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E. E. Antonova - One of the best experts on this subject based on the ideXlab platform.
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Variation of Plasma Pressure at the Auroral Oval Latitudes before, during, and after the Isolated Geomagnetic Substorm on December 22, 2008
Geomagnetism and Aeronomy, 2020Co-Authors: M. Rojas Gamarra, M V Stepanova, J. Gonzalez, E. E. AntonovaAbstract:The change in Plasma Pressure at the latitudes of the auroral oval before, during, and after the isolated geomagnetic substorm on December 22, 2008, were studied using data from the F13, 15, 16, and 17 DMSP satellites. One feature of the studied event was a long period of values of AL index that were close to zero. During this time, there was a more than double increase in the dynamic Pressure of the solar wind. The projection of Pressure maxima on the equatorial plane was carried out using models of the geomagnetic field and a model of the Pressure distribution in the equatorial plane. It was shown that the maximum Plasma-Pressure values at the latitudes of the auroral oval increase with increasing dynamic Pressure of the solar wind during the magnetically quiet period to substorm. The maximum values of the Plasma Pressure for the studied period are recorded during the expansion phase of the substorm. A decrease in the solar-wind dynamic Pressure to values close to the values during the magnetically quiet time before the substorm was not accompanied by a drop in the Plasma Pressure after the substorm. The difference between the Plasma Pressure dynamics during an isolated substorm and the Pressure dynamics during a substorm taking place during magnetic storm is discussed.
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Plasma Pressure under Magnetopause on the Dusk Flank in the Equatorial Plane for Large Negative X GSM
Geomagnetism and Aeronomy, 2018Co-Authors: S. S. Znatkova, E. E. Antonova, Igor Kirpichev, M. S. PulinetsAbstract:The crossings of the magnetopause and low-latitude boundary layer by the THEMIS-B satellite in the spring of 2008 on the dusk flank under large negative XGSM (from –17RE to –19RE) are studied. The parameters of Plasma and magnetic field are analyzed from the data of ESA and MGF instruments. The changes in the total Pressure, magnetic field Pressure, and Plasma Pressure component during the transition from the magnetosheath to the Plasma sheet (PS) are analyzed. The values of Plasma Pressures under the magnetopause at the edge of the PS for the considered events are determined. The applicability of the obtained results to the determination of the position of the boundary between the tail current and the ring current is discussed.
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Plasma Pressure under Magnetopause on the Dusk Flank in the Equatorial Plane for Large Negative Х_GSM
Geomagnetism and Aeronomy, 2018Co-Authors: S. S. Znatkova, E. E. Antonova, I P Kirpichev, M. S. PulinetsAbstract:The crossings of the magnetopause and low-latitude boundary layer by the THEMIS-B satellite in the spring of 2008 on the dusk flank under large negative X _GSM (from –17 R _E to –19 R _E) are studied. The parameters of Plasma and magnetic field are analyzed from the data of ESA and MGF instruments. The changes in the total Pressure, magnetic field Pressure, and Plasma Pressure component during the transition from the magnetosheath to the Plasma sheet (PS) are analyzed. The values of Plasma Pressures under the magnetopause at the edge of the PS for the considered events are determined. The applicability of the obtained results to the determination of the position of the boundary between the tail current and the ring current is discussed.
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Comparison of the Plasma Pressure distributions over the equatorial plane and at low altitudes under magnetically quiet conditions
Geomagnetism and Aeronomy, 2014Co-Authors: E. E. Antonova, Igor Kirpichev, V. G. Vorobjev, O. I. YagodkinaAbstract:The distribution of Plasma Pressure over the equatorial plane is compared with the Plasma Pressure and the position of the electron precipitation boundaries at low altitudes under the conditions of low geomagnetic activity. The Pressure at the equatorial plane is determined using data of the THEMIS international five-satellite mission; the Pressure at low altitudes, using data of the DMSP satellites. Plasma Pressure isotropy and the validity of the condition of the magnetostatic equilibrium at a low level of geomagnetic activity are taken into account. Plasma Pressure in such a case is constant along the magnetic field line and can be considered a “natural tracer” of the field line. It is shown that the Plasma ring surrounding the Earth at geocentric distances of ∼6 to ∼10–12RE is the main source of the precipitations in the auroral oval.
