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Congenital choanal atresia results from the developmental failure of the nasal cavity to connect posteriorly with the nasopharynx. Although congenital choanal atresia is a well-recognized developmental disorder, it is an uncommon condition with an overall incidence of approximately 1 per 10,000 live births. The authors aim to highlight that in very preterm neonates, early diagnosis of bilateral congenital choanal atresia needs a high index of suspicion to avoid life-threatening events. It is considered as one of the neonatal emergencies, and repair is recommended in the first few weeks of life. The authors report an uncommon presentation of a very preterm neonate born at 31 weeks of gestation, diagnosed to have bilateral congenital choanal atresia with repeated failure of a trial of extubation. A transnasal endoscopic repair was performed in the eighth week of life to relieve the life-threatening nasal obstruction. [ABSTRACT FROM AUTHOR]

The present work reveals the variation of nanomechanical properties (nanohardness-H and modulus-E) of black anodic coating on additively manufactured Al–10Si–Mg alloy. The plan-section of the coating has mud-crack-like morphology with various nano/micro-pores, micro-channels, and irregularities. In contrast, the cross-section possesses a compact morphology with minimum surface/sub-surface defects like micro-cracks or irregularities. The H and E are derived from nanoindentation experiments using Berkovich tip at loads 10–50 mN. The nanomechanical properties are higher across the cross-section than the plan section of the coating, attributing to the difference in morphology between the plan- and the cross-sections. Due to characteristic porosities, defects, and nano/micro-cracks in the anodic coating, Weibull statistical analysis has been employed to rationalize the scatter in nanoindentation-based data. For both plan and cross-sections, the H and E values decrease as the indentation load increases from 10 to 50 mN, confirming the indentation size effect (ISE). The well-established Meyer's law, Hays–Kendall approach, elastic recovery model, proportional specimen resistance (PSR) model and the modified PSR model have been used to thoroughly analyze the ISE characteristics. [ABSTRACT FROM AUTHOR]

Chemical reduction of graphene oxide has emerged as one of the most suitable processes for low-cost and large-scale production of graphene for potential applications. Here we report a simple, efficient, scalable, room-temperature method for enhanced reduction of graphene oxide (GO). Nowadays, hydroiodic acid (HI) is being widely used as a reducing agent for synthesizing highly conductive reduced graphene oxide. Herein, aluminum (Al) powder was used in the second step to improve the extent of reduction using HI. Al3+, which is a strong lewis acid, helps further in the reduction and enhances the one-step reduction by HI. Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM), X-Ray Diffraction (XRD), Raman and X-Ray Photoelectron Spectroscopy (XPS) confirmed the formation of GO and assisted in understanding the potential of HI and Al–HI as reducing agents. The comparative analysis demonstrates the enhancement in the reduction properties of the novel Al supplemented reduced GO. Additionally, an electrically conductive dip-coated film with a sheet resistance of 4.56 × 104 Ω/sq was successfully fabricated using this Al-supplemented reduction technique. [ABSTRACT FROM AUTHOR]

Black anodic coating (BAC) is developed on 3D printed or additively manufactured (AM) Al–10Si–Mg alloy by sulphuric acid based anodization technique at low (∼9 °C) temperature. The microstructural and surface properties of the coating are investigated by optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and water contact angle (WCA) measurement techniques. The solar absorptance and infrared (IR) emittance of the coating have been evaluated in the range 200–2500 nm and 3–30 μm, respectively. Nanoindentation technique is employed with low load to evaluate the hardness and modulus of the coating at microstructural length scale. The anodic coating shows superior hardness (∼3.95 GPa) and modulus (∼96 GPa) as compared to reported literature values, possibly due to dense microstructure and the presence of harder ceramic phases, e.g., alumina and kyanite in anodic coating. Further, due to dense microstructure, corrosion resistance improves significantly after anodization of AM alloy. Finally, thermo-optical properties are not altered after the space environmental tests which ensures the usage of the present anodic coating on AM Al alloy for spacecraft thermal control application. The solar absorptance (0.87) and IR emittance (0.78) obtained for the present coating as flat absorber characteristics are higher than the coatings processed on conventional wrought alloys. The present anodic coating shows substantial improvement in mechanical, thermo-optical and corrosion properties due to higher silicon content unlike conventional wrought alloy and refinement in microstructure during additive manufacturing aiding continuous and uniform anodic oxide layer. [ABSTRACT FROM AUTHOR]

