Materials Science Forum Vol. 998

Abstract: Er³⁺ doped potassium sodium niobate (KNN: Er) ultrafine powders have been prepared by pulsed laser ablation in water. X-ray diffraction (XRD) pattern of the sample demonstrated that the as-synthesized powders were crystalized in orthorhombic phase. Scanning electron microscopy (SEM) and transmittance electron microscopy (TEM) images exhibited that the morphology of ultrafine powders are cube-like. Under the excitation of 980 nm laser, the sample exhibits green emission, which is originated from the transition of thermal coupled energy levels (²H_11/2, ⁴S_3/2) to ground state level ⁴I_15/2. Temperature dependent up-conversion emission intensity associated with thermal quenching of total green emission band and the fluorescence intensity ratio (FIR) between two sub-emission bands related to population of thermal coupled energy levels are investigated for temperature sensing in the temperature range of 300 K to 480 K. The temperature sensing performances related to different technique were discussed. A maximum relative sensitivity reaches 1.01% K^-1 at 464 K for emission intensity thermometry and that is 0.84% K^-1 at 374 K for FIR thermometry technique. All these results show that KNN: Er ultrafine phosphors prepared via pulsed laser ablation in water have prospect for non-contact temperature sensing.

Abstract: In this paper, a novel approach for designing tapered periodic meta-surfaces (TPMS) is proposed for suppressing electromagnetic scattering from a trailing edge of a square metallic plate with a given thickness. The TPMS is realized by periodic square metallic patches with tapered dimensions at the direction perpendicular to the considered edge but keeping its period unchanged. Based on the geometric phase interaction, the mechanism of suppressing electromagnetic scattering is analyzed. The lossy material is not required in this design, so it doesn’t generate thermal energy and benefits infrared stealth of military objects. The backscattering properties from the trailing edge with the proposed TPMS loading are analyzed and compared with that of original trailing edge. It is observed that wide angular trailing edge scattering suppressing can be obtained and the average value of mono-static radar cross section (RCS) reduction is 10 dB for L-band, S-band and C-band. Finally, the bi-static RCS properties and energy distribution of the proposed structure are also proposed to explain the mechanism of the electromagnetic scattering suppression of the trailing edge employed with the TPMS.

Abstract: The complex oxide BaLaIn_0.9Nb_0.1O_4.1 with Ruddlesden-Popper structure was obtained for the first time. It was found that the introduction of niobium into indium sublattice leads to the increase in the cell volume. Hydration processes and electrical properties have been investigated. For BaLaIn_0.9Nb_0.1O_4.1 it was proved the capability for water uptake and the appearance of proton current carriers. It was established that niobium doping leads to the increase of conductivity compared to undoped composition BaLaInO₄ at ~1 order of magnitude in whole temperature range.

Abstract: In this study, bulk lithium-ion conducting solid electrolyte of Ga-doped Li₇La₃Zr₂O₁₂ (Li_7-3XGa_xLa₃Zr₂O₁₂) where x = 0.1 (Ga-LLZO) was prepared via hot pressing at 500 °C. Precursor powder for hot-pressing was prepared using conventional solid state reaction method. Planetary ball milling was employed to investigate the particle size effect on the structure and densification of hot-pressed samples. XRD patterns of the bulk hot-pressed sample revealed a crystalline phase of which the major peaks observed can be indexed to a cubic LLZO structure; however, a major impurity phase of La₂Zr₂O₇ was observed for the ball-milled sample. Thermogravimetric and differential thermal analysis showed about 12% weight loss below 900 °C which may have affected the observed hot-pressing structure. Although lower density measurement and an impurity phase of La₂Zr₂O₇ were observed for the ball-milled sample, ball-milling also resulted to a more homogeneous and finer particle size as shown by SEM images results.

Abstract: A lot of interest to simulate piezocomposite actuators with finite element method has been increased recently. However, there are still open questions regarding the modeling methodology, accuracy, and computational time cost. In this work, a new technique for modeling macro fiber composite piezoelectric actuator by finite element analysis is proposed. The presented technique models the piezocomposite actuator as a simple monolithic piezoceramic material with just two electrodes along its longitudinal extremes instead of using the actual large number of electrodes which results in very fine finite element mesh with high computational time cost. The proposed technique is validated successfully by comparing its results with those of the actual detailed model as well as with the published experimental results and manufacturer’s data.

