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Manipulation of mechanical properties of monolayer molybdenum disulfide: Kirigami and hetero-structure based approach
No full textThe two-dimensional monolayer structure of molybdenum disulfide (MoS2) is widely used in the advanced flexible electronic devices due to their unique mechanical, physical, and electronic properties. The main disadvantage of MoS2 is the limited mechanical strain, which restricts its application in flexible and stretchable devices. Therefore, it is required to develop various methods to modify the mechanical behavior of MoS2 monolayer depending on the environmental situation and the complexity of real applications. In this investigation, we have incorporated Kirigami and hetero-structure approaches for the manipulation of the mechanical behavior of MoS2. Kirigami is an ancient Japanese art of paper cutting. Monolayer MoS2 with circular/square/rectangular Kirigami pattern have simulated under uniaxial tensile load using molecular dynamics simulation. We observe that the stretch-ability (mechanical strain) significantly enhanced by the shape/size and location of Kirigami pattern during uniaxial tensile deformation. However, strength (mechanical stress and Young's modulus) of MoS2 can be enhancing by creating a hetero-structure with graphene. A large number of simulations have been performed to explore stress/energy distribution, Young's modulus, the effect of temperature, and strain rate during load applications. We believe that our results will provide extensive information related to enhancement in the mechanical strain and strain toward the application in flexible devices
Dry processing of high ash Indian coal by air fluidized vibrating deck
No full textProcessing of noncoking coals in India is limited due to the high cost
involved in wet processing. In the present study, dry beneficiation of two
high ash Indian non coking coal samples from two different coalfields,
namely, Talcher (coal-A) and Ib Valley (coal-B) having diverse characteristics
are studied using an air fluidized vibrating deck separator. Washing
characteristics of two coal samples indicate that coal-A was easy-to-wash
and coal-B was difficult to wash. The near-gravity materials (NGM) present
in coal-B were higher than coal-A due to different geographical origin. The
responses of dry separation of two coal samples studied under varied
process variables were found to be dependent on the washability characteristics
and the operating parameters used for achieving the desired
product. The performance of dry beneficiation is described by the recovery
of combustibles, ash rejection, ash recovery in clean coal (RA/cc), Ecart
probable error (Ep), and organic efficiency. It is found that Ep of the dry
process was 0.17 for easy-to-wash coal (coal-A) and 0.23 for difficult-towash
coal (coal-B). The organic efficiency of coal-A was 91% and 80% for
coal-B at optimum condition. The prospective of dry separation of high
ash Indian coal using air fluidized vibration technology was found to be
effective for achieving product with 34% ash content
Influence of laser scanning speed on nitrided Ti6Al4V surface
No full textThe influence of laser scan speed during nitriding in the range 30–150 cm min−1 on the physical properties, microstructure and corrosion behaviour of Ti6Al4V was studied. The surface energy of nitrided Ti6Al4V remained almost constant up to the scan speed of 60 cm min−1 followed by an increase in the maximum value at 80 cm min−1. A gradual drop in the microhardness of the coating from the outermost surface was noticed for specimens nitrided up to 80 cm min−1; an abrupt decrease, however, was found at a scan speed ≥100 cm min−1. The laser nitriding produced dendritic microstructure; an exponential decay in the secondary dendrite arm spacing (SDAS) with the increase in laser scan speed was revealed. The SDAS produced was smaller at the interphase and centre of the coating, compared to that at outermost surface. The passivation behaviour of Ti6Al4V at lower potentials shifted to the smaller current side after laser nitriding
Journal of Metallurgy and Materials Science : Special Issue on Advanced Materials
Get PDFMaterials are the heart of technology based growth of contemporary society, ensuring a good quality of socio-economic life while covering the spectrum from implements to implants. Scientists developments in the field of materials, has not only been possible by diffusing artificial boundaries among different scientific disciplines, it has also made “materials” an important tool for addressing and solving problems associated with “grand challenges”, be it energy, safe drinking water, health, resources depletion or safe environment. The present issue of the journal report the role of advanced and functional materials in the field of health, environment and energy, highlighting advancement made both in convectional and non-convectional advanced materials processed conventionally as well as by non-conventional methods
Glass forming ability and soft-magnetic properties of Fe-based glassy alloys developed using high phosphorous pig Iron
Get PDFGlass forming ability (GFA) and soft-magnetic behaviour of melt-spun Fe69C5.5P11.5Mn0.4Si2.3Cr1.8Mo1B8.5
(alloy 2) and Fe68C9P12Mn1Si3Nb2B5, (alloy 3) alloys prepared using high phosphorous pig iron (h-PI,
Fe80C14P2.2Mn0.4Si3.4) has been studied. The glass formation, thermo-physical and soft-magnetic properties
of the alloys were analyzed for different quenching rates by varying wheel speed as 23, 26, 33, 39
and 43 m/s. The simultaneous incorporation of alloying elements (Cr, Mo, Nb) and metalloids (C, B, P, Si)
transforms h-PI to complete glassy alloy, even at low quenching rates. The melt quenching rate influences
the thermal parameters and Curie temperature of glassy ribbons in an opposite way. Amongst
all, FeCPMnSiCrMoB glassy alloy show superior combination of higher glass transition temperature of
788 K, super cooled region of 34 K, glass Curie temperature of 552 K, coercivity less than 13 A/m and
maximum saturation magnetization of 1.1 T. In addition, the annealing treatment at 758 K improves
