The document summarizes a master's thesis on controlling the structure of metal foam using microwave heating. The thesis outlines the background on metal foams and their applications. It then discusses previous work on metal foaming processes and their limitations in controlling structure. The plan is to modify an existing foaming technique called ALULIGHT by incorporating microwave processing to address these limitations. Preliminary experiments involved microwave heating of aluminum and magnesium compacts containing gas-releasing additives. Initial results showed beads forming on the surface due to gas release through porosity. Further experiments will optimize conditions to control foam structure.

1. To Control Metal Foam Structure using Microwave Heating
Master Thesis
Under the Supervision of
Dr. B.S.S. Daniel
Professor
Department of Metallurgical and Materials Engineering
Indian Institute of Technology, Roorkee
2/12/2017 1
Presented by :
Mohit Rajput
(MMT, 12216014)
Indian Institute of Technology Roorkee

2. Outline
1. Introduction
2. Literature Review
3. Plan of Work
4. Experimental Procedure
5. Results and Discussion
6. References
2

3. Introduction
3
Fig 1. Closed cell and Open cell foam
• Metal Foam, a cellular structure often consisting of
a solid metal with large volume fraction filled with
gas-filled pores and these pores can be sealed
(closed-cell) or interconnected (open-cell).
• These metallic structure has attracted interest from
biomedical, electrical, structural and thermal
industrial due to its properties, such as high specific
strength, high stiffness, high energy absorption and
osteoconductivity.
• Beneficial to a wide range of applications such as
orthopaedic implant, electrical screening,
electrodes, light-wt structure, heat exchangers and
many more. [1-4]
[1] Mark P. Staiger, Alexis M. Pietak, Jerawal Huadmai, George Dias, ”Magnesium and its alloys as orthopedic biomaterials: A review”, Biomaterials 2006, 27,1728–1734.
[2] Shwartz, D. S., Shih, D. S., Evans, A. G. “Porous and Cellular Materials for Structural Application”, Materials Research Society Proceedings, 1998, 521,
[3] He Deping, Ma Liqun, “The heat transfer characteristic of foamed metal with open pore”, Chinese J. of Mater. Research, 1997, 11(4): 431434.
[4] D. Schwingel, H.W. Seeliger, C. Vecchionaces, D. Alwes, J. Dittrich, “Aluminium foam sandwich structures for space applications”, Acta Astron., 2007, 61, 326–330.
More application could be seen in Table 2 present in Report

4. Introduction
4
• Microwaves are EM waves with electric and a magnetic field orthogonal to
each other and wavelengths in the range of 1–1000 mm.
• Material processing is dependent on material dielectric and magnetic
properties as it interact with microwaves. [5,6]
• Microwave material processing has gained much interest due to [7]
• Relatively low manufacturing costs
• Both energy and time saving
• Fast sintering process
• Short soaking time
• Higher energy efficiency
• Improved product uniformity
• High yields
• Improved mechanical property
• Eco-friendliness
[5] R.R. Mishra and A.K. Sharma, “Microwave–material interaction phenomena: Heating mechanisms, challenges and opportunities in material processing”, Composites:
Part A, 2016, 81, 78–97.
[6] Clark DE, Sutton WH. “Microwave processing of materials.” Annu Rev Mater Sci., 1996, 26, 299–331
[7] R.F. Schiffman, “Commercializing microwave systems: Paths to success or failure,” in Ceramic Transactions, 1995, 59, 7-17
Fig 2. MHH using SiC block as susceptor

5. Literature Review
5
[8] M. F. Ashby, A. G. Evans, N.A. Fleck, “Metals Foams, A Design Guide”, Oxford:
Butterworth Heinemann, 2000.
[9] David C.Curran, “Aluminium Foam Production using Calcium Carbonate as a
Foaming Agent”, PHD Thesis, University of Cambridge, 2003
Fig 4. Foaming Process [9]
Fig 3. Characteristic of Foaming Process [8]
• There are various metal foaming processes some of which are-
• Direct Foaming of melt
• ALULIGHT
• ALPORAS
• FORMGRIP
• FORMCARP
• Each process results in characteristic
structure, size, regularity of cells and
relative density of the foam.

