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
1/11/2017 1
Presented by :
Mohit Rajput
(MMT, 12216014)
Indian Institute of Technology Roorkee
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]
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
Editor's Notes
Firstly, Good morning to you all, So today I am gonna report to for Mtech evaluation.
My topic for my master thesis is “to control …….” I have been working under the supervison of Daniel Sir.
For the presentation the outline of the slide are firstly the introduction then literature review proceeded by plan of work then Experimental Procedure then summerizing with results and discussions an at the end references used.
Since my work deals with controlling the metal foam structure lets first know about metal foam and microwaves . So Metal foams are…….. And these ……..and because of these property they have proven to be…………in Scientifics studies.
So Microwaves are EM waves which consist of an electric and a magnetic field orthogonal to each other with wavelengths in the range of 1–1000 mm. Microwaves are wave energy that is converted into heat energy depending upon the type of interaction with the target materials.
i.e. the material processing is ……….Microwave rocessing has gained much interest …..
UV<Visible light<IR<microwave<radio wavelength
Also There are range of frequency present between 300 GHz to 300 MHz, The most common microwave frequency used for research is 2.45 GHz (wavelength ~ 12.25 cm), the same as for the domestic microwave ovens; the other allowable frequencies are 915 MHz, 30 GHz and 83 GHz
Now the Literature Review, So Firstly about the foaming processes
Majority of processes produces close-cell foam and some produces open cell foam. Fig 6 shown below showcase some of these characteristics based on the process used.
Still now these foaming process hasn't been optimize to their full potential and still there are various deficiencies in these techniques. First being the lack of ... …. one reason for these problems is the Limited stability of emerging metal foams and the lack of control over these processes.
Vicious cycle has created in this field as Specific Properties based application hasn’t been exploited, because of the limitation of foaming process and lack of detailed knowledge of foam properties, and because of the lack of detailed knowledge of properties and foaming process limitation design engineers would not implement it for application.
……..making the processes more reliable and economically viable.
could be represented as --- as the microwave interaction phenomena is still not well understood
With change material temperature and size, material interaction with microwave changes, updating the power absorbed. And hence heating.
Also there will be presence of metal oxide. It is known that metal oxide has low dielectric loss factor and hence won’t be generating heat with microwave interaction and will provide stability when foaming will be taking place.
Also if require TiH2 can be given pre heat treatment to delay it decomposition temperature.
Heating mechanisms in magnetic materials
The non-magnetic materials are affected only by electric field component of microwave. The two main loss mechanisms for non-magnetic materials (such as Al, Cu, water, polymers, and ceramics) are dipolar losses and conduction losses. Conduction losses dominate in metallic and high conductivity materials whereas dipolar losses dominate in dielectric insulators.
Heating mechanisms in magnetic materials
The heating mechanisms are typically active while microwave processing of magnetic materials such as Iron, Nickel, and Cobalt. These materials are affected by both electric field and magnetic field. The electric field imparts motion to the free electrons, whereas the magnetic field affects the electron spin, domain wall and orientation of domains. The heat loss mechanisms in magnetic materials exhibit conduction losses with additional magnetic losses such as hysteresis, eddy current, domain wall resonance and electron spin resonance [73].
Microwave material processing has gained much interest due to 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
3 instruments has been used till now one being muffle furnace, second being 900W microwave and third being 3kW microwave.
When Conventional material processing route was taken.
•It is evident that the muffle furnace was having error in temperature reading as clearly sample B1-2, B1-3, B1-4 and B4 haven’t melt even when the temperature was raised above melting point of metal matrix.
•Beads formation were observed on sample B1-2 and B1-3. Beads were formed mainly at the corners and the average bead size with B1-3 was higher than with B1-2 without the outliers. Which evident to larger bead will be formed when temperature will be raised to a higher temperature with faster heating rate when the composition was kept same.
•With sample B1-4 this was not observed and with sample B4 this phenomenon was very limited even though this sample went to higher temperature compared to others. (considering that furnace only had calibration error) indicating that composition alteration indeed has effect of foaming (though this isn’t foaming exactly)
•It is believed that bead formation is taking place because to the gas releasing from the samples and encapsulating the melted surface metal and hence more beads are observed at the corners where there is more surface area available for gas to release.
•With sample B1-4 showing much less bead formation compared to B1-2 and B1-3 even when it was heat treated to higher temperature is indicating that the gas was unable to be released this may be because pathways were not formed within the porosity and gas was unable to be released and form beads. The above point also gets reinforced from the fact that because of the presence of SiC within the matrix would have resulted on more porous compact when compared to pure metal matrix. Hence it can be said that porosity plays and important role in foaming and bead formation was observed only because gas was able to create pathways to escape out encapsulating the molten surface material.
•Observing all the evidence indicates that a proper heat treatment needs to be given to the samples also less porous compacts are required for foaming to take place.
When Microwave material processing route was taken. (Position did play a role in treatment)
•It was observed with all the sample B1-1, B2-1, B2-2, B2-4 and B3-3 that because high reflection happening within the chamber was causing the filament to get overheated causing the 3kW microwave to shutdown automatically.
•Samples B2-3, B3-1, B3-2 and B3-4 were treated in 900W microwave in which though we were able to treat sample for longer duration but still no result were obtained. This indicates that 900W microwave power is not sufficient for our work.
•On sample B3-1, B3-2 and B3-3 treated through 900W microwave and also sample B1-1 treated through 3kW microwave shows surface burning and taking in account the susceptor positions it evident that susceptor position plays an important role.
•In all the sample treated through microwave it can be observed that surface texture is more homogenous when treated with microwave as compared to conventional based material processing.
•Point above also indicates that even when using Susceptor based heating in microwave our material is interacting with microwaves and having inside-out heating.
•A trial was make to see if encapsulating our compact with in graphite would be beneficial as microwave is observed to have better interaction with than graphite with metal. For this graphite compact was prepared, sample B2-4. It observed that with this compact 3kW microwave had even smaller uptime and also compact temperature didn’t raise much indicating that using graphite as an encapsulation to enhance heating would have adverse effect with the formation of aluminium carbide and also lesser microwave treatment period.
•With less porous pellet though our foaming characteristics will increase but compact interaction with microwave will suffer.
•For all the samples treated with microwave, the effect of amount of SiC with in the matrix isn’t well understood as our microwave treatment is getting limited because of lesser power input by 900W microwave and with 3kW microwave getting shutdown cause of overheating cause us to use susceptor i.e. hybrid heating for increasing the kinetics of process. In this project, we are aiming to create foam by direct microwave heating without the use of any other add-on like susceptor. So still we are waiting for the 1.4kW microwave to get repaired which is also equipped with IR pyrometer for temperature measurement.