Papers by Keyword: Lanthanum Zirconate

Abstract: Thermal Barrier Coating are highly advanced material systems usually applied to metallic surfaces, such as gas turbine or aero-engine parts, operating at elevated temperatures. They have ceramic and metallic multilayers which have been widely used in the aeroturbine engines to increase the life of metallic components and turbine efficiency. Many different types of coatings are used to protect variety of engineering materials from wear, corrosion and erosion. Of all these, TBC’s play a vital role in providing thermal insulation and protect the material from high temperature environment. In this paper Lanthanum Zirconate (La₂Zr₂O₇) is used as a coating material which is phase-stable to its melting point, Lanthanum Zirconate is a promising material which exhibit lower thermal conductivity and higher thermal stability compared to other TBC system. High quality Lanthanum Zirconate based TBC is developed by plasma spray technique on superalloys. In the present investigation porosity, microstructure, hardness and bond strength of the developed TBC’s were characterized and significant parameters of plasma spray process were identified.

Abstract: Yttria stabilized zirconia (YSZ) based composite topcoats were prepared with three advanced ceramic materials as second phase component; CaZrO₃, (La_0.75Nd_0.25)₂Zr₂O₇ and Nd₂Ce₂O₇. The solid particles erosion (SPE) testing of the air plasma sprayed composite topcoats was carried out at room temperature and 900 °C to study the effects of second phase on erosion behavior. The erodent was angular fused alumina of 40-45 mm size. The erosion mechanism was followed in all topcoats with cracking and fracturing of the plasma sprayed splats due to erodent particles impact and impingement, whereas micro-ploughing was observed after 900 °C SPE testing as an additional feature. The hardness and intrinsic properties of second phase component in the composite topcoats played a crucial role in improving the erosion rate (ER) at ambient as well as 900 °C. The Nd₂Ce₂O₇/YSZ topcoat show lower ER due to combatively higher hardness of Nd₂Ce₂O₇ and good interfacial bonding with YSZ. The overall lowering of ER at 900 °C as compared to that of at ambient conditions was ascribed to the anelastic mechanical response of the ceramic topcoats due to thermal cycling involved in the SPE testing at high temperature.

Abstract: Researching and developing chrome-free refractory becomes a research hotspot at present because hexavalent chromium ions (Cr⁶⁺) may lead to environmental hazard. The additives lanthanum oxide (La₂O₃), effect on mechanism of spinel refractory react with cement clinker, several additives, such as cerium oxide (Ce₂O₃), titanium dioxide (TiO₂), barium oxide (BaO), iron oxide (Fe₂O₃), are researched in this paper. It indicates that La₂O₃ is a suitable additive to MgO-MgAl₂O₄-ZrO₂ brick which not only could stabilize phase transition of dicalcium silicate (C₂S) in cement, but also do not impair the high-temperature-properties of spinel. The new environmentally friendly material spinel and lanthanum zirconate Composite is an excellent refractory for cement kiln which has high thermal shock resistance, good coating adherence, good corrosion resistance, higher mechanical strength, and longer service life than magnesia-chrome brick when they are used for sintering zone in cement kiln.

Abstract: Lanthania (La2O3) and zirconia (ZrO2) powders in ethanol based suspension were mechanochemically treated in a planetary ball mill for 12 hours at 200 rpm, dried and sintered at various temperatures from 400 to 1500 . Particles in nanometer sizes are produced after milling. X-ray diffractometry results show the formation of single phase lanthanum zirconate on subsequent heat treatment for 1h at 1500 . Phase evolution based on the intensities of the XRD plots and BET surface area analysis indicates three stages of crystallization: below 800 , between 800 and ~1100 , and above 1100 where reflections of La2Zr2O7 with pyrochlore structure are increased with further heating. Only endothermic energy peaks are observed in the differential thermal analysis (DTA) curve of the milled powders, which could be attributed to the reactions involving dehydroxylation, decarboxylation and complete disintegration of ethanol. This indicates that probably, lanthanum zirconate has grown on sintering at high temperatures from the very fine particles produced by mechanochemical activation during milling. Thermogravimetric analysis has recorded a total weight loss of ~9% from the original weight of the milled powder on sintering at 1500 . The values of the surface area of the powders are found to decrease while the crystallite size of La2Zr2O7 are increased with increasing temperature.