Introduction to magnesium alloy processing technology and development of low-cost stir casting process for magnesium alloy and its composites

This paper presents the processing of magnesium alloys and its composite through different stir casting technologies.Design and devel-opment of stir casting technology that is suitable for processing of magnesium alloys has been done in this study.The low-cost stir casting processing of magnesium alloy and its composite with flux and without flux has been explained.The magnesium alloy and its composite have been fabricated by both the stir casting process.The micro structural characterization and mechanical properties of the developed composites has been evaluated.The optical emission spectroscopy of the developed alloy and factography of the developed alloy as well as composite was also examined.

Laboratory investigation on damping characteristics of homogeneous and stratified soil-ash system

In this study,the damping responses of uniform soil,equi-proportional fly ash,and local soil as a single unit were investigated.The large-strain cyclic triaxial tests were performed for the specimen compacted at the desired density(95%e99%of maximum dry density).The compacted specimens were tested under the loading frequency of 0.3e1 Hz with medium confinement of 70e100 kPa.Also,the unsymmetrical behavior of the hysteresis loop was analyzed using three different damping estimation approaches,i.e.symmetric hysteresis loop(SHL),asymmetric hysteresis loop(ASHL),and the modified American Society for Testing and Materials(ASTM)method.The outcome of the study shows for fly ash,local soil,and layered soil-ash,the ASHL technique has the highest damping value,followed by ASTM and then the SHL approach.The specimens prepared under high density and subjected to high confinement show low damping values.However,the specimens tested at high frequency exhibits high damping behavior.Similarly,the damping value of fly ash determined using the SHL and ASHL methods has a similar profile and reaches a maximum at 1%shear strain value before decreasing.The composite stratified deposit exhibits more dependency on relative compaction,confining pressure,and less on loading frequency.Based on the results,it is highly recommended to use the ASHL approach,especially under large strain conditions irrespective of soil type.The maximum damping ratio of stratified deposits is always in between the damping ratio of local soil and fly ash.The damping ratio of stratified soil and local soil is slightly larger than that of the other soils,although the damping ratio of fly ash is equivalent to that of the sand and clayey soil.These results may be helpful in the accurate determination of the damping properties of the layered soil-ash system that is required in the seismic response analysis.

Microstructure,mechanical and wear properties of aluminum borate whisker reinforced aluminum matrix composites

The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventional powder metallurgy technique. The aluminium powder and the whisker were effectively blended by a semi-powder metallurgy method. The blended powder mixtures were cold compacted and sintered at 600 ℃. The sintered composites were characterized for microstructural features by optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analysis. Porosity in the composites with variation in ABOw contents was determined. The effect of variation in content of ABOw on mechanical properties, viz. hardness, bending strength and compressive strength of the composites was evaluated. The dry sliding wear behaviour was evaluated at varying sliding distance at constant loads. Maximum flexural strength of 172 MPa and compressive strength of 324 MPa with improved hardness around HV 40.2 are obtained in composite with 10 wt.% ABOw. Further increase in ABOw content deteriorates the properties. A substantial increase in wear resistance is also observed with 10 wt.% ABOw. The excellent combination of mechanical properties of Al-10 wt.%ABOw composites is attributed to good interfacial bonds, less porosity and uniformity in the microstructure.

Microstructure and surface texture driven improvement in in-vitro response of laser surface processed AZ31B magnesium alloy

The present work explored effects of laser surface melting on microstructure and surface topography evolution in AZ31B magnesium alloy.Thermokinetic effects experienced by the material during laser surface melting were simulated using a multiphysics finite element model.Microstructure and phase evolution were examined using scanning electron microscopy,X-ray diffraction,and electron back scatter diffraction.Surface topography was evaluated using white light interferometry.The interaction of surface melted samples with simulated body fluid was monitored by contact angle measurements and immersion studies up to 7 days.Laser surface melting led to formation of a refined microstructure with predominantly basal crystallographic texture.Concurrently,the amount ofβphase(Mg_(17)Al_(12))increased with an increase in the laser fluence.βphase preferentially decorated the cell boundaries.In terms of topography,the surface became progressively rougher with an increase in laser fluence.As a result,upon immersion in simulated body fluid,the laser surface melted samples showed an improved wettability,corrosion resistance,and precipitation of mineral having composition closer to the hydroxyapatite bone mineral compared to the untreated sample.

