Potential of Recycled Aluminium Cans and 215 μm Sized Eggshell Powder for Low Cost Metal Matrix Composites

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1 doi: /me Potential of Recycled Aluminium Cans and 215 μm Sized Eggshell Powder for Low Cost Metal Matrix Composites J. O. Agunsoye *1, S. A. Bello 1,2, A. A. Yekinni 3, I. A. Raheem 1, M. M. Idehenre 1, T. E. Idegbekwu 1 A. D. Oderinde 1 1 Department of Metallurgical and Materials Engineering, Faculty of Engineering, University of Lagos, Lagos, Nigeria 2 Department of Materials Science and Engineering, College of Engineering, Kwara State, University, Malete, Nigeria 3 Department of Mechanical Engineering, Lagos State Polytechnic, Ikorodu Lagos, Nigeria *1 jagunsoye@unilag.edu.ng; 2 sefiu.bellokwasu.edu.ng; 3 kunleyk2003@yahoo.com Abstract The potentials of recycled aluminium cans with 215 μm sized eggshell powders to produce a useful engineering composite material were investigated. the stir cast method was used to enhance proper mixing of the composite melt prior to pouring exercise. the process involves gradual increase of the eggshell powder additions to the aluminium can melt from 2 to 12%. the composite melt was poured into a preheated steel die mould to produce 250 x 120 x 120 mm rectangular bars. the bars were machined to standard samples for mechanical and physical property investigations. morphology of eggshell powders wasexamined with the aids of scanning electron microscope. the results showed a considerable increase in tensile strength, young s modulus of elasticity and hardness values. the increase is attributable to formation of dislocation loop and pile up due to impingement/hindrance to dislocation movement by eggshell powders within the aluminium can matrix. however, there was a noticeable decrease in tensile strain and impact energy respectively. furthermore, the developed composites are lighter (lower density) than the control sample without eggshell powder additions. Keywords Stir Cast; Potentials; Investigation; Mechanical Analysis; Density Introduction Increase in refuse generation places high burden on waste management which affects human s social and economic activities. Harnessing waste materials (discarded aluminium cans and eggshells) to make new and useful engineering materials is means of wealth creation from waste. This research work ultimately contributes to knowledge in the area of recycling particularly in Lagos city where there are huge waste management problems and challenges. There is no better place to cultivate the culture of recycling than University of Lagos; immediate institution to Lagos city. Material development being a form of technological advancement is a result of human s thought and perception. This is the main distinguishing factor that differentiates human beings from other mammals since evolution of mankind. Today, many materials in use are produced in different ways to satisfy human need for housing, heating, furniture, clothes, transportation, entertainment, medical care, defense and all the other trappings of a modern, civilized society [1 3]. Metals have been the most important engineering materials; ferrous metals have been the most significant. Their applications are found in many engineering structures. Among the nonferrous metals, aluminium and its alloys are the most produced for different applications including transport, packaging, building and construction because of its lightness, corrosion resistance, damage tolerance, and ease of formability [4]. This is now being challenged by other important engineering materials such as polymer, ceramics and composites because of their high specific mechanical properties. Composites are mixtures of at least two components, the matrix (continuous phase) and reinforcement (discontinuous phase), having better properties than when each component is used alone. In 24

