IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
Not a member yet
4657 research outputs found
Sort by
Biocompatibility and cyclic fatigue response of surface engineered Ti6Al4V femoral heads for hip-implant application
No full textA major problem with femoral head (FH) for hip implant (HI) applications is that it often fails in service. As a result, revision surgery becomes a must. The related trauma is tremendous for the patient, especially the aged ones. This also implies additional expenses. Keeping these aspects of the problem in view, here we report the development of wear, corrosion and fatigue resistant Ti6Al4V alloy based FH; by a duplex surface engineering (DSE) technique. Thus, the DSE based FHs are developed by a novel combination of plasma nitriding (PN) and Ti/TiN multilayer coating (MLC). The MLCs are formed by magnetron sputtering technique. The Ti6Al4V based FHs are called Ti. The only plasma nitrided FHs are called TiPN. The DSE based FHs are called TiPNML. The corrosion resistances are studied in hank's solution. The sliding wear resistance is studied in simulated body fluid (SBF). The biocompatibilities are studied by the standard MTT assay technique. The cyclic fatigue resistance behaviour up to one million walking cycles is studied in SBF in a HIP simulator with the UHMWPE acetabular cups used as the counter bodies in articulation. The results of the corrosion, biocompatibility, wear, and cyclic fatigue resposnses clearly reveal that the performances of the TiPNML and TiPN FHs are much better than that of the Ti based FHs. The reasons behind such spectacular improvement in biocompatibility as well as corrosion, wear and fatigue resistance are explained in terms of the prevalent phases, microstructural factors, wear mechanisms and surface roughness. The implications of the current results in terms of futuristic FH developments for HI applications are discussed. Such futuristic FH development could provide better HI. These prospects would minimize HI failure and hence, revision surgeries. Thus, the related trauma for numerous patients; especially the aged ones; could be significantly reduced
Conjugated polymer nanostructures displaying highly photoactivated antimicrobial and antibiofilm functionalities
No full textThis work reports the use of conjugated polymer nanostructures (CPNs) as photoactivated antimicrobial compounds against Gram-positive and Gram-negative microorganisms. Two representative CPNs of polythiophene (PEDOT) and polyaniline (PANI) were prepared as nanofibres with an average diameter of 40 nm and length in the micrometer range. Both CPNs exhibited strong antimicrobial activity under UVA irradiation with the same fluence rate as the UVA component of the solar spectrum. The effect was tested using the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Escherichia coli. The reduction of colony forming units (CFUs) reached >6 log for PEDOT concentrations as low as 33 ng mL(-1). For PEDOT nanofibers, a complete inhibition of S. aureus and E. coli growth was reached at 883 ng mL(-1) and 333 ng mL(-1) respectively. The photoactivation effect of PANI nanofibres on S. aureus and E. coli was also high, with a CFU reduction of about 7 log and 4 log respectively for an exposure concentration of 33 ng mL(-1). The antimicrobial activity was only high under light irradiation and was almost negligible for bulk PEDOT and PANI. The effect of polymeric nanofibers could be attributed to the photoinduced generation of reactive oxygen species, which may induce cell membrane damage, eventually leading to bacterial impairment and inhibition of their biofilm forming capacity. CPN PEDOT and PANI coatings were able to keep surfaces free of bacterial attachment and growth even after 20 h of previous contact with exponentially growing cultures in the dark. PEDOT and PANI CPNs demonstrated good cytocompatibility with human fibroblasts and the absence of hemolytic activity. The materials demonstrated advantages in terms of broad antibacterial spectrum, biofilm inhibition, and the absence of acute toxicity for biomedical applications
Role of dew points and Fe pre-coats on the galvanizing and galvannealing of dual phase steel
No full textIn this study, the galvanizing and galvannealing ability of dual phase steel sheet (DP 590), with and without Fe pre-coatings, is investigated with varying dew points using a hot dip process simulator (HDPS). Good quality defect free adherent galvanized coating on the substrate surface is obtained by appropriate selection of the intercritical annealing atmosphere consists of N-2-5%H-2 gas mixture with +10 degrees C dew point without substrate pre-coating. However, the production of defect-free coating on DP 590 substrates is highly challenging when the substrates are without any pre-coating. It is observed that the selective oxidation of manganese on the substrate surface during intercritical annealing is primarily responsible for the appearance of bare spots on the galvanized surface in case of the coated specimen produced without pre-coating. A significant improvement in the reactive wetting behaviour between the liquid zinc alloy and pure Fe results in defect free adherent coatings (both galvanized and galvannealed) with electrodeposited Fe pre-coating on the substrate surface irrespective of dew points. Both the galvannealed specimens prepared with and without iron pre-coatings, exhibit partial passive-active metal characteristics in potentiodynamic polarization corrosion test. Iron pre-coating on the substrate surface is observed to improve the quality of galvannealed coatings by reducing defects and enhancing the formation of more compact and dense delta (delta) phase compared to galvannealed coatings produced without pre-coating under identical conditions. This leads to the improvement in corrosion resistance of galvannealed coating produced with pre-coating by lowering the corrosion potential and corrosion current density compared to that of galvannealed specimens produced without iron pre-coating
