IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Fe-Mn-Cu alloy as biodegradable material with enhanced antimicrobial properties
No full textDegradable iron (Fe) based materials have been widely investigated for fracture fixation to overcome complications of permanent implants. Our study is focused on the development of a new Fe-Mn-Cu alloy with enhanced antimicrobial properties. In this work, Fe-Mn-Cu alloys, with up to 10 wt% copper (Cu), were prepared by powder metallurgy route. Degradation behaviour of the alloys were studied using potentiodynamic polarization test which showed nearly about 6 times increase in corrosion rate for 10 wt% Cu compared to the base alloy. Addition of Cu has significantly increased microhardness for up to 5 wt% and decreased thereafter. Broth micro-dilution test showed increased antimicrobial activity with Cu addition in Fe-Mn alloy while in vitro cytocompatibility study showed more than 70% cell viability for all alloys. Present study indicates that Cu alloying in Fe-Mn makes it a suitable material for internal fracture fixation devices with enhanced antimicrobial properties. (C) 2018 Elsevier B.V. All rights reserved
Thermo-mechanical stability of bulk (Al1-xCrx)(2)O-3 solid solution
No full textBulk alpha-(Al,Cr)(2)O-3 (where, x = 0, 0.1, 0.3, 0.5) sintered compacts were obtained at 1600-1700 degrees C, whose thermo-mechanical behavior were observed upon reheating at 25-1200 degrees C. Unlike bulk alpha-Al2O3 sintered samples, all the bulk alpha-(Al,Cr)(2)O-3 sintered compacts showed a noticeable unusual flexural strength reduction at 600 degrees C. However, thermal shock behavior of all the alpha-(Al1-xCr)(2)O-3 samples (sintered at 1650 degrees C) exhibited a similar trend with retention of 33-38% of initial strength after the 12th cycle. Selected sintered alpha-(Al0.5Cr0.5)(2)O-3 samples were reheated and quenched to observe any changes (phase, structural) using XRD, XPS, and FT-IR. The phase and binding energy did not reveal any change. The characteristics bands of MO6 units exhibited a lowering of wavelength by similar to 2.5 cm(-1) (original peaks at similar to 592 and similar to 648 cm(-1)) when reheated for 1 h and quenched from 600 degrees C. But, on prolonging the reheating time at 600 degrees C for 2 and 6 h, the band position shifted back to its original place. The force constant and bond energy are plausibly responsible for the fluctuational of molecular vibration to reach a time-dependent thermal equilibrium, particularly at similar to 600 degrees C in case of alpha-(Al,Cr)(2)O-3
Photosensitivity and charge injection dynamics of pentacene based thin-film transistors: influence of substrate temperature
No full textIn this work, we have performed an in-depth analysis to investigate the effect of substrate temperature on the molecular packing arrangement and energy levels of pentacene films. We have also explored their influence on the charge injection mechanism and photosensing behaviour of pentacene-based organic field-effect transistors (OFETs). In this study, we find the contact resistance and photosensitivity of the devices to be severely influenced by the active layer processing condition owing to the aforementioned structural and energy level modifications. Contact resistance of the devices at metal-semiconductor interfaces was observed to be reduced significantly upon increase in the substrate temperature; however, above a certain temperature, formation of pentacene thin-films was severely affected and no transistor characteristics were obtained afterwards. Detailed experimental analysis and theoretical investigations revealed that the processing temperature could strongly influence the grain structure and unit cell volume of the pentacene molecules, which consequently enhanced the carrier injection across the interface through a control over carrier mobility and the distribution of electronic states in the proximity of Fermi energy. Furthermore, our study demonstrates the role of substrate temperature in effectively enhancing the photosensitivity of the transistors. This report thus represents a step forward towards understanding a correlation between the processing temperature and the dynamics of charge injection in pentacene based organic transistors. The results also illustrate the viability of using proper substrate temperature to achieve an efficient photosensitivity from OFET devices
Non-suitability of high-energy (MeV) irradiation for property enhancement of structurally stable poly (ethylene oxide) polyvinylidene fluoride blend bromide composite electrolyte membrane
