Etsuro Ota

Specific conditions for Ni catalyzed carbon nanotube growth by chemical vapor deposition

Chemical vapor deposition using 2‐methyl‐1,2′‐naphthyl ketone as a starting material has been done between 1000 and 600 °C on Ni particles with diameters ranging from 10 to 500 nm. The Ni particles were prepared by annealing Ni thin film deposited on quartz glass substrates. The size of the Ni particle was controlled by the thickness of the Ni film. Carbon nanotubes were obtained at 700 °C when the diameter of the Ni particles was about 20–30 nm.

Behavior of Ni in carbon nanotube nucleation

A nucleation model was proposed for a carbon nanotube enclosing a Ni bar which was grown by chemical vapor deposition (CVD) at 700 °C using round Ni particles. At an early stage of CVD, each round Ni particle with a diameter of about 30 nm is covered with graphite layers. The graphite-covered Ni particle is considered to be unstable because the graphite layers have a large curvature. This instability is thought to make the graphite-covered Ni particles transform into a Ni bar enclosed within a carbon nanotube. In order to verify this nucleation model, we show that the size of the round Ni particle is a decisive condition for carbon nanotube formation by CVD, and that an intermediate state of the transformation of the graphite-covered Ni particles to the carbon-nanotube-enclosed Ni bar was observed by transmission electron microscopy.

Graphite thin film formation by chemical vapor deposition

Well‐ordered graphite thin films were obtained by chemical vapor deposition of 2‐methyl‐ 1,2’‐naphthyl ketone on Ni substrates at substrate temperatures higher than 600 °C. Values of interlayer spacing calculated from x‐ray diffraction data were between 3.360 and 3.350 A. Raman scattering spectra of the films showed a peak centering at 1580 cm−1.

Influence of chemical bond of carbon on Ni catalyzed graphitization

Carbon diffuses into metal and recrystallizes as graphite, which is termed graphitization of carbon by metal. This study has revealed that the temperature at which this graphitization occurs depends on the initial state of the carbon. The lowest temperatures at which graphitization by Ni occurs for diamond, diamondlike amorphous carbon, graphite, and graphitelike amorphous carbon were 700, 500, 900, and 700 °C, respectively. It is shown that the temperature ranges at which graphitization by Ni occurs are correlated to the temperature ranges at which graphite can be formed on Ni by chemical vapor deposition using organic substances as starting materials.

Effect of Ni on graphite thin‐film formation from organic materials by chemical vapor deposition

Two functions of Ni in the process of graphite thin‐film formation from organic materials by chemical vapor deposition (CVD) were studied. When dehydrogenation of a certain organic material was enhanced by Ni during CVD at 600 and 700 °C, the graphite thin film could be formed on Ni at these temperatures. On the other hand, a lot of organic materials changed into graphite by CVD on Ni above 800 °C, which corresponds to the obtained result that Ni deposited on disordered graphite changed the disordered graphite to crystalline one by heat treatment above 800 °C.

Graphite formation on Ni film by chemical vapor deposition

Abstract Thin film formation of graphite by chemical vapor deposition using 2-methyl-1,2′-naphthyl ketone as a starting material was carried out on Ni film substrates. On Ni films directly deposited on quartz glass, the graphite films were obtained when the Ni film thickness was above 1 000 A and above 5 000 A at 700 °C and 1 000 °C, respectively. Depositions on thinner Ni film substrates comprise amorphous carbon (a-C) or graphite tubes which was owing to the thermal coagulation of the Ni film into droplets. On the other hand, graphite film was obtained on the Ni film with thickness 10 A when a-C was inserted between the Ni film and the quartz glass. The coagulation of the Ni film is considered to be avoided by inserting a-C layer.

Graphite film formation by chemical vapor deposition on Ni coated sapphire

Graphite thin films can be formed by CVD on Ni films with a thickness of 500 A deposited on sapphire (110), (001) and (012) faces. The c-axis of the graphite film deposited on Ni/sapphire (110) is almost perpendicular to the sapphire surface. However, its structure is not homogeneous nor flat. The Auger analyses for graphite/Ni/(110) indicate that there are Ni islands and the graphite film covers both the Ni islands and the bare sapphire surface. It is also found that oxygen atoms are removed from the sapphire surface during CVD and a mixing layer of Ni and Al appears. The cystallinity, orientation alignment and surface morphology of the graphite films formed on Ni/sapphire (001) and Ni/sapphire (012) are worse than those deposited on Ni/sapphire (110).

Graphite thin‐film formation by chemical‐vapor deposition of o‐methyl‐diaryl ketones

Two kinds of o‐methyl‐diaryl ketones, 2,6‐di(2’,6’‐dimethyl‐1’‐naphthyl)‐naphthalene, (O), and 2‐methyl‐1,2’‐naphthyl ketone, (I), were used as starting materials for chemical‐vapor deposition (CVD). Raman‐scattering measurements and x‐ray diffraction analyses for the obtained films made it apparent that well‐crystallized graphite films could be grown on Ni substrate kept above 900 and 600 °C by using the materials (O) and (I), respectively. In order to obtain the crystalline graphite by CVD, the Ni substrate was necessary and the supply rate of the starting material must be in an optimum range. When the supply rate is too large, the obtained film contained the disordered graphite structure.

Application of Trinitrotoluene-containing Polymer Gel to Thin-layer Chromatography.

トリニトロトルエン(TNT)を架橋ポリビニルアルコール(PVA)ゲル中に分散させ,これを薄層クロマトグラフィーの担体として用いて芳香族化合物の構造異性体の分離を試みた.芳香族化合物としてはトルイル酸とニトロ安息香酸およびそれらのナトリウム塩のo-,m-およびか体を用いた。展開液は水を使用した。薄層はTNTを含むPVAゲル(TNT-ゲル)とセルロース粉末の各種割合の混合物から調製した.比較のために,TNTを含まないPVAゲル(TNT-フリーのゲル)も調製した。トルイル酸の各異性体はセルロースのみからなる薄層上ではまったく同じRf値を示し,この薄層にTNT-フリーのゲルを加えてもそれらのスポットはほとんど分離されなかった。しかし,TNT-ゲルとセルロース粉末の混合物から調製した薄層上ではそれらは相互に分離された。ニトロ安息香酸ではTNT-フリーのゲルをセルロースに加えた薄層でもo-体がm-およびか体から分離され,TNT-ゲルとセルロースの混合物から調製した薄層上ではさらにm-体とか体も分離された。これらの酸のナトリウム塩についても同様の分離効果が認められたが,その分離の程度は遊離酸の場合より低かった。