Journey of Kilogram from Physical Constant to Universal Physical Constant (h) via Artefact: A Brief Review

The redefinition of mass adopted in November 2018 and implemented from 20 May 2019, i.e. World Metrology Day, eliminated the artefact-based approach dependent upon the International Prototype of the Kilogram (IPK), in favour of realizing the kilogram in terms of the Planck constanthby fixing its value as 6.62607015 x 10(-34) J s. In this paper, the authors present a general outline of the circumstances and related developments that paved the way for the new definition that replaced the IPK after a period of 130 years since it was formally sanctioned to define the kilogram in 1889. The new definition opens up fascinating developments in mass metrology which include different realization techniques, realizing the unit at values other than 1 kg, numerous sources for traceability can be envisaged etc

Parametric optimization of fatigue behaviour of hybrid aluminium metal matrix composites

For various aerospace applications aluminium has emerged as most preferred material due to desirable attributes such as superior strength to density ratio, greater specific strength, better corrosion resistance, high toughness and cost effectiveness. The most desirable characteristics for aerospace materials are ability to withstand elevated temperature and sustain higher fatigue loadings. Current experimental investigation was carried out to explore and optimize fatigue characteristics of hybrid composites developed by infusing particulate reinforcements into aluminium alloy. Eggshell particles (wt% 0.5, 1 and 1.5, average particle size approximate to 60 mu m), Silicon Carbide particles (wt% 1, 1.5 and 2, average particle size approximate to 65 mu m) and Aluminium Oxide particles (wt% 1.5, 2 and 2.5, average particle size approximate to 90 mu m) were reinforced into Al 7075-T6 metal matrix through electromagnetic stir casting route as per L9 orthogonal array of Taguchi's approach in order to synthesize hybrid aluminium metal matrix composites with enhanced fatigue resistance. Analysis of variance (ANOVA) was also conducted to observe the effect of different process parameters on fatigue life of developed composites. Nine hybrid composite specimens and one as-cast Al7075-T6 specimen (in three replications) were prepared in accordance with ASTM E 468/606 and were evaluated for low cycle fatigue resistance at a constant load of 2 kg and constant speed of 500 rpms on rotating beam fatigue testing machine. It was observed that at 30 degrees C temperature, hybrid composite specimens exhibited significant enhancement in fatigue resistance in terms of reversible load cycles survived. The as-cast Al 7075-T6 specimen sustained only 94 load cycles while the highest number of load cycles i.e. 4560 were survived by hybrid composite specimen with Al 7075-T6 as base metal reinforced with 1.5 wt% of eggshell particles, 1.5 wt% of SiC particles and 1.5 wt% of Al2O3 particles (total reinforcement content only 4.5%) and mechanically stirred for 360 s

Nickel substituted oxygen deficient nanoporous lithium ferrite based green energy device hydroelectric cell

In green energy generation, recently Hydroelectric cell (HEC) by dissociating the water molecules at room temperature has taken a big stride among other alternative green energy sources. In this work, another unique novel material Ni substituted lithium ferrite (LNFO) for the fabrication of hydroelectric cell to generate green electricity has been reported. Oxygen deficient nanoporous LNFO has been synthesised by the Solid-State reaction method. Special processing steps were taken to control oxygen defect's concentration in the ferrite by varying pre-sintering temperature during its synthesis to deliver more power output. Phase formation of nickel substituted lithium ferrite has been confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The porous microstructure of LNFO has been analysed by Field-emission scanning electron microscope (FESEM) micrographs, BET and DFT techniques. The presence of defects and decrease in their concentration with the increase in pre-sintering temperature has been confirmed by analysing X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. Hydroelectric cell fabricated using LNFO pellets pre-sintered at 750 degrees C and 800 degrees C, delivered output current densities of 3.8 mA/cm(2) and 3.6 mA/cm(2) respectively. The decrease in output current is attributed to reduction in defect concentration as confirmed by PL and XPS spectrum. Generated current densities are two times higher than reported in lithium substituted magnesium ferrite based hydroelectric cell (1.7 mA/cm(2))

Growth of SiO2 microparticles by using modified Stober method: Effect of ammonia solution concentration and TEOS concentration

The unique structural features and suitability of the SiO2 microparticles in different application areas have mobilized a worldwide interest in the last few decades. In this report a classical method known as the Stober method has been used to synthesize silica microspheres. These microparticles have been synthesized by the reaction of tetraethyl orthosilicate (Si(OC2H5)(4), TEOS)(silica precursor)with water in an alcoholic medium (e.g. ethanol) in the presence of KCl electrolyte and ammonia as a catalyst. It has been observed that the size of the microparticles closely depends on the amount of the TEOS and ammonia. A decrease in the size of micro particles from 2.1 mu m to 1.7 mu m has been confirmed as the amount of TEOS increases from 3.5ml to 6.4ml respectively. In similar way a decrease in the diameter of the micro particles from 2.1 mu m to 1.7 mu m has been observed with increase in the ammonia content from 3ml to 9ml

