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Abstract Thermoelectric materials offer a unique solution for active cooling or conversion of heat to electricity within a thermal protection system due to their solid-state nature. Yet, the integration of thermoelectrics into thermal protection systems is hindered by conventional manufacturing processes, which limit the material’s shape. Laser additive manufacturing can enable freeform shapes that allow integration of thermoelectrics into systems that are favorable for thermoelectric energy conversion. Through modeling and experimentation, this work presents single melt line processing and structures of silicon germanium, a high-temperature thermoelectric material, for laser powder bed fusion. Experiments consisted of single melt lines with an Nd-YAG laser and 50-µm spot size on Si₅₀Ge₅₀and Si₈₀Ge₂₀powder compacts. We found that laser processing of silicon germanium alloys causes oxidation and processing defects that are resolved through rescanning strategies. Rapid cooling results in a microstructure with silicon-rich grains and germanium entrapped near grain boundaries for Si₈₀Ge₂₀and dendritic structures in Si₅₀Ge₅₀which are linked to the degree of undercooling during solidification. Laser-processed silicon germanium contains crystalline defects, nanoscale precipitates, and an average grain size of 24 µm. This work informs laser additive manufacturing of silicon germanium parts and uncovers process-structure relationships of laser-processed silicon germanium alloys. 

Additive manufacturing allows fabrication of custom-shaped thermoelectric materials while minimizing waste, reducing processing steps, and maximizing integration compared to conventional methods. Establishing the process-structure-property relationship of laser additive manufactured thermoelectric materials facilitates enhanced process control and thermoelectric performance. This research focuses on laser processing of bismuth telluride (Bi 2 Te 3 ), a well-established thermoelectric material for low temperature applications. Single melt tracks under various parameters (laser power, scan speed and number of scans) were processed on Bi 2 Te 3 powder compacts. A detailed analysis of the transition in the melting mode, grain growth, balling formation, and elemental composition is provided. Rapid melting and solidification of Bi 2 Te 3 resulted in fine-grained microstructure with preferential grain growth along the direction of the temperature gradient. Experimental results were corroborated with simulations for melt pool dimensions as well as grain morphology transitions resulting from the relationship between temperature gradient and solidification rate. Samples processed at 25 W, 350 mm/s with 5 scans resulted in minimized balling and porosity, along with columnar grains having a high density of dislocations. 

Additive manufacturing offers several opportunities for thermoelectric energy harvesting systems. This new manufacturing approach enables customized leg geometries, minimized thermal boundary resistances, less retooling, reduced thermoelectric material waste, and strong potential to manipulate microstructure for higher values of figure of merit. Although additive manufacturing has been used to fabricate thin thermoelectric films, there has been comparatively limited demonstrations of additive manufacturing for bulk thermoelectric structures. This review provides insights about the current progress of bulk thermoelectric material and device additive manufacturing. Each additive manufacturing technique used to produce bulk thermoelectric structures is discussed in detail along with future directions and challenges. 

The development of professional engineers for the workforce is one of the aims of engineering education, which benefits from the complementary efforts of engineering students, faculty, and employers. Typically, current research on engineering competencies needed for practice in the workplace is focused on the experiences and perspectives of practicing engineers. This study aimed to build on this work by including the perspectives and beliefs of engineering faculty about preparing engineering students, as well as the perspectives and beliefs of engineering students about preparing for the workplace. The overall question of the research was, “What and how do engineering students learn about working in the energy sector?” Additional questions asked practicing engineers, “What is important to learn about your work and how did you learn what was important when you started in this industry? For engineering faculty, we asked, “What is important for students to learn as they prepare for work as professionals in the energy industry?” We anticipated that the findings of triangulating these three samples would help us better understand the nature of the preparation of engineering students for work by exploring the connections and disconnections between engineering education in school and engineering practice in the workplace. The aim was to map out the complex ecosystem of professional learning in the context of engineering education and practice. The core concept framing this study is the development of competence for engineering practice—including the education of students in the context of higher education and the practical learning of newly hired engineers on the job. Initial findings of the work-in-progress describe the nature of instruction and learning in higher education, learning in the workplace, along with comparisons and contrasts between the two. As of this point, we have initially mapped the learning ecosystem in the workplace based on in-depth, qualitative interviews with 12 newly hired engineers in the target energy company. In addition, we are analyzing interviews with two managers in the company and three other experienced leaders in the energy industry (this sample is currently in process and will include interviews with more participants). Currently, we are analyzing and mapping the learning and experiences of students in their studies of energy engineering and the instructional goals of engineering faculty teaching and mentoring these students. The map of the higher education ecosystem will connect with the workplace ecosystem to portray a more longitudinal map of the learning and development of professional competence of engineering students preparing for their career in the energy sector. The findings of the analysis of the workplace emphasized the importance of the social and relational systems in the workplace, while very preliminary indications from the educational context (students and faculty) indicate initial awareness of the social context of energy practice and policy. There are also indications of the nature of important cultural differences between higher education and industry. We continue to collect data and work on the analysis of data with the aim of mapping out the larger learning and experience ecosystem that leading to professional competence. 

The ability of thermoelectric (TE) materials to convert thermal energy to electricity and vice versa highlights them as a promising candidate for sustainable energy applications. Despite considerable increases in the figure of merit zT of thermoelectric materials in the past two decades, there is still a prominent need to develop scalable synthesis and flexible manufacturing processes to convert high-efficiency materials into high-performance devices. Scalable printing techniques provide a versatile solution to not only fabricate both inorganic and organic TE materials with fine control over the compositions and microstructures, but also manufacture thermoelectric devices with optimized geometric and structural designs that lead to improved efficiency and system-level performances. In this review, we aim to provide a comprehensive framework of printing thermoelectric materials and devices by including recent breakthroughs and relevant discussions on TE materials chemistry, ink formulation, flexible or conformable device design, and processing strategies, with an emphasis on additive manufacturing techniques. In addition, we review recent innovations in the flexible, conformal, and stretchable device architectures and highlight state-of-the-art applications of these TE devices in energy harvesting and thermal management. Perspectives of emerging research opportunities and future directions are also discussed. While this review centers on thermoelectrics, the fundamental ink chemistry and printing processes possess the potential for applications to a broad range of energy, thermal and electronic devices.