IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Improving visible-light-induced photocatalytic ability of TiO2 through coupling with Bi3O4Cl and carbon dot nanoparticles (vol 238, 116404, 2020)
No full textSpectroscopic comprehension of Mott-Hubbard insulator to negative charge transfer metal transition in LaNixV1-xO3 thin films
No full textThe room-temperature (300 K) electronic structure of pulsed laser deposited LaNixV1-xO3 thin films has been demonstrated. The substitution of early-transition metal (TM) V in LaVO3 thin films with late-TM Ni leads to the decreasing in out-of-plane lattice parameter. Doping of Ni does not alter the formal valence state of Ni and V in LaNixV1-xO3 thin films, divulging the absence of carrier doping into the system. The valence-band spectrum is observed to comprise incoherent structure owing to the localized V 3d band along with the coherent structure at Fermi level. With increase in Ni concentration, the weight of the coherent feature increases, which divulges its origin to the Ni 3d-O 2p hybridized band. The shift of Ni 3d-O 2p hybridized band towards higher energy in Ni-doped LaVO3 films compared to the LaNiO3 film endorses the modification in ligand to metal charge transfer (CT) energy. The Ni doping in Mott-Hubbard insulator LaVO3 leads to the closure of the Mott-Hubbard gap by building of spectral weight that provides the delocalized electrons for conduction. A transition from bandwidth control Mott-Hubbard insulator LaVO3 to negative CT metallic character in LaNiO3 film is observed. The study reveals that unlike in Mott-Hubbard insulators, where the strong Coulomb interaction between the 3d electrons decides the electronic structure of the system, CT energy can deliver an additional degree of freedom to optimize material properties in Ni-doped LaVO3 films
Correlation of structure and ionic-conductivity in phosphate glass using MAS-NMR and impedance spectroscopy: Influence of sodium salt
No full textIn the process of diminishing the safety concerns of sodium-ion batteries, the development of glass-based solid electrolyte materials has received adequate interest. Nevertheless, achieving a high ionic-conductivity at room temperature for glass materials remains a challenging task because of the poor correlation between the conductivity and the glass structure. Here, we attempt to understand the effective influence of NaC1 on the structure and ionic-conductivity of the phosphate-based glass network. For this study, xNaCl-(100-x) (31.725 Na2O-12.69 Al2O3-31.725 P2O5-8.46 NaF-5.40 Na2SO4-10 MoO3) glass systems (mol %) were selected, where x = 0, 5, 10, 15, and 20 mol %. To investigate structural changes with the addition of different NaCl concentrations, Al-27, Na-23, P-31 magic angle spinning nuclear magnetic resonance (MAS-NMR), P-31 two-dimensional (2D) phase-adjusted spinning sideband (PASS), and P-31 2D J-resolved NMR techniques and Raman spectroscopic techniques were utilized. Impedance spectroscopy and ac conductivity spectra were used to assess ionic-conductivity and sodium-ion dynamics, respectively. Impedance spectral analysis reveals that the ionic-conductivity of the base glass is increased by 2.4 times (from 1.85 x 10(-7) to 4.44 x 10(-7) S/cm at 373 K) with the addition of 20 mol % of NaCl. Raman spectra confirm the presence of P-O-Mo and the absence of Mo-O-Mo bonds in these glass systems, and P-31 2D J-resolved spectra indicate the absence of P-O-P bonds. Upon increasing the NaCl concentration, significant changes in the shapes of P-31 and Al-27 MAS-NMR spectra were observed, indicating the effective influence of NaCl on the distribution of alumina and phosphorus structural units. Irrespective of the temperature, sodium-ion dynamic studies show that the mean-square displacement decreases with increasing NaCl concentration up to 10 mol % and then increases with a further increase in NaCl concentration. This investigation aids in understanding the sodium-ion dynamics and the structural information of a multicomponent glass system to enhance the room-temperature conductivity
Observation of structural change-driven Griffiths to non-Griffiths-like phase transformation in Pr2-xSrxCoFeO6 (x= 0 to 1)
