The evidence for the evolution of interplanetary small flux ropes: Boundary layers

We have examined the Wind data in 1996 and identified 21 small interplanetary magnetic flux ropes(SIMFRs),and all the 21 SIMFRs have boundary layer structures.The durations of the boundary layers varied from several minutes to 30 minutes.These boundary layers also have properties of high proton temperature,density,and plasma beta.These boundary layers are formed by magnetic reconnections.In addition,in three events magnetic reconnections were occurring inside the boundary layers.It indicates that the flux rope structures have propagated for some period of time,and their boundaries were still evolving through interaction with the background solar wind.Namely it is very possible that the SIMFRs came from the solar corona.     

SOFC composite electrolyte based on LSGM-8282 and zirconia or doped zirconia from zircon concentrate

The aim of this research is to study zirconia-based electrolyte materials to increase the commercial value of zircon concentrate as a side product of tin mining industries. Synthesis of CaO-Y₂O₃-ZrO₂ (CYZ) and 8mol% Y₂O₃-ZrO₂ (8YSZ) was carried out by solid state reaction. The result shows that ZrO₂ presents in tetragonal phase. Doping of Y₂O₃ into ZrO₂ allows a phase transformation from tetragonal into cubic structure with small percentage of monoclinic phase. Meanwhile, doping of CaO-Y₂O₃ allows a phase transformation into a single cubic phase. These phase transformations enhance the ionic conductivity of the material. Introduction of 10wt% of LSGM-8282 into CYZ (CYZ-L90:10) allows further improvement of inter-grain contact shown by SEM morphological analysis and leads to the enhancement of ionic conductivity.     

Thermodynamics and phase transformations in the recovery of zinc from willemite

Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we proposed a novel extraction method of zinc from willemite by calcified roasting followed by leaching in NH₄Cl-NH₃·H₂O solution. The thermodynamics and phase conversion of Zn₂SiO₄ to zinc oxide (ZnO) during calcified roasting with CaO were investigated. The mechanism of mineralogical phase conversion and the effects of the CaO-to-Zn₂SiO₄ mole ratio (n(CaO)/n(Zn₂SiO₄)), roasting temperature, and the roasting time on zinc-bearing phase conversion were experimentally investigated. The results show that Zn₂SiO₄ was first converted to Ca₂ZnSi₂O₇ and then to ZnO. The critical step in extracting zinc from willemite is the conversion of Zn₂SiO₄ to ZnO. The zinc percent leached in the ammonia leaching system rapidly increased because of the gradual complete phase conversion from willemite to ZnO via the calcified roasting process.     

Field-aligned current distribution and response to interplanetary conditions during a superstorm―CHAMP observation

With geomagnetic measurements on board of CHAMP satellite, the characteristics of global large-scale field-aligned currents （FACs） in the topside ionosphere are investigated along with their responses to interplanetary conditions for the superstorm of November, 2003. It is found that （1） The storm-time FAC densities enhanced greatly in comparison with quiet period and the enhancements show hemispheric asymmetry of both summer-winter and sunlit-dark. （2） For the first time, it is revealed that the lati- tude-integrated FAC density is controlled mainly by solar wind dynamic pressure rather than iMF. （3） FACs expanded equatorward dramatically, with the lowest latitude being 45° MLat or more; on the dayside this expansion was controlled directly by IMF Bz, showing an interaction time scale of about 25 min in the solar wind-magnetosphere-ionosphere coupling system, and a nonlinear saturation of the equatorward expansion when IMF Bz 〈 -30 nT; while on the nightside, the expansion and recovery lagged about 3 h behind the IMF changes but nearly in phase with changes of SYM-H index. （4） During the storm main phase, the nightside FAC latitude coverage extended to 25° or wider, appearing multi-sheet current structure with more than 10 sheets.     

