Research Papers - Department of Materials Engineering

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Start date: 1999Has files: Yes

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Now showing 1 - 10 of 17
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    PublicationOpen Access
    Development of Silica-Copper Nanocomposite for Water Purification
    (SLIIT, 2022-02-11) Angappan, S; Karunaratne, M; Thambiliyagodage, C
    Water pollution is one of the serious concerns across the world at the moment. Industrial wastewater significantly contributes to the negative impacts caused by water pollution. Textile industries discharge large amounts of effluents into water streams with little or no treatment of the discharge because wastewater treatment is an expensive process. Thus, there exists a need for a cheap and effective way to treat textile effluent that contains dyes before being discharged. A high purity silica-based Nano-adsorbent was synthesized by using rice husk as the commercially available main cheap precursor. Copper-loaded silica nanoparticles were successfully functionalized with 3-aminopropyl triethoxysilane (APTES) via the sol-gel pathway to enhance the adsorption performance of organic dyes from textile effluent. The performance of produced Nano-adsorbent was evaluated by using methylene blue as waste adsorbate. As synthesized nanomaterial was characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy, the XRD results confirmed the presence of silicon dioxide (SiO2) and paramelaconite (Cu4O3) as predicted. The FTIR confirmed the presence of Si–O stretching, N-H bending, C–H stretching, Cu–O stretching and O–H bending vibrations thereby suggesting the presence of SiO2, NH2 groups, CH2, Cu4O3 and physisorbed H2O. The optimum conditions for pH and adsorbent dosage were successfully evaluated for the adsorption process. The optimum pH at which the nanomaterial performed best was at pH 4. The optimum mass of the adsorbent that gave maximum adsorption performance was 20 mg. Kinetic studies revealed that the experimented data was in better correlation with pseudo-second-order kinetics. The outcome of this project would be of interest to textile industries looking for a cheap and effective way to treat textile wastewater
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    PublicationOpen Access
    Comparative assessment on the extraction of carotenoids from microalgal sources: Astaxanthin from H. pluvialis and β-carotene from D. salina
    (Elsevier, 2019-03-20) Rammuni, M N; Ariyadasa, Thilini U; Nimarshana, P. H. V; Attalage, R. A
    Astaxanthin and β-carotene are important carotenoids used in numerous pharmaceutical and nutraceutical applications, owing to their vigorous antioxidant properties. The microalgal strains Haematococcus pluvialis and Dunaliella salina accumulate the highest quantities of astaxanthin and β-carotene (up to 7% and 13% dry weight respectively) and are therefore considered as sustainable feedstock for the commercial production of carotenoids. Thus, from an economical perspective, it becomes desirable to optimize recovery of carotenoids from microalgal cells. To this end, here, we have summarized the conventional and modern extraction techniques generally used for the recovery of astaxanthin from Haematococcus pluvialis and β-carotene from Dunaliella salina. Furthermore, we have also discussed the optimum process conditions employed for numerous extraction protocols including solvent extraction, ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE) and supercritical fluid extraction (SFE). Overall, our study highlights the sustainability of integrated co-production of biofuels and carotenoids in a biorefinery framework.
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    PublicationOpen Access
    Designing standalone hybrid energy systems minimizing initial investment, life cycle cost and pollutant emission
    (Pergamon, 2013-06-01) Perera, A. T. D; Attalage, R. A; Perera, K. K. C. K; Dassanayake, V. P. C
    HES (hybrid energy system)s are becoming energy systems of choice for standalone applications due to ever increasing fuel costs and global concern on GHG (Green House Gas) emissions. However, it is difficult to justify the higher ICC (Initial Capital Cost) of renewable energy components, especially for rural electrification projects in developing countries. This paper illustrates the modeling and simulation of HESs, and multi-objective optimization carried out in order to support decision-making in such instances. LEC (Levelized Energy Cost), ICC and GHG emission were taken as objective functions in the optimization and the sensitivity of market prices and power supply reliability was further evaluated. Results depict that Pareto front of LEC, ICC and GHG emission can be simplified as a combination of ICC–LEC and LEC–GHG emission Pareto fronts making the decision-making process simpler. Gradual integration of renewable energy sources in a number of design stages is proposed for instances where it is difficult to bear the higher ICC. Finally, importance of planning integration of renewable energy sources at early design stages of the project is highlighted in order to overcome the difficulties that need to be faced when coming up with the optimum design.
