IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Effect of transition metal ion pairs doping on the dielectric properties of mullite derived by sol-gel route
No full textIn this study, highly crystallized pure mullite was synthesized using the sol-gel method, and transition metal oxides (TiO2 and MoO3) were prepared and incorporated into the structure of mullite by an intensive solid-state mixing process. The derived precursor powders were compacted into tablets by hydraulic pressing and sintered at 1550 degrees C. X-ray diffraction analysis of the sintered compacts clearly indicated the formation of well-crystallized mullite and no other phases were detected. The microstructural features were investigated by scanning electron microscopy, and the findings revealed that the addition of TiO2 and MoO3 induced the mullite grains to grow anisotropically. The dielectric characteristics of the sintered samples were measured at increasing frequencies of 100 kHz to 1 MHz. The findings revealed that the mullite sample co-doped with TiO2 and MoO3 had the highest dielectric constant of 15.85 and the dielectric loss was 0.93 at 100 kHz
Three-dimensional cobalt-nitrogen-co doped carbon shells encapsulated NiFe-LDH as an advanced sensing platform for real-time electrochemical analysis of rutin
No full textIn this work, we designed a metal-organic framework (MOF) derived cobalt nanoparticles encapsulated nitrogenrich carbon with nickel iron-layered double hydroxide (Co-NC@NiFe-LDH) for real time electrochemical analysis of the antioxidant flavonoid-rutin (RUT). The prepared composite was examined by various analytical techniques, cyclic voltammetry, and differential pulse voltammetry. A glassy carbon electrode (GCE) modified with Co-NC@NiFe-LDH (Co-NC@NiFe-LDH/GCE) exhibited superior response for RUT along with excellent reproducibility, sensitivity, and selectivity which is attributed to the synergistic effects between the Co-NC and NiFeLDH, and enable excellent electron transfer across the electrode-electrolyte interface. The Co-NC@NiFe-LDH/ GCE responds linearly to RUT concentrations of 0.01 - 20.10 mu M and 20.10 - 267.31 mu M, with a limit of detection (LOD) and higher sensitivity of 5 nM and 11.898 mu A mu M-1 cm-2, respectively. These exceptional features of Co-NC@NiFe-LDH arise from its significant active sites, substantial surface area, and excellent electrolyte accessibility. The Co-NC@NiFe-LDH/GCE offers improved stability, with the initial oxidation peak current decreasing by <= 5% over 25 days of air exposure. The sensor demonstrated substantial recovery levels of 96.99 98.70%, 96.15 - 99.76%, and 97.86 - 99.74% for real-time analyses of serum, urine, and medicinal samples. This study paves the way for advanced sensing platforms in biomedicine and clinical applications, capitalizing on nanohybrid design
Preparation of stable and regenerable ceramic-supported-polymeric composite nanofiltration membrane with high flux and heavy metal removal performance
No full textNovel thin film composite nanofiltration membranes were prepared over ceramic substrate by interfacial polymerization (IP). Glutaraldehyde (GA) was used as crosslinker between aqueous phase monomer polyethyleneimine (PEI) and the ceramic surface in order to enhance the attachment between polyamide functional layer and ceramic substrate. PEI was further reacted with trimesoyl chloride (TMC) by IP technique to create denser crosslinked structure with lower pore size. The effect of GA crosslinking on IP of PEI and TMC was studied by varying the concentration of GA and PEI. Different coating approaches were explored to form stable and uniform functional layer over ceramic substrate. A series of composite membranes were fabricated and characterized using FESEM, EDX and XPS analyses. The membrane with optimum properties exhibited clean water permeability in the range of 20-32 Lm- 2h-1bar- 1 and highest rejection of 99.5 % for Cu(II), 99 % for Pb(II), 85 % for As(V) and 60 % for Cr(VI) from 5 mg/L aqueous solution. Finally, the robust ceramic substrate was regenerated by removal of the polymeric functional layer with 1000 mg/L & sdot;hr of free chlorine treatment followed by 1 min of ultrasonication at 33.3 KHz. Composite membrane prepared using the regenerated ceramic substrate showed similar flux and rejection properties compared to virgin membrane
Magnetic Chemiresistive Fe-Doped In2O3 Nanocubes to Tunably Detect NO2 at ppm to ppb Concentrations