magnetic softness (1.7 A/m) of the alloy by relaxation of quenched-in stresses. The comparison of
developed glassy alloy with similar Fe-glassy alloys and SENNTIX type alloys show best combination of
thermo-physical and magnetic properties. The glassy alloy prepared using blast furnace high phosphorous
pig iron can be used for uniformly gapped soft-magnetic cores
Al-Monohydrate (Boehmite) to Al-Trihydrate(Bayerite/Gibbsite) Transformation During High-Energy Milling
No full textThe specific focus of this study is on the boehmite–water interaction during attrition milling of a boehmite prepared by thermal dehydroxylation of gibbsite. Various characterization studies confirm the formation of a new phase, bayerite (an Al-trihydroxide polymorph) during milling of boehmite with water as the dispersant. Bayerite is a more stable (thermodynamically) phase than boehmite. By forming bayerite, the free energy of the interacting system (consisting of disordered metastable boehmite and water) gets reduced. Such a transformation is of relevance in the digestion of Al-monohydrates in the Bayer process of alumina production. Furthermore, the presence of water during attrition milling itself is essential for the transformation. Bayerite does not form during attrition milling of the same boehmite in ethyl alcohol media and subsequent soaking in water up to 36 hours. Therefore, bayerite formation does not depend solely on structural degradation
Fluorescence quenching based detection of p-nitrophenol using luminescent silicon nanocrystals and insights into the quenching mechanism
No full textWe demonstrate a simple, rapid, selective and sensitive method for the detection of p-nitrophenol (pNP) using luminescent colloidal silicon nanocrystals (Si NCs). Aqueous suspension of green luminescent Si NCs was prepared at room temperature by simultaneous hydrolysis and redox reaction of (3-aminopropyl)triethoxysilane (APTES) in a remarkably simple one-step method. Trace addition of pNP significantly quenched the luminescence of the Si NCs and the quenching was found to be linearly dependent on the pNP concentration in the range of 0–20 μM of pNP in solution. Beyond 20 μM pNP concentration the quenching varied exponentially. Analysis of steady state absorption and emission, along with photoluminescence decay dynamics revealed that formation of ground state complexes (static quenching) and primary inner filter effect played a combined role in affecting quenching at relatively lower concentration range (0–20 μM); whereas both static and dynamic quenching came into effect at concentrations above 20 μM. Finally, we demonstrate a simple, pH-paper-type sensor based on Si NC coated filter paper and aluminium tape, for detection of aqueous as well as airborne pNP
Flux Development for Dephosphorization of Steel in Induction Furnace
No full textThe secondary steel sectors contribute more than 55 % to total steel production in India. Steel making through induction furnace route is approximately 30 % of the total steel production in India and 70 % of steel is produced by arc furnace route and Integrated steel plants. The average phosphorus content in the steel, produced through induction furnace route using DRI, is reported to be in the range of 0.06 to 0.1 %. According to BIS standard, the phosphorus content in any structural steel is varies between 0.03%.to 0.06% depending on the application of steel. However, Induction Furnace route has its own limitations for the refining of liquid metal and treatment with flux to produce low phosphorus and low sulphur steel. The presence of high phosphorus in engineering steel component causes cold shortness, i.e. the phosphorus increase the brittle ductile transition temperature. Therefore, CSIR- National Metallurgical Laboratory has developed the flux for dephosphorization of steel in induction furnace (5-40 kg scale). It has found that phosphorus content in steel is reduced to 0.01 wt % with addition of developed flux of 2-3 wt % of the liquid steel. Hence, developed flux is suitable for phosphorus removal in induction furnace
Tuning surface resistivity and thermal conductivity of water resistant fly ash waste based polymer composite via tailoring the interfacial polarization
No full textHigh performance environment friendly industrial inorganic waste (fly ash) waste based water resistant electrical insulating hybrid composites are fabricated with very high surface and volume resistivity. Dielectric constant of hybrid composite was decreased significantly from 10900 to 4.98, 5.25, 5.00, 5.81, and 6.69 for filler concentrations of 10, 20, 30, 50 and 60% in epoxy matrix, respectively. Very high surface resistivity of 1013 Ohms/sq. and volume resistivity of 1014 to 1015 Ohms-cm with ultra-low water absorption of 0.14 % were achieved .Thermal conductivity analysis shows a slight increase in the thermal conductivity of the composite sheet and reaches the value of 0.4387 W/mK. Such high resistivity is attributed due to low dielectric constant and interfacial polarization and low water absorption in the samples. Our approach presents new, adaptable and cost-effective means for effectively utilizing waste as eco-friendly electrical and thermal insulating sheet and lowering the thermal loss in microelectronics
Thermodynamic Aspects for Rare Earth Metal Production
No full textRare earth metals are one of the essential constituent of todays evolving green technologies materials. They are used in electric car, high performance magnet based miniatured devices, wind mills turbines, advanced sensors & machinery used in the space & nuclear energy sector, military nevigation devices, communications, information and transportation systems and many more. This book chapter discuss the basics of thermodynamical aspects for the extraction of rare earth metals from its oxides/minerals. Steps relating to thermodynamic feasibility of chemical reactions happening in the system under consideration using Gibbs free energy minimization tools. Thermodyamical steps involved in the processing of rare earth oxides/fluorides to produce rare earth metals by metallothermic reduction route are also stuided