Enhanced insulation temperature and the reduced thermal conductivity of nanostructured ceramic coating systems

Abstract

a b s t r a c tThe theoretical model on the size-dependent thermal conductivity of the nanograins and the composites, based on the phonon confinement and the boundary scattering effects, was developed to predict the 68% reduced thermal conductivity of the nanostructured ceramic coatings made of grains of 40-100 nm compared with the conventional ceramic coatings with micron-scale grains. In order to validate the model, the nanostructured zirconia layers and the corresponding conventional layers were sprayed on the same alloy matrixes, and the insulation temperatures were measured at different temperatures up to 1273 K. It was found that insulation temperature of the nanostructured ceramic systems enhanced about 200 K at most compared with that of the conventional ones. And the average enhancement of the insulation effect is in agreement with the theoretical prediction. The nanostructured ceramic coated systems provide the extending application in thermal barrier engineering, thermoelectric devices and other related applications.

Size-dependent interface adhesive energy and interface strength of nanostructured systems

“…2(c) in Ref. [24]), agreeing with the theoretical estimation. For the bulk splat grains of the conventional ceramic coatings, the diameter is the order of hundred microns and the thickness is about several microns [2].…”

“…The NiCrAlY interface bond coats of about 60 μm thickness, between the ceramic top coatings and the metallic matrixes, were obtained using the high velocity oxygen fuel process [24]. Two kinds of ceramic coatings were prepared by the similar process (Ar/H 2 ) on the Metco 7M atmospheric plasma spray equipment, and the METCO 9MP-DUAL type feedstock system was used.…”

“…The microstructure of one kind of ceramic coatings is in nanoscale prepared from the nanostructured YSZ powder (CM60, Institute of Process Engineering, Chinese Academy of Sciences), and the other is in micron-scale prepared from the conventional YSZ powder with the larger granularity (Metco 204CNS, Sulzer Metco, Westbury, NY, USA) by means of the standard parameters suggested by the manufacturer of the powder and torch (Sulzer Metco). The grain diameter of the nano-coatings is about 40-100 nm [24] (the microstructure detail can be referred to the TEM micrograph in Fig. 2(c) in Ref.…”

Deposition of nanostructured YSZ coating from spray-dried particles with no heat treatment

“…Due to the lower thermal conductivity and the chemical stability of TBC at high temperatures, the underlying alloy can operate at higher temperatures with a longer service life. The advancement of engineering applications dictates that the top ceramic layer of TBC possesses lower thermal conductivity [6,7] and higher thermal shock resistance [8][9][10]. Nanostructured YSZ coatings from agglomerated nanoparticles have demonstrated competitive advantages in extending the performance of TBC by forming both a porous nano-zone [11] and cracks perpendicular to the coating surface that provide lower thermal conductivity, a lower thermal expansion coefficient and lower strain tolerance [12,13].…”

Engineering the Thermal Conductivity of Functional Phase‐Change Materials for Heat Energy Conversion, Storage, and Utilization

“…Ma et al prepared a series of microencapsulated PCMs with binary cores and acrylate‐based copolymer shells and found that the wallboard fabricated with the synthesized microencapsulated PCMs showed an excellent thermal insulation performance . This can be attributed to the reduced thermal conductivity after encapsulation with copolymer shells, simply because the thermal insulation performance is positively correlated with a low thermal conductivity . Meanwhile, Ma et al investigated the reduced thermal conductivity of the polymer.…”