Browsing by Author "Jayasuriya, K.D."

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A Home Made Double Slab Pyranometer for Irradiance Measurements
(Proceedings of the 44th Technical Session of the Sri Lanka Association for the Advancement of Science (SLAAS), 1988) Punyasena, M.A.; Jayasuriya, K.D.
A Mössbauer effect study of barium ferrite ball-milled in air
(Hyperfine Interactions, 1994) Jayasuriya, K.D.; Kaczmarek, W.A.; Wu, E.; Campbell, S.J.
The effects of dry-milling BaFe12O19 in air for periods of 190, 360, 590, 690 and 1000 h have been investigated by X-ray diffraction and M�ssbauer effect measurements. The sizes of the BaFe12O19 particles decrease on milling, as expected, although a partial decomposition of BaFe12O19 to ?-Fe2O3 is found to take place on extended milling (1000 h). The room temperature M�ssbauer spectra are consistent with superparamagnetic relaxation associated with the fine BaFe12O19 and ?-Fe2O3 particles. The X-ray diffraction patterns of all the milled samples exhibit features indicative of a disordered structural state, consistent with the nanoscale particles and a nanostructured state.
A Mössbauer study of ball-milled Co?Fe?Si?B: I: dry milling
(Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1993) Jayasuriya, K.D.; Campbell, S.J.; Calka, A.; Jing, J.
X-ray diffraction and M�ssbauer effect measurements of ball-milled Co?Fe?Si?B material which had first been re-crystallized from amorphous melt-spun ribbon are presented. Fully amorphous powders have been obtained after only 50 h milling with a ball-to-powder ratio of BPR ? 84. The amorphous powders exhibit chemical and structural inhomogeneities compared with the starting melt-spun amorphous ribbons.
A Mössbauer study of ball-milled Co?Fe?Si?B: II: with surfactants
(Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1993) Jayasuriya, K.D.; Campbell, S.J.; Calka, A.; Jing, J.
The use of a range of organic surface active substances in the ball milling of Co?Fe?Si?B has been studied by X-ray diffraction and M�ssbauer effect measurements. Effects characteristic of superparamagnetic relaxation of the magnetic moments are observed in the M�ssbauer spectra of samples milled with either an anionic or a cationic surfactant. This behaviour is linked with the decreased particle size and high shape homogeneity of surfactant-aided milled samples compared with the amorphous powders resulting from standard dry milling. Impurity iron-oxide phases are also found to occur in samples milled in the presence of surfactants.
A Mössbauer study of the oxidation state of Fe in silicate melts
(American Mineralogist, 2004) Jayasuriya, K.D.; O-Neill, H.S.C.; Berry, A.J.; Campbell, S.J.
Fe3+/?Fe ratios were determined from M�ssbauer spectra recorded for a series of 17 anorthite-diopside eutectic glasses containing 1 wt% 57Fe2O3 quenched from melts equilibrated over a range of oxygen fugacities from fO2~ 105 bars (Fe3+/?Fe = 1) to 10?13 bars (Fe3+/?Fe = 0) at 1682 K. Fe3+/Fe2+ was found to be proportional to fO2 to the power of 0.245 � 0.004, in excellent agreement with the theoretical value of 0.25 expected from the stoichiometry of the reaction Fe2+O + 0.25 O2 = Fe3+O1.5. The uncertainty in the Fe3+/?Fe ratios determined by M�ssbauer spectroscopy was estimated as � 0.01 (1?) from the fit of the data to the theoretical expression, which is significantly less than that quoted for previous measurements on silicate glasses; this results from fitting the spectra of a large number of systematically varying samples, which allows many of the ambiguities associated with the fitting procedure to be minimized. Fe3+/?Fe ratios were then determined for samples of the anorthite-diopside eutectic composition equilibrated at selected values of fO2, to which up to 30 wt% Fe2O3 had been added. Fe3+/?Fe was found to vary with ?Fe (or FeOT), but both the 1 wt% and high FeOT data could be satisfactorily fit assuming the ideal stoichiometry (i.e., Fe3+/Fe2+ ?fO2 1/4) by the inclusion of a Margules term describing Fe2+-Fe3+ interactions. The large negative value of this term indicates a tendency toward the formation of Fe2+-Fe3+ complexes in the melt. The resulting expression, using the ideal exponent of 0.25, gave a fit to 289 Fe3+/?Fe values, compiled from various literature sources, of similar quality as previous empirical models which found an exponent of ~0.20. Although the empirical models reproduce Fe3+/?Fe values of glasses with high FeOT reasonably well, they describe the data for 1 wt% FeOT poorly. The non-ideal values of the exponent describing the dependence of Fe3+/?Fe on fO2 at high FeOT are an artifact of models that did not include a term explicitly to describe the Fe2+-Fe3+ interactions. An alternative model in which Fe in the silicate melt is described in terms of three species, Fe2+O, Fe3+O1.5, and the non-integral valence species Fe2.6+O1.3, was also tested with promising results. However, at present there is no model that fits the data within the assessed accuracy of the experimental measurements.
