Browsing by Author "Kumara, L.S.R."

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The 3D atomic scale and electronic structure characterization of novel fcc ruthenium nanoparticles using synchrotron light source
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Kumara, L.S.R.; Sakata, O.; Kohara, S.; Song, C.; Yang, A.; Kusada, K.; Kobayashi, H.; Kitagawa, H.
Ruthenium (Ru) is a 4d transition metal that in the bulk adopts hexagonal closepacked (hcp) structure at all temperature ranges, and novel face-centered cubic (fcc) Ru nanoparticles (NPs) have been observed to be more efficient than conventional hcp Ru NPs larger than 3 nm. It has recently attracted much attention as a potential application in removal of car exhausts due to high catalytic activity for CO oxidation and preventing CO poisoning in fuel-cell system. We here report the 3-dimentational atomic-scale structures of fcc and hcp Ru NPs using high-energy X-ray diffraction (HEXRD), Rietveld analysis, pair distribution function (PDF), and reverse Monte Carlo (RMC) modelling. Hard X-ray photoelectron spectroscopy (HAXPES) can provide important information on the influence of NP size on electronic properties. The HEXRD and HAXPES of Ru NPs were performed at BL04B2 and BL15XU at SPring-8, the world largest third-generation (8 GeV) synchrotron radiation facility located in Hyōgo prefecture, Japan. We observed higher stability of the lattice distortion of fcc Ru NPs with increasing particle size. The PDF analysis results show that the structural disordered Ru NPs at short- to intermediate-range atomic distances. The order parameter for fcc Ru NPs decreased with increasing particle size due to the loosely packing atomic arrangement and may explain an origin of higher catalytic activity of fcc Ru NPs. In this study, the observed trend of increasing catalytic activity of fcc Ru NPs was also discussed using their core-levels and valence band electronic structures. This work was partly supported by ACCEL, Japan Science and Technology Agency (JST) and also partly supported by Ministry of Education, Culture, Sports, Science and Technology of Japan (OS: 15K04616).
Correlation between glaze-colors and structural properties of the HIZEN celadons produced in the Edo period of Japan, by means of X-ray diffraction (?)
(Cer?mica, 2011) Hidaka, M.; Ohashi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Watanabe, M.; Koga, K.; Choi Jae-Young; Sung, N.E.; Park, Y.J.
HIZEN celadons produced at Arita and Imari areas in Japan from 1630's to 1790's (Edo period) have been investigated by means of X-ray fluorescence analysis, and X-ray diffraction and X-ray absorption spectra using synchrotron radiation. It is found that, in the HIZEN celadons, the color brightness of the celadon glazes depends on the structural property of the raw basic ceramics taken at Imaizumi (Arita) and Ohkwachi (Imari), where the former is mainly Quartz-SiO2, and the later is Sanidine ((K,Na)Si3O8). It is confirmed that CaCO3 of natural wood ash added artificially into the raw celadon ceramics makes a glassy glaze on the surface of the basic body of the HIZEN celadons. Transition-metal ions (Cr, Cu, Zn) of very small amount are detected in the celadon glazes, in addition to Fe and Mn of small amount. It is considered that Cu and Cr are related to the color brightness of green-brown and blue-green in the HIZEN celadon glazes, respectively.
Correlation Between Local Structures and Partial Electronic Band States in Ferroelectric Bi4?Xlaxti3o12; 0.0?X?1.46
(Ceramics-Silik�ty, 2009) Hidaka, M.; Wijesundera, R.P.; Kumara, L.S.R.; Noguchi, Y.; Miyayama, M.; Choi Sun-Hee; Sung, N.E.; Kim, M.G.
The local structures and the partial band states near a Fermi level (EF) have been studied at room temperature in the ferroelectric phase of Bi4?XLaXTi3O12 (BLT) with 0.00?x?1.46 by means of X?ray absorption spectra (XAS) including EXAFS and XANES. The EXAFS spectra suggest that, as increasing the substituted La ions, the local structures around Ti and Bi ions in perovskite-blocks of (Bi2?XLaXTi3O10)-2 are gradually deformed till x=0.85, and are largely changed by a structural phase transition occurring between x=0.85 and 1.20. The XANES spectra suggest that there is a strong hybridization between Ti-3d(t2g) and O-2p bands and between Bi-6s and O-2p bands in the valence band states, while between Ti-3d(eg) and O-2p bands and Bi-6p and O-3s bands in the conduction band states. All of the XAS show interesting dependency on the concentration of the substituted La ions in BLT. The results suggest that, in BLT, a reducing spontaneous polarization induced by the La-substitution results from the deformation of the local structures around Ti and Bi ions and from modulation of the hybridized band states near EF.
Correlation between the green-like coloration and the structural and electronic properties of celadon glazes
(Cer�mica, 2012) Hidaka, M.; Takeuchi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Watanabe, M.; Choi Jae-Young; Sung, N.E.