No full textThe study of crystal structure, electronic structure, transport, and magnetic properties of heterovalent Sr2+ doped Pr2-xSrxCoFeO6 (x = 0.0 to 1.0) system have been done. Crystal structure study reveals an occurrence of structural change from orthorhombic (Pnma) to tetragonal (I4/m) phase above x = 0.6. A sudden transformation of the Griffiths-like to non-Griffiths-like magnetic phase is observed as the system changes its crystal structure from Pnma to I4/m. The X-ray photoemission spectroscopy (XPS) study suggests for the existence of mixed oxidation states of the B-site ions viz., Co3+/Co4+ and Fe3+/Fe4+, and it also indicates an increase in the mean oxidation states owing to the hole substitution (Sr2+). The temperature variation of the electrical resistivity of the studied systems follows two different transport mechanisms, such as the variable range hopping (VRH) (in the lower temperature region) and small polaron hoping (SPH) (in the higher temperature region) models. Dc magnetization study shows that a local competing ferromagnetic (FM) exchange interaction increases with Sr doping. Finally, the ac susceptibility study reveals breaking of the long-range-ordering in the system x = 1.0, which appears to be related to the structural change and enhanced spin frustration due to increased competing local FM exchange interactions. In addition, electronic density of states (DOS) calculations of PrSrCoFeO6 (i.e. x = 1.0) using the density functional theory (DFT) have been performed for various Co/Fe atomic distributions. For most of the Co/Fe atomic distributions studied, the calculations show that the total energy of the system with FM coupling among spins has slightly lower energy than that for antiferromagnetic (AFM) coupling
Design of Cuboidal FeNi2S4-rGO-MWCNTs Composite for Lithium-Ion Battery Anode Showing Excellent Half and Full Cell Performances
Get PDFTernary metal sulfides are projected as advanced lithium-ion battery (LIB) anodes due to their superior electronic conductivity and specific capacity compared to their respective oxide counterparts. Herein, a porous composite of cuboidal FeNi2S4 (FNS) with 2D reduced graphene oxide (rGO) and 1D multi-walled carbon nanotubes (MWCNTs) (composite name: FNS@GC) synthesised by an in-situ single-step hydrothermal process. The 1D/ 2D combined thin carbon coatings on the FeNi2S4 prevent aggregation during battery performance by increasing conductivity and resisting the volume changes at lithiation/de-lithiation processes. Consequently, the FNS@GC composite exhibits a commending electrochemical performance with a charge capacity of 797 mAh g(-1) and a first cycle coulombic efficiency of similar to 67% with reversible capacity restoration property and excellent long-term cycling stability. Furthermore, FNS@GC/ /LiFePO4 full cell reveals its practical applicability as a LIB anode with a reversible capacity of 77 mAh g(-1) at 50 mA g(-1) current density
Fundamental understanding of the size and surface modification effects on r(1), the relaxivity of Prussian blue nanocube@m-SiO2: a novel targeted chemo-photodynamic theranostic agent to treat colon cancer
No full textA targeted multimodal strategy on a single nanoplatform is attractive in the field of nanotheranostics for the complete ablation of cancer. Herein, we have designed mesoporous silica (m-SiO2)-coated Prussian blue nanocubes (PBNCs), functionalized with hyaluronic acid (HA) to construct a multifunctional PBNC@m-SiO2@HA nanoplatform that exhibited good biocompatibility, excellent photodynamic activity, and in vitro T-1-weighted magnetic resonance imaging ability (r(1) similar to 3.91 mM(-1) s(-1)). After loading doxorubicin into the as-prepared PBNC@m-SiO2@HA, the developed PBNC@m-SiO2@HA@DOX displayed excellent pH-responsive drug release characteristics. Upon irradiation with 808 nm (1.0 W cm(-2)) laser light, PBNC@m-SiO2@HA@DOX exhibited synergistic photodynamic and chemotherapeutic efficacy (similar to 78% in 20 minutes) for human colorectal carcinoma (HCT 116) cell line compared to solo photodynamic or chemotherapy. Herein, the chemo-photodynamic therapeutic process was found to follow the apoptotic pathway via ROS-mediated mitochondrion-dependent DNA damage with a very low cellular uptake of PBNC@m-SiO2@HA@DOX for the human embryonic kidney (HEK 293) cell line, illustrating its safety. Hence, it may be stated that the developed nanoplatform can be a potential theranostic agent for future applications. Most interestingly, we have noted variation in r(1) at each step of the functionalization along with size variation that has been the first time modelled on the basis of the Solomon-Bloembergen-Morgan theory considering changes in the defect crystal structure, correlation time, water diffusion rate, etc., due to varied interactions between PBNC and water molecules