Feasibility of Al−TiC coating on AZ91 magnesium alloy by TIG alloying method for tribological application

An attempt was made to improve the surface properties of the AZ91 Mg alloy through surface alloying of a mixture of Al and TiC with the help of TIG arc as heat source.The microstructural evolution of the alloyed layer on the AZ91 alloy was analysed through SEM and XRD technique.The micro-hardness and the dry sliding wear behaviour were assessed by Vickers micro-hardness tester and pin-on-disc wear test setup,respectively.It is revealed that almost uniform alloyed layer forms on the AZ91 alloy substrate for a specific current and scan speed employed in the present experiments.The alloyed layer exhibits hardness value up to 305 HV0.25,and almost negligible wear as compared to the as-received AZ91 alloy substrate.

Performance enhancement of IMC-PID controller design for stable and unstable second-order time delay processes

An IMC-PID controller was proposed for unstable second-order time delay system which shows the characteristics of inverse response(RHP zero). A plot of Ms versus λ was suggested to calculate the suitable tuning parameter λ, which provides a trade-off between performance and robustness. Six different forms of process models were selected from literature to show the applicability of the present method. Performance of controller was calculated by ITAE and total variation TV and compared with recently published tuning rules. Undesirable overshoot was removed by using a set-point weighting parameter. Robustness was tested by introducing a perturbation into the various model parameters and closed-loop results show that the designed controller is robust in the case of model uncertainty. The proposed method shows an overall better closed-loop response as compared to other recently reported methods.

Effects of mechanical vibration on the physical,metallurgical and mechanical properties of cast A308(LM21)aluminum alloy

This study investigated the microstructure,physical,and mechanical properties of die-cast A308 alloy subjected to mechanical vibration during solidification.Different frequencies(0,20,30,40,and 50 Hz)at constant amplitude(31μm)were employed using a power amplifier as the power input device.X-ray diffraction,optical microscopy,and scanning electron microscopy were used to examine the morphological changes in the cast samples under stationary and vibratory conditions.Metallurgical features of the castings were evaluated using Image J software.The average values of metallurgical features,including primaryα-Al grain size,dendrite arm spacing,average area of eutectic silicon,aspect ratio,and percentage porosity,reduced by 34%,59%,56%,22%,and 62%,respectively,at 30 Hz frequency compared with stationary casting.Mechanical tests of the cast samples showed that the yield strength(YS),ultimate tensile strength(UTS),percentage elongation(%EL),and microhardness(HV)increased by 8%,13%,17%,and 16%,respectively,at 30 Hz frequency compared with stationary casting.The fractured surface of the tensile specimens exhibited mixed-mode fracture behavior because of brittle facets,cleavage facets,ductile tearing,and dimple morphologies.The presence of small dimples showed that plastic deformation occurred before fracture.

Synthesis and catalytic activity of SBA-15 supported catalysts for styrene oxidation

Cu(II) and Mn(II) metals embedded on mesoporous SBA-15 were synthesized by co-precipitation technique.The support and catalysts were characterized by SEM–EDX,TEM,BET,XRD and ICP-AES methods.The catalytic activity of these catalysts was evaluated for styrene oxidation at various reaction conditions such as styrene to TBHP mole ratio,temperature,catalyst amount by using TBHP as an oxidizing agent.Major reaction products were styrene oxide and benzaldehyde and highest styrene conversion(97.3%) was observed at styrene to TBHP mole ratio of 1:4,temperature at 80 °C and 20 mg of catalyst.Further,the recyclability of the catalysts was observed and found that they can be recycled three times without major loss in their activity and selectivity.