In this work, we show that Microbial Induced Calcite Precipitation (MICP) can be used for making consolidated structures – space bricks – using lunar soil simulant (LSS). Sporosarcina pasteurii was used as a bacterial strain to initiate MICP process via ureolytic pathway. An admixture of a naturally occurring biopolymer (guar gum) and a structural reinforcement material (glass fibre) was used to enhance the mechanical properties of the bio-consolidated bricks. When supplemented with guar gum, the compressive strength of the resulting bricks was found to be significantly higher – by nearly six-fold – making them comparable to commercially used mud bricks. The addition of glass fibre reduced this strength a little, but had the benefit of making the space bricks machinable on a conventional lathe. This latter fact enabled the fabrication of precise and free-form shapes post-consolidation, without the need for specialized casting molds or dies. Details of the MICP process were investigated using field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses. The route demonstrated here holds great potential for making strong structures in extra-terrestrial habitats, while adhering to the principles of in situ resource utilization. [ABSTRACT FROM AUTHOR]

Doped and co-doped vanadium oxide (VO) thin films were deposited on quartz substrates with varying concentrations of doping elements by sol-gel spin coating technique. The VO thin films were characterized by the X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), cross-sectional FESEM and X-ray photoelectron spectroscopy (XPS) techniques. The optical properties, e.g., the average solar absorptance (α s), the average solar reflectance (ρ s) and the average solar transmittance (τ s) of the films deposited on quartz were evaluated by using a solar spectrum reflectometer. Based on the optical characterizations, an optimized doping concentration was identified. Further, a process optimized condition was utilized to grow both doped and co-doped vanadium oxide films on metallic Al6061 substrates; which are generally used in spacecraft. The phase transitions of all as grown vanadium oxide films on Al6061 were characterized by the differential scanning calorimetry (DSC) technique. The thin films showed reversible and repeatable phase transitions at sub-zero level of temperatures e.g., ∼ (̶ 23.3 °C). Thus, the VO thin films developed in the present work emerge out to be of paramount importance for the smart radiative device applications in spacecraft. [ABSTRACT FROM AUTHOR]

Smooth, uniform and crystalline vanadium oxide thin films were deposited on quartz by spin coating technique with four different rpm i.e., 1000, 2000, 3000 and 4000 and subsequently post annealed at 350, 450 and 550 °C in vacuum. Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were utilized for microstructural characterizations and phase analysis, respectively, for vanadium oxide powder and deposited film. Nanorods were observed to be grown after vacuum annealing. X-ray photoelectron spectroscopy (XPS) technique was utilized to study the elemental oxidation state of deposited vanadium oxide films. Thermo-optical and electrical properties such as solar transmittance (τ s ), reflectance (ρ s ), absorptance (α s ), infrared (IR) emittance (ε ir ) and sheet resistance (R s ) of different thin films were evaluated. Based on the optical characteristics the optimized condition of the film processing was identified to be spin coated at 3000 rpm. Subsequently, the nanoindentation technique was utilized to measure hardness and Young's modulus of the optimized film. The measured nanomechanical properties were found to be superior to those reported for sputtered vanadium oxide films. Finally, temperature dependent phase transition characteristics of optimized vanadium oxide films were studied by differential scanning calorimetry (DSC) technique. Reversible and repeatable phase transition was found to occur in the range of 44–48 °C which was significantly lower than the phase transition temperature (i.e., 68 °C) of bulk VO 2 . [ABSTRACT FROM AUTHOR]

The present work provides the first ever report on extraordinarily high antibacterial efficacy of phase pure micro-layered calcium hydroxide nanoparticles (LCHNPs) even under dark condition. The LCHNPs synthesized especially in aqueous medium by a simple, inexpensive method show adequate mechanical properties along with the presence of a unique strain tolerant behaviour. The LCHNPs are characterized by FTIR, Raman spectroscopy, XRD, Rietveld analysis, FE-SEM, TEM, TG-DTA, surface area, particle size distribution, zeta potential analysis and nanoindentation techniques. The LCHNPs have 98.1% phase pure hexagonal Ca(OH) 2 as the major phase having micro-layered architecture made up of about ~100–200 nm thick individual nano-layers. The nanomechanical properties e.g., nanohardness (H) and Young's modulus (E) of the LCHNPs are found to have a unique load independent behavior. The dielectric responses (e.g., dielectric constant and dielectric loss) and antibacterial properties are evaluated for such LCHNPs. Further, the LCHNPs show much better antibacterial potency against both gram-positive e.g., Staphylococcus aureus ( S. aureus) and gram-negative e.g., Pseudomonas putida ( P. putida ) bacteria even in dark especially, with the lowest ever reported MIC value (e.g., 1 μg ml −1 ) against the P. putida bacterial strain and exhibit ROS mediated antibacterial proficiency. Finally, such LCHNPs has almost ~8–16% inhibition efficacy towards the development of biofilm of these microorganisms quantified by colorimetric detection process. So, such LCHNPs may find potential applications in the areas of healthcare industry and environmental engineering. [ABSTRACT FROM AUTHOR]

