Bismuth Telluride Nanocomposites for Micro Thermoelectric Generator Application

要約のみTohoku University小野崇人課

Micro-Thermoelectric Generators: Material Synthesis, Device Fabrication, and Application Demonstration

Micro-thermoelectric generator (TEG) possesses a great potential for powering wireless Internet of Things (IoT) sensing systems due to its capability of harvesting thermal energy into usable electricity. Herein, this work reviews the progress in recent studies on the micro-TEG, including material synthesis, device fabrication, and application demonstration. Thermoelectric materials are synthesized by the electrochemical deposition method. Three kinds of high-performance thermoelectric materials, including thick bulk-like thermoelectric material, Pt nanoparticles embedded in a thermoelectric material, and Ni-doped thermoelectric material, are presented. Besides the material synthesis, novel fabrication methods for micro-TEG can also help increase its output power and power density significantly. Two fabrication processes, micro/nano fabrication technology and assembly technology, are investigated to produce high-performance micro-TEG. Moreover, the fabircated micro-TEG as a power source for portable and wearable electronic devices has been demonstrated successfully

Cyclic Voltammetry And Galvanostatic Charge-Discharge Analyses Of Polyaniline/Graphene Oxide Nanocomposite Based Supercapacitor

Super capacitor is an energy device that is applicable in numerous fields because of its excellent reversibility, long life and high power density. Nevertheless, its universal use is restricted by the reduced energy storage capacity and its high crossed series compared to batteries. Even with the relatively high-level output and extensive use of super capacitor, there is still substantial doubt and ambiguity as to their efficiency in general, especially when it is compared to lithium-ion batteries. The inconsistencies are attributable both to the lack of standardization of the test methods and to the certainty of the strength capacity of the super capacitor after their resistance has been identified. Therefore, in this work, graphene oxide (GO) and polyaniline(PANI)nanocomposite supercapacitor electrode was fabricated and the performance was investigated by means of cyclic voltammetry and galvanostatic charge-discharge analyses. GOwas synthesized using improve Hummers method and PANI using oxidative polymerization chemical synthesis. Three different electrode’s compositions were prepared using PANI/GO nano composite and labelled as PGO30, PGO50 and PGO70. This article will conclude the electrochemical performance of the electrode. From the results, it was found that PGO50electrode(50% PANI/50% GO) hasthe best calculated capacitance with 19.71 F/g compared to the other composite electrodes. This may be attributed from the good electrical conductivity distribution of PANI and graphene oxide. The findings of the work may significantly drive the future of supercapacitor electrode from nanocomposite related materials

Design and development of rehabilitation device for hemiparetic patients

In this thesis, the development of rehabilitation device for patients who encounter walking weakness due to post-stroke effect is presented. . In order to design an efficient new mechanism, studies were carried out regarding kinematic of human walking. In the study, the motion of a healthy physical subject in walking situation of 1 km/h speed is used as guide to design the device. Thereafter, a mechanism was developed to produce similar motion. The device functions to actuate knee and hip rotation. The device is driven by a single actuator to drive both the hip and the knee joints mechanism. The kinematic analysis of constructed device has been performed and the results conformed the functionality of the suggested mechanism. The fabricated prototype shows the combination of DC motor and cam mechanism can actuated the movement of hip and knee joint simultaneously and may significantly reduced the power consumption. The computer based controller has also been developed with simple and practical application. With the combination of the controller and the fabricated model, the output profile of the rehabilitation device is acceptable by comparing with profile of actual data

Analysis of Single Actuator for Rehabilitation Device of Leg Weakness

In this paper, the development of rehabilitation device for patients who encounter walking weakness due to post-stroke effect is presented. The kinematic analysis was carried out in the initial stage of development in order to have an efficient mechanism. As guide to design the device, the walking motion of healthy physical subject for speed of 1 km/h was used and subsequently a mechanism was designed to create similar walking motion. The device functions to inculcate the movement of thigh and calf through appropriate rotation of hip and knee. A single actuator of direct current (DC) motor is used to actuate the rotation of the hip and the knee joints mechanism. The kinematic analysis of constructed device has been performed and the results conformed the functionality of the suggested mechanism. The fabricated prototype proves the combination of DC motor and cam mechanism can actuated the movement of hip and knee joint simultaneously and subsequently reduced the power consumption

Analysis of single actuator for rehabilitation device of leg weakness

In this paper, the development of rehabilitation device for patients who encounter walking weakness due to post-stroke effect is presented. The kinematic analysis was carried out in the initial stage of development in order to have an efficient mechanism. As guide to design the device, the walking motion of healthy physical subject for speed of 1 km/h was used and subsequently a mechanism was designed to create similar walking motion. The device functions to inculcate the movement of thigh and calf through appropriate rotation of hip and knee. A single actuator of direct current (DC) motor is used to actuate the rotation of the hip and the knee joints mechanism. The kinematic analysis of constructed device has been performed and the results conformed the functionality of the suggested mechanism. The fabricated prototype proves the combination of DC motor and cam mechanism can actuated the movement of hip and knee joint simultaneously and subsequently reduced the power consumptio

