Phase Transformation Introduced by Mechanical and Chemical Surface Preparations of Tetragonal Zirconia Polycrystals

Cutting of Y₂O₃-doped TZP rods by a low-speed diamond saw introduces an unidentified, metastable phase X (x -ZrO₂) coexisting with the tetragonal ( t -ZrO₂) and the monoclinic ( m -ZrO₂) phases initially present in the sample. Further mechanical deformation of the cut surface by indentation or polishing sustains the x -ZrO₂. Chemical etching removes the x -ZrO₂ and increases the m -ZrO₂content.     

Evaluation of biogeochemical model simulations using World Ocean Atlas and satellite observations in the Arabian Sea

Model simulations of the Ocean General Circulation Model (OGCM; MOM4p1), coupled with a state-of-the-art biogeochemical model TOPAZ (Tracers of Phytoplankton with Allometric Zooplankton), which includes multi-nutrient limitations including iron limitation, are used to study the seasonal variations of mixed-layer properties and their influence on nutrients and chlorophyll in the Arabian Sea. The spatial variation of nitrate during the Northeast Monsoon (NEM) and Southwest Monsoon (SWM), in the northern and western parts of the Arabian Sea and coast of Somalia, are very well captured by the model and compare well with observations. Modelled chlorophyll and primary productivity are validated with satellite-derived maps for the Arabian Sea.     

A chaotic framework and its application in image encryption

A novel image encryption framework is proposed in this article. A new chaotic map and a pseudorandom bit generator are proposed. Apart from this, a novel image encryption system is designed based on the proposed map and the proposed pseudorandom bit generator. These three are the major contributions of this work that makes a complete cryptosystem. The proposed new chaotic map is proposed which will be known as the ‘RCM map’ and its chaotic property is studied based on Devaney’s theory. The proposed pseudorandom bit generator is tested using the NIST test suite. The proposed method is simple to implement and does not involve any highly complex operations. Moreover, the proposed method is completely lossless, and therefore cent percent of data can be recovered from the encrypted image. The decryption process is also simple to implement i.e. just reverse of the encryption procedure. A scrambling algorithm is also proposed to further enhance the security of the overall system. The simulation, detailed analysis, and comparative studies of the proposed overall image encryption framework will help to understand the strengths and weaknesses of it. The experimental results are very promising and show the prospects of chaos theory and its usage in the field of data security.

     

Improving delamination resistance of carbon fiber reinforced polymeric composite by interface engineering using carbonaceous nanofillers through electrophoretic deposition: An assessment at different in-service temperatures

In this article, modification of carbon fiber surface by carbon based nanofillers (multi-walled carbon nanotubes [CNT], carbon nanofibers, and multi-layered graphene) has been achieved by electrophoretic deposition technique to improve its interfacial bonding with epoxy matrix, with a target to improve the mechanical performance of carbon fiber reinforced polymer composites. Flexural and short beam shear properties of the composites were studied at extreme temperature conditions; in-situ cryo, room and elevated temperature (−196, 30, and 120°C respectively). Laminate reinforced with CNT grafted carbon fibers exhibited highest delamination resistance with maximum improvement in flexural strength as well as in inter-laminar shear strength (ILSS) among all the carbon fiber reinforced epoxy (CE) composites at all in-situ temperatures. CNT modified CE composite showed increment of 9% in flexural strength and 17.43% in ILSS when compared to that of unmodified CE composite at room temperature (30°C). Thermomechanical properties were investigated using dynamic mechanical analysis. Fractography was also carried out to study different modes of failure of the composites.     

Effects of fiber surface grafting by functionalized carbon nanotubes on the interfacial durability during cryogenic testing and conditioning of CFRP composites

Carbon fiber reinforced epoxy (CE) composite is ideal for a cryogenic fuel storage tank in space applications due to its unmatched specific strength and modulus. In this article, inter-laminar shear strength (ILSS) of carbon fiber/epoxy (CE) composite is shown to be considerably improved by engineering the interface with carboxyl functionalized multi-walled carbon nanotube (FCNT) using electrophoretic deposition technique. FCNT deposited fibers from different bath concentrations (0.3, 0.5, and 1.0 g/L) were used to fabricate the laminates, which were then tested at room (30°C) and in-situ liquid nitrogen (LN) (−196°C) temperature as well as conditioning for different time durations (0.25, 0.5, 1, 6, and 12 h) followed by immediate RT testing to study the applicability of these engineered materials at the cryogenic environment. A maximum increment in ILSS was noticed at bath concentration of 0.5 g/L, which was ~21% and ~ 17% higher than neat composite at 30°C and − 196°C, respectively. Short-term LN conditioning was found to be detrimental due to developed cryogenic shock, which was further found to be compensated by cryogenic interfacial clamping upon long-term exposure.     