This work reports the loading rate effect on nanohardness of sapphire. The intrinsic nanoscale contact deformation resistance of sapphire increased with the loading rates following empirical power law dependence with a positive exponent. The results showed a significant enhancement (e.g., ~66%) of the nanohardness of sapphire with the increase in loading rates from 10 to 10,000 μN s −1 . These results were explained mainly in terms of the maximum shear stress generated underneath the nanoindenter, dislocation density and critical resolved shear stress of the sapphire. [ABSTRACT FROM AUTHOR]

Highlights: [•] Three point bending test on SOFC single cell in pre- and post-reduced conditions. [•] Fractrography showed no signature of delamination in the SOFC layers. [•] In-depth nanoindentation study on SOFC single cell in pre- and post-reduced conditions. [•] Scatter of the nanoindentation data analyzed by well established Weibull statistics. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of residual stress in bioactive hydroxyapatite (HAP) ceramic coating by nanoindentation technique has been attempted successfully for the very first time ever in the present work. The HAP coatings were deposited on surgical grade 316L austenitic stainless steel and Ti–6Al–4V substrates by microplasma spraying (MIPS) process. The coatings had Ca/P ratio of 1.67 and were ∼80–90% crystalline. The results showed a residual compressive stress of ∼22MPa for the MIPS-HAP coatings on the SS316L substrates. For the coatings deposited on the Ti–6Al–4V substrates, however, a residual tensile stress of ∼11MPa was estimated. These data matched well with those obtained by XRD based technique. Thus, favorable data comparison provides further support to the efficacy of the nanoindentation based technique utilized in the present work for residual stress estimations. [Copyright &y& Elsevier]

Abstract: Microstructural, corrosion and nanomechanical behaviour of micro arc oxidised (MAO) coating grown on magnesium AZ31B alloy was evaluated. Microstructural characterization of the coating was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) followed by image analysis and energy dispersive spectroscopy (EDX). Linear polarization technique was used to evaluate the corrosion behaviour of the MAO coating. Further, nanoindentation was employed to evaluate nanohardness and Young’s modulus of the MAO coating. The characteristic values of both the nanohardness and the Young’s modulus were calculated through the application of the Weibull statistics. [Copyright &y& Elsevier]

Abstract: The motivation behind this study was the urge to understand how the high strain rate flyer plate impact affects the nanohardness of alumina ceramics. Therefore, the load controlled nanoindentation experiments were conducted with a Berkovich indenter on an as received coarse grain (~10μm), high density (~3.98g.cm3) alumina and the shock recovered tiny fragments of the same alumina. The shocked alumina fragments were obtained from an earlier flyer plate shock impact study in a two stage gas gun. The nanohardness of the as received alumina was much higher than that of the shocked alumina. The shocked alumina showed a relatively much stronger indentation size effect (ISE) while the as received alumina exhibited a mild ISE. A new explanation was given for the presence of the relatively strong ISE in the shock recovered alumina. Additional characterizations such as scanning electron microscopy, field emission scanning electron microscopy, transmission electron microscopy and analysis of the experimental load depth data were utilized for this purpose. Finally, a new, qualitative model was proposed to provide a rational picture of the nanoindentation responses of the as received and shocked alumina ceramics. [Copyright &y& Elsevier]

Abstract: Bismuth ferrite (BiFeO3) is a unique magnetoelectric multiferroic that exhibits the coexistence of ferroelectricity and antiferromagnetism at room temperature. This unique combination of properties has pumped a huge surge in current research on BiFeO3 as a future material for very important technological applications such as magnetic detectors and as an active layer in magnetoelectric memories. For such applications involving miniaturized components and devices, it is essentially important to have an idea of the mechanical integrity of the system at the scale of the microstructure. In spite of the wealth of the literature, however, the attempt to evaluate the mechanical integrity of nano BiFeO3 at a scale comparable with the local microstructural length scale was almost non-existent. Here we report, possibly for the first time the nanoindentation behaviour of a sol–gel process derived nano BiFeO3 having particle size of 5–25nm. The nanoindentation studies were conducted at 100–1000μN loads on a green pellet annealed at a low temperature of only 300°C to avoid particle coarsening. The results showed interesting dependence of nanohardness and Young''s modulus on the nanoindentation load which could be explained in terms of elastic recovery and plastic deformation energy concepts. [Copyright &y& Elsevier]

