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RISS 인기검색어
- 검색키워드
- 저자 : Bipin Kumar Singh (검색결과 4 건)
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Photo Physical Studies of PVP Arrested ZnS Quantum Dots
Ashutosh Kumar Shahi,Bishnu Kumar Pandey,Bheeshma Pratap Singh,Bipin Kumar Gupta,Sukhvir Singh,Ram Gopal 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.2
Monodispersed polyvinylpyrrolidone (PVP) arrested ZnS quantumdots (QDs) having diameter in range ~2-5 nm are synthesized by acolloidal precipitation method using PVP as the stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM),high resolution transmission electron microscopy (HRTEM),selective area electron diffraction (SAED) and Fourier transforminfrared (FT-IR) spectroscopy are probed to investigate thestructural information. The optical properties are studied usingdiffuse UV-visible reflectance and photoluminescence (PL)spectroscopy techniques. TEM images as well as XRD reflectionpeak broadening indicate the nanometer size particles formationwith cubic (sphalerite) phase within the polymer matrix. Opticalabsorbance studies reveal an excitonic peak at around ~310 nmdictates the effect of quantum confinement effect in the ZnS QDs. PL emission spectra for ZnS QDs in PVP exhibit four emissionpeaks at ~382 nm, ~414 nm, ~480 nm and ~527 nm are observed. These excitonic emissions from ZnS QDs are caused by theinterstitial sulfur/Zn vacancies and surface states.
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Comparative study among Al2O3, ZTA, MgO/ZTA & CuO/ZTA composites in terms of Mechanical Properties
G. Gokilakrishnan,Bipin Kumar Singh,M. Vigneshkumar 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.4
Alumina (Al2O3) ceramics are one of the demanded materials in the current scenario due to its cheaper cost, abundance ofavailability and combination of high hardness and fracture toughness by reinforcement of ytrria stabilized zirconia (YSZ),Magnesium oxide (MgO), and Copper oxide (CuO). The effect of such additives inside alumina ceramics are carried out fromlast several decades but still there are many more phenomenons that are still inconclusive. So, a comparative study among thesaid additive in terms of mechanical properties is carried out to reveal the effect of YSZ, MgO and CuO additives insidealumina ceramics. At first, 10 wt. % of YSZ is doped inside the alumina matrix followed by 0.6 wt. % of MgO and 1.5 wt. % of CuO. The developed composites are thoroughly examined in terms of microstructure, bulk density, hardness, andfracture toughness. The results of the microstructure clearly reveal the homogeneous distribution of all additives inside thealumina matrix. A positive effect with YSZ and MgO is noticed on the bulk density and hardness whereas an adverse effectof CuO is observed. The values of fracture toughness are increases with all the additives due to the synergistic effect oftransformation toughening and crack bridging phenomenon.
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K. Raja,M. Dhanabal,Bipin Kumar Singh,P. Ganeshan 한양대학교 청정에너지연구소 2024 Journal of Ceramic Processing Research Vol.25 No.1
Self-lubricating composite, comprises of CuO/ZTA is developed for its application as cutting inserts. The powders of zirconiatoughened alumina (ZTA) is prepared through co-precipitation process, further mixed with MgO particles (act as sinteringaid) and CuO (provide self-lubrication) using mechanical assistance. After mixing the homogeneous composites are usedto fabricate the Inserts obeying powder metallurgy process sintered through Hot isostatic pressing (HIP) and cold presstechnique. The sintered samples are cut to size using diamond wheel on tool grinder machine. The geometry of inserts aremaintained according the international (ISO) standard SNUN 120408. The mechanical characterizations of developedinserts are carried out on mirror polished samples. Crack bridging and crack deflection are the influential phenomenonon the fracture toughness, whereas impurity phases of CuO at grain boundary result in little decrement in hardness. Aftermechanical characterization the inserts are used to machine AISI 4340 steel on conventional N-26 lathe. Flank wear after 5min of machining for all inserts are calculated at fixed set of machining parameters to explore the performance of indigenouslydeveloped inserts. The self-lubrication phenomenon showed its effect on tool life i.e. thin layer (Patchy layer) formationincreases the life of novel inserts.
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P. Ganeshan,Yaramala Sravani,K. Raja,Bipin Kumar Singh 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.5
This investigation focused to develop 5 wt.% cerium oxide (CeO2) reinforced inside Zirconia Toughened Alumina (ZTA)ceramics for evaluation of functional properties which is still unexplored. At first, the homogeneous composites of CeO2/ZTAand ZTA are developed through powder metallurgy process sintered at 1600 oC. The morphological characterization ofdeveloped composites are carried out through field emission scanning electron microscopy (FESEM) and x-ray diffraction(XRD) followed by mechanical characterization on Vickers hardness tester. The morphological study reveals that theincorporation of CeO2 grains increases the average grain sizes of composites, adversely affect on the bulk density. The retentionof high amount of metastable tetragonal phases due to presence of CeO2 grains evaluated through XRD phase analysis showsbeneficial effect on hardness and fracture toughness. Furthermore, the significant improvement of 15.07% in fracturetoughness is attributed to the transformation toughening, crack bridging and deflection phenomenon. Formation of glazy andsmooth surface is responsible for improvement in coefficient of friction (COF) by 24.45% compared to parent matrix. Highabrasion, micro cracks, grain pullout are predominant factors responsible for wear on the ZTA surface, whereas, grain pulloutand micro cracks formation are responsible for wear in CeO2/ZTA.
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