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Dipole magnetic-field disturbance and generation of current systems by asymmetric Plasma Pressure
Geomagnetism and Aeronomy, 2014Co-Authors: V. V. Vovchenko, E. E. AntonovaAbstract:Nonlinear disturbance of the dipole field by nonaxisymmetric Plasma Pressure distribution was analyzed under the assumption of magnetostatic equilibrium for finite values of the Plasma parameter at the Pressure maximum area. The distributions of isolines of the constant value of magnetic-field component B _ Z and the volume of magnetic flux tube in the equatorial plane were obtained. At a finite Plasma Pressure, local minima and maxima of the magnetic field are formed. The formation of these local maxima and minima leads to the formation of contours (not surrounding the Earth) B _min = const, where B _min is the minimum magnetic field on the magnetic field line. This changes the direction of the gradient of the volume of the magnetic flux tube. The configuration of appearing field-aligned currents was determined. The results obtained are discussed in terms of their use in explaining a number of effects observed in the Earth’s magnetosphere.
R. Radhakrishnan - One of the best experts on this subject based on the ideXlab platform.
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Design of experiment approach for sintering study of nanocrystalline SiC fabricated using Plasma Pressure compaction
Science of Sintering, 2009Co-Authors: Manish G. Bothara, Sundar V. Atre, Seong Jin Park, T. S. Sudarshan, Pritha Vijay, Randall M. German, R. RadhakrishnanAbstract:Plasma Pressure compaction (P 2 C) is a novel sintering technique that enables the consolidation of silicon carbide with a nanoscale microstructure at a relatively low temperature. To achieve a high final density with optimized mechanical properties, the effects of various sintering factors pertaining to the temperature–time profile and Pressure were characterized. This paper reports a design of experiment approach used to optimize the processing for a 100 nm SiC powder focused on four sintering factors: temperature, time, Pressure, and heating rate. Response variables included the density and mechanical properties. A L9 orthogonal array approach that includes the signal-to-noise (S/N) ratio and analysis of variance (ANOVA) was employed to optimize the processing factors. All of the sintering factors have significant effect on the density and mechanical properties. A final density of 98.1% was achieved with a temperature of 1600 °C, hold time of 30 min, Pressure of 50 MPa, and heating rate of 100 °C/min. The hardness reached 18.4 GPa with a fracture toughness of 4.6 MPa√m, and these are comparable to reports from prior studies using higher consolidation temperatures.
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Bulk SmCo/sub 5///spl alpha/-Fe composites by Plasma Pressure compaction
2003 IEEE International Magnetics Conference (INTERMAG), 2003Co-Authors: Q. Zeng, Y. Zhang, M.j. Bonder, R. Radhakrishnan, G.c. HadjipanayisAbstract:In this paper, the preparation of bulk SmCo5/a-Fe nanocomposites magnets by Plasma Pressure compaction was presented. Magnetic properties on consolidated samples were made using SQUID and VSM. Microstructural characterization was performed with SEM and XRD.
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Bulk SmCo/sub 5///spl alpha/-Fe composite by Plasma Pressure consolidation
IEEE Transactions on Magnetics, 2003Co-Authors: Q. Zeng, Y. Zhang, M.j. Bonder, G.c. Hadjipanayis, R. RadhakrishnanAbstract:Plasma Pressure consolidation (PPC) was used to synthesize exchange coupled composite magnets. The magnets were processed from a mixture of micrometer-size, anisotropic magnetically hard SmCo/sub 5/ and nanometer size magnetically soft Fe particles. High density magnets were obtained by PPC at a temperature as low as 760/spl deg/C. The compacted SmCo/sub 5///spl alpha/-Fe composite showed single-phase magnetic behavior.
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Effect of pulsed current on reactively synthesised TiB2 consolidated by Plasma Pressure compaction
Powder Metallurgy, 2003Co-Authors: J. Wachsmuth, R. Radhakrishnan, T. S. SudarshanAbstract:AbstractThe effect of pulsed current on TiB2 formed by reactive consolidation between titanium and boron is reported in this paper. This consolidation was performed using the Plasma Pressure compaction (P2C) technique. A comparison between the pulsed and control samples reveals that pulsed current reduces grain growth (pulsed samples had an average grain size of 2·79 μm compared to 5·99 μm) while increasing sintering rates (pulsed samples were on average 15·5% more dense). The reduced grain growth and increased densification is due to the removal of adsorbed oxygen from the surface of the powder.
Tangali S. Sudarshan - One of the best experts on this subject based on the ideXlab platform.