A label-free ultrasensitive microfluidic surface Plasmon resonance biosensor for Aflatoxin B-1 detection using nanoparticles integrated gold chip

The Surface Plasmon resonance (SPR) based label-free detection of small targeted molecules is a great challenge and require substantial signal amplification for the accurate and precise quantification. The incorporation of noble metal nanoparticles (NPs) like gold (Au) NPs for the fabrication of SPR biosensor has shown remarkable impact both for anchoring the signal amplification and generate plasmonic resonant coupling between NPs and chip surface. In this work, we present comparative studies related to the fabrication of self-assembled monolayer (SAM) and the influence of AuNPs on Au chip for Aflatoxin B-1 (AFB(1)) detection using SPRi apparatus. The SAM Au chip was sequentially modified by EDC-NHS crosslinkers, grafting of protein-A and finally interaction with anti-AFB(1) antibodies. Similar multilayer chip surface was prepared using functionalized lipoic acid AuNPs deposited on SAM Au chips followed by in situ activation of functional groups using EDC-NHS crosslinkers, grafting of protein-A and immobilization of anti-AFB(1) antibodies. This multilayer functionalized AuNPs modified Au chip was successfully utilized for AFB(1) detection ranging from 0.01 to 50 nM with a limit of detection of 0.003 nM. When compared to bare self-assembled Au chip which was shown to exhibit a limit of detection of 0.19 nM and a linear detection ranging from 1 to 50 nM, the AuNPs modified Au chip was proven to clearly be a better analytical tool. Finally, validation of the proposed biosensor was evaluated by spiked wheat samples and average recoveries (93 and 90.1%) were found to be acceptable

Luminescence properties of yttrium gadolinium orthovanadate nanophosphors and efficient energy transfer from VO43- to Sm3+ via Gd-3+ ions

In this paper, luminescence properties of orthovanadates, Y1-x-yGdxVO4:ySm(3+) (where x = 0.05-0.50, y= 0.01-0.05), and the energy transfer mechanism from VO43- to Sm3+ via Gd3+ ions were investigated in detail. X-ray diffraction (XRD) analysis confirmed the crystalline phase for synthesized nanophosphor in a tetragonal structure with I41/amd space group. The average crystallite size estimated from XRD was similar to 28 nm. Field-emission scanning electron microscopy coupled with energy dispersive X-ray analysis revealed oval shaped morphology and composition of the nanophosphor, respectively. From high-resolution transmission electron microscopy observations, the particle sizes were found to be in the range 10-80 nm. The photoluminescence studies of Y0.77Gd0.20VO4:0.03Sm(3+) nanophosphor under 311 nm excitation exhibits dominant emission peak at 598 nm corresponding to (4)G(5/2) -> H-6(7/2) transition. The energy transfer occurs from VO43- to Sm3+ via Gd3+ ions was confirmed by applying Dexter and Reisfeld's theory and Inokuti-Hirayama model. Moreover, the energy transfer efficiencies and probabilities were calculated from the decay curves. Furthermore, Commission Internationale de l'Eclairage (CIE) color coordinate (0.59, 0.37) has been observed to be in the orange-red (598 nm) region for Y0.77Gd0.20VO4:0.03Sm(3+) nanophosphor. These results perfectly established the suitability of these nanophosphors in improving the efficiency of silicon solar cells, light emitting diodes, semiconductor photophysics, and nanodevices. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University

Ni-doped Bi0.5Sb1.5Te3 single crystal: a potential functional material for thermoelectricity, topological insulator, and optoelectronics

We report the growth of Ni-doped Bi0.5Sb1.35Ni0.15Te3 single crystal via the self-flux method. The crystalline nature of a grown single crystal was confirmed by the X-ray diffraction technique (XRD). Interestingly, the XRD pattern shows a sharp reflections of type of planes, revealing the growth of the crystal in c-direction. The grown single crystal was subjected for measurement of field dependence magnetization at 300 K and temperature-dependent magnetic moment. The electronic transport property of bulk single crystal was also carried out in a wide range of temperatures from 150 to 450 K. Reasonably large electrical conductivity sigma similar to 1584 S/cm at room temperature was observed which shows similar to 400% enhancement in sigma than the electrical conductivity of bare Bi0.5Sb1.5Te3 single crystal (400 S/cm at 300 K). This enhanced electrical conductivity results to significant power factor similar to 1.68 x 10(- 3)W/m K(2)at 300K which is 163% larger than that of bare Bi0.5Sb1.5Te3 single crystal (6.45 x 10(- 4)W/m K-2). Magnetic properties of a single crystal of Bi0.5Sb1.35Ni0.15Te3 reveal ferromagnetic behavior at 300 K. The photoluminescence (PL) behavior of Bi0.5Sb1.35Ni0.15Te3 single-crystal was also scrutinized. The PL spectra of Bi0.5Sb1.35Ni0.15Te3 single crystal shows the strong red emission peak in the visible region from 600 to 690 nm upon excitation at 375 nm wavelength, which corresponds to the optical bandgap of 2.1 eV

