Carbon nanocoil (CNC), which is synthesized by a catalytic chemical vapor deposition (CCVD) method, has a coil diameter of 300-900 nm and a length of several tens of μm. Although it is very small, CNC is predicted to have a high mechanical strength and hence is expected to have a use in nanodevices such as electromagnetic wave absorbers and field emitters. For nanodevice applications, it is necessary to synthesize CNC in high yield and purity. In this study, we improved the conditions of catalytic layer formation and CCVD. Using optimized CVD conditions, a CNC layer with a thickness of >40 μm was grown from a SnO2/Fe2O3/SnO2 catalyst on a substrate, and its purity increased to 81% ± 2%.

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In the conventional ground improvement method, the strength is exhibited by stirring and solidifying the solidifying material in the ground, so it is difficult to expect a strength higher than the solidifying potential of the solidifying material. In addition, because the soil is directly agitated with solidifying material in the in-situ, there is a concern that the strength may decrease due to the soil quality (physical and chemical properties) of the in-situ ground. In order to solve the above problems, the authors respected the basic principle of soil mechanics that soil becomes hard if voids between soil particles and water are eliminated. That is, the authors thought that the soil would harden by mixing particles of different sizes and compressing each other's particles with a strong force. Then, an original SST method was developed that allows the column to be constructed while compacting. The feature of the SST method is that it is possible to construct high quality columns on the ground where humus soil, that is unsuitable for applying the conventional ground improvement method, is deposited. In this study, the authors will take up two cases where the SST method is applied. As a result, it was clarified that high quality columns can be constructed by the SST method at two sites with different soil characteristics.