No full textApplication of polymer-salt composite in multifaceted modes viz. as electrolyte, dielectric etc. demands its stability in extreme environmental conditions of high energy radiation zones. The present study reports the behavior of poly (ethylene oxide) PEO] - (polyvinylidene fluoride) PVDF]-KBr composite perturbed by swift heavy ion (SHI) irradiation in the range of tens of MeV. Least conducting PEO-PVDF-KBr is subjected to O7+ ion beam (80MeV) with fluence of 5x10(10) and 5x10(11) ions.cm(-2) respectively. FTIR studies confirm the structural stability of such composite in the mentioned SHI energy regime. SHI perturbation is found to reduce the ionic conductivity of PEO-PVDF composite; however, it could be effectively used as dielectric material for the long term as established from the long-term endurance study (18,500h). Mechanical property evaluation reveals significant increment in nanohardness and Young's modulus of the films perturbed by ion beam. These observations from FTIR, impedance, and XRD are correlated with the morphology of these films
Structure and Stability of High CaO- and P2O5-Containing Silicate and Borosilicate Bioactive Glasses
No full textThe present work elucidates about the structure of bioactive glasses having chemical compositions expressed as (mol %) (50.0 - x)SiO2-xB(2)O(3)-9.3Na(2)O-37CaO-3.7P(2)O(5), where x = 0.0, 12.5, 25, and 37.5, and establishes a correlation between the structure and thermal stability. The structural modifications in the parent boron-free glass (BO) with the gradual substitutions of B2O3 for SiO2 are assessed by Raman and Si-29, P-31, B-11, and Na-23 magic angle spinning (MAS)nuclear magnetic resonance (NMR) spectroscopies. The structural studies reveal the presence of Q(Si)(2) and Q(Si)(3) structural units in both silicate and borosilicate glasses. However, Q(Si)(4)(3B) units additionally form upon incorporating B2O3 in BO glass. B-containing silicate glasses exhibit both three-coordinated boron (B-III) and fourcoordinated boron (B-IV) units. The P-31 MAS-NMR studies reveal that the majority of phosphate species exist as isolated orthophosphate (Q(p)(0)) units. The incorporation of B2O3 in B0 glass increases the cross-linking between the SiO4 and BO4 structural units. However, incorporation of B2O3 lowers the glass thermal stability (Delta T), as shown by differential scanning calorimetry. Although both silicate and borosilicate glasses exhibit good in vitro apatite-forming ability and cell compatibility, the bactericidal action against Escherichia coli bacteria is more evident in borosilicate glass in comparison to silicate base glass. The controlled release of (BO3)(3-) ions from boron-modified bioactive glasses improves both the cell proliferation and the antibacterial properties, making them promising for hard tissue engineering applications
Sonication Assisted Hierarchical Decoration of Ag-NP on Zinc Oxide Nanoflower Impregnated Eggshell Membrane: Evaluation of Antibacterial Activity and in Vitro Cytocompatibility
No full textMetal/metal oxide nanoparticles have long been used as an antibacterial substitute, but fabrication of an effective carrier or delivery matrix for achieving a sustain release profile with high bactericidal efficacy alongwith good cytocompatibility is still an unresolved challenge. Herein, the study demonstrates a facile and unique route to fabricate a hierarchical nanobiocomposite with effective loading of ZnO/silver nanoparticles (Ag-NPs) in order to attain excellent bactericidal efficacy with good and sustainable release profile. Surface functionalized eggshell membranes (ESM) were deployed as three-dimensional loading matrices for efficient loading of ZnO/Ag-NPs. A simple sonochemical guided approach was adopted to synthesize ZnO nanoflakes in situ onto the microfibrous ESM and decorate it with Ag-NPs to fabricate a nanobiocomposite. Microstructural analysis confirms successful anchorage of ZnO nanoflakes and Ag-NPs on microfibrous eggshell membrane thus reinstating hierarchical morphology of the nanobiocomposites. FT-IR spectra confirms the biochemical composition whereas XPS analysis ratifies the interaction between ZnO and Ag-NPs further substantiating metallic state of Ag. ICP-MS studies affirms excellent and sustainable release profile of nanoparticles from the nanobiocomposites. Owing to the synergistic activity of ZnO/Ag-NPs, the nanobiocomposites demonstrated exceptional bactericidal activity against Gram-negative, E. coli or P. aeruginosa, and Gram-positive, S. aureus or B. subtilis, bacterial cells. Moreover, inherent antibacterial property of microfibrous natural ESM contributes positively toward the overall bactericidal activity. Further, a direct exposure of nanobiocomposites with NIH 3T3 cells revealed the biocompatible nature of developed matrices. Prolonged exposure also indicated that the 3T3 cells tend to adhere onto the microfibrous nanobiocomposite without any observable deformation in cellular morphology. The architectural tribology and excellent bactericidal performance of the nanobiocomposites along with its cytocompatible nature manifests its application as an alternate platform for varying biomedical applications