2 Journal of Metallurgical Engineering (ME) Volume 4, journal.org accordance with matrix, they are classified as metal, ceramic and polymer matrix composites. Aluminium and magnesium are commonly used metals as matrices for metal matrix composite (MMCs) productions. Aluminium is produced from bauxites whose world biggest producers in 2008 are Australia, Brazil and China in 30, 13 and 10% respectively [7]. However, production of aluminium from bauxites not only consumes a great amount of energy but also emits hazardous gases such as carbon dioxide (CO2) and some floro carbons (FC) which impact negatively on environment. CO2 because of its ability to retain heat, has been rated as one of gases that cause the global warming, thereby causing the melting of global ice, exposing us to dangerous cosmic rays. Aluminium industry alone accounts for 1% of global greenhouse gas emissions [5]. Vast use of aluminium and its alloys in many engineering structures has called for increasing supply of bauxite. Therefore the menaces associated with primary production of aluminium from bauxite increase. Bauxite mining has significant negative environmental and social impacts in Jamaica, Australia, India and Brazil including the contamination of water and fishing supplies, the destruction of land and displacement of local communities. Moreover, menaces associated with aluminium do not end in bauxite mining alone. In Nigeria, the use of aluminium cans in packaging has almost replaced the traditional glass bottle packaging systems. High consumptions of drinks packaged with aluminium cans have increased the number of aluminium cans littering the environments. Indiscriminate dumping of aluminium can and other products after their service life has contributed to other forms of environmental issues (see Figure 1). In order to reduce/eliminate problems associated with waste aluminium products, there is a need for recycling of waste aluminium materials. Critically, the aluminium recycling process uses only 5% of the energy required for its initial extraction and processing and 10 % of the initial capital equipment costs. Recycling also saves 97% of the greenhouse gas emissions generated in the primary production process [5]. Eggshell is the non edible byproducts of eggs with little or no saleable values [6]. Previous study by Hussein et al, (2011) [7] revealed that the eggshell contains 95% weight of calcium carbonate in the form of calcites and 5% by weight of organic materials. Indiscriminate dumping of eggshell has been reported as one of the causes of the worst environmental problems, most especially in countries having highly developed egg product industries. Shuhadah et al, (2008) [8] reported that more than 150, 000 tons of eggshells are disposed in landfills in the United State of America. In Nigeria, eggshells from hatcheries and fast food industries are dumped in canals, gutters, rivers and even on open grounds. These prevent normal flow of water, becoming clogged and releasing bad odour. Benefits of active compounds such as calcite, uronic and salic acids in eggshells can be realized via conversion of the eggshells into useful materials such as fertilizer for improving crop growth; human and animal nutrition; building materials and particulate powder for metal and polymer reinforcement in composite development. FIG. 1 DISCARDED WASTES IN CANAL Agunsoye et al, (2014) [9] have studied effects of cocosnucifera (coconut shell) on the mechanical and tribological properties of recycled waste aluminium can composites. Their experimental results revealed that tensile strength and wear resistance of the composites increased as volume fractions of coconut shell increased whereas there is light reduction in impact energy absorbed by the composites. Also aluminium cans reinforced with 10% volume fraction of coconut shell particles at finest size used (215 μm) displayed the highest tensile strength and optimum wear resistance. Hassan et al, (2012) [10] developed polyester/eggshell particulate composites. Their experimental results showed that carbonised eggshells enhanced the mechanical properties of the polyester matrix composites 25

3 more than uncarbonised eggshells. Effects of casting methods and cooling media were studied on aluminium alloy (Al Mg Si) and the result revealed that in addition to dependence of hardness values of the produced samples on cooling media, samples produced from air cooled dies have the best mechanical properties whereas those produced by sand casting have comparable hardness values but lower tensile strength [11]. The effects of particle size and volume fractions of Al2O3 on the thermal conductivities properties of α Al2O3 particulate reinforced aluminium composites (Al/ Al2O3 MMC) were investigated and the citations revealed that the thermal conductivities of the composites are higher with an Al2O3 particle size of 15 μm than with a particle size of 30 μm [12]. In this present work, aluminium can/eggshell particle composites have been produced. Effects of %weight of the eggshell particle addition to the aluminium cans on physical and mechanical properties of the produced metal matrix composites have been investigated. This research work was aimed at providing solution to problems of poor management of discarded aluminium cans and eggshells within Nigeria. Materials and Methods Materials Waste aluminium cans were obtained from the Waste Management Centre of University of Lagos and eggshells were collected from Fast Food Centre, Jaja Hall of University of Lagos. Processing of Eggshells 10 kg eggshells were rinsed in water to remove the membrane and dried in the sun for 6 hours. The dried eggshells were crushed manually using mortar and pestle (see Figure 2) and finally pulverized using a grinding machine. The eggshell powders obtained were sieved into different mesh sizes using sieves of different sizes: 75, 150, 212, 300 and 600 μm. Eggshell powders retained in each sieve were packed in sample bottles and labelled accordingly. % powder retains in each sieve were calculated (see Table 1) using equation 1. mass retain % Sample retain 100 (1) total mass 215 μm sized eggshell powders of highest % retain in the sieve were used as reinforcement for development of metal matrix aluminium can composites. Morphology of the eggshell particles was examined with the use of scanning electron microscope (SEM): ASPEX The sample was placed in a sample cavity of a standard aluminium plate in a sample stand and scanned in a vacuum at 34.0 kv and beam energy of 63.4%. The scanning electron micrograph (SEMg) of the eggshell was presented in Figure 3. FIG. 2 GRINDING OF EGGSHELLS FIG. 3 SEMG OF THE 215μm EGGSHELL POWDERS TABLE 1 %RETAIN OF EGGSHELL POWDERS IN EACH SIEVE Mesh sizes (μm) %retain

