Additive manufacturing for solid oxide cell electrode fabrication

© The Electrochemical Society.Additive manufacturing can potentially offer a highly-defined electrode microstructure, as well as fast and reproducible electrode fabrication. Selective laser sintering is an additive manufacturing technique in which three-dimensional structures are created by bonding subsequent layers of powder using a laser. Although selective laser sintering can be applied to a wide range of materials, including metals and ceramics, the scientific and technical aspects of the manufacturing parameters and their impact on microstructural evolution during the process are not well understood. In the present study, a novel approach for electrode fabrication using selective laser sintering was evaluated by conducting a proof of concept study. A Ni-patterned fuel electrode was laser sintered on an yttria-stabilized zirconia substrate. The optimization process of laser parameters (laser sintering rate and laser power) and the electrochemical results of a full cell with a laser sintered electrode are presented. The challenges and prospects of using selective laser sintering for solid oxide cell fabrication are discussed

Accuracy and Mechanical Properties of Open-Cell Microstructures Fabricated by Selective Laser Sintering

This paper investigates the applicability of selective laser sintering (SLS) for the manufacture of scaffold geometries for bone tissue engineering applications. Porous scaffold geometries with open-cell structure and relative density of 10-60 v% were computationally designed and fabricated by selective laser sintering using polyamide powder. Strut and pore sizes ranging from 0.4 - 1 mm and 1.2 -2 mm are explored. The effect of process parameters on compressive properties and accuracy of scaffolds was examined and outline laser power and scan spacing were identified as significant factors. In general, the designed scaffold geometry was not accurately fabricated on the micron-scale. The smallest successfully fabricated strut and pore size was 0.4 mm and 1.2 mm, respectively. It was found that selective laser sintering has the potential to fabricate hard tissue engineering scaffolds. However the technology is not able to replicate exact geometries on the micron-scale but by accounting for errors resulting from the diameter of the laser and from the manufacturing induced geometrical deformations in different building directions, the exact dimensions of the manufactured scaffolds can be predicted and controlled indirectly, which corresponds favorably with its application in computer aided tissue engineering.Mechanical Engineerin

Software Testbed for Selective Laser Sintering

Computer software plays an important role in the implementation of Solid Freeform Fabrication (SFF) technologies. This paper describes a software testbed for processing part geometry for a particular SFF technology, selective laser sintering (SLS), that is built around the separation of the slicing and rasterization operations to accommodate geometric information from a variety of sources. The paper also discusses the process control software being developed for a new high-temperat rkstation for SLS of metal powders. This program features a high-resolution data rmat, the ability to interpolate to achieve a desired resolution, and a menu-driven user interface with graphical feedback and process simulation capabilities.Mechanical Engineerin

Polyamide Nanocomposites for Selective Laser Sintering

Current polyamide 11 and 12 are lacking in fire retardancy and high strength/high heat resistance characteristics for a plethora of finished parts that are desired and required for performance driven applications. It is anticipated that nanomodification of polyamide 11 and 12 will result in enhanced polymer performance, i.e., fire retardancy, high strength and high heat resistance for polyamide 11 and 12. It is expected that these findings will expand the market opportunities for polyamide 11 and 12 resin manufacturers. The objective of this research is to develop improved polyamide 11 and 12 polymers with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering (SLS) rapid manufacturing (RM). A nanophase was introduced into the polyamide 11 and 12 via twin screw extrusion to provide improved material properties of the polymer blends. Arkema RILSAN® polyamide 11 molding polymer pellets and Degussa VESTAMID® L1670 polyamide 12 were examined with three types of nanoparticles: chemically modified montmorillonite (MMT) organoclays, surface modified nanosilica, and carbon nanofibers (CNFs) to create polyamide 11 and 12 nanocomposites. Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) were used to determine the degree of dispersion. Injection molded test specimens were fabricated for physical, thermal, mechanical properties, and flammability tests. Thermal stability of these polyamide 11 and 12 nanocomposites was examined by TGA. Mechanical properties such as tensile, flexural, and elongation at break were measured. Flammability properties were also obtained using the Cone Calorimeter at an external heat flux of 50 kW/m2. TEM micrographs, physical, mechanical, and flammability properties are included in the paper. Polyamide 11 and 12 nanocomposites properties are compared with polyamide 11 and 12 baseline polymers. Based on flammability and mechanical material performance, selective polymers including polyamide 11 nanocomposites and control polyamide 11 were cryogenically ground into fine powders and fabricated into SLS parts.Mechanical Engineerin