Abstract: Here we report a comparative study of the healing kinetics of surgically created artificial defects in the tibia of New Zealand white rabbits. Comparison of the healing kinetics was made for uncoated conventional SS316L intramedullary pins, and the same pins with microplasma sprayed (MIPS) pure hydroxyapatite (HAp) and beta-tri calcium phosphate (β-TCP) coatings. After thorough material characterizations including XRD, FTIR, SEM, etc., MIPS coated pins were implanted to such animals. Serum biochemistry, radiology and fluorochrome labelling were used to evaluate the comparative healing kinetics of these implants in vivo. In comparison to those of the uncoated pins, the pins coated with both MIPS HAp and β-TCP showed significant increment of alkaline phosphatase up to 15th postoperative day, insignificant changes in serum phosphorus and calcium with uneventful healing of bone defect. There was development of Havarsian canals and well-defined peripherally placed osteoblasts along with evidence of angiogenesis and comparatively more new bone formation in the defect site. On a comparative scale, the performance of the β-TCP coated intramedullary pins was much better than that of the pure HAp coated pins than the uncoated intramedullary pins. [Copyright &y& Elsevier]

Understanding the mechanical response and failure of consolidated extra-terrestrial soils requires analyses of the interactions between propagating cracks and the material's inherent pore structure. In this work, we investigate the fracture behaviour of lunar soil simulant consolidated using microbially induced calcite precipitation (MICP). We develop a numerical lattice network model using local beam elements to simulate the nucleation, propagation, branching, and merging of multiple cracks within a space brick subject to uniaxial compression. Our simulations capture the effects of local pores on crack paths as well as provide a means to predict the behaviour of samples with varying global porosity and/or uncertainties in local material stiffness. We identify multiple statistical lattice parameters that encode signatures of single or multiple crack growth events. Our results reveal the complexities involved in the fracture process with porous brittle solids and may easily be adapted to understand failure mechanisms and micro/macro crack evolution in other consolidated structures. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC), a non-oxide ceramic with superior thermo-mechanical stability, chemical and radiation resistive properties, finds extensive utilization in optical instruments for terrestrial and space applications. However, its inherent porous texture (α-HCP) becomes a deterrent for high-performance optical telescopes, although several techniques of surface alterations over sintered or reaction-bonded SiC are available. In the present work, the physical vapour deposition (PVD) technique is adopted to deposit a thick (∼5 μm) Silicon dioxide (SiO 2) clad layer on a sintered and optically polished SiC (SSiC) substrate. SiO 2 clad layer coated SSiC (SDO-SSiC) substrate reduces the surface porosity of SSiC which is found to be suitable for optical mirror application. Finally, an Al based reflective and oxides protective coatings are deposited on SiO 2 clad layer to achieve reflective behaviour. The surface figure of 75 nm PV (peak-to-valley) and less than 2 nm surface micro-roughness values are achieved which meets the stringent optical telescope specifications for terrestrial and space applications. The structural and nano-mechanical properties of presently developed SiO 2 clad layer-based SiC telescopic mirror have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-Ray Analysis (EDX), atomic force microscopy (AFM), and nanoindentation techniques. The optical properties are investigated by optical profilometry and wavelength based spectrometric (both in visible and infrared ranges) techniques. Finally, space worthiness studies viz., thermo-vacuum, thermal storage, thermal shock and relative humidity tests have been carried out successfully. The process of cleaning, grinding and polishing at each substrate preparation stage and coatings are also reported comprehensively. [ABSTRACT FROM AUTHOR]

Biological experiments on bacteria in extra-terrestrial environments have recently gained increased importance in the context of space exploration and the human space programme. Here, we demonstrate a modular self-contained device, based on the lab-on-a-chip (LoC) paradigm, for performing miniaturized biological experiments in microgravity or outer space environments. The device is designed to incubate microscopic organisms; in the present work it was employed to incubate bacteria via a suitable actuation mechanism and measure bacterial activity over long term by periodic querying, sensing and data transmission/storage. Growth is measured using optical density measurements using an on-board LED/photo-diode pair. The modular design enables several simultaneous experimental runs arranged in individual cartridges, each containing multiple experiments in separate cassettes. This allows for statistical significance and in-built redundancy in case of remote failure. We use this system to study the growth pattern of Sporosarcina pasteurii , a spore-forming bacteria widely explored for its capability to induce calcite precipitation. Growth in the device was confirmed by continuous monitoring of optical density (OD), as well as post log-phase optical and scanning electron microscopy (SEM). Additionally, the performance of the device was evaluated at multiple temperatures, pressures and under different device orientations, and found to be unchanged within experimental error. Given its modular structure, the proposed platform can be easily adapted as a biological payload for self-contained LoC based studies of other microorganisms in microgravity environments. [ABSTRACT FROM AUTHOR]