Effect of Sm-doping on the morphology and magnetic properties of radio frequency magnetron sputtered Ni-Mn-Ga films

Ni_55.5Mn₂₁Ga_23.5 and Ni₅₄Mn₂₂Ga₂₃Sm₁ films were prepared by radio frequency (RF) magnetron sputtering. The effect of Sm dopant on the morphologic and magnetic properties of Ni_55.5Mn₂₁Ga_23.5 films was investigated. Sm doping can refine the particle size of the films from 100 to 60 nm, and further grain growth is not occurs even after annealing at 1073 K for 3.6 ks. Compared to Ni_55.5Mn₂₁Ga_23.5 films, Sm-doped Ni₅₄Mn₂₂Ga₂₃Sm₁ films are easier to be magnetized and have a lower martensitic transformation temperature. In addition, the Curie temperature can also be adjusted, decreasing from 350 to 325 K after Sm doping. Martensitic transformation is not observed in the Sm-free films, which is close to the Curie temperature in the Sm-doped films, giving rise to the overlap of the structural and magnetic transition temperatures.     

Preparation of Al-Cu-Fe-(Sn,Si) quasicrystalline bulks by laser multilayer cladding

(Al₆₅Cul₂₀Fe₁₅)_100-x Sn_x (x=0, 12, 20, 30) and Al₅₇Si₁₀Cu₁₈Fe₁₅ powders were cladded on a medium carbon steel (45# steel) substrate by laser multilayer cladding, respectively. The phases and properties of the produced quasicrystalline bulks were investigated. It was found that the main phases in the Al₆₅Cul₂₀Fe₁₅ sample were crystalline λ-Al₁₃Fe₄ and icosahedral quasicrystal together with a small volume fraction of θ-Al₂Cu phase. The volume fraction of icosahedral phase decreased as the Sn content in the (Al₆₅Cul₂₀Fe₁₅)_100-x Sn_x samples increased owing to the formation of β-CuSn phase. The increase of Sn content improved the brittleness of the quasicrystal samples. The morphology of the solidification microstructure in the Al₅₇Si₁₀Cu₁₈Fe₁₅ sample changed from elongated shape to spherical shape due to the addition of Si. The nanohardness of the laser multilayer cladded quasicrystal samples was equal to that of the as-cast sample prepared by vacuum quenching. In terms of hardness, the laser cladded Al₅₇Si₁₀Cu₁₈Fe₁₅ quasicrystalline alloy has the highest value among all the investigated samples.     

Characterization and <Emphasis Type="Italic">in-situ</Emphasis> formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

The precursor carbonization method was first applied to prepare W-C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W-C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M₇C₃ carbides. Moreover, net-like structures were confirmed as mixtures of M₂₃C₆ and α-Fe; these structures were transformed from M₇C₃. The coarse herringbone M₃C carbides did not only derive from the decomposition of M₇C₃ but also partly originated from the chemical reaction at the α-Fe/M₂₃C₆ interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M₇C₃ → M₂₃C₆+M₃C.     

Comparative study of a substorm event by satellite observation and model simulation

A substorm event has been simulated for the first time by using SWMF (Space Weather Modeling Framework) developed by the University of Michigan. The model results have been validated using Geotail and Cluster satellite observations. The substorm onset occurs at 22:08 UT on September 28, 2004, as identified from FUV WIC observations on the NASA IMAGE spacecraft. SWMF can couple effectively the magnetosphere, inner magnetosphere and ionosphere processes and is driven by the solar wind and IMF (Interplanetary Magnetic Field) parameters, which are measured by ACE satellite and time delayed to the upstream boundary of the model. It shows that (1) SWMF can predict well the large-scale variations of the magnetospheric magnetic field and ionospheric currents during the substorm event; and (2) the accuracy of the time delay of the solar wind from ACE to the outer boundary of the model has great effects on the model results. Finally, the substorm trigger mechanism has been discussed and the way of improvement of the model has been pointed out.     

Effect of Dy substitution on the microstructure and magnetic properties of nanograin Nd-Fe-B single-phase alloys

Nanocrystalline single-phase alloys with the nominal compositions (at%) of Nd_12.3-xDy_xFe_79.7Zr_0.8Nb_0.8Cu_0.4B_6.0 (x=0, 0.5, 1.5, and 2.5) were prepared by melt-spinning and subsequent annealing. X-ray diffraction analysis shows that the as-spun ribbons were mainly composed of the amorphous phase. A slight content of Dy stabilizes the amorphous phase during annealing treatment. The grain size becomes smaller and the coercivity of the annealed ribbon is gradually improved with the increase of Dy content. Excessive Dy is harmful to the remanence. It is found that no intergranular phase exists between the grains by high-resolution transmission electron microscopy, and the grain boundaries are crystallographically coherent in the optimally annealed sample. The optimum magnetic properties of remanence (J_r=1.09 T), coercivity (H_ci=1048 kA/m), and maximum magnetic energy product ((BH)_m=169.5 kJ/m3) are obtained from the x=0.5 ribbon in a post heat-treated state (700℃, 10 min).     