Generation of pure sinusoidal continuous wave from dual-wavelength neodymium-doped all-fiber laser using bismuth-doped fiber as a filter
No full textDual-wavelength neodymium-doped fiber laser at 1.08 mu m based on bismuth-doped fiber in a ring cavity has been experimentally demonstrated. Using bismuth-doped fiber as a spectral filter introduces intensity-dependent gain to alleviate mode competition caused by homogeneous gain broadening in neodymium-doped fiber. A pure sinusoidal continuous wave with repetition rate of 9.1 MHz was generated at the output. At room temperature, the consistency in output intensity and the wavelength proves the steadiness of the proposed fiber laser. The system is simple, compact and in all-fiber configuration
Novel Dopant Tailored Fibers Using Vapor Phase Chelate Delivery Technique
No full textThe vapor phase chelate delivery (VPCD) technique in conjunction with the modified chemical vapor deposition (MCVD) process is adopted to fabricate fibers with customized doping profiles. The three large-mode area (LMA) step-index fibers with different rare-earth doping profiles in the core region, such as uniform doping, centralized doping, and circumferential doping, are fabricated by optimizing the fabrication parameters. The fibers are tested in a cladding-pumped amplifier configuration and their output beam qualities and signal-to-noise ratio (SNR) are characterized. The investigation reveals that the fiber with centralized doping in the core region exhibits lower M 2 compared with the fibers with uniform and circumferential doping, as it has a lower overlap of the higher-order modes with the doped region. The experimental result is further affirmed through theoretically simulated results. The developed fabrication technique shows potential to fabricate specialty fibers of varied designs, where customized doping profiles are required
Processing of oxide bonded porous silicon carbide ceramic membrane for microfiltration applications
No full textPorous silicon carbide (SiC) ceramics has been considered as an excellent engineering
materials for various industrial application such as diesel particulate filter, mechanical seals,
petroleum refining, catalytic supports, chemical refining, hot gas & molten metal filters, gas
turbine system, heat exchanger, wastewater filtration etc. due to its excellent porous structure
with narrow pore size distribution, high temperature mechanical strength, high hardness, high
thermal conductivity value, low thermal expansion coefficient, good thermal shock
resistance, excellent corrosion resistance and thermal shock value etc. However, a major
problem with SiC based non-oxide ceramic materials is their low sinterability due to their
strong covalent bonds between C and Si. Depending on the application of porous SiC
ceramics, various methods were used to fabricate porous SiC ceramics. In most of these
methods SiC need to be sintered at very high temperatures using selective sintering additives,
expensive atmospheres, costly equipment and delicate instrumentation. Recently porous SiC
ceramics are produced by most simple and cost effective oxide bonding method. In oxide
bonding technique porous SiC compact is heat treated in presence of air and during heat
treatment the oxidised silica coming from the surface of SiC reacts with oxide additives (such
as Al2O3, MgO, CaO etc.) to form secondary bond phases between SiC particles. Considering
the cost of raw materials, ease and repeatability of formation including low temperature
formation possibility of the bond phases the oxide bonds are very popular for SiC systems of
materials, substantial research work has been initiated all over the globe for the development
of oxide bonded porous SiC ceramics; still there are many unresolved issues that need further
attentions. For example, the evolution of the bond phase and the chemical reactions
responsible for bond phase formation and the influence of burning of any carbonaceous pore
former on bond phase formation of SiC and the cost of the final ceramics are the major global
unresolved issues. Finally, effects of the processing parameters on the material and
mechanical properties, permeation behaviour and waste water filtration behaviour of porous
SiC ceramics need systematic investigations. The beginning materials must be well dispersed
with the sintering additive and the pore former in order to achieve significant filter
performance improvements.
