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• 1. K.S. Harishanand, H. Nagabhushana, B.M. Nagabhushana, Parimesh Panda, A H Adarsha, M.M. Benal, N Raghavendra, K R Vishnu Mahesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 1, January -February 2013, pp.1569-1576 Corrosion, Mechanical and Wear Properties of nano-ZnO doped AluminiumK.S. Harishanand1, H. Nagabhushana2, B.M. Nagabhushana3, ParimeshPanda 1, A H Adarsha1, M.M. Benal4, N Raghavendra1, K R Vishnu Mahesh5 1 (Department of Mechanical Engineering, R.V. College of Engineering, Bengaluru-560059, India)2(Department of Physics, Tumkur University, Tumkur-572103, India)3(Department of Chemistry, M.S. Ramaiah Institute of Technology, Bengaluru-560054, India) 4 (Department of Mechanical Engineering, Govt. Engineering College, Kushalnagar-571234, India) 5 (Department of Chemistry, ACS College of Engineering, Bengaluru-560074, India)ABSTRACT Zinc Oxide (ZnO) Nano powder was metal components to the effects of media-drivenproduced by Solution Combustion Synthesis corrosion [1-3].(SCS) at 350 10 C temperature using sugarsolution as fuel. The final product was Superior properties of metal oxides such ascharacterized by means of XRD, SEM and EDX. refractoriness, high hardness, high compressiveThe powder blends of ZnO/Al were prepared bystrength, wear resistance etc. make them suitable forlow energy ball milling and the composite blocksbeing used as reinforcement material in metalof ZnO/Al were fabricated by powder metallurgymatrix. Incorporating ultra-fine particles of metal-technique. The microhardness, wear resistance oxides significantly improves mechanical propertiesand corrosion resistance of ZnO/Al blocks wereof the metal matrix by reducing the inter-particlestudied.The resultsshow that thespacing and providing their inherent properties tomicrohardness, wear resistance and corrosionthe metal matrix since they get embedded uniformlyresistance can be improved significantly with into it. However, fine particles show higheraddition of ZnO nano powder up to 1 wt%; at tendency towards agglomeration. Therefore,the same time, the optimal microhardness andoptimum particle size, amount of reinforcement andmicrostructure were obtained when the massprocessing parameters (compaction pressure,fraction of ZnO nano powder is 1wt% where assintering temperature, sintering time) should besample with 5 wt% of ZnO nano powder show determined for each technique and matrix. Nano-best wear resistance. Corrosion tests reveal that particles represent appropriate wettability with metalthere was a slight mass loss due to corrosion.at the time of sintering and good stability as well[4-8].Keywords ZnO, Microhardness, Wearresistance, Corrosion resistance and Microstructure. ZnO metal oxide plays a very importantrole in many areas of chemistry, physics, and1. INTRODUCTION material science. In technological applications, ZnOAluminium and its alloys are widely usedis used in the fabrication of microelectronic circuits,in services such as transportation, armory andsensors, piezoelectric devices, fuel cells, coatingsmarine industries due to their high strength to for the passivation of surfaces against corrosion.weight ratio. They relatively resist corrosion when The nanometric field is governed by numerousexposed to various aggressive environments. These surface phenomena (photosynthesis, catalysis,environments may include water vapour, acid and precipitation, reactivity, deformation, reflectivity,base solutions. Most of these environments degradeluminosity). This is so because in nanomaterials thethe quality of Aluminium and its alloys and affects number of atoms which are localized on freethe mechanical properties of the system thereby surfaces as well as on internal interfaces may bereducing their life-span. This makes them unstableequal or higher than the number of atoms localizedin certain environment that enhances their chemical inside the grains. On this account, the properties arecombination with other elements in the environmentstrongly influenced by the interfaces presentto form stable compounds. On the return to their(surfaces, grain boundaries) [9-13].natural stable form of ground state known as ores anaccompanying reduction in the free energy of the Among the functional mineral compoundssystem occurs. These structural defects could be asuch as Perovskite (CaTiO3), Rutile (TiO2), CaF2 ,major determinant in the degree of resistance ofSpinel (MgAl2O4), Wurtzite (ZnS) and Zincite(ZnO), the last one being unique because of its dual1569 | P a g e

