44
METALLIC FOAMS aejar Grenl Anne Pinca Cherwin Ayapana aime Tan Jr.

metal foam

Embed Size (px)

Citation preview

Page 1: metal foam

METALLIC

FOAMSMaejar Grenl Anne PincaCherwin AyapanaJaime Tan Jr.

Page 2: metal foam

A metal foam is a cellular structure consisting of a solid metal, frequently aluminium, containing a large volume fraction of gas-filled pores. The pores can be sealed (closed-cell foam), or they can form an interconnected network (open-cell foam). The defining characteristic of metal foams is a very high porosity: typically 75-95% of the volume consists of void spaces. The strength of foamed metal possesses a power law relationship to its density; i.e., a 20% dense material is more than twice as strong as a 10% dense material.Metallic foams typically retain some physical properties of their base material. Foam made from non-flammable metal will remain non-flammable and the foam is generally recyclable back to its base material. Coefficient of thermal expansion will also remain similar while thermal conductivity will likely be reduced

Page 3: metal foam

Metal foam compact heat exchanger for high

temperature service. Foam material is PFCT’s

FeCrAlY.

A closed-cell foam with porosity of about 80% floating on water. 

Page 4: metal foam

AlMgCu foam blown by an

Intrinsic gas source.

This is 3D visualization of

the foam by X-ray

tomography.

A test rig is assembled at NASA’s Glenn Research Center to evaluate the noise reduction of a newly-developed metallic foam liner. Image Credit: NASA

Page 5: metal foam

Application:

• Lightweight aerospace vehicle structures• Military vehicle/structure armor• Structural shock absorbers to protect against earthquake vibration•  Implantable biomedical devices• Sound absorptive material• High temperature Filters• Vehicle crumple zones/collision absorbers• Boat hulls• Oil-well drilling platforms• Fire retardant structuresa

Page 6: metal foam

Two types of Metal Foam: Open Cell Metal Foam

• Closed Cell Metal Foam

Page 7: metal foam

Open Cell Metal Foam

Open celled metal foams are usually replicas using open-

celled polyurethane foams as a skeleton and have a wide variety of

applications including heat exchangers (compact electronics

cooling,cryogen tanks, PCM heat exchangers), energy absorption, flow

diffusion and lightweight optics. Due to the high cost of the material it is

most typically used in advanced technology aerospace and

manufacturing.

Extremely fine-scale open-cell foams, with cells too small to be visible

to the naked eye, are used as high-temperature filters in the chemical

industry.

Metallic foams are nowadays used in the field of compact heat

exchangers to increase heat transfer at the cost of an additional

pressure drop. However, their use permits to reduce substantially the

physical size of a heat exchanger, and so fabrication costs. To model

these materials, most works uses idealized and periodic structures or

averaged macroscopic properties.

Page 8: metal foam

The microstructure of a typical cellular

metal foam having open cells consists of

ligaments forming a network of inter-connected

dodecahedral-like cells, as shown in the upper

picture. The cells are randomly oriented, and

mostly homogeneous in size and shape. Pore

size may be varied from approximately 0.1 to 7

mm. The relative density, defined as the ratio of

the density of the foam to that of the solid of

which the foam is made, can be varied from 3

to 15%. (The relative density of the foam can be

increased by compression, if necessary.) Alloys

and single-element materials are available.

Common materials include copper, aluminium,

stainless steel and steel alloy FeCrAlY (Fe–20 wt.

% Cr–5 wt.% Al–2 wt.% Y–20 wt.%).

Page 9: metal foam

Closed Cell Metal Foam Closed-cell metal foam was first reported in 1926 by

Meller in a French patent where foaming of light metals either by inert gas injection or by blowing agent was suggested. The next two patents on sponge-like metal were issued to Benjamin Sosnik in 1948 and 1951 who applied mercury vapor to blow liquid aluminium.Closed-cell metal foams have been developed since about 1956 by John C. Elliott at Bjorksten Research Laboratories. Although the first prototypes were available in the 50s, commercial production was started only in the 90s by Shinko Wire company in Japan. Metal foams are commonly made by injecting a gas or mixing a foaming agent (frequently TiH2) into molten metal. In order to stabilize the molten metal bubbles, high temperature foaming agent (nano- or micrometer sized solid particles) is required. The size of the pores, or cells, is usually 1 to 8 mm.

