Nanogenerator energy harvesting technologies that transform thermal energies into electricity may help address the growing need for green power. Therefore, this research aims to increase power ...generation by combining waste heat with pyroelectric nanogenerators as a sustainable energy source. Under optimal conditions, an external multi-pulse electric field can be utilized to generate power using thermoelectric cycle power generation. The greatest power may be gathered by applying various pulses of the external electric field at temperature changes on the surface of the pyroelectric materials. To generate pyroelectric power, a C9 BZT sample was used, and the lowest temperature difference for accomplishing this was 20 °C, with all measurements made on a sample with a lower limit of 120 °C. The maximum generation density was 0.104 mJ/cm2°CkV for a pulse width of 10 ms and 20 pulses of a low voltage (250 V/mm) input electric field. A multi-pulse electric field with low input voltage increases the power generation performance ratio (η) with the pulse count. At the largest number of pulses, the greatest η value for 250 V/mm was 7.834. Finally, it was determined that the developed pyroelectric power generation system may be more effective if a low-voltage, multi-pulse electric field is used.
In this study, boride nanoparticles were synthesized via a low‐cost and simple pulsed discharge of compacted crystalline and amorphous B micron‐sized powders for the first time. Borides of Ti, Mo, W, ...and Zr were chosen for synthesis experiments. The as‐synthesized powders were spherically shaped and smaller than 100 nm. X‐ray diffraction patterns indicated the presence of several minor phases in each boride powder in addition to a single main‐phase boride. Specifically, the main phases were TiB2, MoB2, WB4, and ZrB2 for borides of Ti, Mo, W, and Zr, respectively. Energy‐dispersive spectroscopy (EDS) indicated the presence of B and metal in almost all particles of every sample. The observed particles usually exhibited a two‐part structure: a boride phase and B. Small amounts of C, Fe, Cr, and Ni were detected by EDS; however, the contents of Fe, Cr, and Ni were substantially reduced after improvements to the experimental setup.
In the emerging era of aircraft industry, silicon carbide (SiC) is regarded as an appropriate material for gas turbine engine blades. In order to protect this ceramic component against the oxidation ...and volatilization in hot steam environments, environmental barrier coating should be utilized. The composite of SiC/Yb2Si2O7–Yb2SiO5 with self-healing ability is a candidate for the top layer of this coating. In this study, the crack-healing behavior of SiC/Yb2Si2O7–Yb2SiO5 nanocomposites is investigated by pre-cracking followed by annealing in oxidizing environments. Comparing to previous studies, the healing time and healing temperature can be reduced to 15 min and 800 °C by increasing the volume fraction of SiC to 20 %. In addition, nanocomposites with both self-healing ability and superior strength were created in this research by combining two types of SiC filler (whiskers and nanoparticulates). The self-healing mechanism in these composites is the SiC oxidation and silicate transformation associated with their volume expansion, which is evidenced by X-ray diffraction and scanning electron microscope. According to the results, the best volume ratio between whisker and nanoparticulate is determined as 1/3.
Yb2Si2O7/Yb2SiO5 composites dispersed with silicon carbide (SiC) possess a self‐crack‐healing ability that makes them promising top‐coat materials for multilayered environmental barrier coatings ...(EBCs) of SiC/SiC gas turbine blades. Stress‐induced surface cracks can be fully healed at high temperatures by the volume expansion of SiO2 glass and the newly formed Yb2Si2O7 in the composite. The reaction between SiO2 and Yb2SiO5 to form Yb2Si2O7 is considered a critical step that determines the high healing efficiency of this composite, therefore, Yb2SiO5 is considered as the secondary healing agent apart from the primary one, SiC. However, once all the healing agents have reacted, the composite can no longer promote its crack‐healing ability. To retain this property, in this work, Yb2SiO5 is regenerated by a heat treatment in water‐vapor atmosphere at 1073 K. X‐ray diffraction (XRD) and energy‐dispersive X‐ray spectroscopy (EDS) analyses show that the healing agent can be partially recycled after the treatment. In addition, the composite treated in water vapor demonstrates a greater crack‐healing ability compared with the untreated composite. These results open a new path for the development of gas turbine blades and high‐temperature components possessing permanent crack‐healing ability.
Yb2Si2O7–Yb2SiO5–SiC nanocomposites with self‐healing ability are promising materials for environmental barrier coatings. However, once all the Yb2SiO5 healing agents react, the composite loses its fast crack‐healing ability. To retain this property, Yb2SiO5 is regenerated through a heat treatment in steam. Analyses confirm that the healing agent is partially recycled and the crack‐healing ability of the treated‐composite is improved.
Efforts are being made to increase the efficiency of energy consumption by effectively using the dissipated heat as a source of renewable energy. Herein, we focused on a heat source wherein the ...temperature varies with time and recovers electrical energy from thermal energy by the pyroelectric effect. Further, we evaluated the net power density of the (Pb, La) (Zr, Sn, Ti)O3 material that is produced by its phase transformation as a result of increase in temperature. It was measured by the Sawyer-Tower circuit that was installed a diode and switch. The results showed that when the low or high temperature side of the measurement environment is in the antiferroelectric phase, the net power density decreased or became negative. Additionally, we estimated the range of temperature wherein a high-power density could be attained by examining the changes in it due to phase transformation.