2. K.S. Harishanand, H. Nagabhushana, B.M. Nagabhushana, Parimesh Panda, A H Adarsha, M.M. Benal, N Raghavendra, K R Vishnu Mahesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 1, January -February 2013, pp.1569-1576semiconducting and piezoelectric properties. Due to attention in various applications, hence in thisthe combination of interesting piezoelectric, electric, work, the nano-ZnO/Al powder blends were used tooptical and thermal properties, ZnO-doped prepare ZnO/Al blocks by cold pressing followed bynanomaterials are of highinterestforsintering and the performance of the fabricatedmultifunctional applications in gas sensors,blocks were studied for hardness, wear resistanceultrasonic oscillators or transparent electrodes in and corrosion resistance.solar cells [14-18].2. EXPERIMENTALNanostructured ZnO is a material that may 2.1. Synthesis of ZnO powderpresent various structures, whose configurations areThe ZnO powder was prepared bymuch richer than for any known nanomaterial dissolving Zinc Nitrate (Zn(NO3)2.6H2O) and sugarincludingcarbonnanotubes.The n-type solution in a minimum quantity of double distilledconductivity of ZnO is relatively easy to be obtained water in a Pyrex dish. The dish containing theby using Zn in excess or by doping ZnO with Al, solution was introduced into a pre-heated muffleGa, In. The most promising dopants for obtaining p- furnace maintained at 350 10C. The solutiontype conductivity are the elements from the Vth initially boils and undergoes dehydration followedgroup. Different routes to obtain doped ZnO thatby decomposition with the evolution of largehave been studied yet are : the incorporation ofamount of gases. At the point of spontaneoustransition metal ions into a semiconductor photocombustion, the solution begins burning andcatalyst by ion implantation or by co-precipitation;releases lot of heat. All the solution vaporizesintroduction of oxygen vacancies by treating a photoinstantly and becomes a burning solid. The entirecatalyst with hydrogen plasma or X-ray irradiation; combustion process for producing ZnO powdercoupling semiconductors (ZnO or TiO2) with oxides takes only 5 min. The formation of ZnO nanoor sulfides that enable visible light absorption (WO3,powder by combustion synthesis can be representedFe2O3, CdS) by co-precipitation or impregnation;by following reaction:doping of N-atoms into the substitution sites in theZn(NO3)2 + C2H6N4O2 ZnO + 3N2 + 2CO + 3H2Ocrystal structure of a photo catalyst. In the science.. (1)and technology of ZnO, several key issues that haveto be achieved includes controlling the morphology2.2. Preparation of ZnO/Al powder blends andand chemical composition of the ZnO powders,ZnO/Al blockscontrolling the purity and particle size during theZnO nano powder produced by Solutionsynthesis process of ZnO powders, controlling the Combustion Synthesis(SCS) was added to 99.5%amount of the dopants. ZnO powders with different pure commercially available Aluminium powdermorphology (prismatic, ellipsoidal, bi-pyramidal, with wt% of ZnO nano powder varying from 0 todumbbell-like, nanowire, nanorod) have been 5% with an increment of 0.25, 0.5, 1, 2.5 and 5obtained till date [18-23]. wt%. They were mixed for 30 minutes by handmixing and loaded in metal die for compaction. The Different physical or chemical synthetic powder metallurgy technique was used to fabricateapproaches have been developed to produce nano- the ZnO doped Al blocks. Powder blends were coldsized ZnOparticlesincluding thermal pressed at 200 MPa to approximately 90 %decomposition, thermolysis, chemical vaporcompression and then sintered at 500 C for 1 hour.deposition, solgel, spray pyrolysis, precipitation The sintered ZnO/Al blocks were polished with finevapor phase oxidation, thermal vapor transport, emery papers with grit size ranging from 200 tocondensation and