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Influence of Size of Nanoparticles and Plasma Pressure Compaction on Microstructural Development and Hardness of Bulk Tungsten Samples
Advanced Powder Technology, 2013Co-Authors: Tirumalai S. Srivatsan, K. Manigandan, M. Petraroli, Rosa M Trejo, Tangali S. SudarshanAbstract:Abstract Bulk tungsten samples were prepared by consolidating nanosize tungsten powders using the technique of Plasma Pressure compaction. This innovative sintering technique offers the intrinsic capability of producing bulk samples having near theoretical density. Five different powder particle sizes, in the nanoscale, were chosen and bulk samples obtained by consolidating the powders under identical conditions of temperature, Pressure and time using the technique of Plasma Pressure compaction. Microstructural observations and density measurement provide evidence for the presence of minimal porosity following consolidation. The influence of initial size of the powder particles on microstructural development to include the presence and distribution of porosity, density, micro-hardness, stiffness and nano-hardness is presented and discussed.
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Sintering behavior of nanocrystalline silicon carbide using a Plasma Pressure compaction system: Master sintering curve analysis
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 2010Co-Authors: Manish G. Bothara, Tangali S. Sudarshan, R.m. German, Sundar V. Atre, Seong Jin Park, Ramalingam RadhakrishnanAbstract:Nanostructured ceramics offer significant improvements in properties over corresponding materials with larger grain sizes on the order of tens to hundreds of micrometers. Silicon carbide (SiC) samples with grain sizes on the order of 100 nm can result in improved strength, chemical resistance, thermal stability, and tailored electrical resistivity. In this study, nanocrystalline SiC was processed in a Plasma Pressure compaction (P2C) system at a temperature of 1973 K (1700 C) that was much lower than the temperatures reported for other sintering techniques. Microstructure of the resulting samples was studied and the hardness and the fracture toughness were measured. The grain sizes were on the order of 700 nm, the hardness between 22 and 24 GPa, and the toughness between 5 and 6.5 MPaÆm1/2. The master sintering curve (MSC) analysis was used to model the densification behavior of SiC powder sintered by the P2C method. The apparent activation energies for three different Pressures of 10, 30, and 50 MPa were obtained to be 1666, 1034, and 1162 kJ/mol, respectively. Although densification occurs via diffusion, the activation energies were higher than those associated with self-diffusion in SiC (between 570 and 920 kJ/mol). A validation study of the MSC was also conducted and the variation in observed density from the density predicted by theMSC was found to range from 1 to 10 pct.
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Microstructure and Hardness of Copper Powders Consolidated by Plasma Pressure Compaction
Journal of Materials Engineering and Performance, 2001Co-Authors: Tirumalai S. Srivatsan, B.g Ravi, A.s Naruka, Laura Riester, S. Yoo, Tangali S. SudarshanAbstract:Bulk fine-grained copper samples were prepared by consolidating copper powders using the technique of Plasma Pressure compaction (P2C). The specimens were obtained by consolidating the powder particles under conditions of electrical pulse and no-electrical pulse and at two different temperatures. Results reveal that pulsing of the powders prior to consolidation led to higher microhardness values than the samples that were obtained by consolidating the powder particles under no-pulse. Both nanohardness and microhardness increased with an increase in the temperature of consolidation. Samples consolidated at the higher temperature revealed evidence of grain coarsening. The influence of processing variables on microstructure development and hardness is presented and discussed.
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The microstructure and hardness of molybdenum powders consolidated by Plasma Pressure compaction
Powder Technology, 2000Co-Authors: Tirumalai S. Srivatsan, B.g Ravi, M. Petraroli, A.s Naruka, Laura Riester, Tangali S. SudarshanAbstract:Abstract Bulk molybdenum samples were prepared by consolidating molybdenum powders using the technique of Plasma Pressure compaction (P2C). The specimens were obtained by consolidating the powder particles under conditions of pulse and no-pulse and at two different temperatures. Results reveal that pulsing of the powders prior to consolidation had little influence on microhardness when compared to the samples that were obtained by consolidating the powder particles under no-pulse. Both nanohardness and microhardness measurements revealed a marginal decrease with an increase in temperature of compaction. The influence of processing variables on microstructural development and hardness is presented and discussed.
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The microstructure and hardness of silicon carbide synthesized by Plasma Pressure compaction
Journal of Alloys and Compounds, 2000Co-Authors: B.g Ravi, O.a. Omotoye, Tirumalai S. Srivatsan, M. Petrorali, Tangali S. SudarshanAbstract:Abstract Using fine powders of silicon and carbon, silicon carbide was synthesized and compacted using the technique of Plasma Pressure compaction (P 2 C). The test samples were obtained by consolidating the powder particles at temperatures of 1400 and 1800°C. Microhardness measurements revealed an increase with an increase in temperature of compaction and increased hold time. The conjoint influence of temperature and time of hold at temperature on microstructural development and hardness is presented and discussed.
