Thermoelectric performance of electrophoretically deposited p-type Bi2Te3 film

In this study, p-type Bi2Te3 films were fabricated using a fast, cost-effective, electrophoretic deposition method for thermoelectric applications. The sintering process was carried out at 693K, which resulted in compact, dense coatings. SEM investigations showed the uniform and even thicknesses across the green and sintered films. In addition, their microstructures were examined in more depth. Furthermore, the Seebeck coefficient measurements of the green and sintered films were compared and the highest in-plane Seebeck coefficients of 239μV/K have been recorded for the sintered film at 500 K

Preparation of n-type Bi2Te3 Films by Electrophoretic Deposition

A high quality crack-free film of Bi2Te3 material has been deposited for the first time using electrophoretic deposition (EPD) and microstructures of various films have been investigated. One of the most important thermoelectric (TE) applications is Bi2Te3 to manufacture TE generators (TEG) which can convert waste heat into electricity targeting the global warming issue. However, the high cost of the manufacturing process of TEGs keeps them expensive and out of reach for commercialization. Therefore, utilizing EPD as a simple and cost-effective method will open new opportunities for TEG’s commercialization. This method has been recently used for advanced materials such as microelectronics and has attracted a lot of attention from both scientists and industry. In this study, the effect of media of suspensions has been investigated on the quality of the deposited films as well as their microstructure. In summary, finding an appropriate suspension is a critical step for a successful EPD process and has an important effect on both the film’s quality and its future properties

Suspension characteristics and electrophoretic deposition ofp-Type Bi2Te3Films for thermoelectric applications

Electrophoretic deposition (EPD) was utilized to prepare uniform crack-free Bi2Te3 films for thermoelectric applications effectively. A p-type Bi2Te3 film with a coherent structure and even thickness was deposited from Tetrahydrofuran (THF) suspensions and examined using a scanning electron microscope (SEM). The specific weights of the depositions, the effective percentile coverage of the films on the substrate, the zeta potential and the electrical conductivity of different suspensions and the in-plane Seebeck coefficients of the Bi2Te3 films were measured. Although the Seebeck coefficient value of the EPD film (126 μV/K) was approximately 25% lower than the highest value reported for Bi2Te3 in the open literature via the co-sputtering method (160 μV/K), one of the most complex and expensive routes, the cost-effectiveness and speed of the simple EPD process is an undeniable advantage. This could open up new opportunities in the application of films to commercialize thermoelectric generators (TEG). It is interesting to note that the value of the Seebeck coefficient for our EPD-fabricated film was higher than for some of the other types of coatings prepared via more expensive and sophisticated fabrication routes, such as the electrodeposition technique (80 μV/K), for example

Electrophoretic Deposition of p-Type Bi2Te3 for Thermoelectric Applications

Electrophoretic deposition (EPD) of p-type Bi2Te3 material has been accomplished, and a high quality crack-free thick film has been achieved for thermoelectric (TE) applications. TE generators (TEG) can convert waste heat into electricity, which can potentially solve global warming problems. However, TEG is expensive due to the high cost of materials, as well as the complex and expensive manufacturing process. EPD is a simple and cost-effective method which has been used recently for advanced applications. In EPD, when a DC electric field is applied to the charged powder particles suspended in a suspension, they are attracted and deposited on the substrate with the opposite charge. In this study, it has been shown that it is possible to prepare a TE film using the EPD method and potentially achieve high TE properties at low cost. The relationship between the deposition weight and the EPD-related process parameters, such as applied voltage and time, has been investigated and a linear dependence has been observed, which is in good agreement with the theoretical principles of EPD. A stable EPD suspension of p-type Bi2Te3 was prepared in a mixture of acetone-ethanol with triethanolamine as a stabilizer. To achieve a high quality homogenous film on a copper substrate, the optimum voltage and time of the EPD process was investigated. The morphology and microstructures of the green deposited films have been investigated using a scanning electron microscope (SEM). The green Bi2Te3 films have shown good adhesion to the substrate. In summary, this study has shown that not only EPD of p-type Bi2Te3 material is possible, but its thick film is of high quality for TE applications

Investigating the Impact of New Technologies and E-learning on Learners' Emotions and Moods

