Synthesis and luminescent features of NaCaPO₄:Tb³⁺ green phosphor for near UV-based LEDs

Ratnam, B.V.,Jayasimhadri, M.,Bhaskar Kumar, G.,Jang, K.,Kim, S.S.,Lee, Y.I.,Lim, J.M.,Shin, D.S.,Song, T.K. Elsevier Sequoia 2013 JOURNAL OF ALLOYS AND COMPOUNDS Vol.564 No.-

<P>An efficient green emitting Tb3+ doped NaCaPO4 (NCP) phosphor was synthesized by using conventional solid-state reaction for solid-state lighting applications. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), FT-IR, emission and excitation properties were extensively investigated for NCP phosphors. X-ray diffraction analysis confirmed the formation of NaCaPO4 with orthorhombic structure. The excitation spectrum consists of strong 4f-4f transition at around 370 nm, which has higher intensity than the f-d transition. Emission spectra indicated that this phosphor can be efficiently excited by UV light in the range from 250 to 400 nm, and shows strong emission band centered at 547 nm. Analysis of the emission spectra with different Tb3+ concentrations revealed that the optimum dopant concentration for these NCP phosphors is about 5 mol% of Tb3+. Diminishing of D-5(3) level and increasing of D-5(4) level emission intensity with the Tb3+ concentration explained successfully. The emission color was analyzed and confirmed with the help of chromaticity coordinates and color temperature. The excellent luminescent properties of NaCaPO4: Tb3+ phosphor makes it as a potential green phosphor upon near-UV LED excitation. (C) 2013 Elsevier B.V. All rights reserved.</P>

Versatile host-sensitized white light emission in a single-component K₃ZnB₅O₁₀:Dy³⁺ phosphor for ultraviolet converted light-emitting diodes

Dillip, G.R.,Kumar, Grandhe Bhaskar,Bandi, Vengala Rao,Hareesh, M.,Deva Prasad Raju, B.,Joo, S.W.,Bharat, L. Krishna,Yu, Jae Su ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.699 No.-

<P><B>Abstract</B></P> <P>A single-phase white-light-emitting phosphor, K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB>:Dy<SUP>3+</SUP>, has been synthesized by a conventional solid-state reaction method. X-ray diffraction (XRD) analysis was used to determine the monoclinic crystal structure of phosphors. The surface states, B 1s, O 1s, K 2p, Zn 2p, and Dy 3d of the phosphor was quantified by X-ray photoelectron spectroscopy (XPS). Diffuse reflectance spectroscopy (DRS) revealed double absorption edges at 3.27 and 5.46 eV for K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB> matrix. The formation of defect-levels, zinc interstitials ( Z <SUB> n i </SUB> ) , zinc vacancies ( <SUB> V Z n </SUB> ) , oxygen antisites ( <SUB> O Z n </SUB> ) and oxygen vacancies ( <SUB> V O </SUB> ) in K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB>:Dy<SUP>3+</SUP> phosphors were identified by photoluminescent (PL) spectroscopy. The emissions at 405 nm (violet-I), 434 nm (violet-II), and 467 nm (blue) are due to intra-band transitions of ( F X → <SUB> V Z n </SUB> ) , ( Z <SUB> n i </SUB> → <SUB> V Z n </SUB> ) and ( Z <SUB> n i </SUB> → <SUB> O Z n </SUB> ) of the host, respectively. Similarly, the emission at 517 nm (green) corresponds to the transition from free excitons to the oxygen vacancies in the host ( F X → <SUB> V O </SUB> ) . The emissions at 575 and 665 nm are assigned to the <I>f-f</I> transitions of Dy<SUP>3+</SUP> ions within the host matrix. An energy level diagram is proposed to describe the host emission and possible energy transfer from the host to dopant ions in the single-phase phosphor. The phosphor shows good thermal stability with activation energy of 0.52 eV. The combined emissions in the blue, green, yellow, and red regions resulted in white light emission with CIE coordinates of (0.256, 0.258) on the CIE diagram.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Versatile host-sensitized white light emission, K<SUB>3</SUB>ZnB<SUB>5</SUB>O<SUB>10</SUB>:Dy<SUP>3+</SUP> phosphor was synthesized. </LI> <LI> Defect-related surface analysis of phosphor was studied by XPS. </LI> <LI> Energy level diagram was designed to show host to dopant energy transfer process. </LI> <LI> The phosphor has shown good thermal stability with activation energy of 0.52 eV. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Performance of leaf springs made of composite material subjected to low frequency impact loading

