物質・材料研究機 共用基盤部門 強磁場共用ステーション 2008 年度 ...

磁 場 印 加 中 加 熱 による 熱 分 解 炭 素 の 作 製 と 磁 性
Preparation of pyrolytic carbon by heating under magnetic field and its magnetic properties
埼 玉 大 学 大 学 院 理 工 学 研 究 科 神 島 謙 二
Kenji Kamishima
Graduate School of Science and Engineering, Saitama University
Abstract:
It was reported that pyrolysis products from pure organic materials showed ferromagnetism and had spontaneous
magnetization even at room temperature. They are considered to be carbonaceous but not completely graphitized. The
samples were prepared by direct pyrolysis of triethylamine. The chemical liquid was placed at an edge of a quartz tube and
frozen at liquid nitrogen temperature. The quartz tube was evacuated and the center of the tube was heated to a desired
temperature of about 900ºC. When the central temperature became stable, the chemical was melt and introduced to the
heating area. The chemical vapor pressure of about 1 bar and the heating temperature were kept for 30 minutes. After the
pyrolysis, the tube was evacuated again and cooled down to room temperature. Pyrolysis carbonaceous product was obtained
from the inside of the tube, using a nonmagnetic hard titanium-alloy (Ti-Al-V) rod. A ferromagnetic sample was magnetically
separated from the product. We have found that the spontaneous magnetization of pyrolytic carbon is increased by annealing
at about 400ºC under magnetic field.
This enhancement by `annealing under magnetic field' motivated us to improve the synthesis method for a ferromagnetic
carbon sample. We expected that the application of magnetic field `during pyrolysis' would increase the magnetization of
ferromagnetic carbon. We employed a superconductive electromagnet with a large internal diameter of 150 mmf, and
constructed a new electric furnace which can be put in the superconducting magnet. The electric furnace has
vacuum-thermal-isolation and cooling-water jackets. The internal temperature (T in ) of the furnace can be increased up to
around 900ºC. The vacuum-thermal-isolation jacket works well at T in