Present study reports the detailed nanomechanical and corrosion behaviours of crystalline and amorphous plasma electrolytic oxidation (PEO) coatings developed on Aluminium alloy-6061. The concentration of sodium silicate in the electrolyte is tailored to achieve crystalline and amorphous natures of the PEO coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM) and nanoprofilometry techniques are utilized to investigate microstructural and morphological properties of the PEO coatings. XRD studies confirmed that crystalline ceramic phases are obtained at lower silicate concentration while amorphous nature occurred for comparatively higher concentration of silicate in the electrolyte. Nanoindentation technique is utilized to study the mechanical properties such as hardness (H) and Young's modulus (E) of the PEO coatings. The scatter of the data is treated with well-established Weibull statistical method. Finally, in depth corrosion behaviour of the coatings are investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Amorphous coatings exhibited superior mechanical properties compared to the crystalline coatings. This is possibly linked with the presence of aluminosilicate phases and difference in silicon content in the coatings. However, as expected crystalline PEO coatings offer better corrosion resistance than the amorphous coatings and this behaviour is explained in terms of porosity contents of the coatings. [ABSTRACT FROM AUTHOR]

Germanium coated black polyimide (GBP) is often used as passive thermal control element for sunshield membrane of satellite antenna. However, GBP degrades fast while there is no protective coating applied. The present work is aimed towards the development of protective films which could hinder the degradation of GBP. At the same time, the basic characteristic of GBP membrane that is RF transparency should not be trade off. Here, RF transparent and protective vanadium oxide (VO) and vanadium oxide/silicon dioxide (VO/SO) thin films are developed by RF magnetron sputtering technique on GBP at a constant 400 W. Field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) techniques are utilized to investigate microstructural and oxide characteristics, respectively. Thermo-optical properties such as, solar absorptance (α s ) and IR emittance (ε ir ) are also evaluated. Introduction of SiO 2 layer over vanadium oxide layer leads to decrease in α s to about 12%. RF losses e.g. insertion loss and return loss are measured in Ka band (27–39 GHz) and they found to be RF transparent characteristic. Thermal stability of the oxide films are also studied by differential scanning calorimetry (DSC) technique. [ABSTRACT FROM AUTHOR]

The damping capacity of plasma sprayed alumina (Al 2 O 3 ) coatings on AISI 304 stainless steel was investigated in this study as a function of particle size of the starting alumina powder. The coatings were prepared from different sizes alumina powder using commercial air plasma spraying (APS) technique. The damping properties of coated samples were characterized by damping capacity (Q −1 ) measured experimentally using dynamic mechanical analyzer (DMA). The surface morphology of the coatings was studied using scanning electron microscope (SEM). The results revealed that the coating was porous and was able to improve the damping capacity of bare substrate. It was also observed that the powder particle size had a significant effect on the damping characteristics of the coatings. The damping values were found to be increased with the increase in particle size in the measured strain range. This behaviour was correlated with the microstructure investigated by SEM. [ABSTRACT FROM AUTHOR]

Crystalline vanadium oxide-titanium oxide (VO-TO) composite thin films of 197 nm are developed on quartz and silicon substrates by RF magnetron sputtering technique. A thorough structural investigation of deposited thin films is carried out by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. Differential scanning calorimetry (DSC) and temperature-based sheet resistance measurement techniques reveals the Smart (i.e., reversible) phase transition behaviour of VO-TO films at about 45 °C. Further selective depth analysis by XPS on the VO-TO films shows the variation of the Ti doping amount along the thickness. The top region of VO-TO thin film possess lower Ti species, while beyond 50 nm thickness from the surface possess comparatively rich Ti species. This graded Ti species along the depth also results in the variation of nanomechanical properties along the depth as confirmed by nanoindentation. The simulation through the finite element approach is also carried out to depict the experimental results of nanoindentation. The nanohardness and modulus of the presently developed VO-TO composite film were measured as 6.7 GPa and 158.7 GPa, respectively at 50 nm depth. Beyond 50 nm, nanohardness and modulus were 5.6 GPa and 116.6 GPa, respectively. Further, finite element simulation predicted yield stress value of 3.52 GPa at 50 nm depth whereas higher yield stress of 4.68 GPa was predicted beyond 50 nm. [ABSTRACT FROM AUTHOR]

