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Hydration Products, Morphology and Microstructure of Activated Slag Cement
Meena Murmu,Suresh Prasad Singh 한국콘크리트학회 2014 International Journal of Concrete Structures and M Vol.8 No.1
This paper reports the physical properties and hydration products of slag cement that was prepared by activating ground granulated blast furnace slag with commercial lime and plaster of Paris (POP) as activators. The consistency, setting times and soundness of various mixes of slag-lime-POP is reported. The hydration products and formation of bonds in the paste during setting were studied with the help of SEM, FTIR and XRD tests and the same are correlated to the hydration process. The setting times of the mixes are found to be lower than that of the value prescribed for ordinary Portland cement (OPC). Borax is used as a setting retarder and a borax content of 0.4 % by mass gives setting times that are normally prescribed for OPC. In the early stages of setting C?A?S?H gels are found in this cementing material instead of C?S?H gel, as generally observed in the OPC.
Microstructural, Electrical and Magnetic Properties of Erbium Doped Zinc Oxide Single Crystals
P. P. Murmu,J. Kennedy,B. J. Ruck,S. Rubanov 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.6
We report the structural, electrical and magnetic properties of erbium (Er) implanted zinc oxide (ZnO) single crystals. Rutherford backscattering and channeling results showed that the majority of Er atoms resided in Zn substitutional lattice sites. Annealing led to a fraction of Er atoms moving into random interstitial sites. Transmission electron microscopy micrographs revealed that doped Er atoms were located in the nearsurface region, consistent with the results obtained from DYNAMICTRIM calculations. A non-linear Hall-voltage was observed near 100 K, which is associated with inhomogeneous transport in the material. The Er implanted and annealed ZnO exhibited persistent magnetic ordering to room temperature. Ferromagnetism was likely from the presence of intrinsic defects in ZnO, which mediates the magnetic ordering in Er implanted and annealed ZnO.
Mechanical Properties of Alkali Activated Fly Ash Geopolymer Stabilized Expansive Clay
Anant Lal Murmu,Anamika Jain,Anjan Patel 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.9
It has always been a challenge for civil engineers to lay roads in the areas covered by expansive soil. The expansive soil undergoes extreme phase changes from being hard in hot summer to being slushy and without strength in monsoon season. Thus, the engineering properties of the expansive soil must be improved before laying the roads. This paper presents the results of experimental work carried out to improve the engineering properties of an expansive clay i.e. black cotton soil (BCS) by using fly ash geopolymer. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions were mixed in different ratios (0.5, 1, 1.5, and 2) and used for synthesizing the geopolymer. The stabilized BCS samples were characterized in the laboratory for various properties viz., Atterberg’s limits, free swell ratio, and unconfined compressive strength. The untreated and treated BCS samples were also analyzed for their microstructural and morphological properties by using the SEM (scanning electron microscope) images and the XRD (X-ray diffractometer) and FTIR (Fourier-transform infrared spectroscopy) spectra. An increase in the unconfined compressive strength and reduction in free swell ratio as well as shrinkage limit was observed after stabilization with geopolymer. Results also indicate binding of soil particles and formation of dense microstructure resulting in higher strength and less swelling and shrinkage characteristics. Furthermore, the bender element test was used to indicate the improvement in stiffness of the geopolymer stabilized expansive soil in terms of shear wave velocity.