A specific heat study of natural haematite around the Morin transition and the effects of entrapped water
(Journal of Physics and Chemistry of Solids, 1985) Jayasuriya, K.D.; Stewart, A.M.; Campbell, S.J.
The Morintransition in samples of natural haemitite has been examined by specificheat and M�ssbauer measurements. Specificheat measurements on as-received samples reveal an anomaly at ? 273.2 K and irregular behaviour at higher temperatures. However, heat treatment of samples demonstrated that these effects were due to water trapped inside the natural specimens. No anomaly due to the Morintransition was observed in the specificheat although the expected changes in the M�ssbauer hyperfine parameters were observed for the different magnetic phases below and above the Morintransition. The results are consistent with a coexistence of the two phases and a spread of temperatures ? 40 K over which the transitions take place throughout the material of purity 99.6 wt%.
A Study of CuInS2 Thin Films for Photovoltaic Applications
(Proceedings of the Technical Session of Institute of Physics, 1999) Wijesundera, R.P.; Nadesalingam, M.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.; Jayanetti, J.K.D.S.; de Silva, K.T.L.
Thin films of copper indium disulphide (CuInS2) on Ti Substrate were prepared by annealing potentiastatically electrodeposited Cu-In alloy in H2S gas at 5500 C. Films were characteristised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectral response in a polysulphide electrolyte. XRD measurements revealed the formation of the polysrystaline CuInS2 thin films and the abscence of any other phases. SEM showed the formation of crystallites having the size about 0.2 ?m. Variations of spectral response, open-circuit voltage (Voc) and short circuit current (Isc) with annealing in air have been studied. As deposited CuInS2 films exhibit a direct band gap of 1.5 eV, and shows n-type behaviour when used in a Photoelectrochemical (PEC) cell. Heat treatment shows a considerable enhancement of the photoresponse.
An experimental determination of the effect of pressure on the Fe3+/?Fe ratio of an anhydrous silicate melt to 3.0 GPa
(American Mineralogist, 2006) Jayasuriya, K.D.; O-Neill, H.S.C.; Berry, A.J.; McCammon, C.C.; Campbell, S.J.; Foran, G.
The effect of pressure on the Fe3+/?Fe ratio of an anhydrous andesitic melt was determined from 0.4 to 3.0 GPa at 1400 �C with oxygen fugacity controlled internally by the Ru + RuO2 buffer. Values of Fe3+/?Fe were determined by M�ssbauer spectroscopy on quenched glasses with a precision of �0.01, one standard deviation. This precision was verified independently by XANES spectroscopy of the same samples. The XANES spectra show a systematic increase in energy and decrease in intensity of the 1s ? 3d transition with increasing pressure. The results to 2.0 GPa are in good agreement with predictions from density and compressibility measurements fitted to a Murnaghan equation of state, but the datum at 3.0 GPa has higher Fe3+/?Fe than predicted from the trend established by the lower-pressure data. This might be due to a coordination change in Fe3+ at high pressure; although there is no evidence for this in the M�ssbauer spectra, such a change could account for the change in intensity of the 1s ? 3d transition in the XANES spectra with pressure.
Biodegradable Plantain Pith for Galvanic Cells
(2012) Jayashantha, N.; Jayasuriya, K.D.; Wijesundera, R.P.
A number of locally available tubers/yams were studied as an electrolytic material for low cost environment friendly Galvanic cell. The cell was fabricated by sandwiching tissues made out of different types of tubers/yams slices between parallel Zn and Cu plates. A preliminary study revealed that cells made with plantain pith show comparatively better performance among the tested electrolytic materials. The performance of the cell was investigated by varying the separation between the electrodes and also by performing various treatments to the electrolytic material such as boiling and chopping after boiling. Best battery performance was obtained for chopped plantain pith after boiling. Stability of the battery fabricated with chopped plantain pith after boiling was tested by measuring the light intensity of a normal white LED with time. Results revealed that it is possible to light up LEDs for more than 500 hours provided the electrolyte is prevented from drying.