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    PublicationOpen Access
    Comparative assessment on the extraction of carotenoids from microalgal sources: Astaxanthin from H. pluvialis and β-carotene from D. salina
    (Elsevier, 2019-03-30) Rammuni, M N; Ariyadasa, Thilini U; Nimarshana, P H V; Attalage, R.A
    Astaxanthin and β-carotene are important carotenoids used in numerous pharmaceutical and nutraceutical applications, owing to their vigorous antioxidant properties. The microalgal strains Haematococcus pluvialis and Dunaliella salina accumulate the highest quantities of astaxanthin and β-carotene (up to 7% and 13% dry weight respectively) and are therefore considered as sustainable feedstock for the commercial production of carotenoids. Thus, from an economical perspective, it becomes desirable to optimize recovery of carotenoids from microalgal cells. To this end, here, we have summarized the conventional and modern extraction techniques generally used for the recovery of astaxanthin from Haematococcus pluvialis and β-carotene from Dunaliella salina. Furthermore, we have also discussed the optimum process conditions employed for numerous extraction protocols including solvent extraction, ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE) and supercritical fluid extraction (SFE). Overall, our study highlights the sustainability of integrated co-production of biofuels and carotenoids in a biorefinery framework.
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    PublicationOpen Access
    Potential of biomass fuel conservation in selected Asian countries
    (Pergamon, 1999-07-01) Bhattacharya, S. C; Attalage, R. A; Leon, M Augustus; Amur, G. Q; Salam, P Abdul; Thanawat, C
    The potential of savings in the biomass consumed for energy in seven Asian countries—China, India, Pakistan, Nepal, Philippines, Sri Lanka and Vietnam—is estimated, if the centuries-old traditional methods of biomass use are reconsidered and an efficient, rational use is implemented. The present pattern and share of biomass consumption of different traditional biomass energy devices are recorded. The efficiency of traditional technologies and that of improved ones—technologies which are practically applicable or already in use somewhere else—are compared and the potential of biomass savings is calculated. The total biomass saving potential in all seven countries together has been estimated at 322 million tons/year
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    PublicationEmbargo
    Designing standalone hybrid energy systems minimizing initial investment, life cycle cost and pollutant emission
    (Pergamon, 2013-06-01) Perera, A. T. D; Attalage, R. A; Perera, K. K. C. K; Dassanayake, V. P. C
    HES (hybrid energy system)s are becoming energy systems of choice for standalone applications due to ever increasing fuel costs and global concern on GHG (Green House Gas) emissions. However, it is difficult to justify the higher ICC (Initial Capital Cost) of renewable energy components, especially for rural electrification projects in developing countries. This paper illustrates the modeling and simulation of HESs, and multi-objective optimization carried out in order to support decision-making in such instances. LEC (Levelized Energy Cost), ICC and GHG emission were taken as objective functions in the optimization and the sensitivity of market prices and power supply reliability was further evaluated. Results depict that Pareto front of LEC, ICC and GHG emission can be simplified as a combination of ICC–LEC and LEC–GHG emission Pareto fronts making the decision-making process simpler. Gradual integration of renewable energy sources in a number of design stages is proposed for instances where it is difficult to bear the higher ICC. Finally, importance of planning integration of renewable energy sources at early design stages of the project is highlighted in order to overcome the difficulties that need to be faced when coming up with the optimum design.
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    PublicationEmbargo
    A hybrid tool to combine multi-objective optimization and multi-criterion decision making in designing standalone hybrid energy systems
    (Elsevier, 2013-07-01) Amarasinghage, T; Perera, D; Attalage, R. A; Perera, K. K. C. K; Dassanayake, Vishwanath P C
    Hybrid energy systems (HESs) are becoming popular for standalone applications due to global concern regarding green house gas (GHG) emissions and depletion of fossil fuel resources. Research in the optimal design of HESs is ongoing, with numerous optimization techniques giving special emphasis to Pareto optimization, incorporating conflicting objectives. The subsequent decision-making process including the non-dominant set of solutions has yet to be addressed. This work focuses on combining multi-objective optimization with a multi-criterion decision making (MCDM) technique to support decision makers in the process of designing HESs. Four different objectives, i.e., levelized energy cost (LEC), unmet load fraction, wasted renewable energy (WRE) and fuel consumption are used to obtain the Pareto front. A decision support tool based on Fuzzy TOPSIS and level diagrams is proposed to analyze the Pareto front and support the subsequent decision-making activity. A case study is used to illustrate the applicability of the proposed method. The study shows that the novel method is useful when determining the relative weights of objectives, providing a detailed picture of the objective space to the designer when coming up with the optimum system. The technique proposed in this study can be further extended to analyze similar problems in energy system design where MCDM is necessary after multi-objective optimization.