hydrothermal. Generally, these 2000 followed by diamond paste polishing to obtainpreparation methods involve complex procedures, mirror finish surface on the specimen blocks.sophisticated equipment and rigorous experimentalconditions. Most of these techniques require high 2.3. XRD, Surface Morphology, EDX andtemperatures and long processing time. Indeed,Microstructures of ZnO and ZnO/Al blocksthere is great demand for economically viableX-ray Diffractometer (XRD: Shimandzusynthesis techniques.SolutionCombustion 700 S, Japan), Scanning Electron MicroscopySynthesis (SCS) is emerging as a promising(SEM: JEOL, Japan, JSM 840A) were employed totechnique for the preparation of nanopowder. This analyze the powder and morphology of the ZnOprocess is simple, fast, economic and does notpowder and polished surfaces of ZnO/Al blocks.require high temperature furnaces and complicated The grain size and microstructure were studied bylab set-ups. It can be used for the preparation of allusing optical microscope.kinds of oxides [23-28].2.4. Micro-hardness test From the open literature [1-28], the ZnO Micro hardness was tested using Vickersbased Aluminium composites attracted much Micro-hardness tester with diamond indenter in the 1570 | P a g e 3. K.S. Harishanand, H. Nagabhushana, B.M. Nagabhushana, Parimesh Panda, A H Adarsha, M.M. Benal, N Raghavendra, K R Vishnu Mahesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 1, January -February 2013, pp.1569-1576form of right pyramid and a square base. An opticalmicroscope with up to 400X magnification alongwith a Micrometer attachment in the eye piece wasused to observe and measure the length of thediagonal of indentation. Microscope attachmenthelps in determining the distribution of ZnO nanopowder dopant in the Al matrix doped with varyingpercentages ranging from 0 to 5%.2.5. Wear resistance test Pin on disc apparatus was used to measurethe wear resistance of the samples. ZnO/Al samplesof size 101020 mm3 were fabricated and mountedon Pin on disk apparatus and made to rub against therotating stainless steel disk. Area exposed to wearwas 1010 mm2. Relative velocity of wear testFigure.1 XRD Pattern of ZnO nano powdersample with respect to the rotating disk was 2.6 ms-1and sliding distance was 1.57 km. Mass loss due to 3.2. Morphological study using SEM andwear was calculated for each sample afterElemental composition using EDXcompletion of wear test. From the SEM analysis as shown in the Fig.2a, Fig.2b, Fig.2c, Fig.2d, Fig.2e, Fig.2f, it is2.6. Corrosion resistance test observed that the circular shaped primary particles Two separate tests were performed toare agglomerated with varying sizes with aluminumevaluate the corrosion resistance of the ZnO/Alpowder. Here, the particle size was greatlyblocks.dependent on the calcination temperature. As2.6.1. The specimens were soaked in the spray tank calcination temperature increases the size alsowith 3.5% NaCl solution for 50 hr and then wereincreases, due to congregation effect, which isrinsed, dried and weighed. The corrosion resistancereflected in surface area and XRD measurements.was evaluated by mass loss per area, m/S (m is From the EDX Spectrum, it is clearlythe mass loss and S is the surface area).observed that no or relatively a small peak at 0.5 wt2.6.2. The specimens were soaked in the spray tank % ZnO doped aluminum composites sample andwith 0.5 mol MgSO4 solution for 10 hr and then remarkably high peaks of ZnO presence at 5 wt %were rinsed, dried and weighed.ZnO doped Aluminium composites sample is a clear indication shown in Fig.3a and Fig.3b.The3. RESULTS AND DISCUSSIONS spectrum reveals only the presence of Aluminium3. 