Electro-Thermo-Magnetic Effect-Induced Large Thermoelectric Performance of Calcium Cobaltite Nanocomposites.

As attractive thermoelectric oxides, Ca3Co4O9-based materials have been intensively studied for their applications in recent years. However, their thermoelectric performance is enormously limited due to the contradiction of electrical resistivity and thermal conductivity. Herein, BaFe12O19 nanospheres were introduced into the Ca3Co4O9 matrix. The metallic Ag, ferrites, and matrix phase survived together, and a high density of nanoscale BaFe12O19 precipitation was observed. The reduction of work function could lead to band bending and form an interface potential due to the electro-thermo-magnetic effect contributing to the hole migration. As a result, a huge ZT value of 0.51 for the 8 wt % BaFe12O19/Ca3Co4O9 nanocomposites was obtained at 1073 K, accompanied by a low electrical resistivity of 6.7 mΩ·cm and a high Seebeck coefficient of 217.5 µV/K. In addition, a significant reduction of thermal conductivity (1.11 W/(m·K)) occurred, which was due to the nanoscale ferromagnetic phase effectively scattering the mid- and short-wavelength heat-carrying phonons. The synergistic enhancement of thermoelectric performance confirmed that the electro-thermo-magnetic effect is an effective way to solve the challenging problem of performance deterioration in oxide thermoelectric materials.

The application of graphic language personalized emotion in graphic design.

Emotion Recognition is the experience of attitude in graphic language expression and composition. People use both verbal and non-verbal behaviours to communicate their emotions. Visual communication and graphic design are always evolving to meet the demands of an increasingly affluent and culturally conscious populace. When graphic designing works, designers should consider their own opinions about related works from the audience's or customer's standpoint so that the emotion between them can resonate. Hence, this study proposes a personalized emotion recognition framework based on convolutional neural networks (PERF-CNN) to create visual content for graphic design. Graphic designers prioritize the logic of showing objects in interactive designs and use visual hierarchy and page layout approaches to respond to users' demands via typography and imagery. This ensures that the user experience is maximized. This research identifies three tiers of emotional thinking: expressive signal, emotional experience, and emotional infiltration, all of which affect graphic design. This article explores the subject of graphic design language and its ways of emotional recognition, as well as the relationship between graphic images, shapes, and feelings. CNN initially extracted expressive features from the user's face images and the poster's visual information. The clustering process categorizes the poster or advertisement images into positive, negative, and neutral classes. Research and applications of graphic design language benefit from the proposed method's experimental results, demonstrating that it outperforms conventional classification approaches in the dataset. In comparison to other popular models, the experimental results demonstrate that the proposed PERF-CNN model improves each of the following: classification accuracy (97.4 %), interaction ratio (95.6 %), emotion recognition ratio (98.9 %), rate of influence of pattern and colour features (94.4 %), and prediction error rate (6.5 %).

Crystal Structure and Molten Salt Environment Cooperatively Controlling the Morphology of the Plate-like CaMnO3 Template through Topochemical Conversion.

In the field of oxide thermoelectrics, perovskite CaMnO3 ceramics have drawn plenty of attention due to their chemical stability, low cost, and environmental friendliness. By employing Ruddlesden-Poppe phase Ca3Mn2O7 as a precursor, the plate-like CaMnO3 microcrystals were successfully synthesized by the molten salt method combined with topochemical microcrystal conversion (TMC). The plate-like morphology of CaMnO3 was coordinately optimized by modulating the crystal structure of MnO2 and the molten salt environment. Plate-like microcrystals with an average size of ∼14.55 µm and a thickness of ∼2.89 µm were obtained by TMC reaction, demonstrating an obvious anisotropy. When ß-MnO2 was used as the raw material, a length-thickness ratio of 4.77 was obtained, which was attributed to the fact that CaMnO3 inherited the plate-like morphology of the Ca3Mn2O7 precursor during the TMC. The results confirm that the plate-like CaMnO3 microcrystals with obvious anisotropy can provide excellent template seeds for high-quality CaMnO3-based textured ceramics.

The Formation and Phase Stability of A-Site High-Entropy Perovskite Oxides.