Correlation between the Izumiyama porcelain ceramics and the red-overglaze enamels of the Kakiemon-style porcelains
(Ceramics International, 2008) Kajihara, S.; Hidaka, M.; Wijesundera, R.P.; Kumara, L.S.R.; Kobayashi, H.; Koga, M.; Tsuru, T.; Koga, K.; Shimomura, K.; Choi Jae-Young; Sung, N.E.; Park, Y.J.
The Kakiemon-style porcelains made from 17th century at Arita are famous Japanese porcelains, characterized mainly by their colored underglaze and overglaze and by their original design of coloring spatial patterns in the porcelain surface. Raw materials of the red-overglaze enamels have been investigated by means of X-ray diffraction and X-ray absorption spectra using synchrotron radiations. It is found that Izumiyama porcelain ceramics of yellow color can produce the Kakiemon red-overglaze enamels by thermal treatment and water-washing, where Izumiyama is a collecting place of the raw porcelain ceramic at Arita. The brightness of the red-overglaze enamels is related on the local structure around Fe ions and the electronic band states of Fe ions near a Fermi level in ?-Fe2O3, in addition to the spatial density of the ?-Fe2O3 fine particles. The structural and electronic properties are slightly affected by an electron-hybridization between Fe ions of ?-Fe2O3 and oxygen ions of the (SiO2?Al2O3) complexes in the red overglaze.
Local structures and electronic band states of ?-Fe2O3 polycrystalline particles included in the red-color overglazes and the transparent glazes of the Kakiemon-style porcelains by means of X-ray absorption spectra (II)
(Cer�mica, 2009) Hidaka, M.; Horiuchi, H.; Ohashi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Sung, N.E.
Kakiemon-style porcelain is mainly characterized by the porcelain body of white color or milky-white color and the elegant and bright patterns of the colored overglazes on its white body. The porcelains were first developed and completed by Kakiemon-kiln family in 1650-80's. The red-color overglazes and the transparent glazes of the present porcelain pieces, which were produced in the early 17th century to the middle 18th century, have been investigated by means of X-ray absorption spectrum using synchrotron radiation. The structure of ?-Fe2O3 as red-color emission element is slightly deformed in the red-color overglazes by the other surrounding oxides (SiO2, Al2O3, K2O, Na2O, MgO, PbO), and/or the new complexes of (SiO2-Al2O3,) systems constructed by the raw materials. The Fe ions in the transparent glazes are in the glass-state with the other oxides. However, the electronic valence, Fe3+, of Fe ions is the same with that of the ?-Fe2O3 in the red-color overglazes. The lead oxides (PbO, Pb3O4) used in the Edo period to increase the brightness in the fritted red-color overglazes were perfectly decomposed, and Pb ions were in the glass-state of the porcelains.
Local structures and electronic band states of ??Fe2O3 polycrystalline particles in the glazes of the HIZEN celadons produced in the Edo period of Japan, by means of X-ray absorption spectra (II)
(Cer�mica, 2011) Hidaka, M.; Ohashi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Sugihara, S.; Momoshima, N.; Kubuki, S.; Sung, N.E.
HIZEN celadon glazes produced in 1630's to 1790's (Edo period, Japan) have been investigated by means of X-ray absorption spectra (XAS) near a Fe-K edge by using synchrotron radiation and a M�ssbauer spectrum. The XAS suggest that the local structure around Fe2O3 fine powders is slightly different between the Izumiyama ceramics of mainly the Quartz-SiO2 and Ohkawachi ceramics of mainly the feldspar of (K,Na)Si3O8 (Sanidine), and that the glazes of the HIZEN celadons include the Fe2O3 fine powders in the glassy state, though the X-ray diffraction patterns of the glassy celadon glazes do not show any peaks of the Fe2O3 structure. The M�ssbauer spectrum suggests that the celadon glaze of Seiji (m) includes only Fe3+ ions, but not Fe2+ ions. This indicates the existence of Fe2O3 in the celadon glaze. It is interpreted that the colored brightness of the HIZEN celadons is induced by the structural properties of the used raw celadon ceramics and the other transition-metal ions of Cr, Cu, Zn in the celadon glazes, but not by the chemical reaction from Fe2O3 to FeO under the deoxidizing thermal treatment at higher temperature in a kiln.
Pedestrian and vehicular traffic friendly uninterrupted solar powered traffic signal light system
(2006) Kalingamudali, S.R.D.; Harambearachchi, J.C.; Kumara, L.S.R.; de Silva, J.H.S.R.; Piumwardena, D.D.F.; de Silva, L.D.L.; Abeynanda, L.T.; Chameera, K.H.G.G.; Dissanayake, D.P.; Attenayake, A.M.C.R.; Molligoda, S.A.G.N.