1 X-Ray Diffractometer (XRD) Studiesand ZnO elements and the absence of other elementsThe crystallinity and purity of the prepared as the spectrum exhibits the peaks for aluminum andproduct has been confirmed by powder X-ray ZnO only. Therefore, it can be stated that thediffraction. Fig.1 shows PXRD of ZnO physical and mechanical parameters can benanoparticles which shows a well defined peaks attributed to the presence of above said twolocated at Bragg angles (2) = 30, 33, 35 elements in the composition.corresponding to planes having Miller Indices (100),(002), (101) respectively. The characteristic peaksare higher in intensity which indicates that theproducts are of good crystalline nature. No peakscorresponding to impurities are detected, showingthat the final product is purely ZnO. It is observedthat intensity of the peaks increases with thermaltreatment due to agglomeration, which means thatthe crystallinity has been improved. The full widthat half maxima of major peaks decreases andconfirms the grain size growth [29]. Figure.2a SEM Micrograph of Bare Aluminium 1571 | P a g e 4. K.S. Harishanand, H. Nagabhushana, B.M. Nagabhushana, Parimesh Panda, A H Adarsha,M.M. Benal, N Raghavendra, K R Vishnu Mahesh / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1569-1576Figure.2b SEM Micrograph of 0.25% ZnO dopedFigure.2f SEM Micrograph of 5% ZnO doped AlAlFigure.2c SEM Micrograph of 0.5%ZnO doped Al Figure.3a EDX of 0.25% doped ZnO/Al compositeFigure.2d SEM Micrograph of 1% ZnO doped Al Figure.3b EDX of 5% doped ZnO/Al composite 3.3. Micro-hardness or Vickers hardness testHardness of a material is defined as the resistance to deformation, particularly permanent deformation, indentation or scratching. Vickers hardness value increased by 3.3, 9.09, 21.05, 18.91 and 9.09 % with the addition of 0.25, 0.5, 1, 2.5 and 5 wt% ZnO nano powder respectively in AluminiumFigure.2e SEM Micrograph of 5% ZnO doped Almatrix.Micro hardness of nano-ZnO doped Aluminium blocks increased with increase in 1572 | P a g e 5. K.S. Harishanand, H. Nagabhushana, B.M. Nagabhushana, Parimesh Panda, A H Adarsha, M.M. Benal, N Raghavendra, K R Vishnu Mahesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 1, January -February 2013, pp.1569-1576percentage of ZnO up to 1 wt% and further nosignificant increase is observed. The microhardnessgraph shown in Figure4 clearly indicates a slowgrowth in hardness at lower wt% of nano-ZnO. Aremarkable and substantial increment in hardness isobserved at 1 wt% nano-ZnO concentration due touniform distribution of nano-ZnO in the substrate.With further addition of nano-ZnO, adecline in the hardness is observed which could beattributed to an uneven distribution of the nano-ZnOparticles and their tendency to agglomerate atFigure.5a Microstructure of 0.5% doped ZnO/Alconcentrations higher than 1 wt% of nano-ZnO. compositeThis means superior interfacial bond strength andrelated high value of hardness can be achieved at1 wt% of nano-ZnO as the optimal value.Figure.5b Microstructure of 1% doped ZnO/AlcompositeFigure.4 Variation of Wear Resistance withaddition of nano-ZnO3.4. Micro structure and Morphology analysis ofsintered ZnO/Al blocksThe micro structure at different dopingconcentrations is shown in Fig.5a, Fig.5b, Fig.5c,Fig.5d. ZnO particles can be seen well embedded inthe grains of Aluminium matrix shown as a result ofwhich the structure becomes closer and grainscompact. ZnO nano particles are uniformly Figure.5c Microstructure of 2.5% doped ZnO/Aldistributed in Al matrix in case of lower wt% ofcompositeZnO powder up to 1 wt% and agglomeration of ZnOcannot be seen in major part of the Al matrix asshown. This reveals that the sample has uniformstructure and steady performance at dopingpercentages less than 1%. At higher dopingpercentages (2.5% and 5%), agglomeration of ZnOis more common in the aluminium matrix and theZnO particles are not evenly distributed as shown.This uneven distribution and agglomeration of ZnOin the Al matrix leads to density variations from oneregion of the matrix to another. The presence ofnano particles in the grain boundaries was the causeFigure.5d Microstructure of 5% doped ZnO/Alfor suppression of non-coulombic loss of the grains compositeand hence self-corrosion.3.5. Wear resistance test The evaluation of wear resistance of theZnO doped Aluminium samples are carried out onthe basis of mass loss method and the results are 1573 | P a g e 6. K.S. Harishanand, H. Nagabhushana, B.M. Nagabhushana, Parimesh Panda, A H Adarsha,M.M. Benal, N Raghavendra, K R Vishnu Mahesh / International Journal of EngineeringResearch and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1569-1576 placed in Table1 and the corresponding graph ischemical baths; one