Page 10: metal foam

Closed-cell metal foams are primarily used as an impact-absorbing material, similarly to the polymer foams in a bicycle helmet but for higher impact loads. Unlike many polymer foams, metal foams remain deformed after impact and can therefore only be used once. They are light (typically 10–25% of the density of the metal they are made of, which is usually aluminium) and stiff, and are frequently proposed as a lightweight structural material. However, they have not yet been widely used for this purpose.

Closed-cell foams retain the fire resistant and recycling capability of other metallic foams but add an ability to float in water.

Page 11: metal foam

PRODUCTION METHODS FOR METALLIC FOAMS

Under certain circumstances metallic melts can be foamed by creating gas bubbles in the liquid. Normally, gas bubbles formed in a metallic melt tend to quickly rise to its surface due to the high buoyancy forces in the high-density liquid. This rise can be hampered by increasing the viscosity of the molten metal, either by adding fine ceramic powders or alloying elements to form stabilizing particles in the melt or by other means. Metallic melts can be foamed in one of three ways: by injecting gas into the liquid metal from an external source, by causing an in-situ gas formation in the liquid by admixing gas-releasing blowing agents to the molten metal, or by causing the precipitation of gas which was previously dissolved in the liquid.

Page 12: metal foam

MANUFACTURING OF ALUMINUM FOAM The first method of foaming aluminum

and aluminum alloys comprises the preparation of an aluminum melt containing one of the substances, making it a metal-matrix composite (MMC). This step reportedly requires sophisticated mixing techniques to ensure a uniform distribution of particles. A variety of aluminum alloys can be used.

Page 13: metal foam

The melt is foamed in a second step by injecting gases (air, nitrogen, argon) into it using specially designed rotating impellers or vibrating nozzles. These generate very fine gas bubbles in the melt and distribute them uniformly. The resultant viscous mixture of bubbles and metal melt floats up to the surface of the liquid where it turns into a fairly dry liquid foam as the liquid metal drains out. Because ceramic particles are in the melt, the foam is relatively stable. It can be pulled off the liquid surface and is then allowed to cool down and solidify. The resulting solid foam is, in principle, as long as desired, as wide as the vessel containing the liquid metal allows it, and typically 10 cm thick.

Page 14: metal foam

Aluminum FoamCompression Strength 367 psi (2.53 MPa)

Tensile Strength* 180 psi (1.24 MPa)

Modulus of Elasticity (Compression)*

15 × 103 psi (103.08 MPa)

Modulus of Elasticity (Tension)*

14.6 × 103 psi (101.84 MPa)

Vickers Pyramid Number 35 HV

Specific Heat .214 BTU/lb-°F (.895 J/g-C)

Coefficient of Thermal Expansion (0-100°C) 

13.1 × 10-6 in/in--F (23.58 × 10-6 m/m--C)

Bulk Resistivity 2.84 × 10-5 ohm - in   (7.2 × 10-5 ohm - cm)

Melting Point 1220°F (660°C)

Page 15: metal foam

Characteristics:•Low Density•High Strength to Weight Ratio•High Surface area to Volume Ratio•isotropic load response•controlled stress-strain Characteristics•Can be Heat Treated•Brazable•Can be coated and plated