Advances in the Structural Composition of Biomass:Fundamental and Bioenergy Applications

Increased environmental pollution due to the organic wastes over the world is one of the most burning issues.These organic wastes lie under the category of biodegradable waste and can be effectively degraded from their complex compound into simple one by the action of microbes or other living organisms.Moreover,lignocellulosic biomass is a major part of the biodegradable waste and belongs to the group of renewable energy source,which can be very effective for bioenergy production.Biomasses are made up of different compounds such as cellulose,hemicelluloses,lignin and protein.Apart from these components,based on the structural analysis biomass also consist of bioactive substances such as carotenoids,flavonoids,lignin and antioxidants.This review explores a complete overview of the classification,component and the structure of the biomass.Moreover,it discusses how biomasses can play the key role of substrate in many sectors such as industrial bioenergy production including gaseous and liquid biofuels.

Hydrothermal synthesis of Zn-Mg-based layered double hydroxide coatings for the corrosion protection of copper in chloride and hydroxide media

Layered double hydroxides(LDHs)hinder corrosive elements by forming a double layer and locking them between its layers.Hence,LDHs are interesting materials in corrosion inhibition.In this work,Zn-Mg-based LDHs are grown over a copper substrate by using a hydrothermal method.Two types of Zn-Mg-based LDH coating are prepared based on hydrothermal reaction time.Both types are characterized through Fourier transform infrared spectroscopy,Raman spectroscopy,high-resolution scanning electron microscopy,energy dispersive X-ray analysis,atomic force microscopy,and X-ray diffraction.Results show that the two types of LDH coating are successfully grown on copper;however,they differ in thickness and structural configuration.Corrosion testing of the LDH coatings is executed in 0.1 M Na Cl and 0.1 M Na OH through alternating current impedance measurements and Tafel polarization curves.Results show that L48 gives more than 90%protection to copper,which is higher than the protection provided by L24.However,both LDH coatings(L24 and L48)are more effective corrosion inhibitors in Na Cl than in Na OH,suggesting that the LDH coatings can more efficiently exchange Cl ions than OH ions.

Green Synthesis of Silver Nanoparticles: A Review

The bio-molecules from various plant components and microbial species have been used as potential agents for the synthesis of silver nanoparticles (AgNPs). In spite of a wide range of bio-molecules assisting in the process, synthesizing stable and widely applicable AgNPs by many researchers still poses a considerable challenge to the researchers. The biological agents for synthesizing AgNPs cover compounds produced naturally in microbes and plants. More than 100 different biological sources for synthesizing AgNPs are reported in the past decade by various authors. Reaction parameters under which the AgNPs were being synthesized hold prominent impact on their size, shape and application. Available published information on AgNPs synthesis, effects of various parameters, characterization techniques, properties and their application are summarised and critically discussed in this review.

MHD Seismology of a loop-like filament tube by observed kink waves

We report and analyze observational evidence of global kink oscillations in a solar filament as observed in Ha by instruments administered by National Solar Observatory （NSO）/Global Oscillation Network Group （GONG）. An M1.1-class flare in active region （AR） 11692 occurred on 2013 March 15 and induced a global kink mode in the filament lying towards the southwest of AR 11692. We find periods of about 61-67 minutes and damping times of 92-117 minutes at positions of three ver- tical slices chosen in and around the filament apex. We find that the waves are damped. From the observed period of the global kink mode and damping timescale using the theory of resonant absorption, we perform prominence seismology. We estimate a lower cut-off value for the inhomogeneity length scale to be around 0.34-0.44 times the radius of the filament cross-section.

Rheological fluid motion in tube by metachronal waves of cilia

This paper presents a theoretical study of a non-linear rheological fluid transport in an axisymmetric tube by cilia. An attempt has been made to explain the role of cilia motion in the transport of fluid through the ductus efferent of the male reproductive tract. The Ostwald-de Waele power-law viscous fluid is considered to represent the rheological fluid. We analyze pumping by means of a sequence of cilia beats from rowto-row of cilia in a given row of cells and from one row of cells to the next(metachronal wave movement). For this purpose, we consider the conditions that the corresponding Reynolds number is small enough for inertial effects to be negligible, and the wavelengthto-diameter ratio is large enough so that the pressure can be considered uniform over the cross section. Analyses and computations of the fluid motion reveal that the time-average flow rate depends on ε, a non-dimensional measure involving the mean radius a of the tube and the cilia length. Thus, the flow rate significantly varies with the cilia length.Moreover, the flow rate has been reported to be close to the estimated value 6 × 10ml/h for human efferent ducts if ε is near 0.4. The estimated value was suggested by Lardner and Shack(Lardner, T. J. and Shack, W. J. Cilia transport. Bulletin of Mathematical Biology, 34, 325–335(1972)) for human based on the experimental observations of flow rates in efferent ducts of other animals, e.g., rat, ram, and bull. In addition, the nature of the rheological fluid, i.e., the value of the fluid index n strongly influences various flow-governed characteristics. An interesting feature of this paper is that the pumping improves the thickening behavior for small values of ε or in free pumping(?P = 0) and pumping(?P > 0) regions.

