Thermoelectric properties of B-FeSi2 thermoelectric module utilizing cast-iron scrap chips

Semiconducting β-FeSi2 has been considered one of the most promising thermoelectric materials among numerous innovative thermoelectric materials due to its inexpensive cost and exceptional oxidation resistance up to 900 °C. Thermoelectric generation modules consisting of pairs of p-type 0.94C.I.-0.06Co-1.86Si and n-type 0.92C.I.-0.08Mn-1.86Si have been fabricated using Cu sheets as electrodes and Ag paste as bonding material. In an experiment, the maximum power density is measured by using a variable resistor range of 10Ω—10 kohm. Two different temperatures that are tested in this project are 40 and 60 °C. A rectangle and a trapezoid as the thermoelectric leg shape geometry are compared. The percentage difference for voltage is around 21% while the power shows a 41 and 65% difference depending on the temperature difference. The latter percentage difference is possessed by higher T. Based on the comparison with the reference, thermoelectric module from cast iron scrap chips was comparable and better than the reference. Trapezoid shows better geometry than rectangular shape in terms of thermoelectric power density. At 40 °C, the maximum power output are 21.89 and 21.91 μW whilst the maximum power for 60 °C are 28.13 μW and 28.42 μW for rectangle and trapezoid respectively

Generation of Kelly and dip type sidebands soliton employing Topological insulator (Bi2Te3) as saturable absorber

Conventional Kelly sidebands soliton and dip-type sidebands soliton were observed with the employment of Bi2Te3 as saturable absorber (SA) in Erbium-Doped Fiber Laser (EDFL). The fabricated Bi2Te3 possessed the following characteristics: Isat 102 MW/cm2, modulation depth 41.4%, and non-saturable absorption at 10%. The Bi2Te3 solution was transferred to the end of the fiber ferrule by the optical deposition method. Conventional Kelly sidebands soliton was obtained with a fundamental repetition rate and pulse width of 24 MHz and 0.78 ps, respectively. The existing cavity length was extended and with the appropriate tuning of light polarization, dip-peak intensity soliton sidebands with bunched pulses were observed. The oscillation trace revealed the repetition rate of dip-peak intensity sidebands soliton was ascertained at 13.5 MHz, which was in accordance with the cavity length. There was a total of 144 pulses in a single bunch envelope under the maximum available pump power. With the appropriate tuning of light polarization, constructive and destructive interference between soliton and dispersive waves took place in EDFL resulting in the formation of peak intensity (Kelly sidebands) and dip-peak intensity on the soliton spectrum. To the best of the author’s knowledge, this is the first demonstration of dip-peak intensity sidebands soliton using Bi2Te3

Fault localization on power cables using time delay estimation of partial discharge signals

Precise localization of partial discharge (PD) sources on power cables is vital to prevent power line failures that can lead to significant economic losses for electrical suppliers. This study proposes four methods to estimate the time delay of PD signals under electromagnetic interference, including white Gaussian noise (WGN) and discrete sinusoidal interference (DSI), using denoised PD signals with signal-to-noise ratios ranging from 10.6 to -7.02 dB. The maximum peak detection (MPD) and cross-correlation (CC) approaches, as well as two new techniques, interpolation cross-correlation (ICC) and envelope cross-correlation (ECC), are evaluated for their effectiveness in PD source localization. The researchers employ the time difference of arrival (TDoA) algorithm to compute PD location using the double-end PD location algorithm, where the PD location precision serves as an indicator of the accuracy of the time delay estimation methods. The study concludes that CC and ICC are the most suitable methods for estimating the time delay of PD signals in the PD location algorithm, as they exhibit the lowest error rates. These results suggest that CC and ICC can be used effectively for precise PD source localization under electromagnetic interference on power cables

Optoelectronic properties comparison of 10 and 20 multi quantum wells Ga0.952In0.048N0.016As0.984/GaAs p-i-n photodetector for 1.0 µm wavelength

