Search

Calotropis commonly known as ‘Madar’ is a medicinal plant. It is very famous in the name of milkweeds as it contains latex in its leaf and stem. The electro-active nature of the dry latex from the leaf and stem of the plant is like that of a super cooled ionic liquid. The electro-active material potential can be used as a low cost green synthesis agent to develop nano particles of metallic compound. The material in solidified pellet form shows sensitivity towards ammonia gas with faster response and recovery time. [ABSTRACT FROM AUTHOR]

Recently, the cooldown and current charging campaign have been carried out towards the demonstration of the first successful plasma discharge in the steady state superconducting Tokomak (SST-1). The SST-1 machine consists of cable-in-conduit wound superconducting toroidal as well as poloidal coils, cooled using 1.3 kW at 4.5 K helium refrigerator -cum- liquefier (HRL) system. The cryo system provides the two-phase helium at 0.13 MPa at 4.5 K as well as forced-flow pressurized helium at 0.4 MPa and in addition to 7 g-s-1 liquefaction capacity required for the current leads and other cold mass at 4.5 K. The entire integrated cold masses having different thermo hydraulic resistances cooled with the SST-1 HRL in optimised process parameters. In order to maintain different levels of temperatures and to facilitate smooth and reliable cooldown, warm-up, normal operations as well as to handle abnormal events such as, quench or utilities failures etc., exergy efficient process are adopted for the helium refrigerator-cum-liquefier (HRL) with an installed equivalent capacity of 1.3 kW at 4.5 K. Using the HRL, the cold mass of about 40 tons is being routinely cooled down from ambient temperature to 4.5 K with an average cooldown rate of 0.75 - 1 K-h-1. Long-term cryogenic stable conditions were obtained within 15 days in the superconducting coils and their connecting feeders. Afterwards, all of the cold mass is warmed-up in a controlled manner to ambient temperature. In this paper, we report the recent operational results of the cryogenic system during the first plasma discharge in SST-1 as well as the troubleshooting experiences of the cryogenic plant related hardware. [ABSTRACT FROM AUTHOR]

Rare earth doped (R=Ho, Gd and Ce) Bi1+xRxFeO3 for x = 0 and 0.1 ceramics were synthesized by solid state reaction route. XRD analysis showed that incorporation of rare earth (Gd, Ce) nucleates the development of orthorhombic grain growth. However, no structural transformation takes place in Ho doped sample. It is also observed that the materials shows room temperature enhanced ferroelectric polarization as well as ferromagnetization when rare earth ions are critically optimized in the respective composition formula. The value of leakage current greatly suppressed with incorporation of rare earth in BiFeO3. [ABSTRACT FROM AUTHOR]

Nanostructured Bi2O3 was prepared through mechanical alloying method. Detailed microstructural information was obtained after Rietveld refinement of the prepared samples. The Transmission Electron Microscope images confirmed the crystallinity of the sample. The average crystallite size decreases whereas microstrain increases due to milling. The ionic conductivity of the milled sample was found to have increased few orders than the unmilled sample. The change in structural and electrical properties due to milling were discussed and correlated. [ABSTRACT FROM AUTHOR]

Ba1-xCax Zr0.52Ti0.48 O3 ceramics was prepared by sol gel method. The crystallite size was in nano scale range. The dielectric constant was increased with increase in Ca2+ concentration in the sample. The dielectric loss was decreased with increase in ca concentration in the sample. The ac conductivity of the sample was increased with increase in Ca2+ concentration in the sample. The ac conductivity of the sample follows Johnscher power law. AC conductivity analysis shows that the interactions between neighbouring dipoles were decreased with the increase in Ca2+ concentration in the sample. [ABSTRACT FROM AUTHOR]

MgO and TiO2 doped Al-Zr oxide composites of Zr0.95Al1.05MgxO with x = 0,0.01,...,0.05,0.75,1 and Zr0.95-Al1.05-Tiz-O with z = 0, 0.025,....,1 were sintered to high density by both DC thermal plasma assisted rapid sintering as well as conventional sintering. It is observed that the above mentioned MgO and TiO2 doped Al-Zr oxide composites were sintered to high density end products by the thermal plasma heating technique within a short sintering time (a few minutes) as compared to a conventional long range resistive heating schedule (a few tens of hours). It is also noticed that there exists a critical limiting point of MgO doping concentration (x = 0.05 in Zr0.95Al1.05MgxO) for maximum physical densification in both conventional as well as plasma sintered samples. Sintered specimens were analyzed by XRD studies. XRD studies revealed the presence of a high density phase, Mg2Zr5O12 prominently in x = 0.05 sintered sample which resulted in maximum densification of the sample. With increasing doping concentration of TiO2 (i.e. z=0 to 1), ρs (sintered density) of both plasma sintered and conventional sintered specimens were found to follow a concavity like variation with well defined critical limit of TiO2 concentration (i.e. at z=0.05) at which ρs became minimum. However, hardness was found to be maximum at z = 0.05. [ABSTRACT FROM AUTHOR]