containing NaCl and other with displayed in Fig.6. An incremental order was MgSO4 standard solutions. The samples were tested observed in reduction of wear loss from lower to for 50 hours in NaCl solution and 10 hours in higher wt % of nano-ZnO. However a relative steepMgSO4 solution. In both the conditions the drop from 6.0589 % wear loss at pure aluminum to corrosive properties of the nano-ZnO doped 1.590 % wear loss at 1 wt% dopant is the maximum Aluminium have been shown in Table2, Table3 and percentage reduction in wear loss. A further corresponding graphs are displayed in Fig.7, Fig.8. increase in nano-ZnO wt % has shown only a In NaCl solution, the pure Aluminium is having marginal reduction in wear value 1.590 % wear loss 1.0380 % of corrosion and by doping only 0.25 % at 1 wt % to 1.300 % wear loss at 5 wt % nano-ZnO, the corrosion has scale down to 0.3488 %. At 0.5 wt which doesnt indicate much reduction in the wear% dopant corrosion drops to 0.2211% and 5% value. This increase in wear resistance can be dopant the corrosion drops to 0.00127%. A sharp attributed to addition of ultra-fine ceramic drop in corrosion value is observed by adding only a reinforcement which possess high hardness, wearsmall wt % of nano-ZnO to Aluminium substrate. resistance and at the same time a strong interfacial bonding with the host matrix. This may be due to formation of an oxide Table 1. Weight loss in samples after wear layer due to quick reaction. Further drop incorrosion is almost proportion scale that can be as itWt% of0% 0.25 % 0.5 %1%5% is seen 0.2211 % corrosion value at 0.5% dopant toZnO doped 0.00127 % of corrosion at 5% dopant can beAl Blocks tabulated as the corrosion resistance increases 10Initial 4.9365 5.8713 4.4251 4.88525.3963 times by increasing the dopant 10 times.Weight(gm) In MgSO4, the corrosion resistanceFinal 4.6374 5.6608 4.2872 4.80715.3261 property of the nano-ZnO doped AluminiumWeightincreased at and above 0.5 wt% nano-ZnO dopant.(gm)Further the corrosion resistance property of theWeight Loss 0.2991 0.2105 0.1379 0.07810.0702 sample indicated the same trend as in the case of(gm)NaCl solution. It can be inferred from the result thata minimum of 0.5 wt% of nano-ZnO dopant isWear6.0589 3.5852 3.1163 1.59871.3008 sufficient for the corrosion resistance when theResistanceenvironment contains MgSO4.in % weightlossTable 2. After corrosion of 50 hours with 3.5%NaCl solutionWt% of CorrosionZnO Initial Final Weight Resistancedoped weightweightloss (% weightAl(gm)(gm)(gm) loss)blocks0 23.7861 23.5392 0.2469 1.03800.2524.9387 24.8517 0.0870 0.34880.5 23.6523 23.6000 0.0523 0.22111.0 23.9736 23.9725 0.0011 0.00452.5 24.4241 24.4012 0.0229 0.0937 Figure.6 Variation of Wear Resistance with addition of nano-ZnO5 23.5856 23.5853 0.0003 0.0012 3.6. Corrosion resistance test The corrosion test on the nano-ZnO doped Aluminium specimens were conducted in two 1574 | P a g e 7. K.S. Harishanand, H. Nagabhushana, B.M. Nagabhushana, Parimesh Panda, A H Adarsha, M.M. Benal, N Raghavendra, K R Vishnu Mahesh / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 1, January -February 2013, pp.1569-1576nano powder was found to be 1wt% with regard touniform distribution of the reinforcement andhighest micro hardness value for 1 wt % ZnO nanopowder. Increasing trend in wear resistance ofsamples with increase in wt% of ZnO nano powdershows that ceramic particles as nano-reinforcementcan impart superior wear resistance to the hostaluminium matrix. Metal oxide nano particles arevery efficient in imparting their inherent propertiesto the host matrix like high hardness and strengthsince they have high surface area to volume ratio. Figure.7 Variation of Corrosion Resistance with addition of nano-ZnO after corrosion of 40 hours REFERENCES with 3.5% NaCl solutionJournal Papers:1.I. O Owate and E. Chukwuocha, Scientific Table 3 After corrosion of 10 hours with 0.5MResearch and Essay. 3 (2007) 074-080. MgSO4 solution 2.A. I. Ogbonna, S. N. Asoegwu and P. C.Wt% ofWeightCorrosion Okebanama. Journal of Corrosion Science InitialFinal and Technology. 1 (2004) 135-146.ZnO loss in Resistance weight weight3.A. I. 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