Abstract: Tin oxide nanotubes (STs) were synthesized by the hydrothermal process using manganese dioxide nanowires (MWs) as a template and followed by oxalic acid treatment. The effect of the stannous chloride concentration on the structure and crystallite size of the product were investigated. The phase composition was determined by XRD. Morphologies were revealed by FESEM and TEM. Firstly, manganese dioxide nanowires were fabricated from KMnO₄. Then_, tin oxide nanoparticles were coated on the wall surfaces of MWs templates. The template was then leached out by oxalic acid treatment. Nanotubular structure of the final product was formed by the agglomeration of the tin oxide nanoparticles coating on the template surfaces. On increasing the stannous chloride amount, crystallite size and the electrochemical properties increased, while the specific surface area decreased.

Abstract: Ionic liquids (ILs) containing 1-ethyl-3-methylimidazolium (EMIM) cations and carboxylate anions were prepared using solventless sonochemical synthesis followed by a facile halide-to-anion exchange method and were characterized for their structural and electrochemical properties. The structures of the synthesized ILs were found to significantly affect their electrochemical window (EW) and varied anions exhibited different reductive and oxidative limits. Ionic conductivity and cyclic voltammetry measurements revealed that [EMIM] hexanoate and [EMIM]₂[oxalate] offered relatively high ionic conductivity values and wide EWs. A 1:1 binary IL mixture based on the synthesized ILs was prepared and its EW was found to significantly vary as compared with the EWs of the individual component ILs. Supercapacitor prototypes were then fabricated with edge-oxidized graphene sheets as conductive additives for the electrodes and electrospun nanofibers as separator membranes. An electric-double layer capacitive behaviour associated to the ion diffusion process of the electrolyte ions onto the porous electrode surface was shown and quasi-rectangular curves were observed having no redox peaks at any point in the generated repetitive voltammograms. These considerable results have shown valuable insights for further development of binary IL electrolytes for energy storage devices.

Abstract: Controlling process parameters has significant influence in designing and developing nanocomposites materials with tailored dielectric properties. In the present study, polyethylene/TiO₂ nanocomposites were fabricated using ball milling technique. The effects of TiO₂ nanoparticles on the final dielectric properties of the nanocomposites in frequency domain were investigated. The dielectric spectroscopy measurements revealed that relative dielectric permittivity of the nanocompsoites was increased with TiO₂ content. Besides, machine learning approach based on artificial neural networks (ANNs) algorithm was used to predict the dielectric permittivity of the nanocomposites materials. Modeling results showed clearly that the predicted data of the proposed artificial model are in good agreement with the experimental values. Moreover, the present study proved that ANNs can be used as successful tool to predict the dielectric properties of nanocomposites materials.

Abstract: In the fields of automobile unto aviation, the extensive applied metal in many optimized output conditions is Aluminium and its based metal matrix composites, which are now-a-days, are called as Aluminium matrix composites (AMCs). These AMCs are as potential as they processed very much able in their mechanical and physical properties viz., tensile strength, strain, hardness, wear and fatigue. In this review, the properties which are essentially vital in attaining such improved performance in particular applications are discussed along with the special methodologies and their limitations in brief. Hence, the effective factors which are the cause for their output, like, type of reinforcement, amount of reinforcement, size of particulate of reinforcement, temperature and pressure etc., were also scrutinized retrospectively.

Abstract: Polycaprolactone (PCL) is a hydrophobic, semi-crystalline polymer that has been broadly applied in long term implants, drug release applications, and in the tissue engineering field due to its availability, relatively inexpensive price and suitability for modification. Organo-montmorillonite (O-MMT) clay has been extensively used for various polymer-nanocomposite studies and widely used as adsorbent due to its high specific surface area. Most polymer clay nanocomposites are involved in biomedical applications such as in drug delivery systems and wound healing. In this study, O-MMT was incorporated to PCL via solvent casting, which resulted into film membranes that were characterized to identify its surface morphology, chemical structure, wettability, mechanical property, pore size, and antibacterial properties upon its varying concentrations. The SEM and FTIR results indicated the presence of both PCL and O-MMT within the membrane. The mechanical properties of the film membranes showed an improvement upon reaching an optimal point. An increase in pore size was determined relative to its hydrophilicity. The film membrane showed an antibacterial activity only at the higher concentrations of the O-MMT using the S. aureus strain. As such, the results showed that there is an improvement in the mechanical, wettability, water absorption and antibacterial properties of the PCL with the incorporation of the O-MMT, making it a viable candidate dressing material for wound healing.