Advanced Materials Research Vol. 974

Abstract: In this work, hollow carbon nanospheres (HCNs) were synthesized by carbonizing core/shell particles of polymethylmethacrylate (PMMA)/ resorcinol formaldehyde. The core/shell particles were prepared using emulsion polymerization; polymethylmethacrylate as a template and resorcinol-formaldehyde polymer as the carbon source. Spheres were first synthesized by batch mode polymerization and then the shell was polymerized on the surface of the spheres. The composite was stabilized, and then carbonized. The effect of calcination temperature was investigated in the range between 200-500 ^oC. Scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDX), Raman and Fourier transform infrared (FTIR) were used for characterization of the resulting carbon.

Abstract: In this paper, First-principles calculation were used to investigate the effect of Fe substituted Co-free AB₃-type hydrogen storage alloys. (La₃Mg₆Ni₂₇)_1/3 alloy (Hex structure) and (La₃Mg₆Ni₂₆Fe₁)_1/3 alloy's crystal structures were build by Material studio software, Bond structure and DOS results were calculated. To compare with the calculated results, (La₃Mg₆Ni₂₇)_1/3 alloy and (La₃Mg₆Ni₂₆Fe₁)_1/3 alloy were synthesized by vacuum melting method. The effect of Fe on such alloys are discussed according to calculate results and experiment results, as a first-principle investigation.

Abstract: In this paper, the characteristics of melted and annealed Co-free AB₃-type hydrogen storage alloys in low-temperature condition were investigated by electrochemical tests. A series of Co-free AB₃-type hydrogen storage alloys were synthesized with vacuum melting method, and be annealed by low-temperature heat treatment. The structures of alloys are simply discussed through SEM and XRD results. And discharge ability and cycle ability of alloys were tested. Experiment results indicate that characteristics of different AB₃-type hydrogen storage alloys are affected by low-temperature obviously, and heated treatment could increase the discharge capacity of hydrogen storage alloy effectively, and improve the charge-discharge stability of alloy. Furthermore, non-metal element substituted alloy shows better Low-temperature applicability due to its weak crystallization. The discharge capacity of La_0.7Mg_0.3Ni_2.9B_0.05 alloy remains 91.2% after 30 cycles at 273K. And discharge capacity of heated La_0.7Mg_0.3Ni_2.9(FeB)_0.1 alloy could reach to 250mA·g^-1.

Abstract: This paper discussed on the application of NiCrSiB coating on 3-straight cylinder piston of Perodua Kancil 660cc using a high velocity oxygen fuel (HVOF) spraying technique. NiCrSiB coating was known as protective coating that was investigated for its thermal properties. The coating showed a good surface finish as well as the bonding interface. The applied NiCrSiB coating on the piston was tested up to the engine temperature during the operation compared to the uncoated piston. It was found that the uncoated piston had a higher heat transfer than the coated piston. Another test was conducted at several temperatures along the radial of the piston to its centre. The results indicated that the uncoated piston had a higher temperature compared to the coated piston.

Abstract: In this review different aspects of material and structural engineering of metal oxides aimed for application in conductometric gas sensors (chemiresistors) were analyzed. Results, mainly obtained for SnO₂ and In₂O₃–based sensors during surface functionalizing by noble metals have been used for showing an opportunity of material and structural engineering of metal oxides to optimize gas sensing characteristics.

Abstract: In this work, Na₂O-Al₂O₃-BaO-CaO-Sb₂O₃-B₂O₃-SiO₂ glasses doped with Er³⁺ was prepared and investigated for their physical, optical and visible luminescence properties. The increases in density, refractive index and molar volume of the glasses with additional doping content of Er₂O₃ into the network were due to a higher molecular weight and polarizability of Er₂O₃ in comparison with the glass former (SiO₂ and B₂O₃). Ten absorption peaks were observed as a nature of Er³⁺ absorption in glass matrices. The glass exhibited four emission transitions which were assigned to ⁴F_5/2→⁴I_15/2 (460 nm), ⁴F_7/2→⁴I_15/2 (487 nm), ²H_11/2→⁴I_15/2 (522 nm) and ⁴S_3/2→⁴I_15/2 (545 nm) transitions. The strongest intensity was the green emission at 522 nm. The luminescence intensity was found to increase with Er₂O₃ content up to 4 mol% and it was decreased for higher Er₂O₃ contents due to concentration quenching effect.

