氏名　中松　哲也
学位の種類　博士（工学）
学位記番号　博甲第213号
学位授与の日付　平成12年9月30日
学位論文題目　Effects of Manufacturing Process on the Surface Characteristics of Commerical Nitride Ceramic Powders　（市販窒化物セラミックス粉末の製造方法が表面特性に及ぼす影響に関する研究）
論文審査委員
　主査　教授　石崎　幸三
　副査　教授　福澤　康
　副査　助教授　鎌土　重晴
　副査　新潟大学助教授　堀田　憲康

• 論文目次
• 論文要旨

［平成12（2000）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

CHAPTER 1 INTRODUCTION　p.1
1-1 Nitride Ceramics　p.1
1-2 Manufacturing Processes of Nitride Ceramic Powders　p.4
1.2.1 Silicon diimide decomposition　p.4
1.2.2 Carbothermal reduction and nitridation　p.5
1.2.3 Direct nitridation of silicon　p.5
1.2.4 Chemical vapor deposition （CVD）　p.6
1-3 Effect of Powder Surface Characteristics on the Properties of Nitride Ceramics　p.7
1.3.1 Si3N4　p.7
1.3.2 AlN　p.9
1-4 Chemistry and Characterization Techniques for Silicon Nitride Powder Surfaces　p.10
1-5 Definition of "Surface" in the Present Dissertation　p.16
1-6 Scope and Contents of the Present Dissertation　p.17

CHAPTER 2 EXPERIMENTAL　p.19
2.1 Materials　p.19
2.1.1 As-received Si3N4 powders　p.19
2.1.2 Surface modified Si3N4 powders by aqueous washing　p.21
2.1.3 Silicon oxide and oxynitride powder materials　p.22
2-2 Scanning Electron Microscopy　p.23
2-3 X-ray Diffractometry　p.23
2-4 Particle Size Distribution Measurement　p.24
2-5 Specific Surface Area Measurement　p.25
2-6 Oxygen Content Measurement　p.25
2-7 Temperature Programmed Desorption Mass Spectrometry （TPDMS）　p.26
2.7.1 Experimental system　p.26
2.7.2 Data collection　p.26
2.7.3 Data Processing　p.28
2-8 Diffuse Reflection Infrared Fourier Transform Spectroscopy （DRIFT）　p.30
2.8.1 DRIFT measurement in vacuum　p.30
2.8.2 DRIFT measurement at elevated temperatures in vacuum　p.30
2-9 Isoelectric Point Measurement　p.32
2-1O Characterization of Sintering Process and Sintered AlN Made of Carbon Deposited Powders　p.35
2.lO.1 Carbon deposition process　p.35
2.10.2 Sample preparation and characterization　p.35

CHAPTER 3 RESULTS　p.37
3-1 Scanning Electron Microscopy　p.37
3-2 X-ray Diffractometry　p.39
3-3 Particle Size Distribution Measurement　p.42
3-4 Specific Surface Area Measurement　p.46
3-5 Oxygen Content Measurement　p.46
3-6 Temperature Programmed Desorption Mass Spectrometry （TPDMS）　p.48
3-7 Diffuse Reflection Infrared Fourier Transform Spectroscopy （DRIFT）　p.60
3.7.1 DRIFT measurement in vacuum　p.60
3.7.2 DRIFT measurement under elevated temperatures in vacuum　p.62
3-8 Isoelectric Point Measurements　p.65
3-9 Characteristics of Si3N4 and Silicon Oxide Powders　p.67
3-1O Changes in the Sintering Process of AlN made of Carbon Deposited Powders　p.70

CHAPTER4 DISCUSSIONS　p.72
4-1 Surface Characterization Technique for Si3N4 Powders by FTIR, TPDMS, and pHiep　p.72
4.1.1 Aqueous washing surface modification of Si3N4 powders　p.72
4.1.2 Resolution depths of TPDMS and DRIFT surface analyses　p.86
4-2 Effects of Manufacturing Process on the Surface Characteristics of Commercial Si3N4 Powders　p.93
4.2.1 Relative amount of ionizable surface species and desorption below 1300℃　p.93
4.2.2 H2 and N2 evolution of Si3N4 powder surface up to 1450℃ under ultra high vacuum conditions　p.105
4-3 Effects of Carbon Coating of AlN Powder on Sintering Behavior and Thermal Conductivity　p.111
4.3.1 X-ray diffraction analysis　p.111
4.3.2 Carbon content in sintered bodies　p.112
4.3.3 Effect of C content on density and thermal conductivity　p.113

