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Friction Stir Lap Welding of AZ31B and AA6061 Alloys Using Tin as an Inter-Layer
Anil Bandi,Srinivasa R. Bakshi 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
The formation of Mg17Al12and Al3Mg2is inevitable even in solid-state joining of Al and Mg alloys by friction stir welding(FSW). In the present study, the effect of a thin inter-layer of Sn (tin) and FSW parameters (pin length and tool rotationspeed) on the microstructure and strength of friction stir lap welds of 3 mm thick AA6061 Al alloy and AZ31B Mg alloysheets was investigated. A ~ 20 μm thick Sn layer was deposited on AZ31B alloy by displacement plating. The heat generatedduring the welding melted the Sn layer and the rotation action of the tool pushed the molten Sn to the hooks on the advancingside and retreating side. The extent of Mg17Al12and Al3Mg2intermetallic compound formation was reduced with Sninter-layer with limited formation of Mg2Sn. The Sn inter-layer helped improve the lap shear strength at lower tool rotationalspeed (600 RPM) and pin lengths of 3.25 and 3.75 mm compared to joints without Sn inter-layer. Lap welds prepared witha 3.25 mm pin at 600 RPM had a lap shear strength of 245 N/mm which is the highest value reported so far and is 116%higher compared to joints without Sn inter-layer. This was due to elimination of hook at the advancing side and retreatingside and disintegration of intermetallic compounds.
A broad-band capturing and emitting molecular triad: synthesis and photochemistry
Bandi, Venugopal,Ohkubo, Kei,Fukuzumi, Shunichi,D'Souza, Francis The Royal Society of Chemistry 2013 Chemical communications Vol.49 No.28
<P>A novel broad-band capturing and emitting supramolecular triad useful for solar energy harvesting and building optoelectronic devices is reported.</P> <P>Graphic Abstract</P><P>A broad-band capturing and emitting novel supramolecular triad comprised of a zinc porphyrin, a BF<SUB>2</SUB> chelated dipyrromethene and a BF<SUB>2</SUB> chelated azadipyrromethene, useful for solar energy harvesting and building optoelectronic devices, is reported. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cc40471d'> </P>
Bandi, Venugopal,El-Khouly, Mohamed E.,Nesterov, Vladimir N.,Karr, Paul A.,Fukuzumi, Shunichi,D’Souza, Francis American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.11
<P>Using near-IR emitting photosensitizers, viz., zinc phthalocyanine (ZnPc), zinc naphthalocyanine (ZnNc), and BF<SUB>2</SUB>-chelated azadipyrromethene (azaBODIPY), donor–acceptor conjugates have been newly formed using the well-known metal–ligand axial coordination approach. To accomplish this task, the electron-deficient azaBODIPY was functionalized to possess either two pyridine or imidazole ligating entities. The X-ray crystal structure of one such derivative revealed the presence of axial binding capable pyridine entities on the azaBODIPY macrocycle. The structural integrity of the newly formed conjugates was established from optical absorption, emission, <SUP>1</SUP>H NMR, electrochemical, and computational methods. The experimentally determined binding constants suggested moderately stable conjugates. The absence of excitation energy transfer from singlet excited azaBODIPY to either ZnPc or ZnNc in the conjugates was confirmed from the steady-state emission measurements. However, free-energy calculations suggested photoinduced electron transfer to be exothermic from singlet excited ZnPc or ZnNc to azaBODIPY. Femtosecond transient studies confirmed such predictions from where occurrence of ultrafast photoinduced electron transfer was observed. The measured rates of charge separation and charge recombination (<I>k</I><SUB>CS</SUB> and <I>k</I><SUB>CR</SUB>) revealed charge stabilization to some extent in these conjugates.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-11/jp400046b/production/images/medium/jp-2013-00046b_0015.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp400046b'>ACS Electronic Supporting Info</A></P>
Bandi, Vengala Rao,Jayasimhadri, M,jeong, Junho,Jang, Kiwan,Lee, Ho Sueb,Yi, Soung-Soo,Jeong, Jung-Hyun Institute of Physics [etc.] 2010 Journal of Physics. D, Applied Physics Vol.43 No.39