Page 16: metal foam

Copper Foam

PHYSICAL PROPERTIES METRIC ENGLISH

Porosity 65.0 - 95.0 % 65.0 - 95.0 %

Permeability 5.35e-10 - 1.54e-9

5.35e-10 - 1.54e-9

1300 – 4100 1300 – 4100

MECHANICAL PROPERTIES

Tensile Strength, Yield 0.250 - 2.50 Mpa 36.3 - 363 psi

Modulus of Elasticity 0.100 - 0.370 Gpa

14.5 - 53.7 ksi

THERMAL PROPERTIES

Specific Heat Capacity 0.115 J/g-°C 0.0275 BTU/lb-°F

Thermal Conductivity 2.00 - 10.0 W/m-K

13.9-69.4BTU-in/hr-ft²-°F  

Page 17: metal foam

Why focusing on copper foams? Every type of metal, in the shape of a

foam or not, has distinctive properties (oxidation, electrical conductivity, resistance to high temperature, etc). Copper has some interesting thermal conductivity properties compared to other metals. As a result, copper was chosen by Meta foam in targeting the electronics thermal management market.

Page 18: metal foam

The main advantages of this copper foam are:

- Low product cost - High product quality - High metal purity - High metallic ductility - Excellent solder ability - Suitable for adhesive bonding

applications

Page 19: metal foam

Metals Usually Manufactured for Foaming:Carbon Foam

Compression Strength 15-75 psi (0.10-0.52 MPa)

Tensile Strength* 25-50 psi (0.17-0.34 MPa)

Modulus of Elasticity (Tension)*

14.6 × 103 psi (101.84 MPa)

Specific Heat .3 BTU/lb °F (1.26 J/g °C)

Bulk Thermal Conductivity 0.021 - 0.29 BTU/ft ·hr·°F (0.033 - 0.050 W/m °C)

Coefficient of Thermal Expansion (0-100°C)

1.2 × 10-6 in/in°F (2.2 × 10-6 m/m°C)

Coefficient of Thermal Expansion (100-1000°C)

1.8 × 10-6 in/in°F (3.2 × 10-6 m/m°C)

Bulk Resistivity 12.7 × 10-2 ohm · in (32.3 × 10-2 ohm · cm)

Temperature LimitationsIn air

600°F (315°C)

Page 20: metal foam

Characteristics:

Low Density

High Strength to Weight Ratio

High Surface area to Volume Ratio

isotropic load response

controlled stress-strain Characteristics 

Advantages:

Extremely lightweight

Thermally insulating

Electrically conductive

Easily machinable to near-net-shape

Resistant to thermal shock

Chemically inert

Applications:

•Molten metal filtration

•Energy storage devices

•Catalysis

•Biomedical devices

•Furnace fixturing and tooling

•Electric contactors

Page 21: metal foam

Zinc Metal Foam

Zinc Foam is low density permeable material with numerous applications. The defining characteristic of these foams is a very high porosity, typically 75-95% of the volume consisting of void spaces. Metallic foams have found a wide variety of applications in heat exchangers, energy absorption, flow diffusion and lightweight optics.

Page 22: metal foam

The foaming of the zinc or its alloys requires either higher overheating above the melting temperature than it is in the case of aluminium foams, or needs higher amount of foaming agent, providing TiH2 is used for this purpose.

Page 23: metal foam

Shape-Memory Alloy

Page 24: metal foam

Shape-memory alloy A shape-memory alloy (SMA, smart metal,

memory metal, memory alloy, muscle wire, smart alloy) is an alloy that "remembers" its original, cold-forged shape: returning the pre-deformed shape by heating. This material is a lightweight, solid-state alternative to conventional actuators such as hydraulic, pneumatic, and motor-based systems. Shape-memory alloys have applications in industries including medical and aerospace.

