Formation of metastable phases and nanocomposite structures in rapidly solidified Al–Fe alloys

Nayak, S.S.,Chang, H.J.,Kim, D.H.,Pabi, S.K.,Murty, B.S. Elsevier 2011 Materials science & engineering. properties, micro Vol.528 No.18

<P><B>Highlights</B></P><P>► Structures of nanocomposites in rapidly solidified Al–Fe alloys were investigated. ► Nanoquasicrystalline, amorphous and intermetallics phases coexist with α-Al. ► Nanoquasicrystalline phase was observed for the first time in the dilute Al alloys. ► Thermodynamic driving force plays dominant role in precipitation of Fe-rich phases. ► High hardness (3.57GPa) was observed for nanocomposite of Al–10Fe alloy.</P> <P><B>Abstract</B></P><P>In the present work the structure and morphology of the phases of nanocomposites formed in rapidly solidified Al–Fe alloys were investigated in details using analytical transmission electron microscopy and X-ray diffraction. Nanoquasicrystalline phases, amorphous phase and intermetallics like Al<SUB>5</SUB>Fe<SUB>2</SUB>, Al<SUB>13</SUB>F<SUB>4</SUB> coexisted with α-Al in nanocomposites of the melt spun alloys. It was seen that the Fe supersaturation in α-Al diminished with the increase in Fe content and wheel speed indicating the dominant role of the thermodynamic driving force in the precipitation of Fe-rich phases. Nanoquasicrystalline phases were observed for the first time in the dilute Al alloys like Al–2.5Fe and Al–5Fe as confirmed by high resolution TEM. High hardness (3.57GPa) was measured in nanocomposite of Al–10Fe alloy, which was attributed to synergistic effect of solid solution strengthening due to high solute content (9.17at.% Fe), dispersion strengthening by high volume fraction of nanoquasicrystalline phase; and Hall–Petch strengthening from finer cell size (20–30nm) of α-Al matrix.</P>

CONTROLLABILITY, OBSERVABILITY, AND REALIZABILITY OF MATRIX LYAPUNOV SYSTEMS

Murty M.S.N.,Rao B.V. Appa,Kumar G. Suresh Korean Mathematical Society 2006 대한수학회보 Vol.43 No.1

This paper presents necessary and sufficient conditions for complete controllability, complete observability and realizability associated with matrix Lyapunov systems under certain smoothness conditions.

An Efficient and Simple Load Flow Approach for Radial and Meshed Distribution Networks

B. Ravi Teja,V.V.S.N. Murty,Ashwani Kumar,member IEEE 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.2

The main contribution of this paper is: (i) proposing a new efficient and simple load flow method for balanced radial and meshed distribution systems, (ii) impact of load models, different X/R ratios, load growth and tolerance levels to check robustness of proposed load flow method, (iii) impact of number of loops on meshed distribution systems, (iv) Comparison of radial and mesh distribution for voltage profile, total power losses, and number of iterations. The convergence ability of the proposed load flow method is evaluated under these conditions. Computer program has been developed to implement the power flow solution scheme in MATLAB and successfully applied to several practical distribution networks with radial and mesh structure. The convergence ability is quantitatively evaluated for different loading conditions, load growth, R/X ratios, and tolerance levels. Moreover, the effects of static load modeling on the convergence characteristics of the proposed algorithm are also investigated. Effectiveness of the proposed load flow method has been tested on IEEE 33 bus and IEEE 69 bus radial and meshed distribution networks. The proposed load flow method is compared with existing load flow methods, Ghosh et al. [6], Aravindhababu et al. [7], and J.H.Teng [16] to demonstrate its effectiveness.

Controllability, observability, andrealizability of matrix Lyapunov systems

M. S. N. Murty,B. V. Appa Rao,G. Suresh Kumar 대한수학회 2006 대한수학회보 Vol.43 No.1

This paper presents necessary and sufficient conditions forcomplete controllability, complete observability and realizabilityassociated with matrix Lyapunov systems under certain smoothness conditions.

Crystallite Size Effect on Voltage Tunable Giant Dielectric Permittivity of Nanocrystalline CuO

T. Prakash,B.S. Murty,A.R. Kaskhedikar,P.D. Peshwe 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.1

The effect of crystallite size and applied DC bias voltage on dielectric permittivity of CuO was studied using impedance spectroscopy. The measurements were performed at room temperature in a wide frequency range of 1 Hz to 1 MHz under applied DC bias voltages from 0 to 3 V in the periodic increment of 0.2 V. The observed applied DC bias voltage effect on giant dielectric constant (ε' = 104) were analyzed with ‘grain boundary double Schottky potential barrier height model’. The percentage of tunability (T %) at the frequency 100 Hz is found to be 45.5% for the case of nanocrystalline CuO in contrast to 0% tunability in bulk CuO.

