IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Efficacy of Bioactive Glass Nanofibers Tested for Oral Mucosal Regeneration in Rabbits with Induced Diabetes
Get PDFThe healing of oral lesions that are associated with diabetes mellitus is a matter of great concern. Bioactive glass is a highly recommended bioceramic scaffold for bone and soft tissue regeneration. In this study, we aimed to assess the efficacy of a novel formula of bioactive glass nanofibers in enhancing oral mucosal wound regeneration in diabetes mellitus. Bioactive glass nanofibres (BGnf) of composition (1-2) mol% of B2O3, (68-69) mol% of SiO2, and (29-30) mol% of CaO were synthesized via the low-temperature sol-gel technique followed by mixing with polymer solution, then electrospinning of the glass sol to produce nanofibers, which were then subjected to heat treatment. X-Ray Diffraction analysis of the prepared nanofibers confirmed its amorphous nature. Microstructure of BGnf simulated that of the fibrin clot with cross-linked nanofibers having a varying range of diameter (500-900 nm). The in-vitro degradation profile of BGnf confirmed its high dissolution rate, which proved the glass bioactivity. Following fibers preparation and characterization, 12 healthy New Zealand male rabbits were successfully subjected to type I diabetic induction using a single dose of intravenous injection of alloxan monohydrate. Two weeks after diabetes confirmation, the rabbits were randomly divided into two groups (control and experimental groups). Bilateral elliptical oral mucosal defects of 10 x 3.5 mm were created in the maxillary mucobuccal fold of both groups. The defects of the experimental group were grafted with BGnf, while the other group of defects considered as a control group. Clinical, histological, and immune-histochemical assessment of both groups of wounds were performed after one, two and three weeks' time interval. The results of the clinical evaluation of BGnf treated defects showed complete wound closure with the absence of inflammation signs starting from one week postoperative. Control defects, on the other hand, showed an open wound with suppurative exudate. On histological and immunohistochemical level, the BGnf treated defects revealed increasing in cell activity and vascularization with the absence of inflammation signs starting from one week time interval, while the control defects showed signs of suppurative inflammation at one week time interval with diminished vascularization. The results advocated the suitability of BGnf as bioscaffold to be used in a wet environment as the oral cavity that is full of microorganisms and also for an immune-compromised condition as diabetes mellitus
Elucidating the effect of CaF2 on structure, biocompatibility and antibacterial properties of S53P4 glass
No full textThe present work focuses on the synthesis and structural elucidation of fluoride containing bioactive glasses in the system (in mol%) given by (53.86) SiO2 – (22.65) Na2O – (21.77-x) CaO – (1.72) P2O5 – x CaF2, where, x = 0, 5.44, 10.885 and 16.33. The role of the incorporated fluoride and its distribution within the glass were interpreted and analyzed using Molecular dynamics (MD) simulations and the results were compared with the modified random network (MRN) model. The interpretations from the model have been verified using the MAS-NMR spectroscopy technique. According to this model, fluoride containing bioactive glasses have been proposed to consist of silicate rich network regions and modifier cation – fluoride rich inter-network regions. The interface region was found to consist of non-bridging oxygen species (NBO) and phosphate cations which are either isolated orthophosphates (Q0P) or bridged with silicates in the form of pyrophosphate (Q1P) units forming Si–O–P bonds. The gradual substitution of CaF2 for CaO in the base glass resulted in an increase in the silicate network connectivity with a reduction in the NBOs and lead to an increase in the association of modifier cations with fluoride ions. However, fluoride ions were found to show a marginal preference to associate with Na+ cations leading to a decrease in the association of Na+ ions with orthophosphate and silicate units. These overall structural findings were correlated with the in vitro ion dissolution behaviour of the bioactive glasses as well as with the thermal properties. The glasses were tested for their in vitro cell viability towards mouse osteoblast type (MC3T3) cells in which fluoride containing bioactive glasses did not show any toxicity and exhibited better cell proliferation. The antibacterial efficacy of the fluoride containing glasses was tested at various concentrations (5, 10 and 20 mg/ml) in E.coli bacterial inoculum in which bactericidal action was evidenced
Integrated photonic materials for the mid-infrared
No full textWhile silicon photonic integrated circuits for the near-infrared (IR) telecommunication band have attracted great research interest in the past decade, recent advances offer opportunities to extend the operational wavelength to the mid-IR (2.5-20 mu m) for free space communications, sensing, environmental monitoring and much more. In this study, we will comprehensively review the current status of materials available for mid-IR waveguides and waveguide integrated photodetectors, with a few application oriented examples to illustrate the technological importance and significant growth opportunity for integrated photonics in the mid-IR regime. However, this wavelength regime also presents new material design and fabrication challenges. Therefore, we will discuss the critical issues prior to commercialization and will briefly summarize the outlook on future research topics along with opportunities