La0.67Ca0.33MnO3 (LCMO) colossal magnetoresistance (CMR) materials were sintered to highly dense products by an extended arc thermal plasma assisted heating (EATPAH) technique within a short sintering time of 2.5 minutes as compared to conventional long range heating schedule (few hours of time). 2.5 minutes plasma sintered LCMO showed enhanced Tc (272 K), which is closed to TIM (275 K) [1] as compared to the conventional sintered LCMO sample. Specimens are analyzed by X-ray Photoelectron Spectra (XPS) and electron probe microstructure analysis (EPMA) to get idea on elemental distribution and valence spectra of all the elements present in the specimen. The binding energy of La, Ca & Mn are analogous to the conventional sintered LCMO and to the reference spectra [2]. [ABSTRACT FROM AUTHOR]

Chromium nitride (CrN) films were synthesised by reactive pulsed DC sputtering (PMS) of a chromium target in the presence of argon (Ar) and nitrogen (N2) gas mixture operated at 20 kHz and 30% duty cycle. Experiments were conducted to study the effect of target voltage on the structure and mechanical properties of the films. Deposited films were analysed for their structure, hardness and adhesion using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), nanoindentation and nanoscratch. Transition from cubic phase CrN (c-CrN) to hexagonal phase Cr2N (β-Cr2N) was observed with increase in target voltage. A single layer 430 nm thick film deposited at 450 V showed good mechanical properties with hardness of 19.5 GPa and critical load of 18 mN. Further, inter-and multi-layer Cr/CrN films showed the presence of c-CrN phase with a strong (200) reflection along with weak c-CrN (111) and β-Cr2N (110) reflections. Cr interlayered CrN film deposited at a target voltage of 450 V showed a hardness of 19.7 GPa and critical load of 27.7 mN. As compared to a single layer CrN, for a 8 bilayered Cr/CrN film of 1μm thickness, the hardness remained the same (18.2 GPa) while the adhesion of the film improved greatly from a critical load of 18 mN to 86 mN. [ABSTRACT FROM AUTHOR]

Diamond like nanosized structures were deposited where a modified microwave plasma CVD diamond growth recipe was used; here, instead of a clean molybdenum (Mo) holder, the Si(100) substrates were placed on iron oxide coated Mo holder. The growth of micron size diamond crystals were observed on clean areas whereas rod shaped carbon based nanostructures were observed on iron oxide rich areas. Furthermore, the growth of CNTs was also noticed on the plasma exposed parts of the Mo holder. Electron microscopy results suggest that some of the nanorods crystallize in the form of diamond. [ABSTRACT FROM AUTHOR]

Polycrystalline Ho1-xCaxMnO3(x = 0.05,0.1,0.2) bulk ceramic samples were prepared by conventional solid state reaction route. The effect of Ca doping on structural, dielectric and ferroelectric behaviour were investigated carefully. All samples showed orthorhombic phase without any structural transformation after substitution of Ca at Ho site. Interestingly dielectric constant value increase significantly with increase in concentration of x upto 0.1 and decrease with further substitution, which reveals that Ca substitution increase the dipole alignment due charge ordering. Similarly the sample showed a well shaped ferroelectric hysteresis loop having saturation polarization value of 1.5μC/cm2 for x = 0.1. [ABSTRACT FROM AUTHOR]

A small amount of nano Cu addition (2.5 wt %) was found to dramatically decrease the reaction temperature of magnesium and boron, forming MgB2 without any degradation in the transport critical current. The presence of reacted Mg2Cu liquid phase could accelerate the reaction between Mg and B and finally results in the formation of MgB2 phase even at low temperatures. All Cu doped samples heat treated below 650 °C exhibited highly enhanced transport JC at 30 K and the sample heat treated at 550 °C recorded 30-fold increase in transport JC compared to the pure sample. [ABSTRACT FROM AUTHOR]

Nanostructured Bi2O3 was prepared through mechanical alloying method. Detailed microstructural information was obtained after Rietveld refinement of the prepared samples. The Transmission Electron Microscope images confirmed the crystallinity of the sample. The average crystallite size decreases whereas microstrain increases due to milling. The ionic conductivity of the milled sample was found to have increased few orders than the unmilled sample. The change in structural and electrical properties due to milling were discussed and correlated. [ABSTRACT FROM AUTHOR]