Design of Wideband PBG Antenna for New Generation Communication Systems through Simulation

In modern wireless communication system, demand of high bandwidth antennas with low cost are increased. In proposed paper, these requirements have been fully justified by using PBG based wideband antenna. Although, metamaterial is one more option to build this idea, sometimes, negative permittivity or negative permeability or both does not permit to allow easy fabrication and maintaining low cost. An antenna with several periodic rods and organic magnetic materials substrate made it possible to enhance the bandwidth and think off using it for 5G communication systems. Proposed antenna is designed and fabricated for frequency range of 40 GHz - 50 GHz, and 12 × 9 periodic rods with substrate having organic magnetic materials property. Antenna is designed and analyzed using commercial simulation software CST microwave studio (CST STUDIO SUITE 2014) and measured for return loss and VSWR for fabricated design. Obtained results meet the requirement of wider bandwidth of 1.5 - 2 GHz and return loss, ?35 dB, and directivity is 61 dBi with efficiency of 61%.

Light Induced Green Synthesis of Silver Nanoparticles Using Aqueous Extract of Prunus amygdalus

Light driven, photon mediated green synthesis of silver nano-particles (AgNPs) was carried out using aqueous silver nitrate solution (1 mM) and aqueous extract of almond (Prunus amygdalus). Experiments were carried out in dark, diffused sunlight and direct sunlight to study the influence of light intensity as well as by wrapping the reaction tubes with colored cellophane filters (violet, green, yellow and red) to investigate the effect of light color on AgNP synthesis. It was observed that the violet filter enhanced the AgNPs synthesis appreciably. The FTIR spectroscopic analysis confirmed participation of bio-molecules with hydroxyl and amide groups present in the almond extract as reducing and capping or stabilizing agents, respectively. Dynamic light scattering (DLS) studies revealed the particle size distribution of nano-particles as 2 – 400 nm, and scanning electron microscopy (SEM) confirmed their spherical shape with an average size of about 20 nm. Growth analysis of AgNPs revealed an increase in number of nano-particles with time, whereas their rate of growth decreased gradually. The AgNP suspension was stable even beyond 3 weeks.

Metamorphic Evolution of the Amphibolites from Bundelkhand Craton, Central India: P-T Constraints and Phase Equilibrium Modelling

The amphibolites from the Mauranipur and Babina regions are located in the central part of the Bundelkhand Craton(BuC),northern India.During the geodynamic evolution of the BuC,these amphibolites underwent medium-grade metamorphism.This study combines textural observations of amphibolites from two distinct regions(Mauranipur and Babina)with mineral chemistry and phase equilibrium modelling.Observations suggest that the amphibolites of both areas have gone through three stages of metamorphism.The pre-peak stage in the amphibolites from the Mauranipur and Babina regions is marked by the assemblages Ep-Amp-Cpx-Pl-Ilm-Ru-Qz and Ep-Amp-Cpx-Pl-Ab-Ilm-Qz respectively;the peak metamorphic stage is characterized by the mineral assemblages Amp-Cpx-Pl-Ilm-Ru-Qz and Amp-Cpx-Pl-Ilm-Qz-H_(2)O,which is formed during the burial process,and the post-peak stage is represented by the assemblages Amp-Pl-Ilm-Ru-Qz and Amp-Pl-Ilm-Qz-H_(2)O respectively,which is formed by exhumation event.By applying the phase equilibria modelling in the NCFMASHTO system,the P-T conditions estimated from pre-peak,peak to post-peak stages are characterized as 6.7 kbar/510 oC,7.3 kbar/578ºC and>3.0 kbar/>585ºC,respectively,for the Mauranipur amphibolites;and 6.27 kbar/520ºC,5.2 kbar/805ºC and>3.0 kbar/>640ºC respectively for Babina amphibolites.The textural association and P-T conditions of both amphibolites suggest that these rocks were affected by burial metamorphism followed by an exhumation process during subduction tectonism in the BuC.