Inspired by these possibilities in this present thesis work, porous SiC ceramics bonded with
silica and mullite phases were prepared by oxide bonding method at low temperature. In this
work, SiC powder compact were prepared by taking desired amounts of SiC, Al2O3, Clay, Fly
ash (source of bond phase additives) etc. powders. Different volume fractions of pore former were used for generation of porosity. Sintering involves burning out the pore former at a
temperature higher than that at which it burns (mostly at 800°C) in order to create pores.
Temperature higher than 700°C, the SiC particles under slow oxidation, leading to formation
of silica and with increase in temperature, the process become fast. At temperatures (1000 to
1400°C) oxidation derived silica reacted with Al2O3 to form silica, mullite, which bonds SiC
particles together and produced a rigid porous body. Also in this study, cordierite precursor
were incorporated in porous SiC compacts by using an infiltration technique and developed
of oxide bonded porous SiC ceramics following a low temperature sintering method. The
reasons behind the selection of these bond phase systems are their useful properties, such as
high refractoriness, low thermal expansion coefficient nearly with SiC, low oxygen diffusion
coefficient, low dielectric constant, good thermal and chemical stability etc. The effect of
amount of sintering additives, metal catalyst, sintering temperatures, pore formers, on the
bonding phase formation and the properties of the final ceramics are evaluated. Air
permeability, pure water permeability and waste water filtration studied were also studied by
using this ceramic membrane. The thermal shock and corrosion resistance properties were
evaluated.
Mullite bonded SiC ceramic membranes were synthesized by recycling industrial waste fly
ash as a source of bonding phase, SiC as raw materials, and MoO3 as sintering catalyst for
growth of mullite at 1000°C by oxide bonding method. To investigate the effect of MoO3
catalyst on the mullitization reaction, microstructural and mechanical properties of the final
ceramics, four different SiC ceramics compositions having different amount of MoO3 content
were prepared. In the final mixture three different pore forming agent were used to increase
the porosity of the ceramics and observed its effects on the permeability parameters and
filtration characteristics. To characterise material properties of the final ceramics porosity,
density and % oxidation were evaluated. XRD, Rietveld, SEM mechanical properties and
pore size distribution pattern were analysed in order to identify major phases with their
content, morphologies, mechanical strength and pore diameters of porous SiC ceramics. The
porosity, flexural strength and the pore size of the final ceramics were varied from ~36-45
vol%, ~38-28 MPa, and ~2.9-4.0 µm respectively. TG-DTA data indicated that the
mullitization reaction had occurred at comparatively lower temperature at 1000°C in presence
of MoO3. From the air & water permeation study, the ceramics prepared in this work showed
coefficient value k1, k2 and specific water permeability (SP) value in the range of 7.30×10-15
to 2.66×10-13 m
2
, 1.18×10-11 to 2.63×10-8 m, and 1532 to 6113 Lm-2
h
-1
bar-1
respectively. The membranes showed a high separation efficiency of oil, COD, TDS and turbidity of ~93-89%,
~92-82%, ~91-89% and ~94-91% from kitchen wastewater and also it showed high turbidity
removal efficiency 99.5% from synthetically prepared kaolinite turbid water.
In another approach mullite-bonded porous SiC ceramics membranes also prepared using
commercial SiC powder, alumina, alkaline oxide clay as sintering additives, and different
sacrificial pore formers. The effect of pore formers on materials, microstructural properties,
and air and water permeability of porous ceramic were investigated. A variation in porosity
from 38-50 vol%, pore diameter 3.7- 6.5 μm, and flexural strength 28-38 MPa of the final
ceramics were observed depending on the characteristics of the pore former. The Darcian (k1)
and non-Darcian (k2) permeability evaluated from air permeation behaviour at room
temperature was found to vary from 1.48 × 10−13 to 4.64 × 10−13 m
2
and 1.46 × 10−8
to 6.51 ×
10−8 m, respectively. High oil rejection rates (89%-93%) were obtained by all membranes
from feed wastewater containing 1557 mg/L oil. A very high pure water permeability of
13298 Lm-2
h
-1
bar-1 was obtained with membrane having porosity of 48 vol% and mechanical
strength of 31.5 MPa.