Selective Laser Sintering of Polymer Nanocomposites

This paper describes the fabrication and characterization of polymer nanocomposite (PNC) materials for use in the selective laser sintering (SLS) process. PNC materials are of great interest generally because of their excellent physical properties, and offer excellent potential in rapid manufacturing of structural polymeric parts. Three different nano additive materials have been used: cerium oxide IV, yttrium stabilized zirconia, and layered Hectorite clay. These materials have been used to reinforce PA6 polymer using solution blending and spray drying to create powder with particle sizes in the range of 5-40 µm. The mechanical properties and microstructure of the PNC materials have been evaluated and the results compared to those of unfilled polymer.Mechanical Engineerin

Improving the accuracy of products in their building by selective laser sintering using compensating deformations of initial triangulated models

Questions of technological preparation of triangulated models of industrial products for their building by selective laser sintering are considered. The need to implement compensating deformations on the stage of the technological preparation is justified. It is shown that the use of compensating deformation creates preconditions to improve the accuracy of products in their building by selective laser sintering

Selective Laser Sintering of Binary Metallic Powder

A selective laser sintering technique has been used to process metal powders and powder blends. Precursor powders include copper, tin, a 70Pb-30Sn solder and their blends. Excessive balling due to surface free energy effects occurred in single layer tests when the laser fluence was sufficient to cause melting of monolithic tin or solder. Improvements in single layer quality were obtained using copper-solder powder blends in a reducing atmosphere. The binary powder layers were characterized metallographically and the effect of processing parameters such as laser fluence and scan speed were assessed. Post-process annealing improved interparticle wetting and part strength. The influence of ZnCl2 flux was investigated when present as a coating in copper-solder blends. Multiple layer tests were performed on the most promising powder blends and the results are presented.Mechanical Engineerin

Investigation of Joining Micro-Foil Materials with Selective Laser Sintering and Laser Powder Deposition

Continuous and pulse selective laser sintering and laser powder deposition were used to find a solution to the manufacturing of micro-foil lattice structured components. A full factorial test matrix was used for each process to determine the processes capability to produce continuous tracks for joining the micro-foil materials. The samples were evaluated for dimensional profiles, distortion, and cycle times, to develop selection criteria for implementation of the processes into industry. The selective laser sintering processes were able to join the micro-foil materials into lattice structures with continuous tracks. The laser powder deposition processes were not able to properly join the micro-foil materials into lattice structures. The end results showed that micro-foil lattice structures can be produced using continuous and pulse selective laser sintering

Design and manufacturing of a Selective Laser Sintering test bench to test sintering materials

The goal of this project is to design and build a prototype of recoating system for a laser cutting machine to turn it into a selective laser sintering printing machine. This prototype will be used to study new sintering materials and to design, if decided, a SLS 3D printing Machine (Selective Laser Sintering). This project has been developed in the installations and funded by Fundació CIM. The project develops the mechanical design and the electronic system design. Both parts are explained on this paper, so new users can use the machine and can understand the system. With this paper, it is expected that it can be improved in a future to test other parameters and configurations. The paper is divided in three basic blocks that are summed up here: The first block is an introduction to the 3D printing technologies. The most used of them are explained and selective laser sintering is explained in deep. With this block the reader can understand why it is important to develop the SLS technology and what has to be done to improve the machines and the technology. The second block is a discussion on the mechanical design of the machine. The general idea of the machine is explained so the user can understand why the machine is designed in this way. After that, each part is detailed to see how the different mechanical challenges where overtaken. At the end of the block, there is a small calculations section needed on the electronic part. The third block is an extensive explanation of the electronic system that controls and moves the machine. In that block, the different components are explained so the user can understand its basics working principles. It is also explained how the selection of the electronic components was done. Then everything is put together to see the whole electronic system. Along with this paper, there are annexes that provide some extra information for the reader. One of this annexes refers to the mechanical part and the other one has some datasheets and coding for the electronic section. The whole design has been done in SOLIDWORKS cad software and its electric extension ELECWORKS. The programming job was done with Arduino compiler

Application of Factorial Design in Selective Laser Sintering

Selective Laser Sintering (SLS) is a complex process involving many process parameters. These parameters are not all independent. A factorial design technique is utilized to study the effects of three main process parameters, laser power, laser beam scanning speed, and powder packing density as well as their interactions on the sintering depth and fractional density. The results of this investigation provide useful information for the further experimental analysis of the process parameters and for selecting suitable parameters for SLS process.Mechanical Engineerin