1996 Fiscal Year Final Research Report Summary
STUDIES OF BERLINITE REFACTORY FOR DENTAL INVESTMENTS
| Project/Area Number |
07672136
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
補綴理工系歯学
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| Research Institution | ASAHI UNIVERSITY |
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Principal Investigator |
KAMEMIZU Hideo ASAHI UNIVERSITY,SCHOOL OF DENTISTRY,ASSISTANT, 歯学部, 助手 (00152877)
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| Co-Investigator(Kenkyū-buntansha) |
GOTO Takayasu ASAHI UNIVERSITY,SCHOOL OF DENTISTRY,LECTURER, 歯学部, 講師 (30121320)
DOI Yutaka ASAHI UNIVERSITY,SCHOOL OF DENTISTRY,ASSOCIATE PROFESSOR, 歯学部, 助教授 (40116067)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Dental investment / Refractory material / Aluminum phosphate / Berlinite / Hydrothermal synthesis |
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| Research Abstract |
AlPO_4 have been known to have the polymorphism similar to silica. The quarts from (berlinite) has been especially attracted by its superior thermal expansion character to silica, refractory material. Berlinite is suggested to be a promising refractory material for dental investments.
In this research, berlinite refractory material has been synthesized by heating and hydrothermal methods and thermal characteristics of synthetic berlinite were investigated by thermal analysis (TG-DTA,TMA).
With the heating method, amorphous AlPO_4? nH_2O was produced after spatulation with distillled water and changed to crystalline berlinite by heating at 100-700ﾟC for 1h. Berlinite with the reaction system of Al(H_2PO_4)_3-Al_2O_3? 5H_2O showed the highest crystallinity of those with the reaction system used.
Berlinite seed prepared by this heating method, which contained tridymite type and ciristobalite type, were hydrothermally treated in a autoclave at 200-250ﾟC for 1-7 d.The crystalline berlinite alone is detected by X-ray diffraction analysis. The growth run of crystal along the c-axis was observed by SEM.The crystallinity of berlinite showed higher than that of seed and influenced by the concentration of solution and the duration of hydrothermal treatments.
The reconstructive transformation of berlinite to cristobalite from occurred at 965-1,120ﾟC.
The dental investment containing synthetic berlinite showed 4-8% thermal expansion at 1,100-1,200ﾟC.The rapid increase in the thermal expansion occurred at the temperature of reconstructive transformation. The thermal expansion of investments increased with the increasing of both the purerity and the crystallinity of berlinite.
Berlinite refractory was found to be suitable for the use of high thermal expansion invesment, but it is necessary to control the amount of thermal expansion for practial use.
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