To avoid the agglomeration of bond phase additives during powder processing method,
another infiltration assisted method was considered to develop porous ceramics with
homogeneous distribution of bond phases. Following infiltration technique, multi-oxide
bonded porous SiC ceramics were prepared at 1300‐ 1400°C by sintering a powder compact
of SiC and Al2O3, infiltrated with cordierite sol. The microstructures, phase components,
mechanical properties and air permeation characteristics of multi-oxide bonded porous SiC
ceramics were examined and compared with materials obtained via a powder processing
route. A variation in sintering temperature affected porosity, average pore diameter, and
flexural strength of the ceramics. For instance, porosity varied from 33 to 37 vol%, average
pore diameter was ~12‐ 14 μm, and strength varied from 23-39.6 MPa. According to the Xray diffraction results, both cordierite and mullite content increased with the increase in
sintering temperature. Furthermore, the presence of alumina powder in the final ceramics
improved strength due to the formation of mullite in the bond phase in contrast to the samples
prepared without alumina. A single collector efficiency model was used to theoretically
determine the particulate filtration efficiency of the developed ceramics. The result indicated
that the material developed in this study have strong application possibilities in pollution
control. The impact of the amount of bond phase alumina additive and the sintering temperature on
phase evolution, microstructure, pore size distribution, flexural strength, thermal shock
resistance, and corrosion resistance properties of the in-situ mullite bonded porous SiC
ceramics were also studied. The alumina content was varied from 5-10 wt%, and porous SiC
ceramics were fabricated via reaction sintering at 1300-1500°C for 4h. Porous mullite bonded
SiC ceramics prepared at 1400C with 10 wt% alumina additive exhibited highest mechanical
strength of ~ 58 MPa at porosity level ~27 vol%. Temperature-dependent thermal shock
resistance of porous SiC ceramics due to cooling was evaluated as a function of quenching
temperature (from 0°-1200°C) and quenching frequency (up to 10 cycles) using the air and
water-quenching technique. A laboratory corrosion study of SiC ceramics was conducted at
1000°C for 96–240 hours in presence of steam, coal ash, and both steam and coal ash. With
corrosion duration and medium, the apparent change in mass, porosity, and density was
recorded. The corroded samples were evaluated with SEM, XRD, and mechanical tests and
the results indicated water vapour is the perpetrator for strength degradation. Thermal and
other corrosion results indicated that the material has strong application possibilities in hot
gas filtration.
The oxide bonding technique and the utilization low cost starting materials were found to be
an effective way synthesizes cost effective porous SiC membrane at lower temperature with
improved mechanical, corrosion and thermal shock resistance properties. The methods
developed in this study can be effectively utilized in the fabrication of porous SiC ceramics
for various applications such as hot-gas filtration, wastewater filtration, catalytic support, etc
Beneficial effect of Sn doping on bismuth ferrite nanoparticle-based sensor for enhanced and highly selective detection of trace formaldehyde
No full textPure and sn-doped bismuth ferrite (BFO) nanoparticles were synthesized via facile sol-gel technique. Structural and morphological analysis of the nanoparticles were systematically carried out by using X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy and Bru-nauer-Emmett-Teller techniques. The gas sensing properties of the sensors based on prepared nanoparticles towards formaldehyde in the temperature range from 200 ? to 400 ? revealed that the doping of Sn enhances the formaldehyde sensing performance of BFO nanoparticle by few folds. Prepared sensors demonstrate p-type behaviour and high selectivity towards formaldehyde. It was observed that the sensor based on 1.5 % Sn doped BFO nanoparticles exhibited maximum sensing response of 3.05 (R-g/R-a) to 1 ppm formaldehyde. Prepared sensors were ultra-fast (response/recovery time of 2.71 s/25.22 s) and very stable having low detection limit of 100 ppb. The enhancement of formaldehyde sensing property due to sn-doping is a combined effect of variation of charge carriers due to valency mismatch and enhanced oxygen defects as confirmed from X-ray photoelectron spectroscopy study. sn-doped BFO nanoparticles could be a potential candidate for the detection of trace formaldehyde gas towards the monitoring of both indoor and outdoor environmental air quality