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The present investigation deals with grain boundary engineering of a modified austenitic stainless steel to obtain a material with enhanced properties. Three types of processing that are generally in agreement with the principles of grain boundary engineering were carried out. The parameters for each of the processing routes were fine-tuned and optimized. The as-processed samples were characterized for microstructure and texture. The influence of processing on properties was estimated by evaluating the room temperature mechanical properties through micro-tensile tests. It was possible to obtain remarkably high fractions of CSL boundaries in certain samples. The results of the micro-tensile tests indicate that the grain boundary engineered samples exhibited higher ductility than the conventionally processed samples. The investigation provides a detailed account of the approach to be adopted for GBE processing of this grade of steel.
The present work demonstrated the influence of phosphate electrolytes on surface characteristics and biological response of the titanium oxide layer formed via micro-arc oxidation coating. For this purpose, the present coatings were carried out on titanium samples using two different electrolytes containing Na<SUB>3</SUB>PO<SUB>4</SUB> and K<SUB>3</SUB>PO<SUB>4</SUB>. The surface roughness of the oxide layer formed in K<SUB>3</SUB>PO<SUB>4</SUB> electrolyte was higher than that in the Na<SUB>3</SUB>PO<SUB>4</SUB> electrolyte. This was attributed to the higher fraction of the micropores in the oxide layer prepared by the K<SUB>3</SUB>PO<SUB>4</SUB> electrolyte than that by the Na<SUB>3</SUB>PO<SUB>4</SUB> electrolyte. From the results of simulated body fluid test, the precipitation and growth of amorphous calcium phosphate on the oxide layer formed in the K<SUB>3</SUB>PO<SUB>4</SUB> electrolyte was superior to that in the Na<SUB>3</SUB>PO<SUB>4</SUB> electrolyte due to the enhanced surface roughness. In addition, in vitro cell adhesion was triggered in case of the oxide layer formed in the K<SUB>3</SUB>PO<SUB>4</SUB> electrolyte.
We investigate the influence of the contact interface on the electrical properties of a ZnO microwire (MW) with silver (Ag) paste electrodes. The ZnO MW devices that are produced by dropping Ag paste on the ZnO MW surface followed by a curing step at an elevated temperature exhibit linear current-voltage characteristics, whereas the devices with Ag paste electrodes dropped upon a heated ZnO MW exhibit a non-linear electrical behavior. The results of electron microscopy and cathodoluminescence show the effect of the contact interface properties, such as interfacial defects and/or charge trap sites, between the ZnO MW and Ag paste electrodes. An energy band model is suggested to explain the charge transport mechanism for different types of Ag contacts on the ZnO MW.
Three new homochiral metal-organic frameworks (MOFs) based on malate anions and N-donor linkers of different length have been prepared. [Co<SUB>2</SUB>(mal)<SUB>2</SUB>(bpy)].2H<SUB>2</SUB>O (1), [Ni<SUB>2</SUB>(mal)<SUB>2</SUB>(bpy)].2H<SUB>2</SUB>O (2), [Ni<SUB>2</SUB>(mal)<SUB>2</SUB>(bpe)].3H<SUB>2</SUB>O (3) (mal=S-malate, bpy=4,4'-bipyridyl, bpe=trans-1,2-bis(4-pyridyl)ethylene) were characterized by a number of analytical methods including single crystal X-ray analysis. Optical purity of compounds 2 and 3 was confirmed by polarimetry experiments. Compounds 1 and 2 contribute to the family of isoreticular M(II) malates and aspartates ([M<SUB>2</SUB>(asp)<SUB>2</SUB>L] and [M<SUB>2</SUB>(mal)<SUB>2</SUB>L], M=Cu, Co, Ni; L=ditopic rigid organic ligand) where all structural units (metal cations, chiral ligands and bridging ligands) could be changed with retention of the topology in the resulting framework. Compound 3 has a different structure and contributes to a different family of isoreticular homochiral MOFs.
An amorphized composite, Sb/Al<SUB>2</SUB>O<SUB>3</SUB>/C, prepared by a straightforward mechanochemical reduction method, is investigated for use as an anode material for rechargeable Li-ion batteries. X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy analyses reveal that the Sb/Al<SUB>2</SUB>O<SUB>3</SUB>/C composite is composed of amorphized Sb, amorphous Al<SUB>2</SUB>O<SUB>3</SUB>, and amorphous carbon. Electrochemical tests show that the electrochemical performance of the Sb/Al<SUB>2</SUB>O<SUB>3</SUB>/C composite is superior to that of the pure Sb electrode.
