Foamed refractory oxides provide lightweight, reflective thermal insulation materials. The materials have a low bulk density and high thermal shock resistance

Mountvala, A. J.

Nakamura, H. H.

Rechter, H. L.

English

NASA Technical Reports Server

July 1966	 Brief 66-10288 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Improved Thermal Insulation Materials Made of Foamed Refractory Oxides 
The problem: 
To develop improved lightweight, reflective thermal 
insulation materials. The materials should have a low 
bulk density and be capable of withstanding a heat 
flux of up to 40 Btu/ft/sec under mechanical vibra-
tions of 60 cps. The adhesion of the materials to a 
load bearing substrate as well as self-cohesion must 
be sufficient to withstand a minimum flatwise tensile 
stress of 80 psi. 
The solution: 
A series of foamed refractory oxides having a den-
sity of 30 to 100 lb/cu ft, depending on composition. 
How it's done: 
The foamed refractory oxides consist basically of 
granular zircon (Zr02.Si02) or rnullite (3Al203.2SiO2). 
These materials have a low thermal expansion coef-
ficient which provides high thermal shock resistance. 
The zircon or mullite grains, 74 microns or less in 
diameter, are mixed into a slurry with water and an 
alkali silicate binder. A whipping agent is added, and 
the slurry is foamed by a high speed, blade type mixer. 
Protein materials, such as egg albumen, are used to 
form a fine bubble structure and stable suspension. 
Anionic surfactants may also be used. Inorganic fi-
brous materials are added to increase strength, enhance 
moisture resistance, and minimize drying shrinkage of 
the foam. Aluminum silicate, silica, glass, zirconia, 
boron, alumina, and silicon carbide fibers are suitable 
for this purpose. A complexing agent is added to 
retard migration of the alkali silicate binder and to im-
part resistance to bond deterioration by water. The 
preferred agent is sodium silicofluoride. Alkaline
earth or zinc oxides can also be used. The addition of 
small amounts of clay aids in maintaining the sus-
pension of the refractory grains when the foams are 
cast and cured by heating in an oven. 
The composition of a typical foamed ceramic in 
percent by weight is as follows: 
Refractory oxide grain 	 54-75 
Water	 8-16 
Silicate binder	 14-30 
Clay	 0-2.0 
Whipping agent
	 0.15-1.0 
Sodium silicofluoride	 1.0-3.0 
Fibers	 1.5-10 
Notes: 
I. A foamed zircon ceramic had a density of 52 lb/cu 
ft, a conductivity of less than 0.1 Btu/hr/ft/°F in 
the range from room temperature to 1300°F, and 
conductivities of 0.166 and 0.290 Btu/hr/ft/°F at 
1835° F and 2300° F, respectively. A 0.5-inch-thick 
slab remained intact when subjected to a heat flux 
of 40 Btu/ft/sec, with simultaneous vibration of 
60 cps at a double amplitude displacement of 0.5 
inch and acceleration of 90g. The skin exhibited a 
reflectance of over 90 percent in the 0.8 to 1.8 
micron wavelength range. 
2. A related innovation is described in NASA Tech 
Brief B65-10357, November 1965. Inquiries may 
also be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10288
(continued over(eaI( 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19660000287 2020-03-11T17:39:49+00:00Z
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: A. J. Mountvala, H. H. Nakamura,
and H. L. Rechter
of lIT Research Institute 
under contract to
Marshall Space Flight Center
(M-FS-735) 
Brief 66-10288	 Category 03


Improved thermal insulation materials made of foamed refractory oxides

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server