Doctoral Dissertations
Abstract
"Use of organosilicon compounds in the reduction of the hydration tendency of magnesia (MgO) powders was studied. The powders used in this study were refractory grade basic raw materials. The hydration tendency of the grains before and after coating was assessed using an autoclave at 123 °C and/or 152 °C for 3 hours. Two families of organosilicon compounds were evaluated. Six organosilane compounds were employed using a solution treatment procedure. The compounds used were methyltrimethoxy silane, ethyltrimethoxysilane, n-butyltrimethoxysilane, octyltriethoxysilane, dodecyltriethoxysilane and phenyltriethoxysilane. Variables associated with the coating process and considered in this investigation included: type of organosilane, concentration of organosilane, solvent/water ratio, pH of the water, and the purity of the powder. The best results were achieved with methyltrimethoxysilane using an alcohol-water solution. After coating, no heat treatment was necessary to develop the protective coating. The hydration tendency of magnesia powders showed a reduction from 35% (neat) to 0.2% (coated) when tested at 152 °C for 3 hours.
The second organosilicon family used in the test was the reactive polysiloxanes, or more specifically, the silanol-terminated polysiloxanes. A low molecular weight compound and a high molecular weight compound were considered. The variables studied included concentration, type of solvent, and heat treatment condition after coating. Similar to the organosilane compounds, very low values for weight gain were obtained at 152 °C for 3 hours.
Preliminary studies with doloma (MgO·CaO) were also conducted with organosilanes and polysiloxanes. Unfortunately doloma did not respond satisfactorily to the treatments with organosilane or with silanol-terminated polysiloxanes, most likely due to the large amount of CaO present in this material (~ 60 wt%).
Magnesium oxide grains with a natural coating of hydromagnesite on the surface showed a fairly large increase in the hydration resistance compared to the same material without this layer, even when tested at 152 °C for 3 hours"--Abstract, page iii.
Advisor(s)
Moore, Robert E., 1930-2003
Committee Member(s)
Huebner, Wayne
Anderson, H. U. (Harlan U.)
Smith, Jeffrey D.
Kohser, Ronald A.
Samaranayake, V. A.
Department(s)
Materials Science and Engineering
Degree Name
Ph. D. in Ceramic Engineering
Publisher
University of Missouri--Rolla
Publication Date
Fall 2000
Pagination
xx, 210 pages
Note about bibliography
Includes bibliographical references (pages 191-209).
Rights
© 2000 Sergio Luiz Cabral da Silva, All rights reserved.
Document Type
Dissertation - Restricted Access
File Type
text
Language
English
Subject Headings
Hydration
Magnesium oxide
Organosilicon compounds
Siloxanes
Thesis Number
T 7859
Print OCLC #
45665783
Electronic OCLC #
1079366666
Link to Catalog Record
Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.
http://merlin.lib.umsystem.edu/record=b4497239~S5Recommended Citation
da Silva, Sergio Luiz Cabral, "Improvement of the hydration resistance of magnesia and doloma using organosilicon compounds" (2000). Doctoral Dissertations. 1352.
https://scholarsmine.mst.edu/doctoral_dissertations/1352
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