During power failures and power cuts road users suffer immense difficulties due to non-availability of traffic signal lights all over the world. Use of solar cells with lead acid accumulators to provide required power and the use of light emitting diode (LED) displays to function as signal lamps to reduce the stored power consumption will be a feasible solution for the same. Since the LED display consists of a number of LEDs, visibility from side ways is better than the conventional signal lamp having a single light source. Failure of the lamp in the conventional signals halts the entire operation of the signal lamp but in the case of failures of few LEDs in a matrix will not cease the entire operation. In most of the LED display traffic light systems, set of LEDs will not illuminate even when only one of the LEDs burnt out since the set is connected in series. In this design, parallel sets of LEDs are connected in series, and therefore, only the defective LEDs will not be illuminated but all the others will be illuminated. Some major advantages of this system are uninterrupted operation around the clock throughout the year, very low maintenance cost for replacing LEDs and the lead acid batteries, and during the installation of new signal posts it is possible to erect the same as a wireless installation. Solar panel with an accumulator can provide power while infrared sensors and diodes could be used to transfer signals between each signal post, hence it is not necessary to dig across the road for control and power cables. For the safety and the convenience of the pedestrians and vehicular traffic, bi-color seven segment digital displays are available to indicate the waiting time and remaining moving time. Considering the signal light requirement for a country, the above solution will have a considerable impact on the national power grid
Remote Controlling and Monitoring System to Control Electric Circuitry through SMS using a Microcontroller
(2006) Kalingamudali, S.R.D.; Harambearachchi, J.C.; Kumara, L.S.R.; de Silva, J.H.S.R.; Rathnayaka, R.M.C.R.K.; Piyasiri, G.; Indika, W.A.N.; Kumara, H.A.D.P.S.S.; Fernando, M.R.D.B.
Mobile phones have become one of the most popular communication devices among most of the people around the world, and short message service (SMS) is popular among mobile phone users as a cheap and convenient method of communicating. Therefore, SMS technology is a common feature with all mobile network service providers. Since the use of SMS technology is a cheap, convenient and flexible way of conveying data, researchers are trying to apply this technology in many different areas that were not provided by service providers at present. One of such areas that the SMS technology could be used as a cost effective and more flexible way will be remote monitoring and controlling. Therefore, a system has been developed to control and monitor electric circuitry through SMS using the PICmicroreg 16F877A microcontroller remotely. The microcontroller performs all the functions of the system. Standard attention commands are used to control the operation on SMS in the mobile phone. SMS is produced using the concept of protocol data unit.
Structural properties of the red-color overglaze for the HIZEN porcelains produced in the early Edo period of Japan
(Ceramics International, 2009) Hidaka, M.; Ohashi, K.; Kajihara, S.; Wijesundera, R.P.; Kumara, L.S.R.; Choi Jae-Young; Sung, N.E.
HIZEN porcelains made in 1650s to 1750s (early Edo period) in Arita areas sited in south Japan (SAGA) are famous Japanese porcelains, which are characterized by elegant and bright colors in the overglaze and the underglaze. Red-overglazes and transparent glazes of the HIZEN porcelains have been investigated by means of X-ray diffraction (XRD) and X-ray absorption spectra (XAS) using synchrotron radiation. The results suggest that the red-color brightness of the Hizen porcelains is mainly induced by micro-structural correlation between ?-Fe2O3 fine particles of red-color emission element and the oxide complexes of SiO2?Al2O3?CaO?KNaO or SiO2 in the fritted overglazes. The stability of the red-color overglaze on the porcelain body of white-color results from interfacial fusion between both glass-states in the fritted overglaze and the transparent glaze coating the porcelain body. The refined local structures around Fe ions of the ?-Fe2O3 structure taken EXAFS spectra give the technical and historical relation among four kinds of the HIZEN porcelains for fritted materials of the overglazes and thermal treatment at high-temperature in the porcelain kilns.
Structural properties of the red-color overglazes on the Kakiemon-style porcelains produced in the later 17th century by means of X-ray diffraction (I)
(Cer�mica, 2009) Hidaka, M.; Horiuchi, H.; Ohashi, K.; Wijesundera, R.P.; Kumara, L.S.R.; Choi Jae-Young; Park, Y.J.
Kakiemon-style porcelains produced at Arita areas (SAGA) in Kyushu Island are famous Japanese porcelains. The porcelain-techniques creating its elegant and bright red-color underglaze and overglaze were found and developed in 1650's (early Edo period) first by Kakiemon kiln. Red-color overglaze and transparent glaze of the Kakiemon-style porcelains have been investigated by means of X-ray diffraction using synchrotron radiation. The results suggest that the red-color brightness is mainly induced by micro-structural correlation between ?-Fe2O3 fine particles, as red-color emission elements, and other oxides of SiO2, Al2O3, CaO, KNaO, PbO. The stability of the red-overglaze on the porcelain surface is related to interfacial fusion of the glasses existing in the fritted red-overglaze and the transparent glaze on the porcelain body. The ancient porcelain-techniques of the Kakiemon-style porcelains are clearly based on the micro-structural and material properties of the overglazes, the underglazes, and the transparent glazes, though the techniques were experimentally and accidentally found and developed in the Edo period.