氏名　Mohd Imran Bin Zainuddin
学位の種類　博士（工学）
学位記番号　博甲第520号
学位授与の日付　平成21年8月31日
学位論文題目　Application of Polyacrylic Acid （PAA）in Production of Dry-Pressed Alumina Ceramics　（乾式圧縮成形によるアルミナセラミックス製造におけるアクリル系ポリマーの応用）
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　齋藤　秀俊
　副査　准教授　内田　希
　副査　産学融合特任准教授　田中　諭

• 論文目次
• 論文要旨
• 論文審査の結果の要旨

［平成21（2009）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

Table of Contents　p.i
Chapter 1　Introduction and Background
　1.1　Introduction　p.1
　1.2　Objectives and outline　p.3
　1.3　Dry-pressing　p.4
　1.4　Important measure durinf pressing　p.7
　1.4.1　Uniform density　p.8
　1.4.2　High green strength　p.9
　1.5　Spray-drying granulation　p.13
　1.6　Slurry preparation via colloidal processing　p.15
　1.7　Binder segregation during spray-drying　p.18
　1.8　New Polyacreylic acid （PAA） polymer to slove binder segregation problem　p.22
　1.9　Firing　p.23
　1.10　Defects development during sintering and flexural strength　p.25
　1.11　Shape deformation during seintering　p.27
　1.12　Novel observation and measurement methods　p.28
　1.12.1　Liquid Immersion Method （LIM）　p.28
　1.12.2　Liquid Immersion Method with Infrared Microscope　p.30
　1.12.3　Immersion Liquid Method with Infrared Microscope　p.31
　1.12.4　Confocal Scanning Laser Florescent Microscope （CLSM）　p.34
　1.13　Measurement of Degree of Particle Orientation （DPO） using Polarized Optical Micriscopy　p.35
　References　p.36
Chapter 2　Production of granules with uniform binder distribution using PAA bunder system
　2.1　Introduction　p.42
　2.2　Experiments　p.44
　2.2.1　Raw materials: Powder and additives information　p.44
　2.2.2　Slurry preparation　p.44
　2.2.3　Rheology evaluation　p.46
　2.2.4　Spray-dry granuvations　p.47
　2.2.5　Structure observations　p.48
　2.3　Results　p.49
　2.4　Discussions　p.60
　2.5　Conclusions　p.63
　References　p.64
Chapter 3　Effect of binder distribution on structure and strength of sintered alumina compact
　3.1　Introduction　p.67
　3.2　Experimental Produres　p.68
　3.2.1　Raw materials　p.68
　3.2.2　Slurry preparation and grannulation　p.68
　3.2.3　Granules characteriation　p.68
　3.2.4　Forming process6　p.69
　3.2.5　Tests and measurements　p.70
　3.2.5.1　Single granule compaction test　p.70
　3.2.5.2　Compaction behavior of granules　p.70
　3.2.5.3　Flexural strength measurement of sintered compact: Four points bending test　p.71
　3.2.6　Structure observations　p.71
　3.3　Results　p.72
　3.4　Discussions　p.84
　3.5　Conclusions　p.87
　References　p.88
Chapter 4　Effect of PAA polymer on structure and strength of green and sintered alumina compact
　4.1　Introduction　p.91
　4.2　Experimantal Procedures　p.92
　4.2.1　Raw materials　p.92
　4.2.2　Slurry preparation and grannulation　p.92
　4.2.3　Forming process　p.92
　4.2.4　Tensile strength measurement of green compact: Diametral compression Test　p.92
　4.2.5　Flexural strength measurement of sintered compact: Four-point dending test　p.93
　4.2.6　Structure observations　p.93
　4.2.7　Compaction behavior of granules　p.94
　4.3　Results　p.94
　4.4　Discussions　p.107
　4.4.1　Effect of SBL on Granules properties　p.107
　4.4.2　Effect of SBL on green compact　p.108
　4.4.3　Effect of binder distribution on sintered strength of alumina compacts　p.110
　4.5　Conclusions　p.111
　References　p.112
Chapter 5　Effect of Polyacrylic Acid （PAA） Binder System on shrinkage during sintering
　5.1　Introduction　p.114
　5.2　EXperiments　p.117
　5.2.1　Raw materials　p.117
　5.2.2　Granules morphology and internal obvervation　p.117
　5.2.3　Forming process　p.117
　5.2.4　Slurry preparation and granulation　p.117
　5.2.5　Measurement of Degree of Particle Orientation （DPO）　p.117
　5.2.6　Granules compation curve　p.119
　5.2.7　Measurement of sintering shrinkage of compacts　p.119
　5.3　Results　p.121
　5.4　Discussions　p.135
　5.5　Conclusions　p.140
　References　p.141
Chapter 6　Summary and conclusions
　6.1　Summary and conclusions　p.147
　6.2　Proposed processing conditions of PAA polymer as binder system in dry-pressing　p.151
List of Publications　p.156
Acknowledgment　p.158