Computational Study of I-V characteristics of ITO/Cu2 O/Metal junctions, Technical Session of Institute of Physics
(Processing of the Technical Session of Institute of Physics, 1999) Wijesinghe, W.M.P.L.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.
A theoretical model for current-voltage (I-V) characteristics of back-to-back diode systems was developed using the ideal diode equation. A computer model was developed using the language C++ to fit the experimental data to the theoretical equation and to determine the ideality factors and reverse saturation currents of each diode. This model was tested with commercial back-to-back diode systems. The values obtained for the above parameters from the theoretical fits were in very good agreement with the standard values. The experimental I-V characteristics data obtained for fabricated ITO/Cu2O/Metal (Au, Ag and Hg) structures were fitted to the model and values for the relevent parameters were obtained. These values indicate that the fabricated systems are back to back diodes except the ITO//Cu2O/Hg structure. Using this model, a good understanding of I-V characteristics of metal-semiconductor-metal diodes can be gained and thereby the quality of junction devices can be tested.
Computational Study of I-V characteristics of ITO/Cu2/Metal junctions
(1999) Wijesinghe, W.M.P.L.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.
A theoretical model for current-voltage (I-V) characteristics of back-to-back diode systems was developed using the ideal diode equation. A computer model was developed using the language C++ to fit the experimental data to the theoretical equation and to determine the ideality factors and reverse saturation currents of each diode. This model was tested with commercial back-to-back diode systems. The values obtained for the above parameters from the theoretical fits were in very good agreement with the standard values. The experimental I-V characteristics data obtained for fabricated ITO/Cu2O/Metal (Au, Ag and Hg) structures were fitted to the model and values for the relevent parameters were obtained. These values indicate that the fabricated systems are back to back diodes except the ITO//Cu2O/Hg structure. Using this model, a good understanding of I-V characteristics of metal-semiconductor-metal diodes can be gained and thereby the quality of junction devices can be tested.
Construction of a Near Ideal Nanoammeter
(1998) Wijesundera, R.P.; Kalingamudali, S.R.D.; Jayasuriya, K.D.
A near ideal ac/dc nanoammeter was constructed using two operational amplifiers (op-amp) and a voltmeter. Small currents were converted into a voltage by the first op-amp and this was amplified into a larger voltage by the second op-amp. The amplified voltage was measuredby the voltmeter. The constructed meter has 10 and 100 nA ranges for the dc current measurements and 100 nA range for the ac current measurements.All the ranges were calibrated using a digital picoammeter. As compared to commercially available nanoammeters with similar features this meter has higher advantages such as almost zero internal resistance and negligible operating bias current. The construction cost of the meter is very low compared to a commercial ac/dc nanoammeter.
Design and Implementation of a Web-Based Faculty Information System
(University of Kelaniya, 2006) Kumara, K.H.; Munasinghe, L.; Jayasuriya, K.D.; Dias, N.G.J.; de Silva, C.H.; Kalingamudali, S.R.D.
Although Information Systems (IS) are valuable elements for organizations, the private and public sectors in Sri Lanka are reluctant to use IS for decision making, organizing and classifying data, processing transactions, and for many other activities. This is caused by the lack of computer literacy and conventional attitudes of the majority of the Sri Lankan community. Even in the higher education institutions in Sri Lanka, majority of both staff and students who are well aware of information technology, rely on conventional ways of handling information. One major reason for the above issue is lack of availability of application software well suited for their needs. On one hand, such types of software are rarely used by institutes because of their high cost; on the other hand, they are highly organization dependent. Hence steps have been taken to build a Faculty Information System (FIS) for the Faculty of Science, University of Kelaniya. The FIS was developed in a network environment, with the active participation of all those involved by means of continuous dialogues with the aim of both promoting and demonstrating its benefits and by catering to the different needs arising from the faculty community. The FIS consists of three major subsystems, namely FIS Web Based Subsystem (FISW), FIS Intranet Sub System (FISI) and FIS Examination Sub System (FISE). FISW provides www access to FIS users at any time from anywhere. FISI enables the capability of access to FIS via the Faculty office local area network with security restrictions. FISE processes the examination data in a highly secured environment which is separated from both FISW and FISI. FISI and FISW eventually connect with FISE under security restrictions as required. It is clear that development of this type of tool has social, cultural and technological dimensions. What we planned is one thing, what happened in reality and how the stake holders respond to the tool is another. An evidence of the neediness of this type of tool to the faculty is the number of accesses, 41784, in two years. The above figure is not a complete measure of acceptance of FIS. To detect its defects and limitations, in addition it is necessary to take into account the number of pages requested by each registered user in the FIS. These statistics can be used to enhance the features of FIS.
