Na2Ti3O7 two-phase systems or porous platinum as reference electrodes. A comparison of the performance and long-term stability of the prepared sensors was made. More stable behaviour of CO2 sensors was observed for cells prepared from Nasicon while SOx sensors with YSZ used as the solid electrolyte displayed a better performance. The sensing mechanism and long-term stability of the investigated cells was discussed in terms of the possible reactivity of solid electrolytes with the electrode materials and the formation and modification of "ionic-bridges" at the solid electrolyte-electrode interface.

8

A thermomechanical aspect of the ceramic-capped piston of hypothetical adiabatic diesel engine

Jaskólski J., Krzyżak R.

Journal of KONES

|

2006

|

Vol. 13, No. 2

169-177

EN

The paper concerns a hypothetical Al.-alloy piston coated (capped) first by labradore and then capped by YSZ. The labradore, a member of the feldspar group is deemed thermal-shock resistant, the YSZ(PSZ) can be shock-resistant, but the outcome of the two with the Al.-alloy is not known. The analysis were made in two ways by ANSYS 10.0, as wholly isotropic materials and (second) labradore treated as wholly orthotropic one as basing on a designed texture. The above programme was fed up by the FORTRAN95-outcome of temperatures and the other B.C.’s.The temperatures between the ceramics and the alloy (except one node!!, the FORTRAN) are ( from the above two procedures), 222.63 to 270-300 graduate C, at the first groove are about 290 graduate C, and, surely lower (orthotropic). The relatively low (to ceramic) inner tensile stresses are embraced by the compressive ones from all the sides. The only problem is the-alloy bearing capacity at some sections at the ceramic boundary (and only there). But, it was the aim of the work to stick ceramics there.The dangerous stresses can occur at the pin .The ‘orthotropic ‘ results are better than the ‘iso’-ones and more true.. Taking into account that the real loading will be lower (porosity of the ceramics, the mass and the possible subtraction of stresses, i.e. those ceramic-production-confined ones) , the laboratory production of the piston appears worth.

9

New materials and ideas to be used in adiabatic engines

Jaskólski J., Krzyżak R.

Journal of KONES

|

2004

|

Vol. 11, No. 1-2

288-294

EN

This note concerns several topics. Firstly, a review of some less-known topics regarding the contemporary knowledge on TBC and piston caps is given. Then, it turns out that almost unknown New Periodic System of Elements can be of assistance to predict several properties of new TBC materials. Theoretically, there exist a possibility to join Si-AL-piston alloy with yttria-stabilised zirconia (and the like) by means of feId spars (plagioclase). The latter do not attain to melting temperature and can be arrested within the alloy. A shortened integral optical equation in the manner of inverse problem was used to compute the temperature drop accros the piston cap's layers. The YSZ layer operating in this hypothetical engine gave 517.5 graduate K drop, whereas the feldspar gave about 100-50graduate K temperature drop per mm. This arrangement would give minimised radiation and more or less 'cold' engine(piston). Perhaps, oxides of the thalium-sesquioxide-type structure would be better to stick to metal than the commonly used ones.