Efficient chemical vapor deposition (CVD) synthesis of super long (7 mm) aligned carbon nanotubes (CNTs) with highdensity is reported here. Activity of catalyst nanoparticles has been achieved for very long time periods (ca. 12 h) by optimization of experimental parameters. The relative levels of ethylene and water, as well as those of ethylene and H 2 , were found to be most important for achieving extended-time activity of the catalyst. Transmission electron microscope (TEM) images revealed that the nanotubes were mainly double-walled, but very few single-walled and multi-walled nanotubes were also present in the sample.

Millimeter (mm) long vertically aligned carbon nanotubes (CNTs) were grown by the catalyst assisted thermal chemical vapor deposition (CVD) technique. The continuous growth of CNTs as long as 7 mm was observed after 12 h of deposition by adjusting the growth parameters for making the catalyst active for a long time. The direct dependence of the number of walls of mm-long CNTs on the Fe catalyst thickness was observed. The successful syntheses of single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), and multiwalled nanotubes (MWNTs) with high percentages (∼80%) were achieved by varying the catalyst layer thickness. The effect of Al 2 O 3 buffer layer was found to be critical for this controlled synthesis, which has been discussed in detail. The possible growth mechanism is also discussed to better understand this phenomenon.

100-µm-long vertically aligned multiwall carbon nanotubes were grown in 1 s. A thermal chemical vapor deposition method at 700°C was used with a catalyst of iron films and a carbon source gas of acetylene diluted with helium. This study revealed a novel rapid growth mode that appears in the beginning of chemical vapor deposition when the rate of increase in the concentration of carbon source gas is high at the substrate. This new growth mode, which precedes a normal growth mode, provides well-crystallized and straight nanotubes.

We investigated the effect of oxygen incorporated in substrates for forming Fe-based catalytic particles and growing carbon nanotubes (CNTs) by water-assisted catalytic chemical vapor deposition. We examined two types of SiO 2 -covered Si (SiO 2 /Si) and oxygen-free Si 3 N 4 -covered Si (Si 3 N 4 /Si) as substrates for supporting Fe films. Well-aligned CNTs were synthesized at a higher growth rate on Si 3 N 4 /Si compared with those on SiO 2 /Si. The compositions of Fe-based catalytic particles that were formed by heating the substrates were examined using X-ray photoelectron spectroscopy (XPS) to determine the differences. Results show that the concentration ratio of Fe to Fe oxide in the catalytic particles strongly affects the alignment and height of synthesized brushlike CNTs and is well optimized in oxygen-free substrates.

The key technologies to achieve mass production of brushlike multiwalled carbon nanotubes (CNTs) are rapid processing for substrate heating and growing CNTs, and then cooling the substrate. We used chemical vapor deposition at 800 °C with a carbon source gas of acetylene to investigate how substrate heating rate affects CNT growth. The results revealed an effective layered structure of an Fe catalyst for the rapid heating process: an oxidized Fe layer and a metal Fe layer formed on a silicon dioxide layer. The relationship among the given structure of Fe catalysts, the catalyst shape after rapid heating, and the resultant CNTs were investigated.

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We developed vacuum assisted underfill technology for large die (>18 × 18 mm) with fine pitch area array bumps (< 150 m pitch) to solve a critical underfill void issue. Material development and process optimization are the keys to realize a stable process for such an advanced package. It was also confirmed that the newly developed underfill materials have good reliability on the large die package.

Vanadium alloys are attractive candidate fusion reactor materials especially because of its excellent low activation properties. Based on recent research, V-4Cr-4Ti has been selected as a leading candidate alloy. For application to the structural components, both ductility at low temperature and strength at high temperature are· required. The mechanical properties of the alloy are subject to distribution of interstitial impurities (C,O and N) in solution and precipitates· of Ti combined with the impurities. This paper summarizes recent studies to enhance properties of vanadium alloys by controlling the precipitates through thermal and mechanical treatments.In the program of fabricating high purity V -4Cr-4Ti large products, examinations of microstructures with SEM and TEM were carried out during the breakdown and the following thermal and mechanical treatment processes. The resulting alloys (NIFS-HEAT-l and 2 with C, 0, N of 56-69, 148-181 and 103-122 wppm, respectively) were subject to various cold rolling and heat treatment, followed by microstructural observations, Vickers hardness measurements, tensile tests. at room temperature, and Charpy impact tests at 17K. Two-step heat treatments, i.e. solid solution followed by re-precipitation, can control the impurity level in solution, and precipitate size and density. The yield strength and microstructures ofV-4Cr-4Ti (NJFS-HEAT-2) were examined after heat treatments at 1373K for an hour and the following re-heating for an hour at various temperatures. Note that the heat treatment at 1373K resulted in dissolution of the thin Ti-O-C precipitates. The yield stress was increased by the formation of high density of fine precipitate (precipitate hardening) with its peak at -973K. At 873K high density of fme precipitates were also observed in dark-field imaging conditions. The precipitate density and the yield stress decreased with the increase in temperature. The yield stress was again increased above 1173K by the increase in the impurity in solution (solid solution hardening). The change in the yield stress with the. temperature of the second armealing can be explained qualitatively by the combination of the two hardening mechanisms.For the purpose of enhancing the high temperature strength further, combined heat treatment and cold working were given to·V-4Cr-4Ti (NIFS-HEAT-2). Three types of heat treatment, SA (Solution Annealing, 1373 K, Ih), CP (Coarsened Precipitation, 1223K, lh) and FP (Fine Precipitation, 1373K, Ih followed by 873K, 10h) were provided. Fig: I shows Vickers Hardness of SA, CP and FP specimens with and without the following 20% cold working, as a fimction of the temperature of annealing for Ih before the hardness test. Comparing to CP (standard heat treatment), SA and FP enhanced the hardness. The hardness of SA and FP specimens increased by armealing 430 at -973K. With additional 20% cold working, the hardness was increased further in the all cases. Especially, SA or FP with 20% cold working resulted in significantly enhanced hardness. Their har...