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nated by intergranular fracture, while in AJM it was in a manner resembling ductile behavior. Improved surface finishing by AJM resulted in a 15% improvement in flexural strength, compared with both ground and ground-plus-lapped samples. The researchers concluded that a higher compressive residual stress observed on the AJM-processed surface, combined with the smoother surface and a reduction in machining flaws, is responsible for the enhancement of the flexural strength. SHIMING WU

Ceramic-Based Anode for Solid-Oxide Fuel Cell Utilizes Higher-Weight Hydrocarbon Fuels without Coking Solid-oxide fuel cells (SOFCs) based upon hydrocarbon fuels are susceptible to loss of performance due to the deposition of carbon, a process known as coking. The standard anodes in many SOFCs contain high levels of Ni, which is known to promote coking. However, recent studies performed on a ceramic-based anode have led to a method that minimizes the amount of nickel required for SOFCs, so that electrochemical reactions are catalyzed while minimizing the amount of carbon deposited. In the June issue of Electrochemical and Solid-State Letters, Zhiqiang Ji of Applied Thin Films Inc. in Evanston, Ill., and Juang Liu, Brian D. Maddison, and Scott A. Barnett of Northwestern University report that by altering the composition of an electronic conductor, La0.8Sr0.2Cr0.8Mn0.2O3-δ (LSCM), by mixing it with an ionic conductor, Ce0.9Gd0.1O1.95 (GDC), the threephase boundaries increase and thus enable hydrocarbon oxidation without coking. Multilayer fuel-cell pellets were manufactured by pressing GDC powder into pellet form and sintering the pellets at 1500°C for 6 h. The anode was made by mixing metal oxides of lanthanum, strontium, chromium, and manganese in water prior to ballmilling for 24 h, followed by calcining at 1100°C for 2 h. After drying and grinding, the powder was mixed with 50 wt% GDC, 5 wt% NiO, water, and polyvinyl alcohol, ground and then painted on one side of the GDC pellet and sintered at 1100°C for 3 h. The NiO had a 16-nm average particle size, while the average particle size of the GDC was 50 nm. An anode with 50 wt% Ni and 50 wt% GDC was also fabricated in a similar fashion for comparison. The cathode consisted of 50 wt% La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and 50 wt% GDC synthesized in the method described and sintered at 900°C for 3 h. Both the anode and the cathode were ~20 µm thick, with an area of 0.3–0.6 cm2. 490

In tests, both the LSCM-GDC-Ni and Ni-GDC anodes performed about the same in hydrogen; however, when tested with propane, the power density was larger for the LSCM-GDC-Ni anode. No obvious carbon deposits were seen on the LSCM-GDC-Ni anode, but the GDC-Ni anode was heavily covered. As expected for SOFCs, power density increased as temperature increased, with a proportional decrease in cell resistance. Final results show that LSCM, although a poor catalyst for hydrocarbon oxidation, acts as the electronic conductor and the mechanical support, while the nickel acts as the oxidation catalyst. DONALD CARTER

crystals