4 Journal of Metallurgical Engineering (ME) Volume 4, journal.org Development of Composites 5 kg aluminium cans were heated in a crucible using an oil fired pit furnace to C. Slag (due to decorative coat on the cans) floating on the melt of the aluminium can was screamed off after which the melt was cast into small diameter balls through atomization process (in accordance with Bello et al, 2014 [13]). Balls were weighed and the percentage mass loss due to slag formation was calculated using equation 2. The elemental analysis of the representative sample of the ball was carried out using Hilger Polyvac Spectrometer, Model E980C. mass of Al cans mass of Al can balls % mass loss= 100 (2) mass of Al cans Balls were divided into 7 different parts each of mass 500 g. The first pack of the balls was reheated to 670±50 0 C and then poured into a metallic mould. The melt was left in the mould until it cooled to room temperature. This gives a control aluminium can sample. Another pack of aluminium balls was heated to C. 10 g of 215 μm eggshell powders (equivalent 2 %) was added to the melt. The composite melt was stirred until temperature had fallen to 670±50 0 C. Then, the composite melt was poured into the mould and then left to cool to the room temperature. The process was repeated with increasing % weight of eggshell powder additions (up to 12 %) to the aluminium can melt. Samples obtained from different batches of productions were labelled for identification purpose (see Figure 4). Masses of the 60 x 10 x 10 mm samples of control and the composites were measured with the aids of a digital Pioneer balance (by Ohaus Corporation, USA), having a maximum capacity and readability of 210 and ± g. The density of each sample was determined using equation 3. mass Density (3) volume Representative samples from each batch of production were machined into standard sizes for mechanical analysis. Standard tensile samples as shown on Figure 5 were subjected to tensile loading at a strain rate of 10 3 s 1 until fractures occurred after necking. The impact energies of the control and the produced composites were measured with the aids of Avery Denison Universal Impact Testing Machine. The notched 60 x 10 x 10 samples of the control and produced composites were subjected to a striking energy of 300 J by a pendulum released from the upper position equivalent to charpy impact test. The impact energy absorbed by each sample is noted and recorded. The hardness values of the produced materials were determined through Vickers approach using square based pyramid indenter. A right pyramid indenter was pressed on the surface of each sample by a load of 30 kgf for dwell time of 15 seconds. The two diagonals of the indentation left on the surface of the material after removal of the load are measured by the machine. The Vickers hardness is automatically measured by the machine by dividing the kgf load by the square mm area of indentation. FIG. 4 ALUMINIUM CAN/EGGSHELL COMPOSITES FIG. 5 TENSILE SAMPLES Results and Discussion The % composition of the aluminium can balls is presented on Table 2. 27

5 TABLE 2 % COMPOSITION OF ALUMINIUM CAN BALLS Element Al Si Fe Cu Mn Mg Ti %comp % Mass Loss The mass loss during re melting of aluminium cans was 1.5 kg, equivalent to 30 % of the original mass (5 kg) of the aluminium cans. The loss was attributable to the formation of slag floating on the surface of the melt of the aluminium cans. The slag was formed from the decorative coatings on the outer surface of the cans. Densities Figure 6 shows the decrease in densities of the control and the aluminium can/eggshell composites as the %weight of eggshell additions increased. This is attributable to lighter weight of eggshell powders than that of aluminium cans. Tensile Properties FIG. 6 VARIATION OF DENSITIES WITH % EGGSHELL POWDER ADDITIONS Figures 7 9 show the variation of tensile properties with %weight of eggshell powder additions. Figure 7 reveals an increase in tensile strength at break from 5 MPa of the cast aluminium can with 0% eggshell powder additions to a maximum of MPa of aluminium can/12% eggshell composites. Figure 8 indicates a minimum value of Young s modulus ( MPa) of the cast of aluminium can with 0%weight of eggshell addition to a maximum of MPa at 12% eggshell powder additions. This is an indication of increase in the strengths or resistances which the aluminium can/eggshell composites offered to the deformation during tensile test. Figure 9 declares a decrease in tensile strain as the % weight of eggshell powder additions to the melt of aluminium can increases. This implies a lower ductility of the aluminium can/eggshell composites than the cast of aluminium can (control). FIG. 7 TENSILE STRESS AT BREAK WITH %WEIGHT OF EGGSHELL POWDERS 28