6. Literature Review
6
• Deficiencies of various metal foaming techniques are [10,11]-
• Lack of the ability to control structure and morphology.
• Physical properties of foams are not good enough
• Lack of the ability to reproduce constant quality
• Takes a while to produce the foam
• Vicious cycle has created in this field.[10]
• Hence a foaming technique which can accommodate these foaming
deficiencies in order to break this cycle is much needed.
• Modifying current ALULIGHT technique with Microwave material processing
could be a solution
[10] John Banhart, “Metal Foams: Production and Stability”, Advanced Engineering Materials, 2006, 8(9), 781–794.
[11] J. Banhart, “Manufacturing Routes for Metallic Foams”, JOM, 2000, 52 (12), 22-27
Limitation of foaming process and lack of
detailed knowledge of foam properties
Specific Properties based application
hasn’t been exploited

7. Literature Review
7
• Classification of
materials based on
energy absorption [12]
• Transparent
• Absorber
• Opaque
• Mixed Absorber
[5] R.R. Mishra and A.K. Sharma, “Microwave–material interaction phenomena: Heating mechanisms, challenges and opportunities in material processing”, Composites:
Part A, 2016, 81, 78–97.
[12] Clark DE, Folz DC, West JK. “Processing materials with microwave energy”, Mater Sci Eng A, 2000, 287, 153–8
[13] Mondal A, Agrawal D, Upadhyaya A. “Microwave heating of pure copper powder with varying particle size and porosity”, J Microwave Power EE, 2009, 43(1), 5–10
Fig: 5 – microwave interaction with materials (x-axis represent dielectric loss factor) [5]
• Power absorbed by a material could be represented as the energy converted
inside the material to heat which is significantly influenced by the depth up
to which radiation penetrate into it [5].
• With change material temperature and size, material interaction with
microwave changes, updating the power absorbed [13].

8. Literature Review
8
• For our study of metal foaming using microwave, as we can observe from
the trend that metals as a bulk are opaque to microwave hence using metal
powder as well as mixing SiC particle should prove to be beneficial.
• Embedding SiC particle in metal matrix as well as the presence of porosity
should prove to be beneficial by making it microwave absorber [14].
• For our preliminary study using metal having low melting temp. and also
close to the decomposition temp. of TiH2 was selected which are Al and Mg.
• Heating mechanisms in
non-magnetic materials[5]
• Dipolar Loss
• Conduction Loss
[14] Crane, C.A.; Pantoya, M.L.; Saed, M.A.; Weeks, B.L. “Utilizing microwave susceptors to visualize hot-spots in trinitrotoluene”, J. Microw. Power Electromagn. Energy,
2014, 48, 5–12.
[5] R.R. Mishra and A.K. Sharma, “Microwave–material interaction phenomena: Heating mechanisms, challenges and opportunities in material processing”, Composites:
Part A, 2016, 81, 78–97.

9. Literature Review
9
[5] R.R. Mishra and A.K. Sharma, “Microwave–material interaction phenomena: Heating mechanisms, challenges and opportunities in material processing”, Composites: Part A,
2016, 81, 78–97.
[15] Agrawal D., “Microwave sintering of ceramics, composites and metallic materials, and melting of glasses”. Trans Indian Ceram Soc, 2006, 65(3), 129–44
[16] Satnam Singh, Dheeraj Gupta and Vivek Jain, “Recent applications of microwaves in materials joining and surface coatings”, IMechE Part B: J Engineering Manufacture, 2014,
Fig 7. Types of microwave heating (a) direct heating, (b) selective heating and (c) hybrid heating]
Microwave vs Conventional Heating
Fig 7. Temperature distribution in conventional, microwave, and
microwave hybrid heating [16][15]