Ionic Conductivity of Na3Al2P3O12 Glass Electrolytes Role of Charge Compensators
No full textIn glasses, a sodium ion (Na+) is a significant mobile cation that takes up a dual role, that is, as a charge compensator and also as a network modifier. As a network modifier, Na+ cations modify the structural distributions and create nonbridging oxygens. As a charge compensator, Na+ cations provide imbalanced charge for oxygen that is linked between two network-forming tetrahedra. However, the factors controlling the mobility of Na+ ions in glasses, which in turn affects the ionic conductivity, remain unclear. In the current work, using high-fidelity experiments and atomistic simulations, we demonstrate that the ionic conductivity of the Na3Al2P3O12 (Si0) glass material is dependent not only on the concentration of Na+ charge carriers but also on the number of charge-compensated oxygens within its first coordination sphere. To investigate, we chose a series of glasses formulated by the substitution of Si for P in Si0 glass based on the hypothesis that Si substitution in the presence of Na+ cations increases the number of SiOAl bonds, which enhances the role of Na as a charge compensator. The structural and conductivity properties of bulk glass materials are evaluated by molecular dynamics (MD) simulations, magic angle spinning-nuclear magnetic resonance, Raman spectroscopy, and impedance spectroscopy. We observe that the increasing number of charge-imbalanced bridging oxygens (BOs) with the substitution of Si for P in Si0 glass enhances the ionic conductivity by an order of magnitudefrom 3.7 x 10(-8) S.cm(-1) to 3.3 x 10(7) S.cm(-1) at 100 degrees C. By rigorously quantifying the channel regions in the glass structure, using MD simulations, we demonstrate that the enhanced ionic conductivity can be attributed to the increased connectivity of Na-rich channels because of the increased charge-compensated BOs around the Na atoms. Overall, this study provides new insights for designing next-generation glass-based electrolytes with superior ionic conductivity for Na-ion batterie
Mesoporous CuO nanostructures for low-temperature CO oxidation
No full textPreparation of CuO nanostructure was reported by oxalic acid-assisted wet-chemical method in aqueous medium. As-prepared sample was identified as C2CuO4.nH(2)O, which was further transformed into CuO after heat treatment. To enhance the textural property, CTAB was employed as soft-templating agent. DTA-TGA characterization was performed to investigate the thermal stability of as-prepared C2CuO4.nH(2)O sample, whereas Raman and XPS measurements confirmed the presence of CuO. FESEM and TEM studies revealed porous architecture with shelled interior for CuO sample. The formation of porous network could be demonstrated by oxidative decomposition of C2CuO4.nH(2)O due to high temperature calcination. The BET surface area and pore volume were found to be 51 m(2) g(-1) and 0.4492 cc g(-1), respectively. The catalytic activity of sample was investigated for CO oxidation and achived T-50 and T-100 at 133 and 175 degrees C, respectively, which were further compared with commercialized CuO sample and previously reported data
Alloy formation and composition partitioning of plasmonic-magnetic Au-Fe nanoparticles embedded in sol-gel SiO2 films
No full textA gradual compositional evolution has been observed in bimetallic Au-Fe nanoparticles (nps) incorporated in SiO2 films fabricated on glass substrate by the sol-gel technique. UV-vis spectra of these nps embedded films showed a red-shifting of the Au surface plasmon resonance (Au-SPR) band after heat-treatment in reducing gas (H-2-Ar) atmosphere. GIXRD and TEM studies revealed the formation of Au-Fe alloy nps (average Fe content similar to 21.4 at%) after reduction at 800 degrees C in H-2-Ar. At this stage a major fraction of added Fe remains in the amorphous film as -Si-O-Fe- network. Further reduction at 900 degrees C results in crystallization of silica film into cristobalite with expulsion of Fe from the network. The released metallic Fe got dissolved in the existing alloy nps, and formed Au-Fe alloy with relatively higher average Fe-content (similar to 36 at%). A detailed TEM study of the film reduced at 900 degrees C using nano-probe electron beam STEM-EDS technique revealed size dependent compositional change in individual alloy nps. Existence of multiple sets of fcc, and bcc peaks in GIXRD, and XPS analysis confirmed such compositional changes in the nps. The 900 degrees C-an-nealed film showed room temperature soft magnetic behavior with modified plasmonic feature confirming the existence of plasmonic-magnetic dual properties. (c) 2021 Elsevier B.V. All rights reserved
A Preparative Approach of TiO2-ZrO2 Coating Using Aquo-Based TiO2 Precursor Useful for Light Reflective Application