Preparation of ferronickel from nickel laterite via coal-based reduction followed by magnetic separation

The sticking phenomenon between molten slag and refractory is one of the crucial problems when preparing ferronickel from laterite ore using rotary hearth furnace or rotary kiln processes. This study aims to ameliorate sticking problems by using silicon dioxide (SiO₂) to adjust the melting degree of the briquette during reduction roasting. Thermodynamic analysis indicates that the melting temperature of the slag gradually increases with an increase in the SiO₂ proportion (SiO₂/(SiO₂ + Al₂O₃ + MgO) mass ratio). Experimental validations also prove that the briquette retains its original shape when the SiO₂ proportion is greater than 75wt%, and sticking problems are avoided during reduction. A ferronickel product with 8.33wt% Ni and 84.71wt% Fe was prepared via reductive roasting at 1500℃ for 90 min with a SiO₂ proportion of 75wt% and a C/O molar ratio of 1.0 followed by dry magnetic separation; the corresponding recoveries of Ni and Fe reached 75.70% and 77.97%, respectively. The microstructure and phase transformation of reduced briquette reveals that the aggregation and growth of ferronickel particles were not significantly affected after adding SiO₂ to the reduction process.     

The correlations of ions density with geomagnetic activity and solar dynamic pressure in cusp region

A statistical study of the properties of ions (O , He and H ) measured by the Cluster-II in cusp region as a function of the solar wind dynamic pressure and geomagnetic index Kp respectively was made dur-ing the summer and fall of 2001-2003. The main results are that: (1) O ion density responds in a sig-nificant way to geomagnetic index Kp, and He ion density is not correlated with geomagnetic index Kp, both of them have a significant positive correlation with solar wind dynamic pressure; (2) H ion density is also observed to increase with solar wind dynamic pressure, and not correlated with geomagnetic index Kp.     

Microstructure of Ni–Al powder and Ni–Al composite coatings prepared by twin-wire arc spraying

Ni–Al powder and Ni–Al composite coatings were fabricated by twin-wire arc spraying (TWAS). The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the obtained particle size ranged from 5 to 50 μm. The morphology of the Ni–Al powder showed that molten particles were composed of Ni solid solution, NiAl, Ni₃Al, Al₂O₃, and NiO. The Ni–Al phase and a small amount of Al₂O₃ particles changed the composition of the coating. The microstructures of the twin-wire-arc-sprayed Ni–Al composite coatings were characterized by SEM, EDS, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that the main phase of the Ni-5wt%Al coating consisted of Ni solid solution and NiAl in addition to a small amount of Al₂O₃. The main phase of the Ni-20wt%Al coating mainly consisted of Ni solid solution, NiAl, and Ni₃Al in addition to a small amount of Al and Al₂O₃, and NiAl and Ni₃Al intermetallic compounds effectively further improved the final wear property of the coatings. TEM analysis indicated that fine spherical NiAl₃ precipitates and a Ni–Al–O amorphous phase formed in the matrix of the Ni solid solution in the original state.     

First observation of thermospheric neutral wind at Chinese Yellow River Station in Ny-Ålesund, Svalbard

A compact and cost-effective all-sky Fabry-Perot interferometer, which is produced by Wuhan University and used for the observation of the thermospheric neutral wind, was installed at Chinese Yellow River Station in Nylesund, Svalbard in November 2010, and continuously operated in last two winter seasons. The 92-day all-sky interference data acquired from November 1, 2011 to February 26, 2012 were collected to get the velocity of thermospheric neutral wind, which was calculated from the Doppler shift caused by the movement of oxygen atom at the different layers. The database was divided into two periods: (1) The OI 557.7 nm emission was observed from November 1, 2011 to January 12, 2012. Observations showed that the velocity of horizontal wind is normally less than ～40 m/s on the quiet condition, and exceeded 100 m/s on the disturbed condition; and (2) the OI 630.0 nm emission was observed from January 13, 2012 to February 26, 2012. Observations showed that the velocity of horizontal wind is normally less than ～200 m/s, and enhanced to over 300 m/s on strong magnetic activities. It shows that the velocities of meridional and zonal wind are more consistent with the velocities calculated from the model HWM07 at the higher layer, especially for the zonal direction at nightside auroral regions. Ion drag and Joule heating were the two important processes considered in the analysis of the relationship between the wind pattern and aurora, suggesting that wind speed would be increased and accelerated in the direction perpendicular to the aurora arc when the aurora activity becomes strong.     