Black appearance and flat absorber, i.e., high solar absorptance (α s) and high IR emittance (ε ir) surfaces, are essential for optical benches and optical mounts in astronomical and scientific payloads/spacecraft. Generally, these optical benches and optical mounts are fabricated by Ti6Al4V alloy due to its superior mechanical and thermal properties. However, bare Ti6Al4V is restricted for spacecraft thermal control applications due to its low emittance, intermediate absorptance, and moderate corrosion resistance behaviors. Hence, plasma electrolytic oxidation (PEO) technique was utilized to develop black and flat absorber coatings on bare Ti6Al4V alloy. Sodium silicate (SS), sodium hypophosphate (SHP), and potassium fluoride (KF) were used for the preparation of the electrolytic bath. Process parameters such as current density, duty cycle, frequency, the concentration of electrolytes, and duration were judiciously altered to get uniform PEO coatings with the flat absorbing property. Six numbers of PEO coatings were finally chosen for further in-depth characterizations as they showed adequate flat absorbing property. The phase composition, microstructure, roughness, and wettability of those PEO coatings were thoroughly studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), profilometry, and water contact angle measuring techniques, respectively. Thermo-optical properties viz., ε ir and α s of the coatings were recorded by portable IR emissometer and solar reflectometer, respectively, and electrical sheet resistance was measured by two probe method. The Nanomechanical properties of the coatings, such as modulus (E) and nanohardness (H), were evaluated by the nanoindentation technique. The PEO coatings were also investigated with respect to potentiodynamic polarization to investigate corrosion resistance of the PEO coatings. The highest ε ir value of PEO coating was achieved as 0.87 for a 20% duty cycle with a combination of SS + SHP electrolytes, while the maximum α s value was achieved as 0.83 for the same 20% duty cycle with a combination of SS + SHP + KF electrolytes. [ABSTRACT FROM AUTHOR]

Here we report for the first time the combined nanoindentation experiments and finite element modeling to investigate the in-depth nanomechanical behavior of ~1.25 μm indium tin oxide (ITO) film. The ITO film is grown on silicon substrate by a reactive direct current (DC) magnetron sputtering technique. Here, the contributions of both film and substrate are considered in a power law based nonlinear material model. Based on experimental data a detailed study is carried out in the present work to investigate the stress–strain behavior, the related von-Mises stress and equivalent plastic strain of the ITO film. In addition, the effect of the nanoindentation response of the ITO film on the silicon substrate is also evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Here, we report for the first time ever the catalyst free growth of magnesium oxide (MgO) nanoribbons on soda lime silica glass substrates by a green and inexpensive chemical route. The MgO nanoribbons were grown when the precursor magnesium hydroxide (Mg(OH)2) thin films were converted to MgO after 2h of heat treatment in air at 450°C. The MgO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and the related energy dispersive X-ray spectroscopy (EDAX) techniques. Finally, a plausible mechanism is suggested for growth of the MgO nanoribbons. [Copyright &y& Elsevier]

Abstract: The present experiments were focused on nanoindentation behaviour and the attendant “micro-pop-in” in a dense (∼95% of theoretical) coarse-grain (∼20μm) alumina ceramic as a function of loading rate variations at three constant peak loads in the range of 105–106 μN. Based on the experimental results here we report for the first time, to the best of our knowledge, an increase in intrinsic nano scale contact resistance as well as the nanohardness with the loading rate. These observations were explained in terms of the correlation between the nanoscale plasticity and shear stress active just underneath the nanoindenter. [Copyright &y& Elsevier]

Abstract: Shock recovered samples of a coarse grain (10μm), high density (>99.9% theoretical) alumina from asymmetric impact tests conducted at 6.5GPa (e.g. 3.2 times its Hugoniot Elastic Limit) in a single stage gas gun and characterized by X-ray diffractometry, scanning and field emission scanning electron microscopy, and transmission electron microscopy showed prolific presence of reduced crystallite size, higher average microstrain, grain localized micro/nano-scale deformations, micro-cleavages, grain-boundary microcracks, micro-wing crack formation, extensive shear induced deformations and fractures localized at grains, grain boundaries and triple grain junctions, grain localized entanglement of dislocations and their pile up impeded at grain boundaries. A new qualitative model based on micro-shear and micro-twist induced deformation and fracture in single and/or multiple planes in suitably oriented grain and/or grain assembly was developed to explain the experimentally observed damage evolution process. [Copyright &y& Elsevier]

Nano-scale load (P) dependency of fracture toughness (K 1C) of indium tin oxide (ITO) coating on silicon (Si) substrate is evaluated by nanoindentation based direct and energy methods. A Berkovich triangular diamond nanoindenter is used with nine different P values e.g., 10, 15, 20, 30, 40, 50, 100, 150 and 200 mN. Extensive utilization of both optical microscopy (OM) and field emission scanning electron microscopy (FESEM) techniques reveal that up to P ≤ 40 mN only the sharp radial cracks form from three corners of the nanoindent. However, for P > 40 mN, multiple cracks occur over and above the radial cracks. Finally, at P: 150–200 mN coating gets chipped off from the substrate. The K 1C values of the ITO coating are calculated on the basis of both the conventional radial crack length measurement based method and the strain energy release based method. The K 1C values are strongly sensitive to variations in P. Further, the strain energy method results in higher magnitudes of the K 1C values. [ABSTRACT FROM AUTHOR]