Pseudo-Differential Operators of Homogeneous Symbol Class Associated with the Weinstein Transform

In this paper,pseudo-differential operators with homogeneous symbol classes associated with the Weinstein transform are introduced.The boundedness of pseudo-differential operators and commutator between two pseudo-differential operators on H_(α,2)^(r) are proven with the help of the Weinstein transform technique.

Insights into the interface of NiCo_(2)O_(4) spinel/LaCoO_(3) perovskite nano-composite for CO and soot oxidation

In the quest for the development of thermally stable,highly active and low-cost catalysts for use in catalyzed diesel particulate filter,nano-composites are new areas of research.Therefore,we reported the easy synthesis of spinel NiCo_(2)O_(4)/perovskite LaCoO_(3) nano-composite,and its individual oxides NiCo_(2)O_(4)and LaCoO_(3) for comparison.The detailed insights into the physio-chemical characteristics of formed NiCo_(2)O_(4)/LaCoO_(3) nano-composite were done based on various characterization analysis such as X-ray diffraction(XRD),Fourier transform infrared(FT-IR),N_(2) physiosorption,scanning electron microscopy-energy dispersive spectroscopy(SEM-EDX),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).The characterization analysis of NiCo_(2)O_(4)/LaCoO_(3) revealed the successful formation of a chemical interface possessing strong interfacial interaction,resulting in desirable physicochemical characteristics such as small crystallite size,abundant mesoporosity,high specific surface area and activation of surface lattice oxygen.Owing to the desirable characteristics,the activity results over NiCo_(2)O_(4)/LaCoO_(3) nano-composite showed the excellent CO oxidation performance and high soot oxidation activity,recyclability and thermal stability.This work mainly attempts to emphasize the effectiveness of the facile,inexpensive and conventionally used precipitation method for the successful formation of highly efficient nano-composites.

CFD-DEM analysis of particle polydispersity on the performance of fluidised bed reactor during silane pyrolysis Author links open overlay panel

A CFD-DEM model is developed for chemical vapour deposition of silane in a fluidized bed reactor to investigate the effect of polydispersity on local phase dynamics,mass and heat transport,as well as the rate of Si deposition.Both gas-phase fines formation and heterogeneous deposition on the seed particle,as well as the scavenging effect for Si particle growth,are incorporated.The method is first validated against the experimentally measured Si deposition rate,percentage of fine production and minimum fluidisation velocity.Subsequently,the properties,primarily particle intermixing,fluidisation behaviour and bubble dynamics along with the deposition process,are analyzed for several polydisperse beds under various operating conditions.The effect of polydispersity of the bed on a fraction of the bubble size,dense phase expansion and interchange coefficient between various phases is thoroughly investigated to establish a correlation with reactor performance.The results show that broad-Gaussian particle size distribution(PSD)exhibits excellent improvement in fluidisation behaviour,resulting in a high deposition rate,and minimum formation of Si fines.

Estimating rock properties using sound signal dominant frequencies during diamond core drilling operations

In many engineering applications such as mining,geotechnical and petroleum industries,drilling operation is widely used.The drilling operation produces sound by-product,which could be helpful for preliminary estimation of the rock properties.Nevertheless,determination of rock properties is very difficult by the conventional methods in terms of high accuracy,and thus it is expensive and timeconsuming.In this context,a new technique was developed based on the estimation of rock properties using dominant frequencies from sound pressure level generated during diamond core drilling operations.First,sound pressure level was recorded and sound signals of these sound frequencies were analyzed using fast Fourier transform (FFT).Rock drilling experiments were performed on five different types of rock samples using computer numerical control (CNC) drilling machine BMV 45 T20.Using simple linear regression analysis,mathematical equations were developed for various rock properties,i.e.uniaxial compressive strength,Brazilian tensile strength,density,and dominant frequencies of sound pressure level.The developed models can be utilized at early stage of design to predict rock properties.