Materials Science Forum Vol. 982

Abstract: In this work, magnetorheological elastomers (MRE) based on nickel zinc ferrite and natural rubber were prepared. Self-healing capability was employed to the MRE by peroxide induced graft polymerization between zinc thiolate and natural rubber to produce reversible ionic crosslinks that can recover the properties of the fracture materials. Evidence that reversible ionic crosslinks occurred was determined by tensile test of original and healed sample. The results revealed that the tensile strength of the MRE recovered 56% in a minute and almost 100% in 10 minutes at room temperature. The morphology of the fractured surface also showed the fracture area was recovered after the healing processed. The dynamic mechanical analysis of the MREs under cyclic loading were also examined with parallel plate rheometer.

Abstract: Co₃O₄ nanoparticles (NP) have been successfully formed using Moringa oleifera leaves extract (MLE) through two phases’s system of hexane–water. Co₃O₄ NP was further characterized using UV-Vis DRS, FT-IR, TEM, SEM-EDX, XRD and UV-Vis spectrophotometer. FTIR spectra of Co₃O₄ NP had strong absorption bands at wavenumbers of 538 and 670 cm^-1. The bandgap energy value of Co₃O₄ NP was 1.43 eV. In addition, the characterization of SEM and TEM showed that the morphology of Co₃O₄ NP was in the spheres form with particle sizes around 73 nm. The photocatalytic activity of Co₃O₄ NP was carried out for methylene blue (MB) photodegradation. Co₃O₄ NP had photodegradation activity against MB under visible light irradiation of 91% for 120 min.

Abstract: Enhancement of surface-enhanced Raman scattering (SERS) by metal nanoparticles has attracted considerable interest on account of their widespread popularity of SERS-based measurements and devices ranging from life science until materials science. Current study focuses on noble metal SERS substrates with attempting to achieve high and enhanced effect by describe a plasmon-enhanced SERS substrate based on gold-silver, alloy-coated co-polymer (methyl methacrylate-styrene) colloidal sphere. Copolymer was synthesised via surfactant-free emulsion polymerization and was successfully produced a homogeneous colloidal spheres. The homogenous spheres of copolymer would promote periodic array upon fabrication and more, introducing the copolymer medium had improved the thermal degradation of the material compare to single polymer. Gold-silver alloy nanospheres was synthesised via one pot reduction method using citrate stabilizer. The nanoalloy obtained are well within the nanoscale domain (<100 nm) supported by the maximum surface plasmon resonance peak at 436 nm using UV-Visible spectroscopy. The perfect combination of our proposed alloy nanoparticles and copolymer present an ability to enhance Raman scattering by higher than 90 %. The region of high electron density of the substrate is expected to develop a new opportunities for SERS detections in wide analytical area.

Abstract: Calcium titanate (CaTiO₃) was synthesized through combustion in air from calcium sources of raw minerals (lime-stone and calcite), anatase titanium dioxide (A-TiO₂) and magnesium (Mg). The syntheses were divided into two reactant systems (lime-stone/A-TiO₂/Mg and calcite/A-TiO₂/Mg. Before synthesis, the raw minerals and A-TiO₂ were high-energy milled for 30 min. These powders were then separately mixed with Mg by ball milling. After synthesis, the as-combusted products were leached with 2 M HCl solution to remove by-products and impurities. A sequential mechanism for the in-situ combustion was proposed by using data from simultaneous thermal analysis (STA) together with thermodynamic values calculated with HSC^ software. XRD results showed that the as-leached products from both reactant systems mainly contained CaTiO₃. FT-IR spectroscopy indicated that the as-leached products had Ca-Ti-O and Ti-O functional groups. In addition, SEM observation of the as-leached products revealed cuboid-like crystals with a particle size of about 100 nm.

Abstract: Solid-state high-resolution ¹³C/⁷Li nuclear magnetic resonance (NMR) study was performed on the phase structure and chain dynamics of PEG-PPG-PEGn/LiCF₃SO₃ (n=3, 6, 12) copolymer electrolytes. PEG repeating units and Li⁺ form PEG₃:LiCF₃SO₃ crystalline complex and PE₃/Li⁺ amorphous complex in all the samples. PPG repeating units and Li⁺ form different complexes with respect to O:Li⁺ feed ratio (denoted as PP/Li⁺-3/6/12). The ¹³C chemical shifts and half widths of the signals from PP/Li⁺-3/6/12 remain unchanged, which implies the structures of PP/Li⁺-3/6/12 are similar at least in a very short range. The half width of the ⁷Li signals from PP/Li⁺-3/6/12 becomes narrower and narrower as the Li⁺ concentration decreases. This indicates the chain mobility of the amorphous phase increases with the decrease of ionic concentration. Moreover, neat crystalline PEG, neat amorphous PEG and neat amorphous PPG start to appear when O:Li⁺ is greater than 3:1 and their contents increase with the increase of O:Li⁺. Overall, solid-state high-resolution NMR is a powerful and unique method for understanding the phase structure and chain dynamics of solid polymer electrolytes (SPEs), more applications of this technique to studies on SPEs is expecting.

