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Porous Metals Manufactured by Lost Carbonate Sintering Dr. Liping Zhang Department of Engi neering University of Liverpool


Structural Applications Sandwich panel with Al foam core (Courtesy of Fraunhofer Institute)

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Lightweight structures f or buildings and vehicles Energy absorbers, such as bumpers, door inserts and crashboxes in cars


Functional Applications n

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Heat exchangers , such as heat sinks for micromicro -electronic devices Thermal insulators , such as wall panels Sound absorbers , such as exhaust pipe inserts, motorway shields, concert hall ceiling

Al foam heat exchanger (Courtesy of Duecell)

Metal foam silencer (Courtesy of Recemat)


Other Applications n n n n n n

Filters Electrodes of NiMH batteries Electromagneti c shielding Catalyst supports Artificial bones And many others


How are they made?

♫ Birds do it ♪ ♫ Bees do it ♪ … ♫ Let’s do it …… ♪


Technologies to make Melt -Gas Injection Meltn Melt Melt--Foaming Agent n Powder Powder--Foaming Agent n Investment Casting n Melt Infiltration n Powder Powder--Space Holder (LCS) n


LCS - Schematic

metal powder

carbonate powder

metal foam

mixing

compacting

decomposition sintering

K2CO3 recycled

dissolution


Carbonate Removal 950째C, 0.5 hr

temperature

Tm of K2CO 3 850째C, 4 hrs

time

Dissolution: little shrinkage; slow Decomposit ion: quick and clean; some shrinkage


Porous Metals

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A range of metals (Al, Cu, Fe, Ni, Ti) Spherical or irregular shaped pores Uniform, hybrid or gradient structures Pore size: 0.1 – 5 mm Porosity: 50% – 85% Specific surface area: 2.3 – 4.5 mm 2/mm 3


Pore Structure II a

b

0.5 mm

Typical structure of porous (a) Al and (b) Ti


Advantages/Li mitations of LCS n n n n

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Suitable for many metals, especially the metal with high melting point (Cu, Fe, Ni ,Ti) Accurate control of pore morphol ogy, size and porosity Homogeneous di stribution of pores Low producti on cost Porosity range 50 - 85% Carbonate sol ution can attack some metal s


Heat pipe using Porous Cu


Heat Exchange Testing


Heat Transfer Performance Heat exchange coefficient kW/m 2K

160 140

0.3 L/min

120

0.5 L/min

100

0.7 L/min

80

0.9 L/min

60

1.1 L/min

40

1.5 L/min

20

2 L/min

0 30

40

50

60

70

80

90

100

Porosity, %

There is an optimum porosity giving rise to the highest heat transfer coef ficient


Career Development n n n n n n n n

1981 -1985 BEng, DUT, China 19811985--1988 MSc, DUT, China 1985 1988--1992 Lecturer, DUT, China 1988 1992--1995 Career break 1992 1995--1998 PhD, Birmingham University 1995 1998--1999 RA, Birmingham University 1998 1999--2003 Career break 1999 2004--2008 Research Fellow, Liverpool University 2004 supported by Daphne Jackson Trust, Equalitec, Royal Academy of Engineering, Thermacore.


Carbonate in full bloom

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