Mechanical behavior of electrophoretically modified CFRP composites at elevated temperatures: An assessment of the influence of graphene carboxyl bath concentration

The study aims at investigating the mechanical behavior of carbon fiber reinforced polymer (CFRP) composites modified with graphene carboxyl at elevated temperature (ET-110°C) and understanding the effect of electrophoretic deposition bath concentration (0.5 g/L, 1.0 g/L, and 1.5 g/L) on their mechanical behavior at ET. The 1.5 g/L composite has revealed a maximum improvement in energy absorbed before failure of 33.25% at RT and 22.54% at ET for flexural testing and ∼35% at RT for short beam shear testing, over neat CFRP composite. The modified composites have shown an improved flexural strain to failure at both RT and ET, with 1.5 g/L composite exhibiting maximum enhancement of 12.41% at RT and 26.52% at ET over neat composite. However, at ET, modified composites exhibited lower flexural strength and interlaminar shear strength values in comparison to that of neat. Viscoelastic behavior of all composites was studied to understand bath concentration's effect on thermal behavior via dynamic mechanical thermal analysis. Differential scanning calorimetry was employed for governing the glass transition temperature of composites. Fractography of tested samples (both ET and RT) was performed utilizing a scanning electron microscope to determine the prominent failure mode.     

Modulated Triple‐Material Nano‐Heterostructures: Where Gold Influenced the Chemical Activity of Silver in Nanocrystals

For efficient charge separations, multimaterial hetero‐nanostructures are being extensively studied as photocatalysts. While materials with one heterojunction are widely established, the chemistry of formation of multijunction heterostructures is not explored. This needs a more sophisticated approach and modulations. To achieve these, a generic multistep seed mediated growth following controlled ion diffusion and ion exchange is reported which successfully leads to triple‐material hetero‐nanostructures with bimetallic‐binary alloy‐binary/ternary semiconductors arrangements. Ag₂S nanocrystals are used as primary seeds for obtaining AuAg‐AuAgS bimetallic‐binary alloyed metal–semiconductor heterostructures via partial reduction of Ag(I) using Au(III) ions. These are again explored as secondary seeds for obtaining a series of triple‐materials heterostructures, AuAg‐AuAgS‐CdS (or ZnS or AgInS₂), with introduction of different divalent and trivalent ions. Chemistry of each step of the gold ion–induced changes in the rate of diffusion and/or ion exchanges are investigated and the formation mechanism for these nearly monodisperse triple material heterostructures are proposed. Reactions without gold are also performed, and the change in the reaction chemistry and growth mechanism in presence of Au is also discussed.     

Organic light emitting diodes: Energy saving lighting technology—A review

This paper reflects the achievements and the challenges ahead in the field of organic light emitting diodes (OLEDs). The primary intention of this paper is to study different organic materials synthesized so far and the OLEDs fabricated for solid-state lighting. After deep review of literature we have synthesized and characterized rare earth based europium organic complexes Eu(TTA)₃Phen, Eu_(x)Y_(1?x)(TTA)₃Phen, and Eu_(x)Tb_(1?x)(TTA)₃Phen, where x = 0.4 and 0.5 by solution technique maintaining stoichiometric ratio. Blended films of pure and doped Eu complexes that are molecularly doped into polymer resins namely polymethylmethacrylate (PMMA) and polystyrene (PS) are prepared according to weight percentage. Concentration effect on absorption and emission spectra of the blended films was studied for different weight percentages (10, 25, 50, 60%). All the complexes doped in PMMA showed an excellent transparency of 90–97% while the complexes doped in polystyrene showed a transparency of 85–90%, bit less than in PMMA. Energy gap of the synthesized complexes have been determined in PMMA and PS. Considering the facts that these complexes have good solubility in most of the organic solvents, the absorption spectra of Eu(TTA)₃Phen, Eu_0.5Y_0.5(TTA)₃Phen and Eu_0.5Tb_0.5(TTA)₃Phen complexes are studied, and OLED devices having the structure ITO/m-MTDATA/α-NPD/TPBi:Eu_(x)Y_(1?x)(TTA)₃Phen/Alq₃/LiF:Al (where x = 0.4, 0.5) were fabricated and characterized. Significant red emission was observed from fabricated OLED devices at 612 nm when operated in a range of 10–18 V. Thus the synthesized rare earth based organic complexes are the best suitable candidates for fabrication of red OLED devices. The extensive review on OLEDS concludes that our present lighting system can be replaced with white OLEDS, recently developed energy saving lighting technology.     

Design of Dual-Band Beam Switching Array for Adaptive Antenna Applications Using Hybrid Directional Coupler and E-Shape Slot Radiator

Wireless Personal Communications - Applications of wireless sensor networks (WSNs) are increasing tremendously to facilitate and establish a link between the physical world and information system....     

Low Cost Porous Alumina with Tailored Microstructure and Thermal Conductivity Prepared using Rice Husk and Sucrose

This study demonstrates a cost‐effective way to fabricate porous ceramics with tailored porosity and pore microstructure using 5–40 wt% rice husk (RH) in <75 μm, 75–180 μm, 180–355 μm, 355–420 μm, and 420–600 μm size, as pore former. Sucrose, used as binder, also acted as a pore former. Porous alumina compacts with 20%–66% volume fraction porosity and 50–516 μm pore size (length) were successfully fabricated. Microstructure of samples reveal randomly oriented elongated coarse pores and fine pores (avg. size 4 μm), created during burnout of RH and sucrose, respectively. Samples with isolated and/or interconnected pores were fabricated using this process. Thermal conductivity of the samples prepared was measured using Transient Plane Source (TPS) technique. Thermal conductivity ranges from 1.2 to 24 W/mK. Experimental results agree closely with predictions made based on Effective Medium Theory (EMT) for a two‐phase system.