10. Plan of Work
10

11. Experimental Procedure
11

13. Preliminary Results and Discussion
• In bead formation porosity of compact played an important role.
• Bead formation took place because the gas releasing because of decomposition
created pathways within porosity, escaping to the surface and encapsulating the
molten surface metal.
• More beads are observed at the corners because of more surface area for gas to
release from.
• Larger bead will be formed when temperature will be raised to a higher
temperature with faster heating rate when the composition was kept same also
composition alteration indeed has effect of foaming.
• Muffle furnace was having error in temperature reading and hence next time a
proper heat treatment needs to be given to the samples additionally less porous
compacts are required for foaming to take place.
• Though with less porous pellet, ease of foaming will be more but compact
interaction with microwave will suffer.
13

14. • Surface texture were observed to be more homogenous when treated with microwave as
compared to conventional based material processing even when using hybrid heating in
microwave our material was interacting with microwaves and having inside-out heating.
• We had to resort to using susceptor in microwave i.e. going for hybrid microwave heating
for increasing the kinetic of the reaction as our microwave treatment is getting limited
because of lesser power input by 900W microwave and with 3kW microwave getting
shutdown because of filament overheating caused by large reflection taking place in
microwave chamber.
• Using graphite as an encapsulation to enhance heating would have adverse effect.
14
Preliminary Results and Discussion

15. References
[1] Mark P. Staiger, Alexis M. Pietak, Jerawal Huadmai, George Dias, ”Magnesium and its alloys as orthopedic
biomaterials: A review”, Biomaterials 2006, 27,1728–1734.
[2] Shwartz, D. S., Shih, D. S., Evans, A. G. “Porous and Cellular Materials for Structural Application”, Materials
Research Society Proceedings, 1998, 521,
[3] He Deping, Ma Liqun, “The heat transfer characteristic of foamed metal with open pore”, Chinese J. of
Mater. Research, 1997, 11(4): 431434.
[4] D. Schwingel, H.W. Seeliger, C. Vecchionaces, D. Alwes, J. Dittrich, “Aluminium foam sandwich structures for
space applications”, Acta Astron., 2007, 61, 326–330.
[5] R.R. Mishra and A.K. Sharma, “Microwave–material interaction phenomena: Heating mechanisms,
challenges and opportunities in material processing”, Composites: Part A, 2016, 81, 78–97.
[6] Clark DE, Sutton WH. “Microwave processing of materials.” Annu Rev Mater Sci., 1996, 26, 299–331
[7] R.F. Schiffman, “Commercializing microwave systems: Paths to success or failure,” in Ceramic Transactions,
1995, 59, 7-17
[8] M. F. Ashby, A. G. Evans, N.A. Fleck, “Metals Foams, A Design Guide”, Oxford: Butterworth Heinemann,
2000.
[9] David C.Curran, “Aluminium Foam Production using Calcium Carbonate as a Foaming Agent”, PHD Thesis,
University of Cambridge, 2003
15

16. References
[10] John Banhart, “Metal Foams: Production and Stability”, Advanced Engineering Materials, 2006, 8(9), 781–
794.
[11] J. Banhart, “Manufacturing Routes for Metallic Foams”, JOM, 2000, 52 (12), 22-27
[12] Clark DE, Folz DC, West JK. “Processing materials with microwave energy”, Mater Sci Eng A, 2000, 287,
153–8
[13] Mondal A, Agrawal D, Upadhyaya A. “Microwave heating of pure copper powder with varying particle size
and porosity”, J Microwave Power EE, 2009, 43(1), 5–10
[14] Crane, C.A.; Pantoya, M.L.; Saed, M.A.; Weeks, B.L. “Utilizing microwave susceptors to visualize hot-spots
in trinitrotoluene”, J. Microw. Power Electromagn. Energy, 2014, 48, 5–12.
[15] Agrawal D., “Microwave sintering of ceramics, composites and metallic materials, and melting of glasses”.
Trans Indian Ceram Soc, 2006, 65(3), 129–44
[16] Satnam Singh, Dheeraj Gupta and Vivek Jain, “Recent applications of microwaves in materials joining and
surface coatings”, IMechE Part B: J Engineering Manufacture, 2014, 1–15
16