Effect of DC Bias on Dielectric Properties of Nanocrystalline CuAlO2

T. Prakash,S. Ramasamy,B.S. Murty 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.2

Grain boundary effect on the room temperature dielectric behavior in mechanically alloyed nanocrystalline CuAlO2 has been investigated using impedance spectroscopy under the applied DC bias voltages 0 V to 4.8 V in a periodic interval of 0.2 V. Analysis of impedance data confirms the existence of double Schottky potential barrier heights (Φb) between two adjacent grains (left and right side) with grain boundary and its influences in dielectric relaxation time (τ), dielectric constant (ε') and dielectric loss (tan δ) factor. Also, clear evidence on the suppression of Φb was demonstrated in the higher applied bias voltages with the parameter τ. At equilibrium state, τ is 0.63 ms and it was reduced to 0.13 ms after the 3.2 V applied DC bias. These observed DC bias voltage effects are obeying ‘brick layer model’ and also elucidates Φb is playing a crucial role in controlling dielectric properties of nanomaterials.

Maxwelle-Wagner polarization in grain boundary segregated NiCuZn ferrite

R.A. Mondal,B.S. Murty,V.R.K. Murthy 한국물리학회 2014 Current Applied Physics Vol.14 No.12

The present work investigates the polarization response in polycrystalline Ni0.9yCuyZn0.1Fe1.98O4d (y ¼ 0, 0.1, 0.2, 0.3, 0.4, 0.5) ferrite synthesized by solidestate reaction method. X-ray diffraction analysis confirmed cubic spinel phase formation in the calcined samples. Sintered samples contain a continuous network of CuO-rich segregation along the grain boundaries for y 0.2. Dielectric spectra showed a relaxation peak for y 0.2 in the frequency range of 1 kHze1 MHz. This relaxation has been explained based on MaxwelleWagner polarization considering two-layer model in connection with two heterogeneous dielectric media.

Enhanced mangnetoelectric voltage in multiferroic particulate Ni0.83Co0.15Cu0.02Fe1.9O4- δ/PbZr0.52Ti0.48O3 composites – dielectric, piezoelectric and magnetic properties

M. Venkata Ramanaa,N. Ramamanohar Reddy,G. Sreenivasulu,K.V. Siva kumar,B.S. Murty,V.R.K. Murthy 한국물리학회 2009 Current Applied Physics Vol.9 No.5

Multiferroic particulate composites of Ni0.83Co0.15Cu0.02Fe1.9O4-δ – NCCF and lead zirconate titanate (PZT) were prepared conventional ceramic method. The generic formulae x NCCF + (1-x) PZT where x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mole fractions. The presence of two phases in multiferroic was confirmed with XRD technique. The dielectric constant and loss tangent were studied as a function of frequency (100 Hz to 1 M Hz) and temperature (30–500 ℃). The piezoelectric coefficient d33 were also studied on these particulate composites. The hysteresis behaviour was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (μB). The static magnetoelectric (ME) voltage coefficient was measured as a function of dc magnetic bias field. A high value of ME output (3151 mV/Oe.cm) was obtained in the composite containing 50% highly magnetostrictive ferrite component NCCF – 50% highly piezoelectric ferroelectric component PZT. These multiferroic particulate composites are used as phase shifters, magnetic sensors, cables etc. Multiferroic particulate composites of Ni0.83Co0.15Cu0.02Fe1.9O4-δ – NCCF and lead zirconate titanate (PZT) were prepared conventional ceramic method. The generic formulae x NCCF + (1-x) PZT where x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mole fractions. The presence of two phases in multiferroic was confirmed with XRD technique. The dielectric constant and loss tangent were studied as a function of frequency (100 Hz to 1 M Hz) and temperature (30–500 ℃). The piezoelectric coefficient d33 were also studied on these particulate composites. The hysteresis behaviour was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (μB). The static magnetoelectric (ME) voltage coefficient was measured as a function of dc magnetic bias field. A high value of ME output (3151 mV/Oe.cm) was obtained in the composite containing 50% highly magnetostrictive ferrite component NCCF – 50% highly piezoelectric ferroelectric component PZT. These multiferroic particulate composites are used as phase shifters, magnetic sensors, cables etc.