Due to its unique high conductivity and flexibility,
the two-dimensional
MXene material (Ti3C2T
x
) is expected to possess great potential in the thermoelectric
field. However, the low thermoelectric performance from high thermal
conductivity and a low Seebeck coefficient has limited its practical
application. In this report, we demonstrate the uniform growth of
ZnO layers on the laminar Ti3C2T
x
membrane by atomic layer deposition (ALD). Benefiting
from the low-temperature deposition characteristics of the ALD technique,
the ZnO@Ti3C2T
x
composite
films maintain the basic apparent morphology of the original films
after the deposition. We reveal that the Schottky barrier formed between
ZnO and Ti3C2T
x
exhibits
an energy-filtering effect, significantly enhancing the Seebeck coefficient
to result in more than a double increase in the power factor. Meanwhile,
the strong phonon-interface scattering between ZnO and Ti3C2T
x
is found to reduce the
thermal conductivity of the composite films by a factor of four as
compared to pure Ti3C2T
x
ones, further improving the overall thermoelectric properties
of the ZnO@Ti3C2T
x
composite films. Our investigation provides an ALD-based strategy
for growing wide band gap layers on the narrow band gap films to improve
the thermoelectric performance of various MXene materials.
In inertial confinement fusion experiments, fuel quality is determined mainly by the thermal environment of the capsule in the layering procedure. Owing to the absence of a radial thermal gradient, formed deuterium–deuterium (DD) ice shells in the capsule are thermally instable. To obtain a solid DD layer with good quality and long lifetime, stringent demands must be placed on the thermal performance of cryogenic targets. In DD cryogenic target preparation, two issues arise, even after the capsule’s temperature uniformity has been improved by the use of thick aluminized films. The first is the inconsistent ice shape, which is related to the capsule’s thermal field. In this article, some typical fabrication details are investigated, including adhesive penetration during assembly, the presence of the fill tube, the optical properties of the hohlraum and film surfaces, the jacket–hohlraum connection, deviations in capsule location, and asymmetrical contact at the arm–jacket interfaces. Detailed comparisons of the thermal effects of these factors provide guidance for target optimization. The second issue is the instability of seeding crystals in the fill tube due to unsteadiness of the direction of the thermal gradient in the fill tube assembly. An additional thermal controller is proposed, analyzed, and optimized to provide robust controllability of tube temperature. The analysis results and optimization methods presented in this article should not only help in dealing with thermal issues associated with DD cryogenic targets, but also provide important references for engineering design of other cryogenic targets.
Due to the high spatial resolution and contrast, the optical lens coupled X-ray in-line phase contrast imaging system with the secondary optical magnification is more suitable for the characterization of the low Z materials. The influence of the source to object distance and the object to scintillator distance on the image resolution and contrast is studied experimentally. A phase correlation algorithm is used for the image mosaic of a serial of X-ray phase contrast images acquired with high resolution, the resulting resolution is less than 1.0 μm, and the whole field of view is larger than 1.4 mm. Finally, the geometric morphology and the inner structure of various weakly absorbing samples and the evaporation of water in the plastic micro-shell are in situ characterized by the optical lens coupled X-ray in-line phase contrast imaging system.
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