No full textEnhancing the analyte detection limits and responses of a chemiresistive material generally requires modification of its composition and/or crystal-micro-electronic structures through synthesis routes. However, this cannot be applied for in situ tuning of the detection limit and sensitivity of chemiresistors. External stimuli, like temperature and ultraviolet–visible light, have predominantly been employed to improve the performance of a chemiresistor, rather than in situ smart generation of the ability to detect lower concentrations of analytes. Such smart functionality is crucial for multipurpose applications of sensors. Here we show that an external magnetic field instantaneously confers the ability of in situ selective detection of ppb level NO2 to ferromagnetic Fe-doped In2O3 nanocubes, which is otherwise not detectable by the same. Moreover, a remarkable more than five times enhancement in 20 ppm of NO2 response compared to pure In2O3 was achieved by Fe-doped In2O3 under the influence of a 0.5 mT magnetic field at 165 °C. Furthermore, a sensor module has been devised with an in-built electromagnet for in situ ppm to ppb tunable NO2 detection. This technique offers an effective yet simple way of transforming an ordinary sensor into a superior one, as demonstrated on several other chemiresistors. Magneto-chemiresistive behavior of Fe-doped In2O3 reveals an unexpected nonlinear correlation between magnetic field strength and NO2 sensing response. Enhanced adsorption of paramagnetic oxygen species, spin alignment, and electron deflection by Lorentz force are suggested as key factors in improving the sensor’s sensitivity
High-temperature oxidation-resistant glass-ceramic/YSZ composite coatings for gas turbine engine applications
No full textOxidation behavior of a novel double-layered thermal barrier coating (TBC) system consisting of glass-ceramic-25 wt.% yttria-stabilized zirconia (YSZ) bond coat and 8 wt.% YSZ top coat was investigated at 900 degrees C and 1000 degrees C for 100 h. Developed TBC system showed changes in phase, microstructure, and mechanical properties with increasing temperature. Zircon formation in the glass-ceramic during oxidation (1000 degrees C, 100 h) enhanced oxidation resistance of the TBC system. Weight gain per unit surface area was about 0.085 mg/cm(2) after 100 h at 1000 degrees C during oxidation test; whereas, it was much lower (similar to 0.04 x 10(-2) mg/cm(2)) at 900 degrees C after same period of time. Tetragonal zirconia (t-ZrO2) top coat changed to both cubic and tetragonal phases after 100-h exposure at 1000 degrees C. Nanohardness and Young's modulus values of bond coat and top coat were increased with increasing temperature
Effect of process parameters involved in SWJP on surface integrity and biocompatibility characteristics of AZ31B Mg alloy
No full textThis study mainly investigates the influence of combined parametric conditions employed in submerged waterjet peening for biomedical applications. On measuring the microhardness and roughness on the peened surface, the finding corresponded directly with the strengthening of subsurface layers and different parametric combinations. The optimum parametric combination was determined by TOPSIS, considering microhardness and surface roughness as input. Under optimal parametric combinations, surface morphology and topography analysis, XRD analysis, corrosion behaviour examination, and cell morphology and viability analysis were studied and compared to unpeened surface. From the experimental results, the water bubbles create impulsive pressure that impacts the AZ31B Mg alloy's surface, promoting plastic deformation in the subsurface, enhancing the surface morphological and topographical characteristics, and making the alloy more suitable for bioimplant manufacture. Following that, these samples underwent an electrochemical corrosion study, which indicates the peened region's corrosion rate was reduced considerably compared to the unpeened region. In the course of biocompatibility analysis, the non-toxic nature of the peened region in the MG63 cell line was observed after 24 and 72 h
One-pot synthesis of ligand-free highly active Pd catalyst supported on NiFe spinel oxide for Suzuki Miyaura cross-coupling reaction
No full textThis work underscores the development of an easily separable, very simple yet highly active heterogeneous Pd catalyst supported on Ni Fe spinel oxide containing a low percentage of noble metal Pd (only 1 at.) enabling the access to an advanced set of catalysts for SuzukiâMiyaura carbonâ carbon (CC) cross-coupling reaction that are not easily accessible with homogeneous catalysts. A series of catalytic experiments have revealed optimum reaction conditions for CC coupling between aryl bromide and phenyl boronic acid. Among a set of prepared catalysts, NiPdFe-1 (Ni/Pd molar ratio=1:1) is found to be the most active catalyst for the coupling reaction completing in just about 30 min under mild reaction conditions like 100 °C using Na2CO3 as the base in a very common organic solvent, DMF. Interaction between the oxide support and Pd(0) makes the Pd surface more electron-rich which accelerates the rate-determining step of the CC coupling reaction by faster electron transfer from Pd(0) to the aryl halides. Moreover, the catalyst is essentially heterogeneous, stable, magnetically separable and durable for several cycles without losing its activity. Good to excellent isolated yields have been obtained with a variety of functionalities on both the aryl bromide and phenyl boronic acid with varying electronic properties