Abstract: This research examines the effect of ceramic particulate of Si₃N₄ on the hardness, tensile, corrosion, and microstructure of reinforced AA8011 composites. The composites were developed by two steps stir casting process where both the particulates and the alloy matrix were preheated and melted respectively before mixing. 0%, 5%, 10%, 15%, and 20% Si₃N₄ particulates compositions were varied to fabricate the composites. Vickers microhardness tester was employed to study the hardness, the universal testing machine was used to analyze the ultimate tensile strength, the tribological performances of the developed composites AA8011-Si₃N₄ were analyzed under dry sliding condition using Universal Tribometer. The results of the experiment clearly revealed the improvement in the mechanical properties of the composites compared to the primary Al-Fe-Si alloy with excellent strength mechanism recorded at 20% reinforcement. Composites with 20% Si₃N₄ was found to have a better wear resistance hence, lowest wear rate.

Abstract: Traditional acoustic absorbing materials are not effective for low-frequency engineering applications, but on the basis of the locally resonant principle, acoustic metamaterials can utilize the resonance of vibrators to dissipate acoustic energy and realize the subwavelength design of acoustic absorbers, therefore the acoustic metamaterials have great potential applications for noise reduction at low frequencies. This paper firstly employs the Bloch theory to investigate the effects of the parameters of the unit cell of the embedded membrane-and-mass metamaterials on the dispersion characteristics of the metamaterials, and the band gap is verified by the full wave finite element analysis. And then, a model of acoustic metamaterials is constructed by embeding an array of membrane-and-masses into a channel structure filled with acoustic materials. Next the transient frequency response analysis is performed to simulate the wave propagation in the model, the results show that the acoustic metamaterials can absorb the sound through the local resonance of the membrane-and-mass vibrators. Finally, an acoustic metamaterial maze structure is designed and analyzed, in the structure the membrane-and-mass array is embedded and the masses varies periodically. The research illustrates that the acoustic metamaterials with membrane-and-mass unit cells have excellent performances on the sound absorption at low frequency.

Abstract: Microfluidics has great control over the size and uniformity of microspheres, which has been widely used in fabrication of different types of microspheres such as core-shell microbubbles. Gelatin Methacrylate (GelMa) as a biodegradable material that is closely resemble to native extracellular matrix (ECM). Photocrosslinked GelMa microspheres have gained numerous concerns in biomedical applications especially in three-dimensional cell culture and tissue engineering. In this article, we presented a suitable core-shell cell carrier based on biocompatible GelMa microbubbles. Highly monodispersed microbubbles were fabricated using a non-planar flow focusing microfluidic device. Both intact and collapsed microbubbles morphology were characterized through scanning electron microscopy (SEM), where clear hollow structures were found resulting from the gas core collapsing during the manipulation process. Furthermore, human umbilical vein endothelial cells (HUVEC) were seeded in the existence of microbubbles. Cells adhesion, migration and proliferation were observed in one week. It was notable that cells maintained high level of cell viability throughout the experiment. GelMa microbubble surface was also covered with cells, which became a facile carrier for cell culturing and targeted cell delivery.

Abstract: Hyaluronic acid (HA)-based hydrogels are widely used in biomedical applications due to their excellent biocompatibility and enzymatic degradability. In this paper a photo-crosslinking double-network hyaluronic acid-based hydrogel dressing was proposed. Hyaluronic acid can be UV-crosslinked by modification with methacrylic anhydride (HA-MA) and disulfide-crosslinked by modification with 3,3'-dithiobis (propionylhydrazide) (DTP) (HA-SH). The mixings of these two materials at different ratios were produced. All the samples can be quickly gelled at 365 nm for 10 s. The rheological tests show that the storage modulus (G') of the double network (HA-SH/HA-MA) hydrogel is increased with the increase of HA-SH content. The HA-SH/HA-MA hydrogel has porous structure, high swelling ratio and Controlled degradation rate. In vitro degradation tests show that the ratio of HA-SH/HA-MA ratio was 9:1 (S9M1) in 100 U/ml hyaluronidase (Hase) degraded by 89.91±2.26% at 11d. The cytocompatibility of HA-SH/HA-MA hydrogels was proved by Live/Dead stainings and CCK-8 assays in the human dermis fibroblasts (HDF) cells test. All these results highlight the biological potential of the HA-SH/HA-MA hydrogels for DFU intervention.