氏名　税　安澤
学位の種類　博士（工学）
学位記番号　博甲第246号
学位授与の日付　平成14年3月25日
学位論文題目　Origin of sintering deformation of alumina powder compacts　（アルミナ粉末成形体における焼結変形の原因）
論文審査委員
　主査　教授　植松　敬三
　副査　教授　小松　高行
　副査　教授　武藤　睦治
　副査　助教授　斎藤　秀俊
　副査　助教授　内田　希

• 論文目次
• 論文要旨

［平成13（2001）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

1　Introduction　p.3
1.1　Background　p.3
1.2　A new factor of sintering deformation　p.4
1.3　A new characterization technique　p.6
1.4　Aim　p.7
1.5　References　p.8
2　Origin of shrinkage anisotropy during sintering of uniaxially pressed alumina compacts　p.12
2.1　Abstract　p.12
2.2　Introduction　p.12
2.3　Experiments　p.14
2.4　Results　p.18
2.4.1　Properties of raw alumina powders　p.18
2.4.2　Compaction and densification behaviors　p.20
2.4.3　Sintering shrinkage behavior　p.23
2.4.4　Particle orientation structure in the compacts　p.31
2.5　Discussions　p.34
2.6　Conclusions　p.37
2.7　References　p.37
3　Effect of cold isostatic pressing on microstructure and shrinkage anisotropy during sintering of uniaxially pressed alumina compacts　p.40
3.1　Abstract　p.40
3.2　Introduction　p.40
3.3　Experiments　p.42
3.4　Results　p.43
3.5　Discussions　p.49
3.6　Conclusions　p.51
3.7　References　p.52
4　Development of anisotropic microstructure in uniaxially pressed alumina compacts　p.54
4.1　Abstract　p.54
4.2　Introduction　p.54
4.3　Experiments　p.55
4.4　Results　p.56
4.4.1　Anisotropic microstructure in the pressed compacts　p.56
4.4.2　Anisotropic sintering shrinkage of the pressed compacts　p.58
4.4.3　Anisotropic grain growth in the pressed compacts　p.61
4.5　Discussions　p.65
4.6　Conclusions　p.67
4.7　References　p.67
5　Anisotropic sintering shrinkage and grain growth of alumina compacts aligned in super high magnetic field　p.70
5.1　Abstract　p.70
5.2　Introduction　p.70
5.3　Experiments　p.74
5.4　Results　p.76
5.4.1　Spherical particle system　p.76
5.4.2　Spherical particle system　p.82
5.5　Discussions　p.88
5.6　Conclusions　p.91
5.7　References　p.92
6　General summary　p.95
7　Publication Papers　p.97
8　Presentations　p.98
9　Acknowledgments　p.100

　The origin of shrinkage anisotropy （i.e., deformation） of alumina powder compacts during sintering was systematically and quantitatively examined with two types of alumina powders. One was of elongated shape, and the other of spherical shape. The slight particle orientation occurred during uniaxial pressing in compacts of elongated particles, and caused anisotropic shrinkage and grain growth during sintering. The sintering shrinkage always was larger in the pressing direction than its perpendicular direction in the uniaxially pressed compacts of elongated particles. The subsequent CIP （cold isostatic pressing） augmented the particle orientation, and the shrinkage anisotropy. However, no anisotropy was observed in the particle packing and sintering shrinkage in the uniaxially pressed compacts of spherical particles.
　On the other hand, the powder compacts of particle orientation prepared in super high magnetic field showed significant anisotropies of shrinkage and grain growth during sintering, even in the spherical powder compacts. There was a linear relationship between the sintering shrinkage anisotropy and the particle orientation for the elongated and spherical powder compacts. The gradient was two times large for the elongated particle system than the spherical particle system.
　Clearly, the mass transport rate along grain boundary and the grain boundary number per unit length simultaneously influence the sintering shrinkage of a ceramics powder compact. The sintering shrinkage depends on the particle orientation and the particle shape （or aspect ratio）, other than the traditional particle packing density. The origin of the sintering shrinkage anisotropy of alumina powder compacts can be ascribed to the factors such as the particle orientation, the particle shape, the distance between particles or particle packing density, the contact state between particles and the crystal structure or the surface structure. Because the all factors can change the grain boundary number or the mass transport rate during sintering. There has not been a study to clarify this valuable knowledge about the sintering shrinkage anisotropy.
　The sintering shrinkage and the grain growth was particularly and quantitatively discussed in this study for the various alumina powder compacts. This study showed many of valuable data on the sintering shrinkage and the grain growth during sintering, especially on the sintering shrinkage anisotropy. It is expected to largely contribute to the theory of sintering shrinkage and grain growth of ceramics, and the near net shape production of ceramics.