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  2. Chihara Hiroki

Chihara Hiroki

  (茅原 弘毅)

Profile Information

Affiliation
Professor, Department of Architectural and Environmental Design, Osaka Sangyo University
Degree
Ph.D(Osaka University)
博士（理学）(大阪大学)
Researcher number
70379296
ORCID ID
 https://orcid.org/0009-0004-9952-2251
J-GLOBAL ID
200901054903650002
researchmap Member ID
6000000027

Research Interests

 7

Major Research Areas

 3
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Research History

 9
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Education

 3

Papers

 53
  • C. Koike, H. Chihara
    The Astrophysical Journal, 951(1) 24-24, Jun 29, 2023  Peer-reviewed
    Abstract The presence of amorphous silicate particles in interstellar and circumstellar space has been suggested based on the observation of 9.7 and 18 μm emission bands. We have successfully synthesized amorphous silicate samples of an enstatite and forsterite composition by the mechanical milling of mixed powder consisting of SiO2–MgO and SiO2–Mg(OH)2 reagent-grade particles under different rotation frequencies and milling times. These two types of starting materials are prepared to study the effect of the OH bond on synthesis and crystallization. The amorphous samples were characterized by X-ray diffraction and infrared spectroscopy. Amorphous samples with enstatite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2 at 300 rpm and for 300 hr. Amorphous samples with forsterite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2. The samples from SiO2–Mg(OH)2 require 400 rpm and a long milling time of 1600 hr. After crystallization, amorphous samples with an enstatite composition synthesized from SiO2–Mg(OH)2 mainly transform into forsterite with small amounts of amorphous silica SiO2 and enstatite depending on the rotation frequencies and milling time, while those from SiO2–MgO become enstatite. The amorphous samples with a forsterite composition are crystallized to forsterite from both starting materials. The presence of H2O or OH bonds significantly affects the final products after the crystallization of amorphous silicates of enstatite composition.
  • Junya Matsuno, Akira Tsuchiyama, Takayuki Watanabe, Manabu Tanaka, Aki Takigawa, Satomi Enju, Chiyoe Koike, Hiroki Chihara, Akira Miyake
    The Astrophysical Journal, 911(1) 47(16pp)-47, Apr 10, 2021  Peer-reviewed
  • Inoue, Akio K, Hashimoto, Takuya, Chihara, Hiroki, Koike, Chiyoe
    Monthly Notices of the Royal Astronomical Society,, 495(2) 1577-1592, Jun, 2020  Peer-reviewed
  • Takahashi, A, Ootsubo, T, Matsuhara, H, Sakon, I, Usui, F, Chihara, H
    Publication of Astronomical Society of Japan, 71(6) 119, 2019  Peer-reviewed
  • Hiroki Chihara, Chiyoe Koike
    Planetary and Space Science, 149 94-99, Dec 1, 2017  Peer-reviewed
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Misc.

 7
  • IMAI Yuta, KOIKE Chiyoe, CHIHARA Hiroki, NOGUCHI Takaaki, TSUCHIYAMA Akira
    日本鉱物科学会年会講演要旨集, 2010 128-128, Sep 23, 2010  
  • R. Noguchi, K. Murata, A. Tsuchiyama, H. Isobe, H. Chihara, T. Nakamura, T. Noguchi
    METEORITICS & PLANETARY SCIENCE, 43(7) A117-A117, Jul, 2008  
  • Takakura Takashi, Murata Keisuke, Chihara Hiroki, Koike Chiyoe, Tsuchiyama Akira
    Abstracts for fall meeting of the Japanese Society for Planetary Science, 2007 136-136, 2007  
    According to infrared astronomical observation, the silicates of circumstellar dust are an amorphous material and a crystal of olivine and pyroxene while the silicate of interstellar dust is amorphous material. And the crystal hardly contains iron. We synthesized an amorphous silicate with the solar composition by the sol-gel method, and did the heating experiments. Each sample was analyzed by Infrared absorption spectroscopy and X-ray diffraction. We found that the olivine takes magnesium in preference to iron in the process of crystallization from an amorphous silicate.
  • Imai Yuta, Koike Chiyoe, Chihara Hiroki, Murata Keisuke, Tsuchiyama Akira
    Abstracts for fall meeting of the Japanese Society for Planetary Science, 2007 140-140, 2007  
    We produced sub-micron silicate particles as cosmic dust simulants to examine changes in infrared absorption spectra by particle size, shape, and distortion. Quartz from Andhra Pradesh, India and olivine from San Carlos, USA were used as samples. The crystals were crushed in a WC mortar first, and then powdered in an alumina mortar. Sub-micron particles were formed successfully by using a planetary ball mill with zirconia balls in the final step. The sizes and shapes of the particles were observed under an SEM and latticed distortion by crushing was evaluated by XRD. Infrared absorption spectra of the particles were changed by the particle size, shape and lattice distortion compared with result of samples without crushing by the ball mill. Sub-micron powder of olivine crystals obtained in the present experiments will be used as samples in reproduction experiments for Stardust sample recovery in aerogel collectors.
  • SUTO Hiroshi, KOIKE Chiyoe, CHIHARA Hiroki, SOGAWA Hisato, TACHIBANA Shogo
    The Astronomical herald, 99(12) 682-693, Nov 20, 2006  Peer-reviewed
  • Murata Keisuke, Chihara Hiroki, Koike Chiyoe, Tani Atsushi, Tsuchiyama Akira, Honda Mitsuhiko
    Abstracts for fall meeting of the Japanese Society for Planetary Science, 2005 35-35, 2005  
    We have investigated crystallization of amorphous silicate with the chondritic chemical composition. The amorphous sample was synthesized by the Sol-Gel method that has an advantage to get homogeneous amorphous materials at relatively low temperature without loss of volatile elements. The starting material was annealed at constant temperatures (660 – 758<SUP>o</SUP>C) for different durations (0.5 – 12 hrs). The experimental charges were examined by infrared absorption spectroscopy, X-ray diffraction and scanning electron microscopy / energy dispersive X-ray spectroscopy. On the spectrum of the initial amorphous sample, broad and smooth absorption features were observed at approximately 10 and 20 micrometers, that are typical for amorphous silicate originated from Si-O stretching and O-Si-O bending vibration modes. On the spectra of the annealed samples, sharp and prominent features of olivine appeared. The present results show that the crystallization kinetics is different from previous experiments for silicate with a simple composition (e.g. Hallenbeck et al., 1998).
  • Chihara Hiroki, Koike Chiyoe, Tsuchiyama Akira
    Abstracts for fall meeting of the Japanese Society for Planetary Science, 2004 81-81, 2004  
    Infrared spectra of plagioclase feldspar were measured using FT-IR spectrometer.The systematic spectral variation depending on the chemical composition of samples was observed. The dust formation process in the circumstellar region of oxygen-rich stars will be discussed.

Books and Other Publications

 1

Professional Memberships

 4

Research Projects

 4

研究テーマ

 2
  • 研究テーマ（英語）
    宇宙固体物質の光学物性
    キーワード（英語）
    宇宙塵、 赤外線天文学、 赤外線分光
    概要（英語）
    宇宙固体物質の赤外線波長域での光学特性の解明
    研究期間（開始）（英語）
    1999/04/01
  • 研究テーマ（英語）
    誘電体の物性研究
    キーワード（英語）
    固体分光、誘電体、複素誘電率、結晶
    概要（英語）
    誘電体の分光測定から複素誘電率を決定する
    研究期間（開始）（英語）
    1999/04/01
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