Microstructure and phase composition of hypoeutectic Te–Bi alloy as evaporation source for photoelectric cathode

A hypoeutectic 60Te–40Bi alloy in mass percent was designed as a tellurium atom evaporation source instead of pure tellurium for an ultraviolet detection photocathode. The alloy was prepared by slow solidification at about 10-2 K·s-1. The microstructure, crystal structure, chemical composition, and crystallographic orientation of each phase in the as-prepared alloy were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The experimental results suggest that the as-prepared 60Te–40Bi alloy consists of primary Bi₂Te₃ and eutectic Bi₂Te₃/Te phases. The primary Bi₂Te₃ phase has the characteristics of faceted growth. The eutectic Bi₂Te₃ phase is encased by the eutectic Te phase in the eutectic structure. The purity of the eutectic Te phase reaches 100wt% owing to the slow solidification. In the eutectic phases, the crystallographic orientation relationship between Bi₂Te₃ and Te is confirmed as [0001]_Bi2Te3//[1213]_Te and the direction of Te phase parallel to [1120]_Bi2Te3 is deviated by 18° from N(2111)_Te.     

Effect of Li content on the microstructure and properties of lead-free piezoelectric(K0.5Na0.5)1-xLixNbO3 ceramics prepared by SPS

Lead-free piezoelectric (K_0.5Na_0.5)_1-xLi_xNbO₃ (x = 0at%-20at%) ceramics were synthesized by spark plasma sintering (SPS) at low temperature and the effects of LiNbO₃ addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of (K_0.5Na_0.5)NbO₃ was formed; and a secondary phase with K₃Li₂Nb₅O₁₅ structure was observed in the 6at% < x < 20at% compositional range. Furthermore, LiNbO₃ existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K₃Li₂Nb₅O₁₅ and LiNbO₃ like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d₃₃, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K₃Li₂Nb₅O₁₅ and LiNbO₃. The formation of dense microstructure with a single phase is necessary in improving the properties of the (K_0.5Na_0.5)_1-xLi_xNbO₃ ceramics.     

Effects of HNO3 concentration on the pit morphologies of aluminum foil etched in HNO3–HCl and HNO3–H2SO4–HCl solutions

In this work, the effects of HNO₃ concentration on the pit morphologies of high-cubic-texture aluminum foil etched in HNO₃–HCl and HNO₃–H₂SO₄–HCl solutions were investigated. When the aluminum foil was etched in HNO₃–HCl solutions, the morphologies of pits transformed from irregular tunnels to typical tunnels (as inverted pyramids) and shallow cuboids as the HNO₃ concentration in the etchant solution was increased. However, as the HCl concentration in the etchant solution was increased, the morphologies of pits transformed from shallow cuboids to typical tunnels (as inverted pyramids) and irregular tunnels. When the aluminum foil was etched in n N HNO₃–(7.2?n) N H₂SO₄–0.8 N HCl solutions, the morphologies of the pits transformed from typical tunnels (i.e., the number of sub-tunnels formed on the main tunnels increased) to irregular tunnels (corrugated tunnels and polyline tunnels) as the HNO₃ concentration in the etchant solution was increased. These effects are attributed primarily to corrosion on the (100) and (010) faces of pits being accelerated and to the (001) faces being prone to passivation to different degrees when various concentrations of HNO₃ are added to the etchant solutions.     