Thermoelectrical properties of silicon substrates with nanopores synthesized by metal-assisted chemical etching

A silicon substrate consisting of nanoporous silicon film could enhance the thermoelectric performance of bulk silicon due to its low thermal conductivity. Metal-assisted chemical etching (MACE) is a wet method for fabricating diverse nano/micro structures, which uses a noble metal as the catalyst for etching of semiconductor materials. In this study, we report the thermoelectrical properties of silicon substrates with nanopores in different porosities fabricated by MACE employing Ag nanoparticle as a metal catalyst. Different porosities of the nanoporous silicon layer were obtained by adjusting the deposition time of Ag nanoparticles. The lateral nanopores were found on the surface of the vertical nanopores sidewall caused by Ag nanoparticles. With the increase of the porosity, the surface area of the nanopores sidewall became rougher. In comparison with single-crystal silicon, silicon substrates with nanopores can enhance the thermoelectric figure of merit, ZT, due to the relativity high Seebeck coefficient and low thermal conductivity. However, lower electrical conductivity limits the enhancement of the ZT value. The porosity effect on the thermoelectrical properties of silicon substrates with nanopores was evaluated. The Seebeck coefficient has a maximum value at a porosity of 38% and then decreases at a porosity of 49%, and the electrical conductivity and thermal conductivity decrease with the increase of porosity. At a porosity of 38%, the ZT value of silicon substrates with nanopores can reach approximately 0.02, which is 7.3 times larger than that of the original high-doped single-crystalline silicon. Thus the nanoporous silicon film fabricated by MACE can enhance the thermoelectric performance of the bulk silicon

Formation And Evaluation Of Silicon Substrate With Highly-Doped Porous Si Layers Formed By Metal-Assisted Chemical Etching

Porous silicon (Si) is a low thermal conductivity material, which has high potential for thermoelectric devices. However, low output performance of porous Si hinders the development of thermoelectric performance due to low electrical conductivity. The large contact resistance from nonlinear contact between porous Si and metal is one reason for the reduction of electrical conductivity. In this paper, p- and n-type porous Si were formed on Si substrate by metal-assisted chemical etching. To decrease contact resistance, p- and n-type spin on dopants are employed to dope an impurity element into p- and n-type porous Si surface, respectively. Compared to the Si substrate with undoped porous samples, ohmic contact can be obtained, and the electrical conductivity of doped p- and n-type porous Si can be improved to 1160 and 1390 S/m, respectively. Compared with the Si substrate, the special contact resistances for the doped p- and n-type porous Si layer decreases to 1.35 and 1.16 mΩ/cm2, respectively, by increasing the carrier concentration. However, the increase of the carrier concentration induces the decline of the Seebeck coefcient for p- and n-type Si substrates with doped porous Si samples to 491 and 480 μV/K, respectively. Power factor is related to the Seebeck coefcient and electrical conductivity of thermoelectric material, which is one vital factor that evaluates its output performance. Therefore, even though the Seebeck coefcient values of Si substrates with doped porous Si samples decrease, the doped porous Si layer can improve the power factor compared to undoped samples due to the enhancement of electrical conductivity, which facilitates its development for thermoelectric application

Adaptation of Abbreviated Mathematics Anxiety Rating Scale for Engineering Students

Mathematics is an essential and fundamental tool used by engineers to analyse and solve problems in their field. Due to this, most engineering education programs involve a concentration of study in mathematics courses whereby engineering students have to take mathematics courses such as numerical methods, differential equations and calculus in the first two years and continue to do so until the completion of the sequence. However, the students struggled and had difficulties in learning courses that require mathematical abilities. Hence, this study presents the factors that caused mathematics anxiety among engineering students using Abbreviated Mathematics Anxiety Rating Scale (AMARS) through 95 students of Universiti Teknikal Malaysia Melaka (UTeM). From 25 items in AMARS, principal component analysis (PCA) suggested that there are four mathematics anxiety factors, namely experiences of learning mathematics, cognitive skills, mathematics evaluation anxiety and students’ perception on mathematics. Minitab 16 software was used to analyse the nonparametric statistics. Kruskal-Wallis Test indicated that there is a significant difference in the experience of learning mathematics and mathematics evaluation anxiety among races. The Chi-Square Test of Independence revealed that the experience of learning mathematics, cognitive skills and mathematics evaluation anxiety depend on the results of their SPM additional mathematics. Based on this study, it is recommended to address the anxiety problems among engineering students at the early stage of studying in the university. Thus, lecturers should play their part by ensuring a positive classroom environment which encourages students to study mathematics without fear