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Parametric optimization of fatigue behaviour of hybrid aluminium metal matrix composites
Get PDFFor 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
Performance analysis of anomalous photocatalytic activity of Cr-doped TiO2 nanoparticles [Cr(x)TiO2(1-x)]
Get PDFWe report the synthesis and characterisation of pristine and chromium (Cr) metal ion-doped titanium dioxide nanoparticles [Cr(x)TiO2(1-x)] to study the anomalous effect of Cr doping on the photocatalytic property of TiO2. The presence of dopants generates more number of recombination pairs and increases surface coverage sites which decreases photocatalytic activity. We study the structural morphology of the synthesised Cr(x)TiO2(1-x) samples using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis. The effect of Cr3+ ions on the optical properties of TiO2 has been studied using various imaging and spectroscopic techniques. Further, the effect of doping of Cr on the photocatalytic activity of TiO2 has been analysed in detail. The concentration of Cr in TiO2 has been chosen as 0, 1, 5 and 10% by weight. It has been observed that the pristine TiO2 exhibits better photocatalytic activity as compared to Cr-doped TiO2 irrespective of the Cr concentration. This can be attributed to the fact that due to Cr doping in TiO2, the number of available adsorption sites for malachite green reduces which degrades its photocatalytic activity. It is also confirmed by photoluminescence (PL) and time-resolved photoluminescence spectroscopy. PL intensity increases, and lifetime decreases with increase in doping concentration. Radiative recombination of electron and hole pairs of Cr3+ in TiO2 degrades its photocatalytic activity. The degradation efficiency is found to be 96% in the case of pristine TiO2 which reduces to 12% when doped with x = 10% concentration of chromium. Therefore, it is observed that in comparison with Cr-doped TiO2, pristine TiO2 exhibits an improved photocatalytic activity which shows the anomalous effect of Cr doping on the photocatalytic property of TiO2
A Comparative Study of Compressible and Conductive Vertically Aligned Carbon Nanotube Forest in Different Polymer Matrixes for High-Performance Piezoresistive Force Sensors
No full textIn the present scenario, conducting and lightweight flexible polymer nanocomposites rival metallic and inorganic semiconducting materials as highly sensitive piezoresistive force sensors. Herein, we explore the feasibility of vertically aligned carbon nanotube (VACNT) nanocomposites impregnated in different polymer matrixes, envisioned as highly efficient piezoresistors in sensor applications. Polymer nanocomposites are selectively designed and fabricated using three different polymer matrixes, i.e., polydimethylsiloxane (PDMS), polyurethane (PU), and epoxy resins with ideal reinforcement of VACNTs to enhance the thermal stability, conductivity, compressibility, piezoresistivity, and sensitivity of these nanocomposites. To predict the best piezoresistive force sensor, we evaluated the structural, optical, thermal, electrical, mechanical, and piezoresistive properties of the nanocomposites using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), I-V measurements, compressive stress-strain measurements, hysteresis, sensitivity, and force studies. The results demonstrate that the PDMS/VACNT nanocomposite is capable of sustaining large force with almost complete recovery and enhanced sensitivity, thereby fulfilling the desirable need for a highly efficient conductive and flexible force sensor as compared to PU/VACNT and epoxy/VACNT nanocomposites
A facile way to synthesize an intrinsically ultraviolet-C resistant tough semiconducting polymeric glass for organic optoelectronic device application
No full textIn this investigation, we have developed a new semiconductive Polymeric Transparent Matrix (PTM) as a substitute to the glass substrate used in a conventional optoelectronic device. Initially, we have synthesized Poly(methyl methacrylate) (PMMA) and series of its copolymers with Styrene in different weight percent (wt.%) ratio via solution polymerization process. The obtained polymers were characterized using various techniques to understand the effect of introducing different proportions of Styrene comonomers on PMMA backbone. The optimum composition of PTM was chosen based on copolymer's mechanical properties, optical transparency, and ultraviolet (UV) shielding properties. Then, a series of nanocomposites consisting of optimized PTM and various wt.% of Multiwalled Carbon Nanotubes (MWCNT) as a conductive filler were fabricated to increase the conductivity of PTM. A steep increase (10(9) fold) in bulk electrical conductivity was observed in case of 0.25 wt% MWCNT loaded optimized composite matrix, along with the retention of a good amount of optical transparency (88% at 550 nm) and 100% UV-C shielding. This optimized nanocomposite has also shown amelioration in mechanical properties as a result of uniform dispersion of MWCNT. These remarkable attributes favor the use of this optimized semiconducting PTM as a potential transparent substrate for next-generation organic optoelectronic devices
A spin-orbit coupling-induced two-dimensional electron gas in BiAlO3/SrTiO3 heterostructures
No full textBoth LaAlO3 and BiAlO3 are isostructural, isoelectronic and band insulators. Therefore, in analogy to the LaAlO3/SrTiO3 heterostructure, a quasi two dimensional electron gas (q-2DEG) could be anticipated in BiAlO3/SrTiO3 heterostructures. Our density functional theory based scalar relativistic calculations show that BiAlO3/SrTiO3 heterostructures remain insulating for a BiAlO3 film thickness up to 5 unit cells. However, with spin orbit coupling included in the crystal Hamiltonian, we find a thickness dependent insulator to metal transition for BiAlO3/SrTiO3 heterostructures. However, unlike the Ti3+/Ti4+ electronic reconstruction in LaAlO3/SrTiO3, the conductivity in BiAlO3/SrTiO3 is found to originate from the subsurface Bi 6p states. The results suggest that the properties of q-2DEG in BiAlO3/SrTiO3 can be controlled using an external electric field, leading to a wide range of solid state applications