　In ceramic productions, quality of products is normally compromised by their productivity. Production at high rate makes products vulnerable to formation of intrinsic defects as well as exposure to machinery-caused defects which lower the reliability of the product. Products with defects may counter the cost efficiency of the production process resulting in higher cost in product mending and losses. In a high production rate process such as dry-pressing, causes of defects formation must be well understood and controlled in order to harvest the optimum advantage of the process. It is essential to characterize the important parameters contributing to defects formation and recognize ways to totally diminish or at least reduced defects to the lowest level possible. In the present study, the effect and the applicability of newly enhanced PAA binder in the production of alumina ceramics and the effect of the binder system used in developing particle orientation during compaction and its relation to anisotropic shrinkage was investigated in details.

　Chapter1 Introduction: In this chapter the progress in enhancement of internal structure of ceramics and its characterization method was reviewed and the objectives of the present work are stated along with its outlines. Literature review on the topics which are closely related to the present work are stated and discussed in details.

　Chapter 2: Production of granules with uniform binder distribution using PAA binder system. The rheology study of slurry system containing PAA binder was studied and compared to the general dispersant. Granules of various binder distributions were produced and categorized with respect to the formation segregated binder layer （SBL） which indicates non-uniformity of binder distribution within the granules. The samples used in further investigations are based on these categories. SBL was found to form at binder content slightly higher than the binder amount needed to achieve saturated surface adsorption. The state of coverage of SBL over granules and the number of granules containing it was taken into consideration. Granules without SBL were successfully produced at the binder content of 2.5wt% and granules containing fully developed SBL forms in all granules of mean diameter as binder content exceeds 5.0wt%.

　Chapter 3: Effect of binder distribution on flexural strength of sintered alumina compact. In this chapter, the effect of granules without and granules with SBL on flexural strength was studied in detail. Results were discussed with respect to granules mechanical properties, dry-press conditions, and the internal microstructure of green and sintered alumina compacts. Granules with SBL have higher fracture stress and deform at higher stress compared to granules without SBL. The results of PAA compacts were also compared to those of the conventional PVA binder system. PAA binder system shows more homogeneous internal structure in sintered compact with most of the crack-like cavity and granules dimples are successfully eliminated. This improvement contributes to higher flexural strength of alumina compact with PAA binder system compared to PVA binder system.

　Chapter 4: Effect of PAA polymer on green and sintered strength of alumina compact. SBL of PAA binder increases the granules hardness by acting as a shell to support stress. However, at high compaction pressure, it has the ability to deform flexibly in a well plasticized condition. The green strength of alumina compact increases significantly as SBL exists within the granules. High forming pressure in a well plasticized condition of temperature above Tg and high humidity level induces squeezing out of binder molecules from in between primary particles. This contributes to redistribution of SBL between neighboring granules to eliminate pores and simultaneously bonds granules together. Non-uniformity of PAA binder distribution within granules shows no significant effect on sintered strength of alumina compact up to a certain extent. Segregated binder layer of PAA binder successfully shows enhancement of green strength without compromising the compact strength after it is sintered.

