PIM of non-conventional particles

Barreiros, Fátima M.; Vieira, M.T.

doi:10.1016/j.ceramint.2005.03.006

Cited by 14 publications

(20 citation statements)

References 9 publications

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“…Some authors associate this observation with the optimal solid loading. 30 In this sense, as firstly reported by German and Bose,12 the optimal solid loading should be at least 5 % lower than the critical powder volume content (CPVC); i.e. the volume of binder is insufficient to embed all the particles and fill the remaining free volume.…”

Section: Resultsmentioning

confidence: 99%

High-performance Ni–YSZ thin-walled microtubes for anode-supported solid oxide fuel cells obtained by powder extrusion moulding

et al. 2016

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Aiming at the fabrication of microtubular anode-supports for Solid Oxide Fuel Cells (SOFCs) applications, this contribution deals with the production of Ni-YSZ thin-walled tubes (<1 mm thickness) via Powder Extrusion Moulding (PEM). The overall method has been optimized with an emphasis on the effect of NiO particle size using two commercial NiO powders with mean sizes of 0.7 and 8 μm. A thermoplastic binder system based on polypropylene (PP), paraffin wax (PW) and stearic acid (SA) in a volume ratio of 50, 46 and 4, respectively, was used along with corn starch as a pore forming agent. Different feedstocks with solid loadings varying from 45 to 65 vol.% were processed and characterized to determine the optimal formulation. Typically, the mixtures exhibited a pseudoplastic behaviour from 100 to 1000 s-1. Feedstocks with finer NiO particles had the most balanced properties for PEM purpose and an optimal powder volume content of 65 vol.% was established. After extrusion and debinding steps, defect-free and constant cross-section tubes with 15 mm of length and 4 mm of nominal diameter were obtained. Final microstructure and DC conductivity were found to be closely linked to the NiO particle size, yielding a higher amount of open porosity and a better performance when using finer NiO powder. Based on this study, packing mechanism was found to be likely limited by the contribution of steric hindrances when dissimilar and coarse powder are mixed, which may play a decisive role in order to set tailored formulations. IntroductionSolid Oxide Fuel Cells (SOFCs) have emerged as an alternative to conventional power generators because of their high conversion efficiency and environmentally friendly performance while operating between 700 and 1000 °C. The most common configuration consists of a Ni-YSZ anode, a YSZ electrolyte and a lanthanum strontium-doped manganite (LSM) cathode.1,2 Among the different geometric designs of SOFCs, there is an increasing tendency to develop tubular devices because of their better thermo-mechanical properties, sealing simplicity, good thermal shock resistance, rapid start-up/shut-down time and excellent power cycling.3 Additionally, current technology is progressing towards microtubular stacks (MT-SOCF) owing to the enhanced volumetric power density, inversely proportional to diameter.4,5 On this matter, majority of recent works are heading for electrode-supported designs with thinner electrolytes to reduce the operation temperature, and thereby extending the range of SOFCs applications into mobile and portable fields.3 Specifically, anode-supported configurations have been on particular interest to overcome the issues associated with the consolidation of a dense electrolyte layer on the traditionally used cathodesupports.6-10 Nevertheless, in order to expedite the commercialization of MT-SOFCs systems, cell costs need to be remarkably reduced. In this way, the fabrication method of the support still remains as one of the major challenges, as well as the improvement of overall cell efficiency ...

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Section: Resultsmentioning

confidence: 99%

High-performance Ni–YSZ thin-walled microtubes for anode-supported solid oxide fuel cells obtained by powder extrusion moulding

et al. 2016

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“…The CPVC value could not be clarified with this method due to absence of instabilities for solid loading values in the CPVC region. Barreiros et al 8 also note the problem and further present a new methodology for the determination of critical solid loading by torque rheology for unconventional PIM powders, based on the intersection of different linear trends in plots of torque vs. solid loading.…”

Section: Introductionmentioning

confidence: 99%

Torque rheology of zircon feedstocks for powder injection moulding

Hidalgo

Jiménez-Morales

Torralba

2012

Journal of the European Ceramic Society

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“…After calcination, the powder was milled (200 rpm for 2 h) and sieved (d < 45 m). The chemical composition of the calcined powder is similar to the natural powder (noncalcined powder), namely SiO 2 = 54%, Al 2 O 3 = 24% and other oxides ≈20% ( Barreiros et al, 2002;Barreiros and Vieira, 2006). The physical characteristics of the calcined powder were evaluated based on the surface area (BET technique-Micromeritics ASAP 2000), the true density (Micromeritics Accupyc 1330 helium picnometer) and the tap density (vibration method).…”

Section: Methodsmentioning

confidence: 99%

“…The main disadvantage of natural raw materials is they are chemically unstable and undergo phase evolution during debinding and sintering. Therefore, it affects the surface finishing of the final product for technical applications (Barreiros and Vieira, 2006 of this study is to demonstrate the effect of heat treatment to modify the limitation of natural raw materials to obtain good quality products via PIM.…”

Section: Introductionmentioning

confidence: 99%

Structural phase evolution with temperature of non-conventional particles in PIM

Barreiros

Vieira

2008

Journal of Materials Processing Technology

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Inorganic natural powder Phase transformations Calcination Feedstock Powder injection moulding Mechanical properties a b s t r a c t Some inorganic natural powders may be interesting to manufacture complex shapes by powder injection moulding (PIM). However, these powders may evolve chemical and physically with temperature during the manufacturing processes, inducing blusters and geometrical irregularities, particularly loss of circularity. These imperfections were associated to gas liberation and dimensional variations during the debinding and sintering treatments and not to feedstocks' fluidity. Natural powders for manufacturing products by PIM must be previously calcined before conformation, in order to eliminate possible chemical reactions and phase transformation during debinding and sintering. To highlight the effect of the calcination process in the final quality of the sinter, a complex geometrical testing-probe was developed. After sintering, calcined and non-calcined powders have similar mechanical properties ( calcined 0 = 111 MPa, non-calcined 0 = 93 MPa, Weibull modulus = 10). The use of a feedstock of the natural calcined powders leads to PIM products with high geometrical reproducibility and good surface finishing.

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PIM of non-conventional particles

Cited by 14 publications

References 9 publications

High-performance Ni–YSZ thin-walled microtubes for anode-supported solid oxide fuel cells obtained by powder extrusion moulding

High-performance Ni–YSZ thin-walled microtubes for anode-supported solid oxide fuel cells obtained by powder extrusion moulding

Torque rheology of zircon feedstocks for powder injection moulding

Structural phase evolution with temperature of non-conventional particles in PIM

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