6 doi: /me FIG. 8 YOUNG S MODULUS OF ELASTICITY WITH %WEIGHT OF EGGSHELL POWDERS FIG. 9 TENSILE STRAIN WITH %WEIGHT OF EGGSHELL POWDERS Impact Energy Figure 10 shows a variation between impact energy absorbed during charpy impact test and %weight of eggshell additions. It revealed a decrease in the energy absorbed by the tested samples as the eggshell powder additions increased. This is an indication of the lower fracture toughness of the produced aluminium/eggshell composites than the cast aluminium can. This agrees perfectly with Figure 9. The decreasing trend revealed both in Figures 9 10 are attributable to brittleness of the eggshell powders. FIG. 10 IMPACT ENERGY WITH % WEIGHT OF EGGSHELL POWDERS FIG. 11 HARDNESS VALUES WITH %WEIGHT OF EGGSHELL POWDERS Hardness Values Figure 11 describes the resistance of tested samples to surface indentation during hardness value measurement through Vickers approach. It revealed an increase in the hardness values as % weight of eggshell powders additions increased. The slope of the curve at 6% weight eggshell powders addition is steeper than others. This implies higher increase in hardness values at 6% weight eggshell powders addition. Figure 11 agrees perfectly with Figures 6 7. The increase in Young s modulus of elasticity, tensile strength at break and hardness values is attributable to formation of dislocation loop. During deformation of the examined samples, eggshell powders impinge/block dislocation movement. This leads to dislocation pile up or loop. The dislocation pile up/loop increases as the number of grain boundaries or % weight of eggshell powders increases. Therefore, for further dislocation movement to occur, higher external pressure must be furnished. This is an indication of increase in strength, rigidity and hardness values. Hence, the aluminium can/eggshell powders produced can be used in a relatively high strength applications where the excessively high ductility and fracture toughness are not a prime consideration. Conclusions From results and discussion of this research work, the following conclusion can be inferred: 1. Lighter engineering materials have been produced from recycled aluminium can and 215 μm sized eggshell powders. 29

7 2. The produced aluminium can/eggshell metal matrix composites can be used in relatively high strength application where excessively high ductility and fracture toughness are not a prerequisite. 3. The tensile strength, modulus of elasticity and hardness increase with higher %weight of eggshell powder additions. 4. The increase in Young s modulus of elasticity is an indication of enhancement in the rigidity of the aluminium can/eggshell composites. 5. The reduction in tensile strain and impact energy absorbed with an increment in % weight of eggshell powder additions is an indication of decrease in ductility and fracture toughness of the aluminium can/eggshell composites. Hence, such a decrease is attributable to brittleness of eggshell powders. 6. Eggshell powders are potential materials for reinforcement. However, it impacts negatively on the ductility and impact toughness of the materials. 7. Discarded aluminium cans are potential matrix materials which can be harnessed into development of useful engineering materials. ACKNOWLEDGMENT Authors wish to appreciate Prof. S. B. Hassan of Department of Metallurgical and Materials Engineering for his assistance in making this work a reality. REFERENCES [1] Deborah DLC. Applied Materials Science Applications of Engineering, Materials in Structural, Electronics, Thermal, and Other Industries, CRC, Boca Raton London New York Washington, D.C [2] William DC. Materials Science and Engineering: An Introduction 7th Ed., Wiley, New York; [3] Dieter GE. Mechanical Metallurgy, McGraw Hill Series in Materials Science and Engineering, S. I Metric Edition, McGraw Hill Book Company (UK) Limited; [4] Labberton MG. Aluminium Packaging Recycling: The Contribution from Romania towards a More Resource Efficient Europe, Proceeding of European Recycling Society Annual Conference (2nd edition) Bucharest, [5] Zacune J. Aluminium. Media Owner, Proprietor and Publisher: Global 2000 Verlagsges. m.b.h., Neustiftgasse 36, 1070 Vienna,