　Chapter 5: Effect of PAA binder system on particle orientation during dry-pressing. The effect of binder system on the development of particle orientation within compact made by uniaxial pressing was quantitatively studied. Properties of granules such as strength and deformability provided by the binder system shows a significant effect in the development of degree of particle orientation during uniaxial pressing where low strength and high deformability of granules lead to higher degree of particle orientation. Anisotropic shrinkage related to particle orientation is shown by compact of higher relative density and degree of particle orientation; whereas anisotropic shrinkage related to non-uniform packing density is shown by compact of lower relative density and degree of particle orientation. Anisotropic shrinkage remains in the former compact while isotropic shrinkage was obtained for the latter compact at sintering temperature of 1600oC.Subsequent CIP of compacts made by uniaxial pressing shows increase in degree of particle orientation and sintering shrinkage ratio.

　Chapter 6 Summary and conclusions: In this chapter the overall achievements of the present study were summarized. A proposal on processing conditions during usage of PAA as binder system is also given.

　本論文はApplication of Polyacryric Acid （PAA） Polymer in Production of Dry-Pressed Alumina Ceramics （乾式圧縮成形によるアルミナセラミックス製造におけるアクリル系ポリマーの応用）と題し、6章から構成されている。

　第1章「緒言」では、本研究に密接に関連する従来の研究をまとめ、セラミックス製造プロセスの問題点を明らかにしている。特に加圧成形法では、従来のPVAバインダー系においては顆粒表面のバインダー偏析層がセラミックスの構造を不均質とし、特性を下げる重要な因子であることを明らかにしている。また製造時に成形体および焼結体内部で生じる変化を調べる評価法を述べ、本研究の目的と研究方針を述べている。

　第2章「PAAバインダー系による均一バインダー分布をもつ顆粒の製造」では、PAAバインダーを含むアルミナスラリーのレオロジーを従来の分散剤を含む系との比較により行っている。PAAバインダーの粉体表面への吸着平衡濃度は1.5wt%程度であり、この濃度以上では低いスラリー粘度が得られた。また、濃度2.5wt%程度以上では液相の遊離バインダー分子が顕著となり、これにより顆粒表面にはバインダーの偏析層が発生し、その濃度5wt%以上では、総ての顆粒表面がバインダー層で覆われることを明らかにしている。　第3章「バインダー分布がアルミナセラミックスの曲げ強度に及ぼす影響」では、顆粒表面にバインダーの偏析層の存在また存在しないものについて、成形体及び焼結体の構造を比較し、強度特性に及ぼす影響を論じている。従来のPVA系では偏析層をもつ顆粒は高い成形体強度を高めるが、同時に不均質構造も形成しセラミックスの強度を下げることを明らかにしている。一方、PAAバインダーでは顆粒表面の偏析層は成形体強度を高めるが、成形時に容易に変形しセラミックスの均質構造には特に顕著な影響を与えず、従ってセラミックス強度低下を生じないことを明らかにしている。

　第4章「PAAバインダーがアルミナ成形体及びそのセラミックスの強度に及ぼす影響」では、顆粒表面に存在するPAA偏析層の荷重下における挙動を詳細に検討している。偏析層は顆粒の強度を増すが、高荷重下では流動により再分布し、顆粒間の粗大気孔を少なくすると共に顆粒間の接着強度を増す作用をもつことを明らかにしている。さらに偏析量が過剰となると、焼結体中に粗大欠陥を形成し、強度低下を生じることも明らかにしている。

　第5章「加圧成形におけるPAAバインダー系が粒子配向と焼結異方性に及ぼす影響」では、一軸成形体およびそのCIP成形体内部の粒子配向に及ぼすバインダー系の影響を論じている。粒子間を結合するバインダーは成形時の粒子再配列、従って粒子の配向に顕著な影響を及ぼすことを明らかにしている。また、一軸成形後のCIP処理は粒子配向を一層顕著とし、焼結異方性を増すことを明らかにしている。

　第6章「総括」では、本論文で得られた成果をまとめている。よって、本論文は工学上及び工業上貢献するところが大きく、博士（工学）の学位論文として十分な価値を有するものと認める。