Toward High-Power Output of Generators: High-Power-Factor Ag2Te-Ag Thermoelectric Thin Films Using a Layer-by-Layer Method.

The power factor is key to improving the performance of thin-film thermoelectric generators as power sources. The expected large power factor of Ag2Te testifies to its application potential. In this study, Ag2Te-Ag thin films were fabricated using a layer-by-layer method for controlling their composition and improving their thermoelectric properties. In contrast to the traditional low-temperature monoclinic structure, orthorhombic Ag2Te thin films with Ag nanoparticles on top were obtained by the reaction between Ag and Te nanorod thin films. Analysis of the structural and thermoelectric properties showed increased carrier concentration and enhanced electrical properties of the films, while the structural transition between the orthorhombic structure and the face-centered cubic structure improved the films' electrical stability over a wide range of temperatures. Owing to the special structure, a competitive high power factor of 4.66 mW m-1 K-2 at 668 K was achieved. The proposed approach improves the electrical properties of n-type Ag2Te thin films, owing to the special Ag2Te-Ag structure, and provides guidance for designing high-output-power thin-film thermoelectric generators.

Superior Thermoelectric Performance of Robust Column-Layer ITO Thin Films Tuning by Profuse Interfaces.

Indium tin oxide (ITO) thin films suffer from poor chemical stability at high temperatures because of the instability of point defects and structural variations. An interface design strategy was proposed herein to improve this situation, where a robust ITO-based thin film with a column-layer structure was fabricated. Three types of column-layer ITO thin films were fabricated via magnetron sputtering. By tuning the interfaces, we controlled the effective mass and weighted mobility, enhancing the electrical conductivity (2.17 × 106 S m-1) and power factor (1138 µW m-1 K-2). The crack propagation path was prolonged because of the profuse interfaces between the columns and layers in the alternate thin films. Thus, enhanced nanohardness (16.5 GPa) was obtained. The structural evolution and performance of the column-layer ITO thin films annealed under different conditions were investigated. The atoms were restricted by the profuse interfaces, resulting in high-temperature stability. The results demonstrate that the interface design of ITO thin films can efficiently modify the stability of conductive ceramics over a wide temperature range, which has significant potential for applications in microdevices and aero engines.

Defect governed zinc-rich columnar AZO thin film and contact interface for enhanced performance of thermocouples.

The research on the stable thermoelectric properties and contact interface of high-precision thin-film thermocouples lags far behind the demand. In this study, a zinc-rich Al-doped ZnO (AZO) thin film was fabricated, in which the carriers were mainly donated by the Al dopant, and the oxygen defects migrated together, forming cage defects. Then, an indium tin oxide (ITO)/AZO thin-film thermocouple was prepared. It had a special temperature-dependent voltage curve due to the effects of cage defects on the thermoelectric properties of the AZO thin film and interfacial electron diffusion. When the zinc atoms in the cage defects were excited after annealing, a linear relationship between the temperature and voltage was obtained. The Seebeck coefficient of the thermocouple was constant at 168 µV K-1 over the entire measured temperature range. In addition, the calculated error of the thermocouple was lower than 1% from 50 °C to 500 °C, showing good repeatability. These results showed that defect engineering could effectively be used to improve the temperature range stability of thermoelectric materials and optimize the precision of thin-film thermocouples.

Highly oriented platinum/iridium thin films for high-temperature thermocouples with superior precision.

The long-term precise high-temperature measurement of thin-film thermocouples (TFTCs) has attracted attention due to the capability of instantaneous temperature detection. However, related technologies have seen slow development, and there is no one standard TFTC yet. Here, we focus on a new strategy of reducing alloys for the easy preparation and performance enhancement of TFTCs via nanostructure and interface design. To this end, we fabricated a platinum/iridium (Pt/Ir) pure-element TFTC with a well matched interface and few defects, which demonstrated excellent long-term service stability over a high-temperature range. The corresponding polynomial fitting coefficients were ≥0.99999, indicating the accurate acquisition of temperature data. A reduced deviation (<0.21%) between three calibration cycles was obtained over a wide temperature range of 300 °C to 1000 °C, which is better than the maximum precision of a standard wire thermocouple. Superior properties are achieved because of the resulting fewer defects in the Pt and Ir thin films with highly preferential orientation along the (111) plane. The results indicate that our Pt/Ir TFTCs have significant potential for application in many domains such as thermal detection, microelectronics and aero-engines.

Construction of Core-Shell Nanowire Arrays in a Cu-Cu2O Film Electrode for High Efficiency in Heat Dissipation.

Thermal engineering dramatically impacts the efficiency of microelectronics, but the corresponding technology lags far behind the need. For energy-efficient thermal management, a Cu-Cu2O film with highly ordered core-shell nanowire arrays and a good self-protection property was successfully fabricated using the magnetron sputtering method. The dense arrangement of nanowires in the films enhances the electronic transport property (220 mΩ sq-1), while the modified stable Cu2O layer maintained its perfect heat dissipation property, along with long-term thermal stability. The core-shell and nanogaps structure imparted an anisotropic thermal conductivity, where the out-plane electronic thermal conductivity (321 ± 16 W m-1 K-1) was 33.6 times higher than the in-plane value. To study the role of anisotropic properties in heat dissipation, a boiling experiment and thermal simulation were undertaken. The Cu-Cu2O core-shell electrode was beneficial to elevate the heat transfer coefficient, which would cause a fast directional transport and reduction of interfacial superheating. We demonstrated that an advancement of microelectronics could be achieved by integrating Cu electrodes with an ordered architecture.

Assessment of resin perfusion in hepatic failure in vitro and in vivo.

AIM: To observe the adsorbent effect of resin on endotoxin, cytokine, bilirubin in plasma of patients with hepatic failure and to determine the resin perfusion as an artificial liver support system in the treatment of hepatic failure. METHODS: One thousand milliliters of discarded plasma was collected from each of 6 severe hepatitis patients treated with plasma exchange. The plasma was passed through a resin perfusion equipment for 1-2 h via extracorporeal circulation, and then absorbent indicators of transaminase, bilirubin, blood ammonia, endotoxin and cytokines were examined. In the meantime, study of in vivo resin plasma perfusion was performed on 7 severe hepatitis patients to compare the changes of endotoxin and cytokines in blood before and after perfusion. RESULTS: The levels of total bilirubin, endotoxin, interleukin 1beta and TNF-alpha in plasma were significantly decreased after in vitro resin plasma perfusion. The levels of interleukin 1beta, TNF-alpha and endotoxin in blood were also evidently declined after in vivo resin plasma perfusion. Nevertheless, no obvious changes in IL-6, creatinine (Cr) and urea nitrogen (UN), blood ammonia and electrolytes were found both in vitro and in vivo. CONCLUSION: Bilirubin, endotoxin and cytokines in plasma of patients with hepatic failure can be effectively adsorbed by resin in vitro. Most cytokines and endotoxin in plasma can also be effectively removed by resin in vivo. It demonstrates that resin perfusion may have good treatment efficacy on hepatic failure and can be expected to slow down the progression of hepatic failure.