This study proves the addition of quantum wells to the intrinsic regions of p-i-n GaInNAs/GaAs has improved the performance of optoelectronic devices. The optoelectronic properties that contribute to the device's dark current and photocurrent need to be well understood to develop photo-response at longer wavelengths. This study reports an optoelectronic properties comparison of different quantum well number for Ga0.952In0.048N0.016As0.984/GaAs-based dilute nitride multi-quantum wells (MQWs) p-i-n photodetector devices. From photoluminescence (PL) analysis, 20 MQWs shows a higher PL peak than 10 MQWs. The maximum quantum efficiency (QE) is found to be 80.3% for 20 MQWs and 46% for 10 MQWs, where 20 MQWs being the highest QE value ever reported for GaInNAs-based MQWs photodetector. Current versus voltage (I–V) measurement shows that 20 MQWs produces lower dark current than 10 MQWs. Besides, 20 QWs sample produces a higher current density (−12.43 μAcm−2) than 10 MQWs (−7.52 μAcm−2) under illumination. Impedance spectroscopy analysis shows that a lower dark current of 20 MQWs is due to a high intrinsic resistivity and low dielectric loss peak compared to 10 MQWs. SimWindows simulation shows good correlation with responsivity analysis and impedance analysis where at −5 V, 20 MQWs produces higher responsivity (0.65AW-1) due to wider depletion region (deduce from conduction band profile) and lower intrinsic capacitance and dielectric loss (deduces from impedance analysis) than 10 MQWs (0.37AW-1). At room temperature, the detectivity (D*) of the 20 MQWs photodetector (7.12 × 1010 cmHz0.5W−1) is higher than 10 MQWS photodetector (4.89 × 1010 cmHz0.5W−1). Finally, the 20 MQWs's (4.02 × 10−11 WHz−0.5) has produces lower noise-equivalent power (NEP) than 10 MQWs (5.85 × 10−11 WHz−0.5). This study has successfully presenting an understanding of optoelectronic properties and simultaneously producing a sensitive photodetector with high quality, low-noise which is comparable with ∼1010 cmHz0.5W−1 of commercial III-V alloy based near-infrared GaAs-based photodetectors

Impedance spectroscopy analysis of Al/100-plane AlN/p-Si MIS prepared by HiPIMS method for tailoring dielectric properties

The effects of variation of sputtering pressure of AlN HiPIMS deposition on Si substrate to the structure and electrical properties were investigated through XRD, AFM and impedance spectroscopy method. The strong preferred 100-plane AlN was observed for all samples from XRD pattern. The AlN thin film thickness was observed decrease with the increase of sputtering pressure. AFM analysis shows the lowest surface roughness at 0.84 nm for 5 mTorr sputtering pressure. Impedance spectroscopy analysis of Al/100-plane AlN/Si MIS structure shows the electrical conductivity of AlN was directly proportional to the sputtering pressure and stable with temperature ranging from room temperature (299 K) to 353 K. Good dielectric stability was achieved at 3 mTorr sputtering pressure for all variation temperature and the dielectric constant calculated at average 3.5

Performance evaluation of Ag doped TiO2 nanoflowers in Dye-sensitized solar cell

Many attempts have been made over the last few years to create effective visible light-activated photovoltaic using Titanium dioxide as photoanode materials in Dye-sensitized solar cell (DSSC). TiO2 possesses high photocatalytic behavior but has high charge recombination. In this study, the effect of introducing Ag dopant in TiO2 nanoflower morphology as a blocking layer to reduce charge recombination is investigated. The fabricated Ag doped TiO2 nanoflower was characterized using XRD, UV-Vis, IPCE, EIS analyses and Solar simulator under 1M solar illumination. Ag dopant may be considered a great approach to improving electron harvesting by suppressing electron recombination between the interface of TiO2 and electrolyte

Nano-embedded high performance non-toxic solar cell

Dye-sensitized solar cell (DSSC) is a new type of solar cell that is environmentally friendly and proven clean that can bring advantages for photovoltaic technology development. The optimization of photoanode layer is fundamental for conversion of visible light-irradiation into electricity in DSSC device. In this investigation, nanoflowers structure of TiO2-Ag embedded with SrSnO3 is employed as a photoanode layer of DSSC by using hydrothermal technique and RF sputtering to create a larger surface area for anchoring dye

The investigation of chlorpyrifos (Cpy) detection of PEDOT:PSS-MXene(Ti2CTX)-BSA-GO composite using P-ISFET reduction method

MXenes are two-dimensional materials that are attractive for applications as sensors because they possess high conductivity, super hydrophilicity and high surface area. There already exist substantial researches on the use of Ti3C2Tx based MXenes as electrochemical biosensors, but in contrast Ti2CTX based MXenes are rarely discussed due to their inherent resistance instability. However, the use of Ti2CTX based MXenes is still worth exploring as theoretical studies have shown that Ti2CTX possesses a significantly lower bandgap compared to many other MXenes structures. Herein, this study examines the use of Ti2CTX MXene structures in a P-channel ion-sensitive field-effect transistor (P-ISFET) for the detection of Chlorpyrifos (Cpy). Compositing the PEDOT:PSS thin film with delaminated Ti2CTX MXenes flakes with graphene oxide (GO) and bovine serum albumin (BSA) allows it to maintain its sheet resistance at around 100 kOhm for 3 days. Interestingly when using the composite thin film, the minimum threshold voltage required to observe Cpy electroreduction is −0.1 V. This is much lower than that when using titanium dioxide (TiO2), which is −1.5 V. Composite thin films containing Ti2CTX MXene are found to detect Cpy with higher sensitivity compared to thin films without MXene. This is because the presence of Mxene in the PEDOT:PSS composite thin films improves the surface area available for Cpy detection. This study highlights the potential of Ti2CTx MXene-BSA composite as a promising 2D material for enzyme-free CPY detection