Design of an Inexpensive Digital Watt-hour Meter
(2003) Chandana, A.W.S.; Wijesundera, R.P.; Jayasuriya, K.D.; Kalingamudali, S.R.D.
An inexpensive digital watt-hour meter has been designed and tested using MCap 7 simulation package since commercially available digital watt-hour meters are very expensive. One of the major usages of watt-hour meters is to measure the power consumption of electricity consumers for billing purposes. Although digital watt-hour meters are commercially available,all electrical power supply companies through out the world including well-developed countries like the United States ofAmerica and the United Kingdom use analogue watt-hour meters to measure the power consumption. This is probably due the expensiveness ofdigital watt-hour meters. The designed digital watt-hour meter consists with analogue multiplier, analogue to digital converters, adder, registers, digital clocks, dividers, accumulators and digital displaying unit. Basically the current and voltage will be multiplied by using a four-quadrant analogue multiplier and then converted to digital signals using analogue to digital converters, which is clocked at a frequency significantly higher than mains frequency, to produce instantaneous values. The algebraic average of the output product per second will be the power consumption per second Finally, this will continuously be added and sent to the digital displaying unit to display watt-hour output. One of the major advantageous of the digital walthour meter is that the power consumption cannot be tampered like in analogue watt-hour meters where the power consumption can be very easily disturbed by changing the rotation power ofthe rotating disk.
Electrical batteries from plantain pith
(University of Kelaniya, 2011) Jayashantha, N.; Wijesundera, R.P.; Jayasuriya, K.D.
An electrical battery is an electrochemical cell that converts stored chemical energy into electrical energy. Commercially available batteries contain heavy metals such as mercury, lead, cadmium, and nickel, which contaminate the environment when batteries are improperly disposed. Also, they are very expensive to be used for long term lighting purposes. Recently, Golberg et al [1] reported a significant performance improvement in a Zn/Cu-potato galvanic cell. The objective of this study is to find a cheap biodegradable material to fabricate an environment-friendly, low cost battery. In this investigation, the performances of vegetative Galvanic cells made from locally available tubers/yams were studied. The cell was fabricated by sandwiching tissues made out of different types of tuber/yam slices between parallel Zn and Cu plates of area 5  9 cm2. Performance of the cell was optimized by changing the separation between the electrodes (different thicknesses of tuber/yam slices). A preliminary study revealed that cells made with plantain pith and habarala petiole show better battery performance. Untreated, boiled, and chopped after boiling states of plantain pith and habarala petiole were further tested in order to enhance the battery performance. Best battery performance was obtained from chopped plantain pith after boiling. Stability of the battery fabricated with chopped plantain pith after boiling was tested by measuring the light intensity of a normal white LED with time. Results revealed that it is possible to light up LEDs for more than 500 hours provided the electrolyte is prevented from drying. Considering the cost and abundance of the material, plantain pith is a very good candidate for the electrolyte medium of the batteries, although the electrical performances of the plantain pith batteries are slightly lower than potato batteries. In conclusion, it is possible to fabricate a battery easily from cheap and environmentally friendly material of plantain pith for low power applications.
Fabrication and Characterisation of CuinS2/ZnSe/Metal Structures for Solar Cell Applications
(2000) Kalingamudali, S.R.D.; Wijesundera, R.P.; Gunatunga, N.P.; Siripala, W.; Jayasuriya, K.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.
Thin film solar cell structure of Ti/CuInS2/ZnSe/Metal was fabricated using simple electrochemical and sulphurisation techniques. Copper lndium Disulphide (CuInS2 thin films were prepared by sulphurisation of Cu-In alloy on Ti substrates. Films were characterised usrng X-ray diffraction (XRD)1 scanning electron microscopy (SEM), spectral response and t-V measurements. XRD measurements snowed the characteristic peaks of CulnSz and SEM showed that the crystallites are of the size 1-3 J.1m. ZnSe thin fitms were deposited on Ti/CuInS2 using electrodeposition technique, TiCuInS2/ZnSe/Metal structures were characterised using C-V, I-V and spectral response measurements. Light and dark I-V measurements revealed the phctovoltaic activity of the structure while the C-V measurements confirmed the formatlon of the heterojunction. Spectral response showed that the photocarriers are generated by the absorption of light in the CuJnS2 tayer.
