Journal of Metastable and Nanocrystalline Materials Vol. 36

Abstract: The characteristics of shock wave propagation in aluminum single crystal are simulated by using the molecular dynamics (MD) method based on the embedded atom method (EAM) potential function. The structure of the shock front and the Hugonoit relation are obtained. The simulated results show that a two-wave structure exists in the aluminum single crystal for the particle velocity bellower than 2 km/s and the velocity of the elastic wave increases slightly with the shock loading. While only plastic wave exists in the aluminum single crystal for the particle velocity higher than 2 km/s and the width of the shock front decreases by exponent with the normal stress. The MD simulation results are basically consistent with the experimental results.

Abstract: Shape memory alloys (SMAs) are a type of smart material and have excellent engineering and medical applications. TiNi binary alloys possess remarkable shape recovery, mechanical properties, corrosion resistance, and excellent biocompatibility. By ternary elements addition just like Au, Pt, Pd, Hf, and Zr, increases transformation temperatures, leading to high-temperature shape memory alloys (more than 100°C) but other elements (Fe, Cu, Co, and Mo) form low-temperature shape memory alloys, (lower than 100°C). In the present work, it is reported that the effect of ternary element addition on microstructural properties, shape memory properties, mechanical properties, corrosion resistance, and biocompatibility of ternary shape memory alloys. Ag, Au, and Cu-based TiNi ternary alloys have excellent biocompatibility. The addition of ternary elements such as Ag and Nb increases corrosion resistance, Fe rises the hysteresis loop, Hf enhances thermal stability, and Mo raises workability.

Abstract: The production of microbial nanocellulose implicates physical and mechanical methods such as the application of ultrafine grinders and ultrasonicators. Nano-sized microbial cellulose must contain high crystallinity to be utilized as a filler in nanocomposite polymers. This research aimed to optimize the processing time and amplitudes of the ultrasonication process to stimulate nano-sized microbial cellulose with high crystallinity. In this analysis the Surface Responses Method was used, that is Central Composite Design (CCD) with two factors, that is processing time (X₁ = 30, 60, and 90 minutes) and ultrasonication amplitude (X₂ = 70, 80, and 90 %) to the degree of crystallinity. The results indicated the optimum point was obtained at a combination of 60 minutes of processing time and 80% amplitudes with the highest degree of crystallinity of 76.23%. The Fourier Transform Infra-Red spectrum at wavenumbers 3340 cm^-1 to 2899 cm^-1 showed the characteristics of absorption bands in the form of carboxyl groups and hydroxyl groups, which indicate the existence of cellulose compounds. The scanning electron microscope showed the surface morphology of the ultrafine grinding microbial cellulose fibers was denser.

Abstract: This article reports the study of photoluminescence spectra of Di Strontium Magnesium Silicate (Sr₂MgSi₂O₇) doped with various concentration of Europium (Eu³⁺) prepared using solid-state reaction technique. The doping concentration (s) of Eu3+ were 0.2, 0.5, 1.0, 1.5, 2.0, 2.5 mol% respectively. Excitation spectrum monitored at 620 nm wavelength that exhibited two prominent peaks centered at 256 nm and 277 nm. Peak observed at 277 nm was more intense therefore the emission spectra were monitored at 277. Emission Spectra of all the samples revealed intense peaks centred at 607, 618 and 637 are attributed to ⁵D₀ ⁷F₂ of Europium (III) ions accommodated at various lattice sites having different energies. Overall emission was found in the red colour region which was confirmed using a CIE chromaticity diagram with coordinate (0.4805, 0.3763). Critical distance for energy transfer in the concentration, beyond which concentration quenching occurred in PL spectra, was calculated. In this case, the critical distance was found to be 19.87 Å, therefore the mechanism involved in concentration quenching of Sr₂MgSi₂O₇ doped with 2.0 mol % of Europium (III) must be only multipole-multipole exchange whereas the exchange interaction is ineffective.

Abstract: At room temperature, zinc oxide (ZnO) nanoparticles co-doped with praseodymium (Pr) and copper (Cu) using a low-cost chemical co-precipitation method. As a capping agent, polyvinylpyrrolidone (PVP) was used for synthesizing the nanosamples, and a pH of 9 was maintained. The synthesis of nanosamples was then characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and photoluminescence (PL). X-ray diffraction studies revealed the wurtzite hexagonal structure of ZnO, and no impurity peaks were found. The particle size obtained from XRD studies was 32 to 46 nm and is well supported by TEM. SEM micrographs demonstrated the surface morphology of the samples. With Cu dopant concentration, Pr-doped ZnO nanosamples exhibited enhanced luminescence properties.

Abstract: Red light emitting YPO₄: Eu³⁺ and YPO₄: Tb³⁺: Li⁺ nanoparticles were synthesised using polyol method at low temperatures. The phase purity, micromorphology, and luminescence characteristics were studied using Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier Transfer Infrared absorption spectroscopy (FT-IR). Combined XRD and TEM analysis showed that the YPO₄ nanoparticles crystallized into a single phase of tetragonal (I41/amd) structure. The energy transfer from Li⁺ ions to Eu³⁺ ions was tested by studying the photoluminescence properties of YPO₄: Eu³⁺and YPO₄: Eu³⁺: Li⁺ nanoparticles and how it results in the improvement of the luminescence intensity.

Abstract: In this work, PtPd nanostructures have been synthesized via the chemical reduction method with different capping agents (i.e., PVA, PVP, and PEG), whilst the strong reducing agent, NaBH₄, was used in this study to reduce the metal salt to zero-valent PtPd nanostructures. Both PtPd synthesized with PVP and PEG exhibit nanoparticle structures, whereas PtPd synthesized in PVA demonstrates large, interconnected network structures. Pt-Pd synthesized with PVP exhibits a high ECSA value of 692.68 m²/g compared to without capping agent (287.80 m²/g) indicating large active sites, which increases its catalytic function. This study concludes that the presence of a capping agent influences the morphological structure and the catalyst's efficiency in performing a redox reaction at the surface.

Abstract: This study describes the ability of green kyllinga weed extract (GKWE) with silver nanoparticles (AgNPs) as catalysts for the removal of congo red (CR) dye from synthetic coloring wastewater. AgNPs were synthesized using GKWE as a reducing agent, resulting in the formation of AgNPs with an average size of 17.64 nm. For the catalytic study, the experiment was carried out in batch mode. Different parameters such as the effect of pH, amount of AgNPs as a catalyst, initial CR dye concentration, and amount of GKWE were evaluated for the removal of CR dye for 30 mins reaction times. The CR removal was achieved between 91.2% and 96.7% at the optimum condition which is at pH 2, 0.5 mL of 2 mM AgNPs as a catalyst, 60-100 mg/L of initial CR dye concentration, and 1 mL amount of GKWE were used. The result showed that the combination between GKWE and AgNPs had a synergy interaction in enhancing the removal of CR dye from coloring wastewater via the coagulation-flocculation and sedimentation process.