Performance of hybrid SnO2/Li2FeMn3O8 nanostructured electrode for efficient Li ion storage application

Li2FeMn3O8 (LFMO) nanocomposite material for Li-ion battery is synthesized using chemical combustion method. To fabricate a hybrid nanostructure electrode, LFMO is coated on tin oxide (SnO2) nanorods (NR), which is grown using a vapor-liquid solid (VLS) technique on a steel substrate. The surface morphology of the hybrid nanostructure electrode confirms that, single crystalline SnO2 nanorods are grown vertically with spine-like structures, a few microns in length, as evident from field emission scanning electron microscope image. The electrochemical performance of SnO2/LFMO shows very interesting characteristic with enormous charge storage capability. The coin cell shows improved capacity with a higher number of charging and discharging cycles. This SnO2/LFMO hybrid composite electrode shows better specific capacitance value as compared to the pristine SnO2 electrode.

Influence of solution treatment on microstructure and stress rupture properties of K439 nickel-base superalloy

The isochronal solution treatment (4h) in the 1080-1190°C range with air cooling are performed to investigate the effects of solution temperature on the microstructure and stress rupture properties of K439 alloy. The detailed as-cast and solution treated microstructures were analyzed through optical microscopy (OM), scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). The experimental results show that the as-cast alloy exhibited a typical dendritic structure with five phases of γ, γ´, γ/γ´, η and MC. After solution heat treated at 1080°C, although all of the γ´ particles in the dendritic cores were dissolved, there were still some of these precipitates in the interdendritic regions beside η phase. With the solution temperature increasing to 1150°C, all of the γ´ and η solutioned and a uniform microstructure was observed. Furthermore, increasing the temperature to 1210°C, a small amount of incipient melting occurred in the alloy. The stress rupture life of K439 alloy at 760°C/530MPa increased with the rising of solution temperature and reached to the top value under the solution temperature of 1150°C. The optimum solution treatment considered to be 1150 C/4 h followed by air cooling.

Impedance Studies of Thermochemically Activated 316L Stainless Steel

This study proposed a novel thermochemical activation (TCA) method to modify the surface of 316L stainless steel (SS). At the first stage, phosphate ions were introduced to 316L SS surface by a heat-diffusion process. After rapid quenching into calcium citrate solution, calcium and hydroxide ions were sealed in the TCA compound layer. The TCA and original 316L SS were immersed in Hanks’ solution to evaluate their biocompatibility. Electrochemical impedance spectroscopy analysis showed that the surface active compound layer affected the TCA 316L SS, and its total impedances of Bode and Nyquist plots were higher than that of the original ones during immersed in Hank’s from 1 to 14 days. After TCA treatment, the corrosion resistance increased greatly, and thus reducing the release of ions from stainless steel, such as Fe, Cr, Ni and Mo. In the Ca- and P-rich areas, the ions were guided to deposit in the Hanks’ solution, forming bone-like hydroxyl apatite. The treatment has been proven to reduce the ionic release from 316L SS, which is considered to be a great improvement for implanted alloys.

Preparation and Characterization of Molybdenum Thin Films by Direct-Current Magnetron Sputtering

The back contact electrode with molybdenum (Mo) thin film is crucial to the performance of Cu(In, Ga)Se2 solar cells. In this research, Mo thin films were fabricated by direct current sputtering to attain low-resistivity molybdenum films on soda-lime glass substrates with good adhesion. The films were sputtered onto substrates in 500 nm thickness and nominally held at room temperature with deposition conditions of power and working pressure. Low resistivity (17-25 μΩ∙cm) of bi-layer molybdenum thin films were achieved with combination of top layer films deposited at 300 W with different working pressure, and bottom fixing layer film deposited at 300 W with 2.5 mTorr which adhered well on glass. Films were characterized the electrical properties, structure, residual stress, morphology by using the Hall-effect Measurement, X-ray Diffraction, and Field-Emission Scanning Electron Microscopy, respectively, to optimize the deposition conditions.

Innovative Nanoimprint-Assisted Fabrication of Anodic Aluminum Oxide

Anodic aluminum oxide (AAO) templates possess highly-ordered nanoporous structures, with advantages such as high aspect ratio. However, there are limits to control the growth of the traditional AAO arrays, such as interpore distance, pore sizes and densities. In this study, we introduce an innovative nanoimprint process guided AAO fabrication to overcome these limitations of the traditional AAO arrays.

