Enhancment of mechanical properties and performance of anode supported solid oksit fuel cell

Bu yüksek lisans tez çalışmasında, endüstriyel boyutlarda anot destekli katı oksit yakıt pili üretiminde ortaya çıkan eğilme, çatlama problemleri deneysel olarak incelenmiş yüksek mukavemetli ve yüksek performanslı anot destekli KOYP hücresi üretimi için koşullar belirlenmiştir. Performans ve mekanik dayanım iyileştirilmesi yapılmıştır. Deneysel çalışmada anot destek tabaka (ADT) ve anot işlevsel tabaka (AİT) karışım oranları, toz boyutları, tabaka kalınlıkları değiştirilerek, tabakaların uzama miktarları, çekme hızları ve eğrilik miktarları belirlenmiştir. Dilatometre yardımı ile elde edilen çekme hızları ince elektrolit tabakanın çekme hızına yaklaştırılmış ve böylece hücrede sinterleme sonrasında meydana gelen eğilmeler azaltılarak mekanik dayanım iyileştirilmiştir.En az eğriliğe sahip durumlar tespit edilerek 16 cm2 ve 81 cm2 boyutlarında KOYP hücreleri üretilmiş ve performansları ölçülmüştür.Ayrıca şerit döküm cihazı kullanılarak farklı kalınlıklarda elektrolit elde edilmiş ve performans artışı sağlanmıştır. Sinterleme sonrası elektrolit kalınlığıyaklaşık 4 µm olan 81 cm2 lik hücrenin 800 0C de 35 W ürettiği ölçülmüştür. Deneysel ölçümler anot destekli hücre üretiminde en önemli parametrelerin anot destek/elektrolit kalınlıklarının, tanecik boyutlarının ve elektrot/elektrolit karışım oranlarının olduğunu göstermiştir.In this study, the problems of warpage and cracking which occur during the fabricating of industrial size anode supported solid oxide fuel cell(SOFC) have been experimentally investigated and the fabrication parameters required to obtain anode supported SOFC with high strength and performance have been determined. In the experimental study, the effects of composition, the powder size and the thickness of both anode support and anode functional layers on the shrinkage rate and warpage behavior have been studied. The shrinkage rates of these two layers have been modified such that they are close to that of thin electrolyte layer via dilatometring tests and thus the mechanical strength is improved by reducing the warpage behavior during sintering. The cells having 16 cm2 and 81 cm2 with the optimized fabrication parameters are manufactured and tested. In addition, cells with different electrolyte thicknesses are also fabricated via tape casting and tested. İt is found that the cell having the thinnest electrolyte layer 4µm (after sintering) shows the highest performance. As a conclusion, the experimental studies reveal that the most important fabrication parameters for the anode supported SOFC are the thickness of the anode support and the electrolyte layer, the powder sizes and the ratio of the catalyst/electrolyte powders in the anode layers

DEVELOPMENT OF ANODE SUPPORTED SOLID OXIDE FUEL CELL WITH IMPROVED WARPAGE BEHAVIOR

Fuel cells are the devices that convert chemical energy of a fuel directly into electrical energy by electrochemical methods without any intermediate mechanical steps. Among the existing fuel cells technologies, Solid Oxide Fuel Cell (SOFC) have been attracting great interest because of the advantages including high energy conversion efficiency, different fuel options, clean and quiet operation. The most important feature that distinguishes SOFC from other fuel cell and place it in a different category is the high operating temperatures (600-1000 °C). In addition, they do not depend on the limitation of the Carnot cycle thus their efficiency is higher than those of the internal combustion engines. In this study, the problems of warpage and cracking which occur during the fabricating of an industrial size anode supported solid oxide fuel cell (SOFC) have been experimentally investigated and the fabrication parameters which enable to obtain anode supported SOFC with high strength has been determined. In the experimental study, the effects of composition, the powder size and the thickness of both anode support and anode functional layers on the shrinkage rate and warpage behavior have been studied. The shrinkage rates of these two layers have been modified such that they are close to that of a thin electrolyte layer via dilatometry tests and as a result the mechanical strength is improved by reducing the warpage behavior during sintering. The cells having 100 cm2 with the optimized fabrication parameters are manufactured and tested