Mechanical and Wear Behaviour of Hot-Pressed 304 stainless Steel Matrix Composites Containing TiB2 Particles
No full textIn the present article, mechanical and wear behaviour of hot-pressed 304 stainless steel matrix composites containing 2 and 4 vol% TiB2 particles was investigated. A density of over 92% was achieved at optimum hot-pressing temperature and TiB2 particles' content. Microhardness and yield strength of the composites were found to be improved remarkably as compared to their unreinforced counterpart. The enhancement of mechanical properties of the composites was discussed in light of their microstructural aspects and different possible strengthening mechanism models. Taylor strengthening was found to be dominant strengthening mechanism as compared to Orowan strengthening and load-bearing effect. Dry sliding wear behaviour was also investigated under load of 35 N at sliding speed 0.3 m/s. The wear resistance of the composites was found to be improved owing to uniform distribution of hard TiB2 particles. Based on our findings, it was concluded that processing parameters and amount of TiB2 have significant influence on mechanical and wear behaviour of steel matrix composites
Elucidating the formation of Al-NBO bonds, Al-O-Al linkages and clusters in alkaline-earth aluminosilicate glasses based on molecular dynamics simulations
No full textExploring the reasons for the initiation of Al-O-Al bond formation in alkali-earth alumino silicate glasses is a key topic in the glass-science community. Evidence for the formation of Al-O-Al and Al-NBO bonds in the glass composition 38.7CaO-9.7MgO-12.9Al(2)O(3)-38.7SiO(2) (CMAS, mol%) has been provided based on Molecular Dynamics (MD) simulations. Analyses in the short-range order confirm that silicon and the majority of aluminium cations form regular tetrahedra. Well-separated homonuclear (Si-O-Si) and heteronuclear (Si-O-Al) cluster regions have been identified. In addition, a channel region (C-Region), separated from the network region, enriched with both NBO and non-framework modifier cations, has also been identified. These findings are in support of the previously proposed extended modified random network (EMRN) model for aluminosilicate glasses. A detailed analysis of the structural distributions revealed that a majority of Al, 51.6%, is found in Si-O-Al links. Although the formation of Al-O-Al and Al-NBO bonds is energetically less favourable, a significant amount of Al is found in Al-O-Al links (33.5%), violating Lowenstein's rule, and the remainder is bonded with non-bridging oxygen (NBO) in the form of Al-NBO (Al-O-(Ca, Mg)). The conditions necessary for the formation of less favourable bonds are attributed to the presence of a high amount of modifier cations in current CMAS glass and their preferable coordination
A critical note on nanoscale plasticity in 20 ZTA ceramics
No full textThe present work reports the very first observations on initiation of nanoscale plastic events in 20 ZTA (Zirconia Toughened Alumina) ceramics. The nanomechanical properties as well as the intrinsic contact deformation resistance of the present ZTA ceramic are studied here as a function of low loads (i.e., 10-1000 mN). Here we report for the very first time, the detailed mechanisms on the genesis of `micro pop-in' events that characterize the nanoscale plasticity initiation in the 20 ZTA ceramics. These new results along with field emission scanning electron microscopy (FESEM) based evidences confirm that the combined contributions from the maximum shear stress generated underneath the nanoindenter, the formations of shear bands and localized microcracking play significant roles in the initiation of nanoscale plastic events in the 20 ZTA ceramics
Graded-Index Ytterbium-Doped Optical Fiber Fabricated through Vapor Phase Chelate Delivery Technique
No full textHerein, the fabrication of ytterbium-doped graded refractive-index few-mode fiber (GRIN-FMF) is described for the first time following a vapor phase chelate delivery technique. Investigation is carried out to find out the best possible approach to fabricate the preform. The optimization of the process steps along with composition and associated process parameters leads to a parabolic refractive-index profile with a profile parameter of 2 in the developed fiber. A large core of 30 mu m diameter and a low numerical aperture (NA) of 0.08 with graded distribution of dopant ions is achieved with a good repeatability. Amplification gain of more than 20 dB with good beam quality for pulses with kW peak power without any distortion in temporal, spectral, and spatial profile proves the potential of the fiber for many promising applications