Herein, we synthesized non-agglomerated barium hexaferrite nanoparticles by salt-assisted ultrasonic spray pyrolysis at different reaction temperatures. NaCl was used as an added salt, melted at 850, 900, and 950<SUP>o</SUP>C to act as a solvent in the reaction processes. It was found that at 950<SUP>o</SUP>C, the salt melted sufficiently and therefore accelerated the subsequent nucleation and growth of barium hexaferrite nanoparticles. The barium hexaferrite nanoparticles synthesized by the salt-assisted ultrasonic spray pyrolysis method were exquisitely compared with the barium hexaferrite synthesized by conventional ultrasonic spray pyrolysis method. The particles were characterized by XRD, SEM, and TEM analyses. The salt-free barium hexaferrite obtained at 950<SUP>o</SUP>C revealed the presence of hematite, whereas the salt-added barium hexaferrite nanoparticles synthesized at 950<SUP>o</SUP>C showed the existence of only barium hexaferrite phase. The salt-added barium hexaferrite nanoparticles synthesized at 950<SUP>o</SUP>C showed a hexagonal plate shape, 72nm in size and with good crystallinity. The magnetic properties were investigated by vibrating sample magnetometer (VSM) at room temperature. The magnetic properties of the salt added barium hexaferrite at 950<SUP>o</SUP>C showed the coercivity of 5735Oe and saturation magnetization of 63.2emu/g.
We report that the performance of semipolar (11-22) GaN-based light-emitting diodes (LEDs) was improved by increasing the Si-doping concentration of n-type GaN templates. In-plane and out-of plane high-resolution X-ray diffraction demonstrated that crystal defects such as threading dislocation, partial stacking faults and basal stacking faults, were significantly decreased by increasing the Si-doping concentration. This resulted in the increase of carrier mobility due to reduction of the defect-scattering effect. Furthermore, the quality of InGaN/GaN quantum-well interfaces was improved by increasing the Si-doping concentration of the n-type GaN template. Based on these results, we suggest that the light-output power and operation voltage of semipolar (11-22) GaN-based LEDs would be improved by increasing Si doping concentration of n-type GaN templates.
Rb doped 0.94Bi<SUB>0.5</SUB>Na<SUB>0.5</SUB>TiO<SUB>3</SUB>-0.06BaTiO<SUB>3</SUB> (BNT-BT-Rb<SUB>x</SUB>) thin films with xmol% Rb (x=0, 2.5, 5, 7.5, 10) were deposited on Pt/Ti/SiO<SUB>2</SUB>/Si substrate by metal-organic solution deposition method. Experiments were conducted to investigate the effect of Rb doping on phase formation, microstructure, leakage current, and the resulting ferroelectric and piezoelectric property. It was found that substantial enhancement in structural, morphological and electrical properties can be achieved by Rb doping of BNT-BT thin films. Optimal electrical properties were obtained for 5mol% Rb doped BNT-BT thin films, with a dielectric constant, remnant polarization, and effective piezoelectric constant of ~681, ~28.9μC/cm<SUP>2</SUP> and ~86pm/V, respectively. It was suggested that the enhanced electrical properties in the case of 5mol% Rb BNT-BT thin films can be attributed to domain wall movement induced by A-site substitutions, large grain size, and lattice distortion.
This paper addresses the dehydrogenation behavior of MgH<SUB>2</SUB> exposed to air for up to 24h at room temperature, focusing on the effect of the addition of a small amount of NbF<SUB>5</SUB> and Nb<SUB>2</SUB>O<SUB>5</SUB> as a catalytic additive. Although the dehydrogenation reaction of MgH<SUB>2</SUB> with no catalytic additive and Nb<SUB>2</SUB>O<SUB>5</SUB> is significantly retarded after air exposure compared with unexposed samples, the degradation in the dehydrogenation behavior of MgH<SUB>2</SUB> with NbF<SUB>5</SUB> due to air exposure is found to be effectively mitigated. Although differential scanning calorimetry of the air-exposed samples indicates that the activation energy for the dehydrogenation reaction significantly increases after air exposure, the activation energy for MgH<SUB>2</SUB> with NbF<SUB>5</SUB> remains the lowest. Scanning electron microscopy with energy dispersive X-ray spectroscopy shows that the amount of oxygen on the surfaces of air-exposed MgH<SUB>2</SUB> particles catalyzed with NbF<SUB>5</SUB> is much lower than that of air-exposed MgH<SUB>2</SUB> with no catalytic additive and Nb<SUB>2</SUB>O<SUB>5.</SUB> This implies that the addition of NbF<SUB>5</SUB> forms protective layers on the surfaces of MgH<SUB>2</SUB> particles against oxygen and moisture in the air, which seems to be responsible for the positive effect of NbF<SUB>5</SUB> on the degradation of the dehydrogenation behavior of air-exposed MgH<SUB>2</SUB>.
<P>A new form of hybrid texturing is introduced and discussed in terms of friction and wear reduction. Texturing with four pore densities of 5%, 15%, 25%, and 35% was made by laser texturing on steel; the pores were filled with polyphenylene sulfide (PPS) powder followed by curing to form hybrid surface texturing. Ball-on-disk sliding tests were performed under dry conditions at sliding speeds of 0.05, 0.10, and 0.15 m/s, contact load of 9.8 N, and travel distance of 0.36 km. The hybrid texturing protected the metal surfaces by forming a polymer transfer layer. This transfer layer was crucial in the friction reduction and wear resistance of the hybrid texturing. (C) 2015 Elsevier B.V. All rights reserved.</P>