Corrosion of Additively Manufactured Metallic Components: A Review

The unique additive manufacturing (AM) attributes such as tool-less design, on-site fabrication, short production cycle, and complex structures fabrication can make AM market penetration deeper. The sustained improvements in AM’s computational hardware and software, advanced automation, affordable equipment, and process, structural, and metallurgical understanding are likely to contribute to AMs’ more comprehensive commercial adaptation. However, several scientific and technological issues like process-induced defects and microstructural heterogeneity limit its growth in replacing conventional products.AM mechanical properties are comparable to those produced conventionally, and the same is true about its corrosion behavior. However,AMprocess uncertainties can vary part properties, causing significant discrepancies in corrosion results. Controlling corrosion in AM alloys requires a proper understanding of the process and microstructural evolution. Optimizing processing conditions is critical for part’s high productivity and minimal defects. Similarly, post-processing conditions are vital to infuse desired mechanical and chemical properties. Regardless of the processing conditions, corrosion is integral to material stability that needs scientific input to understand and developmechanical and microstructural properties for excellent corrosion-resistant AM materials. This study aims to analyze the scientific work done in the corrosion analysis of AM materials and to suggest future work potentials

Effect of HIP Process and Subsequent Heat Treatment on Microstructure and Mechanical Properties of Direct Metal Laser Sintered AlSi10Mg Alloy

Purpose – The purpose of this paper is to evaluate the effect of post process combinations, e.g. hot isostatic pressing (HIP) only, HIP 1 T6 heat treatments, and T6 only, with different aging time, on surface properties, microstructure and mechanical properties of stress-relieved AlSi10Mg parts produced by direct laser metal sintering. Design/methodology/approach – HIP process and HIP 1 T6 heat treatments were applied to as stress-relieved direct laser metal sintered (DMLS) AlSi10Mg parts. Aging times of 4 and 12 h are selected to examine the optimum duration. To analyze the advantages of HIP process, a T6 heat treatment with 4 h of aging was also applied. Densities, open porosities and roughness values of as stress-relieved, HIPed, HIP 1 T6, and T6-only samples were measured. The samples were characterized by OM and SEM together with EDX analysis. An image analysis study was made to evaluate the inner pore structure, thereby to understand the mechanical behavior. Findings – HIP process does not cause a significant change in surface porosity; yet it has a positive influence on inner porosity. HIP process results in a microstructure of the aluminum matrix surrounded by a network of micron and nano size Si particles. Additional heat treatment results in larger particles and precipitation. After HIPing, ductility increases but strength decreases. Samples aged 4 h present improved yield and tensile strength but decreased elongation, yet samples aged for 12 h reach a combination of optimum strength and ductility. The lower level of tensile strength and ductility in T6-only condition indicates that HIP process plays a crucial role in elimination of the porosity thus improves the effectiveness of subsequent heat treatment. Originality/value – The study investigates the effect of post-process conditions and optimizes the aging time of the T6 heat treatment after HIP process in order to obtain improved mechanical properties. The stress-relieved state was chosen as the reference to prevent distortion during HIPing or heat treatment

Benefits of Laser Beam Based Additive Manufacturing in Die Droduction

The aim of this study was to benefit from the novel design and production freedom of laser manufacturing in order to alter the existing design concept of extrusion dies and to resolve the limits in die production. A two-stage experimental study was carried out to reveal advantages of laser manufacturing on the performance and capabilities of aluminum extrusion dies. In the first stage, geometric forms of hot work tool steel dies used in aluminum extrusion were optimized for Direct Metal Laser Sintering (DMLS) by means of flow dynamics as well as surface quality and mechanical properties of the final part. Simple geometry profiles were extruded to investigate the product quality. In the second stage, dies were tested until failure to determine the performance and lifetime. Dies were produced using EOS M290 and were not subjected to any conventional finishing and/or surface hardening post processes. Field tests were carried out in an industrial aluminum extrusion facility and high-quality profiles were extruded. Dies and extruded profiles were characterized. Results revealed that DMLS can be a favorable method to produce dies having complex inner sections with high accuracy. Production of high quality extruded profiles was possible using additive manufactured dies directly from production