Fabrication of CUO!CU2O Heterojunction and Its Local Structural Characterization
(2011) Siripala, W.; Wijesundera, R.P.; Perera, L.D.R.D.; Jayasuriya, K.D.
Cuprous oxide (Cu20) thin films on Ti substrate were potentiostatically electrodeposited at -200 mV in an acetate bath. For the growth of p-type cupric oxide (CuO) thin films , CU20 thin film s were annealed at 500 oC (for 30 min in air. In order to fabricate CuO/Cu20 hetorojunction, thin film of Cu20 was potentiostatically electrodeposited on Ti/CuO electrode . Deposits were characterized by using X-ray diffraction (XRD) and scanning electron micrographs (SEM). Results revealed that well covered n-tvpe polycrystall ine Cu20 thin film can be electrodeposied on Ti/CuO electrode at -550 mV VS the SCE in an acetate bath. The CuO/Cu20 heterojunction gave the open circuit voltage (Voc)of 210 mV and short circuit current (Jsc) of 310 uA/cm2. Layer by layer structural properties of the electrodeposited Ti/CuO/Cu20 thin film heterojunction have been studied by means of the XRD and the X-ray absorption spectra (XAS) with different grazing angles of the incident Xray beam. Results reveal that Cu20 and CuO are high quality semiconducting thin films but amorphous structure is formed between CuO and Cu20 while Cu20 deposition on CuO. It can be expected that amorphous structure formed in the middle of the CuO/Cu20 heterojunction attributes better lattice matching between CuO and Cu20 interface .
The faculty of Science of the University of Kelaniya: 1967-2008
(University of Kelaniya, 2009) Jayasuriya, K.D.
Growth and Characterisation of CuInS2 Thin Films
(1999) Wijesundera, R.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.; de Silva, K.T.L.; Jayanetti, J.K.D.S.; Samantilleke, A.P.; Dharmadasa, I.M.
Copper Indium Disulphide thin films were grown by electrodeposition of Cu-ln alloy followed by sulphurisation in H2S gas. It was observed that the ionic concentration of Cu2+/ In3+ in the electrodepositing bath determines the composition of the materials formed after the sulphurisation. CuInS2 thin films having the chalcopyrite crystal structure can be produced using this technique and the films are n-type semiconductors.
I-V and C-V characterization of semiconductor thin flms
(2000) Wijesundera, R.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.
Cuprous oxide (CU20) and ZnSe thin films were potentiostatically electrodeposited on indium-doped tin oxide (ITO) substrates in order to investigate the I-V and C-V characteristics of ITO/n-Cu20/(p-CuxS or metal or electrolyte) and ITO/p-ZnSe/electrolyte systems, An electrochemical cell containing aqueous solutions of 0-1 M sodium acetate and 1.6x10-2 M cupric acetate was used for electro deposition of CU20 thin films on ITO-coated glass substrates. Potentiostatic condition of -250 mV against standard calomel electrodes (SEC) was used for the electro deposition, To convert the top layers of the CU20 to Cu.S by sulphidation, exposed the surface to a spray of aqueous solution of sodium sulphide or to a mixture of hydrogen sulphide and nitrogen gases to foam ITO/n-Cu20/p-CuxS system. For the system ITO/n-Cu2O/metal, metal layer was evaporated on to the n-Cu20 surface. An electrolyte of 0.1 M sodium acetate was used in the ITO/n-Cu20/electrolyte system. Electro deposition of ZnSe thin films were carried out under potentionstatic condition at -550 mV against SCE using aqueous solutions of 0.1 M ZnS04 and 10-5 M Se02 at the temperature of 65� C. The theoretical and experimental 1-V characteristics of ITO/n-Cu2O/(P-CuxS or metal or electrolyte) system suggest that CU20 films made on ITO substrate form Schottky type junctions at the back contact in addition to the CU20/(p-CuxS or metal of electrolyte) junctions. Furthermore, C-V characteristics suggest that the doping concentration of the CU20 layer is in the order of 10 18. Light and dark I-V measurements of doped and undoped lTO/ZnSe in KI electrolyte suggest the p-type photoconductivity in this system and C-V measurements confirmed it.