Jana, Milan,Khanra, Partha,Murmu, Naresh Chandra,Samanta, Pranab,Lee, Joong Hee,Kuila, Tapas The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.16
<P>A simple and effective method using 6-amino-4-hydroxy-2-naphthalenesulfonic acid (ANS) for the synthesis of water dispersible graphene has been described. Ultraviolet-visible (UV-vis) spectroscopy reveals that ANS-modified reduced graphene oxide (ANS-rGO) obeys Beers law at moderate concentrations. Fourier transform infrared and X-ray photoelectron spectroscopies provide quantitative information regarding the removal of oxygen functional groups from graphene oxide (GO) and the appearance of new functionalities in ANS-rGO. The electrochemical performances of ANS-rGO have been determined by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy analysis. Charge–discharge experiments show that ANS-rGO is an outstanding supercapacitor electrode material due to its high specific capacitance (375 F g<SUP>−1</SUP> at a current density of 1.3 A g<SUP>−1</SUP>) and very good electrochemical cyclic stability (∼97.5% retention in specific capacitance after 1000 charge–discharge cycles). ANS-rGO exhibits promising characteristics with a very high power density (1328 W kg<SUP>−1</SUP>) and energy density (213 W h kg<SUP>−1</SUP>).</P> <P>Graphic Abstract</P><P>A simple and effective method using 6-amino-4-hydroxy-2-napthalenesulfonic acid (ANS) for the synthesis of water dispersible graphene is described. The as-produced graphene is a promising supercapacitor electrode material. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp54510e'> </P>
Saha, Sanjit,Samanta, Pranab,Murmu, Naresh C.,Kim, Nam H.,Kuila, Tapas,Lee, Joong H. THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2017 Journal of Industrial and Engineering Chemistry Vol.52 No.-
<P><B>Abstract</B></P> <P>Functionalization and electrodeposition of reduced graphene oxide/hexagonal boron nitride (rGO/h-BN) superlattice was carried out by a novel one-step electrochemical process. The sulfanilic acid azochromotrop (SAA) functionalized and electrodeposited nickel foam (SAA@rGO/h-BN@Ni) electrode showed high specific capacitance of ∼1300Fg<SUP>−1</SUP>. An asymmetric supercapacitor cell (ASC) using SAA@rGO/h-BN@Ni as positive and thermally reduced GO as negative electrode showed ∼80% capacitance retention after 10,000 charge–discharge cycles. The ASC showed low relaxation time constant of ∼0.47ms along with high energy density (∼95.3Whkg<SUP>−1</SUP>) and power density (∼7200Wkg<SUP>−1</SUP>) ensuring the utility of SAA@rGO/h-BN@Ni electrode for supercapacitor application.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Behavior and Design of Distributed Belt Walls as Virtual Outriggers for Concrete High-Rise Buildings
Tae-Sung Eom,Hiubalt Murmu,Weijian Yi 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.2
A new lateral force-resisting structural system for concrete high-rise buildings, distributed belt wall system, is proposed. Unlike conventional belt structures, the belt walls infilling the space between perimeter columns are distributed separately along the overall building height. In this study, the force transfer mechanism and performance of the distributed belt walls, acting as virtual outriggers under lateral load, are investigated. For the reinforcement of the belt walls subjected to high shear demand, a reinforcing method using high-strength prestressing strands (i.e. PSC belt wall) is suggested, and the shear strength of the PSC belt walls is estimated based on the compression field theory. By performing nonlinear finite element analysis, the shear behavior of the PSC belt walls, including cracking and yield strengths, is investigated in detail. Based on these investigations, recommendations for the shear design of the belt walls reinforced by high-strength prestressing strands are given.
Facile Electrodeposition Technique for the Fabrication of MoP Cathode for Supercapacitor Application
( Prakas Samanta ),( Souvik Ghosh ),( Naresh Chandra Murmu ),( Joong Hee Lee ),( Tapas Kuila ) 한국복합재료학회 2021 Composites research Vol.34 No.6
The continued environmental pollution caused by fossil fuel consumption has prompted researchers around the world to develop environmentally friendly energy technologies. Electrochemical energy storage is the significant area of research in this development process, and the research significance of supercapacitors in this field is increasing. Herein, a simple electrodeposition synthetic route was explored to develop the MoP layered cathode material. The layered structure provided a highly ion-accessible surface for smooth and faster ion adsorption/ desorption. After Fe was doped into MoP, the morphology of MoP changes and the electrochemical performance was significantly improved. Specific capacitance value of the binder-free FeMoP electrode was found to be 269 F g<sup>-1</sup> at 2 A g<sup>-1</sup> current density in 6 M aqueous KOH electrolyte. After adding Fe to MoP, an additional redox contribution was observed in the redox conversion from Fe<sup>3+</sup> to Fe<sup>2+</sup> redox pair, and the charge transfer kinetics of MoP was effectively improved. This research can provide guidance for the development of supercapacitor electrode materials through simple electrodeposition technology.
Souvik Ghosh,Prakas Samanta,Naresh Chandra Murmu,김남훈,Tapas Kuila 한국복합재료학회 2022 Composites research Vol.35 No.1
The activated carbon is a very good choice for using as supercapacitor electrode materials. Herein, the flower of Shorea robusta a bio-waste material was successfully used to synthesize the activated carbons for application as electrode materials of supercapacitor. The activated carbon was synthesized through chemical activation process followed by thermal treatment at 700oC in presence of N2 atmosphere using KOH, ZnCl2 and H3PO4 as the activating agents. The physicochemical analyses demonstrate that the obtained activated carbons are graphitic in nature and the degree of disorder of the graphitic carbons is changed with changing the activating agents. The activated carbon obtained from Shorea robusta flower (ACSF-K) electrode shows the specific capacitance of ~610 F g-1 at 2 A g-1 current density, which is higher than ACSF-Z (560 F g-1) and ACSF-H (470 F g-1) electrode material under the identical current density. The synthesized graphitic carbons also demonstrate good rate capability and high electrochemical stability as supercapacitor electrode.