The Influence of Annealing Temperature on Microstructure and Magnetic Properties of Fe74Co3Si8B10Al1Nb4 Amorphous Alloy Ribbons

Multi-component alloy ribbons with a composition of Fe74Co3Si8B10Al1Nb4 were prepared by a single roller melt-spinning method. The alloy had a fully amorphous structure, as determined by X-ray diffraction. The alloy ribbons were annealed for 10 min at temperatures of 350, 400, 450, 500, 550 and 600 oC, respectively. Differential scanning calorimetry curves indicated that the glass transition temperature (Tg) and the supercooled liquid range (ΔTx) of the amorphous alloy ribbon were about 494 oC and 43 oC, respectively. The ribbons showed soft magnetic properties, with a Curie temperature (Tc) at 284 oC, high saturation magnetization (Ms) of 1.18 T, and coercive force (Hc) of 33.66 A/m. In the present study, both saturation magnetization and coercive force of amorphous alloy ribbons increased with increasing the annealing temperature, due to precipitations and growth of α–Fe phase nanocrystals in the amorphous matrix. On the other hand, it was found that the coercive force of alloy ribbons reduced as a consequence of precipitations of Nb3Si phase if the annealing temperature reached 600 oC.

Experimental Study of the Influence of Shot Peening on the Microstructure and Properties of Surface Layer of a TC21 Titanium Alloy

The effects of shot peening on microstructure and properties of surface layer of a TC21 titanium alloy have been studied by transmission electron microscopy, electron back-scattered diffraction, X-ray diffraction and Nano-indentation. The results indicated that an elastic-plastic strengthening layer was formed on the surface of the TC21 alloy after the shot peening. During the deformation processing, the activated slip systems were found to be in <a>, <c> and <a/c> planes with high-density dislocations formed as networks in α phase. After the shot peening, the residual stress was found in the strengthening layer, which decreased from the surface to the interior, and the thickness of the surface layer was measured about 370 μm. The hardness by nano-indentation measurement increased two times as compared with the original material. After the shot peening, the fraction of the low-angle boundaries between 0-10º was estimated as 59.3% at the depth of 100 μm from surface. This surface layer microstructure improved resistance of deformation of the TC21 alloy, and therefore increased its fatigue strength.

Phase Equilibrium in Carbothermal Reduction Al2O3 → AlN Studied by Thermodynamic Calculations

As a ceramic with high economic value, aluminum nitride possesses high thermal conductivity, excellent electrical insulation, high mechanical strength and high melting temperature and these all are required in high technologies involving cooling, insulation, thermal expansion and corrosion. This paper deals with thermodynamic parameters which affect the Al2O3→AlN reduction efficiency during a carbothermal reduction. According to the carbothermal reduction reaction γ-Al2O3 + 3C + N2 → AlN + 3CO, if molar mixing ratio of γ-Al2O3:C = 1:3 at 1,601 °C or higher, the γ-Al2O3 can be reduced to AlN. This carbothermal reduction reaction is controlled by main parameters of carbon activity, and partial pressures of nitrogen, carbon monoxide and carbon dioxide. For example, if less carbon is added, a lower carbothermal reduction rate is resulted; however, if extra carbon is added, aluminum carbide (Al4C3) could be produced, or C could remain in AlN. Without N2(g) added in the carbothermal reduction, Al2O3(γ) may react with C to generate Al4C3 at a temperature higher than 2,250 °C. AlN prefers to form with an unity carbon activity, at a lower oxygen partial pressure, a higher carbon monoxide partial pressure, or at a higher temperature. In order to understand the relationship with N2, O2, CO, CO2, C, Al2O3, AlN and Al4C3, the Al-N-C-O system was investigated by thermodynamic calculations.

Magnetic and Thermal Properties of Fe73.5Si13.5B9Cu1Nb3 Amorphous Ribbon and Ball-Milled Powders

This paper reports magnetic and thermal properties of Fe73.5Si13.5B9Cu1Nb3 amorphous ribbon and its powders prepared by ball milling. Differential thermal analysis of the amorphous ribbon showed its Curie temperature at 400 °C, and two crystalline peaks at 500 and 550 °C, respectively. X-ray diffraction analysis demonstrated that a secondary phase Fe2B appeared at 500 °C, causing a maximum strain of 0.195 % in the ribbon at 600 °C. The optimized soft magnetic properties of Fe73.5Si13.5B9Cu1Nb3 ribbon were found in the sample annealed at 450 °C, with saturation magnetization Bm = 1.84×104 G and coercivity Hc = 17.95 Oe. After ball milling, the Fe73.5Si13.5B9Cu1Nb3 powders reached a mean particle size of 10 μm, with partial crystallization during the ball milling process. The ball milling decreased Bm while increased Hc, due to anisotropy induced by stress.