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Lower Thermal Conductivity (lower + thermal_conductivity)
Selected AbstractsThermal Barrier Coatings Design with Increased Reflectivity and Lower Thermal Conductivity for High-Temperature Turbine ApplicationsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2006Matthew J. Kelly High reflectance thermal barrier coatings consisting of 7% Yittria-Stabilized Zirconia (7YSZ) and Al2O3 were deposited by co-evaporation using electron beam physical vapor deposition (EB-PVD). Multilayer 7YSZ and Al2O3 coatings with fixed layer spacing showed a 73% infrared reflectance maxima at 1.85 ,m wavelength. The variable 7YSZ and Al2O3 multilayer coatings showed an increase in reflection spectrum from 1 to 2.75 ,m. Preliminary results suggest that coating reflectance can be tailored to achieve increased reflectance over a desired wavelength range by controlling the thickness of the individual layers. In addition, microstructural enhancements were also used to produce low thermal conductive and high hemispherical reflective thermal barrier coatings (TBCs) in which the coating flux was periodically interrupted creating modulated strain fields within the TBC. TBC showed no macrostructural differences in the grain size or faceted surface morphology at low magnification as compared with standard TBC. The residual stress state was determined to be compressive in all of the TBC samples, and was found to decrease with increasing number of modulations. The average thermal conductivity was shown to decrease approximately 30% from 1.8 to 1.2 W/m-K for the 20-layer monolithic TBC after 2 h of testing at 1316°C. Monolithic modulated TBC also resulted in a 28% increase in the hemispherical reflectance, and increased with increasing total number of modulations. [source] Orientation-Control Synthesis of KTa0.25Nb0.75O3 NanorodsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010Yong-Ming Hu Single-crystalline KTa0.25Nb0.75O3 (KTN) nanorods with an orthorhombic perovskite structure were synthesized via a polymer-assisted hydrothermal method. The preferred crystallographic orientation of the nanorods were found to be controllable by using different types of polymers in the process; that is, [001]-oriented KTN were obtained upon the use of polyvinyl alcohol (PVA) and [110]-oriented ones were formed with the use of a combination of polyacrylic acid and PVA. The two types of nanorods showed different properties. The [110]-oriented nanorods exhibited a better photocatalytic decolorization efficiency but very likely a lower thermal conductivity (as indicated by the Raman spectrum measurements) than the [001] nanorods. [source] Creep Behavior of Plasma-Sprayed Zirconia Thermal Barrier CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007Reza Soltani Thermally sprayed ceramic coatings deposited from nanostructured feedstock powder have often demonstrated improved properties relative to coatings produced from conventional powders. This type of coating has been reported to exhibit better wear resistance and higher adhesion strength compared with conventional deposits. Powder consisting of hollow spherical particles has been reported to produce coating with lower unmelted particles and lower thermal conductivity. In this study, the thermo-mechanical properties of plasma-sprayed yttria-stabilized zirconia coatings deposited using each of these types of powder were investigated. Creep strain and creep rate were measured using free-standing thick coatings loaded in a four-point bend configuration at temperatures ranging from 800° to 1200°C in air under a range of loads. The creep exponent and activation energy were determined. [source] New composites with high thermal conductivity and low dielectric constant for microelectronic packagingPOLYMER COMPOSITES, Issue 2 2010Wei Ling Three composites based on cyanate (CE) resin, aluminum nitride (AlN), surface-treated aluminum nitride [AlN(KH560)], and silicon dioxide (SiO2) for microelectronic packaging, coded as AlN/CE, AlN(KH560)-SiO2(KH560)/CE, and AlN-SiO2/CE composite, respectively, were developed for the first time. The thermal conductivity and dielectric constant of all composites were investigated in detail. Results show that properties of fillers in composites have great influence on the thermal conductivity and dielectric constant of composites. Surface treatment of fillers is beneficial to increase the thermal conductivity or reduce dielectric constant of the composites. Comparing with binary composite, when the filler content is high, ternary composites possess lower thermal conductivity and dielectric constant. The reasons leading to these outcomes are discussed intensively. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] | ||||||||||