Combination of peridynamics and genetic algorithm based topology optimization methods for additive manufacturing-friendly designs

Topology optimization (TO) is a practical tool to generate light-weighted engineering structures for various manufacturing industries. However, manufacturing constraints and surface smoothing are still considerable challenges for TO algorithms. Existing TOframeworks utilize mechanical analysis approaches that discretize the whole domain with elements or particles. Therefore, obtained geometries from TO have been criticized for their complex shapes. In this study, we propose a coupled framework to generate additive manufacturing (AM)-friendly designs which result in less support structure and higher surface quality. For this purpose, the generative topology optimization method (GTO), which uses genetic algorithm to search for the best alternative set of geometry within all the possible topology results, is coupled with the peridynamics topology optimization (PD-TO) method to evolve the PD-TO results into AM-friendly shapes. The PD-TO discretizes the problem domain using equally spaced particles during the TO process. Hence, PD-TO generates a point cloud file with relevant artificial material density values in the final state. Then, the GTO method utilizes the point cloud and material densities as an input file to achieve better final geometry. AM-friendly designs achieved from GTO are compared with the initial results obtained from PD-TO to demonstrate the efficiency and capability of the proposed method

Support Optimization for Overhanging Parts in Direct Metal Laser Sintering

The present work focuses mainly on the utilization of different support profiles for overhang structures in EOS M290 Direct Metal Laser Sintering (DMLS) machine. Maraging steel (MS1) parts with large overhangs were produced using various support parameters to reveal the effects of support profile on dimensional stability of overhang structures and surface quality of the downward facing surfaces. Overhangs supported by weak support profiles require less post processing due to easy support removal and low surface roughness values at the cost of dimensional stability. On the other hand, parts with stronger support profiles are less prone to thermal warping and provided better dimensional stability at the cost of surface quality. The hardness shows no remarkable variation along the overhang surface in the same structure as well as between different parts. The study reveals that the designer should choose different support assemblies depending upon the overhang surface size and location

Support optimization for overhanging parts in direct metal laser sintering

The present work focuses mainly on the utilization of different support profiles for overhang structures in EOS M290 Direct Metal Laser Sintering (DMLS) machine. Maraging steel (MS1) parts with large overhangs were produced using various support parameters to reveal the effects of support profile on dimensional stability of overhang structures and surface quality of the downward facing surfaces. Overhangs supported by weak support profiles require less post processing due to easy support removal and low surface roughness values at the cost of dimensional stability. On the other hand, parts with stronger support profiles are less prone to thermal warping and provided better dimensional stability at the cost of surface quality. The hardness shows no remarkable variation along the overhang surface in the same structure as well as between different parts. The study reveals that the designer should choose different support assemblies depending upon the overhang surface size and location

Malignancy and lymphoid proliferation in primary immune deficiencies; hard to define, hard to treat

Background Regarding the difficulties in recognition and management of the malignancies in primary immune deficiencies (PIDs), we aimed to present the types, risk factors, treatment options, and prognosis of the cancers in this specific group. Methods Seventeen patients with PID who developed malignancies or malignant-like diseases were evaluated for demographics, clinical features, treatment, toxicity, and prognosis. Results The median age of malignancy was 12.2 years (range, 2.2-26). Lymphoma was the most frequent malignancy (n = 7), followed by adenocarcinoma (n = 3), squamous cell carcinoma (n = 2), cholangiocarcinoma (n = 1), Wilms tumor (n = 1), and acute myeloid leukemia (n = 1). Nonneoplastic lymphoproliferation mimicking lymphoma was observed in five patients. The total overall survival (OS) was 62.5% +/- 12.1%. The OS for lymphoma was 62.2% +/- 17.1% and found to be inferior to non-PID patients with lymphoma (P = 0.001). Conclusion In patients with PIDs, malignancy may occur and negatively affect the OS. The diagnosis can be challenging in the presence of nonneoplastic lymphoproliferative disease or bone marrow abnormalities. Awareness of susceptibility to malignant transformation and early diagnosis with multidisciplinary approach can save the patients' lives