S. Rajesh,G. B. Bhaskar,J. Venkatachalam,K. Pazhanivel,Suresh Sagadevan 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

This paper illustrates the possibility of replacing existing conventional steel-leaf spring by the leaf spring made by tailoring the layup of composite laminates. The dimensions of the existing conventional middle leaf (spring) of a commercial vehicle were chosen for the design and manufacture of die for moulding the composite leaves. Accordingly, suspension springs of composites of different layups with glass and carbon were fabricated and tested for flexure response. It is to be noted here that the cross sectional area of the composite leaf spring was the same as of the conventional leaf spring. By using universal testing machine, load per deflection and maximum load for each of the composite leaf springs were evaluated. Apart from these, the specimens were exposed to low frequency impact loading with specific duration of cycles and subsequently the flexure response was also evaluated. The low frequency impact on the composite leafs was effected with a laboratory loading set-up in a milling machine. Experimental results indicated the superior flexure response of the hybrid composites (with glass fiber at starting phase and carbon fiber at the end) and suggested possible alternative on comparison with the conventional spring.

Evaluation and Comparison of Mechanical Properties of Natural Fiber Abaca-sisal Composite

K. Venkatesan,G. B. Bhaskar 한국섬유공학회 2020 Fibers and polymers Vol.21 No.7

With the high usage of the synthetic fiber, the amount of the waste materials has increased as the degradationprocess is quite slow and with the burning of the synthetic fibers creates toxic gas and other environmental hazards.Presentlynatural fibershas many implications like low density, cheap, high specific properties, non-abrasive and less harmful duringmanufacturing and most importantly the abundance in nature and can be made by planting. Because of which it is giving agood run compare to conventional glass and carbon fibers composites. The glass fiber composite is replaced by natural fibercomposites for environmental sustainability. Fiber extracted from plants is renewable and low levels of embodied energycompared to synthetic fibers. This paper deals with comparison of mechanical properties of a hybrid composite (abaca +sisal) and comparing the results with the ABAQUS simulation results. This hybrid composite consists of three layers with topand bottom layers of sisal fibers and the middle layer is made up of abaca fiber. These hybrid composites (sisal + abaca) werefabricated with different orientations (0 °, 45 °, 90 °) of fiber. The above said composite is fabricated by using hand layupmethod. Epoxy resin along with Huntsman Resin 951 hardener was used as the binding agent throughout the layer. Theultimate tensile strength and percentage elongation of the composite were 90 ° oriented fiber composite is found to be highervalue compared to 0 °, 45 ° oriented fiber. Flexural strength of the composite was 45 °, 90 ° orientedfiber composite havingsame value, whereas 0 ° fiber-oriented composite having least value. The ultimate shear strength of composite was 45 °oriented fiber composite is found to be higher value compare to the other two oriented fiber composites (90 °, 0 °). Thebreaking load of composite 0 ° oriented fiber composite is high value compareto the other two oriented fiber composites(45 °, 90 °). Scanning electron microscope is used to analyse the internal structural of the broken specimen.

Mechanical characterisation of glass fibre reinforced with aluminium wire mesh under various analysis

A. Manikandan,G.B. Bhaskar 한양대학교 청정에너지연구소 2024 Journal of Ceramic Processing Research Vol.25 No.2

GFRP (Glass Fiber Reinforced Plastic) known for its high strength and cost-effectiveness. Aluminium wire mesh is alightweight reinforcement material made from aluminium wires woven into a mesh pattern, chosen for its availability,strength, and ability to improve the strength of GFRP structures without adding extra weight. The purpose of this research isto figure out how to make glass fiber metal laminates using aluminium wire mesh and GFRP. Aluminium was chosen for itsavailability, good balance of strength and cost-effectiveness. Glass fibers were also chosen for their strength and affordability. This study’s aim is to enhance the strength of GFRP structures without adding extra weight. To achieve this, the researchersuse Aluminium wire mesh as reinforcement. The purpose of this study is to make better Aluminium wire mesh samples usinga common method without making them heavier. The aim is to make GFRP structures stronger without making them heavier,making them better for their intended use by the conventional hand-layup method.