Spark plasma sintering processed alpha-SiAlON bonded tungsten carbide: Densification, microstructure and tribomechanical properties
No full textProcessing, microstructure and tribomechanical performance of spark plasma sintering (SPS) processed alpha-SiAlON bonded tungsten carbide (WC) have been reported. SPS at 1750 degrees C under 40 MPa for 25 min resulted in almost theoretically dense composites. Microstructure analysis using scanning and transmission electron microscopy revealed formation of principally micron sized, equiaxed WC grains surrounded by sub-micron to micron sized alpha-SiAlON having both equiaxed (higher concentration) and elongated (lower concentration) grain morphology. Sharp and clean WC/alpha-SiAlON interface regions were noticed without any interfacial reaction product. As evidenced from elemental mapping under HAADF-STEM, the alpha-SiAlON grain boundary region was found to be rich in yttrium and oxygen, whereas, presence of characteristics elements were identified in alpha-SiAlON and WC grains. Addition of alpha-SiAlON in WC matrix resulted in progressive improvement in tribomechanical performance of the composites compared to pure WC. The 40 wt% alpha-SiAlON bonded WC matrix composite offered almost 30-33% higher Vickers hardness and toughness than those obtained for pure WC. Three point flexural strength of the 40 wt% alpha-SiAlON/WC composite was found to be around 425 MPa. Unlubricated wear tests also indicated significantly higher damage of hard and tough beta-Si3N4 ball when sliding against the composites compared to pure WC. Formation of progressively thicker and adherent tribolayer containing broken particles of WC and alpha-SiAlON having sharp edges was possibly the primary reason that caused severe abrasive wear of the counterbody. Results indicated the efficacy of SPS processed alpha-SiAlON bonded WC composites having improved tribomechanical performance over conventional monolithic WC
Intermittent events due to spectral filtering induced multi-pulsing instability in a mode-locked fiber laser
No full textIn this paper, numerical simulations of an all-normal dispersion ring cavity mode-locked fiber laser have been reported, revealing the existence of rogue waves in the chaotic transition regime between a stable single-pulse state and a multi-pulse state. The chaotic states manifest as a result of multi-pulsing instability induced by the intra-cavity spectral filtering effect and were studied by gradually decreasing the filter bandwidth from a stable or quasi-stable state to a stable multi-pulsing state. For a specific set of cavity parameters and a range of Gaussian-shaped filter bandwidths, stable dissipative solitons characterized by a cat-ear-shaped spectrum were obtained. Reducing the filter bandwidth below the stable range first produced non-stationary quasi-stable states containing multiple soliton explosions and then eventually a stable multi-pulsing state with individual dissipative solitons. The histograms of spectral intensities in the quasi-stable states exhibited long-tailed distributions containing rogue waves. Rogue waves were also observed during the build-up of the dissipative soliton from white Gaussian noise even though the pulse finally evolved to a stable state. By modifying the cavity parameters, noise-like pulses (NLPs) were obtained which are by nature a quasi-stable state and exhibited rogue waves in the spectral intensity histogram. In the NLP state of operation, the reduction of filter bandwidth below a certain range produced multiple dissipative solitons with stable waveform. Additionally, the influence of different filter shapes on the state transition dynamics was also explored. It was found that the range of filter bandwidths for which chaotic states exist varies for different filter shapes depending on their spectral confinement. (C) 2020 Optical Society of Americ
Preparation of colloidal hydrated alumina modified NaA zeolite derived from rice husk ash for effective removal of fluoride ions from water medium
No full textAlumina is found to be a good adsorbent for the removal of fluoride. In the present study, rice husk ash-derived NaA zeolite has been modified with colloidal hydrated alumina in a cost-effective process for efficient removal of fluoride ions. The prepared NaA zeolite powder was added into colloidal hydrated alumina under stirring at 70 degrees C/2 h followed by drying at 100 degrees C/6 h to obtain modified zeolite. The product reveals enhanced adsorption efficiency (95-99%) for the removal of fluoride ions at wide ranges of adsorbate concentration (similar to 5-200 mg/L), adsorbent concentration (0.5-10 g/L), pH (3-10), and temperature (30-70 degrees C). Regeneration study shows that adsorption remained >90% up to third cycle followed by gradual decrease of adsorption for consecutive cycles. Kinetics study of fluoride adsorptions shows best fit for pseudo-second-order model demonstrating chemisorption process through a monolayer formation. The adsorption isotherm reveals that Langmuir isotherm is the best fit model indicating maximum adsorption capacities of 104.16, 68.12 and 36.13 mg/g for the adsorbent doses of 0.5, 1 and 2 g/L, respectively. Colloidal hydrated alumina modified NaA zeolite derived from rice husk ash could be utilized as low cost adsorbent for effective removal of fluoride ions from water