Metal-organic frameworks-derived titanium dioxide-carbon nanocomposite for supercapacitor applications

The pyrolysis of metal-organic frameworks (MOFs) to derive porous nanocarbons and metal oxides has attracted scientific attention due to the advantageous properties of the final products (eg, high surface areas). In the present research, MIL-125 (MIL = Materials of Institute Lavoisier, a Ti-based MOF) has been subjected to a single-step pyrolysis treatment in argon atmosphere. The combination of uniformly linked titanium metal cluster and oxygen-enriched organic linker has acted as a template to yield a titanium dioxide (TiO2)-carbon nanocomposite. The TiO2 nanoparticles infused in carbon skeleton structure (TiO2/C) has been investigated as an electrode material for supercapacitor applications. TiO2/C electrodes have delivered an excellent electrochemical performance, for example, in terms of charging-discharging efficiency. Two equally weighed TiO2/C electrodes have been used to assemble a solid-state symmetrical supercapacitor (SC) device, containing a gel electrolyte (poly vinyl alcohol in 1 M H2SO4). The above device has delivered a high value of energy density (43.5 Wh/kg) and an excellent power output of 0.865 kW/kg. The symmetrical SC could retain almost 95% of its initial capacitance even after 2000 charging-discharging cycles. The electrochemical performance of the TiO2/C SC was better than most MOF-based SCs reported previously. Such performance is attributed to the synergistic combination of electrically conducting MOF-derived carbon and redox active TiO2 nanocrystals with a large specific surface area

Metal oxide-nanoparticles and liquid crystal composites: A review of recent progress

Liquid Crystals (LCs) are soft materials lying in the midway between solids and liquids which have enjoyed considerable success due to their tremendous display and non-display applications in various areas of science and technology such as physics, chemistry, biology, material science, telecommunication etc. On the other hand, nanotechnology, an emerging research area, has brought revolutionary developments through its nanomaterials and nanoscale approaches creating enormous expectations over the number of years. In order to enhance various electro-optical, dielectric, physico-chemical properties, structural rearrangements of LCs, much work has been done through the incorporation of suitable nanoscale dopants into the host LC material. Metal oxide nanoparticles (MO-NPs) have attracted a great deal of interest on the grounds of their diverse properties in the recent times. Taking advantage of their varied desirable aspects, researchers have successfully dispersed suitable MO-NPs in LCs for winning noteworthy outcomes. In this review article, we have revisited successful doping of MO-NPs in LCs and observed that the doping established by mastering the intricacies of working with LCs and MO-NPs, their composites had resulted in desired and effective properties. This review deals with the detailed analysis of the contribution of MO-NPs in the domains of LCs and their applications. The focus in this work is laid on the doping effects of MO-NPs in various LCs and developing status of doping MO-NPs in LCs. The parameters which got affected after doping have also been summarized according to the type of MO-NPs doped. An extended analysis of the characteristics that were enhanced or suppressed after doping is systematically reviewed. Based on these discussions, possible future outcomes and prospects that might lead to major developments in the scientific technology regarding this work are put forward

Forster resonance energy transfer in organic photovoltaics devices fabricated by electric field assisted spray technique

Thin films of the ternary polymer blend (donors PCE-10 and PCDTBT with the acceptor PC71BM in chlombenzene) were fabricated by using spray coating technique without and with applied voltage to the nozzle during deposition. The increased absorption range from 400 nm to 800 nm indicates that Forster resonance energy transfer (FRET) is occurring for the films deposited under the electric field. This is also supported by photo-luminescence measurements and suggesting that under the applied voltage the orientation of polymer chains are changing at desired distances to facilitate FRET phenomenon to occur due to repulsion between uniformly charged ultrafine droplets. The size of droplets further reduced at higher applied voltage. Absorption, photo-luminescence, femtosecond transient absorption spectra and Kinetics traces were recorded to elucidate the role of applied DC voltages during the deposition of these films on photovoltaic performance of bulk heterojunction organic solar cell. The effect of FRET in polymer-polymer thin film under applied voltage during the deposition is observed, which indicates enhancement in the power conversion efficiency with the maximum value of 6.86% (J(sc) of 15.81 mA/cm(2) and V-oc of 0.77 V) at an applied voltage of 750 V