The Space Shuttle Columbia tragedy brought home the risks of defects
in the thermal protection systems (TPS) of space vehicles. To address
this need, a high-temperature refractory adhesive system has been
developed for the in-space repair of the TPS for the Space Shuttle
and the proposed Crew Exploration Vehicle (CEV). Developed by Mrityunjay
Singh and Tarah Shpargel of QSS Group, Inc., along with researchers
from NASA Glenn Research Center, both of Cleveland, Ohio, the Glenn
Refractory Adhesive for Bonding and Exterior Repair (GRABER)
can be cured with orbital sun heat and has excellent plasma performance
under reentry conditions.
The repair system, for which there are no competitors, consists
of preparing an adhesive paste of a ceramic in a polymer/phenolic
resin matrix with appropriate additives, such as surfactants. Numerous
tests have already been conducted in vacuum glove boxes, on KC-135
tests, and in tool development activities at various NASA, DOD,
and military/aerospace subcontractor facilities.
A Healthy Fiber-Free Diet
Short mineral fibers, such as those used in fiberglass, ceramics,
and mineral wool, have been characterized as possible carcinogens,
skin irritants, and have been involved in human airway dysfunctions.
The problem is that these fibrous materials have become nearly ubiquitous
in their application and resultant waste disposal. Jenq Liu and
Jainagesh Sekhar of Micropyretics Heaters International and Mattech
Corp., both of Cincinnati, Ohio, have developed a Fractal,
Fiber-Free Material that eliminates the health issues of
conventional fibrous materials, while providing improvements on
their competitive physical characteristics.
The process for manufacturing these fractal materials involves
processing nano-alumina into fractally shaped ball refractories,
which are then stacked, making large refractories. Compared to their
fibrous competitors, fractal materials have a higher service temperature
(2000° C vs 1800° C), lower density (0.8 g/cc vs 1.0 g/cc),
and a significantly lower thermal conductivity (0.2 vs 0.8 W/m K).
Fractal materials also can absorb effluents, which their competitors
cannot. The primary use of these materials is in high temperature
furnaces, filters, kiln furniture, combustion burners, and fire
protection.
Anyway You Want It
A team of researchers at The Dow Chemical Co., Freeport, Texas, has developed
the EXO Overmolding Technology, a unique, fully automated
polymer injection molding process.
This technology allows natural materials, like fabric, leather, wood,
and metal, to be overmolded with an engineering polymer in an automated,
high temperature, high pressure injection molding process. New techniques
for preparing the surface materials, and for operating the molding process
were developed to bring the materials to the marketplace.
The molding process consists of three main steps, starting with the
placement of a precut natural material insert into the mold cavity. This
is followed by an injection of a rigid thermoplastic, like polycarbonate,
onto the backside of the natural material. A second injection of an elastomer
then encapsulates the edges of the first two materials, creating the finished
part. Wood veneers as thin as 1.3 mm can be used, while metal foils going
down to 1 mm thick can be used in the process. The metal foils could also
be employed as EMI (electro-magnetic interference) shields, or protection
against wear and friction.