A Review on the Statistical Methods and Implementation to Homogeneity Assessment of Certified Reference Materials in Relation to Uncertainty
Get PDFAn importance of data analysis, methods for homogeneity test and standard uncertainty evaluation associated in any measurement for exact quantification of certified value of any product is vital to be stressed in the scientific community. Herein, we have collectively summarized the detailed discussion on the basics of statistical parameters such as mean, median, mode, standard deviation, variance, range, normal distribution, and central limit theorem. Various statistical analysis methods such asztest,ttest, Chi-squared test, and ANOVA includingFtest have also been discussed in great detail to test the homogeneity of samples for certification of the reference material. The ISO guide 35 (2006) and Guide to Uncertainty in Measurement (GUM) are primarily considered to describe the basic concept of evaluating the associated uncertainty in the light of GUM modelling approach to avoid the error in the measurement which normally occurs in many scientific reports
Flexible perylenediimide/GaN organic-inorganic hybrid system with exciting optical and interfacial properties
Get PDFWe report the band gap tuning and facilitated charge transport at perylenediimide (PDI)/GaN interface in organic-inorganic hybrid nanostructure system over flexible titanium (Ti) foil. Energy levels of the materials perfectly align and facilitate high efficiency charge transfer from electron rich n-GaN to electron deficient PDI molecules. Proper interface formation resulted in band gap tuning as well as facilitated electron transport as evident in I-V characteristics. Growth of PDI/GaN hybrid system with band gap tuning from ultra-violet to visible region and excellent electrical properties open up new paradigm for fabrication of efficient optoelectronics devices on flexible substrates
GaN Nanotowers Grown on Si (111) and Functionalized with Au Nanoparticles and ZnO Nanorods for Highly Responsive UV Photodetectors
No full textVertically aligned GaN nanotowers (NTs) were grown on the Si (111) substrate by plasma-assisted molecular beam epitaxy to design a highly responsive ultraviolet (UV) photodetector. The UV detector fabricated on a bare GaN-NT array yielded highly sensitive and repeatable device characteristics attributed by high responsivity (R), low noise equivalent power (NEP), and a high external quantum efficiency (EQE) of 484.77 A/W, 1.76 x 10(-13) W.Hz(-1/2), and 1.85 X 10(5) %, respectively. Furthermore, the developed UV photodetector demonstrated fast response with excellent stability when functionalized with Au nanoparticles and ZnO nanorods. This hybridized GaN-NT-based device with ZnO nanorods and Au nanoparticles significantly accelerated the performance of the device where a prominent threeorder reduction under dark current is observed along with gigantic R, lower NEP, and an extremely enhanced EQE of 7042 A/W, 1.84 X 10(-14) W.Hz(-1/2), and 2.7 X 10(6)%, respectively. The mechanism elaborating the enhanced device performance with a localized surface plasmon effect has been discussed through an energy band diagram. The fabricated highly sensitive device can lead the path toward future optoelectronic applications of integrated III-nitride technology
Growth and Characterization of Single Crystals ofl-Histidine Hydrochloride Monohydrate for Nonlinear Optical Applications
Get PDFIn the present study, we have focused on the growth of semi-organic single crystals, as they play a vital role in the generation of a terahertz pulse and its potential applications. The single crystals ofl-histidine hydrochloride monohydrate (LMHCL) were grown by slow evaporation solution growth by using deionized water as a solvent in a controlled atmosphere. Good quality crystals of the required size were obtained within 2 weeks. To estimate the lattice dimensions and get the structural information, powder x-ray diffraction (PXRD) study was performed in which we have found that the crystal belongs to the orthorhombic crystal system with space groupP2(1)2(1)2(1). The functional groups and the corresponding vibrational mode were confirmed using Fourier transform infrared (FTIR) and Raman spectroscopy, respectively. To study the optical properties UV-Vis transmission spectrum and photoluminescence (PL) were recorded. It was observed that the single crystal has a high value of transmission over a long range of wavelength which signifies that the crystal is a good candidate for nonlinear optical (NLO) applications. The UV cut-off wavelength is found to be 236 nm. The grown single crystals were studied by time-domain terahertz spectroscopy (THz-TDS) for photonic applications and the refractive indices were calculated and it is found that the refractive index is nearly equal to 3.4
Hikami-Larkin-Nagaoka (HLN) Fitting of Magneto Transport of Bi2Se3 Single Crystal in Different Magnetic Field Ranges
Get PDFWe report the detailed study of structural/micro-structural and high magnetic field magneto transport properties of Bi2Se3 single crystal. Bi2Se3 single crystal is grown through conventional solid-state reaction route via the self-flux method. Rietveld analysis on Powder X-ray Diffraction (PXRD) showed that the studied Bi2Se3 crystal is crystallized in single-phase without any impurity. The surface morphology analyzed through Scanning Electron Microscopy (SEM) study which shows that as-grown single crystal exhibit layered type structure and the quantitative weight% of the atomic constituents (Bi and Se) are found to be close to the stoichiometric amount in energy-dispersive X-ray spectroscopy (EDS) analysis. Low temperature (2.5K) magneto-resistance (MR) exhibited a v-type cusp around origin at lower magnetic field, which is the sign of weak anti-localization (WAL) effect. Further, Bi2Se3 single crystal magneto conductivity data is fitted by well-known HLN equation in different magnetic field range of 2Tesla, 4Tesla and 6Tesla and the resultant found that the conduction mechanism of Bi2Se3 is dominated by WAL state