This paper has investigated the fabrication process of porous Ni-YSZ anodes by the powder injection molding method, in which a powder space holder (PSH) is used. Polymethyl methacrylate (PMMA) has been used as a PSH for mixing with NiO-YSZ powders. For this study, five kinds of feedstock containing 0%, 10%, 20%, 30%, and 40% PMMA by volume were prepared. The thermoplastic binder used for the process had a fixed 35 vol.%, and the powder loads formed the remaining 65, 55, 45, 35, and 25 vol.% of the feedstock. After molding and debinding, the parts were sintered at 1,500°C. The obtained results showed that increasing the PMMA portion of the feedstock and reducing its powder load causes the viscosity of the feedstock to decrease. The amount of shrinkage of the samples containing 0-30% PMMA showed an almost linear increase with the increase of the PMMA content, and for the samples with 40% PMMA, this increase of shrinkage was higher. The amount of porosity in the samples having 0-30% PMMA increased with the rise in the PMMA content, but in the samples containing 40% PMMA, the amount of porosity decreased, such that it was less than that of the samples with 30% PMMA. The electrical conductivity and flexural strength of all the samples were also studied in this work.

Solid oxide fuel cells (SOFC) are a promising high-efficient power generating system that can directly convert chemical fuel to electrical power. Cost reduction of materials and processing is one of the key issues for commercialization of SOFCs. SOFCs, as the electrochemical devices consist of anode and cathode, separated by the ion conducting material called electrolyte. The main SOFC element is anode, whose function, apart from oxidation the hydrogen, is to carry the mechanical loads which occur in the whole cell. Anode features the cell skeleton supporting electrolyte and cathode. Due to the rising interest in SOFC a high demand for them in future is expected, therefore, one should use the powder forming method applicable for mass production of such elements. Powder injection molding is the best solutions in this case. This method offers the possibility of fabricating tubes or plates which can be assembled into packets making increase of the SOFC power possible.Powder injection molding (PIM) is a manufacturing technology for the net-shape production of small, intricate, and precise metal or ceramic components. The PIM process includes mixing of either metal or ceramic powders with a binder to produce a feedstock, injection molding to form a green part with the desired shape by making the feedstock flow into and fill a mold under pressure, debinding to form a brown part by removing the binder components, and sintering to near full density.The powders (NiO and ZrO2) were mixed with a binder system which consists of stearic acid (SA), polypropylene (PP) and paraffin wax (PW). Mixing of components was done using two blades at the temperature of 170 o C at the speed of 40 rpm. Five selected mixtures of powders with binder are studied. Rheological characterization of all type of feedstocks were performed in a Rheoflixer capillary rheometer at 170, 180 and 190ºC over a range of shear rates from 10 to 10000 s -1 . Feedstocks were injected on the injection molding machine to make the test pieces. The debinding process of green samples was made by two different steps. First the injected samples were debound in a bath with the heptanol and next by thermal debinding. The sintering process took place immediately after the debinding. Debound pieces were sintered by heating from 1150 to 1450ºC and by soaking at these temperatures for one hour. Results of the rheological and torque investigations have essential importance for further search of the optimum feedstock to injection molding machines making forming possible of shapes for fuel cells anodes, which require in addition debinding of the binder and sintering. High viscosity of the feedstock in which there are hard ceramic particles cause fast wear of screws, dies, heads, and cylinders of injection molding machines and extruders, therefore binder portion increase is required. One may state based on bending strength tests and density examinations of the sintered and reduced anodes that the sintering temperature should not be lower than 1250 o C. Lower sintering temperatur...

Solid oxide fuel cells (SOFC) are a promising high-efficient power generating system that can directly convert chemical fuel to electrical power. Cost reduction of materials and processing is one of the key issues for commercialization of SOFCs. Powder injection molding is a good solution for producing low cost and defect free components and is adapted with mass production. In this study, effect of five powder loading and sintering temperature and holding time on porosity and thermal shock characteristics of SOFC substrate is investigated. Finally, the results show powder loading is not key factor in porosity and thermal shock characteristics and it is better to use high powder loadings. High sintering temperature for long time leads to high density sintered parts and are not suitable for SOFC substrate. All parts show high thermal shock characteristics.

The degree of machine wear decisively determines the economic feasibility of powder injection molding. According to higher hardness of alumina powders (ca. 2000HV), manufacturing of ceramic components via PIM requires hard wear resistance equipments to overcome the wear phenomena. The wear test is based on the ASTM rubber wheel but the rubber wheel is replaced by a steel wheel of the same grade used in the barrel of an injection molding machine. The potential of hard coatings for wear protection in feedstock processing units is investigated in the present study. Model wear tests were carried out to demonstrate the tribological situation inside the screw/barrel system of extruders and injection molding machines. The substrate material was AISI 4140 steel which is used for PIM machine components. Hard coatings prepared by physical vapor deposition (PVD) and chemical vapour deposition (CVD) offer a good opportunity for wear protection. Due to higher temperature of feedstock and compression, the amount of wear in the metering zone is higher in comparison with other zones. The wear behavior also was strongly influenced by the characteristics of the feedstock (e.g. amount, size, shape and hardness of ceramic particles).