Synthesis and in-vitro Evaluation of Zr-doped Radiopaque Bioactive Glass: A Possible Biomaterial for Endodontic Application
No full textWe have synthesized a sol-gel derived multifunctional silicate based bioactive glass composition[(70-x)SiO2-(30-y-z)CaO-xB2O3-yAg2O-zZrO2,wherein 1<x < 5,0.5<y < 2,0.005<z < 2 mol%] with radiopacity and antibacterial potency, for possible endodontic applications such as vital pulp therapy of paediatric population worldwide with a prevalence of dental caries and primary tooth decay. The composition was physicochemically characterized by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy –Energy Dispersive X-ray Analysis (FESEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), and ThermoGravimetric analysis –Differential Scanning Calorimetry (TG-DSC). The textural properties were measured by Brunauer-Emmett-Teller (BET) surface area measurement and N2 adsorption/desorption study. Next, the in-vitro bioactivity was assessed by soaking the sample in simulated body fluid (SBF).Apart from these, the in-vitro biological properties were assessed by performing cell migration assay, MTT[(3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide] colorimetric assay for cytotoxicity and proliferation assay, matrix mineralization assay on a embryonic fibroblast cell line which can differentiate into other type of cells depending upon the medium. In vitro antibacterial assay was performed on a gram + ve streptococcus.sp. bacterial strain which is the most susceptible oral bacteria and in situ radiopacity was evaluated by taking X-ray digital image and post processed to qualitatively analyze the radiopacity level. In summary the results revealed that the current composition has optimum radiopacity, antibacterial potency and has excellent migration/proliferation capability including calcium mineralization ability that is indicative of its application as a regenerative pulp capping material in endodontic application
Submicron graphite platelet-incorporated PVDF composite: an efficient body motion-based energy harvester for flexible electronics
No full textThe fast expanding field of wearable technology requires light-weight, low-cost, scalable, flexible and efficient energy harvesters as a source of uninterrupted green power. This work reports fabrication of sub-micron graphite platelet/PVDF composite film-based flexible piezoelectric energy harvester (PGEH) for scavenging the wasted mechanical energy associated with human body motion. The addition of graphite platelet leads to the enhancement of electroactive beta phase in PVDF; consequently, the piezoelectric and dielectric properties of the composite are enhanced. 0.5 wt% filler-loaded composite has 96% beta phase fraction and dielectric constant 32 at 100 Hz (tan delta = 0.18).The PGEH produces open circuit voltage of 40 V and instantaneous power density of 3.35 mW cm(-3) with energy conversion efficiency of 22.5% under periodic finger tapping. It can generate fair electrical output under gentle heel (0.8 V) and toe movements (1.2 V). A PGEH is directly employed for powering 50 commercial LEDs and quick charging of a 2.2-mu F capacitor upto 19.2 V. The device is also employed as self-powered dynamic pressure sensor which shows high sensitivity (0.9 VkPa(-1)) with fast response time (1 ms). Therefore, this durable, flexible, efficient PGEH can have promising applications in wearable electronics as a green power source cum self-powered mechanosensor
Hybrid Reduced Graphene Oxide/GaN Nanocolumns on Flexible Niobium Foils for Efficient Photoelectrochemical Water Splitting
No full textWe present the photoelectrochemical (PEC) water-splitting properties of pristine and reduced graphene oxide (rGO)-coated GaN nanocolumns (NCs) on flexible niobium (Nb) metal foils. The structural, optical, and electronic structure analyses of rGO-coated GaN-NCs on Nb foils revealed the formation of a rGO/GaN-NCs hybrid structure. Further, the valence-band studies of pure GaN-NCs shows valence-band maxima at similar to 3.0 eV below the Fermi level, which decreased to similar to 2.8 eV for rGO/GaN-NCs. The PEC measurement performed on pristine GaN-NCs under standard (1 Sun) conditions shows an effective photocatalytic nature with a photocurrent density of similar to 60 mu A/cm2 at 0.8 V (vs Ag/AgCl) in a 1 M oxalic acid electrolyte, which increases to similar to 110 mu A/cm2 for rGO/ GaN-NCs. The efficient PEC characteristics of rGO/GaN-NCs are attributed to the effective charge separation/transport of photogenerated carriers. Furthermore, transient photocurrent measurement reveals that hybrid and pristine GaN-NCs on flexible metal foil have a fast and stable photoresponse in an aqueous solution. The development of a hybrid nitride nanostructure-based PEC device on flexible metal foils paves the way toward developing scalable PEC devices for hydrogen production applications