CHAPTER 5 CONCLUSIONS　p.116

ACKNOWLEDGEMENTS　p.119

REFERENCES　p.121

RESEARCH ACTIVITIES　p.1

　For the fundamental importance in the manufacturing of nitride ceramics, the surfaces of commercial Si3N4 and AlN powders were modified and investigated.
　The surface characteristics of seven commercially available Si3N4 powders produced by three different nitridation methods were examined mainly by temperature programmed desorption mass spectrometry （TPDMS）, diffuse reflection Fourier transform infrared spectroscopy （DRIFT） and isoelectric point measurement. From the comparisons of the TPDMS and pH of isoelectric point （pHiep） results obtained for the different powders, it is shown that there is a good agreement between the relative amount of surface acidic and basic groups evaluated by the two techniques. Furthermore, it is shown that by TPDMS it is also possible to obtain absolute quantitative estimation of the different surface groups. On the other hand, from the changes observed in the DRIFT spectra of the powders insitu heated under vacuum, it is difficult to draw definite conclusions regarding the surface groups.
　Two Si3N4 powders, one produced by the silicon diimide precipitation as well as another one produced by the carbothermal reduction and nitridation of silica were aqueous-washed using a Soxhlet apparatus. For both powders decreases in oxygen content （from 1.12 to 0.62 mass% and from 2.19 to 1.74 mass%）, acidity measured by the pHiep （from 6.2 to 8.2 and from 1.7 to 4.6）, and SiOH surface groups, measured from the TPDMS desorbed H2O molecules （from 0.24 to 0.06 nm-2 and from 0.42 to 0.18 nm-2） and differential DRIFT spectra were observed. Previously reported desorption reactions for H2O, NH3, and N2 were confirmed, and modified for H2.
　The effect of nitridation process, nitridation media and final treatment on the surface characteristics of the Si3N4 powders investigated can be summarized as follows: The powders produced by the direct nitridation of silicon subjected to an acid and aqueous washing as a final treatment showed the lowest oxygen content （0.76 and 0.86 mass%）, and lowest acidity as measured by the pHiep （8.2 and 7.9） and the TPDMS H2O to NH3 desorbed molecules ratio （0.16 and 0.26） of all the powders studied. Another powder manufactured by the same process but without final washing treatment presented higher oxygen content （0.92 mass%）, acidity （6.1） and H2O to NH3 desorbed molecules ratio （1.5）. For the powders produced by the carbothermal reduction and nitridation of silica and heated in air as a final treatment, the one using N2 and C showed the highest acidity （1.7） and H2O to NH3 desorbed molecules ratio （2.3）, of all the powders studied but not the highest oxygen content （2.19 mass%）. On the other hand, the one using NH3+ CH4 presented lower acidity （4.4） and H2O to NH3 desorbed molecules ratio （0.49） than the former and the highest oxygen content （2.85 mass%） of all the powders. The powders produced by the silicon diimide decomposition process and heated in N2 as a final treatment, one using NH3（l） and the other NH3（g）, showed similar oxygen content （1.12 and 1.08 mass%）, acidity（6.2 and 6.4） and H2O to NH3 desorbed molecules ratio （0.60 and 0.79）.
　From the results of this study it is concluded that the surface characteristics of Si3N4 powders can be tailored by adjusting the nature of the nitridation media and the application of controlled washing treatments.
　AlN powder surface modification by a carbon coating method to achieve high thermal conductivity is applied. The effects of carbon coating on sintering behavior and thermal conductivity is discussed based on the density of sintered body as well as the kinds and quantities of grain boundary phases. High thermal conductivity AIN ceramics doped with Y2O3 were obtained and the highest thermal conductivity of 224 W/（m・K） was obtained which occurs for 0.56 mass% of C addition. Also it was found that with further C incorporation, both the reduction of the powder surface and residual carbon suppress the densification and increase porosity that reduces thermal conductivity due to CO2 gas formation.