Abstract: Realizing the growing extraordinary interest in the development of polymer hydrogels, successful attempt has been made for synthesis of copolymer hydrogels from aqueous solution of acrylamide/bacterial cellulose (AAm/BC) with irradiation processing technology using Co-60 gamma source. The study envisaged to: (i) develop a novel high strength polymer nanocomposite hydrogels containing natural BC, and (ii) investigate chemical structure, morphology, and mechanical strength properties of the formed gels. The effectiveness of AAm/BC hydrogel for wound dressing application was also tested. Structure and properties of composite were investigated using Fourier Transform Infrared spectrophotometer (FTIR), Differential Scanning Calorimetry (DSC), and Atomic force microscopy (AFM). While investigating the influence of irradiation dose and concentration of acrylamide on gel content, swelling properties and thermal stability of copolymer hydrogel,maximum gel content of prepared hydrogel was obtained at the radiation dose of 40 kGy. Swelling ratio and equilibrium water content increased with increasing irradiation dose and concentration of acrylamide in feed solution. The water absorption of hydrogel increased with increased standing time in swelling medium. It was rapid up to 24 h and got slowed down thereafter. The water absorption also increased with increasing concentration of irradiation dose in the feed solution. The water absorption of copolymer hydrogel obtained at 40 kGy irradiation dose decreased from 1800 to 1400%. This type of diffusion of prepared hydrogel was found to be a non Fickian diffusion. The thermal stability of copolymer hydrogel prepared at the irradiation dose of 40 kGy increased with increasing amount of AAm in the feed solution. The mechanical behavior of composite hydrogels at optimum irradiation dose performed value of tensile and strain at 46.3MPa and 36.6%, respectively.

Abstract: Chitosan and hyaluronan were used as biocompatible materials for biomedical application. In here, we prepared the Hyaluronan (HA) coated metal nanostructures. The chitosan (CS) films containing various concentrations of HA-coated Au or HA-coated Ag@Au nanostructures. We demonstrated that HA-coated spherical-like gold (HA-AuS), HA-coated wire-like gold (HA-AuW) or HA-coated Ag@Au could be dispersed in chitosan matrix by mixing and in aqueous solution casting. The introduction of HA-AuS, HA AuW and HA-Ag@Au nanostructures could not only improve the physical properties of CS, but also enhance the biocompatibility. The results revealed that the HA-AuS, HA AuW and HA-Ag@Au nanostructures enhanced the crystallinity of CS films. Besides, the hydrophilicity of CS films were improved by the HA-AuS, HA AuW and HA-Ag@Au nanostructures.

Abstract: Rubber reinforcement in general depends on the type of filler used in the rubber mixture. Instead of carbon black, Silica filler has been widely accepted in tyre making due to its low rolling resistance property. In recent years, there is a trend in using higher curing temperature in order to improve productivity of vulcanisation line without drawbacks in the performance of tyres. In this work, effect of vulcanisation temperature based on the silica filled ENR curing behaviour was studied. Results indicate that time-dependant reversion behaviour of ENR was similar to that of unmodified Natural Rubber. The physical properties slowly deteriorated as the curing temperature approached 180°C which related to low crosslink density. Carbon Black filled ENR compound was used as a comparison.

Abstract: Metallic nickel (Ni) nanoparticles with a mean diameter of about 70 nm are successfully formed by electroless deposition in an aqueous solution at 273 K. The formation of Ni nanoparticles is investigated by in situ mixed potential measurement in combination with thermodynamic calculation. The deposition rate of Ni is measured using an electrochemical quartz crystal microbalance (EQCM). The mixed potential of reaction solution drastically decreases below the oxidation-reduction potential of Ni (II)/Ni redox pair at about-0.60 v vs SHE after 30 min reaction. This coincides with a sharp increase in the deposited mass, suggesting Ni deposition.