The research group of this study demonstrates how Nanosecond Pulsed Electric Field can be used to tune the localization and formation of conducting carbon black (CB) assembles into linear structures ...with various thicknesses inside an insulating polymer matrix. The Electrorheology phenomenon of CB assembles in pre-polymer of polysiloxane under application of either DC or nanosecond pulsed electric field was observed utilizing optical microscopy method. Comparing to the typical DC electric field which has a value of 1875 V/mm, the nanosecond pulsed electric field facilities the increase in its electric field strength; generated between two constructed electrodes with a space size of 160 μm, to a value reaching 7500 V/mm. This type of electric field can overcome the voltage breakdown that occurs within the tested materials. The conduction structure of CB forms linear assemblies that anchor the composite film surfaces inside the matrix, which could be developed to much thicker percolation structures over five times by the application control of the nanosecond pulsed electric fields. Furthermore, the formation of vertically upright electrical percolation structures attributed to the remarkable decrease of the electrical resistivity of the resulting composites to 3 order of magnitude compared to the composites with a uniform distribution of filler. The electrorheology phenomenon under pulsed field was also tested by the optical observation method. The thickness as well as the concentration of CB particles were able to be controlled via the increasing in the nanosecond pulsed electric field. The novelty of this study lies in the utilizing of nanosecond pulsed field with a high electric strength that overcomes the electrical breakdown during tuning the carbonaceous filler assemblies. This unique technology is energy saving through fabricating polymer-based conductive materials without using surface modification or increasing the filler content.
A novel electro-thermodynamic cycle with a higher waste heat recovery efficiency than the conventional Olsen cycle was introduced by Kim et al. in 2015. Thus, in the present study, the importance of ...the temperature factors was investigated, revealing the sensitivity and effectiveness of the Kim cycle on the fluctuating properties of the applied heat source over the Olsen cycle. Power generation tests at different frequencies and temperature ranges were performed using nontoxic lead-free Ba(Zr0.1Ti0.9)O3 pyroelectric ceramics. As the frequency increased, the original isodisplacement process of the Kim cycle successfully improved the pyroelectricity and increased the internal electric field of the sample, thereby enhancing the energy density of the recovery process. This phenomenon compensated for the energy density loss from the poor heat conduction, which was the factor that saturated the power density when measured with the Olsen cycle. Therefore, the Kim cycle was more effective than the Olsen cycle when considering the fluctuating frequency factor. In addition, adjusting the temperature range factor induced a power density enhancement owing to the internal electric field increase mechanism. The power generation ability of the Kim cycle was significantly improved compared to that of the Olsen cycle. This research study revealed the sensitivity and effectiveness of the Kim cycle for recovering waste heat from a high-fluctuating rate source. Thus, the new Kim cycle has the potential to be investigated for its energy conversion ability in the next decade.
A two‐step processing was developed to prepare Yb2Si2O7‐SiC nanocomposites. Yb2Si2O7‐Yb2SiO5‐SiC composites were first fabricated by a solid‐state reaction/hot‐pressing method. The composites were ...then annealed at 1250°C in air for 2 hours to activate the oxidation of SiC, which effectively transformed the Yb2SiO5 into Yb2Si2O7. The surface cracks purposely induced can be fully healed during the oxidation treatment. The treated composites have improved flexural strength compared to their pristine composites. The mechanism for crack healing and silicate transformation have been proposed and discussed in detail.
Rare-earth silicates are promising environmental barrier coatings (EBCs) that can protect SiC
f
/SiC
m
substrates in next-generation gas turbine blades. Notably, RE
2
Si
2
O
7
(RE = Yb and Ho) shows ...potential as an EBC due to its coefficient of thermal expansion (CTE) compatible with substrates and high resistance to water vapor corrosion. The target operating temperature for next-generation turbine blades is 1400°C. Corrosion is inevitable during adhesion to molten volcanic ash, and thus, understanding the corrosion behavior of the material is crucial to its reliability. This study investigates the high-temperature corrosion behavior of sintered RE
2
Si
2
O
7
(RE = Yb and Ho). Samples were prepared using a solid-state reaction and hot-press method. They were then exposed to volcanic ash at 1400°C for 2, 24, and 48 h. After 48 h of exposure, volcanic ash did not react with Yb
2
Si
2
O
7
but penetrated its interior, causing damage. Meanwhile, Ho
2
Si
2
O
7
was partially dissolved in the molten volcanic ash, forming a reaction zone that prevented volcanic ash melts from penetrating the interior. With increasing heat treatment time, the reaction zone expanded, and the thickness of the acicular apatite grains increased. The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb
2
Si
2
O
7
but decreased considerably over time for Ho
2
Si
2
O
7
. The Ca in volcanic ash was consumed and formed apatite, indicating that RE
3+
ions with large ionic radii (Ho > Yb) easily precipitated apatite from the volcanic ash.
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