Simulation Tool Demonstrates Double-Gate Transistor with 10-nm-Long Electrodes
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under a flow of 10%H2/F2 to produce black powders of Pd@MCM-48 and Pd@SBA-15. X-ray diffraction and transmission electron microscopy (TEM) analysis show that the Pd is distributed locally inside the pores and does not block the channel entrances. The sizes of the ballshaped Pd domains obtained have an average diameter of 35–40 nm. They are connected in a three-dimensional network, that is, the Pd domains fill the pores in the cubic matrix of MCM-48 with Ia3d symmetry. To verify that the Pd domains were free and the major product of the experiment, after the Pd@MCM-48 was treated with 20% HF to dissolve the silicate matrix, TEM analysis showed that “the Pd ball-shaped domains consist of three-dimensionally interconnected networks” whose shape and pores are “a replication of the MCM-48 template,” according to the article. Using the same method, Pd nanowires were obtained. SBA-15 was used as a template, resulting in 150-nm ellipsoidal domains with average diameters of 9 nm. This is almost the same as the diameter of the channel in the SBA-15 matrix. IULIA MUNTELE
Low-Strain Warm Pressing of Multilayer Composites Yields Layers with Longer-Range Protection from Crack Deflection To obtain a strong material with good crack-deflection properties, a delicate balancing act between a strong matrix material and a weak, crack-blunting second phase is required. In a study conducted by E.J. Winn and I.-W. Chen of the Department of Materials Science and Engineering at the University of Pennsylvania, crackpropagation mechanisms of zirconiabased composites containing an alumina second phase were examined. Despite the presence of a second phase, the samples demonstrated high bending strengths. As reported in the December 2000 issue of the Journal of the American Ceramics Society, the two sample types used in the experiments had identical configurations. They were composed of 16 zirconia matrix layers, with 15 alumina (glue) interlayers. The matrix element was fabricated with zirconia slurries cast into strips of tape 100 µm thick. The interlayer glue consists of a porous alumina solution. A type of polymer known as AST, or alkalisoluble swellable thickener, was added to a mixture of alumina powder and acidic water (pH 4). While stirring, the pH of the mixture slowly changes to 9 with NaOH. The change in pH causes the AST to expand, adding volume but not weight. Subsequent sintering causes the AST to MRS BULLETIN/FEBRUARY 2001
disintegrate, leaving large pores behind. The layered samples were assembled by stacking 1.5 in. × 1 in. × 100 µm layers of zirconia tapes with a thin layer of glue between them. The first sample was fabricated from the above formula and warm-pressed at 90°C to 20% of its true strain value. The second sample was prepared by pressing at the same temperature, but to 100% of its true strain value. Both samples were sintered for 30 min at 1350°C. Polished samples were subjected to the three-point bend test at 0.2 mm/min displacement. The mean strengths recorded for the two samples are 580 MPa and 540 MPa, respecti
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