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    PublicationEmbargo
    MCrAlY creep behaviour modelling by means of finite-element unit cells and self-consistent constitutive equations
    (SAGE Publications, 2009-01-01) Hermosilla, U; Karunaratne, M. S. A; Jones, I. A; Hyde, T. H; Thomson, R. C
    The MCrAlY bond coats (BCs) used in thermal barrier coatings (TBCs) undergo severe microstructural changes that affect their creep behaviour. One method to take into account the effect of the high-temperature degradation in the creep properties of these alloys is by means of unit cell calculations that reproduce the microstructure present in the alloy. However, this method is not suitable to be included in large-scale calculations and a self-consistent constitutive model, based on Eshelby's inclusion technique, is presented for that purpose, showing good numerical agreement. Results are compared with experimental data obtained for several MCrAlY BCs.
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    PublicationEmbargo
    Diffusion and activation of dopants in silicon and advanced silicon-based materials
    (IOP Publishing, 2006-08-17) Pichler, Peter; Ortiz, Christophe J; Colombeau, Benjamin; Cowern, Nicholas E B; Lampin, Evelyne; Uppal, Suresh; Karunaratne, M. S. A
    A quantitative description of the transient diffusion and activation of boron during post-implantation annealing steps is one of the most challenging tasks in the simulation of silicon doping processes. In industrially relevant situations, simulations needs to address diffusion at extrinsic concentrations, the agglomeration of self-interstitials, and the formation of boron-interstitial clusters. This paper describes the experimental work performed or used to calibrate model parameters as independently as possible. The combined model is then applied to ultra-shallow junction formation by annealing boron implanted into crystalline or preamorphized silicon. In comparison to bulk silicon, much less is known about diffusion of dopants in SiGe and germanium which are considered as technological options for future technology nodes. Therefore, dedicated experiments were performed to clarify open points in the diffusion behaviour of dopants in these materials.
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    PublicationEmbargo
    Effect of fluorine implantation dose on boron transient enhanced diffusion and boron thermal diffusion in Si/sub 1-x/Ge/sub x/
    (IEEE, 2005-03-21) Mubarek, H.A.W.E; Karunaratne, M. S. A; Bonar, J. M; Dilliway, G. D; Wang, Y.; Hemment, P. L. F
    This paper studies how boron transient enhanced diffusion (TED) and boron thermal diffusion in Si/sub 1-x/Ge/sub x/ are influenced by a high-energy fluorine implant at a dose in the range 5 /spl times/ 10/sup 14/ cm/sup -2/ to 1 /spl times/ 10/sup 16/ cm/sup -2/. Secondary ion mass spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine SIMS profiles and transmission electron microscopy (TEM) micrographs to establish the conditions under which boron diffusion is suppressed. The SIMS profiles show that boron thermal diffusion is reduced above a critical F/sup +/ dose of 7 - 9 /spl times/ 10/sup 14/ cm/sup -2/, whereas boron TED is suppressed at all doses. Fitting of the measured boron profiles gives suppressions of boron TED diffusion coefficients by factors of 6.8, 10.6, and 12.9 and of boron thermal diffusion coefficient by factors of 1.9, 2.5, and 3.5 for F/sup +/ implantation doses of 9 /spl times/ 10/sup 14/, 1.4 /spl times/ 10/sup 15/, and 2.3 /spl times/ 10/sup 15/ cm/sup -2/ respectively. The reduction of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the SIMS profile in the vicinity of the boron marker layer, which is attributed to vacancy-fluorine clusters. This reduction of boron thermal diffusion is explained by the effect of the clusters in suppressing the interstitial concentration in the Si/sub 1-x/Ge/sub x/ layer. The suppression of boron TED correlates with a deep fluorine peak around the range of the fluorine implant and TEM micrographs show that this peak is due to a band of dislocation loops. This suppression of boron TED is explained by the retention of interstitials in the dislocation loops, which suppresses their backflow to the surface. The fluorine SIMS profiles show that the fluorine concentration in the Si/sub 1-x/Ge/sub x/ layer increases with increasing germanium concentration and that the fluorine concentration in the Si/sub 1-x/Ge/sub x/ layer after anneal is much higher than after implant. This indicates that fluorine is transported into the Si/sub 1-x/Ge/sub x/ layer from the adjacent silicon, and is explained by the lower formation energy for vacancies in Ge than in Si. This accumulation of fluorine in the Si/sub 1-x/Ge/sub x/ layer during anneal is advantageous for devices like SiGe heterojunction bipolar transistors, where the boron must be kept within the Si/sub 1-x/Ge/sub x/ layer.