Here, we investigate the effect of temperature on solution combustion synthesized MnFe 2 O 4 nanoparticles (NPs) as supercapacitor electrode material that would affect the structural, optical, electrochemical, magnetic and sensing properties. The variation in temperature influences the structure and morphology of synthesized NPs which in turn produces defect states in NPs. Powder X-ray diffraction studies confirms the presence of cubic spinel structure with increase in crystallinity and crystallite size with increase in temperature. Scanning electron microscopy analysis indicates the morphology change in NPs from spherical to network like interlinking to the formation of polyhedron structure at higher temperature. Photoluminescence, energy dispersive X-ray analysis, X-ray photoelectron scpectroscopy and UV-visible diffused reflectance spectroscopy studies emphasize the increase in surface oxygen vacancies concentration with narrowing of band gap from 2.9 to 2.5 eV. Electrochemical studies designate the excellent performance and desirable cyclic stability of synthesized NPs. In particular, the specific capacitance of synthesized NP increases with increase in temperature, reaching highest specific capacitance from CV was 297.7 F/g for 0.1 M HCl and 158.85 F/g for 0.1 M NaNO 3 electrolytes for NP synthesized at 500 °C. The synthesized NPs show excellent stability with high capacity retention in both the electrolytes. The graphite modified electrode can also sense Paracetamol and d -Glucose at a very low concentration of 1–5 mM. Meanwhile, it acts as a very good photocatalyst to decolourize Methylene Blue and Alizarin Red S dye under Sunlight illumination due to the increase in concentration of surface oxygen vacancies with narrow band gap. Finally, the synthesized MnFe 2 O 4 NP can be used as a potential supercapacitor electrode with excellent stability and recyclability, to sense the analyte even at very low concentration and also act as a photocatalyst with high recyclability with the help of magnetic nature towards environmental cleaning. [ABSTRACT FROM AUTHOR]

We have fabricated VO 2 nano-columns (NCs) on the aluminized quartz glass substrates using glancing angle deposition (GLAD) technique inside the electron beam (e-beam) evaporator chamber. An e-beam deposited TiO 2 thin cap-layer has been introduced on the top of the VO 2 NCs to protect VO 2 phase which is usually unstable and turns to stable higher oxidation state, i.e., V 2 O 5. The X-ray diffraction (XRD) analysis of TiO 2 thin film (TF) coated VO 2 NCs shows the presence of VO 2 phases along with the other oxidation states. The Fourier-Transform-Infrared-Spectroscopy (FTIR) confirms the presence of Ti–O–V, V–O vibrations bands in VO 2 NCs/TiO 2 TF samples. The VO 2 NCs/TiO 2 TF sample possesses a sharp drop (~103 order) in resistance at the transition temperature (T c) ~66 °C. This sample also shows a stable semiconducting to metallic phase (vice versa as well) transition temperature (PTT) hysteresis even after one month which ensures the stable performance in terms of phase transition characteristic. Small-radius polaron model (SRPM) is used to calculate the sheet resistance of the VO 2 NCs, where we consider the effect of thermal lattice vibrations on the overlap integral of the crystal atoms. The temperature dependency of constants A and ε have been observed uniquely. The Fermi-Dirac (F-D), Migdal distribution (MD) model have been taken into account for the first time to calculate the conduction band carrier density of VO 2 NCs and ratio of the resistance in the semiconducting (R S), metallic phase (R M) is also calculated. The calculated electron concentration (n c) is 3.1 × 1019 cm-3 at the point of PTT (66 °C). [ABSTRACT FROM AUTHOR]

Solar selective colored chromium oxide coatings were prepared on the SS304 substrate through the electrochemical deposition route to provide more options and flexibility in aesthetically design solar absorbers with acceptable energy performance. The variation of colors in the coatings was achieved by varying the coating thickness as a function of deposition time. Color changes in the coatings were also evident in the samples that were annealed under vacuum. Electron microscopic images show that nanometer sized pores are present on the coating surfaces. The pore-density, pore-size distribution and surface roughness exhibit significant changes with variations in deposition time and annealing temperature. Initially, the selectivity factor of 6.08 was recorded in the as prepared sample coated for 30 min, which improved to 7.36 on annealing the samples under vacuum at 700 °C, however, it drops to 4.22 when annealed at 900 °C. A similar trend was also observed for samples that are coated for 60 min. The results indicate that the pore-density, pore-size distribution and surface roughness play a dominant role in governing the solar selectivity of the coatings. Nanoindentation tests were performed on the coated samples and the results show that mechanical properties of the solar absorber coatings degrades with the increase in coating thickness but improve significantly with increase in annealing temperature. [ABSTRACT FROM AUTHOR]