No full textTiO2-ZrO2 composite coating was prepared onto glass substrate via sol-gel dip-coating technique using aquo-based titanium(IV) oxysulphate (TOS) and zirconium(IV) n-propoxide (ZP) as the precursor sources of TiO2 and ZrO2, respectively followed by calcination at 500oC/1 h. The samples were characterized by FTIR, Raman, UV/visible/ NIR, GIXRD, FESEM, TEM and XPS studies. The thickness and RI of the coating were measured ellipsometrically. The coated glasses with coating thicknesses of 110±10 nm having refractive index of 1.95±0.05 were found to be uniform with good hardness (≥3H) and adhesion properties. The bonding nature of Ti-O and Zr-O was confirmed by FTIR and XPS analyses while Raman and GIXRD studies revealed the crystalline nature of TiO2-ZrO2 composite. FESEM and TEM images revealed crack-free and spider web-like nature of the deposited coating, respectively. The coated TiO2-ZrO2 composite showed >20% of average reflection within wavelength range of 350-2500 nm. The above nanocomposite based coated glass could be used as heat reflecting window for efficient energy saving building components
Material extrusion additive manufacturing of bioactive glass/high density polyethylene composites
No full textBioactive glasses (BAG) are renowned for their unique ability to bond with tissues and therefore are used extensively for bone repair and functional recovery. In this work, high density polyethylene (HDPE) reinforced with BAG is processed using material extrusion additive manufacturing (MEAM) for potential orthopaedic applications. The constituents are melt compounded by varying BAG proportions (5, 10, and 20 wt %) and subsequently extruded into filaments. DSC curves show an insignificant change in the peak melting temperature, increase in crystallization temperature, and a decrease in the crystallinity of HDPE with BAG addition. Warpage analysis confirms that the enhanced temperature parameters and BAG addition result in reduced warpage and improved dimensional stability. Rheological results show that the addition of BAG increases complex viscosity, storage and loss modulus. Melt behavior and print parameters are tailored to improve first layer adhesion and interfacial bonding rendering dimensionally stable prints without any print induced defects. Dynamic mechanical analysis (DMA) of printed samples show an increase in storage (E'), loss (E `') modulus, and a decrease in damping factor (Tan delta) with BAG addition. MEAM of the developed H/BAG composites shows a strong potential for developing customizable scaffolds and implants as bone replacements
Long Period Fiber Grating Near Turn Around Point: Suitable Design for Bio-Sensing
No full textWe report our experimental study on the add-layer sensitivity of LP0,11 cladding mode (CM) of Long Period Fiber Grating (LPFG) near turn around point (TAP). The CM response was tuned by controlled modification of the cladding diameter and deposition of overlay layers of polymer material. In this process an add-layer sensitivity of 2.308 nm(WL)/nm(TH) has been achieved. It is interesting to observe that add-layer sensitivity obtained in this process is close to the sensitivity of the same CM operated nearthe mode transition (MT). The advantage is that, the sensor designed as per the proposed methodology will not be plagued by the basic limitations of operating a CM near MT, i.e. loss of contrast of the resonant band and limited dynamic range. In our experiment, the dynamic range has found to be similar to 100 nm where the contrast remains greater than -10 dB throughout the range of measurement which is practically impossible to get for any CM operating at MT. The experimental result was supported by theoretical calculations. Also the SRI sensitivity of the sensor was found out to be 6400 nm/SRIU
Effect of Vanadium Oxide on the Structure and Li-Ion Conductivity of Lithium Silicate Glasses
No full textThe commercially ubiquitous liquid electrolytes for lithium-ion batteries have several shortcomings in terms of safety. Therefore, development of solid electrolytes, especially those that are glass-based, has been gaining increasing interest in recent times. However, the fundamental understanding of the changes in the glass structure and the corresponding changes in the properties due to the addition of dopants is necessary for the development of glasses. Therefore, here, we report a study on the role of vanadium on the glass structure, ionic conduction, crystallization behavior, and other properties of lithium silicate-based glasses (23Li(2)O-2.64K(2)O-2.64Al(2)O(3)-71.72SiO(2)) as a solid electrolyte for high-temperature Li-ion battery applications. Furthermore, we proposed a mathematical model to describe/quantify the ion-conducting channels' connectivity in glasses. The experimental glass structures were assessed using Si-29, V-51, Al-27 nuclear magnetic resonance, Fourier transform infrared, and ultraviolet-visible spectroscopy techniques. The ionic conductivity was measured by impedance spectroscopy, and the crystallization behavior was studied by optical microscopy and X-ray diffraction. Furthermore, molecular dynamics simulations were also used to gain structural insights of the glasses. In the designed compositions, the addition of vanadium decreased the overall concentration of Li+ ions. However, the results revealed that the ionic conductivity improved with the addition of vanadium in spite of a decrease in the number of charge carriers. This suggests that vanadium makes the pathways easier for the conducting ions. Thus, we conclude that vanadium modifies the conduction channels to promote better hoping of the ions from one site to another