Effects of radio-frequency power on structural properties and morphology of AlGaN thin film prepared by co-sputtering technique

To date, the deposition of AlGaN thin film using the co-sputtering technique at room temperature has not been reported yet. The use of AlGaN for electronic devices has been widely known because of its ultra-wide bandgap. However, to deposit the AlGaN thin film and achieved high quality of AlGaN films, higher temperature or extra time deposition are needed, which is not compatible with industrial fabrication process. Here, a co-sputtering technique between two power supplies of magnetron sputtering (which are RF and HiPIMS) is introduced to deposit the AlGaN thin films. The AlGaN thin films were deposited at various RF power to study their effect on structural properties and morphology of the thin films. AlGaN films were sputtered simultaneously on silicon (111) substrate for short time and at room temperature using GaN and Al target. Then, the films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and surface profiler to study their properties. XRD shows the GaN (101) and (013) plane for the AlGaN deposited at RF power of 30 W. Also there only GaN (101) for the AlGaN with 50 W RF power. Yet, the 70 W RF power shows the amorphous structure of AlGaN. The roughness and the grain size of AlGaN film from AFM analysis showed the trend of decreasing and increasing respectively. The roughness of the AlGaN films with 30 W power was 0.82 nm, 0.85 nm for 50 W, and 0.46 nm for 70 W RF power. The grain size of the AlGaN films was 30.06 nm, 32.10 nm, and 37.65 nm for RF power of 30 W, 50 W, and 70 W respectively. The profilometer found that the thickness of the AlGaN films was decreasing with increasing of RF power. This paper can demonstrate a successful co-sputtering technique of AlGaN. Despite AlGaN crystal structure was not able to found out in the XRD analysis, the effect of RF power has been studied to give significant effects on AlGaN thin film deposition

Optimisation of octahedral metal complexes through spin-crossover modulation for harversting thermoelectrochemical energy / Megat Muhammad Ikhsan Megat Hasnan

Thermo-electrochemical cell (TEC) technology allows the conversion of a thermal gradient into electricity due to the Seebeck effect using inert electrodes and active redox electrolyte. TEC require a high entropy difference for high power density. This study proposes the use of a family of spin crossover (SCO) metal complexes as the TEC material. The change of spin states from high spin (HS) to low spin (LS) or vice versa, is utilized as the key mechanism in enhancing the entropy difference, and hence Seebeck coefficient of the system. The scope of this study is divided into three: (1) molecular modeling of the SCO complexes, (2) SCO composite optimisation and (3) proposing micro-TEC device design and fabrication process for future work. The SCO materials used in this work are based on an octahedral structure of transition metals (Iron, Cobalt and Manganese). Density Functional Theory (DFT) is used to correlate between molecular conformation and electrochemical HOMO-LUMO gap that provides a fundamental understanding of the SCO molecule as a function of its spin states. The SCO complexes synthesised is analysed using electrochemical impedance spectroscopy and cyclic voltammetry to provide a comprehensive picture of the thermoelectric performance of these SCO composite. The lower electrochemical HOMO-LUMO gap energy of a high in stable LS Fe in MPN obtained from molecular modeling and CV analysis explained the basis high ionic conductivity of Fe in MPN by three orders magnitude higher compared to Fe, Mn and Co in DMSO. Interestingly, the agglomeration of the Fe complex in MPN, in the form of spherical micelles (diameter ~200 nm,) provided an explanation its high Seebeck coefficient, as the high entropy of such an agglomeration resulted in a high Seebeck coefficient. The optimised micelle stability of Fe complex through 1% wt of PMMA additive to form gel TEC material shows power output of one order of magnitude higher (60μWm-2 at ΔT=60°C) than power output of the conventional KI-KI3 redox couple and complexes in solution (3-5 μWm-2). As a final study, module of TEC generators was fabricated using MEMS technology to provide a realistic platform for waste heat energy harvesting. Then, this work provide a systematic study of optimization of SCO metal complexes for energy harvesting from fundamental molecular design to SCO material synthesis and analysis to device fabrication. The gel Fe complex was the best SCO material compared to Mn and Co due to high SCO molecular stability and stable micelles formation capability thus enhance TEC performance through enhancement of both Seebeck coefficient and conductivity simultaneously