Metal Foam

Patrick
McAlpine
Chemistry of Materials Literature Review 1
Submitted January 31, 2018

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ABSTRACT

Metal foam is a very interesting
material. Imagine a solid ingot of metal. It can be heavy depending on the
material that it is made of. Now imagine a sponge, it is a very light squishy
material that is absorbent and porous. Metal foam is a material similar to both
of them.  Metal foam, which is usually
made of aluminum, starts out as melted metal that has gas added and kept under
a constant pressure. As the metal cools the gas precipitates within the metal. The
metal hardens and keeps the gas bubbles inside of it making the material act as
a sponge but still be metal. Metal foam is a very unique material because it is
strong, yet it is able to absorb a shock. It is also used to increase the
strength of structures. This material is also much lighter than the original
metal. All of these properties make it a very good material to use in cars to
help reduce the weight of the car because this material is light and strong.
Also if someone got in a car crash with this metal foam behind their bumper, going
thirty miles per hour and crashing would feel like you are going 5 miles an
hour and crashing. This is a very unique property because it is very absorbent
and could help save many lives.

INTRODUCTION

Metal foam is defined as a
cellular structure of solid metal with gas filled pores that make up a large
portion of the volume. Most commonly aluminum is used as the metal in the
foaming, but they also use titanium and tantalum too.

 

HISTORY

Metal foams were created in the
1940’s

 

PROCESS

 

There are three different ways to
make metal foams. The first way is by injection of gas into the metal from an
external source. The mixing techniques should be kept the same to ensure that that
the distribution of particles in the melt will be uniform. The next step is
using rotating impellers or vibrating nozzles to inject air, nitrogen, or argon
into the melt creating the foam.  The
second way is having the gas be dissolved in the liquid metal. For this method certain
compounds like carbonates are added to the melt. Once the decomposition happens
the heated metal forms gas bubbles. Titanium hydride is used as a blowing agent
to release hydrogen gas in the liquid after the desired viscosity is reached. As
the melt begins to cool, it expands and starts to fill the foaming vessel. During
the foaming it must keep under a consistent pressure until it is cooled and
becomes a solid. The third way is by using gas releasing blowing agents on the melted
metal. This method is similar to the last, but the metals are melted in a
hydrogen atmosphere with a high pressure. Over time the melt begins to solidify
causing the gas to precipitate and become trapped within the metal.

 

MICROSTRUCTURE

The metal foam goes from a molten
metal to a sponge like piece of metal due to the gas bubbles within the metal
getting trapped within. The metal becomes a porous

PROPERTIES

Even though metal foams have a
metal base, they are an ultralight material since between 75 and 90 percent of
the space is taken up by the void spaces making them become highly porous.  

–         
Compression strength is very high

–         
High strength

–         
Low Thermal conductivity level

Metal foams are becoming a more
common material used in our lives. It is being used in cars to help with reducing
the impact in car accidents and used to help lighten the weight of the car too.
Another place it is being used is in military vehicles to help with armor piercing
bullets. Also, bullet-proof vests are being made out of this type of material
because it is not only strong, it is very impact resistant too. Like stated
above, metal foam is a

 

 

PROBLEMS WITH
THE MATERIAL

 

 

USE OF THE
MATERIAL

–         
Metal foams are used for many structural situations
requiring load-bearing features

–         
Saving weight

–         
Impact absorbent

–         
Used as vibration and sound absorbers

–         
Used as a filtration tool

–         
Being experimented with prosthetics in animals

Lots of cars in the industry use
metal foams because they reduce a lot of weight, reduce the number of parts
making up the main frame, help reduce the overall cost, and improve the performance
also.

ORIGINAL
PROPOSAL

 

REFRENCES

http://www.tms.org/pubs/journals/JOM/0012/fig2a.gif

https://www.helmholtz-berlin.de/media/media/spezial/people/banhart/html/A-Journals/open/postprint/a093_banhart2006.pdf

 

 

Thomas, G. P. Metal Foams – Properties, Production and
Applications https://www.azom.com/article.aspx?ArticleID=8097 (accessed Jan 29,
2018).

Banhart, J. Light?Metal Foams-History of Innovation and
Technological Challenges
http://onlinelibrary.wiley.com/doi/10.1002/adem.201200217/full (accessed Jan
29, 2018).

Metal foam https://en.wikipedia.org/wiki/Metal_foam
(accessed Jan 29, 2018).

Rik Myslewski 29 Jun 2011 at 04:13
tweet_btn(). Boffins triple battery life with metal foam
https://www.theregister.co.uk/2011/06/29/aluminum_celmet/ (accessed Jan 29,
2018).

Yoon, T.-H.; Hong, L.-Y.; Kim, D.-P. Fabrication of
SiC-Based Ceramic Microstructures from Preceramic Polymers with Sacrificial
Templates and Softlithography Techniques. Lithography 2010.

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