Due to the lack of direct communication between teacher and learner in the e-learning environment, learners in this environment need education with good support and personal redemption. Using this research, you can have new technology in e-learning on the emotions and moods of learners. The statistical population of Farzanegan 7 high school math students is 75 people. In order to find 5 different types of learners' emotions, students are divided into 5 groups of 15, each of which is specifically exposed to different conditions. You have to experience happiness, anger, fear, frustration and hatred, and their face information is posted through the webcam. Your videos are recorded and the learners' emotions are measured and detected in different situations according to the neural network's deep learning algorithms by the Face Reader incremental software system. There has been a research method of designing a fuzzy expert system and a fuzzy inference system. And makes learners discover. And reject. Created within ranges. This change indicates that it increases the feeling and increases the negative feeling. Keywords: Internet of Things, e-learning, learners' emotions

Residual stress measurement in engine block—an overview

Significant residual stresses are often generated during the manufacturing of cast Al-Si alloy engine blocks due to differential cooling rates, the mismatch in the thermo-physical properties of adjacent materials in direct contact and volumetric changes caused by solid-state phase transformations during cooling. These may be modified during heat treatment and operation. These residual stresses may lead to distortion (affecting performance and economy) or premature failure of the engine block. For this reason, it is of fundamental importance to have reliable numerical and experimental methods for characterizing the residual stresses in the engine blocks at several steps during the manufacturing process. Sectioning and neutron diffraction techniques have been widely used to determine the residual stresses in the engine blocks. Numerical techniques have been developed to predict these residual stress but require experimental validation. The authors reviewed several numerical and experimental studies of residual stress evolution in engine blocks and showed how the residual stresses, microstructures, and mechanical properties are correlated

Techno-economic Feasibility of Modified Pulse Arc Deposition on Thick Section of Quenched and Tempered Steel

Quenched and Tempered (Q&T) steels welded structures that have numerous applications, particularly in the defence industry. However these steels are particularly prone to Hydrogen Assisted Cold Cracking (HACC) and require a highly-skilled welder to fabricate defect-free structures. This is due to the selection of the manual metal arc welding process of shielded metal arc welding (SMAW). The introduction of Modified Pulsed arc mode of depositions; a variation to Pulsed Arc deposition, has advanced deposition rates and can be employed by welders with a greater variation in skill. In this body of work, full strength butt welds are fabricated on 20mm, sections of Q&T AS/NZS 3597 Grade 700 steel under a high level of restraint using Modified Pulse Gas Metal Welding (GMAW-P) and conventional Shielded Metal Arc Welding (SMAW). The study investigates the economic feasibly of the two modes of deposition and the propensity for cracking when welded under high restraint. The study concluded that modified GMAW-P achieved reduction of 63% in the ‘Arc-On' time and an 88% reduction in the total normalised fabrication time. However, due to the increased propensity to lack of fusion type defects, strict controls must be employed in optimising the welding procedure to mediate for such defects if GMAW-P is to provide a techno-economically beneficial alternative to conventional SMAW when welding Q&T steels

Semi-Solid Processing of Alloys and Composites

A quick look through the past two centuries tells us that we may be in our third industrial revolution [...

Experimental Investigation of Welding Stresses in MWIC Weldability Test

The use of high-strength steels in the manufacture of energy pipelines, coupled with the transition to larger pipe diameters and greater wall thicknesses, has led to an increased potential for cracking including hydrogen assisted cracking of energy pipelines due to higher constraint induced stresses. In the present study, a modified version of the Welding Institute of Canada (MWIC) restraint test was used to simulate the constraint conditions of full-scale girth welds on energy pipelines, allowing the influence of welding process parameters on crack formation to be assessed. MWIC test samples of X70 grade high-strength low alloy pipeline steel were manually welded using two different welding processes, namely shielded metal arc welding (SMAW) and modified short-arc welding (MSAW). Residual strains, and hence stresses, in these samples were analysed quantitatively using neutron diffraction technique. Overall, results indicate that the modified WIC restraint test produces significant residual stresses and so is effective in constraining the root run and in consequence studying the hydrogen assisted cracking of high-strength pipeline steels