High entropy perovskite oxides (HEPOs) were a class of advanced ceramic materials, which had attracted much scientific attention in recent years. However, the effect of factors affecting the phase stability of high entropy perovskite oxides was still controversial. Herein, 17 kinds of A-site HEPOs were synthesized by solid-state methods, and several criteria for the formation of HEPOs and phase stability were investigated. Single-phase solid solutions were synthesized in 12 kinds of subsystems. The results show that the phase stability of a single-phase solid solution was affected by the size disorder and configurational entropy. The electronegativity difference was the key parameter to predict the evolution of the cubic/tetragonal phase, rather than the tolerance factor. Cubic HEPOs were easily formed when the electronegativity difference was <0.4, while the tetragonal HEPOs were easily formed when the electronegativity difference was ≥0.4. This study can further broaden the family of HEPOs and is expected to design the phase stability of HEPOs through electronegativity difference.

Regulating Multiscale Defects to Enhance the Thermoelectric Performance of Ca0.87Ag0.1Dy0.03MnO3 Ceramics.

Achieving high thermoelectric properties of CaMnO3 ceramics is significant for its applications at high temperature. Herein, Ca0.87Ag0.1Dy0.03MnO3 ceramics with plate-like template seeds additives were prepared by using a solid-state reaction method. The multiscale defects, including grain boundaries, oxygen defects, and Ag nanoprecipitations, which were regulated by the different sintering atmospheres, were beneficial for electron transport and phonon scattering. The grain boundaries as coherent interfaces could act as an alternative phonon scattering source. Oxygen vacancies coupled with Ag nanoprecipitations were verified by geometric phase analysis and annular bright-field analysis. The decrement in oxygen vacancies concentration strongly depended on the enriched oxygen environment, which could reduce electrical resistivities. Compared to the sample sintered at Ar atmosphere, a 17.5 times increment in power factor and a 20.1% reduction of the total thermal conductivity were obtained for the sample sintered at O2 atmosphere. As a result, the maximum ZT value of 0.22 was obtained at 500 °C. It is an effective way for improving the thermoelectric performance of oxide-based thermoelectric materials.

Anisotropic Piezoelectric Properties of Porous (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Ceramics with Oriented Pores through TBA-Based Freeze-Casting Method.

Porous (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) piezoelectric ceramics with an oriented directional hole structure were prepared by using the tertbutyl alcohol (TBA)-based freeze-casting method. The influences of sintering temperatures on the microstructure and piezoelectric properties of porous BCZT ceramics were investigated both perpendicular and parallel to the freezing direction. With the increase in sintering temperatures and the porosities decreased from 58% to 42%, the compressive strength increased from 14.0 MPa to 25.0 MPa. In addition, the d33 value of 407 pC/N for the sample sintered at 1400 °C was obtained parallel to the freezing direction, which was 1.40 times that of the other direction.

Effect of Current Density on the Microstructure and Mechanical Properties of 3YSZ/Al2O3 Composites by Flash Sintering.

The 3YSZ/40 wt% Al2O3 composites were prepared by flash sintering at a low furnace temperature (700 °C). The effects of the current density on the relative density and Vickers hardness of the composites were systematically investigated. The results showed that the relative densities and Vickers hardness of the samples increased gradually with the increasing of the current densities, and the relative density was as high as 94.2%. The Vickers hardness of 11.3 GPa was obtained under a current density of 102 mA/mm2. Joule heating and defects generation are suggested to be the main causes of rapid densification in flash sintering. The microstructure of the molten zone showed the formation of eutectic structures in the composite, suggesting that grain boundary overheating may have contributed to the formation of the molten zone.

Rapid sintering of silicon nitride foams decorated with one-dimensional nanostructures by intense thermal radiation.

Silicon nitride foams were prepared by direct foaming and subsequent rapid sintering at 1600 °C. The intense thermal radiation generated under the pressureless spark plasma sintering condition facilitated necking of Si3N4 grains. The prepared foams possessed a porosity of ∼80 vol% and a compressive strength of ∼10 MPa, which required only ∼30 min for the entire sintering processes. Rapid growth of one-dimensional SiC nanowires from the cell walls was also observed. Thermodynamic calculations indicated that the vapor-liquid-solid model is applicable to the formation of SiC nanowires under vacuum.