Properties of multiple oxide-bonded porous SiC ceramics prepared by an infiltration technique
No full textMultiple oxide-bonded porous SiC ceramics were fabricated by infiltrating a porous powder compact of SiC and alumina with cordierite sol followed by sintering at 1300-1400 degrees C in air for 3 hours. The microstructures, phase components, mechanical properties, and air permeation behavior of the developed porous ceramics were examined and compared with materials obtained by the traditional powder processing route. The porosity, average pore diameter, and flexural strength of the ceramics varied from 33 to 37 vol%, similar to 12-14 mu m and similar to 23-39.6 MPa, respectively, with variation in sintering temperature. The X-ray diffraction results reveal that both the amount of cordierite and mullite as the binder increased with increase in sintering temperature. In addition, it was found that the addition of alumina in powder form effectively enhanced the strength due to formation of mullite in the bond phase in contrast to the samples prepared without alumina additive. To determine the suitability of the material in particulate filtration application, particle collection efficiency of the filter material was evaluated theoretically using single collector efficiency model
Study of non-centrosymmetric to centrosymmetric structural transformation in Zr-doped Barium Titanate
No full textNon-centrosymmetric to centrosymmetric structural transformation of BaZrxTi1-xO3 (x = 0, 0.05, 0.1, 0.3) as prepared by soilid state reaction was investigated from X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), pair distribution function (PDF) and Raman spectra. Tetragonal BaTiO3 transformed to orthorhombic phase for lower Zr concentration (x = 0.05) and changed to tetragonal to cubic with increasing Zr concentration at room temperature. Dielectric constant changed with the addition of Zr due to the change in local atomic arrangement and achieved highest value 1444 for mole fraction x = 0.1. Change occurred in the intensity for the first Ti-O pair in the PDF pattern due to the incorporation Zr in barium titanate lattice. An extra shoulder due to addition of Zr for the cubic phase of BZT has appeared at 5.64 angstrom in the PDF pattern. Structural and electrical properties of BZT were influenced by additions of Zr due to the change in local atomic arrangement
Synthesis and characterization of Nanocrystalline Ba0.6Sr0.4Co0.8Fe0.2O3 for application as an efficient anode in solid oxide electrolyser
No full textNanocrystalline Ba0.6Sr0.4Co0.8Fe0.2O3 (BSCF-6482) powder is synthesized by combustion synthesis technique. Powder calcined at 1000 degrees C reveals phase pure cubic perovskite. Transmission electron microscopic (TEM) analysis exhibits soft agglomerates of average size similar to 50 nm wherein interplanar spacing for (110) and (221) resembles to the cubic lattice. While DC electrical conductivity of 23 S cm(-1)@800 degrees C is observed, interfacial polarization measured by electrochemical impedance spectroscopy is found to be the least 850 degrees C (0.18 Omega cm(2)). Cell performance has been compared among BSCF-6482, BSCF-5582 and LSCF-6482 mixed ionic and electronic conducting (MIEC) and conventional electrode (LSM). Higher performance (1.37 A/cm(2)@1.3 V,800 degrees C) with high hydrogen generation rate (0.57 Nl/cm(2)/h) is found during steam electrolysis with cell fabricated using BSCF-6482 having minimal area specific resistance 0.33 Omega cm(2). Under similar operating condition, BSCF-5582, LSCF-6482 and LSM exhibit hydrogen generation rate of 0.35, 0.28 and 0.23 Nl/cm(2)/h respectively. Cell microstructure is clinically correlated with the higher reactivity of BSCF-6482 air electrode in steam electrolysis. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
PDMS/ceramic composite membrane synthesis and evaluation of ciprofloxacin removal efficiency
Get PDFThe present study employs an unexplored, one-step route for remediation of ciprofloxacin, an emerging contaminant, using hydrophobically modified ceramic membranes. Hydrophobic interaction between the membrane and the target contaminant, i.e., ciprofloxacin, is the governing factor responsible for its removal. The hydrophilic surface of hollow, single channel, macroporous clay-alumina membranes was made hydrophobic using cross-linked polydimethylsiloxane. The influencing parameters-concentration of polymer, cross-linking agent, catalyst and coating time-were optimized by Taguchi analysis to yield a membrane with enhanced ciprofloxacin rejection and high permeate flux. The synthesized membrane was characterized for its contact angle, clean water permeability, degree of swelling, degree of cross-linking, X-Ray diffraction, atomic fluorescence microscopy, field emission scanning electron microscopy. Effect of various operating parameters-cross flow velocity, transmembrane pressure, filtration time, solution pH-was investigated upon removal of ciprofloxacin in cross flow membrane filtration. Maximum rejection of 99.3% was obtained by the hydrophobic membrane having contact angle of 138.5 degrees for 5 mg/L feed solution. The stability of the membrane was judged in terms of change in ciprofloxacin rejection upon filtration for five consecutive cycles, each cycle being 180 min. The developed PDMS/ceramic composite membranes could have great prospect for long-term application in removal of emerging contaminants from water