Author: M. TriollierPublisher:
ISBN:
Category :
Languages : en
Pages : 11
Book Description
Effect of the Method of Preparation of Calcium Sulfate Hemihydrate on Its Hydration in the Vapor Phase
Author: M. TriollierWorld Translations Index
Author: The kinetics of the hydration of calcium sulfate hemihydrate &.
Author: Lenore Wiegman-HoJournal of Research of the National Bureau of Standards
Author: United States. National Bureau of StandardsPublisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 712
Book Description
Technical Report ... of the Division of Building Research
Author: National Research Council Canada. Division of Building ResearchPublisher:
ISBN:
Category : Building
Languages : en
Pages : 596
Book Description
Predictability Gap Between Science and Technology of Cements
Author: Angus T. SherwoodPublisher:
ISBN:
Category : Building
Languages : en
Pages : 98
Book Description
CALCIUM SULPHATE HEMIHYDRATE
Author: 陳國柱Publisher: Open Dissertation Press
ISBN: 9781361111437
Category : Medical
Languages : en
Pages : 172
Book Description
This dissertation, "Calcium Sulphate Hemihydrate: Effect of Humidity in Storage" by 陳國柱, Kwok-chu, Timmy, Chan, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: ABSTRACT Calcium sulphate hemihydrate and its products are the most used materials in dentistry. However, the hemihydrate can react with atmospheric water vapour and be converted into dihydrate. This premature reaction may alter the materials' working qualities and also affect the accuracy of dental appliances produced using them. Despite its importance, very little work, and of poor quality, has been done on this subject, and has mostly been using indirect methods of low sensitivity. However, Torrance and Darvell (1990) demonstrated the utility of a gravimetric approach, and this was adopted for the present study of dental artificial stone, plaster of Paris, impression plaster and a gypsum-bonded casting investment material over a range of temperatures. The intention was to examine the behaviour in greater detail in an attempt to understand possible mechanisms. The gravimetric method was found to be direct, sensitive, precise, and non- destructive. It could be easily monitored from graphs of data when the reaction was completed or how far it had gone. The following conclusions were reached: Firstly, the reaction of stone, plaster and impression plaster will start after a certain amount of water is absorbed. The logarithm of the time to initiation of reaction is linearly related to the relative humidity and not, as might be expected, the water vapour pressure. Thirdly, the investment material was extremely sensitive, commencing reaction in less than twenty hours even at 75% relative humidity, behaviour which is probably due to hygroscopic additives not present in the other types of hemihydrate product. Finally, i the maximum rate of absorption and reaction was found at 35C; at 40C, the reaction was slower than at 25C. It is evident that all hemihydrate products should be well-protected in storage if there is any risk of high humidity. This has implication for the design, running and operating practices of dental laboratories. ii DOI: 10.5353/th_b2112952 Subjects: Calcium sulphate Hydrates Dental materials
Ceramic Abstracts
Author: American Ceramic SocietyPublisher:
ISBN:
Category : Ceramics
Languages : en
Pages : 1000
Book Description
The Effect of Sorbed Water on the Determination of Phase Composition of CaSO4 . H2O Systems by Various Methods
Author: L. BouniniPublisher:
ISBN:
Category : Anhydrite
Languages : en
Pages : 9
Book Description
The efficiency of calcination processes is monitored by careful phase analysis of CaSO4 . H2O systems. The usual method of determining a small amount of gypsum in such systems involves the determination of sorbed (free) water, water of crystallization (combined water), and Ca++/SO4-- ratio. The removal of free water from CaSO4 . 1⁄2H2O and active orthorhombic calcium sulfate occurs at about the same temperature range as the decomposition of CaSO4 . 2H2O, which then becomes a most critical stage in the phase analysis of these systems. This paper discusses (1) relative merits of various methods utilized in removing free water, which includes several thermal methods and microwave drying, and (2) the state of the sorbed water as it develops from exposure to radically varying relative humidity conditions.
Official Gazette of the United States Patent and Trademark Office
Author: United States. Patent and Trademark OfficePublisher:
ISBN:
Category : Patents
Languages : en
Pages : 1076
Book Description