Manish G. Bothara - One of the best experts on this subject based on the ideXlab platform.
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Sintering behavior of nanocrystalline silicon carbide using a Plasma Pressure compaction system: Master sintering curve analysis
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 2010Co-Authors: Manish G. Bothara, Tangali S. Sudarshan, R.m. German, Sundar V. Atre, Seong Jin Park, Ramalingam RadhakrishnanAbstract:Nanostructured ceramics offer significant improvements in properties over corresponding materials with larger grain sizes on the order of tens to hundreds of micrometers. Silicon carbide (SiC) samples with grain sizes on the order of 100 nm can result in improved strength, chemical resistance, thermal stability, and tailored electrical resistivity. In this study, nanocrystalline SiC was processed in a Plasma Pressure compaction (P2C) system at a temperature of 1973 K (1700 C) that was much lower than the temperatures reported for other sintering techniques. Microstructure of the resulting samples was studied and the hardness and the fracture toughness were measured. The grain sizes were on the order of 700 nm, the hardness between 22 and 24 GPa, and the toughness between 5 and 6.5 MPaÆm1/2. The master sintering curve (MSC) analysis was used to model the densification behavior of SiC powder sintered by the P2C method. The apparent activation energies for three different Pressures of 10, 30, and 50 MPa were obtained to be 1666, 1034, and 1162 kJ/mol, respectively. Although densification occurs via diffusion, the activation energies were higher than those associated with self-diffusion in SiC (between 570 and 920 kJ/mol). A validation study of the MSC was also conducted and the variation in observed density from the density predicted by theMSC was found to range from 1 to 10 pct.
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Design of experiment approach for sintering study of nanocrystalline SiC fabricated using Plasma Pressure compaction
Science of Sintering, 2009Co-Authors: Manish G. Bothara, Sundar V. Atre, Seong Jin Park, T. S. Sudarshan, Pritha Vijay, Randall M. German, R. RadhakrishnanAbstract:Plasma Pressure compaction (P 2 C) is a novel sintering technique that enables the consolidation of silicon carbide with a nanoscale microstructure at a relatively low temperature. To achieve a high final density with optimized mechanical properties, the effects of various sintering factors pertaining to the temperature–time profile and Pressure were characterized. This paper reports a design of experiment approach used to optimize the processing for a 100 nm SiC powder focused on four sintering factors: temperature, time, Pressure, and heating rate. Response variables included the density and mechanical properties. A L9 orthogonal array approach that includes the signal-to-noise (S/N) ratio and analysis of variance (ANOVA) was employed to optimize the processing factors. All of the sintering factors have significant effect on the density and mechanical properties. A final density of 98.1% was achieved with a temperature of 1600 °C, hold time of 30 min, Pressure of 50 MPa, and heating rate of 100 °C/min. The hardness reached 18.4 GPa with a fracture toughness of 4.6 MPa√m, and these are comparable to reports from prior studies using higher consolidation temperatures.
G.c. Hadjipanayis - One of the best experts on this subject based on the ideXlab platform.
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Bulk SmCo/sub 5///spl alpha/-Fe composites by Plasma Pressure compaction
2003 IEEE International Magnetics Conference (INTERMAG), 2003Co-Authors: Q. Zeng, Y. Zhang, M.j. Bonder, R. Radhakrishnan, G.c. HadjipanayisAbstract:In this paper, the preparation of bulk SmCo5/a-Fe nanocomposites magnets by Plasma Pressure compaction was presented. Magnetic properties on consolidated samples were made using SQUID and VSM. Microstructural characterization was performed with SEM and XRD.
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Bulk SmCo/sub 5///spl alpha/-Fe composite by Plasma Pressure consolidation
IEEE Transactions on Magnetics, 2003Co-Authors: Q. Zeng, Y. Zhang, M.j. Bonder, G.c. Hadjipanayis, R. RadhakrishnanAbstract:Plasma Pressure consolidation (PPC) was used to synthesize exchange coupled composite magnets. The magnets were processed from a mixture of micrometer-size, anisotropic magnetically hard SmCo/sub 5/ and nanometer size magnetically soft Fe particles. High density magnets were obtained by PPC at a temperature as low as 760/spl deg/C. The compacted SmCo/sub 5///spl alpha/-Fe composite showed single-phase magnetic behavior.