Page 25: metal foam

3 main types of shape-memory alloys Copper-zinc aluminum nickel

Copper-aluminium-nickel,

Nickel Titanium (NiTi) alloys

Page 26: metal foam

Crystal structures

Many metals have several different crystal structures at the same composition, but most metals do not show this shape-memory effect. The special property that allows shape-memory alloys to revert to their original shape after heating is that their crystal transformation is fully reversible. In most crystal transformations, the atoms in the structure will travel through the metal by diffusion, changing the composition locally, even though the metal as a whole is made of the same atoms. A reversible transformation does not involve this diffusion of atoms, instead all the atoms shift at the same time to form a new structure,

Page 27: metal foam
Page 28: metal foam

Manufacture Shape-memory alloys are typically made by casting, using

vacuum arc melting or induction melting. These are specialist techniques used to keep impurities in the alloy to a minimum and ensure the metals are well mixed. The ingot is then hot rolled into longer sections and then drawn to turn it into wire.

The way in which the alloys are "trained" depends on the properties wanted. The "training" dictates the shape that the alloy will remember when it is heated. This occurs by heating the alloy so that the dislocations re-order into stable positions, but not so hot that the material recrystallizes. They are heated to between 400 °C and 500 °C for 30 minutes. Typical variables for some alloys are 500 °C and for more than 5 minutes.

They are then shaped while hot and are cooled rapidly by quenching in water or by cooling with air.

Page 29: metal foam

Properties

The yield strength of shape-memory alloys is lower than that of conventional steel, but some compositions have a higher yield strength than plastic or aluminum. The yield stress for Ni Ti can reach 500 Mpa. The high cost of the metal itself and the processing requirements make it difficult and expensive to implement SMAs into a design. As a result, these materials are used in applications where the super elastic properties or the shape-memory effect can be exploited.

Page 30: metal foam

Applications

Piping

The first consumer commercial application for the material was as a shape-memory coupling for piping, e.g. oil line pipes for industrial applications, water pipes and similar types of piping for consumer/commercial applications.

Page 31: metal foam

Medicine

Shape-memory alloys are applied in medicine, for example, as fixation devices for osteotomies in orthopaedic surgery, in dental braces to exert constant tooth-moving forces on the teeth. Optometry

Eyeglass frames made from titanium-containing SMAs

are marketed under the trademarks Flexon and

TITANflex.

Page 32: metal foam

Spider

Silk

Page 33: metal foam

Spider silk is an extremely strong material and is on weight basis stronger than steel. It has been suggested that a pencil thick strand of silk could stop a Boeing 747 in flight.Spider silk is one of nature’s most extraordinary substances. It is exceptionally flexible, elastic, and lightweight, yet tough—three times as strong as Kevlar and five times as strong as steel! And because it is natural, it is biodegradable and can be produced pollution-free. Furthermore, one of the most important qualities of spider silk is its endless versatility. Spider silk, synthetically made, could be used in countless applications with significant commercial impact and improvement to human life

Page 34: metal foam

The possible uses for synthetic spider silk are endless. They include applications in the industrial, medical, and military fields as well as in everyday uses. Spider silks could be used to create strong and flexible artificial ligaments and tendons, bandages, and surgical thread. Spider silk could also be used to construct protective clothing or body armor. It would make an exceptional material for this use because it is one of the toughest materials on Earth that can be woven into a fiber and is estimated to be three times as strong as Kevlar (the material currently use to make bullet-proof vests). Also, spider silk is more environmentally sound because it does not use any of the toxic, acidic processes used to produce Kevlar and it is biodegradable. Spider silk could be used to make paper for important documents, because it would be flexible and could not be torn. Other possible uses for this important technology could include:

Page 35: metal foam

• textiles• nets• parachutes• seat belts and airbags• ropes• sporting goods• Used for making artificial tendons and ligaments for supporting

weak blood vessels.• For making rust-free panels on motor vehicles or boats.• Making bandages and surgical threads.• Manufacturing rip-proof, and light weight clothing.• Making biodegradable bottles.• Can be used in ropes, seat belts, and parachutes due to its

tensile strength.

Page 36: metal foam

Types of Spider Silk:Different spiders have different glands for producing different kinds of silk, and for different reasons, like web construction, capturing prey, defense, or mobility. Each fibre gives a different kind of silk.