<P>A series of red phosphors Ca<SUB>1−<I>x</I></SUB>ZrSi<SUB>2</SUB>O<SUB>7</SUB> : Eu<SUB><I>x</I></SUB> (<I>x</I> = 0.5,1,5,10,12 mol%) were prepared by a solid-state reaction technique at various temperatures and their structural and optical properties were investigated. The x-ray diffraction profiles showed that all peaks could be attributed to the monoclinic phase CaZrSi<SUB>2</SUB>O<SUB>7</SUB> doped with Eu<SUP>3+</SUP>. SEM, FTIR, TG and DTA profiles have also been characterized to explore their structural properties. The luminescence properties of these resulting phosphors have been characterized by photoluminescence spectra. The host matrix itself has shown a strong blue emission which has its maximum intensity at 470 nm. The excitation spectra of CaZrSi<SUB>2</SUB>O<SUB>7</SUB> : Eu<SUP>3+</SUP> revealed two excitation bands at 395 and 464 nm which correspond to the sharp <SUP>7</SUP>F<SUB>0</SUB>–<SUP>5</SUP>L<SUB>6</SUB> and <SUP>7</SUP>F<SUB>0</SUB>–<SUP>5</SUP>D<SUB>2</SUB> transitions of Eu<SUP>3+</SUP> and matches well with the two popular emissions from n-UV/blue GaN-based LEDs. The prominent red emission was obtained at 615 nm by the excitation transitions <SUP>5</SUP>L<SUB>6</SUB>, <SUP>5</SUP>D<SUB>2</SUB> of Eu<SUP>3+</SUP> through the non-radiative energy transfer process from the host to the Eu<SUP>3+</SUP> ion. The effects of charge compensation by monovalent ions on the luminescence behaviour of a red emitting phosphor CaZrSi<SUB>2</SUB>O<SUB>7</SUB> : Eu<SUP>3+</SUP> were investigated. The high colour saturation and the low thermal quenching effect of these phosphors make it a potential red component for white light emitting diodes (w-LEDs).</P>
Peak Pressures Acting on Tall Buildings with Various Configurations
Bandi, Eswara Kumar,Tanaka, Hideyuki,Kim, Yong Chul,Ohtake, Kazuo,Yoshida, Akihito,Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2013 International journal of high-rise buildings Vol.2 No.3
Twenty six pressure models of high rise buildings with various cross-sections including twisted models were tested in a boundary layer wind tunnel. The cross-sections were triangular, square, pentagon, hexagon, octagon, dodecagon, circular, and clover. This study investigates variations in peak pressures, and effects of various cross-sections and twist angles on peak pressures. To study the effects of various configurations and twist angles on peak pressures in detail, maximum positive and minimum negative peak pressures at each measurement point of the building for all wind directions are presented and discussed. The results show that peak pressures greatly depend on building cross-section and twist angle.
Carbon dots attached nanocellulose as a recyclable nanozyme for colorimetric biosensing
Rajkumar Bandi,Ramakrishna Dadigala,Song-Yi Han,Jeong-ki Kim,Gu-Joong Kwon,Seung-Hwan Lee 강원대학교 산림과학연구소 2022 강원대학교 산림과학연구소 학술대회 Vol.2022 No.10
Carbon dots (CDs) are widely employed as peroxidase mimics in biosensing. However, as colloidal nanozymes, CDs suffer from the drawbacks of substrate induced aggregation and difficulties in recovery and reuse. Nanocellulose is proposed as a support material to overcome these drawbacks and two immobilization strategies were explored here. In first strategy, peroxidase mimicking Fe-doped CDs (FeCDs) were immobilized on TEMPO-oxidized cellulose nanofibrils (TOCNF) via physical entrapment involving hydrogen bonding interactions. Peroxidase activity of the composite nanopaper was evaluated using TMB as chromogenic substrate and applied to the colorimetric detection of H2O2 and glucose. Under optimal conditions, this method afforded linear ranges of 6– 42 μM and 10–70 μM and detection limits of 0.93 and 1.73 μM for the H2O2 and glucose, respectively. In another strategy, amine functionalized, Fe, N-doped CDs (FeNCDs) were immobilized on dialdehyde cellulose nanofibrils (DACNF) via Schiff base reaction and reductive amination. DACNF served as an excellent matrix for FeNCDs to retain the fluorescence and peroxidase activities. Colorimetric assays based on ABTS oxidation offered linear ranges of 10–80 μM and 50–400 μM and detection limits of 0.70 and 3.72 μM for H2O2 and cholesterol respectively. Further the nanocomposite presented a long shelf life and excellent reusability for 10 cycles. Overall, nanocellulose acted as a great support material for the colloidal nanozyme that prevented them from aggregation and made them easy to recycle and reuse.