Acquiring good adhesion of ITO thin films on polymer substrate is a major concern, especially for space related applications. Delamination of ITO coating on these polymers can seriously damage the spacecraft. This paper presents the development of highly transparent and conducting ITO thin films on as-received and surface treated fluorinated ethylene propylene (FEP) and Kapton ® substrates by reactive direct current magnetron sputtering. Stability of the ITO coating on FEP and Kapton ® substrates was studied in simulated space environments. Environmental tests such as: relative humidity, thermal cycling and thermo vacuum were performed. Thermo-optical properties and sheet resistance of ITO coated FEP and Kapton ® substrates were studied before and after environmental tests. Optimized ITO coating with thickness of ~ 15 nm on FEP and Kapton ® substrates showed sheet resistance in the range of 2–4 kΩ/sq. with high average transmittance and high IR emittance. Adhesion of ITO coating on FEP substrate was improved by Ar plasma etching. X-ray photoelectron spectroscopy and field emission scanning electron microscopic studies of etched FEP substrate showed defluorination and high roughness of the etched surface which helped for better adhesion of ITO coating. We demonstrated that ITO coated plasma etched FEP substrate showed no change in the sheet resistance and thermo-optical properties. Moreover, ITO coated etched FEP substrate showed good environmental stability than ITO coated untreated FEP substrates. [ABSTRACT FROM AUTHOR]

A scalable, cost effective synthesis of reduced graphene oxide (RGO)-magnesium oxide (MgO) hybrid nanocomposite (RGOMOHNC) is reported in the present work. The process involves an in-situ sonication method in aqueous medium at room temperature e.g., 30 °C. The as synthesized graphene oxide (GO) and RGOMOHNC powders are characterized by the XRD, FESEM, TEM, FTIR, RS and XPS techniques. The results indicate that in-situ growth of 20–30 nm MgO nanoparticles effectively increases the graphitic nature of the layered RGO microstructure. The experimentally measured cyclic voltammetry (CV) plots show that the specific capacitance of the RGOMOHNC powders is three orders of magnitude higher than that of the GO powders. A mechanism of RGOMOHNC formation has been proposed. [ABSTRACT FROM AUTHOR]

Transparent and conducting ITO/Ag/ITO (IAI) multilayer coatings were deposited on glass and flexible fluorinated ethylene propylene (FEP) substrates by reactive sputtering using metallic In:Sn (90%:10%) and Ag targets at room temperature. Middle Ag layer thickness was optimized to obtain maximum figure of merit ( ϕ ) and the optimum Ag layer thickness was found to be ~13 nm. The optimized IAI multilayer on glass substrate showed transmittance of ~88.6% and sheet resistance of ~7.1 Ω/sq. The transmittance increased to ~91.4% for the IAI multilayer deposited on one side etched glass. The optimized IAI multilayer coating was also deposited on flexible FEP substrates. The electrical, optical, structural and morphological properties of IAI deposited on glass and FEP substrates were compared. IAI deposited on FEP substrate showed transmittance of ~90.2% at λ = 550 nm, sheet resistance of ~6.9 Ω/sq. and figure of merit of ~52 × 10 −3 Ω −1 . Bending test of IAI deposited FEP proved the high flexibility of IAI multilayer for the flexible transparent electrode applications. Solar selectivity study of IAI on FEP substrate showed it can effectively reflect the higher wavelength region of solar spectrum and can be used as a flexible solar spectrum segregator. Optical haze measurements of IAI coated glass and FEP show that high haze value can be achieved by increasing the roughness on non-coated side of the FEP substrate. [ABSTRACT FROM AUTHOR]

Present study reports for the first time laser cutting of multilayered coatings on both side of ultra thin (i.e., 75 µm) glass substrate based rigid optical solar reflector (OSR) for spacecraft thermal control application. The optimization of cutting parameters was carried out as a function of laser power, cutting speed and number of cutting passes and their effect on cutting edge quality. Systematic and in-detail microstructural characterizations were carried out by optical and scanning electron microscopy techniques to study the laser affected zone and cutting edge quality. Sheet resistance and water contact angle experiments were also conducted locally both prior and after laser cut to investigate the changes of electrical and surface properties, if any. [ABSTRACT FROM AUTHOR]

ITO/Ag/ITO (IAI) multilayer coatings were designed for spectral beam splitter applications and these coatings were deposited on glass substrates by magnetron sputtering method. The thicknesses of the component layers, namely, Ag and ITO were varied to achieve high visible transmittance, high NIR-IR reflectance and optimum cut-off wavelength. The optimized ITO/Ag/ITO exhibits high visible transmittance (∼88%) and high NIR-IR reflectance (>90%) with an optimum cut-off wavelength (∼900 nm). A novel chemical etching method was used to improve the transmittance of the plain glass substrate. The optimized IAI multilayer coating deposited on single side etched glass substrate resulted in increase in transmittance (∼91%), which is due to the nano-porous morphology of the etched glass substrate. The angular and polarization dependence studies of IAI multilayer coatings were also studied in detail. [ABSTRACT FROM AUTHOR]