Dragline silk: This fibre is used as the outer rim of the web. It is tough, and strong as steel.

Tubiliform silk: This fibre is used for protecting egg sacs. Its nature is very stiff.

Capture-spiral silk: This fibre is extremely sticky, and stretchy by nature, and is used for the capturing lines of the web.

Minor-Ampullate silk: This fibre is used for web construction purposes.

Aciniform silk: This fibre is used to wrap the captured prey. This is three times tougher than the dragline silk.

Page 37: metal foam

Mechanical PropertiesEach spider and each type of silk has a set of mechanical properties optimised for their biological function.Most silks, in particular dragline silk, have evolved exceptional mechanical properties. They exhibit a unique combination of high tensile strength and extensibility (ductility). This enables a silk fibre to absorb a lot of energy before breaking (toughness, the area under a stress-strain curve).

Page 39: metal foam

StrengthIn detail a dragline silks’ tensile strength is comparable to that of high-grade steel (1500 MPa), about half as strong as aramid filaments, such as Twaron or Kevlar(3000 MPa).

DensityConsisting of mainly protein, silks are about a fifth of the density of steel (1.31 g/cm^3). As a result, a strand long enough to circle the Earth would weigh less than 500 grams (18 oz).

ExtensibilitySilks are also especially ductile, with some able to stretch up to four times their relaxed length without breaking.

Page 40: metal foam

ToughnessThe combination of strength and ductility gives dragline silks a very high toughness (or work to fracture), which "equals that of commercialpolyaramid (aromatic nylon) filaments, which themselves are benchmarks of modern polymer fibre technology".

TemperatureWhilst unlikely to be relevant in nature, dragline silks can hold their strength below −40 °C and up to 220 °C.

SupercontractionWhen exposed to water, dragline silks undergo

supercontraction, shrinking up to 50% in length and behaving like a weak rubber under tension. Many hypothesis have been suggested as to its use in nature, with the most popular being to automatically tension webs built in the night using the morning dew.

Page 41: metal foam

Highest-PerformanceThe strongest known spider silk is produced by the species Darwin's bark spider (Caerostris darwini): "The toughness of forcibly silked fibers averages 350 MJ/m3, with some samples reaching 520 MJ/m3. Thus, C. darwini silk is more than twice as tough as any previously described silk, and over 10 times tougher than Kevlar“

Page 42: metal foam

Spider Silk Production May Lead to Super-Strength Materials

30 November 2004 - Protein engineering may be the key technique in producing artificial spider silks for super-strength industrial products, according to a review published in the November issue of Microbial Cell Factories. Each of the 34,000 recognized species of spider has a specific “tool-kit” of silks with different properties, purposes, and functions, explained Thomas Scheibel, a chemistry professor at Technische Universität in München, Germany.

“The combination of strength and stretchiness [in spider silk] gives…a toughness…greater than elastin, tendon, silkworm silk, bone, synthetic rubber, Kevlar and high-tensile steel,” Scheibel reported.

Page 43: metal foam

One problem facing the mass-production of spider silk is that spiders are cannibalistic and thus cannot be raised en masse. Scheibel explained that spider silk genes can be inserted into other DNA hosts like E. coli to create silk proteins, eliminating the need for massive amounts of spiders. In addition, artificial types of spider silk could be produced through the creation of recombinant “silk-like” proteins in host cells.

Another major obstacle in the way of commercial silk production is the spinning of these recombinant silk proteins into fibers mimicking real spider silk fibers, according to Scheibel. Currently, the diameter of artificial silk fibers produced by “microfabricated” spinnerets is much wider than that of natural silks. Some researchers are exploring silicon micro-spinnerets in hopes of solving the fiber-spinning problem.

Page 44: metal foam

Surgery sutures, parachutes, body armor and lightweight airplane construction are some of the materials that spider silk could revolutionize if large-scale production took place.In fact, Scheibel predicts that eventually “industrially produced spider silk could out-compete man-made fibers.”