Effects of additives on the phase transformation,occurrence state,and the interface of the Ti component in Ti-bearing blast furnace slag

The influences of additives on the phase transformation, occurrence state, and the interface of the Ti component in Ti-bearing blast furnace slag were investigated. After oxidation, most of the Ti component in the slag was enriched into the perovskite phase, which served as the Ti-rich phase during the crystallization process. The phase transformation, occurrence state, and the interface of the Ti component were observed to be affected by the addition of different types of agents. During the oxidation process, titanaugite and Ti-rich diopside phases gradually transformed into non-Ti phases (anorthite: CaMgSi₂O₆ and CaAl₂Si₂O₈) in the form of dendrites or columns, which were observed to be distributed at the surface of the perovskite phase. Several more cracks appeared along the grain boundaries of the perovskite phase after the addition of P₂O₅, facilitating the liberation of the perovskite phase. Composite additives combining both an acid and a base, such as CaO + CaF₂ or P₂O₅ + CaF₂, were used. We observed that the disadvantages of using single additives were successfully overcome.     

Synthesis of titanium oxycarbonitride by carbothermal reduction and nitridation of ilmenite with recycling of polyethylene terephthalate (PET)

An innovative and sustainable carbothermal reduction and nitridation (CTRN) process of ilmenite (FeTiO₃) using a mixture of polyethylene terephthalate (PET) and coal as the primary reductant under an H₂-N₂ atmosphere was proposed.The use of PET as an alternative source of carbon not only enhances the porosity of the pellets but also results in the separation of Fe from titanium oxycarbonitride (TiO_xC_yN_z) particles because of the differences in surface tension.The experiments were carried out at 1250℃ for 3 h using four different PET contents ranging from 25wt% to 100wt% in the reductant.X-ray diffraction (XRD),scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX),and LECO elemental analysis were used to study the phases and microstructures of the reduced samples.In the case of 75wt% PET,iron distinctly separated from the synthesized TiO_xC_yN_z phase.With increasing PET content in the sample,the reduction and nitridation rates substantially increased.The synthesis of an oxycarbonitride with stoichiometry of TiO_0.02C_0.13N_0.85 with minimal intermediate titanium sub-oxides was achieved.The results also showed that the iron particles formed from CTRN of FeTiO₃ exhibited a spherical morphology,which is conducive for Fe removal via the Becher process.     

Primary beneficiation of tantalite using magnetic separation and acid leaching

Primary beneficiation was successfully performed prior to dissolution of manganotantalite (sample A) and ferrotantalite (sample C) samples obtained from two different mines in the Naquissupa area, Mozambique. Magnetic separation removed the majority of iron and titanium, whereas H₂SO₄ leaching removed a large portion of thorium and uranium in these samples. Analytical results indicated that 64.14wt% and 72.04wt% of the total Fe and Ti, respectively, and ~2wt% each of Nb₂O₅ and Ta₂O₅ were removed from sample C (ferrotantalite) using the magnetic separation method, whereas only 9.64wt% and 8.66wt% of total Fe₂O₃ and TiO₂, respectively, and ~2wt% each of Nb₂O₅ and Ta₂O₅ were removed from sample A (manganotantalite). A temperature of 50°C and a leaching time of 3 h in the presence of concentrated H₂SO₄ were observed to be the most appropriate leaching conditions for removal of radioactive elements from the tantalite ores. The results obtained for sample A under these conditions indicated that 64.14wt% U₃O₈ and 60.77wt% ThO₂ were leached into the acidic solution, along with 4.45wt% and 0.99wt% of Nb₂O₅ and Ta₂O₅, respectively.     

Characterization of Fe3Si-based coatings on low silicon steel by pulsed Nd:YAG laser cladding

The Fe₃Si based coating was produced on the Fe-1 Si steel surface by a pulsed Nd:YAG (yttrium aluminum garnet) laser. Its phase constitution and microstructure were characterized by using X-ray diffraction (XRD), optical microscope (OM), and field emission scanning electron microscope (FESEM) with associated energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The hyperfine structure of the coating was studied by Mrssbauer spectra (MS) and the magnetic property was also measured at room temperature by a vibrating sample magnetometer (VSM). The obtained coating is pore and crack-free with dense microstructure and high Si content. The metallurgical bonding between the coating and the substrate was realized. The microstructure of the coating is typical fine dendrites. The major phase was confirmed by XRD and TEM to be the ordering D0₃ structured Fe₃Si phase. In addition, there were smaller amounts of the Fe₅Si₃ phase and the γ-Fe phase in the coating. Compared with the substrate, the laser cladding coating has a lower saturation magnetization and a higher coercive force. The poor magnetic property might be because of rapid solidification microstructure and phase constitution in the coating.